Research On DML-based Optical Self-interference Cancellation Technology For In-band Full-duplex Systems

With the development of the wireless communication,the bandwidth of the signals used in the wireless communication is wider and wider,but the corresponding spectrum resources is more and more scarcity.In order to save the spectrum resources and maximize the spectrum resources utility,in-band full-duplex(IBFD)technology has emerged as a research hotspot to enhance the spectral efficiency.IBFD technology meets the transmission capacity requirements of wireless communications by improving the spectrum utilization,alleviating the problem of the increasingly tense of spectrum resources.However,since the IBFD transmission antenna is close to the receiving antenna in physical position,the high-power transmission signal is received by the receiving antenna and interferes the lower power co-frequency receiving signal.Self-interference effect will reduce the quality of the received signal seriously,the signals-of-interest will be buried in the selfinterference signal and cannot be detected,thus restricting the realization of full-duplex technology.Therefore,the primary problem of implementing an in-band full-duplex system is eliminating the co-frequency self-interference signal.However,the existing self-interference cancellation(SIC)techniques are based on electronic schemes,cancellation depth lies in the limitation of RF components such as precision deficiency and constrained bandwidth.Hence,it is urgent to study SIC technology with higher frequency band,larger bandwidth and higher cancellation ratio.In this thesis,an optical SIC scheme based on optical signal processing is proposed,taking advantage of high precision and wider bandwidth of optical devices.Laying the foundation for the next generation 5G wireless communication applications.Several theoretical and experimental studies are implemented as follows:Firstly,the optical SIC technique based on DML is proposed for the first time,and it is low-cost than other optical self-interference cancellation methods.In addition,the system has the characteristics of large bandwidth and high cancellation ratio.Secondly,we built an IBFD transmission simulation system using the DML-based SIC system.The SIC technology and system performance in IBFD scenarios are studied.At last,the influence of amplitude and phase mismatch on SIC performance is analyzed.The optical SIC scheme and the simulation system provide a theoretical basis for the practical research of IBFD system.