Resource Allocation For Device-to-Device Communication In OFDM Systems

Bringing D2D technology into the traditional cellular system can reduce the power of transmitters, offload the burden of BS and improve the system spectrum efficiency, which copes with the problem lacking of spectrum resource in wireless communication system to a certain extent. However, there exists interference between D2D and cellular uses by introducing the new technolgy. Allocating channel and power for users rationally to coordinating the interference has caught more and more attention.The method of spectrum sharing between D2D and cellular users and the model of uplink and downlink interference are analyzed in this thesis. After studying the impact of power control on systems, the common channel allocation mechanisms are given. The concrete details are as followed:(1) Centralized resource allocation algorithm in D2D system is studied. D2D users communicate via muti-carrier in this algorithm, where the transmit power of both D2D and cellular users are optimizated at the same time. The resource of D2D and cellular users are allocated in a centralized way, so BS needs to collect channel informations of all the users. In order to offload the burden of BS, distributed resource allocation method is adopted. D2D users collect channel information by itself. Cellular users’ transmit power is fixed and the transmit power of D2D users is optimizated. D2D users usually communicate via singal carrier, in order to make which into practice an algorithm of optimizating both D2D and cellular users’ transmit power is studied. The complexity of this algorithm is much lower. However the system performance of this algorithm is decreased. The simulation results of the three algorithms are demonstrated.(2) A resource allocation algorithm for D2D users which establishes an optimization problem aimed at maximizing D2D users throughput and guaranteeing cellular users QoS is proposed. To solve the problem there need two steps. First, the sub-carrier allocation process based on balancing the quality of both cellular and D2D users is given, and then the sub-gradient method of power allocation is shown. Simulation results prove that the throughputs of both D2D system and the total system are comparatively improved with the proposed algorithm.(3) A joint carrier and power allocation algorithm based on graph theory and game theory is proposed to diminishing the interference in the hybrid system. Firstly, the carrier allocation based on graph theory is given. To guaranteeing the QoS of cellular users the available carriers for D2D users are adjusted. After that the directed and weighted graph is constructed in D2D system, based on which D2D users adjust their sets of available carriers again. Secondly, the transmit power for D2D users on each carrier is allocated based on game theory. And the existence of Nash Equilibrium is demonstrated while the uniqueness of Nash Equilibrium is verified through the simulation results. Simulation results show that the proposed algorithm improves the performance of D2D and the whole system also assures the QoS of cellular users.