Power Allocation And Performance Analysis Of D2D Communication System Based On Relay Assistance

Wireless communication technology is developing at a rapid pace,especially the popularization and promotion of the fifth generation mobile communication technology,making our production and life more intelligent and convenient.However,the rapid growth of the number of smart terminals will lead to a surge in mobile data traffic,which will adversely affect key indicators such as the data transmission rate,system capacity,network delay,and spectrum utilization of communication systems.Device-to-device(D2D)is one of the key technologies of 5G communication.It uses the user's short-range data transmission to improve the end-to-end data transmission rate,which can reduce the burden on the base station and improve the spectrum utilization rate.When the distance between two D2D users is large or the channel quality is poor,the introduction of relay technology can further improve the reliability of data transmission between D2D users.This paper combines D2D communication and relay technology.For the D2D communication scenario assisted by AF relay and DF relay,a low-complexity power optimization algorithm and a mode selection scheme are proposed respectively,which effectively improves the communication system.performance.The details are as follows:First,for the D2D communication scenario assisted by the bidirectional AF relay,the power optimization problem based on the reachability and maximum rate of the cellular link and the D2D link is studied.Using the reachability and rate of the cellular link and D2D link as the objective function,an optimization model is established to obtain the optimal power distribution coefficient,and then a low-complexity power optimization method is proposed.Simulation results show that this method can effectively improve the performance of D2D communication and cellular communication.Next,for the D2D communication scenario assisted by DF relay,the transmission performance of two users in different cells in traditional D2D transmission mode,D2D transmission mode based on unidirectional DF relay and D2D transmission mode based on bidirectional DF relay is analyzed.According to the different interference between the D2D link and the cellular link,the system achievable rates in the three modes are respectively derived.According to the difference in distance between two users,a low complexity mode selection scheme is proposed,which is given in the form of a closed expression.The simulation results show that according to the proposed mode selection scheme,the system can switch to the mode with the best communication performance according to the change of the distance between the two users,which improves the communication quality of D2D users.