快变信道环境下OFDM频谱感知算法

摘要

针对基于慢变信道假设的认知无线电不适合高速移动场景的问题,提出一种基于广义似然比的OFDM频谱感知算法.利用OFDM信号自身相关性得到OFDM检测统计量,通过研究其统计分布特性得到OFDM广义似然比检测统计量,构建快变信道检测模型进行频谱感知.在原算法的基础上,用检测窗口的宽度近似替代检测统计量的方差,得到广义似然比的改进算法.仿真结果表明,两种感知算法在低信噪比、快变信道环境中都具有很高的认知度,而且改进算法对噪声和干扰还具有很好的鲁棒性.%Since the cognitive radio based on the assumption of a slowly-varying channel is unsuitable for the high-speed mobile scenario,an orthogonal frequency division multiplexing(OFDM)signal's spectrum sensing algorithm based on generalized likelihood ratio is proposed,in which the autocorrelation of OFDM signal is used to get the OFDM detection statistics.Its statistics distribution characteristic is studied to get the OFDM detection statistics of generalized likelihood ratio,and construct the fast-varying channel detection model for spectrum sensing. On the basis of the original algorithm,an improved algorithm of the generalized likelihood ratio is obtained by the approximate replacement of the variance of the detection statistics with the width of the detection window. The simulation results show that the two perception algorithms both have high recognition rate in the low signal-to-noise ratio and fast-varying channel environments,but the improved algorithm has stronger robustness against noise and interference.