Publications Journal article · Satellite IoT · 2026
DORSAL: Downlink Optimization for Robust Direct-to-Satellite LoRaWAN
IEEE Internet of Things Journal, vol. 13, no. 15, pp. 35318–35331, 2026
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Abstract
Delivering downlink (DL) ACKs to Class A LoRaWAN devices via low Earth orbit (LEO) satellite constellations requires predicting end-to-end propagation delays of 10–500 ms to hit a 1-s receive window, a timing challenge absent from terrestrial schedulers. We present downlink optimization for robust direct-to-satellite LoRaWAN (DORSAL), the first mixed-integer linear programming (MILP) scheduler for DL delivery in direct-to-satellite (DtS) LoRaWAN networks. It introduces the downlink arrival receive-window timing (DART) as the central constraint to jointly optimize gateway (GW) selection and packet injection timing across ISL-capable and bent-pipe architectures. Evaluation on a Walker 5× 5 polar constellation (25 satellites, 650 km) and a commercial ground station (GS) network yields five results: 1) DART infeasibility blocks 73% of bent-pipe deliveries regardless of scheduler quality: DART-unaware approaches collapse from 93% nominal to only 20% real delivery; 2) ISL routing raises %ACK by + 67.4 pp over bent-pipe (91.6% versus 24.2% at n_mathrm GS=3 ground stations, ISM band) by eliminating the three-way simultaneous-visibility constraint, with 73% of ACKs delivered via ≥ 2 -hop paths; 3) ISL %ACK is nearly flat across n_mathrm GSin 3,6,12 GSs (91.6%–92.7%), showing that a minimal three-station polar network captures the full scheduling benefit of an ISL-equipped constellation; 4) ISL hardware speed has negligible impact up to 300 ms/hop: %ACK is flat from 0 to 300 ms, then degrades in two discrete steps (−5.3 pp at 500 ms, −2 pp at 700 ms) as successive hop-count tiers lose causal injection feasibility; and 5) the MILP solves to proven optimality within seconds for up to 10^3 devices, confirming that the sparse conflict-graph structure keeps the problem tractable at realistic Internet of Things (IoT) subscriber counts.
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BibTeX
@article{fraire2026dorsal,
author = {Fraire, Juan A. and Iova, Oana and Fernandez Hernandez, Carlos and Valois, Fabrice and Rivano, Herv{\'e} and Azurdia-Meza, Cesar and Diaz, Marcos and Guti{\'e}rrez Gait{\'a}n, Miguel and Dujovne, Diego and Montejo S{\'a}nchez, Samuel and Demo Souza, Richard},
title = {{DORSAL}: Downlink Optimization for Robust Direct-to-Satellite LoRaWAN},
journal = {IEEE Internet of Things Journal},
volume = {13},
number = {15},
pages = {35318--35331},
publisher = {IEEE},
year = {2026},
doi = {10.1109/jiot.2026.3696890}
}