|
Welcome to the new home of the Celtnet Mobiles in formation site. This page is the third in a series of eight articles that takes you through how mobile phones work. You can either page through the aritcles, below, or you can use the navigation menu on the left to find the page you want.
In the first part of this series we saw what happens when a mobile phone is first turned on. What hasn't been mentioned so far is that all the communications between the phone and the network discussed in part 1 is actually conducted via a special channel called the control channel. This is a specific frequency employed by each cell so that any phone can communicate with a base station. Indeed, if a phone cannot locate a control channel to listen to then the phone knows that it is out of range of a base station and displays a 'no service' message.
However, if a control channel is actually located then, as well as the security checks already described in first part of this introduction to mobile phones the phone itself also transmits a registration request that the cell network's MTSO (Mobile Telephone Switching Office) uses so that it can track the location of your phone within its database. This way the MTSO knows which individual cell you are in.
How Calls are Made — Control Channels
In terms of being able to make and receive mobile telephone calls then the control channel of the mobile telephone network is all important as it's this that infroms the network where your phone is so that you can connect to the appropriate cell. As mentioned above, it's the control channel that tells the system which cell you are in, so that this information can be stored in the system's database. It is entirely because of this that an incoming call can be routed to your phone. When another person dialls your mobile telephone number then the call is routed via the network's MTSO.
The network then sends a message to your phone saying that there's an incoming call. This message is routed to the cell that represents the last location that the system knows your phone to have been in. Just to be sure the same message is also transmitted to that cell's immediate neighbours, just in case you have moved since the last time your location was recorded. Even if you have wandered out of this cluster of cells the network should have recorded this and updated its database. In fact your mobile phone can be located to within a few tens of metres using the principle of triangulation. A control panel signal can be broadcast to your phone from the three cells nearest to you. The time it takes for the signals to reach your phone is measured and this can be used to pinpoint the location of your phone.
How Calls are Made — Control Channels and Traffic Channels
Once a call is connected via the control channel then the call still has to be maintained. The data are transmitted to and from your phone via traffic channels (for a description of how these work see the next part of this series) and to maximize the number of phones that can be used on a network these traffic channels are different between adjacent cells. Therefore if you move from one cell to the next and your phone wasn't told you had moved then because of the different traffic channels used in each cell your phone actually wouldn't work!
To overcome this problem a process called 'hand-over' is employed. Whilst your mobile phone is in use it actually constantly monitors the control channels of up to sixteen of the neighbouring cells closest to it. The phone then works out which of these cells produce the strongest signals and broadcasts a list of the top six cells by signal strength back to the base station to which it is currently connected. If a phone moves away from the base station then the signal the phone produces is boosted to generate a clearer signal. However, if this boosting of signal strength no longer works then the network consults its database and instructs your mobile phone to switch to another cell. This triggers a handover where the phone adjusts its reception and transmission frequencies so that it can now work with the closest cell that will give the bast signal strength. Generally this handover is seamless and you notice no drop in the quality or reception of your telephone call. However, as anyone who has used a fast-moving tranin has found out the system is not completely infallible and delays in switching can result in calls 'dropping out' or even being dropped entirely.
Not found what you're looking for? Search the web:
Phone Information: 48
iPhone is a revolutionary cell phone and has changed the cell phone industry completely. But it is cell phone which is out of reach of many. There are a lot of websites which are offering free iPhones.
Phone Information: 48
Many people love apple¡¯s products and think apple as a perfect enterprise, but in my point of view, there are some mistakes apple have taken in this year.
Phone Information: 48
Mobile downloads for all mobiles of latest Bollywood Wallpapers, Celebrity Gossips, Ring tones, Themes, Animations, screensavers, actress and actor’s wallpapers mobile downloads Cricket, Games, and Mobile fun-Bringing Asian Lifestyle to your Mobile. Instant downloads to Mobile for UK.
Phone Information: 48
Perception System has professional Iphone Games developers to built different levels of iPhone games as per your cost, budget and requirements within a certain period of time. Perception System http://perceptionsystem.com/iphone-game-development.html , offers great value at affordable cost to deliver our customers high quality game services.
Phone Information: 147
You can now enjoy Cable TV on the go on your mobile device. With this new innovative app that just launched, having thousand of channels at your fingertips is now possible.
Phone Information: 48
Many people in the world enjoy all the products manufactured by Microsoft and they buy phones that use the new Windows Mobile 7. Actually there is a strong business rival on the market called Android, Microsoft has managed to entice a lot of people by applying their own OS.
Phone Information: 147
You are more than likely familiar with e-commerce but have you heard of m-commerce? M-commerce is a way of selling products or services via a mobile phone or smartphone. This matches the increased demand for mobile websites in which shopping is cited as one of the most popular activities along with many others.
Phone Information: 146
Bangalore: Verity Technologies, a mobile applications company with focus on Authentication and Identity Management Services, today announced a strategic alliance with Kores (India) Limited, a 76 year old highly diversified business house with all India network and market leadership in stationery and office products. Kores has relationships with most Indian Banks. The alliance paves way for Kores to distribute Verity’s highly acclaimed Blue ID, a new generation technology – that secures financial transactions, manage access and provides biometric identity to masses on a pan India basis.
Phone Information: 48
Everything you want to know about mobile phone service.
Phone Information: 48
Mobile phones are often 'locked' that is, electronically tied to a certain country and a certain service provider. This maximizes the service providers' profits and forces the phone purchaser to stick to one service provider. However, it is possible to unlock your phone so that you can use different SIM cards in it and take it to different countries. This article discusses mobile phone unlocking.
click here for the full story
printer version