非数据辅助的OFDM系统联合同步算法设计

研究了正交频分复用(orthogonal frequency division multiplexing, OFDM)系统中非数据辅助的同步问题,通过对OFDM时域信号延时相关函数进行分析,设计了一种非数据辅助且具有较低复杂度的联合采样频率、载波频率及符号定时同步算法。算法根据延时相关函数以OFDM符号率为周期的周期特性,首先从延时相关函数的模中提取OFDM符号的周期标记,通过对收端和发端在相同时间内的采样点数之比进行采样频率偏差(sampling frequency offset, SFO)估计;然后通过对延时相关函数的模进行分段平均,从中提取去除循环前缀(cyclicprefix,CP)的开始时刻,从而进行符号定时同步和载波频率偏差(carrier frequency offset, CFO)估计。仿真结果表明,算法性能受累积时间长度和CP长度影响较大,而受OFDM基带调制方式影响较小;与其他同类文献相比,本文的联合同步算法具有较低复杂度和较好的性能。

Design of non-data-aided joint synchronous algorithm for OFDM systems

This paper studies non-data-aided joint synchronization for orthogonal frequency division multiplexing (OFDM) systems, and a low complexity non-data-aided joint sampling frequency, symbol timing and carrier frequency synchronization algorithm is proposed based on time-delay correlation of received time -domain- OFDM signals. From the property of time-delay correlation that the period of time-delay correlation is the OFDM symbol rate, the period marker of the proposed algorithm is firstly obtained from the inherit property of cyclic prefix based OFDM. Then sampling frequency offset (SFO) could be estimated by comparing the received samples number with transmitted samples number in the same time, and the OFDM symbol start time and carrier-frequency- offset (CFO) could be estimated from the averaging result of the amplitude of time-delay correlation in subsection. Finally, the performance of the proposed algorithm is evaluated by computer simulation, and the simulation results show that the performance of the proposed algorithm is mainly affected by the cumulate time and  cyclic prefix (CP) length, and less affected by the modulation type of OFDM subcarrier. The proposed algorithm has lower implementation complexity and better performance compared with many other similar algorithms.