The Research On Wireless Resource Management For D2D Communication Based On Cellular System

The last decades have seen a great development in mobile communications. However, the demands for transmission rates by wireless applications are growing rapidly with the extremely limited wireless resource. In order to improve the spectrum efficiency in cellular networks, the concept of Device-to-Device (D2D) communications is proposed. The basic idea of D2D communications is terminal devices can communicate directly with each other by reusing cellular resources, while terminal devices in D2D connections remain con-trolled by the system. D2D communications can improve the spectrum efficiency and decrease transmitting power of terminal devices as well as loads of the base station in the cellular communication networks. To enable D2D communications in cellular communication networks, we propose a wireless resource allocation in this paper.We employ frequency division duplexing (FDD) in cellular communication networks and focus on a dedicated scenario for D2D communications. In this scenario, we divide wireless resource into two parts, one for D2D communication and the other for conventional users. In such dedicated scenario, the interference between D2D communications and cellular users can be avoided. For the communication scenario mentioned above, we study the conflict-graph-based resource allocation method for D2D communications in cellular networks first. And the method to construct the conflict graph is illustrated.The proposed conflict-graph-based resource allocation method for D2D communications consists three steps:1) Transform the problem of wireless resource allocation problem in multi-cell system into a single-cell system by fractional frequency reuse (FFR) scenario with the inter-cell interference coordination algorithm.2) Divide D2D communications in each cell into several groups, and each group can only use the corresponding resource. During the procedure of grouping, we have to ensure the balance of loads and interference as much as possible.3) With the proposed slot scheduling algorithm, we schedule D2D communications in every group on the time domain to improve the spectrum efficiency. Simulation results show that the proposed resource allocation method can effectively improve the spectrum efficiency.In order to enable the proposed resource allocation method, we propose a new protocol to construct the conflict graph for D2D communications. It is an iterative process with broadcasting and acknowledgement (ACK). D2D users check if they can receive the broadcasting signal and ACK signal from others. If it can be received successfully, interference exists between the pair of users upon the same frequency resource assigned. There may be some conflicts in receiving broadcasting signals and ACK signals, thus we need to construct the conflict graph for D2D communications in a iterative way until it appears no conflicts. This protocol has an lower complexity and latency, and it can accurately construct an effective conflict graph for D2D communication in cellular networks.To verify the feasibility of proposed conflict-graph-based resource allocation method and the conflict graph constructing protocol, theoretical analysis and simulation experiments are shown in this paper. It can be indicated that the theoretical results match well with the simulation results. Furthermore, the proposed conflict-graph-based resource allocation method for D2D communications can improve spectrum efficiency effectively in cellular networks.