Assessing DTN architecture reliability for distributed satellite constellations: Preliminary results from a case study

Networked small satellites constellations can yield, in general, not only higher revisit rates but new mission opportunities with important cost and risk saving by means of successive small launches and distributed functionalities such as payload, storage, processing, or data downlink. Nevertheless, as this networks operates in challenged environments, they usually face resources constraints; moreover, orbital dynamics might impose sporadic channel availability. As a result, these intermittent inter-satellite communications challenges existing networking protocols as they assume persistent connectivity. To this end, Delay Tolerant Networking (DTN) has emerged as an automated store-carry-and-forward communication architecture capable to cope with contact disruption. In order to assess DTN reliability, we generalize the communications disruptions to also include transient and permanent component faults so as to demonstrate that DTN architecture result inherently fault tolerant as failures no longer implies a service outage but an overall system capacity degradation. To this end, we developed a network model encompassing DTN communication protocols, routing algorithms, and satellite failure models to measure the system capacity degradation under specific constellation topologies.