The present document is an introduction to Release 3 of the GMR-1 system (GMR-1 3G) and the associated Release 3 of the air interface specification. It is intended to point out some of the differences between the cellular 3GPP and GSM system and the mobile satellite GMR-1 system.

The GMR-1 system is designed to provide mobile services via a single geostationary satellite as compared to the thousands of geographically separated cell sites that are used by a typical GSM system. This offers both challenges to be overcome and opportunities for enhanced services and features.

GMR-1 3G is an extension of the published ETSI TS 101 376 and TIA (S-J-STD-782) specifications for mobile satellite communications, GMR-1, to support IMT-2000 services. GMR-1 is currently used in mobile satellite systems covering Europe, Africa, Asia and Middle East. GMR-1 3G is currently being deployed in North America.