Cross-Link Interference (CLI)

Technical Explanation

When a network cell runs SBFD, its high-power DL sub-band emits severe interference directly into the UL sub-band of adjacent cell sites (gNB-to-gNB CLI). Simultaneously, a UE transmitting in the UL can desensitize a nearby UE receiving in the DL (UE-to-UE CLI). Rel-18 defines CLI measurement reference signals (CLI-RSSI and SRS-RSRP) and Xn coordination signaling to resolve these interference loops.

Key Functions

• Standardizes CLI-RSSI and SRS-RSRP measurement frameworks for user equipment
• Coordinates spatial beam nulling over the Xn interface between neighboring base stations
• Schedules transmitting UEs and receiving UEs on non-conflicting frequency resource blocks
• Prevents catastrophic throughput degradation in dense urban macro and microcell deployments