Wireless Networks Part I - Massey University€¦ · Wireless Networks Part I ... • New generations of wireless networking ... • More robust system as Base Station problem only

Wireless Networks Part I

ICT Technical Update Module

Prof. Dr Harsha SirisenaElectrical and Computer EngineeringUniversity of Canterbury

Post Graduate Certificate in Professional Development Slide 2

Outline

• Course Objective and Additional References• Motivation• Some History• Future Wireless Network Technology• Design Challenges • Current Wireless Systems• Emerging Wireless Systems• Spectrum Regulations and Wireless Standards• IEEE 802.11 Family – WLAN• Wireless Routing Protocols


Course Objectives

• Demonstrate understanding of the fundamental problems, tradeoffs, and design issues that arise in wireless networking, as well as identify and critically evaluate wireless network technologies and solution approaches

• Understand the details of several particular protocols, as example implementations of fundamental principles, and digest descriptions of specific protocols, extracting the salient concepts

• Engage in original work and research in the area of wireless networks

After studying this course, you are expected to


Additional References

• Wireless communications : principles and practice ,2nd Edition Theodore S. Rappaport.

• Computer networks 3rd Edition Andrew S. Tanenbaum.• Data and computer communications, 7th Edition William

Stallings.


Motivation- Why wireless networks?

• No cost for installing wires or rewiring- Communications can reach where wiring is infeasible or

costly, e.g., rural areas, mountains, old buildings, battlefield.

- “Auto-magical” instantaneous communications without setup physical connection, e.g., WLAN

- Communication satellites, global coverage, e.g., Iridium system

• Roaming allows flexibility to keep contacted Anywhere and Any time


Motivation (cont.)

• Rapidly growing market trigger the public need for mobility and uninterrupted communications

• Consumers are used to the flexibility and will demand instantaneous, uninterrupted, fast access regardless where and when .

• Consumers and businesses are willing to pay for it• Increasing dependence on telecommunication services for

business and personal reasons


Some Wireless History• Ancient Systems: Smoke Signals, Carrier Pigeons, …

• “The Birth of Radio” - Radio invented in the 1880s by Guglielmo Marconi

• Sophisticated military radio systems were developed during and after the WW2

• 1979 - NTT/Japan deploys first cellular communication system • 1983 - Advanced Mobile Phone System (AMPS) deployed in U.S. in 900 MHz

Band: supports 666 duplex channels• 1989 - Group Special Mobile defines European digital cellular standard, GSM • 1991 - US Digital Cellular phone system introduced • 1993 - IS-95 code-division multiple-access (CDMA) spread- spectrum digital

cellular system deployed in U.S. • 1994 - GSM system deployed in US, relabeled “Global System for mobile

communications”• 1995 - FCC auctions off frequencies in Personal Communications System

(PCS) band at 1.8 GHz for mobile telephony • 1997 - Number of cellular telephone users in U.S. > 50M • 2000 - Third generation cellular system standards… Bluetooth standards..


Generations of Wireless Networking• 1G: deployed in the 1980s was based on analog FM technologies.

• 2G: introduced on market in 1991 with applied digital technologies such as, TDMA,GSM, cdmaOne. 2G offered short messages and low-rate data services for customers.

• “2.5G”: introduced ability to use packet switched (vs. circuit switched) radio connections. For GSM system, this is called General Packet Radio Service (GPRS). GPRS offers users the opportunity to be always online, while only being charged for data transferred.

• 3G: achieves a maximum bit rate of 2 Mbps and offers packet-switched multimedia services (data, video, etc.) as well as voice services. GSM/TDMA operators can evolve towards EDGE or WCDMA with higher and variable bit rates and improved spectrum efficiency. cdmaOne operators can evolve to cdma2000

• 4G: Expected to build upon 3G and evolved 3G systems. A current discussion is a 4G of wireless networks envisaged available in about a decade


Future Trends and Technologies

• Multi-input and Multi-output i.e., multi-antenna systems (MIMO)• Ultra Wideband (UWB)• Software-Defined Radio (SDR)• Ad hoc and Sensor Networks• Fixed (or semi-fixed) Broadband• 4G Cellular… (discussed already)• New generations of wireless networking (terrestrial wireless i.e., cellular or

satellite) will result in higher rate integrated multimedia communications• The complexity of the management of network resources (e.g. bandwidth,

power, capacity) will be significant with increasing generation or evolution.


Design Challenges

• Wireless channels are a difficult and capacity-limited broadcast communications medium

• Traffic patterns, user locations, and network conditions are constantly changing

• Applications are heterogeneous with hard constraints that must be met by the network

• Energy and delay constraints change design principles across all layers of the protocol stack


Multimedia Requirements

Voice VideoDataDelay

Packet LossBER

Data Rate

Traffic

<100ms - <100ms

<1% 0 <1%10-3 10-6 10-6

8-32 Kbps 1-100 Mbps 1-20 MbpsContinuous Bursty Continuous

One-size-fits-all protocols and design do not work well


Current Wireless Systems

• Cellular Systems and its evolution - GSM- GPRS - UMTS

• Satellite System• Bluetooth

Wide Area Cellular Services


The Cellular Principle

• Relies on the concept of concurrency- delivered through channel reuse i.e. reusing channels in different cells

• Total coverage area is divided into cells- only a subset of channels available in each cell

• All channels partitioned into sets- sets assigned to cellsRule: assign the same set to two cells that are sufficient geographically distant so that interference is small

Purpose: increased capacity!


Advantages of Cellular Networks

• More capacity due to spectral reuse• Lower transmission power due to smaller transmitter/receiver

distances• More robust system as Base Station problem only effects the

immediate cell• More predictable propagation environment due to shorter

distances


Disadvantages of Cellular Networks

• Need for more infrastructure• Need for fixed network to connect Base Stations• Some residual interference from co-channel cells• Handover procedure required


Architecture of a GSM Network

SD

Mobile Station

BTSMSC/VLR

SIM MEBSC

Base StationSubsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

+

PSTN

PLMN

Internet


Mobile Station (MS)

Mobile Equipment- Fixed- Portable - International Mobile Equipment Identity (IMEI) number

Subscriber Identity Module (SIM)- Personal Identification Number (PIN)- International Mobile Subscriber Identity (IMSI) number- Enables access to subscribed services- Smart card


Base Transceiver Station - BTS

• Usually referred to as the Base Station• Provides the interface to the network for the

MS• Handles all communications with the MS• Less “intelligent” than analogue equivalent

- cheaper than analogue systems- bypass analogue in less wealthy countries

• “intelligence” now deployed on MS- for example, when to perform a handover

• Transmitting power determines cell size


Base Station Controller - BSC

• Controls Base Stations- up to several hundred depending on

manufacturer• Manages radio channels

- allocation and release• Coordinates Handover• Physical location may vary• Abis interface

- between BSC and BTS


Mobile Switching Centre (MSC)

• Performs all switching/exchange functions• Handles

- Registration- Authentication- location updating

• A GSM network must have at least one MSC• May connect to other networks, e.g., PSTN

- Gateway MSC (GMSC)


Home Location Register (HLR)

Administrative information for all subscribers• IMSI number• actual phone number• permitted supplementary services• current location i.e. which VLR subscriber is currently

registered with• parameters for authentication and ciphering

One HLR per GSM PLMN


Integrating GPRS

SD

Mobile Station

BTSMSC/VLRBSC


GMSC

Network Subsystem

AUCEIR HLR

Other Networks


GGSNSGSN

SIM ME

+

PSTN

PLMN

Internet


GPRS MSTwo Components

- Mobile Terminal (MT)- SIM card

Three Classes of terminal- Class A - simultaneous circuit switched (GSM) and

packet switched (GPRS) traffic- Class B- supports both GSM and GPRS connections

but not both at the same time. One call is suspended for the duration of the other

- Class C - handless both GPRS or GSM but can only be connected to one at the same time.


GPRS NSSTwo new nodes introduced for packet data

• Serving GPRS Support Node (SGSN) : handles all packet data for the appropriate geographic area

- monitors GPRS users- handles security and access control- may be regarded as the packet switched equivalent of

the circuit-switched MSC• Gateway GPRS Support Node (GGSN)

- internetworking functionality- routes incoming data to correct SGSN- translates between different protocols and formats

• Details of data services added to HLR


GPRS Characteristic

• Data capacity increased considerably• Depending on configuration

• @ 14.4 kb/s per channel, 115.2 kb/s achieved• @ 21.4 kb/s per channel, 171.2 kb/s achieved

• BUT up to 8 users per channel!• Minimum set-up time• “always-on” connection• Charging determined by actual data not time


Integrating EDGE

• Minimum changes to the existing network• New Modulation scheme

- 8 phase shift keying (8PSK)- 3 bits of information per signal pulse- data rates increased by a factor of three


EDGE - NSS

• Minimum impact on the core network• SGSN & GGSN practically independent of data rates• Some minor software upgrades


3G - UMTS

SD

Mobile Station

MSC/VLR


GMSC

Network Subsystem

AUCEIR HLR

Other Networks


GGSNSGSN

BTS BSC

NodeB

RNC

RNS

UTRAN

SIM ME

USIMME

+

PSTN

PLMN

Internet


UMTS - MS

User Equipment• Mobile Equipment• UMTS SIM (USIM)• Air interface

• UMTS Terrestrial Radio Access (UTRA)- W-CDMA- TD-CDMA


UMTS BSS

• Radio Network Subsystem• Two new network elements

– Node B• equivalent of a BTS

– Radio Network Controller• supports a number of Node Bs• equivalent of a BSC

• Obviously, UMTS has major implications for the BSS


CDMA BASIC

• CDMA (Code Division Multiple Access) splits calls into fragments and send them over different frequencies simultaneously

• The use of multiple frequencies gives CDMA effective protection against interference and lost calls

• CDMA supports true packet switching and does not use time slots, therefore is more bandwidth efficient than TDMA -- also a more direct path to 3G


Why do carriers want to move to 3G?

• Faster speeds--able to handle more calls• Efficiencies in data handling

- Integration with the Internet technology• More capable, multi-media handsets and devices• Global interoperability and roaming• Advanced services and more profitable revenue

opportunities


Some Urgent 3G Drivers

• Need to increase wireless data revenues and ARPU as voice prices decline

• Staggering investment already made in preparing for 3G upgrades

• Pressure by device makers and governments- 3G License clock ticking in Europe

• Dramatic success stories: - Korea, Japan markets are embracing 3G

• Fear of falling even further behind - Competition from WiFi as the high-speed alternative


3G Systems Overview

3G MigrationSOURCE: CDMA Development Group (CDG)


Mobility Overview• Future mobility will be provided with

higher data rates and Ubiquitous access

- This implies the need for seamless wide area and office coverage

- Future remote access techniques will mirror existing to protect current investments

• Higher data rates and better coverage will be realized using disparate types of Wireless Technologies

- Mobility across disparate networks is a significant change to the paradigm of current mobile networks.

- Mobility is attributed to L2 and L1 abstraction through use of IP (Mobile IP).

Data Rates and Ranges of Wireless Technologies

SOURCE: ITU


Standards Evolution to 3G Worldwide

Japan Europe/Parts of Asia Americas/Parts of Asia

1st Gen TACS NMT/TACS/Other AMPS

2nd Gen PDC GSM TDMA CDMA

3rd Gen EDGE cdma2000W-CDMA/UMTS

Instead of solving the 2G network differences via 3G, we will continue to have W-CDMA and cdma2000 as separate networks. Both will be “optional implementation modes” in one 3G standard specification. Basic 3G phones will support one or the other. “Global phones” will be able to roam from one to the other.

cdma2000


Application Platforms for Cellular Networks

• WAP: discredited in first outing, but still alive and well as a backend mobile server standard

• SMS: proven worldwide but just emerging in US; limited to plain text messaging

• MMS: standard behind the exchange of pictures from camera phones; also for many audio and graphic formats

• iMode: proven in Japan; export still in doubt• J2ME (Java for mobile): large developer following and handset

deployment; confused business models• BREW: CDMA app platform: big in a few areas; clearer business

and distribution model


Examples: Evolution of messaging

Vers

atili

ty o

f Con

tent

and

Use

r Ben

efits

Time

Text

SMS

Text &Graphics

PictureMessaging

Digitalimageinput

MultimediaMessageService

Newcontenttypes

MobileMultimedia

Rich Call

Browsing

Messaging


SMS

SMS=Short Message Service=Current Worldwide “Killer Application”• A basic text messaging service for sending messages up to 160 characters to mobile phones• Runs on separate channel from voice traffic-much cheaper for operators to carry text messages (started out as free service inmany countries)• Overwhelming user uptake in Europe and A/P --billions of messages sent each month; very profitable for carriers


Emerging Systems

• Ad hoc wireless networks• Ultra Wideband Network

Ad hoc Networks


Introduction and Basic Concepts


Ad Hoc Network Definition• In Latin, "ad hoc" literally means " for this purpose only " • An ad-hoc network is a wireless LAN, in which some devices are part

of the network only for the duration of a communication session or while in some close proximity to the rest of the network.

• A "mobile ad hoc network " (MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links forming an arbitrary graph. Routers are free to move randomly and organize themselves arbitrarily; network topology may change rapidly and unpredictably. May operate in a stand-alone fashion, or may be connected to the Internet.

• An ad hoc network can be regarded as a "spontaneous network " : a network that automatically "emerges " when nodes gather together.


Ad Hoc Networks Advantages

• Ease of deployment• Speed of deployment• Decreased dependence on infrastructure


Applications of Ad Hoc Networks


Characteristics and RequirementsAutonomous and spontaneous nature of nodes• Distributed Algorithms to support security, reliability and

consistency of exchanged and stored informationTime-varying network topology (no pre-existing infrastructure or central

administration)• Scalable routing and mobility management techniques to face network

dynamicsFluctuating link capacity and network resources• Enhanced functionalities to improve link layer performance, QoS

network support and end-to-end efficiencyLow-power devices• Energy conserving techniques at all layers


Challenges

• Broadcast nature of the wireless medium- Limited wireless transmission range - Hidden terminal problem- Exposed terminal problem- Capture problem- Intruding terminal problem

• Packet losses due to transmission errors • Mobility-induced route changes • Mobility-induced packet losses • Battery constraints • Potentially frequent network partitions• Ease of snooping on wireless transmissions


Multi Hopping• Data routes may traverse multiple links to reach a

destination• It increases overall network capacity since the spatial

domain could be reused for concurrent but physically separate sessions

• It conserves transmit energy resources ⇒ reduces interference.

Ultra Wideband Networks


What is Ultra WidebandShort pulse waveforms• “Carrier-free”, “baseband”, “impulse”• A few cycles of an RF carrier

Very large fractional bandwidths• Bandwidth inversely proportional to pulse duration• Typically > 20% (FCC 2002 definition)• Low duty cycles resulting in low average energy

densities

Typically produced by “impulse- or step-excited” antennas, filters, etc.

• Not all UWB is non-interfering (Regulatory issues)• Spectrally filtered• Spectrally unfiltered


UWB Bandwidth

FCC ‘report and order Part 15’(Feb,2002) pave the way for commercialization of UWB


Unique UWB PropertiesAdvantages:1.Low-power operation : transceiver circuitry power requirements are low, under noise roof2.Low cost: the complexity of the analogy front-end is drastically reduced due to its intrinsic baseband transmission,. 3.Low probability of detection& jamming: low energy per frequency band and the use of precisely timed patterns4.Ability to penetrate walls in indoor environment: the lower frequencies used5 Higher immunity to multi-path fading effects: increased signal diversity (frequency diversity)6.Availability of precise location information: precise nanosecond pulses for transmission

Disadvantage:1.Long channel acquisition time in the order of milliseconds, compared to microseconds in narrow band system2.Regulatory considerations over such a wide bandwidth will limit the radiated power( mobile service distance)


Major UWB Application Areas

Communications• LPD (Low Probability of Detection)• Wireless Audio, Data & Video Distribution• RF Tagging & IdentificationRadar• Collision/Obstacle Avoidance• Precision Altimetry• Intrusion Detection (“see through wall”)• Ground Penetrating RadarPrecision Geolocation• Asset Tracking• Personnel localization


Spectrum Regulation

• Spectral Allocation in US controlled by FCC (commercial) or OSM (defense)

• FCC auctions spectral blocks for set applications.

• Some spectrum set aside for universal use

• Worldwide spectrum controlled by ITU-R

Regulation can stunt innovation, cause economicdisasters, and delay system rollout


Standards

• Interacting systems require standardization

• Companies want their systems adopted as standard- Alternatively try for de-facto standards

• Standards determined by TIA/CTIA in US- IEEE standards often adopted

• Worldwide standards determined by ITU-T- In Europe, ETSI is equivalent of IEEE


Conclusion

• The wireless vision encompasses many exciting systems and applications

• Technical challenges transcend across all layers of the system design

• Wireless systems today have limited performance and interoperability

• Standards and spectral allocation heavily impact the evolution of wireless technology

Wireless Networks Part I - Massey University€¦ · Wireless Networks Part I ... • New generations of wireless networking ... • More robust system as Base Station problem only

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