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Networking Media (Tutorial-5)


Transmission Media

        A medium is a carrier of something.

Coaxial Cable

Coaxial Cable
  • Consists of a central copper core surrounded by an insulator, a braided metal shielding, called braiding, and an outer cover, called the sheath or jacket 
  • High bandwidth – Up to 400 MHz 
  • Max. used data rates – 100 Mbps 
  • High quality of data transmission 
  • Signal loss at high frequencies



Thicknet Coaxial Cable
  • Is a rigid coaxial cable approximately 1-cm thick used for the original Ethernet networks 
  • Also called ‘thick Ethernet’, ‘yellow Ethernet’ 
  • IEEE designates Thicknet as ‘10Base5’ Ethernet, interpreted as follows – 
  • ‘10’ for transmission rate of 10 Mbps 
  • ‘Base’ for baseband transmission 
  • ‘5’ for the max. segment length of a Thicknet cable, which is 500 m

    • Thicknet Coaxial Cable
Thinnet Coaxial Cable
  • Popular medium used in Ethernet LANs in the 1980s 
  • IEEE designates Thinnet as ‘10Base2’ Ethernet, interpreted as follows – 
  • ’10’ for transmission rate of 10 Mbps 
  • ‘Base’ for baseband transmission ‘2’ for the max. segment length which is around 200 m

Thinnet Coaxial Cable
Twisted Pair Cable
  • Consists of colour-coded pairs of twisted & insulated copper wires 
  • Used extensively in telephone cables 
  • Number of twists per unit length is known as ‘twist ratio’. More the twist ratio, lesser the noise and therefore better the quality 
  • Is inexpensive, flexible, and easy to install 
  • One drawback to twisted-pair is that, because of its flexibility, it is more prone to physical damage than coaxial cable
    All twisted pair cables fall into two categories –

    Shielded Twisted Pair (STP)‏
    Unshielded Twisted Pair (UTP)‏
Shielded Twisted Pair (STP)‏
  • The insulated inner twisted pairs are surrounded by an additional shielding usually made of metallic foil or braid. 
  • The shielding acts as a barrier to external signals, thus reducing noise . 
  • The shielding may be grounded to enhance its protective effect.

Shielded Twisted Pair (STP)‏

Unshielded Twisted Pair (UTP)‏

  • Does not contain additional shielding 
  • Advantage over STP is that it is less expensive 
  • Absence of shielding, however, makes it more prone to noise
Straight Through Cable
Straight Through Cable
  • It is a type of UTP cable 
  • The color coding of the internal wires inside both ends of the cable are similar 
  • Straight through cables could be used to connect dissimilar devices like 
  • Connecting a router to a hub or switch 
  • Connecting a server to a hub or switch
Table Straight Through Cable

Crossover Cable
Crossover Cable

  • It is a type of UTP cable 
  • The colour coding of the internal wires inside both ends of the cable are dissimilar 
  • Straight through cables could be used to connect similar devices like 
  • Connecting hubs to switches 
  • Connecting 2 hubs
Table Crossover Cable


UTP Types
Fiber Optic Cable
  • Cables contain fiber lines in their cores instead of the usual copper wires 
  • Technique uses light pulses to transmit information through these optic fibers 
  • Very high bandwidths of up to several Gbps 
  • Could be used for long distances covering hundreds of kilometers 
  • Provide very high bandwidth – up to 20, 000 MHz 
  • Low interference provides highly efficient transmission High costs are currently the only drawback

Fiber Optic Cable

Radio
  • Radio - 10 Khz to 1 Ghz. It is broken into many bands including AM, FM, and VHF bands. The Federal communications Commission (FCC) regulates the assignment of these frequencies. Frequencies for unregulated use are:902-928Mhz - Cordless phones, remote controls. 
  • 2.4 Ghz 
  • 5.72-5.85 Ghz
Microwave
  • Terrestrial - Used to link networks over long distances but the two microwave towers must have a line of sight between them. The frequency is usually 4-6GHz or 21-23GHz. Speed is often 1-10Mbps. The signal is normally encrypted for privacy. Two nodes may exist. 
  • Satellite - A satellite orbits at 22,300 miles above the earth which is an altitude that will cause it to stay in a fixed position relative to the rotation of the earth. This is called a geosynchronous orbit. A station on the ground will send and receive signals from the satellite. The signal can have propagation delays between 0.5 to 5 seconds due to the distances involved. The transmission frequency is normally 11-14GHz with a transmission speed in the range of 1-10Mbps.
Infrared
  • Infared is just below the visible range of light between 100Ghz and 1000Thz. A light emitting diode (LED) or laser is used to transmit the signal. The signal cannot travel through objects. Light may interfere with the signal. The types of infared are 
  • Point to point - Transmission frequencies are 100GHz-1,000THz . Transmission is between two points and is limited to line of sight range. It is difficult to eavesdrop on the transmission. The speed is 100Kbps to 16MbpsBroadcast - The signal is dispersed so several units may receive the signal. The unit used to disperse the signal may be reflective material or a transmitter that amplifies and retransmits the signal. The transmission frequency is normally 100GHz-1,000THz with transmission distance in 10's of meters. Installation is easy and cost is relatively inexpensive for wireless. 
  • Broadcast - The signal is dispersed so several units may receive the signal. The unit used to disperse the signal may be reflective material or a transmitter that amplifies and retransmits the signal. The transmission frequency is normally 100GHz-1,000THz with transmission distance in 10's of meters. Installation is easy and cost is relatively inexpensive for wireless.
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