多径衰落信道下MIMO OFDM系统的定时同步算法

Timing Synchronization Algorithm for MIMO OFDM Systems in Multi-Path Fading Channels

提出了一种多径衰落信道下多输入多输出正交频分复用(MIMO OFDM)系统的定时同步算法.算法将恒幅零自相关码作为训练序列,每根发射天线采用修正的循环延迟序列,在接收端分别计算本地序列和接收信号的互相关和接收信号的对称自相关,再将二者结合起来以确定定时位置.为了对抗多径信道中第1径不是最强径的情况,还采用了多径后向搜索技术,并利用可变阈值进行判决,以改善同步性能.通过仿真对算法在加性高斯白噪声信道和多径信道下的性能进行了验证和比较.

A timing synchronization scheme using constant amplitude zero auto correlation sequence as training sequence is proposed for multiple input multiple output （MIMO） orthogonal frequency division multiplexing （OFDM） systems in multi-path fading channels. A modified cyclic delay sequence is used in each antenna. The cross correlation between local sequence and received signal and the symmetrical correlation of received signal are calculated respectively. The two correlations are then combined together to detect the time offset of each transmitter element. Furthermore, multi-path backward searching tech- nique is employed at the receivers to cope with the situation where the first path is not the strongest. The threshold is variable at different signal to noise ratios in order to guarantee acceptable synchronization per- formance. Performance of this proposed scheme is verified and compared by simulations in both additive white gaussian noise and multi-path fading channels.