Optimizing Age-of-Information in Piggyback Networks with Recurrent Data Generation

Age-of-information ({AoI}) is a critical metric that quantifies the freshness of data in communication systems. In the era of the Internet of Things ({IoT}), data collected by resource-constrained devices often need to be transmitted to a central server to extract valuable insights in a timely manner. However, maintaining a stable and direct connection between a vast number of {IoT} devices and servers is often impractical. The Store-Carry-Forward ({SCF}) communication paradigm, such as Piggyback networks, offers a viable solution to address the data collection and transmission challenges in distributed {IoT} systems by leveraging the mobility of mobile nodes. In this work, we investigate {AoI} within the context of patrolling data collection drones, where data packets are generated recurrently at devices and collected by a patrolling drone to be delivered to a server. Our objective is to design a patrolling route that minimizes the Maximum Age-of-Information ({MAI}) across the system. We demonstrate that determining whether a route with an {MAI} below a certain threshold can be constructed is {NP}-Complete. To address this challenge, we propose two approaches with approximation guarantees. Our evaluation results show that the proposed approaches can achieve near-optimal routes in reasonable time across various scenarios