Research On Joint Channel Estimation And Equalization Technology In FBMC System

The Filter Bank Multi-Carrier(FBMC)technology,with its good time-frequency characteristics,low out-of-band leakage and high spectrum efficiency,is widely regarded as an effective multi-carrier technology to deal with the scarcity of wireless communication spectrum resources.According to different baseband modulation modes,i.e.,Offset Quadrature Amplitude Modulation(OQAM)and Quadrature Amplitude Modulation(QAM),the FBMC system can be divided into FBMC/OQAM and FBMC/QAM.Due to the lack of cyclic prefix,the two FBMC systems will generate residual interference after passing through the multipath channel,which brings challenges to the channel estimation and channel equalization in the communication system.In addition,channel estimation and data equalization alone are limited to improving the anti-interference ability of the receiver.Therefore,this thesis mainly studies the joint channel estimation and equalization algorithm in the FBMC system.The main work of the thesis is as follows:This thesis first describes the basic principles of the FBMC system,introduces the typical channel estimation algorithms and channel equalization algorithms,and presents the characteristics of the wireless fading channel.Then the research and performance simulation of the joint channel estimation and equalization is carried out on the FBMC/OQAM and FBMC/QAM systems.Finally,the summary and prospect of our work is illustrated.Aiming at the FBMC/OQAM system under the traditional Interference Approximation Method(IAM)pilot structure,only the interference is used to suppress the noise part during channel estimation,and the interference and noise seriously affect the equalization performance during channel equalization.A joint channel estimation and equalization algorithm is proposed based on the Recursive Least Squares(RLS)channel estimation algorithm.The proposed algorithm first uses the IAM pilot structure to perform channel estimation and equalization initialization,then combines the data equalization information in the previous symbol with the interference coefficient to reconstruct the pseudo pilot,and finally uses the channel estimation and reconstruction information at the previous two symbols to derive the current channel information.This algorithm can not only eliminate the impact of interference on channel estimation,but also track channel information in real time,thereby reducing the channel estimation errors and improving the equalization performance.The simulation results show that the algorithm has a significant improvement in channel estimation performance compared to the traditional algorithm in frequency selective channels,and as the number of recursions increases,the performance improvement becomes greater;in terms of channel equalization,the joint algorithm can effectively improve the signal-to-noise ratio gain when compared with the traditional channel estimation and equalization algorithm.In view of the traditional Iterative Interference Cancellation(IIC)algorithm in FBMC/QAM system,the involved channel estimation does not consider the noise,which seriously degrades the calculation accuracy of residual interference and the system equalization performance.An improved iterative interference cancellation algorithm is proposed based on the Minimum Mean Square Error(MMSE)channel estimation.The proposed algorithm suppresses the noise interference in channel estimation,reconstructs and feeds back equalization information through an iterative algorithm,and continuously calibrates the calculation accuracy of residual interference,which finally improves the channel estimation and equalization performance.The simulation results show that,compared with the traditional IIC algorithm,the channel estimation performance and equalization performance of this algorithm under the frequency selective fading channel are significantly improved under the low signal-to-noise ratio regimes.