Modeling And Performance Analysis Of NOMA System Based On Cooperative Communication And Energy Harvesting Technology

Multiple access scheme is the one of the core technologies of wireless communication.It has a great contribution to increasing network capacity and improving spectral efficiency.And the development of wireless communication is the interconnection of all things,which puts forward higher requirements for system capacity and spectrum efficiency,but the existing multiple access technology cannot meet them.Compared with the traditional way of orthogonal multi-access,non-orthogonal multiple access(NOMA)superposes multiple users in the same time-domain,frequency-domain,and code-domain,but in different power-domain,which effectively improve the spectrum efficiency,and increase the number of concurrent users.Therefore NOMA is widely regarded as one of the key technologies of 5G.Among the numerous research directions of NOMA,the combination with cooperative communication(CO-NOMA)can further increase system capacity and enhance the reliability of NOMA system.Besides energy harvesting technology(EH)can collect and store energy from the surrounding RF signals,combining EH with CO-NOMA technology can solve the specific problems in communication practice,and further expand the application scenario of CO-NOMA.Based on above,in this paper we explore the integration of CO-NOMA and EH technology,modeling and analysis of two communication systems.The results can be summarized as follows:1.we establish a NOMA networks communication model under Nakagami-m fading channels,which in coordinated direct and relay transmission.Taking the system outage behavior and channel capacity as the research emphasis,the approximate closed-form expressions for the outage probability of the proposed scheme are derived.And in the high-signal-to-noise ratio(SNR)regime we explicitly characterize the diversity order and ergodic sum capacity of the network.Finally,numerical examples are conducted to confirm the validity of our analysis and show that the NOMA system with direct link and relay link can obtain higher channel capacity.2.we analyze outage probability of cooperative NOMA model in multi-relay multiuser network.In contrast to conventional cooperative networks,relays in the considered network have no embedded energy supply,they need to rely on the energy harvested from the signals broadcasted by the source for their cooperative NOMA transmission.Based on this structure,a new relay selection scheme is proposed considering both channel state information(CSI)and battery status of relays.Assuming each relay has infinite energy storage for accumulating the energy,we use the infinite Markov chain to derive the approximate closed-form expressions for the outage probability of the proposed scheme.All theoretical results are validated by numerical simulations.We conclude the superiority of NOMA and find that by carefully choosing the parameters of the energy harvesting threshold or forwarding threshold,acceptable system performance can be guaranteed even if the relays do not use their own batteries to power the relay transmission.The research results provide theoretical support for the practical application of the three technologies.