lte-wi max

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LTE AND WIMAX

Prof. N P GAJJAR

EC DEPARTMENT

INSTITUTE OF TECHNOLOGY

NIRMA UNIVERSITY

[email protected]

Overview of LTE

History Introduction to LTE LTE specification MIMO and different input output schemes OFDMA and SC-FDMA

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History of Mobile Communication Standards

The 0th generation ( 0G). The first generation (1G) analog systems The second generation (2G) digital systems. The Third generation (3G) systems. The Fourth generation (4G) systems.

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0 G

Mobile radio telephoneTechniques: PTT : Push To Talk MTS: Mobile Telephone Services, through

operator IMTS improved MTS, no operator AMTS – Advanced Mobile Telephone

System.

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1 G

Wireless telephone technology Voice during call was modulated @ 150 MHz

carrier using Analog modulation. Standards

NMT: Nordic Mobile Telephony

AMPS: Advanced Mobile Phone Systems

NTT: Nippon Telegraph and Telephone TACS: Total Access Communication Systems

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2 G

Digital encrypting of all telephone calls Launched “SMS” data services

for mobile

More efficient 2 techniques:

TDMA and CDMA

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2G systems – • GSM • CDMA

2G systems were primarily designed • To support voice

communication• Data transmission

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Multiplexing technologies in 2G

TDM CDMA FDM

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TDMATime division multiple access

Channel access method for shared medium networks

TDMA is a type of Time-division multiplexing, with the special point that instead of having one transmitter connected to one receiver, there are multiple transmitters

GSM,PDC and IDEN

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GSMGlobal System for Mobile communication

Digital, circuit switching with full

duplex voice telephony – 2G Circuit switched data transport Improved Packet data transport via GPRS – 2.5 G Packet data transport with enhanced speed -2.75 G TDMA and FDMA GMSK  Gaussian minimum-shift keying 

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EDGE…the road to 3G Enhanced Data rates for GSM Evolution (EDGE)   Pre-3G radio technology Improved data transmission rates. backward-compatible extension of GSM threefold increase in capacity and performance compared with

an ordinary GSM/GPRS connection. Peak bit-rates of up to 1Mbit/s and typical bit-rates of

400kbit/s can be expected. Evolved EDGE continues in Release 7 of the 3GPP standard

providing reduced latency and more than doubled performance e.g. to complement High-Speed Packet Access (HSPA)

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CDMA Code division multiple access

 Allows several transmitters to send information simultaneously over a single communication channel

CDMA is a form of spread-spectrum signalling, since the modulated coded signal has a much higher data bandwidth than the data being communicated.

Standards:

cdmaOne, cdma 2000 1x ,cdma 2000 3x

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Problem with 1G and 2G

1G Narrow band analogue Network so only voice calls. We can contact within premises of nation , No roaming

2G More clarity to the conversation and can send SMS. GPRS is not available , No packet data transmission. In 2.5G packet data service is available but slow data

rates.

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Way to 3G

The ITU-R initiative on IMT-2000 (international mobile telecommunications 2000) paved the way for evolution to 3G.

Requirements peak data rate of 2 Mb/s and support for vehicular mobility

were published under IMT-2000 initiative. Both GSM and CDMA standards formed their own

separate 3G partnership projects (3GPP and 3GPP2, respectively) to develop IMT-2000 compliant standards based on the CDMA technology.

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Way to 3G (cont.) GSM 3G (3GPP )-

Wideband CDMA(WCDMA) because it uses a larger 5MHz bandwidth.

CDMA ( 3GPP2 )- CDMA2000 and it uses 1.25MHz bandwidth. 5MHz version supporting three 1.25MHz

subcarriers referred to as cdma2000-3x.

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Enhanced 3G system

Problems with 3G 3G standards did not fulfil its promise of high-speed data

transmissions as the data rates supported in practice were much lower than that claimed in the standards.

The 3GPP2 first introduced the HRPD (high rate packet data) system that supported high speed data transmission. HRPD requires a separate 1.25Mhz for data transmission

and no voice service. So it is referred to as cdma-1x EVDO system.

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Enhanced 3G system(cont.)

The 3GPP introduced HSPA (high speed packet access) enhancement to the WCDMA system. A difference relative to HRPD, however, is that both voice

and data can be carried on the same 5MHz carrier in HSPA.

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4G systems...beginning WIMAX –

IEEE 802 LMSC(LAN/MAN Standard Committee) introduced the IEEE 802.16e standard for mobile broadband wireless access.

Enhancement to an earlier IEEE 802.16 standard for fixed broadband wireless access.

Technology - OFDMA (orthogonal frequency division multiple access)

Better data rates and spectral efficiency than that provided by HSPA and HRPD.

Known as WiMAX (worldwide interoperability for microwave access) .

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Development at 3GPP and 3GPP2 side

The introduction of Mobile WiMAX led both 3GPP and 3GPP2 to develop their own version of beyond 3G systems based on the OFDMA technology and network architecture similar to that in Mobile WiMAX.

The beyond 3G system in 3GPP is called evolved universal terrestrial radio access (evolved UTRA) and is also widely referred to as LTE (Long-Term Evolution) while 3GPP2’s version is called UMB (ultra mobile broadband).

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Introduction to LTE

LTE is also known as Long Term Evolution and it is considered a system beyond existing 3G systems.

The goal of LTE – High-data-rate, low-latency and packet-optimized radio

access technology supporting flexible bandwidth deployments.

Because of OFDMA and SC-FDMA access schemes, LTE system supports flexible bandwidth.

In LTE , uplink access is based on SC-FDMA and downlink access is based on OFDMA.

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LTE supports flexible carrier bandwidths, from 1.4MHz up to 20MHz as well as both FDD (Frequency Division Duplex) and TDD (Time Division Duplex).

LTE architecture is referred to as EPS and comprises the E-UTRAN on the access side and EPC via SAE ,on the core network side.

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Basic info of LTE system attributes

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Big Question- Why LTE ?

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LTE advantages

Increased downlink and uplink peak data rates. Scalable channel bandwidths of 1.4, 3, 5, 10,

15, and 20 MHz in both the uplink and the downlink.

Spectral efficiency improvements. Sub-5 ms latency for small internet protocol

(IP) packets. Optimized Performance.

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Downlink and Uplink peak data rates

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Introduction to Input-Output schemes

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SISO – Standard transmission mode. Single transmitter , single receiver.

SIMO – Single transmitter , multiple receiver. It aids received data integrity , where signal to

noise ratio is poor due to multipath fading. MISO –

Multiple transmitter , single receiver. The transmitters send the same underlying user

data, but in different parts of the RF frequency space.

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MIMO (Multiple Input Multiple Output)

Multiple transmitter , multiple receiver. LTE provides multiple access and that is

explained using concept of MIMO. MIMO is also known as spatial multiplexing. MIMO is required to increase high band width

application such as streaming video. Multiple antennas improve capacity.

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OFDMA & SC - FDMA

OFDMA – It is FDM used as a digital multi carrier modulation

method. A large number of closely-spaced orthogonal sub-carriers are used to carry data.

The data is divided into several parallel data channels. Each sub-carrier is modulated with a conventional modulation scheme such as QAM or PSK at a lower rate.

Total data rates similar to single carrier modulation schemes in the same bandwidth.

Due to low symbol rate, guard interval can be provided between symbols and hence ISI can be eliminated.

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SC-FDMA – SC-FDMA can be interpreted as a linearly precoded

OFDMA scheme, in the sense that it has an additional DFT processing preceding the conventional OFDMA processing.

In SC-FDMA, multiple access among users is made possible by assigning different users, different sets of non-overlapping Fourier-coefficients (sub-carriers).

A prominent advantage of SC-FDMA over OFDMA is that its transmit signal has a lower peak-to-average power ratio (PAPR).

Due to low PAPR ,it benefits the mobile terminal in terms of transmit power efficiency.

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Downlink Access

In LTE , OFDMA scheme is used for downlink access.

The basic principle of OFDM is to divide the available spectrum into narrowband parallel channels referred to as subcarriers and transmit information on these parallel channels at a reduced signalling rate.

The name OFDM comes from the fact that the frequency responses of the sub channels are overlapping and orthogonal.

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Reason of using OFDMA scheme

The multi-path interference problem of WCDMA increases for larger bandwidths such as 10MHz – 20MHz required by LTE.

Difficult to employ multiple 5MHz WCDMA carriers to support 10 and 20MHz bandwidths.

Lack of flexible bandwidth support as bandwidths supported can only be multiples of 5MHz and also bandwidths smaller than 5MHz cannot be supported.

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Uplink Access

In LTE , SC-FDMA scheme is used for uplink access.

SC-FDMA enables a lower peak-to-average ratio (PAR) to conserve battery life in mobile devices.

Single-carrier FDMA scheme provides orthogonal access to multiple users simultaneously accessing the system.

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Requirement of SC-FDMA –

Uplink transmissions should be of low peak signal due to the limited transmission power at the user equipment (UE).

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LTE Architecture

Introduction LTE Architecture and Network LTE Radio Interface Architecture and different

parameters MIMO Spatial Multiplexing

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Introduction

Things which we have covered in review-1 Basic Introduction of 1G,2G,2.5G,2.75G,3G and

4G. Introduction of LTE LTE attributes LTE uplink and downlink

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LTE Architecture

The LTE network architecture is designed with the following goals.

Supporting packet-switched

traffic with seamless mobility

Quality of service (QoS)

Minimal latency

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Architecture

LTE encompasses the evolution of: The radio access through the E-UTRAN The non-radio aspects under the term System

Architecture Evolution (SAE) Entire system composed of both E-UTRAN and

SAE is called the Evolved Packet System (EPS)

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Network

The LTE network is comprised of: Core Network (CN), called Evolved Packet Core

(EPC) in SAE Access network (E-UTRAN)

CN is responsible for overall control of UE and establishment of the bearers.

A bearer is an IP packet flow with a defined QoS (Quality of service) between the gateway and the User Terminal (UE).

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Network

The LTE network is comprised of: Core Network (CN), called Evolved Packet Core

(EPC) in SAE Access network (E-UTRAN)

CN is responsible for overall control of UE and establishment of the bearers.

A bearer is an IP packet flow with a defined QoS (Quality of service) between the gateway and the User Terminal (UE).

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LTE Architecture ( parts of architecture )

Main logical nodes in EPC are: PDN Gateway (P-GW) Serving Gateway (S-GW) Mobility Management Entity (MME)

EPC also includes other nodes and functions, such: Home Subscriber Server (HSS) Policy Control and Charging Rules Function (PCRF)

E-UTRAN solely contains the evolved base stations, called eNodeB or eNB

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LTE Architecture

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LTE Architecture

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LTE Architecture ( E-UTRAN)

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Brief Info and functions of diff parts of Architecture

All the network interfaces are based on IP protocols. The eNBs are interconnected by means of an X2

interface and to the MME/GW entity by means of an S1 interface.

The S1 interface supports a many-to-many relationship between MME/GW and eNBs.

The functional split between eNB and MME/GW is shown in following figure,

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Functions of eNB

Radio resource management IP header compression and encryption Selection of MME at UE attachment Routing of user plane data towards S-GW Scheduling and transmission of paging messages and

broadcast information Measurement and measurement reporting

configuration for mobility and scheduling

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Functions of MME

Non-access stratum (NAS) signaling and NAS signaling security

Access stratum (AS) security control Idle state mobility handling EPS bearer control Roaming, authentication Security negotiations. Authorization and P-GW/S-GW selection

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S-GW provides these functions:

Mobility anchor point for inter eNB handovers Termination of user-plane packets for paging reasons Switching of user plane for UE mobility

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PDN gateway (P-GW) functions include:

UE IP address allocation Per-user-based packet filtering Lawful interception

This was all about functions of different components in LTE architecture. Now we will see about LTE Radio Interface and its architecture.

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LTE Radio Interface Architecture

User plane Protocol

Control plane protocol

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Protocol Layers

IP packets are passed through multiple protocol entities: Packet Data Convergence Protocol (PDCP)

IP header compression based on Robust Header Compression(ROHC)

Ciphering and integrity protection of transmitted data Radio Link Control (RLC)

Segmentation/Concatenation Retransmission handling In-sequence delivery to higher layers

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Protocol Layers ( Cont. )

Medium Access Control (MAC) Handles hybrid-ARQ retransmissions Uplink and Downlink scheduling at the eNodeB

Physical Layer (PHY) Coding/Decoding Modulation/Demodulation (OFDM) Multi-antenna mapping Other typical physical layer functions

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Communication Channels

RLC offers services to PDCP in the form of radio bearers MAC offers services to RLC in the form of logical

channels PHY offers services to MAC in the form of transport

channels

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LTE Air Interface Radio Aspects

It includes

• Radio Access Modes• Transmission Bandwidth• Supported Frequency Bands• Peak single user data rates and UE capabilities

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Radio access modes

LTE air interface supports FDD and TDD Another mode half duplex FDD.

Half-duplex FDD allows the sharing of hardware between the uplink and downlink since the uplink and downlink are never used simultaneously.

The LTE air interface also supports the multimedia broadcast and multicast service (MBMS)

Transmission bandwidths

LTE specifications include variable channel bandwidths selectable from 1.4 to 20 MHz, with subcarrier spacing of 15 kHz.

A subcarrier spacing of 7.5 kHz is also possible. Subcarrier spacing is constant regardless of the channel bandwidth.

The smallest amount of resource that can be allocated in the uplink or downlink is called a resource block (RB). An RB is 180 kHz wide and lasts for one 0.5 ms timeslot. Thus involving FDD as well as TDD.

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Supported frequency bands

The LTE specifications inherit all the frequency bands defined for UMTS.

FDD spectrum requires pair bands, one of the uplink and one for the downlink, and TDD requires a single band as uplink and downlink are on the same frequency but time separated. As a result, there are different LTE band allocations for TDD and FDD. In some cases these bands may overlap.

Frequency bands for FDD duplex mode and TDD duplex mode is shown in following figure.

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Peak single user data rates and UE capabilities

The estimated peak data rates feasible in ideal conditions 100 to 326.4 Mbps on the downlink 50 to 86.4 Mbps on the uplink

These rates represent the absolute maximum the system could support and actual peak data rates will be scaled back by the introduction of UE categories. A UE category puts limits on what has to be supported.

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Peak data rates for UE categories

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Mimo spatial multiplexing

MIMO (Multiple Input Multiple Output)

Multiple transmitter , multiple receiver. As we have seen in the attributes of LTE that LTE

provides multiple access and that is explained using concept of MIMO.

MIMO is also known as spatial multiplexing. MIMO is required to increase high band width

application such as streaming video. Multiple antennas improve capacity.

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Physical channels:   These are transmission channels that carry user data and control messages.

Transport channels:   The physical layer transport channels offer information transfer to Medium Access Control (MAC) and higher layers.

Logical channels:   Provide services for the Medium Access Control (MAC) layer within the LTE protocol structure.

LTE channel types

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Downlink:Physical Broadcast Channel (PBCH):   This physical channel carries system information for UEs requiring to access the network.

Physical Control Format Indicator Channel (PCFICH) Physical Downlink Control Channel (PDCCH) :   The main purpose of this

physical channel is to carry mainly scheduling information. Physical Hybrid ARQ Indicator Channel (PHICH) :   As the name implies,

this channel is used to report the Hybrid ARQ status. Physical Downlink Shared Channel (PDSCH) :   This channel is used for

unicast and paging functions. Physical Multicast Channel (PMCH) :   This physical channel carries

system information for multicast purposes. Physical Control Format Indicator Channel (PCFICH) :   This provides

information to enable the UEs to decode the PDSCH.

LTE physical channels

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Uplink:Physical Uplink Control Channel (PUCCH) :   Sends Hybrid ARQ acknowledgement

Physical Uplink Shared Channel (PUSCH) :   This physical channel found on the LTE uplink is the Uplink counterpart of PDSCH

Physical Random Access Channel (PRACH) :   This uplink physical channel is used for random access functions.

LTE physical channels

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Physical layer transport channels offer information transfer to medium access control (MAC) and higher layers.

Downlink:Broadcast Channel (BCH) :   The LTE transport channel maps to Broadcast Control Channel (BCCH)

Downlink Shared Channel (DL-SCH) :   This transport channel is the main channel for downlink data transfer. It is used by many logical channels.

Paging Channel (PCH) :   To convey the PCCH Multicast Channel (MCH) :   This transport channel is used to

transmit MCCH information to set up multicast transmissions.

LTE transport channels

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Uplink: Uplink Shared Channel (UL-SCH) :   This

transport channel is the main channel for uplink data transfer. It is used by many logical channels.

Random Access Channel (RACH) :   This is used for random access requirements.

LTE transport channels

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Control channels:Broadcast Control Channel (BCCH) :   This control channel provides system information to all mobile terminals connected to the eNodeB.

Paging Control Channel (PCCH) :   This control channel is used for paging information when searching a unit on a network.

Common Control Channel (CCCH) :   This channel is used for random access information, e.g. for actions including setting up a connection.

Multicast Control Channel (MCCH) :   This control channel is used for Information needed for multicast reception.

Dedicated Control Channel (DCCH) :   This control channel is used for carrying user-specific control information, e.g. for controlling actions including power control, handover, etc..

LTE logical channels

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Traffic channels:Dedicated Traffic Channel (DTCH) :   This traffic channel is used for the transmission of user data.

Multicast Traffic Channel (MTCH) :   This channel is used for the transmission of multicast data.

LTE logical channels

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References

LTE for 4G Mobile Broadband by Farooq Khan LTE-Advanced Signal Generation and Measurement

Using System Vue Application Note By Jinbiao Xu, Agilent EEsof EDA

En.wikipedia.org Long Term Evolution (LTE) - A Tutorial by Ahmed

Hamza, Network Systems Laboratory, Simon Fraser University

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WIMAX

Introduction of WiMAX Back Ground How WIMAX works ? WIMAX feature Advantages of WIMAX Channel Access Comparison of LTE and WIMAX

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Introduction to WiMAX

Emerging technology for broadband wireless access. Both fixed and mobile broadband wireless Internet access.

Defines deployment of broadband wireless metropolitan area networks.

Promises high data rates and wide coverage at low cost.

Allows accessing broadband Internet even while moving at vehicular speeds of up to 125 km/h.

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IEEE 802.16-2004 and IEEE 802.16e-2005 air-interface standards.

The WiMAX Forum is developing mobile WiMAX system profiles that define the mandatory and optional features of the IEEE standard that are necessary to build a mobile WiMAX compliant air interface which can be certified by the WiMAX Forum.

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• Fixed (IEEE 802.16-2004)• Mobile(IEEE 802.16e-2005)

Types of

WIMAX

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WiMax Forum

It is a non-profit industry body dedicated to promoting the adoption of this technology and ensuring that different vendors’ products will interoperate.

It is doing this through developing conformance and interoperability test plans and certification program.

WiMAX Forum Certified™ means a service provider can buy equipment from more than one company and be confident that everything works together.

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WiMax is well suited to offer both fixed and mobile access

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Background

Channel ( TDM – FDM )

Access network

Internet access (Dial-up, DSL and cable modem, Broadband Wireless Access )

point-to-point (PTP) telecommunications

point-to-multipoint (PMP) telecommunications

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How WiMAX Works?

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WiMAX network consists of WiMAX base station Multiple WiMAX subscriber stations (fixed or

mobile). WiMAX base station is mounted on a tower. WiMAX subscriber station is a WiMAX customer

premise equipment (CPE) that is located inside the house.

WiMAX base station on the tower is physically wired to the Internet service provider's (ISP) network through fibre optic cables.

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WiMAX Features

OFDMA High Data Rates:

Peak downlink (DL) data rates up to 128 Mbps Peak uplink (UL) data rates up to 56 Mbps

Quality of Service (QoS): Fundamental premise of the IEEE 802.16

architecture is QoS.

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Scalability : It utilizes scalable OFDMA (SOFDMA) and has

the capability to operate in scalable bandwidths from 1.25 to 20 MHz to comply with various spectrum allocations worldwide.

Security: Most advanced security features Extensible Authentication Protocol (EAP) based

authentication, Advanced Encryption Standard (AES) based authenticated encryption, and Cipher-based Message Authentication Code (CMAC) and Hashed Message Authentication Code (HMAC) based control message protection schemes.

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Channel Access

Uplink and Downlink Transmissions Duplexing TDD and FDD

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Uplink and Downlink

Transmission from base station to subscriber stations is called downlink transmission.

Transmission from subscriber station to base station is called uplink transmission.

Uplink uses Time Division Multiple Access (TDMA). Downlink uses Time Division Multiplexing (TDM).

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WiMax Evolution Path

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Advantages of WiMAX

WiMAX provides broadband speeds for voice, data, and video applications

WiMAX provides wide coverage, high capacity at low cost

WiMAX enjoys a wide industry support WiMAX being a wireless technology, costs less

because there is no need for service providers to purchase rights-of-way, dig trenches and lay cables.

WiMAX is standards-based. (IEEE)

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WiMAX can be used for fixed and mobile broadband Internet access for data and voice using VoIP (Voice-over-IP) technology.

Because WiMAX is based on wireless technology, and because it is cost-effective, it is easier to extend broadband Internet access to suburban and rural areas. This helps in bringing wireless broadband to the masses and to bridge the digital divide that exists especially in developing and underdeveloped countries.

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WiMax Applications

According to WiMax Forum it supports 5 classes of applications:

1. Multi-player Interactive Gaming.2. VOIP and Video Conference3. Streaming Media4. Web Browsing and Instant Messaging5. Media Content Downloads

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Comparison of LTE-WiMAX

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Comparison of LTE and WiMAX

Both LTE and WiMAX both are considered to be standards for 4G mobile communication.

LTE is the most recent in the line of the GSM broadband network evolvement. 

WiMAX evolved from a Wi-Fi, IP-based background. IEEE standard 802.16.

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Differences b/w LTE-WiMAX

1. Both use orthogonal frequency division multiple access (OFDMA) in the downlink. But WiMax optimizes for maximum channel usage by processing all the information in a wide channel. LTE, on the other hand, organizes the available spectrum into smaller chunks.

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2. LTE uses single-carrier frequency division multiple access (SC-FDMA) for uplink signalling, while WiMax sticks with OFDMA. A major problem with OFDM-based systems is their high peak-to-average power ratios. LTE opted for the SC-FDMA specifically to boost PA efficiency.

3. Although both the IEEE 802.16e standard and the LTE standard support FDD and TDD, WiMax implementations are predominantly TDD. LTE seems to be heading in the FDD direction because it is true full-duplex operation: Adjacent channels are used for uplink and downlink.

3GPP & Mobile WiMAX Timeline

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Mobile WiMAX time to market

advantage

IMT-Advanced

2008 2009 2010 2011 2012

CDMA-Based OFDMA-Based

Mobile WiMAX

Rel 1.0802.16e-2005

Rel 1.5802.16e Rev 2

Rel 2.0802.16m

IP e2e Network

LTE & LTE Advanced

IP e2e Network

3GPP

HSPA+Rel-7 & Rel-8

Ckt Switched Network

HSPARel-6

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Parameter LTE Mobile WiMAX Rel 1.5

Duplex FDD and TDD FDD and TDD

Frequency Band for Performance Analysis

2000 MHz 2500 MHz

Channel BW Up to 20 MHz Up to 20 MHz

Downlink OFDMA OFDMA

Uplink SC-FDMA OFDMA

DL Spectral Efficiency1 1.57 bps/Hz/Sector (2x2) MIMO2

1.59 bps/Hz/Sector (2x2) MIMO

UL Spectral Efficiency1 0.64 bps/Hz/Sector (1x2) SIMO2

0.99 bps/Hz/Sector (1x2) SIMO

Mobility Support Target: Up to 350 km/hr Up to 120 km/hr

Frame Size 1 millisec 5 millisec

HARQ Incremental Redundancy Chase Combining

Link Budget Typically limited by Mobile Device Typically limited by Mobile Device

Advanced Antenna Support

DL: 2x2, 2x4, 4x2, 4x4UL: 1x2, 1x4, 2x2, 2x4

DL: 2x2, 2x4, 4x2, 4x4UL: 1x2, 1x4, 2x2, 2x4

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References

Introduction to WiMax and Broadband Access Technologies By M. Farhad Hussain

WiMAX - An Introduction by N. Srinath (Department of Computer Science and Engineering, Indian Institute of Technology Madras)

WiMAX INTRODUCTION by Paul DeBeasi Introduction to mobile WiMAX Radio Access

Technology by Dr. Sassan Ahmadi (Wireless Standards and Technology, Intel Corporation)

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Thank you….