Boost your CERN mobile service connectivity by changing your CERN SIM card or eSIM

Many of us have suffered communication problems since Swisscom’s antennae were replaced by those of Orange in France for regulatory reasons. The connectivity issues arise when a mobile phone remains connected to a mobile operator until it loses signal, while another operator could offer a much better service. Communication cuts, missed calls and no signal are some of the results of this phenomenon.

Although CERN, Swisscom and Orange worked together to ease the transfer between operators when crossing the border, experience has unfortunately shown that this phenomenon depends on the phone, its operating system configuration and even its firmware version. Put simply, many phones resist connecting to Orange/Swisscom as they should, instead staying connected to Swisscom/Orange.

Since 2019, CERN and the two operators have studied various approaches to improving the service. The simplest solution is to have a phone switch between network cells based simply on signal quality, ignoring the name of the operator. To this end, the E-PLMN (Equivalent Public Land Mobile Network) project was launched in early 2020, with Swisscom and Orange working together to deliver an improved service for CERN users.

The idea behind the E-PLMN project is simple: a telephone considers both Orange and Swisscom as equivalent networks and switches between network cells depending only on the signal quality. A phone automatically connects to the best available network but, as this only happens when idle, ongoing calls could still be cut if coverage is lost mid-conversation.

Although a simple concept, such a configuration is the first to be employed in an international setting. Fortunately, after extensive pilot testing and network reconfiguration by both operators, we now have a very successful service.

To enjoy the benefits of the improved network service, you need to:

• change your SIM card¹ at any time convenient for you at the Telecom Lab, 600/R-010 (Mon-Fri: 8.30-12.30, 13.30-17.30)
• change your eSIM¹ by simply creating a ticket (https://cern.service-now.com/service-portal/?id=sc_cat_item&name=request&fe=mobile-telephony)
• ensure your phone is configured to select the network operator automatically (i.e. not set to prevent roaming);
• activate 4G if you have not already done so; and
• activate VoLTE and Wi-Fi calling if available on your phone.

Please note that roaming charges and restrictions still apply while connected to Orange. For more information, visit this link and remember that you can monitor your monthly roaming data consumption via Swisscom's cockpit.

¹ All SIM cards and eSIMs delivered as from 1 June will have this option activated by default.