gNB [X310] [RF ] [W] Real-time failure in RF: late

[Ahmed-Chyad]

I am running srsRAN Project 25.10.0 with Open5GS in a Split 8 configuration. The setup works perfectly in SISO (1x1) mode; UEs attach and have full internet connectivit.

However, when I enable MIMO (2x2) by configuring 2 DL/UL antennas, I immediately encounter [RF] [W] Real-time failure in RF: late errors. Given the high-spec server hardware, I suspect a configuration or threading issue or else rather than a resource bottleneck .

Hardware & Environment:

OS: Ubuntu 24.04 (Noble)

Software: srsRAN_Project 25.10.0 (Split 8) + Open5GS

Radio: USRP X310 (UHD Driver 4.9.0)

Server Specs: 128 CPUs, 128 GB RAM

Network: 10GbE NIC (MTU set to 9216)

Configuration:

Working Config (SISO): nof_antennas_dl: 1, nof_antennas_ul: 1

Failing Config (MIMO): nof_antennas_dl: 2, nof_antennas_ul: 2 

Logs / Error Output: When running the MIMO configuration, the gNB log shows repeated RF late arrivals:
Plaintext

[RF ] [W] Real-time failure in RF: late

(Attached is the full gNB log file, and gnb.yml configuration
gnb.log-50mhz-mimo.txt
gnb_x310_50mhz_MIMO.yml
)

Steps Taken:

Verified 10GbE connection is optimized (MTU 9216).

Verified SISO configuration runs stable with attached UEs.

Enabled 2x2 MIMO in config.

Encountered late packets immediately upon start.

Question: Are there specific threading or thread-pinning configurations required for X310 MIMO on high-core-count machines to prevent these late errors?

[xavierarteaga]

Hi @Ahmed-Chyad,
I suggest the following steps:

1. Reproduce the issue using UHD benchmark;
2. Configure UHD to use DPDK. Guide here.
3. Isolate cores to prevent the OS from interrupting the radio operation.

Once you have a clean benchmark, try the gNB again with the same configuration.