Wireless Service

From SIM to eSIM to iSIM — The Evolution of Device Identification

By
Kyle Reyes
May 16, 2023

We all have cell phones. They are integrated as a near-necessity in our daily lives, and every one of our devices needs to connect to the mobile network, and companies need to keep track of us so they can figure out how much we owe for our service. The SIM card, or “subscriber identity module,” does the heavy lifting in that connection. SIM cards have been around for a long time, and steps are being taken (eSIMs and iSIMs) to upgrade the tech and reduce the space necessary information takes up in our devices. 

You may still have a SIM card in your device because cell providers want to keep SIM cards active on their carrier for as long as possible. If a carrier said they would deactivate all their SIM cards and force people onto eSIM cell phone plans, they would likely lose a chunk of their user base as anyone who wanted to keep their physical SIM card would move to a carrier that allowed that. The switch will happen eventually, but there are a lot of forces keeping physical SIMs active. 

This article will cover SIM cards, eSIM cards, the Internet of Things, and iSIM cards. While there’s a lot of talk about SIM cards and how the transition to eSIM will affect your mobile device, real breakthroughs are happening in smart devices worldwide. As the name suggests, embedded SIM cards are stuck in the device. As a result, they are remotely reprogrammable, which is huge for companies with thousands or millions of smart devices spread out across a factory or urban area. More on that later. Let’s jump into our article and start with the history of SIM cards.

The SIM Card

Smartphones are getting increasingly complicated, and to keep them functioning fully, they need to optimize all they can. It follows that they turned to the SIM card to save space. 

SIM cards have been around for a rather long time. They started as a way for users to track their phone usage so companies could charge them accurately each month. SIM cards started out with some serious size, but that was when phones were much larger than they are today. As phones have gotten smaller and more complicated, SIM cards have reduced in size to keep up with the new technology. Nano SIM cards, the smallest standard size, are now way bigger than they need to be compared to the information they have to store. SIM cards store the information that designates your phone and lets it connect to the network, but it stores the same information they did in the nineties. Let’s travel back there to a time when SIM cards were the size of a credit card and look at — The Standard SIM

The Standard SIM Card

In an age where phones were much larger, people would carry around, in essence, a credit card with SIM information that contained their billing information. Whenever they got to a phone, they would slot it in and could use the phone to make calls. This was a nice way to utilize phones, as you could move any number of phones a day and pay for each of them on the same account rather than carrying around enough change for payphone use. Interestingly, the chip on physical SIM cards is the same model as chips in credit cards (ISO/IEC 7816). When swapping phones was this ordinary, the slot to input a Standard SIM was easy to access and operate, not like the tiny SIM slots we have on phones today. 

As phones increased in portability and decreased in size, there was a need for smaller SIM cards. The actual SIM portion never took up the whole card, so it was easy to design a smaller model to fit into a phone and stay there. Thus, the Mini SIM came to be. This much smaller card saved on space and became semi-permanent in devices. If they so chose, people could still swap out their SIM cards, but they no longer had to, as they always carried their personal phones with them.

What Does a SIM Card Do?

What connects your smart device to a mobile network? A SIM card, of course! They use a bit of your phone’s power to broadcast your phone to the network. They have some storage space (usually 265 KB) but are very size-inefficient compared to the alternatives. With increases in technology, the size of a nano SIM card (holding 256 KB) if converted to storage, could hold around 1 TB of data. That’s a pretty significant difference. If you recall the outrage about removing headphone jacks in the past, you may deduce that phone manufacturers take their space pretty seriously. Every phone's millimeter must be optimized to maximize storage, processing power, camera strength, and battery life. In the age of this optimization, we arrive at the eSIM card. Let’s get into it. 

The eSIM Card

Smartphones are not where eSIMs are making the most splash, and many cell phone carriers are not that into making the change. It is the cell phone manufacturers that are driving the change to eSIMs. 

The physical SIM card has gotten smaller over the years but remains an insertable chip into your phone. With the entrance of eSIM (embedded SIM) cards, they no longer are a chip inserted into your phone, they are a part of the hardware inside. 

Phone manufacturers have embedded SIM cards to save major space within the device. Nano SIM cards are pretty much as small as physical SIMs can get in their current form, so a more efficient card is needed to become hardware embedded within the device. They still do the same things but are much smaller and can now be reprogrammed with different carriers and wireless providers as needed. Embedded SIM cards started at about half the size of nano SIM cards and are now about 2mm square. The switch to an embedded SIM card saves a lot of space as it also means there is no SIM card tray or SIM card opening. These open up a lot of space saved. The first eSIM cards were on smartwatches, where the space starts smaller, and eSIM cards let them connect to the internet without worrying about the whole physical SIM card aperture. 

Flagship Phones are Transitioning to eSIM Only

As we said in the opening, the desire for backward compatibility has kept SIM slots in many phones, but some of the newest phone models are without SIM card compatibility. The iPhone 14 series is eSIM only, as well as some of the Galaxy S23 series. This puts a soft cap on how long physical SIMs will remain on the market. When, for instance, the iPhone 13 series gets so old that they are no longer functional, then iPhones will be eSIM only! The exact timeline may depend on when carriers start moving to eSIM only, but only time will tell. 

Transferring Accounts from physical SIM to eSIM

The switch from physical SIM to eSIM on the same phone is relatively straightforward. If you are changing devices, all you need to do is choose a mobile phone that supports eSIM cards, pick out a plan, and choose the eSIM option when you check out. 

In terms of operation, eSIM cards make switching carriers a bit easier and harder to switch devices. At the end of the day — not a big deal. 

For now, when you choose a cell phone and cell phone plan, you are likely able to choose between a physical SIM card or an eSIM card, depending on your personal preference. Importantly — both provide the same benefits to your device. If you are comfortable with your current setup, you will not need to switch to an eSIM immediately. 

The Internet of Things 

There are so many smart devices around. Any device connected to the internet is considered a smart device, be it a toaster, a fridge, or a lamppost. 

The Internet of Things describes all small objects connected to the Internet. Objects like traffic lights, watches, appliances, security systems, and all “smart” technology are devices on the Internet of Things. Many of these devices are small or optimized to be as small as possible. An eSIM card instead of a physical SIM card allows those devices to stay tiny and easier to manufacture. The gradual decrease in SIM card sizes lets manufacturers optimize their devices more and more, utilizing space for other key electronics. Alongside the decreased size, the eSIM is soldered into the device, nixing any need for a SIM card slot that’s reachable from the outside. Integrating eSIMs into smart devices instead of physical SIMs opened many doors for product designers to find better models for their electronic devices. 

A Brief History of the Internet of Things

The true beginning of the internet of things was back in the early 1980s. That’s right, before the internet as we know it even existed. It all started with a Coca-Cola vending machine on Carnegie Mellon’s Campus. This machine was connected to an early version of the internet (called ARPANET), and it used that connection to deliver two pieces of data: the machine’s inventory and the temperature of the drinks. 

Time went on, and more and more devices were connected to the internet. As that number grew so did the possible applications of their interconnectivity. Back in the late 2000s, the number of devices connected to the internet surpassed the number of people on the planet. Now, in 2023, there are more than 10 billion devices connected to the internet. This staggering number is opening doors every day as people research and develop ways that we can leverage all of this connectivity to better our lives. 

Remote Programmability with eSIM Cards

Perhaps the most significant change, however, is the ability to reprogram the SIM cards of devices with eSIMs remotely. This marks a huge difference in IoT device functionality and opens up a much more flexible workflow. Whenever a device requires a software update or a change to its mobile network, that change can originate from the main building rather than at each device individually. 

The transition from physical SIM cards to eSIM cards helped this development. As iSIM cards become more popular, devices will likely change from eSIM to iSIM for further optimization. 

Applications of Smart Devices

This ability for remote change means eSIM or iSIM management can happen in bulk. Manufacturing plants with thousands of machines in their warehouses can send a blanket order to all their devices with a button. Using eSIMs also assists companies that provide mobile service plans to their employees. If thousands of employees use company phones and the company decides to change providers, all of those changes can happen simultaneously rather than waiting on the bulk shipment of physical SIMs. Overall, corporate management of cell phone plans is made much easier by integrating eSIM cards and plans. 

IoT devices provide great boons to manufacturers interested in increased remote control over the software in their devices. In many industries, connecting more and more devices to a central network greatly benefits the company and the employees. Smart devices increase efficiency and automate various processes throughout a company. While eSIMs are popular in various industries, major wireless providers have not always been keen on adopting eSIMs over physical SIM cards. Embedded SIM cards have many advantages over physical SIMs in small, numerous machines, but the differences in a smartphone specifically are much less noticeable. 

The iSIM Card 

Moving on from eSIMs, which are still very popular today, we arrive at iSIMs. The transition to eSIM saves a lot of space in relation to physical SIM cards, but SIM cards can get smaller than that. Another kind of technology is called a System on a Chip or an SoC. The SoC is a single-chip package that combines many common components, like the CPU, GPU, audio, and modem. The SoC is designed to include anything universal across any model. The integration of SoC results in lower power usage and a smaller board footprint. This is crucial in smartwatches where, like the integration of eSIMs, it lets them pack much more power and battery in the small devices. Adding a SIM card to the SoC makes a lot of sense for smart devices. SIM cards are a simple component to add to the SoC, meaning the iSIM card becomes really, really small. It ends up being less than one millimeter by one millimeter. A lot of the latest and greatest smartphones have SoCs integrated into them. 

A SIM business named Kigen states, “[iSIMs are] 98 percent smaller, 50 percent cheaper, and use up to 70 percent less power” than eSIM cards. That is quite the sell. iSIMs are programmed to function similarly to eSIMs in terms of activating devices, changing the account within the chip, and using the same system as eSIMs so any carrier that is okay with eSIM will also be okay with iSIM. 

There are a lot of devices that use iSIMs, but it has not made it into the smartphone scene just yet. While the size, cost, and power reductions are nice, they are tremendously small relative to the rest of the device. These big reductions are much more important in other Internet of Things devices, and their prevalence in that sphere is a testament to that optimization process. That being said, we think that the jump from eSIMs to iSIMs will happen much faster than the switch from physical SIM to eSIM. 

Smart devices are everywhere. eSIMs and iSIMs occupy these devices, letting them connect to the internet. 

From physical SIM to eSIM to iSIM, the basic technology has remained the same throughout the decades. Our ability to squeeze that information into smaller and smaller spaces has increased significantly and, in our quest for optimization, we have designed miniscule receptacles for the SIM information. Before you go, we wanted to put together some key takeaways from this information-laden article. 

  • In the beginning, there were SIM cards the size of credit cards that people carried with them to use the phone. 
  • When phones transitioned to be more mobile, SIM cards reduced in size to accommodate the change. 
  • The rise of eSIM cards is most popular in other industries, with the cell phone industry lagging behind.
  • The flagship phones of big manufacturers no longer have physical SIM slots, and just about every major wireless carrier and MVNO has eSIM compatibility. 
  • There are a lot of eSIM and iSIM applications on the Internet of Things that are still being researched and developed. 

SIM vs eSIM vs iSIM does not affect your phone’s operation, but physical SIM cards will gradually phase out from popularity over the next few years.

Kyle Reyes
Kyles Reyes is a journalist from Pittsburgh, PA that specializes in the wireless industry, phone plan comparisons & advice.
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