Dynamic Cell-Specific Reference Signal Signaling in Shared Spectrum

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Solution Overview

Problem

In wireless communication systems, the shared radio frequency spectrum band is not always available for transmitting and receiving cell-specific reference signals (CRS) during every downlink subframe, leading to limited CRS-based signaling and potential inefficiencies in resource usage due to poor clear channel assessment (CCA) success rates.

Innovation Solution

Techniques are implemented to limit CRS transmissions to sparse downlink CCA-exempt subframes or periodic CCA subframes, and to dynamically generate CRS based on downlink subframe configurations, allowing CRS-based signaling in available subframes, with signaling of CRS presence through downlink control information to enable efficient operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If CRS transmissions are limited to sparse downlink CCA-exempt subframes or periodic CCA subframes, then resource usage efficiency is improved, but CRS-based signaling capability deteriorates

Engineering Contradiction:

Improveresource usage efficiencyVSAvoidCRS-based signaling capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements dynamic CRS transmission by generating CRS in available downlink subframes based on LBT outcomes rather than using fixed periodic transmissions. The base station dynamically determines CRS presence in each subframe according to channel availability, allowing the system to adapt transmission patterns to actual channel conditions while maintaining signaling capability where resources are available

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the transmission parameter of CRS from a fixed periodic pattern to a variable pattern determined by LBT success and subframe availability. The CRS transmission parameter (presence/absence) is modified based on channel access outcomes, transforming the static transmission schedule into a dynamic one that responds to shared spectrum conditions

Inventive Principle:

Principle #35Parameter changes

2Reliability

If CRS is transmitted in every downlink subframe, then CRS-based signaling capability is maintained, but resource waste increases due to poor CCA success rates

Engineering Contradiction:

ImproveCRS-based signaling capabilityVSAvoidresource waste

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Instead of transmitting CRS in every downlink subframe (excessive action), the system transmits CRS only in subframes where channel access is successful and resources are available (partial action). This avoids wasting transmission resources in subframes where LBT fails or the channel is unavailable, while still providing CRS-based signaling where it can be effectively delivered

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If UEs are programmed to decode CRS in every downlink subframe, then CRS reception capability is maintained, but UE power consumption increases

Engineering Contradiction:

ImproveCRS reception capabilityVSAvoidUE power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system uses feedback mechanisms where UEs are informed about CRS presence in each subframe through downlink control information. UEs can adapt their decoding behavior based on this feedback, only attempting CRS decoding in subframes where it is actually present, thereby reducing unnecessary power consumption while maintaining reception capability when needed

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP3207655B1Techniques for cell-specific reference signal (CRS)-based signaling in a shared radio freqyebct spectrum band

Publication Date: 2020.03.25 QUALCOMM INC

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AI summary

Techniques are described for wireless communication. A first method includes identifying a configuration of a downlink subframe in a shared radio frequency spectrum band, and generating, based at least in part on the configuration of the downlink subframe, a cell-specific reference signal (CRS) for the downlink subframe. A second method includes dynamically determining a presence of a CRS in a downlink subframe in a shared radio frequency spectrum band, and performing at least one operation during the downlink subframe in response to the dynamic determination.