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20/40MHz Operation in 2.4 GHz Effectiveness of Overlapping BSS Scanning

20/40MHz Operation in 2.4 GHz Effectiveness of Overlapping BSS Scanning. Date: 2007-09-18. Authors:. References. Potential resolution to CID 2148 Scanning mechanism is based on P802.11n D2.06. Objectives. Maintain scanning mechanism as described in 614/r10 and D2.07

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20/40MHz Operation in 2.4 GHz Effectiveness of Overlapping BSS Scanning

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  1. 20/40MHz Operation in 2.4 GHzEffectiveness of Overlapping BSS Scanning Date: 2007-09-18 Authors: Peter Loc, Marvell

  2. References • Potential resolution to CID 2148 • Scanning mechanism is based on P802.11n D2.06 Peter Loc, Marvell

  3. Objectives • Maintain scanning mechanism as described in 614/r10 and D2.07 • Re-instate the values of the MIB attributes into the next 802.11n Draft Peter Loc, Marvell

  4. Residential Deployment - Scenario 1Most typical use of 40 MHz After completing an overlapping BSS Scan, a FC-HT-AP would select channels for 20/40MHz operation as shown FC-HT-AP Ch 4-8, 40 MHz AP 1 Ch 1 AP 3 Ch 11 Peter Loc, Marvell

  5. Residential Deployment - Scenario 1 Overlapping BSS Scanning Has No Effect AP1 and AP3 do not normally change their channels that were initially configured Scanning for overlapping BSS has no effect regardless of how often or how long HT-STA scans FC-HT-STA STA1 AP 1 Ch 1 FC-HT-AP Ch 4-8, 40 MHz AP 3 Ch 11 STA2 Peter Loc, Marvell

  6. Residential Deployment - Scenario 1 Overlapping BSS Scanning Has No Effect AP1 and AP3 do not change their channels that were initially configured Scanning for overlapping BSS has no effect regardless of how often or how long HT-STA scans even when AP1 or AP3 powered off/on FC-HT-STA STA1 AP 1 Ch 1 FC-HT-AP Ch 4-8, 40 MHz AP 3 Ch 11 STA2 Peter Loc, Marvell

  7. Residential Deployment - Scenario 2Crowded – HT-AP settled for 20 MHz operation After completing an overlapping BSS Scan, Draft 2.0x FC-HT-AP would only operate in 20MHz Scanning for overlapping BSS does not yield any new results AP3 Ch 11 FC-HT-AP Ch 1/6/11 20 MHz AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  8. Residential Deployment – Variation 1 on Scenario 2 Overlapping BSS Scanning Has No Effect AP1 is powered off Scanning for overlapping BSS does not yield any new results AP3 Ch 11 FC-HT-AP Ch 1/6/11 20 MHz AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  9. Residential Deployment – Variation 2 on Scenario 2 Overlapping BSS Scanning Has No Effect AP3 is powered off Scanning for overlapping BSS does not yield any new results AP3 Ch 11 FC-HT-AP Ch 1/6/11 20 MHz AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  10. Residential Deployment – Variation 3 on Scenario 2 Overlapping BSS Scanning Has No Effect AP2 is powered off FC-HT-AP switched to 40 MHz, channels 4-8 Scanning for overlapping BSS does not yield any new results FC-HT-AP switches to 40 MHz, channels 4-8 AP1 Ch 1 AP3 Ch 11 AP2 Ch 6 Peter Loc, Marvell

  11. Residential Deployment – Variation 3 on Scenario 2 Overlapping BSS Scanning Has Some Effect AP2 is powered on Any STA associated with AP2 is only affected if it is situated in the shaded area Scanning is effective only if HT-STA is situated in the shaded area FC-HT-AP switched to 40 MHz channels 4-8 AP3 Ch 11 AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  12. Residential Deployment – Scenario 3 Less crowded • AP1 and AP2 do not change their operating channels that were initially configured • Scanning for overlapping BSS has no effect regardless of how often or how long HT-STA scans FC-HT-AP Ch 11, 20 MHz AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  13. Residential Deployment – variation on Scenario 3 Overlapping BSS Scanning Has Some Effect AP2 is powered off FC-HT-AP switched to 40 MHz AP2 switched on Any STA associated with AP2 is only affected if it is situated in the shaded area Scanning is effective only if HT-STA is situated in the shaded area FC-HT-AP switched to 40 MHz channels 6-10 AP1 Ch 1 AP2 Ch 6 Peter Loc, Marvell

  14. Conclusions (1) Scanning is effective only in specific residential deployment scenarios such as variation 3 of scenario 2 and variation 1 on scenario 3 Frequent scanning in most residential deployment scenarios would be unnecessary in most cases Requirement for HT-STAs to perform frequent scanning in most deployment scenarios places an unnecessary burden on HT-STAs, causing STAs to consume more power but getting no substantial benefits for consumers in return Peter Loc, Marvell

  15. Conclusions (2) Deployment in an enterprise environment is not affected by scanning very much since the channels are pre-assigned prior to installation A smart, adaptive scanning mechanism may be employed by devices to provide effective scanning if the MIB values are reasonably defined Peter Loc, Marvell

  16. Proposal - strawpoll Reinstate the values of the MIB attributes that are shown in doc.: IEEE 802.11-07/0614r10 Yes No Abstain Peter Loc, Marvell

  17. MIB Attributes (1) • dot11FortyMHzOptionImplemented OBJECT-TYPE • SYNTAX TruthValue • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute, when TRUE, indicates that the STA is capable of transmitting and receiving on a 40 MHz channel using a 40 MHz Mask.” • DEFVAL { false } • ::= { dot11HTStationConfigEntry 17 } • dot11FortyMHzIntolerant OBJECT-TYPE • SYNTAX TruthValue • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute, when TRUE, indicates that the STA requests that 40 MHz Mask PPDUs are not transmitted within range of the STA.” • DEFVAL { false } • ::= { dot11OperationEntry 33 } Peter Loc, Marvell

  18. MIB Attributes (2) • dot11BSSWidthTriggerScanInterval OBJECT-TYPE • SYNTAX INTEGER (10…1800) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the maximum interval in seconds between scan operations to be performed to detect BSS width trigger events.” • DEFVAL { 600 } • :::= { dot11OperationEntry 34 } Peter Loc, Marvell

  19. MIB Attributes (3) • dot11BSSWidthChannelTransitionDelayFactor OBJECT-TYPE • SYNTAX INTEGER (5…100) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the minimum ratio between the delay time in performing a switch from 20 MHz BSS operation to 20/40 MHz BSS operation and the maximum interval between overlapping BSS scan operations.” • DEFVAL { 5 } • :::= { dot11OperationEntry 35 } • dot11OBSSScanPassiveDwell OBJECT-TYPE • SYNTAX INTEGER (20…1000) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the minimum amount of time in TU that the STA continuously scans each channel when performing a passive OBSS scan operation.” • DEFVAL { 20 } • :::= { dot11OperationEntry 36 } Peter Loc, Marvell

  20. MIB Attributes (4) • dot11OBSSScanActiveDwell OBJECT-TYPE • SYNTAX INTEGER (10…1000) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the minimum amount of time in TU that the STA continuously scans each channel when performing an active OBSS scan operation.” • DEFVAL { 10 } • ::= { dot11OperationEntry 37 } • dot11OBSSScanPassiveTotalPerChannel OBJECT-TYPE • SYNTAX INTEGER (200…10000) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the minimum total amount of time in TU that the STA scans each channel when performing a passive OBSS scan operation.” • DEFVAL { 200 } • ::= { dot11OperationEntry 38 } Peter Loc, Marvell

  21. MIB Attributes (5) • dot11OBSSScanActiveTotalPerChannel OBJECT-TYPE • SYNTAX INTEGER (20…10000) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates the minimum total amount of time in TU that the STA scans each channel when performing an active OBSS scan operation.” • DEFVAL { 20 } • ::= { dot11OperationEntry 39 } • dot112040BSSCoexistenceManagementSupport OBJECT-TYPE • SYNTAX TruthValue • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute, when TRUE, indicates that the STA supports the transmission and reception of the 20/40 BSS Coexistence Management frame.” • DEFVAL { false } • ::= { dot11OperationEntry 40 } Peter Loc, Marvell

  22. MIB Attributes (6) • dot11OBSSScanActivityThreshold OBJECT-TYPE • SYNTAX INTEGER (100…500) • MAX-ACCESS read-write • STATUS current • DESCRIPTION • “This attribute indicates in hundredths of percent, the maximum total time that a STA may be active on the medium during a period of dot11BSSWidthChannelTransitionDelayFactor * dot11BSSWidthTriggerScanInterval seconds without being obligated to perform OBSS Scan operations. The default value of this attribute is 300, which equates to 3.0%.” • DEFVAL { 500 } • ::= { dot11OperationEntry 41} Peter Loc, Marvell

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