Can you find your lost Mobile Hanset in the current telecom setup

[gaurav_cyril]

Number System/Arrangement in GSM Network
A number system is required in a GSM network to trace any subscriber in the network also for:
Billing
Privacy
Call History
To chase Fraudulent subscribers (if any)
The arrangement consists of the following seven terms:
1. IMSI – International Mobile Subscriber Identity.
2. TMSI – Temporary Mobile Subscriber Identity.
3. MSISDN – Mobile Subscriber ISDN Number.
4. MSRN – Mobile Subscriber Roaming Number.
5. IMEI – International mobile Equipment Identity.
6. IMEISV – IMEI Software Version.
7. LAI – Local Area Identity.

IMSI - International Mobile Subscriber Identity
• It is a permanent number
• It is HLR (Home Location Register) based, also stored in HLR.
• It is used to identify the unique user in the network.
• It is a maximum 15 digit number that is never placed in the AIR due its confidentiality.
TMSI - Temporary Mobile Subscriber Identity
• To ensure IMSI security TMSI number is used.
• It is a Temporary number.
• It is VLR (Visitor Location Register) based, hence stored temporarily in VLR.
• The VLR assigns this TMSI number which is a unique number that is locally used.
• Placed in AIR as TMSI is not a confidential number.

MSISDN – Mobile Subscriber ISDN Number
• It is the Directory number that is given uniquely to every user. Example: 9871944755.
• It is not a secret number, it is meant to be known to everyone.
• As shown in example above it is always a TEN digit number.
• It is permanent, local network based number.
• As it is permanent it is HLR based (Home Location Register)
• It is stored in SIM also.
• It consists of the followings:
 Country Code
 Network Code
 HLR Code
 Number (Last 5 digits)
The format is: Country Code + Network Code + HLR Code + Number

MSRN – Mobile Subscriber Roaming Number
• It is a temporary number
• Temporary hence VLR (Visitor Location Register) based
• It is used in Handoff
• Very essential in location tracking





IMEI – International Mobile Equipment Number
• It is a permanent 15 digit mobile equipment number.
• It is EIR (Equipment Identity Register) based
• EIR - It is a register containing information about the mobile equipments (IMEI). More particularly, it contains a list of all valid terminals equipments.
• The EIR tells that weather the mobile is:
 Black Listed
 White Listed
 Grey Listed
• It consists of the following:
 TAC – Type Approval Code
 FAC – Factory Assembly Code
 SNR – Serial Number
 SP – Spare Digits
• The Sequence is:
TAC + FAC + SNR + SP

IMEISV – International Mobile Equipment Number (IMEI) Software Version
• It shows the IMEI Software version.
• It is a 16 digit number.






LAI – Location Area Identity
• It is also Known as location area code i.e. LAC
• It is a temporary number used in routing purpose in the network.
• For example when a Mobile Station moves from Sector 125 Amity Campus to say in the 44 Amity Campus, then this LAC changes but with the campus of Sector 125 it may or may not change.