What is Multi-IMSI (And Why Is It Better Than eUICC)

M2M & IoT services and applications in its majority typically work through SIM enabled devices which are deployed in local markets and throughout the world. When these SIM enabled devices move out of the local home network, it can result in data roaming that could drastically affect the service delivery charge. Once a connected device is powered on, it will perform an authentication action with the network, which uses the IMSI as the key for this network. 


What is an IMSI?

IMSI stands for International Mobile Subscriber Identity. It is a number used to authenticate a SIM on a cellular network. This ID is standardized by the International Telecommunication Union (ITU).

Each IMSI has an allowed network coverage list attached. In other terms, a limited number of Operator Networks can be attached for a specific IMSI. This limit is depending on the number of roaming agreements which have been negotiated and agreed between an operator and his network partners. 

The network coverage list is defined by a whitelist of Network Roaming Partners where the IMSI is allowed to attach. 

For example, Using the following IMSI: 2620111, the network operator knows this information:

multi-imsi table-1 

 The problem with a single IMSI solution 

The main issues with single IMSI are a lack of coverage and susceptibility to network faults. With a single IMSI, the SIM is geographically dependent which means it can only attach to one specific operator in the country which belongs to the IMSI. For instance, taking the example above, the SIM could only attach to ‘T-Mobile’ in Germany. This could result in the device lacking in coverage in Germany. However, in other countries, the SIM would be roaming and has the potential to reach multiple networks, dependent on negotiated roaming agreements.


Multi-IMSI solution: The benefits over eUICC 

UICC (Universal Integrated Circuit Card), stores information and applications securely to a SIM profile.   With a UICC, it is commonplace that one SIM card holds one profile, and all the information needed for it to function. Often, this was assigned to one operator which meant one connectivity option per SIM.  Operators can change their prices, suffer downtime or have their technology go out of date. Therefore, it's not feasible for an IoT deployment to rely on one operator.    

However,  eUICC (Embedded Universal Integrated Circuit Card) can accommodate multiple SIM profiles, so one SIM card can hold numerous connectivity options, with users able to choose between the different options, and it can be provisioned over-the-air (OTA).  This specification allows users to change to another network provider for their device, without the need to remove the SIM from the device.  


eUICC Benefits 

eUICC makes it possible to manage, download, and delete carrier profiles over-the-air. The Global System for Mobile Communications (GSMAs) embedded SIM specification provides a standard mechanism for remote provisioning and management of IoT connections. This allows for OTA provisioning of your SIM. This enables a SIM to be connected to an initial operator and provides the option to change your subscription remotely from one operator to another.  

However, with a regular SIM (UICC), it must be physically replaced from the old SIM to the new SIM if changing carriers.   


eUICC Downside 

The network architecture for eUICC is designed so that no data can be transferred between channels or profiles, as it requires authorization from the central certificate authority which ensures legitimacy and no interference between profiles.  

Many IoT manufacturers want to offer a plug and play solution that works straight away, and with many IoT devices on the move, it can be difficult to estimate where the device and SIM are deployed.  Any IoT deployment, using eUICC, that wants to change operator can do so. However, it is required first to check that the Mobile Network Operator (MNO) that owns the network can be easily changed to a new operator.   

MNOs have a series of rules and controls they are subjected to as they lease bandwidth from each countries' regulatory body. If switching between MNOs, IoT deployments could suffer significant downtime while checking it meets new network controls and rules.  


The Multi-IMSI Effect 

An IMSI (International Mobile Subscriber Identity) is a globally unique number used to authenticate the device on a cellular network. The 16-digit IMSI is made up of three components: mobile country code, mobile network code, and subscriber number.  

A Multi-IMSI card can also be changed remotely, via over-the-air (OTA) technology. However, the difference is that it can host multiple identities, each with multiple operator roaming agreements, meaning it can give the best possible coverage where ever the device is located. 

With Multi-IMSI,  EMnify can offer multiple profiles in one. Users can switch between different network infrastructures instantly, allowing the use of several profiles within the same data channel. In this case, the EMnify SIM appears as a single operator, but with the ability to instantly switch operators and share data between profiles contained in one channel of the SIM.


Multi-IMSI Solution: The Benefits  

With the EMnify Multi-IMSI solution, the IMSI can be changed automatically. If a country is not covered, it means there is no existing roaming agreement with a local network operator. Thus, the SIM will swap IMSI to use an IMSI with an existing roaming agreement.   

Our Multi-IMSI connectivity means services are instantly available in over 180 countries and 540+ mobile networks.     

EMnify's platform provides the capabilities needed to operate SIM cards fitted with multiple IMSIs in a single and unified environment.    

EMnify's integrated Multi-IMSI offers the following additional benefits:  

  • Pre-configured Multi-IMSI and network roaming partners can be managed via a single interface    
  • The same MSISDN (phone number) is independent of the actual IMSI used    
  • Possibility to update IMSI via OTA, to add/remove IMSI during the lifetime of a SIM  


The Multi-IMSI use case

The benefits of a Multi-IMSI SIM card may not be felt as much as in the automotive industry, which is arguably the industry that IoT has grown fastest in. Application developers, car manufacturers and suppliers can overcome the challenges they face by running their IoT/M2M app on an IoT connectivity platform.

With EMnify’s embedded SIM, car manufacturers and suppliers can integrate embedded SIM cards much earlier in the automobile manufacturing process or on-board units. These embedded units tend to be more resistant to temperature changes and impacts, making it ideal for fleet tracking regardless of what terrain their vehicles are in.

EMnify’s Multi-IMSI SIM card ensures that fleet management benefits from network independent connectivity. This includes great coverage with our multi-carrier SIM and our on-board units are connected to the network with the best latency.


A typical 10-step IMSI swap scenario

In the example below, we describe the IMSI swap scenario. In this scenario, a vehicle with an embedded SIM is connected through a device to a German Network Partner with a specific IMSI (IMSI1). Later on, the vehicle is redeployed to Argentina and connects to an Argentine Network Partner of EMnify with a new IMSI (IMSI2).

  1. SIM is initially provisioned with IMSI 1 as an active IMSI 
  2. SIM attaches the German Network (MCC 262) 
  3. SIM moves to Argentine (MCC 722)
  4. SIM tries to reach network in Argentina with IMSI1
  5. No roaming agreement is allowed. IMSI1 is rejected by the visited network.
  6. The following message is displayed on the EMnify User Interface: "Location update rejected from VLR 34656022000 for IMSI 26201101234567891. This operator is currently not supported for this IMSI. A different IMSI or operator will be used for the network registration."
  7. SIM applet finds Argentina (MCC 722) as the new location 
  8. SIM Applet overwrites the active IMSI. IMSI1 is replaced with IMSI 3 according to IMSI Selection Table
  9. SIM sends a refresh command to the device and a new network attach with IMSI3 is performed
  10. SIM is connected with IMSI3 on an Argentine Network Partner of EMnify 

At EMnify, we specialize in providing IoT connectivity in the cloud and secure service management for your IoT devices. For more information on how we can help with your IoT connectivity needs, reach out to our team of IoT experts via email: or phone:  +49-30-5557-33333.

Are you searching for the right IoT solution
for your business?

Check out our Introductory Guide to Wireless Connectivity
to make the best decision for your IoT use case.
Download our introductory guide to wireless connectivity

Subscribe to the Blog

    Recent Posts