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Wireless Data |
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Overview |
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| In modern times, we depend on e-mail
and on the World Wide Web. We have access to these resources
at home and at the offices, and we would like to use these resources
while traveling. This is the goal that "wireless data" hopes
to accomplish. In the following section, we will discuss various
types of wireless data systems that run on top of cellular networks.
Systems that run on other systems, such as ricochet, which runs
on the pager network, will not be discussed. |
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| Analog modems |
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| Analog modems are the simplest type
of wireless data. Analog modems work on any cellular system
by simply encoding the digital data as audio signals. Analog
cellular modems make the same squealing sounds as an ordinary
desktop computer’s analog modem, but operate at far slower speeds.
On an analog modem, these modems typically average between 4800
to 9600 bits per second. This is slower than the maximum possible
rate because of the inefficiency of converting digital to analog.
It should also be noted that digital cell systems do not support
analog modems since their data compression would damage the
analog modem signal, preventing it from being decoded by the
receiving modem. |
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| Packet Data
(CDPD over IS-136 and AMPS networks) |
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| By using some of the channels of
the TDMA or FDMA (IS-136 and AMPS standards) network as large
aggregated digital data lines, packetized digital data may be
sent over this line. CDPD describes how every cell phone on
the network may insert packets on this shared data channel without
causing collisions, which would happen if two packets were sent
at the same time by two different phones. CDPD is useful since
it runs on top of old FDMA systems as well as newer TDMA systems
and offers a 19.2 kilobits per second data rate. Using a TDMA
system, the CDPD protocol can be scaled by adding more frequency
channels. |
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| GSM |
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| GSM uses an intriguing method to
send data. By simply sending computer data as it would send
voice data, GSM allows every phone to be "data enabled." Since
the GSM network is already a packet network of sorts because
of its frequency hopping, it requires no additional hardware
to support data. GSM allows data rates in multiples of 300 bits
per second, up to 64 kilobits per second. |
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Source: http://cellphones.about.com |
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designed and developed by DDA Infotech
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