Investigation Of Optical Self Interference Cancellation For In-Band Full-Duplex Communication

With the research and deployment of the next generation of mobile communication networks,various novel wireless multimedia services are emerging constantly,and the user's demand for the transmission rate and capacity of the wireless communication system is constantly increasing.Inband full-duplex(IBFD)can support bidirectional simultaneous wireless transmission within the same band at the same time.Compared to frequency-division duplex(FDD)and time-division duplex(TDD)schemes,IBFD can double the spectrum efficiency of wireless systems and realize high density and high efficiency network access.In band self-interference cancellation is the key technique in IBFD communications.The main SIC schemes are divided into electrical selfinterference cancellation(ESIC)and optical self-interference cancellation(OSIC).Compared with the ESIC schemes,the OSIC schemes can achieve high-precision attenuation and delay matching and break through the bandwidth and the working band limit of the ESIC,thus to meet the requirements of large-capacity long-distance transmission of IBFD wireless communication systems.In this dissertation,theoretical modeling and experimental verification of optical self-interference cancellation based on DML and DDMZM are carried out.In the theoretical modeling,we first analyze the cancellation bandwidth and deduce that the delay deviation is the key factor that affects the cancellation bandwidth,and quantitatively prove the bandwidth advantage of the optical solution compared with the electrical solution.Secondly,the cancellation depth is analyzed.The important factors affecting the narrow band cancellation are the attenuation and the delay deviation.The main factors affecting the broadband cancellation are the frequency selective amplitude and phase mismatch.The research shows that this model can be applied to most typical linear modulation optical self-interference cancellation systems.In DML-based self-interference cancellation experiments,the logarithmic periodic antenna is used to transmit and receive wireless signals.The theoretical prediction and the actual cancellation effect in the wireless frequency band can be well matched,which proves the accuracy of the proposed theoretical model.The experimental results show the broadband suppression effect of the optical self-interference cancellation system.The cancellation depth of 22 dB can be achieved in the 450 MHz bandwidth near 900 MHz and the cancellation depth of 25 dB can be achieved in the 440 MHz bandwidth near 2.4GHz.On the other hand,in DDMZM-based selfinterference cancellation experiment,the simulation system is built by using Optisystem and Matlab software,and the feasibility and good transmission performance of the in-band full-duplex optical wireless system based on DDMZM are proved.Finally,this paper introduces the large bandwidth advantage of optical self-interference cancellation system into full-duplex MIMO(MultipleInput Multiple-Output)and proposes DML and DDMZM based OSIC system for 2 × 2 MIMO full duplex system.The feasibility of the scheme is verified in the simulation experiment.