Wireless Network Technologies and Standards (1)

Part I
Wireless Network Technologies and Standards

CHAPTER 1
Introduction to Wireless Networking

Many organizations utilize traditional wire-based networking technologies to establish connections
among computers. These technologies fall into the following three categories:
• Local area networks (LANs)
• Metropolitan area networks (MANs)
• Wide area networks (WANs)
LANs support the sharing of applications and printers, transfer of files, and sending e-mail within a room
or building. Today, the industry standard for LANs is ethernet technology with 10baseT Category 5
twisted-pair wiring. MANs, which can cover the size of a college campus or large city, interconnect
LANs by using protocols such as FDDI (Fiber Distributed Data Interface) and depend on leased circuits
and optical fiber for transmission of the data. WANs, on the other hand, utilize telephone circuits, leased
lines, and private circuits to support worldwide networking by using circuit and packet switching
protocols.
Traditional networking technologies offer tremendous capabilities from an office, hotel room, or home.
Activities such as communicating via e-mail with someone located in a faraway town or conveniently
accessing product information from the World Wide Web are the result of widespread networking. But,
limitations to networking through the use of wire-based systems exist because you cannot utilize these
network services unless you are physically connected to a LAN or a telephone connection.
Over the last thirty years, researchers and companies have been busy developing protocols and systems
that provide wireless connectivity for LANs, MANs, and WANs. This work has not been easy and has
met much resistance from end users. Today, though, products are available that fit into all categories of
networks and satisfy the need for mobility. This chapter introduces wireless networking by describing the
following:
• The history of wireless networks
• Wireless network architecture
• The benefits of wireless networking
• Concerns surrounding the implementation and use of wireless networks
• The wireless network market
• The future of wireless networks

The History of Wireless Networks

The first indication of wireless networking dates back to the 1800s and earlier. Indians, for example, sent
information to each other via smoke signals from a burning fire. The sender would simply wave a deer
skin over the fire—in sequences similar to Morse code—to send messages warning others that a war was
imminent, or just to say, “I’ll be late for dinner.” This smoke signal system was a true network. People
manning intermediate fires would relay messages if a great distance separated the source of the message
and the destination. The world has seen much progress since those days. Messengers on horseback
eventually became a more effective means of transferring information, while later the telephone made
communications much easier and faster.
Prior to the nineteenth century, scientists thought light was the only wavelength component of the
electromagnetic spectrum. During the nineteenth and twentieth centuries, researchers learned that the
spectrum actually consists of longer wavelengths (lower frequencies) as well. Experiments showed that
lower frequencies, such as radio waves and infrared light, could be sent through the air with moderate
amounts of transmit power and easy-to-manufacture antennas. As a result, companies began building
radio transmitters and receivers, making public and private radio communications, television, and
wireless networking possible.
Network technologies and radio communications were brought together for the first time in 1971 at the
University of Hawaii as a research project called ALOHANET. The ALOHANET system enabled
computer sites at seven campuses spread out over four islands to communicate with the central computer
on Oahu without using existing, unreliable, expensive phone lines. ALOHANET offered bi-directional
communications, in a star topology, between the central computer and each of the remote stations. The
remote stations had to communicate with each other via the centralized computer. ALOHANET became
popular among network researchers because of the unique combination of packet switching and
broadcast radio. The U.S. military embraced the technology, and DARPA (Defense Advanced Research
Projects Agency) began testing wireless networking to support tactical communications in the battlefield.
Because of limited spectrum allocations, radio-based networks could only deliver very low data rates.
Research done at the University of Hawaii and DARPA, however, helped pave the way for the
development of the initial ethernet technology, as well as fueled the development of radio-based
networks available today.
The advent of the wired ethernet technology steered many commercial companies away from radio-based
networking components toward the production of ethernet-related products. Companies did not mind
running cable throughout and between their facilities to take advantage of ethernet’s whopping 10 Mbps
data rates. In the eighties, amateur radio hobbyists, “hams,” kept radio networking alive within the U.S. and Canada by designing and building Terminal Node Controllers (TNCs) to interface their computers
through ham radio equipment (see fig. 1.1). These TNCs act much like a telephone modem, converting
the computer’s digital signal into one that a ham radio can modulate and send over the airwaves by using
a packet switching technique. In fact, the American Radio Relay League (ARRL) and the Canadian
Radio Relay League (CRRL) have been sponsoring the Computer Networking Conference since the early
eighties in order to provide a forum for the development of wireless WANs. Thus, hams have been
utilizing wireless networking for years, much longer than the commercial market.
Figure 1.1 The ham radio terminal node controllers.
In 1985, the Federal Communications Commission (FCC) made the commercial development of radiobased
LAN components possible by authorizing the public use of the Industrial, Scientific, and Medical
(ISM) bands. This band of frequencies resides between 902 MHz and 5.85 GHz, just above the cellular
phone operating frequencies. The ISM band is very attractive to wireless network vendors because it
provides a part of the spectrum upon which to base their products, and end users do not have to obtain
FCC licenses to operate the products. The ISM band allocation has had a dramatic effect on the wireless
industry, prompting the development of wireless LAN components.
During the late eighties, the decreasing size of computers from desktop machines to laptops allowed
employees to take their computers with them around the office and on business trips. Computer
companies then scrambled to develop products that would support wireless connectivity methods. In
1990, NCR began shipping WaveLAN, one of the first wireless LAN adapters for PCs. Motorola was
also one of the initial wireless LAN vendors with a product called Altair. These early wireless network
adapters had limited network drivers, but soon worked with almost any network operating system.
Rapidly, companies such as Proxim, Xircom, Windata, and others began shipping their products as well.
These initial companies were pioneers in the wireless networking arena. They felt their wireless products
would feed a market desperately wanting to meet mobility needs. Network managers and system
administrators, however, did not trust the technology enough to purchase the pricy wireless adapters. The
WaveLAN network adapters, for example, initially listed for $1,400 each. Vendors quickly found that
they had to reduce prices. Businesses were afraid these new wireless products lacked security, were too
slow (at least slower than ethernet), and were not standardized. Over time, though, vendors began
incorporating encryption to protect data transmissions, and operation at higher frequencies increased the
bandwidth to near-ethernet speeds. The market also saw a substantial drop in price to $300–$500 per
card. The lack of standards, however, limited widespread use of wireless LAN products.
The current depressed state of the wireless LAN market should change as standards mature. The Institute
for Electrical and Electronic Engineers (IEEE) 802 Working Group, responsible for the development of
LAN standards such as ethernet and token ring, initiated the 802.11 Working Group to develop a
standard for wireless LANs. This group began operations in the late eighties under the chairmanship of
Vic Hayes, an engineer from NCR. At the present time, 802.11 is still working on the standard. A final
standard should pass in 1997.
End users and network managers have had a difficult time showing a positive business case for
purchasing wireless LAN components in the office unless there is a requirement for mobility. Most sales
of wireless LAN adapters to date have been in healthcare and financial environments. Sensing a bleak
market for wireless LAN products, wireless LAN vendors began equipping their wireless LAN
components in 1995 with directional antennas to facilitate point-to-point connections between buildings
located within the same metropolitan area. These wireless MAN products satisfy a widespread need—the
capability to connect facilities where traditional cable installation and leased circuits are costly. The sales
of these wireless MAN products have been favorable.
The most widely accepted wireless network connection, though, has been wireless WAN services, which
began surfacing in the early nineties. Companies such as ARDIS and RAM Mobile Data were first in
selling wireless connections between portable computers, corporate networks, and the Internet. This
service enables employees to access e-mail and other information services from their personal appliance
without using the telephone system when meeting with customers, traveling in the car, or staying in a hotel room.
Narrowband Personal Communications Services (PCS), a spectrum allocation located at 1.9 GHz, is a
new wireless communications technology offering wireless access to the World Wide Web, e-mail, voice
mail, and cellular phone service. Vice President Al Gore kicked off the FCC PCS auction in 1995 by
selling 30-MHz licenses to television and telephone companies. The total take for 1995 was $7.7 billion.
The U.S. government expects to raise $15 billion from the auctioning during 1996.
Because of PCS, the wireless industry is quickly gaining momentum. As a result, a vast number of
wireless networking products should appear on the market in 1997. SkyTel began shipping the first PCS
product in 1996, a pocket-sized two-way pager, which can receive pages as well as respond.