多径信道下调制信号识别新方法

Novel method for digital modulation signal identification in the multipath fading channel

针对多径信道中存在调制信号识别难以实现及识别率低的问题,提出了一种全盲的基于小波变换和高阶循环累积量相结合的算法(W-HOCC).该算法利用小波变换的线性性质和循环累积量的叠加性质构造识别特征,即把接收信号在小波变换前后的四阶累积量的比值作为识别特征参数.从理论上证明了该算法能够消除多径信道参数的影响.仿真结果表明:在信噪比为0dB的多径瑞利衰落信道下,分类2ASK、2PSK和4QAM信号的识别率几乎达到100%;与基于高阶累积量的算法相比,在识别BPSK和QPSK时,W-HOCC算法的性能明显优于基于高级累积量的算法,而且具有更强的抗噪声和抗多径能力.

Two major drawbacks of digital modulation identification are its low probability of correct classification （Pcc） and difficulty in classifying a variety of digital signal types in the multipath fading channel. Thus, a new blind classification method using the wavelet transform and higher-order cyclostationary cumulants （W-HOCC） is presented, in which a new classification feature is extracted using the linearity property of WT and the Superposition property of HOCC. Through theoretical analysis, it is proved that the extracted feature parameter can eliminate the influence of the multipath channel parameter. Monte Carlo simulation results show that in identification of 2ASK, 2PSK and 4QAM signals the proposed method yields the Pcc of 100% in the muhipath fading channel when the signal-to-noise ratio （SNR） is 0dB. Compared with the higher-order cumulants-based method, the W-HOCC method can lead to better identification performance. Also, the WHOCC method can bring about highly accurate recognition even for a low SNR.