利用CAZAC序列共轭对称性的OFDM时频同步算法

符号定时和载波频率偏差将严重影响OFDM系统的性能。基于具有重复结构的CAZAC序列，提出了一种仅利用一个CAZAC符号实现符号定时、整数倍频偏与小数倍频偏估计的同步算法。首先，所提算法在完成粗定时同步的同时得到整数倍频偏估计。然后根据整数倍频偏估计值对定时估计进行修正，最后完成小数倍频偏估计。分析与仿真结果表明，该算法相比于传统PARK算法，不仅完成了定时估计，而且得到了频偏估计；相对于经典SC算法，不但提高了传输效率，还显著改善了OFDM系统的定时与频偏估计性能；相比于利用CAZAC序列的同步算法，提高了算法的估计精度以及对多径信道的适应性。 

Timing and Frequency Synchronization Algorithm Based on CAZAC Sequences for OFDM Systems

Symbol timing offset and carrier frequency offset will seriously deteriorate the performance of the OFDM system. Based on the CAZAC sequences which have the repetitive structure, this paper presents a synchronization algorithm for OFDM system. The proposed algorithm utilizes only one symbol to realize the synchronization of symbol timing offset, integer frequency offset and fractional frequency offset. First, the proposed algorithm completes the coarse timing synchronization and integer frequency offset estimation simultaneously. Then, we use the integer frequency offset to update the timing offset estimation. At last, we get the fractional frequency offset. The analysis and simulation results demonstrate that compared with classical synchronization algorithms, the proposed algorithm not only increases the transmission efficiency of the OFDM systems, but also significantly improves the performance of the estimation of timing offset and frequency offset. Therefore, compared with other CAZAC synchronization algorithms, the proposed algorithm enhances the adaptability to the multi-path channel.