Due to flexibility, autonomy and low operational cost, unmanned aerial vehicles (UAVs), as fixed aerial base stations, are increasingly being used as \textit{relays} to collect time-sensitive information (i.e., status updates) from IoT devices and deliver it to the nearby terrestrial base station (TBS), where the information gets processed. In order to ensure timely delivery of information to the TBS (from all IoT devices), optimal scheduling of time-sensitive information over two hop UAV-relayed IoT networks (i.e., IoT device to the UAV [hop 1], and UAV to the TBS [hop 2]) becomes a critical challenge. To address this, we propose scheduling policies for Age of Information (AoI) minimization in such two-hop UAV-relayed IoT networks. To this end, we present a low-complexity MAF-MAD scheduler, that employs Maximum AoI First (MAF) policy for sampling of IoT devices at UAV (hop 1) and Maximum AoI Difference (MAD) policy for updating sampled packets from UAV to the TBS (hop 2). We show that MAF-MAD is the optimal scheduler under ideal conditions, i.e., error-free channels and generate-at-will traffic generation at IoT devices. On the contrary, for realistic conditions, we propose a Deep-Q-Networks (DQN) based scheduler. Our simulation results show that DQN-based scheduler outperforms MAF-MAD scheduler and three other baseline schedulers, i.e., Maximal AoI First (MAF), Round Robin (RR) and Random, employed at both hops under general conditions when the network is small (with 10's of IoT devices). However, it does not scale well with network size whereas MAF-MAD outperforms all other schedulers under all considered scenarios for larger networks.

翻译：由于灵活性、自主性和低运作成本,无人驾驶飞行器(无人驾驶飞行器)作为固定的空军基地站,越来越多地被用作“textit{relays}”,从IOT设备收集时间敏感信息(即状态更新)并将其传送到附近的地面基地站(TBS),信息在地面站得到处理。为了确保向TBS(所有IOT设备)及时发送信息,在两个自动自动自动更新的IOT网络(即IOT设备在UAV[Hop 1]和UAV至TBS[Hop 2]上的最佳时间敏感信息时间安排。为了解决这个问题,我们提出了信息时代(AOI)最晚在二手UAV-Relayed IOT网络(所有IOT装置的所有兼容性MAF-MA系统)最晚时间安排,在UAV(H1)和最大AWO(MA-MAF) 最晚进度列表下,在MAF-MAF-Mo(我们最晚的IMA-R-R) 最晚的IA-R(MAF-ro-ro-la-la-lax) 时间列表在MAF-ro-la-la-lax Fl-lax Fl-ro-la-lax Fl)在三MA-ro-la-la-lax misl-mo-lax Fl-ro-ro-mocal Stal Stal Stal Stal Stal 的M-rol 政策中,在MF-mo-routal-ladal-ladal-lades 期间,在三的MF-ladal-lad-mo-lad-lad-lad-ladal-lad-lad-lad AS AS-lax Procisl ro Prot 期间,在3-lad lad lad 期间,在3-lad lad lad lad lax lad-lad-lad-lad-lad-lad-mo-lad-lad-lad-l-lad-l-lad-lad-l-l-l-l lax lax lax lax