| The mobile communication system has experienced a long evolution in the past decades.The multiple access technology used in it has grown from frequency division multiple access,code division multiple access,time division multiple access to orthogonal frequency division multiple access.However,faced with the exponential growth of global mobile traffic,new multi-access technologies emerge.Non-orthogonal multiple access(NOMA)technology breaks through the orthogonality limitation of traditional orthogonal multiple access technologies at the cost of improving the complexity of the receiver,and enables multiple users to be accessed within the same time-frequency resource block and obtains higher spectral efficiency.At the same time,cooperative communication technology can effectively improve the system communication quality and communication range.Therefore,the application of cooperative communication technology in NOMA system can better improve the system performance of weak users in the system.In addition,due to the limited spectral efficiency of cooperative NOMA(CNOMA)systems operating in half duplex mode,a CNOMA system using full duplex relay is proposed.Although the ground mobile cellular networks have been mature,the ground mobile cellular networks have never been able to provide large-scale coverage for remote areas,and satellite communications have become an integral part of the future mobile communications system as they break the geographical constraints of terrestrial mobile communications.In this thesis,the outage performance and secrecy outage performance of a terrestrial CNOMA network and a satellite-terrestrial hybrid network integrated with CNOMA are analyzed respectively.The specific work and main contributions of this thesis are as follows:(1)For a terrestrial CNOMA network,the outage performance is discussed.The network contains two base stations,two near users and a common far user.The two base stations serve their respective near users and a common far user,while it is assumed that there is no direct link between the base station and the far user,with the near user collaboratively forwarding information to the far user.In this thesis,it is assumed that the near users support both the half-duplex relaying mode and the full-duplex relaying mode.Due to the residual self-interference under full-duplex mode,the system performance under full-duplex mode is not always better than that under half-duplex mode.Therefore,a duplex mode selection strategy is proposed.Based on the proposed strategy,the outage probabilities of all users are derived.The correctness of the theoretical results is verified by Monte Carlo simulation.Simulation results show that the duplex mode selection strategy proposed in this thesis can provide low outage probablities for both near and far users.(2)For a combination of terrestrial CNOMA and satellite satellite hybrid network,the secrecy outage performance is discussed.The network contains a satellite source,two terrestrial NOMA users and a terrestrial eavesdropper.There is a direct link between the satellite source and the near user and the eavesdropper,while the direct link between the satellite source and the far user is unavailable.As a result,the near user acts as a user relay to relay the signal to the far user,while the eavesdropper can eavesdrop on the information broadcast by the satellite source and forwarded by the near user.In this thesis,the closed-form exact expressions for the secrecy outage probability(SOP)of the near user are derived,and the closed-form approximate expressions for the SOP of the far user are derived based on the Gaussian-Chebyshev quadrature.The accuracy of the theoretical results is verified by Monte Carlo simulations,and the effects of various system key parameters on the performance are studied.In particular,it is shown that the system performance under full-duplex mode is better than that under half-duplex mode when the received signal-to-noise ratio at the near user is low or the residual self-interference is low. |
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