Unmanned aerial vehicles (UAVs) hold significant potential for sensing services in a large scope of area, thanks to their wide coverage and adaptable deployment. Considering the complex environment dynamics and limited sensing range, navigating multiple UAVs in a distributed way becomes challenging to implement cooperative data sensing and transmission tasks. In this paper, we optimize the trajectory design of UAVs by jointly considering the collected data volume, geographical fairness and limited energy reserve during their service period. To achieve the long-term serving objective, a memory augmented multi-agent deep reinforcement learning approach is presented to ensure energy-efficient distributed trajectory design with partial observations. Specifically, the intrinsic criterion is developed to enhance UAV spatial exploration when reaching the boundary of explored regions. Then, to address the information loss caused by incomplete observations, the spatial-temporal memory augmented actor-critic architecture is designed to extract historical contextual features for multi-UAV cooperative navigation. Furthermore, the prioritized experience replay mechanism is incorporated to enhance important experience exploitation for UAV collaboration. Extensive simulations using two real-world datasets in Shenzhen and Beijing demonstrate that the proposed method outperforms the state-of-the-art methods in terms of data collection ratio, geographical fairness, and energy consumption ratio.

Mobile crowdsensing (MCS) by human participants and unmanned aerial vehicles (UAVs) is an emerging air-ground collaborative data collection paradigm by navigating a group of UAVs to collaborate with human participants to provide large-scale and fine-grained sensing services. In this paper, we aim to optimize the trajectory design of UAVs by jointly considering the collected data volume, geographical sensing fairness, and limited energy reserve during the serving period. To achieve the long-term serving objective, we propose a human participants distribution prediction based multi-agent deep reinforcement learning method for efficient UAV navigation to collaborate with human participants in performing MCS tasks. Specifically, we first introduce a region division based human participant spatial distribution prediction method to help UAVs to collaborate with human participants by the predictive mobility flows. Then, we present the multi-agent proximal policy optimization (MAPPO) based method for efficient UAV navigation decision-making. Extensive simulations and trajectory visualization using the real-world mobility dataset in KAIST show that the proposed method consistently outperforms the state-of-the-art in terms of the energy efficiency when varying the number of UAVs and human participants.

With the rapid development of vehicle-to-everything technology, vehicular edge caching has emerged as a crucial component for managing frequently accessed content at the network’s edge. However, due to vehicles’ high mobility, it is challenging to determine where and which content needs to be cached. To address this issue, a mobility and context-aware precache strategy is proposed to proactively prefetch and replace content in two steps. First, by integrating the traffic features from vehicles and roads, a spatial-temporal informer-based model is designed to predict long-term vehicle trajectories. Subsequently, a proactive context-aware precache strategy is proposed. By analyzing the context of different cache types, the required content can be further accurately estimated according to the cache type and workload. Extensive simulations based on real-world mobility scenarios are conducted to validate the performance of the proposed method. The results show that the proposed method can improve prediction accuracy and cache hit rate by 34.56% and 18.89%, and reduce mean response time and total energy cost by 6.1% and 2.65% compared to the existing precaching methods.

The increasing number of connected vehicles exacerbates the scarcity of spectrum resources in vehicle-to-everything (V2X) communication. To optimize the utilization of wireless resources, it is crucial to allocate the limited spectrum blocks to each roadside unit (RSU) based on the real-time bandwidth demand of vehicles within their coverage. However, the complex mobility patterns of vehicles and dynamic traffic conditions make it challenging to accurately and promptly estimate the bandwidth demand. To address this issue, a spatial-temporal multi-attentional network (STMA-net) is designed to predict the future bandwidth demand of RSUs. Based on the predicted bandwidth demand, a prediction error-compensable proactive bandwidth allocation algorithm is proposed to adaptively allocate spectrum resources and narrow the discrepancy between predicted and actual demand. Experimental results with realistic traffic in Bologna demonstrate that the proposed STMA-net achieves 11.25% higher prediction accuracy compared to state-of-the-art methods. Furthermore, the proposed proactive bandwidth allocation method outperforms existing methods, providing the highest throughput and serving 5% more vehicles while reducing the service drop rate by an order of magnitude.