Please use this identifier to cite or link to this item: https://www.um.edu.mt/library/oar/handle/123456789/98676
Title: Variable-length error-correcting codes
Authors: Buttigieg, Victor
Keywords: Error-correcting codes (Information theory)
Algorithms
Decoders (Electronics)
Coding theory
Issue Date: 1995
Citation: Buttigieg, V. (1995). Variable-length error-correcting codes (Doctoral dissertation).
Abstract: Variable-length error-correcting (VLEC) codes are considered for combined source and channel coding. Instantaneous decoding algorithms for VLEC codes treated previously in the literature are found to suffer from loss of synchronisation over the binary symmetric channel, consequently resulting in poor performance. A novel maximum likelihood decoding algorithm, based on a modified form of the Viterbi algorithm, is derived for these codes by considering the spatial memory due to their variable-length nature. This decoding algorithm achieves a large coding gain (from 1 to 3 dB) over the instantaneous algorithms because of its good synchronisation properties. The performance of these codes with maximum likelihood decoding when compared to standard cascaded source and channel coding schemes with similar parameters is found to be slightly better (about 0.5 dB gain). However, the decoding complexity for VLEC codes is greater. This problem is solved by implementing a sequential decoding strategy, which, for almost the same performance, offers a much reduced computational effort( about an order of magnitude less) when the signal-to-noise ratio on the channel is relatively high. The synchronisation performance of VLEC codes with maximum likelihood decoding over channels which admit symbol deletion or insertion errors is also found to be good (synchronisation is recovered within less than two source symbols following an error). Various properties of VLEC codes influencing their performance both with maximum likelihood and sequential decoding are defined and characterised. A union bound on their performance over the binary symmetric channel is derived. Several different constructions for VLEC codes are given, one of which optimised the average codeword length for a given source while attaining the required error-correcting power.
Description: PhD
URI: https://www.um.edu.mt/library/oar/handle/123456789/98676
Appears in Collections:Scholarly Works - FacICTCCE

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