Poor NB-IoT Signal

[Arend]

Good day, 

I have noticed that cellular reception is very weak using an NRF9151 SMA DK. For more context, we have been using SIMCOM7080G modems in NB-IoT mode with all bands configured, we primary work on Band 3 since this is what our operators use. With the SIMCOM we are able to get and RSSI of 3-4 in poor receptions areas(around 20km from the nearest tower). Now using the exact same antenna on the NRF9151, with the exact band configuration as the SIMCOM, the NRF9151 was not able to even produce any signal reception. 

When searching for signal we keep in the search for signal state for up to 10 minutes, occasionally polling AT+CESQ and AT+CSQ
We have tested with NB-IoT mode only, NB-IoT and CAT-M. We have set it to lock on only band 3 and to also have no lock.

Is there any other configurations that need to be setup on the software side?

[Carl Richard]

Hello Arend!

Thank you for reaching out. Some questions to get us started:

• Please share your modem firmware version and what test application you are using (including nRF Connect SDK version).
  
  
• Are you getting reception on the nRF9151 SMA DK in better conditions (closer to the cell tower for example)?
  
  
• What antenna are you using? I guess this says itself, but make sure it's connected to J1 on the DK.
  
  
• Can you confirm the band settings with AT%XBANDLOCK?, AT%XCBAND=? and AT%XCBAND. Please share the output here
  
  
• How are you powering the DK? If you are using USB it may degrade RF performance. As documented here, we recommend: "Feeding VDD_nRF from an external, clean power supply is recommended during RF evaluation, characterization, and production testing as it might improve RF performance."

If you are able to do a modem trace during your testing that would also be nice to have.

Best regards,
Carl Richard