11 04 0903-00-000n turbo codes partial proposal presentation slides

7/28/2019 11 04 0903-00-000n Turbo Codes Partial Proposal Presentation Slides

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doc.: IEEE 802.11-04/903-00-0000n

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September 2004

France TelecomSlide 1

Partial Proposal:

Turbo Codes

Marie-Helene Hamon, Olivier Seller, John Benko France Telecom

Claude Berrou ENST Bretagne

Jacky Tousch TurboConcept

Brian Edmonston iCoding


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Outline

Part I: Turbo Codes

Part II: Turbo Codes for 802.11n

Why TC for 802.11n?

Flexibility

Performance


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Outline

Part I: Turbo Codes


Why TC for 802.11n?

Flexibility

Performance


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September 2004


Known applications

of convolutional

turbo codes

Application turbo code termination polynomials rates

CCSDS(deep space) binary,16-state tail bits 23, 33, 25, 37 1/6, 1/4, 1/3,1/2

UMTS,

CDMA2000

(3G Mobile)

binary,

8-state

tail bits 13, 15, 17 1/4, 1/3, 1/2

DVB-RCS

(Return Channelover Satellite)

duo-binary,

8-state

circular 15, 13 1/3 up to 6/7

DVB-RCT

(Return Channel

over Terrestrial)

duo-binary,

8-state

circular 15, 13 1/2, 3/4

Inmarsat

(M4)

binary,

16-state

no 23, 35 1/2

Eutelsat

(Skyplex)

duo-binary,

8-state

circular 15, 13 4/5, 6/7

IEEE 802.16

(WiMAX)

duo-binary,

8-state

circular 15, 13 1/2 up to 7/8


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Main progress in turbo coding/decoding since 1993

Max-Log-MAP and Max*-Log-MAP algorithms

Sliding window

Duo-binary turbo codes

Circular (tail-biting) encoding

Permutations

Parallelism

Computation or estimation of Minimum Hamming

distances (MHDs)

Stopping criterion

Bit-interleaved turbo coded modulation

Simplicity

Simplicity

Performance and simplicity

Performance

Performance

Throughput

Maturity

Power consumption

Performance and simplicity


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September 2004


kbinarydata

permutation

Y1

Y2

X

permutation

k/2binarycouples

pol ynom i al s 15, 13 ( or 13, 15)

kbinarydata

permutation

Y1

X

permutation

k/2binarycouples

(a) (b)

The TCs used in practice


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September 2004


The turbo code proposed for all sizes, all coding rates

permutation

(N)N = k/2

couplesof data

co

deword

systematic part

redundancy part

1

2

punctu-ring

Y

A

B

A

B

Y

systematic part

redundancy part+

circular (tail-biting)encoding

Very simple algorithmic permutation:

i =0,, N-1, j = 0, ...N-1

level 1: ifj mod. 2 = 0, let (A,B) = (B,A) (invert the couple)

level 2:

- ifj mod. 4 = 0, thenP= 0;

- ifj mod. 4 = 1, thenP=N/2 +P1;

- ifj mod. 4 = 2, thenP=P2;

- ifj mod. 4 = 3, thenP= N/2 +P3.

i =P0*j +P+1 mod.N

No ROM

Quasi-regular (no routing issue)

Versatility

Inherent parallelism


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September 2004


Decoding

Max-Log-MAP algorithm

Sliding window

FER

5

5

5

5

10-3

10-4

10-1

10-2

Eb/N0 (dB)3 4

Full MAP Max-Log-MAP

Theoretical limit

(sphere packing bound)

Gaussian,

1504 bits,

R = 4/5

+ inherent parallelism, easy connectivity (quasi-regular permutation)


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Decoding complexity

Useful rate: 100 Mbps with 8 iterations

5-bit quantization (data and extrinsic)

Gates

164,000 @ Clock = 100 Mhz

82,000 @ Clock = 200 Mhz

54,000 @ Clock = 400 Mhz

RAM

Data input buffer

+

8.5xkfor extrinsic information

+ 4000 for sliding window

(example: 72,000 bits for 1000-byte block)

No ROM

For 0.18m CMOS

Duo-binary TC decoders are already available from several providers

(iCoding Tech., TurboConcept, ECC, Xilinx, Altera, )


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Outline

Part I: Turbo Codes


Why TC for 802.11n?

Flexibility

Performance


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September 2004


Introduction

Purpose

Show the multiple benefits of TCs for 802.11n standard

Overview of duo-binary TCs

Comparison between TC and .11a Convolutional Code

High Flexibility Complexity

Properties of Turbo Codes (TCs)

Rely on soft iterative decoding to achieve high coding gains

Good performance, near channel capacity for long blocks

Easy adaptation in the standard frame (easy block size adaptation to the MAC layer)

Well controlled hardware development and complexity

TC advantages led to recent adoption in standards


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September 2004


Duo-Binary Turbo Code

s1 s3s2A

B

W

systematic part

redundancy partY

permutation

(k/2)N = k/2 couples

of data

c

o

de

w

o

r

d

systematic part

redundancy part

1

2

puncturing

Y1 or 2W1 or 2

A

B


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September 2004


Duo-Binary Turbo Code

Duo-binary input: Reduction ofLatency & Complexity (compared to UMTS TCs)

Complexity per decoded bit is 35 % lower than binary UMTS TCs.

Better convergence in the iterative decoding process

Circular Recursive Systematic Codes

Constituent codes

No trellis termination overhead!

Original permuter scheme

Larger minimum distance

Better asymptotic performance


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# of Iterations vs. Performance

The number of

iterations canbe adjusted for

better

performance

complexity

trade-off


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September 2004


Simulation Environment

Both Turbo Codes and 802.11a CCs simulated

Simulation chain based on 802.11a PHY model SISO configuration

CC59 and CC67 followed

Simulated Channels: AWGN, models B, D, E No PHY impairments

Packet size of 1000 bytes.

Minimum of 100 packet errors

Assume perfect channel estimation & synchronization

Turbo Code settings: 8-state Duo-Binary Convolutional Turbo Codes

Max-Log-MAP decoding

8 iterations


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Performance: AWGN

3.5-4 dB

gain over

802.11a CC


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September 2004


Performance: model B

~3 dB

gain over

802.11a

CC


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Performance: model D

~3 dB

gain over

802.11a

CC


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September 2004


Performance: model E

~3 dB

gain over

802.11a

CC


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September 2004


Flexibility

All Coding Rates possible (no limitations)

Same encoder/decoder for: any coding rate via simple puncturing adaptation

different block sizes via adjusting permutation parameters

4 parameters are used per block size to define an interleaver

Higher PHY data rates enabled with TCs: High coding gains over 802.11a CC ( =>lower PER)

More efficient transmission modes enabled more often. Combination with higher-order constellations

Better system efficiency ARQ algorithm used less frequently


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September 2004


Conclusions

Mature, stable, well established and implemented

Multiple Patents, but well defined licensing All other advanced FECs also have patents

Complexity: Show 35% decrease in complexity per decoded bit over UMTS TCs

Performance is slightly betterthan UMTS TCs

Significant performance gain over .11a CC: 3.5 - 4 dB on AWGN channel

3 dB on 802.11n channel models


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September 2004


References

[1] IEEE 802.11-04/003, "Turbo Codes for 802.11n", France Telecom R&D, ENSTBretagne, iCoding Technology, TurboConcept, January 2004.

[2] IEEE 802.11-04/243, "Turbo Codes for 802.11n", France Telecom R&D,iCodingTechnology, May 2004.

[3] IEEE 802-04/256, "PCCC Turbo Codes for IEEE 802.11n", IMEC, March 2004.

[4] C. Berrou, A. Glavieux, P. Thitimajshima, "Near Shannon limit error-correctingcoding and decoding: Turbo Codes", ICC93, vol. 2, pp. 1064-1070, May 93.

[5] C. Berrou, "The ten-year-old turbo codes are entering into service", IEEECommunications Magazine, vol. 41, pp. 110-116, August 03.

[6] C. Berrou, M. Jezequel, C. Douillard, S. Kerouedan, "The advantages of non-binaryturbo codes", Proc IEEE ITW 2001, pp. 61-63, Sept. 01.

[7] TS25.212 : 3rd Generation Partnership Project (3GPP) ; Technical SpecificationGroup (TSG) ; Radio Access Network (RAN) ; Working Group 1 (WG1); "Multiplexingand channel coding (FDD)". October 1999.

[8] EN 301 790 : Digital Video Broadcasting (DVB) "Interaction channel or satellitedistribution systems". December 2000.

[9] EN 301 958 : Digital Video Broadcasting (DVB) "Specification of interactionchannel for digital terrestrial TV including multiple access OFDM". March 2002.

11 04 0903-00-000n turbo codes partial proposal presentation slides

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