Timer T301 expires after RL re-establishment.
SUMMARY
Branch: Develop
After successfully testing the fact that the T310 does NOT expire after the Radio Link Failure (RLF), I was expecting a (successful) RAR procedure and the UE could again be synchronized with the gNB in both DL and UL. Instead, a RAR procedure is started by the UE, but immediately after the transmission of MSG2, the timer T301 expires and the UE goes to the IDLE mode (The Timer T301 starts at transmission of RRC Connection Re-establishment request and stops at the reception of RRC Connection Re-establishment or RRC Connection Re-establishment Reject message as well as when the selected cell becomes unsuitable). The steps to reproduce this issue , are shown below:
- Right after the UE is connected to the gNB, connect to the telnet server (at the UE side), increase the noise_power to trigger the RLF and right after that decrease it:
sudo telnet $(UE_IP) $(UE_PORT)
channelmod modify 0 noise_power_dB 20
channelmod modify 0 noise_power_dB -20
- Right after the decrease of the noise_power, we should be able to check a successful re-sync by the UE. What we actually see though, is a re-initialization of the RAR procedure which freezes at the MSG3 reception.
UE LOGS:
gNB LOGS:
What I observed (which I'm not 100% sure it's relevant with the existing issue), is that the gNB assignes a different TC-RNTI in the re-sync phase than the initial synchronization. The first TC-RNTI that was assigned to the UE was 5bec, while the last TC-RNTI that was assigned to the UE is d770. Still, if we connect to the telnet server at the gNB side and execute : ci get_single_rnti , we get the initial RNTI (single UE RNTI 5bec).
Attached, you can find the gNB and UE configuration files. ue.conf