 | |  |
|
Welcome to the information base section of the site.
How does the mobile phone network work?
GSM mobile phones are a means of connecting the user to the telephone network. The phone number is associated with the Subscriber Information Module (SIM) card, a small "smartcard" that also stores the user's address book.
In a call, speech is converted to a stream of data and passed to and from the base station, at the same time as both the handset and the base are monitoring what's going on to help decide whether there is a better cell to transfer to.
When not in a call, the mobile keeps tabs on what base stations it can reach, and the network keeps track of where the mobile is.
All this is done in a way that uses as little battery power, radio transmission and computing overhead as possible.
Base stations provide coverage in a series of cells, arranged rather like the patches in a patchwork quilt. Each cell can be from 50 metres across to tens of miles across.
How does the network find the mobile phone?
With TACS (Total Access Communication System) and ETACS (Extended TACS), as used on Vodafone and Cellnet, when a mobile is switched on it sends a registration message to a local cell (usually the one with the strongest signal). Data about where that mobile is can then be sent to (& stored in) a special database called a "home location register", usually kept at the Network Control Centre. This database can be interrogated by any switch on the network that is trying to call that mobile.
When mobiles move from one cell to another, they can detect that the control channel has changed and then they re-register on the new cell - and the Home Location Register is updated.
At regular intervals (between 15 minutes and an hour - depending on how busy the local area is) the network sends out a data message asking all phones to re-register: this ensures that the Home Location Register is fairly uptodate. When a call is made to a mobile, calling signals will be sent out to the area in which the mobile last registered. If that signal isn't acknowledged by the mobile, the network then tries to find the mobile by calling in all areas. Obviously if it had to do this on every call, there would be a tremendous overhead of unnecessary signalling !
How do mobile phones work in tunnels?
Using 'leaky feeders'. Basically run a length of thick coax and cut sections of the outer shielding off (about 6" to a foot) every now and again. This is being done in the Channel Tunnel too.
Check out phonehistory.co.uk for more information on how mobile phones work including the past, present and future of mobile phone technology.
| |
 | |  |
|
|
|
This site has information on mobile phones, network providers, telecoms, cell phones and cellular technology. We also have information
on mms, sms, picture messaging, video chat, ringtones and realtones.
|
