CLI (Cross Link Interference) is a problem in TDD when a base station receiving in the uplink is facing interference from another base station transmitting in the downlink.
It can happen across network operators due to out-of-band emissions.
CLI can be mitigated by time-synchronization across base stations, that is, they share a common clock, phase reference and frame structure.
Even within the same operator network, CLI can occur since cell neighbours may be using different TDD DL/UL patterns.
CLI can be mitigated by gNBs coordinating their configuration over Xn and F1 interfaces.
If capable, a 5G UE measures and reports CLI-RSSI.
These reports can also include SRS-RSRP measurements on Sounding Reference Signal (SRS), which are uplink signals coming from other UEs.
This quantifies interference on downlink due to nearby uplink transmissions.
Both CLI-RSSI and SRS-RSRP are measured within the active DL BWP. These are applicable only for RRC_CONNECTED intra-frequency in TDD mode.