Research On Misalignment OAM Communication System Based On UCA

Orbital Angular Momentum(OAM)can effectively solve the problem of spectral resource shortage in future mobile communication.Theoretically,OAM with infinite multiple modes has natural advantages in improving spectral utilization of communication system.At present,the OAM communication system based on Uniform Circular Array(UCA)is the most studied model,which is also the most likely to be applied.OAM communication system based on UCA requires perfect alignment of receiver and transmitter arrays,which is difficult to achieve in reality.Based on the practical application,this paper analyzes the characteristics of OAM beam amplitude and phase distribution of the system,and puts forward a solution to the misaligned OAM communication system.Aiming at the misalignment problem of OAM communication system based on UCA.In this paper,a beam scanning and beam matching scheme based on OAM is proposed by referring to NR beam management scheme.At the receiving and sending end,the matched beam can be obtained by beam scanning,and the information can be sent and received by matching beam pair without prior information.Simulation results show that the scheme has 20-30dB improvement in BER and 5-10dB gain in system capacity compared with the traditional receiving method.Moreover,OAM simulation beam control has high cost and great complexity.This paper proposes a digital precoding design based on OAM,which realizes the adjustable and controllable OAM beam through digital precoding,improves the flexibility of the system,and is compatible with the traditional Multiple Input Multiple Output(MIMO)system.OAM beam control can be realized by making the base band pass the Discrete Fourier Transform(DFT)or Fast Fourier Transform(FFT).Aiming at the problem of intermodal interference in multimodal multiplexing.In this paper,a modal selection algorithm is proposed.By selecting some modes as transmission modes,the interval between modes is increased,the interference between modes is reduced,and the energy efficiency of the system is improved.Simulation results show that the system capacity of Zero Force(ZF)and Minimum Mean Square Error(MMSE)algorithms based on modal selection has 0.2-1.5dB gain compared with traditional ZF and MMSE algorithms.On the basis of modal selection,a modal combination index feedback scheme is proposed to reduce the modal combination feedback cost in order to avoid excessive feedback cost at the receiving end.