The emerging paradigm of Direct-to-Satellite Internet of Things (DtS-IoT) represents a significant advancement in linking terrestrial Low-Power Wide Area Network (LPWAN) technologies with Low-Earth Orbit (LEO) satellites. Through this new paradigm, IoT devices communicate using well-established terrestrial technologies such as LoRaWAN to transmit data directly to satellites, even without ground infrastructure. DtS-IoT enables efficient and seamless connectivity for global-scale applications such as international asset tracking, cross-border environmental monitoring, and global data collection and distribution. DtS-IoT also facilitates the development of applications in remote regions that would otherwise be challenging to cover with low-cost terrestrial IoT connectivity, like oceanic monitoring and remote agriculture.
While LPWAN technologies such as LoRaWAN suit DtS-IoT connectivity, existing prototypes and validations have predominantly emphasized data uplink communication (from end devices to satellites); however, downlink communication (from satellites to end devices) is of the utmost importance for ensuring robust data communication and user access to all the deployed end devices. This includes acknowledging successfully received uplink packets. Data flows from the Internet to ground devices through the LEO satellite network in these cases. Additionally, the downlink channel enables the LoRaWAN network and application servers to utilize a control channel to remotely configure end devices and operate actuators via the DtS-IoT network. This postdoc is focused on proposing and testing efficient medium access techniques within the DtS-IoT landscape, utilizing LEO satellite networks, and addressing the constraints of IoT communications in space.
- State-of-the-Art and Problem Definition
- Review DtS-IoT systems with focus on random access protocols, LoRaWAN adaptations, and LEO constellation constraints.
- Identify key challenges: massive access scalability, collision dynamics, intermittent connectivity, and link budget variability.
- MAC and Power Control Design
- Design a satellite-aware MAC protocol for LoRaWAN.
- Develop distributed transmit power control strategies adapting to satellite geometry and channel conditions.
- Explore cross-layer approaches coupling access decisions with PHY parameters (power, data rate).
- Define key metrics: delivery ratio, collision probability, latency, energy efficiency, fairness.
- Evaluate the proposed solutions in realistic LEO constellations and large device populations, across different constellation setups and traffic regimes.
- Benchmark against baseline schemes and analyze trade-offs between energy, reliability, and scalability.
- Publish results in leading venues (e.g., IEEE ICC, GLOBECOM, IEEE Internet of Things Journal).
Bibliography
[1] LoRa Alliance, LoRaWAN 1.1 Specification, 2017.
[2] J. A. Fraire, O. Iova, and F. Valois, Space-Terrestrial Integrated Internet of Things: Challenges and Opportunities, in IEEE Communications Magazine, vol. 60, no. 12, pp. 64-70, 2022.
[3] F. A. Tondo, J. M. d. S. Sant’Ana, S. Montejo-Sánchez, O. L. A. López, S. Céspedes and R. D. Souza, "Nonorthogonal Multiple-Access Strategies for Direct-to-Satellite IoT Networks," in IEEE Transactions on Aerospace and Electronic Systems, vol. 61, no. 6, pp. 16267-16279, Dec. 2025.
[4] G. G. M. de Jesus, R. D. Souza, C. Montez and A. Hoeller, "LoRaWAN Adaptive Data Rate With Flexible Link Margin," in IEEE Internet of Things Journal, vol. 8, no. 7, pp. 6053-6061, 1 April1, 2021.
[5] C. Christelle, A. Guitton, O. Iova , and F. Valois, The Impact of Downlink Scheduling Policy on the Capacity of LoRaWAN, in IEEE Global Communications Conference (GLOBECOM), 2024.
[6] FLoRaSat simulator: https://gitlab.inria.fr/jfraire/florasat
