Broadband satellite systems

• Authors: D. J. Bem;T. W. Wieckowski;R. J. Zielinski
• Venue: IEEE Communications Surveys & Tutorials
• Year: 2000

Recently, the interest in broadband satellite multimedia (BSM) systems has grown rapidly. Advancements in transmission technology have led to the availability of low-cost satellite earth terminals. The superior remote access capabilities of satellite networks are foreseen to provide broadband services to geographically diverse user groups. The desire to support a wide range of broadband services in satellite networks implies that many features present in terrestrial multimedia networks will also emerge in satellite networks. The interest in TCP/IP, DVB, and ATM is also demonstrated by the architecture of some proposed new satellite systems. Access to broadband services via satellites is one of the major issues and depends on the type of orbit of the satellite system. This is the motivation for discussing orbits and their features in this article. Different technical features can be achieved when the satellite system serves as an access system and when it serves as an access and core (transport) system. Broadband services need broadband frequency channels. The discussion about spectrum availability led to the conclusion that BSM systems can operate at higher bands, i.e., Ka and V, or they must use unique solutions to be compatible with the existing systems. The problem of electromagnetic compatibility is discussed in many places in this article. There is also a classification of user terminals and a list of services the BSM systems can offer. Of course, for each particular system this list depends on the features of the BSM system, which is selected by the designer and the future operator. Three types of protocols/platforms can be identified when BSM systems are considered. There are TCP/IP and ATM protocols and the DVB-S platform. This article presents three BSM system concepts: ARCS, Teledesic, and Skybridge. They have been chosen to present several technical aspects, i.e., how to use geostationary satellites in BSM, highly asymmetrical links, bandwidth on demand, - beam diversity, spectrum efficiency, EMC aspects, etc. ARCS is a geostationary system with both links provided by the satellite. Many other BSM GSO systems plan to use similar concept (e.g., Direct PC), but only ARCS is well advanced in the standardization process and use of satellite links in both directions. Two other systems, Teledesic and Skybridge, use LEO orbits and are designed with a completely different architecture. Teledesic provides satellite access as well as a satellite core network, while Skybridge is a satellite access system. They differ in coverage, frequency utilization, constellation, and many other important parameters. Considering all this, presenting these three concepts, it is possible to show many technical issues. Other solutions of broadband multimedia systems based on high altitudes platform systems (HAPS) are also presented. The conclusion presents an opinion about the future of BSM systems.