Key Technologies Of Co-frequency Interference Cancellation In Spectrum Symbiosis Systems

In recent years,the contradiction between the explosive growth of wireless communication services and the increasing shortage of electromagnetic spectrum resources has become increasingly prominent,leading to the urgent demand for spectrum symbiosis in military and civil fields.For example,the signal sent by a radio station in a military command vehicle interferes with another radio station in the same vehicle,resulting in poor voice and shortened communication distance.For another example,in full duplex communications,the self-interference caused by near-end transmitted signal to the receiving channel leads to the decline of system throughput.The mutual interference caused by spectrum symbiosis reduces the goal achievement degree of military equipment and civil equipment,which is an urgent problem to be solved in the realistic society.This dissertation focuses on the key technologies of co-frequency interference cancellation in spectrum symbiosis systems,trying to make the spectrum symbiosis possible under the constraints of the real environment.The main contributions are summarized as follows.The reconstruction errors and cancellation performance of symbiotic interference are analyzed.First,according to the environmental characteristics of spectrum symbiotic wireless communication,the comprehensive effects of non-ideal engineering factors such as time-varying and multipath channel,and phase noise on the reconstruction errors and cancellation performance of symbiotic interference are analyzed,where the interference cancellation ratio(ICR)is derived as closed-form expression.Then,the upper bound of ICR and the lower bound of capacity loss are analyzed by considering that the time-frequency synchronization and channel estimation reach their Cramer-Rao bounds.A time-amplitude-phase joint cancellation algorithm for spectrum symbiosis interference is proposed.First,by considering imperfect time synchronization and channel estimation,the closed-form expression of the residual reception power at the authorized node under raised cosine filtering is derived.Then,a time-amplitude-phase joint cancellation algorithm for spectrum symbiosis interference is proposed to minimize the residual reception power,where theoretical analysis and simulation results show that the proposed algorithm has lower space and time complexity.An optimal symbiotic power allocation scheme is proposed.First,for a physical layer secure communication system protected by symbiotic interference,considering the residual interference introduced by imperfect time-frequency synchronization at the authorized node,a symbiotic power allocation scheme is proposed to maximize the secrecy capacity,and the closed-form expression of optimal power allocation factor is derived.Then,for the scenario of imperfect symbiotic interference cancellation,the relative relationship between the optimal interference power,the authorized channel,and unauthorized channel is analyzed.The experimental verification platform of spectrum symbiosis is built.Firstly,taking a point-to-point communication system as an example,the architecture of symbiotic interference cancellation in a typical physical layer security scenario is studied.Secondly,a reconfigurable experimental platform based on field programmable gate array(FPGA)is built.Finally,the proposed architecture is verified by experiments.Experimental results show that with carrier frequency of 100 MHz,symbiotic interference bandwidth of 100 k Hz,expected signal bandwidth of 50 k Hz,total transmitting power budget of 20 d Bm,and noise power spectral density of-95 d Bm/Hz,the proposed architecture can provide the symbiotic interference cancellation capability of 51 d B.The research results of this dissertation can be widely used in wireless communication systems such as physical layer security,full duplex,ambient backscatter,satellite communication,relay forwarding,and electronic countermeasures,so as to enhance the spectral efficiency,improve the electromagnetic compatibility,and meet the era requirements of information equipment.