Page 129 - DMGT505_MANAGEMENT_INFORMATION_SYSTEM

Management Information Systems

Notes 6.7.1 Cable
Cable Internet links are provided by television cable firms. The medium is the same as for
television reception, but the firms connect the cable to an internet server. At the subscriber’s
residence, the cable is split one part is connected to the television set, and the other us connected
to computer via a bridge that is often called a cable modem. Both television transmission and
data are transmitted through the same line. The cable link is always on, so the computer is
constantly connected to the internet. More than 90 percent of cable operators in the United States
offer internet access.
The major downside of cable is that cable nodes are shared by all the subscribers connected to
the node. Therefore, at peak times, such as television prime time (7-11 p.m.), communication
speed slow down. The speed also slow down as more subscriber’s join service in a given territory.

6.7.2 Digital Subscriber Line (DSL)

With normal landline telephone service, the telephone company filters information that arrives
in digital form and then transforms it to analog from; thus, it requires a modem to transform the
signal back to digital form. This conversion constraints and capacity of the link between your
telephone and the telephone company’s switching center to a low speed of 56 Kbps.
With Digital Subscriber Line (DSL) data remains digital throughout the entire transmission; it is
never transformed into analog signals. So, the telephone company can transmit to subscriber’s
computers at significantly higher speeds up to 8 Mbps (although speed rarely exceeds 1.5 Mbps).
To provide DSL service, the telecommunications company connects your telephone line to a
DSL bridge. At the telephone company’s regional central office, DSL traffic is aggregated and
forwarded to the ISP or data network provider with which the subscriber has a contract. Often,
the telephone company is also the ISP.

Point to Interest: The United States, a Broadband Laggard
Because of little competition among telecommunications companies and a high proportion of
rural communities, the United States lags behind other countries in the proportion of households
that enjoy broadband links to the internet. Moreover, the communication speeds offered to
households in some other countries ate significantly higher while the cost per Gpbs is significantly
lower. Seventy percent of American households had broadband in 2007 (mainly through cable
and DSL). The maximum speed that U.S. households can receive is 30 Mpbs at a cost of $180 per
month. Practically all South Koreans can receive 100 Mbps for $10 per month, and 73 percent of
households in South Korea had broadband service in 2007, the highest proportion in the world.
Japan and most European nations are also ahead of the United States in terms of broadband
speed and monthly fees. In 2007, only 75 percent of U.S. households had any link to the internet
at all, including dial-up. About 20 percent of U.S. households could not have access to broadband
even if they chose to subscribe to the service, because broadband is not offered where they live.
DSL generally can be placed in one of two categories:
1. Symmetric
2. Asymmetric
Asymmetric DSL: Asymmetric DSL allows reception at a much faster rate than transmission that
is it is faster downstream than upstream. The reason for the faster download is that home users
and small businesses usually receive significantly more information than they transmit.
Symmetric DSL: Symmetric DSL is designed for short-distance connections that require high
speed in both directions. Some ADSL technologies let subscribers use the same telephone lines
for both internet connection and analog voice telephone service. Symmetric DSL lines cannot
share lines with telephones.

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