WiMax the Ultimate Broadband Solution

WiMax the Ultimate Broadband Solution

CHAPTER 1

BASIC CONCEPT ON COMPUTER NETWORK

1.1 Network History :

Each of the past three centuries has been dominated by a single technology. The 18th

centuries was the era of the great mechanical system accompanying the Industrial Revolution. The 19th century was the age of the steam engine. During the 20 th century, the key information gathering, processing and distribution. Among other developments, we saw the installation of worldwide telephone networks, the invention of radio and television, the birth and unprecedented growth of the computer industry, and the launching of communication satellites.

The Internet is the largest data network on earth. The Internet consists of many large and small networks that are interconnected. Individual computers are the sources and destinations of information through the Internet. Connection to the Internet can be broken down into the physical connection, the logical connection, and applications.

Basically computer network can be separated into 2 categories based on there connectivity.

a) Wired Network.b) Wireless Network

To discuss about the term Network a question comes at first that is,

1.1.1 “What is Network?”

A network is a set of devices connected by communication links. A mode can be a computer, printer or any other device capable of sending and receiving data generated by other nodes on the network.

Networking is the practice of linking computing devices together with hardware and software that supports data communications across these devices. The simplest kind of home network contains exactly two computers. You can use this kind of network to share files, a printer or another peripheral device, and even an Internet connection. To connect two computers for sharing network resources, consider these alternatives.

1.1.2 Distributed Processing:

Most networks use distributed processing, in which a task is divided among multiple computers. Instead of a single large being responsible for all aspects of process, separate computers handle a subset.

1.1.3 Network Criteria:

A network must be able to meet a certain number of criteria. The most important of these are performance, reliability and security.

1.1.4 Performance :

Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. The performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.

1.1.5 Reliability:

I addition to accuracy delivery, network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe.

1.1.6 Security:

Network security issues include protecting data from unauthorized access.

1.2 Networking Categories :

Now a days we r generally referring to four primary categories of networks. These four categories networks differ from their size, their ownership, the distance they cover, and their physical architecture.

Fig- 1.1 : Network Categories

1.3 Local Area Network(LAN) :

Network

Local-area Network

(LAN)

Metropolitan- area Network (MAN)

Wide-area Network

Personal-area

Network

A local area network is privately owned and links the devices in a single office or campus. Depending on the needs of an organization and type of technology used, a LAN can be as simple as two PCs and a printer in someone’s home office or it can extend throughout a company and include audio and video peripherals.

LANs are designed to allow resources to be shared between personal computers or workstation. The resources to be shared can include hardware, software or data. A common example of a LAN, found in many business environments, links a workgroup of task-related computers for example engineering workstations or accounting PCs. One of the computers may be given a large capacity disk drive and may become a server to the other clients. Software can be stored on this central server and used as needed by licensing by the whole group.

Fig-1.2 : LAN connection among the computer accessories

1.4 Metropolitan-Area Network (MAN):A metropolitan area network is designed to extend over an entire city. It may be a

single network such a cable television network, or it may be a means of connecting a number of LANs into a larger network so that resources may be shared LAN-to-LAN as well as device-to-device. For example, a company can use a MAN to connect the LANs in all its offices throughout a city.

1.5 Wide Area Network (WAN): A wide area network provides long distance transmission of data, voice, image, and

video information over large geographic areas that may be a country, a continent or even the whole world. WANs interconnect LANs, which then provide access to computers or file servers in other locations.A WAN that is wholly owned used by single company is often referred to as an enterprise network.

Fig-1.3 : WAN connection among the computer accessories

WANs are designed to do the following:

Operate over a large and geographically separated area Allow users to have real-time communication capabilities with other users

Provide full-time remote resources connected to local services

Provide e-mail, Internet, file transfer, and e-commerce services

1.6 WIRELESS LANA wireless LAN is one in which a mobile user can connect to a local area network

(LAN) through a wireless (radio) connection The IEEE 802.11 group of standards specify the technologies for wireless LANs.

Fig 1.4 : Wireless LAN

1.7 Wireless pan

A WPAN (wireless personal area network) is a personal area network - a network for interconnecting devices centered around an individual person's workspace - in which the connections are wireless. Typically, a wireless personal area network uses some technology that permits communication within about 10 meters - in other words, a very short range. One such technology is Bluetooth.

1.8 Wireless man

A data network intended to serve an area the size of a large city. Such networks are being implemented by innovative techniques, such as running optical fibre through subway tunnels.

Fig 1.5 : Wireless LAN

1.9 Authentication,Authorization, Accounting (AAA) Technologies and Protocols

Authentication, Authorization and Accounting (AAA) is a framework for intelligently controlling access to computer network resources, enforcing policies, auditing usage, and providing the information necessary to bill for services. These combined processes are considered important for effective network management and security. The AAA is sometimes combined with auditing and accordingly becomes AAAA.

Authentication refers to the process of validating the claimed identity of an end user or a device, such as a host, server, switch, router, and so on. Authentication is accomplished via the presentation of an identity and credentials. Examples of types of credentials are passwords, one-time tokens, digital certificates, and phone numbers (calling/called).

Authorization refers to the act of granting access rights to a user, groups of users, system, or a process, based on their authentication, what services they are requesting, and the current system state. Authorization may be based on restrictions, for example time-of-day restrictions, or physical location restrictions, or restrictions against multiple logins by the same user. Authorization determines the nature of the service which is granted to a user. Examples of types of service include, but are not limited to: IP address filtering, address assignment, route assignment, QoS/differential services, bandwidth control/traffic management, compulsory tunneling to a specific endpoint, and encryption.

Accounting refers to the methods to establish who, or what, performed a certain action, such as tracking user connection and logging system users. This information may be used for management, planning, billing, or other purposes. Real-time accounting refers to accounting information that is delivered concurrently with the consumption of the resources. Batch accounting refers to accounting information that

is saved until it is delivered at a later time. Typical information that is gathered in accounting is the identity of the user, the nature of the service delivered, when the service began, and when it ended.

Auditing refers to an evaluation of an organization, system, process, project or product. Audits are performed to ascertain the validity and reliability of information, and also provide an assessment of a system's internal control.

There are many technologies and protocols defined to achieve the goals defined in the AAA (or AAAA) framework. Some of the AAA Technologies and Protocols are listed below:

1. CHAP: Challenge Handshake Authentication Protocol2. DIAMETER Protocol: This protocol is designed to replace the RADIUS.

3. EAP: Extensible Authentication Protocol

4. Kerberos

5. MS-CHAP (MD4)

6. PAP: Password Authentication Protocol

7. PEAP: Protected Extensible Authentication Protocol

1.10 Wireless Roaming

Microsoft Research has developed a wireless roaming service architecture that enables personalized, seamless, and secure connectivity for mobile customers when moving across different types of wireless networks, such as cellular or wireless local-area networks (WLAN). Wireless Roaming maintains connectivity by using connection/session management when customers roam across different networks.

Wireless Roaming is compatible with MIPv6. The technology provides intelligent personalized service by supporting device and service mobility. Device mobility means that Wireless Roaming provides seamless mobility support for portable devices. For example a customer initiates a VoIP call from a SmartPhone in an office building with Wi-Fi. Leaving the building, the customer will maintain connectivity by automatically switching to GPRS or CDMA. Wireless Roaming works in a manner that is seamless and transparent to the customer. The voice conversation continues uninterrupted. Service mobility means that services like the above VoIP call survive hand-offs between different networks. Another example for improved service mobility is a customer streaming a video on a cell phone automatically experiencing improved quality when moving from a GPRS network to WLAN.

Value-added services such as video entertainment, instant messaging or internet browsing are enhanced by enabling dynamic federation/collaboration among different types of networks and devices. Wireless Roaming guarantees a trustworthy environment following the IPSec standards for secure communication and encryption.

CHAPTER 2

OSI Reference Model

2.1. What is OSI Reference Model ?

The International Organization for Standardization (ISO) began developing the Open Systems Interconnection (OSI) reference model in 1977.  It was created to standardize the rules of networking in order for all systems to be able to communicate.  In order for communication to occur on a networking using different device drivers and protocol stacks, the rules for communication must be explicitly defined.  The OSI model deals with the following issues;

How a device on a network sends it's data, and how it knows when are where to send it

How a device on a network receives it's data, and how to know where to look for it.

How devices using different languages communicate with each other.

How devices on a network are physically connected to each other.

How protocols work with devices on a network to arrange data.

The OSI model is broken down into 7 layers.  Although the first layer is #1, it is always shown at the bottom of the model.  We'll explain why later.  Here are the seven layers.

1. Physical Layer 2. Data Link Layer

3. Network Layer

4. Transport Layer

5. Session Layer

6. Presentation Layer

7. Application Layer

2.1. Protocol Stacks

In order for each layer of the model to communicate with the levels above and below it, certain rules were developed.  These rules are called Protocols, and each protocol provides a specific layer of the model with a specific set of tasks or services.  Each layer of the model has it's own set of protocols associated with it.  When you have a set of protocols that create a complete OSI model, it is called a Protocol Stack.  An example of a protocol stack is TCP/IP, the standard for communication over the internet, or AppleTalk for Macintosh computers.

As stated before, protocols define how layers communicate with each other.  Protocols specifically work with ONLY the layer above and below them.  They receive services from the protocol below, and provide services for the protocol above them.  This order maintains a standard that is common to ALL forms of networking.

In order for two devices on a network to communicate, they must both be using the same protocol stack.  Each protocol in a stack on one device must communicate with it's equivalent stack, or peer, on the other device.  This allows computers running different operating systems to communicate with each other easily, such as having Macintosh computers on a Windows NT network.

2.2 Communications Between Stacks

When a message is sent from one machine to another, it travels down the protocol stack or layers of the model, and then up the layers of the stack on the other machine.  As the data travels down the stack, it picks up headers from each layer (Except the physical layer).  Headers contain information that is read by the peer layer on the stack of the other computer.  As the data travels up the levels of the peer computer, each header is removed by it's equivalent protocol.  These headers contain different information depending on the layer they receive the header from, but tell the peer layer important information, including packet size, frames, and datagrams.  Each layer's header and data are called data packages, or service data units.  Although it may seem confusing, each layer has a different name for it's service data unit.  Here are the common names for service data units at each level of the OSI model

Application Messages and Packets

Presentation Packets

Session Packets

Transport Datagrams, Segments, and Packets

Network Datagrams and Packets

Data Link Frames and Packets

Physical Bits and Packets

3. The Physical Layer

The lowest layer on the OSI model, and probably the easiest to understand is the physical layer.  This layer deals with the physical, electrical, and cable issues involved with making a

network connection.  It associates with any part of the network structure that doesn't process information in any way.

The physical layer is responsible for sending the bits across the network media.  It does not define what a bit is or how it is used merely how it's sent.  The physical layer is responsible for transmitting and receiving the data.  It defines pin assignments for serial connections, determines data synchronization, and defines the entire network's timing base.

Items defined by the physical layer include hubs, simple active hubs, terminators, couplers, cables and cabling, connectors, repeaters, multiplexers, transmitters, receivers, and transceivers.  Any item that does not process information but is required for the sending and receiving of data is defined by this layer.

Figure 1.2 : Task of physical layer is transmitting stream of bytes through the transmission medium.

There are several items addresses by this layer.  They are;

Network connections types, including multi-point and point-to-point networks. Network Topologies, including ring, star, bus, and mesh networks.

Analog or Digital signaling.

Bit Synchronization (When to send data and when to listen for it).

Baseband Vs. Broadband transmissions.

Multiplexing (Combining multiple streams of data into one channel).

Termination, to give better signal clarity and for node segmentation. 

4. The Data Link Layer

The Data Link Layer is responsible for the flow of data over the network from one device to another.  It accepts data from the Network Layer, packages that data into frames, and sends them to the Physical Layer for distribution.  In the same way, it receives frames from the physical layer of a receiving computer, and changes them into packets before sending them to the Network Layer.

The Data link Layer is also involved in error detection and avoidance using a Cyclic Redundancy Check (CRC) added to the frame that the receiving computer analyses.  This second also checks for lost frames and sends requests for re-transmissions of frames that are missing or corrupted at this level.

The most important aspect of the Data Link Layer is in Broadcast networks, where this layer establishes which computer on a network receives the information and which computers relay or ignore the information.  It does so by using a Media Access Control (MAC) address, which uniquely identifies each Network Interface Card (NIC).

Bridges, Intelligent Hubs, And NICs are all associated with the Data Link Layer.

The Data Link Layer is sub-divided into two layers.  This is done because of the two distinct functions that each sub-division provides.

Logical Link Control - Generates and maintains links between network devicesMedia Access Control - Defines how multiple devices share a media channel

The Logical Link Control provides Service Access Points (Saps) for other computers to make reference to when transporting data the to upper layers of the OSI Model.

Media Access Control gives every NIC a unique 12 digit hexadecimal address.  These addresses are used by the Logical Link Control to set up connections between NICs.  Every MAC address must be unique or they will cause identity crashes on the network.  The MAC address is normally set at the factory, and conflicts are rare.  But in the case of a conflict, the MAC address is user set-able.

5. The Network Layer

The third layer of the OSI model is the Network layer.  This layer is responsible for making routing decisions and forwards packets that are farther then one link away.  By making the network layer responsible for this function, every other layer of the OSI model can send packets without dealing with where exactly the system happens to be on the network, whether it be 1 hop or 10 hops away.

In order to provide it's services to the data link layer, it must convert the logical network address into physical machine addresses, and vice versa on the receiving computer.  This is done so that no relaying, routing, or networking information must be processed by a level higher in the model then this level.  Essentially, any function that doesn't provide an environment for executing user programs falls under this layer or lower.  

Because of this restriction, all systems that have packets routed through their systems must provide the bottom three layers' services to all packets traveling through their systems.  Thus, any routed packet must travel up the first three layers and then down those same three layers

before being sent farther down the network.  Routers and gateways are the principal users of this layer, and must fully comply with the network layer in order to complete routing duties.

The network layer is also responsible for determining routing and message priority.  By having this single layer responsible for prioritization, the other layers of the OSI model remain separated from routing decisions.

This layer is also responsible for breaking large packets into smaller chucks when the original packet is bigger then the Data Link is set.  Similarly, it re-assembles the packet on the receiving computer into the original-sized packet. There are several items addresses by this layer.  They are;

Addressing for logical network and service addresses. Circuit message and packet switching

Route discovery and selection

Connection services, including layer flow control and packet sequence control.

Gateway Services

6. Transport Layer

The transport layer's main duty is to unsure that packets are send error-free to the receiving computer in proper sequence with no loss of data or duplication.  This is accomplished by the protocol stack sending acknowledgements of data being send and received, and proper checksum/parity/synchronization of data being maintained. 

The transport layer is also responsible for breaking large messages into smaller packets for the network layer, and for re-assembling the packets when they are received from the network layer for processing by the session layer.

7. Session Layer

The session layer is the section of the OSI model that performs the setup functions to create the communication sessions between computers.  It is responsible for much of the security and name look-up features of the protocol stack, and maintains the communications between the sending and receiving computers through the entire transfer process.  Using the services provided by the transport layer, the session layer ensures only lost or damaged data packets are re-sent, using methods referred to as data synchronization and checkpointing.  This ensures that excess traffic is not created on the network in the event of a failure in the communications.

The session layer also determines who can send data and who can receive data at every point in the communication.  Without the dialogue between the two session layers, neither computer would know when to start sending data and when to look for it in the network traffic.

8. The Presentation and Application Layers

The presentation layer is responsible for protocol conversation, data translation, compression, encryption, character set conversion, and graphical command interpretation between the computer and the network.

The main working units in the presentation are the network redirectors, which make server files visible on client computers.  The Network redirector is also responsible for making remote printers appear as if they were local.

The application layer provides services that support user applications, such as database access, e-mail services, and file transfers.  The application layer also allows Remote Access Servers to work, so that applications appear local on remotely hosted servers.

CHAPTER 3

Wireless Broadband Access

3.1 Defining Wireless Broadband:

The term wireless broadband generally refers to high-speed hundred kilobits data transmission occurring within an infrastructure of more or less fixed points, including both stationary subscriber terminals and service provider base station. This is distinct from mobile data transmission where the subscriber can expect to access the network while in transmit and where only the network operator’s base stations occupy fixed locations. We can expect that this distinction will become somewhat blurred in the future inasmuch as several manufacturers are developing very high-speed wireless networking equipment that will support mobility or stationary usage almost equally emphasis of high-speed wireless service providers serving stationary subscribers will remain. Broadband wireless, as it’s today, is properly a competitor to optical fiber, hybrid fiber coax, DSL, and to a much lesser extent, broadband satellite.

Third-generation (3G) and 2.5G cellular telephone networks, which have special provision fro delivering medium-speed packet data services, are not, in most instance, directly competitive with broadband wireless services. They share a radio frequency air link and, in some cases, core technologies, but they serve a different type of customer and present different type of customer and present different types of services offerings.

3.2 Introducing IEEE 802.16 Standards

The IEEE 802.16 Working Group on Broadband Wireless Access Standards, which was established by IEEE Standards Board in 1999, aims to prepare formal specifications for the global deployment of broadband Wireless Metropolitan Area Networks. The Workgroup is a unit of the IEEE 802 LAN/MAN Standards Committee. A related future technology Mobile Broadband Wireless Access (MBWA) is under development in IEEE 802.20.

Although the 802.16 family of standards is officially called WirelessMAN, it has been dubbed “WiMAX” by an industry group called the WiMAX Forum. The mission of the

Forum is to promote and certify compatibility and interoperability of broadband wireless products.

3.2.1 802.16 Standards:

The first 802.16 standard was approved in December 2001. It delivered a standard for point to multipoint Broadband Wireless transmission in the 10-66 GHz band, with only a line-of-sight (LOS) capability. It uses a single carrier (SC) physical (PHY) standard.

802.16a was an amendment to 802.16 and delivered a point to multipoint capability in the 2-11 GHz band. For this to be of use, it also required a non-line-of-sight (NLOS) capability, and the PHY standard was therefore extended to include Orthogonal Frequency Division Multiplex (OFDM) and Orthogonal Frequency Division Multiple Access (OFDMA). 802.16a was ratified in January 2003 and was intended to provide "last mile" fixed broadband access.

802.16c, a further amendment to 802.16, delivered a system profile for the 10-66 GHz 802.16 standard.

In September 2003, a revision project called 802.16d commenced aiming to align the standard with aspects of the European Telecommunications Standards Institute (ETSI) HIPERMAN standard as well as lay down conformance and test specifications. This project concluded in 2004 with the release of 802.16-2004 which superseded the earlier 802.16 documents, including the a/b/c amendments.

An amendment to 802.16-2004, IEEE 802.16e-2005 (formerly known as IEEE 802.16e), addressing mobility, was concluded in 2005. This implemented a number of enhancements to 802.16-2004, including better support for Quality of Service and the use of Scalable OFDMA, and is sometimes called “Mobile WiMAX”, after the WIMAX forum for interoperability.

Amendments in progress

Active amendments:

802.16e-2005 — Mobile 802.16

802.16f-2005 — Management Information Base

802.16g-2007 — Management Plane Procedures and Services

802.16k-2007 — Bridging of 802.16 (an amendment to 802.1D)

Amendments under development:

802.16h — Improved Coexistence Mechanisms for License-Exempt Operation

802.16i — Mobile Management Information Base

802.16j — Multihop Relay Specification

802.16Rev2 — Consolidate 802.16-2004, 802.16e, 802.16f, 802.16g and possibly 802.16i into a new document.

Amendments at pre-draft stage:

802.16m — Advanced Air Interface. Data rates of 100 Mbit/s for mobile applications and 1 Gbit/s for fixed applications, cellular, macro and micro cell coverage, with currently no restrictions on the RF bandwidth (which is expected to be 20 MHz or higher).The proposed work plan would allow completion of the standard by December 2009 for approval by March 2010

3.2.2 802.16e-2005 Technology

The 802.16 standard essentially standardizes 2 aspects of the air interface - the physical layer (PHY) and the Media Access Control layer (MAC). This section provides an overview of the technology employed in these 2 layers in the current version of the 802.16 specification (which is strictly 802.16-2004 as amended by 802.16e-2005, but which will be referred to as 802.16e for brevity).

PHY

802.16e uses Scalable OFDMA to carry data, supporting channel bandwidths of between 1.25 MHz and 20 MHz, with up to 2048 sub-carriers. It supports adaptive modulation and coding, so that in conditions of good signal, a highly efficient 64 QAM coding scheme is used, whereas where the signal is poorer, a more robust BPSK coding mechanism is used. In intermediate conditions, 16 QAM and QPSK can also be employed. Other PHY features

include support for Multiple-in Multiple-out (MIMO) antennas in order to provide good NLOS (Non-line-of-sight) characteristics (or higher bandwidth) and Hybrid automatic repeat request (HARQ) for good error correction performance.

MAC

The 802.16 MAC describes a number of Convergence Sublayers which describe how wireline technologies such as Ethernet, ATM and IP are encapsulated on the air interface, and how data is classified, etc. It also describes how secure communications are delivered, by using secure key exchange during authentication, and encryption using AES or DES (as the encryption mechanism) during data transfer. Further features of the MAC layer include power saving mechanisms (using Sleep Mode and Idle Mode) and handover mechanisms.

A key feature of 802.16 is that it is a connection oriented technology. The subscriber station (SS) cannot transmit data until it has been allocated a channel by the Base Station (BS). This allows 802.16e to provide strong support for Quality of Service (QoS).

IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:

1. Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX'.

2. Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.

3. Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (HARQ)

4. Improving capacity and coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology

5. Increasing system gain by use of denser sub-channelization, thereby improving indoor penetration

6. Introducing high-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance

7. Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa

8. Enhanced Fast Fourier Transform algorithm can tolerate larger delay spreads, increasing resistance to multipath interference

9. Adding an extra QoS class (enhanced real-time Polling Service) more appropriate for VoIP applications.

Certification

Because the IEEE only sets specifications but does not test equipment for compliance with them, the WiMAX Forum runs a certification program wherein members pay for certification. WiMAX certification by this group is intended to guarantee compliance with the standard and interoperability with equipment from other manufacturers. The mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products.

QoS

QoS in 802.16e is supported by allocating each connection between the SS and the BS (called a service flow in 802.16 terminology) to a specific QoS class. In 802.16e, there are 5 QoS classes:

802.16e-2005 QoS classes

Service Abbrev Definition Typical Applications

Unsolicited Grant Service

UGSReal-time data streams comprising fixed-size data packets issued at periodic intervals

T1/E1 transport

Extended Real-time Polling Service

ertPSReal-time service flows that generate variable-sized data packets on a periodic basis

VoIP

Real-time Polling Service

rtPSReal-time data streams comprising variable-sized data packets that are issued at periodic intervals

MPEG Video

Non-real-time Polling Service

nrtPSDelay-tolerant data streams comprising variable-sized data packets for which minimum data rate is required

FTP with guaranteed minimum throughput

Best Effort BEData streams for which no minimum service level is required and therefore may be handled on a space-available basis

HTTP

The BS and the SS use a service flow with an appropriate QoS class (plus other parameters, such as bandwidth and delay) to ensure that application data receives QoS treatment appropriate to the application.

3.3 Introducing Wireless Broadband Technologies

In this section we need to discuss with the several of wireless network technologies provided all over world. This discussed technologies are basically based on the wireless network unit. So we are going discuss about it in below one by one.

3.3.1 CDMA(Code Division Multiple Access)

Code division multiple access (CDMA) is a channel access method utilized by various radio communication technologies.

One of the basic concepts in data communication is the idea of allowing several transmitters to send information simultaneously over a single communication channel. This allows several users to share a bandwidth of frequencies. This concept is called multiplexing.

CDMA employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel.

By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a form of "spread-spectrum" signaling, since the modulated coded signal has a much higher data bandwidth than the data being communicated.

An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can understand each other.

Uses1. One of the early applications for code division multiplexing—predating, and

distinct from cdmaOne—is in GPS. 2. The Qualcomm standard IS-95, marketed as cdmaOne.

3. The Qualcomm standard IS-2000, known as CDMA2000. This standard is used by several mobile phone companies, including the Globalstar satellite phone network.

4. CDMA has been used in the OmniTRACS satellite system for transportation logistics

Technical detailsCDMA is a spread spectrum multiple access technique. In CDMA a locally generated code runs at a much higher rate than the data to be transmitted. Data for transmission is simply logically XOR (exclusive OR) added with the faster code. The figure shows how spread spectrum signal is generated. The data signal with pulse duration of Tb is XOR added with the code signal with pulse duration of Tc. (Note: bandwidth is proportional to 1/T where T = bit time) Therefore, the bandwidth of the data signal is 1/Tb and the bandwidth of the spread spectrum signal is 1/Tc. Since Tc is much smaller than Tb, the bandwidth of the spread spectrum signal is much larger than the bandwidth of the original signal.

Fig 3.1: CDMA signal Processing

Each user in a CDMA system uses a different code to modulate their signal. Choosing the codes used to modulate the signal is very important in the performance of CDMA systems. The best performance will occur when there is good separation between the signal of a desired user and the signals of other users. The separation of the signals is made by correlating the received signal with the locally generated code of the desired user. If the signal matches the desired user's code then the correlation function will be high and the system can extract that signal. If the desired user's code has nothing in common with the signal the correlation should be as close to zero as possible (thus eliminating the signal); this is referred to as cross correlation. If the code is correlated with the signal at any time offset other than zero, the correlation should be as close to zero as possible. This is referred to as auto-correlation and is used to reject multi-path interference.

3.3.2 GSM (Global System for Mobile)

Global System for Mobile communications (GSM) is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 82% of the global mobile market uses the standard.GSM is used by over 3 billion people across more than 212 countries and territories. Its ubiquity makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs from its predecessors in that both signalling and speech channels are digital, and thus is considered a second generation (2G) mobile phone system. This has also meant that data communication was easy to build into the system.

The ubiquity of the GSM standard has been an advantage to both consumers and also to network operators.GSM also pioneered a low-cost, to the network carrier, alternative to voice calls, the Short message service, which is now supported on other mobile standards as well. Another advantage is that the standard includes one worldwide Emergency telephone number, 112. This makes it easier for international travellers to connect to emergency services without knowing the local emergency number.

GSM security

GSM was designed with a moderate level of security. The system was designed to authenticate the subscriber using a pre-shared key and challenge-response. Communications between the subscriber and the base station can be encrypted. The development of UMTS introduces an optional USIM, that uses a longer authentication key to give greater security, as well as mutually authenticating the network and the user - whereas GSM only authenticated the user to the network (and not vice versa). The security model therefore offers confidentiality and authentication, but limited authorization capabilities, and no non-repudiation. GSM uses several cryptographic algorithms for security. The A5/1 and A5/2 stream ciphers are used for ensuring over-the-air voice privacy. A5/1 was developed first and is a stronger algorithm used within Europe and the United States; A5/2 is weaker and used in other countries. Serious weaknesses have been found in both algorithms: it is possible to break A5/2 in real-time with a ciphertext-only attack, and in February 2008, Pico Computing, Inc revealed its ability and plans to commercialize FPGAs that allow A5/1 to be broken with a rainbow table attack [1]. The system supports multiple algorithms so operators

Subscriber Identity Module

One of the key features of GSM is the Subscriber Identity Module (SIM), commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information and phonebook. This allows the user to retain his or her information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM locking, and is illegal in some countries.

GSM Network structure

The network behind the GSM system seen by the customer is large and complicated in order to provide all of the services which are required. It is divided into a number of sections and these are each covered in separate articles.

o The Base Station Subsystem. o The Network and Switching Subsystem.

o The GPRS Core Network

o All of the elements in the system combine to produce many GSM services like voice calls and SMS.

Fig 3.2: The structure of a GSM network

3.3.3 GPRS (General Packet Radio Service)

General Packet Radio Service (GPRS) is a packet oriented Mobile Data Service available to users of Global System for Mobile Communications (GSM) and IS-136 mobile phones. It provides data rates from 56 up to 114 kbit/s.

GPRS can be used for services such as Wireless Application Protocol (WAP) access, Short Message Service (SMS), Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is using the capacity or is in an idle state. GPRS is a best-effort packet switched service, as opposed to circuit switching, where a certain Quality of Service (QoS) is guaranteed during the connection for non-mobile users.

Services and hardware

GPRS upgrades GSM data services providing:

Multimedia Messaging Service (MMS) Push to talk over Cellular PoC / PTT

Instant Messaging and Presence -- Wireless Village

Internet Applications for Smart Devices through Wireless Application Protocol (WAP)

Point-to-point (PTP) service: internetworking with the Internet (IP protocols)

Short Message Service (SMS)

Future enhancements: flexible to add new functions, such as more capacity, more users, new accesses, new protocols, new radio networks.

USB GPRS modem

USB GPRS modems use a terminal-like interface USB 2.0 and later, data formats V.42bis, and RFC 1144 and external antennas. Modems can be add in cards (for laptop) or external USB devices which are similar in shape and size to a computer mouse.GPRS can be used as the bearer of SMS. If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute

3.3.4 EDGE (Enhanced Data Rates for GSM Evolution) & EGPRS(Enhanced GPRS)

Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), is a digital mobile phone technology that allows increased data transmission rates and improved data transmission reliability. EDGE is generally classified as 2.75G, although it is part of ITU's 3G definition.EDGE has been introduced into GSM networks around the world since 2003, initially by Cingular (now AT&T) in the United States.

EDGE can be used for any packet switched application, such as an Internet connection. High-speed data applications such as video services and other multimedia benefit from EGPRS' increased data capacity. EDGE Circuit Switched is a possible future development.

EDGE Evolution continues in Release 7 of the 3GPP standard providing doubled performance to complement High-Speed Packet Access (HSPA).

Technology

In addition to Gaussian minimum-shift keying (GMSK), EDGE uses higher-order PSK/8 phase shift keying (8PSK) for the upper five of its nine modulation and coding schemes. EDGE produces a 3-bit word for every change in carrier phase. This effectively triples the gross data rate offered by GSM. EDGE, like GPRS, uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. It introduces a new technology not found in GPRS, Incremental Redundancy, which, instead of retransmitting disturbed packets, sends more redundancy information to be combined in the receiver. This increases the probability of correct decoding.

EDGE can carry data speeds up to 236.8 kbit/s for 4 timeslots (theoretical maximum is 473.6 kbit/s for 8 timeslots) in packet mode and will therefore meet the International Telecommunications Union's requirement for a 3G network, and has been accepted by the ITU as part of the IMT-2000 family of 3G standards. It also enhances the circuit data mode called HSCSD, increasing the data rate of this service.

Classification

Whether EDGE is 2G or 3G depends on implementation. While Class 3 and below EDGE devices are clearly not 3G, class 4 and above devices perform at a higher bandwidth than other technologies conventionally considered as 2G as 1xRTT). Because of the variability, EDGE is generally classified as 2.75G network technology.

EDGE Evolution

EDGE Evolution improves on EDGE in a number of ways. Latencies are reduced by lowering the Transmission Time Interval by half (from 20 ms to 10 ms). Bit rates are increased up to 1 MBit/s peak speed and latencies down to 100 ms using dual carriers, higher symbol rate and higher-order modulation (32QAM and 16QAM instead of 8-PSK), and turbo codes to improve error correction. And finally signal quality is improved using dual antennas. An EDGE Evolution terminal or network can support some of these improvements, or roll them out in stages.

3.3.5. 3G (3rd Generation) Mobile Phone System

3G is the third generation of mobile phone standards and technology, superseding 2G, and preceding 4G. It is based on the International Telecommunication Union (ITU) family of standards under the International Mobile Telecommunications programme, IMT-2000.

3G technologies enable network operators to offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. Services include wide-area wireless voice telephony, video calls, and broadband wireless data, all in a mobile environment. Additional features also include HSPA data transmission

capabilities able to deliver speeds up to 14.4Mbit/s on the downlink and 5.8Mbit/s on the uplink.

Speed

The ITU has not provided a clear definition of the speeds users can expect from 3G equipment or providers. Thus users sold 3G service may not be able to point to a standard and say that the speeds it specifies are not being met. While stating in commentary that "it is expected that IMT-2000 will provide higher transmission rates: a minimum speed of 2Mbit/s for stationary or walking users, and 348 <sic> kbit/s in a moving vehicle", the ITU does not actually clearly specify minimum or average speeds or what modes of the interfaces qualify as 3G, so various speeds are sold as 3G intended to meet customers expectations of broadband speed. It is often suggested by industry sources that 3G can be expected to provide 384 kbit/s at or below pedestrian speeds, but only 128 kbit/s in a moving car. While EDGE is part of the 3G standard, some phones report EDGE and 3G network availability as separate things, notably the iPhone.

Advantages of a layered network architecture

Unlike GSM, UMTS is based on layered services. At the top is the services layer, which provides fast deployment of services and centralized location. In the middle is the control layer, which helps upgrading procedures and allows the capacity of the network to be dynamically allocated. At the bottom is the connectivity layer where any transmission technology can be used and the voice traffic will transfer over ATM/AAL2 or IP/RTP.

3G evolution

The standardization of 3G evolution is working in both 3GPP and 3GPP2. The corresponding specifications of 3GPP and 3GPP2 evolutions are named as LTE and UMB, respectively. 3G evolution uses partly beyond 3G technologies to enhance the performance and to make a smooth migration path.

There are several different paths from 2G to 3G. In Europe the main path starts from GSM when GPRS is added to a system. From this point it is possible to go to the UMTS system. In North America the system evolution will start from Time division multiple access (TDMA), change to Enhanced Data Rates for GSM Evolution (EDGE) and then to UMTS.

Issues

Although 3G was successfully introduced to users across the world, some issues are debated by 3G providers and users:

Expensive input fees for the 3G service licenses Numerous differences in the licensing terms

Large amount of debt currently sustained by many telecommunication companies, which makes it a challenge to build the necessary infrastructure for 3G

Lack of member state support for financially troubled operators

Expense of 3G phones

Lack of buy-in by 2G mobile users for the new 3G wireless services

Lack of coverage, because it is still a new service

High prices of 3G mobile services in some countries, including Internet access.

Current lack of user need for 3G voice and data services in a hand-held device

High power usage

CHAPTER 4

Introducing WiMAX: The Ultimate Broadband Solution

4.1 Defining WiMAX technology & its basics

4.1.1 What is WiMAX?

WiMAX(Worldwide Interoperability for Microwave Access) is a telecommunications technology aimed at providing wireless data over long distances in a variety of ways, from point-to-point links to full mobile cellular type access.WiMAX is a wireless digital communications system, also known as IEEE 802.16, that is intended for wireless "metropolitan area networks". WiMAX can provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 – 15)

for mobile station. WiMAX is a second-generation protocol that allows for more efficient bandwidth use, interference avoidance, and is intended to allow higher data rates over longer distances.4.1.2 How WiMAX is operated?

In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to those remote locations.

A WiMAX system consists of two parts:

A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles (~8,000 square km).

A WiMAX receiver - The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today.

A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection. It can also connect to another WiMAX tower using a line-of-sight, microwave

link. This connection to a second tower, along with the ability of a single tower to cover up to 3,000 square miles, is what allows WiMAX to provide coverage to remote rural areas.

What this points out is that WiMAX actually can provide two forms of wireless service:

There is the non-line-of-sight, WiFi sort of service, where a small antenna on your computer connects to the tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength transmissions are not as easily disrupted by physical obstructions -- they are better able to diffract, or bend, around obstacles.

There is line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so

It’s able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more bandwidth.

Fig 5.1: How does WiMAX work?

WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65 square km of coverage, which is similar in range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX to achieve its maximum range.

4.2 Uses of WiMAX technology

The bandwidth and reach of WiMAX make it suitable for the following potential applications:

Connecting Wi-Fi hotspots with each other and to other parts of the Internet.

Providing a wireless alternative to cable and DSL for last mile broadband access. Providing high-speed data and telecommunications services.

Providing a diverse source of Internet connectivity as part of a business continuity plan. That is, if a business has a fixed and a wireless Internet connection, especially from unrelated providers, they are unlikely to be affected by the same service outage.

Providing nomadic connectivity.

4.3 Subscriber units

WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self-install indoor units are convenient, but radio losses mean that the subscriber must be significantly closer to the WiMAX base station than with professionally-installed external units. As such, indoor-installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or DSL modem. Outdoor units are roughly the size of a laptop PC, and their installation is comparable to a residential satellite dish.

With the advent of mobile WiMAX, there is an increasing focus on portable units. This includes handsets (similar to cellular smartphones) and PC peripherals (PC Cards or USB dongles). In addition, there is much emphasis from operators on consumer electronics devices (game terminals, MP3 players and the like); it is notable this is more similar to Wi-Fi than 3G cellular technologies.

4.4 Mobile Handset Applications

Different cello phone companies are now working to provide their best technologies cello phone to the users’ hands under WiMAX technology. For this purposes cello phone companies are eagerly wanted to provide better qualities mobile handset as early as possible to the users.

Motorola Company gets ready to launch mobile WiMAX:

Motorola plans to introduce two hand-held WiMAX devices for the US next year, will sell to Indian operators if interested. Wimax is the standard that is capable of data speeds of 10 megabits per second up to 2 km away from a radio transmitter. Motorola is only three big consumer electronics companies building Wimax hand-held devices ground up from the chip level. During its year-long trials and testing, Motorola has already developed one device, based on its ultra-slim Razr platform, which supports both CDMA and Wimax, but the full-impact of the high-speed capabilities of the network is better appreciated on large-screen MIDs.

Nokia to start selling Wimax phones in early 2008:

Nokia expects to start selling mobile devices using WiMAX Internet technology in early 2008. WiMAX will make wireless broadband much cheaper to deliver -- up to 10 times cheaper than current third-generation cellular telephony networks. But, while it provides fast

Internet access, it is not very well suited for wireless voice calls. Nokia all support the open-standard WiMAX as an alternative wireless broadband Internet connection alongside third generation mobile telephony networks, on which Internet access can be slowed if networks fill up with voice callers. Nokia all support the open-standard WiMAX as an alternative wireless broadband Internet connection alongside third generation mobile telephony networks, on which Internet access can be slowed if networks fill up with voice callers.

Spring Nextel announced to invest for Wimax technology:

Sprint Nextel announced that it would invest about US$ 5 billion in a WiMAX technology build out over the next few years. As this project in partnership with Clear wire has been shelved, but the project could be revived with or without Clear wire. Now it’s announced that Sprint's WiMAX network will go live in a soft launch in Chicago, Baltimore, and Washington DC. Full commercial launch is still expected to be approximately spring of 2008. It’s reported that Sprint's soft launch in the three test markets went live as of January 11, 2008.Sprint hopes to use WiMAX as a springboard past its competitors and past concerns about its shrinking user base and concerns about the financial wisdom of the large WiMAX deployment.

4.5 Technical Information

4.5.1 MAC layer/Data link Layer

In Wi-Fi the media access controller (MAC) uses contention access — all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis. This can cause subscriber stations distant from the AP to be repeatedly interrupted by closer stations, greatly reducing their throughput. This makes services such as Voice over IP (VoIP) or IPTV, which depend on an essentially-constant Quality of Service (QoS) depending on data rate and interpretability, difficult to maintain for more than a few simultaneous users.

In contrast, the 802.16 MAC uses a scheduling algorithm for which the subscriber station need compete once (for initial entry into the network). After that it is allocated an access slot by the base station. The time slot can enlarge and contract, but remains assigned to the subscriber station, which means that other subscribers cannot use it. In addition to being stable under overload and over-subscription (unlike 802.11), the 802.16 scheduling algorithm can also be more bandwidth efficient. The scheduling algorithm also allows the base station to control QoS parameters by balancing the time-slot assignments among the application needs of the subscriber stations.

4.5.2 Physical Layer

The original version of the standard on which WiMAX is based (IEEE 802.16) specified a physical layer operating in the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004,

added specifications for the 2 to 11 GHz range. 802.16-2004 was updated by 802.16e-2005 in 2005 and uses scalable orthogonal frequency-division multiple access (SOFDMA) as opposed to the OFDM version with 256 sub-carriers (of which 200 are used) in 802.16d. More advanced versions, including 802.16e, also bring Multiple Antenna Support through Multiple-input multiple-output communications (MIMO) See WiMAX MIMO. This brings potential benefits in terms of coverage, self installation, power consumption, frequency re-use and bandwidth efficiency. 802.16e also adds a capability for full mobility support. The WiMAX certification allows vendors with 802.16d products to sell their equipment as WiMAX certified, thus ensuring a level of interoperability with other certified products, as long as they fit the same profile.

4.5.3 System Architecture

The WiMAX Forum has defined an architecture that defines how a WiMAX network connects with other networks, and a variety of other aspects of operating such a network, including address allocation, authentication, etc. An overview of the architecture is given in the illustration. This defines the following components:

SS/MS: the Subscriber Station/Mobile Station ASN: the Access Service Network BS: Base station, part of the ASN ASN-GW: the ASN Gateway, part of the ASN CSN: the Connectivity Service Network HA: Home Agent, part of the CSN AAA: AAA Server, part of the CSN NAP: a Network Access Provider NSP: a Network Service Provider

Fig 5.2: Wimax system architecture

4.5.4 Silicon implementations

A critical requirement for the success of a new technology is the availability of low-cost chipsets and silicon implementations.

Intel is a leader in promoting WiMAX, and has developed its own chipset. However, it is notable that most of the major semiconductor companies have to date been more cautious of involvement and most of the solutions come from specialist smaller or start-up suppliers. For the client-side these include ApaceWave, GCT Semiconductor, Altair Semiconductor, Beceem, Comsys, Runcom, Motorola with TI, NextWave, Sequans, Redpine signals, Wavesat, Coresonic & SySDSoft. Both Sequans and Wavesat manufacture solutions for both clients and network while TI, DesignArt, and picoChip are focused on WiMAX chip sets for base stations. The large number of suppliers during introduction phase of WiMAX demonstrates the low entry barriers for IPR.

4.6 WiMAX Association

WiMAX Forum

The WiMAX Forum is the organization dedicated to certifying the interoperability of WiMAX products.Those that pass conformance and interoperability testing achieve the "WiMAX Forum Certified" designation and can display this mark on their products and marketing materials. Some vendors claim that their equipment is "WiMAX-ready", "WiMAX-compliant", or "pre-WiMAX", if they are not officially WiMAX Forum Certified.

WiMAX Spectrum Owners Alliance (WiSOA)

WiSOA is the first global organization composed exclusively of owners of WiMAX spectrum with plans to deploy WiMAX technology in those bands. WiSOA is focussed on the regulation, commercialisation, and deployment of WiMAX spectrum in the 2.3–2.5 GHz and the 3.4–3.5 GHz ranges. WiSOA are dedicated to educating and informing its members, industry representatives and government regulators of the importance of WiMAX spectrum, its use, and the potential for WiMAX to revolutionise broadband.

4.7 WiMAX Limitation

1. A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 50 kilometers. In reality, WiMAX can do one or the other — operating over maximum range (50 km) increases bit error rate and thus must use a lower bitrate. Lowering the range allows a device to operate at higher bitrates.

2. Fixed WiMAX networks have a higher-gain directional antenna installed near the client (customer) which results in greatly increased range and throughput.

3. Mobile WiMAX devices typically have an omni-directional antenna which is of lower-gain compared to directional antennas but are more portable.

4. In practice, this means that in a line-of-sight environment with a portable Mobile WiMAX CPE, speeds of 10 Mbit/s at 10 km could be delivered.

5. In urban environments they may not have line-of-sight and therefore users may only receive 10 Mbit/s over 2 km. In current deployments, throughputs are often closer to 2 Mbit/s symmetric at 10 km with fixed WiMAX and a high gain antenna.

6. It is also important to consider that a throughput of 2 Mbit/s can mean 2 Mbit/s, symmetric simultaneously, 1 Mbit/s symmetric or some asymmetric mix

7. Higher-gain directional antennas can be used with a Mobile WiMAX network with range and throughput benefits but the obvious loss of practical mobility.

8. Like most wireless systems, available bandwidth is shared between users in a given radio sector, so performance could deteriorate in the case of many active users in a single sector.

9. In practice, many users will have a range of 2-, 4-, 6-, 8-, 10- or 12 Mbit/s services and additional radio cards will be added to the base station to increase the capacity as required.

10. various granular and distributed network architectures are being incorporated into WiMAX through independent development and within the 802.16j mobile multi-hop relay (MMR) task group.

11. This includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

4.8 Competing other technologies

Speed

Mobility

Fig 5.3: Area possession of WiMAX in network graph

Within the marketplace, WiMAX's main competition comes from existing widely deployed wireless systems such as UMTS and CDMA2000, as well as a number of Internet oriented systems such as HIPERMAN and WiBro.

4.9.1 3G and 4G Celluler Phone System:

Both major 3G systems, CDMA2000 and UMTS, compete with WiMAX. Both aim to offer DSL-class Internet access in addition to phone service. UMTS has also been enhanced to compete directly with WiMAX in the form of UMTS-TDD, which can use WiMAX oriented spectrum and provides a more consistent, if lower bandwidth at peak, user experience than WiMAX

3G cellular phone systems usually benefit from already having entrenched infrastructure, being upgraded from earlier systems. Users can usually fall back to older systems when they move out of range of upgraded equipment, often relatively seamlessly.

The major cellular standards are being evolved to so-called 4G, high bandwidth, low latency, all-IP networks with voice services built on top. With GSM/UMTS, the move to 4G is the 3GPP Long Term Evolution effort. For AMPS derived standards such as CDMA2000, a replacement called Ultra Mobile Broadband is under development. In both cases, existing air interfaces are being discarded, in favour of OFDMA for the downlink and a variety of OFDM based solutions for the uplink, much akin to WiMAX.

4.9.2 Mobile Broadband Wireless Access

Mobile Broadband Wireless Access (MBWA) is a technology being developed by IEEE 802.20 and is aimed at wireless mobile broadband for operations from 120 to 350 km/h. The 802.20 standard committee was first to define many of the methods which were later funneled into Mobile WiMAX, including high speed dynamic modulation and similar scalable OFDMA capabilities. It apparently retains fast hand-off, Forward Error Correction (FEC) and cell edge enhancements

4.9.3 Internet Oriented System

Early WirelessMAN standards, the European standard HIPERMAN and Korean standard WiBro have been harmonized as part of WiMAX and are no longer seen as competition but as complementary. All networks now being deployed in South Korea, the home of the Wibro standard, are now WiMAX. As a short-range mobile Internet solution, such as in cafes and at transportation hubs like airports, the popular Wi-Fi 802.11b/g system is widely deployed, and provides enough coverage for some users to feel subscription to a WiMAX service is unnecessary.

4.9.4 Comparison

The following table should be treated with caution as it only shows peak rates which are potentially very misleading. In addition the comparisons listed are not normalized by physical channel size this obfuscates spectral efficiency and net through-put capabilities of the different wireless technologies listed below.

Standard Family Primary Use

Radio Tech

Downlink

(Mbit/s)

Uplink

(Mbit/s) Notes

802.16e WiMAX Mobile Internet

MIMO-SOFDMA

70

70

Quoted speeds only achievable at very short ranges,more practically 10 Mbit/s at 10 km

WiBro WiBro Mobile Internet

OFDMA 50 50 Mobile range(900 m)

EDGE Evolution

GSM Mobile Internet

TDMA 1.9 0.9 3GPP Release 7

UMTS-TDD

UMTS/3GSM Mobile Internet

CDMA

16 16

Reported Speeds according to IPWireless using 16QAM modulation similar to HSPA

LTE UMTS

UMTS/4GSM Generral 4G

OFDMA/MIMO/SOFDMA >100 >50 Still in development

Fig 5.4: Comparison of Mobile Internet Access methods

CHAPTER 5

Microwave Communication

5.1.1 Basic Concepts of Microwave

Microwave is electromagnetic wave with frequency from 300MHz to 300GHz and it is a finite frequency band of the entire electromagnetic wave spectrum. According to the microwave transmission feature, microwave can be viewed as plane wave. Along the transmission direction, the plane wave has no longitudinal components of electric field and magnetic field. Both electric field and magnetic field are vertical to the transmission direction.

For the application of each frequency band in the microwave spectrum, see figure

Figure 5.2.1.a: application of each frequency band in the microwave spectrum

In figure 5.2.1.a, VHF and LF are ground wave which is very capable of diffraction and can diffract hundreds of kilometers; they are mainly used in radio and navigation. MF is used in broadcast and is less capable of diffraction than VHF and LF. HF is not ground wave, and it is reflected to the ionosphere. VHF and UHF are used in TV. Though UHF is used in TV, (that is, the microwave is involved) it is not called microwave. After the microwave, it is optical wave which is also a type of electromagnetic wave.

Digital microwave communication refers to a type of communication mode which uses microwave (frequency) to carry digital information through the electric wave space, transmit independent information and conduct regeneration. Microwave is weak in diffraction and it is only line-of-sight communication, therefore, it has a limited transmission distance. In long-distance transmission, relay is needed to connect sites. Thus, it is called microwave relay communication. Microwave communication uses microwave as the carrier of signals, which is similar to optical fiber communication that uses light as the carrier of signals. Simply speaking, transmitting module and optoelectronic inspection module used for receiving in the optical fiber transmission system are similar to the transmitting and receiving antenna. Compared with the optical fiber communication with wire channels, microwave channel is wireless and microwave communication is much more complicated.

Other methods of microwave communications, for example:

(1) Point to multi-point microwave communication system (PMP): it has two categories of user line type and relay line type, the radio user loop in the microwave frequency band can belong to the PMP. PMP is mainly used in remote areas such as countryside, islands, and dedicated communication networks.

(2) Microwave spreading data transmission system, such as point-to-point 2.4GHz spreading microwave, point to multi-point 2.4GHz spreading microwave data network.

(3) Temporary microwave communication, which adopts upper frequency band point-to-point microwave communication system and can easily settle burst matters in the communications.

(4) Local multi-point distributed service, which works at the frequency band from 25 to 28 GHz and can be used in the future wideband services access, it is called wireless fiber.

5.1.2 Microwave frequency band choice and RF Channel Arrangements

Frequency bands frequently used in microwave transmission include 7G/8G/11G/13G/15G/18G/23G/25G/32G/38G (defined by Rec. ITU-R). Each frequency band is used as follows:

Figure5.2.2.a: the use of common frequency band

(1) For long-distance PDH microwave circuit (more than 15 km), use 8 GHz frequency band. If the distance is not more than 25 km, use 11 GHz. Choose specific frequency band based on the local weather condition and microwave transmission cross section.

(2) For short-distance PDN microwave circuit (normally used in the access layer, within 10 km), consider using 11 GHz, 13 GHz, 14 GHz, 15 GHz and 18 GHz.

(3) For long-distance SDH microwave circuit (normally exceeding 15 km), use 5 GHz, 5 GHz, 7 GHz and 8 GHz. If the distance is not more than 20 km, consider using 11 GHz. Choose specific frequency band based on the local weather condition and microwave transmission cross section.

Frequency bands 7G, 8 G, 11G, 13G, 15G, 18G, 23G are not contiguous, for the microwave frequency resources are internationally defined and radar needs to use some frequency bands. The microwave used in transmission is above 4G, 2G is used by mobile communication. Microwave communications previously use 1.5G, and later ITU-T decides to allocate 2G to mobile communication and 5G to meteorological radar.

In each frequency band, various frequency ranges, transmitting and receiving(T/R) spacing and channel spacing are defined. The channel spacing is equal to channel bandwidth. In using a certain frequency band, there are specifications for the center frequency, T/R spacing and channel spacing. And the specification can be looked up in relevant frequency specifications.

Figure5.2.b simple concepts of microwave frequency band arrangements

After deciding the microwave frequency band, configure the RF channels. To configure RF channels is to subdivide the specific frequency band, to make the bands adapt to frequency spectrum that the transmitter needs.

In configuring RF channel, following factors should be considered:

(1) Utmost economy and efficiency of the RF frequency

(2) Enough spacing between transmitting frequency and receiving frequency in a microwave station to avoid serious interference generated by transmitter to receiver.

(3) In multi-channel working system, adjacent channels must have enough

frequency spacing to avoid interference generated by each other.

(4) Enough guard bands should be reserved at the edge of the distributed frequency band to avoid generating interference with the system working on the adjacent frequency band

(5) Most RF channel arrangements are based on the homogeneous patterns

5.1.3 Digital microwave communication system model

Figure 5.2.3a Digital microwave communication system model

Signal source of the transmit end is the equipment that provides original signals, it outputs digital signals. Channel coding is to improve the reliability of transmitting digital signals. For noise and interference may inevitably exist in the channel, the digital signals transmitted may generate error bit. To make the code element automatically checked and corrected at the receive end, channel coder is used to add some additional code elements to the input digital hierarchy based on certain rules, and form new digital hierarchy. At the receive end, signals are checked based on the rules of the new digital code element hierarchy.

Modulation is to modulate the digital signals to the carrier of higher frequencies to make it adapt to radio channel transmission.

5.1.4 Digital Microwave equipment classification

Based on different classification methods, the digital microwave equipment can be classified based on the following modes:

Table 5.7. Microwave equipment classification

Mode Digital microwave Analog

Multiplexing mode PDH SDH

capacity 2-15E1 STM-0

34M STM-1

2*STM-1

structure All-indoor microwave eliminated

Split-microwave

Al-outdoor microwave

Currently, common classification method is, based on structure, to classify the microwave equipment into split microwave, all-indoor microwave and all-outdoor microwave.

All-indoor microwave is commonly called big microwave. Its RF unit (RFU), signal processing unit (SPU) and multiplexer reside indoor, only the antenna is outdoor. It has a high transmission capacity and is suitable to backbone line transmission, but its cost is high.

Figure 5.2.4.a All-indoor microwave

All the units of all-outdoor microwave reside outdoor. All-outdoor microwave is easy to install and saves equipment room space. For it is outdoor, it is easily damaged.

Figure 5.2.4.b All-outdoor microwave

Figure5.2.4.c Split microwave

Split microwave equipment consists of ODU and IDU. The antenna and ODU are connected by waveguide pipe, and the IDU and ODU are connected by IF cable. IF cable is used to transmit the IF service signals between IDU and ODU and the IDU/ODU communication control signals and provides power to the ODU. Split microwave equipment has a low capacity and is easy to install and maintain and available in quickly building networks. It is the most widely used microwave equipment for the present.

5.1.5.Microwave antenna and feeder

5.1.5.1 Microwave antenna

The antenna is used to directionally radiate the microwave power emitted by the transmitter ODU and transmit the microwave power received to the receiver ODU. Commonly used microwave antenna includes parabolic antenna and cassegrain antenna. The diameter of the microwave antenna produced by China is 0.3, 0.5, 1.2, 1.5, 2.0, 2.5, 3.2m, and that is

imported from abroad is 0.3, 0.5, 1.2, 1.8, 2.4, 3.0m. There are many types of antennas. Antenna of different diameters has different specifications for different frequencies. Ericsson Mini-link has 45 types of antennas.

Figure 5.2.5.1a Parabolic antenna Figure 5.2.5.1b Cassegrain antenna

5.1.6 Classification of microwave antenna

Based on installation method, microwave antenna can be classified as hanging antenna and seating antenna. Based on electric feature, it can be classified as standard antenna and high-performance antenna. The front and rear of the high-performance antenna is larger than that of the standard antenna with more than 10 dB. 2.2.3 Feeder System Feeder system consists of the feeder connecting branching system to antennas and the waveguide components, and it has several installation methods. Currently, elliptical waveguide is commonly used.

5.2.5(a) Elliptical waveguide 5.2.5b(b) Flexible twist waveguide

Figure 5.2.5 Typical feeders

Elliptical waveguide has lower loss in certain length and is suitable for long feeders. Normally, it is used in frequency band from 2 to 11GHz and it is the most typical microwave feeder. Now, elliptical waveguide is widely used in frequency band ranging from 4 GHz to 15 GHz as the feeder for it makes the layout and installation of the feeders easier.

Flexible twist waveguide is used to connect the ODU and the antenna. It is easy to install and can ensure the connection accuracy, and it has function of twisting.

The disadvantage of the flexible twist waveguide is huge loss. Coaxial cable has huge loss in certain length. It is better to use the coaxial cable in occasion that the antenna is near the transceiver. Normally, it is used in the frequency band lower than 2 GHz. currently, it is seldom used.

There are two ways of connecting elliptical waveguide and branching system:

a) Waveguide: using hard waveguide, E bend and H bend or flexible waveguide.

b) Coaxial: using coaxial cable In addition, the access layer typically uses portable PDH and SDH microwave systems and adopts indoor/outdoor structure. The indoor unit and the outdoor unit (transceiver) are connected by IF cable. Outdoor unit and antenna are connected by flange interface (the feeder loss is reduced) or flexible waveguide of 0.5–0.5 m (the caliber is more than 1.2 m).

Following figures show how the PDH/SDH microwave antenna is connected to the ODU (transceiver):

Figure 5.2.5.c Antenna connected to ODU

5.1.7 Branching System

Normally, in microwave communication, many channels share the same set of an antenna and feeder system, which needs branching system to separate them. The branching system consists of circulator, branching filter, terminator and connection waveguide. The filter is installed in the rack. Branching filter consists of bandpass filter, it only allow designed certain frequency band to pass and the frequencies that outside the band cannot pass the filter. The terminator is used to absorb the emitting waves, and the loop makes the signals progress in a certain direction.

5.1.7.1 Installation and adjustment of split microwave system

Split microwave system can be divided into two parts: outdoor installation and indoor installation. Indoor installation is similar to that of box-shape equipment. This section describes outdoor installation which mainly consists of antenna and ODU installation. There are two methods of outdoor installation: integrated mounting and separate mounting. Integrated mounting does not need feeder, and it directly connects ODU to the antenna. Separate mounting uses feeder to connect ODU to the antenna.

See figure 5.8.1.a

Figure 5.2.7.1.a Outdoor installation

When the antenna is mounted, the key process is to adjust the directional angle of the antenna.

Figure 5.2.7.1.b Antenna side view and top view

When antenna at two ends are leveled, they may become sligtly up 1–2 dB is wasted to prevent refraction interference.

Fig 5.2.7.1.b Microwave Station Types

Based on station types, the microwave station can be classified as:

Terminal station: stations located at two ends of the microwave link, the communication is unidirectional and voice channels need to be added/dropped.

Relay station: stations in the middle of any two stations of a microwave link, the communication is to directions and the voice channels can be added/dropped (baseband transfer) or cannot be added/dropped (IF or RF transfer).

Pivotal station: the station located in the middle of the microwave link, the communication is to more than three directions, and voice channels need to be added/dropped. Based on communication frequency, stations can be classified as:

Upper station: station where the receiving frequency is higher than transmitting frequency.

Lower station: station where the receiving frequency is lower than transmitting frequency.

Obviously, due to microwave frequency configuration, upper and lower stations are arranged alternatively. See figure 5.2.7.1.c

Figure5.2.7.1.c microwave station types

5.1.8 Relay Station

Microwave frequency band has higher frequencies. The microwave beam is transmitted along a straight line and it is incapable of diffraction when it encounters obstacles. Therefore, there should be no obstacles in the line-of-sight range between two communication points. Otherwise, a microwave relay station should be added at the obstacle point or other suitable place to communicate the two communication points.

Microwave relay station can be classified into two types: passive relay station and active relay station.

5.1.9 Passive Relay Station

Passive relay station is like a beam diverter, it makes the microwave beam

surpass the obstacle and form path.

Figure5.2.5a Passive relay station

Figure 5.2.5.b Dual parabolic antennas passive relay station

5.1.10 Plane antenna and passive relay station

A metal plane that is smooth to some extent, has proper available area, and a suitable angle and distance to two communication points, is also a microwave passive relay station. The station uses the reflection function of the metal plane to change the propagation direction of the microwave beam and round the obstacle to achieve communication.

5.1.10.1 Active relay station

There are two types of microwave active relay station: RF direct station and regenerative relay station.

5.1.10.2 RF Direct Station

RF direct station is an active, bidirectional, non-frequency-shift RF relay system. For it amplifies signals directly on the RF, it is called RF direct station. It can be used as a relay station that needs not add/drop voice channels in the microwave system. It can be used to solve the block problem caused by mountains and large building, and it can also be inserted in the newly built and already established microwave to increase fading margin.

5.1.10.3 Regenerative relay station

Regenerative relay station is a high-frequency repeater with high performance. Regenerative relay station is similar to back-to-back terminal station, including an entire set of RF unit with regenerative microwave signals. It can extend the signal transmission path and change transmission direction to round obstacles, but it is incapable of adding/dropping voice channels. It can be used to break the distance limit of microwave transmission system or

divert the transmission direction to round line-of-sight obstacles, and the signal quality is not degraded.It receives signals, fully regenerates and amplifies the signals and then transmits the signals.

5.1.11 Diversity reception

Diversity reception: a resultant signal is obtained by combining or selecting signals, from two or more independent sources, that have been modulated with identical information-bearing signals, but which may vary in their fading characteristics at any given instant. Diversity reception is used to minimize the effects of fading.

5.1.11.1 Classification of Diversity Reception

Diversity reception is classified into the following types:

(1) Space diversity (SD): a method of transmission or reception, or both, in which the effects of fading are minimized by the simultaneous use of two or more physically separated antennas, ideally separated by one or more wavelengths. As the antennas are separated physically, the correlation is small. The count of antennas decides the count of diversity.

Figure 5.2.11.1.a Space diversity

(2) Frequency diversity (FD): Transmission and reception in which the same information signal is transmitted and received simultaneously on two or more independently fading carrier frequencies to reduce the effects of fading. The frequency diversity uses the irrelevance of fading in different frequencies. that is, a feature with low probability of co-interruption on two frequencies.

In frequency diversity systems, the correlation of two diversity received signals (frequency correlation) should be small. Only in this event, deep fading on two frequencies can be avoided in a given path and good diversity effect can be implemented. The bigger the spacing of two frequencies is, the smaller the correlation of deep fading at the same time. When the diversity in the same frequency uses 2% of the working frequency as a frequency spacing, the diversity improvement effect can be obtained.

Figure 5.2.11.1.b Frequency diversity

(3) Polarization diversity: Diversity transmission and reception wherein the same information signal is transmitted and received simultaneously on orthogonally polarized waves with fade-independent propagation characteristics. Compared to other diversities, the effect of polarization diversity is smaller.

(4) Angle diversity: Diversity reception in which beyond-the-horizon troposphere scatter signals are received at slightly different angles, equivalent to paths through different scatter volumes in the troposphere. The second beam can be provided by an independent antenna or dual-feed antenna .

Figure 5.2.11.1.c Angle diversity

Microwave yet has some disadvantages : given bellow,

1. Line-of-sight transmission conditions should be ensured2. Transmission distance between two stations should be not too long3. Frequencies need to be applied for4. Communication quality is greatly affected by the environment and5. Communication capacity is limited

CHAPTER 6

Optical Fiber Communication

6.1.1 What is fiber optics?

Picture sending signals zipping along from one location to another in the form of light

Guided through thin fibers of glass or plastic. These signals can be analog or digital - Voice,

data or video information and fiber can transport more information longer distances in less

time than any copper wire.

6.1.2 Optical Fiber:

Thin strands of highly transparent glass or sometimes plastic that guide light. Plastic optical

fiber (POF): is a large core (about 1mm) multimode fiber that can be used for short, low

speed networks.

Core: The center of the fiber where the light is transmitted.

Cladding: The outside optical layer of the fiber that traps the light in the core and guides it

along even through curves.

Buffer coating or primary coating: A hard plastic coating on the outside of the fiber that

protects the glass from moisture or physical damage.

Mode: A single electromagnetic field pattern (think of a ray of light) that travels in fiber.

Multimode fiber: has a bigger core (almost always 62.5 microns - a micron is one one

millionth of a meter - but sometimes 50 microns) and is used with LED sources at

wavelengths of 850 and 1300 nm for short distance, lower speed networks like LANs.

6.1.3 Metric System

Metric System Unit

Meter 36.37 inches.

Kilometer 1000 meters / 3,281 feet / 0.62 miles.

Micron 1/1,000,000 th of a meter. 25 microns equal 0.001 inch. This is the

common

Fiber Optics, as a universal technology, utilizes the metric system as the standard form of

measurement. Several of the more common terms:

6.1.4 Transmitters Fiber optic transmitters are devices that include an LED or laser source, and signal

conditioning electronics, to inject a signal into fiber. The modulated light may be turned on or

off, or may be linearly varied in intensity between two predetermined levels. Light Emitting

Diodes (LEDs) have relatively large emitting areas and as a result are not as good light

sources as laser diodes. However, they are widely used for short to moderate transmission

distances because they are much more economical. Laser diodes can couple many times

more power to optical fiber than LEDs. They are primarily used for applications that require

the transmission of signals over long distances

Important performance specifications to consider when searching for fiber optic

transmitters include data rate, transmitter rise time, wavelength, spectral width, and

maximum optical output power. Data rate is the number of data bits transmitted in bits per

second. Data rate is a way of expressing the speed of the transceiver. In the approximation

of a step function, the transmitter rise time is the time required for a signal to change from a

specified 10% to 60% of full power. Rise time is a way of expressing the speed of the

transmitter. Wavelength refers to the output wavelength of the transceiver. The spectral

width refers to the spectral width of the output signal.

6.1.5 Receivers

Fiber optic receivers are instruments that convert light into electrical signals. They contain a

photodiode semiconductor, signal conditioning circuitry, and an amplifier. Fiber optic

receivers use three types of photodiodes: positive-negative (PN) junctions, positive-intrinsic-

negative (PIN) photodiodes, and avalanche photodiodes (APD). PIN photodiodes have a

large, neutrally-doped region between the p-doped and n-doped regions. APDs are PIN

photodiodes that operate with high reverse-bias voltages. In short wavelength fiber optic

receivers (400 nm to 1100 nm), the photodiode is made of silicon (Si). In long wavelength

systems (600 nm to 1700 nm), the photodiode is made of indium gallium arsenide (InGaAs).

With low-impedance amplifiers, bandwidth and receiver noise decrease with resistance. With

trans-impedance amplifiers, the bandwidth of the receiver is affected by the gain of the

amplifier. Typically, fiber optic receivers include a removable adaptor for connections to

other devices. Data outputs include transistor-transistor logic (TTL), emitter-coupled logic

(ECL), video, radio frequency (RF), and complementary metal oxide semiconductor (CMOS)

signals. Also, it uses many types of connectors.

6.1.5 Fiber Fiber is the medium to guide the light form the transmitter to the receiver. It is classified into

two types depending on the way the light is transmitted: multimode fiber and single-mode

fiber.

6.1.6 Multimode Fiber

Multimode fiber designed to transmit more than one light at a time. Fiber diameter ranges

from 50-to-100 micron. Multimode fibers can be divided in to two categories Multimode

Step-index Fiber and Multimode Graded-index Fiber.

In Multimode Step-index Fiber the lights are sent at angles lower than the critical angle or

straight (or simply the angle is zero). Any light angle exceed the critical angle will cause it to

penetrate through cladding (refracted) and being lost as shown in Figure 1. Obviously light

with lower angle which has less number of reflection, reach the end faster than those with

larger angle and this will result in unstable wave light. To avoid this problem there should be

spacing between the light pulses, but this will limit the bandwidth and because of that it is

used for very short distance.

Figure 6.3.6.a, Multimode Step-index Fiber

The Multimode Graded-index Fiber designed to reduce the problem in Multimode

Step-Index fiber by making all the beams reaching the receiver at the same time. This can be

done by slowing down the ones with shorter distance and increasing the speed for ones with

longer distance, see Figure 2. This is done in fiber implementation by increasing its refractive

index at the center and gradually decreases it toward the edges. In the Figure 2 we can see the

light near the edges is curved until it is reflected, this is due to the refraction caused by the

change in density.

Figure 6.3.6.b, Multimode Graded-Index Fiber

6.1.7 Single-Mode Fiber

In single-mode, only one light is transmitted in the fiber which diameter ranges from

8.3 to 10 microns, see Figure 3. Since there is only one light the problem associated with the

multimode fiber does not exist and by this we can have a higher transmission rate and also it

can be used for longer distance. To utilize the fiber a Wave-Division-Multiplexing (WDM) is

used as it will be described later.

This type of fiber has been improved over years and that result in three types of single-mode

fiber. The first is Non Dispersion-Shifted Fiber (NDSF) which was used to transmit light with

wave length 1310 nm, but some systems use it with a wave length of 1550 nm and this wave

length causes dispersion (losing pulse mode) with this type of fibers. The second type is

Dispersion-Shifted Fiber (DSF), in this type the dispersion is shifted so that the dispersion at

the wave length 1550 nm is zero and in this way we could solve the problem of the first. But

system with DWDM (Dense Wavelength Division Multiplexing) found to be nonlinear with

this type of fiber. The term Dense Wavelength Division Multiplexing (DWDM) came from

the tremendously increase in use of WDM. The third type is Non Zero-Dispersion-Shifted

Fibers (NZ-DSF) which is designed to solve the problems with the previous two.

Figure 6.3.7.a , Single-Mode Fiber

6.1.8 Fiber CablesAs with copper wires optical fiber need to be protected from the surrounding environment.

Grouping fibers into one cable has other advantages as well which are Ease of Handling,

Protection, Crush Resistance and Degradation. Fiber cables fall into three basic categories:

loose tube cable, tightly buffered fiber and ribbon cables.

Fig 6.3.8.a Cables (L>R): Zipcord, Distribution, Loose Tube, Breakout

6.1.9 Loose tube cables

In loose tube design, a coated fiber is contained in a tube, with inner diameter much larger

than the fiber diameter. To make the fiber move freely inside the tube, it is installed in a loose

helix and also by this the fiber can be protected from the stresses applied to the cable in

installation or service, including effects of changing temperature. Loose tubes can be used

without any filling. However if they are to be used outdoors, they are normally filled with a

jelly like material. The gel acts as a buffer, keeping out moisture and letting the fibers move

in the tube, Figure 4.

Figure6.17.a, Loose Tube Cable

6.1.10 Tightly Buffered CableIn Tightly Buffered Cable the fiber is coated then encased in plastic layer. The coating is a

soft plastic that allows deformation and reduces forces applied to the fiber. The resulted fiber

is then surrounded by a harder plastic, to provide physical protection, Figure 5. Tight

buffering assures that the fibers are in precisely predictable positions, making it easier to

install connectors. A major advantage of tight buffered cable for indoor use is its

compatibility with fire and electrical codes. Although losses are somewhat higher than in

loose tube cables, indoor transmission distances are short enough that it's not a problem.

Figure 6.3.10 a Tightly Buffered CableRibbon Cable: This cable offers the highest packing density, since all the fibers are laid out

in rows, typically of 12 fibers, and laid on top of each other. This way 144 fibers only has a

cross section of about 1/4 inch or 6 mm! Some cable designs use a "slotted core" with up to 6

of these 144 fiber ribbon assemblies for 864 fibers in one cable! Since it's outside plant cable,

it's gel-filled for water blocking.

Figure 6.3.10 .b, Ribbon Cables

Simplex and zip cord : Simplex cables are one fiber, tight-buffered (coated with a 600

micron buffer over the primary buffer coating) with Kevlar (aramid fiber) strength members

and jacketed for indoor use. The jacket is usually 3mm (1/8 in.) diameter. Zip cord is simply

two of these joined with a thin web. It's used mostly for patch cord and backplane

applications, but zip cord can also be used for desktop connections.

Distribution cables: They contain several tight-buffered fibers bundled under the same

jacket with Kevlar strength members and sometimes fiberglass rod reinforcement to stiffen

the cable and prevent kinking. These cables are small in size, and used for short, dry conduit

runs, riser and plenum applications. The fibers are double buffered and can be directly

terminated, but because their fibers are not individually reinforced, these cables need to be

broken out with a "breakout box" or terminated inside a patch panel or junction box.

Breakout cables: They are made of several simplex cables bundled together. This is a

Strong, rugged design, but is larger and more expensive than the distribution cables. It is

suitable for conduit runs, riser and plenum applications. Because each fiber is individually

reinforced, this design allows for quick termination to connectors and does not require patch

panels or boxes. Breakout cable can be more economic where fiber count isn't too large and

distances too long, because is requires so much less labor to terminate.

Armored Cable: Cable installed by direct burial in areas where rodents are a problem

usually have metal armoring between two jackets to prevent rodent penetration. This means

the cable is conductive, so it must be grounded properly.

Aerial cable: Aerial cables are for outside installation on poles. They can be lashed to a

messenger or another cable (common in CATV) or have metal or aramid strength members to

make them self supporting.

Even More Types Are Available: Every manufacturer has it's own favorites, so it's a good

idea to get literature from as many cable makers as possible. And check out the little guys;

often they can save you a bundle by making special cable just for you, even in relative small

quantities.

In Tightly Buffered Cable the fiber is coated then encased in plastic layer. The coating

is a soft plastic that allows deformation and reduces forces applied to the fiber. Guide to Fiber

optic connectors

ST (an AT&T Trademark) has been the

most popular connector for networks, like

most buildings and campuses. It has a

bayonet mount and a long cylindrical

ferrule to hold the fiber. Most ferrules are

ceramic, but some are metal or plastic. It is

being used less as the SC and LC gain in

market share.

SC is a snap-in connector that is widely

used in singlemode systems for it's

excellent performance. It's a snap-in

connector that latches with a simple push-

pull motion. It is also available in a duplex

configuration. It is very popular in both

OSP and premises networks, although the

LC is becoming the connector of choice for

fast (Gb/s) networks.

LC is a new connector that uses a 1.25

mm ferrule, half the size of the ST.

Otherwise, it's a standard ceramic ferrule

connector, easily terminated with any

adhesive. Good performance, highly

favored for singlemode and fast (Gb/s)

networks.

FC/PC has been one of the most popular

singlemode connectors for many years. It

screws on firmly, but make sure you have

the key aligned in the slot properly before

tightening. It's being replaced by SCs and

LCs.

Bellow are some of the new small from

factor(SFF) connectors:

MT-RJ is a duplex connector with both

fibers in a single polymer ferrule. It uses

pins for alignment and has male and

female versions. Multimode only, field

terminated only by prepolished/splice

method.

Opti-Jack is a neat, rugged duplex

connector cleverly designed around two

ST-type ferrules in a package the size of a

RJ-45. It has male and female (plug and

jack) versions.

Volition is a slick, inexpensive duplex

connector that uses no ferrule at all. It

aligns fibers in a V-groove like a splice.

Plug and jack versions, but field terminate

jacks only.

LX-5 is like a LC but with a shutter over

the end of the fiber.

MU looks a miniature SC with a 1.25 mm

ferrule. It's more popular in Japan.

MT is a 12 fiber connector for ribbon

cable. It's main use is for preterminated

cable assemblies.

6.2 Some ApplicationDue to the advantages of fiber optic over the traditional connectivity networks, networks are

being changed to the new technology of fiber optic. Here is some applications use fiber optics

for the communication:

1. Long Haul telecommunication systems on land and at sea to carry many

simultaneous telephone calls (or other signals) over long distances. These include

ocean spanning submarine cables and national backbone networks for telephone

and computer data transmission.

2. Interoffice trunks that carry many telephone conversations simultaneously

between local and regional switching facilities.

3. Connections between the telephone N/W and antennas for mobile telephone

service.

4. Links among computers and high resolution video-terminals used for such

purposes as computer aided design.

5. Transmission of signals within ships and aircraft.

6. Local area Networks operating at high speeds or over large areas, and backbone

systems connecting slower local area Networks.

7. High speed interconnections between computer and peripherals devices, or

between computers, or even within segments of single large

Chapter 7

Access Service Network

Access Service Network (ASN), a concept in the mobile WiMAX network, provides full mobility, seamless handoffs, Quality of Service, security and subscriber/connection/resource management. The ASN Gateway provides a critical piece of the end-to-end WiMAX network architecture connecting the WiMAX radio access network to a common IP core and offering a centralized platform for those functions best served by localized management including security and mobility management.

7. Functionalities:

Access Service Network functionality can be discussed by showing some roles in the basis of WiMax technology.

Access service networks (ASN) provide a means to connect mobile subscribers using OFDMA air link to IP backbone with session continuity. ASN comprises base stations (BS) and access gateways named ASN-GW. The interface between the ASN and mobile subscriber is through BS with IEEE 802.16e-2005 (IEEE 80w.16-2004 for some previous fixed configurations) standard.

An Access Service Network is a set of network functions that includes:

1) Network discovery and selection of the preferred CSN/NSP.2) Network entry with IEEE 802.16e-2005 based layer 2 connectivity and AAA proxy.3) Relay function for IP Connectivity.4) Radio Resource Management.5) Multicast and Broadcast Control.6) Intra-ASN mobility.7) Foreign agent functionality for inter-ASN mobility8) Paging and Location Management.9) Accounting assistance.10) Data forwarding11) Service flow authorization

7.1 ASN Gateway roles in WiMAX network:

Roles of ASN GW :

1. A WiMAX network element acting as a logical entity in the WiMAX system.2. To represent an aggregation of control plane functional entities that paired with :

a corresponding function in the ASN, or a resident function in the CSN or a function in another ASN

3. To perform user plane routing or bridging functionASN Gateway Functionalities :

full mobility, seamless handoffs, user plane forwarding, bridging and tunnel switching

Radio Resource control QoS enforcement and classification functions security management.

ASN Gateway Decomposition

ASN Gateway Enforcement Point – bearer plane functions ASN Gateway Decision Point – non-bearer plane functions

Figure 7.1 : ASN Gateway Decomposition

7.2 ASN Reference Model containing multiple ASN-GW :

1) R1: Reference point between MS and BS: implements IEEE 802.16e-2005.2) R2: Reference point between MS and ASN-GW or CSN: logical interface used for

authentication, authorization, IP host configuration and mobility management

3) R3: Reference point between ASN and CSN: supports AAA, policy enforcement, and mobility-management capabilities. Implements tunnel between ASN and CSN.

4) R4: Reference point between ASN and ASN: used for MS mobility across ASNs.5) R5: Reference point between CSN and CSN: used for internetworking between home

and visited network

6) R6: Reference point between BS and ASN: Implements intra-ASN tunnels and used for control plane signaling.

7) R7: Reference point between data and control plane in ASN-GW: used coordination between data and control plane in ASN-GW.

8) R8: Reference point between BS and BS: used for fast and seamless handover.

Figure 7.2 - ASN Reference Model containing multiple ASN-GW

Figure 3 shows that an ASN may be composed of one or more BS and one or more ASN-GWs. The WiMAX NWG Release 1 defines three profiles that classify the distribution of functions between BS and ASN-GW: Profile A, Profile B, and Profile C.

7.3 WiMAX accesses two types of infrastructure:

7.3.1 WiMAX access to Cellular infrastructure

Figure 7.3: Cellular infrastructure of wimax access

WiMAX access to DSL infrastructure

Figure 7.4: DSL infrastructure of wimax access

7.4 ASN gateway Data Path Function:

Managing the data path setup and includes procedures for data packet transmission control between two functional elements.

Setting up data path to carry user plane packets (either IP or Ethernet packets) between BS and ASN over R6 interface or between ASNs over R4 interface. Tunnel protocol: GRE.

Setting up data path to carry user plane packets between ASN and HA over R3 interface. Tunnel protocol: IPinIP.

Figure 7.5: Protocol Layer Architecture for IP-CS

Figure 7.6 shows the distribution of functional entities in ASN for Profile C. The only difference in Profile A is the RRM and HO controller which resides in the ASN-GW and corresponding RRM and HO agent resides in the BS. Profile B does not expose the R6 reference point and functional entities in BS and ASN-GW can be distributed freely. Profile B only complies with R1, R2, R3, and R4 interfaces.

Figure 7.6 - WiMAX NRM architecture for Profile C

CSN complements ASN with IP related connectivity. AA or Home Agent residing in CSN allocates the IP address. AAA also performs authentication, authorization, and accounting. Communication is through RADIUS protocol Data packets arriving Home Agent are tunneled to ASN and data path shift to new ASN is executed with inter-ASN mobility is executed. The policy server residing in ASN is responsible to store the policy and QoS info of each subscriber, which is communicated to ASN during service flow creation.

CSN is also responsible to access other IP networks; Location Based Services, Peer-to-peer,, VPN, IP multimedia services, law enforcement, messaging, etc. Network Management Services and Element Management Services also reside in the CSN for network and equipment configuration.

7.5 Access Service Network Functional Protocols :

Protocol Layering of WiMAX considers end-to-end protocol layering. Data and control packets are forwarded from the MS to the CSN in uplink. The traffic is concentrated in the ASN-GW and forwarded to the CSN and same way, concentrated in the ASN-GW for downlink and distributed to the MSs residing in different BSs. IP packets use IP convergence sublayer (IP-CS) or Ethernet convergence sublayer (ETHCS) over IEEE 802.16e. The IP-CS with IP-in-IP encapsulation between BS and ASN-GW is considered in most designs. Bridging is also another way of routing packet within ASN.

Network Discovery and Selection implements manual or automatic selection of the appropriate network. MS first discovers all the NAPs where each has an Operator ID embedded into Base Station ID and transmitted with DL-MAP of each frame. And MS continue to listen the channel for SII-ADV signal which system identity information advertisement to advertise NSP IDs. The MS selects one NSP from the list according to an algorithm and performs network entry and provide its identity and its home NSP domain with a network access identifier (NAI). The ASN selects the next AAA hop from the realm portion

of the NAI.

IP Address Assignment is done through DHCP or AAA: ASN hosts DHCP relay or DHCP proxy respectively. In order to deliver the point of attachment IP address to MS. For IPv6 there is access router in ASN to obtain globally routable IP address. The MS gets the care-of-address (CoA) from ASN and home address (HoA) from CSN.

Authentication and Security Architecture implements 802.16e security with IETF EAP framework. AAA framework is used for service flow authorization, mobility management and policy control. AAA framework is based on pull model in which supplicant sends a request to ASN and ASN forwards it to AAA server. The AAA return with appropriate response to ASN which set up the service and inform the MS.

Figure 7.7 - Authentication Relay Inside the ASN

User and device authentication is supported with PKMv2 and EAP. PKMv2 is between MS and BS and BS relays this EAP messages to ASN-GW where AAA client encapsulates the EAP and forwards to AAA server in the CSN over RADIUS. EAP-AKA, EAP-TLS, EAP-SIM, EAP-PSK, EAP-TTLS are the supported EAP types. Both user and device authentication is performed with double-EAP and device credentials are in the form of digital certificate, secret key, or X.509 certificate.

Quality of Service Architecture in WiMAX complements the QoS framework in IEEE 802.16e-2005 QoS model. The QoS provides rich set of variety: per user and per service flow basis differentiated levels; admission control; bandwidth optimization. QoS provides static and dynamic service flow creation. For each service there is provisioned, admitted, and active states. When flow is in active state it starts getting the service. Entities are Policy function and AAA server residing in CSN, Service flow management residing in BS, and Service flow authorization residing in ASN-GW.

Mobility Management implements mobility with the ASN and across the ASNs anchored mobility is when MS moves within the same Foreign Agent domain residing in ASN-GW. Control signals use R6 and R8 reference points and data path shift happens in ASN-GW with new R6 to target BS when handover is complete. CSN-anchored mobility additional to ASN-anchored mobility triggers the FA change through Home Agent. Now, R3 and R4 reference points also become active.

Radio Resource Management is responsible to fully utilize the network by information gathering and implementing decisions. The information such as radio-related measurements; base station spare capacity reports are concentrated to assist handover decision and load balancing decisions.

Paging and Idle Mode Operation is responsible to maintain a track and alert for MS when it is in idle mode for battery power saving reasons. Paging is executed to alert MS when there is an incoming message. Figure 8 illustrates the paging operation along with paging and idle mode elements in the system. MS is tracked when it is in the idle mode and information is stored to a location register (LR). Granularity of track is bigger than cell size since a paging group (PG) is composed of multiple cell and when a MS moves across paging groups, location update occurs via R6 and/or R4. Paging Controller (PG) in ASN-GW retrieves the location from LR and alerts the paging agent in (PA) in BS to signal to MS.

ASN-GW is responsible to authorize service flows according to the subscriber’s profile. Admitted service flows and active service flows can change over time and ASN-GW irresponsible to provide admission control for downlink traffic. ASN-GW creates a GRE tunnel per service flow and encapsulates downlink traffic along with IP Sec.

7.6Radio Resource Management (RRM):

Standardized RRM procedure: Information reporting – collecting Radio Resource Indicators from RRA to RRC. 1) Spare capacity reporting per BS – available RR per BS.

2) PHY service level reporting -- assessment of link quality perMS.

Decision support – communicating suggestions or hints of aggregated RRM status 1)Neighbor BS radio resource status update.

7.7 Paging control and location management :

Paging group – one or more Pas reside NAP boundary Paging Agent – handle interaction between PC and IEEE 802.16e related paging

functionalities Paging Controller – administrate activities of idle mode MS. Location register – database contains location information of idle mode MS. PC and LR entry is created when MS enters idle mode. User plane tunnel between FA, data

path and BS removed, but signaling is not impacted. LR updated when idle MS cross the boundary of PG. LR entry cancelled when MS exist.

Figure 7.8 – Paging operation

ASN-GW has the location information provides paging service as well. Paging service tracks subscriber when it is operating in the idle mode. Paging signal is broadcasted when downlink traffic

is received. During active operation also location information is updated as mobile subscriber moves to new BS.

The next generation network is a convergence of different technologies. Inter technology mobility is a must and it is being designed in WiMAX, 3GPP, 3GPP2, DSL, and WiFi. Interworking of these technologies increase the importance of ASN-GW since for instance in WiMAX connectivity to 3GPP, 3GPP2, DSL and WiFi are provided via ASN-GW. Interworking may provide common billing and seamless inter-technology handover.

7.8 Elements :

To derive the elements of ASN (Access Service Network) we’ve to first discuss the gateway

in below:

7.8.1 ASN-GW

ASN-GW is placed at the edge of ASN and it’s the link to the CSN. ASN-GW assists mobility and security in the control plane and handles the IP forwarding. The Figure 9 gives an overview of the feature set together with which reference points (Ri) ASN-GW uses to communicate with other entities in ASN and CSN.

Figure 7.9- QoS Functional Elements

ASN control is handled by ASN-GW and BS. ASN-GW Control plane handles all the radio-independent control and feature set includes authorization, authentication, and accounting (AAA), context management, profile management, service flow authorization, paging, radio resource management, and handover. Data plane feature set includes mapping radio bearer to the IP network, packet inspection, tunneling, admission control, policing, QoS and data forwarding.

ASN-GW has the authenticator and key distributor to implement AAA framework along with AAA relay in order to transmit signals to AAA server wherein the user credentials during network re/entry are verified with EAP authentication. Security context is created during AAA session and keys (MSK and PSK) are generated and shared with BS and MS. AAA module in the ASN-GW provides also flow information for accounting since every single detail about a flow such as transferred or received number of bits, duration, and applied policy is present and directly retrievable from the data plane.

ASN-GW is responsible for profile management together with policy function residing in the connectivity network. Profile management identifies the user and its subscribed credentials such as allowed QoS rate, number of flows, type of flows, etc.

Figure 7.10 - ASN Reference Model containing multiple ASN-GW

Along with profile management, ASN-GW maintains context per mobile subscriber as well as per BS with higher granularity. Context of each subscriber keeps its profile, security context and characteristic of mobile device. This context is retrieved and exchanged between serving BS and target BS during handover and it moves as mobile subscriber moves to another ASN-GW.

7.9 Base Station

The BS implements IEEE 802.16e interface to the MS and defined by one sector with one frequency. The air link scheduler resides in BS for uplink and downlink resource allocation, traffic classification, and service flow management as seen in Figure 6. BS provides the tunneling to ASN-GW and relaying functionality for services like authentication, reception and delivery of traffic encryption key and key encryption key.

Base station has the local control of the network and gets assistance from ASN-GW for some features and implements the decision of the gateway for others.

Figure 7.11: Wimax Base Station

Wimax supports some kinds of Base Station equipment of different capacity:

1) High Density Base Station :

The High Density base station is a carrier class 8U high cPCI shelf that fits into standard 19” or 22” (ETSI) racks. The chassis contains a Network Processor Unit, multiple Access Unit modules, Power Supply and Power Feeding modules.

2) Micro Base Station :

The micro base station provides cost-effective broadband services in low-density

rural areas. It is comprised of a stand-alone module that connects to the same outdoor

radio unit.

3) Broadband Data CPE

The BreezeMAX broadband data CPE acts as a bridge between the wireless and wireline media, supporting up to 512 MAC Addresses.

4) Broadband Voice Gateway

The broadband voice gateway CPE provides integrated voice and data services for

residential and SOHO users and is available in two models.

7.10 Capacity :

WiMAX™ is based upon the IEEE 801.16 standard enabling the delivery of wireless broadband services anytime, anywhere. WiMAX products can accommodate fixed and mobile usage models. The IEEE 802.16 standard was developed to deliver non-line-of-sight (LoS) connectivity between a subscriber station and base station with typical cell radius of three to ten kilometers. All base stations and subscriber stations claiming to be WiMAX compliant must go through a rigorous WiMAX Forum Certified™ testing process. WiMAX Forum Certified systems can be expected to deliver capacity of up to 40 Mbps per channel. This is enough bandwidth to simultaneously support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity. The WiMAX Forum expects mobile network deployments to provide up to 15 Mbps of capacity within a typical cell radius of up to three kilometers. WiMAX technology already has been incorporated in notebook computers and PDAs to deliver high speed mobile Internet services anytime, anywhere.

WiMAX will provide broadband connectivity anywhere, anytime, for any device and on any network.

• High speed internet access where it is currently unavailable

• Substantially increase data speeds for applications to include online gaming, streaming video, video conferencing, VoIP and location based services

• Drive wireless Internet equipment and access prices to a competitive price point comparable to cable, DSL, and fiber Internet services

• With a robust telecommunications infrastructure already in place in the U.S. Mobile WiMAX services from Sprint and Clear wire will reach more than 150 million consumers by year end 2008.

• This wireless broadband technology is perfectly suited for regional and rural areas and the purchase and installation process of WiMAX technology is faster, simpler and cheaper than other offered solutions. Additionally, the non-line-of-sight (NLoS) capability means that WiMAX technology can provide coverage despite the challenges of geography and the limited footprint of wire line.

Conclusion:

Access Service Network for the wimax technology is briefly discussed in the above. In this way the gateway of the total network is adjusted for wimax technology. Here three topics are discussed about ASN. But the discussion about ASN can be verified in many way with many other suitable examples and points.

Chapter 8

Wimax connectivity service network (CSN)

8.1 Introduction

The CSN consists of various functions within the core data network and forms an integral part of an end-to-end WiMAX network that is in accordance with 802.16e standards. Some of the functions outlined by the CSN are mobility management, subscriber services

and IP services. The IP Core platforms available as part of Nortel’s CSN solution are ready for deployment today and are best-in-class solutions from Nortel’s portfolio and partners. These are field-proven solutions that provide the performance, capacities, scalability, services and non-disruptive migration required by operators. Figure 1 depicts

the architecture. Functions that comprise the CSN ecosystem are as follows:

• AAA: Provides authentication, accounting, authorization, management of users’ service profiles and data records for billing WiMAX subscribers

• DNS/DHCP server: Provides initial IP Address look-up and allocation for WiMAX Mobile Stations

• Home Agent (HA): Provides Mobile- IP functionality that allows traffic to mobil e devices to be routed transparently to the ASN Gateway and is also the anchor for WiFi access points

• Routers: Fundamental for routing and aggregating traffic within the CSN and across multiple ASN networks

• Firewall/NAT: Critical multi-layer packet inspection for extra protection from advanced hackers and attackers

• Policy Function: Provides a subscriber’s access to the network and the levels of service for individual sessions. The Policy Function dynamically configures the service flow based on the subscriber profiles and also serves as the interface node to the IMS infrastructure

CSN and IMS network

Nortel’s WiMAX CSN is available for deployment together with a Nortel IMS core. Nortel’s IMS solution gives service providers unprecedented levels of flexibility

in both integrating elements from different applications to create unique

services while exploiting a variety of information — such as access type,

presence, location and device type — to optimize the experience for end

users. The policy function node provides the control mechanism to

provide access to the IMS infrastructure, offering dynamic levels of service

for individual sessions.

8.2Applications on the

CSN network

Nortel provides solutions that comprise voice, video, data and multimedia with mobility.

• VoIP: Essential solution that provides voice over the IP network; Nortel is a leader in VoIP solutions in wireless, wireline, cable and enterprise and is

ranked number one in carrier VoIP

• Video: Next-generation video applications such as Video Telephony, Video Conferencing, Video Streaming and Mobile TV

• Data and Multimedia applications:

- Presence Enabled

- Web Collaboration Tools, Web Browsing

- Instant Messaging, E-mail,Buddy List

- Conferencing (audio/video)

- Instant File Transfer

- Contact, Call Management Tools

• Other customized applications

such as Hotlining and Prepaid are also available with the WiMAX CSN solution

• Legal Intercept: Required data intercept of the subscriber data session defined by standard CALEA J-Standard 025

• OSS: Back-office essentials such as billing, mediation, subscriber provisioning and services provisioning can be deployed with the CSN

8.3CSN traffic & performance model

This section describes the dimensioning of the CSN elements including AAA server

HA, DHCP and firewall. In dimensioning the mentioned elements, the node performance parameters are taken into account. This section also provides the description of the traffic and performance model of the HA, AAA servers, DHCP server and firewall.

Home Agent (HA)

The performance parameters for the HA are the Mobile IP (MIP) registration rate, binding capacity, throughput and packet rate. HA also generates accounting events that constitute

additional load to the system. The MIP registration rate is the sum of the MIP registration due to powered on plus percentage of active subscribers in the R3 interface. HA also handles additional AAA authentication requests due to MIP renewal and R3 mobility. The binding capacity is the number of subscriber stations in the CSN. With

the number of subscribers in the R3 interface proportional to subscribers in the CSN, the binding capacity of HA results into 29,000 subscribers. In mobile WiMAX release 1.1 [28] ASN gateway does not support redundancy of the HA, therefore HA redundancy can depend on the redundancy of the deployed home agent only. Load sharing for the Home Agent is implemented by the following means:

● Dividing subscribers in groups and configuring different HA addresses

for each subscriber group.

● AAA server assigns HA address out of pool of HA addresses in each

access request.

● By implementing a mechanism in the AAA server to reply a different

HA address depending on the HA load information.

AAA Server

The performance parameters for the AAA server are the database capacity for

authorisation and accounting, authentication transactions and accounting transactions. The required database capacity for authentication is the number of all subscribers, 80,000. The required database capacity for accounting depends on the average size of the accounting ticket, the number of accounting transactions and the time that accounting ticket needs to be stored. The accounting transaction load is the sum of accounting events due to powered on subscribers, subscribers in the R3 interface, MIP renewal and

subscribers due to accounting update. An accounting update is triggered by an expiration of an accounting timer. As in HA, the redundancy depends on the redundancy of the AAA server.

DHCP server

The node performance parameter for the DHCP server is the number of transactions or requests. The DHCP is dimensioned according to the total number of DHCP requests during the busy hour with respect to its handling capacity in terms of requests per second. The transactions or requests occur during power on/off and in case of DHCP renewal. DHCP renewal depends on the configured DHCP renewal time. The firewall is dimensioned based upon the total required traffic during the

Firewall

busy hour with respect to the equipment processing capacity. The firewall is expected to be implemented on an “n+1” configuration running the Virtual Router Redundancy protocol (VRRP) for equipment redundancy and load sharing functionality.

8.4 CSN architecture includes –

1. DNS/DHCP2. mobile home agent(HA)3. AAA(authentication authorization & accounting)4. prepaid server5. Hotlining application server 6. billing 7. policy function8. border gateway 9. interworking gateway

fig: 8.1wimax CSN architecture

8.5 Functionality & features of the CSN architecture

Border gateway

A border gateway is a collection of functions that provide internetworking between the operator’s network and the internet. Typical functions include firewall, network address Translation (NAT), and inter-domain routing.

fig: 8.2 border gateway

8.6 CSN Gateway

More and more, mobile subscribers are embracing WiMAX connectivity to stay connected with family and friends, do business, and are entertained, this growth is accompanied by an increasing demand for a robust mobile broadband environment that is equivalent to the wire line experience. To meet this demand, many operators are looking to Mobile WiMAX as a key ingredient to further build their broadband access networks. As part of this transition, operators will need to deploy Access Service Network (ASN) and the Connectivity Service Network (CSN) as key enablers for their Next Generation Network.

 The ASN aggregates traffic across multiple Base Transceiver Stations (BTS) and supports security, handoffs and Quality of Service (QoS). The CSN manages core network operations and enables internetworking with non-WiMAX networks.

 CSN solution enabler forms a key component of WiMAX CSN Gateway solutions. The CSN solution enabler performs core network functions, including policy and admission control, IP address allocation, billing and settlement. It hosts the Mobile IP Home Agent (HA), the IP and AAA servers, and PSTN and VoIP gateways. The CSN is also responsible for internetworking with non-WiMAX networks (e.g. 3G, DSL) and for roaming through links to other CSNs. 

The following are the broad features supported:

1. QoS, Admission Control and Service Flow Management.2. Wimax-IMS Interworking.

3. Policy Interworking.

4. AAA.

Performance

1. CSN gateway solution enabler is a modular, scalable and portable framework which demonstrates high performance attributes and enables our customers to achieve time to market benefit.

2. Help design and implement a complete CSN Gateway product as per the customer’s specific requirements.

3. Help design and implement a complete Convergence Solution along with ASN Gateway Solution Enabler.

4. Seamless Integration of the various modules of the WiMAX compliant framework that ensures the interoperability with various ASN, CSN and BTS offerings in the market.

5. System testing of the OEM’s CSN solution using in-house tools that expedite the validation cycles. Load and performance testing services for the CSN gateway solution is also underway.

6. In house Test Automation framework acts as an execution engine which can help automate the execution and Plan, monitor, track and analyze the results of test cases with the availability of the test suites .

8.7 Common IP Address for DHCP server in WiMAX

A network comprising a network component configured with a common internet protocol (IP) address, wherein a similar network component in a similar network is configured with the common IP address, and wherein the network is in communication with the similar network. The disclosure includes a network component comprising a processor configured to implement a method comprising communicating with a mobile station (MS) using an IP address that is common for similar elements in similar networks, and receiving a dynamic host configuration protocol (DHCP) context associated with the MS. Also disclosed is a first access network in communication with a second access network, the first access network comprising a first DHCP proxy configured with a substantially identical IP address as a

second DHCP proxy in the second access network, and an agent configured to promote transfer of a DHCP context to the second access network.

What’s claimed is:

1. A network comprising: a network component configured with a common internet

protocol (IP) address, wherein a similar network component in a similar network is

configured with the common IP address, and wherein the network is in communication

with the similar network.

2. The network of claim 1, where in the network component is a dynamic host

configuration protocol (DHCP) proxy.

3. The network of claim 1, further comprising an agent configured to promote the transfer

of a DHCP context to a similar agent in the similar network.

4. The network of claim 3: wherein the network component is a dynamic host

configuration protocol (DHCP) proxy associated with a mobile station (MS), wherein

the agent is associated with the MS, and wherein the agent and the DHCP proxy

relocate substantially simultaneously.

5. The network of claim 4, wherein the MS does not support mobile IP,

6. The network of claim 1, wherein the network is a worldwide interoperability for

microwave access (WiMAX) network.

7. The network of claim 1, wherein the IP address is public.

8. The network of claim 1, wherein the network is configured such that any packets or

messages containing the common IP address as a source address or a destination

address are prohibited from leaving the network.

9. The network of claim 1, wherein the network component is configured to communicate

with a mobile station (MS) using the common IP address.

10. The network of claim 9, wherein the network component is configured to use the

common IP address as the source IP address in a message sent to the MS.

11. A network component comprising: a processor configured to implement a method

comprising: communicating with a mobile station (MS) using an internet protocol

(IP) address that is common for similar elements in similar networks; and receiving a

dynamic host configuration protocol (DHCP) context associated with the MS.

12. The network component of claim 11, wherein the DHCP context is received using a

foreign agent relocation message.

13. The network component of claim 11, wherein the IP address is used exclusively by a

plurality of DHCP proxies.

14. The network component of claim 11, wherein the MS does not support mobile IP.

15. A first access network in communication with a second access network, the first

access network comprising: a first dynamic host configuration protocol (DHCP)

proxy configured with a substantially identical internet protocol (IP) address as a

second DHCP proxy in the second access network; and an agent configured to

promote transfer of a DHCP context to the second access network.

16. The first access network of claim 15, wherein the first DHCP proxy communicates

with a mobile station (MS) that does not support mobile IP.

17. The first access network of claim 15, wherein the first access network and the second

access network belong to a single network access provider.

18. The first access network of claim 15, wherein the DHCP context comprises a mobile

station IP address and a mobile station IP address lease time.

19. The first access network of claim 15, wherein the first access network comprises only

one DHCP proxy.

20. The first access network of claim 15, wherein the DHCP proxy and the agent are

implemented at a common node.

8.8 Wimax AAA in CSN

Authentication:

Authentication refers to the confirmation that a user who is requesting services is a valid user of the network services requested. Authentication is accomplished via the presentation of an identity and credentials like digital certificates.

Authorization:

Authorization refers to the granting of specific types of service (including "no service") to a user, based on their authentication, what services they are requesting, and the current system state. Authorization may be based on restrictions, for example time-of-day restrictions, or physical location restrictions, or restrictions against multiple logins by the same user. Authorization determines the nature of the service which is granted to a user. Examples of types of service include, but are not limited to: IP address filtering, address assignment, route assignment, QoS/differential services, bandwidth control/traffic management, compulsory tunneling to a specific endpoint, and encryption.

Accounting:

Accounting refers to the tracking of the consumption of network resources by users. This information is used for billing and planning. Online accounting refers to accounting information that is delivered concurrently with the consumption of the resources e.g. Prepaid services. Offline accounting refers to accounting information that is saved until it is delivered at a later time. Typical information that is gathered in accounting is the identity of the user, the nature of the service delivered, when the service began, and when it ended.

8.9 Authentication and Authorization Procedures 1. After SS enters in to the network, it immediately initiates authentication process

with BS. Scanning downlink channel, sync with uplink channel, Paging and Ranging are steps for SS to enter in to the network.

2. All SS have factory-installed X.509 digital certificate. X.509 digital certificate is unique for each SS and contains SS's MAC address and RSA public key. SS have RSA private/public key pairs or have capability to generate it dynamically, both are widely used scheme.

3. SS begins authentication by sending an Authentication Information message to its BS. The Authentication Information message contains the SS manufacturer’s X.509 certificate. The Authentication Information message is strictly informative; i.e., the BS may choose to ignore it. However, it does provide a mechanism for a BS to learn the manufacturer certificates of its client SS.

4. Immediately, the SS sends an Authorization Request message to its BS. This is a request for an AK, as well as for the SAIDs identifying any Static Security SAs the SS is authorized to participate in. SA, SAID, AK and such terms are explained in the later section.

Authorization Request includes:

1. A X.509 certificate.2. A description of the Cryptographic algorithms the SS supports i.e. SS’s cryptographic

capabilities.

3. The SS’s Basic CID (Connection Identifier) , which SS got during initial ranging.

In response to an Authorization Request message, a BS validates the requesting SS’s identity (of course by verifying X.509 digital certificate), determines the encryption algorithm and protocol support it shares with the SS, activates an AK for the SS, encrypts it with the SS’s public key, and sends it back to the SS in an Authorization Reply message. The authorization reply includes:

1. An AK encrypted with the SS’s public key.2. A 4-bit key sequence number, used to distinguish between successive generations of

AKs.

3. A key lifetime.

4. The SAIDs and properties of the single primary and zero or more static SAs the SS is authorized.

Certainly, there is a question that why the message is “Authorization Request” instead of “Authentication Request”? Of course SS has to authenticate itself before it is authorized for any service. It's little bit tricky in a way that authentication is implicit here. So when SS is asking for authorization it is also sending material for authentication. They (WiMAX Forum) would have given message name that justifies both the process (Authentication and Authorization).

Again, how authentication is done is purely protocol dependent. Protocols PKMv1, PKMv2 and EAP are used to performs authentication. Depends upon the protocol, authentication procedure varies slightly.

8.10Role of AAA Client -Server for Authentication and Authorization Procedures1. When SS requests for Authentication, the request is submitted to AAA client.2. AAA client request to AAA server for to authenticate SS. AAA client and AAA

server communicates over RADIUS (Remote Access Dial In User Service) messages.

3. AAA server validates/rejects AAA client request.

4. If SS is in visited NSP, AAA server of visited NSP calls AAA server of home NSP to validate SS.

Accounting Procedures

Accounting procedures are performed by means of accounting agent, AAA server and AAA client. Following is accounting terminology.

1. Airlink Records: Airlink record is the measure of radio resources being used by particular SS.

2. UDR (Usage Data Records) : UDR is rated usage of SS. Usage of resources by SS is being aggregated and rated to form UDRs.

3. Negative Volume Count : Any unsent or discarded data is considered as Negative Volume Count. Accounting agent keeps track of it and submit the report to AAA client.

4. Offline Accounting: In Offline accounting user is not charged on the spot while he is being served, instead UDRs are generated. After billing cycle ends, bill is generated.

5. Online Accounting: In Online accounting user is continuously monitored against its remaining balance. Once he consumes its prepaid balance, he is denied to be served.

Role of AAA Client -Server for Offline Accounting1. BS generates Airlink records : When SS connects to BS, it sends “Active Start

Airlink Record” and when disconnects it sends “Active Stop Airlink Record”. 2. On receiving of Airlink messages (and several other triggers) AAA client

generates and maintains UDRs. When SS gets disconnected, AAA client send UDRs to AAA servers.

Role of AAA Client- Server for Online Accounting1. There is a Prepaid Server (PPS) which maintains SS's prepaid information. A

Prepaid Client (PPC) handles prepaid accounting request and response. PPS generally implemented as a part of AAA server only.

2. Whenever an Authorization request is made by AAA client (which is originated by SS) , PPS allocated fraction of subscriber’s balance to a quota.

3. When subscriber consumes allocated quota, it again sends Authentication request to request new quota.

8.11 Hot-Lining

The Hot-lining feature provides a WiMAX operator with the capability to efficiently address issues with users that

would otherwise be unauthorized to access packet data services. When a problem occurs such that a user MAY no longer be authorized to use the packet data service, a wireless operator using this feature MAY hot-line the user, and upon the successful resolution of the problem, return the user’s packet data services to normal. When a user is hot24

lined, their packet data service is redirected to a Hot-line Application (HLA) which notifies the user of the reason(s) that they have been hot-lined and offers them a means to address the

concerns meanwhile blocking access to normal packet data services. Reasons for hot-lining a user are: prepaid users whose account has been depleted; or users who

have billing issues such as expiration of a credit card; or users who have been suspected of fraudulent use. As a result, hot-lining performs the following four fundamental activities:

1. Blocking normal packet data usage.2. Notifying MS that packet data usage is blocked.3. Directing MS to rectify blockage.4. Restoring normal operations when the User has rectified issues that triggered the hot-

lining of their service. Or,5. Terminate service if the user failed to address the issues that triggered the hot-lining

of their service. Hot-lining would help provide a consistent user experience for all users, irrespective of which MS application is using the packet service. This includes preventing negative user experience resulting from arbitrarily blocking packet data service without notifying the MS of packet data block and a mechanism to rectify the blockage. Hot lining would further provide consistency across all applications that utilize the packet data service plus it would lower operating costs.

Hot-Lining Capabilities

The following section describes the general hot-line capabilities supported for this release: a) Hot-lining is supported for both CMIP and PMIP operations both at the ASN and the CSN. b) A user can be hot-lined at the start of their packet data session or mid-session as described below:

ACTIVE -Session Hot-lining:

The user starts a packet data session. In the middle of the session it is hot-lined

and after the account is reconciled by some manner, the hot-lining status off

the session is removed. The hot-lining is done with RADIUS Change of

Authorization (COA) message.

New-Session Hot-lining:

The user’s session is hot-lined at the time of packet data session establishment.

In this scenario the RADIUS Access-Accept message is used to hot-line the

session.

c) Similarly, hot-lined status can be removed mid-session 1 or at the start of a new session.

There are two methods in which the HAAA indicates that a user is to be hot-lined:

Profile-based Hot-lining

The HAAA sends a hot-line profile identifier in the RADIUS message. The

hot-line profile identifier selects a set of rules that are pre-provisioned in the

Hot-line MS (HLD) that cause that user’s packet data session to be redirected

and/or blocked.

Rule-based Hot-lining

The HAAA sends the actual redirection-rules (HTTP or IP) and filter-rules in the RADIUS messages that cause the user’s packet data session to be redirected and/or blocked.

In order to properly account for the hot-lining state of the user, the user’s hot-line state SHOULD be recorded in the accounting stream. The following capabilities are not covered by this specification but are described in so far that they are needed to implement a complete hot-lining solution:

The trigger(s) that cause an operator to hot-line a user is not in scope for this specification. These triggers could come from a number of sources such as a billing system, fraud detection system, etc. The means to notify the HAAA that a user is to be hot-lined is not in scope for this specification. The means by which the user is notified that they have been hot-lined is not in scope of this specification. Typically, the user will be notified that they have been hot-lined via their browser or other means. The means by which the user interacts with the system to correct the symptoms that caused them to be hot lined are not in scope for this specification. The means by which the system notifies the HAAA that user need not be hot-lined, that their packet data session is to be returned to normal is not covered as part of this specification. The details of what happens when the ASN or CSN performs Profile-based Hot-lining are out of scope. It is assumed that the user’s traffic is blocked and that the user gets notified. When the packet data session is hot-lined some IP flows will be blocked and some IP flows will be redirected. The intent of the redirection is not to continue the normal operation of the flow but rather to provide information to the Hot-line application so that the Hot-line application can determine how to notify the user of their hot-lined state.

Hot-Lining Operation

Hot-lining involves the following packet data network entities • Visited/Home CSN

• ASN

• HAAA

• VAAA

The CSN and ASN contain certain MSs that implement the hot-lining rules requested by the HAAA. In this document, any of these MSs that apply the hot-line rules for a user is called the Hot-lining MS (HLD). The role of the VAAA with respect to Hot-lining is to act as proxy and as such will not be discussed further.

Hot-liningApplication (not in scope) AAA-Hot-Line

Signaling (not in scope)HAAA CSN Hotline Device ASN Hotline Device RADIUS RADIUS Packet data Packet data Packet data Mobile-Hot-lining Application interaction: e.g., Web

Hot-lining also involves the Hot-Line Application (HLA). The Hot-Line Application is a functional entity that performs the following roles:

1. Determines when the user SHOULD be hot-lined.2. Initiates the hot-lining signaling with the HAAA.3. Hot-lined flows are redirected to the Hot-Line Application.4. Responsible for initiating notification of the hot-line status to the MS. This could be

done via a delivery of an HTML page to the subscribers’ browser or via some other means.

5. Provides a mechanism for the user to rectify the issue that triggered hot-lining.6. Upon successful resolution of the problem, return the user back to normal operating

mode.7. • Upon unsuccessful resolution of the problem, terminate the user’s packet data

session.

The implementation of the Hot-Line Application is not within scope of this document. The interface between the Hot-Line Application and the various entities is out of scope.

The Hot-Line Application can reside over multiple servers in the network. For example, the Hot-Line Application could reside in its entirety on a web server. Or certain parts of Hot-line Application can reside on ASN or CSN as shown in Hot-lining of a user’s packet data service starts when the Hot-Line Application determines that the user’s service is to be hot-lined. This determination is entirely deployment specific and can be a result of many factors. Details are not in scope for this document. To initiate Hot-lining of the user, the Hot-Line Application will notify the HAAA that the user is to be hot-lined. The method of notification is out of scope. Upon receiving the notification from the Hot-Line Application, the HAAA records the hot-lining state against the user record. The HAAA will determine if the user is currently in-service or out-of-service. If the user is in-service the HAAA initiates the Active-Session Hot-Lining procedure, if the user is out-of-service the HAAA initiates the New-Session Hot-Lining procedure. Hot-lining requires that the Hot-lining MS be able to support Profile-based Hot-lining and or Rule-based Hot-lining. When support for Active Session Hot-lining is not provided the operator could utilize RADIUS Disconnect Message to terminate the user’s session or specify a time period after which the session would be terminated by the Hot-lining MS. To participate in Hot-lining an access MS (ASN-GW/FA or HA) SHALL advertise its Hot-lining capabilities using the Hot-line Capability VSA sent in a RADIUS Access-Request message. The HAAA uses the contents of the Hot-line Capability VSA and other local policies to determine which access MS will be the Hot-lining MS for the session. The hot-line signaling for a given packet data session is communicated by the HAAA to the Hot-line MS by sending the Hot-Line Profile Id VSA; or by sending HTTP/IP Redirection Rule VSAs and Filter Rule VSAs.

8.12 Network Management System

Networks has selected a best-in-class combination of products and services to provide an open industry, standards-based NMS. This approach includes customer-centric, and scalable OSS/BSS components that are quick to deploy and can be easily expanded as the network and services grow. Harris Stratex can integrate an operator’s existing NMS components or use best-in-class products to tailor-fit the management function set needed for your network.

1. Service Assurance – Integrated Network Management System (INMS) FCAPS (Fault, configuration, Accounting, Performance, and Security) functions per ITU-T TMN reference architecture. The INMS also manages: BS and SS, Wireless Backhaul, and ASN-GW in addition to CSN Systems and Applications.

2. Inventory Management and Trouble Ticketing of Assets Network physical assets, logical topology for tracking, with capacity management for new circuits, and analysis of network alarms and service impacts. Trouble ticketing to organize tickets and work orders for proper resolution.

3. Customer Care and Billing Central point for interfacing with customers — management of customer information including pricing, billing and usage, together with service provisioning and mediation for billing and service issues.

4. Operations – NOC and Call Centers Based on the experience of Harris Corporation’s own 24x7 Network Operations Centers, Harris Stratex can provide knowledge and guidance on the build-out of Network Operations and Control Centers. The Call Center system provides a single IP communications platform and pre-integrated application suite or handling inbound/outbound customer interactions via telephone, e-mail, Web, online forms and fax.

8.13 THE policy function in wimax

The WiMAX Forum has specified a framework for Service Management and QoS. Service Flow Agent (SFA) and Service Flow Manager (SFM) are the entities that act as policy decision and enforcement points respectively for Service Management and QoS. The following figure depicts the policy framework for WiMAX networks:

Fig: 8.10 policy framework in wimax

In the above illustration:

1. The SFM Entity: Is responsible for the creation, admission, activation, modification, and deletion of 802.16 service flows. It consists of an Admission Control (AC) function and the associated local resource information.

2. The Policy Functions (PFs): Reside in both home and the visited network, comprising their respective databases. The databases include general policy rules as well as application-dependant policy rules.

3. The AAA Server: Holds the subscriber's QoS profile and the associated policy rules per subscriber

4. Service Flow Authorization (SFA): Is responsible for evaluating any service request against the subscriber's QoS profile

8.14Online Accounting (Prepaid)

28 This section describes the online (prepaid) accounting procedures in the WiMAX network. The prepaid packet data service allows a user to purchase packet data service in advance based on volume or duration. Account status is stored on a prepaid server (PPS) that is located in the user’s home network and accessed via the HAAA server. To provide service to roaming prepaid users, the visited ASN or CSN needs to support the prepaid service and the local and broker AAA servers need to forward the new prepaid accounting attributes transparently to and from the home AAA server. The HAAA server and the prepaid server could be collocated or could be separate entities From the ASN perspective, the HAAA and the prepaid server are indistinguishable. Although this document does not make assumptions

about the prepaid server – HAAA interface, the call flows MAY show the prepaid server and the HAAA as separate entities. The prepaid billing solution can provide the following services: a) Simple IP based service metering in real time. b) Undifferentiated Mobile IP services in real time with support for multiple Mobile IP sessions per user. “Undifferentiated” means that all the Mobile IP sessions for a single user will be rated equally. c) Rating measurement based on data volume and/or call duration. Data volume is measured as total octets, uplink octets, downlink octets, total packets, uplink packets or downlink packets and total duration. The rating function can be done either by the prepaid client or prepaid server. Prepaid service for multiple simultaneous data sessions is also allowed. As the network does not have any a priori knowledge of the user usage behavior, the solution is built on an iterative authorization paradigm. The prepaid server will apportion a fraction of subscriber’s balance into a quota, each time an authorization request is made. Multiple sessions from the same user will each obtain their own quota, each session needs to seek reauthorization when the previously allocated quota is depleted thus minimizing any leakage. The granularity and the magnitude of the quota are implementation details of the prepaid server; therefore, it is beyond the scope of this specification. The limitation with this method is as the number of session increases, the quota for each session will be diluted. The user might need to close some sessions in order to collect all remaining quota that was allocated to his active sessions. In order to support prepaid packet data service the ASN and/or the CSN SHALL support the prepaid client (PPC) function and the prepaid server (PPS) function MAY be collocated with the Home RADIUS server. In this specification, the prepaid packet data service supports a set of capabilities as described in the next section. Additional capabilities MAY be supported in future revisions of this specification. When the prepaid account of user is depleted, the PPC SHALL stop the online accounting service. If the user also has a postpaid account and is authorized to hand off off-line accounting base on profile or rule, the PPC of the ASN can notify the AAA client of ASN that SHALL create the UDR and send an off-line RADIUS accounting-request to AAA server but the service flow SHOULD not be terminated.

Online Accounting Capabilities

1. In this revision of the specification, the following prepaid capabilities are supported: Volume based prepaid, with quota assigned at a service flow level if the PPC resides in the ASN.

2. Volume based prepaid with quota assigned at the packet data session level (IP/NAI) if the PPC is located in the CSN.

3. Duration based prepaid, with quota assigned at a service flow level if the PPC resides in the ASN.

4. Duration based prepaid, with quota assigned at the packet data session level (IP/NAI) if the PPC is located in the CSN.

5. Ability for the Home AAA/PPS to allow/deny/select a PPC based on the Home AAA/PPS policy, user profile, Prepaid Accounting Capability (PPAC) VSA and the Session Termination Capability (STC) VSA of the ASN and/or the CSN.

6. The prepaid packet data service is based on the RADIUS protocol.7. Home AAA/PPS ability to manage the prepaid packet data service when the

quota allocated to a PPC is consumed or a pre-determined threshold value is reached, through triggers provided to the PPC.

8. The capability of the PPC based in the ASN to support Volume Quota and a tariff switch time interval concurrently per service flow. The capability of the PPC based in the CSN to support Volume Quota and a tariff switch time interval concurrently per packet data session.

9. The capability in the PPC and the Home AAA/PPS to provide tariff switch volume based prepaid packet data service, with tariff switch trigger controlled at the Home AAA/PPS. This capability includes:

10. Charged by volume, different tariff for different time of a day. o Charged by volume, different tariff for different volume consumed, and the PPS SHALL allocate the quota so that the quota does not overlap the two charging rates.

o Charge by volume, different tariff for different QoS. When the Qos is changed, the PPC can report the consumed volumes before the change and the PPS SHALL allocate the new quota for new QoS. Tariff switching with duration based prepaid at the Home AAA/PPS. This capability includes:

1. Charged by duration, different tariff for different time of a day.2. Charged by duration, different tariff for different duration consumed, and the PPS

SHALL allocate the quota so that the quota does not overlap the two charging rates.3. Charged by duration, different tariff for different QoS.4. Account balance updated by the Home AAA/PPS according to the quota consumed

by the user and reported by PPC and the tariff information in the user’s profile.5. The prepaid account SHALL be reconciled at the Home AAA/PPS at inter-ASN

handoff. Wimax Forum Network Architecture - Stage 2 Part 2 - Release 1.1.08.15CSN Requirements for Prepaid

The prepaid capable CSN SHALL support prepaid for packet data sessions identified by IP/NAI. The prepaid capable home CSN SHALL enforce reverse tunneling for all the authorized volume based prepaid packet data sessions. The prepaid capable CSN SHALL send a RADIUS Access-Request message to the Home RADIUS/PPS upon receiving the initial RRQ, re-registration and updated (new CoA) RRQ. The RADIUS Access-Request message SHALL include the additional VSAs: PPAC, STC and a Acct-Multi-Session-Id generated by the CSN. For the initial RRQ, the CSN SHALL include in the RADIUS Access-Request the MIP Lifetime VSA containing the RRQ Lifetime Sub-Type with the value corresponding to the lifetime received from the RRQ message. For the re registration or the updated RRQ (new CoA) for the user, the CSN SHALL include the Session Continue VSA set to TRUE, the Correlation ID VSA with the same Acct-Multi-Session-Id value that is in use and the MIP Lifetime VSA WiMAX Forum Network containing both the RRQ Lifetime 1 Sub-Type (lifetime value received in the RRQ) and the Used Lifetime From 2 Existing Session Sub-Type (value of used lifetime of the existing Mobile IP session) if duration based prepaid is being provided for the session. If the RADIUS Access-Accept message from the Home RADIUS/PPS contains the PPAC VSA indicating that prepaid accounting SHOULD be provided for the user, the RADIUS Access-Accept message SHALL include a PPAQ VSA with an initial quota unless the Acct-Multi-Session-Id sent in the RADIUS Access-Request is the same as an existing prepaid session for which there exists an outstanding quota. If a new MIP Lifetime VSA is included in the RADIUS Access-Accept message from the Home RADIUS/PPS, the prepaid capable CSN SHALL include the value in the MIP RRP back to

the ASN. If both Duration Quota and Tariff Switch Interval are received for the same prepaid packet data session, the prepaid capable CSN SHALL discard the Tariff Switch Interval and SHALL provide prepaid based on the Duration Quota only. If the PTS VSA is received, it SHALL include the Tariffs witch Interval (TSI) Sub-Type, and MAY include the Time Interval after Tariff Switch Update timer (TITSU) Sub-Type. TITSU Sub-Type MAY be included when more than one tariff switch boundary exists, and the user MAY not reach the Volume Threshold before the next tariff switch boundary is crossed. The prepaid capable CSN SHALL monitor both the Volume and the Duration concurrently to support tariff switching. The detailed accounting procedures for various prepaid services (Volume-, Duration- and Tarrif-Switched-base) are specified in the stage 3 of this specification

8.16Mobile Wireless Home Agent in a WiMAX Environment

WiMAX is a fourth-generation (4G) wireless solution based on the IEEE 802.16e standard for delivering advanced broadband wireless services in emerging, high-growth, and developed markets. WiMAX offers significant benefits, including lower deployment costs through the use of an all-data, all-IP architecture, lower spectrum acquisition costs, and a wide range of IP-enabled applications, many of which come from the IP broadband domain. The Cisco Mobile Wireless Home Agent is part of the Core Service Node in the WiMAX End-to-End Reference Model. The WiMAX End-to-End Reference Model consists of the following logical entities: Mobile Subscriber Station (MSS), Access Service Network (ASN), and Connectivity Services Network (CSN). Further ASN decomposition is shown in Figure 4. The Network Reference Model (NRM) is a logical representation of the network architecture. The NRM identifies functional entities, and reference points over which interoperability may be achieved between functional entities.

Description Benefit  

Standards compliance • Complies with 3GPP2 TSG-P TSG-X (TIA/EIA/IS-835)

• Complies with IETF RFCs

• Complies with WiMAX Network Working Group NWG 1.1 RFCs

• Provides interoperability with other standards-compliant components

WiMAX support • PMIP/CMIP extensions for WiMAX

• WiMAX AAA RADIUS Attribute support

• Provides mobility services for WiMAX deployments

• Supports PMIP/CMIP ASN-GW deployments

Mobile IP-to-L2TP support

• Allows a Mobile IP session to negotiate an L2TP to LNS

• Support advanced enterprise deployments

Home agent address • Supports dynamic home agent • Offers load balancing by

assignment address

• Supports static home agent address

distributing mobile clients among pool of home agents

• Provides deployment flexibility

• Facilitates scaling

• Eases provisioning

• Minimizes the impact of network changes

Virtualized home agent (VHA)

• Ability to virtualize home agent for full VPN service type

• VPN transport as VLAN, tunneling (IP-in-IP, GRE, IPsec),

• MPLS/VPN, Frame Relay (DLCI), ATM

• Applicable per domain and/or per user

• Offers support per AAA

• Reduces amount of equipment needed

• Simplifies administration

• Supports multiple VPNs on same home agent

• Allows address overlapping

• Supports separate routing tables

• Helps with IPv4 address scarcity

Home agent redundancy • Provides local and geographical redundancy

• Provides stateful redundancy intra and inter chassis

• Active/standby mode

• Active/active mode

• Avoids service disruption if active home agent fails; the standby home agent takes over with no noticeable impact to user

• Scales without disrupting service

• Enhances availability and reliability

• Maintains accounting integrity during failover

• Facilitates software and hardware upgrades

Mobile IPsec • Protects data flow between home agent and foreign agent

• Offers security services at IP level

• Provides secure tunnel between home agent and

PDSN or foreign agent

• Protects data confidentiality, integrity, and authentication

Resource management • Supports MIP resource revocation (IS.835 C)

• Supports Packet of Disconnect (IS.835 C)

• Frees resources as quickly as possible

• Enables provider to have greater control and to take action toward a specific user

Standard Cisco hardware platforms

• Cisco hardware platforms are proven in some of the largest networks in the world

• Minimizes risk; speeds rollout of network

Cisco IOS® Software Feature Set

• Cisco Home Agent runs with the standard Cisco IOS Software Feature Set, which includes rich IP, security, Mobile IP, and voice and data integration capability

• Helps accelerate time to market with advanced features

• Provides a more competitive solution

Network Address Translation (NAT) traversal

• Supports an intermediate device performing NAT

• Offers increased flexibility of network design and address allocation

• Allows the mobile node to be behind a NAT entity address

Hot-lining • Offers redirection IP and HTTP traffic, profile- or rule-based

• Supports the IS835D hot-lining standard

• New session and active session support

• Dynamically redirects users during a session

• Can be used for monitoring or security purposes

Mobile network support • Provides ability to configure and utilize the Cisco 3200 Series Mobile Access Router to enable mobile subnets

• Supports mobility with mobile subnets

• Offers ability to extend services to vertical markets

such as public safety

Call Admission Control • Monitor load information and manage system availability, for example through dynamic feedback protocol (DFP) to the Home Agent server load balancing function

• Ability to configure maximum bindings per Home Agent

• Enhanced availability and scalability

Simple IP roaming • Support for the LNS capability to enable simple IP roaming scenarios

• Allows the home agent to support access via an L2TP tunnel, enhancing roaming scenarios

Mobile-node address management

• Offers local pool, with priority metrics, thresholds and traps

• Offers Dynamic Host Configuration Protocol (DHCP) with AAA

• Offers on-demand address pools (ODAPs)

• Offers alarms thresholds

• Supports public and private addresses

• Supports NAT/PAT

• Enhances mobile-node address management efficiency and minimizes provisioning

Access control list (ACL) per user

• Enables per-user ACLs • Per-user access list information can be retrieved from AAA server to customize access to network resources and services

QoS per user • Supports use of Cisco IOS MQC

• Can be used to identify, classify, and mark traffic

• Reflects inner to outer ToS/DSCP marking

• Provides ability to police traffic

• Provides ability to retrieve per-user policing and shaping information (from AAA server)

• Helps to enhance user experience for services such as voice over IP (VoIP) and push-to-talk (PTT)

Increased AAA functionality fine-tuning

• Offers AAA group, retry, timer

• Delivers broadcasting capability

• Offers enhanced authentication granularity based on Electronic Serial Number (ESN), Mobile Station Identifier (MSID), and service option

• Offers customization of Mobile IP re-authentication and handoff

• Offers per-domain AAA

• Provides AAA accounting synchronization for session redundancy

• Improves AAA availability (groups and broadcast)

• Minimizes RADIUS messages toward AAA servers

• Helps operator to further authenticate mobile user accounting

• Helps ensure accounting integrity for session redundancy

Policy-based routing (PBR)

• Delivers Cisco IOS Software routing capability plus PBR

• Provides further granularity and control to steer mobile network traffic

Transparent roaming and easy mobility across access technologies

• Mobile IP delivers ubiquitous access

• Supports CCOA and non-CCOA modes

• Supports NAT traversal

• Home agent can be used as an anchor point for CDMA2000, HC-SDMA, GPRS, UMTS, WLAN, WiMAX, and upcoming 4G technologies to help enable transparent mobility services and is a key component in

• Supports mobile network and multicast services

fixed mobile convergence and mobile networks

Advanced billing and service-selection capability

• Offers advanced billing feature

• Offers advanced service-selection feature

• Provides advanced billing capability by looking at transaction and content all the way to Layer 7

• Provides per-user "walled" and "open garden" service selection

Advanced and user-friendly debugging

• Provides conditional debugging based on username and mobile station ID

• Allows multiple simultaneous conditions

• Provides trace functionality

• Delivers GUI-based full packet decoding capability

• Enhances and eases troubleshooting

Domain Name System (DNS)

• Provides IP Reach ability (IS-835 C)

• Provides IP DNS server address (IS.835 D)

• Enhances user experience and services by facilitating user-to-user communication

8.13 mobile wireless specification table

CHAPTER 9

Orthogonal Frequency Division Multiple Access

(OFDM)

Abstract

There is significant interest worldwide in the development of technologies for broadband

cellular wireless (BCW) systems. One of the key technologies which is becoming the defacto

technology for use in BCW systems is the orthogonal frequency division multiple access

(OFDMA) scheme. In this section, we discuss the reasons for the popularity of OFDMA and

outline some of the important concepts which are used in OFDMA as applied to BCW

systems. We shall use the IEEE 802.16 based WiMAX standards for highlighting some of the

significant ideas in the practical use of OFDMA systems.

9.1. Introduction

The orthogonal frequency division multiple access (OFDMA) based systems are being

adopted for use in different flavors of BCW systems The IEEE 802.16d and 802.16e standards

which are popularly known by the industry forum name WiMAX are being considered for

BCW systems and are the first standards to use the OFDMA technique.

One of the challenges in wireless systems is the severe frequency selective fading (FSF)

caused due to the multipath channel between the transmitter and the receiver. The signal

bandwidth in BCW systems typically exceeds the coherence bandwidth of the multipath

channel. Consequently, FSF results and this leads to intersymbol interference (ISI) which is

usually dealt with by physical (PHY) layer solutions like orthogonal frequency division

multiplexing (OFDM) which can address the problem in an elegant manner. Also, the use of

multiple antennas to enhance spectral efficiency and reliability.

Consequently, a BCW system should take multicellular deployment with tight frequency reuse

into perspective so as to achieve high spectral efficiencies.

Thus, one can summarize the challenges in BCW systems as follows:

Frequency selective fading leading to ISI

Incorporation of multiple antenna techniques to enhance spectral efficiency and

reliability.

Handling multiple users with different service/traffic requirements efficiently.

Multicellular deployment with tight frequency reuse to achieve high spectral

efficiency.

9.2. OFDM Review

The OFDM transmission technique has established itself as an elegant and popular method for

overcoming the FSF in broadband wireless systems .The IEEE 802.11 a/g standards for

wireless local area networks (WLANs) which are popularly known as WiFi have used OFDM

to achieve speeds of the order of 50 Mbps in an indoor multipath environment. The discrete

multitone (DMT) system used in the ADSL modems also uses OFDM to achieve high bit-rates

in the telephone channel. The WiMAX standards have proposed various OFDM based

methods for use in fixed and mobile environments. Various other systems that use OFDM

include powerline communications, digital audio and video broadcasting systems, and

ultrawideband based systems for short range wireless.

Some of the key concepts in OFDM include the use of orthogonal subcarriers for

sending several data symbols in parallel resulting in better spectral efficiencies and simple

equalization methods at the receiver. The samples of the transmitted OFDM signal can be

obtained by performing an IFFT operation on the group of data symbols to be sent on

orthogonal subcarriers. Similarly, the recovery of data symbols from the orthogonal

subcarriers is accomplished using a FFT operation on a block of received samples. Thus, the

IFFT and FFT blocks at the transmitter and at the receiver, respectively, are important

components in an OFDM system.

The time-frequency view of an OFDM signal is shown in fig. 9.1, where the important

parameters like subcarrier spacing and OFDM symbol period are shown.

Fig.9.1 Time-Frequency view of OFDM signal

One can see from the figure that even though the subcarrier signals are overlapping in the time

and frequency domains, there is no mutual interference when the sampling is done at certain

spe/ific points in the frequency domain called as subcarrier positions. This is one of the

important properties of an OFDM signal and this leads to higher spectral efficiencies as

compared to a frequency division multiplexed (FDM) system. The granularities in the time

and frequency domain are the OFDM symbol period (T os) and the sub-carrier spacing ()f ,

respectively. In addition, a cyclic prefix (CP) is added to the OFDM symbol to protect against

interference between OFDM symbols and against the loss of orthogonality due to the

multipath channel.

For example, in a typical WLAN application where mobility is not an issue, the channel delay

spread and the frequency offset are important factors in the design of the OFDM parameters.

However, in mobile WiMAX systems, the Doppler spread has to also be considered along

with the above mentioned parameters in the design. For WiFi, the subcarrier spacing is about

300 KHz while in mobile WiMAX the is around 11 KHz while the CP duration value is

around 800 nanoseconds for WiFi and is typically about 10 microseconds for WiMAX.

Adaptive modulation and coding (AMC) on the different subcarriers is another feature in

OFDM systems which has been successfully used in the DMT standard and has been

proposed for use in WiMAX and in high speed extensions of WiFi referred to as 802.11n. The

frequency domain variations of the multipath channel are used effectively with AMC so as to

obtain advantages like higher data rates and lesser transmitted power when compared with an

uniformly loaded system.

9.3. OFDM Based Multiple Access

Various multiple access schemes can be combined with OFDM transmission and they include

orthogonal frequency division multiplexing-time division multiple access (OFDM-TDMA),

OFDMA, and multicarrier code division multiple access (MC-CDMA). In OFDM-TDMA,

time-slots in multiples of OFDM symbols are used to separate the transmissions of multiple

users as shown in fig. 9.2.This means that all the used subcarriers are allocated to one of the

users for a finite number of OFDM symbol periods. In WiMAX, one of the allowed

transmission mode uses OFDM-TDMA wherein the base station allocates the time-slots to the

users for the downlink (DL) and uplink (UL) transmissions.

fig.9.2 Time – Frequency view of an OFDM-TDMA Signal

In OFDMA systems, both time and/or frequency resources are used to separate the multiple

user signals. Groups of OFDM symbols and/or groups of subcarriers are the units used to

separate the transmissions to/from multiple users. In fig.9.3, the time- frequency view of a

typical OFDMA signal is shown for a case where there are 3 users. It can be seen from fig. 3

that users’ signals are separated either in the time-domain by using different OFDM symbols

and/or in the subcarrier domain. Thus, both the time and frequency resources are used to

support multiuser transmissions.

fig.9.3 Time – Frequency view of an OFDMA Signal

In MC-CDMA systems, a data symbol is sent on multiple subcarriers by using a spreading

code, which is different for the multiple access users . Multiple user signals overlap in the

time and frequency domain but they can be separated at the receiver by using the knowledge

of the spreading codes. Thus, MC-CDMA can be considered as a combination of OFDM and

CDMA schemes resulting in benefits due to both these approaches. Various other variants of

MC-CDMA systems have also been discussed in the literature .

9.4. Orthogonal Frequency Division Multiple Access

In OFDMA systems, the multiple user signals are separated in the time and/or

frequency domains. Typically, a burst in an OFDMA system will consists of several OFDM

symbols. The subcarriers and the OFDM symbol period are the finest allocation units in the

frequency and time domain, respectively. Hence, multiple users are allocated different slots in

the time and frequency domain, i.e., different groups of subcarriers and/ or OFDM symbols

are used for transmitting the signals to/from multiple users. For instance, we illustrate an

example in fig. 9.4 where in the subcarriers in an OFDM symbol are represented by arrows

and the lines shown at different times represent the different OFDM symbols. We have

considered 3 users and we have shown how resources can be allocated by using the different

subcarriers and OFDM symbols.

fig.9.4 Example allocation of resources to users in an OFDMA system

9.4.1 Subchannels in OFDMA

The allocation in the frequency domain is not addressed at the level of subcarriers.

Typically, subchannels which are the smallest granular units in the allocation are created by

grouping subcarriers in an OFDM symbol in various ways. The formation can be classified

into 2 types; one is the mapping of a contiguous group of subcarriers into a subchannel called

as the adjacent subcarrier method (ASM) and the other is the diversity/permutation based

grouping called as diversity subcarrier method (DSM) wherein the subchannel typically

contains non contiguous subcarriers. An example of the allocation using the two methods is

illustrated in figs.6a and 6b, respectively.

In the ASM method, a subchannel typically contains a group of contiguous subcarriers and it

is expected that the channel frequency responses on the subcarriers in a subchannel will be

strongly correlated. In the DSM, subcarriers from seemingly random positions in the

frequency domain are grouped into a subchannel.

The time granularity for ASM and DSM is in multiples of OFDM symbols; for example, the

same subchannel in two OFDM symbols could be the basic allocation unit. Users are typically

allotted one or more subchannels for one or more OFDM symbols depending on the allocation

and the requirements.We shall see some practical examples and understand the advantages by

considering the WiMAX system.

fig. 9.5. Subchannelization example (a) ASM method (b) DSM method

8.5. Subchannelization in WiMAX

The DSM method and explore an example of a sub channel formation in the WIMAX

systems. In WiMAX, the number of subcarriers is not fixed and we shall consider a system

with a maximum of 2048 subcarriers which typically is used with a 20 MHz deployment. For

spectral roll off reasons, only 1680 subcarriers are used and the edge subcarriers are unused as

shown in fig. 9.6.

fig. 9.6 Typical subcarrier view of an OFDM symbol in WiMAX

The DL PUSC allocation method specified in WiMAX groups 24 randomly

positioned subcarriers (defined in the standard) into a subchannel which enables leveraging of

the frequency diversity. The same subchannel is allocated in 2 consecutive symbols thus

making 48 subcarriers as the basic resource unit in this method. Hence, the user data is

partitioned into 48 symbols for fitting this slot mentioned in WiMAX. The details of the

subchannelization are specified in detail so that all users clearly know the specific subcarriers

that are grouped in a specific subchannel.

9.5.1 Use of frequency Diversity

To show how frequency diversity is used in the PUSC method, let us consider the

positions of the subcarriers constituting a subchannel. We illustrate the steps in the PUSC

subchannel formation in fig. 8 when the total number of subcarriers is 2048 as outlined in the

802.16 standards. The 1680 used subcarriers are split into 120 clusters of 14 contiguous

subcarriers each and these are called as physical clusters. The 120 physical clusters are

rearranged as shown in the second step and logical clusters are formed and numbers are

shown.

fig. 9.7 Subchannel formation in Wi-MAX DL PUSC

A subchannel which consists of 24 subcarriers in this case is formed by picking a subcarrier

from adjacent logical clusters which means that the subcarriers constituting the subchannel

come from different positions in the frequency domain over the entire spectrum used as

outlined in fig. 9.7 leading to frequency diversity in a subchannel.

9.5.2. ASM in WiMAX:

The ASM is optional in wimax and different ways of forming a subchannel are Specified. A

simple modification to the PUSE method that are discussed above Can be used in ASM.

Instead of rearranging the physical clusters into logical clusters, 2 consecutive physical

clusters cam be grouped to form a subchannel. Channel knowledge is essential as transmitter

and feedback mechanism is specified in wimax.for instatance, special slotes are allocated in

uplink part of the frame for the users to feedback to channel information. the channel

information typically Contains the SINR values are measured by the mobile in certain

frequency bands which is used by the BS to perform AMC on the different associated

subchannels. Channels feedback is also used in the DSM. But it is used to infer the average

channel strength in the entire band of operation, i.e., it roughly indicate the distance Of the

mobile from BS. Suitable modulation can be chosen for all the subscribers Use for the

particular user by using this information so as to achieve higher throughputs.

A BS can use different subchannelization methods in a frame by informing the associated

mobiles about the sub channelization procedure followed in a particular duration. For

example, a typical frame starts by using subchannels formed using DBM,however in the latter

part of the frame,ASM and other subchannelization Methods can be used after proper

signaling information is broadcast to the associated users as shown in fig 9.8.

Fig 9.8 : OFDM Frames with multiple zones

9.6. Multicellular Operation in wimax

Typical deployment of wide-area wireless systems uses a cellular approach so that the

spectrum can be used efficiently. Hence, tight frequency reuse will be a major selling point for

a technology which is a candidate for BCW systems. To satisfy this requirement, WiMAX

has specified subchannelization methods which take this challenge into account. In

multicellular OFDMA systems, where tight frequency reuse is used, there is no inherent

protection from the ensuing cochannel interference (CCI).

Let us consider an unit frequency reuse scenario as an example as this is potential deployment

scenario in WiMAX which is enabled by the FUSC method.

fig.9.9. Interference in multicellular operation

Let the desired user be in cell1 and let us consider the UL transmission in that cell. Let us

assume that slow power control is also in effect as this is a standard operation in most cellular

systems. The mobile will use one or more subchannels for transmitting data to the BS in the

cell. At the same time, other mobiles in the neighboring cells could also be transmitting to

their respective BS. Due to unit frequency reuse, there is a potential for severe CCI as some of

the users in the neighboring cells could be reusing the subcarriers used by the desired mobile

in cell 1. However, note that it is likely that all the interferers are not going to be at the same

distance and location from the desired BS receiver as illustrated in fig.9.9. This fact is used in

the subchannelization in the different cells. The subcarriers that constitute a subchannel are

also determined by the cell identification number (CELL_ID) which is different for the cells in

the neighborhood. Thus, the interference seen in the subcarriers of a subchannel in our desired

cell is likely to come from different subchannels in the neighboring cells because of the

difference in the

subchannel definitions in the neighborhood. Thus, it is likely that the interference in a

subchannel is likely to come from different users in the neighborhood and these users are

likely to be in different locations.

This can potentially lead to an interference diversity effect, i.e., the interference powers on the

subcarriers constituting a subchannel can be different as illustrated in fig. 11. Here, 3

subcarriers belonging to subchannel 1 in cell 1 are shown in pink. In cell2, the same

subcarriers are part of different sub channels which are used by different users at different

locations from the BS in cell1. The heights of the arrows indicate the power received on these

subcarriers at BS of cell 1, i.e., it is the of the arrows indicate the power received on these

subcarriers at BS of cell 1, i.e., it is the interference power as seen at the BS. Note that the

difference in heights of the subcarrier arrows could be due to the different locations of the

users that are allocated these subchannels.

fig.9.10 Illustration of interference diversity in multicelluar systems

9.7. Scalable OFDMA

In WIMAX deployments around the globe, the bandwidth of operation can vary from 1.25

MHz to 20 MHZ depending on the spectrum allocation in different countries. This means that

the OFDM parameters like the subcarrier spacing and the OFDM symbol period can vary

between deployments if the same number of subcarriers is used as shown in fig. 9.11.

fig.9.11 Illustration of the subcarrier spacing for different bandwidths

In WiMAX, the number of subcarriers range from 128 to 2048 depending on the bandwidth

leading to the same subcarrier spacing of around 11 KHz.

fig.9.12. Illustration of the subcarrier spacing in SOFDMA

9.8. Multiuser Diversity using OFDMA

One of the advantages of OFDMA over CDMA is the ability to perform scheduling using both

the time and frequency responses of the channel. For instance, consider the frequency

responses of two users at different locations in a cell as shown in fig.15.

fig.9.13. Illustration of multiuser diversity

This diversity across the channels for different users is called multiuser diversity which can

be used advantageously by allocating subchannels which fall in the good portion for the 2

corresponding users leading to advantages like higher rate support. Such an approach is

suitable when combined with the ASM based subchannelization as the channel response on

contiguous subcarriers is highly correlated leading to easier identification and allocation of

good and bad bands for an user. In the extensions to 3G cellular systems like HSDPA and

EVDO, only time based scheduling is used whereas in OFDMA based systems the ability to

also use the frequency responses make it more appealing for the next generation cellular

services which are striving to support higher bit-rates.

Conclusions

We have outlined some of the major challenges for BCW systems and we have

discussed the use of OFDMA systems in that context. The FSF channel and the ISI problem is

tackled by the use of OFDM leading to elegant equalization. The resource requirements of

different services like voice, video, and data is met by forming units of resources called as

subchannels which can be allocated flexibly based on service requirements. Moreover, there

are different ways in which the subchannels can be formed leading to different gains as seen in

the ASM and DSM techniques. Tight frequency reuse is likely to be the norm in BCW

systems and the use of interference diversity in OFDMA can enable such usage. We have

used the WiMAX system as an example for discussing the concepts so that the reader can get

a concrete feeling of the ideas in OFDMA. We have also discussed SOFDMA and multiuser

diversity ideas which are important in future generation of cellular systems.

CHAPTER 10

Fixed WiMAX Installation

10.1 WiMAX Transmitter

WiMAX Transmitter consists of WiMAX Base and WiMAX Antennas.Usually a tower-like structure supports the WiMAX antennas. This is similar in concept to a mobile phone mast which is typically connected to the network using a standard wired, high-speed connection.

WiMAX typically uses a microwave link to establish a connection to the network. A single WiMAX tower can provide coverage to an area up to 8,000 square km.

Fig 10.1: WiMAX Transmitter

10.1.1WiMAX Base

Fig 10.2: Physical dimention of WiMAX Base

Table 10.1: The different ports on the bottom panel.

Port interfaces DescriptionDB 15 IDU/ODU interfaceDB 9 Engineering applicability (Technical

Service only)RJ95 (with cover) For future use

N Type RF connector - relevant when

implementing external antenna

External antenna connection

10.1.2 Power Factor

The device Called SDA is used which is a switch providing the base -98 VDC power supply, and 9/90BaseT interface with the subscriber's PCs/network.

Fig 10.3: Power Device for WiMAX Base

Fig 10.4: Connection between Power Device with WiMAX Base and PC/router/switch

10.1.3 WiMAX Antennas

Fig 10.5: Different antenna types are designed for different applications

WiMAX antennas, just like the antennas for car radio, cell phone, FM radio, or TV, are

designed to optimize performance for a given application. The figure above illustrates the

three main types of antennas used in WiMAX deployments. From top to bottom are an

omni directional, sector and panel antenna each has a specific function

10.1.3.1 Omni directional antenna

Fig 10.6: An omni-directional antenna broadcasts 360 degrees from the base station

Omni directional antennas are used for point-to-multipoint configurations. The main drawback to an omni directional antenna is that its energy is greatly diffused in broadcasting 360 degrees. This limits its range and ultimately signal strength. Omni directional antennas are good for situations where there are a lot of subscribers located very close to the base station. An example of omni directional application is a WiFi hotspot where the range is less than 90 meters and subscribers are concentrated in a small area.

10.1.3.2 Sector antennas

Fig 10.7: Sector antennas are focused on smaller sectors

A sector antenna, by focusing the beam in a more focused area, offers greater range and

throughput with less energy. Many operators will use sector antennas to cover a 360-

degree service area rather than use an omni directional antenna due to the superior performance of sector antennas over an omni directional antenna.

10.1.3.3 Panel antennas

Fig 10.8: Panel antennas are most often used for point-to-point applications

Panel antennas are usually a flat panel of about one foot square. They can also be a configuration where potentially the WiMAX radio is contained in the square antenna enclosure. Such configurations are powered via the Ethernet cable that connects the radio/ antenna combination to the wider network. That power source is known as Power over Ethernet (PoE). This streamlines deployments as there is no need to house the radio in a separate, weatherproof enclosure if outdoors or in a wiring closet if indoors. This configuration can also be very handy for relays.

10.2 WiMAX receiver (or Customer Premises Equipment - CPE):

The technical term for customer premise equipment (CPE) is subscriber station. The generally accepted marketing terms now focus on either “indoor CPE” or “outdoor CPE”.

10.2.1 Outdoor CPE

Fig 10.9: An outdoor CPE device.

mounting brackets for outdoor mounting on roof or side of building Outdoor CPE, very simply put, offers somewhat better performance over indoor CPE given that WiMAX reception is not impeded by walls of concrete or brick, RF blocking glass or steel in the building’s walls. In many cases the subscriber may wish to utilize an outdoor CPE in order to maximize reception via a line of sight connection to the base station not possible with indoor CPE. Outdoor CPE will cost more than indoor CPE due to a number of factors including extra measures necessary to make outdoor CPE weather resistant.

10.2.2Indoor CPE

Fig 10.9: An indoor CPE device.

The most significant advantage of indoor over outdoor CPE is that it is installed by the

subscriber. This frees the service provider from the expense of “truck roll” or installation. In

addition, it can be sold online or in a retail facility thus sparing the service provider a trip to

the customer site. Indoor CPE also allows a certain instant gratification for the subscriber in

that there is no wait time for installation by the service provider. Currently, many telephone

companies require a one month wait between placement of order and installation of T1 or E1

services. In addition, an instant delivery of service is very appealing to the business

subscriber in the event of a network outage by the incumbent service provider.

10.2.3Power Factor

Fig 10.11: Power Device for CPE

The device is an integrated Ethernet and AC/DC power supply adapter that simply plugs into a standard electrical wall outlet (19/290 VAC).

Fig 10.12: Connection between Power Device with WiMAX CPE and PC/router/switch

10.3 Service Types

There are two types of wireless service provided by WiMAX. These are; Line of Sight (LOS) and Non-Line of Sight (NLOS) – both can be seen in Figure 5.12.

10.3.1 Line of Sight (LOS)

A fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The LOS connection carries a higher bandwidth with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At these higher frequencies, there is less interference and lots more bandwidth. This makes them a popular choice for providing a backhaul service.

Fig 10.13: LOS and NLOS

10.3.2 Non Line of Sight (NLOS)

This is comparable to a Wi-Fi service, where a small antenna on a computer communicates to the tower antenna. In this mode, WiMAX uses a lower frequency range of 2GHz to 11GHz (similar to Wi-Fi). Shorter wavelength or lower frequency transmissions are not as easily disrupted by physical obstructions, they are better able to diffract, or bend around obstacles.

Fig 10.19 : NLOS CPE location

In a NLOS link, a signal reaches the receiver through reflections, scattering, and diffractions. The signals arriving at the receiver consists of components from the direct path, multiple reflected. paths, scattered energy, and diffracted propagation paths. These signals have different delay spreads, attenuation, polarizations, and stability relative to the direct path. The multi path phenomena can also cause the polarization of the signal to be changed. Thus using polarization as a means of frequency re-use, as is normally done in LOS deployments can be problematic in NLOS applications. How a radio system uses these multi path signals to an advantage is the key to providing service in NLOS conditions. A product that merely increases power to penetrate obstructions (sometimes called “near line of sight”) is not NLOS technology because this approach still relies on a strong direct path without using energy present in the indirect signals. Both LOS and NLOS coverage conditions are governed by the propagation characteristics of their environment, path loss, and radio link budget.

There are several advantages that make NLOS deployments desirable. For instance, strict planning requirements and antenna height restrictions often do not allow the antenna to be positioned for LOS. For large-scale contiguous cellular deployments, where frequency re-use is critical, lowering the antenna is advantageous to reduce the co channel interference between adjacent cell sites. This often forces the base stations to operate in NLOS conditions. LOS systems cannot reduce antenna heights because doing so would impact the required direct view path from the CPE to the Base Station.

NLOS technology also reduces installation expenses by making under-the-eaves CPE installation a reality and easing the difficulty of locating adequate CPE mounting locations. The technology. also reduces the need for pre installation site surveys and improves the accuracy of NLOS planning tools.

The NLOS technology and the enhanced features in WiMAX make it possible to use indoor customer premise equipment (CPE). This has two main challenges; firstly overcoming the building penetration losses and secondly, covering reasonable distances with the lower transmit powers and antenna gains that are usually associated with indoor CPEs. WiMAX makes this possible, and the NLOS coverage can be further improved by leveraging some of WiMAX’s optional capabilities. This is elaborated more in the following sections.

10.4 Basic Architecture

10.4.1 Point-to-Point (P2P)

Point to Point is used where there are only two points of interest: one sender and one receiver. This is also a scenario for backhaul or the transport from the data source (data centre, central office etc) to the subscriber or for a point for distribution using PMP architecture. As the architecture calls for a highly focused beam between two points, range and throughput of point-to point radios will be higher than that of PMP products. This is an example of a LOS service.

Fig 10.15: PMP & P2P/PTP

10.4.2 Point-to-Multipoint (PMP)

The most typical WiMAX-based architecture includes a base station mounted on a building, which communicates on a Point-to-Multi-Point (PMP) basis with a subscriber station (SS) (or CPE) located in business offices and homes. As seen in Figure 2, PMP is synonymous with distribution. One base station can service hundreds of dissimilar subscribers in terms of bandwidth and services offered.

10.5 WiMAX Spectrum

In worldwide the centimeter spectrum contains a significant and last mile market. IEEE 802.16d known as fixed which no line of sight is supplants DSL and cable access for last mile service becoming the base for the first wave deployment of WiMAX. As technology moving forward IEEE 802.16e added mobility and portability to applications such as

notebooks, laptops and PDAs for spectrum of range below 6GHz. In utilizing of spectrum, licensed and unlicensed spectrums include in deployments.

Fig 10.16: 2 to 6GHz centimeter bands available for Broadband Wireless Access (BWA)

Licensed and Unlicensed Spectrum

Figure 9.19 shows the various bands available for broadband wireless access in the 2 to 6 GHz range. Note that these bands are identified as either licensed or unlicensed. Licensed bands and the bands that are “owned” by carriers or companies that have paid for using the service of these bands. Unlicensed bands are freely available for any experimental or enterprise applications. IEEE 802.11a/b/g based Wi-Fi allocated in unlicensed bands which has proven to be very robust in competing the new technologies within these bands. As compare to millimeter bands channels data rates are limited as band channel spacing is narrowband. Many Wireless Internet Service Providers interested to utilize

unlicensed bands because they are free to use, saving both money and time for local network deployment. Using this unlicensed band reduces costs for the internet subscriber and provides a competitive optionalternative to DSL and cable modem services. On the other hand majorcarriers or companies that have authorities to use licensed spectrum can

market it for business class service and provide the reliability androbustness.

Band Distinctions

3.5GHz Band: In many European and Asian countries the 3.5GHz band is licensed spectrum that is available for Broadband WirelessAccess, but not use in the United States. It is the most heavilyallocated band representing the largest global Broadband WirelessAccess market. It Covers 300MHz of bandwidth which is rangefrom 3.3GHz to 3.6GHz. For large pipeline backhauling in WideArea Network services this band is very useful and it provides agreat flexibility. In this licensed spectrum, major carriers andcompanies will be able to offer competitive internet subscriber feesin market of Wireless technology through the economy and lowerequipment costs that WiMAX broadband wireless access brings.

5GHz U-NII & WRC Bands: The Unlicensed NationalInformationInfrastructure (U-NII) bands have three main frequency bandswhich are as follows, low and mild Unlicensed National InformationInfrastructure bands range from 5150 to 5350, World RadioConference range from 5970 to 5725, and upper UnlicensedNational Information Infrastructure band range from 5725 to 5850.Most WiMAX deployment activities are in the upper UnlicensedNational Information Infrastructure bands range from 5725 to 5850because at that allocated spectrum there are lesser competinginternet subscribers and interferences

WCS: The two Wireless Communication Service band are identical 15MHz slots range from 2305 to 2320MHz and 2395 to 2360MHz respectively. The 25MHz gap between these bands is assigned to the Digital Audio Radio Service. For the successful deployment of these bands we need exceptional spectral efficiency such as offered by very famous modulation technique Orthogonal Frequency Division Multiplexing and RF modulation technique which commonly used by Wi-Fi and WiMAX.

2.9GHz ISM: The frequency in the range of 2.9GHz used by Industrial, Scientific and Medical which is unlicensed and offers roughly 70MHz of bandwidth for broad band wireless access deployment. In future WiMAX technology contains more advanced features which specify interoperable baseband processorrequirements will bring the two services together forcomplementary operation which will deliver wide area mobility to the internet user.

10.6. Frequency Planning and Sectoring

Frequency planning is required to determine a proper frequency-reuse factor and a geographic-reuse pattern. The frequency-reuse factor f is defined as f≤1

Where f=1 means that all cells reuse all the frequencies. Accordingly, f=1/3 implies that a given frequency band is used by only one of every three cells. The reuse of the same frequency channels should be intelligently planned in order to maximize the geographic distance between the co channel base stations. Figure 9.17 shows a hexagonal cellular system model with frequency-reuse factor f=1/7, where cells labeled with the same letter use the same frequency channels. In this model, a cluster is outlined in boldface and consists of seven cells with different frequency channels.

Fig 10.17: Hexagonal cellular system model with frequency-reuse factor f=1/7

A popular technique is to sectorize the cells, which is effective if frequencies are reused in each cell. Using directional antennas instead of an omni directional antenna at the base station can significantly reduced the co channel interference. An illustration of sectoring is shown in Figure 10.17. Although the absolute amount of bandwidth used is three times before (assuming three sector cells), the capacity increase is in fact more than three times. No capacity is lost from sectoring, because each sector can reuse time and code slots, so each sector has the same nominal capacity as an entire cell. Furthermore, the capacity in each sector is higher than that in a no sectored cellular system, because the interference

is reduced by sectoring, since users experience only interference from the sectors at their

frequency. In Figure 9.18, if each sector 1 points in the same direction in each cell, the interference caused by neighboring cells will be dramatically reduced.

Fig 10.18: (a) Three-sector (120 degree) cells and (b) six-sector (60 degree) cells

10.7.1General Considerations

Ability to install one or more antennas—Is the roof adequate to support the antenna(s) or will it require structural reinforcement? Will a tower have to be constructed? Are permits required?

Possibility of future obstructions—Will trees grow high enough to interfere with the signal? Are there plans to erect buildings between the sites that may obstruct the path?

Availability of grounding—Good grounding is important in all areas of the world, but in areas prone to lightning, it is especially critical.

Availability of power—Are redundant power systems available if the area is prone to outages.

Weather-It is important to research any unusual weather conditions that are common to the site location.

10.7.2Path Planning

To get the most value from a wireless system, path planning is essential. In addition to the fact that radio signals dissipate as they travel, many other factors operate on a microwave signal as it moves through space. All of these must be taken into account, because any obstructions in the path will attenuate the signal.

10.7.2.1 GPS(Global Positioning System) machine Handling

From the GPS machine we can find out the client location. We get the longitude and latitude value form the GPS machine .Then putting in to the google earth software. Finally google earth software shows us the respective location. We also collect the air distance between our base and Client location. The Way point show us where our base station is located. When we identified our base station then we observe the sight to clarify the Line of Sight.

Fig 10.19: GPS machine

10.7.2.2 Fresnel Zone

The characteristics of a radio signal cause it to occupy a broad cross-section of space, called the Fresnel Zone, between the antennas. Figure 2-1 shows the area occupied by the strongest radio signal, called the First Fresnel Zone, which surrounds the direct line between the antennas.

Fig 10.20 : The first fresnel zone

Fresnel Zones define the amount of clearance required from obstacles. These zones are composed of concentric ellipsoid areas surrounding the straight-line path between two antennas. Thus, the zone affects objects to the side of the path and those directly in the path.The first Fresnel Zone is the surface containing every point for which the distance from thetransmitter to any reflection point on the surface point and then onto the receiver is one-half wavelength longer than the direct signal path. One method for clearing the Fresnel Zone is by increasing the antenna height.

The first Fresnel Zone radius is calculated by the following equation:

where

H = Height of the First Fresnel Zone (in feet)

D = Distance between the antennas (in miles)

F = Frequency in GHz

Typically, at least 60% clearance of the first Fresnel Zone is considered as LOS. To ensure the ground does not enter into the first Fresnel Zone, both antennas (i.e. at Base Station and subscriber) must be mounted at least 0.6 x r meters above ground level (or clutter level).

Examples, using the formula above,

For a link of 9 km, at 3.5 GHz produces a first Fresnel Zone radius clearance of about 9.3 meters, meaning the antennas should be mounted at a height of at least 5.6 meters (60% of 9.3 meters) above ground level (or clutter level).

10.7.2.3 Earth Bulge

When planning for paths longer than seven miles, the curvature of the earth might become a factor in path planning and require that the antenna be located higher off the ground. The additional antenna height needed can be calculated using the following formula:

Where

H = Height of earth bulge (in feet)

D = Distance between antennas (in miles)

10.7.2.4 Minimum Antenna Height

The minimum antenna height at each end of the link for paths longer than seven miles (for smooth terrain without obstructions) is the height of the First Fresnel Zone plus the additional height required to clear the earth bulge. The formula would be:

Where

H = Height of the antenna (in feet)

D = Distance between antennas (in miles)

F = Frequency in GHz

10.7.2.5 Calculating a Link Budget

A link budget is a rough calculation of all known elements of the link to determine if the signal will have the proper strength when it reaches the other end of the link. To make this calculation, the following information should be available:

• Frequency of the link

• Free space path loss

• Power of the transmitter

• Antenna gain

• Total length of transmission cable and loss per unit length at the specified frequency

• Number of connectors used

• Loss of each connector at the specified frequency

• Path length

10.7.3.1 Free-Space Path Loss

A signal degrades as it moves through space. The longer the path, the more loss it experiences. This free-space path loss is a factor in calculating the link viability. Free-space path loss is easily calculated for miles or kilometers using one of the following formulas:

10.7.3.2 Antenna Gain

Antenna gain is an indicator of how well an antenna focuses RF energy in a preferred direction. Antenna gain is expressed in dBi (the ratio of the power radiated by the antenna in a specific direction to the power radiated in that direction by an isotropic antenna fed by the same transmitter). Antenna manufacturers normally specify the antenna gain for each antenna they manufacture.

10.7.3.3 Cable and Connector Loss

There will always be some loss of signal strength through the cables and connectors used to connect to the antenna. This loss is directly proportional to the length of the cable and generally inversely proportional to the diameter of the cable. Additional loss occurs for each connector used and must be considered in planning.

10.7.3.9 Fade Margin

A fudge factor of the link budget to ensure that the signal will be strong enough come what may.

Because of the variableness of wireless links, it is not uncommon to "pad the budget" much as a project manager may do for "risk factors" in a project. This padding of the budget is needed because the weather does change and trees grow and buildings are built. These factors, and others, can cause the signal to degrade over time. By including a few extra dB of strength in the required link budget, you can provide a link that will endure longer. This extra signal strength actually has a name, and it is fade margin. You do not add to the link budget/SOM dBm value, but instead you take away from the receive sensitivity. For example, you may decide to work off of an absolute receive sensitivity of -80 dBm instead of the -99 dBm supported by the Cisco Aironet card mentioned earlier. This would provide a fade margin of 19 dBm.

10.7.3.5 Receive Signal Strength Calculation

The example below is based on the following assumptions:

Frequency : 3.5 GHz

Length of Path : 15 km or 9.32 mile

Transmitter Power: 29 dBm

Number of Connectors Used : 9 (~ 0.5 dB loss per connector)

Antenna Gain : 15 dBi transmit, 15 dBi receive

Receiver Threshold :–88 dBm

Required Fade Margin 9 dB (minimum)

Antenna Height:

Antenna Height for 60% Fresnal zone clearance:

Here, D=9.32 mile

F=3.5GHz

.So, H=35.32 meter or 115 ft from ground level

it is longer than 7 mile so we have to calculate earth bulge

So , H =9.85 ft

Minimum Antenna height:

So, H =125.85 ft from ground level

Free-Space Path Loss :

Here, F=3.5 Ghz

D=15 km

Lp =Free space path loss in db

So, Lp = 126.8 db

Received Signal:

The received signal can be calculated with the formula:

Received signal = transmitter power – transmitter cable and connector loss + transmitter antenna gain - free space path loss + receiver antenna gain – receiver cable and connector loss

So, Received signal= 29dBm – 2 dB + 15 dB – 126.8 dB + 15 dB – 2 dB = –76.8 dBm

The following formulas can be used to determine if the fade margin meets the requirement:

Fade margin = received signal – receiver threshold

So, Fade Margin = -76.8-(-88.0)

= 11.2 dBm

Our required Fade Margin is 9 dBm .If the Fade Margin is less than 9dBm then the received signal is not acceptable.Here the Fade Margin is greater than 9dBm. So, The Received signal is acceptable.

10.7.3.6 Site Survey Report Form

Site survey report form probably just like this-

1. Client Name2. Client Location (GPS Value)3. Base name9. Base Sector Name 5. Distance from Base6. Frequency7. Minimum Antenna Height8. Required Receive Signal Strength 9. Have sufficient Fade Margin

WiMAX Modem Management Software

10.8.1Features in the Software

Fig 9.18 : Features in the software

10.8.2 IP Settings

Fig 9.19 : IP Settings

10.8.3 Channel Table Settings

We have to select our required channel Bandwidth which is 3.5 MHz .Then submits to the next page.

Fig 10.20 : Channel Table Settings

Fig 10.21: Select desired Sector frequency

Then we have to select our desired sector frequency. Then the next page will show the uplink and Downlink frequency.

Fig 10.22: Show the Uplink and Downlink Frequency

10.8.5 Selecting Base Station ID

Fig 10.23: Select Base Station ID

If two base stations use same frequency in their respective sectors, we can select the base station ID in the CPE

10.8.6 Transmit Power

Fig 10.29 : Select Transmit Power

In the Transmit Power page we can select the maximum transmit power.

10.8.6 Signal Parameters

Fig 10.25: Showing Signal Parameters

In the signal parameters page we can see the Downlink-Uplink frequency, Transmit power,

SNR, Received signal strength and Modulation.

10.8.7 Performance Monitor

Fig 10.26: Showing SNR and RSSI value in the graph

CHAPTER 11

FIXED WiMAX INSTALLATION IN DHAKA

METROPOLITAN AREA

11.1 Installation Consideration

We have done a Study work which is setting up fixed WiMAX installation in Dhaka

Metropolitan Area. We maintain the following consideration,

Used frequency: 3.11 GHz

Number of Base Stations: 3

Sector in each base station: 3 ( Each sector cover 120 degree)

Name Of the Base Stations :

1. Pirozali Base Station

2. Zia International Base Station

3. Narayangonj base Station

Client Information:

1. Client B (Located in Gazipur)

2. Client C (Located in Motijheel)

11.2 Base stations

Fig 11.1: Pirozali Base Station

Fig 11.2: Zia International Base Station

Fig 11.3: Narayangonj Base Station

11.2.1 Theoretically Three Base Stations

Fig 11.4 : Theoretically Three Base Stations

11.2.2 Practically Three base Stations

Fig 11.11 : Practically three base Station

Fig 11.6 : Clear view of Practically Three Base Stations

It might seems to be a problem because three base stations coverage area are overlapping

with each other. Here Base 1, Sector 2 use frequency F2 and Base 2 Sector 2 also use

frequency F2. But actually that is not a problem. Because we can fixed the sector id in each

CPE by using WiMAX Modem Management Software.

11.3 Installation for Client B:11.3.1 Site Survey Report

1. Client Name Client B

2. Client Location (GPS Value) Latitude: 23°47'13.84"N

Longitude: 90°23'113.02"E

3. Base name Pirozali

4. Base Sector Name 3

11. Distance from Base 111 km

6. Frequency 3.11 GHz

7. Minimum Antenna Height 1211.811 ft from ground level

Approximately 130 ft

8. Required Receive Signal Strength -76.8 dBm

9. Have sufficient Fade Margin (Yes) Fade Margin= -76.8-(-88.0)

= 11.2 dBm

Fig 11.7: Distance Between PIROZALI Base Station to Client B (Uttora)

Fig 11.8: Close view (Client B)

11.3.2 Signal Parameters From Software

Fig 11.9 : Showing signal Parameters from software

11.3.3 Performance Monitor from Software

Fig 11.10: Showing Performance Characteristics from software

11.3.4 Case Study

From this installation we observe that theoretical Receive signal strength is -76.8 dBm and

practically from the software we have -72.2 dBm. Actually the value is fluctuating. We see in

the performance monitor graph that the RSSI value in between -77dBm to 611 dBm. Here

fade margin is 11.2 dBm which is greater than our required fade margin(10 dBm). So, we can

say that it is a good link.

Installation for Client C:

11.3.3 Site Survey Report

1. Client Name Client C

2. Client Location (GPS Value) Latitude: 23°117'19.74"N

Longitude: 90°26'23.32"E

3. Base name Pirozali

4. Base Sector Name 3

11. Distance from Base 10 km or 6.11 mile

6. Frequency 3.11 GHz

7. Minimum Antenna Height 911 ft from ground level (No Earth

Bulge)

Approximately 100 ft

8. Required Receive Signal Strength -64.118 dBm

9. Have sufficient Fade Margin (Yes) Fade Margin= -64.118-(-88.0)

= 23..42 dBm

Fig 11.11: Distance between Narayangonj Base Station to Client C (Motijheel)

Fig 11.12: Close view (Client C)

11.4.2 Signal Parameters From Software

Fig 11.13 : Showing signal Parameters from software

Fig 11.14: Showing Performance Characteristics from software

Case Study

Here we see that the client location is near from Zia International base station but we can’t

select Zia International Base station as Base because there is no line of sight. From

Narayangonj Base station distance is 10 km but there is a clear line of sight and for this here

we have good receive signal.. From this installation we observe that theoretical Receive

signal strength is -64.118 dBm and practically from the software we have -64.8 dBm. Here

fade margin is 23.42 dBm). So, we can say that it is an excellent Link.