Roaming SIM, modem configuration and network attachement

[Kevin Barron]

We have purchased a radio fitted with the nRF9160 modem and fitted it with a roaming SIM for NB-IoT use, we are in UK and have Band 20 EE and Vodafone.

What are the initial radio AT commands used to select the MNO 

How is network selection determined?

In the event of a loss of an MNO. What thresholds are used to move the SIM to the 2nd MNO?

When a MNO is selected, on a power cycle, is that the 1st MNO checked therefore the radio should go back to previous MNO or does it rescan ?

[Syed Maysum Abbas Zaidi]

Hi,

Thanks for waiting.

I had a discussion internally regarding the threshold question, In LTE/NB-IoT, this behavior is entirely governed by 3GPP standards (TS 23.122 + TS 36.304). By default, the nRF9160 modem runs in automatic network selection mode.

• Day-to-Day Reselection: The exact dBm and quality thresholds used for cell selection are dynamically broadcast over-the-air by the network operators (EE/Vodafone) via System Information Blocks (SIBs). The modem reads these RSRP/RSRQ values and timers in real-time at the RRC level to determine if a cell is acceptable.
• Loss of Service Trigger: The modem will not switch to a competitor's network just because a signal gets weak. If the signal drops too far everywhere and it can no longer camp on any cell of the current provider, that triggers a 'loss of service'.
• Network Switch: At that point, the NAS (Non-Access Stratum which is functional layer that handles communication directly between your modem and network) layer kicks off automatic PLMN selection to find and jump to the next available allowed network (example transitioning from EE to Vodafone) based on the priority order programmed on your roaming SIM.

Regarding +COP command, you can program it yourself to selects a mobile network automatically or manually. I hope it helps