Resource Allocation For UAV Assited D2D Heterogeneous Networks

With the rapid growth of wireless data traffic demand,the communication system has a shortage of spectrum resources,which brings great challenges to the traditional cellular network.Device-to-Device(D2D)communication is considered to be an effective solution to improve the spectrum efficiency of the system.Unmanned Aerial Vehicle(UAV)can directly serve D2 D heterogeneous networks due to its flexible deployment and low cost.Its controllable mobility and line of sight(LOS)channel conditions help to improve system performance.In addition,UAVassisted communication becomes a good option to supplement ground communication when ground stations are destroyed due to natural disasters.However,due to the complex interference in D2 D heterogeneous networks,resource allocation is crucial when user communicating with drones.Therefore,this paper focuses on the resource allocation in D2 D heterogeneous networks under different application scenarios.For the scenario of static UAV relay assisted D2 D communication,in order to improve the transmission performance of D2 D users under fading channel,this thesis studies the equivalent conversion method of maximizing user data rate under certain outage probability.The closed-form expression of the outage probability in the case of the existence of interference from other cellular users in the heterogeneous network is derived statistically.With the goal of minimizing the outage probability of the system,the UAV position deployment and power allocation scheme are separately studied.For UAV deployment issues,the optimal deployment scheme of the UAV is revealed by analyzing signal to interference plus noise ratio(SINR)in each hop of the relay system in different situations.For the power allocation issues,the optimal power allocation scheme is given by analyzing the convexity of the outage probability function.The simulation results show that the proposed algorithm can effectively reduce the system outage probability and improve system performance.In the application scenario of the UAV as the emergency base station,the dynamic movement characteristics of the UAV are utilized,and the design of the flight path can establish a good channel condition with the real-time communication user.Interference in the heterogeneous network can be controlled.While improving the system capacity,in order to ensure the fairness of the downlink channel users and the Quality-of-Service(Qo S)of the D2 D users,an optimization problem aiming at maximizing the minimum average rate is established.Since the problem is a Mixedinteger Non-convex optimization problem,the method of successive convex optimization(SCO)is used to decompose the optimization problem into downlink channel user scheduling,trajectory planning,power allocation of D2 D user and UAV.The three sub-problems are analyzed.By transforming the problem into a convex problem,the CVX toolbox is used for optimization.Finally,the block coordinate descent algorithm is used to solve iteratively.The validity of the algorithm is demonstrated by simulation.