收发频谱不一致条件下的变换域通信系统基函数设计

Basis function design for transform domain communication system in the presence of spectral mismatches

针对变换域通信系统收发频谱不一致条件下接收端基函数存在错误而导致系统性能下降的问题,提出了具有信噪比次优解的基函数设计方法。详细分析了系统的收发过程,在此基础上研究了系统误码率的最优化与接收端基函数组成的关系,在收发频谱不一致而无法获得最优基函数的情况下,采用类似等增益合并的方法设计了接收端基函数,从而以该基函数完成数据解调。仿真结果表明:在单用户和多用户环境下,当收发频谱不一致比例较高时,接收端采用类似等增益合并的基函数设计方法可以完成系统的次优接收。在单用户环境下,相比不一致比例为40%时,次优接收方法的信噪比增益可达4dB左右,并且发送端频谱可用率为80%时,相比最优接收法的信噪比损失在1.5dB以内。

The errors of the basis function in the receiver, caused by the difference of the spectrum environment between the transmitter and receiver of Transform Domain Communication System （TDCS）, will degrade the system performance significantly. A design method of the basis function, which has suboptimal solution of the Signal-to-Noise Ratio （SNR）, is proposed to solve this problem. Based on a detailed study of the data sending and receiving process, the optimized Bitter Error Rate （BER） of the system and its relationship with the basis function of the receiver is discussed. In the case that the system with spectral mismatches can not obtain the optimal basis function, a design method of the basis function similar to equal-gain combing is proposed, and then this basis function is used for modulation. Simulation results show that, in the conditions of both multi-user and singleuser with high spectral mismatch ratio, the receiver is suboptimal when the basis function is designed similar to equal-gain combing. In the single-user condition, the BER performance improvement ofsuboptimal reception is approximately 4 dB compared with the reception method when the mismatch ratio is 40%, and the SNR loss is below 1.5 dB at the spectral efficiency of 80% compared with the optimal reception.