An overview of the IRIDIUM (R) low Earth orbit (LEO) satellite system

This paper provides a tutorial overview of the IRIDIUM(R) low earth orbit (LEO) satellite system. Section I contains an introduction to the IRIDIUM(R) network as well as the system specifications. Section II discusses the satellite constellation design, orbital parameters, and horizontal pointing angles between satellites. Section III introduces the idea of time dependent connectivity in a mobile network, and analyzes the cycle of network connectivity for IRIDIUM(R). Section IV discusses the IRIDIUM(R) Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) schemes and uses these to calculate the overall system capacity. Section V examines the call processing procedure to include user location and call set up. Finally, Section VI analyzes the network performance in terms of end-to-end delay and hop count.