A growing number of electronic devi

A growing number of electronic devices, such as cell phones, PDAs, digital cameras, and video
game consoles, are equipped with wireless circuitry. This rids their owners of the need to
physically connect a device to a computer or a router for communication. For example, with a
wireless-enabled digital camera you can send digital pictures from your camera to your PC, or
directly to a friend via a hotspot over the Internet.
IEEE 802.15 Bluetooth
Named after a Scandinavian king who unified many tribes, the Bluetooth
standard was developed for devices that communicate with each other
within a short range of up to 10 meters (33 feet) in the office, at home, and
in motor vehicles. It transmits voice and data. Bluetooth was later adopted
by IEEE as its 802.15 standard. Typical Bluetooth devices include wireless
keyboards and mice, wireless microphones for cellular phones (especially for
use in cars while driving), wireless headsets for hands-free mobile phone
use, and increasingly, digital entertainment devices. For example, you can
purchase a wrist-worn MP3 player that uses Bluetooth to transmit the music
to earbuds or headphones, avoiding the wires that typically connect a
portable player to headphones. Bluetooth is considered a personal area
network (PAN) technology, because it typically supports a network used by
only one person. Bluetooth uses the 2.4–2.5 GHz radio frequency to
transmit bits at a rate of 1 Mbps.
IEEE 802.16 WiMAX
IEEE 802.16,Worldwide Interoperability for Microwave Access (WiMAX), increases the range and
speed of wireless communication. It might potentially reach up to 110 kilometers (about 70
miles) with a speed of 100 Mbps; however, it typically reaches 13–16 kilometers (8–10 miles).
Experts say that with an investment of no more than $3 billion, WiMAX can cover 98 percent
of American homes. This is a much lower investment than required for laying fiber optic cables.
WiMAX uses licensed radio frequencies of 2–11 GHz. This standard can cover entire metropolitan
areas and provide Internet access to hundreds of thousands of households that either cannot
afford an Internet service or for some reason cannot obtain access. Many municipal governments
wanted to establish such service for a fee or for free. However, this has created a threat to the
business of ISPs, who count on subscriber fees for revenue, because an entire metropolitan area
can become one huge hotspot, and the fees, if any, are collected by the local government rather
than an ISP. Therefore, several states in the United States legislated against municipalitysponsored
networks. However, some cities are using the technology, which enables households
that cannot afford Internet connectivity to have access to this important resource. Philadelphia
was the first American metropolis to do so. The city was exempt from a Pennsylvania law
forbidding municipal networks.
WiMAX is a metropolitan area network (MAN) technology. Figure 6.5 shows how WiMAX
works. A household, office, or public hotspot can use a router to link multiple devices either by
linking directly to a WiMAX base antenna that is linked to the Internet, or by using a relay
antenna that receives the signal and retransmits it to the Internet-linked antenna. If a mobile
user’s equipment included the proper WiMAX communication device, the user could communicate
with the Internet moving at speeds of up to 150 Km/H (about 94 MPH), which enables
convenient use of the Internet while sitting in a moving vehicle (though the driver should not
be going that fast!). An extension of this standard, 802.16e, supports mobile Internet
communication. The telecommunications company HorizonWi-Com started the construction of
802.16e networks in Boston, New York, Philadelphia, Washington, D.C., Baltimore, Pittsburgh,
Buffalo, Richmond, and Cincinnati. The installation was scheduled to be completed by the end
of 2007. Similar efforts have taken place in other countries, notably Pakistan. However, a newer,
special standard dedicated to mobile communications is 802.20.
IEEE 802.20 MBWA
Mobile Broadband Wireless Access (MBWA) functions similarly to cell phone communications,
because it controls communication from stationary towers. The purpose of MBWA is to
provide mobile communication that is compatible with IP services. This should enable worldwide
deployment of affordable, always-on wireless access. The principle is simple: place wireless
routers on towers so that mobile phones can use VoIP and access other Internet resources over
wide areas, and, eventually, globally. MBWA is expected to work at speeds over 1 Mbps, using
licensed radio frequencies below 3.5 GHz. If the standard is successfully implemented globally, it
will reduce subscriber fees significantly and pose severe competition to providers of cell phone
services.
The 802.20 standard is designed to be compatible with 802.11 (Wi-Fi) and 802.15 (Bluetooth).
It can support Internet communication at a moving speed of up to 250 Km/H (156 MPH). MBWA
promises to support practically everything that we now do with telephones and through the
Internet:Web browsing, file transfer, e-mail, VoIP, video telephony and videoconferencing, audio
streaming (such as listening to transmitted music), Web-based gaming, and file sharing. The
technology includes security measures that meet the standards of the U.S. Department of Defense
for protection of sensitive but unclassified information. To a large extent, this standard is still
under development.
Figure 6.6 summarizes relevant features of the 802.xx wireless protocols discussed here.