Research On Channel Estimation For OFDM/OQAM Systems

With the rapid development of wireless mobile communication technology,users have higher requirements for the transmission rate of the system.To meet the demand of 5G to10 Gbps,more spectrum resources must be used to meet the demand.As a kind of non-renewable resource,spectrum has become very scarce.It is necessary to improve the spectrum utilization by using new waveforms.Orthogonal Frequency Division Multiplexing/Offset Orthogonal Amplitude Modulation(OFDM/OQAM)technology has attracted wide attention in wireless applications due to its excellent spectral concentration characteristics.However,as a technical standard,it faces the problems of low accuracy and high complexity of channel estimation.Because the system has inherent interference,the traditional multi-carrier mature technology cannot be used directly.Aiming at the problem of high complexity of channel estimation and how to pursue higher spectrum efficiency,the channel estimation technology of OFDM/OQAM system is deeply studied.Firstly,this paper introduces the implementation principle of OFDM/OQAM system,focuses on the fast implementation algorithm of OFDM/OQAM system and the pulse shaping filter function,which has an important impact on channel estimation,and analyses the OQAM modulation.The simulation results show that OFDM/OQAM system has better performance than OFDM system.Secondly,the pilot design of OFDM/OQQAM system and channel estimation technology in non-sparse channel is studied.The pilot design based on interference utilization is mainly studied,and the performance of different pilot structures is analyzed.On the basis of pilot design,the interference cancellation method,interference utilization method and LMMSE estimation method are studied.In view of the fact that the channel covariance matrix cannot be predicted beforehand,the LMMSE channel estimation method is improved,and the channel covariance matrix is estimated by iterative method.The simulation results show that the improved LMMSE channel estimation has better BER performance.Finally,channel estimation for OFDM/OQAM systems in sparse channels is studied.Several commonly used compression sensing reconstruction algorithms are studied andtheir reconstruction performances are analyzed.By introducing the idea of threshold,an improved ASP algorithm based on subspace matching pursuit algorithm is proposed.The ASP algorithm is applied to sparse channel estimation,the simulation results show that the ASP algorithm improves the performance of reconstruction and bit error rate greatly.