Unlicensed Band Channel Access Method for DRS Multiplexing

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Solution Overview

Problem

The challenge of using unlicensed frequency bands in wireless communication systems is the difficulty in maintaining communication quality due to interference with existing devices and the need for a robust coexistence mechanism to ensure efficient sharing of wireless channels.

Innovation Solution

A channel access method for uplink/downlink transmission in unlicensed bands, where a base station selects between two channel access types based on the duration and duty cycle of Discovery Reference Signal (DRS) and non-unicast data transmission, using either a random backoff with a variable-size contention window or a single time interval LBT, and adjusts the contention window size based on Hybrid Automatic Repeat Request (HARQ)-ACK feedback.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a base station uses unlicensed frequency bands for transmission, then spectrum availability and capacity are improved, but interference with existing devices and communication quality deteriorate

Engineering Contradiction:

Improvespectrum availabilityVSAvoidinterference with existing devices

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The base station performs channel sensing and LBT procedures before transmitting DRS and non-unicast data in unlicensed bands. By checking channel availability in advance and selecting appropriate channel access types based on transmission conditions, the system prevents interference with existing devices while ensuring successful transmission when the channel is clear

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts channel access parameters including contention window size, backoff counter values, and LBT time intervals based on channel conditions and transmission requirements. This allows optimization of spectrum utilization while maintaining coexistence with other unlicensed band users

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a base station performs frequent DRS transmission to improve discovery performance, then user discovery and connection establishment are improved, but channel occupancy and interference with other devices increase

Engineering Contradiction:

Improvediscovery performanceVSAvoidchannel occupancy and interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The base station dynamically selects between different channel access types (first type with variable contention window and second type with single time interval LBT) based on transmission duration and duty cycle conditions. This dynamic adaptation allows frequent DRS transmission when channel conditions permit while reducing transmission frequency or adjusting parameters when interference risk increases

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses HARQ-ACK feedback to adjust channel access parameters including contention window size. By monitoring transmission outcomes and adjusting parameters based on feedback, the system optimizes discovery performance while maintaining appropriate channel occupancy levels to avoid excessive interference

Inventive Principle:

Principle #23Feedback

3Reliability

If a base station uses random backoff with variable contention window for channel access, then collision avoidance and coexistence are improved, but channel access time and latency increase

Engineering Contradiction:

Improvecollision avoidanceVSAvoidchannel access time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The base station dynamically selects between two channel access types based on transmission conditions. The first type uses random backoff with variable contention window for general transmissions, while the second type uses single time interval LBT for transmissions meeting specific duration and duty cycle conditions, thereby reducing access time when appropriate

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system adjusts contention window size based on HARQ-ACK feedback and transmission conditions. By dynamically changing the contention window parameter, the system balances collision avoidance with channel access efficiency, reducing unnecessary backoff delays while maintaining collision protection

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250113378A1Channel access method for carrying out transmission in unlicensed band, and device using same

Publication Date: 2025.04.03 WILUS INSTITUTE OF STANDARDS & TECHNOLOGY INC

AI summary

Disclosed are wireless communication system base stations. Each wireless communication base station comprises a communication module and a processor. When the base stations carry out DRS- and nonunicast data-multiplexed transmission, the processors select one channel access type among two channel access types according to whether both of two conditions are satisfied, the two conditions being that the duration of the DRS- and nonunicast data-multiplexed transmission is 1 ms or less, and the duty cycle of DRS transmission is 1/20 or less. Among the two channel access types, the first type is channel access in which random backoff is carried out using a variable-size contention window (CW), the size of the CW being determined according to channel access priority class; and the second type is channel access in which only single time interval-based LBT is carried out.