GPRS for mobile satellite communication systems^General Packet Radio Service

摘要

This paper proposes a novel scheme for data packet applications, an integral part of future global Satellite Personal Communication Systems (SPCS). ^In order to keep compatibility with the terrestrial packet subsystem counterpart proposed for GSM/DCS, General Packet Radio Service (GPRS), we follow the same approach for the Satellite-GPRS (S-GPRS). ^Problems of S-GPRS raised due to Discontinuous Transmission (DTX), unidirectional transmission, and long transmission delays are addressed. ^Solutions to tackle these obstacles in handover, timing advance, and Medium Access Control (MAC) layer are proposed. ^A multislot reservation-based multiple access protocol is specifically tailored for lengthy round-trip delays and long delay-spread. ^Then, this MAC layer is examined for the ICO constellation system, which represents the worst case amongst the proposed non-GEO constellations in terms of propagation delay. ^Numerical evaluations of the system performance for different traffic models are presented. ^Results show an acceptable and efficient performance. ^Finally, applicability and feasibility of S-GPRS for other constellations, such as Iridium, is discussed. ^It is concluded that S-GPRS will perform more efficiently for lower altitude constellations. ^(Author)