IMSI or International Mobile Subscriber Identity corresponds to a unique number for all mobile phone users. Basically, this is attached to your phone’s SIM (Subscriber Identity Module) and is sent to the network via your phone. The IMSI applies to all mobile networks that are interconnected with other networks. Meanwhile, it can either be provided directly along with the phone or along with your R-UIM card.

While an IMSI normally consists of 15 digits, there are others that only have 14 digits. The first three digits represents the Mobile Country Code, and then the next 2 or 3 digits represent the Mobile Network Code. The remaining digits are the mobile subscriber’s identification number within a given network.

These numbers have two functions:

  1. It identifies the GSM network operator where the user is subscribed to.
  2. It is also used to identify the unique subscriber’s identity.

The process of IMSI analysis is done to identify the network to which a given subscriber belongs to. Aside from that, it also aims to specify the access privileges that a subscriber has for a given network. This includes the roaming agreement for non-local subscribers.

Although the network to which a user subscribes allocates an IMSI, he or she can be assured of its anonymity and privacy. The number is used mainly to identify a subscriber for future exchanges.

However, if a given subscriber is not from the network of the provider, a conversion of the IMSI to a Global Title is necessary. The network can then use it to gain access to the subscriber’s data on the remote HLR. This tool is very efficient for global roaming.

Users need to negotiate a roaming agreement with their network in order for their IMSI to be recognized by other networks.

To mobile subscribers outside of North America, the IMSI is converted into a Mobile Global Title format, which still complies with the standard E.214. The E.214 standard enables the conversion of the IMSI number so it can be routed internationally.

With the rapid growth of mobile phone devices, you can also expect a continued rise in the number of mobile phone users for the next few years. Indeed, the use of IMSI will help facilitate for a smoother communication process, whether within or between other network operators.