In this work, a sequential decoder for convolutional codes over channels that are vulnerable to insertion, deletion, and substitution errors, is described and analyzed. The decoder expands the code trellis by introducing a new channel state variable, called drift state, as proposed by Davey-MacKay. A suitable decoding metric on that trellis for sequential decoding is derived, in a manner that generalizes the original Fano metric. Under low-noise environments, this approach reduces the decoding complexity by a couple orders of magnitude in comparison to Viterbi's algorithm, albeit at relatively higher frame error rates. An analytical method to determine the computational cutoff rate is also suggested. This analysis is supported with numerical evaluations of frame error rates and computational complexity, which are compared with respect to optimal Viterbi decoding.
翻译:在这项工作中,对易于插入、删除和替代错误的渠道的连锁代码的顺序解码器进行了描述和分析。解码器通过引入新的频道状态变量(即Davey-MacKay建议的称为漂移状态)来扩展代码轨迹。在这项工作中,得出了用于连续解码的新的频道状态变量(即Davey-MacKay建议的漂移状态)的合适的代码器,其方法将原始法诺度值加以概括。在低噪音环境中,这种方法比维泰比的算法减少解码复杂性,尽管其框架误差率相对较高。还提出了用于确定计算截断率的分析方法。这一分析得到了框架误差率和计算复杂性数字评估的支持,与最佳维泰比解码法的比较。