X2 Link Failure Alarm

X2 Link Failure Alarm

Yesterday, during a conversation with a LinkedIn connection, my interlocutor raised some questions about the X2 alarm, which motivated me to write this text.

I hope this content will be useful for those working with mobile networks and facing similar scenarios.

What is X2?
The X2 is the interface that connects network elements such as eNodeBs (4G) and gNodeBs (5G), enabling the exchange of information and actions like handovers (HO), which ensure service continuity when a user moves between cells.

The X2 Link Failure alarm occurs when there is a communication failure between two eNodeBs or between an eNodeB and a gNodeB. This failure can be caused by IP connectivity issues, incorrect neighbor configurations, or even excessive delays in data transport.

Impact on Handover (HO):
If the X2 is unavailable, handovers between neighboring cells may not occur directly through the X2 interface. Instead, they will be carried out via S1, a less efficient path that can increase latency and degrade the user experience.

How critical is this alarm?
Although the X2 alarm is not considered critical in most cases, it does deserve attention.

  • Not critical: The failure does not cause immediate service interruption, as handovers can still occur via S1.
  • Potential impact: It may increase latency and consume more network resources, affecting the user experience in high-mobility scenarios.

How to resolve it?
Here are some best practices for tuning and analysis:

Tuning HO parameters:

  1. HO Thresholds: Adjust thresholds for events like A3 and A5 to ensure the handover occurs at the optimal moment.
  2. Timers (TTT and HO Prep): Configure appropriate times to avoid premature or delayed HO decisions.
  3. Neighbors (ANR): Ensure neighbors are properly configured and that the X2 is enabled.

Verify IP connectivity:
Ensure the links between eNodeBs/gNodeBs are operational and have low latency.

Monitor KPIs:
Track metrics such as HO success rate and X2 failures to identify improvement areas.

Conclusion
The X2 alarm reminds us that, in mobile networks, even “non-critical” failures offer valuable lessons. Adjusting the right parameters can not only resolve the immediate issue but also optimize overall network performance.

Keeping the site free of X2 alarms is an investment in handover efficiency and user experience—a small adjustment that makes a big difference.

LinkedIn (in Portuguese): :point_down:

1 Like

Hi,

Do you have any idea why some eNodeBs create X2 with other eNodeB that are Far away ?? Which is not Logic.

Thanks in advance.

1 Like

Nope, I thought it was just the neighbors. Faraway sites are new info for me.
Thanks for sharing.