MIMO-OFDM同步门限值方法

Synchronization for MIMO-OFDM using threshold method

正交频分复用(OFDM)技术由于其对抗多径能力强和频谱利用率高而被视为下一代无线通信的核心技术,多输入多输出天线系统(MIMO)利用空间复用进一步提高频谱效率。二者已经应用于多种高速宽带通信系统中。MIMO-OFDM与SISO-OFDM相似,对定时同步错误和频率偏移敏感。任何不同步都可能会破坏接收帧结构,因此准确的符号定时同步和精确的载波频偏估计是系统可靠工作的前提。本文中首先用CAZAC序列构建出共轭交错结构作为训练序列,然后应用门限值方法改进定时同步估计,并基于这种交错结构进行载波频率偏移估计,确定影响门限值性能的参数值。仿真数据显示,在多径信道条件下,该方法可以使系统的误码率相对传统方法得到进一步减小,有效提高系统同步性能。

OFDM is viewed as key technology of the next generation of wireless communication due to its strong ability of anti-multi-path and high frequency efficiency,and Multiple Input and Multiple Output（MIMO） can further increase spectrum utilization ratio.MIMO and OFDM techniques have been used in various high-speed wireless systems.Similar to SISO-OFDM,MIMO-OFDM is very sensitive to timing synchronization error and carrier frequency offset,i.e.,the received frame structure could be damaged if timing or carrier frequency is out of synchronization.Therefore correct symbol timing and precise carrier frequency offset estimation are necessary for MIMO-OFDM.This paper first uses CAZAC sequences to construct a conjugate staggered structure as training sequences,then proposes an algorithm based on this structure to improve carrier frequency and timing synchronization by applying threshold method.Meanwhile,the parameters that influence the threshold are determined according to the simulation results.The simulation results show that,compared to the conventional methods in multipath channel,the proposed method can reduce BER and effectively improve synchronization performance.