September 2004 doc IEEE 802 11 040 xxxr

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 Multiple NAV Protection - Revisited Mathilde Benveniste Avaya Labs, Research September 2004 Submission M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 NAV protection • Current NAV protection is not adequate to provide reliable virtual carrier sensing • The NAV of a station should be set or reset by considering all stations or functions involved • The NAV rules do not protect QBSS properly when OBSS exists Submission 2 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 HCF Polling NAV Reset • HC overrules the NAV values – HC can reset NAV of QSTAs by sending CF-END – HC can reset NAV of QSTAs by sending Qo. S (+)CF-poll to itself with Dur/ID = 0 Submission 3 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 History of the “NAV Problem” In July 2003 comments to LB 51 raised the following problem: Several sources of NAV setting; the NAV should be set always to the longest value. The problem arises when NAV must be reset because a source requests so. How can we know which source set the NAV in order to cancel it? The Problem was identified initially in 2001 by S. Choi, A. Soomro, and J Del. Prado – See 01/272 Comments to LB 51 were addressed by providing a solution, an optional feature, proposed by M. Benveniste, M. Sherman, and C. Wright - See 03/594 r 1 and 03/565 r 1 The solution has been present in D 5, D 6, D 7, D 8 (SP 1) Submission 4 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 History of the “NAV Problem” - 2 There were three comments on the NAV method in SP 1: Kandala in 36 and 44 -- requests returning to the 802. 11 -1999 standard method Hansen 8 – likes the new NAV method (as opposed to the 802. 11 -1999) and requests expanding it As a resolution to all 3 comments to SP 1, the deletion of the method introduced in July 2003 and return to the 802. 11 -1999 standard method was proposed The resolution did not address Hansen/8 The justification provided in the Kandala comments was erroneous The resolution was passed as part of a block (people missed it) The resolution gave rise to new ‘No’ comments in SP 2 Submission 5 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 Motion • Move to accept the normative text changes in doc 04/1070 r 1 • Comments addressed by this motion: 31 and 166 Submission 6 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 NAV Problem Solution Define NA: address TXOP holder causing NAV to be set Keep a set of the n longest NAV values, ANAV. Discard the shorter NAV values. For each NAV retain the NA of the node setting it. When an HC sets the NAV, the NA is the address of the HC When the NAV is set through an RTS, the NA is the address of the station sending the RTS In general, a station will refrain from transmitting if a ANAV component >0 When a component of ANAV expires it becomes 0 A new NAV is retained among the n ANAV components if it exceeds the length of the shortest NAV retained, which it replaces. Reset the ANAV component of the source requesting reset. Set a ANAV[NA]=0 when NA coincides with the address of a node responsible for NAV cancellation, unless at least one NAV value has been discarded and none of the non-discarded NAV values has since expired Submission 7 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 Example – 2 NAV values retained in ANAV Reset NAV NA=XA NAV value=3 NA=XC ANAV 9, XA 2, XB 3, XC Discarded=F Discarded=T 6, XA … 0, XA 0, XC Discarded=F +3 +1 Time • • 10, XA Discarded=F +1 NAV setting requests received from XA, XB, and XC Discarded is set to True when ANAV[XB] is discarded Discarded is reset to False when ANAV[XC] expires XA requests NAV reset 5 time-units later, and the ANAV[XA] is cleared Submission 8 M. Benveniste -- Avaya Labs, Research

September 2004 doc. : IEEE 802. 11 -04/0 xxxr 0 Example – 2 NAV values retained in ANAV Reset NAV NA=XA NAV value=5 NA=XC ANAV 9, XA 2, XB 5, XC Discarded=F Discarded=T … +3 +1 Time • • 10, XA 6, XA 1, XC 2, XC 0, XA Discarded=F +1 NAV setting requests received from XA, XB, and XC Discarded is set to True when ANAV[XB] is discarded Discarded is reset to False when ANAV[XC] expires XA requests NAV reset 5 time-units later, and the ANAV[XA] is cleared Submission 9 M. Benveniste -- Avaya Labs, Research