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Transmission-Media

By Ashik
 Transmission-Media
Transmission Media or Communications media are the paths, or physical channels, is that, over which information travels from one place to another. A key aspect of communication is the movement of information electronically from one place to another. It may be as simple as sending information from one office to another in the same building, or it may be as far- reaching as sending information around the word. Whatever the case, information/signal must travel over some path from its source to its destination.

What are the types of Transmission media?

Signals are usually transmitted over some transmission media that are broadly classified in to two categories.

Guided Media/bounded: These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.

Unguided Media/unbounded: This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.


Classes of Transmission Media
  •     Conducted or guided media     
  •    use a conductor such as a wire or a fiber optic cable to move the signal from sender to receiver     
 
  •       Wireless or unguided media
 
  •   use radio waves of different frequencies and do not need a wire or cable conductor to transmit signals


 
Design Factors for Transmission Media

  1.  Bandwidth: All other factors remaining constant, the greater the band-width of a signal, the higher the data rate that can be achieved. 
  2. Transmission impairments: Limit the distance a signal can travel.
  3.  Interference: Competing signals in overlapping frequency bands can distort or wipe out a signal
  4.  Number of receivers: Each attachment introduces some attenuation and distortion,    limiting distance   and/or data rate.

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