2.03 - Transmission media Flashcards
What are the 3 types of network cables?
- Twisted pair cable
- Coaxial cable
- Fibre - optic cable
Which cable costs the most?
Fibre optic cable
Which cable costs the least?
Twisted pair cable
Which cable has the highest bandwidth?
Fibre optic cable
Which cable has the least bandwidth?
Twisted pair cable
Which cable is most affected by attenuation?
Coaxial cable
Which cable is least affected by attenuation?
Fibre optic
Which cable is most affected by interference?
Twisted pair cable
Which cable is least affected by interference?
Fibre optic cable
Which cables need repeaters often?
Twisted pair and Coaxial cables
Which cable need repeaters less often?
Fibre optic
Name
A simmilarity between Coaxial and Twisted pair cables
Both use copper for transmission medium
Name
Factors to consider when choosing a cable for a given application
- Cost of cables and connecting devices
- Bandwidth
- Attenuation
- Interference
- Need for repeaters
Which 2 factor effect performance during transmission throgh cables?
Attenuation and Intereference
What are the 3 types of wireless transmission?
- Radio waves
- Microwaves
- Infrared / Satellites
Name
Frequencies of radiowaves, microwaves and infrared
Radio waves (3KHz-3GHz)
Microwaves (3-300GHz)
Infrared (300GHz-400THz)
Use of twisted pair cables?
Used for high speed LANs and connecting telephone handsets to telephone lines
Which cable can either be shielded or unshielded?
Twisted pair cable
Shielding affects the use of cable
Use of Coaxial cable?
Used in cable television companies and in MANs
Use of Fibre optic cables?
Long distance cabling
Name
The layers of the Coaxile cable (from out to in)
1st - Plastic jacket
2nd - Metallic shield
3rd - Dielectric insulaltor
4th - centre core
Name
Factors, apart from the cable ones, needed to consider when choosing wireless transmission
- Ability to transmit through solid barriers
- Ability to focus transmission in a specific direction
Which wireless transmission has the greatest ability to transmit through solid bariers?
Radiowaves
Which wireless transmission has the highest bandwidth and why?
Infrared due to high frequency
Which wireless transmission is mostly affected by attenuation?
Infrared
Which wireless transmission is best for indoors?Why?
Infrared. Because of the increased attenuation during transmission and the transmission cannot escape through the walls and cause unwanted interference
Which transmission needs government permission to use?
The use of certain wireless transmission media is regulated by government agencies therefore requires permission
Name
A disadvantage of using cables that relate to getting permission.
Cables can only be laid in the ground with the permission of the land lord
For global communications, which wired and wireless transmission is used?
Wired - Fibre optic underground / under the sea bed
Wireless - satellites
Name
Disadvantages of using Wireless data transmission
- The use of certain wireless transmission frequencies is regulated by government agencies, therefore permission is required to use it
- Interference is much more significant and its extent is dependent on which frequencies are used for different applications
Name
Advantages of using Wireless data transmission
- Repeaters are needed less often for wireless transmission
- Mobile phones now dominate Internet use and for these, only wireless can be used
- For home or office, both are equally efficient although not having to add cables favours wireless
Name
Disadvantages of using wired data transmission
- Cables can only be laid in the ground with the permission of the landlords
- For home or office, both are equally efficient although not having to add cables favours wireless
What are satellites?
Satellities are components of mordern communication systems and can directly connect with ground-base components
What are the Van Allen Belts?
Van Allen Belts are areas containing high levels of electrically chargered particles particles, which interfere with satellites
What are the three tyes of Van Allen Belts?
- GEO
- MEO
- LEO
Define GEO
Geo (Geostationary Earth Orbit) - The highest altitude over the equator and these are used to provide long-distance telephone and computer network communications.
(Only three of these are needed for full global coverage)
Define MEO
MEO (Medium Earth Orbit) - Closer to Earth and provide the Global Positioning System (GPS)
(10 for global coverage)
Define LEO
LEO (Low Earth Orbit) - Work in constellations to supplement mobile phone networks
(50 for global coverage but currently there are several 100)
What does Geostationary mean?
‘Geostationary’ means that the satellite orbits at the same speed as the Earth spins, therefore from a point on Earth the satellite always appears to be at the same place in the sky
Why can satellites cause transmission delays?
Satellites can cause transmission delays due to their greater distance from the Earth’s surface.
Why has Fibre optic cabling reduced the need for satellites?
Fibre-optic cabling has reduced the need for satellites in Internet communication due to lower costs.
