MIB SIB1 with nrscan

[johst-source]

Hi!

Thank you for this great application. Im wondering if is decodes MIB and SIB1 for nrscan as well or is it just for when searching for a specific cell?

I do manage to find some commercial cells. However, when scanning (no matter the band) I get Overflow and the message
"The offset 100000 is NOT multiple of the subcarrier spacing 15000"
or
"The offset 1000000 is NOT multiple of the subcarrier spacing 15000"

like

Start scaning GSCN number 2213
Absolute freq 8.8565e+08
the offset 1000000 is NOT multiple of the subcarrier spacing 15000
Update RF's meas central freq to 8.8565e+08
Update min ssb center detect boundary to 8.81074e+08
Update max ssb center detect boundary to 8.88226e+08
2025-03-12T12:11:33.496962 [RF     ] [I] Mapping RF channel 0 (device=0, channel=0) to logical carrier 0 on f_rx=885.6 MHz
2025-03-12T12:11:33.501726 [PHY    ] [I] [    0] Cell search: Setting SSB configuration srate=15.36 MHz; c-freq=885.650 MHz; ss-freq=885.650 MHz; scs=15kHz; pattern=A; duplex=fdd;
2025-03-12T12:11:33.505648 [RF     ] [I] Overflow

Running on a USRP B205mini with the config

nof_usrp_dev: 1
usrp_setting_0:
  #scan_bands: [1]
  ssb_freq: 622850000 # Set to the ssb frequency of the cell, could be obtained with the cell scan function
  rf_args: "clock=internal,type=b200" # For B210
  # rf_args: "clock=external,type=x300,serial=32B0F2F,master_clock_rate=200000000,sampling_rate=25000000" ## For TwinRX daughterboard
  # rf_args: "clock=external,type=x300,sampling_rate=23040000" ## For CBX daughterboard
  rx_gain: 75 # for x310 CBX, max rx gain is 31.5, for b210, it's around 80, for x310 TwinRX, max rx gain is 90
  min_rx_gain: 0
  max_rx_gain: 80
  srate_hz: 15360000 # the sampling rate of USRP, integer division of 200MHz for TwinRX, and 5G sampling rate for CBX: 11520000 or 23040000
  srsran_srate_hz: 15360000 # the sampling for real signal processing, should be in 5G sampling rate, multiple of 1.92 MHz. 
  nof_carriers: 1 # srsRAN rf setting, always set to be 1 for now. 
  nof_antennas: 1 # srsRAN rf setting, always set to be 1 for now.
  scs_index: 0 #(0: 15kHz, 1: 30kHz, ..., the u in standard)
  rf_log_level: "debug"
  nof_rnti_worker_groups: 4 # number of of threads for DCI decoding, each will divide the UEs into small groups
  nof_bwps: 1 # number of BWP of the cell
  nof_workers: 4 # using worker pool to asynchronously process the slot data
  cpu_affinity: false # pin the worker's thread into CPU or not.

  log_name: "a.csv"
  google_dataset_id: "ngscope5g_dci_log_wanhr"

Any suggestions on what might be wrong?

[XuyangCaoPrinceton]

Hi!

The nrscan scans all possible frequency points where a cell may exist. It does SSB shape detection and decodes MIB, but will not decode SIB1.

You could ignore those messages. The USRP is trying another frequency scan without a USRP reconfiguration. If not possible, it will issue a USRP frequency reconfiguration and scan the new frequency (and the offset message gets printed). The overflow message is also OK, as we are just doing SSB detection here (so missing a few RF points are fine).

After you find particular cells (e.g., with NRSCAN), you could use NRSCOPE to listen to that cell and SIB1 shall be decoded.