新型互补序列设计及其在OFDM系统改进同步算法中的应用

New complementary sequence design and its application in improved synchronization algorithm of OFDM system

定时偏移是影响OFDM系统精准同步的主要原因,尤其在低信噪比下系统对定时偏移更为敏感。应用相关性良好的互补序列可以解决这类问题,为此,通过新的映射关系和级联构造出一种新型16QAM Go⁃lay互补序列,该序列因具有良好的相关特性可有效应用于OFDM系统中。为进一步提高系统的定时精度,提出一种同步改进算法,该算法基于新型16QAM Golay互补序列和CAZAC序列,通过设计训练序列的共轭对称结构,对原有的滑动窗口进行改进,采用2组窗口同时对2组序列进行相关运算,从而能够应对系统在低信噪比下的同步问题。仿真结果表明,与经典同步算法相比,改进算法在低信噪比的情况下仍可实现精准同步,并且副峰对主峰的影响较小,可以提高系统的定时精度。

Timing offset is the main reason that affects the accurate synchronization of OFDM systems.Especially under low signal-to-noise ratio,the system is more sensitive to timing offset.This kind of problem can be solved by applying complementary sequences with good correlation.Therefore,a new 16QAM Golay complementary sequence is constructed through new mapping relationships and concatenation.The sequence can be applied to OFDM systems effectively be⁃cause of its good correlation characteristics.In order to further improve the timing accuracy of the system,an improved synchronization algorithm is proposed.The algorithm is based on the new 16QAM Golay complementary sequence and CAZAC sequence.By designing the conjugate symmetrical structure of the training sequence,the original sliding window is improved.Correlation calculations are performed on two sets of sequences at the same time,which can cope with the synchronization problem of the system under low signal-to-noise ratio.The simulation results show that compared with the classical synchronization algorithm,the improved algorithm can still achieve accurate synchronization under the con⁃dition of low signal-to-noise ratio,and the secondary peak has less influence on the main peak,which can improve the timing accuracy of the system.