Multi-Link AP Signaling for CAC-Aware Link Association
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Solution Overview
Problem
Legacy devices are unable to discover or associate with an Access Point (AP) that is in Channel Availability Check (CAC) state, leading to missed detection of links temporarily unavailable due to DFS channel usage, which affects throughput and latency in multi-link device communication.
Innovation Solution
Introduce new signaling mechanisms, such as the ML probe request/response frames and redefined RNR and ML elements in Beacon frames, to convey CAC status related information of APs within an AP MLD, allowing non-AP MLDs to make informed association decisions and reschedule traffic based on CAC state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If legacy devices operate on DFS channels without CAC status information, then they can maintain simple association procedures, but they cannot detect temporarily unavailable links causing missed detection and reduced throughput
Solution Approach 1:
The patent applies preliminary action by having the AP MLD proactively notify non-AP MLDs about upcoming CAC states before the channels actually become unavailable. The notification includes CAC start time and duration information, allowing non-AP MLDs to prepare by switching to alternative channels or rescheduling traffic before the CAC event occurs, thus preventing throughput loss while maintaining relatively simple signaling.
Solution Approach 2:
The patent uses management frames (Beacon frames, Probe Response frames, and Announcement frames) as intermediaries to convey CAC status information from AP MLD to non-AP MLDs. These existing Wi-Fi management frames are extended to include CAC-related information elements, serving as the communication medium without requiring a completely new signaling protocol, thereby balancing information delivery with signaling simplicity.
2Reliability
If devices perform CAC on DFS channels to detect radar signals, then regulatory compliance is achieved, but links become temporarily unavailable affecting communication continuity
Solution Approach 1:
The patent implements preliminary action by notifying non-AP MLDs in advance about the scheduled CAC operation on DFS channels. The notification includes the CAC start time and expected duration, allowing non-AP MLDs to proactively switch to alternative non-DFS channels or reschedule their traffic before the CAC begins, thus maintaining communication continuity while the AP performs required regulatory compliance checks.
Solution Approach 2:
The patent changes the operational parameters of multi-link communication by dynamically adjusting which links are active based on CAC status. When CAC is detected or announced on a DFS channel, the system transitions that link from an active state to an inactive or standby state, and redirects traffic to alternative links, thereby adapting the communication parameters to maintain availability during regulatory-required channel checks.
3Productivity
If non-AP MLDs associate with APs without CAC status information, then association decisions are simple, but traffic cannot be rescheduled to avoid unavailable links
Solution Approach 1:
The patent applies preliminary action by providing CAC status information to non-AP MLDs before they need to make association or traffic scheduling decisions. The notification frames include CAC start time, duration, and affected channel information, enabling non-AP MLDs to proactively reschedule traffic to alternative channels or time periods before the CAC event causes disruption, thus preventing throughput loss.
Solution Approach 2:
The patent implements feedback by establishing a communication loop where AP MLDs notify non-AP MLDs about CAC status, and non-AP MLDs can respond with their traffic scheduling decisions or alternative channel preferences. This feedback mechanism ensures that CAC status information is not only transmitted but also utilized for optimal traffic management, preventing information loss and maintaining productivity.
Data Source
AI summary
Various embodiments provide a method for multi-link communication. The device supporting multi-link communication receives a first notification message comprising AP unavailable information indicating one or more APs within a first AP device being unavailable from the first AP device supporting multi-link communication, and makes association decision with the first AP device based on the AP unavailable information.