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Exposure to Computer Disciplines

Notes people to connect to it (since it can route, or support multipoint to multipoint connections),
while the modem is made for one connection.

Figure 6.8: T-Mobile Universal Mobile Telecommunications System PC Card Modem

Most of the GSM wireless modems come with an integrated SIM cardholder (i.e., Huawei E220,
Sierra 881, etc.) and some models are also provided with a microSD memory slot and/or jack for
additional external antenna such as Huawei E1762 and Sierra Wireless Compass 885. The CDMA
(EVDO) versions do not use R-UIM cards, but use Electronic Serial Number (ESN) instead.

Figure 6.9: Huawei CDMA2000 Evolution-Data Optimized USB Wireless Modem

The cost of using a wireless modem varies from country to country. Some carriers implement
flat rate plans for unlimited data transfers. Some have caps (or maximum limits) on the
amount of data that can be transferred per month. Other countries have plans that charge a
fixed rate per data transferred per megabyte or even kilobyte of data downloaded; this tends
to add up quickly in today’s content-filled world, which is why many people are pushing
for flat data rates.
The faster data rates of the newest wireless modem technologies (UMTS, HSPA, EVDO, WiMax)
are also considered to be broadband wireless modems and compete with other broadband
modems below.

6.3.4 Broadband
ADSL modems, a more recent development, are not limited to the telephone’s voiceband audio
frequencies. Some ADSL modems use coded orthogonal frequency division modulation (DMT,
for Discrete MultiTone; also called COFDM, for digital TV in much of the world).

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