QAM中基于LLR的软输出Viterbi译码器的实现

QAM调制技术作为有吸引力的调制技术被广泛应用。将QAM信号解映射成相应的比特量有其特殊性,特别是如何表示此映射的似然度,而这在软输出Viterbi译码中是必须的。介绍了在LLR准则下的QAM信号的解映射方法,并将其推广到BPSK和QPSK信号的解映射。同时根据LLR准则的特点给出了一种分支度量算法,最后给出相应Viterbi译码器算法的FPGA实现。

Implementation of Viterbi Decoder Based on LLR Soft Output in QAM Scheme

QAM which is an attractive modulation scheme is widely applied. It is special that the QAM signal is demapped to the corresponding bit. Particularly, how to present the likelihood of the demapping. However, it is necessary to the soft output Viterbi decoding algorithm. The method of the demapping QAM signal in LLR (Log Likelihood Ratio) criterion is introduced, and extends it to the demapping of BPSK and QPSK signal. A kinds of branch metric algorithm based on the character of LLR criterion is presented. At last, the detail that using FPGA implements the corresponding Viterbi decoding algorithm is given.