Satellite Installations

In Table 26-1, a list of the satellite installations by country is shown. The list shows the main providers and users of satellite transmission systems.

Table 26-1: Number of satellites in orbit by country around the world

Country

In Orbit

Argentina

1

Australia

6

Brazil

6

Bulgaria

1

Canada

16

China

15

CIS (Former Soviet Union)

1,322

Czechoslovakia

1

France

24

Germany

15

Hong Kong

1

India

11

Indonesia

6

Israel

1

Italy

4

Japan

55

Korea (South)

2

Luxembourg

4

Mexico

4

Portugal

1

Spain

3

Sweden

4

Thailand

2

Turkey

1

United Kingdom

18

United States

658

Arab States

3

Europe

27

International

51

NATO

8

TOTAL

2,271

The technological and regulatory hurdles to create true high-speed satellite networks are fast becoming past tense. Low- and mid-bandwidth systems such as Motorola's Iridium and Hughes' DirecPC can handle some of the needs immediately. These systems are nothing compared to the promise of 2 Mbps, 20 Mbps, and even 155 Mbps streaming down from the sky. All that is necessary is a small antenna, a black box, and a service provider. This will approximate the way we buy service from an ISP today.

Is it ready for prime time yet? Not yet! Iridium's universal telephone didn't kill the cellular telephone. So broadband satellite systems won't kill terrestrial lines. Broadband satellite creators agree that broadband satellite systems will complement terrestrial networks. These satellites will provide high-speed service where terrestrial infrastructure does not exist. However, high-speed, low-cost landlines are here to stay.

Is there an application for the high-speed satellite networks? What makes them different from each other? Each of the main systems is very different. Some of the most visible ones may prove the most difficult to implement. Some of the most staid-looking systems may beat every other system to the punch.

Satellite communications are nothing new. For years, you could hook up a Very Small Aperture Terminal (VSAT) system and buy time on a satellite. The VSAT can deliver up to 24 Mbps in a point-to-multipoint link (for example, a multicast) and up to 1.5 Mbps in a point-to-point link. These systems are fine for predictable and quantifiable data transmission, but if you need to conduct business on the fly, they can be a problem. New techniques are required to handle the on-demand usage. Primary among them are more tightly focused beams and digital signal technology, which together can increase frequency reuse (and thereby increase bandwidth) and reduce dish size from meters to centimeters. Accordingly, you also need a large unused chunk of the electromagnetic spectrum.

In 1993, NASA launched its Advanced Communication Technology Satellite, (ACTS). ACTS is an all-digital, Ka-band (20 to 30 GHz), spot-beam, GEO satellite system capable of delivering hundreds of megabits per second of bandwidth. NASA showed that such a system could work. The

FCC has since granted orbital locations and Ka-band licenses to 13 companies including the following:

All these companies aim to bring us bandwidth up to 155 Mbps to our home and office. These broadband systems are not going online before 2000.

What will we do with this speed and capacity? Anything you want! Whatever landlines can do, the satellite systems of the new millennium will also be able to do. In Table 26-2, the list of applications covered by broadband satellite communications is shown. These are representative applications; others will be developed.

Table 26-2: Applications for high-speed satellite communications

Applications_

Desk-to-desk communications

Videoconferencing_

High-speed Internet access

E-mail_

Digital and color fax_

Telemedicine_

Direct TV and video_

Transaction processing_

Interactive distance learning News and financial information Teleradiology_

Most of the market that needs data services seems to be well served by landlines. So, why is the emphasis on the use of airborne technology? An obvious market is in places that have underdeveloped communications infrastructures. In some countries, stringing copper or fiber is out of the question because of the initial cost and the terrain where it is needed. Still, a wireless telephone has some merit. You don't need a broadband satellite to make telephone calls; Iridium and other LEO systems will likely serve that market.

So who does need this new class of broadband satellite communications? The answer is multinational corporations. The main problem that satellite systems solve is getting high-bandwidth access to places without a high-bandwidth infrastructure. It's unlikely that a satellite system could compete with Digital Subscriber Line (xDSL) to the home or fiber to the office.

LEO Versus GEO

However, bandwidth is only half the story. The other half is latency. It's easy to talk about high-bandwidth satellite systems, but that technology has existed in VSATs for years. GEO satellites located at 22,300 miles above the equator induce 250 milliseconds (ms) of round trip delay. With that kind of latency built into the system, (not counting latency added by the various gateways and other translations), a telephone conversation is annoying. Any interactive data intense application has to be nonlatency-sensitive. Online transaction processing will have a problem using a GEO satellite system.

Moving the satellites closer to earth will help significantly. That's just what systems such as Teledesic[1] , Skybridge[2] , and Celestri[1] will do. With LEOs under 1,000 miles, these systems reduce latency to .1 second. While GEOs are a well-known technology, LEOs are new. The biggest problem is that you need a lot of them to get global coverage. At one point, Teledesic planned a constellation of more than 842 satellites^. Until recently, the concept of launching dozens or hundreds of multimillion-dollar satellites was a pipe dream. Each of Teledesic's 288 satellites is estimated to cost $20 million.

Price is only one issue. Finding a company to launch all these satellites poses another obstacle. Teledesic set an 18-month to 2-year launch window to get its 288 satellites airborne. LEO system planners are talking about putting more satellites into orbit in the next 5 years than the world has put into orbit over the past 40 years. Once the LEO satellites are in orbit, there's an entirely new set of problems. There's the matter of space junk.

[1] Teledesic is a joint venture between Microsoft and McCaw Cellular.

[2] Skybridge is a venture of Alcatel of Belgium.

[3] Teledesic dropped the number of required LEO satellites to 288 since the first announcement.

Niches in the GEO Sphere

LEOs will be good for high-speed networking, teleconferencing, Telemedicine, and interactive applications. GEOs will be better for information downloading and video distribution, such as broadcasting and multicasting. We're able to use GEO satellites to transport at least 24 Mbps of broadcast IP data and over 2 Mbps of point-to-point TCP/IP data. The latter uses technologies such as TCP spoofing. Several vendors have been using this technique for years to deliver Internet and intranet content at high speed. Ground terminals can use similar TCP spoofing technologies. Nevertheless, there's still the 250 ms delay that you just can't get around. Any lossless protocol is going to have problems with this latency. Even if TCP spoofing works, TCP's 64 Kb buffer makes this somewhat suspect, there's the matter of other protocols such as IBM's SNA and other real-time protocols that are designed around landline performance.

LEO Meets GEO

Motorola's Celestri plans an initial LEO constellation of 63 satellites coupled with one GEO satellite over the United States. The LEO constellation and the GEO satellites will be able to communicate directly through a satellite-to-satellite network.

The hybrid configuration will enable Celestri to take advantage of LEO's shorter delays for interactive uses and GEO's power in the broadcast arena.

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