Characteristics of Transmission Media

Syllabus 

Types of transmission media including; twisted pair, fibre optic, satellite, microwave cellular, wireless

Background

  • A computer can be used to send or receive information.
  • It is the network that does this.
  • no network = no internet
  • Movement of data by upload or download is called transmission of data.
  • For this data to move, it needs to go through the air or through cables.

Wired twisted pair - ethernet cable

  • Contains 4 pairs of wires
  • Is set on the 802.3 standard
  • Twisted every cm in a tight twist to minimize electrical interference
  • Sometimes shielded completely in aluminium foil to prevent electrical interference (shielded twisted pair)
  • Has an rj-45 male connector on each end
  • Plugs into an rj-45 female connector wall
  • Data speed on a category 5 (cat5) cable less than 90 metres is capable of 100 Mbps 
  • Data speed on a category 6 (cat6) cable less than 90 metres is capable of 1000 Mbps
  • For 100 Mbps 2 wires are commonly used.
  • For 1000 Mbps all 4 pairs of wires are commonly used

Optic fibre

  • Optical fibre cabling has very long strands of glass inside a cable
  • Data travels inside the strands of glass as pulses of light
  • The size of the strand of glass = the size of a human hair
  • Data = light
  • Each optic fibre cable can carry 1 or more strands of glass
  • Centre part of the optic fibre cable is the strands of glass
  • Outside of this is a cladding to reflect the light back into the cable
  • Outside of this is buffer coating to protect the cable
  • Disadvantages; expensive, difficult to join
  • Advantages; fast, no interference

Satellite

  • A communication satellite receives a radio wave signal from a ground station on earth, then bounces the signal back down to a different ground station on earth.
  • The satellite not only bounces it back down, but is like a repeater in that it amplifies the signal, so it can keep going further.
  • This means that a radio wave can go much further in distance than just 'line of sight' on the ground.
  • Remote areas often use satellites to get communications because it is costly with other choices.

Microwave

  • Commonly used to extend TV and/or telephone calls into country or remote areas.
  • Has a series of large towers following a path from one town/location to the next.
  • The signal goes from one tower, is amplified, and sent on to the next. About 20-50kms away.
  • It is 'line of sight' and can't go through mountains or major forests.

Cellular

  • Commonly used for telephone systems.
  • Works on a network or collection of cells, each having base station and mast.
  • Phone calls travel back and forth along these cells.
  • You can see these masts in your big cities.
  • Cellular doesn't work in most remote areas as there are no cells available.
  • Sometimes the masts are owned by companies, so if you are with company A, you may or may not get a signal.
  • For example in the north west of Western Australia, if you are with Telstra - you get signal, if with another company you may not.

Wireless

  • Uses radio waves on the frequency range of 2.4 Ghz or 5 Ghz
  • Must have a transmitter to send data and a receiver to receive data.
  • Standard 802.11 provides details on set up of wireless. egs 802.11a, 802.11b, 802.11g, 802.11n
  • Must be configured prior to working, usually a network name, username and password
  • The working range indoors is up to 20 metres depending on wall construction and type of wireless setup
  • The working range outdoors is up to 100 metres, depending on the type of wireless setup

Wireless - bluetooth

  • Used for short distances up to 10 metres
  • Uses short range radio waves around the 2.45 Ghz frequency. Wikipedia states between 2.400 and 2.483
  • It is a small microchip that can transmit and receive data
  • It is very common in mobile devices
  • The bluetooth controller is the Link Manager (LM)
  • The Link Manager identifies other bluetooth devices, creates links, sends and receive data
  • The Link Manager also controls the operation mode, eg standby (wake each 2 secs to listen), master/slave (initiating link=master), inquiry (causes devices to ID), park (wakes at intervals, listens syncs), hold (power saving, but discoverable)

 For You To Do

  1. Locate the wireless access points in your school. Draw a rough map of these wireless access point locations.
  2. Make up some advantages and disadvantages for the wired and wireless systems.
  3. Explain types of wired networking in your own words.
  4. Explain types of wireless networking in your own words.
 Learn more about optical fibre from youtube, 
 
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