The Research Of Energy-Efficient Resource Allocation For Secure D2D Communications Based On UAV

Unmanned Aerial Vehicle(UAV)has huge application potential in the public and civil fields due to its mobility and flexible deployment characteristics.UAVs are applied to wireless systems,such as Device-to-Device(D2D)communication system,which can provide or enhance communication services for ground users.On the one hand,UAVs can be used as flight relays to forward information between users to guarantee their strict Quality of Service(QoS)requirements.On the other hand,when the ground base station(BS)is unavailable,the UAV can be used as an aerial base station to assist the ground D2D communication system through flexible deployment to improve coverage,spectrum efficiency and system performance.UAVs are usually deployed at a certain height and have a dominant air-to-ground(ATG)line-of-sight(Lo S)channel with ground users.Therefore,UAV-enabled communication networks are more vulnerable to eavesdropping and interference attacks from malicious nodes on the ground than ground communication system.In order to ensure the energy-saving and security requirements of massive wireless data transmission in 5th-Generation(5G)and next-generation networks,this paper mainly studies the energy-efficient resource allocation in UAV-based D2D communications,considering two scenarios: UAV as a relay and UAV as an aerial base station.The main contributions are as follows:·In this paper,we first investigate the resource allocation problem of auxiliary D2D communication in the static UAV relay scenario.The UAV acts as a relay between D2D users who cannot satisfy the communication requirements.This paper proposes the energy efficiency(EE)maximization problem of the UAV relay system,which aims to maximize the energy efficiency of the UAV while guaranteeing the constraints of power and time delay.The optimization problem is a fractional programming problem,which is converted into an equivalent subtraction form through Dinkelbach method at first.And then the optimal resource allocation strategy is obtained through Karush-Kuhn-Tucker(KKT)conditions and bisection method.Simulation results verify the effectiveness of the algorithm,and the superiority of the proposed algorithm is verified by comparison with other algorithms.·For the scenario of UAV as an aerial base station,this paper investigates the joint optimization problem of energy efficiency and security under the UAVassisted secure D2D communication system.The UAV is deployed as a flying base station to communicate with wireless users and an eavesdropper is arranged in a cell.We aim at maximizing the total energy efficiency of all D2D pairs while guaranteeing the QoS requirements and secrecy rate of all ground users and D2D users via joint power control and channel allocation.The considered optimization problem is a mixed-integer nonlinear programming(MINLP)problem.At first,Dinkelbach method performs as an outer loop,which is applied to transform the original fractional programming problem into a subtractive form.Then in the inner loop,the equivalent optimization problem is decomposed into two sub-problems: the power control sub-problem and the channel allocation sub-problem.In the power allocation sub-problem,we derive the optimal power with closed-form solution using Lagrangian dual and KKT conditions.Second,Hungarian algorithm is used to obtain the optimal channel allocation based on the power control strategy.As a result,an iterative resource allocation algorithm is proposed to efficiently solve the proposed optimization problem.Simulation results indicate that the proposed algorithm converges to the optimal solution in a small number of Dinkelbach method’s iterations.In addition,the proposed approach is compared with other methods to show its superior performance and can greatly reduce the time complexity of the system.