时域同步正交频分复用系统的频偏估计

针对时域同步正交频分复用系统现有的频偏估计精度低的问题,提出了一种精确频偏估计算法(FFDE).该算法将接收信号中相邻的2个帧头分别与对应的本地PN序列作相关运算,将相关结果共轭相乘,再取相乘结果的辐角,最后再除以帧头间的时间间隔,即可得到频偏估计值.FFDE算法具有复杂度低,精度高,抗噪声、抗多径能力强等优点.理论分析表明,FFDE算法具有极低的性能界,在高斯白噪声信道条件下,在合理的信噪比范围内,其归一化估计值的方差在10叫.以下.仿真结果与理论分析完全一致,即使在多径环境下,在信噪比为15 dB时,FFDE算法的绝对估计误差的标准差只有0.5 Hz,仅为子载波间隔的0.03%,是传统方法的1%.

Frequency Deviation Estimation for TDSOFDM System

A fine frequency deviation estimation algorithm(FFDE)is proposed to improve the low accuracy of the existing frequency deviation estimation algorithm for time-domain synchro-nous orthogonal frequency division multiplexing(TDS-OFDM)systems.The algorithm corre-lates the adjacent frame headers in receiving sequences with local PN sequences,respectively,and then the correlation results are conjugatively multiplied.The argument of the product is divided by the time interval between the adjacent frame headers to get the frequency deviation estimation.The algorithm has advantages of low computation complexity,accurate estimation,strong capa-bilities of suppressing channel noises and multipath interferences.The analytical results show that the algorithm has an extremely low bound of estimation error variance.The normalized esti-mation error variance is lower than 10~(-11) under the channel condition of additive white Gaussian noise within the normal signal to noise ratio(SNR)range.Simulation results are fully consistent with the analytical results.Simulations under multipath environment and SNR equal to 15 dB show that the standard deviation of estimation error is 0.5 Hz,which is only 0.03%of the sub-carrier spaces of the system,and 1% of traditional methods.