What is an IoT SIM Card and How is it Used in IoT devices?

An IoT SIM card, also known as M2M SIM Card (machine-to-machine), is a Subscriber Identity Module that is used in IoT (Internet of Things) devices to identify them as they try to connect to a 2G, 3G, 4G-LTE, Cat-M, NB-IoT, or 5G wireless cellular network. IoT SIM cards are typically billed monthly through IoT Data Plans.

M2M SIM cards, also called Universal Integrated Circuit Cards or UICC, store the credentials and security keys that uniquely identify a cellular subscription. The SIM uses a so-called IMSI number, or International Mobile Subscriber Identity, which is unique for every connected device on or off the network, anywhere in the world. SIMs also run an application that passes that identity information to an onboard cellular modem. The modem in turn, also known as "radio" or "radio module", conducts the actual attachment operation to the network. The application that the SIM card runs, by the way, is also referred to as UICC, i.e. the acronym is often used synonymously with the card or chip itself.

For global IoT depoyments, i.e. connected devices that are running anywhere in the world, IoT SIM card technology needs to provide multi-network access to multiple carriers without requiring different cards for each country or region. These SIM cards are also sometimes called global SIM cards. Global SIM cards come in two different models: 

• a traditional SIM model, also known as roaming SIMs, where the home provider uses partnerships around the world to give access to one network per visited country or region. These SIM cards typically do not provide the IoT connectivity and reliability needed to run IoT deployments successfully, as there are no fallback networks in case of outages or changing partner agreements. Furthermore, the business deploying their M2M devices has no control over which networks the connected devices should use. 
• the modern SIM model that leverages so-called Multi-IMSI SIMs. These SIM cards store multiple IMSIs on a single SIM profile, where each IMSI gives access to dozens or even hundreds of networks. In sum, this creates an overlapping list of networks to offer IoT and M2M solution companies the level of choice and control needed. 

IoT SIM cards come in different sizes or form factors

Just like traditional SIMs known from smartphones or tablets, IoT SIM cards come in different form factors, from mini to micro to nano SIMs. These are common in any cellular-connected hardware, as opposed to devices that, e.g., only connect through WiFi. A Look at the Fragmented Landscape of IoT Connectivity.

Common sizes / form factors of IoT SIM cards are:

• 2FF, also known as Mini SIM: 25mm x 15mm
• 3FF, also known as Micro SIM: 15mm x 12mm
• 4FF, also known as Nano SIM: 12.3 x 8.8mm

For many types of IoT devices that are smaller in size, such as wearables, these SIM form factors are still too large to be practical. The predominant form factor for an industrial SIM is embedded SIMs, which are directly mounted and pre-soldered onto the circuit board (PCB), as opposed to sitting as swappable SIM cards in a slot. The most common form factor for embedded SIMs is MFF2, a 6x5mm microchip soldered onto your circuit board. 

What are examples of IoT devices?

IoT connected devices come in all shapes and forms, and are generally any piece of hardware that is connected to the Internet and sends data on either itself or the environment the device is in. IoT devices are used in a variety of industries, such as Utilities and Energy, Healthcare, Retail, Manufacturing, Real Estate, Transportation & Logistics, Government / Public Sector / Smart Cities, Insurance and Banking, Agriculture / Smart Farming, or Automotive. 

Examples of connected devices include:

• In utilities: Solar panels, wind turbines, pipes, valves, batteries, tanks, electricity poles, electricity meters, tablets for staff
• In healthcare: Human body parts, drug dispensers, medical equipment, tablets for staff
• In retail: POS devices/terminals, store shelves, vending machines
• In manufacturing: materials, containers, finished goods, vehicles, factory machines, robot arms, worker wearables, warehouse equipment
• In government / public sector or office space: Forests, rivers, air quality sensors, lights, HVAC, water, elevators, doors, garbage cans and dumpsters, parking space, locks, security cameras, desks, office rooms, signs, billboards, kiosks
• In real estate or smart homes: Locks, lock boxes, cameras, thermostats, lights, media devices, kitchen devices
• In transportation / logistics: Trucks (drivetrain, brakes, ...), cars, EV charge points, railways, roads, bridges, airport facilities, buses, trains, trams, subways, (temporary) road signs 
• In agriculture / smart farming: Tractors, irrigation units, livestock, farming equipment 

Twilio Super SIM is a modern, multi-IMSI IoT SIM that provides global access to M2M networks around the world, while offering choice and control. For an overview of what use cases companies are realizing on Super SIM today, explore our solutions showcase. 

Interested in Super SIM? Get your free trial SIM now!

Tobias Goebel is a technology practitioner and educator with almost 2 decades of experience in business software and product/solution development. After developing, architecting, and selling contact center and customer service technologies in the ‘00s, he moved to defining and evangelizing the potential and business benefits of artificial intelligence concepts and all sorts of emerging communications technologies in the 10’s, such as business messaging, chatbots, embedded voice & video, or multi-modal interfaces. As a product marketing principal at Twilio IoT, he now works on defining and evangelizing technology solutions that leverage the potential of connecting the physical world to the Internet.