Frequency location of PointA and SSB across different bandwidths

Using the X310 SDR and a Quectel RM520N-GL modem in a lab setting (1-2 meter distance), we have been struggling with getting strong reception on our modem. Measuring the signal at the modem, we only get an SNR of 3-5 dB, which significantly impacts the SDR's performance.

We employed a spectrum analyzer to troubleshoot, measuring the X310 SDRs signal at approximately 30 dB above the noise floor. So, we are confused about why the modem only reports the SNR of 3-5 dB.

Furthermore, we compared the modem measurements with a B210 SDR-based setup, resulting in 25-30 dB measurements at zero attenuation. For the B210, increasing the attenuation lowers the measured SNR. For the X310, we cannot increase or decrease the measured SNR across different attenuation levels at both 80 MHz and 40 MHz bandwidth.

It seems that the relationship between frequency point A and SSB provided in the config files provided in Git is not the optimal solution, and this has a significant impact on the performance of OAI.

Below, we have added a brief overview comparing the 2 SDRs and some different attenuation configurations.

B210 20 MHz (0/0 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-86 dBm' SNR: '28.5 dB' RSRQ: '-11 dB'

B210 40MHz (0/0 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-87 dBm' SNR: '26.0 dB' RSRQ: '-11 dB'

B210 40 MHz (12/12 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-97 dBm' SNR: '15.5 dB' RSRQ: '-11 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-98 dBm' SNR: '15.5 dB' RSRQ: '-11 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-97 dBm' SNR: '15.0 dB' RSRQ: '-11 dB'

USRPX310 80MHz (0/0 att_tx/att_rx) TX gain: 31.5 RX gain: 37.0

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-80 dBm' SNR: '4.0 dB' RSRQ: '-13 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-80 dBm' SNR: '3.5 dB' RSRQ: '-13 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-80 dBm' SNR: '3.0 dB' RSRQ: '-13 dB'

USRP X310 80MHz (6/12 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '4.0 dB' RSRQ: '-13 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '4.5 dB' RSRQ: '-12 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '4.0 dB' RSRQ: '-12 dB'

USRP X310 80MHz (0/12 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-86 dBm' SNR: '4.0 dB' RSRQ: '-13 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-85 dBm' SNR: '4.0 dB' RSRQ: '-13 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-86 dBm' SNR: '4.0 dB' RSRQ: '-13 dB'

USRP X310 40MHz (0/0 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-81 dBm' SNR: '6.5 dB' RSRQ: '-12 dB'

USRP X310 40MHz (11.5/22.5 att_tx/att_rx)

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '6.5 dB' RSRQ: '-12 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '6.0 dB' RSRQ: '-12 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '6.5 dB' RSRQ: '-12 dB'

[/dev/cdc-wdm0] Successfully got signal info 5G: RSRP: '-90 dBm' SNR: '7.0 dB' RSRQ: '-12 dB'

Edited Sep 20, 2025 by Sebastian Grøsvik