| With the rapid development of mobile communication technology,the contradiction between the explosive growth of Wireless applications' rate demand and the shortage of wireless spectrum resources is emerging day by day,techniques that can increase the limited spectrum efficiency attract much attention in recent years.Among them,the Device-to-Device(D2D)communication,which behaves as an underlay to cellular and reuses the cellular resources,can relieve the wireless spectrum congestion to some extent.As an improtant technology in D2 D communication,D2 D relay technology can expand the communication radius and improve the rate of D2 D communication.In this thesis,the joint resource allocation and mode selection problems of relay-assisted D2 D communication in cellular networks are studied in order to improve the system throughput or energy efficient.The main content of this article is as follows:Firstly,in a cellular network,which supports relay-assisted D2 D communication,there are three communication modes: cellular communication,D2 D direct communication and D2 D relay communication.A scheme of mode selection and relay selection in D2 D relay communication mode using Lagrange dual algorithm is proposed,which ensures the normal communication of cellular users and D2 D users,and improves the throughput of system.Secondly,in a cellular network,which supports D2 D communication,the optimal power allocation values in all cases are deduced.Then the Hungarian algorithm is proposed for links' resource allocation,which ensures the normal communication of cellular users and D2 D users,and maximizes the energy efficiency of system.Thirdly,in a cellular network,which supports relay-assisted D2 D communication,the optimal power allocation values in all cases are deduced.Then the Hungarian algorithm is proposed for links' joint resource allocation and mode selection,which ensures the normal communication of cellular users and D2 D users,and maximizes the throughput of system.At last,in a cellular network,which supports relay-assisted D2 D communication,the optimal power allocation values in all cases are deduced.Then an improved greedy algorithm with low complexity and high reliability is proposed to solve an assignment problem with three-dimensional decision variables of joint resource allocation,mode selection and relay selection,which ensures the normal communication of cellular users and D2 D users,and maximizes the energy efficiency of system.Compared with greedy algorithm,the higher reliability of improved greedy algorithm is proved by simulation. |
