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Wireless Networks

Notes An aeronautical satellite was proposed in the mid-1970s. A contract was awarded to General
Electric to build the satellite, but it was canceled--INMARSAT now provides this service.
Although INMARSAT was initially conceived as a method of providing telephone service and
traffic-monitoring services on ships at sea, it has provided much more. The journalist with a
briefcase phone has been ubiquitous for some time, but the Gulf War brought this technology to
the public eye.
The United States and Canada discussed a North American Mobile Satellite for some time. In the
next year the first MSAT satellite, in which AMSC (U.S.) and TMI (Canada) cooperate, will be
launched providing mobile telephone service via satellite to all of North America.

Example: Mobile Satellite Communications Operator Inmarsat
Inmarsat was the world’s first global mobile satellite communications operator, founded in the
late 1970s. It focuses on communications services to maritime, land-mobile, aeronautical and
other users. Inmarsat now supports links for phone, fax and data communications at up to 64
Kbps to more than 210,000 ship, vehicle, aircraft and portable terminals.
The range of Inmarsat systems includes mobile terminals from handhelds to consoles, with
easy set-up mechanisms that allow users wherever they are to connect via a global fleet of
geostationary Inmarsat satellites to the terrestrial communications network and to carry out
telephone conversations, data transfers, and increasingly multimedia applications and Internet
access. Inmarsat is aimed at professionals who need a reliable communications system wherever
they are: ship owners and managers, journalists and broadcasters, health and disaster-relief
workers, land transport fleet operators, airlines, airline passengers and air traffic controllers,
government workers, national emergency and civil defence agencies, and peacekeeping forces.
The cost is rather high while the capacity is still rather limited: voice/fax/data systems achieve a
maximum data rate of 64 Kbps at connection costs starting at almost US$ 3 per minute. Dedicated
mobile IP systems can achieve a maximum download speed of up to 144 Kbps.

Prospect and Retrospect
Arthur C. Clarke’s 1945 vision was of a system of three “manned” satellites located over the major
land masses of the earth and providing direct-broadcase television. The inherent “broadcast”
nature of satellite communications has made direct-broadcast a recurrent theme--yet one never
brought to fruition. The problems are not technical--they are political, social, and artistic.
What will people be willing to pay for? This is the question-- especially with the availability of
120-channel cable systems. Hughes is apparently about to enter this field and may encourage
others to do the same. Only then will Clarke’s prophetic vision be fulfilled.
There are currently six companies providing fixed satellite service to the U.S.: GE Americom,
Alascom, AT&T, COMSAT, GTE, and Hughes Communications. They operate 36 satellites with a
net worth of over four billion dollars. The gound stations which communicate with these satellites
are innumerable and may have a similar net worth. INTELSAT has had competition in the
international market from Pan American Satellite since 1986. Orion Satellite is expected to begin
international service in 1994. Since Canada began domestic satellite service in 1972, that country
has been joined by the United States (1974), Indonesia (1976), Japan (1978), India (1982), Australia
(1985), Brazil (1985), Mexico (1985), and many others. Each year from 10-20 communications
satellites are launched valued at about $75 million each. The launch vehicles placing them in orbit
have similar values. Both satellites and launch vehicles are multi-billion dollar businesses. The
earth station business is equally large. Finally the communications services themselves are multi-
billion dollar businesses. John R. Pierce was right--it would be worth a billion dollars.

12.1.2 How Satellites Work

Not so long ago, satellites were exotic, top-secret devices. They were used primarily in a
military capacity, for activities such as navigation and espionage. Now they are an essential part

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