What is a SIM card?
In its familiar card format, A SIM (subscriber identity module) consists of a contact chip encased in protective plastic. This chip contains a device’s authentication credentials, enabling the device to access a cellular network. For business users, IoT SIM cards perform additional useful roles, making it easier to monitor and configure devices, and manage your IoT projects remotely.
Here’s a closer look at traditional SIM cards, alongside the more recent embedded (eSIM) format.
What are the different types of SIM cards?
Smartphone SIM cards vs. IoT SIM cards
A smartphone SIM card is essentially an authentication tool: it contains key device information to enable the user to connect with the network.
An IoT SIM card performs this basic connectivity task, but it also does a lot more. An IoT SIM card can store and transmit device and data usage information, which can then be collected and aggregated on a cloud-based platform. This allows you to manage and configure your IoT devices remotely. For instance, you might need to temporarily disable connections on some devices at certain times, for security or cost reasons.
Unlike most phone SIM cards, a single IoT SIM can enable access to multiple networks. This helps ensure maximum coverage and a more reliable connection.
Dynamic vs fixed IP SIM cards
Consumer devices usually use dynamic IP addresses: i.e. the address changes every time the device connects to the internet (this helps preserve the consumer’s privacy).
In an IoT system however, dynamic addresses can make it more difficult to keep track of devices. This is why static (fixed) IP addresses – i.e. addresses that never change – may be preferable for IoT usage. The optimal set-up should give you visibility over your devices, along with suitable data encryption to ensure end-to-end security
Industrial and automotive IoT SIM cards
Industrial IoT SIM cards are designed to be resistant to temperature extremes, vibration and corrosion. This durability makes them suitable for heavy duty applications such as plant temperature sensors and production line monitoring equipment. Likewise, automotive SIMs are made to withstand all weathers, vibrations and motion, for use on fleet vehicles.
SIM card form factors
In terms of size, these are the main categories of removable SIM:
- Mini-SIM (2FF) (25mm x 15mm).
Typically seen in larger and fixed-location devices such as refrigeration units and payment points.
- Micro-SIM (3FF) (15mm x 12mm).
Used most often in portable devices such as hand-held trackers, tablets and monitoring equipment.
- Nano-SIM (4FF) (12.3mm x 8.8mm).
A popular form factor for wearables.
How do SIM cards work?
A SIM card contains the information necessary for two or more devices to connect with each other via a cellular network. In simple terms, when a device needs to make a connection, the SIM starts by looking for networks. Once a network is found, the SIM sends certain code numbers (see below) to the network tower. The network then checks whether the device is authorised to connect. If so, it gives the device network access and locks it in.
What information is stored on SIM cards?
The authentication credentials stored on both regular and IoT SIMs are as follows:
- ICCD (integrated circuit card identifier). This is the unique identifier allocated to each SIM.
- Authentication Key (Ki). This unique authentication key is used to verify whether the device is authorised to access the network.
- Location Area Identity (LAI). Consisting of a mobile country code (MCC), mobile network code (MNC) and location area code (LAC), the LAI allows the network to identify the location of the SIM card.
What are eSIMs?
With an eSIM, “e” stands for embedded. Instead of being incorporated into a removable plastic card, the eSIM is embedded into the device’s circuitry.
An eSIM is equipped with a “bootstrap” profile, allowing remote provisioning. So let’s say you are deploying a new IoT device in the field. To get the device initially set up on your network of choice, the network provider simply sends a SIM profile to the device to override the bootstrap. If you want to change provider later on, the new operator can send over a new profile to overwrite the existing one. There’s no physical swapping of cards required, which means less hassle and lower reconfiguration costs.
eSIMs are also designed to last for the lifetime of the device, which again helps to ensure lower maintenance costs.
How are SIM cards used in IoT?
For all industrial, commercial and customer-facing IoT applications, SIM cards are essential both for ensuring reliable connections between devices, as well as for enabling easier IoT project management. With multiple options available, it should also be possible to choose a form factor that meets your connectivity needs while keeping costs as low as possible for maximum lifetime value.
Learn more about the different areas of the world of IoT here.