Aerial testbed/DGX Spark: no UL packet

Accelerated Computing Aerial Forum
1

Hi Aerial team,

the setup:

DU act as the PTP master, the system clock sync with NTP, RU act as the slave.

scenario:
RU can receive the DL C/U plane on time, but no UL packet is sent from RU. the mobile phone can’t find the default network{mcc = 001; mnc = 01}

question:

  1. any method to check whether PBCH is broadcasting the PLMN in DU log?
  2. can UE search/attach the network while there is no GPS in network?

Thanks!

2

Hi Alex,

  1. Please try below:
    a. Capture the FH PCAP and FAPI PCAP.
    b. Find a SFN/slot number where PBCH is assigned in the FAPI PCAP.
    c. Find the frame/subframe/slot number corresponding to the SFN/slot number in the FH PCAP.
    d. Check if DL U-plane packets are sent on the frame/subframe/slot and their PRB matches with the FAPI info.
  2. Yes, it should be possible.

For 1., please check L2/L3 configs, e.g., NR-ARFCN, bandwidth, etc. This is critical if the UE doesn’t support the configured band.
Also, please check RU’s actual transmission power as well. If the actual transmission power is pretty low, transmission power-related parameters should be tuned. From Aerial perspective, if your O-RU’s digital power scaling fully complies with the O-RAN spec., fs_offset_dl/ul should be set to 0.

Thank you.

3

thanks @nhashimoto ,

the fapi pcap, the pcap collected at ru/du side is attahced.

Is it a known issue that the ul u-plane can’t be decoded in wireshark because the related c-plane set udCompHdr as 0, although du/ru both agreed to use bfp, no udCompHdr field in u-plane.

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sep11.zip (3.6 MB)

4

after choose “udCompHdr filed” as “not present” once, the wireshark work fine!

Can you do this in UL as well?

BTW, PBCH is a DL channel. Please check DL packets.

5

thanks @nhashimoto ,

yes, I did as you said. But it still work, I tried v4.6.8 and the dev version.

6

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fapi/fh pcap’s time seem synced.

7

DL U-plane packets were sent and UL U-plane packets were received. That indicates the PHY and the interfaces to the PHY have no problem. Please check the RF and RRC.

8

thank @nhashimoto , the UL u-plane can be seen in RU port, but not received in DU.

9

Does that mean there is a network configuration issue?

10

thank @nhashimoto ,

not sure, the switch has issue in capturing the pcap.