Research On Computation Offloading And Trajectory Optimization Of UAV-assisted Mobile Edge Computing System

With the development and maturity of 5G communication,a large number of new applications have emerged,but the resources of the Internet of Things terminals are limited and can not meet the communication and computing requirements of applications with low latency.Mobile Edge Computing(MEC)technology has become an effective solution because it can provide efficient and reliable computing services on network edges with relatively low access burden and transmission delay.However,in complex environments,traditional fixed MEC servers may face the problem of inaccessibility,and deploying a large number of MEC servers will increase costs and be unrealistic,thus not bringing good services to users.Unmanned Aerial Vehicle(UAV)has outstanding advantages such as high mobility,rapid deployment and excellent link quality.The wireless communication system with UAV-assisted MEC can make up for the above shortcomings of fixed MEC servers.Wireless communication supported by UAV can serve rural or remote areas where there is no infrastructure or insufficient ground infrastructure.It is worth noting that better line-of-sight transmission channels enable UAV to cover more users than ground communication,so they can be used to fly close to users to establish a strong communication link,which can improve the performance of wireless communication systems.Although an UAV can get good communication channels by approaching ground users,the airborne battery energy it carries is limited,and its flight trajectory can generate enormous power consumption for propulsion.Therefore,it is very important to optimize the trajectory of the UAV to reduce its energy consumption.Since the battery capacity of ground users is also limited,energy savings are also required to improve the user’s ability to process task data.In addition,due to potential eavesdroppers on the ground,it is very likely that users will be eavesdropped when they offload a computing task to an UAV,which may result in security attacks.Therefore,secrecy offloading is an important factor to consider.However,in the UAV aided MEC system energy consumption of the optimization research is still incomplete.Therefore,the energy consumption optimization for secrecy offloading of full duplex UAV-assisted MEC system is studied in this paper.The main work is as follows:(1)In the presence of ground eavesdroppers,an UAV equipped with a MEC server is deployed to serve multiple ground users in a limited time,and multiple ground users offloading large computing tasks onto the UAV to relieve computing pressure.To enhance the security of the system,a full-duplex UAV is used,and interference signals are transmitted from the full-duplex UAV to the ground listeners.The weighted energy consumption of the UAV and the user is minimized under constraints such as secrecy offloading rate by jointly optimizing the trajectory of UAV,task allocation and the transmit power of users.To solve this difficult non-convex problem,an alternating iterative optimization algorithm based on successively convex approximation is presented to obtain a suboptimal solution to the original problem.Simulation results show that the algorithm can effectively reduce the total energy consumption of the system.(2)Given that Internet of Things terminals are usually powered by batteries with limited capacity,Wireless Power Transfer(WPT)technology is expected to extend the operating time of Internet of Things terminals with limited capacity in order to power these devices and avoid manual battery replacement.Currently,WPT-based technology is capable of transmitting power over a distance of up to tens of meters,so it is suitable for transmitting energy for Internet of Things terminals.The WPT architecture supported by UAV can improve energy transfer efficiency by using them as energy transmitters for ground users.In addition,considering that there are potential eavesdroppers on the ground,the secrecy offloading of the system is also a factor to consider.For this reason,this paper presents an energy consumption optimization method based on WPT for secrecy offloading of full-duplex UAV-assisted MEC system.Full-duplex UAV with energy transmitter and MEC server provides energy and computing services for multiple ground users to help them complete their computing tasks.Full-duplex UAV transmits interference signals to ground listeners to enhance the security of the system.Minimize UAV energy consumption through joint optimization of the trajectory of UAV,scheduling factor,resource allocation and the transmit power of users.To solve this difficult non-convex problem,an alternating optimization algorithm is proposed to obtain a suboptimal solution of the original problem.Simulation results show that the algorithm can get good results.