Demodulation Reference Signals with OCC Handling for Orphaned Elements

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Solution Overview

Problem

The limitation of orthogonal demodulation reference signals in multi-user multiple-input multiple-output (MU-MIMO) systems due to orphaned resource elements, which restricts the number of communication devices that can be scheduled simultaneously, thereby limiting system throughput.

Innovation Solution

Implementing an orthogonal cover code (OCC) for demodulation reference signals even when they are mapped to resource elements that are not a multiple of the OCC length, allowing communication devices to form separate channel estimates for orphaned and non-orphaned elements, and signaling capability to handle such mappings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If an orthogonal cover code (OCC) is applied to demodulation reference signals for MU-MIMO, then the number of simultaneously scheduled communication devices can be increased, but the system is limited when the number of demodulation reference signal resource elements is not a multiple of the OCC length, causing orphaned resource elements that reduce effectiveness

Engineering Contradiction:

Improvesystem throughputVSAvoidfrequency bandwidth allocation flexibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent segments the demodulation reference signal resource elements into two distinct groups: those that form complete OCC sets and those that are orphaned elements. This segmentation allows the system to handle different types of resource elements differently, with complete sets being processed using standard OCC-based channel estimation and orphaned elements being processed using alternative methods, thereby resolving the contradiction between maintaining OCC orthogonality and adapting to flexible bandwidth allocations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial OCC action by allowing the OCC to be applied to only a portion of the demodulation reference signal resource elements (those that form complete sets), while the orphaned elements are handled separately. This partial application of the OCC principle enables the system to maintain orthogonality where possible while accommodating flexible bandwidth allocations that would otherwise be restricted.

Inventive Principle:

Principle #16Partial or excessive action

2Productivity

If the number of demodulation reference signals is increased to support more communication devices in MU-MIMO, then system throughput improves, but the number of orthogonal signals that can be transmitted on the same time-frequency resources is limited

Engineering Contradiction:

Improvesystem throughputVSAvoidnumber of orthogonal demodulation reference signals

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent extends the OCC application into the time domain by applying OCC across multiple OFDM symbols in addition to the frequency domain. This dimensional extension effectively doubles the number of orthogonal demodulation reference signals that can be transmitted on the same time-frequency resources, allowing more communication devices to be scheduled simultaneously in MU-MIMO while maintaining orthogonality.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If demodulation reference signals are mapped to resource elements not divisible by OCC length, then frequency bandwidth allocation flexibility is improved, but orphaned resource elements create challenges for channel estimation and demodulation

Engineering Contradiction:

Improvefrequency bandwidth allocation flexibilityVSAvoidchannel estimation complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary processing approach for orphaned resource elements, where these elements are handled through alternative channel estimation methods that do not rely on the full OCC structure. This intermediary handling mechanism allows the system to accommodate flexible bandwidth allocations with orphaned elements while maintaining overall system performance through separate processing paths.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20250247187A1Demodulation Reference Signal in a Communication Network

Publication Date: 2025.07.31 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A communication device (12) transmits signaling (20) indicating that the communication device (12) is capable of demodulating a data channel (16) using a demodulation reference signal (18) scheduled without a scheduling restriction on a number of resource elements, resource blocks, or resource block groups to which the demodulation reference signal (18) is mapped, e.g., the scheduling restriction restricts the number of resource elements, resource blocks, or resource block groups to which the demodulation reference signal (18) is mapped to being a multiple of a length of a frequency-domain orthogonal cover code applied to the demodulation reference signal (18). Depending on whether the communication device (12) is so capable, the demodulation reference signal (18) is scheduled with or without applying the scheduling restriction.