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GLOSSARY 829control due to high noise interference and poor
physical level characteristics of the wireless medium. This
is achieved using a PCN packet sequence number filed in
the header along with a standard 2-byte CRC frame check
sequence trailer. HDLC-style retransmission can be used
for connectionless data.
Since wireless ATM may use 16- or 24-byte cells, seg-
mentation and reassembly is required. As a handoff is
an important characteristic of wireless networks, a soft
handoff without any data loss is vital and should be
transparent. This can be implemented by using bits in
the header, which indicates PDUs before and after the
handoff.FUTURE PHONES
The wireless Internet industry is unsure about what type
of devices people will want, or more accurately, what
they can persuade consumers to buy. The consensus is
around smart phones. There are two competing philoso-
phies about the future of mobile devices:Personal area network—This assumes a modular system,
whereby people continue to carry a plethora of devices
as they do now. The difference is that all are linked
together by a short-range radio system such as Blue-
tooth, with the cellphone acting as central hub and
router.
Integrated device—This assumes that people will want
to carry only one device but vary it according to the
situation. A user might want to travel light and use
only voice communication. At other times, he/she will
want to use a full feature computer with an internal
high-speed wireless data connection. The mobile net-
work automatically detects which terminal is in use
and routes calls accordingly.Wearable Computers
Anything smaller than a telephone will need a headset
containing an earpiece and a microphone. For video on
the move, several vendors have proposed putting tiny
screens inside sunglasses or contact lenses. The latter has
the potential to immerse users completely in virtual real-
ity. The problem with any small mobile terminal is that
its battery will quickly run down. Shoes can be used to
contain a reasonable-sized battery.Smart Phones
A smart phone is a mobile phone with some extra
computer-type functions, like a WAP browser. Besides
mobile data capabilities, smart phone features include
location-based services and sophisticated address books
that can interface with a computer.Tablets
A tablet PDA is one that doesn’t have a keyboard and relies
on a touch-sensitive screen for input.Clamshell
Before the arrival of large, touch-sensitive screens, nearly
all PDAs use the same clamshell design as laptops.Subnotebooks
Subnotebooks sit on the borderline between PDAs and
full-fledged laptop computers. The first subnotebook was
Atari Portfolios. It was designed to be IBM compatible,
running MS-DOS.CONCLUSION
The Web is going wireless. It is expected that by 2003,
more people will access the Internet via mobile phones
than through computers. Most existing mobile phone sys-
tems are 2G. Third generation terminals will support high-
speed data services. Most 2G systems, including CSM, are
based on TDMA. CDMA is a more advanced technology,
but does not have the installed base of GSM. It is used
as the basis for 3G systems. TDMA usually allows each
user to transmit or receive only part of the time. There
are three main 3G systems: W-CDMA, CDMA 2000, and
EDGE. They are collectively known as IMT-2000 and will
offer packet-switched data at rates exceeding 384 Kbps.
W-CDMA, known as UMTS, is designed to be backward
compatible with GSM, and requires new spectrum. CDMA
2000 is an upgrade to CdmaOne; EDGE is an upgrade
to GSM and is compatible with other TDMA systems.
The wireless Web opens up many new business oppor-
tunities, the most important of which use location-based
technology. Phones and computers are converging, but
no one knows exactly what the result will be. Computers
may eventually become wearable, but several problems
must be overcome. These include battery life and user
input.GLOSSARY
ATM Asynchronous transfer mode.
CBS Cell broadcast service.
CDMA Code division multiple access.
C-HTML Compact HTML.
CSMA/CA Carrier sense multiple access/collision
detection.
D-AMPS Digital advanced mobile phone system.
EDGE Enhance date rates for GSM evolution.
FDMA Frequency division multiple access.
FTP File transfer protocol.
GPRS General packet radio service.
GPRS Global packet radio service.
GSM Global system for mobile communication.
HDML Handheld device markup language.
HiperLan 1 Wireless LAN standard based mainly upon
the Ethernet, although its radio access technology was
taken straight from GSM, and createed due to the need
for high-speed connection.
HiperLan 2 Uses the same spectrum as HiperLan 1, but
is otherwise much closer to IEEE 802.11a.
HomeRF Designed for home networking and based on
the original FHSS version of 802.11.
HSCSD High-speed circuit-switched data.