Comment Resolution Regarding MDAOP End and NAV Clearing May 2007 Comment Resolution Regarding MDAOP End and NAV Clearing Date: 2007-05-01 Authors: Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. Michelle Gong, Cisco

Outline Background Comments regarding the start and the end of MDAOP May 2007 Outline Background Comments regarding the start and the end of MDAOP Suggested resolution Michelle Gong, Cisco

The start and the end of MDAOP can set and reset NAVs in MDA devices May 2007 The start and the end of MDAOP can set and reset NAVs in MDA devices Section 9.21.1 MDA Opportunity (MDAOP) “This can be done by setting their NAVs for the duration of the MDAOP at the beginning of the MDAOP” Section 9.21.11 Access during MDAOPs “At the beginning of an MDAOP that is not owned by the MP (it is not the transmitter) but is part of the Neighborhood MDAOP Times, the MP sets its NAV to the end of the MDAOP. Instead of setting the NAV, it can also use other means to not initiate a new transmission sequence during the MDAOP. The NAV setting may be reduced to a shorter time on the receipt of either a QoS+CF-Poll frame with a duration of 0 or a CF-end frame.” Michelle Gong, Cisco

NAV clearing with CF-End resets NAVs in all neighboring MPs May 2007 NAV clearing with CF-End resets NAVs in all neighboring MPs Resetting NAVs is a double-edged sword On one hand, every node that hears this CF-End frame will reset its NAV and can immediately start transmitting On the other hand, “legitimate” NAVs can also be cleared. If an MDA MP has updated its NAV based on newly received packets, clearing its NAV will result in collisions. CF-End frames also resets NAVs in non-MDA MPs mistakenly Non-MDA MPs do not set their NAVs at the beginning of the MDAOP since they do not recognize MDA-related signaling Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time Node 4 NAV DATA 0 to 1 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time Node 4 NAV DATA 0 to 1 DATA 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time Node 4 NAV DATA ACK 0 to 1 DATA ACK 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time Node 4 NAV DATA ACK DATA 0 to 1 DATA ACK CF-End 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time Node 4 NAV DATA ACK DATA DATA 0 to 1 DATA ACK CF-End 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

Clearing NAVs in all neighboring MPs can result in collisions May 2007 Clearing NAVs in all neighboring MPs can result in collisions Node 4 starts to transmit after its NAV is reset by node 2, causing a collision at node 1 Time NAV DATA Node 4 DATA ACK DATA 0 to 1 DATA ACK CF-End 2 to 3 3 Node 2 and 3: MDA MPs 1 4 2 Node 0, 1 and 4: any MPs Michelle Gong, Cisco

MDA devices do not need to set their NAVs during MDAOPs May 2007 MDA devices do not need to set their NAVs during MDAOPs As already described in Section 9.21.11, “Instead of setting the NAV, it can also use other means to not initiate a new transmission sequence during the MDAOP. ” The current text is confusing and clarification/rewording of the text is necessary The following procedures can achieve the same effect as setting and resetting the NAVs An MP that is not the owner of an MDAOP shall not transmit during the advertised MDAOP At the end of MDAOP, MPs can resume data transmission An MDA MP refrains from transmitting either when its NAV setting is non-zero or during someone else’s MDAOP Michelle Gong, Cisco

May 2007 Clarification and rewording of the text are needed to address the following comments Comments on MDAOP start and MDAOP NAV setting CIDs 1530, 1536, 1539, 2187, 3550, 3556, 3822, 4205 Comments on truncating MDAOP and MDAOP NAV clearing CIDs 1301 1532 1535 1537 1540 1625 3550 3555 3827 3828 4204 4205 Michelle Gong, Cisco

May 2007 Suggested Resolution Clarify that NAV setting and NAV clearing are not needed at the start and the end of an MDAOP For instance, it can be simply stated that “An MP that is not the owner of the advertised MDAOP shall not transmit during the duration of MDAOP.” Instead of using CF-End, a new action frame can be defined to end the current MDAOP Michelle Gong, Cisco