6.12.0 Overview

In Multiple Transmit/Receive Point (multi-TRP) operation, a serving cell can schedule the UE from two TRPs, providing better coverage, reliability and/or data rates for PDSCH, PDCCH, PUSCH, PUCCH, and SRS.

There are two different operation modes to schedule multi-TRP PDSCH transmissions: single-DCI and multi-DCI. For both modes, control of uplink and downlink operation can be done by physical layer and MAC layer, within the configuration provided by the RRC layer. In single-DCI mode, the UE is scheduled by the same DCI for both TRPs and in multi-DCI mode, the UE is scheduled by independent DCIs from each TRP.

There are two different operation modes for multi-TRP PDCCH: PDCCH repetition as in Clause 5.2.3 and Single Frequency Network (SFN) based PDCCH transmission. In both modes, the UE can receive two PDCCH transmissions, one from each TRP, carrying the same DCI. In PDCCH repetition mode, the UE can receive the two PDCCH transmissions carrying the same DCI from two linked search spaces each associated with a different CORESET. In SFN based PDCCH transmission mode, the UE can receive the two PDCCH transmissions carrying the same DCI from a single search space/CORESET using different TCI states.

For multi-TRP PUSCH repetition, according to indications in a single DCI or in a semi-static configured grant provided over RRC, the UE performs PUSCH transmission of the same contents toward two TRPs with corresponding beam directions associated with different spatial relations. For multi-TRP PUCCH repetition, the UE performs PUCCH transmission of the same contents toward two TRPs with corresponding beam directions associated with different spatial relations.

For inter-cell multi-TRP operation, for multi-DCI PDSCH transmission, one or more TCI states can be associated with SSB with a PCI different from the serving cell PCI. The activated TCI states can be associated with at most one PCI different from the serving cell PCI at a time.

For inter-cell and intra-cell multi-DCI multi-TRP operation, up to two TAGs with associated TAG IDs can be configured per serving cell. Each UL/Joint TCI state is associated with a TAG ID and the UE applies the timing advance of the TAG ID associated with the UL/joint TCI state utilized for UL transmission. For inter-cell without multi-DCI multi-TRP operation and intra-cell without multi-DCI multi-TRP operation, up to two TAGs can be configured in the serving cell, and each UL/Joint TCI state for PUSCH, PUCCH, and SRS transmission can be associated with any one of the two TAGs.

For single-DCI multi-TRP Simultaneous Transmission with Multi-Panel (STxMP) Spatial Domain Multiplexing (SDM) PUSCH transmission, different layers of one PUSCH are separately transmitted towards two TRPs. For single-DCI multi-TRP STxMP SFN PUSCH transmission, same layers of one PUSCH are transmitted towards two TRPs. For multi-DCI based multi-TRP STxMP PUSCH+PUSCH transmission, two PUSCHs are transmitted towards two TRPs. For single-DCI multi-TRP STxMP SFN PUCCH transmission, one PUCCH is transmitted towards two TRPs.

For inter-TRP delay, frequency, and phase calibration for coherent joint transmission (CJT), CSI-RS per TRP is transmitted and the UE measures the CSI-RS(s) and estimates the reporting quantity including inter-TRP delay offset(s), frequency offset(s), and phase offset(s). A CSI report associated with the reporting quantity is carried on a PUSCH.