TRANSMISSION MEDIA

TRANSMISSION MEDIA

1. Anything that carry information from source to destination

2. Guided media (wired)

   • ---->Provide a physical conductor from one device to another ---->Signal travel directed and contained by the physical limits of the medium
     • Use metallic (copper) conductor to transport signal in form of electric current
       • Coaxial Cable
         • standard
           • ---->Each RG number denotes a unique set of physical specification----->Each cable defined by an RG rating is adapted for specialized function
         • ---->has core conductor ---->Metal foil used as shield against noise
         • connector
           • ----->Most common connector is (Bayone-Neil-Concelman) ----->Popular types + BNC connector - used to connect in TV set +BNC T connector - used in Ethernet networks +BNC terminator - prevent he reflection of the signal
       • Twisted pair cable
         • ----> consists two conductors,each with own plastic insulation, twisted ---->Cumulative effect of the interference is equal on both wires and the total effect is 0 ---->Data rate up to 600Mbps
           • Unshielded Twisted Pair
             • connector
               • RJ45 (registered jack)
                 • a keyed connector
           • Shielded Twisted Pair -> has metal shield to prevent the penetration of noise or crosstalk, bulkier and more expensive
         • Application
           • telephone line (provide voice and data channels)
           • LAN
     • Made of glass or plastic an transmit signal in form of light
       • Fiber-Optic Cable
         • Optical fiber are defined by the ratio of the diameter of their core to the diameter of the cladding
         • connectors
           • ---> Subscriber channel (SC) connector - for cable tv (use push and pull locking system) -----> Straight Tip (ST) - connecting cable to networking device (use bayonet locking system) -------> MT-RJ - (same size with RJ45)
         • Propagation modes
           • Multimode -> Multiple beams from a light source move through the core in the different paths
             • Step Index
               • Density of the core remains constant from the center to the edge
             • Graded Index
               • Density highest at the center of the core and decrease gradually to its lowest at the edge
           • Single Mode-> Smaller diameter,limits beam to a small range of angles, all close to horizontal

3. Unguided media (wireless)

   • Wireless transmission
     • Infrared
       • --->Frequency between 300MHz to 400THz --->High frequency thus cannot penetrate walls (prevent interference between one system and another) -->can be used for short-range communication (such as between PC and a peripheral device ,and indoor LAN)
     • Microwave
       • -->frequency range between 1 and 300GHz -->Unidirectional(sending and receiving antenna need to be aligned) --> Characteristic of microwave propagation 1. Line-of-sight 2. Very high-frequency microwaves cannot penetrate walls 3. microwave is relatively wide. ---> Used for unicast communication such as cellular telephones,satellite networks, and wireless LANs.
     • Radio Wave
       • --> frequency range 3kHz to 1GHz --->Omdirectional(send out signals in all direction) --->can penetrate walls ---> used for multicast communication(radio,television and paging system)
   • --> transport electromagnetic waves using a physical conductor --> referred as wireless communication

4. located below physical layer

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