Gateway Earth Stations for Future LEO Communications Satellite Systems

Abstract

The most important technical and operational challenges for new mobile satellite services (MSSs) in low and medium earth orbits (LEOs, MEOs) currently being proposed and expected to be operational by the end of the decade, are often referred to the Space Segment, i.e. to the need for launching quite a large number of satellites, maintaining them in orbit and replacing failed units. Somewhat less emphasis is usually placed on the Ground Segment, and in particular on the fixed earth stations acting as “gateways” to the terrestrial network, them implicitly being considered to involve more conventional techniques and technologies. In reality, these gateway stations deserve careful consideration because of their potentially significant impact on the overall system economics. With reference to the specific case of Globalstar, this paper is addressed to defining the main guidelines for a gateway design optimization. After a brief description of the main characteristics of the Globalstar system, this paper describes the most important tradeoffs affecting the integration into the terrestrial network, and the design of the RF subsystem of the gateway.