Most people are familiar with SIM cards for cell phones. Though an IoT SIM card is similar, it’s different in that it supports IoT devices specifically with their network requirements and unique data consumption rates (check-in rates). Few people understand how IoT SIM cards work and the unique identifiers essential to driving their capabilities. In this post, we’ll unveil the mystique behind IoT SIM cards, including ICCID and IMEI numbers and their importance.
An Integrated Circuit Card Identifier, or ICCID, is a unique number assigned to a SIM card to distinguish it from others. Think of it as you would your social security number — the ICCID is specific to the SIM card. However, unlike a social security number, an ICCID is globally unique and not only established in the SIM card’s country of origin.
For physical SIM cards as well as eSIMs and virtual SIM cards, an ICCID is typically 19 to 20 characters long (though it can range from 18 to 22) and specifies the industry, region, network, and device of the SIM card. The identifier is stored digitally, though it’s often also engraved into the physical SIM card. As the ICCID number is tied directly to its corresponding SIM card, it cannot be modified.
An ICCID number follows this format: MMCC-IINN-NNNN-NNNN-NN C(X). It consists of groupings that represent various identifiers and codes, making each SIM card unique.
The Major Industry Identifier (MII) comprises the first two digits of the ICCID, and it serves to differentiate the card from other types of chip cards. An IoT SIM card will always start with the numbers 89 for the MII, distinguishing it from something like a credit card.
The country code follows the IoT SIM card identifier. It specifies the operating region and is assigned by the International Telephony Union (ITU). The country code can be two or three digits long. In the United States, for example, the country code can often be 01. There are occasionally exceptions to this rule, however.
Next is the issue identifier (II), also known as the mobile network code (MNC). This is a one- to four-digit code that identifies the home network — the mobile network that issued the SIM. This identifier comes into play with roaming, as the mobile network code identifies the device to the new network to connect. It’s usually issued by the network that provided the SIM card, though a partner company could also generate it.
The account number, or account ID, is unique to the SIM card. It serves to distinguish the SIM card from any other in the world. The account ID can be up to 10 digits long.
The sum in the ICCID is a calculation of the other digits using the Luhn algorithm.
Lastly, there may be an additional digit added at the end of the ICCID code. Though this is technically not part of the ICCID, you may see it listed.
There are other numbers typically found on SIM cards. They could include a UPC, Part number, SKUs or other stuff like that used by the manufacturer or the carrier relating to the SIM Card.
Cellular networks use the IMSI to identify the connectivity service a SIM uses, such as a subscription service. The IMSI uniquely identifies every user of a cellular network, and the network uses it to establish a connection with the device. It’s different from the ICCID, which is used to identify SIM hardware and not connectivity. The IMSI is usually a 15-digit number, though it may be shorter.
The IMEI is a unique identifier for every device. It’s often found printed on the device packaging, or on the device in the example of some types of routers, though it’s not required to be. Some manufacturers take a different approach and include the IMEI on the Settings menu in the device’s software application. When the device is connected, the IMEI is checked against a global IMEI database to identify the device to the network. Some carriers use the IMEI to determine if the device has even been certified for use on their network, and will prevent devices that have not been certified. In efforts to further improve security, carriers now also use the IMEI to determine if a device has been stolen - preventing those devices from being activated on the network.
An IoT SIM card contains the following components:
eSIMs, or embedded SIMs, are an integrated circuit (IC) surface mounted on the board of an IoT device. This eSIM works in the same way as a traditional SIM card to identify the device to the network carrier. They serve to:
To understand eUICCID numbers, you need to know what an eUICC is. It’s an embedded universal circuit card, and is responsible for remote provisioning of SIM profiles. It’s what enables networks to provision eSIMs without physically handling the device. The eUICCID is created for eSIMs, and may be used on traditional SIMs as well.
The eUICCID is a newer and unique identification number established for eSIMs to distinguish them from others. To avoid confusion, given the potential involvement of multiple businesses in the process, eSIMS are assigned both an ICCID — which is created with the eSIM profile — and an eUICCID number.
The eUICCID was established because network carriers have the choice to use their own eSIM profiles or the chip manufacturer's profiles, or to work with a third party to create the profiles. This opens up extra room for confusion, so the eUICCID was introduced to help uniquely identify each eSIM regardless of how many parties are involved.
This topic can be quite complex, so in closing, here are a couple of additional resources for further exploration.
First, keep in mind that M2M/IoT is very different from the consumer eSIMs used with cell phones. It’s critical to use IoT-approved solutions for IoT deployments. Read more about the differences in this post.
Second, the Global System for Mobile Communications Association (GSMA) defines the standards for these identifiers. They offer a great whitepaper on eSIMs that is very helpful for understanding them.
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