Mobile and Satellite Phones

1. Mobile and Satellite Phones Chapter 3

2. This presentation will: • Help you understand how cellular phones and satellite phones operate. • You should be able to understand the advantages and disadvantages of both methods and understand when and where they should be used.

3. Introduction • Mobile technology has allowed us to make calls whilst being mobile. • Gone are the days of having to find a pay phone when someone has beeped us... • Gone are the days of trekking for miles when your car breaks down... • Gone are the days...oh you get the point!

4. Cellular Phone Network [how it works] • Cellular telephone networks are divided into cells. • They consist of the following things: • Mobile Stations (MS) • E.g. Mobile Phones • Base Station Transceivers (BST) • aka – mobile phone mast • Mobile Switching Centres (MSC) • Controls all the calls taking place on the network • Base Station Controller (BSC) • Controls communication between the BST and MSC • Public Switched Telephone Network (PSTN) • Calls from mobile devices to a landline must make use of the PSTN

5. Cellular Phone Network [how it looks] Cell BST MS Connection Established BSC BSC MSC PSTN

6. Cellular Phone Network [Calls to landlines] • Calls taking place to a landline involves the following stages: • The call is passed from the mobile device to the BST. • The BST then transfers the call to the MSC. • The MSC checks: • There is enough credit on the phone to make the call • The dialled number is valid • The MSC connects the call through the PSTN and allocates a frequency to the MS.

7. Cellular Phone Network [Calls to other mobiles] • Calls taking place to other mobiles involves the following stages: • The MSC receives a request to establish a connection to another mobile phone. • The MSC uses it’s active database to find out which BSC the mobile phone is connected to and the request is past to that BSC. • The dialling request is then broadcast through all the BSTs that are connected to the BSC. • The mobile phone being called receives the request and acknowledges this to the BST. • The call is then connected by the MSC using a frequency allocated to voice calls.

8. Cellular Phone Network [On the move] • What happens if a mobile phone passes from one cell to another? • The mobile phone will connect to the new BST. • Sometimes BST’s signals can overlap...in which case the mobile phone will connect to the strongest signal.

9. Cellular Phone Network [On the move] • Keeping a call active whilst moving through different cells requires the MSC to constantly update... • The MSC has an active database meaning that it constantly updates itself as a mobile phone registers to new BSCs. • The only time you can really notice a change is when you move from a strong signal to a low signal area. • This is how people can track where you are using your mobile phone.

10. Cellular Phone Network [Applications] • Mobile phones are so popular these days that the UK is almost saturated with them! • In fact...there are more mobile phones in the UK than there are people! (Approx 1.6 mobiles for every 1 person) • So how are they used? • Business calls • Contacting friends and family to organise events • Texting and picture messaging • Browsing the internet and checking emails. • Smart phones also allow you to: • Listen to music and radio • Built in navigation software allows you to use your phone as a SatNav system. • Taking pictures and videos. • Playing games

11. Cellular Phone Network [Pros and Cons]

12. Fun activity • Using the diagram of the cell phone network, create a series of slides which show the process of calling another mobile phone on a different BSC. Your animation should show the processes but also should contain a text box explaining what is happening during the process. When you have done that try creating another version which makes a call to a landline number.

13. Cellular Phone Network [how it works] • Satellite calls are similar to those on the mobile phone network but with a difference...the calls are connected via satellite! DUH. • There are two types of connections which can be made: • Low Earth Orbit (LEO) • Geosynchronous Earth Orbit (GEO)

14. Low Earth Orbit (LEO) • The Iridium network consists of 66 satellites that orbit Earth at altitudes of about 900 km. • Each satellite orbits Earth about twice every hour! • Because of this global coverage is always ensured as the satellites move over. • This means that obstacles, such as mountains, do not interfere with calls. Note: Iridium is just one example of a LEO satellite

15. Low Earth Orbit (LEO) • This diagram shows how calls can be made via satellite phones to a mobile phone. • The satellite phone connects to a iridium satellite, which passes the call to other satellites. • The call is then passed back down to a gateway which connects to the wireless switch...the rest you know!

16. Geosynchronous Earth Orbit (GEO) • These are satellites which orbit Earth in a fixed location at an altitude of approximately 35,000 km. • Because of the great distance there is often a short delay between sending and receiving the communication. • Thuraya satellites are an example of this type of satellite connection. • Because of their fixed location, obstacles such as mountains can impede communications.

17. Thuraya Satellite Coverage • The Thuraya satellites provide cover for: • Europe • Africa • The Middle East • Australia

18. Satellite connections • If a call is placed to a landline from a satellite phone then the connection must go through the PSTN. • If the call is placed to another satellite phone then the call is passed back to the satellite in space and sent down to the receiving phone.

19. Satellite connections [Applications] • If you are in a remote place then satellite phones are the must have accessory! • The army make use of them because there aren’t many mobile phone masts out in the desert! • Natural disasters often knock out mobile phone communications but satellite phones are unaffected. • Using satellite phones also makes it difficult to ‘tap’ calls. Its why it is used by naughty people! • The text book mentioned terrorists...but I couldn’t find any information on this! How about you try looking!

20. Satellite connections[Pros and Cons]

21. Activity • Describe the following types of phone: • Mobile Phone • Satellite Phone Remember: Identify, Amplify and Exemplify • Complete the following table

22. Questions • Describe the five components of a cellular network. • Identify the limitations of using a mobile phone to make an emergency call. • Identify three ways in which a while might use a mobile phone. • Why would a user use a satellite phone instead of a mobile phone? • Give two reasons why a user would prefer to use a mobile phone rather than a satellite phone.