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Communication Concepts for Self-Organizing Distributed Small Satellite Systems

Subject Area Security and Dependability, Operating-, Communication- and Distributed Systems
Term from 2016 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 329050216
 
Final Report Year 2024

Final Report Abstract

In this project, we considered communication with and within groups of small satellites. Such multi satellite systems caused a paradigm shift in satellite technology. Individual satellites in such systems can be much smaller and much cheaper than traditional satellite systems, which facilitates larger formations (in orbits close together) or constellations (in distinct, complementary orbits). Suitable communication protocols between such satellites or for the data exchange between ground stations and multi satellite systems, however, still pose many open questions. In this context, we contributed, among others, new routing and scheduling approaches in the context of so-called contact plan routing. Contact plan routing makes use of the predictability of communication opportunities, given by the known orbits, which is then leveraged to schedule temporary storage and forwarding of data. We were able to achieve substantial improvements by taking knowledge about the geometrical configuration of the satellite system into account, and therefore about the properties of the wireless medium. This allows to co-optimize routing and scheduling of transmissions. We also devised particularly efficient approaches for the transmission of sensor data from multiple satellites to the ground using distributed source coding, and of identical data (e. g., software updates) from ground stations to multiple satellites using network coding. One of the specific use cases that we considered in the project is the periodic transmission of position beacon messages for tracking the location of transponders. Such systems are, for instance, used in maritime and air traffic to exchange position data between vessels or airplanes. If such position beacons are to be captured by satellites in order to track movements, parallel transmissions by senders at different positions on the ground can reach the satellite at the same time and interfere with each other there – even if the senders are far apart and the Earth’s curvature prevents their radio ranges from intersecting on the ground. Our contributions include new techniques to avoid the resulting message collisions, while the satellites still remain purely passive observers. To the best of our knowledge, we contributed the first medium access scheme which does not require any information exchange beyond the single-hop neighborhood of transponders, and still effectilvely avoids parallel transmissions over arbitrarily chosen distances.

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