How to choose the best IoT SIM card

When choosing cellular connectivity for your device, you’ll need a Subscriber Identification Module (aka SIM). It’s the SIM that gives your device access to a cellular network.

Not all SIMs are created the same. Some SIMs are more durable than others (industrial vs consumer SIMs), some SIMs can store multiple operator profiles while others can only store one, and SIMs also come in different sizes.

You’ll also find many IoT SIM providers on the market purporting to offer features like the best global connectivity, the best pricing, and the best platform.

This article guides you through some important things to think about when looking for the best IoT SIM provider and connectivity platform for your use case.

IoT SIM card form factors

SIM cards come in several different standard sizes, or form factors:

• Full-Size (FF1).
• Mini-SIM (FF2).
• Micro-SIM (FF3).
• Nano-SIM (FF4).
• Embedded SIM (MFF2, previously referred to as VQFN-8).

It’s important to note here that radio modules in post-2018 devices can utilize software SIMs (aka SoftSIMs). This evolution requires no SIM hardware; the SIM functionality is purely virtual, and is a new and exciting category of SIM form factor.

You can read more on SoftSIMs and how they fit into the SIM landscape in this article from GSMA, an industry body that creates standards and aims to unify the mobile ecosystem: Understanding SIM evolution (PDF).

Traditional IoT SIM cards vs eSIMs

Traditional SIMs are carrier-specific and only have one profile (e.g., Vodafone, T-Mobile, or Orange). Therefore, if you want to change carriers to access different prices, new technologies, or new markets, you also have to replace the SIM.

eSIMs were introduced to take away the pain of one-profile SIM cards.

At its core, eSIM is a way to remotely provision carrier profiles on IoT devices. As a result, there’s no need to manually swap SIMs when changing carriers, something that would be incredibly impractical for IoT devices deployed at scale, globally.

However, it’s important to understand that people use the term eSIM to describe two related but separate concepts in the industry.

1. Embedded SIM form factor: eSIM means embedded SIM, a non-removable SIM card form factor that can be mounted (soldered) directly onto the surface of a circuit board.
2. eUICC software on SIMs: eSIM is also used to describe the eUICC (Embedded Universal Integrated Circuit Card) architecture that allows a SIM to have multiple network profiles.

While GSMA defines eSIM as the eUICC architecture, it’s often bundled with the embedded SIM chip when marketed to the IoT industry.

Sadly, these two ideas are often confused with each other. However, the SIM chip form factor (hardware) and eUICC architecture (software) are independent properties when selecting your IoT connectivity.

Pricing for IoT SIM cards

You may have noticed that IoT SIMs are not priced the same as everyday SIMs. The advertised consumer SIMs are cheaper per MB/GB than IoT/M2M SIM cards. This is mainly because Mobile Network Operators (aka MNOs, mobile network carriers, or wireless carriers), such as Vodafone, Telenor, and T-Mobile, know that consumers don’t get anywhere near their data limits on average and adjust their pricing model accordingly.

For instance, the average user in the OECD uses about 5.8 GB per subscription per month. Even if a few people use all of their 100 GB per month, the operator still makes money on average.

On the other hand, B2B IoT SIM users clearly understand how much data they use and prefer pricing based on actual data usage. But this is not normally the case. You’ll find the vast majority of IoT SIM card operators offer subscription based pricing with limitations on which networks you can access and data pooling.

This is a consequence of how databases are set up in the telco industry and commercial decisions by operators.

Data subscriptions for IoT are the cause of many limitations on the expansion of IoT solutions:

• Once activated, SIM cards start costing money. Meaning, perfectly timing SIM activation and avoiding time-on-shelf after testing are paramount.
• Many operators have created workarounds that involve manual activation and deactivation of SIMs, Zapier integrations, or special pricing plans for post production testing, which require a switch once in the hands of the end-user. This adds up to time and reources spent managing SIMs.
• Forecasting becomes a big part of planning when SIM card pricing is based on regional pricing baked into the SIM, which is often the case.

We believe the ideal model for IoT SIM data pricing is to pay for what you use. If you only pay for data when you use data and aren’t penalized with active SIM fees or other data subscription limitations, then value creation and data costs are inextricably linked, making scaling IoT much much easier.

Avoid custom code on IoT SIM cards

Many IoT SIM providers put proprietary code on their SIM cards. For example, some SIMs have Multi-IMSI applets, a custom code that helps the SIM jump between operators depending on where the device is located.

One issue with custom code is that it isn’t GSMA compliant, meaning SIMs may not work on some devices.

Custom code locks businesses into using one SIM operator, in most cases. If you want to change operators, you’ll need to revisit the device after deployment to switch the SIM. But revisiting devices isn’t financially viable, practical, or possible for most use cases. You can read more about changing the operator credentials on a SIM over the air in the next section.

Another consequence of custom code is that it makes it more expensive to bake-in cellular connectivity during device manufacture. If you’re shipping devices globally, you’ll often find you want a different SIM for each region. This means stopping production, switching SIMs, and then restarting production.

Having different regional SIMs also means devices are locked into specific regions, and avoidable forecasting becomes integral to execution.

As a default, Onomondo doesn’t add any custom code to SIMs. This means we stay 100% GSMA compliant, so every device (that is also compliant) can use Onomondo SIMs, saving unexpected headaches for solution developers.

Keep ownership of your IoT SIM cards

It’s 2021 and switching SIM cards when changing operators is still a thing.

It’s common for device ROI to be ruined if you need to access an IoT device to switch a SIM. Now imagine having to change SIMs in thousands of devices around the world. This will affect not only your IoT business case – but your business as a whole.

Fortunately, all SIM form factors can have the operator updated over the air (OTA) without needing to be reissued according to standards from 3GPP.

You can switch operators by transferring the SIM’s International Mobile Subscriber Identity (IMSI), subscriber authentication key (Ki key), and Derived operator code (OPC key).

IMSI is easy to transfer; however, the Ki and OPC keys are typically held by operators. Although it’s technically possible to switch operators OTA, businesses cannot do this.

An increasingly popular method of dealing with global IoT roaming is eUICC/eSIM mentioned earlier. eUICC makes it possible to host multiple operator profiles on a device.

However, the problem of vendor lock-in still exists for eUICC. For example, managing eUICC profiles requires an eUICC platform that is hard coded onto SIMs during production, something that’s not possible to switch.

We recommend that all businesses negotiate with carriers to keep the IMSI, Ki and OPC keys as their property. It’s entirely possible, but almost no-one is doing it. Freedom to leave is essential for us, and we believe it will be a standard in the future. Otherwise, IoT will continue to struggle to take off.

Onomondo generates the IMSI, Ki, and OPC keys internally. With them, our customers can switch to any GSMA-certified entity without friction (like revisiting thousands of devices to change SIMs!).

Consider avoiding PLMN lists

When you get an IoT SIM card from an operator, the SIM will often have a Public Land Mobile Network (PLMN) list on it. This list is a way to hardcode a prioritized list of networks you would like to use on the SIM.

Typically, the PLMN list is based on commercial agreements. For example, an operator will have contracts in various countries for your SIM to connect to specific networks whenever you roam outside of their network. Global IoT operators will use PLMN lists to restrict devices to certain networks so that they get the best possible return on the data subscriåption fees they charge.

A little known negative consequence of a PLMN list is that your device could prioritize networks with weak signals over networks with strong signals.

If there is no PLMN list, 3GPP states that the radio module should attach to a strong enough network (also called -85 dBm, it’s a signal strength that is strong enough to deliver a consistent, stable data connection).

Consider the benefits of allowing the radio module on your device to choose a strong enough network according to 3GPP standards by default.

Test before you deploy

With IoT connectivity, the real effectiveness can only be determined by trying IoT SIM providers in the field.

Fortunately, the vast majority IoT SIM operators offer pricing packages for PoC (proof of concept) and testing.

Consider asking these questions when looking for operators to test with:

• Do I pay for SIMs when they are not in use?
• Do you offer multiple networks per country?
• Do I have real-time connectivity insights in every country?
• Can I transfer SIMs to a new operator post-deployment?
• Do the SIMs contain custom code on them?
• Do you offer pay-as-you-go data pricing?