认知无线电多址接入系统的研究

针对认知无线电(Cognitive Radio)频谱不连续,随机性和变化性大,以及TDMA,FDMA,CDMA不适用的问题,提出了一个基于变换域通信(Transform Domain Communication System)平台的认知无线电多址接入系统.该系统发射机通过将非空闲的频谱幅度置0,实现对授权用户的躲避;采用m状态序列产生的伪随机相位矢量,生成近似正交的调制基函数实现用户的多址接入;接收端通过本地基函数与接收信号相关估计出原始数据,并理论分析了系统的误码率.仿真表明,系统的检测概率,多址接入的用户数以及收发两端基函数的不一致会影响系统的性能.该系统能利用非连续频谱,并且基函数能够自适应变化,适合认知无线电。

Research on system about multiple access of cognitive radio

Aimed at the problem that TDMA, FDMA and CDMA do not adapt to cognitive radio (CR) for its non-continuous, random and variable spectrum, a system about multiple access of CR based on transform domain communication system (TDCS) is proposed. It avoids disturbing the primary users through making the amplitude of busy spectrum be zero. The m state sequences are adopted to produce random phase vectors. Basis functions on modulation produced by phase vectors are orthogonal and can achieve multiple access. Data are estimated through making the correlation of the signal and basis functions of receiver, and the theoretical BER of this system is analyzed. Simulations show that the detection probability, the number of accessed users and the difference of basis functions between the transmitter and receiver will affect the performance of this system. This system can use the non-continuous spectrum, and its basis functions are self-adaptive, which make it be used in CR.