VLSI Design and Embedded Systems Group

Inter-Satellite Links in LEO Constellations of Small Satellites

Incorporating IP-compliant technologies could potentially allow seamless interoperability and connectivity between all subsystems in a single spacecraft as well as between spacecraft in a constellation or formation. An inter-satellite link (ISL) network distribution system based on IP-compliant wired and wireless protocols and implemented using commercial-off-the-shelf (COTS) components will contribute significantly to the implementation of Internet in the sky.

In this research we will investigate the impact of inter-satellite links on the performance of the IEEE 802.11 standard for LEO satellites in polar orbit. The performance of the protocol will be optimised to account for the complexity of LEO satellite networks. The IEEE 802.11 physical and medium access control (MAC) layers will be optimised for ISL ranges without any modification to the standard by re-defining the inter-frame signals and using antenna null steering. Recently, there has been increasing interest in integrating both the physical and MAC schemes for use in ad hoc networks where nodes are equipped with smart agile directional antennas, however space applications have not been addressed.

Our proposed IEEE 802.11 architecture with the integration of smart antennas will allow the seamless connectivity between modules and spacecraft in a changing LEO topology. The use of high-gain and agile antennas and the integration of a MAC-layer protocol will enable the finding and tracking-over-time of every in-range neighbouring satellite with minimal interference.

This research is also aimed at building an IEEE 802.11/SpaceWire communication platform that will achieve a fault tolerant connectivity between all subsystems in a single spacecraft as well as between spacecraft in a constellation or formation. This will give less redundancy and more flexibility, which is of particular benefit to smaller spacecraft that are constrained by mass and volume.

Publications:

K. Sidibeh and T. Vladimirova. IEEE 802.11 Optimisation Techniques for Inter-Satellite Links in LEO Networks - accepted for the 8th International Conference on Advanced Communication Technology, IEEE ICACT2006, Towards the Era of Ubiquitous Networks and Societies, 20-22 February 2006, Phoenix Park, Korea.

K. Sidibeh and T. Vladimirova. A Fault Tolerant High Speed Network for Inter Satellite Links - Proceedings of the 8th Military and Aerospace Applications of Programmable Logic Devices and Technologies International Conference (MAPLD'2003), P-144, September 7-9, 2005, Washington DC, US, NASA.