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  1. ICT IGCSE Satellite and mobile network communications

  2. Objectives: You should have an understanding of a wide range of work-related IT applications which make use of satellite and/or mobile network technology, including • Mobile phone networks • Embedded Web technology (EWT) • Global positioning Systems (GPS)

  3. Mobile phone networks • Mobile phones communicate by using towers that are located in many networked cells. • These towers (masts) allow the transmission of data throughout the mobile phone network. A network of mobile phone cells

  4. How the Mobile Phone Network works • Each tower transmits within its own cell • When you get to the edge of a cell the signal gets weaker • This is recognized by the network, so • The phone picks up the signal in one of the adjacent cells

  5. MPT and computers • Mobile Phone Technology can now be used by computers to allow internet access. • A USB network device allows the computer to connect to the mobile network. Very convenient BUT • Slow • Expensive • Monthly contract • Download limits apply

  6. WAP • early mobile phones could only be used to send and receive calls and SMS. • Wireless Application Protocol allows smaller handheld devices to access cut-down/ simplified web-based content

  7. WAP • The wireless device has a ‘microbrowser’ • Your device connects with a service provider • Your website request is sent to a gateway server • This retrieves the information using HTTP and encodes it as WML

  8. EWT • This is an emerging technology that uses the internet in real time to control or interact with a device in the home • The device must contain an embedded microprocessor

  9. Uses of EWT • The device can be controlled by an authorised user from a computer anywhere on a network or from a web-enabled mobile phone

  10. GPS • Global Positioning satellite systems can pinpoint your location, give directions to your destination and provide information about nearby businesses. • In-car GPS is often referred to as a satellite Navigation system

  11. How GPS works • Satellites surrounding the earth transmit data – this includes the satellite’s position and time • Embedded computers receive and interpret these signals • The exact location of the device is calculated based on the data from at least three satellites

  12. How GPS works Satellite 1 Satellite 2 Satellite 3

  13. How GPS works • The on-board computer contains pre-stored road maps • The phone(or car)’s exact location (based on the satellite positioning) is shown on the map • You are given verbal directions, eg “turn left in 100 metres” etc • A screen shows your position in relation to the road network

  14. Advantages of GPS • No need to consult maps while driving – safer • Warns about road closures/one way streets etc • Location of speed cameras • Gives fastest route + alternate routes • Useful info eg fuel stations • Estimated time of arrival

  15. Disadvantages of GPS • Maps MUST be kept up to date, otherwise they can give incorrect instructions • Loss of satellite signal can cause problems • GIGO – incorrect start/end positions will cause the system to give incorrect information

  16. Other features of mobile phones • Accelerometer – senses tilt, orientation, angle • GPS • Touch screen technology • Apps • Email/internet • Intelligent maps • Memory: • SD (Secure Digital) cards • SDHC (SD High Capacity)

  17. Homework • Use all the links to How Stuff Works/ the videos/new stories and make the following notes: • What is GPS? • What can it be used for? • What devices are required for GPS to work properly? • What can affect the accuracy of GPS devices? • What is WAP? • Why is it needed? • What devices use it?