CSI Bitmap Reporting for Coherent Joint Transmission Overhead

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Solution Overview

Problem

The Rel-16 enhanced Type II codebook for multiple TRP (mTRP) coherent joint transmission (CJT) in wireless communication networks results in significant overhead due to the need to report non-zero coefficient (NZC) bitmaps for TRPs that are not selected by the user equipment (UE), leading to inefficient use of uplink resources.

Innovation Solution

The proposed solution involves the UE reporting indicators for selected and non-selected NZP CSI-RS resources, allowing omission of NZC bitmaps for non-selected TRPs and transmission layers, thereby reducing CSI reporting overhead by explicitly indicating which TRPs are not used for transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If non-zero coefficient (NZC) bitmaps are reported for all TRPs in mTRP coherent joint transmission, then complete channel state information is provided to the network, but significant overhead is generated due to reporting NZC bitmaps for TRPs that are not selected by the UE

Engineering Contradiction:

Improvechannel state information completenessVSAvoidCSI reporting overhead

Core Design Contradiction:

Loss of informationVSQuantity of substance

Solution Approach 1:

The patent extracts and removes the unnecessary NZC bitmaps for non-selected TRPs from the CSI report. The UE identifies which TRPs are not selected based on channel measurements and omits reporting NZC bitmaps only for those non-selected TRPs, while still reporting complete information for selected TRPs. This selective extraction reduces overhead while preserving essential channel state information.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of reporting NZC bitmaps for all TRPs (excessive action), the patent applies partial action by reporting NZC bitmaps only for selected TRPs that contribute to the transmitted layers. The UE determines the subset of TRPs that are actually used for transmission and reports information only for those, avoiding the overhead of reporting for all configured TRPs.

Inventive Principle:

Principle #16Partial or excessive action

2Reliability

If NZC bitmaps are reported for all configured TRPs, then the network has complete information for precoding decisions, but uplink resources are inefficiently used

Engineering Contradiction:

Improveprecoding decision accuracyVSAvoiduplink resource efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies local quality by providing different levels of information detail for different TRPs based on their selection status. For selected TRPs, complete NZC bitmap information is reported to ensure accurate precoding decisions. For non-selected TRPs, no NZC bitmap is reported since they do not contribute to transmission. This localized information provision optimizes uplink resource usage while maintaining reliability for actual transmission.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If the UE reports indicators for selected and non-selected NZP CSI-RS resources, then unnecessary NZC bitmaps can be omitted, but the complexity of CSI report generation increases

Engineering Contradiction:

ImproveCSI reporting overheadVSAvoidCSI report generation complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by having the UE perform channel measurements and identify selected versus non-selected TRPs before generating the CSI report. The UE uses the NZP CSI-RS resources configured by the network to measure channel quality and determine which TRPs should be selected for transmission. This preliminary identification simplifies the subsequent report generation process, as the UE already knows which TRPs require NZC bitmap reporting and which do not.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20260025253A1Reporting non-zero coefficient bitmap for coherent joint transmission with codebook

Publication Date: 2026.01.22 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method performed by a user equipment (UE) according to some embodiments includes receiving (502) an indication from a network node for a plurality of non-zero power (NZP) channel state information reference signal (CSI-RS) resources for channel measurement, and performing (504) channel measurement on the plurality of NZP CSI-RS resources. The UE selects (505) one or more NZP CSI-RS resources from the plurality of NZP CSI-RS resources, and generates (506) a CSI report based on the channel measurement and the selected one or more NZP CSI-RS resources. The CSI report includes indicators for the one or more selected NZP CSI-RS resources, and non-zero coefficient bitmaps corresponding to the one or more selected NZP CSI-RS resources. The UE transmits (508) the CSI report to the network.