Abstract: An improved symbol timing synchronization algorithm for OFDM systems is proposed to solve timing ambiguity and high interference peak. The reasons for these problems are analyzed, and two new training symbols are designed. These symbols can estimate symbol timing offset and carrier frequency offset. A new timing metric function is presented and analyzed. The proposed algorithm has an impulse-shaped timing metric with different cyclic prefix length and almost has no interference peaks. Computer simulation results show that the performance of the proposed algorithm is better than that of the previous algorithms, and the mean and variance are equal to zero when Signal Noise Ratio（SNR） is greater than 5 dB in Additive White Gaussian Noise（AWGN） channel, so the rigorous timing synchronization may be accomplished.

Key words: orthogonal frequency division multiplexing, symbol timing, training symbol, conjugate symmetric

摘要： 针对先前一些算法存在定时模糊以及干扰峰峰值较大的问题，提出了一种改进的OFDM符号定时同步算法。分析了先前算法问题产生的根源，设计了两种同时具备频偏估计能力的新训练符号，并给出了相应的定时尺度函数。对新算法的定时尺度函数进行了分析，得知它的定时尺度非常尖锐，几乎不存在干扰峰，而且不受循环前缀长度的影响。仿真结果表明新算法克服了已有算法的缺点，有效地提高了定时估计的精度。当信噪比大于5 dB，在加性白高斯噪声信道下定时估计的均值与方差都为零，可以实现精确的定时同步。

关键词: 正交频分复用, 符号定时, 训练符号, 共轭对称