Sidelink Channel Access Adjustment via HARQ-ACK Contention Windows

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Solution Overview

Problem

Existing sidelink communication technologies face challenges in maintaining channel access in unlicensed spectra due to interference from other radio access technologies, leading to inefficiencies and reliability issues, particularly in scenarios with varying HARQ-ACK feedback mechanisms.

Innovation Solution

A method for channel access adjustment in sidelink communication that involves transmitting physical sidelink shared channels using Type 1 procedures and adjusting the contention window based on hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback to optimize channel sensing times, accounting for various HARQ-ACK scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Type 1 channel access procedures are used in unlicensed spectrum, then channel access can be initiated, but interference from other radio access technologies leads to reliability issues

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidinterference from other radio access technologies

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The contention window size is dynamically adjusted based on HARQ-ACK feedback received from sidelink transmissions. When NACK feedback is detected, the contention window size is increased to reduce collision probability; when ACK feedback is detected, the contention window size is decreased to improve channel access efficiency. This dynamic adaptation resolves the contradiction by making the channel access mechanism responsive to actual interference conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a feedback mechanism where HARQ-ACK information from sidelink transmissions is used to adjust the contention window size for subsequent channel access attempts. This closed-loop feedback system allows the UE to adapt its channel access strategy based on the success or failure of previous transmissions, thereby improving reliability in the presence of interference from other radio access technologies.

Inventive Principle:

Principle #23Feedback

2Reliability

If contention window size is increased to reduce collisions, then channel access reliability improves, but channel access delay increases

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidchannel access delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The contention window size is not fixed but dynamically adjusted based on real-time HARQ-ACK feedback. When transmission failures are detected (NACK), the contention window is increased to reduce collisions; when transmissions succeed (ACK), the contention window is decreased to minimize access delay. This dynamic behavior resolves the contradiction by adapting the window size to current channel conditions rather than using a static value.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of contention window size based on HARQ-ACK feedback conditions. The contention window size is modified from its initial value through multiplication factors applied when NACK is received, and reset to minimum values when ACK is received. This parameter adaptation allows the system to balance between reliability (larger window) and delay (smaller window) based on actual transmission outcomes.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If channel sensing time is extended to improve detection accuracy, then interference detection capability improves, but communication latency increases

Engineering Contradiction:

Improveinterference detection accuracyVSAvoidcommunication latency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The channel sensing mechanism is dynamically adjusted based on HARQ-ACK feedback. When transmission failures occur, the system extends sensing efforts by increasing contention window sizes, effectively increasing detection accuracy for subsequent access attempts. When transmissions succeed, the sensing time is minimized by using smaller contention windows, thereby reducing latency. This dynamic adjustment resolves the contradiction between detection accuracy and latency.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250220691A1Method of channel access adjustment for sidelink communication, user equipment and chip

Publication Date: 2025.07.03 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A method of channel access adjustment for sidelink (SL) communication in a shared/unlicensed spectrum by a user equipment (UE) includes transmitting, by the UE, at least one physical sidelink shared channel (PSSCH) transmission in a reference duration for a latest channel occupancy initiated using Type 1 channel access procedures and performing, by the UE, a contention window adjustment operation based on at least one hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback corresponding to the at least one PSSCH transmission.