A Satellite Selection Method for Walker Delta LEO Satellite Networks

Yoshiaki NEMOTO

IEICE TRANSACTIONS on Communications   Vol.E87-B    No.8    pp.2124-2131
Publication Date: 2004/08/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Fundamental Technologies for Broadband Satellite Communications)
Walker Delta Constellation,  satellite selection,  geographical location information,  satellite networks,  

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Low Earth Orbit (LEO) satellite constellations have been proposed in recent years to provide broadband network access. This research focuses on Walker Delta type constellation. Walker Delta has overlapping ascending and descending orbits. Although Inter Satellite Links (ISLs) can be utilized between satellites orbiting in the same direction, ISLs cannot be utilized between satellites orbiting in opposite directions. As a result, a Walker Delta Constellation with ISLs has two locally separate overlapping meshes, an ascending and a descending mesh. To reach from one local mesh to the other, the traffic has to pass through the highest latitude intra-plane ISLs. Therefore the propagation delay between terminals connected to different meshes is greater than between terminals connected to the same mesh. Due to characteristic handover of LEO satellites, terminals can connect to a satellite in the other mesh during communication, causing drastic variation of propagation delay which results in degradation of communication quality. These issues can be solved by continuously connecting the communication terminals to the same mesh. In this paper, a satellite selection method for Walker Delta Constellations with double mesh coverage is proposed. It employs geographical location information of the communicating terminals, to connect them to the same mesh. In addition, the proposed method selects the mesh that minimize propagation delay for that communication session. It is shown through simulation that the proposed method is effective in reducing delay and jitter for a connection while improving overall communication quality of the network.