1. July 2008
doc.: IEEE /1021r0
November 2008
Proposal to Add Optional non n Radio Scans for 40 MHz Operation in 2.4 GHz
Authors:
Date:
Peter Loc & Kiran
Luke Qian etc, Cisco

2. Abstract From LB136 CID 10025 Comment
July 2008
September 2008
doc.: IEEE /1101r3
doc.: IEEE /1021r0
November 2008
Abstract From LB136 CID Comment
The recommendation for the HT-STA not to transmit any 40 MHz mask PPDUs if it has knowledge of non devices operating in the area does nothing to ensure that n devices with such knowledge will not interfere with non n devices. In fact, it inadvertently creates a class of devices that knowingly interfere with non devices. If a device has the capability to detect the presence of other non devices, it should act upon such detection. The capability to detect non devices operating in the same area should be an option in the standard to address concerns relating to coexistence with non devices.
Slide 2
Peter Loc & Kiran
Page 2
Luke Qian etc, Cisco
John R. Barr, Motorola, Inc.

3. From LB136 CID 10025 Proposed Resolution
July 2008
September 2008
doc.: IEEE /1101r3
doc.: IEEE /1021r0
November 2008
From LB136 CID Proposed Resolution
Proposed changes:
1) In subclause , use the reserved bit B3 of the Extended Capabilities field for the HT AP or HT STA to declare its support for non radio scans.
2) In subclause , insert after line 12 , page 223:
Before an AP or IDO STA that is capable of detecting non radios (bit B3 of the Extended capabilities field is set to 1) starts a 20/40 MHz BSS, it shall perform overlapping BSS scans to search for non radios.
3) In subclause , insert after line 65 , page 223, the following:
An FC HT AP 2G4 that is capable of detecting non radios shall keep the value of 20/40 Operation Permitted to FALSE if a presence of non radio is detected.
4) Insert the following paragraph at the end of subclause , page 230, after line 13
An FC HT STA 2G4 that is associated with an FC HT AP 2G4 and is capable of performing non radio scans (bit B3 of the Extended Capability field is set to 1) shall perform at least one non radio scan every dot11BSSWidthTriggerScanInterval seconds., unless the FC HT STA 2G4 satisfies the conditions described in
Slide 3
Peter Loc & Kiran
Page 3
Luke Qian etc, Cisco
John R. Barr, Motorola, Inc.

4. Reasons for accepting the CID 10025 comment resolution as proposed
July 2008
September 2008
doc.: IEEE /1101r3
doc.: IEEE /1021r0
November 2008
Reasons for accepting the CID comment resolution as proposed
To remove the notion that the recommendation in the current IEEE802.11n Draft 7.0 creates a class of n devices that knowingly interfere with non devices
Results from new interference measurement tests (shown later in this submission) indicate that Bluetooth services (especially voice calls) are severely affected when a 40 MHz BSS is started or the BSS switches from 20 MHz to 40 MHz in 2.4 GHz
Slide 4
Peter Loc & Kiran
Page 4
Luke Qian etc, Cisco
John R. Barr, Motorola, Inc.

5. Effects of 40 MHz operation in 2.4 GHz
July 2008
doc.: IEEE /1021r0
November 2008
Effects of 40 MHz operation in 2.4 GHz
Interference measurement tests so far indicated various degrees of interferences – See the following list of documents
vht-reponse-to-official-comments
n-additional-40-mhz-scanning-proposal
n mhz-11n-interference-on-bluetooth
n-11n-40-mhz-and-bt-coexistence-test-results vht-reponse-to-official-comment
ieee n-40-mhz-impact-on-bt-performance
It is observed that results of most measurement tests were taken when Bluetooth devices have already adapted to a new hopping sequence to avoid interfering channels
Slide 5
Peter Loc & Kiran
Luke Qian etc, Cisco

6. BSS started a 40 MHz operation BSS switched from 20 MHz to 40 MHz
July 2008
doc.: IEEE /1021r0
November 2008
Interference Measurement Tests Focusing on BSS starting and switching to 40 MHz
Severe interference to existing Bluetooth service was observed for a period of up to 90 secs after
BSS started a 40 MHz operation
BSS switched from 20 MHz to 40 MHz
Slide 6
Peter Loc & Kiran
Luke Qian etc, Cisco

7. Test Setup November 2008 July 2008 doc.: IEEE 802.11-08/1021r0
11n - AP
~10m
Bluetooth
Headset
11n - STA
~1m
Bluetooth
dongle
Agilent Spectrum Analyser
Peter Loc & Kiran
Luke Qian etc, Cisco

8. Test setup (ctn) 11n Continuous Tx-Rx mode, Channel 5
July 2008
doc.: IEEE /1021r0
November 2008
Test setup (ctn)
11n
Continuous Tx-Rx mode, Channel 5
Bandwidth switched at noted time-stamp
Bluetooth
Mustek Wireless Stereo Headset, MBT-A120
single tone sent from the laptop to headset through the dongle
Peter Loc & Kiran
Luke Qian etc, Cisco

9. Nominal Behaviour Top : on@40MHz  20MHz  40MHz
July 2008
doc.: IEEE /1021r0
November 2008
Nominal Behaviour
off
40MHz
20MHz
40MHz
off
20MHz
40MHz
20MHz
Start (11n off): 0s
11n-on : ~10s
11n-switch-BW : ~60s
11n-switch-BW : ~120s
Top :  20MHz  40MHz
Bottom :  40MHz  20MHz
Peter Loc & Kiran
Luke Qian etc, Cisco

10. Worst Case Top : on@40MHz  20MHz Bottom : on@20MHz  40MHz
July 2008
doc.: IEEE /1021r0
November 2008
Worst Case
off
40MHz
20MHz
off
20MHz
40MHz
Start (11n off) : 0s
11n-on : ~10s
11n-switch-BW : ~130s
Top :  20MHz
Bottom :  40MHz
Peter Loc & Kiran
Luke Qian etc, Cisco

11. AFH-Settling Times November 2008 Nominal Startup Transition Trial 1
July 2008
doc.: IEEE /1021r0
November 2008
AFH-Settling Times
Nominal Startup
Transition
Trial 1
Trial 2
Trial 3
Average
25s
29s
24s
26s
33s
31s
40MHz->20MHz 0s
1ms?
20MHz->40MHz
10s 5s 6s 7s
Worst Case Startup
62s
Trials are all randomly started and are
unrelated across the rows/columns
? : a blip was heard
86s
Peter Loc & Kiran
Luke Qian etc, Cisco

12. Explanation (AFH) November 2008 July 2008 doc.: IEEE 802.11-08/1021r0
11n-40MHz Bluetooth n-20MHz
40MHz(adapt) MHz(adapt)
Peter Loc & Kiran
Luke Qian etc, Cisco

13. Explanation (on a BW switch)
July 2008
doc.: IEEE /1021r0
November 2008
Explanation (on a BW switch)
20MHz  40MHz MHz20MHz
(needs time to adapt) (has no extra interference)
(lower available Bandwidth) (extra Bandwidth)
Peter Loc & Kiran
Luke Qian etc, Cisco

14. Conclusions Bluetooth AFH-adaptation Time 11n Switch-on
July 2008
doc.: IEEE /1021r0
November 2008
Conclusions
Bluetooth AFH-adaptation Time
11n Switch-on
Both 20MHz and 40MHz cause interferences to Bluetooth device
40MHz takes Bluetooth longer time to adapt
Worst case can result in more than 1 minute disruption
After AFH adapts, the effect of 11n is not perceived
11n Bandwidth-switch
40MHz  20MHz does not affect Bluetooth
20MHz  40MHz results in ~5-10s disruption
Peter Loc & Kiran
Luke Qian etc, Cisco

15. Proposal part 1 November 2008
July 2008
doc.: IEEE /1021r0
November 2008
Proposal part 1
Add non n Radio Scan for 40 MHz Operation in 2.4 GHz as an option in the IEEE802.11n Draft 7.0 by countering the comment resolution as proposed by CID 10025
In subclause , use the reserved bit B3 of the Extended Capabilities field for the HT AP or HT STA to declare its support for non radio scans.
In subclause , insert after line 37 , page 223:
Before an FC HT AP 2G4 or FC HT STA 2G4 that is capable of detecting non radios (bit B3 of the Extended capabilities field is set to 1) starts a 20/40 MHz BSS, it shall perform overlapping BSS scans to search for non radios.
In subclause , insert after line 65 , page 223, the following:
An FC HT AP 2G4 that is capable of detecting non radios shall keep the value of 20/40 Operation Permitted to FALSE if a presence of non radio is detected.
Insert the following paragraph at the end of subclause , page 230, after line 13
An FC HT STA 2G4 that is associated with an FC HT AP 2G4 and is capable of performing non radio scans (bit B3 of the Extended Capability field is set to 1) shall perform at least one non radio scan every dot11BSSWidthTriggerScanInterval seconds., unless the FC HT STA 2G4 satisfies the conditions described in
Peter Loc & Kiran
Luke Qian etc, Cisco

16. July 2008
doc.: IEEE /1021r0
November 2008
Proposal part 2
2) Adopt the “non radio scan” procedure described on slide 10 of the document
n-additional-40-mhz-scanning-proposal (John R. Barr, Motorola Inc.)
The “non radio scan” shall be able to detect presence of 1 MHz GFSK transmissions in channels centered on f=2402+k MHz for k=0..78 with a power level greater than –35 dBm that appear on at least 20 channels in a 10 mSec time period, and 5 MHz DSSS O-QPSK transmissions with a 2 MHz chip rate in channels centered on f= (k-11) MHz for k=11-26 with a power level greater than –38 dBm that appear on channels affected by the proposed 40 MHz channel in a 10 mSec time period. If either transmissions are detected “non radio scan” result is positive otherwise it is negative.
Peter Loc & Kiran
Luke Qian etc, Cisco

17. July 2008
doc.: IEEE /1021r0
November 2008
Final Conclusion
Accepting this proposal will surely alleviate concerns on coexistence between 40 MHz capable n devices and others that share the 2.4 GHz band
This will speed up approval of the n draft during the sponsor ballot.
Pay now to save later
Peter Loc & Kiran
Luke Qian etc, Cisco

18. Thank You Q&A November 2008 July 2008 doc.: IEEE 802.11-08/1021r0
Peter Loc & Kiran
Luke Qian etc, Cisco