MIMO OFDM系统联合时频同步算法

为了解决多输入多输入多输出(Multiple imput multiple output,MIMO)正交频分复用(Orthogonal frequency division multiplexing,OFDM)系统的时间和频率偏移估计问题,提出了一种基于恒幅零自相关(Constant amplitude zero auto correlation,CAZAC)序列的联合时频同步算法。同步前导包括两个相同长度的训练符号。在接收端,分别计算两个本地训练序列与接收信号的互相关,利用CAZAC序列的特性可以检测出所有收发天线对之间的时间偏移和整数频率偏移;然后对接收信号进行整数频偏补偿,利用两个训练符号之间的关系可以估计出小数频率偏移。分析和仿真结果表明,该算法与传统的同步算法相比,不但具有更高的同步概率,而且能够估计出所有收发天线对之间的频率偏移。

Joint time and frequency synchronization method for MIMO OFDM systems

To address the problem of time and frequency offset estimation for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, a joint time and frequency synchronization algorithm based on constant amplitude zero auto correlation (CAZAC) sequences is proposed. The synchronization preamble consists of two training symbols with the same length. At the receivers, cross correlations between two local sequences and the received signal are calculated respectively, utilizing the unique properties of CAZAC sequences to detect the time offsets and integer frequency offsets of all the transmitter and receiver pairs. After compensating for the integer frequency offsets, fractional frequency offsets are obtained using the relationship between the two training symbols. Analysis and simulation results demonstrate that the proposed method not only has a significantly higher synchronization probability than conventional algorithm but also can estimate the frequency offsets of all the transmitter and receiver pairs.