AMPS operation:
A simple diagram of how AMPS system handles various calls and other responsibilities as shown in below diagram. As the power up, all mobile station is in the range of a base station which go through a registration with AMPS before actual service starts. According to the state of the system, the incoming and outgoing calls are handled. When handoff has occurred to the adjacent cells mobile station will undergo the registration process.
To perform various functions in AMPS three identification numbers are required they are:
Electronic serial number (ESN):
A 32-bit binary number uniquely identifies a cellular unit or mobile station and established by the manufacturer at the factory. Therefore it is unique, any mobile station will be identified by using this number. For some security reasons, this number should not be alterable and should be present in all mobile stations.
System identification number (SID):
A 15-bit unique binary number assigned to a cellular system. Every cellular system is assigned with a system identification number which is used by all mobile stations registered in the service area this number is given by the Federal communication commission (FCC). This number is given to the mobile station for transmitting data which handles the calls. The SID serves as a check and can be used in determining if a particular mobile station is registered in the same system.
Mobile identification number (MIN):
Where the particular location of the mobile station is not predictable. With this, a question arises how a mobile station knows when it receives a call. The answer for this is the message passed on the control channels. Whenever the mobile station is not in service, it tunes to the strongest channel to find out useful control information. The same happens at the base station as well. There are two important control channels: reverse control channels (ROCC from base station to mobile station, and forward control channels from mobile station to base station both are operating at 10kbps (FOCC).