nRF9151-DK – NCELLMEAS Command Returning Only a Single Cell

[fabricio.almeida]

Hello,

I'm currently using the nRF9151-DK hardware to develop our product based on the nRF9151 SiP. We selected the ncs-serial-modem firmware, and the modem is controlled via AT commands by our main MCU.

We are evaluating the nRF Cloud Location feature to determine device position using cellular or Wi-Fi data. I have implemented and tested this functionality in multiple areas around Uberlândia, Brazil.

However, I’ve observed that Single Cell Location does not provide the accuracy we need, so I tried using the Multi-Cell Location service. According to the documentation (https://docs.nordicsemi.com/bundle/addon-serial_modem-latest/page/app/NRFCLOUD_AT_commands.html), the NCELLMEAS command should perform a neighboring cell scan.

During my field tests at over 15 different locations across the city, every NCELLMEAS scan returned only one cell after a few hundred milliseconds — as shown in the AT command output below. On the nRF Cloud Location web interface, my results always appear as Single Cell, never Multi-Cell.

[SER] 2023-01-01T00:00:15 TX Modem 14 bytes: AT%NCELLMEAS
[SER] 2023-01-01T00:00:15 RX Modem 6 bytes: OK
[SER] 2023-01-01T00:00:15 RX Modem 71 bytes: %NCELLMEAS: 0,"05314208","72405","9CC6",48,9610,411,71,26,7060,6733
[SER] 2023-01-01T00:00:15 TX Modem 21 bytes: AT#XNRFCLOUDPOS=2,0
[SER] 2023-01-01T00:00:15 RX Modem 6 bytes: OK
[SER] 2023-01-01T00:00:16 RX Modem 46 bytes: #XNRFCLOUDPOS: 0,-18.905003,-48.241289,546

In the coverage area of my residence, I have already observed the nRF9151 connecting to three different Cells, so I believe there is neighboring cell coverage available.

I also rebuilt and flashed the ncs-serial-modem firmware with trace logging enabled to analyze the behavior. The same issue persisted — only a single cell is reported in each scan. I’ve attached the trace log file for reference.

Could you please clarify if there are:

1. Any specific commands or configuration parameters required to enable multi-cell scanning?

2. Any known hardware limitations on the nRF9151 that prevent multi-cell measurements?

Thank you for your support.

trace-2025-11-18T12-54-25.346Z.mtrace

[Hakon]

Modem team;

When using search types 0-2, no neighbor cells are returned because the network has not sent SIBs containing neighbor cell information.

With GCI search types 3-5, there’s a limitation that the GCI search can not be performed when in RRC connected state. The application should wait until the RRC connection is released, and then perform the neighbor cell measurement with GCI search type 3-5.

[fabricio.almeida]

Okay, got it. Thanks for the information!

But how can I check if the modem is in the RRC Connected state, and when it is released? Is there a way to force a release?

In my area, the operator doesn’t support PSM neither eDRX.

[Achim Kraus]

AFAIK, the "+CSCON" notifications are enabled by default and reported in the lte_lc_evt_handler_t set with lte_lc_connect_async.

Usually (I'm not common to your networks), the modem switches from RRC-active to RRC-idle after a timeout (set by the network) without traffic. Usually something about 10-30s. Not sure, what you will get.

[fabricio.almeida]

Hi Achim,
The NCELLMEAS command is now working correctly. I wait for the +CSCON: 0 URC (indicating Idle) before issuing the #NCELLMEAS command. After that, the module performs the cell scan and successfully detects multiple neighboring cells as expected.
For my network this happens after 30s without traffic.