频率选择信道下STBC-OFDM信号盲识别

针对多输入单输出(multiple input single output, MISO)通信系统的空时分组编码正交频分复用(space-time block codes-orthogonal frequency-division multiplexing，STBC-OFDM)信号盲识别问题,提出了一种基于四阶统计量的盲识别算法。该方法首先对MISO通信系统的STBC-OFDM信号进行建模;然后利用STBC-OFDM信号编码矩阵的相关性,构造了不同时延向量下接收信号OFDM块的时延四阶矩作为特征函数;最后通过时延四阶矩理论值与实验值的最小欧式距离盲识别发射端STBC-OFDM信号的编码方式。该方法不需要信道系数、噪声信息和调制信息等先验信息,适合非合作通信场合。仿真结果表明，所提出的算法即使在低信噪比(SNR=0 dB)下识别效果接近100%,且对载波频偏、时间同步偏差和多普勒频移不敏感,实用性较强。

Blind classification algorithm for STBC-OFDM signals over frequency-selective channels

An efficient method for blind classification of space-time block codes-orthogonal frequency-division multiplexing (STBC-OFDM) signals based on fourth-order statistics is proposed, when a single antenna is employed at the receiver. Firstly, the model of the received STBC-OFDM signals in MISO systems is built. Secondly, the discrimination features function provided by fourth-order lag moment of the received OFDM blocks is constructed by using the correlation of the coding matrices of STBC-OFDM signals. Finally, the automatic classification of STBC-OFDM signals is realized by selecting the signal which minimizes the distance between the theoretical values and the experimental ones. The proposed algorithm does not need the estimation of the channel, noise statistics and modulation type, and consequently, is well-suited for non-cooperative communication context. The simulation result shows that the proposed algorithm performs well even at a low signal to noise ratio (SNR=0 dB), and is robust to carrier frequency offset, timing offset and Doppler frequency shift.