Research Con Resource Allocation Of D2D Communication System Based On Convex Optimization Theory

The popularity of intelligent mobile devices causes the lack of spectrum while it brings convenience to modern life.In order to improve the spectrum utilization rate of traditional cellular networks,the device-to-device(D2D)communication technology in non-orthogonal mode that proximity users transmit information directly by reusing cellular spectrum is attracting more researchers' attention.How to allocate resources such as spectrum resource blocks and power reasonably to the cellular users and D2D users to improve the transmission rate and resource utilization rate of the whole D2D communication system is the focus of resource allocation research.On the other hand,network security issue is becoming more important because of the deterioration of the network environment and the increase in the number of mobile users.The limitations of the communication system itself or the external environment make the uncertainty of the channel parameters ubiquitous.The robust resource allocation problem when channel state information(CSI)is not perfectly known becomes one of the hotspots.Therefore,for the D2D communication underlaying cellular networks in the non-orthogonal mode,considering the performance of both cellular subsystem and D2D subsystem,this thesis establishes and solves the optimization problem under the communication scenarios of ideal channel condition without eavesdropping,ideal channel condition with eavesdropping and non-ideal channel conditions without eavesdropping,respectively.Moreover,the resource allocation strategy is simulated and analyzed in this thesis.The main works are as follows:(1)This thesis briefly introduces the background and theoretical basis of the resource allocation research in D2D communication underlaying cellular networks,such as D2D communication technology,physical layer security,robust optimization theory and convex optimization theory.(2)Under the condition where the CSI is perfectly known,we study the joint resource allocation problem in the D2D communication system without and with eavesdropping,respectively.We maximize the non-confidential sum rate or security sum rate of the D2D subsystem and meanwhile consider the rate quality of service of cellular subsystem.Through the optimization of the power distribution and resource block allocation of cellular users and D2D users,the optimization problems are established.Furthermore,the optimization problem of mixed integer nonlinearity is transformed into convex subproblem which can be solved by Lagrangian dual approach,and the optimal solution of the original optimization problem is obtained by one-dimensional search method.Based on the above research,the advantages of the joint resource allocation strategy proposed in this thesis are analyzed and the influence of D2D communication security on the system performance is studied by the simulation results.(3)Under the condition of non-ideal channel where the CSI is not perfectly known,we study the joint resource allocation problem in the D2D communication system without eavesdropping.We utilize the robust optimization theory where uncertainty in CSI is defined by a bounded distance between its estimated and exact values and formulate a robust optimization problem which contains two sets of uncertain parameters:one in the objective function and another in the constraints.For the two sets of uncertain parameters,we divide the original robust optimization problem into two parts and solve them by the worst case robust optimization approach.To reduce the cost caused by the worst case robust optimization approach,we utilize the chance constraint approach to achieve a tradeoff between robustness and optimality.Furthermore,using sensitivity analysis,we get insight into how the protection function affected the achievable D2D sum-rate.Additionally,the effect of robustness on the system performance is presented in simulation results.