Tuesday, July 28, 2009

what is wireless

- Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carrythe signal over part or all of the communication path. Some monitoring devices, such as intrusionalarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.
The first wireless transmitters went on the air in the early 20th centuryusing radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voicesand music via wireless, the medium came to be called "radio." With theadvent of television, fax, data communication, andthe effective use of a larger portion of the spectrum, the term "wireless" hasbeen resurrected.

Common examples of wireless equipment in use today include:

cellular phones and pagers -- provide connectivity for portable and mobile applications, both personal and business

Global Positioning System (GPS) -- allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth

Cordless computer peripherals -- the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless

Cordless telephone sets -- these are limited-range devices, not to be confused with cell phones

Home-entertainment-system control boxes -- the VCR control and the TV channel control are the most common examples; some hi-fi sound systems and FM broadcast receivers also use this technology

Remote garage-door openers -- one of the oldest wireless devices in common use by consumers; usually operates at radio frequencies

Two-way radios -- this includes Amateur and Citizens Radio Service, as well as business, marine, and military communications

Baby monitors -- these devices are simplified radio transmitter/receiver units with limited range

satellite television -- allows viewers in almost any location to select from hundreds of channels

wireless LANs or local area networks -- provide flexibility and reliability for business computer users

Wireless technology is rapidly evolving, and is playing an increasingrole in the lives of people throughout the world. In addition, ever-larger numbersof people are relying on the technology directly or indirectly. (It has beensuggested that wireless is overused in some situations, creating a social nuisance.) More specialized and exotic examples of wireless communications and control include:

Global System for Mobile Communication (GSM) -- a digital mobile telephone system used in Europe and other parts of the world; the de facto wireless telephone standard in Europe

General Packet Radio Service (GPRS) -- a packet-based wireless communication service that provides continuous connection to the Internet for mobile phone and computer users

Enhanced Data GSM Environment (EDGE) -- a faster version of the Global System for Mobile (GSM) wireless service

Universal Mobile Telecommunications System (UMTS) -- a broadband, packet-based system offering a consistent set of services to mobile computer and phone users no matter where they are located in the world

Wireless Application Protocol (WAP) -- a set of communication protocols to standardize the way that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access

i-Mode -- the world's first "smart phone" for Web browsing, first introduced in Japan; provides color and video over telephone sets

Wireless can be divided into:
fixed wireless -- the operation of wireless devices or systems in homes and offices, and in particular, equipment connected to the Internet via specialized modems
Mobile wireless -- the use of wireless devices or systems aboard motorized, moving vehicles; examples include the automotive cell phone and PCS (personal communications services)
Portable wireless -- the operation of autonomous, battery-powered wireless devices or systems outside the office, home, or vehicle; examples include handheld cell phones and PCS units
IR wireless -- the use of devices that convey data via IR (infrared) radiation; employed in certain limited-range communications and control systems

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