OFDM系统中一种符号定时和载波频率同步算法

New algorithm for symbol timing and frequency synchronization in OFDM systems

针对正交频分复用(OFDM)系统提出了一种新的符号定时和载波频率同步算法.该算法将整个OFDM符号分成多段,在连续多个OFDM符号中采用相关累加的方法得到对系统同步的估计函数.当分段长度小于相邻OFDM符号间的无符号间干扰(ISI)区长度时,算法可以分辨这一区间,从而得到最优符号定时同步以及载波频偏估计.分析表明最大似然(ML)算法和Karthik算法是它的一种特殊情况,计算机仿真结果表明该算法不仅可以跟踪时变信道而且其均方估计误差(MSE)要远远小于最大似然(ML)估计.

A new symbol timing and carrier frequency synchronization scheme applicable to orthogonal frequency division multiplexing （OFDM） system was presented. The OFDM symbol was divided into several parts. We used correlation and accumulation in several OFDM symbols to acquire estimation function for synchronization. When the length of part was smaller than that of ISI （Inter-symbol interference） free region, the estimator can distinguish it. Then optimal symbol timing and carrier frequency offset can be acquired. Analysis showed ML and Karthik algorithm were special cases of the presented method. The computer simulation results show that the proposed algorithm can track time varying channel condition and has much smaller MSE （mean square error） than that of ML estimation algorithms.