Global Quantum Key Distribution Advances with Opportunistic Satellite Scheduling
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Quantum key distribution via satellite represents a leading approach to secure global communication, and researchers are now addressing critical challenges in optimising these systems.
Md Zakir Hossain from the University of Connecticut, alongside Nitish K. Panigrahy from Binghamton University, Walter O. Krawec from the University of Connecticut, Don Towsley from the University of Massachusetts Amherst, and Bing Wang from the University of Connecticut, present a new method for scheduling satellites in a single-downlink architecture. This innovative approach tackles a previously unstudied problem, moving beyond existing dual-downlink systems to create secure keys between ground stations even when they are too distant for traditional methods.
The team’s opportunistic scheduling algorithm maximises key rates across all ground station pairs, while also ensuring fairness, and their results demonstrate significant improvements in both total and minimum key rates, highlighting the importance of factors like seasonal changes and cloud cover in real-world satellite deployments. Satellite Scheduling for Quantum Key Distribution This research focuses on developing fair and efficient scheduling strategies for satellite-assisted Quantum Key Distribution (QKD) systems, maximizing performance and ensuring reliable, secure quantum communication between ground stations and satellites. The work explores optimal allocation of limited satellite resources, such as observation time and bandwidth, to multiple ground stations, considering scalability for larger systems. The research builds upon foundational work in QKD, satellite communication, network optimization, and quantum information theory, including pioneering contributions by Bennett and Brassard, and recent advances by Pirandola and colleagues. Experimental verification of satellite-to-ground QKD by Yin and Liao’s teams has proven the technology’s feasibility, while studies by Spangelo and Xhafa demonstrate optimization algorithms for satellite scheduling. Single-Downlink Scheduling for Satellite Quantum Key Distribution This work pioneers a novel approach to satellite-based QKD, focusing on a single-downlink architecture where satellites establish keys individually with ground stations and act as trusted nodes to extend key sharing. Researchers developed a scheduling method that maximizes key rates and ensures fairness among ground station pairs, demonstrating the potential of single-downlink architectures to achieve higher rates and connect distant stations. Scientists define the secret key rate as the size of the final key, obtained after error correction and privacy amplification, divided by the total quantum signals exchanged. They employ classical sampling methods to estimate error rates, allowing the satellite and ground station to analyze a portion of the raw key. Establishing a shared key involves the satellite utilizing existing key pools and securely transmitting one to the other via one-time pad encryption. The study meticulously models the free-space optical channel, accounting for loss and noise. Researchers calculate end-to-end transmissivity, representing the probability of successful photon detection, considering free-space loss, atmospheric effects, and optical hardware losses. Researchers investigated both dual-downlink and single-downlink architectures, focusing on the latter due to its potential for higher rates and connecting distant stations.
The team developed an opportunistic scheduling method that balances fairness among ground station pairs while dynamically adapting to satellite channel conditions. Experiments demonstrate that a single satellite can potentially serve up to five ground stations at 1000km altitude, while a ground station can be within range of up to eleven satellites. Analysis of a global QKD setting, with eleven ground stations across five continents, shows that the average number of available time slots ranges from 3537 to 8999, depending on altitude.
The team compared opportunistic scheduling schemes, Op-RR and Op-Greedy, against traditional methods like Round-Robin and Greedy heuristics.
Results demonstrate that Op-RR and Op-Greedy consistently generate a larger number of key bits per satellite and ground station pair, compared to RR and Greedy alone.
The team developed opportunistic scheduling schemes, notably Op-RR, which effectively leverage dynamic communication channels to establish secure keys between distant locations. Evaluations demonstrate that Op-RR achieves strong performance, balancing fairness in key distribution with maximizing the total key rate. The work highlights the advantages of single-downlink architectures, which offer the potential for higher key rates and connectivity beyond the reach of traditional dual-downlink systems. Through extensive simulations, the researchers demonstrated the impact of realistic factors such as seasonal changes and cloud cover on QKD performance, emphasizing the importance of considering these elements in system evaluation. 👉 More information 🗞 Opportunistic Scheduling for Single-downlink Satellite-based Quantum Key Distribution 🧠 ArXiv: https://arxiv.org/abs/2512.12514 Tags: