Dave,
Thanks for your comments.
I would just like to point out that 802.19 is just a TAG and as such is a
forum for having technical discussions. The decision on the 802.11n
draft is in the hands of the WG and the WG/Sponsor ballot voters, the EC,
RevCom and the SB, not the 802.19 TAG.
The TAG is not setting policy it?s a forum for technical
debate.
There was a request for such a discussion. Are you suggesting that I
tell those who requested such a discussion that the TAG will not allow for
such a technical discussion? I think not.
Regards,
Steve
From: David
Bagby [mailto:david.bagby@xxxxxxxx]
Sent: Wednesday, October 22, 2008 4:16
PM
To: Shellhammer, Steve;
STDS-802-19@xxxxxxxxxxxxxxxxx
Subject: RE: [802.19] Possible 802.11n
spectrum scanning requirements
I honestly do
not think that .19 should go down that road.
If it does, I
strongly suggest that requirements to scan for other 802 family wireless
devices would have to apply to ALL 802 wireless devices.
1) The ISM bands are
what they are: ISM band devices are required by law to accept
any interference received from other ISM devices.
2) Another factoid is
that 802 devices constitute a small portion of the things found in ISM bands.
(ref the tutorial given by the hospital guys re what they saw in ISM bands
when they scanned).
3) Independent
of if we like it or not, the mixture of signals in the ISM bands is not static
- what one accounted for in yesterday's design may or may not be good enough
tomorrow - the band signal content is dynamic.
4) The law
has no analogy of a homestead act for spectrum in the ISM bands
- Ownership of spectrum is not conveyed by sales of devices.
5) The source of what
one's device perceives as "interference" is not really
relevant (in that it does not matter if it is from another
802 device or a non-802 device).
6) Channel width used
by a device is also not relevant (100 1MHZ adjacent channels fill the same
amount of spectrum as 1 100MHz channel).
My
pragmatic conclusion, developed over many years, is that if
one wants to play in the ISM bands, one had better be able to operate in
the ISM environment, including accepting the interference one is likely
to receive. If one's device can't handle that, don't expect to have a
successful product.
SO then I ask
why scan for 802 devices?
Presumably because
"someone" wants "something" to happen to make their operation "better"
when the "other" devices are found....
Who is to say what
use of the ISM band is more important that another?
The only consistent
answer to those questions I would expect to hear is "mine is more important
than yours"; a rat hole argument that can never be
"won".
I've
observed that people tend to react emotionally along the lines
of "just don't interfere with me"....
ISM band
reality is that if ISM product operation depends on assumptions
that can not be guaranteed in the ISM band, one may not have made a good
choice of spectrum for the product design.
When I consider these
points, I wonder what is the benefit of having 802 devices looking for
only other 802 devices?
What will they do
when they find them?
Who gets out of the
way of whom?
based on what
objective or criteria?
Having found 802
devices, does it matter given the full extent of devices operating in the ISM
band?
Seems to me like a
lot of work to address a rather small percentage of the ISM "interference
sources".
Suppose 802 did
eventually require that all 802 devices look for other 802 devices....
how would 802 keep
that updated as new devices are invented?
Cross coupling
operational aspects of different 802 standards in that manner would seem
to be an enormous complication; and one that I don't see a payback
for. The pace of the 802 standards process pretty much tells me that by
the time that "802 family scanning" were standardized, the assumed mixture of
devices would be obsolete. And what would old 802 devices do wrt to new ones?
they would have no way to know how to scan for them...
I think it very
unwise for .19 to attempt to extend simple "coexistence" (which is not and has
never been a synonym for "zero interference interaction") into "cross 802
wireless standard awareness" or (even more complicated) "dynamic spectrum
management between 802 devices".
I suspect that
anyone which sticks a toe in that tar pit is unlikely to ever see
their toe (or foot or...) again...
-----Original
Message-----
From:
Shellhammer, Steve [mailto:sshellha@xxxxxxxxxxxx]
Sent: Wednesday, October 22, 2008 3:05
PM
To:
STDS-802-19@xxxxxxxxxxxxxxxxx
Subject: [802.19] Possible 802.11n
spectrum scanning requirements
All,
On the 40MHz 11n coexistence conference call it was suggested that the
802.19 TAG start to look at possible Spectrum Scanning
Requirements. A proposal was made to add include an option for
spectrum scanning in the standard. The proposal was made by John Barr
and can be found at,
https://mentor.ieee.org/802.11/file/08/11-08-1101-04-000n-additional-40-mhz-scanning-proposal.ppt
While the 802.11 WG discusses the merits of this proposal, the 802.19 TAG is
a good forum for having technical discussions on possible requirements and
technical feasibility. This information may be useful to 802.11 in
making its decision on how to address this proposal. The text on Slide
6 of John?s presentation beings to discuss possible requirements. That
may be a good place to look at to stimulate thinking on this
topic.
During the conference call it was suggested that the primary non-802.11
systems that are of concern are 802.15.1 (Bluetooth) and 802.15.4 (Zigbee)
since they both operate in the 2.4 GHz band.
Anyone who would like to prepare a presentation on possible spectrum
scanning requirements for these non-802.11 systems please notify me.
We can discuss any such presentations on the next conference call on
November 3 or at the Plenary meeting in Dallas.
Thanks,
Steve