DM-RS Precoder Selection via Channel State Information

Solution Overview

Problem

Current precoder selection in wireless communication systems, particularly in LTE, relies on sounding reference signals (SRS) that may provide inaccurate channel state information (CSI), leading to suboptimal performance and increased overhead, as CSI obtained from SRS can deviate from actual radio channel conditions.

Innovation Solution

The use of demodulation reference signals (DM-RS) to obtain CSI for precoder selection, allowing for precoder selection without additional SRS transmissions, thereby reducing overhead and providing more reliable CSI, which can be used for link adaptation and power control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sounding reference signals (SRS) are used for precoder selection, then channel state information can be obtained, but the CSI accuracy deteriorates and overhead increases

Engineering Contradiction:

ImproveCSI accuracyVSAvoidSRS overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The DM-RS is designed to serve dual purposes: it acts as both a demodulation reference signal for channel estimation and a sounding reference signal for CSI acquisition. By making the DM-RS multi-functional, the system eliminates the need for separate SRS transmissions, thereby reducing overhead while maintaining or improving CSI accuracy through the use of precoded reference signals that directly reflect the actual transmission channel conditions

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the functions of DM-RS and SRS into a single signal structure. The DM-RS is transmitted through the precoded channel along with data, allowing the base station to simultaneously perform demodulation and channel state estimation without requiring additional dedicated sounding resources, thus combining multiple functions into one efficient transmission mechanism

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If additional SRS transmissions are performed to improve CSI accuracy, then measurement precision improves, but system overhead increases

Engineering Contradiction:

ImproveCSI accuracyVSAvoidsystem overhead

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The DM-RS is designed to serve dual purposes: it acts as both a demodulation reference signal for channel estimation and a sounding reference signal for CSI acquisition. By making the DM-RS multi-functional, the system eliminates the need for separate SRS transmissions, thereby reducing overhead while maintaining or improving CSI accuracy through the use of precoded reference signals that directly reflect the actual transmission channel conditions

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent extracts the CSI acquisition function from the separate SRS transmission mechanism and integrates it into the existing DM-RS framework. By taking out the redundant SRS function and merging it with DM-RS, the system achieves CSI measurement without the additional overhead and complexity associated with separate sounding signal transmissions

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If SRS transmissions are reduced to lower overhead, then system efficiency improves, but CSI accuracy deteriorates

Engineering Contradiction:

Improvesystem efficiencyVSAvoidCSI accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the fundamental parameter of the reference signal by applying precoding to the DM-RS, transforming it from a simple demodulation aid into a dual-purpose signal that also provides accurate CSI. This parameter change (adding precoding to DM-RS) enables the system to maintain high CSI accuracy without requiring frequent or additional SRS transmissions, thus improving overall system efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The DM-RS is designed to serve dual purposes: it acts as both a demodulation reference signal for channel estimation and a sounding reference signal for CSI acquisition. By making the DM-RS multi-functional, the system eliminates the need for separate SRS transmissions, thereby reducing overhead while maintaining or improving CSI accuracy through the use of precoded reference signals that directly reflect the actual transmission channel conditions

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9191087B2Methods and systems for precoder selection assisted by demodulation reference signals (DM-RS)

Publication Date: 2015.11.17 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Systems and methods according to these exemplary embodiments provide for using demodulation reference signals (DM-RSs) to obtain channel state information (CSI) for precoder selection. A method includes: receiving a DM-RS in at least one subframe, determining the CSI from the DM-RS; and using the CSI to perform at least one function.