ICT IGCSE

Satellite and mobile network communications

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)

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

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

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

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

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

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

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

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

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

How GPS works

Satellite 1

Satellite 3

Satellite 2

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” etcA screen shows your position in relation to the road network

Advantages of GPS

No need to consult maps while driving – safer

Warns about road closures/one way streets etc

Location of speed camerasGives fastest route + alternate

routesUseful info eg fuel stationsEstimated time of arrival

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

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)

Homework

Use all the links to How Stuff Works/ the videos/new stories and make the following notes:

What is WAP? Why is it needed? What devices use it?

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?