Java Reference
In-Depth Information
GPRS —General Packet Radio Service. A packet-based wireless communication
service that promises data rates from 56-114Kbps and continuous connection to
the Internet for mobile phone and computer users.
3G —The next generation of wireless technology beyond PCS. The World
Administrative Radio Conference assigned 230 MHz of spectrum at 2GHz for
multimedia 3G networks. These networks must be able to transmit wireless data
at 144Kbps at mobile user speeds, 384Kbps at pedestrian user speeds, and
2Mbps in fixed locations.
GSM —Global System for Mobile Communication. A digital mobile telephone
system that is widely used in Europe and other parts of the world. GSM uses a
variation of timed-division multiple access (TDMA).
CDMA —Code Division Multiple Access. A spread spectrum air interface technol-
ogy used in some digital cellular, personal communications services, and other
wireless networks.
CDPD —Cellular Digital Packet Data. Also referred to as Wireless IP . A method of
sending and receiving information through mobile devices that uses the
Advanced Mobile Phone System (AMPS) and enables information to be trans-
mitted on idle cellular voice channels.
Why WAP?
WAP was designed from the ground up to deliver content and applications to mobile devices
with small screens, a variety of data input capabilities, and low communications bandwidth run-
ning on a variety of network transports (including GSM, TDMA, CDMA, and CDPD). This sec-
tion will present the various considerations that were taken into account when designing WAP.
This discussion will hopefully clarify why a separate wireless standard was needed as opposed
to simply reusing the venerable HTTP—HTML—TCP/IP technologies of the wired world.
Screen Size Considerations
One feature that will always separate mobile devices from their larger wired desktop counter-
parts is the actual size of the devices. Size is a premium consideration: the smaller, the better.
Faced with this reality, most mobile device screens are tiny—a PalmOS device features a lofty
160 pixel screen! Larger screen sizes also require additional battery power—a driving
constraint in the design of mobile devices.
WAP, and specifically its markup language WML, were designed to ease the pain of a small
screen. (If you've looked at the HTML specification, it's clear that many advanced features
would never work on a tiny screen.) WML delivers content in a single document composed of
multiple “cards.” The purpose of this is that a single trip to the server could return multiple
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