Research On Wideband Digital Self-interference Cancellation Technology Based On Perfect Reconstruction

Full-duplex technology allows local transceivers to send and receive signals in the same frequency band at the same time,which has become an effective solution to improve spectrum utilization,and is widely used in radar,aerospace,communications and other fields.Meanwhile,the key problem to be solved urgently in the co-time and co-frequency fullduplex(CCFD)system is its self-interference(SI),that is,the signal sent by the local transmitter will seriously affect the local receiver.In order to realize an ideal full-duplex system,it is necessary to perform self-interference cancellation(SIC)in the spatial domain,analog domain and digital domain.Among them,the digital self-interference cancellation(DSIC)technology has a direct impact on the final self-interference suppression effect,especially in full-duplex systems.At present,adaptive DSIC technology is widely used in full-duplex systems due to its strong flexibility and wide application range.In this paper,a DSIC technology based on perfect reconstruction(PR)is proposed to solve the problem of performance degradation of traditional full-band DSIC technology when suppressing instantaneous broadband SI signals.The performance of the proposed algorithm is analyzed by theoretical derivation and simulation experiments,and the proposed algorithm is applied to the long-term evolution(LTE)communication system.The specific research content of this article is as follows:Firstly,this paper analyzes the performance of traditional SIC cancellation methods in broadband scens.Aiming at the problem that the performance of traditional SIC deteriorates with the increase of signal bandwidth,a DSIC technology based on PR has been proposed.Above all,the SIC model and algorithm based on PR are introduced.In this method,broadband signals are divided into narrow-band channels by using analysis filter banks,and SIC is carried out in each sub-channel,and then the cancelled sub-signals in each channel are reconstructed into full-band signals by using DSIC,thus realizing broadband SIC.Then,this paper takes the residual SI signal power,interference cancellation ratio and computational complexity as evaluation factors,analyzes the performance of the proposed method,and discusses the influence of parameters such as the number of channels,the number of extractions,and the step size factor on the performance of the algorithm.Finally,the traditional cancellation method and the cancellation method based on PR are simulated respectively.The experimental results show that under broadband conditions,although the computational complexity of the DSIC method based on PR is higher than that of the traditional method,its SIC effect is better,and the residual SI power after cancellation is lower.Second,this paper analyzes the application effect of DSIC technology based on PR in LTE wireless communication system.Above all,the requirements of the LTE full-duplex system for SIC capabilities and time-frequency synchronization are analyzed.Then,the influence of DSIC performance on time-frequency synchronization error and bit error rate(BER)is studied.With the increase of the number of channels,the performance of SIC based on PR is better,the ISI and ICI caused by time-frequency synchronization errors are smaller,the signal-to-interference-to-noise ratio increases while the BER decreases.Finally,the LTE system is modeled and simulated.The experimental results show that compared with the full-band NLMS cancellation method,the DSIC method based on PR significantly reduces the BER of the LTE communication system.The above-mentioned research results provide theoretical and methodological support for DSIC technology in wideband FD systems.In practical engineering,the DSIC technology based on PR proposed in this article can be applied to the FD systems such as next-generation mobile communication and radar repeater jammer.