Network Access & Information Sharing Technologies
Throughout this chapter, we discuss a variety of wireless devices, networks and other communications
systems, each using technologies to communicate with other devices, networks
or systems. This section focuses on four major technologies that allow these devices
to share information with one another—radio frequency, infrared, laser and Bluetooth.
10.5.1 Radio Frequency (RF)
Radio frequency (RF) is the backbone of most wireless communications technologies. Radio
frequency uses radio signals to communicate over long distances using a portion of the
spectrum. Radio frequencies are used by cell phones, radio broadcasts, networks and others
communications media. Radio frequencies in the United States are regulated by the Federal
Communications Commission (FCC) and licensing for these frequencies is discussed in
Chapter 7, Legal and Social Issues; Wireless Accessibility.
Radio Frequency WLANs (RF WLANs) are often used by network devices which are
not close to one another. RF WLANs have two competing standards under development—
HomeRF™ and Wireless-Fidelity (Wi-Fi). HomeRF Wireless Home Networking was
designed specifically for home and small office environments. HomeRF operates on a
variety of data and voice products, providing data networking among devices such as PCs,
printers and cordless phones. HomeRF has a range of up to 150 feet and can send and
receive signals through walls and floors. HomeRF integrates voice, data and entertainment
and is expected to reach data rates of 20Mbps by early 2002. [***W. Casswell, “Faceoff:
Which is Better-Wi-Fi or HomeRF?,” Network World 9 April 2001: 47.***].
Shared Wireless Access Protocol (SWAP) is the technology behind HomeRF. SWAP
is a new specification for wireless and voice networking in home environments. It combines
cordless telephone standards and WLANs to supports speeds of one to two Mbps.
SWAP uses FHSS technology (FHSS was discussed earlier in this Section 10.4.1) and is
compatible with TDMA and CDMA networks. [***”The Technology Behind SWAP,”
<www.homerf.org>***]. CDMA and TDMA are discussed in detail in Chapter 10,
Wireless Communications Technologies Part II.
A Look to the Future: IBM and PANs
Using the human body to conduct electrical currents and pass information is a futuristic
use of WPAN technology. An external electrical field can be passed through the human
body. This field allows a person to receive information just by touching another person.
IBM believes that WPANs could be used for such transactions as exchanging business
cards through a simple handshake. In addition, a user can upload information from a
page or a computer and then press send on a cell phone to transmit the information. Radio
frequency sensors could be placed on products, so that stores eliminate lines. Customers
would walk through sensors and have all personal information scanned and
billed appropriately. [***T. Zimmerman, “High Tech, High Touch: Personal
Area Networks” <www.research.ibm.com/research/pan.html> ***]
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©Copyright 2001 Deitel and Associates Inc. All Rights Reserved
Fig. 10.9 HomeRF (Courtesy of HomeRF Working Group Inc.)
Wireless Fidelity (Wi-Fi) is part of the 802.11b standard and is being deployed in airports,
restaurants and other areas. Most laptops manufactured by Dell, Apple, IBM and
Toshiba have Wi-Fi technology built into their devices. Wi-Fi offers speeds of up to
11Mbps and covers 30 percent more area than HomeRF. Wi-Fi has several disadvantages
including high power consumption and low reliability for areas that have high network
traffic.[***D. Eaton, “Face-off: Which is Better- Wi-Fi or Home RF?,” Network
World 9 April 2001: 47.***]
Mice, stereo components and computer connections use radio frequency technology.
Gyration, a mouse manufacturer, produces the Gyromouse Pro™ (www.gyration.
com). The Gyromouse allows the user to operate the cordless mouse on a desktop
and in the air. This enables users to navigate while sitting in front of a computer or even
during a standing presentation.
Akoo’s Kima™ is a stereo component that allows users to play MP3s and Internet radio
stations. Kima’s base unit connects to the user’s computer. The receiving unit, which can
be placed near, or connected to, the user’s radio can receive signals from the base unit for
a distance up to 1000 feet. When the radio is tuned to 88.1–88.3 FM, the computer’s audio
is broadcast for the user to hear. [***<www.akoo.com>***].
10.5.2 Laser and Infrared Technology
Laser technology connects buildings. It is reliable, easy to install, and portable. Transceivers
(towers that send and receive laser signals) are place on top of the rooftops of two office
buildings. The transceivers send the signal between the buildings and then link to the network
using fiber-optic cable. [***<www.lsainc.com/products/connectivitysolutions/
highperflacomm/products.html>.***]To learn more about
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laser WLANs, visit www.lsainc.com/products/connectivitysolutions/
highperflacomm/products.html and www.astroterra.com.
Infrared technology was standardized for PCs in 1993. Today, infrared is used in over
100 million devices including Palm devices, Pocket PCs and WebTV. [***R. Fisco,
“Infrared: Facing the Firing Squad?,” PC Magazine 3 April 2001: 56.***]. It can be
used only for distances up to 30 feet. Light pulses sent or received from another device or
network are used to complete transmissions. However, there must be nothing blocking the
receiver when the transmission exchange occurs. Infrared technology is more cost efficient
than laser technology, the equipment has a longer life span and it is less susceptible to
weather conditions. [***<www.jolt.co.il, www.levcom.co.il/olencom/
Slow speeds (up to 115.2 Kbps) and other emerging technologies (e.g., Bluetooth). are
two areas of concern for Infrared technology supporters. These concerns pose challenges
for infrared’s continued popularity in mobile devices and networks. For more information
about infrared networking systems, visit www.jolt.co.il, www.levcom.co.il/
olencom/navigator/index.htm and www.plaintree.com/
wire_pro.htm. Additional discussions about infrared technology appear in Chapter 11,
Palm and Palm OS and Chapter 12, Windows CE, Pocket PC and Stinger.
Bluetooth is one of many technologies under development today. More than 2,200 companies
are members of the Bluetooth Consortium (www.bluetooth.com). Bluetooth technology
is based on radio frequency technology and is used in the development of WPANs
and other networks. Bluetooth technology supports point-to-point and point-to-multipoint
connections as well as FHSS packet-switching technology discussed earlier in this chapter.
Bluetooth technology eliminates the need for cables and wires and does not have line of
sight limitations. Bluetooth can recognize and connect to different networks and up to 200
different devices. The connection range is limited to ten meters or approximately 30 feet
and operates on the 2.4GHz band. [***<www.bluetooth.com>***]. This can cause
interference problems because most WLAN standards operating on the same frequency.
Bluetooth technology allows networks to recognize and communicate with devices as
soon as they enter the network’s coverage area. For example, a user schedules a meeting on
a PDA with another user in the network. This information is transferred simultaneously to
both users’ desktop computer calendars. When both users return to their desktop computers,
the information stored on their PDAs is already available on the desktops as well.
This eliminates the need for users to perform a synchronization process later to update
devices. Bluetooth is discussed detail in Chapter 21, Bluetooth.