What is an iSIM?

24-01-2022 |   |  By Robin Mitchell

Recently, Qualcomm demonstrated the worlds first smartphone using an iSIM. What is an iSIM, what advantages does it bring, and could it be problematic for future designs?

What is an iSIM?

Subscriber Identity Modules, also known as SIM cards, are an essential piece of hardware needed to communicate with cellular networks. A SIM card holds all the required credentials, keys, and decoding algorithms needed for a device to authenticate itself with the mobile network. Over the years, SIM cards have reduced in size thanks to improvements in technology, and it has gotten to the point where SIM cards are now the size of the chip and associated contact pads.

While SIM cards are a reliable method for authenticating devices, continuing improvements in technology combined with the desire for smaller devices puts pressure on device manufacturers to remove wasted space. Of all components in a modern phone, SIM cards have the biggest space to functionality ratio, meaning that they use up large amounts of space for what they provide. For example, a silicon die the size of a SIM card would be able to have multiple cores, a large cache, a graphics processor, and other peripherals.

This need for reduced device size has resulted in the eSIM, a SIM card that is just the chip and directly mounted to a device PCB. But engineers have now recognised that mobile processors and SIM cards are almost always used in the same application and thus have developed the iSIM, a SIM card integrated into a mobile processor.

What advantages does an iSIM present?

The first significant advantage of iSIM technology is the reduced PCB footprint. SIM cards are always needed in cellular devices, and because mobile devices almost always use a mobile processor, moving the SIM chip into the mobile processor only makes logical sense.

The second major advantage to iSIM technology is security. It is surprisingly easy for an attacker to remove a SIM card from modern phones, and once obtained, can use this SIM card to look through messages, make calls, and even steal an individual’s identity. Considering that mobiles are increasingly being used for verification for banks and other services, gaining access to someone’s text messages could be the only thing needed to access sensitive information. By integrating the SIM into the processor itself, attackers cannot access the SIM card, nor can they remove it.

The third major advantage to iSIM technology is that it can help to improve the useability for consumers. Traditional SIM cards are fixed to a specific service provider, which means that consumers need to obtain a new SIM if a different service provider is chosen. iSIM, however, can allow for reprogramming without needing to make any hardware changes.

What challenges could iSIMs present?

While iSIMs could provide a wealth of advantages to consumers, they are not without their flaws. However, the shortcomings associated with iSIMs mainly arise from how a manufacturer implements their use.

By far, the biggest threat that devices face when using iSIMs is if the manufacturer of the mobile devices disables reprogramming of the iSIM. This will likely be done by mobile network operators looking to lock customers into plans that make it impractical to switch networks.

The second major challenge faced with iSIMs is that if they do not support reprogramming, then switching networks will require a new device entirely. Not only will this potentially violate consumer laws regarding monopolies and freedom of choice, but it could even result in increased amounts of unnecessary e-waste as customers purchase new phones to move to different networks.

The third major challenge presented by iSIMs is that the SIM card itself may be challenging to dispose of. A device that is thrown away or sold off will still have the iSIM inside it, and if the iSIM does not allow for reprogramming, then it would leave the original owner at serious risk.

In conclusion, moving SIM technology into mobile processors only makes sense, but it is essential that manufacturers using iSIM technology must allow for reprogramming and erasing of SIM data.


By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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