Relay Selection Study Based On V2X-NOMA Collaborative Network

With the rapid development of wireless communication networks,people have higher requirements on the reliability of communication transmission.Non-Orthogonal Multiple Access(NOMA)can improve the system capacity and spectrum efficiency,and guarantee the fairness between users at different distances by allocating power to the target users,and reduce the probability of interruptions,so it is suitable for the fifth generation mobile communication(The 5th Generation,5G)including Vehicles to Everything(V2X).It is therefore suitable for the 5th Generation(5G)of mobile communications,including Vehicles to Everything(V2X).Collaborative communication technology can achieve indirect communication through collaborative forwarding,extend the communication coverage area,and improve the Signal to Noise Ratio(SINR)at the reception point,thus reducing the outage probability of the whole network.As a key component of collaborative communication,the relay selection strategy can not only select effective relays to participate in collaborative gain,but also improve the quality of service(Qo S)and system throughput of users.In addition,a reasonable Energy Harvesting(EH)technique can solve the problem of energy limitation of relay nodes to improve the reliability of NOMA collaborative network system.In summary,this paper introduces the background and current status of NOMA technology,collaborative communication and energy harvesting technology,studies the relay selection strategy of traditional V2X-NOMA collaborative network,and further analyzes V2X-NOMA collaborative network with energy harvesting technology to improve the stability of the system.The study contains two main aspects as follows:(1)A V2X-NOMA-based collaborative communication network system is constructed,in which the base station sends information containing the target vehicle to a Road Side Unit(RSU)relay,and the RSU relay forwards this information to the target vehicle through Decode and Forward(DF).For this system,two relay selection strategies are proposed to optimize the system interruption performance,namely,conditional relay selection strategy and guaranteed farther user relay selection strategy.The performance of each node is analyzed to derive a closed-form expression for the interruption probability,and then the impact on the system interruption performance is analyzed by running the results with different numbers of roadside units and different transmitting powers.By comparing different strategies,it is verified that the proposed strategies have a more significant improvement on the interruption performance and the applicability of each strategy is illustrated.(2)Based on this V2X-NOMA collaborative communication network system,the impact of Simultaneous Wireless Information and Power Transfer(SWIPT)technology on the disruption performance at energy-constrained nodes is further considered.In this paper,we derive closed-form expressions for the signal-to-noise ratio and the final outage probability at each node under different protocols,and analyze the impact of different number of roadside units,different transmitting power and different energy harvesting coefficients on the outage performance of the system through operational results.Finally,the differences between using Time Switching-Based Relaying(TSR)and Power Splitting-Based Relaying(PSR)protocols are compared by setting different splitting factors,and the applicability of each protocol is illustrated.