Multi-User EDCA Backoff Management for 802.11ax QoS Fairness
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Solution Overview
Problem
The introduction of MU UL OFDMA transmissions in 802.11ax networks disrupts the ability of EDCA backoff counters to mirror the relative priorities of access categories, leading to a loss of QoS handling and unfairness in medium access between 802.11ax and legacy stations.
Innovation Solution
A communication apparatus and method that decrements queue backoff counters based on channel availability and switches between legacy and MU contention modes, allowing reactive adjustment of backoff values to restore QoS and fairness by maintaining EDCA-like behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MU UL OFDMA transmissions are introduced to improve network capacity and reduce collisions, then productivity increases, but the QoS handling capability deteriorates because backoff counters can no longer mirror access category priorities
Solution Approach 1:
The patent segments the backoff counter mechanism by introducing separate backoff counters for each access category (AC) rather than using a single unified backoff counter. This segmentation allows each AC to maintain its own backoff state independently, preserving the ability to mirror priorities while enabling MU UL OFDMA transmissions. The segmented approach resolves the contradiction by allowing simultaneous support for both high network capacity and reliable QoS handling.
Solution Approach 2:
The patent implements dynamic backoff counter management where backoff counters are selectively frozen or decremented based on the transmission mode (legacy EDCA vs. MU UL OFDMA) and the specific access category being used. This dynamic behavior allows the system to adaptively maintain QoS priorities during mode transitions, resolving the contradiction between improved productivity and maintained reliability.
2Productivity
If backoff counters are frozen during MU UL OFDMA transmissions to improve efficiency, then productivity increases, but fairness in medium access deteriorates
Solution Approach 1:
The patent applies local quality by selectively freezing backoff counters only for the specific access category currently being used for MU UL OFDMA transmission, while leaving other access categories' backoff counters active. This localized approach ensures fairness is maintained for non-transmitting ACs while efficiency is improved for the transmitting AC, resolving the contradiction between productivity and ease of operation.
Solution Approach 2:
The patent implements dynamic backoff counter management where backoff counters are selectively frozen or decremented based on the transmission mode (legacy EDCA vs. MU UL OFDMA) and the specific access category being used. This dynamic behavior allows the system to adaptively maintain QoS priorities during mode transitions, resolving the contradiction between improved productivity and maintained reliability.
3Ease of operation
If AIFSN values are modified to control medium access probability, then ease of operation improves, but loss of information increases because priority mirroring is lost
Solution Approach 1:
The patent segments the backoff counter mechanism by introducing separate backoff counters for each access category (AC) rather than using a single unified backoff counter. This segmentation allows each AC to maintain its own backoff state independently, preserving the ability to mirror priorities while enabling MU UL OFDMA transmissions. The segmented approach resolves the contradiction by allowing simultaneous support for both high network capacity and reliable QoS handling.
Data Source
AI summary
The invention relates to wireless network comprising an access point and non-AP stations. The station has traffic queues and associated a backoff counters which are decremented over time upon continuously sensing the medium as free during more than respective AIFS durations. To compensate additional opportunities provided by OFDMA RUs, a queue switches to an MU mode upon transmitting its data in an RU provided by the AP. To restore dynamicity of the backoff counters, frozen in the MU mode in the known techniques, embodiments provide the following at each expiry of one of the queue backoff counters: the current mode of the expiring traffic queue is determined; in case of legacy mode, the station accesses the channel to transmit data from the queue; whereas in case of MU mode, a new backoff value is drawn to reset the expiring backoff counter, without having data from the queue being transmitted.