SATLOCK: Handover-Coupled Scheduling for Weather-Resilient Quantum Key Distribution over LEO Constellations
Cryptography and Security
Summary
The authors study how to send secure quantum keys using satellites in low-Earth orbit, which is tricky because satellites switch connections often, weather can block signals, and short connections don’t work well. They created SATLOCK, a system that models these real-world problems, calculates the best possible routing of keys, and uses machine learning for smart, weather-aware routing. Tests show their system performs close to the best mathematically possible, especially when there is less competition for satellite access. Their learning method handles changing weather well but struggles when many demands need coordination.
Authors
Mohammad Arif Hossain, Md Jafrin Hossain
Abstract
Routing quantum keys over low-earth-orbit (LEO) satellite constellations is harder than classical routing: satellite handovers couple consecutive scheduling decisions, stochastic cloud cover can silently zero a ground link, and finite-key effects eliminate short, low-elevation passes entirely. We present SATLOCK, a handover-aware Quantum Key Distribution (QKD) routing framework that combines (i) a composite channel model incorporating atmospheric loss, pointing jitter, Markov cloud cover, decoy-state estimation, and finite-key correction; (ii) an integer linear program (ILP) giving a provable handover-aware throughput upper bound; and (iii) a decentralized deep Q-network (DQN) baseline for weather-adaptive online routing. We evaluate two contention regimes on a Walker constellation serving intercontinental demands. In low contention (16 satellites, 6 demands), the ILP delivers 1,311 Mbit while the strongest heuristics reach 95--96\% of ILP. In high contention (8 satellites, 12 demands), where handovers become binding, heuristics drop to 89.5\% of ILP. The DQN agent reaches 91.8\% and 84.6\% of ILP in the two regimes; it learns effective per-demand weather policies but is limited in aggregate by the lack of cross-demand coordination.