WIRELESS TRANSMISSION


Introduction:

Wireless Transmission is a form of unguided media.

Wireless communication involves no physical link established between two or more devices, communicating wirelessly.

Wireless signals are spread over in the air and are received and interpreted by appropriate antennas.

When an antenna is attached to electrical circuit of a computer or wireless device, it converts the digital data into wireless signals and spread all over within its frequency range.

The receptor on the other end receives these signals and converts them back to digital data.

Wireless or unguided transmission media is data signals that flow through the air.

They are not guided or bound to a channel to follow.

Wireless transmission can be used as the medium in both LAN and WAN environments.

 

Types of Wireless Transmission Media:

  • Radio Transmission
  • Microwaves Transmission
  • Satellite Transmission

Radio Transmission:

§  Radio frequency is easier to generate and because of its large wavelength it can penetrate through walls and structures alike.

§  Its frequency is between 10 kHz to 1GHz. It is simple to install and has high attenuation.

§  These waves are used for multicast communications such as radio, television and paging system. It uses omni directional antennas.

§  Radio waves can have wavelength from 1 mm to 100,000 km and have frequency ranging from 3 Hz to 300 GHz.

Types of Propogation:

Radio Transmission uses different types of propogation. These are as follows:

  • Troposphere

 

  • Ionosphere

Troposphere:

§  The lowest portion of earth’s atmosphere extending outward approximately 30 miles from the earth’s surface. Clouds, jet planes, wind is found here.

Ionosphere:

§  The layer of the atmosphere above troposphere, but below space.

§  It contains electrically charged particles.


Microwaves Transmission:

§  Microwaves are used for unicast communication such as cellular telephones, satellite networks and wireless LANs.

§  It travels at high frequency than the radio waves.

§  It requires the sender to be inside of the receiver.

§  It operates in a system with a low gigahertz range.

§  It is mostly used for unicast communication.

§  Microwaves can have wavelength ranging from 1 mm to 1 meter and frequency ranging from 300 MHz to 300 GHz.

§  Microwave antennas concentrate the waves making a beam of it.

§  They do not penetrate wall like obstacles.

§  Microwave transmission depends highly upon the weather conditions and the frequency it is using.

Types of Microwaves:

  • Terrestrial Microwave

 

  • Satellite Microwave

Advantages:

§  Microwaves are used for long distance telephonic communication.

§  Microwaves carry 1000s of voice channels simultaneously.

Disadvantages:

§  Very Costly.

§  Attenuation by solid objects: birds, rain, snow and fog.

§  Reflected from flat surfaces like water and metal.


Satellite Transmission:

§  Satellite is a microwave repeater in space.

§  There are 750 satellite in space ,most of them are used for communication.

§  They are wide area coverage of the earth’s surface.

§  Satellite plays a very important role in telephone communication, TV and radio program distribution and other certain communications.

§  These communication systems are now become an integral part of major area telecommunication networks through the world.

§  Satellites are transponders (units that receive on one frequency and retransmit on another) that are set in geostationary orbits directly over the equator.

§  These geostationary orbits are 36,000 km from the Earth’s surface.

§  At this point, the gravitational pull of the Earth and the centrifugal force of Earth’s rotation are balanced and cancel each other out.

§  The uplink is the transmitter of data to the satellite. The downlink is the receiver of data.

§  Uplinks and downlinks are also called Earth stations because they are located on the Earth.

Advantages:

§  Flexibility.

§  Speedy deployment.

§  Provides coverage over the globe.

§  Can be cheaper over long distances.

§  High bandwidth.

Disadvantages:

§  Satellite manufacturing cost is very high.

§  Cost of launching satellite is very expensive.

§  Transmission highly depends on whether conditions, it can go down in bad weather.

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