衰落信道下的格形码设计

衰落信道下ＴＣＭ好码的设计准则是使有效码长度最长，同时使其对应路径的欧几里德距离乘积最大。本文首先从理论上得到有效码长度与卷积编码器的状态数，并行输入数之间的关系。提出了一种能达到最大自由长的状态转移图－标准拓扑篱笆图的概念，在此基础上，对衰落信道下采用速率为（２／３）８ＰＳＫ信号集合时的ＴＣＭ好码进行搜索，与文献中已有码相比，利用准则判别和进行蒙特－卡洛模拟都说明了新码在抗衰落方面的良好性能。

Design of Trellis Codes for Fading Channels

The most important design criterion for trellis coded modulation on fading channels is to maximize the efficient code length and then, to maximize the minimum product distance, In this paper, the relationship between the efficient code length and the numher of parallel inputs to the encoder, the number of encoder states is investigated, and a form of state transition diagram which has a maximum free length, called the standard topological trellis is proposed. Based on these analysis, the 8PSK trellis codes for fading channels are constructed. The theoretical analysis and the results of the Monte-Carlo simulation show that the new codes have a better error performance than the existing codes.