iNET系统多径衰落信道下的两步频偏估计算法

针对多径衰落信道下的载波同步问题，通过分析修正的经典估计器不能同时兼顾估计范围和估计精度的缺陷，提出了一种两步频偏估计算法.对于iNET系统采用的SOQPSK-TG信号，利用前导码的周期性，对多径衰落信道下的频偏估计进行了研究.首先在保持iNET帧结构导频开销不变的前提下，对前导码结构进行改进；然后基于改进Kay算法进行粗估计，再用L&R算法进行细估计；推导了改进前导码结构下的Kay估计子和L&R估计子.理论分析和仿真结果表明，所提同步方案的估计范围扩大了一倍，估计精度也可以达到克拉美罗界.

A Two Step Frequency Offset Estimation Algorithm Using the iNET Preamble in Multipath Fading Channels

Aiming at the carrier synchronization problem in multipath channels,a two-step estimation algorithm is proposed by analyzing the defects of the modified classical estimators that can't take account of the range and the accuracy of the estimation simultaneously.For SOQPSK-TG signal used in iNET system,the frequency offset estimation in multipath fading channels is studied by using the periodicity of the preamble.First,the structure of the preamble is improved,keeping the pilot overhead of iNET frame structure unchanged.The improved Kay algorithm is used to ensure the estimation range.And then,the L&R algorithm is used for fine estimation.Also,the modified Kay and L&R estimators are derived under the improved preamble structure.Theoretical analysis and simulation results show that the range of the proposed estimation synchronization scheme is two times the range of the classical estimators,and the estimation accuracy can reach CRB.