A key element in an IoT device powered by cellular technology is the Subscriber Identity Module, more commonly known as the SIM card. The SIM card stores the identity and keys necessary for authentication and registration of your UE to the network, through a service provider, either a mobile network operator (MNO) or a mobile virtual network operator (MVNO).
Just like regular cellular services we use every day, cellular IoT technologies are also subject to their service provider. It is not guaranteed that what works in a certain region or country will work in others. This depends on a list of factors, like whether LTE-M and NB-IoT have been deployed in that area, what the coverage is like, what your SIM card supports and what the service provider you are using supports.
Mobile network operator (MNO): Provider of cellular network services that owns or controls all the elements necessary to sell and deliver services to an end user.
Mobile virtual network operator (MVNO): Provider of cellular network services that buys access to the network services through an MNO.
The GSMA (Global System for Mobile Communications Association) has a mobile IoT deployment map, which lists the deployment of LTE-M and NB-IoT in a country-by-country basis. The map shows which countries support LTE-M, which countries support NB-IoT, which countries support both, and which countries support neither. It is worthwhile to check the map and make sure that the country you intend on deploying your application in is covered by the needed cellular IoT technology.
Although the deployment map depicts coverage over a whole country, the coverage can also vary by region within that country. Therefore you need to check with the specific network operator operating in that area to get a more detailed coverage map.
The type of coverage and subscription you will get depends on your SIM card and the service provider you bought it from. It is important to note that the type of SIM card you need is usually different from the SIM card used for communication between cell phones.
Roaming SIM cards are designed to be used anywhere where the SIM card provider has a roaming agreement with the local service providers, giving the user ease of mobility.
For example, you may need to develop your IoT solution to operate in more than one country. In this case, you might be able to purchase a roaming SIM card that operates in the intended countries. However, contact your SIM card provider to make sure that PSM and eDRX are supported with the roaming SIM card, as that’s not always the case.
For local cellular applications, you can use a local SIM card from a service provider already present in your country instead of needing a roaming SIM card. Though make sure the service provider supports the cellular technology you intend to connect with.
SIM cards securely store the identity and related keys that the UE needs to connect to the networks. Traditionally, SIM cards are physical plastic cards containing your specific carrier profile, that you insert into the UE. This poses a few problems, for one removable cards are more vulnerable to theft and damage. Switching carrier profiles requires manually switching out each SIM card with a new one. Standard SIM cards also draw an unnecessary amount of current, which can be detrimental to applications with low-power constraints.
Embedded SIM’s (eSIMs): eSIMs refer to a specific SIM form factor that can be soldered onto the circuit board, called the MFF2. either to eUICCs (Embedded Universal Integrated Circuit Card) or a specific SIM form factor, the MFF2, the can be soldered onto the circuit board.
Integrated SIM’s (iSIMs): A SIM that is built into a dedicated Tamper Resistant Element on the SoC. While eSIMs are soldered onto the circuit board, iSIMs are a dedicated component of the cellular chip.
Software SIMs (softSIM): An entirely software-based solution, a virtual SIM that’s stored either in the application or the modem.