Unable to connect srsUE to srsRAN gNB

[jonebert]

Hi all,
I'm currently trying to setup srsRAN by following this tutorial.
Sadly srsUE won't connect to the gNB and fails with the error message Scheduling request failed: releasing RRC connection....
From the pcap's I can see that UE sends the "RRC Setup Complete" message but the gNB does not receive it.
I could only find this issue in the srsRAN_4G repo, which reported the same error but adjusting the time_adv_samples parameter did not fix this issue for me (I checked all values from 0 to 350 in 5 steps).
I use an USRP B200mini for the UE and an USRP B200mini-i for the gNB, but I also tried two B210 which also failed with the same error.
Here are my configurations, logs and pcaps.
logs_and_configs.tar.gz

Thank you in advance for any help!

[pgawlowicz]

could you try to increase the rx_gain in the srsgnb config?

[jonebert]

Thanks for the quick response. I tried it with rx_gain values from 40 to 75 but every time I got the same error.

[pgawlowicz]

could you post logs? also how is the setup connected? over the air or rf cables?

[jonebert]

The setup is over the air.
Here are the logs for a rx_gain of 75:
gnb.log
ue.log

[pgawlowicz]

PDSCH received by UE has a good SNR:

2024-06-26T11:01:17.055298 [PHY0-NR] [I] [ 2081] PDSCH: cc=0 pid=0 si-rnti=0xffff prb=(1,8) symb=(2,13) CW0: mod=QPSK tbs=80 R=0.380 rv=0 CRC=OK iter=1.0 evm=0.21 t_us=193 epre=+5.2 snr=+17.6 cfo=+553.4 delay=+0.0  ack_tti_tx=2082

But the problem is with PUSCH at gnb:

PUSCH: rnti=0x460c h_id=0 prb=[3, 6) symb=[0, 14) mod=QPSK rv=0 tbs=11 crc=KO iter=6.0 sinr=-19.4dB t=211.4us uci_t=0.0us ret_t=0.0us

So the downlink from GNB to UE is good, but there is an issue with uplink. you need to tune gnb rx_gain and srsue tx_gain.

[pgawlowicz]

could you repeat with debug logging mode at gnb?

[jonebert]

Sure here is the gNB log
gnb.log

[pgawlowicz]

It seems that CFO of the PUSCH is very high and fluctuates a lot, for example:

  cfo=-923.6Hz
  cfo=+1592.2Hz
  cfo=+1882.3Hz
  cfo=+1652.2Hz
  cfo=+1264.5Hz

Probably, you will need to use better clocks for your b200s.

[pgawlowicz]

@jonebert any update on this issue?

[jonebert]

Hi, yes the issue was resolved when I switched one of the minis with another one. It seems that the one I was using is faulty.