SoftSIM vs eSIM vs iSIM: Comparing modern SIM form factors

The SIM, or subscriber identity module, is what identifies a particular user and allows your phone or IoT device to access its mobile plan. It does this using an IMSI (international mobile subscriber identity) number and key, a unique 19- or 20-digit serial number that’s assigned to the SIM. 

Traditional SIM cards come in several sizes or form factors:

• 1FF – 85.60 mm × 53.98 mm × 0.76 mm
• 2FF (mini) – 25mm x 15mm x 0.76mm
• 3FF (micro) – 15mm x 12mm x 0.76mm
• 4FF (nano) – 12.3mm x 8.8mm x 0.67mm
• MFF2 (embedded) –  5mm x 6mm x 1mm
• WLCSP (embedded) –  2.7mm x 2.5mm
• MFF-XS (embedded) – 2.6mm x 2.4mm

Now, new SIM standards are shaking up what is possible. When comparing IoT SIMs that offer global coverage and optimise battery usage, you should now consider eSIM vs iSIM vs SoftSIM.

Let’s compare these three modern SIM form factors.

Evolution of the SIM

Historically, the SIM was almost a computer in itself. Developed in 1991 by Giesecke & Devrient, the original SIM card was the size of a credit card (85mm x 53mm).

Subsequent models shrank smaller, first with the mini-SIM, then the micro-SIM. Each one had the same functionality and contact points and circuitry as the original SIM card, but was more compact, helping to enable connectivity for smaller devices.

The tiny nano-SIM (roughly 12mm x 9mm) emerged in 2012, reducing the contact area but maintaining the arrangement of components. The iPhone 5 was the first device to use the nano-SIM, and it’s still used in most smartphones today. 

What is eSIM?

The SIM’s footprint got even smaller with the introduction of the eSIM in 2016. The eSIM is an embedded SIM card (aka MFF2) that’s physically attached to the device — soldered to the motherboard — and cannot be removed. 

Typically, eSIMs go hand-in-hand with the eUICC architecture. This means that rather than removing and replacing physical SIM cards, device operators can use remote provisioning to swap out the subscriber identity module “over the air” (OTA).

This ability to seal the SIM into the device makes eSIM an excellent option for devices that need to be airtight or watertight and be able to withstand vibrations (often called ruggedized in the industry). Prime use cases for eSIM-equipped devices include manufacturing, asset tracking, wearables, and connected vehicles.

Learn more about eSIM with this in-depth explainer: What are eSIMs?

What is iSIM?

Introduced by Qualcomm/Thales in 2022, The Integrated SIM or iSIM takes the idea of the eSIM even further.

Rather than a chip soldered to the circuit board, the iSIM is located inside the device’s system-on-a-chip (SoC). Because it’s built directly into the device processor, it introduces a new level of streamlined operations between the SIM and the device system.

Older SIM cards and eSIM chips were still separate systems that needed to interface with the device system, while the iSIM integrates SIM features more closely with the device hardware. 

Still, iSIM requires an integrated chip, so it’s not quite unified with the device’s hardware.

What is a software SIM (SoftSIM)?

Enter the Software Sim (SoftSIM), a completely software-based SIM that removes the SIM hardware from the equation altogether.

The first fully software SIM, the Onomondo SoftSIM has no hardware component. It’s downloaded from the cloud onto an existing module on a device, where it co-exists with other applications.

The SoftSIM serves the same function as a SIM card or SIM chip, but does it entirely through running a software program on the device’s existing hardware.

The SoftSIM is a library that can handle Application Protocol Data Unit (APDU) commands.

These commands are typically passed between the module and the physical SIM, but for the modules integrating SoftSIM, they are passed to the SoftSIM component instead. Then, the SoftSIM component manages access to key material and other relevant files or assets, using the keys to authenticate the network and the device.

SoftSIM follows GSMA guidelines, so the user interface is identical to that of a regular SIM. In other words, it looks and acts like a traditional SIM.

Comparing eSIM vs iSIM vs SoftSIM

Representing steps in a rapid evolution of SIM technology, the eSIM, iSIM, and SoftSIM all offer advantages for IoT applications over their predecessor, the physical SIM card.

Let’s take a closer look at the pros and cons of each SIM iteration to help you evaluate which is best for your device application:

• Size
  Clearly, SoftSIM wins in this category because it’s entirely software-based and uses no physical space. That means you don’t have to consume power or use space on a circuit board for it. While both require physical elements, iSIM chips edge out eSIM chips in the size category as they’re usually a bit smaller.
  
• Power consumption
  Of the three, eSIM consumes the most power as it’s a computer of its own with a CPU and memory, both of which cause a significant battery drain. Some newer and more expensive IoT SIMs allow for aggressive power-saving modes (PSMs), but these do not make economic sense for many use cases. While it’s integrated more with the device system than the eSIM, the iSIM still drains more power than does the SoftSIM. The SoftSIM takes power usage to a minimum while still offering the same SIM functionality as an iSIM or eSIM, helping to extend the lifetime of batteries in your IoT devices. 

• Compatibility
  Because they include physical hardware, the eSIM and iSIM must be included in device designs and built into modules at the time of manufacture. However, they are compatible with most IoT hardware components and modules. SoftSIM is chipset agnostic and can work on any device with a modem, microcontroller, and radio module — meaning that most IoT devices are capable of using it. Currently, the SoftSIM interfaces with a limited number of hardware configurations (see the current list of devices supporting SoftSIM), but that will change as it goes into wider release. You can also hook a device’s modem up to the microcontroller, which acts like a SIM card, presenting a SIM interface to the modem. Internally, the microcontroller uses SoftSIM to implement the protocol and uses the peripheral controllers to implement the physical interface. This “dummy” SIM card workaround requires some minor hardware changes, though, so it isn’t a practical choice for existing devices. 

• Cost
  SIM hardware comes at a cost — and the more sophisticated the hardware, the higher that cost. That means in this category, eSIMs are the most expensive to manufacture and incorporate in your IoT devices, with iSIMs offering significant cost savings (up to 50% cheaper). With no hardware components involved, however, SoftSIM is less than half the price of an iSIM and offers greater flexibility within the commercial model. With SoftSIM, you won’t have to pay for a SIM until it comes into use — rather than having to buy a SIM for every device at the point of manufacture.

• Security
  Because eSIM, iSIM, and SoftSIM are not physically removable, they all offer a security advantage over a traditional non-embedded SIM, which can be pulled from its original device and plugged into another one for unauthorized use or nefarious purposes. Like traditional SIMs, SoftSIM securely uploads information about each device to the cloud. The communication process between the device and the cloud is fully encrypted at each step — and with SoftSIM, each SIM profile has unique credentials, helping to protect devices and networks from attacks. 

• Sustainability
  According to a Trusted Connectivity Alliance report, SIM card production resulted in 560,000 tons of CO₂ emissions and 18,000 tons of plastic in 2021. And SIM production is expected to scale rapidly as the number of connected IoT devices increases to 27 billion by 2025. While embedded SIMs such as eSIM and iSIM use less plastic than their predecessors, they still require physical components and manufacturing efforts. Because it uses no physical elements and doesn’t need to be manufactured, the SoftSIM is the most environmentally friendly of the three SIMs. 

The SIM has come a long way since the early 1990s, evolving from a large, removable physical card to an invisible software-based entity.

SoftSIM makes digitizing analogue processes and industries easier, less expensive, and more future-proof.

Would you like to try the SoftSIM for yourself? Then head to the SoftSIM product page for more information.