采用时频分析的变换域通信系统基函数设计

为使变换域通信系统基函数充分利用背景信号的频谱分布信息以进一步提高系统抗干扰能力,提出了采用多进制序列设计基函数幅度谱的方法.首先在干扰存在的条件下,对单码片成型基函数调制及解调信号的短时频谱特性进行分析,由此推导出系统误码率的解析表达式,将求解系统误码率解析式的最优化问题转化为求最大信号干扰噪声比问题,利用随机相位的均匀分布特性对最大信号干扰噪声比问题进行求解,从而得到多进制序列基函数.仿真结果表明:该系统具有更好的抗干扰性能,在高干信比条件下也具有良好的通信效果；当干信比为25～41 dB且信噪比为-6～3 dB时,系统误码率均低于二元序列基函数的系统误码率；干信比为36 dB、信噪比为O dB 时,系统误码率可低于10-4.

Design of Basis Functions for Transform Domain Communication Systems Using Time-Frequency Analysis

It is an effective way to improve the system anti-jammer ability that the basis function of a transform domain communication system(TDCS) is constructed by making full use of the distributing information of spectrum of background signal.According to the principle,a method to design the basis function is proposed by utilizing array sequences to express the spectrum amplitude.With the coexistence of jamming,the short-term spectra of both the single-chip waveform coded basis function modulated signal and the demodulated signal are studied,and then the analytical expression of bit error rate(BER) is derived obtained.The optimization solution of BER is converted into the calculation of the maximum signal-to-interference-plus-noise ratio(SINR).The maximum SINR problem is solved by using the uniform distribution property of random phase,and the new basis function is obtained.Simulation results show that the proposed system exhibits a better anti-jammer performance and has an excellent performance under the condition of high jamming-to-signal ratio.When the interference-to-signal is 25-41 dB and the signal-to-noise ratio is-6-3 dB,the BER of the system with array sequences is less than that of the system with binary sequences.When the interference-to-signal is 36 dB and the signal-to-noise ratio is 0 dB,the BER of the system is lower than 10-4.