Juan A. Fraire

Researcher in Space Networking and Informatics

Inria CONICET Saarland University

Publications Conference paper · Delay-tolerant networks · 2026

CGR*: A* Search for Contact Graph Routing

Simon Rink, Olivier De Jonckère, Juan A. Fraire, and Holger Hermanns

IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Space-Terrestrial Internetworking Workshop (STINT), 2026

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Abstract

Routing in space Delay-Tolerant Networks relies on Contact Graph Routing (CGR), standardized within the CCSDS Schedule-Aware Bundle Routing (SABR) framework. Existing SABR implementations use Dijkstra's algorithm, which ignores any information about the remaining cost to the destination and therefore explores many unnecessary states. We propose CGR*, an A*-based variant that exploits domain-specific heuristics to prune this search. Two heuristics are designed: h_Delay, an admissible heuristic suited to delay-dominated deep-space networks, and h_Geo, a greedy geographic heuristic for near-Earth networks, where contact availability rather than propagation delay drives arrival time. Experiments on realistic orbital scenarios show that h_Delay accelerates routing on deep-space networks by up to an order of magnitude with no loss of optimality, while h_Geo speeds up near-Earth routing at the cost of arrival times up to ∼2.5× the optimum — revealing cost-model design, rather than heuristic design alone, as the open challenge for A*-based routing in near-Earth scenarios. CGR* and its heuristics are released as part of the open-source A-SABR library.

Cite

BibTeX
@inproceedings{rink2026cgrstar,
  author    = {Rink, Simon and De Jonck{\`e}re, Olivier and Fraire, Juan A. and Hermanns, Holger},
  title     = {{CGR*}: A* Search for Contact Graph Routing},
  booktitle = {IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Space-Terrestrial Internetworking Workshop (STINT)},
  year      = {2026}
}

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