wireless technology

wireless technology

Much of the development effort in new wireless technology makes use of portions

of the frequency spectrum that do not, in many countries, require licensing. In the

United States, two such frequency bands are Industrial, Scientific, and Medical

(ISM) band near 2.4 GHz and the newly allocated unlicensed radio band, the Unlicensed

National Information Infrastructure (UNII) band. UNII was created by the

FCC (Federal Communications Commission) to allow manufacturers to develop

high-speed wireless networks. In order to find enough bandwidth to satisfy needs,

the band was established at 5 GHz, making it incompatible with 2.4-GHz equipment.

The free, unlicensed portions of the radio spectrum enable manufacturers to

avoid billions of dollars in licensing fees.

For years, these radio frequencies were neglected, the lonely domain of cordless

phones and microwave ovens. In recent years however, spurred by consumer

demand and active standards bodies, considerable research and development is

underway. The first significant fruit of this activity is Wi-Fi (Wireless Pidelity), the

very popular wireless LAN technology based on the IEEE 802.11 standards. In

essence, Wi-Fi refers to 802.11-compatible products that have been certified as

interoperable by the Wi-Fi Alliance, a body specifically set up for this certification

process. Wi-Pi covers not only office-based LANs, but also home-based LANs and

publicly available hot spots, which are areas around a central antenna in which people

can wirelessly share information or connect to the Internet with a properly

equipped laptop. Wi-Pi is examined in some detail in Chapter 14.

Wi-Fi is just the first major step in utilizing these bands. Four other innovative

technologies are working their way through the research, development, and standardization

efforts: WiMAX, Mobile-Fi, ZigBee, and Ultrawideband. We survey

these technologies briefly in this section.

WiMAX is similar to Wi-Pi. Both create hot spots, but while Wi-Pi can cover

several hundred meters,WiMAX has a range of 40 to 50 km. Thus,WiMAX provides

a wireless alternative to cable, DSL, and TlIEl for last-mile broadband access. It will

also be used as complimentary technology to connect 802.11 hot spots to the Internet.

Initial deployments of WiMAX are in fixed locations, but a mobile version is

under development. WiMAX is an interoperability specification based on IEEE

802.16 and is discussed in more detail in Chapter II.

Mobile-Fi is similar to the mobile version of WiMAX in terms of technology.

The objective with Mobile-Pi is to provide Internet access to mobile users at data

rates even higher than those available in today's home broadband links. In this context,

mobile truly means mobile, not just movable. Thus, a Mobile-Pi user could

enjoy broadband Internet access while traveling in a moving car or train. Mobile-Pi

is based on the IEEE 802.20 specifications.

ZigBee functions at a relatively low data rate over relatively short distances,

compared to Wi-Fi. The objective is to develop products that are very low cost, with

low power consumption and low data rate. ZigBee technology enables the coordination

of communication among thousands of tiny sensors, which can be scattered

throughout offices, farms, or factories, picking up bits of information about temperature,

chemicals, water, or motion. They're designed to use little energy because

they'll be left in place for 5 or 10 years and their batteries need to last. ZigBee

devices communicate efficiently, passing data over radio waves from one to the other

like a bucket brigade. At the end of the line the data can be dropped into a computer

for analysis or picked up by another wireless technology like Wi-Pi or WiMAX.

Ultrawideband serves a very different purpose than the other technologies

mentioned in this section. Ultrawideband enables the movement of massive files at

high data rates over short distances. For example, in the home, Ultrawideband

would allow the user to transfer hours of video from a PC to a TV without any

messy cords. On the road, a passenger who has a laptop in the trunk receiving data

over Mobile-Fi could use Ultrawideband to pull that information up to a handheld

computer in the front seat.