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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