OFDM系统基于重复共轭对称序列的时频同步算法研究

Time-frequency synchronization algorithm for OFDM systems based on repeated-conjugate symmetric sequence

针对基于共轭对称序列的OFDM同步算法的不足,设计了具有重复共轭对称并加权PN序列因子的新型同步训练序列,提出了一种适用于OFDM系统的时频同步联合估计算法。利用训练序列的重复共轭对称性和伪随机序列的相关性来完成定时同步。在定时同步的基础上利用去除PN序列后的重复共轭对称序列计算小数倍频偏估计。仿真结果显示,与已有算法相比,所提算法在定时方面可以有效消除Park算法的侧峰,在瑞利衰落信道下定时准确性较高,在AWGN环境下频偏估计性能也有明显的改善。

A novel synchronization training sequence with the repeated-conjugated symmetry and weighting PN sequence fac-tors was designed to overcome the weakness of orthogonal frequency division multiplexing (OFDM) synchronization algorithm based on the conjugated symmetric sequence. A time- frequency synchronization joint estimation algorithm suitable for OFDM systems is proposed. The time synchronization is accomplished by using the repetitive conjugate symmetry of the training se-quence and the correlation of the pseudo-random sequence. On the basis of the timing synchronization,the fractional frequen-cy synchronization are finished by utilizing the good autocorrelation of the training sequence to eliminate the repeated-conjugated symmetric sequence after PN sequence. The simulation results show that,compared with the available algorithms,the modified timing synchronization method can eliminate the ambiguity of Park algorithm,has more timing accuracy in Rayleigh fading chan-nel,and results in more obvious improvement of frequency offset estimation performance in AWGN environment.