Synchronized LBT for Multi-Carrier Unlicensed Spectrum Access

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Solution Overview

Problem

Current LTE systems face challenges in multi-carrier operation on unlicensed carriers due to asynchronous Listen-Before-Talk (LBT) procedures, leading to interference and reduced utilization of available carriers, as each carrier may have different intended transmit times and interference levels, limiting the probability of using multiple carriers simultaneously.

Innovation Solution

Implementing synchronized LBT procedures across multiple carriers using the same starting time and equal random back-off values to ensure coordinated access, reducing interference and enhancing multi-carrier operation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If asynchronous LBT procedures are used on each carrier independently, then each carrier can be accessed autonomously, but interference occurs and multi-carrier utilization is reduced

Engineering Contradiction:

Improveautonomous carrier accessVSAvoidinterference between carriers

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent merges the LBT procedures across multiple carriers by synchronizing their starting times and using the same random back-off values. This coordination prevents the interference that occurs with independent asynchronous LBT procedures, while still allowing each carrier to be accessed autonomously based on its own channel conditions.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If synchronized LBT procedures are used across multiple carriers, then interference is reduced and multi-carrier utilization improves, but coordination complexity increases

Engineering Contradiction:

Improvemulti-carrier utilizationVSAvoidLBT coordination complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent changes key parameters of the LBT procedure to achieve synchronization: setting the same starting time for LBT on all carriers and using identical random back-off values. These parameter changes enable coordinated access that improves multi-carrier utilization while keeping the implementation relatively simple.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If different random back-off values are used on each carrier, then each carrier can adapt to its specific interference conditions, but the probability of simultaneous multi-carrier access decreases

Engineering Contradiction:

Improvecarrier-specific interference adaptationVSAvoidsimultaneous multi-carrier access probability

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent combines the random back-off values across all carriers by using the same value for each carrier. This merging approach increases the probability that multiple carriers will complete their LBT procedures simultaneously, enabling better multi-carrier utilization while still allowing adaptation to individual carrier conditions through the shared back-off mechanism.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3272176B1Listen-before-talk for multi-carrier operation in unlicensed spectrum

Publication Date: 2021.10.06 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A first communication device (100) and respective methods performed for operating on least two carriers that are accessed by an LBT procedure. The methods performed by the first communication device (100) comprises e.g. performing (S1) synchronized LBT procedures, on the at least two carriers and accessing (S2) the carriers based on the result of the synchronized LBT procedures.