新的四进制CPM调制方案

New Multilevel Continuous Phase Modulation Scheme

针对连续相位调制解调端过于复杂的问题,提出了一种新的网格编码连续相位调制方案。该方案通过在连续相位调制前对信号进行预编码,消除了采用与QPSK类似的方式对CPM信号进行正交解调时所引入的错误倍增对维特比译码性能的影响。接收端先对信号进行正交解调,解调后的结果送入与调制端编码网格相匹配的维特比译码器进行网格译码,恢复出发送的原始数据。仿真结果表明,加入预编码后误比特率为10-5时所需的Eb/N0比不加预编码时减小了1dB。

In this paper we present a four dimensional （4D） multilevel trellis coded continuous phase modulation （CPM） scheme. In order to use a coherent linear receiver the transmitted signal is pre-coded so that the information is in the received phase and not in the phase difference between the two consecutive phase samples. The receiver is composed of a simple quadrature demodulator, followed by a symbol-rate sampler and a Viterbi decoder matched to the code trellis. BER performance shows 1 dB improvement at the BER of 10^-5.