A Space–Time Graph Based Multipath Routing in Disruption-Tolerant Earth-Observing Satellite Networks

In this paper, we consider the problem of routing in disruption-tolerant-networking-based earth-observing satellite networks, which are characterized by a frequently changing topology and potentially sparse and intermittent connectivity. To handle the routing challenges posed by these properties, we propose a joined space-temporal routing algorithmic framework for those networks, where the time-varying topology is modeled as a space-time graph leveraging the predictability of satellites' relative motions. Based on this graph model, we devise a multipath routing algorithm [minimum-cost constrained multipath (MCMP)] to find a feasible set of available routing paths, through which a certain amount of mission data can be transferred back to ground stations within a tolerable delay with a minimum cost. To comparatively evaluate the performance of MCMP, moreover, we design an earliest arrival multipath routing policy (EAMP) algorithm based on the typical contact graph routing algorithm. The performance comparisons among MCMP, EAMP, and direct transfer strategy are simulated and analyzed.