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What’s the difference between SIM and eSIM?

Connectivity technologies are confusing for people, and the industry is loaded with perplexing acronyms and buzzwords.

One of the most recent areas commonly fostering misconceptions is the difference between SIMs and eSIMs. This article is going to break it down in way that will hopefully help to inform your connectivity conversations.

Understanding SIMs
The abbreviation SIM means “Subscriber Identity Module” and the devices were originally created to identify which subscriber is associated with a phone. Most people have a specific physical impression of a SIM, which is a little plastic card that we slide into a phone. In fact, there are a number of different physical manifestations of what you would know as a SIM card.

The industry has different media on which a subscriber for a device can be identified. In general, manufacturers of rugged connectivity equipment strongly prefer and heavily leverage the MFF2 (M2M form factor). This is also sometimes referred to as a Machine Identification Module, or “MIM.” The reason manufacturers prefer these MFF2 units is because the vibratory specifications for aircraft and off-highway equipment are very unfriendly to SIM cards like the 3FF. During rigorous vibration tests, the shaking of the SIM card against its cage (which creates a phenomenon called fretting corrosion) wears through the very thin metal deposited on the plastic and destroys the card, resulting in the cellular function to stop working. Not cool.

Regardless of whether or not you have a 2FF, 3FF, 4FF, or MFF2 SIM/MIM, that hardware is really just a carrier for the UICC (universal integrated circuit card). This UICC is a read-only network profile. In other words, the device manufacturer will get a pile of chips (in any of the hardware manifestations shown above) that are pre-loaded with keys that cannot be changed during, or after, device manufacture.

Recently, it has become possible to purchase hardware that contains an eUICC (embedded universal integrated circuit card). This change means that instead of having a read-only network key on the SIM/MIMs that the manufacturers receive, this hardware can now be programmable and can host keys from multiple carriers on a single SIM/MIM. Some people initially think “great, I can tell AT&T to get lost and just program my unit over the air to work on Verizon whenever I want.” Unfortunately that isn’t true. Although that would be a great capability and introduce helpful flexibility for a lot of customers in many applications, you simply cannot do that today with an eUICC.

However, this is still really cool for manufacturers.
Here is why you should be excited about eSIM capabilities. Device manufacturers will often work with a carrier partner (e.g. AT&T, KPN, Rodgers, T-Mobile, Verizon, Vodafone, etc.) to certify a device with a specific carrier. Then, behind that carrier are dozens of local networks that will support these devices.

What the eSIM allows people to do is have multiple network profiles for local carriers on a single product, and update those over the air. When a vehicle travels from geography to another while using the same carrier, your device manufacturer can update the device to provision it for the local network, without changing a SIM. This is really powerful for getting products into geographies where cellular plan and regulatory constraints have historically driven a multitude of additional device SKUs and given manufacturers significant headaches managing equipment export — or equipment travel from one geography from another.

Some examples:

You build a vehicle in North America or Europe and export that vehicle to Brazil. This has historically been a really painful thing for manufacturers, requiring them to manage a SKU specifically for Brazilian equipment or have a local service representative input SIMs and execute local provisioning in a very manual way. All of this has a lot of friction in the manufacture and distribution of connected vehicles.

You have a vehicle that typically operates in one geography travel into another. If an aircraft flies, for example, from the United States to Brazil or from western Europe to Russia, sometimes such network transfers have been challenging for onboard connectivity equipment. The eSIM technology will significantly simplify such transitions.

For equipment manufacturers, eSIMs are going to be a powerful tool for simplifying connectivity of a fleet while minimizing the burden on the manufacturer and reducing the number of device SKUs required to achieve truly global connectivity.

David Batcheller – President & CBO