Publications Conference paper · Delay-tolerant networks · 2026

Lifespan-Aware Contact Plan Design for Interplanetary Free-Space Optical Networks

Alejandro M. Toledo, Jason Gerard, Sandra Céspedes, and Juan A. Fraire

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

Abstract

Free-space optical (FSO) communication promises to relieve the capacity bottleneck in radio-frequency deep-space networks, but its narrow beams demand precise pointing, acquisition, and tracking (PAT), which in turn requires that link opportunities be scheduled in advance through contact plan design (CPD). Existing CPD schedulers for optical interplanetary backhaul maximize throughput, while battery state-of-charge has been considered only for RF networks, yet none model the irreversible decay of radioisotope thermoelectric generator (RTG) power or its effect on long-term survivability. We extend the Laser Link Scheduler (LLS) with three resource-aware variants: energy-, battery-, and lifespan-aware, that fold RTG decay and optical-terminal consumption into per-node lifetime constraints, and evaluate the trade-off between capacity, fairness, and survivability across Mars-to-Earth constellations of increasing size. We define network lifetime as the point at which data-producing source nodes can no longer transmit, and find that the capacity-greedy LLS schedules 45 to 55% more data than the fairness baseline while consuming the lowest amount of energy. However, we find that survivability is governed by the hardware power margin, not by scheduling, and stays nearly identical across all schedulers at both end-of-life and beginning-of-life RTG power levels. These distinctions matter for mission operations, where expensive scientific payloads must balance data backhaul rate against mission lifetime.

Cite

BibTeX

@inproceedings{toledo2026lifespan,
  author    = {Toledo, Alejandro M. and Gerard, Jason and C{\'e}spedes, Sandra and Fraire, Juan A.},
  title     = {Lifespan-Aware Contact Plan Design for Interplanetary Free-Space Optical Networks},
  booktitle = {IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Space-Terrestrial Internetworking Workshop (STINT)},
  year      = {2026}
}

More on delay-tolerant networks

Comparing Statistical, Analytical, and Learning-Based Routing Approaches for Delay-Tolerant Networks Pedro R. D'Argenio, Juan A. Fraire, Arnd Hartmanns, and Fernando D. Raverta ACM Transactions on Modeling and Computer Simulation, 2025
Abstract
In delay-tolerant networks (DTNs) with uncertain contact plans, the communication episodes and their reliabilities are known a priori . To maximise the end-to-end delivery probability, a bounded network-wide number of message copies are allowed. The resulting multi-copy routing optimization problem is naturally modelled as a Markov decision process with distributed information. In this paper, we provide an in-depth comparison of three solution approaches: statistical model checking with scheduler sampling, the analytical RUCoP algorithm based on probabilistic model checking, and an implementation of concurrent Q-learning. We use an extensive benchmark set comprising random networks, scalable binomial topologies, and realistic ring-road low Earth orbit satellite networks. We evaluate the obtained message delivery probabilities as well as the computational effort. Our results show that all three approaches are suitable tools for obtaining reliable routes in DTN, and expose a tradeoff between scalability and solution quality.

HAL Publisher
Autonomous Max-Flow Interplanetary Laser Link Scheduling for Martian Exploration Jason Gerard, Andre Ibrahim, Juan A. Fraire, and Sandra Céspedes IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), 2024
Abstract
New communication technologies like delay and disruption-tolerant networking (DTN) and free-space laser communications are being developed to handle massive planetary telemetry data. However, existing infrastructure cannot meet the scalability and autonomy demands of future space missions, resulting in 95% of data left on the mission planet. Manual scheduling of deep-space laser transmissions by operators is inefficient and error-prone, limiting mission parallelization, while autonomous scheduling, though promising, may limit optimal network routes reducing the network capacity. We hypothesize that autonomously scheduling contact opportunities will enable acquisition, tracking, and pointing (ATP) for free-space lasers and increase the capacity of interplanetary backhaul networks. In this work, we propose the Laser Link Scheduler (LLS), which combines a novel max-flow network capacity model and a decision-making algorithm for contact selection. We define a series of deep-space communication scenarios where data is collected from orbiters around Mars and backhauled to Earth. LLS is evaluated in simulations using contact plans generated based on realistic conditions and orbital dynamics. Our results confirm that autonomous contact scheduling increases network capacity by 1.5-2x, reducing operational costs and enabling highly parallel space exploration missions.

HAL Publisher
Ring Road Networks: Access for Anyone Marius Feldmann, Juan A. Fraire, Felix Walter, and Scott C. Burleigh IEEE Communications Magazine, 2022
Abstract
Several billion people currently lack reliable access to the Internet and thus to a tremendous source of knowledge. In this article, we describe a field-tested communication approach combining CubeSat platforms and delay-tolerant networking (DTN) solutions to provide asynchronous connectivity to populations and regions that are underserved by the Internet. The resulting class of networks is known as ring road networks (RRNs), a networking approach that is built on technology developed for the construction of a solar system Internet. The necessary self-sufficiency of DTN nodes enables network access to be deployed incrementally at low cost, supporting communities that cannot be profitably served by Internet satellite constellations. We present the RRN architecture and evaluate the expected performance by means of simulations. Based on the latter, we discuss µD3TN: a lightweight and open source DTN protocol stack for RRNs and other DTN classes. µD3TN has been flight-tested in ESA's OPS-SAT in low Earth orbit during December 2020 and May 2021. This work discusses the experiment results as we validated the RRN approach in concrete application use cases. The reported outcomes motivate a new application domain.

HAL Publisher

Delay-tolerant networks: the topic page All 84 papers on this topic