Satellite Communictions

In recent years the demand for high-speed networking, driven mainly by the rapid expansion of the Internet, has been growing at an exponential rate. While a wide range of wireline and wireless solutions offering broadband connectivity are or will shortly be available, communication satellites are beginning to emerge as an attractive solution in providing broadband connectivity to a variety of users.

The wide area or global coverage of satellites enables service provision to a large number of dispersed users and solve the expensive "last-mile" issue without dedicating to each user cable, fiber, switching equipment ports, etc. The broadcast nature of satellites supports efficiently the transmission of the same message to a large number of stations, making satellites the natural choice for multicasting services. Satellites are also attractive for interconnection of geographically distributed high-speed networks, or for providing other multimedia services to both home and business users. Hence, while much broadband communication today is carried via terrestrial links, satellites will come to play a greater and more important role. This can be demonstrated by the increasing commercial interest in this area and the large number of systems that are currently under development.

On the other hand, considerable research work is under way to overcome some of the serious shortcomings inherent in satellite-based systems, such as significant propagation delays, wireless channel quality, exposure of systems to space radiation, etc. The service focus and nature of satellite systems themselves is also changing, with revolutionary new technologies such as onboard switching, spot-beam technology, inter-satellite links and constellations of systems in a variety of orbits (LEO, MEO, GEO, or Hybrid Orbits), that represent new challenges for the satellite industry.

As with any hot topic today, the World Wide Web offers a wealth of information on satellite systems and networks. In these pages we try to collect some of this information in a somewhat organized manner. We try to focus on links relevant to Broadband Satellite Systems, although we also provide links and information to related topics in the more general areas of satellite systems and communication networks. There is material here that could be useful to a satellite expert, an engineering professional who is new to this topic, or even anyone curious to find out more about satellite networks.

The demand for Internet bandwidth has grown rapidly in the past few years. A new generation of broadband satellite constellations promises to provide high speed Internet connectivity to areas not served by optical fiber, cable or other high speed terrestrial connections. However, using satellite links to supply high bandwidth has been difficult due to problems with inefficient performance of the Internet's TCP/IP protocol suite over satellite. We describe an architecture for improving the performance of TCP/IP protocols over heterogeneous network environments, especially networks containing satellite links. The end-to-end connection is split into segments, and the protocol on the satellite segment is optimized for the satellite link characteristics. TCP congestion control mechanisms are maintained on each segment, with some coupling between the segments to produce the effect of end-to-end TCP flow control. We have implemented this design and present results showing that using such gateways can improve throughput for individual connections by a large factor over paths containing a satellite link.

SAN ANTONIO--(BUSINESS WIRE)--April 24, 2000--The explosion of the Internet in the 1990s and subsequent demand for high-speed Internet connections has put an immense strain on terrestrial communications networks.

Consequently, satellite broadband technology is now emerging as an important alternative to land-based services such as cable or DSL.

According to strategic research conducted by Frost & Sullivan (<http://www.frost.com/>), "World Broadband Satellite Service Markets," revenues for the total market have climbed by more than 100 percent to $198.6 million in 1999. Rapid market growth is anticipated to continue through 2006.

Despite the promise of this nascent industry, satellite technology will have to find its niche in the marketplace. Ultimately, providers might find the best opportunities in remote regions with weak infrastructures.

"Satellite technology remains an efficient way to serve rural or remote areas due to its wide-area coverage and low marginal cost for providing service to areas with low subscriber density," say Frost & Sullivan analysts Maya Tse and Clara Sigrid Lo.

As multimedia applications are increasingly used in areas served by cable infrastructure, users who live or work beyond major metropolitan