6A.4 Precoding control indication (PCI) definition

25.2143GPPPhysical layer procedures (FDD)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6A.4.1 PCI definition when the UE is configured in MIMO mode

The UE uses the CPICH(s) transmitted from antenna 1 and antenna 2 to calculate the preferred precoding vectors to be applied at Node B to maximise the aggregate transport block size that could be supported under current channel conditions. No matter whether one or two transport blocks are preferred, it is sufficient to signal from the UE to the Node B only the preferred primary precoding vector , since the optional secondary precoding vector will be a unique function of the primary one. When single-stream restriction is not configured the information on whether one or two transport blocks are preferred is part of the CQI reporting as defined in subclause 6A.2.2. Since the first precoding weight of the preferred primary precoding vector is constant, it is sufficient to determine the precoding weight for antenna 2. In each TTI during which the UE derives a composite PCI/CQI report, the UE shall calculate the optimum precoding weight for antenna 2.

If the UE is not configured with precoding weight set restriction by the higher layers, the optimum precoding weight for antenna 2 is taken from the set:

If the UE is configured with precoding weight set restriction by the higher layers, the optimum precoding vector weight for antenna 2 is taken from the set as defined in table 7J0.

Table 7J0 : Selection of the precoding weight set when the precoding weight set restriction is configured by higher layers

Number of Transport Blocks preferred in the composite PCI/CQI report	Precoding weight set from which the optimum precoding weight for antenna 2 is taken.
1 (always the case when single-stream restriction is configured to the UE)
2

The precoding weight is mapped to PCI values as defined in table 7J.

Table 7J : Mapping of preferred precoding weight to PCI values.

	PCI value
	0
	1
	2
	3

6A.4.2 PCI definition when the UE is configured in MIMO mode with four transmit antennas

This section applies only when the UE is configured in MIMO mode with four transmit antennas.

The UE uses the CPICHs transmitted from antenna 1, antenna 2, antennas 3 and antenna 4 to calculate the preferred precoding matrix to be applied at Node B to maximise the aggregate transport block sizes that could be supported under current channel conditions.

The preferred precoding information PCI (pci₀, pci₁, pci₂, pci₃) is defined as the precoding weight information in subclause 4.6D.2.7 of [2] with the following PCI mapping to table 14B.7:

pci₀, pci₁, pci₂, pci₃= x_pwibp,1, x_pwibp,2, x_pwibp,3, x_pwibp,4.

The number of transport blocks corresnponding corresponding to table 14B.7 used in the PCI derivation corresponds to the number of transport blocks preferred (NTBP) reported in the composite NTBP/PCI/CQI report carrying the corresponding NTBP.