Discovery Reference Signal Transmission on Unlicensed Carrier

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Solution Overview

Problem

In LTE communication systems, the transmission of discovery reference signals over unlicensed bands poses challenges due to the need to avoid interfering with other devices, requiring Listen-Before-Talk (LBT) procedures to ensure the carrier is unoccupied, which can lead to inefficient synchronization and cell discovery processes.

Innovation Solution

The method involves transmitting control information via a licensed band to identify time-frequency resources for periodic transmission opportunities of discovery reference signals on a secondary component carrier in an unlicensed band, determining if the unlicensed band is unoccupied before transmission, and using Short Control Signals (SCS) to transmit these signals without prior LBT, facilitating opportunistic and aperiodic transmission strategies to maintain user device synchronization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If Listen-Before-Talk (LBT) procedures are performed before transmitting discovery reference signals on unlicensed bands, then interference with other devices is avoided, but synchronization efficiency and cell discovery performance deteriorate due to transmission delays and dropped signals

Engineering Contradiction:

Improveinterference with other devicesVSAvoidsynchronization efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent segments the transmission control mechanism by separating the LBT procedure from the actual discovery reference signal transmission. The base station performs LBT independently before transmitting control information to user equipment, allowing the UE to transmit discovery reference signals without performing additional LBT, thus reducing overall transmission delays while still avoiding interference through the base station's prior channel assessment

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The base station performs the LBT procedure in advance before transmitting control information to the user equipment. This preliminary action ensures the channel is clear before the UE begins transmission, eliminating the need for the UE to perform separate LBT and reducing synchronization delays while maintaining interference avoidance

Inventive Principle:

Principle #10Preliminary action

2Reliability

If discovery reference signals are transmitted periodically on unlicensed bands, then user device synchronization is maintained, but energy consumption increases and transmission opportunities are lost when the carrier is occupied

Engineering Contradiction:

Improveuser device synchronizationVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic transmission control where the periodicity and actual transmission of discovery reference signals are adjusted based on channel conditions. The base station monitors the unlicensed band occupancy and dynamically configures the UE to transmit discovery reference signals only when the channel is clear, maintaining synchronization reliability while adapting to varying channel conditions to reduce unnecessary energy consumption

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the transmission parameters of discovery reference signals based on channel occupancy conditions. When the unlicensed carrier is occupied, the base station modifies the transmission configuration to suspend or reduce discovery reference signal transmissions, thereby avoiding energy waste on transmissions that would be dropped anyway, while maintaining sufficient transmission frequency to preserve user device synchronization

Inventive Principle:

Principle #35Parameter changes

3Productivity

If discovery reference signals are transmitted on unlicensed bands without prior LBT, then transmission efficiency improves, but interference with other devices may occur

Engineering Contradiction:

Improvetransmission efficiencyVSAvoidinterference with other devices

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The base station acts as an intermediary that performs LBT on behalf of the user equipment before discovery reference signal transmission. The base station's control information to the UE includes indications of whether the channel is clear, allowing the UE to transmit efficiently without performing its own LBT while still ensuring interference avoidance through the base station's prior channel assessment

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11463943B2Transmission of discovery reference signals on unlicensed carrier in a wireless network

Publication Date: 2022.10.04 NOKIA SOLUTIONS & NETWORKS OY

AI summary

An example technique may include transmitting, by a base station via a component carrier in a licensed band, control information including a resource allocation that identifies time-frequency resources for periodical transmission opportunities to be used for the conditional transmission of discovery reference signals via a secondary component carrier in an unlicensed band, determining, prior to each transmission opportunity, whether the secondary component carrier in the unlicensed band is unoccupied, and transmitting, if the secondary component carrier in the unlicensed band is unoccupied, the discovery reference signals via the secondary component carrier in the unlicensed band using the identified time-frequency resources to one or more user devices.