AoI-based UAV Relay Communications

With the development and deployment of the fifth-generation mobile communication system,more and more emerging Internet of Things(Io T)applications appear in daily life,such as unmanned driving,remote surgery,and intelligent industrial control.In an Io T system for real-time applications,devices need to perceive the surrounding physical environment and monitor the state of the system in real time,to provide timely and effective information for intelligent decision-making and control.For such time-sensitive information,if the decision-making end obtains outdated information,it will lead to invalid decision-making and even wrong control,which may cause huge security problems.Besides,in the future sixth-generation mobile communication network,new services and new applications have increasingly higher requirements for information freshness.In order to characterize the freshness of information effectively,the academic world has proposed the concept of Age of Information(AoI).At present,AoI has quickly become one of the new performance indicators and research hotspots of wireless communication systems.In addition,in response to the challenges of inflexible topology and remote coverage blind spots in Io T,Unmanned Aerial Vehicle(UAV)can become an effective solution to the above challenges due to its high mobility,flexible deployment,and line-of-sight communication.Therefore,this paper studies the UAV-assisted relay transmission for AoI minimization,and investigates the joint optimization of UAV flight trajectory and wireless communication resources to minimize the peak Age of Information(PAoI),so as to ensure the real-time information acquisition in the communication system.The main contribution of this paper is as follows.This paper investigates using UAV to provide information relay service for a pair of source-destination nodes in the remote coverage blind zone.Ensuring that the short data packet carrying the sensor update information can be transmitted successfully,the uplink transmission time and downlink transmission time of the packet,the transmission power of the source node and the UAV,and the flight trajectory of the UAV are jointly optimized to Minimize the PAoI of UAV relay transmission system.Aiming at the modeled non-convex problem,this paper proposes an iterative algorithm based on successive convex approximation.The simulation results show that the proposed algorithm is significantly better than the algorithm based on alternating optimization in terms of PAoI and convergence performance.This paper further extends the above problem to a single UAV multi-sensor node information relay system.For wireless sensor networks without ground communication infrastructure,consider multiple sensor nodes to upload information to UAV through Frequency Division Multiple Access(FDMA)and Time Division Multiple Access(TDMA)respectively.In this paper,the UAV’s flight trajectory and wireless communication resources are jointly optimized to minimize the maximum PAoI of each sensor in the relay system.Firstly,by introducing auxiliary variables and using perspective functions to decouple the optimized variables,and an algorithm based on successive convex approximation is proposed to iteratively solve the non-convex problem.Finally,The simulation results show that the influence of various wireless communication resources on UAV flight trajectory and PAoI,and verify the applicability of the proposed algorithm in general scenarios.In summary,this paper uses AoI as the performance index to design the trajectory and communication resources of the UAV-assisted sensor network.The simulation results show that by jointly optimizing flight trajectories and wireless communication resources,PAoI can be significantly reduced,thereby supporting various services that are sensitive to information timeliness.