Uplink Beamforming Quality Determination via CSI Process Reports

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Solution Overview

Problem

In Frequency Division Duplex (FDD) wireless communication systems, obtaining accurate channel estimates for uplink beamforming is challenging due to high overhead requirements for transmitting and receiving reference signals, especially with large numbers of antennas, which hinders efficient beamforming and power control.

Innovation Solution

Introducing CSI processes for different uplink beamforming directions allows wireless devices to determine beam quality through CSI process reports, enabling user-controlled and network-controlled beamforming and improving channel state measurements by associating uplink and downlink CSI processes, thereby reducing overhead and enhancing beamforming efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If reference signals are transmitted periodically for CSI reporting in FDD systems, then channel state information can be obtained, but overhead requirements become excessively high especially with large numbers of antennas

Engineering Contradiction:

Improvechannel state information accuracyVSAvoidreference signal overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent segments the channel estimation task by having the wireless device estimate channel for multiple uplink beamforming directions independently using separate CSI processes. Each CSI process corresponds to a specific beamforming direction, allowing the device to report channel quality for each direction separately without requiring exhaustive reference signal transmission for all directions simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses downlink CSI process reports as copies or proxies for uplink channel state information. Since FDD systems have non-reciprocal channels, the device estimates uplink channel based on downlink reference signals and reports CSI that reflects uplink beamforming quality. This copying approach avoids transmitting separate uplink reference signals for each beamforming direction, significantly reducing overhead.

Inventive Principle:

Principle #26Copying

2Adaptability or versatility

If multiple CSI processes are configured for different uplink beamforming directions, then beam quality determination is enabled, but device complexity increases

Engineering Contradiction:

Improvebeamforming direction selection capabilityVSAvoidCSI process management complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes the CSI reporting mechanism universal by using the same downlink reference signals and CSI calculation procedures for multiple uplink beamforming directions. The wireless device uses a single CSI reporting framework that works across different beamforming directions, avoiding the need for separate specialized mechanisms for each direction and reducing overall complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent performs preliminary channel estimation and CSI calculation for multiple beamforming directions before actual uplink transmission. The wireless device estimates channels and determines beam qualities in advance using downlink reference signals, then selects the optimal beamforming direction based on these pre-calculated CSI reports. This preliminary action avoids complex real-time decisions during transmission.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If uplink reference signals are transmitted for each beamforming direction, then accurate beam quality measurement is achieved, but transmission resources are consumed

Engineering Contradiction:

Improvebeam quality measurement accuracyVSAvoiduplink transmission efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent inverts the traditional approach by having the wireless device estimate uplink channel quality based on downlink reference signals rather than transmitting uplink reference signals for estimation. The device uses downlink CSI-RS to calculate uplink CSI reports that reflect beamforming direction quality, eliminating the need for separate uplink reference signal transmissions for each direction and preserving uplink transmission resources.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP3427395B1A wireless device, a network node and methods therein for determining the quality of uplink beamforming directions in a wireless communications network

Publication Date: 2021.04.28 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A method performed by a wireless device (121) for determining the quality of uplink beamforming directions in a wireless communications network (100) is provided. The wireless device (121) receives configuration information indicating uplink channel state information, CSI, processes for uplink beamforming directions. Then, the wireless device (121) transmits reference signals for one or more uplink beamforming directions on uplink transmission resources of corresponding one or more uplink CSI processes. The wireless device (121) also receives one or more uplink CSI process reports for the one or more uplink CSI processes. Then, the wireless device (121) determines the quality of at least one uplink beamforming direction using the one or more uplink CSI process reports. A wireless device (121) for determining the quality of uplink beamforming directions in a wireless communications network (100) is also provided. Furthermore, a network node and a method therein for enabling a wireless device (121) to determine a quality of uplink beamforming directions in a wireless communications network (100) are also provided.