Cooperative Wi-Fi Trigger Framing to Clear NAV Before TB PPDU
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Solution Overview
Problem
In multi-link concurrent transmission in a multi-basic service set (BSS), the failure of a second station associated with a slave AP to send a second TB PPDU to the slave AP occurs due to a set Network Allocation Vector (NAV) when a master AP sends an announcement frame, causing a breakdown in the cooperation procedure.
Innovation Solution
The duration field of announcement and trigger frames is set to ensure the NAV of the second station is reduced to 0 before transmitting the TB PPDU, using preset rules to determine the duration field values, thereby allowing successful transmission without additional signaling overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the master AP sends an announcement frame to the slave AP, then the slave AP can be notified of the transmission opportunity, but the second station associated with the slave AP fails to send the second TB PPDU because the NAV is set to a non-zero value
Solution Approach 1:
The slave AP performs preliminary action by setting its own NAV to 0 before sending the trigger frame to the second station. This preliminary NAV clearing ensures that when the second station receives the trigger frame and attempts to send the TB PPDU, its NAV is already 0, allowing successful transmission. This resolves the contradiction by preparing the transmission environment in advance.
2Reliability
If the duration field of the announcement frame is set to a long value to ensure NAV is reduced to 0, then the second station can successfully transmit, but the transmission time is extended
Solution Approach 1:
The slave AP sets its NAV to 0 in advance (preliminary action) before the actual data transmission begins. This allows the duration field to be set to a shorter value that still ensures successful transmission, as the NAV clearing is already completed. This resolves the contradiction by performing the NAV clearing action before the transmission duration starts.
Data Source
AI summary
A cooperative communication method receives an announcement frame from a master access point. The announcement frame includes a duration field, a value of the duration field is set to a first duration, an end time of the first duration is not later than an end time of a target trigger frame or is not later than a start time of a target trigger based (TB) physical layer protocol data unit (PPDU), the target trigger frame is a next radio frame of the announcement frame, the target TB PPDU is a response frame for the target trigger frame, the target trigger frame comprises a second trigger frame, and the target TB PPDU comprises a second TB PPDU. The slave access point sends the second trigger frame to a second station associated with the slave access point, and receives the second TB PPDU from the second station.