What is an iSIM, and how does it work?

eSIM technology has already disrupted the telecom industry, making physical SIM cards less important and changing the way devices connect. Now, iSIM technology is taking things a step further with an even more integrated approach. But what is an iSIM, and why should you care? Let's break it down and see how it stacks up against traditional SIMs and eSIMs.

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8 min read

What is an iSIM, and how does it work?

What is an iSIM (integrated SIM)?

An iSIM (integrated SIM) is a SIM card built directly into a device's chipset. Like an eSIM, it’s used to connect a device to a mobile network without a physical SIM card. But unlike traditional SIM cards or eSIMs, which are separate components, the iSIM is embedded at the hardware level, removing the need for a SIM slot altogether.

This innovation is the next step in SIM technology. Traditional SIMs have served us for decades and eSIMs introduced more flexibility, but iSIM goes further by embedding SIM functionality directly into the device's processor. iSIM’s integration into the chipset allows for smaller, sleeker devices and boosts security and energy efficiency.

iSIM also makes switching networks or adding new services much simpler. Users can download subscription profiles directly from the service provider, avoiding the hassle of handling physical SIM cards or visiting a store.  

What is the function of iSIM? 

iSIM technology allows devices to connect to cellular networks without a traditional SIM card or an embedded SIM (eSIM) soldered onto a printed circuit board. It securely stores network credentials and facilitates communication between devices and mobile carriers.

iSIMs aren't just for smartphones — they can provide cellular connectivity to devices with size constraints, like smartwatches, and to battery-powered IoT devices. Freed from a physical SIM, iSIM technology allows manufacturers to design devices in entirely new shapes and forms, with fewer limitations. This is especially important as 5G and low-power wide area (LPWA) networks expand, allowing more IoT devices to connect in large, inter-communicating systems.

Here's how iSIM works in different use cases:

  • Wearables. Smartwatches, fitness trackers, and other small devices use iSIM’s tiny size to provide secure mobile connectivity without compromising on design.

  • Internet of things (IoT). iSIM offers reliable and secure data transmission for various connected devices, from smart fridges to industrial sensors.

  • Connected cars. In vehicles, iSIM supports secure and reliable communication for features like real-time traffic updates, remote diagnostics, and even autonomous driving.

How does iSIM work? 

iSIM works by running SIM functionality within a secure enclave embedded in a device's system-on-chip (SoC). The SoC is a single chip that integrates all the necessary electronic components for the device and hosts the SIM operating system. The secure enclave replaces the removable SIM card, making sure sensitive data like subscription details and security keys are tightly protected on the device's hardware.

When the device powers on, the iSIM uses its secure integration to authenticate the device with the mobile network provider — just like a traditional SIM, but without a physical card.

SIM vs. eSIM vs. iSIM

To understand the impact of iSIM, it helps to see how SIM technology has evolved over time. Let's compare traditional SIM cards, eSIMs, and iSIMs.

Traditional SIM cards

A traditional SIM card is a removable card that you insert into a device. While it’s been the standard for decades, it has obvious limitations:

  • Physical changes. Switching cellular networks requires physically replacing the SIM card, which is inconvenient.

  • Device design constraints. They need a dedicated slot in the device, taking up valuable space that could be used for other components.

  • Fixed functionality. A traditional physical SIM card comes pre-programmed and linked to a single mobile network operator.

For cellular IoT applications, these limitations become even more problematic. Devices may be deployed in remote or hard-to-access locations, making it impractical to replace SIM cards manually. Many of these issues are addressed by eSIM technology.

eSIM (embedded SIM)

eSIM (embedded SIM) cards are built directly into the device but are not part of the processor. They're non-removable and support remote provisioning, making it easy to switch network carriers without swapping a physical card. The eSIM technology also frees up space in devices by eliminating the need for a SIM slot.

In consumer devices, eSIM is often associated with downloadable software profiles, activated through QR codes.

For more on how eSIM compares to traditional SIM cards, check out our eSIM vs. SIM guide.

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iSIM (integrated SIM)

iSIMs take SIM technology to the next level by embedding SIM functionality directly into a device's system-on-chip (SoC). They offer the same network authentication, security, and connectivity as eSIMs but with some key advantages.

Because they're fully integrated into the chipset, iSIMs use less power, enhance security, and save even more space inside devices. This makes them perfect for smaller devices and IoT applications. 

Benefits of iSIM

iSIM offers several key advantages for both consumers and manufacturers. 

Smaller size

An iSIM card is tiny, with a surface area of less than one square millimeter. Compared to a physical SIM or an eSIM, which require dedicated space in a device, an iSIM frees up valuable room for other components and enables more compact devices. This is great news for IoT device manufacturers, who often work with tight size constraints. For example, it's very useful in applications like electricity meters, medical equipment, or vehicle telematics systems. In telematics — especially for autonomous vehicles — iSIM plays a key role in monitoring critical data, such as navigation, diagnostics, and traffic conditions.

Cost efficiency

By integrating SIM functionality directly into the chipset, iSIMs remove the need for SIM slots or additional soldered components. This reduces manufacturing costs, allowing device makers to pass these savings on to consumers.

Lower power consumption

Without the need for extra hardware, iSIMs have much lower standby power consumption than traditional SIMs and eSIMs, allowing to extend battery life. This is especially important for IoT devices, where longer battery life is a critical feature.

Improved security

iSIM technology improves device security by being inherently harder to steal than traditional SIMs. An iSIM is embedded in a secure enclave within the device’s system-on-chip (SoC). This enclave is protected by a tamper-resistant element (TRE) — a hardened silicon layer with cryptographic functionality, recognized by the Trusted Connectivity Alliance for its security. The lower number of components also reduces the device's overall attack surface.

iSIM future

As iSIM technology matures and becomes more widely adopted, it's set to unlock new possibilities and transform industries. 

Imagine smart devices that collect and share data seamlessly, helping businesses improve both physical assets and their operations. For example, Vodafone has proposed using iSIM-powered smart labels to track parcels in real time. These labels could monitor their location and condition throughout the shipping process, offering a modern alternative to RFID tags.

Looking further ahead, iSIM could help reshape device design. For example, if processing capabilities for consumer devices like mobile phones shift to cloud servers, an energy-efficient iSIM would be key to providing seamless connectivity. 

Integrating iSIM into IoT devices today comes with challenges, but the benefits — smaller designs, lower manufacturing costs at scale, and better energy efficiency — are hard to ignore. It’s only a matter of time before iSIM becomes a standard feature in everything from wearables to household devices.

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    saily blog author ugne zieniute
    Ugnė Zieniūtė

    Ugnė thrives on exploring new places and capturing moments on the go, so it’s no surprise her social media comes back to life whenever she’s abroad. An avid traveler, she believes staying connected with an eSIM is as essential as packing a passport, ensuring seamless adventures wherever she roams.