Performance Analysis On Physical Layer Security Of NOMA System With Imperfect SIC

With the continuous acceleration of the commercialization of the fifth generation mobile communication system(5G)and the development of the Internet of Things(Io T),the scarcity of spectrum resources,massive connections,low latency,etc.have become the most important issues currently facing.Due to good fairness for users,high spectrum efficiency,supporting multiple devices to simultaneously access the network at the same frequency,low transmission delay and signaling cost,etc.,non-orthogonal multiple access(NOMA)has a bright prospect for building 5G Io T networks.Besides,due to the openness of the 5G Io T network,communication security issues have become more prominent.Based on the random time-varying nature of the underlying channel,Physical layer security(PLS),as a supplement to cryptography in the upper layer of the protocol stack,theoretically ensures the absolute security of information transmission.The PLS performance research of the NOMA system is laying the base for the construction and evaluation of 5G Io T networks.The contents of the research are summarized as follows:1.The PLS performance characteristics of a single-eavesdropping and downlink two-user NOMA system are investigated when the successive interference cancelation(SIC)is imperfect.Firstly,through the reliability outage probability(ROP)of the NOMA users,the minimum transmit signal-to-noise ratio of the system that satisfies the interruption constraint is derived;Secondly,the exact and asymptotic analytical expressions for the secrecy outage probability(SOP)of the NOMA system in both strong and weak eavesdropping situations are derived;then,the definition of effective secrecy throughout(EST)is extended to the NOMA system,and the exact analytical expressions of EST are derived;Finally,the quantitative relationships between the reliability(ROP)and security(SOP and EST)of the NOMA/OMA system are analyzed and investigated.The results show that balancing the reliability and security of the NOMA system can optimize the overall performance of the system.When the ROP constraint is low,the security performance of the NOMA system is better than that of the OMA system;when the ROP constraint is high,the OMA system is more securer than the NOMA system.2.Considering the limitations of general PLS performance indicators(SOP and EST,etc.)for evaluating wireless communication systems,the application of Meta distribution theory in the evaluation of PLS performance of NOMA systems is investigated.Based on the related knowledge of probability theory and random geometry,the PLS performance of the multi-eavesdropping downlink two-user NOMA system is researched and analyzed.The accurate closed-form analytical expressions of the Meta distribution of the security rate of NOMA user under perfect and imperfect SIC are derived respectively,and the influence of each system parameter on the Meta distribution is analyzed,which makes up the gap in the research field of the PLS performance of the NOMA system in the research of Meta distribution theory.