About Reference Channels with MIMO and Beamforming Measurements (5G NR/5G-Advanced)

For MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. or beamforming measurements that involve multiple NR physical channels or signals transmitted across several measurement channels, the Ref. Channel parameter (under Channel) together with the Reference Channel setting (under Input & Antenna), the Ref. Antenna Port setting (under PDSCH, PUSCH, CSI-RS and SRS) and the Channel ID setting (under Channel) defines which physical channel or signal, on which measurement channel and antenna port, is used as the reference when calculating the TAE and Phase Error results in the corresponding MIMO Info table and the Beam Weights trace.

Ref. Channel = Individual: Each physical channel or signal uses its own reference path. The image below illustrates an example of two single-layer PDSCHs (PDSCH0 and PDSCH1). Each PDSCH Physical Downlink Shared Channel has a single DMRS port (indicating it is single layer) (PDSCH0_DMRS_Port0 and PDSCH1_DMRS_Port0), and both are mapped across eight measurement channels (Ch1 through Ch8). Since each PDSCH is single-layer, the Ref. Antenna Port is 1000. When the Reference Channel is set to Ch2, all eight results for PDSCH0 are measured relative to PDSCH0_DMRS_port0 Ch2, and all eight results for PDSCH1 are measured relative to PDSCH1_DMRS_Port0 Ch2. In this mode, the Channel ID parameter is not used.

Ref. Antenna Port = 1000 (Port0 in DMRS MIMO Info Table):

Reference Channel = Ch2 (Ch2 in DMRS MIMO Info Table):

Measurement result:

Another option is based on a specific signal type. This allows the user to manually select a physical channel or signal type to be used as the reference. Supported channels and signals include SSB, CSI channel state information-RS, PDSCH-DMRS and PDCCH-DMRS for downlink, as well as SRS and PUSCH-DMRS for uplink. In addition to the Ref. Channel setting, the user must also configure the Reference Channel, Ref. Antenna Port, and Channel ID (when multiple physical channels or signals are present) to fully specify the reference.

Example: Using the same input signal as in the earlier example, to use PDSCH1_DMRS Ch2 as the reference, set Ref. Channel to PDSCH DMRS, Channel ID to 1 (for PDSCH1), Reference Channel to Ch2, and Ref. Antenna Port to 1000 (this is the only option for single layer). In this case, the reference for TAE, Phase Error and Beam Weights is PDSCH1_DMRS_Ch2.

Ref.Channel = PDSCH DMRS and Channel ID = 1 (PDSCH1_DMRS in DMRS MIMO Info Table):

Measurement Result:

For PDSCH, if multiple PRB bundle sizes are present, the first bundle is used as reference.

For SSB, if multiple SSB blocks or transmission periods exist, the first active block in the first period is used as the reference.

The Ref. Channel setting only affects the MIMO Info table and Beam Weights traces. It does not apply to the Beam Patterns or Beam Peaks traces.