Construction of Time-Varyng Convolutional Codes

随着1993年turbo码的发现，自Shannon于1948年发表具有里程碑意义的论文以来，AWGN信道的近容量性能首次实现。最近PI和其他人已经证明涡轮码是时变卷积码的一种特殊实现；这与过去30年的实践有很大的不同，在过去的30年里，强调的是时不变卷积码。本文提出的工作是对构造时变卷积编码器和解码器类的方法的初步研究。特别是，目标是寻找或构建具有稀疏距离频谱和长块长度的时变代码，而不是传统的最大化自由距离的目标。

With the discovery of turbo codes in 1993, near-capacity performance on the AWGN channel was realized for the first time since Shannon published his landmark paper in 1948. It has recently been shown by the PI and others that turbo codes are a particular implementation of time-varying convolutional codes; this differs significantly from the practice of the last 30 years, in which time-invariant convolutional codes have been emphasized. The propose work is a preliminary study of methods for constructing classes of time-varying convolutional encoders and decoders. In particular, the goal is to find or construct time-varying codes with a sparse distance spectrum and long block length, as opposed to the traditional goal of maximizing free distance.