TCSC: A Novel File Distribution Strategy in Integrated LEO Satellite-Terrestrial Networks

Integrated Satellite-Terrestrial (IST) networks consisting of low earth orbit (LEO) satellite constellation and terrestrial users are widely developed for potentially attractive requirements of content distribution, benefiting from low deployment cost and broader coverage capability. However, orbital paradigm of LEO constellation, as well as an accordingly time-changing topology, makes a huge challenge for distributing objective file due to heavy lack of end-to-end paths. To address this issue, in this paper, a Time-evolving Covering Set instructed in-network Caching (TCSC) mechanism is proposed to achieve file distribution in the IST networks with high efficiency. In the proposed mechanism, a novel Event Updating Graph (EUG) is put forward for capturing fine-grained topological information in time domain. With it, a Minimum Time-evolving Covering Set (MTCS) is constructed for designing the caching-in-network mechanism with appropriate intermediate nodes. Furthermore, a Query-based Minimum Delay Distribution Path (QMDP) algorithm is proposed for rapidly fetching objective file from cache nodes in MTCS by fully exploiting EUG-based topological information. The simulation results verified the proposed method can obviously degrade the overall overheads and access delay of all users, compared respectively with Network Central Location (NCL) metric, Random Cache metric and Maximum Node Degree Cache (MDC) metric.