What is eSIM and how does it work?

eSIM is not new in the world, it has been there for some time, but few people understand what it is. In talking to people around me, I realized that many have never heard of it. In this article, I will explain, as always, as easily as possible what eSIM is and how it works.

I touched on this technology in an article on SIM card sizes and wrote that there will be a separate article on eSIM - and here it is.

So, eSIM is an abbreviation for "Embedded SIM", more precisely "Embedded Subscriber identity module". We could translate it into Serbian as a "built-in SIM card", which it is.

Advantages of eSIM

SIM cards have shrunk overtime to make more room for other components in the phone. So we came from the classic SIM to the Nano-SIM and stopped there - more. What next? The solution is simple: install the chip in the mobile device itself, which will have the function of a SIM card.

This is especially suitable for smartwatches. Since smartwatches are small, every millimeter is important. The Nano SIM card adapter is too big for a smartwatch, so eSIM is the ideal solution.

Then the speed and ease of changing operators and/or service packages. The user does not have to go to the operator if they want to switch to someone else, they can do it all from home. All it takes is to go into the phone setup and download the operator configuration available in its environment.

Roaming? Perhaps the biggest advantage of this technology is that we will be able to change operators abroad while keeping our number. So, you cross the border, choose an operator from that country in a few moves, and you are left with your number and you are not roaming anymore.

And finally: IoT devices. Because the eSIM chip itself is small and programmable, it is suitable for IoT devices. The IoT network will be bigger and bigger and that is why it is important to facilitate the process of connecting hardware to that network.

How does eSIM work?

The eSIM chip is installed by the manufacturer of the mobile device in the motherboard of that device. This chip has all the features of a classic SIM card, but it also has the  M2M (Machine to Machine) protocol and Remote Provisioning capabilities.

When the manufacturer installs this chip on the motherboard, it is empty. However, in the production process, the so-called Bootstrap profile This profile is the same as any other (created by mobile operators), except that it only allows the device to make the first connection with M2M.

The request is then sent to the desired mobile operator, and it sends a request to the SIM vendor to create a SIM profile for that user. In the end, that SIM profile is written in the eSIM chip in the user's phone, and the "Bootstrap" factory profile is deleted.

When the user wants to change the operator, all he needs to do is request a new SIM profile from another mobile operator and it will be written to the chip and the old one will be deleted. It's all very simple for the user, it all ends in a few steps.

As for the dual-eSIM situation, I only found information on one site - digitaltrends - that it will be possible as well. Specifically, they stated that the GSM Alliance (GSMA) has promised support for multiple accounts, but also that they are still not sure how they will perform it.

When will eSIM be available with us?

Update 2022: all operators in Serbia (finally) have support for eSIM.

As always, Serbia will be late with the world for several years, so I am not very optimistic in this case either. VIP does not support (I did not find anywhere to support), MTS does not support, and Telenor does not support either.

As far as the world is concerned, in the USA this technology is supported by  AT&T, T-Mobile USA, and Verizon Wireless mobile operators. Truephone, which operates in more than 80 countries around the world (including Croatia), also supports eSIM - link.

In short: we will not see eSIM in our country soon, at least not in wide use, but I would like to be wrong, of course.