基于差分和集相关的OFDM定时同步算法的改进

多径衰落信道中,同步技术是保证OFDM系统得以实现的关键环节。但目前已有的定时同步算法在多径衰落信道及低信噪比条件下性能尚不理想。为了改善定时同步的性能,本文在集相关和差分相关算法的基础上提出一种改进的定时同步方法。通过在集相关运算中利用多点相关和在组合算法中选择适当的加权系数,算法利用了两者在不同信噪比下的优点。改进的算法在较高信噪比的条件下不损失性能,在低信噪比环境下也可以准确定时。仿真结果表明,改进算法对符号定时位置的误判率更低,尤其在低信噪比时。并且,由于算法不依赖频偏估计,不受频偏对符号定时的影响。

An improved timing and frequency estimation method for OFDM systems based on energy difference and set correlation

Synchronous technology is the key technology for realization of OFDM systems in multi-path fading channels.But the performance of existing timing synchronization algorithms is not ideal under low SNR.In order to improve the performance of the timing synchronization,an improved timing synchronization method based on energy difference and set correlation is proposed in this paper.By using multiple point in set correlation and choosing appropriate weighting coefficients,the algorithm make use of the two merits selectively under different SNR.The modified method can work with no loss of performance in high SNR environments,and also can get accurate timing in low SNR environments.Simulation results shows that the wrong judgment rate of the improved algorithm is lower in symbol timing,especially when SNR is low.As the algorithm doesn＇t use the frequency shift estimation,it isn＇t affected by frequency shift in symbol timing.