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I agree with Steve here,
Although everybody has the right to use the park
and everybody must tolerate that other people can use the park does not grant
the right to an individual to monopolise two thirds of the parl to through a
personnal praty, thereby bullying everyone else out of the park.
I think alot of the problem here is that the fact
11n can eat by itself 40 out of 60 MHz make 11n look like a resource bully who
tries to initimidate every body else to move out of their way, as if "they"
owned the park. I think we are all there to look at how we could have socail
rules that make that 11n can operate gracefully within the confines of this
spectrum while allowing other devices to continue to simultaneously have
a reasonable shore of the same spectrum.
Ivan Reede
=========================================================
----- Original Message -----
Sent: Friday, October 24, 2008 1:15
PM
Subject: Re: [802.19] Fw: [802.19]
Possible 802.11n spectrum scanning requirements
All,
This perspective is along the lines of treating RF Spectrum as Property.
This is of course the view taken by the FCC.
So I thought I would make some comments from this
perspective.
- Generally the best solution to
the Tragedy of the Commons is to maximize private property. This is in
fact the primary solution applied to Spectrum rights. Most of the
frequency bands are licensed private property (Broadcast, cellular,
etc.)
- However
not all property, or spectrum, is private. We have public parks, road
and beaches and we also have unlicensed frequency bands.
- There
are two primary methods to avoid the Tragedy of the Commons in public
property: laws and civil behavior between individuals
- In the
public parks we have laws against vandalism and littering. In the
unlicensed bands we have laws limiting TX power, bandwidth constraints,
and at one time we had spread spectrum processing gain
rules.
- In
public parks most individuals behave in a civil manner toward one
another. They may even make some agreements (often implied in civil
society) so that everyone gets to enjoy the public property. This
civil behavior could be thought of as social etiquette. This is the
closes analogy to coexistence in the unlicensed frequency bands.
Wireless networks behave in a manner that allows other wireless networks
to also utilize the public spectrum. We are currently in a debate
about whether these networks should behave in a manner that is analogous
to civil behavior between individuals sharing public
property.
Regards,
Steve
From: Bill
Shvodian [mailto:bill.shvodian@xxxxxxxx]
Sent: Thursday, October 23, 2008 11:16
AM
To:
STDS-802-19@xxxxxxxxxxxxxxxxx
Subject: Re: [802.19] Fw: [802.19]
Possible 802.11n spectrum scanning requirements
Is
everyone familiar with the concept of The Tragedy of the Commons?
http://en.wikipedia.org/wiki/Tragedy_of_the_commons
The
idea is that if there is a public resource (like common grazing land) that is
free for everyone to use, then individuals will decide it is in their best
interest to use more and more of it until eventually it is so overused that it
is useless (like overgrazed land). The analogy could be applied to the
ISM band. It is great spectrum and it is free and everyone can use as
much as they like as long as they are willing to accept interference.
However, as devices gradually are built to use more and more of this resource
at one time, it becomes more and more crowded and eventually unusable for
everybody.
We have heard anecdotal evidence that a device
transmitting on 40 MHz will transmit for a shorter time and so the net
interference will be the same. However, the simulations presented by TI
show that the aggregate throughput for the resource is decreased when 40 MHz
channels are used. Likewise other technologies are potentially crowed
out when 802.11n uses wider bands. And the argument we have heard that
40 MHz is required to enable new applications says that individual devices
would be using more of the resource themselves. This push for using more
and more spectrum is analogous to overgrazing making the land less useful for
all users.
Limiting 802.11n devices to 20 MHz in the ISM band would go
a long way to keeping the ISM ban useful to all users, and not befalling the
fate of the Tragedy of the Commons. Alternatively, the TAG has been
discussing sensing other technologies to avoid degrading their performance
when they are present. Is it ideal for the 802.11n manufacturer?
Of course not. Limiting 802.11n to 20 MHz in the ISM band would be much
easier for device manufacturers to implement, but that has so far been
rejected. Sensing appears to be the next best option.
Bill
On Thu, Oct 23, 2008 at 1:59 PM, Ivan Reede <i_reede@xxxxxxxxxxxx>
wrote:
I think your
comment addresses a fundamental question.
I think you are
correct in some ways in your assertion that "nobody owns this spectrum" and
"everybody may expect intereference" and "everybody has to live with
it".
However, I
remember some time back, not so long ago, where 802.11 was really worried
about 802.15.1 devices not following CSMA/CD rules and interfereing with
802.11 operations... worry which from my perception ultmiatly led to the EC
froming 802.19 ... the intent being that although "noboy owns the spectrum" we
also have "and 802 devices should play nice to each
other".
So the question
is, eihter "we elect to play nice to each other and really work at
implementing mechanisms enhancing playing nice to each other within 802
devices" or we drop all that and just start having fun clobering each-other.
Personally, I rather work together.
----- Original Message -----
Sent:
Wednesday, October 22, 2008 8:36 PM
Subject: Re:
[802.19] Possible 802.11n spectrum scanning
requirements
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
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
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