采用截断循环前缀的OFDM系统码元盲同步

为提高低信噪比下抗干扰能力，提出一种更加稳健的正交频分复用( OFDM )系统盲同步方案。所提方法不需要预先估计信噪比( SNR)信息，而是根据循环前缀( CP)和距离分析，进行定时偏移的盲估计。算法利用CP和对应码元尾部的相似性，在频域最小化码间距离。为减少计算复杂度，距离测量同样可在时域进行。为提高算法性能，剥离多径干扰，使用了截断CP技术。仿真结果表明，在SNR为0 dB时，算法依然可正确识别定时偏移位置，较以往基于CP的盲同步算法，所提方案在低信噪比下性能更加稳健。这使得所提算法更适合一些低SNR情况下的应用，如混合直接序列扩频技术的OFDM系统。

Blind symbol synchronization using truncated cyclic prefix in OFDM systems

In order to improve the anti-interference capability of orthogonal frequency-division multiplexing ( OFDM) systems in low signal-to-noise ratio( SNR) condition,a robust blind symbol synchronization al-gorithm is proposed. According to cyclic prefix( CP) and distance analysis,this algorithm realizes the blind estimation of timing offset in frequency-domain without the information of SNR. The basic idea is to ex-plore the comparability between cyclic prefix( CP) and corresponding tail of the symbol body and minimize the distance between symbols in frequency domain. The distance may also be measured in time domain to decrease the implement complexity greatly. In order to strip the multipath interference and improve per-formance as much as possible,a truncated CP is used,which is shortened by cutting the top. Simulation re-sults show that the minimum of this function necessarily points to the correct timing offset at 0 dB. The pro-posed algorithm is robust and outperforms previous CP-based algorithms, particularly when SNR is low. Hence,this algorithm may be more suited for low SNR applications,such as systems combining the direct sequence spread spectrum technology with OFDM.