多径衰落信道下的OFDM时频联合同步算法

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。这种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,该算法相对经典算法,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CAZAC序列算法,提升了多径信道下的同步性能。

Timing-and-Frequency Synchronization Algorithm for OFDM Systems in Multipath Fading Channels

Symbol timing offset and carrier frequency offset would seriously deteriorate the performance of OFDM system. Based on the CAZAC sequences with repetitive structure, a novel synchronization algorithm is proposed,which uses merely one CAZAC symbol to realize the synchronization of symbol timing offset, integer frequency offset and fractional frequency offset. Firstly, the proposed algorithm completes the coarse timing synchronization while obtaining integer frequency offset estimation. Then, the timing offset estimation is correted in accordance with the integer frequency offset estimation. Finally the estimation of fractional frequency offset is done in the final process. Analysis and simulation results indicate that compared with classical synchronization algorithm, the proposed algorithm could increase the transmission efficiency and significantly improve the estimation performance of timing offset and frequency offset for OFDM system. Meanwhile, the synchronization performance in multipath channels is enhanced as compared with CAZAC sequence algorithm.