Research On The IP Routing In LEO Satellite Constellation Networks

The Low Earth Orbit (LEO) satellite constellation networks will be an integral part of the next generation telecommunications infrastructures. By inter-satellite links (ISLs), LEO satellite constellation networks are immune to the geographical factors and independent of the ground infrastructures. This merit shapes the LEO satellite constellation network into a real global communication system with continuous and seamless global coverage, and attracts research interests around the world. Due to the highly dynamic topology of the LEO constellations, the routing algorithms for terrestrial networks are not suitable for LEO satellite constellation networks. Designing effective IP routing algorithms for LEO satellite constellation networks is an extremely challenging task.This dissertation focuses on the On-Board-Routing (OBR) technology supporting IP traffic in LEO constellation networks. Explicitly, the following topics are discussed in detail.(1) After setting up the network model, the features and difficulties of the OBR problem in LEO constellation networks are analyzed. It is pointed out that the space segment of the satellite network can be considered as an autonomous system. Using private routing protocols and tunneling technology, the routing process can be decomposed into two independent procedures: the mobility management and the inter-satellite routing.(2) With the analysis of the dynamic topology properties of LEO satellite constellation networks, we verified through traversal simulations the following: a) the least delay path (LDP) belongs to the least hop path (LHP) set in typical LEO constellations, such as Iridium, Globalstar and LEO48, b) the delay variation in the LHP set is within the acceptable range. Therefore, LHP criterion can be adopted as a substitution of LDP criterion, which helps reduce the computational complexity and can be implemented in the distributed way. (3) The static routing algorithms in LEO satellite constellation networks are studied. After the detailed analysis of the Snap Shot Sequence (SSS) algorithm, a novel routing algorithm, named as the Reverse Detection Based Routing (RDBR), is proposed. Comparing with the SSS algorithm, the performance of RDBR is verified by the routing performance and signaling cost in simulation.(4) The dynamic routing algorithms in LEO satellite constellation networks are studied and a novel routing algorithm, named as the Reverse Detection Based Adaptive Routing (RDBAR), is proposed. The simulation results show that with the acceptable low overhead signaling, the RDBAR algorithm can achieve better performance compared with the static SSS algorithm. Moreover, the RDBAR algorithm can work adaptively to the abnormal disruption of ISL even under heavy network load. Finally, the OBR scheme providing Quality of Service (QoS) for real-time services is given based on the DiffServ model and RDBAR protocol, and the performance is verified by simulations.