基于相位差的TD-SCDMA终端频偏估计

A frequency estimation for TD-SCDMA UE based on phase difference

提出一种TD-SCDMA系统小区搜索过程频偏估计方法。在扰码和Midamble码(中导码)识别之前,用下行同步(synchronous downlink,SYNC-DL)码部分数据做频偏估计,在控制复帧同步之前,用Midamble码部分数据做频偏估计,且2个阶段的频偏估计采用同一个64 chip(码片)输入的频偏估计结构,节省资源。仿真表明,通过多子帧平均或者无限脉冲响应数字滤波器(infinite impulse response,IIR)滤波,该方法能够将残余频偏控制在0.05百万分比(part per million,PPM)之内,满足TD-SCDMA系统对频偏的要求。

The new method to implement frequency offset estimation in cell search of the TD-SCDMA system is proposed in this paper. The received partial data of the synchronous downlink（SYNC-DL） code is used to calculate frequency offset be- fore the scrambling code and the Midamble ID is identified. The received midamble data can be used to calculate frequency offset before controlled Multi-frame synchronization. The frequency offset estimation with two stages can use the same 64chip to calculate structure, and the hardware resources can be also conserved. The simulation results show that the meth- od can control the residual frequency offset within 0. 05PPM （part per million）by smoothing of sub-frame or fiR filtering, which matches with the requirements of TD-SCDMA system for residual frequency.