一种基于异周期结构的OFDM频偏估计方法

Heter-cycle abutted Cyclic Prefix based OFDM carrier frequency synchronization

本文设计了一种具有异周期毗邻结构的新型循环前缀(Heter-cycle abutted CP,HCA-CP),在此基础上提出了相应的OFDM频偏估计算法。该异周期毗邻结构循环前缀由短循环前缀CP_1和长循环前缀CP_2两部分构成。采用该异周期毗邻结构的OFDM符号具有双周期特征,其中短循环前缀CP_1对应的周期为整个循环前缀的长度L,长循环前缀CP_2对应的周期为OFDM符号的数据长度N。论文中频偏估计方法利用短循环前缀CP_1做相关运算获得整数倍频偏,利用长循环前缀CP_2做相关运算获得引小数倍频偏,通过引入较短的CP_1,牺牲极少的资源,可以有效克服现有频偏估计方法中的固定频偏估计范围的缺陷,同时具有频偏估计范围大,精度高的特点。

This paper proposes a heter-cycle abutted CP structure and designs a two-step OFDM carrier frequency estimation algorithm. The heter-cycle abutted cyclic prefix is made up of CP, and CP2, which are the duplicates of the leading and ending part of the OFDM symbol respectively. The OFDM symbol with the heter-cycle abutted cyclic prefix possesses double-cycle characteristic. The short cycle equals the length of CPt , the long cycle is equal to the length of data part of the OFDM symbol. Base on above, coarse frequency offset can be estimated by correlation calculating on received CP2 signal, then fine frequency offset can be estimated by correla- tion calculating on received CP2 signal. By introducing a short CP~ and consuming the little resource, the proposed frequency estimation algorithm in this paper can achieve larger frequency estimation range and overcome the defect of fixed frequency offset estimation range in current frequency estimation method, while obtaining fine frequency calibration.