Research On Narrow-Band Interference Suppression In OFDM System

OFDM technology has become the most commonly used MCM technique because of its advantages of high spectrum utilization,strong anti-multipath ability.Many wireless communication systems adopt OFDM technology.But in the past few years,the explosive growth of wireless services has led to the increasing demand for spectrum,resulting in interference between different independent communication systems.NBI is one of the most common interference.NBI suppression technology has gradually become one of the key technologies in OFDM systems.In this paper,the influence of different types of NBI on OFDM system is simulated.At the same time,the commonly used methods of NBI suppression are simulated.The results show that NBI has a great impact on the performance of OFDM system because of the frequency leakage of NBI caused by the receiver in FFT process,and at the same time,it not only suppresses NBI but also loses useful signals in the process of frequency-domain zero setting.So in order to eliminate the influence of NBI on the system,two improved algorithms are proposed in this paper.They are to reduce the loss of useful signals and avoid the leakage of interference energy,respectively,to suppress the influence of NBI on the performance of OFDM system.In this paper,an improved algorithm is proposed to estimate and reconstruct the parameters of NBI in frequency domain,so as to eliminate the interference.Firstly,the ML estimation method combined with zero filling interpolation method is used to estimate the interference frequency initially,and then the WPA algorithm is used to obtain the accurate estimation of the interference frequency.The simulation results show that the improved algorithm can effectively improve the BER performance of the system under different NBI conditions.This paper also proposes a NBI cancellation technique based on interference alignment for OFDM,which can reduce the impact of spectrum leakage by estimating the frequency of monotone interference and moving it to the frequency point orthogonal to the OFDM subcarrier.The performance comparison between this method and zero-setting method is verified by simulation,and an adaptive interference suppression scheme is proposed.