On The Research Of Physical-Layer Network Coding Based Interference Cancellation Technique

With the rapid development of Beyond the 5-th Generation(B5G)mobile communication systems,intelligent mobile Internet has been widely deployed in recent years,leading an explosively growing trend in wireless services.Targeting at the three typical application scenarios,namely broad bandwidth,low latency,and massive connectivity,B5 G has been fully integrated with many vertical industrial areas,such as Internet of Things(IOT)and smart home,thereby imposing higher requirements on the effectiveness and reliability of wireless communication networks.With the rapid growth of the number of user nodes in the system,the inherent resource-constrained characteristics of wireless channels will inevitably lead to the performance degradation due to the increasing interference among users.Therefore,aiming at the actual application scenarios,fully utilizing the advantages of B5 G systems by implementing interference cancellation under limited frequency band resources,has great significance in both academic research and industrial application.The existing research work on interference cancellation can be categorized into two types:self-interference cancellation and multiple access interference cancellation.In selfinterference cancellation,the current popular implementation methods can be divided into antenna domain self-interference cancellation,radio-frequency domain self-interference cancellation,and digital domain self-interference cancellation.Sophisticated processing algorithms and additional high-power dedicated devices cannot meet the requirements of practical application scenarios with limited energy and power.In multiple access interference cancellation,the existing research results mainly focus on Non-Orthogonal Multiple Access(NOMA),which improves the access performance under the limited orthogonal resources such as traditional time/frequency/codes by the reuse of nonorthogonal resources such as power domain.However,there exist some problems in the classic Successive Interference Cancellation(SIC)such as error propagation,and long multiuser queuing delay.In view of the above reasons,this thesis takes throughput and outage probability as the starting point,conducts the research on physical-layer network coding(PNC)-based selfinterference cancellation and multiple access interference cancellation technology in typical wireless communication scenarios of backscatter communication and downlink NOMA,which improves the effectiveness and reliability of the system.The main contributions of this thesis can be summarized as follows:1.PNC-based self-interference cancellationIn energy/power-limited backscatter communication scenarios,a dual-antenna architecture is proposed to achieve simultaneous co-frequency full-duplex communication.For the selfinterference problem,a PNC-based backscatter mapping model is constructed.Then a PNC information domain self-interference cancellation algorithm is proposed,which achieves information recovery under self-interference conditions through multi-state superposition packet exclusive-or demodulation.The simulation results show that the throughput performance gain of the proposed method can reach up to 100%.Based on the above results,a circuit prototype is designed for self-interference cancellation enabled full-duplex backscatter circuit.With this prototype,the actual test results are derived to further demonstrate the effectiveness of the proposed method.2.PNC-based two-user multiple access interference cancellationAiming at the multiple access interference problem in the downlink two-user full-duplex cooperative NOMA scenario,we propose a PNC-based cooperative NOMA multiple access interference cancellation strategy and a joint demodulation model of PNC and SIC.Compared with the traditional SIC,the proposed strategy makes full use of solvable information,provides a demodulation diversity gain,and improves the probability of information recovery under multiple access interference conditions.Furthermore,we derive the closed-form expression of outage probability under Rayleigh fading channel,which proves the effectiveness of the proposed method.The simulation results show that compared with the traditional SIC-based cooperative NOMA strategy,the outage probability of the proposed method is reduced by an order of magnitude.3.PNC-based multi-user multi-access interference cancellationAiming at the problem of multiple access interference in the downlink multi-user NOMA scenario,we proposed a PNC-based multiple access interference cancellation strategy(Network-Coded Interference Cancellation,NCIC)is proposed on the basis of the aforementioned PNC-based two-user NOMA interference cancellation strategy.Compared with the traditional SIC,the proposed NCIC strategy can recover the superimposed information as a whole packet,which improves the outage performance.Furthermore,we deduce the boundary conditions of the NCIC strategy and further propose a boundary condition-based adaptive interference cancellation strategy(Adaptive NCIC,A-NCIC).According to the boundary conditions,the SIC and NCIC strategies are dynamically selected for multi-user multiple access interference cancellation.The simulation results show that the outage probability of the proposed A-NCIC strategy is one order of magnitude lower than that of the traditional SIC.