Research On Channel Estimation Of FBMC System Based On Preamble Design

Orthogonal frequency division multiplexing(OFDM)system has been unable to fully meet the demand of future mobile communications because of poor ability to resist the carrier frequency offset(CFO),large side lobes and low utilization of spectrum resources.The Filter Bank Multi-carrier(FBMC)system,which is an alternative modulation scheme for 5G,uses a filter with better time-frequency localization characteristics to resist inter-carrier interference(ICI)and inter-symbol interference(ISI).At the same time,it has the advantages of high spectrum utilization and small side lobes.However,compared with OFDM system,FBMC system relaxes the subcarrier orthogonal conditions,that is only orthogonal in the real domain,which makes the receiver symbols have imaginary interference problems.And traditional OFDM channel estimation algorithm cannot be directly applied to the FBMC sys tem.This paper studies the imaginary interference problems and proposes some improved algorithms for channel estimation in FBMC system.The specific work and contributions of the paper are listed as follows:(1)Two preamble structures and channel estimation algorithm based on FBMC system is proposed.The first pilot structure,denoted by the new IAM,where the opposite of data is placed on the other side of the pilot as auxiliary pilots,as a result it will reduce a row of pilot symbols.The second pilot structure,named by new POP,where it introduces an imaginary number to increase the equivalent pilot power,and improves the channel estimation performance.And the paper analyzed the performance of two new pilot structure algorithms theoretically.Simulation results show that the new pilot IAM algorithm can reduce the 1/3 pilot cost compared to IAM-R,IAM-C algorithms and improve the data transmission efficiency and is suitable for highefficiency data transmission.The new pilot POP algori thm introduces the imaginary pilot to increase the equivalent pilot power and reduces the noise interference and is suitable for scenarios with low signal to noise ratio(SNR).(2)An interference cancellation channel estimation algorithm based on the preamble correlation is proposed in FBMC system.In this paper,a new interference eliminating pilot structure is designed.On the basis of this,the channel estimation performance is improved by using the adjacent subcarrier correlation of the receiving pilot,and finally the algorithm is extended to the K subcarrier correlation to further improve the performance.Simulation show that the improved algorithm can obtain the smallest preamble peak compared with the traditional IIE and IEM algorithms.At the same time,when the signal to noise ratio(SNR)is in the range of 5 to 20,the new algorithm can improve its performance by approximately 1~2dB in the vehicle environment.(3)An amplitude-phase separation filtering algorithm based on FBMC system is proposed.According to the characteristics of imaginary interference between preambles,the paper designs a specific preamble sequence so that the amplitude and phase of different parity subcarriers are not affected by the surrounding data.The corresponding amplitude and phase extraction algorithms are used at the receiver and the channel estimation are obtained by combining the amplitudes and phase.Compared with the traditional algorithm,the new algorithm can thoroughly filter the interferen ce of the data around the pilot.The simulation results show that the BER and MSE of the new algorithm is better than the traditional amplitude-phase separation algorithm when the SNR is greater than 9dB,and it is more suitable for multi-path fading channel scenarios.