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一种基于CRS插值的频偏估计方法
胡晓玲,张治中,程方
0
(重庆邮电大学 通信与信息工程学院,重庆 400065)
摘要:
针对正交频分复用系统对频率偏移异常敏感导致接收机无法正确解调信号的问题,提出了一种小区特定参考信号(Cell-special Reference Signal,CRS)改进的频偏估计方法。首先,对发送的CRS与接收的CRS进行互相关运算,得到信道估计值;然后,对CRS在频域进行插值,使得每个时隙中不同OFDM符号对应子载波位置的参考信号相同;最后,对两个不同OFDM符号中的参考信号部分进行相关性运算,求出频偏。与基于CRS的频偏估计方法相比,该方法用信道估计值做互相关运算,消除了噪声和多径干扰带来的影响;通过对CRS进行插值,提高了频偏估计精度;通过减小计算相关性的两OFDM符号间的距离,使频偏估计范围由\[-1 kHz,1 kHz\]扩大到\[-1.75 kHz,1.75 kHz\]。
关键词:  OFDM系统  频偏估计  CRS插值
DOI:
基金项目:国家科技重大专项(2015ZX03001013);重庆市重点产业共性关键技术创新重大主题专项(cstc2017zdcy-zdzx0030)
A frequency offset estimation method based on cell-special reference signal interpolation
HU Xiaoling,ZHANG Zhizhong,CHENG Fang
(School of Communication and Information Engineering,Chongqing University of Posts and Telecommunications,Chongqing 400065,China)
Abstract:
Because an orthogonal frequency division multiplexing(OFDM) system is extremely sensitive to the frequency offset,the receiver can′t demodulate the signal correctly.To solve the problem,this paper proposes a frequency offset estimation method based on cell-special reference signal(CRS) interpolation.Firstly,it calculates the cross-correlation between the transmitted and received CRS in frequency domain to obtain channel estimation values.Then,the CRS is interpolated in the frequency domain to ensure that each reference symbol transmits the same reference signal in each time slot corresponding to the subcarrier position.Finally,the frequency offset error is obtained by performing correlation operations between two OFDM symbols.Compared with CRS-based frequency offset estimation method,the proposed algorithm has higher estimation accuracy by interpolating CRS.By calculating the correlation of channels estimated value,it eliminates the influence of noise and multipath interference.By closing the distance between the two OFDM symbols with calculation correlation,it makes the frequency offset estimation range extended from\[-1 kHz,1 kHz\] to \[-1.75 kHz,1.75 kHz\].
Key words:  OFDM system  frequency offset estimation  CRS interpolation
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