Research On Propagation Characteristics And Cancellation Technology Of Far-field Reflected Self-interference Signal

Nowadays,In-band full-duplex(IBFD)has become an active research topic to promote spectrum efficiency.Within an IBFD system,a transceiver simultaneously transmitting and receiving signal in the same frequency band.While signal transmitted by local transceiver inevitably causes self-interference to the reception of desired signal.This thesis mainly focuses on far-field reflected self-interference signal,and its propagation and cancellation.Firstly,fading characteristic of wireless channel and IBFD technology are introduced.Self-interference signals in IBFD are also classified and causes of far-field reflected self-interference is analyzed emphatically.Calculation of far-field reflected self-interference signal is given with reference to radar echo.Techniques for self-interference cancellation are also described,including channel estimation,self-interference reconstruction,and cancellation in digital domain.It also introduces commonly used methods of channel estimation.Secondly,far-field reflection channel is mathematically modeled.According to the model,representation of reflected self-interference signal,desired signal,half-duplex performance SNR and IBFD performance SINR are given.After that,applicable scenarios of IBFD are qualitatively analyzed.By simulation calculation,the conclusion is drawn as follows: when there is no LOS signal,IBFD can not communicate effectively unless reflectors are distributed around the opposite end,therefore self-interference cancellation must be performed.Thirdly,a cancellation scheme of Rayleigh fading channel is designed,which includes generation of estimation signal,construction of self-interference channel,channel estimation,and self-interference cancellation.In the part of channel estimation,six channel estimation algorithms are compared,and then MMSE channel estimation algorithm based on DFT is selected.Finally,self-interference cancellation is made for WIFI and Microcell scenarios by simulation.SIR/SINR and spectrum efficiency are also analyzed based on different factors,such as distribution of scatters,communication distance,and power ratio of transmitted signal to noise.Results show that: for Microcell scenario,base station can not work in the mode of IBFD when reflectors are nearby,even if self-interference cancellation is performed,because self-interference power is too strong.For WIFI scenario,spectrum efficiency is greater and almost twice over half duplex.