Complete Guide to IoT SIM Cards: Types, Form Factors, and Connectivity

An IoT SIM card is a Subscriber Identity Module intended for internet of things devices that require mobile connectivity, and primarily focus on machine to machine (M2M) communications. These SIM cards often use multi-IMSI or eUICC (eSIM) technology to switch between network operators to ensure seamless coverage worldwide, durability, and management capabilities tailored for IoT applications. 

IoT SIM cards are available with support for various connectivity standards, including 2G, 3G, 4G, and emerging 5G networks. They support IoT ecosystems by offering scalable solutions that meet the requirements of low-power, wide-area IoT networks.

This is part of a series of articles about Subscriber Identity Module (SIM).

Differences Between IoT SIM Cards and Standard SIM Cards

IoT SIM cards are built to endure harsh environmental conditions, making them more durable than standard SIM cards. They can withstand extreme temperatures, humidity, and physical stress, which are common in industrial and outdoor settings. 

This robustness extends their lifespan, from 3 years in typical consumer SIMs to around 10 years for IoT SIMs, which is critical for most IoT devices, given that it can be difficult or impossible to replace the SIM when devices are deployed in the field.

Manufacturers often improve these SIM cards with additional protective coatings and materials to ensure longevity. This contrasts with consumer-grade SIM cards, where the life span of a cellular contract is lower than three years and replacing a SIM is not a complex task.

Network Connectivity and Coverage

IoT SIM cards offer superior network connectivity and coverage options for IoT deployments. They often include multi-network support, business logic support, automatic SIM switching, and improved reliability. This connectivity flexibility ensures that devices stay connected without manual intervention.

Unlike standard SIM cards, IoT SIMs can connect to low-power, wide-area networks (LPWAN) such as NB-IoT and LTE-M, which are designed for IoT connectivity. This ability to connect to various network types allows for more efficient data transmission, lower power consumption, and reduced connectivity costs.

SIM Management and Control

IoT SIM cards are controlled by management software that allows for remote control and monitoring. Network administrators can activate, deactivate, or reconfigure SIMs over-the-air, providing greater control over the IoT devices’ connectivity. This capability is essential for managing large-scale deployments where manual handling of SIMs is not feasible.

These management features are typically accessible through specialized platforms, offering insights into data usage and device statuses. IoT SIMs also support automated alerts and diagnostics that help identify and resolve connectivity issues promptly.

Types of IoT SIM Cards

Standard IoT SIMs

Standard IoT SIM cards support typical IoT communication needs. They are suitable for non-demanding IoT applications where environmental challenges are minimal. These SIMs generally support multiple networks, ensuring consistent connectivity as devices move across regions.

Industrial IoT SIMs

Industrial IoT SIMs are built for use in rigorous industrial environments. These SIM cards are heavily shielded against harsh elements such as temperature variations, moisture, and chemical exposure. Their design enables them to maintain cellular connectivity in scenarios where consumer-grade SIMs would fail, such as in manufacturing plants or on shipping containers.

The improved durability of industrial IoT SIMs also includes extended lifespans, reducing the frequency of replacements. This durability ensures that connected machinery and infrastructure systems can operate reliably over long periods.

Automotive IoT SIMs

Automotive IoT SIMs are tailored for vehicular applications, supporting high mobility and connectivity needs. They offer reliable performance in dynamic environments, maintaining reliable connections that are essential for modern vehicle telematics solutions such as GPS tracking and automotive diagnostics. 

These SIMs cater to the rapid movement and handover between networks that vehicles experience. They are also designed to withstand the vibration and temperature fluctuations typical in automotive scenarios. Automotive IoT SIMs often include features that allow seamless cross-border connectivity, critical for fleet management solutions operating internationally.

Technologies Used in IoT SIM Cards

Embedded SIM (eSIM) vs. Integrated SIM (iSIM)

An embedded SIM (eSIM) is a physical SIM chip that is soldered directly onto a device’s circuit board. Embedded SIM support both single profile SIM and Remote SIM provisioning (RSP) type of SIM allowing users to switch carriers or profiles without needing physical replacements. This flexibility is useful for IoT deployments where devices operate across regions and require carrier changes.

eSIMs supporting RSP are commonly used in smartphones, tablets, wearables, and a range of IoT devices, including connected cars and industrial sensors. They offer advantages such as compact designs, improved durability, and the ability to store multiple carrier profiles. However, since eSIMs are still physically embedded, they require dedicated hardware components, limiting their use in devices with extreme size constraints.

An integrated SIM (iSIM) takes the integration further by embedding SIM functionality directly into the device’s main processor or system-on-chip (SoC). This eliminates the need for a separate SIM chip, freeing up space and reducing power consumption. iSIM technology is particularly useful for ultra-compact and power-constrained IoT devices.

Since iSIMs are integrated at the chip level, they provide an even smaller footprint than eSIMs and improve security by leveraging the device’s existing security framework. They also support remote provisioning like eSIMs, but their tighter integration makes them more cost-efficient for large-scale IoT deployments, especially in low-cost or low-power devices.

Single-IMSI vs. Multi-IMSI (Single Carrier vs. Multi-Carrier)

A single-IMSI (International Mobile Subscriber Identity) SIM card is configured with a single, static IMSI number. This means the SIM connects to one mobile network operator (MNO), which limits its ability to switch networks. While adequate for devices deployed within a single region or under a long-term agreement with a specific operator, single IMSI SIMs lack flexibility in terms of network coverage. 

If the home network is unavailable or weak, the device may lose connectivity, which can be problematic for IoT applications requiring reliable global coverage. Single IMSI SIMs are often more cost-effective compared to their multi-IMSI counterparts. However, they are less versatile and are better suited for stationary deployments, such as smart meters or sensors operating within a well-defined network footprint.

Multi-IMSI SIM cards are designed with multiple IMSI profiles, enabling them to connect to several mobile networks. This capability allows a device to switch networks dynamically based on signal strength, coverage, or cost efficiency. Multi-IMSI technology ensures connectivity across regions and is particularly advantageous for IoT deployments in industries like logistics, transportation, or global asset tracking, where devices frequently move across borders.

The multi-IMSI approach also provides resilience by automatically switching to an alternate operator if the primary network fails or becomes unavailable. This level of redundancy is crucial for mission-critical IoT applications, such as healthcare devices or emergency response systems, where uninterrupted connectivity is essential.

IoT SIM Card Form Factors and Software Functionality

Full-Size (1FF)

The full-size SIM, or 1FF, is the original and largest SIM card size, now largely obsolete. Initially used in the early days of mobile technology, it measures 85.6 mm by 54 mm.

Although virtually extinct in new IoT implementations, these legacy devices might still exist in certain niche markets or specialized equipment where modern alternatives have not replaced older technology.

Mini-SIM (2FF)

The Mini-SIM (2FF), introduced in the late 1990s, was the first step toward reducing SIM card sizes in response to the growing demand for compact mobile devices. Measuring 25mm by 15mm, it was half the size of its predecessor, the full-size SIM (1FF), and quickly became the global standard.

Despite its smaller size, the Mini-SIM maintained backward compatibility with older mobile networks. It offered the same core functionality, including storing the IMSI (International Mobile Subscriber Identity), authentication keys, and limited user data such as contacts and SMS. This form factor enabled manufacturers to design slimmer phones by freeing up internal space.

Micro-SIM (3FF)

The Micro-SIM (3FF) emerged in the late 2000s, with dimensions of 15mm by 12mm—about 52% smaller than the Mini-SIM. Its reduced size provided additional space inside mobile devices, supporting the development of larger batteries, faster processors, and more features in smartphones.

Despite the smaller plastic frame, the Micro-SIM retained the same electrical contacts and network functionality, ensuring that it could store IMSI, encryption keys, and user data. Its introduction was critical during the smartphone boom, as manufacturers needed to balance space efficiency with performance. 

Nano-SIM (4FF)

The Nano-SIM (4FF), introduced in the early 2010s, is the smallest traditional SIM card, measuring 12.3mm by 8.8mm. Designed to meet the demands of slimmer and more compact devices, it enables manufacturers to allocate more internal space to larger batteries, advanced sensors, and additional components.

Although smaller, the Nano-SIM provides the same core functionality as its predecessors, including storing the IMSI and cryptographic keys. It played a key role in enabling sleek device designs in modern smartphones and tablets. However, its smaller size presents challenges, such as being easier to lose and requiring more precise manufacturing processes.

Embedded SIM (MFF2)

The MFF2 (Miniaturized Form Factor 2) is an embedded SIM chip measuring 6mm by 5mm, designed to be soldered directly onto a device’s printed circuit board (PCB). This form factor improves reliability and security, protecting the SIM from damage caused by shock, corrosion, or extreme environments.

The MFF2 SIM can come as a single profile sim or eSIM that supports remote provisioning and over-the-air updates, making it ideal for IoT devices like sensors, industrial equipment, and smart meters. By eliminating the need for physical SIM card slots, it saves space and reduces manufacturing complexity, enabling ultra-compact device designs. Its integration with technologies like LTE-M and NB-IoT further optimizes IoT connectivity and performance.

iSIM

An integrated SIM (iSIM) is a step beyond embedded SIMs, with the SIM functionality integrated directly into the device’s processor or system-on-chip (SoC). Unlike eSIMs, which are separate components soldered to a device, iSIMs eliminate the need for a standalone SIM chip entirely, reducing the size and complexity of device design. 

iSIM technology improves security by leveraging the device’s existing secure processing environment, providing protection against physical tampering and remote attacks. Its integration also simplifies large-scale IoT deployments, as remote provisioning and over-the-air (OTA) updates allow for efficient management of devices in the field. iSIMs are particularly suitable for ultra-compact devices like wearables, medical sensors, and smart meters.

Connectivity Options for IoT Devices

Steered vs. Non-Steered Multi-Network Roaming

Steered multi-network roaming prioritizes predefined preferred networks selected by the SIM provider, ensuring cost optimization. However, connectivity may suffer if those networks fail to deliver optimal signal strength. Non-steered roaming allows IoT devices to latch onto the strongest available network, prioritizing connection reliability over cost control.

For IoT applications, choosing between steered and non-steered depends on the balance between budget constraints and connectivity requirements. Non-steered solutions provide better service quality and are particularly advantageous for mission-critical applications needing consistent connectivity, whereas steered options might appeal for cost-efficiency.

Automatic Network Selection

Automatic network selection involves IoT devices dynamically choosing the best available network regardless of operator, ensuring optimal connectivity at all times. This feature allows smart management of connectivity resources, particularly useful in changing network conditions or where multiple networks provide variable coverage strength.

This functionality supports seamless transitions, minimizing business disruptions due to connectivity changes and ensures uninterrupted data transmission for IoT applications. Automatic selection is useful for devices in mobile or remote locations where network availability can be unpredictable.

5 Best Practices for Implementing IoT SIM Cards

Organizations should consider the following measures when using IoT SIM cards.

1. Automate to Prevent Overage Charges

Managing IoT deployments at scale requires more than just monitoring data usage. Organizations should utilize SIM management platforms with proactive features, such as real-time monitoring and automated actions. Instead of relying solely on alerts, these platforms should have the capability to deactivate devices when unusual data consumption is detected or trigger alerts within existing IT systems through APIs. 

By quickly identifying rogue devices or excessive data usage, organizations can address issues before they escalate into expensive overage charges or service complaints. Automated management helps improve the reliability of IoT deployments.

2. Maintain Ownership of IoT SIM Cards

To achieve flexibility and avoid vendor lock-in, organizations should negotiate agreements that allow them to switch providers . Solutions like eUICC and eSIM can offer multiple operator profiles, but companies should ensure they can switch providers without being tied to proprietary eUICC platforms.

3. Avoid Hardcoded Public Land Mobile Network (PLMN) Lists

Hardcoded PLMN lists prioritize network selection based on pre-set agreements with operators, often prioritizing cost over signal strength. This can result in devices connecting to networks with poor coverage, leading to unreliable connectivity. To ensure optimal network selection, organizations should avoid PLMN lists and instead allow devices to connect to the strongest available network as per 3GPP standards.

By allowing the radio module to select networks dynamically based on real-time conditions (e.g., signal strength above -85 dBm), organizations can improve connectivity reliability and maintain stable data transmission. This approach is especially important for mission-critical IoT deployments requiring consistent performance.

4. Conduct Thorough Testing Before Deployment

Field testing IoT SIM cards in real-world conditions is essential to ensuring their performance meets operational requirements. Organizations should run proof-of-concept (PoC) tests to evaluate coverage, data usage, and network compatibility across different regions and environments.

When selecting IoT SIM providers, organizations should inquire about features like pay-as-you-go pricing, real-time connectivity insights, and the ability to switch operators post-deployment. Comprehensive testing reduces the risk of deployment failures and ensures that IoT devices can maintain uninterrupted connectivity throughout their lifecycle.

Managing IoT SIM Deployments with floLIVE

The evolution of IoT has brought rapid growth in the number of connected devices as well as the variety of use cases. Alongside, the extensive use of battery-powered devices and the introduction of LPWA devices requires new business models.

floLIVE’s cloud-based Connectivity Management Platform (CMP) is the answer for any IoT deployment it offers a flexible, scalable and cost-effective means for managing and operating IoT networks. The CMP is offered as a service and supports flexible deployment models.

floLIVEs SIM provides the flexibility to choose any type of SIM: plastic SIM on all its variants, embedded SIM, and iSIM. Regardless of the chosen form factor, flolIVE SIMs can support any technology to run on the SIM i.e.: single SIM, Multi-IMSI SIM, eSIM (remote SIM provisioning).

floLIVE SIMs support all the features required to run and manage a successful IoT network. 

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