Relay Selection And Power Allocation In NOMA Collaborative Vehicle Network System

Non-orthogonal Multiple Access(NOMA)technology is considered as one of the key technologies to improve the performance of wireless communication systems because of its advantages of high frequency spectrum efficiency and high device access,which contributes to the construction of higher capacity and lower delay wireless communication networks.Cooperative communication technology has the characteristics of resisting multipath effect,effectively expanding communication coverage area and improving system diversity gain.With the application of NOMA technology in collaborative communication,relay selection strategy and power control have become a research focus.In the communication system of Internet of vehicles,the optimal relay selection strategy can not only guarantee transmission reliability and improve interrupt performance,but also effectively improve spectrum efficiency.A reasonable power control scheme can ensure the rights and interests of remote users as far as possible and maintain the fairness of the system.Based on this,this paper studies the relay selection and power control of NOMA-based collaborative vehicle network system,mainly including the following two aspects:(1)The full duplex single-user downward NOMA vehicle system is constructed.Considering the practical consideration,the base station sends relay vehicles and purpose of all information.And then,through the analysis of all relay vehicles and users,relay selection strategy is presented,that can maximize the purpose of user communication rate.Furthermore,the expressions of channel capacity and outage probability are deduced.Then,the effects of relay number,user distance and SNR on channel capacity and interrupt performance of user vehicle are analyzed.The effectiveness and correctness of the proposed strategy is verified by comparing with Max-SR,Max-RD and random relay strategies.(2)Based on the multi-relay NOMA cooperative communication system,the downlink NOMA system of multi-user vehicle is further studied.Base station transmits mixed signals,and a joint Max-Min relay selection and power allocation strategy is proposed in light of the priority of aliased signals.Then the expression of interrupt probability for two vehicle users is deduced.The influences of relay number,relay power and SNR on system interrupt probability and channel capacity are analyzed by simulation.The effectiveness and correctness of the proposed strategy is verified by comparison with Max-SR,Max-RD,random relay,and Max-Min relay selection and fixed power allocation strategies.