Hi all,
Since John Barr chose to mention me by
name, I suppose I have to give the background on the comment resolution to his
comment.
- I
posted an email to the 802.11n reflector announcing my submission for
40MHz comments on May 7.
- As
chair of the TGn Coexistence Ad Hoc Committee, I also posted an email to
the 802.11n reflector on May 7 announcing the TGn Coexistence Ad Hoc
agenda for the interim meeting. Included was a list of submissions. My
submission was included in the list.
- I
presented my submission on May 13 in the TGn Coexistence Ad Hoc meeting during the TGn time slot
allocated to the Coexistence Ad Hoc. There was no objection to the
resolution of his comment.
- The
role of the Ad Hoc is only to prepare resolutions. All resolutions are
later motioned in a full TGn meeting. I sent an announcement to the
802.11n reflector on May 14 that the motion will take place during the
full TGn meeting on May 15.
- If
I remember correctly, John Barr came to me to inquire about the resolution
to comment on May 14. To allow him to speak on behalf of his comment, I
separated his comment into a separate motion from the other Coexistence Ad
Hoc comment resolutions to allow ample opportunity for discussion.
As demonstrated, we have an extremely open
and flexible process in 802.11n. There are numerous announcements made
regarding comment resolution. Furthermore, multiple opportunities are given for
commentors to address their comments before the group.
Regarding John Barr’s comment
regarding lack of speakers for the motion, we have been addressing such
comments for several years now. I surmise that participants in 802.11n did not
have any new to add to the discussion that wasn’t already stated many
times in the last several years.
Regards,
Eldad
From: John Barr
[mailto:john.barr@motorola.com]
Sent: Tuesday, May 27, 2008 10:52
AM
To: Shellhammer, Steve;
stds-802-19@ieee.org; bkraemer@marvell.com; carl.stevenson@ieee.org;
david.cypher@nist.gov; Perahia,
Eldad; I_reede@amerisys.com; Joseph.Levy@InterDigital.com; Mark.austin@ofcom.org.uk; mjlynch@nortel.com; nada.golmie@nist.gov; ppiggin@nextwave.com; bheile@ieee.org; sli@sibeam.com;
swhitesell@vtech.ca; Gupta, Vivek G
Cc: Paul Nikolich
Subject: Re: [802.15_GENERAL] TGn
Letter Ballot Support
I raised the issue since 802.11n
has repeatedly ignored my comments and has not scheduled any discussion (with
me) on this topic. I found out late that Eldad had submitted a rejection
without any comments or discussion so had to attend the TGn session were
comment approval was rolled up from individual subcommittees. As I said in my
note, I sent out an email noting my objections, and then spoke against the
motion to approve the comment resolution. No one spoke for the comment
resolution and the vote was 26-1-0. Seems odd that no one was willing to
support the motion to approve the rejection, but everyone voted for that
action.
I read the rejection comment and then reviewed the TGn draft to determine if
this would be appropriate. I found the following:
Here is the resolution of my comment:
Reject because: “ COEX: 2008-05-13 15:22:51Z Reject - A 20/40 MHz BSS
coexistence solution is defined in draft D4.0, which includes signaling of
Forty MHz Intolerance. Clause T.3.2 describes these mechanisms to promote
sharing with an example of 802.15.1 WPAN devices.”
Clause T.3.2 is a normative portion of the amendment that begins with:
“Before starting a 20/40 MHz BSS, an FC HT AP is required by the rules
defined in 11.14.5 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.” And later:
“The rules that are applied when determining whether a 20/40 MHz BSS can
be established are intended to avoid a full or partial overlap of the secondary
channel of the 20/40 MHz BSS with an existing primary channel of either a 20
MHz BSS or a 20/40 MHz BSS.”
To this point all they intend to protect is existing 20 MHz BSSs.
The next paragraph seems to be what was added: “An additional constraint
on establishing a 20/40 MHz BSS includes the allowance for any 802.11 device to
explicitly prohibit the operation of the 20/40 BSS mode due to other
considerations. For example, if an 802.15.1 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 802.15.1 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 802.15.1 WPAN channels,
possibly pushing the available channels below that threshold.”
And the next paragraph says how this information can be noted: “To
promote sharing of the spectrum resource under such circumstances, it might be
desirable to prohibit the operation of a 20/40 MHz BSS. As such, the 20/40 BSS
coexistence mechanism allows a STA to transmit management frames containing a
value of 1 for the Forty MHz Intolerant field. (The MIB attribute
dot11FortyMHzIntolerant determines the setting of the value of the Forty MHz
Intolerant field in transmitted frames, and the setting of the value of the MIB
attribute is beyond the scope of this standard.)” Note that this can only
be done by a device which is implementing IEEE 802.11-2007 with the 802.11n
amendment.
And when you read clause 11.14.5 you get: “An overlapping BSS scan
operation is a passive or active scan of a set of channels that are potentially
affected by 20/40 MHz BSS operation.”, “When an AP transmits an
Overlapping BSS Scan Parameters element, the values of each of the fields of
the
element shall be no less than the associated MIB variable minimum values and
the field values shall be no greater than the associated MIB variable maximum
values.”, and “Upon transmission of a frame containing an
Overlapping BSS Scan Parameters element, an AP shall update the values of its
MIB variables that are used during overlapping BSS scanning operations and
20/40 MHz BSS switching operations according to the mapping between the frame
fields and MIB variables as defined in 7.3.2.55 (Overlapping BSS Scan
Parameters element).” Still nothing about what prevents 40 MHz
operation...
In 11.14.3.3 the following line appears: “An AP shall not start a 20/40
MHz BSS in 2.4 GHz if the value of the local variable 20/40 Operation Permitted
is FALSE (see Equation (11-4)).” which is “20/40 Operation
Permitted = (P == OPi for all values of i) AND (P == OTi for all values of i)
AND
(S == OSi for all values of i)” and “OTi is member i of the set of
channels that comprises all channels that are members of the channel set C that
were listed at least once in the Channel List fields of 20/40 BSS Intolerant
Channel Report elements received during the previous
dot11BSSWidthChannelTransitionDelayFactor * dot11BSSWidthTriggerScanInterval
seconds and all channels that are members of the channel set
C and that are the primary operating channel of at least one 20 MHz BSS that
were detected within the AP's BSA during the previous
dot11BSSWidthChannelTransitionDelayFactor * dot11BSSWidthTriggerScanInterval
seconds” and “C is the set of all channels that are allowed
operating channels within the current operational regulatory domain and whose
center frequency falls within the 40 MHz affected channel range given by
Equation (11-3)” which does not seem to cover all possible channels in
2.4 GHz spectrum if the Primary and Secondary channels for 40 MHz operation are
selected at one end of the 2.4 GHz spectrum. This makes it impossible for one
device operating at one end of the 2.4 GHz spectrum in cooperation with say a
Bluetooth device that needs protection across the entire 2.4 GHz spectrum from
properly notifying a 20/40 MHz devices attempting to operate at the high end of
the 2.4 GHz spectrum. Why isn’t there a special case for preventing 20/40
MHz operation in 2.4 GHz if a device operating on any 2.4 GHz channel indicates
Forty MHz Intolerant?
It looks to me that TGn is protecting legacy 20 MHz devices and nothing else.
During this process of attempting to find anyplace where it is obvious that
some protection is provided, I found in 7.3.2.61 the 20/40 BSS Coexistence
element definition, but this clause is not referenced by anything else in the
802.11n amendment except for table 7-57c1. Maybe this is all that is needed.
Maybe 11.14.7 needs to be updated to include a (see 7.3.2.61) following
“A STA can include the 20/40 BSS Coexistence element”.
Also, I did find “reception of a Beacon frame that does not contain an HT
Capabilities element” in 11.14.12 regarding TE-A that seems to imply
detection of non-TGn 802.11 devices, but I was unable to decode exactly how
this information was used.
Maybe it would help to have someone from TGn explain exactly how they envision
their proposed solution to really work?
Regards, John
On 5/25/08 1:38 PM, "Shellhammer, Steve"
<sshellha@qualcomm.com> wrote:
IEEE 802.19 TAG,
Paul
Nikolich would like the opinion of the 802.19 members on the 40 MHz 802.11n
discussion.
If you
have an opinion to share please “reply-all” so that everyone can
hear your opinion.
Regards,
Steve
From: Paul
Nikolich [mailto:paul.nikolich@att.net]
Sent: Saturday, May 24, 2008 7:06
AM
To: Shellhammer, Steve
Subject: Fw: [802.15_GENERAL] TGn
Letter Ballot Support
Steve,
What is dot19's opinion on the below debate?
--Paul
----- Original Message -----
From: Matthew Fischer <mailto:mfischer@BROADCOM.COM>
To: STDS-802-WPAN@LISTSERV.IEEE.ORG
Sent: Friday, May 23,
2008 10:29 PM
Subject: Re:
[802.15_GENERAL] TGn Letter Ballot Support
I will be voting YES on TGn LB129, and I would
urge others who are interested in defending 802.15.x devices' access to the ISMii
band to vote YES as well.
The current draft of the 802.11 TGn amendment
contains normative language describing a mechanism (i.e. the 40 MHz Intolerant
bit) that allows non-related devices to signal to the 40 MHz TGn devices that
they cannot send 40 MHz transmissions, effectively allowing other users of the
ISMii band to restrict the use of 40 MHz transmissions by TGn devices. 40 MHz
802.11 TGn devices are required to obey this signaling whenever it occurs.
If 40 MHz operation is forbidden in ISMii by
802.11 TGn, then 40 MHz operation will be implemented as a set of
vendor-specific non-standardized modes with variable degrees of good
citizenship regarding spectrum sharing and with little or no opportunity for
such devices to be controled by other users of the ISMii band.
For these reasons, it is in the best interest of
802.15.x technology providers and other users of the ISMii band to vote YES on
the TGn-standardized mode of 40 MHz operation that includes specific
requirements to force TGn devices to cease 40 MHz operation when requested.
Matthew Fischer
Nice Guy
+1 408 543 3370 office
+1 650 796 9206 mobile
mfischer@broadcom.com <mailto:mfischer@broadcom.com>
From: John Barr [mailto:john.barr@MOTOROLA.COM]
Sent: Friday, May 23, 2008 8:36 AM
To:
STDS-802-WPAN@LISTSERV.IEEE.ORG
Subject: [802.15_GENERAL] TGn
Letter Ballot Support
As mentioned in Jacksonville,
the current draft of TGn includes use of 40 MHz channels in 2.4 GHz spectrum.
This will significantly impair ability of other IEEE standards using 2.4 GHz
spectrum to coexist with TGn devices running at 40 MHz. Even though the
rejection of my comment number 6069 states that there is provision for
coexistence with other radio systems using 2.4 GHz spectrum, the actual text
for this is informative and does not actually include tests for IEEE 802.15.1
nor IEEE 802.15.4 devices. See attached note to TGn I sent during the Jacksonville meeting. At
the one session where there was any discussion on my comment, I spoke against
the resolution and no one spoke for the resolution rejecting my suggested
change (not to allow any use of 40 MHz channels in 2.4 GHz spectrum). (See
attached)
As it current stands there is no clear method to prevent use of 40 MHz channels
in 2.4 GHz when IEEE 802.15.1 and 802.15.4 devices are operating in the same
spectrum.
You can vote against the current TGn letter ballot by referencing my comment
(6069) that is unresolved (not accepted by the submitter) and requesting the
same resolution: In 20.3.15 change "When using 40 MHz channels, it
can operate in the channels defined in 20.3.15.1 and 20.3.15.2." to
"When using 40 MHz channels, it can only operate in the channels defined
in 20.3.15.2."
James Gilb may be able to clarify just how to vote on this. Voters who
previously approved the original LB can change their vote to disapprove based
on this comment.
Thank you for your support.
Regards, John
--
John R. Barr (John.Barr@Motorola.com)
Director, Standards Realization - <http://www.motorola.com>
Vice Chairman of the Board, Bluetooth SIG - <http://www.bluetooth.org>
(847) 576-8706 (office) +1-847-962-5407 (mobile) (847) 576-6758 (FAX)
--
John R. Barr (John.Barr@Motorola.com)
Director, Standards Realization - <http://www.motorola.com>
Vice Chairman of the Board, Bluetooth SIG - <http://www.bluetooth.org>
(847) 576-8706 (office) +1-847-962-5407 (mobile) (847) 576-6758 (FAX)