Design and system operation of GlobalstarTM versus IS - 95 CDMA – similarities and differences ∗ Leonard Schiff

The GlobalstarTM system provides telephone and data services to and from mobile and fixed users in the area between ±70 degrees latitude. Connection between user terminals and the PSTN is established through fixed terrestrial gateways via a constellation of low earth orbiting (LEO) satellites. Globalstar uses an extension of the IS-95 CDMA standard that is used in terrestrial digital cellular systems. The LEO satellite link is sufficiently different from the terrestrial cellular link that certain departures from IS-95 were needed both in signal design as well as in system operation. This paper describes some of the similarities and differences of Globalstar air interface versus IS-95.