Trouble to attach COTS UE to Benetel 550 O-RU with srsRAN gNB

[MaximeZingraff]

Hi SRS community,

We are having an issue to attach a COTS UE to our O-RU using srsRAN.

Setup:

• CPU: Intel Core i9-14900K
• OS: Ubuntu 22.04.5 LTS with kernel 5.15.0-1033-realtime
• NIC: Intel E810-XXVDA4T
• O-RU: Benetel 550, firmware RAN550-1v1.0.4-605a25a
• gNB: srsRAN split 7.2 (commit d8bfdc9)
• CN: Open5GS, PLMN 90170
• UE: OnePlus Nord 5G (AC2003), Android 11

We use PTP / phc2sys for synchronization between the RU and the DU, with the NIC acting as the PTP grandmaster.

We use band n78 with 3558.18 MHz center frequency (ARFCN 637212), 100 MHz bandwidth, 30 kHz SCS, 4x2 MIMO.

After a lot of different configuration files, we are able to see the network on different COTS UE, including the OnePlus Nord. But when trying to connect to the network, there's no particular log in the gNB and the UE is not able to connect, even after registering the SIM in the CN and setting up the APN according to srsRAN tutorial.

I disabled PRACH CP (is_prach_cp_enabled: false), when it's enabled I have this kind of log:

2025-07-22T23:16:17.280265 [OFH     ] [W] Sector#0: missed incoming User-Plane PRACH messages for slot '135.19'
2025-07-22T23:16:17.280268 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '4'
2025-07-22T23:16:17.280312 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '5'
2025-07-22T23:16:17.280333 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '4'
2025-07-22T23:16:17.280335 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '5'
2025-07-22T23:16:17.280337 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '4'
2025-07-22T23:16:17.280339 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '5'
2025-07-22T23:16:17.280340 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '4'
2025-07-22T23:16:17.280342 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '5'
2025-07-22T23:16:17.280343 [OFH     ] [I] Sector#0: dropped received Open Fronthaul message as no uplink PRACH context was found for slot '135.19' and eAxC '4'

Maybe there's a link with the attach issue?

We tried what is advised in similar discussions [1] [2] but without success.

If you have any hints on what's happening, I'll be really grateful!
Thanks,
Maxime

Attached:

• gnb.log with PRACH CP disabled
• gnb.log with PRACH CP enabled
• kpi.sh output from the Benetel RU when the gNB is running: kpi_benetel.log
• ru_config.txt from the Benetel RU
• srsRAN gNB configuration file: gnb_ru_ran550_tdd_n78.txt

[aibtw]

I don't see DPDK configured. In my experience DPDK is almost a must, Especially for higher bandwidths like 100MHz. I suggest you look at the DPDK guide in the docs.