Multi-IMSI SIM Roaming for MVNOs
To become a successful MVNO and allow your subscribers to call in different countries cheaper, you need to use Multi IMSI roaming solutions.
You can choose how to use the network’s resources in order to provide your subscribers the exact services they need. For example, the Multi IMSI technology is used for travel SIMs. There are a lot of MVNOs that built their business based on travelers. They are offering lower roaming prices for subscribers whom travel often.
Read on and find out how you can benefit from Multi-IMSI technology. This page will cover the following topics:
What is Multi IMSI?
IMSI (Multiple International Mobile Subscriber Identity) is a unique code used by a network to identify and authenticate a subscriber when they attempt to connect to the network. It has the following format:
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MCCMobile Country Code
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MNCMobile Network Code
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MSINThe unique number that identifies the subscriber
Multi IMSI (Multiple International mobile subscriber identity) is used to switch between the identities of the SIM using just one card. The Multi IMSI technology allows to switch between up to usually 10 identities of the SIM using a single card and a single IMSI at a time.
To address this limitation, MVNOs need a technical expert of this technology to change the IMSI of the SIM. Luckily, this can be done by giving the SIM autonomous capabilities using Java-based applet. Another alternative is to allow the network to order the change of the IMSI via Over-the-Air (OTA) interfaces. Of course, there are cases when both ways are combined when you have, for example, the main IMSI that’s owned by the MVNO and also has some IMSIs taken from foreign donors. The donor IMSI can be from the MNO you interconnected with, or national operators of the countries your subscribers travel to.
Once the change of the IMSI has been executed successfully, the identity of the SIM changes, allowing authentication and registration of the subscriber. An applet in the SIM will enable switching the IMSI stored in the SIM to allow the subscriber to connect to the visited network without roaming costs.
Multi IMSI Roaming
The fact that multi-IMSI allows operators to switch from the primary IMSI to an IMSI of another country highlights its meaning for roaming.
With the multi IMSI technology, you can provide cheaper services to your subscribers, according to your business model. Traditionally, roaming was executed using a single SIM paired with a single MSISDN. The only problem is the high interconnection charges required by foreign operators to facilitate your connection. To mitigate this financial burden, you need to roam using a SIM with Multi IMSI functionality.
Multi IMSI can be used to switch the primary IMSI to another IMSI from the visited network’s range. This will allow the subscriber to be recognized and charged as a local subscriber. Usually, this shifting process is done by a Java applet. For example, this applet in the SIM will enable switching the MCC, MNC and MSIN to new numbers stored in the SIM.
When your subscribers are traveling to another country things get more complicated. This implies some requirements from the operator of that country. One of them is to have an MSISDN matching the visited network. This means it would change not only the SIM identity, but it would also change the subscriber’s known identity (MSISDN). In this case, whenever there is a Mobile-terminated call to the primary MSISDN and the visited network’s phone number is assigned to that subscriber, the GMSC sends the routing number request to the HSS/HLR.
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Multi-IMSI registration
✔ When the SIM is trying to register it is seeking the recommended network. It is sending requests to the networks of the visited country until one of them accepts the request.
✔ If none of the networks accepts its attempt to register in a given time, the SIM will switch to another IMSI and start the registration again. -
MO call
✔ If the donor IMSI is national and purchased from the MNO you interconnected with, then the Mobile-Originated call is regular. The technical explanation is the fact that the MCC of the IMSI code matches the MSISDN’s country code and the IMSI change goes unnoticed.
✔ The other scenario that could happen is the IMSI code belongs to the country your subscriber is roaming to, and the MSISDN belongs to your network. This means you need to implement both Multi IMSI and Multi MSISDN features. The technical solution for this situation is adding a CAMEL subscription that will know to contact the home network whenever there is a MO call. The home network will divert the call using the primary MSISDN. -
MT call
✔ For Mobile-Terminated calls the procedure is simple. The call arrives in the home network and the HSS/HLR has the IMSI tracking in its database and routes the call to the current IMSI of the subscriber. -
SMS
✔ The hone network’s SMSC is written on the SIM card. Whenever the Multi IMSI technology is used, the SMSC number is also changed.
✔ Whenever your subscriber is using Multi IMSI in roaming and wants to send an SMS, the Proxy gateway of the visited network sends the message to the home network’s SMSC.
Why is multi IMSI important for MVNOs?
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Multi IMSI is the technical solution to achieve their business model
✔ Some places are expensive to roam into. If your business model is providing services to people that travel to expensive countries, you could use an IMSI of a national operator and access local prices instead of roaming prices.
✔ The fact that the target audience is very small means that big MNO will waste their resource to serve the needs of this niche with such low prices. On the other hand, this is your target audience, therefore, you need to give them more value than any other big MNO with attractive offers. This is the bedrock of a solid and successful MVNO. To obtain this, you need to harness the powers of multi-IMSI to optimize roaming not only for the retention of your subscribers but also to provide value-added services to your clients. -
You can deploy your network faster
✔ When deploying an MVNO network and getting your MCC and MNC you need to have roaming agreements with all the other operators world wide. This kind of arrangements takes a lot of time and you can not deploy your network until you’re all set.
✔ Using the Multi IMSI technology you can borrow a range from a donor that already has agreements with the operators around the world or with a roaming hub. This covers you for all the scenarios your subscribers might roam into.
Yate-based solution equipment for Multi IMSI
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✔ YateHSS/HLR stores and manages the SIM database for mobile networks. It also manages multiple subscriber identities (from different technologies) in one server, providing seamless services over different networks
✔ You can use this product for both Circuit-switching and Packet-switching, so your subscribers can roam from a 4G network to a 2G/3G network and back.
✔ YateHSS/HLR supports Multi IMSI and Multi MSISDN features.
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✔ A system that provides the functions required to manage SIM configurations using Over-The-Air messages over SMS.
✔ YateOTA uses RAM (Remote Application Manager) application to install or update Multi IMSI applet and send custom application commands to the installed applet
✔ Updates files on SIM via the standard RFM (Remote File Manager) application.
MiniCore - Core network for tests and research
The MiniCore is a small factor PC computer that can be used as a test LTE/GSM Core Network. It has installed the MSC/VLR, GMSC, MME/SGW/SGSN, PGW/GGSN, IMS CSCF software components. The MiniCore can also work as an AuC, HLR, HSS for Subscriber management.
