What is a Multi-IMSI SIM?

multi-imsi sim
Illustration: © IoT For All

Multi-IMSI technology is essential for cellular IoT providers that plan on deploying globally or creating mobile applications. Multi-IMSI is an abbreviation for Multiple International Mobile Subscriber Identities. An IMSI is a key component of a Subscriber Identity Module (SIM), which is stored on a SIM card. Each one allows a device to connect to a limited number of networks. It enables subscribers to switch carriers as needed and connect to significantly more networks.

What is an IMSI?

To understand what a Multi-IMSI is, you first need to know what IMSI is.

An International Mobile Subscriber Identity (IMSI) is a unique 15-digit number that identifies every mobile network user globally. The IMSI is divided into two parts. The first part is a six-digit or five-digit number based on the North American or European standards, respectively. The initial set of numbers identifies the mobile network operator in a specific country to which the user is subscribed. The second part of the IMSI number is allocated by the network operator to uniquely identify the subscriber.

The IMSI number is not always printed on the SIM card and you would have to look deep in the settings for it to show on your device. The IMSI is stored in the Subscriber Identity Module (SIM) inside mobile devices and is sent by the mobile device to the appropriate network in which the SIM is associated. When a mobile device is powered on, the device indicates its IMSI number to the associated cellular network to perform a location update – this is referred to as the attach procedure. This update is also carried out when a handover occurs to another base station (cell tower). This update is received by the corresponding visitor location register which updates the home location register of the new location. When the mobile device is powered off, an IMSI detach procedure occurs. This shows that the device is no longer connected.

What is a Multi-IMSI SIM?

Now that you know what an IMSI is, a multi-IMSI is simply a SIM with more IMSIs. That means that a SIM card can decide which IMSI to use in any country. Having multiple IMSIs can help you get better data costs and coverage based on the country used. When a SIM card enters a different country, it automatically selects the best IMSI.

Benefits of a Multi-IMSI

You don’t notice any differences looking at a multi-IMSI SIM, but there are plenty of benefits.

1. Better coverage. A single network provider might not have agreements around the world with all the operators and, even if they do, they might not offer the best rates.

2. National Roaming. You cannot access multiple networks in the country where the SIM card originates from. You might have noticed that your regular phone SIM card is attached to your provider and you cannot use other networks in your area – Multi-IMSI fixes that.

3. Better rates. You can get better rates both locally and globally based on the provider you choose to use.

4. Worldwide Access. Multi-IMSI IoT SIM offers cards with multiple IMSIs that, if needed, provide access to different countries and continents at a better rate. This means that a single SIM card is enough for global deployment.

As some IoT devices are moving constantly (such as GPS trackers), having good rates and coverage is important.

eUICC and eSIM

eUICC is a new technology that offers the ability to change service providers over the air (OTA). That means you do not have to switch operators by replacing the card, but you can do it remotely which is convenient as you do not have to store these profiles on the card itself and these profiles can be changed anytime depending on your needs.

There is some confusion on the difference between eUICC and eSIMs. As some refer to eSIM and eUICC (Embedded Universal Integrated Circuit Card) interchangeably. eUICC is the programmable part of the SIM, while eSIM is embedded directly into a device without the ability to remove it. It can have over-the-air support, but it is not something that you could use in a regular SIM card slot. eUICC can be removable (just like any other regular SIM card) and non-removable (embedded) SIM cards.

eUICC vs. Multi-IMSI

Both eUICC and Multi-IMSI are great technologies that allow options to change coverage, pricing, and MNOs. eUICC is a technology that seems very beneficial, but it can be tricky for non-enterprise customers. With Multi-IMSI cards, IMSIs can be written into the SIM card during the manufacturing process and can be changed over the air. 

However, the ability to change these profiles over the air is not a straightforward change as one might expect. You can have profiles tailored for one continent such as North America, and if you decide to move your device to Europe, you can switch your profiles that are more tailored for European use. In order to swap the SIM profile the selected carrier needs to support the provisioning as well. Often this depends on the manufacturer of the SIM cards. These manufacturers provide the software to perform the swap and this is proprietary for each manufacturer. The support of this feature isn’t free of charge, so expect additional fees for both the more complex SIM as well as the licensing fees that are needed to support eUICC. It gives flexibility and means that you always do not have to swap the card out, you can simply update it. The costs and processes make it a little harder to get started with, but it’s a great option for large enterprise customers.

Technologies for Flexibility

To decide which product is better for you, evaluate where you are going to be using your IoT device and how important it is for you to switch profiles to restricted roaming markets such as Turkey and Brazil.

Simbase, an All-in-One IoT Connectivity Platform with pay-per-use IoT connectivity, networking, and great support.
Simbase, an All-in-One IoT Connectivity Platform with pay-per-use IoT connectivity, networking, and great support.