how solve Real-time failure in low-phy???

[unknownman-li]

amf.txt
gnb.txt

Hello everyone,

I am seeking help with an issue I've encountered while setting up a private 5G standalone (SA) network. I have been stuck on this for some time and would greatly appreciate any guidance.

My Setup:

• Software: srsRAN 4G/5G suite and Open5GS core network.

• Hardware: Ettus Research B210 USRP.

• SIM: A writable blank "white" card, properly provisioned with the credentials from Open5GS.

• Test Device: iPhone 16 Pro.

• gNB Host: A mini-PC running Linux, with an AMD Ryzen 5 4500U (6 cores/6 threads, base 1.4GHz, max 2.375GHz) and 8 MB L3 cache.
  The Problem:
  The gNB process starts successfully and appears to run without critical errors. My iPhone 16 Pro can detect the cell's signal (PLMN) when the SIM is inserted. However, when I attempt to connect to it, the connection fails silently.

• The iPhone shows the network name but does not progress to "5G" or register.

• Crucially, the Open5GS AMF logs show no indication of a UE registration attempt. This suggests the issue occurs before or during the initial random-access process, pointing towards the gNB or the radio link.

Key Error Messages:
In the srsRAN gNB logs, I consistently see the following real-time warnings:

[W] Real-time failure in low-phy
[W] Real-time failure in RF: underflow

My research indicates these are typically related to real-time performance, where the system cannot process samples fast enough.

What I've Tried/Checked:

• I have verified my Open5GS configuration AMF is correct.
• The SIM card credentials have been double-checked in both the Open5GS database and the SIM profile.
• I believe the mini-PC meets the minimum requirements for a low-bandwidth n1 cell.

My Questions:

1. Given that the AMF sees no registration request, does this confirm the problem is isolated to the gNB and the radio link?
2. Are the RF: underflow errors the root cause of the connection failure? How can I systematically diagnose and resolve these real-time issues on my mini-PC?
3. Could there be a mismatch in my gNB configuration that would prevent the initial access procedure from completing?

I am still new to the RAN side of 5G and would be very grateful for any insights. Please let me know what other information—such as full logs, configuration files, or system specs—would be helpful.

Thank you for your time and support.

[robertfalkenberg]

This looks rather like an issue with your UE or SIM rather than with real-time capabilities of your system.

In particular, newer iPhone devices have strict requirements on the network and the SIM, see here and here.

I suggest you try a different UE for initial connection tests. Once you have that running, you can take the challenge of attaching an iPhone. Good luck!