Research On Channel Estimation And Equalization Algorithm For FBMC System

Nowadays,CP-OFDM(Cyclic-Prefix Orthogonal Frequency Division Multiplexing)is the most widely used modulation scheme in many current standards such as 4G LTE(Long Term Evolution)and 5G NR(New Radio).However,the poor stop-band attenuation of the sub-carrier filters deteriorates the spectral efficiency of OFDM system.FBMC(Filter Bank Multi-Carrier)system based on OQAM(Offset Quadrature Amplitude Modulation)modulation is considered as a candidate waveform to replace OFDM,which offers higher spectral efficiency,lower off band radiation and does not require cyclic prefix.This paper first introduces the basic principles of CP-OFDM and FBMC-OQAM modulation,and uses the concept of prototype filter to summarize the two multi-carrier modulation technologies into a unified mathematical model.This paper uses PHYDAYS prototype filter to build FBMC-OQAM transceiver system.Through simulation,it is proved that FBMC-OQAM has better out-of-band performance,higher spectrum utilization,and better bit error rate performance than CP-OFDM in frequency selective channel.Since FBMC-OQAM system suffers from an inevitable interference.Thus,conventional channel and CFO(Carrier Frequency Offset)estimation methods in OFDM is not suitable for FBMC system any more.In this paper,we present a novel CIR(Channel Implues Response)and CFO estimation method with scattered pseudo-pilots and iterative decision feedback structure.By using computer Simulation,we show that the proposed algorithm has better channel estimation performance than the estimation method based on auxiliary pilot.Moreover,time-frequency resources that used for pilot in the proposed algorithm is only half of auxiliary pilot based method.Finally,this paper introduces the correlation of the inherent interference in FBMC system,and demonstrates that this correlation will rapidly weaken as the channel multipath delay increases.Therefore,the algorithm that uses correlation to improve the system's resistance to inherent interference does not work well in the actual wireless channel environment.This paper proposes an interference cancellation algorithm based on decision feedback.This algorithm greatly improves the BER performance of the FBMC system and overcome the error floor of traditional algorithms.