How multi-IMSI and cellular IoT work together

‍Multi-IMSI technology is transforming how IoT devices maintain connectivity across borders and networks. For businesses deploying connected devices globally, understanding this technology is essential for making informed decisions about your connectivity strategy.

In this article, we'll explain what multi-IMSI is, break down its core components, compare it to eUICC technology, and explore real-world use cases. Plus, we highlight how Hologram's approach delivers more reliable connectivity for your IoT deployments.

Key takeaways

• Multi-IMSI technology stores multiple International Mobile Subscriber Identities on a single SIM card, allowing IoT devices to automatically switch carriers across geographical regions without roaming fees.
• Traditional multi-IMSI solutions can cause devices to cycle repeatedly through profiles even when stationary, resulting in longer registration times and inconsistent connectivity.
• Multi-IMSI and eUICC serve similar purposes but differ in implementation. Multi-IMSI switches profiles automatically while eUICC typically requires over-the-air provisioning, though both can be combined in a single deployment.
• High-mobility IoT applications like fleet telematics, autonomous vehicles, and healthcare wearables benefit most from multi-IMSI connectivity where continuous cross-region coverage is required.

What is multi-IMSI?

Multi-IMSI is a cellular technology that allows a single SIM card to store multiple International Mobile Subscriber Identities (IMSIs), enabling devices to switch between carriers as they move into different geographical areas. This capability is essential for cellular IoT because it lets devices connect through whichever network is strongest in their current location without manual intervention or expensive roaming fees.

For global IoT deployments, multi-IMSI technology promises flexibility because it allows devices to find and connect to local service providers automatically, without the coverage restrictions of having one particular carrier or the limitations (and added expenses) of roaming.

But when deployed, multi-IMSI connectivity can cause some headaches. Many solutions load multiple profiles on a SIM, which can lead to devices constantly cycling through options even when staying in the same physical place.

This constant searching results in:

• Longer registration times
• Inconsistent service experience
• Frustration for telecom providers as devices switch constantly between competitors

Components of an IMSI

To fully understand multi-IMSI, let's break down what an IMSI is and why it matters for your connected devices.

Typically, an IMSI has 15 digits broken into three components:

• Mobile Country Code (MCC): The first 2–3 digits identifying the subscriber's country of origin
• Mobile Network Code (MNC): The next 2–3 digits identifying the mobile service network
• Subscriber ID: The remaining 8–10 digits that uniquely identify the specific device like a car's serial number

Mobile network operators (MNOs) use IMSIs to determine a subscriber's country of origin, mobile service network, and specific device identity. When the device leaves its home region, it must connect to another network within its MNO's collection of roaming partners.

Are multi-IMSI and eUICC the same thing?

There are some similarities between multi-IMSI and eUICC connectivity, but essentially they're different technologies. Let's take a closer look at eUICC and then at how they differ.

eUICC

An embedded universal integrated circuit card (eUICC), often associated with the embedded SIM (eSIM), lets users switch carriers and store different SIM profiles. Here's how it works:

• The device comes preloaded with a bootstrap profile to make an initial network connection
• Once connected, the device downloads SIM profile(s) through over-the-air (OTA) provisioning from a provider
• The eUICC confirms successful installation via SMS and the SIM becomes active

eUICC technology comes in handy for international IoT device deployments — you can preload the profiles you'll need and ensure that your devices will operate anywhere in the world. And eUICC allows companies to simplify their supply chain by using the same SIM card or embedded eSIM chip for every device because the SIMs can be programmed remotely after deployment.

eUICC vs. multi-IMSI

Both technologies allow your devices to connect to local networks anywhere in the world, but they accomplish this differently.

While both eUICC and Multi-IMSI technologies allow devices to connect to local networks globally, they differ in several ways. eUICC is a GSMA standard that typically requires over-the-air (OTA) provisioning for profile switching and can be simplified in supply chains, though it may require manual provisioning.

In contrast, Multi-IMSI requires custom applet support and features automated switching as a device moves, but it can potentially cycle through profiles repeatedly, which may impede connectivity. Notably, these technologies can be used together, as an eUICC profile can include multi-IMSI service.

Both technologies are useful for IoT deployments and can even be used together for maximum benefits and flexibility.

Multi-IMSI use cases

Let's consider a few use cases where multi-IMSI technology can assist IoT device deployments in significant ways.

Healthcare and emergency management

Frontline healthcare workers and first responders take their devices with them into the field and they need to stay connected. Multi-IMSI connectivity allows wearable health monitors and other connected health devices to switch between available networks automatically, saving time and effort for essential workers and keeping devices and data online.

Telematics

In fleet tracking and commercial applications, telematics depends on continuous connectivity as vehicles move across a country or continent. A multi-IMSI SIM card allows the service provider to switch profiles and carriers automatically, keeping real-time data flowing for location tracking, maintenance monitoring, and driver behavior analysis.

Autonomous vehicles

Autonomous cars rely on continuous connectivity to power GPS, radar, LIDAR, and AI decision-making systems. Losing signal when driving out of range of a home network could pose a major safety problem. With multi-IMSI, autonomous vehicles automatically switch to the strongest available network as they travel.

Multi-IMSI vs. Hologram

While multi-IMSI is a useful technology with much potential, it has some limitations. A multi-IMSI SIM shuffles between multiple profiles based on available networks. This switching logic can cause longer registration times and varying service experience.

Hologram's global IoT SIM and eUICC SIM platform takes a different approach:

• Automatic carrier switching: Devices switch between carriers without delays, always optimizing for the best coverage.
• Maximum carrier access: One profile with access to as many carriers as possible for your deployment.
• Localize once: No more watching devices cycle through IMSI profiles in the field.

Frequently asked questions

What is multi-IMSI technology?

Multi-IMSI allows a single SIM card to store multiple International Mobile Subscriber Identities, enabling devices to switch between carriers as they move across different geographical areas without manual intervention or roaming fees.

How does multi-IMSI differ from eUICC?

Multi-IMSI automatically switches between stored profiles as devices move locations, while eUICC typically requires over-the-air provisioning to change profiles though some eUICC platforms now support automatic switching and both technologies can work together.

What are the three components of an IMSI?

An IMSI consists of the Mobile Country Code (2-3 digits identifying the country), Mobile Network Code (2-3 digits identifying the network), and Subscriber ID (8-10 digits uniquely identifying the specific device).

Why do multi-IMSI devices cycle through profiles?

Multi-IMSI devices can cycle repeatedly through stored profiles when searching for the strongest signal, which leads to longer registration times and inconsistent service—even when the device stays in the same physical location.

When is multi-IMSI connectivity most useful for IoT deployments?

Multi-IMSI proves valuable for healthcare wearables, fleet telematics, and autonomous vehicles that need continuous connectivity across regions where single-carrier coverage may be unreliable or unavailable.

How does Hologram's approach differ from traditional multi-IMSI?

Hologram provides one optimized profile with access to multiple carriers that switches automatically without delays, eliminating the profile-cycling issues common in traditional multi-IMSI implementations.