变长码软译码的同步恢复与状态模型降阶
Synchronization recovery and state model reduction for soft decoding of variable length codes
摘要：
当在噪声信道上传输时，可变长度码表现出去同步问题。基于最大后验（MAP）估计器的网格解码技术通常用于最小化估计序列上的出错率。如果解码器已知所传输的符号和/或比特的数量，则可以在解码过程中并入终止约束。网格中所有不会导致有效序列长度的路径都被抑制。本文提出了一种分析方法，以评估预期的错误弹性的VLC时，网格解码与序列长度约束。该方法是基于计算，对于一个给定的代码，所带来的约束的信息量。然后表明，该量以及严格意义上的VLC解码器不重新同步的概率不会因适当的网格状态聚合而显着改变。这证明了通过在聚合状态模型上运行长度受限的维特比解码器所获得的性能接近用比特/符号网格获得的性能，具有显著降低的复杂性。然后，它示出的复杂性，可以进一步降低通过投影的状态模型上的两个状态模型的大小减小。
英文摘要：
Variable length codes exhibit de-synchronization problems when transmitted over noisy channels. Trellis decoding techniques based on Maximum A Posteriori (MAP) estimators are often used to minimize the error rate on the estimated sequence. If the number of symbols and/or bits transmitted are known by the decoder, termination constraints can be incorporated in the decoding process. All the paths in the trellis which do not lead to a valid sequence length are suppressed. This paper presents an analytic method to assess the expected error resilience of a VLC when trellis decoding with a sequence length constraint is used. The approach is based on the computation, for a given code, of the amount of information brought by the constraint. It is then shown that this quantity as well as the probability that the VLC decoder does not re-synchronize in a strict sense, are not significantly altered by appropriate trellis states aggregation. This proves that the performance obtained by running a length-constrained Viterbi decoder on aggregated state models approaches the one obtained with the bit/symbol trellis, with a significantly reduced complexity. It is then shown that the complexity can be further decreased by projecting the state model on two state models of reduced size.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
