Multiple access techniques and spectrum utilisation of the GLOBALSTAR mobile satellite system

The GLOBALSTAR system is a low Earth orbit (LEO) satellite-based mobile communications system that is interoperable with the current and future public land mobile network. The GLOBALSTAR system concept is based upon technological advancement in two key areas: LEO satellite technology; and cellular telephone technology, including the commercial applications of code division multiple access (CDMA) technologies, progress in time division multiple access technologies. The GLOBALSTAR system uses elements of CDMA technology, combining with satellite multiple beam antenna technology. The following techniques are exploited in obtaining high spectral efficiency and affordable cost per channel, with minimum coordination among different systems: power control in open and closed loops; voice activation; spot beam satellite antenna for frequency reuse; weighted satellite antenna gain; multiple satellite coverage; and satellite changeover. The GLOBALSTAR system design will use the frequency bands 1610-1626.5 MHz for the up-link and 2483.5-2500 MHz for the down-link