Tutorial on OFDMA

January 2005

Doc.: IEEE802.22-05-0005r0

Tutorial on Multi Access OFDM (OFDMA) TechnologyIEEE P802.22 Wireless RANs Authors: Name CompanyEli Sofer Runcom Technologies Yossi Segal Runcom Technologies

Date: 2005-01-04 Phone [email protected] [email protected]

Address

2 Hachoma St., 75655 +972 3 9528440 Rishon Lezion, Israel 2, achoma St. 75655 +972 3 952 8440 Rishon Lezion, Israel

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Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

AbstractThe contribution presents a tutorial on Multi Access OFDM (OFDMA) technology which has been endorsed in leading standards such as- ETSI DVB-RCT and IEEE802.16a,d and 16e. Essential parameters of UpLink and DownLink and simulation results are presented. System capabilities and advantages are also discussed. The tutorial could offer an insight and understanding of OFDMA technology to be considered as a candidate for WRAN system

Submission Runcom Technologies Ltd.

Slide 2 2

Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Tutorial on Multi Access OFDM (OFDMA) TechnologyEli Sofer Runcom Technologies Ltd

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Contents OFDMA System Architecture Illustrated Example OFDMA System Properties Coverage and Capacity

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

OFDMA System Architecture

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Duplexing TechniqueFDD/TDD

Multiple Access MethodTDMA/OFDMAOFDM Symbols allocated by TDMA Sub-Carriers within an OFDM Symbol allocated by OFDMA

DiversityFrequency, Time, Code (CPE and BS), Space Time Coding, Antenna ArraySubmission Runcom Technologies Ltd. Slide 6 6 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Duplexing - PrinciplesFDD (Frequency Division Duplexing ) Uses One Frequency for the DownLink, and a Second Frequency for the UpLink. TDD (time Division Duplexing) Uses the same frequency for the Downlink and the Uplink. In any configuration the access method is OFDMA/TDMA .DownLink UpLink

FDDF1 - Frequency band F2 - Frequency band

DownLink

UpLink

TDDF1 - Frequency band F1 - Frequency band

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

OFDMA-TDMA PrinciplesUsing OFDMA/TDMA, Sub Channels are allocated in the Frequency Domain, and OFDM Symbols allocated in the Time Domain.t

TDMA

m

TDMA\OFDMA

NSubmission Runcom Technologies Ltd. Slide 8 8 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

DownLink OFDMA Symbol

Symbol Pilots

Sub-Channel Data Carriers

Total Frequency BandGuard Band Guard Band

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

DownLink Specification Burst Structure is defined from one Sub-channel in the Frequency domain and n OFDMA time symbols in the time domain, each burst consists of N data modulated carriers. Adaptive Modulation and Coding per Sub-Channel in the Down-Link Forward APC controlling (+6dB) (-6dB) digital gain on the transmitted Sub-Channel Supporting optional Space Time Coding employing Alamouti STC. Supporting optional Adaptive Array.Submission Runcom Technologies Ltd. Slide 10 10 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Example- DownLink Specification FFT size : 2048 Guard Intervals : , 1/8, 1/16, 1/32 Coding Mandatory: concatenated RS GF(256) and Convolutional coding (k=7,G1=171,G2=133, keeping overall coding rate to = , Coding Optional: Convolutional Turbo Code (CTC), Turbo Product Code (TPC) with coding rates close to = , QPSK, 16QAM, 64QAM modulation Modulo 4, Pilot based Symbol Structure. 32 Sub-Channels of 48 data carriers eachSubmission Runcom Technologies Ltd. Slide 11 11 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Downlink Pilot and Data Carriers Allocation Schemecarrier index symbol index n

L=0 0 12 24 N used -1

n+1

L=2 0 6 18 30 N used -1

n+2

L=1 0 3 15 27 N used -1

n+3

L=3 0 9 21 N used -1

n+4 time

L=0 0 12 Variable Location Pilot 24 N used -1 Fixed-location Pilot Data

Allocation Key:

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

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Space Time CodingIFFT Subcarrier modulation IFFT input packing Tx diversity encoder IFFT Filter DAC RF Filter DAC RF Tx

Rx

RF

DAC

Filter

FFT

Diversity Combiner

Subchannel demod.

LogLikelihood ratios

Decoder

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

UpLink OFDMA SymbolPilots Carriers Sub-Channel #1 Data Carriers Sub-Channel #1 Pilots Carriers Sub-Channel #1 Data Carriers Sub-Channel #x

Total Frequency BandGuard Band Guard Band

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Example of UpLink Specification Burst Structure is defined from one Sub-channel in the Frequency domain and 3 OFDMA time symbols in the time domain, each burst consists of 144 data modulated carriers. Adaptive Modulation and Coding per User in the UpLink User Can be allocated 1 up to 32 Sub-Channels 2 Sub-Channels are used as the Ranging Sub-Channels for User Ranging and fast Band-Width Request.Submission Runcom Technologies Ltd. Slide 15 15 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Example of UpLink Specification FFT size : 2048 Guard Intervals : , 1/8, 1/16, 1/32 Coding Mandatory: concatenated RS GF(256) and Convolutional coding (k=7,G1=171,G2=133, keeping overall coding rate to = , Coding Optional: Convolutional Turbo Code (CTC), Turbo Product Code (TPC) with coding rates close to = , QPSK, 16QAM, 64QAM modulation Modulo 13, Pilot based Sub-Channel Structure. 32 Sub-Channels of 53 carriers each, 5 carriers used as pilots, 48 carriers used for dataSubmission Runcom Technologies Ltd. Slide 16 16 Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Example for UpLink Sub-Channel Pilot and Data Carriers Allocation Schemefrequency symbol index n L=0 0 n+1 L=2 0 2 n+2 L=4 0 4 17 26 30 44 52 15 26 28 42 52 13 26 27 40 52

n+11

L=9 0 9 22 26 36 49 52

n+12

L=11 0 11 24 26 38 51 52

n+13 time

L=0 0 13 26 27 40 52

Allocation Key:

Variable Location Pilot

Fixed-location Pilot

Data

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Using Special Permutations for carrier allocation

All usable carriers are divided into 32 carrier groups named basic group, each main group contains 53 basic groups.block 1 1 2 3 30 31 32

Frequency band1each group contains 53 carriers

2 3

Submission Runcom Technologies Ltd.

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Eli Sofer, Runcom

January 2005

Doc.: IEEE802.22-05-0005r0

Using Special Permutations for carrier allocation Carriers are allocated by