Sidelink HARQ Feedback Using TX Location and Zone-Based Filtering

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Solution Overview

Problem

Existing wireless communication systems face challenges in optimizing channel congestion and signaling overhead in sidelink (SL) groupcast communications, particularly in vehicle-to-everything (V2X) scenarios, due to the lack of efficient hybrid automatic repeat request (HARQ) feedback mechanisms.

Innovation Solution

Implementing location-based HARQ feedback transmission for SL groupcast by configuring user equipment (UE) to determine HARQ feedback based on reference signal received power (RSRP) and transmitter-receiver (TX-RX) distance, using SL control information (SCI) to signal TX location, and defining hierarchical zone configurations for optimized resource and signaling configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If HARQ feedback is transmitted for all SL groupcast communications, then reliability of data transmission is improved, but channel congestion and signaling overhead increase

Engineering Contradiction:
Improvereliability of data transmissionVSAvoidchannel congestion and signaling overhead
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by making HARQ feedback transmission conditional rather than universal. Different UEs transmit HARQ feedback based on their specific conditions (distance to transmitter, RSRP threshold, zone configuration), so that only those who need to provide feedback actually do so, reducing overall signaling overhead while maintaining reliability where needed

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent implements dynamic HARQ feedback transmission where the decision to transmit feedback changes based on real-time conditions such as UE location, distance to transmitter, received signal power, and hierarchical zone configurations. This dynamic approach allows the system to adapt feedback transmission to actual communication needs, reducing congestion when feedback is unnecessary while maintaining reliability when needed

Inventive Principle:
Principle #15Dynamics

2Quantity of substance

If location-based filtering is implemented to reduce HARQ feedback transmissions, then channel congestion is reduced, but device complexity increases due to location tracking and distance calculation

Engineering Contradiction:
Improvechannel congestionVSAvoiddevice complexity
Core Design Contradiction:
Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-configuring hierarchical zone information and RSRP thresholds before HARQ feedback transmission decisions are made. UEs are provided with zone configurations that define geographic areas and associated feedback requirements in advance, allowing them to make quick decisions based on their current location relative to these pre-defined zones, rather than performing complex real-time analysis

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent introduces hierarchical zone configurations as an intermediary layer between raw location data and HARQ feedback decisions. The zone system acts as a mediator that simplifies the decision-making process by providing pre-defined geographic boundaries and associated feedback rules, reducing the computational complexity required for location-based filtering

Inventive Principle:
Principle #24Intermediary (Mediator)

3Quantity of substance

If selective HARQ feedback transmission is enabled, then signaling overhead is reduced, but communication efficiency may be compromised for distant UEs

Engineering Contradiction:
Improvesignaling overheadVSAvoidcommunication efficiency
Core Design Contradiction:
Quantity of substanceVSProductivity

Solution Approach 1:

The patent implements a multi-level feedback mechanism where HARQ feedback is selectively transmitted based on hierarchical zone configurations. UEs in zones where feedback is configured to be transmitted will do so, ensuring communication efficiency is maintained for UEs that need it, while reducing signaling overhead for UEs in zones where feedback is not required

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP4395221B1Location based sidelink (SL) hybrid automatic repeat request (HARQ) feedback transmission
Publication Date: 2026.04.08 APPLE INC
  • EP4395221B1 patent drawingFigure 1
  • EP4395221B1 patent drawingFigure 2
  • EP4395221B1 patent drawingFigure 3

AI summary

A process for performing a sidelink (SL) communication includes determining a configuration, for a communication zone of a set of communication zones, the configuration being indicative of at least one a resource configuration or at least one signaling configuration for a communication of data. The process includes generating SL control information (SCI) that indicates a transmitter (TX) location based on the configuration of the communication zone of the set of communication zones. The process includes communicating the SCI indicating the TX location.