Globalstar - System Architecture

System Architecture

Globalstar satellites are simple "bent pipe" repeaters. A network of ground gateway stations provides connectivity from the 40 satellites to the public switched telephone network and Internet; users are assigned telephone numbers on the North American Numbering Plan in North America or the appropriate telephone numbering plan for the country that the overseas gateway is located in, except for Brazil, where the official Globalstar country code (+8818) is used.

Due to the lack of inter-satellite linking, a satellite must have a gateway station in view to provide service to any users it may see. The use of gateway ground stations provides customers with localized regional phone numbers for their satellite handsets. But if there are no gateway stations to cover certain remote areas (such as areas of the South Pacific and the polar regions), service cannot be provided in these remote areas, even if the satellites may fly over them. As of May 2012, voice full-duplex service is currently non-functional over much of Africa, the South Asian subcontinent and most mid-ocean regions due to lack of nearby gateway earth stations.

The Globalstar system uses the Qualcomm CDMA air interface; however, the Ericsson and Telit phones accept standard GSM SIM cards, while the Qualcomm GSP-1600/1700 phones do not have a SIM card interface, but use CDMA/IS-41 based authentication. Therefore the Globalstar gateways need to support both the CDMA/IS-41 and the GSM standards, which not all gateways do. This results in the lack of coverage for GSM authentication based phones in the Eastern Asian and Caribbean region, as stated on the coverage map:

Most Globalstar providers have roaming agreements with local cellular operators, enabling the use of a cellular SIM card with a Globalstar handset and vice versa.