Mode Selection And Resource Allocation For D2D Communication System

In recent years, with the development of different kinds of multimedia services, there is an ev-er increasing demand for higher data rate transmission and larger system capacity. For this reason, Device-to-Device (D2D) communication underlaying cellular networks such as IMT-Advanced, proposed by3GPP, has received increasing attentions as a promising technology to improve spec-tral efficiency and provide safe and QoS guaranteed communication. It can enhance spectrum efficiency, decrease the load of BS, lower the power of terminals and BS, and increase system throughput. In this paper, we analyze the mode selection and resource allocation problems in LTE system when both cellular users and D2D users are present in the system.Firstly, the problem of resource allocation for D2D pairs is studied. Future cellular networks are expected to allow underlaying direct D2D communication for spectrum efficiency. However, enabling D2D communication in a cellular network presents a challenge in resource allocation due to the potentially severe interference it may cause to the cellular network by reusing the spectrum with the cellular users. There are two kinds of interference between cellular communication and D2D communication. One is the interference from cellular transmission to D2D communication, and the other is the interference from D2D transmission to cellular links. Mode selection and re-source allocation are considered as the most efficient ways to manage the interference. However, mode selection can only determine whether there is interference between cellular communication and D2D communication, while the magnitude of interference should be managed by resource al-location. In this paper, we analyze the resource allocation problem in a single cell system when both cellular users and D2D users are present in the system and propose a dynamic resource al-location scheme for D2D communication underlaying cellular networks. The proposed schemes maximize the number of permitted D2D communication pairs in a system meanwhile avoiding the strong interference from D2D links to the cellular links. We first consider the scenario where cel-lular users and D2D users are allocated resource independently and propose an optimal algorithm and a heuristic algorithm, and then extend the methods to the scenario where cellular users and D2D users are allocated resource jointly.Secondly, the problem of joint mode selection and resource allocation for D2D pair is studied. In the study of the problem of resource allocation, we assume that all the D2D pairs have already done mode selection and will not choose cellular mode. However, mode selection is also anoth-er way to manage the interference between cellular communication and D2D communication. If jointly considering mode selection and resource allocation, spectrum utilization will be more effi-cient and interference will be much smaller. In this paper, we model the optimization problem of joint mode selection, channel allocation, power allocation, and propose a heuristic algorithm. All of the three modes, cellular mode, dedicated mode, reused mode, are considered in this paper. As to the heuristic algorithm, according to the number of channels needed by the system and the num-ber it can supply, we divide it into three different cases and propose corresponding method for each case. The joint mode selection and resource allocation algorithm, proposed according to the num-ber of channels needed by the system and the number it can supply, provides different allocation methods for different cases and makes the jointly allocation much easier for the case when there are enough available free channels in the system. Besides, for the case when the system can not provide enough available free channels, the proposed joint mode selection and resource allocation algorithm makes sure that every D2D pair can be guaranteed to access the network, every channel is utilized and avoids the high computational complexity of exhaustive searching algorithm at the same time.