The IMSI (International Mobile Subscriber Identity) code is a unique identification number associated with a mobile subscriber. It is stored on the SIM card and is used by the mobile network to identify and authenticate the subscriber on the network.
The IMSI is composed of three parts:
1. Mobile Country Code (MCC): A three-digit code that identifies the country where the subscriber's SIM card was issued.
2. Mobile Network Code (MNC): A two or three-digit code that identifies the mobile network operator within the country.
3. Mobile Subscriber Identification Number (MSIN): A variable-length number that uniquely identifies the subscriber within the mobile network.
When a mobile device is powered on and attempts to connect to a mobile network, it sends its IMSI to the network for authentication. And When work with Turbosim, input the IMSI code directly, would be easier and fast to capture the carrier signal, there has an example for Heicard RS operate link with IMSI activating. Then the network would verify its database to grant access to services.
The IMSI is a critical piece of information in mobile communication systems and is used for various purposes, including roaming, billing, and security/authentication. However, it's important to note that the IMSI is sensitive information and should be handled with care to prevent unauthorized access or misuse.