一种短延时Turbo编码调制系统的设计

A Design for Turbo TCM Systems with Short Time Delay

本文设计了一种比传统体制减少了一半延时的Turbo编码调制系统 ,介绍了交织器的相关限制 .提出了一种在译码过程中对信道值的估计方法 ,使得外信息的计算更加趋于精确 ,从而提高了译码性能 .这种迭代译码算法是标准格码调制译码算法的一种自然推广 ,同时也类似于二元Turbo码在BPSK调制下的逐比特译码算法 .采用吞吐率为 2bits/s/Hz的 8PSK调制 ,比特错误率为 10 -5所需的信噪比与Shannon限相距不到 0 4dB .

A design for Turbo trellis coded modulation (TCM) systems is proposed with nearly half of the encoding delay caused by the conventional scheme.An introduction is also given to the associated constraint that the interleaver has to satisfy.An estimate of channel values in decoding is suggested so as to improve the accuracy of extrinsic information calculations and thus the decoding performance.The proposed iterative decoding algorithm,a natural extension of the standard decoding algorithm for TCM,is similar to the bit wise one for binary turbo codes with the BPSK modulation.The bit error rate 10 -5 of this scheme needs signal to noise ratios within 0.4dB from the Shannon limit 2.85dB for the throughput 2bits/s/Hz with the 8PSK modulation.