Page 130 - DMGT505_MANAGEMENT_INFORMATION_SYSTEM

Unit 6: Business Networks and Telecommunications

The bit rates of DSL lines are closely related to the distance of the subscriber’s computer from the Notes
regional central office of the telephone company. Telecommunications companies might offer
the service to subscribers as far as 6,100 meters from the central office, but the speed then is
usually no faster than 144 Kbps, unless the company has installed a DSL repeater on the line.
Some companies do not offer the service if the if the subscriber’s address is not within 4,500
meters of the central office. Most subscribers have ADSL so the upstream speed is significantly
lower than the downstream speed.

6.7.3 T1 and T3 Lines

T1 and T3 lines are point-to-point dedicated digital circuits provided by telephone companies.
A T1 line is made up of 24 channels of 64 Kbps each. T3 lines are made up of 672 channels of
64 Kbps. T1 and T3 lines are expensive. Therefore, only businesses that must rely on high speeds
are willing to accept the high cost of subscribing to the service. Most universities as well as large
companies use T1 and T3 lines for their backbone and internet connections.

6.7.4 Satellite

Businesses and households in rural and other regions that do not have access to cable or DSL
might be able to obtain satellite services, which use microwave radio transmission. In fact,
satellite service providers target these households. The service provider installs a dish antenna
that is tuned to a communications satellite. Satellite connections might reach a speed of
45 Mbps. The antenna for satellite communication can be fixed, as the roofs for large trucks. Most
of the subscribers of fixed satellite dishes are households most mobile dish users are shipping
and trucking businesses. Subscribers to fixed satellite service must purchase the dish antenna,
with a typical cost of $400, and pay a monthly fee of about $50. Trucking companies must have
an antenna installed on each truck.
Many people use a free satellite service the Global Positioning System (GPS). While a proper
device is required to enable reception from the satellites, anyone van communicate free of
charge. The satellite transmits back to any GPS device its location on earth by longitude and
latitude.

6.7.5 Fixed Wireless

Another alternative for households and small business that cannot obtain cable or DSL connections
to the internet is fixed wireless. Fixed wireless is point-to-point transmission between two
stationary devices, usually between two buildings, as opposed to mobile wireless in which
people carry a mobile device. Companies such as Sprint, AT&T, and many ISPs offer the service.
ISPs that specialize in fixed wireless services are often referred to as WISPs wireless ISPs. They
install microwave transceivers on rooftop instead of laying physical wires and cables. Subscribers
connect their computers to the rooftop transceiver. They can communicate at speed up to 2
Mbps. Repeaters are installed close to each other to enhance the signal, which can deteriorate in
the presence of building trees, and foul weather. Transmission rates depend on the distance
between the receiver and the base station. Up to 14 kilometers from the base station, the speed
is 100 Mbps, speeds drop to about 2 Mbps at about 56 kilometers from the base.
Fixed wireless is highly modular the telecommunications company can add as many transceivers
as it needs to serve a growing number of subscribers. Unlike cable service, the company does
not need franchise licenses. The technology is suitable for both urban and rural areas.

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