Research On Crosstalk Suppression Of OAM-MIMO Sysyem In Atmospheric Turbulence Channel

Orbital Angular Momentum(OAM)multiplexed communication can increase the channel transmission capacity,but due to the influence of atmospheric channels,the orthogonality between OAM modes could be destroyed during the transmission process,which could caused crosstalk.Like the traditional wireless optical communication,the Multi-Input Multi-Output(MIMO)equalization method can be used to reduce the inter-mode crosstalk and inter-symbol interference of the OAM multiplexed communication system.Aiming at the situation that the traditional blind equalization algorithm applied to OAM multiplexed communication system can not recover multiple signals at the same time,the blind equalization algorithm combined with blind source separation is used to simultaneously suppress multi-channel crosstalk.The main work is as follows:1.This paper introduced the blind equalization algorithm based on cross correlation function(CC)to suppress the crosstalk generated by the OAM multiplexing communication system under atmospheric channel transmission,thereby improving the performance of the communication system.Through numerical simulation,it analyzed the constellation recovery of the output signal,the average bit error rate of the system and the convergence speed of the algorithm under the effect of this algorithm.2.The multiuser kurtosis(MUK)maximization algorithm was a kind of blind source separation algorithm.It can also achieve the function of source separation when it acts on the OAM multiplexing communication system alone,thereby reducing the crosstalk of the communication system.It compared and analyzed its equalization effect with Constant Modulus Algorithm(CMA)through simulation.3.This paper introduced a high-order statistics based blind equalization Algorithm,which combines MUK Algorithm with Modified Constant Equalization Algorithm(MCMA).Then,it was applied to OAM multiplicated communication system,and its performance of suppressing crosstalk is analyzed by simulation.The research results show that both the CC-MCMA algorithm and the MUK-MCMA algorithm can recover multiplexed signals at the same time,and the latter has a better recovery effect on the output signal constellation diagram than that of the former.The comparison and analysis of MUK-MCMA algorithm,CC-MCMA algorithm,CMA algorithm and MUK algorithm's reduction of the system average bit error rate and convergence speed show that the equalization effect of MUK-MCMA algorithm is better than other algorithms.In the case of a certain signal-to-noise ratio,the MUK-MCMA algorithm is an order of magnitude better than the CC-MCMA algorithm in reducing the bit error rate,and its convergence speed is faster.