Embedded-SIM Intro – Part 6 – Companion Devices

Wow, this is already part 6 of my introduction series on embedded SIM cards and it’s not going to be the last, there are still a few topics left. Today, a few words about what are referred to as ‘companion’ devices.

As discussed in previous posts, one requirement to download a virtual SIM (a profile) into an eSIM (i.e. the eUICC) is an Internet connection. That’s not a problem for devices such as smartphones and tablets as they can initially use their Wifi interface to download a virtual SIM. But there are other devices such as smartwatches that only include a cellular modem and Bluetooth to talk to other devices nearby, i.e. a paired smartphone. In the ‘companion’ device approach, that watch uses the smartphone and the Bluetooth link to connect to the Internet. Interestingly, this particular mechanism has not been standardized by the GSMA but is vendor specific.

At first I thought that the LPA app runs on the smartphone and interacts with the eUICC on the companion device, e.g. the watch. But this is not the case, the LPA app runs directly on the watch as shown in Chapter 4.8 of GSMA SGP.21. The GSMA spec leaves it open if the LPA offers a user interface for downloading and managing virtual SIM cards directly on the companion device or on the ‘primary’ device, e.g. the smartphone. In many cases a mix might be necessary, for example if the companion device does not have a camera to scan the 2D barcode with.