Coded Caching for Combinatorial Multi-Access Hotplug Networks from $t$-Designs

Abstract: We study hotplug coded caching in combinatorial multi-access networks, which generalizes existing hotplug coded caching models by allowing users to access multiple caches, while only a subset of caches is online during the delivery phase. We first generalize the Hotplug Placement Delivery Array (HpPDA) framework to the combinatorial multi-access setting. Based on this generalized framework, we propose a t-design-based coded caching scheme for combinatorial multi-access networks. We characterize a class of design parameters under which every active user has access to a sufficient number of coded subfiles to decode its requested file, and show that appropriate parameter choices allow for the elimination of redundant multicast transmissions. As a result, the proposed scheme achieves a family of rate memory trade offs with flexible subpacketization. We present numerical comparisons illustrating that the proposed t-scheme outperforms existing hotplug coded caching schemes in certain memory regimes.