Sequential decoding

About: Sequential decoding is a research topic. Over the lifetime, 8667 publications have been published within this topic receiving 204271 citations.

On variable length codes for iterative source/channel decoding

Abstract: We focus on a trellis-based decoding technique for variable length codes (VLCs) which does not require any additional side information besides the number of bits in the coded sequence. A bit-level soft-in/soft-out decoder based on this trellis is used as an outer component decoder in an iterative decoding scheme for a serially concatenated source/channel coding system. In contrast to previous approaches using this kind of trellis we do not consider the received sequence as a concatenation of variable length codewords, but as one long code word of a (weak) binary channel code which can be soft-in/soft-out decoded. By evaluating the distance properties of selected variable length codes we show that some codes are more suitable for trellis-based decoding than others. Finally we present simulation results which show the performance of the iterative decoding approach.

Expander-based constructions of efficiently decodable codes

Abstract: We present several novel constructions of codes which share the common thread of using expander (or expander-like) graphs as a component. The expanders enable the design of efficient decoding algorithms that correct a large number of errors through various forms of "voting" procedures. We consider both the notions of unique and list decoding, and in all cases obtain asymptotically good codes which are decodable up to a "maximum" possible radius and either: (a) achieve a similar rate as the previously best known codes but come with significantly faster algorithms, or (b) achieve a rate better than any prior construction with similar error-correction properties. Among our main results are: i) codes of rate /spl Omega/(/spl epsi//sup 2/) over constant-sized alphabet that can be list decoded in quadratic time from (1-/spl epsi/) errors; ii) codes of rate /spl Omega/(/spl epsi/) over constant-sized alphabet that can be uniquely decoded from (1/2-/spl epsi/) errors in near-linear time (this matches AG-codes with much faster algorithms); iii) linear-time encodable and decodable binary codes of positive rate (in fact, rate /spl Omega/(/spl epsi//sup 2/)) that can correct up to (1/4-/spl epsi/) fraction errors.

Low-Complexity Soft-Output Decoding of Polar Codes

Abstract: The state-of-the-art soft-output decoder for polar codes is a message-passing algorithm based on belief propagation, which performs well at the cost of high processing and storage requirements. In this paper, we propose a low-complexity alternative for soft-output decoding of polar codes that offers better performance but with significantly reduced processing and storage requirements. In particular we show that the complexity of the proposed decoder is only 4% of the total complexity of the belief propagation decoder for a rate one-half polar code of dimension 4096 in the dicode channel, while achieving comparable error-rate performance. Furthermore, we show that the proposed decoder requires about 39% of the memory required by the belief propagation decoder for a block length of 32768.

Hardware Architecture for List Successive Cancellation Decoding of Polar Codes

Abstract: This brief presents a hardware architecture and algorithmic improvements for list successive cancellation (SC) decoding of polar codes. More specifically, we show how to completely avoid copying of the likelihoods, which is algorithmically the most cumbersome part of list SC decoding. The hardware architecture was synthesized for a blocklength of N = 1024 bits and list sizes L = 2, 4 using a UMC 90 nm VLSI technology. The resulting decoder can achieve a coded throughput of 181 Mb/s at a frequency of 459 MHz.

Non-binary convolutional codes for turbo coding

Abstract: The authors consider the use of non-binary convolutional codes in turbo coding. It is shown that quaternary codes can be advantageous, both from performance and complexity standpoints, but that higher-order codes may not bring further improvement.