瑞利衰落信道中基于分集技术的MQAM信号的识别

Spatial Diversity Based MQAM Modulation Classification in Rayleigh Fading Channel

针对在瑞利衰落信道下正交幅度调制(QAM)信号识别难的问题,利用多天线空间分集可以提高接收信号信噪比的特点,提出了一种基于多天线接收分集技术的识别方法.首先给出等增益分集用于调制分类的模型,然后使用非线性最小二乘估计器联合估计正交幅度调制信号的载波频偏和衰落相位,并推导合并器输出信号的四阶累积量和六阶累积量的理论值,最后使用四阶累积量和六阶累积量两个特征联合进行分类识别.仿真结果表明所述算法的有效性和正确性,且与已有的混合似似然比检测(qHLRT)方法相比,有较小的计算复杂度和较强的实用性.

Considering the difficulty in classifying quadrature amplitude modulation （MQAM） signals over rayleigh fading channel, an algorithm based on antenna arrays for identifying MQAM signals in Ray- leigh fading channels is presented. The characteristic that spatial diversity reception can improve the SNR of received signals is used. First, the equal gain diversity model for modulation classification is given. Then, the nonlinear least-squares estimator is presented to estimate the frequency offsets and phase off- sets. Finally the normalized fourth-order and sixth-order cumulants of the signal at the output of the com- biner are estimated, that can be used as modulation classification features. Simulations demonstrate that the proposed scheme is efficient in rayleigh fading channel. Compared to the existing quasi hybrid likeli- hood ratio test （qHLRT） method, the proposed method has lower computational complexity and stronger practicability.