(BSC). The BSC controls multiple BTSs within a small geographical area. The BSC forwards the received signals
to Mobile Switching Centre (MSC) and the MSC interrogates its databases (Home and Visitor Location Register
(HLR and VLR)) for the location information about the destination mobile handset. If the signal originates or
terminates at the fixed telephone line network then the signal will be routed from the MSC to the Gateway MSC
(GMSC). If the received signal is an SMS message then the message would be stored in the Short Message
Service Centre (SMSC) and the message will wait to be delivered. Even after the SMS is delivered, the message
content still maintains in the SMSC persistence database. If the signal needs to be redirected internationally then
the signal will be routed via the International Switching Centre (ISC) to another country. The maintenance is
controlled by the Operation and Management Centre (OMC). The Equipment Identity Register and
Authentication Register (EIR and AUC in respective order) databases are used for equipment verifications and
user authentication