Turbo Codes for IEEE 802.11n

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Turbo Codes forIEEE 802.11n
March 2004
Marie-Helene Hamon, Vincent Le Nir, Marilyne
Helard, Franck Lebeugle France Telecom RD,
Rennes, France (contact mhelene.hamon_at_rd.francet
elecom.com) .
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Contents

• TC for 802.11n
• Duo-Binary Turbo Codes
• Simulation assumptions
• Results
• Conclusion

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Turbo Codes Iterative FEC for 802.11n

• Powerful error correcting codes are considered in
  802.11n discussions
• Turbo Codes, and more specifically Duo-Binary
  Turbo Codes 4, the latest generation of
  convolutional turbo codes, have been introduced
  in contribution IEEE 802.11-04/003 1 at the
  last meeting
• The numerous advantages of these Turbo Codes,
  including the large performance gains enabled and
  their high flexibility, have been demonstrated in
  this previous contribution. This presentation
  will focus on the performance of these Turbo
  Codes in 802.11a PHY reference model.

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Duo-Binary Turbo Codes

• Very good performance better than LDPC codes
• - for any code rate
• - for any block size lt10000 bits
• - for any BER gt10-9
• - for any associated modulation
• Highly flexible solution Duo-Binary Turbo Codes
  adjust easily to any code rate and block size,
  resulting in a better granularity

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Simulation assumptions

• Simulation chain based on 802.11a PHY model
• Perfect channel estimation, synchronization and
  front end (SISO configuration)
• Channels
• - AWGN channel
• - BRAN A channel

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Simulation Assumptions

• The turbo code and the 802.11a convolutional code
  both simulated, with packet size 200 bytes, code
  rates ½ and ¾
• Turbo Codes
• - 8-state Duo-Binary Convolutional Turbo Codes
• - Max-Log-MAP decoding, 8 iterations
• Convolutional Code
• - Viterbi decoding algorithm

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Simulation Results AWGN
2 to 2.5 dB gain at PER 1
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Simulation Results BRAN A
1.8 to 2.4 dB gain at PER 1
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Turbo Codes and MIMO

• MIMO techniques employed Space-Time Block Coding
  (2x1) Alamouti scheme
• Channel model uncorrelated Rayleigh fading
  channels

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Simulation results STBC 2x1
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Conclusions

• Turbo Codes, and more specifically Duo-Binary
  Turbo Codes, provide large performance gains in
  802.11a context, as well as combined with MIMO
  techniques
• Their flexibility is an important advantage,
  allowing a finer granularity in block size and
  coding rate (cf 1)
• Incorporated in a complete system, these Turbo
  Codes will represent a significant advantage to
  achieve 802.11n goals.

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References

• 1 IEEE 802.11-04/003, "Turbo Codes for
  802.11n", France Telecom RD, ENST Bretagne,
  iCoding Technology, TurboConcept, January 2004.
• 2 C. Berrou, A. Glavieux, P. Thitimajshima,
  "Near Shannon limit error-correcting coding and
  decoding Turbo Codes", ICC93, vol. 2, pp.
  1064-1070, May 93.
• 3 C. Berrou, "The ten-year-old turbo codes are
  entering into service", IEEE Communications
  Magazine, vol. 41, pp. 110-116, August 03.
• 4 C. Berrou, M. Jezequel, C. Douillard, S.
  Kerouedan, "The advantages of non-binary turbo
  codes", Proc IEEE ITW 2001, pp. 61-63, Sept. 01.
• 5 TS25.212 3rd Generation Partnership
  Project (3GPP) Technical Specification Group
  (TSG) Radio Access Network (RAN) Working
  Group 1 (WG1) "Multiplexing and channel coding
  (FDD)". October 1999.
• 6 EN 301 790 Digital Video Broadcasting
  (DVB) "Interaction channel or satellite
  distribution systems". December 2000.
• 7 EN 301 958 Digital Video Broadcasting (DVB)
  "Specification of interaction channel for digital
  terrestrial TV including multiple access OFDM".
  March 2002.