March 2005
doc.: IEEE 802.11-05/0146r1
Advanced Coding Comparison
Marie-Helene Hamon, John Benko
Claude Berrou
Jacky Tousch
Brian Edmonston
Submission
France Telecom
ENST Bretagne
TurboConcept
iCoding
Slide 1
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Outline
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Coding proposals in TGn
Advanced FEC Code Requirements for TGn
Comparing Codes
LDPCC vs. Turbo Codes
Facts & Recommendations
Submission
Slide 2
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Coding Proposals in TGn
Partial (13):
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Nokia
Infocomm Research
ST Micro
Nortel
Panasonic
Hughes
Inprocomm
Sharp
Philips
Trellisware
France Telecom
Motorola
Wwise
LDPC
LDPC
LDPC
LDPC
LDPC
LDPC
LDPC
7/8 CC
Concatenated RS
Hybrid LDPC/TurboCode
Turbo Code
Turbo Code
Turbo Code
TGnSync
Wwise
MitMot
Qualcomm
LDPC
LDPC
Turbo Code
None
(Historical)
Full:
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Submission
Optional
Optional
Optional
Slide 3
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Advanced FEC Code Requirements
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Performance
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Much better than 802.11a CC
Must have good performance for all blocksizes (small as well as large)
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Small blocksize example: VoIP packets (as small as 50 bytes)
Large blocksize example: Streaming HD-Video
Latency
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Low, < 6 us
Good performance with a small number of iterations
Implementation
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Submission
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
Slide 4
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Complexity Comparison
Chip Area
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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
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Number of Iterations
Degree of Parallelism
Clock Frequency used (typical Fclk=200 MHz)
Code
Turbo
Code*
Max Encoded
Block Size
Fclk
2048 bits
duo-binary
*Estimates from [4]
+Estimates from [1]
P
Nit
Total
Memory
Decoded
Rate(Max)
200
8
5
59 kbits
320 Mbps
4.8 ms
1.4 mm2
200
12
5
68 kbits
480 Mbps
3.2 ms
2.0 mm2
200
12
8
68 kbits
200 Mbps
5.12 ms
2.0 mm2
MHz
Max
Area
Latency (.13 mm)
Wwise
LDPC+
1944 bits
240
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12
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300 Mbps
6.0 ms
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Sync
LDPC
1728 bits
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Submission
Slide 5
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
ST-Micro (Wwise)* LDPCC vs. TC
• SISO AWGN
• BPSK+
• N=1744 bits
TC v. LDPC (ST-Micro), AWGN, R=1/2, BPSK, 972 info bits
1
LDPC 972b 12i
TC 976b 4i
TC 976b 6i
0.1
•Wwise LDPCC
TC 960b 8i
FER
-972 bits (121.5 bytes)
12i
=> 600kGates, 6 us
0.01
•Duo-Binary TC
-976 bits (122 bytes)
8i, P=12 => 2.0 mm2, 5.12 us
0.001
* 5 bit quant
* max-Log MAP
•TGnSync LDPCC
-Equivalent not found
TC
0.0001
1.4
1.6
1.8
2
Eb/N0
2.2
2.4
2.6
*Wwise Results from Berlin presentation [1]
+BPSK, R=1/2 proposed as optional mode in Wwise
Submission
Slide 6
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Wwise LDPCC*, TC and CC
2x2 SDM, AWGN
64-QAM, R=3/4
Gains over CC @ 10-2 PER
•TC
: ~3.2 dB
(8 iterations)
•LDPCC: ~2.4 dB
(12 iterations)
TC
LDPCC
CC
*Wwise Results taken from [2]
Submission
Slide 7
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
LDPCC from .16e*
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
TC
TC
LDPCC
•N=576 : 0.3 dB
(increase with smaller block size)
LDPCC
*LDPCC here [3] is slightly different
from what is used in TGnSync
Submission
Slide 8
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
LDPCCs vs. Turbo Codes (TCs)
LDPCCs
TCs
History
History
Discovered in 60’s by Gallager
-Implemented only in past few years
-Original Patent expired, but
-Since March 2001, 152 Patents have been
applied for/ granted concerning LDPCCs [5]
Discovered in early 90’s by Berrou, et al.
-Patents exist, but
-Well defined licensing program
Technology
Technology
New Development
-Hot Research Topic at many universities
-No common implementation available
Mature, Stable
-Well established & implemented
-Ongoing Research at select universities
- Turbo Decoders are already available
(Implementation targeted for ASIC, but also FPGA)
Performance*
Improves as the block size increases
Performance*
Good performance for all .11n block sizes
(given latency requirements)
*Generalization
Submission
Slide 9
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
Facts & Recommendations
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Modularity
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Performance of the FEC code is independant of system
Codes proposed can be easily put in WWise and TGnSync
Difficult to compare
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From FRCC, code performance seen only in context of full system
Current two proposed specfications differ
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Wwise nor TGnSych provided simulation results for their code with other proposal
Codes compared in performance should be of similar complexity
Very little complexity results have been seen to this date
Mature code
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Enables pre and 1st production devices to ship with advanced coding options.
Action Item?
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Submission
We need to re-think(create) the advanced coding selection process or we might get
stuck with an advanced coding scheme that is not in the best interest of the 802.11n
Suggestion: Form a separate coding sub-group
Slide 10
John Benko, Marie-Helene Hamon, France Telecom
March 2005
doc.: IEEE 802.11-05/0146r1
References
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[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 errorcorrecting 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.
Submission
Slide 11
John Benko, Marie-Helene Hamon, France Telecom