Delay and disruption-tolerant networks are becoming an appealing solution for extending Internet boundaries toward challenged environments where end-to-end connectivity cannot be guaranteed. In particular, satellite networks can take advantage of a priori trajectory estimations of nodes to make efficient routing decisions. Despite this knowledge is already used in routing schemes such as contact graph routing, it might derive in congestion problems because of capacity overbooking of forthcoming connections (contacts). In this work, we initially extend contact graph routing to provide enhanced congestion mitigation capabilities by taking advantage of the local traffic information available at each node. However, since satellite networks data generation is generally managed by a mission operation center, a global view of the traffic can also be exploited to further improve the latter scheme. As a result, we present a novel strategy to avoid congestion in predictable delay-and disruption-tolerant network systems by means of individual contact plans. Finally, we evaluate and compare the performance improvement of these mechanisms in a typical low Earth orbit satellite constellation.
KEYWORDScontact graph routing, congestion management, delay and disruption tolerant networks, satellite networks
INTRODUCTIONTraditionally, Earth observation satellites have been designed to periodically gather data from large ground areas. However, the increasing need of timely and on-demand data (images, videos, etc) is demanding a paradigm shift toward better acquisition rates and improved data delivery. To this end, recent research has shown that low Earth orbit (LEO) satellite networks can meet these requirements by significantly enhancing both coverage and revisit time among other benefits. 1 In particular, this spatial diversity not only allows for unprecedented applications by combining sensors for wider aperture, better footprint, or sensing diversity but also presents additional opportunities for data downlink to ground stations. 2 Indeed, by relying on intersatellite links (ISLs) among the orbiting assets, traffic can flow through multiple hops toward its destination on Earth improving both system capacity and data delivery time. However, maintaining a persistent end-to-end connection between the origin of the data and its destination in orbiting constellations demands strict flight-formation requirements 3 and might require prohibitive amounts of communication resources. 4 As a result, embracing delay-and disruption-tolerant networks (DTNs) 5 as the underlying communications architecture has recently been recognized as an alternative solution for building future satellite applications. 6Originally studied to develop a network architecture for the interplanetary Internet, 7 DTN has been specified as a communication architecture for environments where communications can be challenged by either latency, bandwidth, errors, or stability issues. 8 In particular, to overcome disruption, DTN nodes implement a temporary storage where d...