1. Additional 40 MHz Scanning Proposal
October 2008
doc.: IEEE /1101r4
October 2008
Additional 40 MHz Scanning Proposal
Date:
Authors:
John R. Barr, Motorola, Inc.
John R. Barr, Motorola, Inc.

2. October 2008
doc.: IEEE /1101r4
October 2008
Abstract
Due to the number of negative comments that have been cast in the recent letter ballots regarding use of 40 MHz channels in 2.4 GHz spectrum, it is proposed to add optional scanning requirements to clause for FC HT AP 2G4 and FC HT STA 2G4 devices to detect presence of non radios operating in 2.4 GHz spectrum before allowing transmission of 40 MHz PPDUs and set the Forty MHz Intolerant field to 1 in transmitted HT Capabilities elements if scanning is not implemented.
John R. Barr, Motorola, Inc.
John R. Barr, Motorola, Inc.

3. Coexistence with other IEEE 802 Standards
October 2008
Coexistence with other IEEE 802 Standards
Current draft n provides substantial coexistence language for legacy IEEE devices via mandatory scanning prior to enabling operation of 40 MHz channels.
40MHzIntolerant bit is used to inform other devices in BSS that operation of 40 MHz channels is not allowed.
Note recommending not using 40 MHz channels when non devices are “in the area”.
Adding optional scanning for non-IEEE devices operating in 2.4 GHz should satisfy negative letter ballot comments and improve the draft as long as 40 MHz channels not allowed if optional scanning not implemented.
John R. Barr, Motorola, Inc.

4. D 7.0 Comment 10025 (10027 and 10029) October 2008 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
John R. Barr, Motorola, Inc.

5. October 2008
D 7.0 Comment 10047
Promote the Note 2 recommendation in to the main body of the subclause. Add the following normative sentence: "If a STA is operating in the 2.4GHz ISM band and has no mechanism to know whether any non communication devices are operating in the area or has knowledge that a non communication device is operating in the area, then it shall assert the 40MHz Intolerant bit in its HT Capabilities IE."
John R. Barr, Motorola, Inc.

6. “non-802.11 radio scan update”
October 2008
“non radio scan update”
Add clause defining “non radio scan”:
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 100 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 100 mSec time period. If either transmissions are detected “non radio scan” result is positive otherwise it is negative.
John R. Barr, Motorola, Inc.

7. October 2008
Situation
40 MHz n channels in 2.4 GHz significantly interfere with other standard implementations:
Legacy radios (protection required in D 7.0)
IEEE Std ™-2005 (Bluetooth)
Reduction of available channels from 79-27
Increased OOC noise due to n skirts
Mandatory Scanning for legacy radios in D 7.0
Note recommending not to use 40 MHz channels when non radios also present in D 7.0
Comments recommending non radio scan from LB 136
Motion from WG for conditional approval for sponsor ballot as “WG11 balloters are largely satisfied with the draft and its time for the transition to the next phase.”
John R. Barr, Motorola, Inc.

8. October 2008
Proposed Text
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 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 a non radio scan 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 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
In subclause , change “dot11FortyMHzIntolerant is TRUE” to “dot11FortyMHzIntolerant is TRUE or dot112G4RadioScanEnabled is FALSE”
TBD - Add dot112G4RadioScanEnabled in appropriate places and define as performance of non radio scan
John R. Barr, Motorola, Inc.

9. October 2008
Proposal
Acceptable text necessary to add optional non radio scanning and setting of 40MHzIntolerant to TRUE when scanning not enabled be prepared for consideration in November.
IEEE TAG and WG strongly recommend that proposed text be incorporated in D 8.0 prior to conditional approval for sponsor ballot of n.
John R. Barr, Motorola, Inc.

10. References 11-08-0779-01-000n-coex-40-mhz-comments.doc
October 2008
References
n-coex-40-mhz-comments.doc
n-tgn-lb134-coex-comments.xls
n mhz-11n-interference-on-bluetooth.ppt
n-additional-40-mhz-scanning-proposal.ppt
n-11n-40-mhz-and-bt-coexistence-test-results.ppt
n-lb134-cid-9044.doc
n-tgn-lb136-composite-comments.xls
Draft P802.11n_D6.0 and P802.11n_D7.0
pdf
pdf
John R. Barr, Motorola, Inc.

11. 802.11n Transmit Spectral Mask
October 2008
802.11n Transmit Spectral Mask
Skirts detected by AFH.
John R. Barr, Motorola, Inc.

12. October 2008
John R. Barr, Motorola, Inc.

13. Coexistence Alternatives
October 2008
Coexistence Alternatives
Fair and reasonable cooperative solution allows reasonable sharing of 2.4 GHz spectrum with multiple radio systems:
802.11n 40 MHz BSSs provide advertised performance when possible.
Consumers have no complaints about devices failing to work at odd times.
Everyone for themselves:
802.11n only protects legacy devices
Other radio systems adapt to increased levels of interference:
devices raise transmitted power level and turn off AFH to maintain necessary QoS. Allowed to transmit up to 100mW.
devices would increase frequency of transmissions due to larger number of retransmissions required to get message passed.
802.11n 40 MHz BSSs fail to provide advertised performance due to increased levels of interference.
John R. Barr, Motorola, Inc.

14. October 2008
Draft 6.0 Comments Follow
Comments for Draft 6.0 proposed to prevent operation of 40 MHz channels in 2.4 GHz spectrum.
Not fully considered to to lack of time to prepare suggested text.
Note added to Draft 7.0 to recommend not using 40 MHz channels in 2.4 GHz when presence of non radios “known”.
John R. Barr, Motorola, Inc.

15. Current Coexistence Language
October 2008
Current Coexistence Language
Normative:
: “An FC HT AP 19 that detects either of the BSS channel width trigger events TE-B or TE-C or that determines that the value of its variable 20/40 Operation Permitted has changed from TRUE to FALSE shall set the Secondary Channel Offset field to SCN in transmitted HT Operation elements beginning at the next DTIM or next TBTT if no DTIMs are transmitted to indicate that no secondary channel is present (i.e., that the BSS operating width is 20 MHz).”
Informative:
T.5.2: “Before starting a 20/40 MHz BSS, an 40 MHz capable HT AP is required by the rules defined in to examine the channels of the current regulatory domain to determine whether the operation of a 20/40 MHz BSS might unfairly interfere with the operation of existing 20 MHz BSSs. The AP (or some of its associated HT STAs) is required to scan all of the channels of the current regulatory domain in order to ascertain the operating channels of any existing 20 MHz BSSs and 20/40 MHz BSSs.”
John R. Barr, Motorola, Inc.

16. Current Coexistence Language (2)
October 2008
Current Coexistence Language (2)
Informative:
T.5.2: “An additional constraint on establishing a 20/40 MHz BSS includes the allowance for any device to explicitly prohibit the operation of the 20/40 BSS mode due to other considerations. For example, if an WPAN device is operating in the area, that device is likely to be unable to communicate successfully with a paired receiver if the number of available WPAN channels falls below a given threshold. Operation of a 20/40 MHz BSS in the 2.4 GHz band can contribute to the reduction of the number of available WPAN channels, possibly pushing the available channels below that threshold.”
John R. Barr, Motorola, Inc.

17. October 2008
doc.: IEEE /1101r4
October 2008
Over the Air Measurements Confirms that devices are negatively affected
Number of retransmissions for A2DP increase by a factor of 15. (Increases energy requirements)
Number of error free packets reduced by a factor of 2. (Reduces throughput)
Number of available hopping channels reduced to 27% of normal (79 to 22 channels). (Reduces noise immunity and ability to share channel)
Results in numerous stereo audio drop outs.
Adaptive Frequency Hopping (AFH) enabled, but typical detection algorithms can’t handle 100% larger channels and intermittent use of that channel.
John R. Barr, Motorola, Inc.
John R. Barr, Motorola, Inc.

18. Current Negative Comments Suggest
October 2008
Current Negative Comments Suggest
Resolution:
Clause , line 22, replace "When using 40 MHz channels, it can operate in the channels defined in and " to "When using 40 MHz channels, it can operate in the channels defined in "
Rationale:
Due to the large number of devices based on IEEE Std ™-2005 (e.g., > TWO Billion Bluetooth wireless devices), the probability of sharing the spectrum with n devices will be high.
John R. Barr, Motorola, Inc.

19. 40 MHz Effect on IEEE Std 802.15.1™-2005
October 2008
40 MHz Effect on IEEE Std ™-2005
Two interference measurement tests have shown that it is necessary to remove 67% of the available 2.4 GHz spectrum to allow applications to operate without degradation from 40 MHz channels in 2.4 GHz:
n mhz-11n-interference-on-bluetooth.ppt
n-11n-40-mhz-and-bt-coexistence-test-results.ppt
This does not reflect reasonable coexistence per accepted IEEE 802 definitions.
IEEE and should have equal protection from 40 MHz operation as does legacy BSSs.
John R. Barr, Motorola, Inc.

20. Alternative Proposal Add clause to 11.14 20/40 MHz BSS Operation:
October 2008
doc.: IEEE /1101r4
October 2008
Alternative Proposal
Add clause to /40 MHz BSS Operation:
FC HT AP 19 and FC HT STA 19 devices shall perform a “non radio scan” prior to establishing/joining a 20/40 MHz or 40 MHz BSS and at least once per dot11BSSWidthTriggerScanInterval seconds during operation of a 20/40 MHz or 40 MHz BSS. A positive scan result shall cause the 20/40 Operation Permitted local variable to be set to FALSE in an FC HT AP 19 and the dot11FortyMHzIntolerant MIB attribute set to TRUE. A negative scan result shall have the opposite effect. FC HT STA 19 devices that already have the dot11FortyMHzIntolerant MIB attribute set or are exempt from OBSS scanning ( ) are not required to perform this scan.
Note that the exact integration of scan event results may also be integrated into clause
John R. Barr, Motorola, Inc.
John R. Barr, Motorola, Inc.

21. “non-802.11 radio scan” Add clause defining “non-802.11 radio scan”:
October 2008
“non radio scan”
Add clause defining “non radio scan”:
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.
John R. Barr, Motorola, Inc.

22. Background - “non-802.11 radio scan”
October 2008
Background - “non radio scan”
Front end of n radio can be used to detect features of and radios with minimal cost impact.
IEEE (Bluetooth) wireless devices utilize a low cost scanning mechanism to detect presence of frequency hopping signals with pseudo-random hopping sequences.
IEEE (Zigbee) wireless devices use energy detection and feature recognition to detect devices.
A combination of these methods can be used to define the “non radio scan” algorithm and detection limits.
Similar to DFS algorithm used for radar detection
Detection limits based on expected signal level of non radio within range of likely interference by 40 MHz n transmissions (e.g., 2-3m).
Confirmation of algorithm and detection limits from at least Bluetooth SIG and Zigbee Alliance.
John R. Barr, Motorola, Inc.

23. October 2008
Process
TGn develops language for insertion of “non radio scan” into clause and other clauses as necessary.
Bluetooth SIG and Zigbee Alliance provide details on detection of their radios and recommended detection limits.
TGn approves detection method clause referenced by changes to clause for inclusion in n draft.
Sponsor Ballot...
John R. Barr, Motorola, Inc.