M.Ing. / In practical transmission or storage systems, the convolutional encoding and Viterbi decoding scheme is widely used to protect the data from substitution errors. Two independent insertion/deletion/substitution (IDS) error correcting designs, working on the convolutional encoder and the Viterbi decoder respectively, are shown in this thesis. The Levenshtein distance has previously been postulated to be a suitable branch comparison metric for the Viterbi algorithm on channels with not only substitution errors, but also insertion/deletion errors. However, to a large extent, this hypothesis has still to be investigated. In the first coding scheme, a modified Viterbi algorithm based on the Levenshtein distance metric is used as the decoding algorithm. Our experiments give evidence that the modified Viterbi algorithm with the Levenshtein distance metric is suitable as an applicable decoding algorithm for IDS channels. In the second coding scheme, a new type of convolutional code called the path-pruned convolutional code is introduced on the encoder side. By periodically deleting branches in a high rate convolutional code trellis diagram to create a specific insertion/deletion error correcting block codeword structure in the encoded sequence, we can obtain an encoding system to protect against insertion, deletion and substitution errors at the same time. Moreover, the path-pruned convolutional code is an ideal code to use for unequal error protection. Therefore, we also present an application of the rate-compatible path-pruned convolutional codes over IDS channels.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:8147 |
| Date | 26 February 2009 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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