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Re: [STDS-802-11-TGBN] P-EDCA 97us problem

Thank you, Dmitry, for working on resolving this issue. 

  • Regarding the Duration of the contention period 

As I mentioned in my comment during the presentation, updating VHT behavior is not an option. The baseline states that when the STA receives the RTS, it checks for NAV. If the NAV is not 0, it should not send a CTS. 



Screenshot 2026-03-11 at 11.01.08 AM.png

To avoid any issues, we should limit the NAV to the shortest duration. For AIFSN[2]+RTS_duration= 34+28=62. This is problematic because it will cover only 5 slots where the AP can win the channel with AIFSN=1 in 62+25=87us from the DS-CTS reception.


Additionally, some legacy STAs, depending on their implementation, might decide to go to sleep when receiving a frame from a STA outside their BSS (DS-CTS). This will prevent the response to the DS-CTS. Legacy devices were never designed to respond to frames received from STAs other than their BSSID during NAV set by STAs.


So if we wanted to go with this solution we need to reduce the contention slots to 5 which limit the performance of P-EDCA significantly.


The major issue is the AP sending DS-CTS and targeting Legacy STAs and UHR STAs. This is already problematic to make it work in addition it create unbalanced UL/DL flows, where UL for legacy can’t use P-EDCA while DL for Legacy can use P-EDCA. That is a bug by itself.
Limiting P-EDAC to UHR devices and updating NAV behavior rules for UHR devices would resolve this problem and maintain the fairness for UL and DL for legacy devices. This should be the cleanest solution with no corner cases. 


  • Regarding the variation in behavior between 5/6gHZ and 2.4Ghz

This is not an issue. The signal extension duration (6us) introduced in 11g OFDM-based PHYs to accommodate processing delays while maintaining compatibility with legacy 802.11b devices makes the periods for both 2.4GHz and 5/6GHz kind of equivalent. This ensures consistent 16us physical turnaround time across all bands. During transmission and reception, PPDU adds a signal duration of 6us before signaling the end of transmission or reception, or even the CCA ideal. Therefore, there is no need to define two different behaviors for 2.4 and 5/6GHz. 


  • Regarding changing the RTS rate based on the Backoff value

This is very problematic to consider at this point of time since it’s the most complicated option for implementation. 


Thanks 
Mohamed


On Mar 11, 2026, at 10:24 AM, Akhmetov, Dmitry <Dmitry.Akhmetov@xxxxxxxxx> wrote:

Greetings everyone,
 
This is to start discussion thread on P-EDCA 97us. I encourage everyone interested in P-EDCA topic to use this thread to provide comments and share opinion on a problem.
 
Quick summary:
Four options presented, option 4 is proposed as a solution. The document 0210 describe pros/cons of options 1-3.
 
  1. Limit P-EDCA operations to UHR STAs. UHR STAs may ignore NAV set from DS-CTS and respond to an RTS received when NAV is set from DS-CTS frame
  2. Shorten protected duration to 72us
  3. Make RTS rate dependent on selected slot number, i.e. if STA chose backoff slot =0, RTS rate shall be MCS0 and so on, If BK=1-> rate can be MCS0 or MCS1
  4. Shorten duration to 77us for 5/6Ghz and 71us for 2.4Ghz and make adjustment to SIFS transmission time
 
Contribution 0210r2:
 
 
Again, comments/suggestions are highly appreciated
 
Dmitry

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