srsue fails to find cells when nof_antennas = 2 and mulltiple dl_earfcn's are configured

[nedsana]

Issue Description

Hi, I am facing a problem with cell detection, when I use 2 antennas and configure multiple channels in "dl_earfcn" entry.
I detected it by listening to the nearby operator cells.

Below I will place full config file. Here I will only list the significant, in my opinion, settings and will give some explanations:

Experiment 1 ue.conf:

• dl_earfcn = 1400,1425,1499
• nof_antennas = 2

Expected behavior: my personal phone is connected to cells from Band 3, dl_earfcn 1425, so I was expecting the SDR to be able to detect some or all of these cells (in my case they were 420, 434, 499). The rest dl_earfcns 1400 and 1499 are not used by any operator, so no cells are expected there.

Actual behavior: no cell were detected and on the second pass through the dl_earfcn list I started getting error
[ERROR] SetNCOFrequency(index = 0) - Frequency(4.95 MHz) out of range [0-3.84) MHz.

Experiment 2 ue.conf:

• dl_earfcn = 1275,1425,1575
• nof_antennas = 2

Expected behavior: my personal phone is connected to cells from Band 3, dl_earfcn 1425,. The other dl_earfcns 1275 and 1575 are used by other operators. So I was expecting the SDR to be able to detect cells on any of the channels.

Actual behavior: no cells were detected

Experiment 3 ue.conf:

• dl_earfcn = 1425,1400,1575
• nof_antennas = 2

Expected behavior: my personal phone is connected to cells from Band 3, dl_earfcn 1425,. 1575 is used by other operators and 1400 is not used. So I was expecting the SDR to be able to detect cells on 1425 and 1575.

Actual behavior: cells were detected on 1425, as I would expect. Nothing was detected for 1400, as expected. And nothing was detected for 1575, not as I would expect. And after ~5 seconds I start getting:
[ERROR] SetNCOFrequency(index = 0) - Frequency(15 MHz) out of range [0-7.68) MHz

Two more observations:

• if I run the above examples with nof_antennas = 1, the result is just as expected - cells are found for channels 1425,1275,1575.
• if I run the above examples with nof_antennas = 2 and do not use a list of values in dl_earfcn, but set a single channel, like
  dl_earfcn=1425 or dl_earfcn=1575 or dl_earfcn=1275, cells are detected correctly.

I use the following command line for the experiments
/srsue ~/.config/srslte/ue.conf --rf.device_args="rxant=LNAH,rxant=LNAH" --rf.rx_gain=40

Setup Details

Hardware:

• LimeSDR-USB v1.4,
• CPU: Intel(R) Core(TM) i7-4710MQ CPU @ 2.50GHz, 8 cores,
• 2xLNA amps for the input signal

Software:

• SoapySDR, branch "soapy-sdr-0.7.2", from 12.01.2020
• LimeSuite, branch "stable", v20.07.02
• srsLTE, branch "master", tag "rel_20_10"
• OS Ubuntu 20.04

I am attaching a zip file with the logs and the configuration for the above tests.
DlEarfcnTests.zip

Please share any comments,
Greetings.

[andrepuschmann]

Thanks for reporting this. It indeed seems to be a bug on our side. We'll investigate.

[nedsana]

Any news on this one?

[therustyalex]

Any update on this?