Research On Non-Orthogonai Multiple Access Theory And Technology

In order to satisfy the application requirements such as high capacity,high spectral efficiency,massive connection and low latency for the fifth generation mobile communi-cation scenarios including enhanced mobile broadband,massive machine type of commu-nications,ultra-reliable and low latency communications,non-orthogonal multiple access(NOMA)has become a hot research topic in academia and industry.From the first gener-ation to the fourth generation,the mobile communication systems always adopt orthogonal multiple access(OMA)technology.In particular,each user employs orthogonal wireless resources independently.However,OMA encounters some problems such as low spectral efficiency,limited connections and poor fairness.Thus,OMA cannot meet the application requirements for the future communication scenarios.With the development of hardware processing ability,the transceiver can perform more complex signal processing,which lays a solid foundation for the NOMA implementation,although it introduces some tolerable complexity.Importantly,NOMA can improve the spectrum efficiency,connection number,user fairness and so on.This paper mainly focuses on NOMA theory and related technologies.It extends from the basic single-cell NOMA to the cooperative NOMA.Furthermore,the single-cell NO-MA is stretched to the multi-cell NOMA while introducing energy harvesting/full duplex technology.Also,the physical layer security of cooperative NOMA is investigated.The research includes the cornpute-and-forward based uplink NOMA system,the cooperative NOMA system based on energy harvesting and full-duplex relaying,the physical layer se-curity of cooperative NOMA system,and the multi-cell cooperative NOMA system based on energy harvesting.The main contributions of this paper are listed as follows:1.For the decoding problem of the uplink SIC based NOMA(SIC-NOMA),firstly,this paper analyzes the decoding performance of uplink SIC-NOMA.Secondly,we introduce the idea of network coding into NOMA and propose a compute-and-forward based NOMA system(CF-NOMA).Also,we investigate the relationship between the SIC-NOMA and CF-NOMA.In fact,the SIC-NOMA can obtain the two point of Pareto-optimal solutions in the multiple access channel capacity region.On the other hand,the CF-NOMA can obtain more Pareto-optimal solutions.Thus,the SIC-NOMA can be regarded as a special case of the CF-NOMA.In other words,CF-NOMA can provide more choices which can improve the system performance in terms of the user fairness and average outage probability.Moreover,we provide a algorithm which can obtain more the Pareto-optimal solutions by choosing the"best possible"Gaussian-integer coefficients.Finally,the simulation results show that the CF-NOMA can achieve higher user fairness and lower average outage probability compared with the SIC-NOMA.2.For the existing problems in cooperative NOMA networks,such as the limited en-ergy of relay users and the rate loss caused by half-duplex relay,this paper investigates a cooperative NOMA system based on energy harvesting and full-duplex relaying and its transmission mechanism.We derive the outage probabilities and ergodic rates for the near user and far user.The simulation results verify the correctness of theoretical analysis and the advantages of the EH-FD-NOMA over EH-FD-OMA.3.For the security problem of cooperative NOMA network:eavesdropper may wiretap the information from the base station and relay user.This paper introduces a eavesdropper node in a cooperative NOMA network and investigates the physical layer security of the system.The secrecy outage probabilities and the ergodic secrecy rates of two users are derived.The correctness of the analytical results and the superiority of EH-FD-NOMA over its counterpart are demonstrated by the simulation results.4.For the problem of multi-cell NOMA networks:the low rates and the high outage probabilities of the cell-edge users due to the serious inter-cell interference,this paper studies a multi-cell cooperative NOMA system with energy harvesting technology based on the single-cell NOMA network.Moreover,we derive the coverage probabilities,ergodic rates of two users and the energy efficiency of the system by stochastic geometry.The simulation results validate the correctness of the theoretical analysis and the advantages of proposed multi-cell cooperative NOMA with energy harvesting compared with OMA.