Research On QoS-based Resource Allocation And Trajectory Optimization In UAV Communication Systems Based On NOMA

With the rapid development of wireless communication technology,unmanned aerial vehicles(UAVs)have attracted great attention in the industry and academia due to their versatility and maneuverability.Compared with the ground wireless communication system with fixed base stations,UAV-assisted wireless communication can provide better line-of-sight links and create better channel condition due to its flexible mobility.Therefore,UAV-assisted wireless communication is a promising solution to improve the performance of existing communication systems.Specially,an important design aspect of the UAV system is trajectory planning.Especially in the case of UAV-assisted wireless communication,applicable trajectory planning may significantly shorten the communication distance,which is essential to improve system capacity.However,with the increasing demand of mobile Internet,UAV communication network needs to face the challenging requirements of high spectrum efficiency and large-scale connectivity proposed by future wireless communication network.Non-orthogonal multiple access(NOMA)technology has been considered an important technique for 5G network its superiority in providing higher spectral efficiency and user fairness.Therefore,this paper integrates the integration of NOMA into UAV-assisted wireless system,and considering two different UAV communication scenarios with NOMA,NOMA transmission protocol can further improve spectrum efficiency,and UAV’s trajectory can be optimized strategically so that NOMA can obtain the better performance.Based on the optimal wireless resource allocation and UAV path planning,the following two kinds of UAV communication with NOMA transmission strategies are proposed.(1)Considering a UAV-ground communication system with NOMA under quality of service(QoS)requirements.Firstly,a UAV downlink communication system model based NOMA has been established,in which a UAV deployed as an aerial base station to communicate with two fixed ground users by applying NOMA transmission protocol.In consideration of different users’ QoS require,I proposed an optimization problem for the average sum-rate maximization via jointly optimizing the UAV’s power allocation coefficients and the trajectory as well as the user’s successive interference cancellation(SIC)decoding order based on mathematical theory and convex optimization techniques.Extensive simulations show that the superiority of applying NOMA in the mobile UAV network and validate better the performance gain under the various QoS guarantee.(2)Considering a UAV-ground communication system with NOMA on multi-user pair under QoS-based.In this scenario,I consider a UAV base station to serve multiple users during a limited flight time.When NOMA is implemented among all users simultaneously,this would degrade the decoding performance and increase SIC decoding complexity,meanwhile the cochannel interference will be strong in NOMA systems.Therefore,in general,users are divided into different groups,then NOMA is implemented within each group,and I apply a low complexity dynamic user grouping strategy based on the instantaneous channel gain of users.In addition,I also use the user scheduling based on non-orthogonal multiple access to adjust the corresponding relationship between the UAV and the user group.In addition,the QoS-based power allocation optimization scheme in each NOMA user group has been considered under the constraints of the user’s QoS demand.My goal is to jointly optimize the user grouping,user scheduling,UAV power allocation factor,and UAV trajectory in each time slot in a limited amount of time to achieve the average sum-rate maximum,and to indicate that the NOMA-based UAV system provides the benefits of achieving a better air-ground communication compared to OMA scheme and other benchmark schemes.