TRP Beam Selection for MU-MIMO Co-Scheduling

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Solution Overview

Problem

Current 3GPP NR Rel-15 downlink beam management solutions face challenges in determining if two UEs can be co-scheduled for MU-MIMO transmission and in selecting the best TRP TX beams, as it is unclear which panels the UEs are receiving the different TRP TX beams, leading to potential interference and suboptimal signal quality.

Innovation Solution

The TRP measures signal and interference for each panel in both UEs based on UL beam management for a set of candidate TRP beams, determining if multi-user transmission is possible and selecting suitable TRP beams for each UE to maximize signal quality and minimize interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If downlink beam management is used to determine TRP TX beams for MU-MIMO, then beamforming capability is achieved, but it is unclear which panels the UEs are receiving the beams, leading to interference

Engineering Contradiction:

Improveco-scheduling accuracyVSAvoidinterference between UEs

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the traditional downlink beam management approach by using uplink beam management procedures to determine downlink TRP TX beams. Instead of having the TRP transmit downlink reference signals to identify receiving panels, the TRP uses uplink reference signals from UEs to identify transmitting panels, thereby clearly determining which panels should be used for downlink transmission to each UE and reducing inter-UE interference.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces uplink reference signals as an intermediary mechanism to bridge the information gap in panel identification. By having UEs transmit uplink reference signals, the TRP can indirectly identify which UE panels are active and should receive downlink beams, without requiring direct downlink transmission for panel detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple TRP TX beams are transmitted to different UEs simultaneously, then system capacity increases, but interference between co-scheduled UEs increases

Engineering Contradiction:

Improvesystem capacityVSAvoidinterference between UEs

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by identifying suitable TRP TX beams for each UE before performing MU-MIMO co-scheduling. Using uplink beam management procedures, the TRP determines the appropriate downlink beams in advance, ensuring that beams are directed to the correct UE panels. This preliminary beam identification prevents interference before MU-MIMO transmission begins, enabling safe simultaneous transmission to multiple UEs.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If downlink reference signals are used for beam management, then TRP TX beams can be identified, but the receiving panels at UE cannot be determined

Engineering Contradiction:

Improvebeam identification accuracyVSAvoidpanel identification information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent inverts the measurement approach by using uplink reference signal transmission from UEs instead of downlink reference signal reception at UEs. When UEs transmit uplink reference signals, the TRP can identify which UE panels are transmitting and therefore which panels should receive downlink beams. This inversion recovers the panel identification information that is lost in traditional downlink-only beam management.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11464028B2Apparatuses and methods for multi-user transmissions

Publication Date: 2022.10.04 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A TRP selects two UEs that have potential for MU-MIMO transmission, and the TRP then measures signal and interference for each panel in both UEs based on UL beam management for a set of one or more candidate TRP beams. Based on the measurements, the TRP determines if multi-user transmission (i.e., co-scheduling of the two UEs) is possible.