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Ticket #1236 (new defect)

Opened 15 years ago

Last modified 15 years ago

TXOP and duration field

Reported by: sangho@cs.columbia.edu Assigned to:
Priority: minor Milestone:
Component: madwifi: 802.11 stack Version: v0.9.2
Keywords: TXOP Cc:
Patch is attached: 0 Pending:

Description

According to the 802.11e standard:

"The intention of using the multiple frame transmission shall be indicated by the QSTA through the setting of the duration/ID values in one of the following two ways (see 7.1.4): a) Long enough to cover the response frame, the next frame, and its response frame. b) Long enough to cover the transmission of a burst of MPDUs subject to the limit set by dot11EDCATableTXOPLimit."

However, according to my observations, the duration fields of the frames sent at the beginning or during TXOP are set as the duration of "SIFS+ACK" only.

I guess this is because the exact TXOP duration cannot be determined when setting the duration field by the driver. Right? Is there any way to fix it?

Thanks,

Sangho

Change History

04/26/07 20:35:02 changed by mike.taylor@apprion.com

The duration field is not for accounting. It is used to update the NAV on the stations that hear the packet.

The point is that from the time they RECIEVE your packet they should not use the media until the duration specified ends. AFTER your packet is received, SIFS+ACK is how long your ACK should take to come back to you and for you to be done with the radio. All stations will update their NAV counters so they do not start listening for clear channel assessment until after that ACK is through.

This ensures that your transaction remains "atomic". Then, after this time elapses they will wait for the media to be idle using the normal DIFS + CWmin/max backoff.