MPPSK-OFDM复合调制系统的解调性能分析

Demodulation Performance of Hybrid MPPSK-OFDM System

多元位置相移键控与正交频分复用技术(MPPSK-OFDM)组成的复合调制系统,其接收端采用OFDM解调方式进行混合信号的接收,对于MPPSK信号来说,这种解调方式势必会带来一定的干扰。首先给出复合调制系统的结构及解调方案,然后从MPPSK-OFDM复合调制信号的时域结构出发,逐步推理,最终得出即使在无噪声信道中,接收端解调出的也是一个对发端星座点的有偏估计,且接收信号呈现以发端星座点为均值,方差随K∶N呈正比的高斯分布的结论。

Since a hybrid m-ary position phase shift keying （MPPSK） system uses orthogonal frequency division multiplexing （OFDM） to demodulate hybrid signals, interference to the MPPSK signal may occur. We first propose a hybrid system structure, which combine the MPPSK and OFDM. Then, we analyze the time-domain expression of the hybrid signal and give the conclusion that even in a noise-free environment, the demodulated signal is a biased estimate of the transmitted signal. The mean of the received signal is located at a biased point in the constellation and the dis-tance obeys Gaussian distribution with a variance proportional to K /N.