The SIM Card Is Evolving. Source: Adobe Stock

The traditional SIM card, the physical chip that must be inserted into a mobile device, is also used in IoT devices. However, as new IoT use cases arise, the limitations of the physical IoT SIM mean newer forms of SIM, such as IoT eSIM and IoT iSIM will become prominent. We explain the differences.

Keeping up with acronyms in cellular technologies, specifically the subscriber identity module (SIM), can be confusing. The evolution of the classic SIM card from once being a credit-card size object to a now tiny onboard chip, and soon maybe just a piece of software, is a perfect example of new additions to concept of “SIM.”

When mobile phones came to market, credit card size cards had to be inserted to enable connectivity. On the card: a tiny chip that held identity and authentication keys to enable the phone to connect with its provider. Over the years, with smaller and more compact phones emerging, the SIM card also became smaller. In the end, only the chip itself had to be placed into the device.

But nowadays it is not only phones that are being connected with the outside world. The Internet of Things brought connectivity to all kind of devices . Sometimes it is only a mass-produced tiny sensor that needs connectivity. But manually inserting even a tiny IoT SIM card into it, is neither effective nor user friendly.

eSIM vs iSIM explained

Once again, the customer market is pioneering the new formats. With more sophisticated smartphones or wearables like smart watches or fitness trackers gaining popularity, better ways than manually inserting a SIM card become necessary.

Not just for smartphones: The days of the SIM slot are numbered. Photo: Adobe Stock

This is the time for integrated solutions such as the IoT eSIM, and the IoT iSIM.

The former is soldered directly onto the circuit; the new form factor not only reduces the risk of physical tampering, but also allows easier control of the devices, no matter where they are. The IoT iSIM goes another step further. It consists only of software and will be integrated into the device’s processor, saving even more space on the circuit board.

Let’s take a more detailed look at the IoT eSIM and IoT iSIM.

Embedded SIM – What is an IoT eSIM

eSIM is short for embedded SIM, which is another form of the traditional SIM card. Just like the latter, eSIM is also an integrated circuit (IC) that stores identity and authentication keys to secure customer-specific personal data. The information, also considered to be the operator profile stored on the SIM, is listed below:

• a unique serial number to identify the SIM card – the Integrated Circuit Card Identifier (ICCID),

• the identity of the user of a cellular network – the International Mobile Subscriber Identity (IMSI),

• encryption keys to identify and authenticate the SIM as a valid subscriber to the network,

• temporary local network information,

• access service list,

• Personal Identification Number (PIN), and

• a Personal Unblocking Key (PUK).

The eSIM is the natural evolution of traditional SIMs decreasing in physical size. In an eSIM, the IC chip is soldered/attached/welded directly onto the device at the time of manufacturing instead of being inserted onto the device after manufacturing. This method of embedding the SIM to a device addresses both the size considerations (you can now design more compact and energy efficient hardware) and theft concerns (you avoid the act of physically tampering with the device to remove the SIM to prevent unauthorized uses)

You can add software on the eSIM chip (eUICC software) to run an application that allows you to remotely change your current connectivity service operator to another (remote provisioning). Theoretically this can also be done with a classic reprogrammable SIM card. You may want to do this for cost or quality of connectivity reasons. To do this in a traditional or physical SIM IoT deployment, you need to physically swap out the SIM cards manually and in the field. The eSIM chip and eUICC software eliminate the manual and physical swap by enabling over-the-air (OTA) remote subscription management. This effort is further streamlined as specifications are laid out by GSMA and ETSI , using the term eUICC to distinguish from the eSIM chip.

Because of the eUICC software and SIM’s secure data storage capabilities, you have the option of additional security features without adding to the computing or size burden of your device. For example, OTA capabilities allow you to send firmware updates or security patches simultaneously and remotely over the air for the lifetime of your devices. With the SIM, in whatever form, as the root of trust, you can document and ensure only devices with the correct credentials can gain access to the right network. The responsibility for vulnerability patching may be voluntary now, but we expect this to become a regulatory requirement. Already, the UK government announced the Product Security and Telecommunications Infrastructure Bill in November 2021. Among other requirements, the bill requires device manufacturers, importers, and distributors to stipulate how long customers will receive security patches to fix reported vulnerabilities. This will put the burden of compliance on ensuring OTA capabilities in the first place. Other countries will likely follow similar high threshold of security requirements.

Integrated embedded SIM: What is an IoT iSIM?

iSIM means integrated embedded SIM, which means it is an evolution from the eUICC software functionality. It does everything that the eSIM chip and eUICC software do, and more. It is an improvement in the sense that the eUICC software is designed into a system on chip (SoC) architecture, so cellular connectivity is integrated into the device as one component. This is an upgrade from eSIM because a traditional cellular-enabled device is made up of a processor, modem and eSIM chip or physical SIM -- three components to pay and space to account for. iSIM’s cost of material and footprint benefits means it is best suited to small sized devices that do not have physical space for computing, storage, or security resources. This is ideal for those low energy consumption, resource-constrained devices, such as sensors running on low power wide area networks like NB-IoT.

iSIM is an emerging technology that gives the market something to consider when designing connected products. Because the nature of iSIM’s connectivity and security requirements can be now evaluated at the product engineering design stage, the enterprise customer can expect a more cost effective and secure connected product to come to market. In theory, the fewer components in a product, the lower the cost of manufacturing. Unfortunately, there is not enough commercial adoption by enterprises to provide evidence of comparable capex and opex.

It is early days for iSIM in IoT, but the direction of growth is positive and further reinforces the development of IoT connectivity into a feature that customers can buy as easily as they buy apps on their phones. Operational friction will occur among IoT vendors and customers before we get there but staying digital and agile will deliver answers.

The 1NCE Industrial IoT eSIM in MMF2 Format

At the 1NCE online web shop, we offer all the classic IoT SIM card formats and MMF2 SIM chip format, also labeled as 1NCE Industrial IoT eSIM . It is important to understand that this version does not support eUICC functions as described above. UICC functionality can currently only be offered in selected customer projects and are not yet available as a standard offering via our shop. More details can be found in this 1NCE Industrial IoT eSIM Datasheet .