CAMBRIDGE - A Level -IT- Networks - Satellite Communications

Networks - Satellite Communication - What does GPS stand for?

• Good Point Server

• Point of Service Globe

• Great Personality Selector

• Global Positioning System

Networks - Satellite Communication - geostationary earth orbit - What does this describe?

• A low earth orbit level - 500-1500k from earth requiring 40-80 satellites.

• An alternative to butter.

• A medium earth orbit level - 5000 - 12500 km from earth requiring 8 - 20 satellites for earth coverage.

• A satellite orbit level - 35 800km from earth requiring just 3 satellites for global coverage.

Networks - Satellite Communication - Where is satellite data transfer best suited?

• In remote areas that are not covered by wireless or wired broadband connections. these could be rural deserts, at sea or in deprived communities.

• Interplanetary communications.

• Where real time data applications are required.

• Outside of the earths orbit.

Networks - Satellite Communication - Identify the orbit layers in which satellites operate.

• Low earth orbit (LEO)

• 38000 ft......transmitted from globally travelling planes.

• The GEO layer - geostationary earth orbit - 35800 km from earth - requiring only 3 satellites for global coverage.

• Medium earth orbit (MEO)

Networks - Satellite Communication - What are the two main methods of satellite data transfer?

• One way satellite broadband - sends data for download from the internet and uses a public switched (PTSN) connection for the client to upload data.

• Public telephone

• Two way satellite broadband - allows data to be uploaded and downloaded directly from the satellite.

• Hand held transmogrifiers.

Networks - Satellite Communication - Identify some drawbacks.

• Tends to be more expensive than other broadband connections.

• Easier to set up than other broadband connections.

• Bandwidth is often not as high as other broadband connections.

• There are no drawbacks.

Networks - Satellite Communication - Television and Radio - Why can Satellite broadcasting offer more channels than traditional radio or cable?

• Satellites are not restricted to areas or frequencies as they have global coverage and transmit microwaves.

• Cable broadcasts are limited to areas of infrastructure provision.

• It cannot!

• Radio waves are dependent on frequencies available.

Networks - Satellite Communication - GPS - How does it work?

• GPS works through the standard mobile network. Mobiles receive signals from the masts, pinpointing the location.

• GPS is a government tracking service that follows and records the actions of individuals.

• GPS works by receiving signals from at least 3 satellites and through 'trilateration' determines the distance between each satellite and the receiver. There are 24 LEO satellites that orbit the earth twice each day and at least 4 of these are in line of site from any position on earth.

• GPS works by having a dedicated satellite to each receiver. Scrambled secure signals ensure that people are never unsure of their position on earth.

Networks - Satellite Communication - Identify areas in which GPS may be used.

• Locating vehicles - Taxis, emergency services, company vehicles.

• Navigation systems - Cars, Hill-walking- cycling.

• Tracking people or objects.

• Television signals.

Networks - Satellite Communication - Identify advantages and disadvantages of using GPS systems.

• A disadvantage may be that line of site is required. Tunnels and large earth objects may cause errors in positioning.

• GPS can provide real time information on a live map. Ideal for car navigation systems.

• GPS may be dangerous in a car as people tend to amend them whilst driving.

• A disadvantage may be that atmospheric conditions may distort signals, causing errors in location.