The subscriber identity module (SIM) in plastic card format has become the ubiquitous means of identifying a subscriber to a mobile network. It has provided an easy to use, globally-accepted way for mobile network operators (MNOs) to authorize and allow devices to connect to their networks, safe in the knowledge that they can bill the subscriber and they know what devices are connecting to their infrastructure. However, while plastic cards work well for consumer devices and many connected devices, the massive volumes associated with hyperscale IoT deployments means plastic SIMs are impractical.

There are several further drawbacks. A significant issue with the traditional plastic SIM is cost. This is cheap in the context of a human mobile subscriber but for IoT devices, the SIM has to be manufactured, distributed and installed and the IoT device needs to have the appropriate socket into which a card can be slid. This issue is compounded if a SIM needs to be replaced and causes huge expense in terms of truck roll as people go out into the field and swap SIMs over. This limits choice of mobile network and constrains the business case for many lower value IoT applications.

The SIM remains vital because it is a secure element, it contains user information and keys, and it simplifies the device activation and deployment process. Embedded SIM – or eSIM – builds on the simplicity of the plastic SIM card and enables remote provisioning with the SIM which is now a profile that is able to be downloaded into a secure element. This means there is no need for plastic cards and SIM sockets, through which dust and moisture can enter a device, and an eSIM can be preinstalled onto a device with upgrades and operator changes handled over the air.

Critically, eSIM is a GSMA global specification and it maintains the equivalent level of security and protection offered by traditional SIMs. On first connection, an eSIM utilizes a preloaded bootstrap profile and then connects to a mobile network operator to perform an initial profile transaction. In this way, eSIM enables greater design and deployment flexibility but there are still constraints because operators do not want to open their IT systems to outside control.

Remote provisioning therefore involves the exchange of sensible information and the business case for the mobile operator or mobile virtual operator is based on a closed subscription model. The full promise of remote provisioning has not been reached today because, even though that is technically possible, hurdles remain to be overcome for the business model.

There are several different SIM-related options now available to IoT organizations. These include the software SIM that runs SIM code inside and IoT module, chipset or MCU and emulates a physical SIM. These are also sometimes called virtual SIMs.

Integrated or iSIMs are now increasingly popular and as the name suggests, these are integrated into modules and chipsets that programmed at the factor and currently don’t support over-the-air (OTA) updates. iSIMs also rely on large order quantities of more than 200,000 per year. Developed by Kigen, an ARM company, iSIM is support by Quectel modules based on Sony Semiconductor IL (formerly Altair) chipsets, such as the Quectel BG770, for example.

Finally, the virtual SIM or vSIM is an ongoing development supported by Quectel modules based on Qualcomm and ASR chipsets. Similarly to iSIMs, vSIM need to have large order numbers and are programmed at the factory without OTA update capabilities.

Ultimately the market will move to eSIM, utilizing embedded universal integrated circuit card (eUICC) technology to eventually enable OTA updates and enormous operational flexibility while still retaining the security aspects of traditional SIMs. The next few years will see sustained efforts to refine the business case and foster further standardization so eSIM can be used in global markets. Inevitably this will take time but the IoT market’s direction of travel away from plastic SIMs – whatever the form factor – is set.

The opportunities and challenges associated with eSIM design and development have been explored in greater detail in a recent Quectel Masterclass that brought together the company’s SIM experts with a live audience. The Masterclass also featured a Q&A session in which many useful insights were provided. You can listen to the master class here.