LB97 20/40 BSS Coexistence Date: 2007-05-24 Authors: July 2007 doc.: IEEE 802.11-07/2021r0 July 2007 LB97 20/40 BSS Coexistence Date: 2007-05-24 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>. Matthew Fischer, Broadcom Matthew Fischer, Broadcom

July 2007 doc.: IEEE 802.11-07/2021r0 July 2007 Abstract An explanation of what is in 11-07-0614, and more generally, what is found in TGn draft subclause 9.20.4. Matthew Fischer, Broadcom Matthew Fischer, Broadcom

July 2007 20/40 MHz BSS Coexistence TGn draft contains rules for 20/40 MHz BSS operation Coexistence with 20 MHz BSS Means to prohibit 20/40 MHz BSS operation See sublcauses 9.20.4, 11.9.8.x 11-07-0614r5 contains modifications to these subclauses A couple of significant changes Change in BSS Width Trigger conditions Change from AP-directed Overlapping BSS Scanning to STA-initiated OBSS Scanning Move 20/40 BSS Coexistence Management Action frame to Spectrum Management Action category to achieve Class 1 designation A lot of other minor changes that do not change the basic function See listing near the end of the presentation Matthew Fischer, Broadcom

New terms to assist in clarification of applicability July 2007 New terms to assist in clarification of applicability STA vs AP STA in 2.4 GHz vs 5 GHz HT vs non-HT IBSS vs infrastructure E.g. FC-HT-STA-19 Forty MHz Capable HT STA operating on a Clause 19 channel NOTE FC = 40 MHz CAPABLE – not necessarily operating as 40 MHz 3 Definitions Matthew Fischer, Broadcom

July 2007 Before starting a 20/40 BSS FC-HT-AP shall scan all channels in the band Rules for 2.4 GHz: A 20/40 MHz BSS is allowed only if: The Primary channel of the 20/40 MHz BSS matches the primary channel of all other BSS(s) in the channel range [ (P+S)/2 – 20, (P+S)/2 + 20] Forty MHz Intolerant bit has not been found == 1 Rules for 5 GHz: No restrictions, but recommendation for choosing the Primary and Secondary channels: 1st choice: Primary and secondary channels both in an unoccupied channel 2nd choice: Primary co-located with an existing primary and the secondary channel in an unoccupied channel 3rd choice: Primary co-located with an existing primary and the secondary co-located with an existing secondary 4th choice: Other 11.9.8.3 Scanning requirements for 20/40 MHz BSSs Matthew Fischer, Broadcom

FC-HT-STA-19-initiated Overlapping BSS Scanning July 2007 FC-HT-STA-19-initiated Overlapping BSS Scanning Overlapping BSS Scan operation FC-HT-STA-19 periodically scan for Beacons on all channels in the 2.4 GHz band Only when associated with an FC-HT-AP-19 But independently of the current BSS operating width I.e. if AP is capable of changing BSS to 20/40 MHz, then scanning must be performed Exception for low-bandwidth STA Low bandwidth = variable percentage of medium time, as set by the AP, within the range 0.0% through 3.0% 11.15.1a Scanning and reporting requirements for 40 MHz capable STA Matthew Fischer, Broadcom

FC-HT-AP-19 control of Overlapping BSS Scanning July 2007 FC-HT-AP-19 control of Overlapping BSS Scanning FC-HT-AP-19 controls the parameters of the Overlapping BSS Scanning operations E.g. frequency of scanning operation, time to scan per channel, low-bandwidth exclusion value, etc. Transmits OBSS Scan Parameters element to change parameter values Associated STA accept the AP-supplied parameter values Use defaults if AP does not supply any values Default Scan Interval = 1800 seconds 11.15.1a Scanning and reporting requirements for 40 MHz capable STA 7.3.2.52a Overlapping BSS Scan Parameters element Matthew Fischer, Broadcom

FC-HT-STA-19 BSS Width Trigger events July 2007 FC-HT-STA-19 BSS Width Trigger events A) Detection of “Legacy” Beacon No HT Capabilities element present B) Detection of Forty MHz Intolerant bit == 1 In any frame The detecting FC-HT-STA-19 reports these events to the associated FC-HT-AP-19 using the 20/40 BSS Coexistence Management Action frame Containing 0 or more AP Channel Report elements And in the 20 MHz BSS Width request bit of the 20/40 BSS Coexistence Management field 9.20.4 Switching between 40 MHz and 20 MHz Matthew Fischer, Broadcom

FC-HT-AP-19 BSS Width Trigger events July 2007 FC-HT-AP-19 BSS Width Trigger events A) Detection of “Legacy” Beacon No HT Capabilities element present B) Detection of Forty MHz Intolerant bit == 1 In any frame C) Detection of 20 MHz BSS Width Request == 1 In a frame that is addressed to the FC-HT-AP-19 and sent by a STA that is ASSOCIATED with that AP The detecting FC-HT-AP-19 responds to any of these events by: Re-examining Primary/Secondary channel overlap/co-location rules Using AP Channel Report information Switching channels or switching from 20/40 MHz BSS operation to 20 MHz BSS operation, if necessary 9.20.4 Switching between 40 MHz and 20 MHz Matthew Fischer, Broadcom

Responses to specific Trigger events July 2007 Responses to specific Trigger events Legacy Beacon Channel of legacy beacon examined to determine if an overlap exists as defined by the rules Forty MHz Intolerant bit Disallows any 20/40 MHz operation in the 2.4 GHz band 20 MHz BSS Width Request bit 9.20.4 Switching between 40 MHz and 20 MHz Matthew Fischer, Broadcom

Trigger response hysteresis July 2007 Trigger response hysteresis Single trigger event detection causes change E.g. in response to ONE detected event, BSS must change channel or switch from 20/40 MHz BSS to 20 MHz BSS (if necessary) Multiple OBSS Scan intervals with NO trigger events required to revert to 20/40 MHz BSS operation The multiple is determined by MIB attribute dot11BSSWidthChannelTransitionDelayFactor, with a minimum value of 4 and default value of 4 I.e. cannot revert to 20/40 MHz BSS operation until there have been FOUR successive scans with no BSS Width Trigger events 9.20.4 Switching between 40 MHz and 20 MHz Matthew Fischer, Broadcom

20/40 MHz BSS Control Bits Forty MHz Intolerant bit July 2007 20/40 MHz BSS Control Bits Forty MHz Intolerant bit HT Capabilities element 20/40 BSS Coexistence Management Action frame STA sets the bit to ONE whenever dot11FortyMHzIntolerant MIB attribute is TRUE i.e. whenever a STA wants As per trigger condition b), can be received/detected/obeyed by any BSS (not just the sender’s BSS) 20 MHz BSS Width Request Sent by STA to associated AP Only received/detected/obeyed by AP of associated STA 9.20.4 Switching between 40 MHz and 20 MHz Matthew Fischer, Broadcom

New Element – OBSS Scan Parameters July 2007 New Element – OBSS Scan Parameters Overlapping BSS Scan Parameters element Allows AP control over the parameters of the Overlapping BSS Scanning operations performed by associated STA Includes values to force setting of all MIB attributes associated with OBSS Scanning E.g. dot11BSSWidthTransitionDelayFactor, dot11OBSSScanInterval, etc. Matthew Fischer, Broadcom

New Element – 20/40 BSS Coexistence July 2007 New Element – 20/40 BSS Coexistence 20/40 BSS Coexistence Management element Formerly a field of the 20/40 BSS Coexistence Management Action frame, converted to an element for greater application space Note that 20/40 BSS Coexistence Management Action frame was formerly called HT Information Exchange Action frame Contains Forty MHz Intolerant bit 20 MHz BSS Width Request bit Information Request bit Matthew Fischer, Broadcom

MIB attributes [units] (default value, range) July 2007 MIB attributes [units] (default value, range) dot11FortyMHzOptionImplemented (FALSE) dot112040BSSCoexistenceManagement (FALSE) dot11FortyMHzIntolerant (FALSE) dot11BSSWidthTriggerScanInterval [seconds] (1800, 10-3600) dot11BSSWidthChannelTransitionDelayFactor (4, 4-100) dot11OBSSScanPassiveDwell [TU] (20, 20-1000) dot11OBSSScanActiveDwell [TU] (10, 10-1000) dot11OBSSScanPassiveTotalPerChannel [TU] (200, 200 – 10000) dot11OBSSScanActiveTotalPerChannel [TU] (20, 20 – 10000) dot11OBSSScanActivityThreshold [bp i.e. 1%/100] (300, 0-300) i.e. 300 bp <=> 3% Matthew Fischer, Broadcom

Miscellaneous changes in 11-07-0614r5 July 2007 Miscellaneous changes in 11-07-0614r5 Add Extended Capabilities element to various frames E.g. to Beacons, Association Request, etc. Extended Capabilities element has existed for years – TGn draft proposes to add a bit for signalling support of the 20/40 BSS Coexistence Management action frame Add 20/40 BSS Coexistence Management element to various frames Change HT Information Exchange Action frame to 20/40 BSS Coexistence Management Action frame And change the HT Information field to the 20/40 BSS Coexistence Management element Rearrange subclauses for readability Fix Class 1 and Class 3 designations Matthew Fischer, Broadcom

References 11-07-0614r6 Draft-P802.11n_D2.0.pdf July 2007 doc.: IEEE 802.11-07/2021r0 July 2007 References 11-07-0614r6 Draft-P802.11n_D2.0.pdf Draft P802.11n_D2.02.pdf P802.11-REVma-D9.0-red-line-all-pages.pdf Matthew Fischer, Broadcom Matthew Fischer, Broadcom