Two woman in Paris, France. One woman riding an e bike and another an e scooter looking at a phone.

What is Multi-IMSI?

SIM cards can be loaded with several IMSIs, allowing subscribers to switch carriers when the device moves to a new geographical area. Multi-IMSI connectivity is important for cellular IoT because it allows devices to connect through different networks and carriers—whichever are strongest in their current location. A human operator can choose the network, or the device can be programmed with automated logic to initiate the best available connection. 

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 current multi-IMSI solutions load multiple profiles on a SIM to enable coverage in different situations. In the field, this can lead to devices constantly cycling through the options, switching profiles even when they’re staying in the same physical place. This constant searching can result in longer registration times—and frustration for telecom providers as the device’s service switches constantly between them and their competitors.

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. Every eUICC-enabled device comes preloaded with a bootstrap profile to make an initial connection to the network. Once connected, the device receives and downloads a SIM profile (or multiple profiles) sent over the air (OTA) from a provider. Once the new profile is enabled, the eUICC confirms a 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

eUICC and multi-IMSI both allow your devices to connect to local networks anywhere in the world, but the way they accomplish this feat is quite different. With eUICC, in most cases, the devices must be provisioned OTA to change profiles and network providers. But some eUICC platforms now allow IoT devices to switch between profiles automatically.

Multi-IMSI connectivity provides a similar automated switch—as the device moves into a new geographical area, it shifts to the strongest available network. Sometimes, though, the SIM keeps cycling through multi-IMSI profiles, impeding connectivity. And while eUICC for IoT is a GSMA industry standard for handling interoperability of different carrier profiles and network providers, multi-IMSI applets require custom support and development.

Both technologies are useful for IoT deployments—and can even be used together for maximum benefits and flexibility. For example, one of an eUICC’s profiles could be for a multi-IMSI service.

Components of an IMSI

Now, let’s break down what an IMSI is and why it’s important. 

Typically, an IMSI has 15 digits. The first 2–3 digits are the mobile country code (MCC), and the next 2–3 are mobile network code (MNC). The remaining digits identify the line of service, or what’s called the subscriber. Like a car’s serial number, this set of around 8–10 digits is distinctive, creating an IMSI that’s one-of-a-kind.

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. 

How Multi-IMSI Helps

Most of the time, single IMSI devices can only access one operator in their region. (That’s not the case with Hologram’s carrier-agnostic connectivity, though—our SIMs and eSIMs grant your devices access to multi-network redundancy around the globe.) If the MNO doesn’t provide redundant coverage, multi-IMSI can supply that lack. When the original IMSI fails to connect, the device’s multi-IMSI applet will try another option.

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 health devices to switch between available networks automatically, saving time and effort for essential workers and keeping devices and data online.

Telematics

In both fleet tracking and commercial applications, telematics depends on continuous connectivity for vehicles as they move across a country or continent. The vehicle’s onboard computer may be tracking location, mechanical maintenance, and driver behavior and relaying that data to managers at a remote location. To keep the data flowing in real-time, a multi-IMSI SIM card allows the service provider to switch profiles and carriers as needed during the journey.

Autonomous Vehicles

Like fleet vehicles, autonomous cars depend on continuous connectivity to keep services running. Self-driving cars use a variety of connected sensors including GPS, radar, and light imaging detection and ranging (LIDAR) to build internal maps, avoid obstacles, and make decisions with the help of artificial intelligence (AI) engines. All these sophisticated features require connectivity to operate, and if the car loses signal when it drives out of range of its home network, that could pose a major problem. With a multi-IMSI system, autonomous cars can easily switch to the network with the strongest signal in a given area 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—and this switching logic can cause longer registration times and varying service experience. 

In contrast, Hologram’s global IoT SIM and eUICC SIM platform (Hyper) give IoT devices the power to switch automatically between carriers without delays, always optimizing the best possible coverage in a given area. Our goal is to provide the best possible profile with access to as many carriers as possible for your deployment. That way, you can localize once to a great profile, rather than potentially watching your devices cycle through IMSI profiles in the field.

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