Analog Feedback Digital Self-interference Suppression Key Technology And Verification Of 2×2 Full-duplex System

Full duplex communication can improve spectrum utilization and increase transmission speed by sending and receiving information at the same time and same frequency.But full duplex system can't distinguish between the local signal and the far-end signal,the local transmission signal will affect the remote signal,thus forming the self-interference signal.The self-interference suppression technology can be divided into three kinds: spatial domain,RF domain,digital domain interference suppression technology.In this thesis,we studied the architecture and algorithm of digital self-interference suppression,proposed the analog feedback form self-interference suppression,analyzed its working principle,deduced the Simulink simulation,and realized based on FPGA.Details are as follows:First of all,we explored the non-feedback form self-interference suppression model and its shortcomings and limitations;Then,we introduced the 2×2 analogy feedback form self-interference suppression model,and theoretically deduced its working performance,which showed that analogy feedback form model can effectively reduce the phase noise part and nonlinear part of self-interference.The simulation results showed that the suppression result of feedback architecture closely improved 12 dB than non-feedback architecture under the same self-interference phase noise and nonlinear part.Then,we researched on the self-interference cancellation performance based on the different modulation of full-duplex's emission signal.This paper theoretically analyzed the self-interference suppression performance of two modulation modes QAM and CPM.Theory and simulation showed that the system used CPM modulation improved about 2dB self-interference rejection than the system used QAM modulation.Finally,on the basis of the 2×2 LTE full duplex project,the architectural design and logical implementation of the key modules of analogy feedback digital self-interference suppression technology based on FPGA are realized.On the hardware platform,we tested the function of self-interference cancellation module.In a variety of scenarios,we measured the performance of interference cancellation module and found that the test results coincide with the theoretical analysis.The proposed analogy feedback self-interference suppression key technology researched in this thesis has been successfully applied in the 2×2 full duplex communication,which provides a theoretical and engineering reference for the further study of Co-Time Co-Frequency full duplex digital self-interference suppression technology.