High loss rate on RAN550

[aibtw]

High loss rate on RAN550

[aibtw]

Update and more details:

We upgraded to RAN550 V1.0.4, still facing the same issue:

Doing iperf on the downlink makes the loss a little better:

But it is still inconsistent, and the loss shoots up frequently.

New configuration file:
gnb_RAN550v1_srs.txt

RU set to 20MHz, frequency adjusted to 3.6GHz, and set to MIMO 4x4 mode.
At "warning" level of logs, I can see couple of messages repeating:

2024-03-27T19:08:41.850434 [OFH     ] [W] Potentially lost '1' messages sent by the RU
2024-03-27T19:09:11.207036 [OFH     ] [W] Missed incoming User-Plane PRACH messages for slot '279.19' and sector#0
2024-03-27T19:09:11.207042 [OFH     ] [W] Missed incoming User-Plane uplink messages for slot '279.19', symbol '9' and sector#0
2024-03-27T19:09:16.650447 [OFH     ] [W] Potentially lost '1' messages sent by the RU
2024-03-27T19:09:16.705013 [SCHED   ] [W] [  830.15] UL HARQ rnti=0x460a cell=0 h_id=4: Discarding HARQ. Cause: HARQ-ACK wait timeout (256 slots) was reached, but there are still missing HARQ-ACKs and none of the received ones are positive.

gnb.log

Pcaps:
https://drive.google.com/drive/folders/1MSPd8TEAv-Bdkhr7sXkZ3nfQbdU-vKaL?usp=sharing

I would also add that on the RU side, when running kpi.sh, all packets appear to arrive on time:

Regarding synchronization, we are doing it in LLS-C1 topology (i.e. direct link between RU and DU, running ptp on both sides, while DU is synchronized to GNSS signals).
The offset we are getting is very low (less than 5ns on DU on both phc2sys and ts2phc, and <5ns on the RU as well)

I would really appreciate the help.

[andrepuschmann]

Hey @aibtw - sorry for the delayed response. I've noticed you solved the issue in the meantime using the newer firmware and updated configs as you reported in #487 (comment). I am going to close the issue therefore. Please confirm. Thanks

[aibtw]

Hi @andrepuschmann , would you mind opening the issue again? As you might have misinterpreted my other reply, where I said "However, there is still high loss rate on both uplink and downlink in all the configurations we tried", indicating that we are still facing the problem even with v1.0.4

Would really appreciate if some of you guys can have a look at my reply above.
Thanks.

[andrepuschmann]

Hi @aibtw - we are still looking at the RAN550 ourselves here but have already seen reasonable results. Could you comment on your setup a bit more please? Is it wired? What modem are you using?

Have you tried with LLS-C3 sync already? LLS-C1 is not straight-forward to get right.

A few notes on the config, please try to set:

ru_ofh:
  iq_scaling: 10
cell_cfg:
  pdsch/pusch:
    olla_target_bler: 0.1

[aibtw]

Hi @aibtw - we are still looking at the RAN550 ourselves here but have already seen reasonable results. Could you comment on your setup a bit more please? Is it wired? What modem are you using?

Have you tried with LLS-C3 sync already? LLS-C1 is not straight-forward to get right.

A few notes on the config, please try to set:

ru_ofh:
  iq_scaling: 10
cell_cfg:
  pdsch/pusch:
    olla_target_bler: 0.1

The setup is not wired, we aren't using a standalone modem. We are testing with over-air connection, using multiple android phones like OnePlus Nord N30 5G and realme 9i 5G, all of which work fine with SDRs.

For the sync type, we tried C1 and C4, with similar behavior. We still haven't tried C3 though, still trying to get a suitable GM/switch.
Do you suspect this behavior to be a sync issue that could be solved solely by moving to C3?

[aibtw]

Hey @andrepuschmann
quick update, we just tried LLS-C3, unfortunately we're still facing the same behavior that we saw in c1 and c4.

[ismagom]

Hi @aibtw , could you give us an update on this issue? Several users have been able to successfully use the RAN550.

[aibtw]

Hi @ismagom,
We are still trying to understand this issue. We tried different configs combinations, but none solved the issue until now.

Have other users you guys talked to, reported normal behavior for the UL BLER? cause that's our main issue.

we'll be grateful If you could point us to which combination of RU-DU configurations that solved the issue for other users.

[ismagom]

Can you try following the guide here: https://docs.srsran.com/projects/project/en/latest/tutorials/source/oranRU/source/rus/r550.html

I think you should also upgrade the RU firmware version