802.11ax Trigger Frames for Legacy-Node Collision Reduction

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Solution Overview

Problem

In wireless networks, particularly in dense environments, the inefficiency of resource unit utilization in 802.11ax networks leads to increased collision risks due to legacy nodes misinterpreting underutilized channels as idle, resulting in collisions with active data traffic.

Innovation Solution

Implement a communication apparatus and method that includes sensing energy levels on resource units and transmitting only when the energy exceeds a threshold, and using trigger frames to manage resource unit allocation, ensuring legacy nodes set their Network Allocation Vectors (NAV) correctly, thereby optimizing channel usage and reducing collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If resource units are split in the frequency domain to increase channel capacity, then bandwidth efficiency is improved, but collision risk increases due to legacy nodes misinterpreting underutilized channels as idle

Engineering Contradiction:

Improvebandwidth efficiencyVSAvoidcollision risk

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces trigger frames as intermediary control signals sent by the access point to coordinate between HT nodes and legacy nodes. These trigger frames act as mediators that convey channel occupancy information to legacy nodes, ensuring they correctly interpret the busy state of resource units even when split into finer granularity channels, thus preventing collisions while maintaining high bandwidth efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements preliminary channel sensing and trigger frame transmission before actual data transmission. The access point performs clear channel assessment and sends trigger frames in advance to reserve the channel and notify legacy nodes of the upcoming transmission, preventing legacy nodes from mistakenly accessing what they would interpret as idle channels

Inventive Principle:

Principle #10Preliminary action

2Productivity

If composite channels of varying bandwidths are used to optimize throughput, then channel capacity is improved, but device complexity increases due to multiple sensing and duplication mechanisms

Engineering Contradiction:

Improvechannel capacityVSAvoidsensing and control mechanism complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the communication channel into multiple resource units in the frequency domain, allowing flexible bandwidth configuration. This segmentation enables the system to support various channel bandwidths (20MHz, 40MHz, 80MHz, 160MHz) while managing complexity through standardized resource unit definitions and trigger frame formats that work across all bandwidth configurations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates universal trigger frames that serve multiple functions: they reserve the channel, notify legacy nodes of occupancy, and work across all resource unit configurations. This multi-functional approach reduces device complexity by eliminating the need for separate control mechanisms for different channel bandwidths and node types

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP4283881B1Trigger frame indication for energy sensing of an 802.11 communication channel before transmitting

Publication Date: 2025.07.23 CANON KK

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AI summary

In an 802.11ax network with an access point, a trigger frame offers scheduled and random resource units to nodes for data uplink communication to the access point. The access point indicates, through the trigger frame, whether the nodes have to sense an energy of the medium below a threshold before transmitting data on one or more resource units.