利用二次谱盲估计多速率 DS/CDMA 伪码周期

摘要

The blind periodic estimation of the PN sequence in variable-spreading-length(VSL) multirate direct-sequence code division multiple access(DS / CDMA) systems is considered. The method of the re-processing of the power spectrum which is used to estimate the period of general DS-SS signal is extended to multirate DS / CDMA model. Firstly,the received signal is sampled and its power spectrum is estimated, then Fourier transform is directly used to the power spectrum to modulo and square the value,and so repro-cessing of the power spectrum is obtained. The derivation proves that the power spectrum reprocessing of the multirate DS / CDMA signal will arise varied amplitude sharp pulse with interval equal to the period of these different rates users’ PN sequence,accordingly,the periods of the different rates users’ PN sequence can be acquired. The computer simulation results show that the method can work well under the lower sig-nal-to-noise ratio(SNR) input signals and it is able to estimate many rates by taking advantage of less da-ta at the same time at -15 dB SNR.%针对可变扩频长度(VSL)的多速率 DS / CDMA 信号伪码周期的盲估计问题进行了研究，将一般单速率直扩信号二次功率谱伪码周期估计的方法扩展到多速率 DS / CDMA 模型。该方法首先将接收的多速率 DS / CDMA 信号进行采样，并对其求一次功率谱，再将一次谱作为输入信号作傅里叶变换并取模、平方，从而得到信号的二次功率谱。通过推导证明，多速率 DS / CDMA 信号的二次功率谱在扩频码周期的整数倍处出现尖锐的谱线，且不同速率用户的二次谱线幅度是不同的，利用这些幅度差异区分不同速率并通过估计谱线之间的距离即可获得不同速率信号的伪码周期。仿真表明该算法在低信噪比下适用，在-15 dB能够利用较少数据同时估计多组速率的伪码周期。