Energy-Efficient Mode Selection And Resource Allocation For D2D Communications

With the complexity and diversification of mobile communication data services,the power consumption of mobile terminals has increased sharply.How to improve the energy efficiency(EE)of the terminal and extend the terminal usage time have become the hotspots of current research.Device-to-device(D2D)communication is one of the effective technical ways to solve this problem.The D2D transmitter(DT)and the D2D receiver(DR)can communicate directly or through the base station.In the communication process,the D2D user(DU)can reuse the spectrum of the cellular user(CU)or use the dedicated spectrum.Selecting different communication modes for different communication scenarios can effectively improve the terminal EE.If the DU chooses to reuse the spectrum of the CU,serious inter-frequency interference will occur between users.It is necessary to design an effective resource allocation scheme including channel allocation and power control to mitigate interference and improve EE.In addition,with the growth of mobile data traffic,dense heterogeneous network has become an inevitable development trend.Introducing D2D communication into heterogeneous network(HetNet)can further reduce energy loss during transmission.However,due to the increase in the type and number of base stations(BS),the mode selection and resource allocation of D2D communication will become more complicated,and further research is needed.Based on the above challenges,this thesis first analyzes the EE optimization problem of D2D communication in single-cell cellular network,and then expands it into a two-layer heterogeneous network.The main contributions and innovations of the paper are summarized as follows:(1)The EE optimization problem of D2D communication in single-cell cellular network is studied.The system EE is maximized by mode selection,channel allocation and power control under the condition of ensuring the maximum transmission power and the minimum transmission rate of CUs and DUs.The EE maximization problem is non-convex,in order to reduce the complexity of the solution,the problem is solved in two steps:firstly,given the transmission power of all users.by considering the influence of the number of idle spectrum resources in the system,a heuristic mode selection and channel allocation algorithm is proposed.Then based on the results obtained in the first step,the power control scheme is studied.For the non-interfered user,the optimal power can be obtained according to the nature of the objective function and the value range of the power.For the interfered user,the power optimization problem is modeled as a non-cooperative game problem,an iterative power control algorithm is proposed to find the optimal power.The simulation results show that the proposed algorithm has good convergence.It can significantly improve the system EE and achieve the performance close to the exhaustive algorithm.(2)The EE optimization problem of D2D communication in HetNets is studied under the premise of satisfying the maximum transmit power and minimum transmission rate of CUs and DUs.Firstly,aiming at maximizing the total EE of D2D users,a complete set of mode selection,channel allocation and power control schemes is proposed.The mode selection is solved in the outer layer by an iterative algorithm,and the channel allocation and power control are placed in the inner layer using the fractional programming and the Lagrangian dual method.Then considering the fairness between DUs and aiming to maximize the minimum EE of DUs,a three-step strategy is proposed.In the first step,a heuristic channel allocation algorithm is proposed under the given mode selection and power control variables.In the second step,using the mode selection variable given in the first step and the obtained channel allocation variable,the power is optimized through fractional programming and the Lagrangian dual method.The third step is to use the results of the first two steps to determine the mode selection scheme.The simulation results show that the proposed algorithm in the EE maximization scheme converges quickly,and the performance approximates the optimal performance achieved by the exhaustive algorithm.The proposed scheme to maximize the minimum EE of DUs can effectively improve the minimum EE of D2D users and ensure fairness between users.