From IMSI to MSSIDN, the telecommunications ecosystem loves its acronyms. Some of the common questions we get when it comes to cellular connectivity are:
- What is an IMSI?
- Why does it matter if a SIM can hold multiple IMSIs?
- Is an IMSI the same as IMEI?
- What about the ICCID and MSSIDN?
In this article, we lend clarity to all these concepts and the vital role they play in cellular IoT connectivity and security.
What is an IMSI?
An IMSI (International Mobile Subscriber Identity) is a 15-digit unique number. It is stored on the SIM card to identify the relationship between GSMA mobile networks and users.
The first 3 digits of an IMSI is the MCC (Mobile Country Code). This is followed by the MNC (Mobile Network Code) which is 2 digits long (EU) or 3 digits long (North America). The MSIN (Mobile Subscription Identification Number) is the remaining 10 digits of the code to identify the subscriber and their service plan.
If a deployed IoT device attempts to establish a connection to a cellular network, the network identifies it by the IMSI, while the mobile station performs a location update.
So an IMSI is not an IMEI?
No. The IMEI is a 15 digit unique International Mobile Equipment Identity that is inscribed on all physical cellular devices. IMEI numbers contain information on the phone’s model, origin, and serial number, among other things.
The IMEI essentially identifies a device and not the SIM card itself. If your device is lost or stolen, the IMEI number can be used to block your device and secure it from malicious activity.
What about the ICCID and MSISDN?
The ICCID (Integrated Circuit Card Identifier) is used to verify SIM cards. It is 19-20 digits and written on all physical SIM cards. It is part of the SIMs hardware and can be thought of as the SIM card’s ID.
MSISDN (Mobile Station International Subscriber Directory Number) is simply your whole phone number.
Why is the IMSI Important for cellular IoT?
An IMSI is critical in device authentication and ensures that the device gets routed to the correct network. When a IoT device attempts a connection to a cell tower, the IMSI enables the operator to identify and verify data plans and usage.
The IMSI is also useful for network roaming. When a device is deployed in a different country or region, networks can identify it by its IMSI and determine service agreements and rates.
A common security risk is the use of fake base stations or cell towers. When a device connects to a fake base station, it may lead to the leakage of private information. For additional protection, look into advanced security options such as our patented Anti-IMSI catcher.
Limitations of IMSIs in IoT
In cellular IoT deployments, your needs are a little different from consumer devices.
Single Network Limitations
If a smart waste operator wants to deploy smart bins across Europe, they face connectivity challenges if they rely on a single-IMSI SIM. The operator may also have to negotiate several roaming agreements with each planned location, delaying deployment times and increasing operating costs.
Poor Coverage
A Cellular IoT SIM with a single IMSI can only connect to the network defined in its country code and network code. With a regional MNO, devices might be fine within the home area but struggle to stay connected in other regions.
Multi-IMSI eUICC eSIMs
Embedded universal integrated circuit card (eUICC)-enabled eSIMs are loaded with several IMSIs. This allows subscribers to seamlessly switch carriers when the IoT device moves to a new region.
It promises flexibility for global deployments because devices can find and connect to local service providers. This bypasses coverage restrictions of a particular carrier, or the added roaming expenses of another.
Some eUICC-enabled eSIMs also allows for remote provisioning over-the-air (OTA) to change profiles and network providers. Provision the SIM with a new profile OTA without manual intervention.
Try ZARIOT SIMs for your IoT devices, or meet one of our industry experts to find out how we can customize and accelerate your IoT projects.