SIM & eSIM
I was asked earlier in the week what is the difference between a SIM and an eSIM.
At the simplest level an eSIM is the software version of the plastic SIM card. eSIM origins are primarily around the drive by smartphone manufacturers to find ways to save space in their devices for other features such as second and third cameras, video processors, and of course larger batteries. The reduced real estate requirements of an eSIM also leads to the opportunity for cellular capability to be implemented into much smaller devices such as location tracking devices and smartwatches where a SIM slot may not be practical. It is expected that Internet of Things (IOT) devices will drive dramatic uptake of eSIM.
The first Subscriber Identification Module (SIM) cards were the size if your Visa/Mastercard Credit Cards. A little known fact is that a SIM card and a “chip” credit card are technically identical except they have a different “application” on the chip. The chip is underneath the gold contacts. Both SIM cards and Credit cards are mini computers known as Java Engines that use external power such as from the phone battery or eftpos machine, to run the computer and startup an application. In the case of the SIM card the application is an authentication program to request access to a mobile/cellular network. The Credit Card has a financial banking credit/debit application.
Each SIM card (and Credit card) has a globally unique ID known as the Universal Integrated Circuit Card Identifier (UICCID).
Within the SIM card (or eSIM) each “authentication application” has a globally unique identifier known as International Mobile Subscriber Identifier (IMSI). The IMSI links the SIM/eSIM to a specific mobile/cellular network so that, both at home and when you are roaming internationally, your SIM/eSIM and its associated authentication can be routed to your home network and you can get service. The home network being the company you pay your mobile bill to. One thing the SIM/eSIM does not contain is your phone number.
One of the big disruptions eSIM brings to the telecommunications industry is to the companies and logistics processes needed to manufacture and distribute credit card size pieces of plastic. With eSIM none of these companies or processes are required.
Other than space saving the other key aspiration for eSIM is to enable you to change your mobile/cellular provider by simply going to their website and downloading an eSIM for their network directly to your phone, usually via wifi. No going to stores or waiting for courier parcels to turn up to get your new SIM card. The international standards allow for multiple eSIM instances to be held on a single device.
The full-size SIM (or 1FF, 1st form factor) was the first form factor to appear. It was the size of a credit card (85.60 mm × 53.98 mm × 0.76 mm).
From <https://en.wikipedia.org/wiki/SIM_card>
Types of SIM cards
Different form factors (FF) co-exist:
The credit-card sized SIM is obsolete
A regular SIM or 2FF measures 15 millimeters by 25 mm
A smaller version of the SIM called the micro-SIM, or 3FF SIM card (Third Form Factor), is 12mm by 15mm
The nano-SIM or 4FF is 8.8 mm by 12.3 mm
From <https://www.thalesgroup.com/en/markets/digital-identity-and-security/technology/sim>