Uplink Channel Reciprocity for Wireless MIMO Feedback

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Solution Overview

Problem

Conventional wireless communication systems face challenges in efficiently managing uplink (UL) multiple-input multiple-output (MIMO) communications due to interference and the need for precise channel feedback, which increases signaling overhead and latency, especially in next-generation wireless networks operating at higher frequencies.

Innovation Solution

The implementation of UL channel reciprocity techniques, including partial and full reciprocity methods, such as UL Angle reciprocity, Asymmetric Interference (AI) Avoidance, and Precoded Sounding Reference Signals, to estimate and manage UL channels, reduce interference, and minimize feedback overhead, allowing for efficient beamforming and precoding without relying on extensive base station feedback.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional channel feedback methods are used in UL MIMO communications, then channel information can be obtained, but control signaling overhead and latency increase

Engineering Contradiction:

Improvechannel information accuracyVSAvoidcontrol signaling overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The WTRU autonomously determines UL channel information by measuring DL channel characteristics and applying reciprocity principles, eliminating the need for extensive base station feedback. The system serves itself by using locally available DL measurements to infer UL channel state, thereby reducing control signaling overhead while maintaining channel information accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Instead of the base station providing UL channel feedback to the WTRU, the patent inverts the approach by having the WTRU measure DL channel characteristics and use channel reciprocity to infer UL channel information. This inversion eliminates the need for UL channel feedback from the base station, significantly reducing control signaling overhead.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If conventional channel feedback methods are used in UL MIMO communications, then channel information can be obtained, but latency increases

Engineering Contradiction:

Improvechannel information accuracyVSAvoidfeedback latency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The WTRU performs DL channel measurements and prepares UL channel information estimates in advance, before UL transmission is required. By continuously monitoring DL channel characteristics and maintaining updated channel estimates through reciprocity, the system has channel information ready when needed, reducing feedback latency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The WTRU autonomously generates and updates channel information using local DL measurements, eliminating the time delay associated with waiting for base station feedback. This self-service approach ensures channel information is immediately available for UL MIMO operations without incurring feedback latency.

Inventive Principle:

Principle #25Self-service

3Reliability

If extensive base station feedback is used for beamforming and precoding, then UL MIMO performance can be optimized, but control signaling overhead increases

Engineering Contradiction:

ImproveUL MIMO performanceVSAvoidcontrol signaling overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The WTRU autonomously determines beamforming and precoding parameters by measuring DL channel characteristics and applying reciprocity principles. The WTRU calculates the appropriate beamforming vectors and precoding matrices locally, eliminating the need for base station feedback while maintaining UL MIMO performance optimization.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Instead of the base station providing beamforming and precoding feedback to the WTRU, the patent inverts the approach by having the WTRU measure DL channel characteristics and use reciprocity to autonomously determine the optimal beamforming and precoding parameters for UL transmission.

Inventive Principle:

Principle #13The other way round (Inversion)

4Quantity of substance

If channel reciprocity techniques are implemented, then control signaling overhead is reduced, but autonomous WTRU decision complexity increases

Engineering Contradiction:

Improvecontrol signaling overheadVSAvoidWTRU processing complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The WTRU autonomously determines UL channel information, beamforming parameters, and precoding matrices by measuring DL channel characteristics and applying reciprocity principles. This self-service approach shifts processing complexity to the WTRU but eliminates the need for extensive base station feedback and coordination.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20240340045A1Methods, apparatus, systems and procedures for uplink (UL) channel reciprocity

Publication Date: 2024.10.10 INTERDIGITAL PATENT HOLDINGS INC

AI summary

Methods, apparatus and systems are disclosed. One representative method implemented by a wireless transmit/receive unit includes determining a first beamforming matrix; sending, to a network entity, an indication of the first beamforming matrix; and receiving, from the network entity, an indication of a second beamforming matrix determined by the network entity from at least the first beamforming matrix for beamforming data for transmission.