What is Xn Interface?
The Xn interface is the logical interface interconnecting gNBs with each other and with ng-eNBs (upgraded 4G base stations connected to the 5GC) in the NG-RAN. It is the 5G equivalent of the 4G X2 interface and enables direct base-station-to-base-station communication for handover coordination, dual connectivity, and interference management.
How Does Xn Interface Work?
The Xn interface carries the XnAP (Xn Application Protocol) for control plane procedures: handover preparation (conditional handover, Xn-based handover), UE context transfer, dual connectivity (EN-DC, NR-DC, NE-DC) setup and modification, and SON (Self-Organising Network) load management. Xn also provides a user plane path (Xn-U) for indirect data forwarding during handovers to avoid packet loss.
Use Cases
Seamless handover between gNBs as users move between 5G cells, EN-DC dual connectivity coordination between eNB and gNB, interference and load coordination in dense deployments.
3GPP / Standards Reference
3GPP TS 38.423 (XnAP — Xn Application Protocol), TS 38.420 (Xn General Aspects and Principles)
Related Terms
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