Normative Text for TXOP Ending Rule

July 2001doc.: IEEE 802.11-01/605r0

IEEE P802.11
Wireless LANs

Normative Text for TXOP Ending rule

Date:October 11, 2001

Author: Srinivas KandalaKen Nakashima
Sharp Labs of AmericaSharp Corporation
Camas WA 986832613-1 Ichinomoto-cho Tenri Nara Japan
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Abstract

This document contains the material proposed to Tge for inclusion in the draft in the form of insertions into and replacements for material in of IEEE std 802.11-1999, as updated by IEEE STd 802.11e/D1.3, October 2001.

Editorial notes appear in bold italic Times New Roman font, informative notes appear in normal Arial font, and normative text appears in normal Times New Roman font. Open issues arehighlighted using red text in normal Arial font, and begin with "OPEN ISSUE:". Changes to existing text in current standard are shown underlined and in red for additions and red with strikethrough for deletions.

Modify clause 7.1.3.5.3 as follows:

7.1.3.5.3Non-final field

The Non-final field is one bit in length and is set to 1 in frames transmitted by ESTAs in a QBSS if that ESTA intends to to transmit another frame during the same TXOP. The Non-final field is set to 0 in the sole or final frame transmitted by an ESTA during each TXOP, as well as in any frame with a QoS data subtype that includes CF-Poll transmitted by the HC. If the sender of the final frame is a non-HC ESTA, then this final frame of the TXOP shall be addressed to the HC. If the ESTA has no frames to be sent to the HC, it shall send a QoS Null to the HC. If the final QoS data type frame transmitted during a TXOP contains an initial or intermediate frament of an MSDU, that QoS data type frame is sent with its Non-final field set to 0 and More Fragments field set to 1. This indicates that the frame is the final transmission of the current TXOP, but that one or more fragments of the same MSDU remain to be sent during a subsequent TXOP.

Modify the last paragraph of Clause 9.10.2 immediately above clause 9.10.2.1 as follows:

Any frame exchange sequence containing a management type frame as well as any frame exchange sequence containing a data type frame of any subtype that does not include QoS, must the the sole or final frame exchange sequence in the TXOP. Multiple frame exchange sequences containing only control frames and QoS data type frames can be sent in a single TXOP, with the Non-final bit in the QoS control fields of all but the final such frame exchange sequence set to 1 to indicate that the ESTA intends to send another frame during the TXOP. If an expected Ack response does not occur to a frame with Non-Final set to 1, the ESTA awaiting the Ack should send either its next frame exchange sequence., or a QoS Null, starting a PIFS period after the end of the last transmission. When the Non-Final bit is set to 0 and the sender is a non-HC ESTA, the recipient of the frame shall be HC. If there are no frames to be sent to the HC, then the ESTA shall send a QoS Null with No Ack bit set to 0 to the HC. If the non-HC ESTA does not receive the expected Ack response for this final frame, it shall retransmit the frame or transmit a QoS Null frame, with Non-Final bit set to 0 and No Ack bit set to 0, until such time that it receives an acknowledgement or when there is not enough duration remaining in the TXOP for sending such a frame. This is to avoid the situation where the HC may not receive the frame and may result in an inefficient use of the channel. If the HC does not have any more ESTAs to be polled, it shall send a CF-End to reset the NAVs of the ESTAs.

Modify the second paragraph of clause 9.10.2.1 as follows:

When an ESTA updates its NAV setting using the duration value from a (+)CF-Poll containing the BSSID of this QBSS, that ESTA also saves the TXOP holder address, which is the MAC address from the RA field of the frame containing the (+)CF-Poll. If an RTS, Probe, data type or QoS data type frame is received with an SA value which matches this saved TXOP holder address the ESTA sends the appropriate response after SIFS, without regard for, and without resetting, the NAV. This saved TXOP holder address is cleared whenever the NAV is reset, the NAV counts down to 0, when a QoS data type frame is received with an SA value which matches the saved TXOP holder address and has Non-final bit in the QoS control field set to 0, or when a data type frame of subtype not including QoS is received. When the ESTA receives a CF-End frame containing the BSSID of this QBSS or a QoS CF-Poll with the RA matching the HC MAC address and Duration/ID equal to zero, that ESTA clears its NAV.

Delete the third paragraph of clause 9.10.2.1

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