4G/LTE - SIM  

 

 

 

eSIM/Electronic SIM/Embedded SIM

This is called by many different names. Some say embedded SIM, some say Electronic SIM and other say eSIM. There would be other names coming out until the industry standard is finalized and adopted widely in the area. Whatever we call, the fundamental idea of this SIM is to distribute the SIM (UICC) as a non-removable/fixed component of a user device (e.g, M2M terminal, Mobile Phone etc). The device manufacturer program the SIM card to load different set of informations required by specific situation (e.g, location, network operator etc)

I will call this as eSIM throughout this page since 'e' can imply many different things(e.g, it can imply 'Electronic', 'Embedded' and even 'Enhanced').

Why eSIM ?

For some people especially who is working on modem development and device testing, it would sound like counter-intuitive evolution path because 'anything fixed/non-removable' may imply 'less flexibility and less controllability'. Then how come this kind of concept is getting more and more frequently talked about (as of Aug 2015).

In engineering, for anything coming out anew, there is some reason/motivation. What is the reason/motivation for this new concept of SIM ?

Motivation for M2M/IoT devices

I think the biggest motivation is related to M2M/IoT devices.

  • M2M/IoT Devices and SIM Accessibility Challenges
    • Unlike mobile phones, most M2M/IoT devices are not easily reachable.
    • Even if accessible, it may not be possible to easily decap and plug in a SIM card.
    • To address this, UICC was implemented as a fixed chipset attached to each device.
  • Uncertain Information at Manufacturing:
    • It is often unclear what information should be stored in the chip at the time of manufacturing.
    • The network operator and installation location may not be known ahead of time.
    • Programmability is required so that the chip can be configured based on different requirements, eliminating the need to replace SIM cards.
  • Mechanical Issues with Removable SIMs/Vibration Concerns:
    • Removable SIM cards are not suitable for devices in high-vibration environments, such as automobiles or industrial machinery.
    • Electrical contacts of removable SIMs are less robust compared to soldered electrical contacts of eSIMs, leading to reliability concerns.
  • Cost Efficiency:
    • According to GSMA reports, the cost of removable SIM cards is approximately 10 times higher compared to eSIMs.
    • Logistical Benefits of eSIMs
  • Simplified Connectivity:
    • For mobile phones in areas with no roaming or expensive roaming, users need to order a local SIM card and replace it manually.
    • Similar challenges occur when switching network operators.
    • In automotive contexts, the logistics of changing SIM cards are more cumbersome:
      • Ordering a new SIM card and visiting a dealership to replace it.
      • Automotive manufacturers do not allow users to change SIM cards due to potential electrical issues from improper handling.

In short, Anyway there seem to be many reasons for moving towards eSIM cards

Is it going to be used only for M2M device ? It doesn't seem to be restricted to M2M/IoT device only and there seems to be some trends towards adopting this technology to mobile phone as well. Read following articles.

Motivation for Mobile Phones

Would there be any motivation of using eSIM for Mobile Phones ? The motivation may be different, but the answer is 'Definately YES'.  

eSIM is gradually becoming more popular as mobile carriers and device manufacturers support it more widely. The convenience, security, and flexibility of eSIM technology make it an attractive option for both casual users and professionals.  

  • Convenience and Flexibility
    • Switching Carriers Easily: eSIM allows you to switch between mobile carriers without needing a physical SIM card. You can activate a new carrier plan directly on your phone by scanning a QR code or entering an activation code.
    • No Physical Card Required: You don’t need to visit a store or wait for a new SIM card in the mail to change carriers or get a new number.
  • Multiple Profiles
    • Multiple Phone Numbers: eSIM allows multiple profiles on one device, making it possible to have more than one phone number without swapping physical cards. This is ideal for dual-SIM functionality, like using separate work and personal numbers on the same device.
    • International Travel: When traveling, you can activate a local eSIM plan without changing your physical SIM. This means you can keep your primary number active while also using a local number for cheaper data and calls.
  • Quick Activation and Setup
    • Instant Activation: You can activate an eSIM instantly, often directly from the phone settings or a carrier app. There is no waiting for a SIM card to arrive in the mail or visiting a store.
    • Easy Plan Switching: Users can easily switch between different plans or carriers, which is beneficial if you need to frequently switch between data packages or international roaming options.
  • Improved User Experience
    • Better Coverage with Multiple Carriers: By using dual-SIM capabilities (physical + eSIM), you can benefit from improved network coverage by leveraging two different carriers simultaneously.
    • Business Travelers and Frequent Roamers: For people who travel frequently, the ability to quickly change to a local carrier’s plan helps save on roaming charges and provides a more seamless experience.
  • Space Saving for Device Manufacturers
    • Smaller Devices: Since eSIMs are embedded in the phone and take up less space, manufacturers can design smaller, slimmer devices or use the extra space for other components like larger batteries or additional hardware features.
    • Durability: Removing the physical SIM slot can make devices more water-resistant and less prone to mechanical damage.
  • Improved Security
    • Less Likely to be Stolen or Lost: Unlike a physical SIM, an eSIM is embedded into the device, making it less prone to theft or loss. If your phone is stolen, the eSIM cannot be removed, which could potentially make the device easier to track or protect against unauthorized use.
    • Remote Management: Carriers can remotely lock or wipe the eSIM profile, making it more secure in situations where the device is compromised.
  • Better for the Environment
    • Less Plastic Waste: With no need for physical SIM cards, eSIMs reduce plastic waste and the energy involved in producing, packaging, and distributing SIM cards.
    • No Packaging: Eliminates the need for SIM card packaging and minimizes the overall carbon footprint.

How to program (provision) the SIM ?

Now the question is how you can load information (profile) into each eSIM card within the device ? The simplest idea is to implement a special programming port directly connected to the eSIM and electrically load the information into it, but the ideal (final goal) would be to load the information (profile) over the air (this is called 'Remote Provisioning').

The critical issues is how to design/implement a remote provisioning. Since this remote provisioning should be applicable to devices from various vendors and applicable to different network operators, there should be some international standard and very detailed procedures (protocols) should be defined. For now, GSMA is leading this activity. Even though the specification is not finalized yet (as of Aug 2015), you can have pretty detailed idea of Remote Provisioning process from GSMA document : Embedded SIM Remote Provisioning Architecture (Visit Reference [1] to find the document)

It may look complicated and require a lot of readings to understand the overall process, but with recent implementation (as of Oct 2024) it found it much more easiear/simpler than I thought. Followings are some of methods to install eSIM profile.

Installation with QR Code

Usually when we install eSIM on mobile phone, we purchase an eSIM in the form of QR code and take picture of it with mobile phone camera and the phone install it. You can see an example of this case at this tutorial in Amarisoft TechAcademy

This it show this process works in the background

  • QR Code Data: The QR code contains SM-DP+ (Subscription Manager Data Preparation) server information, including:
    • An activation code.
    • Server address.
    • Encrypted data for secure profile download.
  • Secure Communication: After scanning, the phone establishes a secure connection with the SM-DP+ server using the information from the QR code.
  • Profile Download: The server verifies the request and sends the eSIM profile (carrier data and credentials) to the device over this secure channel.
  • Profile Installation: The eUICC (embedded UICC) inside the phone stores the downloaded profile, and the device switches to the new network using this profile.

NOTE : Usually the eSIM activation process is done through the internet rather than SMS or other traditional methods. When you scan the QR code, your phone uses the information in the QR code to establish a secure HTTPS connection with the SM-DP+ server (Subscription Manager Data Preparation server). Through this connection, the eSIM profile is downloaded directly to your device's eUICC over the internet. This allows for a secure and efficient transfer of the necessary data, enabling your phone to activate the eSIM without needing a physical SIM card.

Installation with mobile App / In-App Provisioning

Some eSIM provider allows you to install and manage eSIM via a specific mobile App. Using an app can simplify the process by automating the steps, making it user-friendly while maintaining secure communication.

When using a special app from an eSIM vendor to install an eSIM, the process is similar to scanning a QR code but provides a more streamlined experience. Here’s how it works:

  • App Authentication: The app may require user authentication or verification, such as logging into an account with the eSIM vendor.
  • Profile Request: The app sends a profile request to the SM-DP+ server over the internet.
  • Secure Download: The app initiates a secure HTTPS connection for downloading the eSIM profile directly onto the device.
  • Profile Activation: The downloaded profile is stored in the eUICC, and the app guides the user through activating the eSIM.

How LPA is involved in this process ? Is LPA always involved ?

The LPA (Local Profile Assistant) is always involved in the eSIM installation process, whether you use a QR code, a vendor app, or any other method. The LPA is a component in the mobile device that manages communication with the eUICC and the SM-DP+ server. Here’s how it fits into the process:

  • Profile Download Management: The LPA handles the downloading of the eSIM profile from the SM-DP+ server.
  • Secure Connection: It ensures that a secure channel (typically HTTPS) is used for this download.
  • Profile Installation: The LPA then transfers the profile to the eUICC and manages its installation and activation.

The LPA essentially acts as the interface between the device’s user interface (like the app or QR scanning functionality) and the eUICC, making it a crucial part of the eSIM provisioning process.

eUICC Architecture/Information Flow

Following is overall Architecture and Information flow modified from GSMA Technical Specification. (I just a couple of items below the dotted line. Everything above the dotted line is exactly same as in GSMA Technical Specification : Figure 1 in GSMA-Embedded-SIM-Remote-Provisioning-Architecture-Version-1.1).

Probably the most of the readers including myself are not very familiar with each of these entities for now (Aug 2015) and inter-relations of each of these entities are also quite complicated.  Most of the people would be interested (or involved) in only a couple of path shown here. I will just keep updating the descriptions of possible path combinations (interactions) among these entities as I learn along.

    Figure 1 : Functional Arichitecture of eSIM Operation

< Path Example 1 : (1), (2), (3) >

Probably this can be a kind of minimum functional flow.

First, SM-DP should get the necessary tools or services from EUM (eUICC Manufacturer) that is required to program the eUICC.

Next, SM-DP should get input data from MNO (Mobile Network Operator) that will be used to create a Profile (or Many Profiles) for the target eUICC. Some examples of the input data are as follows.

  • Quantity of Profiles to be created
  • IMSI Value(s) or Range
  • ICCID Value(s) or Range
  • Unpersonalized Profile Type(s)
  • Information about target eUICC(s), e.g, EID

eSIM Hardware

eSIM hardware refers to an Embedded SIM module that is built directly into a mobile device's hardware, rather than being a removable physical SIM card. Here are the key components of eSIM hardware:

  • Embedded UICC (eUICC): A secure microcontroller, similar to a traditional SIM but permanently soldered onto the device’s circuit board.
  • Non-removable Memory: Stores profiles (carrier data and user credentials) for multiple carriers, allowing over-the-air provisioning.
  • Secure OS: Manages the storage and switching of different carrier profiles and ensures secure communication.
  • Connectivity Interface: Uses protocols like ISO/IEC 7816 and secure channels for communication with the device’s modem.

The eUICC technology enables devices to switch between network carriers without changing physical SIM cards, making it ideal for applications like IoT and devices that require remote provisioning

NOTE : Difference between eSIM hardware and normal SIM hardware

The eSIM hardware is fundamentally similar to a regular SIM card (UICC) in terms of its core functions, such as storing carrier profiles, handling user authentication, and enabling secure communication with mobile networks. The key differences are:

  • Non-removable: Unlike traditional SIM cards, eSIM is embedded directly into the device’s motherboard and cannot be physically removed.
  • OTA Upgradability: eSIM supports over-the-air (OTA) profile provisioning, allowing users to download, activate, or switch between carrier profiles remotely without needing to insert a new physical card.

These features make eSIM more versatile, especially for devices where space is limited, or remote management is required, such as in IoT applications and newer smartphones.

How SM-SR/SM-DP communicate to eUICC ?

How SM-SR can communicate to eUICC ? This is the point that I am personally most interested in (You may be more interested in other parts). This communication is supposed to be over-the-air ? Then you might ask 'what kind of OTA technology' and which specific Radio message will be used to carry these information.

I think this should be determined by each MNO and each MNO would use different technology. GSMA Specification mentions of some of possibile mechanism as follows. (In Ref [1], the section A.2 MNO-SM-DP Interface describes as follows).

    All relavant known information on the Target eUICC and its SM-SR e.g:

    • The method to be supported by SM-SR to communicate with eUICC (e.g, support of SMS and/or RAM over HTTP(s) over LTE/EPS)

Once this OTA mechanism is determined, the higher level protocol is relatively clearly defined in the following sections in following sections of Ref [1]

  • 3.5.1 eUICC Registration at SM-SR
  • 3.5.3 Profile Ordering
  • 3.5.4 Profile Download and Installation
  • 3.5.5 Master Delete
  • 3.5.6 Profile Enabling
  • 3.5.7 Profile Enabling via SM-DP
  • 3.5.8 Profile Disabling
  • 3.5.9 ISD-P Deletion
  • 3.5.10 ISD-P Deletion via SM-DP
  • 3.5.11 SM-SR Change

What is in a Profile ?

A Profile is a set of UICC parameters that is required to attach a Network and perform various functions that the device subscribes. There are roughly three Categories of informaton as follows. (Based on the section 3.4.1 of GSMA Specification (Ref [1]))

    i) Authentication/Security Algorithm Parameters : Algorithms would be Milenage in most of the live network. or it can be 3GPP Test algorithm if it is configured for test. The parameters would be as follows.

    • OPc
    • ri
    • ci
    • K

    ii) Policy Rules attached to the Profile

    iii) Other UICC Parameters described TS 31.102 (Many of these parameters might be related to Policy Rules)

Common Use Case

As of now (Sep 2015), there is no international standard about eUICC Profile update method that is commonly adopted even though there are some cases where eUICC are used in terms of hardware. So, the use model listed here would be a kind of idea level.

    Case 1 : eSIM is embedded in the device and IMEI (device ID) & ICCID (UICC Serial Number) is informed to end user (or a specific Service Center). And then, the end user (or Service Center) can ask Network Operator (MNO) to activate of eUICC.

As of now (Oct 2024), it seems eSIM has become much more common. Interestingly it seems it became more common to regular mobile phone (smart phone) than in IoT device.

Reference :