Research On The Channel Equalization For FBMC-OQAM Systems

In recent years,the Filter Bank Multi-Carrier combine with Offset Quadrature Amplitude Modulation(FBMC-OQAM)system has attracted more and more attention.In the FBMC-OQAM system,influenced by the characteristics of the filter function in time domain and frequency domain,transmitted signal will subject to inherent interference.Under the ideal channel,this interference can be eliminated by the receiver filter.However,the signal transmit in the wireless channel will produce serious distortion,the receiver using the traditional equalization method can not effectively eliminate the inherent interference,which resulted in high bit error rate(BER).Therefore,it is significant to study the channel equalization algorithm in the FBMC-OQAM system.At present,the research of channel equalization technology in FBMC-OQAM system is not very mature,and the literature on this problem is relatively small.The research of this problem needs to be further combined with the traditional equalization algorithm and the FBMC system's own characteristics to redesign the equalization algorithm.In this thesis,the channel equalization algorithm of FBMC-OQAM system is studied mainly from the following aspects:1.The principle of FBMC-OQAM system is briefly described,and the condition of orthogonalization of multi-carrier system is analyzed.The reasons why FBMC system should introduce OQAM modulation and the real field domain orthogonal can only be realized are elaborated.compared FBMC-OQAM system to traditional Cyclic prefix-Orthogonal Frequency Division Multiplexing(CP-OFDM)system on the time-frequency distribution,the time-frequency filter focus,the bit error rate(BER)these three aspects,so the superiority of FBMC-OQAM is shown.The three kinds of concrete realization scheme of FBMC-OQAM system is listed,and the realization scheme of poly-phase network(PPN)filter bank is described in detail.2.The principle of the traditional linear equalization algorithm is deduced in detail,and the reason of the existence of the inherent interference is analyzed by the signal demodulation model of FBMC-OQAM system.The traditional zero-forcing(ZF)algorithm and the least mean square error estimation(MMSE)algorithm is applied for the FBMC-OQAM system.Combined with the simulation results,the shortcomings of the two traditional equalization algorithm in suppressing inherent interference isanalyzed.This thesis analyzes two MMSE equalization algorithms based on interference power estimation,and proposes a simplified MMSE equalization algorithm for interference power estimation by referring to the noise estimation method of OFDM system.3.Because the traditional equalization algorithm can not effectively eliminate the inherent interference of FBMC-OQAM system,this thesis analyzed the principle of the existing iterative interference cancellation algorithm.The existing algorithm has the problem of high computational complexity and high processing delay.Therefore,an interference cancellation algorithm which based on fast Fourier transform(FFT)is proposed,calculated the interference terms by FFT means that greatly reduces the complexity of the system.Based on further analysis,it is proved that the inherent interference is related to the phase of the channel gain of the frequency domain.Therefore,an interference cancellation algorithm based on channel phase preprocessing is proposed.The complexity of the algorithm is very low and the processing delay is small.