LTE系统小区搜索中SSS时频同步算法的研究

Time and frequency synchronization algorithm based on SSS of cell search in TD-LTE system

时频同步是终端小区搜索过程中的核心模块,其性能的好坏将直接影响系统的解调性能。通过对时分长期演进(time division-long term evolution,TD-LTE)系统小区搜索过程中时频同步算法的研究,结合辅同步信号(secondary synchronization signal,SSS)序列时域信号特性,给出了一种基于SSS对称相乘的时频同步算法。该算法利用SSS信号的时域共轭对称性能够准确地估计出SSS信号的中心共轭对称点,进而获取定时同步;同时,定时同步位置所对应的小数倍频偏计算结果即为小数倍频偏估计值。在MATLAB中对该算法的性能进行仿真与分析。仿真结果表明,利用SSS进行定时同步能够很好地抵制大载波频偏对定时同步性能的影响。从计算过程来看,该算法仅利用接收信号的对称相乘运算来估计小数倍频偏估计,极大降低了计算复杂度。该时频同步算法性能良好、复杂度低,较常规算法可靠性有较大提高。

Time and frequency synchronization is the core module of the telainal cell search process ; its performance will af- fect the performance of demodulation system directly. Based on the research on cell search time and frequency Synchronization algorithm in TD-LTE system, according to the secondary synchronization signal （SSS） sequence character, a timing and fre- quency synchronization algorithm based on SSS is proposed in this paper. The center of symmetry conjugate point for SSS sig- nal could be estimated according to the conjugate symmetry in time domain of SSS signal, and then the timing synchronization can be obtained. At the same time, the fractional frequency offset is estimated corresponding to the timing position of the frac- tional frequency offset calculation results. The properties of the algorithm are simulated and analyzed in the MATLAB, the simulation results show that SSS timing synchronization algorithm can resist the impact of large carrier frequency offset on tim- ing synchronization performance. From the calculation process, the algorithm only uses the symmetric multiplication of the re- ceived signal to estimate the frequency offset estimation, which greatly reduces the computational complexity. The algorithm＇ s performance is perfect and complexity is low, and it improves the reliance in comparison with the normal methods.