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Ugweje WL040/Bidgolio-Vol I WL040-Sample.cls June 19, 2003 17:10 Char Count= 0
182 RADIOFREQUENCY ANDWIRELESSCOMMUNICATIONSTable 2Variants of Wireless LAN Systems and BluetoothProperties IEEE 802.11 HiperLAN Ricochet HomeRF BluetoothSpectrum 2.400–2.4835; 5.15–5.35, 5.15, 17.1 0.902–0.928 2.404–2.478 2.402–2.480
(GHz) 5.525–5.825
Range 150 feet 150 feet 1000 feet <150 feet 10cm–100 m
Power Consumption Not specified Not specified Not specified 100 mW 1 mW, 10 mW and
100 mW
Energy Conservation Directory based Yes Unknown Directory based Yes
Physical DSSS/ DFS with FHSS 162 FHSS 50 FHSS 1600 hops/s
Layer FHSS/IR BPSK/QPSK/ hops/s hops/s
QAM
Channel CSMA/CA TDMA/TDD TDMA Hybrid TDMA FHSS, Master slave
Access and TDMA
CSMA/CA
Mobility Support Not specified Yes Yes No No
Raw Data 2, 11, 6–54 Mbps 23.5, 54 Mbps 288 kbps 1 and 2 Mbps 1 Mbps
Rate
Traffic Data (DCF) Data Data Voice+Data Voice or Data
Speech Unknown OFDM Not available ADPCM, 64 kbps with
Coding 32 bps CSVD/log PCM
Security 40 bit RC4 DES, 3-DWS RSARC-4 Blowfish Minimal in PHY
Communication Peer-to-peer, Peer-to-peer, Peer-to-peer Peer-to-peer, Master/slave
Technology MS-BS MS-BS MS-BSservice. The most significant segment of this technology
is the cellular mobile radio. It is the fastest growing seg-
ment of the telecommunications industry. Based on the
number of new subscribers worldwide and the number of
services, the cellular mobile radio system has evolved as
the dominant wireless communication system. Its history
dates back many decades, but the modern-day mobile ra-
dio became widespread in the 1980s (Rappaport, 2002).
The cellular mobile radio system is discussed further
below.
Wireless networks and protocols include systems such
as wireless local area networks (W-LAN), wireless local
loops (WLL), wireless application protocol (WAP), and
Bluetooth. These systems are used mainly to provide data
communication. W-LAN is an extension to, or an alterna-
tive for, a wired LAN. W-LAN provides the functionality of
wired LAN, without the physical constraints of the wire
itself, combining data connectivity with user mobility
(Bing, 2000; Geier, 1999; Wenig, 1996). W-LANs have the
potential to support user mobility and constant and un-
limited access to information by linking several wireless
devices to the wired infrastructure network. In W-LAN,
packets of data are converted into radio waves that are
sent to other wireless devices or to a wireless access point
(AP)–client connection from the wired LAN to the mobile
user. The AP can reside at any node on the wired net-
work and acts as a gateway for wireless users’ data routed
to the wired network. W-LANs require special MAC layer
protocols due to the broadcast nature of radio commu-
nication (Chen, 1994). A detailed discussion of W-LAN is
beyond the scope of this chapter. W-LANs have gained
strong popularity lately and are used widely in health
care, industry, commerce, warehousing, and academia.
An important feature of the W-LAN is that it can be
used independent of a wired network. That is, it can beused as a stand-alone network anywhere to link multiple
computers together without extending a wired network.
W-LAN uses one of the three basic transmission protocols,
namely, direct sequence spread spectrum (DSSS), fre-
quency hopping spread spectrum (FHSS), or low-power
narrowband. The majority of RF-based W-LANs operate
in the industrial, scientific, and medical (ISM) frequency
bands, which are located at 902 to 928 MHz, 2.4 to 2.483
GHz, and 5.725 to 5.85 GHz, respectively. The different
architectures of W-LAN based on (Agrawal & Zeng, 2003)
are summarized in Table 2.
WLL is a system that connects telephone subscribers
to the public switched telephone network using radio
waves (International Engineering Consortium, 2003b).
With WLL, the traditional copper wire-providing link be-
tween the subscriber and the local exchange is replaced by
a wireless RF network. WLL is advantageous for remote
areas where the cost of wire would be prohibitive, i.e., ad-
verse terrain or widely dispersed subscriber areas. With
WLL new service providers can quickly deploy wireless
networks to rapidly meet the customer’s telephony needs.
Existing landline operators can extend their networks
using WLL. Cellular telephone companies can deliver resi-
dential service using WLL without going through the local
telephone company.
WAP is an application environment and set of com-
munication protocols (application, session, transaction,
security, and transport layers), which allow wireless de-
vices easy access to the Internet and advanced telephony
services (Wireless Application Protocol, 2000; Stallings
2002). WAP offers the ability to deliver an unlimited range
of mobile services to subscribers, independent of their
network, manufacturer, vendor, or terminal. With WAP,
mobile subscribers can access information and services
from wireless handheld devices. WAP is based on existing