Multi-AP Synchronization Frames for Co-Channel Interference Control

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Solution Overview

Problem

In multi-AP coordination, synchronization issues between neighboring access points (APs) lead to co-channel interference, affecting wireless communication efficiency and reliability due to unsynchronized BSS transmissions.

Innovation Solution

A method involving a coordinator device that sends a resource sharing frame granting a TXOP with a shared frequency band and a synchronization frame at a predefined sync time, ensuring inter-group synchronization among coordinated APs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple APs transmit simultaneously on the same frequency band, then bandwidth utilization is improved, but co-channel interference increases due to lack of synchronization

Engineering Contradiction:

Improvebandwidth utilizationVSAvoidco-channel interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by having the coordinator AP send a synchronization frame before the actual data transmission. This frame establishes the timing reference and aligns the preambles of multiple APs in advance, ensuring that when simultaneous transmissions occur, they do so with proper synchronization to avoid co-channel interference while maintaining high bandwidth utilization

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If APs operate independently without coordination, then device complexity is reduced, but transmission reliability deteriorates due to interference

Engineering Contradiction:

ImproveAP operation independenceVSAvoidtransmission reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces an intermediary mechanism in the form of a synchronization frame transmitted by the coordinator AP. This intermediary element coordinates the independent APs by establishing a common timing reference, allowing them to operate independently while maintaining transmission reliability through synchronized preambles that prevent co-channel interference

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12563595B2Methods and apparatuses for synchronization in a multi-AP coordination

Publication Date: 2026.02.24 CANON KK

AI summary

In a 802.11be multi-AP collaboration, collaborated BSSs obtaining shared resource from a collaborator AP. Co-channel interferences arise from misalignment of PHY preambles between the various collaborated and collaborator BSSs. This misalignment results from the independency of each BSSs during the shared TXOP. To overcome this deficient situation, a synchronization frame is sent by the collaborator AP at a predefined sync time over the shared frequency bands, even if the collaborator AP does not belong to the BSSs operating on these bands. The predefined sync time may derive from the UL Length field specified in the initial trigger frame. Consequently, all the stations are ready to receive the synchronization frame and therefore to start again their MU or P2P transmission a SIFS after the synchronization frame. PHY preambles in adjacent channels are therefore fully aligned.