DMRS Mapping Patterns for LTE Uplink Orthogonality

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Solution Overview

Problem

Current wireless communication networks, particularly in LTE Rel-10, face limitations in scheduling flexibility and orthogonality in MIMO systems due to constraints in UL-DMRS allocation, leading to suboptimal channel estimation and complex resource allocation procedures.

Innovation Solution

Proposed nDMRS to nDMRS(2) mapping patterns allow for CS and OCC selection to achieve minimum effective orthogonality, with semi-static nDMRS being independently configurable for each UL CC in cross-CC scheduling, and modified PHICH allocation formulas incorporating dynamic and semi-static CS values to enhance scheduling flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple cyclic shift indices are explicitly signaled for all layers, then DMRS orthogonality is improved, but signaling overhead increases significantly

Engineering Contradiction:

ImproveDMRS orthogonalityVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent extracts only the necessary cyclic shift index information from the full set of possible indices. Instead of signaling all cyclic shift values for all layers, the system signals a reduced set of indices that are then used to derive the complete DMRS configuration through predetermined rules, thereby reducing overhead while maintaining orthogonality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent establishes predetermined mapping rules and derivation algorithms in advance that allow the receiver to calculate the complete cyclic shift configuration from a reduced set of signaled indices. This preliminary structuring of the parameter space enables efficient signaling without loss of orthogonality information

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If UL-DMRS allocation constraints are maintained, then system compatibility is preserved, but scheduling flexibility is reduced

Engineering Contradiction:

Improvesystem compatibilityVSAvoidscheduling flexibility

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent segments the DMRS allocation into independently configurable components: cyclic shift indices, orthogonal cover codes, and layer mappings. This segmentation allows each parameter to be optimized independently for scheduling flexibility while maintaining overall system compatibility through standardized interfaces

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamically adjustable DMRS parameters that can be configured based on channel conditions and scheduling requirements. The system transitions from static, constrained allocation to dynamic allocation where parameters such as cyclic shift values and OCC lengths can be adapted in real-time while preserving backward compatibility

Inventive Principle:

Principle #15Dynamics

3Device complexity

If simple cyclic shift signaling is used, then signaling complexity is reduced, but channel estimation performance deteriorates

Engineering Contradiction:

Improvesignaling complexityVSAvoidchannel estimation performance

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent applies different levels of signaling complexity to different layers and transmission conditions. For example, simpler cyclic shift signaling may be used for certain layers while more sophisticated indexing is applied to others, optimizing the balance between signaling overhead and channel estimation accuracy for each specific transmission scenario

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent combines multiple DMRS parameters (cyclic shift indices, orthogonal cover codes, layer-specific mappings) into a composite signaling structure. This composite approach allows the system to achieve high channel estimation performance through the combined effect of multiple parameters while keeping individual signaling components simple

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9001771B2Optimized signaling of demodulation reference signal patterns

Publication Date: 2015.04.07 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Orthogonality in cyclic shift (CS) and orthogonal cover code (OCC) selection for DMRS in MIMO is improved by new nDMRS to nDMRS(2) mapping patterns. Values in the mapping tables are arranged in sets, with minimum CS separation between the values in each set. Additionally, the semi-static nDMRS is independently configurable for each UL component carrier (CC) in the case of cross-CC scheduling in carrier aggregation, and the PHICH allocation formula that defines the allocation of the PHICH process relative to the kth codeword (CW) on the cth UL CC is a function of both the CS index nDMRS,k,c(2) that is dynamically assigned to a certain layer of the considered CW and the semi-static CS offset nDMRS,c(1) for the cth CC.