基于双向逐幸存路径处理的空时格形码软判决自适应解码

本文提出一种针对TDMA下行链路的空时格形码自适应解码算法.为充分利用下行链路相邻时隙前导序列中的正交导引信号,该解码算法采用了双向逐幸存路径处理技术——正向处理利用基于当前时隙前导序列的自适应信道估计实现正向解码,并将软判决结果传递给反向处理模块;以正向软判决为先验知识,反向处理利用基于下一时隙前导序列的自适应信道估计实现反向解码,并将反向软判决作为最终结果输出.计算机仿真结果表明:在存在卷积外码的情况下,与基于最大似然序列检测的单向硬判决解码相比,基于所提出算法的软判决解码在多普勒频移小于60赫兹的时变信道中可提供1～2dB的增益.

Soft-decision Adaptive Decoding of Space-time Trellis Code Based on Bi-directional Per survivor-Processing

We propose an adaptive decoding algorithm for space-time trellis code(STTC) used in the TDMA downlink.The bidirectional per survivor processing(BD-PSP) is adopted in this algorithm to fully utilize the preambles of successive slots.First,the forward PSP makes soft-decision with adaptive channel tracking based on the preamble of current slot.Then the backward PSP,taking the primary soft-decision from forward PSP as the a-priori knowledge,makes improved final soft-decision output with adaptive channel tracking based on the preamble of next slot.Computer simulation show that in the presence of a convolution outer code,the proposed soft-decision adaptive decoding outperforms max imum likelihood sequence detection(MLSD) based hard-decision decoding by 1~2dB over slowly or moderately fast time-varying channels characterized by the Doppler frequency shift less than 60Hz.