At The Same Time, The Same Frequency Full Duplex Self-interference Suppression Technology Research

Frequency Division Duplex and time division duplex are two types of half-duplex communication modes in today's wireless communications.Frequency division duplexing or time division duplexing is a waste of time resources or frequency resources,and the spectrum utilization is low.Co-time co-frequency full duplex overcomes the shortcomings of low utilization of half-duplex communication spectrum,and its spectrum utilization is twice that of half-duplex.Co-time co-frequency full duplex has its own advantages,but at the same time it faces some challenges.The biggest challenge is that the locally transmitted power of the near-end signal affects the far-end weaker power transmitted by the far-end spatially fading environment.The ability of the signal to receive,that is,the interference of the local signal to the far-end signal.In order to suppress the near-end signal interference,antenna domain,analog domain,and digital domain self-interference suppression techniques are currently used.The thesis makes a brief introduction to these three technologies respectively,and focuses on the digital domain self-interference suppression technology based on WCDMA-based co-time co-frequency full-duplex communication.The digital domain self-interference suppression technology focuses on the digital domain self-interference based on reference signals.The suppression technique analyzes the effects of residual self-interfering signals on time synchronization,frequency synchronization,and bit error rate after digital self-interference suppression.Finally,simulations are performed separately.Firstly,describes the application scenario of the research object of this thesis and cotime co-frequency full duplex full-duplex communication system based on WCDMA is set up.The digital domain self-interference suppression algorithm is briefly introduced.A digital domain self-interference suppression algorithm based on reference signals is designed and simulated and verified the algorithm's self-interference suppression capability in the established link.The simulation results show that the interference signal power is smaller than the original signal before and after the self-interference suppression.When the SIR(interference signal ratio)is 40 dB,the self-interference suppression ability of the algorithm used in this paper can reach about 60 dB.Secondly,the influence of residual self-interfering signals on time synchronization and frequency synchronization is analyzed.The residual signal contains residual selfinterference signals,useful signals,noise.And residual self-interference signals will inevitably affect the time synchronization of the useful signal and affect frequency synchronization.This thesis designs the time synchronization algorithm and frequency synchronization algorithm for WCDMA based co-time co-frequency full-duplex communication and simulates the effect of residual self-interfering signals on time synchronization and frequency synchronization.The simulation results show that the residual self-interference signal will affect the time synchronization and frequency synchronization;the residual self-interference signal will make the time synchronization acquisition probability smaller,the normalized mean square error of the frequency offset estimation in the frequency synchronization will become larger.When the signal-to-noise ratio is fixed,with the increase of the interference-to-signal ratio,the time synchronization acquisition probability and the normalized mean square error of the frequency offset estimation are basically unchanged.Finally,the influence of the residual self-interference signal on the bit error rate is analyzed.The simulation shows that the residual self-interference signal will affect the bit error rate.The residual self-interference signal will increase the bit error rate;when the signal to noise ratio is fixed,the bit error rate will remain basically unchanged with the increase of interference-to-signal ratio.This thesis studies the digital domain self-interference suppression technology of WCDMA-based simultaneous co-channel full-duplex communication system.At the same time,it studies the influence of residual self-interfering signal on time synchronization,frequency synchronization and bit error rate after self-interference suppression.And it provides a certain theoretical basis for engineering practice.