Research Of D2D System Communication Mechanism Optimization For Imt-a

IMT-A will offer a high bandwidth up to100MHz for higher data rates in the future. Many candidate radio interface technologies have been submitted to the International Telecommunications Union (ITU) to prepare new technology components for LTE to meet IMT-A requirements. Among which, Device-to-Device (D2D) communication has received increasing attentions as a promising component to improve spectrum efficiency. Device-to-device (D2D) communications underlaying a cellular infrastructure has been proposed as a means of taking advantage of the physical proximity of communicating devices, increasing resource utilization, and improving cellular coverage. Relative to the traditional cellular methods, there is a need to design new device discovery methods, mode selection algorithm and radio resource management algorithms that help realize the potential advantages of D2D communications.Firstly, this thesis describes in detail the key technologies of D2D communication underlaying a cellular infrastructure, and then introduces definition of device discovery, deployment scenarios, and performance indicators. The state-of-the-art progress of device discovery is reviewed, and a comparison and assessment of several discovery algorithms are made. And then, the part introduces several communication modes in detail, and analyses the interference introduced by D2D in the cellular network, especially when D2D reuse cellular resources.Secondly, the thesis introduces the new features of scene and analyses requirements of the current discovery algorithms. To against the defects of current algorithms, this paper proposes a new neighbor discovery algorithm based on OFDM physical layer that can be applied to areas with base station or without base station coverage. With the same physical layer channel structure, our algorithm can significantly reduce the complexity of the terminal. Meanwhile, with a flexible cycle in our algorithm, the number of available resources of each cycle varies when the number of UE in environment changes.Finally, a new D2D relay scene is added to the current mode selection scenes. The features of this new scene and selection criteria of D2D relay are described in detail. The thesis describes the three different scenarios and gives the overall architecture of the system. And then we formulate the mode selection and resource allocation problem into a network throughput optimization considering both of power and sub-channel, and then propose a mode selection and resource allocation scheme aiming to maximize the capacity. Firstly, the mode selection and resource allocation problem is modeled as a mixed integer programming problem without considering the reuse of cellular resources. With relaxing subchannel sharing, the problem is transformed into a convex optimization problem which can be solved by a dual decomposition approach. Then we propose UE pairing resource reusing algorithm with reduced complexity to exploiting spatial reuse gain in cellular networks. According to the result of simulation, the approach proposed is proved effective.