Precoded Sounding Reference Signals for Partial Reciprocity CSI

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Solution Overview

Problem

Existing wireless communication systems face challenges in accurately estimating downlink channel state information (CSI) due to partial reciprocity between uplink and downlink channels, leading to inefficient use of computing and network resources for separate CSI reporting and determination.

Innovation Solution

A method and apparatus for a user equipment (UE) to determine downlink CSI and transmit a first and second sounding reference signal (SRS), where the second SRS is precoded based on the downlink CSI, allowing the base station to estimate both downlink and uplink CSI efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If separate CSI reporting and determination are performed for downlink and uplink, then channel state information accuracy is maintained, but computing and network resources are inefficiently consumed

Engineering Contradiction:

Improvechannel state information accuracyVSAvoidcomputing and network resource consumption

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent combines downlink CSI reporting and uplink CSI determination into a unified process by having the UE transmit a single SRS that enables the BS to derive both downlink CSI (for transmission precoding) and uplink CSI (for reception beamforming), eliminating the need for separate CSI reporting mechanisms and reducing overall resource consumption

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sounding reference signal is designed to serve multiple functions simultaneously: it acts as both a downlink channel quality indicator and an uplink channel estimator, allowing the base station to extract both downlink and uplink channel state information from a single signal transmission, thereby improving resource efficiency while maintaining measurement precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If precoding is applied to sounding reference signals based on downlink CSI, then resource utilization is optimized, but the complexity of signal processing increases

Engineering Contradiction:

Improveresource utilization efficiencyVSAvoidsignal processing complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The UE performs downlink CSI measurement and precoding calculation in advance before transmitting the SRS, allowing the base station to receive a pre-processed signal that already incorporates channel state information, thereby simplifying the BS's processing requirements while improving overall resource utilization efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The precoded SRS acts as an intermediary that carries embedded channel state information from the UE to the BS, enabling the base station to recover both downlink and uplink CSI without requiring complex real-time processing, thus balancing resource efficiency with processing complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP4098043B1Precoded sounding reference signals for partial reciprocity

Publication Date: 2025.11.19 QUALCOMM INC

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AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may determine downlink (DL) channel state information; and transmit a first sounding reference signal (SRS) and a second SRS, wherein the second SRS is precoded based at least in part on the DL channel state information. Numerous other aspects are provided.