MEDIA CHARACTERISTICS

          

  Coaxial Cable



Used extensively in LANs.
Single central conductor surrounded by a circular insulation layer and a conductive shield.
High bandwidth : Upto 400 Mhz.
High quality of data transmission.
Max. used data rates : 100 Mbits/s.
Problems : signal loss at high frequencies.


  Twisted Pair Cable



Extensively used in telephone circuits, where several wires are insulated and put together.
Bandwidth :250 Khz.
Low signal to noise ratio (cross talk) -> Low data rate.
Good for short-distance communications.
Used in LAN (UTP or 10baseT).


  Optical Fiber



High quality and high bandwidth data transmission applications.
Use light instead of electric pulses for message transmission.
Very high frequency ranges (20,000 Mhz).
Single fiber can support over 30,000 telephone lines.
Data transmission rates of 400 Mbits/s and more.
Becoming very popular for MAN and LAN, also used for intercontinental links.
High signal to noise ratio, difficulty in tapping (security).
Cost is the single biggest drawback (currently).


  Wireless Media



For WANs satellites provide global communication over the world, receiving signals from transmitters and relaying them back to the receivers.
With geostationary satellites senders and receivers always points the same direction.
High communication capacity. Big latency : 0.25 secs.
For MANs microwave radio technology is widely used (2 to 24 Mbit/s).
For LANs Spread Spectrum radio technology is becoming very popular (up to 2 Mbit/s).
Infrared : Line of sight limitation.