一种新的突发OFDM传输系统定时和载波频率捕获联合算法

A Novel Joint Algorithm of Timing and Carrier Frequency Acquisition for Burst OFDM System

提出了一种新的正交频分多路 (OFDM)传输系统定时和载波频率捕获联合算法 .该算法仅需要一个训练符号 ,既用于定时恢复 ,也用于载波频率捕获 ,额外开销量小 ,因此 ,提出的算法适合于突发模式的OFDM传输系统 .定时和频率捕获算法的实现均在时域进行 ,而且OFDM帧同步和符号同步能一次完成 ,简化了同步实现的复杂度 .由于使用自相关处理 ,定时恢复对频率偏差具有较强的鲁棒性 .此外 ,训练符号中参考符号的重复扩展了频率估计范围 ,频率捕获的范围完全满足突发OFDM传输系统的要求 .仿真结果表明 ,即使在频率选择性衰落信道中 ,提出的算法也能快速地实现定时和频率捕获 .

This paper describes a novel joint acquisition algorithm of timing and carrier frequency for burst orthogonal frequency division multiplexing (OFDM) transmission system. Only one training symbol is used for symbol timing recovery and carrier frequency acquisition, the overhead is small, and so the proposed method is suitable for burst OFDM transmission system. The realization of timing recovery and carrier frequency acquisition is achieved in time domain, and the timing offset of frame and symbol can be estimated simultaneously, thus the complexity of synchronization is reduced. As autocorrelation is used, timing recovery of the proposed algorithm is robust against carrier frequency offsets. Comparing to the OFDM system timing recovery algorithm proposed at foretime, authors’ method avoid the phenomenon of plateau or multi-peak in timing metric. Ever for very low single-to-noise ratio, a dominant peak could be present in timing metric while the proposed algorithm is used. Moreover, the repetition of the reference symbols in training symbol extends the range of carrier frequency acquisition, and so the operation rang completely satisfy the requirement of the bust OFDM transmission system. In order to improve the frequency estimation, averaging is applied. Simulations show that the proposed algorithm can estimate the timing offset quickly and exactly and the coarse frequency offset estimator operating range can fulfill a worst-case scenario of carrier frequency offset for bust OFDM transmission system even for a frequency selective fading channels.