Two SIM cards on a desk next to a keyboard, mouse, and succulent

As IoT modules start to include embedded SIM technology (eSIM), there’s a lot of confusion around terminology. Most people assume that an eSIM denotes over-the-air (OTA) profile provisioning—but eSIM hardware does not provide that capability. It’s the embedded universal integrated circuit card (eUICC) that makes OTA provisioning possible.

Contrary to popular belief, eUICC does not only work with eSIM. Many SIM providers, including Hologram, are beginning to offer removable SIM cards equipped with eUICC to allow remote profile provisioning after deployment.

The eUICC represents a huge step forward for cellular connectivity because of the flexibility it creates. It’s a piece of software located inside the eSIM chip that allows you to send out and store multiple SIM profiles. Based on the older GSMA standards for UICC, it functions much like the software within a physical SIM, with some variations around test specifications (which can’t be performed the same way in eUICC-enabled eSIM because the software is internal to the device). And it’s considerably larger: while a physical SIM typically has a memory of either 64KB or 128KB, an eUICC can hold at least 512KB of data and support several profiles.

Think of it as a travel passport with multiple visas inside. You can use a different visa each time you enter a new country. If you find yourself in an unexpected country without a visa, you can apply for one, receive it immediately, and go on your way. It’s a convenient way to travel. (Your IoT devices will think so, too.)

How Does eUICC Benefit IoT Device Deployments?

Simplifies Manufacturing

The eUICC gives you the ability to send out SIM profiles to IoT devices after deployment. This saves you the logistical headache of manufacturing different versions of the devices with embedded SIMs suited to their destinations, and it cuts inventory and production costs because even for a global deployment, you only need one SKU. It also speeds deployment because the devices are ready to be brought online as soon as they are in the field, rather than having to wait for a final SIM installation.

Provides Flexibility

eUICC also allows you to swap out one SIM profile for another if a device is recalled from the field and redeployed in another location. While you can’t access the eSIM form factor to make changes, you can provision a new profile remotely if you need to switch carriers. The eUICC can also store multiple profiles at a time and operators can shift between them as needed if the devices move from one carrier domain to another.

Makes Devices Future-Proof

The ability to switch out SIM profiles also means that your devices will be future-proofed against coming network sunsets and other carrier and technology shifts. Software updates can be delivered remotely and regularly, allowing your devices to stay current with the latest features and carrier offerings without needing to be recalled from the field.

How Does eUICC Work?

The benefits of eUICC are clear, but how does the software actually work? The OTA provisioning process is what sets this technology apart from traditional SIMs. Let’s take a look at the steps involved in profile provisioning—but first, a few terminology definitions:

Bootstrap Profile

Every eUICC-enabled device is equipped with a bootstrap profile at manufacture. Once the device is in the field, the bootstrap allows it to make an initial connection to the network to download a profile (or multiple profiles) that will make it operational.

Short Message Service (SMS)

The eUICC uses SMS to communicate with the cellular network. The SMS channel provides a route of communication between the SIM card and the OTA Gateway.

Subscription Management Platform (SM)

The SM platform is responsible for downloading, installing, and managing operator profiles on the device. It includes the subscription manager – data preparation (SM-DP), which stores profiles and delivers them to the eUICC, and the subscription manager – secure routing (SM-SR), responsible for managing profile status and ensuring that profile data is transferred securely.


Now, imagine you’re in the field and have just received a device that’s ready to be deployed. What happens when you turn on the device?

Initial Connection

First, the eUICC device connects to the server via its bootstrap profile. The bootstrap doesn’t allow the device to perform any function other than making a connection to download a profile. Once that initial connection is made, a platform provider on the backend can send out the profile your device needs to function in its current locale.

New Profile is Enabled

Once the SM-DP completes the download to the eUICC, it’s time for the SM-SR to do its thing. As the manager for profile status, the SM-SR can tell the eUICC to disable, enable, or delete a profile. In this case, it enables the new profile.

eUICC Talks to Device

The eUICC then communicates with the device module to say it’s received an SMS and needs to download a profile. The module affirms this action.

New Profile Downloaded

The profile is fully downloaded onto the device.

Success Confirmed

Finally, the eUICC confirms a successful profile installation via SMS. The message is received through the OTA gateway and the profile becomes active. Congratulations, your device is now up and running.

While eUICC is set for wide adoption in IoT, there are some lingering challenges. Logistically, there's some murkiness around carriers giving up their SIM profiles in the new eSIM/eUICC ecosystem. To enable connectivity around the world, more carrier agreements will need to emerge.

But while carriers try to find their way in the new environment, you can sidestep potential problems by choosing a carrier-neutral partner (such as Hologram). We're always onboarding new carriers and networks to orchestrate the best possible connectivity and SIM scenario for your deployment. And eUICC will give us more flexibility than ever. With the traditional SIM model, we had one shot at manufacturing to nail the best connectivity. But as we roll out eUICC, we can send out connectivity updates OTA, meaning connectivity and features can improve over time.
In other words, we’re constantly adding visas to your passport, giving you more flexibility to roam into new countries and situations around the world—and stay connected.

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