Precoded Reference Signaling for MU-MIMO Beamforming

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Solution Overview

Problem

Existing MIMO-SDMA systems face challenges in efficiently conveying precoding matrix information to receivers without prior knowledge of other receivers or base station scheduling algorithms, leading to high signaling overhead and limited feed forward data rates.

Innovation Solution

A generalized reference signaling scheme using arbitrarily precoded reference signals is implemented, where precoded reference signals are fed forward to convey downlink transmit beamforming matrix information, allowing receivers to extract beamforming vectors and precoding matrix information using hypothesis tests, thereby reducing the need for explicit feedback and enhancing MMSE decoding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If explicit feedback mechanisms are used to convey precoding matrix information, then reliability of information transfer is improved, but signaling overhead increases

Engineering Contradiction:

Improveprecoding matrix information transferVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent introduces precoded reference signals as an intermediary carrier to convey precoding matrix information. Instead of direct explicit feedback, the base station transmits reference signals that are precoded using the same beamforming matrix, allowing receivers to extract precoding information indirectly through hypothesis testing, thus reducing signaling overhead while maintaining reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates copies of the precoding matrix information by encoding it into multiple precoded reference signals. Each reference signal carries the same precoding matrix information in a different form, enabling receivers to recover the original information through hypothesis testing without requiring explicit feedback channels

Inventive Principle:

Principle #26Copying

2Productivity

If feed forward data rate is increased to convey precoding information, then productivity of information transfer is improved, but device complexity increases

Engineering Contradiction:

Improveprecoding information transfer rateVSAvoidsignal processing complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent transmits more precoded reference signals than the minimum required, allowing receivers to perform hypothesis testing across multiple candidates. This partial redundancy enables efficient information extraction without requiring high feed forward data rates, balancing productivity and complexity

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent replaces complex explicit feedback mechanisms with a simpler hypothesis testing approach. Instead of using sophisticated signal processing to extract precoding information from high-rate feed forward channels, receivers use computationally efficient hypothesis testing against a codebook, reducing device complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If receivers require prior knowledge of precoding vectors, then measurement precision of channel information is improved, but adaptability to different scheduling algorithms decreases

Engineering Contradiction:

Improvechannel information accuracyVSAvoidscheduling algorithm flexibility

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent segments the precoding matrix information into multiple precoded reference signals, each corresponding to a different receiver. This segmentation allows each receiver to independently extract its relevant precoding information through hypothesis testing without needing to know other receivers' precoding vectors, maintaining both precision and adaptability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a universal hypothesis testing mechanism that works with any scheduling algorithm. The same precoded reference signal transmission and hypothesis testing approach can be applied regardless of the specific scheduling algorithm used by the base station, enhancing adaptability while maintaining measurement precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8934564B2Generalized reference signaling scheme for multi-user multiple input, multiple output (MU-MIMO) using arbitrarily precoded reference signals

Publication Date: 2015.01.13 APPLE INC

AI summary

A multi-user multiple input, multiple output (MIMO) downlink beamforming system is provided to enable transmit beamforming vectors to be efficiently provided to a subset of user equipment devices, where spatial separation or zero-forcing transmit beamformers (wi) are computed at the base station and used to generate precoded reference signals. The precoded reference signals are fed forward to the user equipment devices, which apply one or more hypothesis tests to the precoded reference signals to extract the precoding matrix (W), including the specific transmit beamforming vector (WUE) designed for the user equipment, and this extracted information is used to generate receive beamformers (vi).