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What is an iSIM? (iSIM vs eSIM, 2024)

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An iSIM (or integrated SIM) is a software implementation of a SIM card that is embedded into a device’s processing hardware to perform the functions of a traditional SIM card. 

This advanced technology offers both businesses new opportunities for implementing connectivity in smaller and more miniaturised devices. 

iSIM technology is already used in some consumer devices such as mobile phones, tablets, and wearables. In addition, many manufacturers and network operators are assessing its appropriateness for Internet of Things (IoT) operations.

Before we get into the technical aspects of how an iSIM differs from an eSIM, the potential benefits of iSIM and how it can be used for IoT applications, we should first establish and clarify some terminology:

What is a SIM card?

A Subscriber Identity Module (SIM) is a smart card inside a piece of technology that carries unique and secure information that is produced by an approved SIM card manufacturer to a Mobile Network Operator’s (MNO’s) specification or configuration. This, via MNO’s or MVNO’s network platforms, can be linked to a device, client’s, or subscriber’s account.

SIM cards are mostly known for their use within mobile phones, together with their ability to store SMS messages and provide secure authentication for cellular access.

Most people, however, don’t always consider their wider roles and capabilities outside of their phone contract. SIM cards are also vital for authenticating IoT devices and routers which need to establish connectivity as part of their everyday functions.

As SIM cards have developed through the years, they have naturally become smaller, smarter and more efficient. These developments have challenged numerous industries’ thoughts on what SIM cards and mobile connections can be used for, as they and modems become smaller and more efficient.

What is the difference between an eSIM and an iSIM?

One of the major evolutions of the SIM card in the last decade was the embedded SIM (eSIM).

An eSIM, as the name suggests, is embedded into a device’s motherboard or main PCB. 

While an embedded SIM or ‘chipsim’ is effectively just describing the MFF2 form factor, around 2016 the concept of eSIMs began to change. The emerging Embedded Universal Integrated Circuit Cards (eUICC) standards offered the synergistic potential of providing the ability to flexibly switch carriers Over-the-Air (OTA)

Given the rigidity of a soldered chipsim being virtually impossible to change out without major reengineering, this seemed to be the way of replacing the flexible replacement of plastic sims in slots with a more sophisticated OTA solution. These solutions provide the ability to change providers, localise network profiles and save costs.

The problem with the adoption of eUICC was that consumer and IoT markets operated in different structures and, as a result, had different pathways of adoption. 

Major mobile phone manufacturers could implement eUICC standards on chipsim for their phones and smart watches as they had a sophisticated device which could manage the setup and network selection processes in conjunction with prompted user selections. 

The immense bargaining power of such mobile phone manufacturing companies meant that eUICC would be adopted by mobile network operators keen to sell these popular devices via their retail channels with 2- or 3-year deals. 

In effect, the eUICC functionality was used to allow a single product SKU to be manufactured and then configured by, or for an operator locally.

IoT was less able to unanimously adopt eUICC owing to the need to cater for a plethora of different or unique devices. Many IoT applications also lacked the bargaining power to mobilise MNOs to release secure credentials through fear of losing business once the client switched provider OTA. 

The lack of a user interface to select choices on startup, and the autonomous and nuanced nature of many IoT devices, meant that practical problems remained for IoT device applications seeking to use eUICC technology. 

As a result, consumer and IoT standards for eUICC began to diverge. That said, many IoT device manufacturers perceive the consumer eUICC standards as a better fit for their application as these standards have been developed as they are more mature and proven.

As consumer devices and wearables have advanced, SIM card technology has also developed. One of these adaptations has been the introduction of the iSIM.

Also known as the Integrated Universal Integrated Circuit Card (IUICC), the iSIM is essentially a more integrated version of an eSIM. 

Instead of relying on an external chip on a motherboard, the iSIM enables the eUICC standard to be embedded directly into a device’s main processor or secure socket architecture. Not only does this have spatial benefits for devices, but it also reduces power consumption.

The emergence of iSIM technology means that manufacturers can produce even smaller and more advanced devices, allowing more space for larger batteries and newer components. This will ultimately lead to even more efficient and powerful devices and new features.

The iSIM will also pave the way for new types of miniaturised devices, such as wearables and smart-home sensors, which require an even more space-efficient SIM card to fit into confined or sealed spaces.

While eSIM and iSIM share many similarities, it is important to note the differences between their implementations, especially regarding their cost, efficiency and practicality within IoT operations and the expected life cycle of devices:

Benefits of iSIM applications

There are benefits to using an iSIM implementation above other SIM form factors for an IoT connectivity operation. These include:

1) Size and Form Factor

As established, the iSIM is by far the smallest SIM form factor available on the market, which in and of itself opens the opportunity to optimise a device’s internal space.

By having a smaller SIM card on hand, IoT devices could reduce in size or weight, or even create more space to add other useful components.

Through using an integrated SIM card, businesses can in theory eliminate costly logistic complexities related to cellular connectivity. This is because the SIM is installed directly in the device’s own hardware, rather than being soldered onto the circuit board as it would be with an eSIM.

This, however, is not as simple as it seems. While mobile network operators may be willing to donate their SIM credentials to major, trusted manufacturers, there are approval processes and business case criteria that need to be met.

For example, any bootstrap profile that is applied at manufacture and is used for the first connection of the device will likely be subsequently replaced by a localised or preferred MNO profile. This change requires commercial agreements to be in place which means the MNOs need to be on friendly terms or non-competitive, able to specify and agree on the cost of the change of profiles, and of course the commercial model for the bootstrap profile MNO.

eUICC OTA platforms themselves represent significant infrastructure and costs vary. MNOs and MVNOs have already and are continuing to invest in eUICC platforms, however, they need to be integrated so that cross-transactional processes can occur and be managed. This is especially the case where multiple IMSI profiles are implemented side-by-side for resilience or a greater global footprint.

2) Low power usage

Because an iSIM is software embedded in a Tamper-resistant element on the device’s system-on-a-chip (SoC), it does not need a separate microprocessor to function. In turn, this means that an iSIM has a low power withdrawal.

As technology continues to advance and higher gigabit speeds become more commonplace in commercial and residential functions, the low-power drain of iSIM architectures may become useful in certain IoT applications where power budget is seen as critical. For example, smart clothing, wearables or household and consumer products.

While some types of IoT operations could also consider narrowband IoT (NB-IoT) for power-saving benefits, this technology isn’t ideal for every IoT operation. Performance may be too slow in terms of latency, network inflexibility (caused by there being no cell handover capability) and low bandwidth capability meaning that it is insufficient for many use cases.

3) Security

Although an iSIM integrates eUICC into the native hardware of the device itself, the technology is generally perceived as being as secure as chip eSIMs and physical SIM cards.

The integrated nature of iSIM technology does make it more difficult for the layperson with unauthorised access to steal or compromise.

While physical SIM cards might, in theory, be more easily physically stolen, SIM management platforms, however, enable them to be quickly deactivated and rendered useless. IoT SIM cards also have usage limits which can be used to warn and then deactivate SIM cards that are in breach of their data limits.

4) Network capabilities

Most IoT devices require maximum up-time for their operations, so connectivity is pivotal.

While in theory, an iSIM’s OTA capabilities allow for seamless network switching enabling a device to connect to multiple networks and select the most optimal one automatically, this is subject to the bootstrap profile, its roaming coverage, as well as the other profiles that are integrated into the service.

IMSI profiles are secure and vital credentials and not all mobile network providers are willing to donate them outside of their core supply chains. If so, they will be subject to inter-operator agreements and authorised eUICC integration with acceptable partners.

However, IMSI profiles also come at a cost. Even if a profile is not actively used, it is likely to be charged for by the MNO; at least on a per-device licence (or access fee) basis.

As with all types of SIM cards, an iSIM can use a private APN network with a VPN to provide more network security for the most security-critical applications.

5) Scalability and IoT application

Considering the contingent benefits of iSIM, it’s clear to see the obvious potential in the technology’s scalability in terms of devices that require miniaturisation and more integrated ways of managing device connectivity. 

Manufacturers can create even smaller IoT devices that can be placed in more locations. This, however, tends to be only possible for those who can manufacture at scale and are able to leverage the needed MNO donor SIM credentials and agreements beyond the simple provision of a global bootstrap. 

This is because it is likely that a global bootstrap profile will not cover every territory or provide the most cost-effective solution for the end user. For example, roaming is barred in some countries such as Brazil and Turkey and restrictions are tightening in Canada and Australia. In these cases, the iSIM will need to be localised on startup.

With iSIM implementations, however. monitoring of networks by IoT devices will be potentially more seamless due to a unified, integrated approach to device design.

As discussed, IoT operations are currently not the major beneficiary of iSIM technology.

For example, consumer devices remain the main applications of iSIM and it is estimated that by 2025 over 850 million consumer devices will be using iSIM technology (, 2022), with Apple potentially removing the physical SIM slot altogether on future devices. 

This example highlights the potential the technology can bring to global consumers and demonstrates the commitment of large consumer device organisations to the architecture and approach.

iSIM for IoT: Opportunities and challenges

While iSIM technology offers potential benefits to businesses considering integrating it into their IoT operations, there are also significant challenges to be aware of.

One of the greatest challenges is the cost of implementing iSIM technology. This is currently high compared to other SIM form factors. However, this cost could plateau as the technology is adopted and more modules such as modems integrate the technology.

Another challenge is integrating iSIM technology into existing IoT ecosystems, which can require significant development resources, investment or procurement costs. The majority of IoT devices are not compatible with iSIM software, making it difficult or impossible to switch to this SIM form factor without redesigning the device.

On the other hand, the opportunities offered by iSIM technology for large-scale IoT operations or manufacturers of devices create greater opportunities to miniaturise and optimise devices.

Applications that rely on 5G may benefit from this optimisation and help synchronise use cases that require minimal latency on public and private 5G networks. For example, medical and automotive applications.

Security is comparable to traditional SIM formats and being embedded as software could make them, in theory, less prone to malicious physical attack or theft


As iSIM technologies continue to evolve and become more adopted and streamlined, they will likely revolutionise some industries by making new applications and devices possible.

While there remain challenges associated with integrating iSIM technology into many IoT operations, the benefits of increased miniaturisation, cost of manufacture at scale, and energy efficiency, will mean that the technology will become more prevalent. This is, especially in consumer devices, wearables, and household goods. 

Connectivity as a service does come at a cost, however, and the residency of IMSI profiles on devices needs to be justified and methods of payment for these services over the lifespan of the device need to be considered and factored in by manufacturers.

Businesses looking to develop new devices, upgrade, scale or start up their own IoT operations should look no further than Caburn Telecom. We are industry leaders in IoT connectivity solutions at scale, helping our partners and clients across a range of sectors stay connected in their mission-critical operations.

To discover more about how you could optimise your IoT operations and achieve maximum uptime, contact a member of our team today. We will be more than happy to help you achieve success with your operation.