Internet speed
and connections
Let's start
with the most popular method of connecting to the Internet: Analog
Modems. The word Modem itself is a combination
of two words, modulate and demodulate. A modem
is, basically, a device that takes a digital signal and converts or modulates
it into an analog signal that another modem can later convert back, or demodulate
into digital form again. Analog connections suffer from busy signals,
dropped connections and the need to dial up each time, but they are the
cheapest type of Internet connection available. The main factor affecting
a modem's speed and dependability is the electro-magnetic interference
(also called 'static'), caused by various sources of electro-magnetic
waves intercepting the phone-lines used to transmit the signal from and to
a modem. These waves could be radio waves or a burst in the sun's
activity, but they cause electrical current fluctuation thus forcing the
electronics to slow down ('fall back') to lower connection speeds.
DSL
(Digital Subscriber Line) operates over conventional phone lines
but achieves higher data rates using different electronics and coding
schemes.
ADSL
(Asymmetric Digital Subscriber Line) is one of the iterations of
DSL technology, and is an asymmetric technology. That is, the data
download and upload speeds are not the equal. With ADSL, for example, a
customer may have only 128Kbps of bandwidth for sending data, but may be
able to receive data at speeds of 8Mbps. An ASDL is not a dial-up
connection and is more expensive, but, it is also a dedicated connection,
available for business and is always on.
SDSL
(Symmetric Digital Subscriber Line) is another derivative of DSL
and provides the same fast download and upload of data.
RADSL
(Rate adaptive ADSL) is under development and is supposed to carry
data at different rates for different prices.
HDSL
(High bit-rate DSL) allows a very high speed connection over the
basic copper line instead of the fiber line.
IDSL
(ISDN DSL) provides ISDN-like
speed over copper line, is moderately fast and moderately expensive, and
allows business or home users far away from faster lines to benefit from
the DSL links.
Some cable TV
companies provide Internet access over the TV cable with the help of Cable
modems. This is a relatively inexpensive (now) and fast (with
speeds of up to 10 Mbps) option which has become the preferred way for
home Internet users to get online. Today, most cable companies charge
about US$40 for a cable modem and service. Unfortunately, cable connection
is not available everywhere...
ISDN
(Integrated Services Digital Network). Basically, ISDN is a digital
telephone line used for voice, fax, and data communications like a regular
telephone line, but five times faster (or more) than a 28.8Kbps
modem. It also allows you to talk on the phone while also sending data to
another.
T-1
is a high-speed digital data connection that operates at 1.54Mbps and
requires a two-pair (four wire) connection between the telephone company
and the customer.
