ASSESSMENT OF A PUBLIC MOBILE SATELLITE SYSTEM COMPATIBLE WITH THE GSM CELLULAR NETWORK

The integration between cellular networks and satellite systems is a very promising issue, since it permits the immediate provision of the radio services offered by the cellular networks to areas lacking in terrestrial facilities. In this paper the viability of a full integration between the GSM cellular network and a satellite system is dealt with. The L-band land mobile payload has been assumed as a reference; nevertheless the presented results can be extended to other payloads. The basic requirement of full integration is that the insertion of the satellite system does not entail any modification of the already existing GSM network. The integration analysis has been carried out by examining both the link feasibility and the network architecture. As far as link feasibility is concerned, the analysis is performed by means of an ad hoc simulation tool developed at CSELT (Turin). The simulation results are displayed for GSM speech channels at both full-rate (TCH/FS) and half-rate (TCH/HS). Such results are used in order to compute the satellite link budgets and the satellite system capacity. The characteristics of the satellite propagation channel, of the satellite-compatible mobile station and of the reference payload are explained as well. As far as the network architecture is concerned, the paper identifies the most promising satellite system configuration and the satellite system counterpart of the GSM functional areas (cell, location area, MSC area). Moreover, the problems and the relevant solutions related to the extension of the main GSM procedures (e.g. call set-up, cell selection/reselection, handover) to the integrated network are dealt with. This paper is based upon the work performed by the authors in the framework of the European Space Agency (ESA) study: 'Assessment of a public mobile satellite system compatible with the GSM cellular network'. Telespazio (Rome) is the prime contractor of this study. The opinions herewith reported are not necessarily those of ESA.