一种短码直扩信号分层盲解扩算法

摘要

针对非合作低信噪比条件下短码二进制频移键控(Binary phase shift keying,BPSK)/直接序列扩频(Direct sequence spread spectrum,DSSS)信号的盲解扩问题,提出了一种分层的处理方法.算法首先估计序列扩频周期,然后利用短码DSSS信号的相关特性寻找短码序列的起始位,构造两个扩频周期长度的滑动窗口.通过两窗口序列内积的符号判断相邻码字的相对极性.每轮迭代通过滑动对起始位进行修正,提高算法的鲁棒性.仿真实验表明,信噪比高于-2 dB时盲解扩算法可以实现低于2×10-4的误码率,算法具有一定的工程应用价值.%Aiming at the problem of blind despreading of short-code BPSK/DSSS signals under non-coop-erative and low signal-to-noise-ratio (SNR) circumstances ,an algorithm which hierarchically deals with the signal is proposed .Firsly the sequence′s spreading period are estimated .Then the initial bit of a short-code sequence is figured out by employing the auto-correlation properties of short-code DSSS signals .Two windows whose length is spreading period are constructed at the same time ,and by inner products of the two windows the relative polarities of all the adjacent information bits can be estimated .The robustness of the proposed algorithm is improved by correction of short-code sequence′s initial bits via a sliding method in every iteration .Simulation results show that a BER lower than 0 .0002 could be achieved under a SNR above -2 dB ,which proves the engineering application value of the propsed algorithm .