ABSTRACT In this paper, a directed acyclic graph (DAG) task‐based computing offloading strategy is proposed aiming to minimize the delay‐energy weighted cost (DEWC) of the whole system. In this scenario, multiple unmanned aerial vehicles (UAV) act as mobile servers for processing DAG tasks with different structures from multiple user equipment (UE). By considering the connection scheduling, computing frequency allocation and UAVs' trajectories, a mixed integer nonlinear programming (MINLP) problem is formulated and solved approximately. Specifically, a greedy computing frequency allocation algorithm is proposed based on task level division, and then a heuristic connection scheduling algorithm is put forward for each UE selecting UAV with minimal DEWC. Finally, the UAVs' trajectories are optimized by using the Soft Actor‐Critic (SAC) algorithm. Our strategy DGS is compared with Proximal Policy Optimization (PPO), Deep Deterministic Policy Gradient (DDPG), Particle Swarm Optimization (PSO) and baseline algorithms. The results verified the advantages in terms of convergence and DEWC.

Aiming at the real-time computing problems in large-scale internet of things devices (IoTDs) scenarios, a framework for terahertz (THz) -based mobile edge computing (MEC) network with multi-unmanned aerial vehicles (UAV) collaboration is proposed. In this framework, a utility model based on latency and connection scheduling is first presented. Its significance lies in enabling high-priority tasks to obtain more computing resources, thereby reducing computing latency. Then, we formulate an optimization problem that jointly optimizes connection scheduling, computing resource allocation, and UAV flight trajectories under the objective of maximizing the average utility of IoTDs. To solve this Mixed Integer Nonlinear Programming Problem (MINLP), we use Deep Reinforcement Learning (DRL) based on learning rate decay and Prioritized Experience Replay (PER) to optimize the UAVs trajectories, and design a low-time complexity heuristic algorithm to solve the connection scheduling and resolve the computing resource allocation by an iterative algorithm. Subsequently, to evaluate the performance of our proposed algorithm, we compare it with Soft Actor-Critic (SAC), Proximal Policy Optimization (PPO), Deep Deterministic Policy Gradient (DDPG), and Particle Swarm Optimization (PSO). Simulation results show that our proposed algorithm significantly improves the average utility of IoTDs and reduces the latency of high-priority tasks. Besides, our proposed algorithm has better convergence than the above algorithms.

Autonomous aerial vehicles (AAV) can alleviate the computational burden on edge devices through assisted computing. However, with the increase in the number of Internet of Things Devices (IoTDs), it is essential to establish a task queue on the AAV to schedule computing tasks from IoTDs. In addition, the load fairness of AAVs should be optimized to fully utilize the computing resources. Therefore, a multi-AAV-assisted mobile edge computing (MEC) network framework based on the queuing model is proposed, which aims at optimizing the average delay of all user devices and the load fairness of AAVs. Firstly, we prove that the arrangement of tasks with different computing delays on the AAV queue can affect the user’s average delay, so a short-job-first (SJF) queuing model is proposed to minimize the average delay of users. On this basis, a joint optimization problem related to the AAV’s three-dimensional trajectory and user connection scheduling is formulated. A SJF based low-complexity connection scheduling algorithm is proposed and combined in a deep reinforcement learning (DRL) to solve this NP-hard problem. To evaluate the performance of the proposed algorithm, we compare it with deep deterministic policy gradient (DDPG), particle swarm optimization (PSO), random moving (RM), and local computing (LC). Simulation results show that our algorithm effectively reduces user average delay and enhances AAV load fairness. Finally, SJF is compared with the traditional first-come-first-served (FCFS) queuing model on different algorithms. The results indicate that the average delay of SJF is significantly lower than that of FCFS.

It is well-established that terrestrial communication systems may fail during emergencies such as earthquakes, tsunamis, and floods. Fortunately, with the rapid advancement of unmanned aerial vehicle (UAV) network technology, deploying UAV nodes as aerial base stations (BSs) is assuming an increasingly crucial role in facilitating downlink transmissions and restoring ground communication capabilities. However, a single UAV node is not sufficient to meet the requirements. Inspired by distributed communication, we introduce a performance analysis framework based on stochastic geometry to analyze the distributed coordinated multi-point (CoMP) UAV-assisted communication network. Specifically, we assume that all UAV nodes follow a homogeneous Poisson point process (PPP) and maintain a constant altitude. The entire space is tessellated by multiple hexagons, with multiple UAV nodes within each hexagonal region working together to serve terrestrial user equipments (UEs). For this region-centric cooperative model, we derive an exact expression for the coverage probability to quantify the performance improvement enabled by UAVs, analyze the upper bound of the coverage probability, and provide a simplified approximation. We then compare this model to a user-centric model. Our numerical findings demonstrate that the cooperation of UAV nodes can significantly enhance the coverage probability and save spectrum resources.

As the number of Internet of Things Devices (IoTDs) increases, the building Structural Health Monitoring (SHM) system is subject to the enormous amount of data collected from sensors. To tackle this challenge, we investigate an Unmanned Aerial Vehicle (UAV)-enabled Wireless Powered Communication Network (WPCN) in a building SHM scenario where a UAV is dispatched to provide wireless charging and data relaying services for IoTDs on the building. For preventing the channel blockage caused by the building, we place the UAV and Access Points (APs) in specific trajectory and locations, respectively. To improve the system’s throughput, we maximize the minimum data volume among devices in a given period by formulating an optimization problem in which we jointly optimize the link schedule, the power and time allocation and the hovering positions of the UAV. However, the formulated problem is a mixed-integer nonlinear programming and is hard to solve. Therefore, we adopt a bottleneck-aware idea to reduce the dimensionality of the optimization variables in order to obtain a simplified problem that can be solved in a low-complexity way. Also, the Block Coordinate Descent (BCD) method is applied to reduce the complexity of the problem. Meanwhile, we further propose a method to deal with the heterogeneous problem for improving the generalizability of our algorithm. To estimate the performance of our proposed algorithm, we compare it with the Monte Carlo (MC) method, Game Theory (GT) and Particle Swarm Optimization (PSO). The simulation results indicate that our algorithm can obtain better performance.

Mobile edge computing (MEC) has been proposed in recent years to process resource-intensive and delay-sensitive applications at the edge of mobile networks, which can break the hardware limitations and resource constraints at user equipment (UE). In order to fully use the MEC server resource, how to maximize the number of offloaded tasks is meaningful especially for crowded place or disaster area. In this paper, an optimal partial offloading scheme POSMU (Partial Offloading Strategy Maximizing the User task number) is proposed to obtain the optimal offloading ratio, local computing frequency, transmission power and MEC server computing frequency for each UE. The problem is formulated as a mixed integer nonlinear programming problem (MINLP), which is NP-hard and challenging to solve. As such, we convert the problem into multiple nonlinear programming problems (NLPs) and propose an efficient algorithm to solve them by applying the block coordinate descent (BCD) as well as convex optimization techniques. Besides, we can seamlessly apply POSMU to UAV (Unmanned Aerial Vehicle) enabled MEC system by analyzing the 3D communication model. The optimality of POSMU is illustrated in numerical results, and POSMU can approximately maximize the number of offloaded tasks compared to other schemes.

With the increasing number of electric vehicles (EVs), temporary charging demands grow rapidly. Unlike charging at home or workplace, temporary charging requires less waiting time. In this article, a mobile edge computing (MEC)-enabled charging and discharging networking system algorithm (CDNSA) is proposed to minimize the waiting time for EVs in charging stations (CSs). A software-defined network (SDN) paradigm is adopted to enhance the data transmission efficiency for MEC servers. In CDNSA, the optimization problem is formulated as a mixed-integer nonlinear programming (MINLP). A heuristic algorithm is proposed to solve the optimal CS selection variables for EVs that needs to be charged (EVCs) and EVs that can be discharged (EVDs), and then a remaining problem nonlinear programming (NLP) is obtained. By verifying the convexity of each continuous variable, the NLP is solved by adopting the block coordinate descent (BCD) method. In simulation, the optimality of CDNSA is verified by comparing with the exhaustive algorithm in terms of minimizing maximal waiting time (MMWT) of CSs. We also compare CDNSA with other benchmarks to illustrate its advantage.

With the increase of the number of electric vehicles (EVs), it is of vital importance to develop the efficient and effective charging scheduling schemes for all the EVs. In this article, we aim to maximize the social welfare of all the EVs, charging stations (CSs) and power plant (PP), by taking into account the changing demand of each EV, the changing price, the capacity and the congestion balance between different CSs. To this end, two efficient scheduling algorithms, i.e., Centralized Charging Strategy (CCS) and Distributed Charging Strategy (DCS) are proposed. CCS has a slightly better performance than the DCS, as it takes all the information and make the decision in the central control unit. On the other hand, DCS dose not require the private information from EVs and can make decentralized decision. Extensive simulation are conducted to verify the effectiveness of the proposed algorithms, in terms of the performance, congestion balance, and computing complexity.

In this paper, a congestion balanced green charging networks is proposed for the electric vehicles (EVs) in smart grid. Firstly, a problem about the congestion probability balance among the charging stations (CSs) is analyzed and formulated, and then a two-layer optimization model is established based on the profit functions of power plant (PP), CSs and EVs. In the first layer, the optimal generation capacities as well as the charging capacities of CSs are determined, while in the second layer, the sum of each CS's profit and that of the EVs which want to charge at the CS is formulated as a profit maximization problem. The two-layer optimization model solves the congestion probability balance problem in the iterative manner, and finally the congestion balanced smart charging algorithm (CBSCA) is obtained. By comparing with other benchmarks, the results show that CBSCA is converged in an acceptable time, and the congestion probabilities among the CSs are balanced.

In this paper, we consider a smart power model, where some subscribers share several energy providers and there are some malicious users in this power grid. The energy providers are managed by a power market scheduling center (PMSC), which broadcasts electricity price to subscribers and energy providers. The energy providers and subscribers update their capacities and energy consumption requirements, respectively, according to the electricity prices received. In order to identify the malicious users and the unstable energy providers, the mechanism of identification and processing (MIP) for the malicious users and unstable energy providers is proposed. By integrating the MIP, we proposed a heuristic algorithm called the dynamic pricing algorithm with malicious users and unstable energy providers (DPAMU) to get the optimal electricity price as well as the optimal power requirement and the load capacity. Finally, the simulation results show that the proposed DPAMU has good convergence performance and can shave and clip the peak load effectively.

In order to guarantee pay-TV services, data of digital television (DTV) programs are scrambled by conditional access systems (CAS). In practical applications, some DTV transmitting nodes need descramble the scrambled DTV programs for editing purposes. After editing, how to re-scramble these edited programs is a challenging task since building CAS at transmitting nodes is expensive and insecure. In this paper, we proposed a novel scheme to solve this problem. Together with the recommended scheme, we also proposed techniques regarding video key data selection and extraction, synchronization of scrambled and descrambled transport stream (TS) packets, and scrambled/unscrambled interleaving multiplexer. The proposed scheme requires much lower complexity than existing methods while maintaining enough security for practical applications. Neither professional CAS equipment nor real-time common key (CK) transmitting is required by our re-scrambling scheme. Various experimental results demonstrated that the proposed re-scrambling scheme achieved superior performance in practical DTV systems, and it also obtained good compatibility with different CAS algorithms.