相干DS-SS／MPSK系统中频差影响的简化评估

Simplified Evaluation for the Effect of Frequency Offset in Coherent DS-SS/MPSK Systems

该文针对单径慢衰落信道模型下的相干DS-SS／MPSK系统,分析了频差对系统性能的影响,得到了误比特率的封闭表达式。首先推导了匹配滤波解扩符号的信噪比特性和相干相位估计误差的分布;然后给出了衰落信道中误比特率的精确积分式,并利用MPSK条件误符号率的麦克劳林级数形式,推导了AWGN,Nakagami-m衰落和瑞利衰落信道中BPSK,QPSK误比特率的简化逼近式。最后的数值结果表明:逼近式的精度非常高,基本没有损失,可应用于实际系统设计和性能评估。

Focusing on coherent DS-SS/MPSK system in single path slow fading channel model, this paper analyzes the effect of frequency offset on system performance, and the closed-form Bit Error Rate （BER） expressions are also obtained. Firstly, the Signal Noise Ratio （SNR） characteristic of matched filter despread symbol and the distribution of coherent phase estimation error are derived. Secondly, the exact integration formula of BER for fading channel is presented, moreover, by using the Maclaurin series expansion of MPSK conditional Symbol Error Rate （SER）, the simplified BER approximations for BPSK and QPSK are derived over AWGN, Nakagami-m fading and Rayleigh fading channel. Finally, numerial results show that the approximations provide excellent accuracy without loss and can be applied to practical system design and performance evaluation.