Handling Demand Heterogeneity in UAV-aided Content Caching in Communication-challenged Environments

This article proposes an unmanned aerial vehicle (UAV) aided content provisioning system in communication-challenged disaster scenarios. In such scenarios, without the availability of static base stations and their wireline backhauls, community of stranded users can access contents from a network of static and traveling UAVs. A set of relatively static anchor UAVs with vertical as well as lateral links can provide content access to its local users. A set of ferrying UAVs with only lateral links, but with wider mobility, can provision content to users while visiting different communities of users. The objective is to design a content dissemination system that handles user demand heterogeneity while maximizing content availability to the requesting users. This work proposes a popularity-based caching policy which tackles heterogeneity in content popularity across a disaster region. A novel value-based caching policy is developed which considers the popularity and the tolerable access delay of the content requests from the users to make caching decisions. The paper develops a novel approach called Joint Deployment of Ferrying UAVs (JDFU) Algorithm to exploit the collective storage of ferrying UAVs which boosts content distribution for users. Through analytical modeling and simulation experiments it is demonstrated that content availability can be maximized by choosing an optimal cache storage segmentation factor, JDFU configuration and hover time of ferrying UAVs. This analysis is done for different user-specified tolerable access delay, heterogeneous popularity distributions and intercommunity geographical characteristics. The paper does functional verification and performance evaluation of the proposed caching framework under a wide range of network size, UAV distribution, content popularity, and ferrying UAV trajectories.