1 / 22

Partial Proposal: Turbo Codes

Partial Proposal: Turbo Codes. Marie-Helene Hamon, Olivier Seller, John Benko France Telecom Claude Berrou ENST Bretagne Jacky Tousch TurboConcept Brian Edmonston iCoding. Outline. Part I: Turbo Codes Part II: Turbo Codes for 802.11n Why TC for 802.11n? Flexibility

heba
Télécharger la présentation

Partial Proposal: Turbo Codes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Partial Proposal: Turbo Codes Marie-Helene Hamon, Olivier Seller, John Benko France Telecom Claude Berrou ENST Bretagne Jacky Tousch TurboConcept Brian Edmonston iCoding France Telecom

  2. Outline Part I: Turbo Codes Part II: Turbo Codes for 802.11n • Why TC for 802.11n? • Flexibility • Performance France Telecom

  3. Outline Part I: Turbo Codes Part II: Turbo Codes for 802.11n • Why TC for 802.11n? • Flexibility • Performance France Telecom

  4. 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 Channel over 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 Known applications of convolutional turbo codes France Telecom

  5. 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 France Telecom

  6. The TCs used in practice France Telecom

  7. The turbo code proposed for all sizes, all coding rates Very simple algorithmic permutation: i =0, …, N-1, j = 0, ...N-1 level 1: if j mod. 2 = 0, let (A,B) = (B,A) (invert the couple) level 2: - if j mod. 4 = 0, then P = 0; - if j mod. 4 = 1, then P = N/2 + P1; - if j mod. 4 = 2, then P = P2; - if j mod. 4 = 3, then P = N/2 + P3. i = P0*j + P +1 mod. N • No ROM • Quasi-regular (no routing issue) • Versatility • Inherent parallelism France Telecom

  8. Decoding Max-Log-MAP algorithm Sliding window + inherent parallelism, easy connectivity (quasi-regular permutation) France Telecom

  9. 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 + 8.5xk for extrinsic information + 4000 for sliding window (example: 72,000 bits for 1000-byte block) For 0.18m CMOS No ROM Duo-binary TC decoders are already available from several providers (iCoding Tech., TurboConcept, ECC, Xilinx, Altera, …) France Telecom

  10. Outline Part I: Turbo Codes Part II: Turbo Codes for 802.11n • Why TC for 802.11n? • Flexibility • Performance France Telecom

  11. 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 France Telecom

  12. Duo-Binary Turbo Code France Telecom

  13. Duo-Binary Turbo Code • Duo-binary input: • Reduction of Latency & 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 France Telecom

  14. # of Iterations vs. Performance The number of iterations can be adjusted for better performance – complexity trade-off France Telecom

  15. 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 France Telecom

  16. Performance: AWGN 3.5-4 dB gain over 802.11a CC France Telecom

  17. Performance: model B ~3 dB gain over 802.11a CC France Telecom

  18. Performance: model D ~3 dB gain over 802.11a CC France Telecom

  19. Performance: model E ~3 dB gain over 802.11a CC France Telecom

  20. 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 France Telecom

  21. 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 France Telecom

  22. References • [1] IEEE 802.11-04/003, "Turbo Codes for 802.11n", France Telecom R&D, ENST Bretagne, iCoding Technology, TurboConcept, January 2004. • [2] IEEE 802.11-04/243, "Turbo Codes for 802.11n", France Telecom R&D,iCoding Technology, 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-correcting coding 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", IEEE Communications Magazine, vol. 41, pp. 110-116, August 03. • [6] C. Berrou, M. Jezequel, C. Douillard, S. Kerouedan, "The advantages of non-binary turbo codes", Proc IEEE ITW 2001, pp. 61-63, Sept. 01. • [7] 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. • [8] EN 301 790 : Digital Video Broadcasting (DVB) "Interaction channel or satellite distribution systems". December 2000. • [9] EN 301 958 : Digital Video Broadcasting (DVB) "Specification of interaction channel for digital terrestrial TV including multiple access OFDM". March 2002. France Telecom

More Related