Soracom Air for Cellular

Introduction to SIM Identification in IoT

In IoT connectivity, effectively managing SIM cards requires an understanding of the various identifiers associated with them. Depending on the type of SIM, these identifiers may include ICCIDs, eICCIDs, and IMSIs. To simplify and unify the management of these identifiers, Soracom introduces the concept of a "SIM ID."

What are ICCIDs and IMSIs?

ICCID (Integrated Circuit Card Identifier): The ICCID is a unique 19- or 20-digit identifier assigned to a physical SIM card. It is used globally to manage and track the SIM throughout its lifecycle. In traditional, non-eUICC (embedded Universal Integrated Circuit Card) compatible SIMs, the ICCID is the primary identifier, and each SIM may contain one or more IMSIs.

IMSI (International Mobile Subscriber Identity): The IMSI is a unique number used by mobile networks to identify and authenticate a mobile subscriber. Each ICCID can have multiple IMSIs, enabling different operational scenarios like connecting to different networks or switching profiles.

Here’s how the hierarchical structure looks for a non-eUICC SIM:

SIM ID

ICCID

IMSI_1
IMSI_2
IMSI_3
...

What is an eICCID?

eICCID: In the context of eUICC-compatible SIMs (often referred to as eSIMs), the eICCID serves as the unique identifier for the embedded SIM. Unlike traditional SIMs, eUICC-compatible SIMs can store multiple profiles, each with its own ICCID. Within each profile, one or more IMSIs may be associated, allowing the eSIM to switch between different network operators or configurations dynamically.

Here’s how the hierarchical structure looks for an eUICC SIM:

eUICC SIM

ICCID 1

IMSI_1
IMSI_2
...

ICCID 2 (uncommon)

IMSI_1
IMSI_2
...

The Role of SIM IDs

Given the two patterns of SIM identification, with traditional SIMs identified by ICCIDs and eUICC compatible SIMs identified by eICCIDs, Soracom introduces the "SIM ID" as a unified identifier.

SIM ID: The SIM ID is the same as the ICCID (for non-eUICC compatible SIMs) or the eICCID (for eUICC compatible SIMs). This abstraction allows users to manage their SIMs consistently, regardless of the underlying technology. The SIM ID provides a logical way to reference the physical SIM, aligning with how users typically manage their devices.

When to Use SIM IDs vs. IMSIs

Use SIM ID: When you need to manage or track the physical SIM as a whole within your system, particularly in cases involving both traditional SIMs and eUICC-compatible SIMs. The SIM ID ensures consistency and simplifies management tasks, such as activation, deactivation, and inventory control.

Use IMSI: When interacting with or identifying the specific mobile subscriber within a network. This is essential for tasks related to network authentication, billing, and routing of communications. The IMSI is crucial when the focus is on the operational aspects of connectivity rather than on the physical SIM itself.