MS Power On [Under GSM]
1) When MS is powered on, software and hardware entities are initialised in priority order. MMI is initialised in the end.
2) During its initialisation, MMI sends activate request to Protocol Stack (PS) - AT+CFUN command.
3) PS now activates SIM. Stack entities now start getting information from SIM (MM/RR look for MM/RR information like operator identification (MCC, MNC), frequencies, Adaptation layer look for phonebook/SMS/feature capability (SIM service table) data etc.)
3a) During activation SIM may indicate that it require (4 digit) PIN (Personal Identification Number) if it is enabled. PS informs this error to MMI. Once PIN is entered by user and given to PS (AT+CPIN command), SIM activation proceeds further.
4) MMI now need to send request to PS to register to network (AT+COPS). By this time, RR would have already requested L1 to get synchronised to frequency (ies) which it received from SIM or MM. Adaptation layer informs MM, which in turn start "location update" procedure.
We will continue with "how GSM signaling works" in next article.
References: GSM book by Mouly and Pautet, GSM Networks book by Heine.
© Copyright Samir Amberkar 2010
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