By Juan Pedro Tomás

Multi-SIM is a type of service offered by mobile carriers for users with multiple connected devices. Multi-SIM is a service in which carriers give users a second or several SIM cards that share the same number or data rate as the original SIM card included in the contract. In this way, if users have two phones or a phone and another device such as a tablet or smartwatch with connectivity, they can share the same data rate among all these devices.

According to Ericsson, Multi-SIM means an opportunity to provide a more flexible voice service and thereby increase customer loyalty. “The mobile devices used need to have Multi-SIM capability to be able to connect to the same mobile number. Multi-SIM capability for voice calls means that you can be reached via these devices without connecting via the smartphone,” the Swedish vendor said.

Ericsson noted that this capability also requires that multi-SIM for voice calls is implemented in the operator’s network. This can be done using a Voice over LTE (VoLTE) network that has implemented multi-SIM voice call functionality.

“With the introduction of VoLTE, operators can leverage the all-IP based network architecture to ensure and improve voice quality, while also opening up for a broader range of communication capabilities such as video calling, multi-device support, and multi-SIM support. This will potentially increase the voice traffic, but above all it will increase customer loyalty and reduce churn. The fact that new types of devices are connected to the operator’s network could also mean a potential for new types of services yet to be defined and, thereby, potential new revenue opportunities.”

Multi-SIM detailed by 3GPP in Release 17

According to a previous report by 5G Americas, Multi-SIM devices enable use of multiple subscriptions, potentially for different networks, in one device. As of today, multi-SIM devices are supported with no specific support within the 3GPP specifications. The Release-17 work item on Support for Multi-SIM Devices aims to introduce such support, thereby enabling enhanced performance and user experience in case of a multi-SIM device

“One objective of the work item is to address the issue of collision of paging messages from two different networks for multi-SIM devices. Another objective is to specify mechanisms that a multi-SM device can use to notify the current network when it, for some reason, switches to another network associated with a different SIM,” 5G Americas said.

A previous document by the 3GPP stated: “Multi-USIM devices have been more and more popular in different countries. The user may have both a personal and a business subscription in one device or has two personal subscriptions in one device for different services. However, support for multi-USIM within a device is currently handled in an implementation-specific manner without any support from 3GPP specifications, resulting in a variety of implementations and user equipment (UE) behaviours (e.g. Dual SIM Single Standby, Dual SIM Dual Standby, Dual SIM Dual Active, etc.). Such situation may cause increased complexity for UE vendors, unpredictable UE behaviour for network vendors and/or operators, resulting to degraded network efficiency and user experience.”