说明：  用极坐标解码，转变的符号时，Viterbi译码之前，振幅信息被忽略，只有接收到的符号相受雇于度量计算阶段。
(Decoding using polar coordinates, the symbol of change, prior to Viterbi decoding, the amplitude information is ignored, and only received symbols employed in the metric calculation stage.)