Research On Digital Self-interference Cancellation In Co-time Co-frequency Full Duplex Systems

At present,5G wireless communication technology has entered the stage of formal commercial.6G research has also been put on the agenda and a series of related technologies of communication have been applied.How to rationally utilize wireless spectrum resources is also facing a huge challenge during the increase of users and business volume.Co-time Co-frequency Full Duplex(CCFD)is different from the traditional Time Division Duplexubg(TDD)and Frequency Division Duplexing(FDD).CCFD can achieve signal transmission using the same frequency channel in the same time interval.This means that compared with TDD and FDD modes,the use of CCFD mode of communication can greatly improve the utilization efficiency of wireless spectrum resources,thereby effectively solve the contradiction between the substantial increase in users and the depletion of wireless spectrum resources.Although the CCFD mode has attractive prospects,there will be a problem of excessive self-interference signals when performing wireless communication in the CCFD mode.In order to realize the normal communication of CCFD,the work of self-interference cancellation is inevitable.Existing self-interference cancellation technologies mainly include self-interference cancellation technologies such as antenna,analog domain,and digital domain.This article mainly studies the CCFD digital domain self-interference cancellation technology.Aiming at the deficiencies of the existing digital domain self-interference cancellation schemes,a self-interference improvement scheme in the digital domain is proposed.The research contents of this paper mainly include:Firstly,Introduced the working principle of CCFD and various self-interference cancellation techniques in detail,pointed out that the traditional digital domain self-interference cancellation method has the problems of poor interference cancellation ability and inability to track the channel in real time,indicating that the necessity of adopting adaptive filtering method in the cancellation in the self-interference digital domain.A self-interference cancellation model in the digital domain based on adaptive filtering is established,combined with subsequent simulation experiments,to prove the feasibility of the scheme.Secondly,an improved variable step-size Least Mean Square(LMS)algorithm is introduced,and the problems existing in traditional adaptive filtering methods and the existing variable-step LMS algorithm are analyzed in detail.A new variable step size LMS algorithm(IVSSLMS)is proposed based on the hyperbolic tangent function,which improves the performance of existing algorithms.In this paper,the principle and performance of the algorithm are explained in detail,focusing on the convergence conditions of the algorithm,and the interference cancellation ratio(Interference Cancel Ratio,ICR)of the algorithm in the steady state is given.Through simulation experiments of IVSSLMS algorithm and other existing algorithms,it is concluded that the performance of this algorithm is better than that of existing algorithms.Finally,A digital domain self-interference cancellation model based on the IVSSLMS algorithm is established in the digital domain self-interference cancellation,and the specific process of using this algorithm for digital domain self-interference cancellation is explained.The final simulation experiment shows that using IVSSLMS as a self-interference cancellation algorithm in the digital domain has better performance in terms of ICR and convergence time.