Mohamed A A R Madni

CubeSats operating in a swarm are characterized by a mix of scheduled intermittent connectivity, high delays, and high failure rates. Each CubeSat is limited in size, usually has low data rates and has a low mass. Consequently, they have limited space for solar panels, and thus limit their available energy. Profitably, CubeSats can function in swarms using inter-CubeSat links as well as ground links. Accordingly, any routing protocols developed for CubeSats must be energy aware. We propose two novel Shortest and Energy Reliable Path (SERP) routing protocols; namely, SERPBreadth-First Search (SERP-BFS) and SERP-Dijkstra. Both algorithms aim to minimize the overall energy cost and maintain connectivity over time. Both choose shortest paths that have CubeSats energy levels higher than or equal to an energy reliability threshold. We have compared our SERP algorithms with Epidemic algorithm. The results show the outperformance of our proposed algorithms in terms of saving the overall energy cost. Keywords—energy reliability; delay tolerant network; spacetime graph; picosatellites; cubesat swarms.

Inter-CubeSat communications or satellite to satellite communications is very critical as it enables an efficient networking between CubeSats in a swarm [1, 2]. We propose a Low Earth Orbit (LEO) inter-CubeSat DTN architecture. DTN is a networking paradigm intended to offer data communication services according to store-and-forward mechanism in space environment, which is characterized by regular and extended temporary disconnections and long delays. The space DTN concepts were originally introduced and evaluated as a solution to tackle the challenges of deep space communications and to support an Interplanetary Internet IPN [3]. Even though DTN protocols and some conventional Internet protocols, such as TCP and UDP, were assessed to be acceptable in a space environment, interconnecting CubeSats requires more research to be done to prove its feasibility [4]. Inter-CubeSat communication is constrained by some challenges such as the limited size, i.e., 1U-3U Cubesats, small mass, i.e....

CubeSats, which are limited by size and mass, have limited functionality. These miniaturised satellites suffer from a low power budget, short radio range, low transmission speeds, and limited data storage capacity. Regardless of these limitations, CubeSats have been deployed to carry out many research missions, such as gravity mapping and the tracking of forest fires. One method of increasing their functionality and reducing their limitations is to form CubeSat networks, or swarms, where many CubeSats work together to carry out a mission. Nevertheless, the network might have intermittent connectivity and, accordingly, data communication becomes challenging in such a disjointed network where there is no contemporaneous path between source and destination due to satellites’ mobility pattern and given the limitations of range. In this survey, various inter-satellite routing protocols that are Delay Tolerant (DTN) and Non Delay Tolerant (Non-DTN) are considered. DTN routing protocols ar...

—CubeSats operating in a swarm are characterized by a mix of scheduled intermittent connectivity, high delays, and high failure rates. Each CubeSat is limited in size, usually has low data rates and has a low mass. Consequently, they have limited space for solar panels, and thus limit their available energy. Profitably, CubeSats can function in swarms using inter-CubeSat links as well as ground links. Accordingly, any routing protocols developed for CubeSats must be energy aware. We propose two novel Shortest and Energy Reliable Path (SERP) routing protocols; namely, SERP-Breadth-First Search (SERP-BFS) and SERP-Dijkstra. Both algorithms aim to minimize the overall energy cost and maintain connectivity over time. Both choose shortest paths that have CubeSats energy levels higher than or equal to an energy reliability threshold. We have compared our SERP algorithms with Epidemic algorithm. The results show the outperformance of our proposed algorithms in terms of saving the overall energy cost.

Inter-CubeSat communications or satellite to satellite communications is very critical as it enables an efficient networking between CubeSats in a swarm [1, 2]. We propose a Low Earth Orbit (LEO) inter-CubeSat DTN architecture. DTN is a networking paradigm intended to offer data communication services according to store-and-forward mechanism in space environment, which is characterized by regular and extended temporary disconnections and long delays. The space DTN concepts were originally introduced and evaluated as a solution to tackle the challenges of deep space communications and to support an Interplanetary Internet IPN [3]. Even though DTN protocols and some conventional Internet protocols, such as TCP and UDP, were assessed to be acceptable in a space environment, interconnecting CubeSats requires more research to be done to prove its feasibility [4]. Inter-CubeSat communication is constrained by some challenges such as the limited size, i.e., 1U-3U of Cubesats, small mass, i.e., 1.3 kg, low data rate, i.e., 9.6 Kbit/s, and limited power, i.e., 2 W, in addition to challenges of orientation and limited buffer space [5]. Based on the small size and cost efficiency of CubeSats, CubeSat swarms have recently gained research interest [2].  This is because CubeSat swarms can provide higher data rates and redundancy in terms of power budget, bandwidth and communication opportunities, hence increasing usefulness and reducing mission failure rates. Moreover, CubeSat swarms can collect data from different parts of space in the same time instant. Hence, these swarms can also help in Earth monitoring, atmospheric measurements and supporting research missions concerned with space weather. For instance, in [6, 7], the QB50 project is aiming to launch a swarm of 50 CubeSats which are developed by participating Universities. The main purpose of these CubeSats is to perform science experiments in the lower thermosphere (90 to 300 km). In this paper, we propose a routing framework where data can be routed between different CubeSats without intervention from the ground stations. Any two CubeSats can communicate by forwarding data to the ground station which has the option of using ground links to another ground station and then onto the destination CubeSat. This proposed architecture allows for cooperative and non-cooperative CubeSat swarms to communicate with each other. It may also provide continuous communication with all CubeSats. Further, it permits for many alternative paths and allows for optimisation for routing based on power use, charging rate and buffer capacity of the different CubeSats along the path.