Preemption Indication Mechanism for Low Latency WLAN Data

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Solution Overview

Problem

In wireless local area networks (WLANs), devices with low latency traffic often face delays as they wait for the end of a transmission opportunity (TXOP) assigned to another device, leading to increased latency in transmitting low latency data.

Innovation Solution

The proposed solution involves a method where a first wireless communication device receives a physical layer protocol data unit (PPDU) from a second device indicating an allocation of a resource unit (RU) for a preemption indication associated with low latency data. The first device then transmits a preemption indication after the end of the first PPDU and before the scheduled start time of a second PPDU, allowing it to preempt the second PPDU and transmit low latency data within the TXOP.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If a device waits for the end of a TXOP assigned to another device to transmit low latency traffic, then the transmission opportunity structure is maintained and resource allocation is orderly, but the latency for low latency data increases

Engineering Contradiction:

Improvelatency for low latency dataVSAvoidtransmission opportunity structure

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The system performs preliminary actions by allocating a specific resource unit (RU) within the TXOP structure that is reserved for preemption indications. This allows a device to transmit a preemption indication during the TXOP before the scheduled transmission of low latency data, enabling the receiving device to preempt its scheduled transmission and reduce latency without disrupting the overall TXOP structure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A preemption indication message acts as an intermediary between the device with low latency traffic and the TXOP holder. This intermediary signal triggers the preemption mechanism, allowing the low latency device to interrupt the current TXOP transmissions without direct conflict, thus resolving the contradiction between maintaining order and reducing latency

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If one physical layer protocol data unit is transmitted per TXOP, then the transmission structure is simple and resource allocation is straightforward, but devices with low latency traffic must wait until the end of the TXOP causing delay

Engineering Contradiction:

Improvetransmission efficiency for low latency dataVSAvoidwaiting time for low latency traffic

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The TXOP is segmented into multiple functional parts: the original PPDU transmission, a preemption indication transmission in a designated RU, and the ability to insert additional PPDUs for low latency traffic. This segmentation allows the system to maintain the original simple structure while adding capability for low latency preemption without requiring complete structural redesign

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system introduces dynamic behavior by allowing the TXOP structure to be modified based on preemption indications. When low latency traffic is detected, the TXOP can be dynamically adjusted to accommodate the urgent transmission, transforming the static single-PPDU-per-TXOP structure into a flexible multi-PPDU structure when needed

Inventive Principle:

Principle #15Dynamics

3Loss of time

If a device transmits low latency data by preempting within a TXOP, then latency is reduced and responsiveness improves, but the complexity of managing preemption indications and resource allocation increases

Engineering Contradiction:

Improvelatency for low latency dataVSAvoidpreemption indication management

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The preemption indication mechanism uses universal signaling methods that can be applied across different TXOP scenarios and device types. The same RU allocation and indication format can be used whether the TXOP holder is an AP or a STA, reducing the need for device-specific complex management logic and simplifying implementation across the network

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250132871A1Preemption techniques for low latency devices

Publication Date: 2025.04.24 QUALCOMM INC

AI summary

This disclosure provides methods, components, devices and systems for preemption techniques for low latency devices. Some aspects more specifically relate to preemption techniques to enable transmission of low latency data. In some examples, an access point (AP) may transmit a first physical layer protocol data unit (PPDU) using a dedicated resource unit (RU) and a broadcast RU. The broadcast RU may indicate information for a preemption indication, such as a resource unit within the same transmission opportunity (TXOP) for the preemption indication. A wireless station (STA) with pending low latency data may transmit the preemption indication via the RU indicated by the first PPDU. The preemption indication may indicate that a subsequent scheduled PPDU in the TXOP will be preempted for the STA to transmit a PPDU and convey the low latency data.