Mobile Subscriber ISDN (MSISDN)
The MSISDN is the subscriber's phone number. It is the number that another person would dial in order to reach the subscriber. The MSISDN is composed of three parts:
Country Code (CC)
National Destination Code (NDC)
Subscriber Number (SN)
MSISDN
Country Code (CC) - This is the international dialing code for whichever country the MS is registered to.
National Destination Code (NDC) - In GSM, an NDC is assigned to each PLMN. In many cases, a PLMN may need more than one NDC.
Subscriber Number (SN) - This is a number assigned to the subscriber by the service provider (PLMN).
The combination of the NDC and the SN is known as the National (significant) Mobile Number. This number identifies a subscriber within the GSM PLMN.
National (significant) Mobile Number
International Mobile Subscriber Identity (IMSI)
The IMSI is how the subscriber is identified to the network. It uniquely identifies the subscriber within the GSM global network. The IMSI is burned into the SIM card when the subscriber registers with PLMN service provider. The IMSI is composed of three parts:
Mobile Country Code (MCC)
Mobile Network Code (MNC)
Mobile Subscriber Identification Number (MSIN)
IMSI
Mobile Country Code (MCC) - This number identifies which country the subscriber's network is in. It has 3 digits.
Mobile Network Code (MNC) - This number identifies the home GSM PLMN of the subscriber (Cingular, T-Mobile, etc.). It has 2 or 3 digits. Some networks may have more than one MNC allocated to it.
Mobile Subscriber Identification Number (MSIN) - This number uniquely identifies a user within the home GSM network.
International Mobile Equipment Identity (IMEI)
The IMEI uniquely identifies the Mobile Equipment itself. It is essentially a serial number that is burned into the phone by the manufacturer. The IMEI is composed of three parts:
Type Allocation Code (TAC) - 8 digits
Serial Number (SNR) - 6 digits
Spare (SP) - 1 digit
IMEI
Type Allocation Code (TAC) - This number uniquely identifies the model of a wireless device. It is composed of 8 digits. Under the new system (as of April 2004), the first two digits of a TAC are the Reporting Body Identifier of the GSMA approved group that allocated this model type.
Serial Number (SNR) - This number is a manufacturer defined serial number for the model of wireless device.
Spare (SP) This number is a check digit known as a Luhn Check Digit. It is omitted during transmission within the GSM network.
On many devices the IMEI number can be retrieved by entering *#06#
Former IMEI Structure
Prior to April, 2004 the IMEI had a different structure:
Type Allocation Code (TAC) - 6 digits
Factory Assembly Code (FAC) - 2 digits
Serial Number (SNR) - 6 digits
Spare (SP) - 1 digit
Former IMEI Structure
As of April 2004, the use of the FAC was no longer required. The current practice is for the TAC for a new model to get approved by national regulating bodies, known as the Reporting Body Identifier.
International Mobile Equipment Identity/Software Version (IMEISV)
This is a newer form of the IMEI that omits the Spare digit at the end and adds a 2-digit Software Version Number (SVN) at the end. The SVN identifies the software version that the wireless device is using. This results in a 16-digit IMEI.
Type Allocation Code (TAC) - 8 digits
Serial Number (SNR) - 6 digits
Software Version Number (SVN) - 2 digits
IMEISV