Low-earth orbit global cellular communications network

Technical aspects of the recently announced Iridium system are discussed. Iridium is a worldwide, digital, satellite-based, cellular, personal communications system primarily intended to provide commercial, low-density, mobile service via portable, mobile, or transportable user units, employing low-profile antennas, to millions of users throughout the world. Calls can be made and received anywhere in the world with a personal, portable unit. Seventy-seven small (340 kg), smart satellites are internetted to form the network´s backbone. Small, battery-powered, cellular-telephone-like user units communicate directly to the satellites. Gateways (earth stations) interface from the satellites to the individual Postal, Telephone and Telegraph Authorities (PTTs). The system is intended to complement the terrestrial cellular telephone systems installed, or being installed, in densely populated areas