Research And Implementation Of Channel Estimation And Equalization In SC-FDE System

Single carrier frequency domain equalization(SC-FDE)technology is the key technology of IEEE802.16 a standard.It can effectively resist multipath fading and overcome the shortcoming of high peak to average ratio of OFDM technology,and its complexity is lower than the time domain equalizer.Therefore,SC-FDE technology has attracted wide attention in many fields.With the continuous increase of data transmission rate,the traditional channel estimation and equalization algorithms often get good communication performance at the expense of increased complexity.This paper focuses on the research of low complexity channel estimation and equalization algorithms.The main contents are as follows:(1)The Clarke channel model of flat fading channel is analyzed and combined with tapped delay model to model and simulate the classical frequency selective channel SUI channel.Secondly,the mathematical basic principle of SC-FDE is described in detail,and the frame structure of SC-FDE system is discussed.Finally,the peak to average power ratio,bit error rate and channel capacity of SC-FDE technology and OFDM technology are compared and analyzed.(2)In view of the shortcoming of traditional channel estimation algorithm which is prone to noise interference,an improved channel estimation algorithm for noise reduction is proposed.First,the traditional frequency domain LS estimation algorithm in the SCFDE system,the frequency domain MMSE estimation algorithm and the time domain LS estimation algorithm are studied in detail.The advantages and disadvantages of the three traditional channel estimation algorithms are compared,and the simulation verification is carried out.Among them,the LS estimation algorithm is simple and easy to be realized,but it is greatly affected by noise.Therefore,based on the time domain LS estimation algorithm,this paper proposes a simplified matrix operation process based on UW sequence correlation calculation to estimate the maximum delay extension of the channel,which achieves the goal of noise reduction and improves the estimation precision.(3)In view of the high complexity of the nonlinear equalizer,an improved low complexity block iterative decision feedback equalizer is proposed at low SNR.Firstly,the traditional linear equalizer's zero forcing algorithm and the least mean square error algorithm,the block iterative decision feedback equilibrium of the nonlinear equalizer and the block iterative decision feedback equalizer with low complexity are studied in detail,and the advantages and disadvantages of the equalization algorithm are compared,and the imitation true verification is carried out.The results show that linear equalization is simple but easy to be affected by noise.Although the nonlinear balance is good in performance,its complexity is too high.Therefore,in the case of low signal to noise ratio,this paper proposes an improved algorithm of block iterative decision feedback equalizer based on low complexity.It performs signal compensation before decision and further eliminates Intercode interference.The simulation verification is carried out,and the performance is better than that of the traditional algorithm.(4)According to the carrier frequency offset of the SC-FDE system,a correlation algorithm is proposed to estimate the carrier frequency offset value.The carrier frequency offset compensation is carried out before the equalization processing,and the carrier frequency offset problem is solved.(5)The channel estimation and equalization algorithm of SC-FDE system is realized based on FPGA.The whole hardware system is divided into modulation and demodulation module,multipath channel module,channel estimation module,channel equalization module and decision module.The FPGA implementation is carried out according to the modularization idea.The hardware test results show that the performance of the SC-FDE channel estimation and equalization algorithm is consistent with the theoretical analysis.