10.1 Introduction

Satellites are raising their profile in the access network, migrating from their traditional role as trunk connections between core networks. This migration is being driven in part by fibre installation around the globe and in part by increasing demand for mobile and IP-based services to which satellites are well suited. This chapter provides an overview of those satellite technologies that can be used to deliver IP-based broadband services to customers.

Satellite communications have some unique properties when compared to the other access technologies described in this book. Current communications satellites comprise two basic types. The first type, which is by far the most common, operates only at layer 1 (physical) of the OSI model; they receive radio signals from earth in one frequency range, translate the radio signals to another frequency range, then they transmit the signals back to earth. They are therefore 'transparent' to layers 2 and above. These satellites are used for data rates from 16 kbit/s to 155 Mbit/s and all are in geostationary ^[1] orbit (GEO). The second type, of which Iridium was an example, operates at layers 1 and 2. These satellites translate the radio frequency as in the first type and in addition have ATM-like cell switches on-board that operate at layer 2 (link layer).

In terms of future communications satellites, proposals worth over $30B are filed with the FCC that describe around 20 'next generation' satellite systems operating in various orbits with varying quantities and...