1. Month Year
doc.: IEEE /xxxxr0
20/40MHz Operation in 2.4 GHz Effectiveness of Overlapping BSS Scanning
Date:
Authors:
Peter Loc, Marvell
Peter Loc, Marvell

2. References Potential resolution to CID 2148
Month Year
doc.: IEEE /xxxxr0
References
Potential resolution to CID 2148
Scanning mechanism is based on P802.11n D2.06
Peter Loc, Marvell
Peter Loc, Marvell

3. Objectives Maintain scanning mechanism as described in 614/r10
Month Year
doc.: IEEE /xxxxr0
Objectives
Maintain scanning mechanism as described in 614/r10
Re-instate the values of the MIB attributes to the next n Draft
Peter Loc, Marvell
Peter Loc, Marvell

4. Residential Deployment - Scenario 1 Most typical use of 40 MHz
Month Year
doc.: IEEE /xxxxr0
Residential Deployment - Scenario 1 Most 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
Peter Loc, Marvell

5. Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

6. Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

7. Month Year
doc.: IEEE /xxxxr0
Residential Deployment - Scenario 2 Crowded – 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
FC-HT-AP
Ch 1/6/11
20 MHz
AP3
Ch 11
AP1
Ch 1
AP2
Ch 6
Peter Loc, Marvell
Peter Loc, Marvell

8. Month Year
doc.: IEEE /xxxxr0
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
FC-HT-AP
Ch 1/6/11
20 MHz
AP3
Ch 11
AP1
Ch 1
AP2
Ch 6
Peter Loc, Marvell
Peter Loc, Marvell

9. Month Year
doc.: IEEE /xxxxr0
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
FC-HT-AP
Ch 1/6/11
20 MHz
AP3
Ch 11
AP1
Ch 1
AP2
Ch 6
Peter Loc, Marvell
Peter Loc, Marvell

10. Month Year
doc.: IEEE /xxxxr0
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
AP1
Ch 1
FC-HT-AP
switches to 40 MHz, channels 4-8
AP3
Ch 11
AP2
Ch 6
Peter Loc, Marvell
Peter Loc, Marvell

11. Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

12. Residential Deployment – Scenario 3 Less crowded
Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

13. Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

14. Month Year
doc.: IEEE /xxxxr0
Conclusions
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
Requirement for HT-STAs to perform frequent scanning in most deployment
scenarios places unnecessary burden on HT-STAs, causing STAs to consume
more power but getting no benefits for consumers in return
Deployment in an enterprise environment is not affected by scanning very
much since the channels are pre-assigned prior to installation
Peter Loc, Marvell
Peter Loc, Marvell

15. to be reinstated in the next 802.11n Draft
Month Year
doc.: IEEE /xxxxr0
Proposal - strawpoll
As a start, the values of the MIB attributes that relate to 20/40 MHz operation as shown in
doc.: IEEE /0614r10
to be reinstated in the next n Draft
Peter Loc, Marvell
Peter Loc, Marvell

16. MIB Attributes (1) 2007-09-18 Month Year doc.: IEEE 802.11-06/xxxxr0
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
“This attribute, when TRUE, indicates that the STA requests that 40 MHz Mask PPDUs are not transmitted within range of the STA.”
::= { dot11OperationEntry 33 }
Peter Loc, Marvell
Peter Loc, Marvell

17. MIB Attributes (2) dot11BSSWidthTriggerScanInterval OBJECT-TYPE
Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell

18. MIB Attributes (3) 2007-09-18 Month Year doc.: IEEE 802.11-06/xxxxr0
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)
“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
Peter Loc, Marvell

19. MIB Attributes (4) 2007-09-18 Month Year doc.: IEEE 802.11-06/xxxxr0
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)
“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
Peter Loc, Marvell

20. MIB Attributes (5) 2007-09-18 Month Year doc.: IEEE 802.11-06/xxxxr0
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
“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
Peter Loc, Marvell

21. Month Year
doc.: IEEE /xxxxr0
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
Peter Loc, Marvell