March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 1

doc.: IEEE 802.11-05/0146r1

Submission

Advanced Coding Comparison

Marie-Helene Hamon, John Benko France TelecomApurva Mody Independant

With Contributions from :Claude Berrou ENST BretagneJacky Tousch TurboConceptBrian Edmonston iCoding

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 2

doc.: IEEE 802.11-05/0146r1

Submission

Outline

• Coding proposals in TGn• Advanced FEC Code Requirements for TGn• Comparing Codes

– Complexity– Performance

• Facts & Recommendations

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 3

doc.: IEEE 802.11-05/0146r1

Submission

Coding Proposals in TGn (Historical)

Partial (13):– Nokia LDPC– Infocomm Research LDPC– ST Micro LDPC– Nortel LDPC– Panasonic LDPC– Hughes LDPC– Inprocomm LDPC– Sharp 7/8 CC– Philips Concatenated RS– Trellisware Hybrid LDPC/TurboCode– France Telecom Turbo Code– Motorola Turbo Code– Wwise Turbo Code

Full:– TGnSync LDPC Optional– Wwise LDPC Optional– MitMot Turbo Code Optional– Qualcomm None

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 4

doc.: IEEE 802.11-05/0146r1

Submission

Advanced FEC Code Requirements

• Performance

– Much better than 802.11a CC– Must have good performance for all possible blocksizes (small and large)

• Small blocksize example: VoIP packets (as small as 50 bytes)• Large blocksize example: Streaming HD-Video

• Latency

– Low, < 6 us– Good performance with a small number of iterations

• Implementation

– Low Cost – small die size (memory and logic)– Mature, 802.11 – Chipsets require fast time to market

Should not be held up due to a FEC without a well-defined implementation

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 5

doc.: IEEE 802.11-05/0146r1

Submission

Complexity ComparisonChip Area

– Number of Gates– Technology used (ex. ASIC 0.13 mm, average density of 222 kgates/mm2)– Degree of Parallelism (relates also to max decoded bit-rate)

Latency < 6 ms– Number of Iterations– Degree of Parallelism– Clock Frequency used (typical Fclk=200 MHz)

Example Comparison Chart

Code Max Encoded

Block Size

Fclk

MHz

P Nit Total Memory

Decoded Rate(Max)

Max Latency

Area (.13 mm)

Wwise LDPC+

1944 bits 240 ? 12 ? 300 Mbps 6.0 s ?

Sync LDPC

1728 bits ? ? ? ? ? ? ?

Turbo Code* duo-binary

2048 bits 200 8 5 59 kbits 320 Mbps 4.8 s 1.4 mm2

200 12 5 68 kbits 480 Mbps 3.2 s 2.0 mm2

200 12 8 68 kbits 200 Mbps 5.12 s 2.0 mm2

*Estimates from [4]+Estimates from [1]

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 6

doc.: IEEE 802.11-05/0146r1

Submission

Performance Comparison

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 7

doc.: IEEE 802.11-05/0146r1

Submission

TC v. LDPC (ST-Micro), AWGN, R=1/2, BPSK, 972 info bits

0.0001

0.001

0.01

0.1

1

1.4 1.6 1.8 2 2.2 2.4 2.6Eb/N0

FE

R

LDPC 972b 12i

TC 976b 4i

TC 976b 6i

TC 960b 8i

* 5 bit quant* max-Log MAP

TC

ST-Micro (Wwise)* LDPCC

• SISO AWGN• BPSK+

• N=1744 bits

•Wwise LDPCC -972 bits (121.5 bytes) 12i => 600kGates, 6 us

•Duo-Binary TC -976 bits (122 bytes) 8i, P=12 => 2.0 mm2, 5.12 us

•TGnSync LDPCC -Equivalent not found

*Wwise Results from Berlin presentation [1]+BPSK, R=1/2 proposed as optional mode in Wwise

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 8

doc.: IEEE 802.11-05/0146r1

Submission

Wwise LDPCC*

2x2 SDM, AWGN64-QAM, R=3/4

Gains over CC @ 10-2 PER

•LDPCC: ~2.4 dB(12 iterations)

•TC : ~3.2 dB (8 iterations)

*Wwise Results taken from [2]

TC LDPCC CC

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 9

doc.: IEEE 802.11-05/0146r1

Submission

LDPCC from .16e*

*LDPCC here [3] is slightly different from what is used in TGnSync

SISO, AWGN, QPSK, R=1/2

LDPCC - 50 iterations (unrealistic)TC - 8 iterations (realistic)

TC Gains over LDPCC@ 10-2 PER

•N=2304: 0.2 dB

•N=576 : 0.3 dB (increase with smaller block size)

TC LDPCC

TC LDPCC

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 10

doc.: IEEE 802.11-05/0146r1

Submission

Facts & Recommendations

• Modularity

– Performance of the FEC code is independant of system – Codes proposed can be easily put into WWise and TGnSync

• Difficult to compare

– From FRCC, code performance seen only in context of full system– Current two proposed specfications differ

• Wwise nor TGnSych provided simulation results for their code with other proposal – Codes compared in performance should be of similar complexity– Very little precise complexity results have been seen to this date

• Mature code

– Enables pre and 1st production devices to ship with advanced coding options.

• Action Item?– Re-thinking (creating) an advanced coding selection process will decrease the

chances of selecting an advanced coding scheme that is not in the best interest of TGn

– Suggestion: Investigate coding options in a separate coding sub-group

March 2005

John Benko, Marie-Helene Hamon, France TelecomSlide 11

doc.: IEEE 802.11-05/0146r1

Submission

References

• [1] IEEE 802.11-04/400r4, " ST Microelectronics LDPCC Partial Proposal for 802.11n CFP”, ST Micro, September 2004.

• [2] IEEE 802.11/04-0877-09-000n, “WWiSE proposal response to functional requirements and comparison criteria.”

• [3] IEEE 802.16e-0/006,  " LDPC Coding for OFDMA PHY", January 2005.• [4] IEEE 802.11-04/1382r1, "Turbo Codes: Complexity Estimates",

TurboConcept France Telecom R&D, November 2004.• [5] http://www.uspto.gov• [6] C. Berrou, A. Glavieux, P. Thitimajshima, "Near Shannon limit error-

correcting coding and decoding: Turbo Codes", ICC93, vol. 2, pp. 1064-1070, May 93.

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

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