Research On Self-interference Cancellation Technology Of Full-duplex Wireless Communication System Based On USRP And GNU Radio

The useful spectrum resources are almost exhausted.How to improve the spectrum utilization rate has become one of the research hotspots in the field of wireless communication.FD communication can simultaneously transmit and receive signals in the same time and frequency using the same transmission channel and equipment.Compared with the existing communication mode,the utilization rate of FD spectrum resources is doubled.However,the main problem of the full duplex system is the existence of serious self-interference.If the self-interference signal in the full-duplex wireless communication system cannot be sufficiently suppressed,the performance of the full-duplex radio will be seriously affected.In this paper,the following methods are proposed for the self-interference cancellation of full-duplex systems.Firstly,in the analog domain elimination,we design a low complexity double-tap adaptive vector reconstruction cancellation structure which simulates a self-interference channel.This circuit simulates the self-interference channel with a double-tapped circuit structure and reconstructs the self-interference signal at the receiving terminal after sending the signal through the circuit.The difference subtracter at the receiving terminal subtracts the reconstructed signal from actual self-interference signal to achieve self-interference signal cancellation.Aiming at the gain control of double-tap circuit,we propose an adaptive gain control algorithm based on the minimum residual mean square error to achieve the best self-interference cancellation.Then,in the digital domain cancellation,based on the software Radio hardware platform USRP and software platform GNU Radio,we designs a full-duplex communication platform and proposes the baseband model of full-duplex OFDM system.For the baseband model of the full-duplex OFDM system mentioned above,we also proposes a self-interference cancellation algorithm based on training sequence,which can eliminate self-interference signals in both frequency domain and time domain.This algorithm uses the estimated value of the self-interference channel and the known transmitting signal samples to reconstruct the self-interference signal?The self-interference estimation signal is subtracted from the quantized total received signal to eliminate self-interference.Finally,we experimentally verify the proposed double-tap adaptive vector reconstruction cancellation structure and digital domain cancellation algorithm.The experimental results show that the analog domain self-interference signal cancellation circuit designed in this paper can achieve an elimination level of up to 50 dB under different transmission signal bandwidths.The baseband model of full-duplex OFDM system is practical,and the digital domain self-interference elimination algorithm can effectively suppress 20 dB self-interference signals in the digital domain.