How Satellites Provide Cell Device Coverage

Have you ever wondered just how mobile devices work?  What are cells?  Is it satellites that make them work?  If so, what makes these things different from satellite phones? 

Cell devices let you speak to people on other mobiles or on landlines by using small base stations that each cover a certain area, referred to as a cell.  Base stations are designed and placed to cover as much area as possible, so that you can move from one zone to the next and your call will simply be passed from one to the next. 

The ability to switch from one zone to the next during the same call is made possible by the capability for sending a special kind of signal back and forth from the mobile device to the base stations that are taking care of the call.  The call is then connected with the Public Switched Telephone network (PSTN) by the Mobile Telephone Switching Office (MTSO).  The MTSO is also responsible for controlling each of the different zones in which calls can be made.  Every mobile device in use is registered with the MTSO control channel so that the overall system is always able to locate the mobile device no matter what zone it's in.

Ideally, the entire world would be covered by cells, making its coverage look like a giant honeycomb.  Unfortunately, this kind of coverage is simply not possible at this time.  At present, it is in no way cost effective for telecom service providers to erect coverage towers all over very rural areas, or in many developing nations where the use of mobile devices would be, and is, extremely low.  This means that there are large parts of the United States and the rest of the world that don't have zones or designated areas in which your phone will be able to make calls. 

Enter the satellite phone.  These don't require a zone or a cell tower in order to function.  They use signals to satellites in order to make a call.  Making a call from a satellite unit sends a signal to the nearest compatible satellite.  That signal is then sent back down to earth where it is received by either a gateway or a ground station and it is directed to the intended destination for the call.These types of mobile devices are generally able to function normally, regardless of what type of area you happen to be located in.