Network Node SU MIMO Precoding via DMRS Covariance Estimation

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Solution Overview

Problem

Current wireless communication networks face limitations in SRS capacity and coverage, which restrict the performance of Single User MIMO transmissions in LTE and NR systems.

Innovation Solution

The method involves selecting an allowed precoding matrix set and estimating a raw covariance matrix based on the DMRS of the Physical Uplink Shared Channel (PUSCH) received from the User Equipment (UE), allowing for precoding matrix and rank selection for SU MIMO transmissions without relying on SRS resources, thereby decoupling SU MIMO from SRS limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If SRS (Sounding Reference Signal) is used for rank and precoding matrix indication in uplink SU MIMO, then channel information can be obtained, but SRS capacity and coverage are limited

Engineering Contradiction:

Improvechannel information estimation accuracyVSAvoidSRS capacity and coverage

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts the channel information estimation function from SRS and relocates it to DMRS. By using DMRS which is already transmitted with PUSCH for uplink data, the system eliminates the need for separate SRS resources, thereby resolving the capacity and coverage limitations of SRS while maintaining accurate channel estimation for SU MIMO operations

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes DMRS serve multiple functions: it acts as both the demodulation reference signal for PUSCH and the channel information estimation signal for SU MIMO rank and precoding matrix indication. This multi-functionality eliminates the need for dedicated SRS resources, resolving the contradiction between measurement precision and resource capacity

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If SRS is transmitted for SU MIMO operations, then channel information can be obtained, but UE power consumption increases

Engineering Contradiction:

Improvechannel information estimation accuracyVSAvoidUE power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the DMRS that is already being transmitted for PUSCH demodulation purposes to also serve channel estimation for SU MIMO. The UE does not need to transmit additional SRS signals, as the existing DMRS transmissions provide the necessary channel information, thereby reducing power consumption

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12021584B2Network node and method in a wireless communications network

Publication Date: 2024.06.25 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method performed by a network node for handling a Single User (SU) Multiple Input Multiple Output (MIMO) transmission from a User Equipment (UE) in a wireless communications network is provided. The network node selects an allowed precoding matrix set for the SU MIMO transmission. The network node further estimates a raw covariance matrix for the SU MIMO transmission, based on a Demodulation Reference Signal, DMRS, of a Physical Uplink Shared Channel, PUSCH, received from the UE. The network node then selects a precoding matrix and a rank for the SU MIMO transmission, based on the estimated raw covariance matrix and the selected allowed precoding matrix set.