Wireless Channel Estimation Using Implicit Uplink Feedback

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Solution Overview

Problem

Existing MIMO wireless communication systems face challenges in obtaining accurate channel estimates for precoding downlink transmissions across a wide coverage area while conserving resources and maintaining data rates, particularly for devices at the cell edge with low signal quality.

Innovation Solution

A method that combines uplink-downlink reciprocity and implicit channel information feedback, where a wireless device transmits an uplink signal that implicitly conveys channel information, allowing the radio network node to determine a more accurate downlink channel estimate without additional uplink resources or power, enabling improved multi-user interference cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If pure codebook-based precoding is used, then channel estimation accuracy is improved, but uplink resources and downlink resources are significantly consumed

Engineering Contradiction:

Improvechannel estimation accuracyVSAvoiduplink resources and downlink resources

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent merges the channel information feedback function into the uplink reference signal transmission. The wireless device transmits uplink reference signals that carry both uplink channel information and downlink channel information (through implicit feedback), combining multiple functions into a single transmission to reduce resource consumption while maintaining estimation accuracy

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The uplink reference signal is given multiple functions: it serves both as an uplink channel estimation reference and as a carrier for downlink channel information feedback. This multi-functionality eliminates the need for separate dedicated feedback signals, thereby reducing the overall resource requirement while preserving measurement precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Quantity of substance

If pure reciprocity-based precoding is used, then resource consumption is reduced, but downlink channel estimation accuracy deteriorates for cell-edge devices

Engineering Contradiction:

Improveresource consumptionVSAvoiddownlink channel estimation accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent introduces implicit feedback mechanisms where the wireless device selects uplink reference signals based on downlink channel conditions and transmits them to convey channel information. This feedback loop enables the network node to obtain accurate downlink channel estimates even for cell-edge devices while maintaining low resource consumption through reciprocity-based estimation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the parameter of channel estimation by combining uplink channel estimates with implicitly conveyed downlink channel information. The radio network node processes both uplink reference signals and the embedded channel information to derive accurate downlink channel estimates, improving measurement precision without increasing resource consumption

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If cell-edge devices focus transmit power in a small fraction of frequency band, then uplink channel estimation quality is improved, but data rate is greatly reduced

Engineering Contradiction:

Improveuplink channel estimation qualityVSAvoiddata rate

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent performs preliminary channel estimation using uplink reference signals transmitted with concentrated power, then uses this initial estimate to guide subsequent downlink transmissions. The implicit feedback mechanism allows the system to refine the channel estimate without requiring the device to maintain high power concentration throughout the entire data transmission, thereby preserving data rate

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances downlink channel estimation accuracy, particularly for devices with low signal quality, without increasing uplink resource usage, thereby improving data rates and interference cancellation.

Implementation Method 1

the radio network node may then exploit uplink-downlink reciprocity to determine the downlink channel estimate from the uplink channel estimate

Methodology Applied

Scientific EffectUplink-downlink reciprocity:

Data Source

PatentUS12549412B2Channel estimation in a wireless communication network

Publication Date: 2026.02.10 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A wireless device (14) receives a downlink reference signal (24) from a radio network node (12) over a downlink channel (16), and determines channel information (28) based on measurement of the downlink reference signal (24). The wireless device (14) then transmits, to the radio network node (12) over an uplink channel (18), an uplink signal (30) that implicitly conveys the determined channel information (28). The radio network node (12) jointly (i) identifies which candidate uplink signal in a set (32) of candidate uplink signals (30-1 . . . 30-N) is received; and (ii) determines an estimate (42) of the uplink channel (18) from the received uplink signal (30). The radio network node (12) determines the channel information (28) implicitly conveyed by the identified candidate uplink signal, and then determines an estimate (22) of the downlink channel (16) based on the determined channel information (28) and the determined estimate (42) of the uplink channel (18).