利用重复结构训练符号的OFDM同步算法性能分析

Performance Analysis of OFDM Synchronization Method Based on Repeated-structured Training Sequence

在OFDM同步算法中,利用重复结构训练符号的同步算法具有结构简单、频偏估计精度较高等优点,因此被广泛使用,但很少有研究结果分析这类算法所适用的信道环境,以及多普勒效应对算法性能的影响。为此,开展了对利用重复结构训练符号的OFDM同步算法性能的研究,通过理论分析和仿真实验,指出了这类算法所适用的信道环境:在AWGN信道、多径信道以及多普勒信道下,该算法能进行准确的定时同步和频偏估计,但在信道中同时存在多径衰落和多普勒效应时,这类算法的定时同步性能会迅速下降,且小数频偏估计将成为有偏估计。即利用重复结构训练符号的OFDM同步算法对多径衰落和多普勒效应均具有较强的鲁棒性,但当信道中二者同时存在时,该算法的鲁棒性较差.

Among the OFDM synchronization algorithms, the algorithm based on repeated- structured training sequence is widely used because of its simple structure and high accuracy of frequency estimation. But few research results have pointed out the channel environments where this kind of algorithm is applicable and the influence on the algorithm imposed by Doppler shift. To this issue, the performance of OFDM synchronization algorithm based on repeated-structured training sequence is analyzed. Theoretical analysis and simulation results show that in AWGN channel, multipath channel, and Doppler channel, such kind of algo- rithm can realize accurate timing estimation and frequency estimation, but in the channel en- vironment where muhipath fading and Doppler shift exist simultaneously, the performance of timing estimation decreases rapidly and the frequency estimation becomes biased estimation.That is, the algorithm based on repeated-structured training sequence is robust against multipath fading and Doppler shifts, but when the two kinds of fading exist simultaneously, the robustness of the algorithm is weak.