Research On Energy Efficiency Of Device-to-Device Communication

With the staggering increase of energy consumption caused by the wireless communications during the recent years and the even more tightening competition for the spectrum resources, D2D(Device-to-Device) emerges as a brand new complement technology to the traditional cellular network and draws much attention due to its advantage of enhancing the spectral efficiency, decreasing the energy consumption and increasing the energy efficiency. However, D2 D still has a long way to go regarding that it just came into existence. This essay focuses on the study of decrease of energy consumption and optimization of energy efficiency.Firstly, we briefly introduce the basic D2 D knowledge and the urgent necessity that drives the relevant researches. Then we analyze the energy efficiency of three modes, namely the Non-Orthogonal mode, the Orthogonal mode and the Cellular mode. After that, knowing that the quasi-concave of the energy efficiency functions, we apply the convex optimization and the game theory to achieve the Nash equilibrium to reach the energy-efficient power allocation scheme. We continue to work on the single D2 D user and single cellular user scenario and analyze its performances at different distances.In the multiple D2 D users and multiple cellular users’ scenario, we combine resources allocation schemes and power allocation schemes: through auction we allocate the best channel to the users whose power has been previously determined. From the single user’s perspective, we apply convex method and the game theory that is discussed before. Both methods have improved the energy efficiency.And then we apply the Lagrange optimization to reduce the transmitting power under certain rate constrains. We analyze the JRPA and SRPA methods to achieve longer working time. From a single user’s standpoint, we propose a modified auction method to increase the device’s working time. We research this from two aspects: the system level and the individual level. The simulation shows that the latter two methods approach the capacity of the first one method and the latter two are of less complexity.Lastly, with the high speed of D2 D communication on its short-distance link and bearing the principle of fairness in mind, we group different D2 D users into different clusters. Let the cluster head relay the data from the basestation to the other users in the same cluster. Due to its shorter transmission time compared to direct communications with the basestation, less energy consumption is achieved. Furthermore, we apply the fairness into the optimization to avoid unnecessary power cost of a single D2 D cluster head. We distribute the data relatively fairly by Min-max method. Though the overall energy consumption is slightly increased when taking into account of fairness, it is important to note that we have reduced the degree of unfairness among the users, thus avoiding the problem of severely impairing the working time of one single user.