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WiMAX Tutorial

This wimax tutorial covers what is wimax,wimax standards,wimax terminology,WiMAX Frame Structure,WiMAX Network Architecture, wimax Protocol Stack,wimax physical layer,wimax MAC layer,802.16m,fixed wimax versus mobile wimax,wiBro versus mobile wimax, Wimax Base station and subscriber station suppliers.

Introduction

WiMAX is used for providing broadband internet using wireless medium mainly at 2.5GHz,3.5GHz and 5.8GHz radio frequencies. It is also known as 4G technology. It delivers about 4 times fast internet compare to its 3G counterpart. OFDM is behind this increase in speed as it carry multiple carriers, each carrying more than one data bits based on modulation techniques(QPSK,16QAM). This carriers are concisely packed together to save bandwidth.Intel is behind the developement and proliferation of wimax throughout the world. This wimax tutorial covers what is wimax,wimax standards,wimax terminology,wimax physical layer,wimax MAC layer,802.16m,fixed wimax versus mobile wimax,wiBro versus mobile wimax,Wimax Base station and subscriber station suppliers.

WiMAX is referred as one of the metropolitan area network. It replaces DSL technologies for providing wireless internet at about 70Mbps upto the distance of 35 Km. There are two main versions of wimax viz. fixed wimax and mobile wimax. In Fixed wimax terminal or subscriber is fixed to a location and in mobile wimax they can move at various speeds. Fixed wimax is referred as 802.16d or 16d and mobile wimax is referred as 802.16e or 16e.

There are many physical layers as per IEEE 802.16 standard. The mainly used among them are Single carrier,OFDM and OFDMA. Single carrier is used for 10-66 GHz of frequency range while OFDM/OFDMA is used for 2-11GHz frequency band. OFDM is employed in fixed wimax and OFDMA is employed in mobile wimax.

wimax network architecture
Refer WiMAX Network Architecture➤ and WiMAX Network Entry Procedure➤.

•  WirelessMAN-SC PHY:
-Single carrier modulation
-Targeted for 10-66 GHz frequency band
• WirelessMAN-SCa PHY:
-Single carrier modulation
-Frequency bands below 11GHz for NLOS
• WirelessMAN-OFDM PHY:
-OFDM modulation with a FFT size of 256
-Frequency bands below 11GHz for NLOS
-AAS and MIMO (also for OFDM-PHY)
• WirelessMAN-OFDMA PHY:
-OFDM modulation with scalable FFT sizes
-Frequency bands below 11GHz for NLOS
-Hybrid ARQ
-Fast-feedback mechanisms
-Handover support

Fixed WiMAX System Features

Following are the features of Fixed WiMAX System.


Feature Fixed wimax support
IEEE Standard 802.16-2004 OFDM PHY/MAC, 16d
Symbol Parameters Cyclic Prefix (1/4,1/8,1/16,1/32),FFT size(256),
Channel Bandwidth(1.75/2.5/3/3.5/5/5.5/7/10MHz)
Long Preamble for Downlink sub frame and Short Preamble for Uplink Bursts
Frame duration 2.5, 4, 5,8, 10, 12.5, 20 ms
Modulation DL BPSK,DL QPSK, DL 16 QAM, DL 64 QAM,UL BPSK, UL QPSK,UL 16 QAM, UL 64 QAM
Channel Models SUI channel models
Channel coding Randomization, Concatenated RS-CC, Interleaving

Useful Calculations

Sampling Frequency Fs= (n* BW/8000)*8000
if n=144/125 has been chosen,
For BW of 20MHz
Fs=23.04MHz

Sub carrier Spacing Delf=Fs/Nfft
Delf =23.04/256= 90KHz, Sub carrier spacing

Symbol Time without CP , Tb=1/Delf
Tb=11.11µs
Guard Period, Tg ( Tb/4=2.77µs;Tb/8=1.39µs;Tb/16=0.69µs;Tb/32=0.35µs;)

Total Symbol Time , Ts=Tb + Tg;
Ts=11.8 µs , symbol time with CP of Tb/16

Sampling Time , Tb/ Nfft =0.04375µs

Physical Slot(PS) duration =4/Fs , Unit of BW allocation
Hence PS= 4/23.04MHz=0.174µs

Mobile WiMAX System Specifications

Feature Mobile wimax support
IEEE Standard 802.16-2005 OFDMA PHY/MAC,16e
FFT Size 2048/1024/512/128
Sampling Factor If channel bandwidth is a multiple of 1.75MHz then n=8/7 else if channel bandwidth is a multiple of any of 1.25, 1.5,2 or 2.75 MHz then n=28/25 else if not otherwise specified then n=8/7.
Cyclic Prefix 1/8
Frame Size 5 ms
DL Subcarrier allocation PUSC,FUSC,AMC2x3
UL Subcarrier allocation PUSC,AMC2x3
DL Modulation QPSK,16QAM,64QAM
UL Modulation QPSK,16QAM
Convolutional Coding Tail biting/CTC
MAP Type Normal/Compressed
DL MIMO 2-antenna, matrix A, 2-antenna, matrix B vertical encoding
UL MIMO Collaborative SM for two MS with single transmit antenna

Useful Calculations

For FFT size( Nfft ) of1024 and System BW of 10MHz
Sampling Frequency, Fs=n*BW
Fs=28/25*10MHz
Fs=11.2MHz
Subcarrier frequency spacing, Delf=Fs/Nfft,
Delf =11.2/1024=10.9375KHz
Useful symbol time, Tb=1/?f, this is without CP
Tb=91.4285µs
Guard time, Tg=Tb/8 =11.4285 µs.
OFDMA symbol time=Ts=Tb+Tg=102.8571 µs;

STEP By STEP GUIDE on WiMAX OFDM PHY and MAC layer

wimax physical layer transmitter

Refer following links which describes WiMAX Physical layer transmitter step by step.
WiMAX OFDM PHY layer protocol➤   Fixed wimax MAC layer protocol➤

Links to WiMAX MAC Layer resources

REG REQ and REG RSP   SBC REQ and SBC RSP   DSA REQ and DSA RSP   UCD,UIUC,DCD,DIUC   DLMAP and ULMAP   WiMAX Ranging Procedure   WiMAX Bandwidth Request procedure   WiMAX Network Entry Procedure   WiMAX CID vs SFID   WiMAX FCH header format   WiMAX TLV Format basics   WiMAX Timers   WiMAX Network Interface types   WiMAX QoS Classes  

More WiMAX RELATED LINKS

WiMAX-OFDMA PHY   wimax network architecture  WiMAX protocol stack  Fixed wimax versus mobile wimax  what is wimax  wibro versus mobile wimax  WiMAX Frame Structure  WiMAX Terminology  wimax versus lte  wimax tutorial  WiMAX Hardware vendors  WiMAX Base station  WiMAX System on Chip  WiMAX subscriber station  RF circulator for WiMAX  RF isolator for WiMAX  WiMAX MAC IP Core  WiMAX PHY IP Core   wireless channel emulator 


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