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A Reconfigurable TDMP Decoder for Raptor Codes

Abstract

A Raptor code is a concatenation of a fixed rate precode and a Luby-Transform (LT) code that can be used as a rateless error-correcting code over communication channels. By definition, Raptor codes are characterized by irregularity features such as dynamic rate, check-degree variability, and joint coding, which make the design of hardware-efficient decoders a challenging task. In this paper, serial turbo decoding of architecture-aware Raptor codes is mapped into sequential row processing of a regular matrix by using a combination of code enhancements and architectural optimizations. The proposed mapping approach is based on three basic steps: (1) applying systematic permutations on the source matrix of the Raptor code, (2) confining LT random encoding to pseudo-random permutation of messages and periodic selection of row-splitting scenarios, and (3) developing a reconfigurable parallel check-node processor that attains a constant throughput while processing LT- and LDPC-nodes of varying degrees and count. The decoder scheduling is, thus, made simple and uniform across both LDPC and LT decoding. A serial decoder implementing the proposed approach was synthesized in 65 nm, 1.2 V CMOS technology. Hardware simulations show that the decoder, decoding a rate-0.4 code instance, achieves a throughput of 36 Mb/s at SNR of 1.5 dB, dissipates an average power of 27 mW and occupies an area of 0.55 mm2.

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Acknowledgements

We would like to thank Professor Fadi Kurdahi and Mr. Xiaoliang Chen, from the University of California, Irvine, for their vital help in the synthesis of the decoder.

Author information

Correspondence to Mohammad M. Mansour.

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Zeineddine, H., Mansour, M.M. A Reconfigurable TDMP Decoder for Raptor Codes. J Sign Process Syst 69, 293–304 (2012). https://doi.org/10.1007/s11265-012-0680-8

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Keywords

  • Raptor codes
  • Reconfigurable decoder
  • Error-correcting code
  • Decoder architecture