Restrictions on Multi-Link Device Probe Requests
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Solution Overview
Problem
The high overhead and potential for channel congestion due to the large number of MLD Probe Request/Response frames in EHT multi-link discovery processes, leading to the 'Probe Storm' issue, are not effectively addressed by existing technologies.
Innovation Solution
Implementing restrictions on MLD Probe Request frames, similar to those applied in the 11ax 6 GHz band, to limit their use and prevent excessive transmission, including prohibiting blind MLD Probe Requests, limiting frequency, and preventing transmission when complete information has already been received, thereby reducing the number of frames sent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If MLD Probe Request frames are transmitted to discover complete MLD information, then the multi-link discovery function is achieved, but the channel becomes severely congested and overhead increases
Solution Approach 1:
The patent applies partial action by allowing Probe Request frames to be transmitted only when necessary - specifically when a non-AP STA has not yet discovered complete MLD information. Once the information is obtained, further Probe Requests are suppressed, preventing excessive channel usage while ensuring complete information is acquired when needed.
Solution Approach 2:
The patent implements feedback mechanisms where non-AP STAs monitor whether they have received complete MLD information from Probe Response frames. This feedback controls subsequent Probe Request transmissions - when information is complete, further requests are blocked; when incomplete, requests continue until discovery is successful.
2Adaptability or versatility
If multiple non-AP STAs transmit MLD Probe Request frames independently, then each STA can discover MLD information, but the number of frames increases causing probe storm
Solution Approach 1:
The patent merges the discovery function at the MLD level rather than individual STA level. When one non-AP STA within an MLD discovers complete MLD information, this discovery result is shared across all non-AP STAs in the same MLD, preventing other STAs from transmitting redundant Probe Requests and thus reducing the total number of frames.
Solution Approach 2:
The patent creates a universal discovery state for the entire non-AP MLD. The discovery status is not specific to individual STAs but is a shared state - once any STA obtains complete MLD information, this knowledge becomes available to all STAs in the MLD, enabling them to all stop transmitting Probe Requests simultaneously.
3Loss of information
If MLD Probe Request frames include complete MLD information, then information completeness is achieved, but frame overhead increases
Solution Approach 1:
The patent applies preliminary action by including complete MLD information in the Probe Response frame in advance. This allows the non-AP STA to obtain all necessary information in a single response, eliminating the need for multiple follow-up Probe Requests and reducing overall frame overhead while maintaining information completeness.
Data Source
AI summary
A non-AP STA of a multi-link device (STA MLD) may be configured to encode a multi-link (ML) probe request frame for transmission to an access point STA (AP) of an AP MLD comprising a plurality of affiliated APs. When the probe request frame is sent outside the context of active scanning, to discover an AP of the AP MLD the ML probe request frame may be encoded to have an Address 1 field set to a broadcast address and an Address 3 field set to a BSSID of the AP, or encoded to have the Address 1 field set to a basic service set identity (BSSID) of the AP's BS. The non-AP STA may refrain from transmitting the ML probe request frame to the AP of the AP MLD in a corresponding link when another non-AP STA of the AP MLD has already received a ML probe response that included complete information from any one of the APs of the AP MLD in any link.