[srslte-users] Lower sampling frequency for pdsch_ue or srsue

[Nazir Ikhtiari]

Hi all,

When running pdsch_ue from my laptop with usb 3.0 and I get very high
PDSCH-BLER and PDCCH-Miss. I believe this is because my laptop is dropping
samples and should not occur if sampling rate is lowered. I only need to
monitor the centre 6 RBs (PSS, SSS, and BCH). I've tried setting nof_prb =
6, but if look at the DEBUG INFO samp rate is still 30.72 MHz (*----
Receive 30720 samples  ---- *). Also turnign off srsGUI doesn't help
either.

I believe lowering the samp rate should solve this issue, if someone know
how to do this please let me know.

NB: Although the log is showing PDSCH-BLER at 0% near the end of logs, this
usually fluctuates quite a lot. It was just at 0% when I captured it.

*****************************************************************************************************************************************************
naz at naz-HP-naz@naz-HP-Spectre:~/Downloads/srsLTE/build/lib/examples$ sudo
./pdsch_ue -f 1840000000 -p 6 -d
linux; GNU C++ version 7.3.0; Boost_106501; UHD_003.010.003.000-0-unknown

Opening RF device with 1 RX antennas...
Opening USRP with args: type=b200,master_clock_rate=30.72e6
-- Detected Device: B200mini
-- Operating over USB 3.
-- Initialize CODEC control...
-- Initialize Radio control...
-- Performing register loopback test... pass
-- Performing CODEC loopback test... pass
-- Asking for clock rate 30.720000 MHz...
-- Actually got clock rate 30.720000 MHz.
-- Performing timer loopback test... pass
Starting AGC thread...
Tunning receiver to 1840.000 MHz
Searching for cell...
 Found Cell_id: 174 CP: Normal  , DetectRatio=67% PSR=17.90, Power=19.2 dBm
 Found Cell_id:   0 CP: Normal  , DetectRatio= 0% PSR=0.00, Power=-inf dBm
*Found Cell_id: 176 CP: Normal  , DetectRatio=100% PSR=25.23, Power=23.6 dBm
Decoding PBCH for cell 176 (N_id_2=2)
Setting sampling rate 30.72 MHz
 - PCI:             176   6.3, FrameCnt: 0, State: 1
 - Nof ports:       2
 - CP:              Normal
 - PRB:             100
 - PHICH Length:    Normal
 - PHICH Resources: 1
 - SFN:             392
Decoded MIB. SFN: 392, offset: 3
    Tx scheme: Diversity
   nof layers: 2
nof codewords: 1
          CFO: +2102.08 Hz
         RSRP: +35.3 dBm |  -inf dBm
          SNR:  +7.0 dB |  -inf dB
           Rb:   0.00 /   0.01 /   0.04 Mbps (net/maximum/processing)
   PDCCH-Miss: 88.56%
   PDSCH-BLER: 14.29%
         TB 0: mcs=2; tbs=144
         TB 1: mcs=0; tbs=0

Press enter maximum printing debug log of 1 subframe.

    Tx scheme: Diversity
[DEBUG]:  ----  Receive 30720 samples  ----
[INFO]: SYNC TRACK: sf_idx=6, ret=1, next_state=1
    Tx scheme: Diversity
[DEBUG]:  ----  Receive 30720 samples  ----
[INFO]: SYNC TRACK: sf_idx=4, ret=1, next_state=1
O    Tx scheme: Diversity
[DEBUG]:  ----  Receive 30720 samples  ----
[INFO]: SYNC TRACK: sf_idx=6, ret=1, next_state=1
Finding PSS... Peak:      6.7, FrameCnt: 0, State: 10
   nof layers: 2
nof codewords: 1
          CFO: +2124.67 Hz
         RSRP: +36.2 dBm |  -inf dBm
          SNR:  +4.4 dB |  -inf dB
           Rb:   0.01 /   0.03 /   0.05 Mbps (net/maximum/processing)
   PDCCH-Miss: 82.00%
   PDSCH-BLER:  0.00%
         TB 0: mcs=2; tbs=144
         TB 1: mcs=0; tbs=0

Press enter maximum printing debug log of 1 subframe.

  SIGINT received. Exiting...
   nof layers: 2
Bye codewords: 1
naz at naz-HP-Spectre:~/Downloads/srsLTE/build/lib/examples$
         RSRP: +35.8 dBm |  -inf dBm
          SNR:  +2.9 dB |  -inf dB
           Rb:   0.01 /   0.02 /   0.06 Mbps (net/maximum/processing)
   PDCCH-Miss: 82.40%
   PDSCH-BLER:  0.00%
         TB 0: mcs=2; tbs=144
         TB 1: mcs=0; tbs=0

Press enter maximum printing debug log of 1 subframe.

*****************************************************************************************************************************************************

regards

Nazir Ikhtiari
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