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Wireless Communication

WIRELESS COMMUNICATION
Introduction:-
Wireless communication is the communication between two or more points that are not connected by an electrical conductor. It permits services, such as long-range communications, that are impossible or impractical to implement with the use of wires
The common wireless technologies use electromagnetic wireless telecommunications, such as radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including  cellular telephones ,personal digital assistants (PDAs), and wireless networking . Other examples include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones .Less common methods of achieving wireless communications include the use of light, sound, magnetic, or electric fields.
                 
 The first wireless transmitters went on the air in the early 20th century using radiotelegraphy (Morse code). Modulation made it possible to transmit voices and music via wireless, the medium came to be called "radio." With the advent of television, fax , data communication, and the effective use of a larger portion of the spectrum, the term "wireless" has been resurrected.



Examples of wireless equipment in use today include:
·        Cellular phones and pagers which provide connectivity for portable and mobile applications, both personal and business
·        Global Positioning System (GPS) which 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.
·        Remote garage-door openers which is one of the oldest wireless devices in common use by consumers; usually operates at radio frequencies
·        Two-way radios which 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


Types of Wireless Transmission   Media
·        INFRARED (IR):-Is a wireless transmission media that sends signals using infrared light waves. This transmission requires a line of sight transmission that is the sender and receiver must be aligned so that nothing obstructs the path of infrared light wave.

·        COMMUNICATION SATELITE: - This is a space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signal back over a wide area to any number of earth-based stations. A transmission from the earth to a satellite is called an uplink; a transmission from a satellite to an earth station is called a downlink. Communication satellites are used in application such as air navigation, television and radio broadcast,   videoconferencing and paging.

·        MICROWAVES: - These are radio waves that provide a high-speed signal transmission; from one microwave station to another; which are normally located on the top of buildings, towers or mountain. These signals must be transmitted in as straight line with o obstructions between microwave antennas.

·        BLUETOOTH:-This is an open wireless protocol for exchanging data over short distances  from fixed and mobile devices. It can connect several devices, overcoming problems of synchronization.


·        Wi-Fi: - It is a wireless local area network that enables portable computing devices to connect easily to the Internet. This has become the standard for access in private homes, within offices, and at public hotspots. 

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