Submitted: October 2023
Abstract
Modern societies and economies require fast, reliable, and continuous connectivity for dependable communication and business development. This necessity extends to remote areas, such as at sea or in the air, and particularly in developing countries. Connecting ships or airplanes to the fiber-optic network is not feasible, just as it is almost impossible to provide a connection for every individual via wired links. One solution are low-Earth orbit satellite constellations, which, thanks to their low altitude and ability to exchange traffic using inter-satellite links, enable continuous and fast connections even in the most remote areas or on ships and aircraft.
Finding a suitable path from a source through several intermediate satellites to a last satellite that finally transmits the data to a destination is a non-trivial task and is referred to as routing. Routing in general, is a well-researched area, but since the topology is subject to frequent changes due to the Earth’s rotation and the movement of satellites, algorithms capable of coping with these evolving topologies are needed. Numerous algorithms for routing in low-Earth orbit have been proposed in the past, but the performance classification between those algorithms is hard because there is no general methodology, including benchmark scenarios, simulation platform, and evaluation questions, that allows for a comprehensive comparison. Instead, it is common practice to create a custom simulator for the algorithm study and evaluate a handful of characteristics. This approach lacks comparability with peer algorithms because the modeled orbital behavior of the satellites, the behavior of the inter-satellite links, and the packet processing implementation are not equal, resulting in potential performance impacts.
To achieve better comparability, this work investigates whether it is possible to develop a generally applicable methodology by proposing a set of benchmark scenarios with associated evaluation questions, together with the development of an extensible simulation platform that enables the creation of dynamic low-Earth orbit Walker constellations, the dynamic establishment and tear-down of inter-satellite links, and a comprehensive collection of statistics.
To validate that the proposed set of benchmarks, with the developed platform, enables the desired comprehensive study of algorithm properties and performance, the description of the platform development is followed by a comparison of two routing algorithms for Walker-Star and two for Walker-Delta using the created simulator. Since it has been shown that the simulator, first, can be extended with any low-Earth orbit routing algorithm due to its modularity, and, second, allows the creation of a consistent constellation and routing topology environment, a satisfactory level of comparability is established that allows the desired, generally applicable comparison. Future research can utilize the developed methodology to eliminate the need to create benchmark scenarios and develop simulators, resulting in a decrease in overall research efforts. Researchers will be able to add new algorithms as modules and focus on improving them instead of spending time creating a test environment. Furthermore, as far as the established benchmarks are considered, a minimum level of comparability between algorithms should be established.