Re: [802.19] WhiteSpace Coexistence Use Cases
Ben,
speaking for myself, thank you for your thoughtful and
helpful comments.
I will respond to your questions.
The Study Group decided to have
fairly well-defined scopes for its tasks --- which I view as a good
thing.
It is my recollection that the purpose of the Coex Use
Cases document is to identify the Use Case scenarios, and to also include in it
an assessment of how various technologies coexist. This can be seen in
Section 4 of the document, with the red-green matrix. This is where the
"identify potential limitations" wording comes from in the sentence I added, and
upon which you commented was negative and with good insight you asked, "why only
examine limitations?" These are great comments and questions, and the
reason is simply this is what the group decided the scope of THIS particular
document should be; it is a step in the work flow for this group. More
analysis and perhaps developing solutions or improvements is then a logical next
step (and is in our work plan).
I believe this addresses your excellent question about
why the limitation... it is only a limitation in our Step One.
I like your redlines in the second sentence, and
believe "enhance" is a better choice. I hope that the authors of the
document will use the wording I suggested, but alter it as you have
suggested.
About your question relating to "develop mechanisms,"
in honesty I did not originate that language --- I was only trying to keep the
gist of the idea that was already in that paragraph --- about work which would
or could follow this first step document. I added the wording about
possible modifications to base standards, because that is directly from our work
plan (my recollection --- I did not actually go back and check Steve's document
or the minutes on this, I admit).
I like your questioning of what is meant by "develop
mechanisms," because I too had some reluctance over that terminology. I
would rather be more specific than overly general, and this sounds a bit funny
to me when you really try to interpret what it means. I personally would
rather stick with commenting on standards. I would like to hear more about
exactly what others mean when they have written "...developing mechanisms that
can be used by industry..."
I suggest in response to your question about what is
meant by "develop mechanisms," that it would be an improvement for this
paragraph to just stop at the last comma, making that a
period.
As such, the new proposed wording:
The purpose of this document is to identify and examine
potential limitations on operation and use of the White Space spectrum when more
than one radio technology is attempting to use a band. A goal is to lay
the foundation for further investigations into the feasibility and effort
required to operate devices more efficiently in such coexistence situations in
the White Space. Such future work enabled by this document may include
investigation of modifications to base standards to enhance efficient White
Space use.
later, tjk
Some editorial remarks in red. Not intended to be contentious, just
trying to help ;-). I agree that this is a more specific description of
purpose than the CBer reference, which is vague at best and meaningful mostly to
people beyond a certain age. Better instead to keep it simple and
clearly state the problem - interference will be a limiting factor on capacity
in Whitespace (did I get it right?).
I think that making the goal of 19 to recommend
potential tweaks to existing standards and to produce coexistence
recommendations (as a recommended practice perhaps) makes good sense and fits
nicely the role of dot-19. Coexistence guidance for development of new 802
standards is clearly within the scope of dot-19, as would be I think application
and deployment recommendations as well.
Not sure I got your other points, but agree
it is useful to catalogue the likely
technologies that will come to play in WS, identify the coexistence properties
of each, and define some likely usage scenarios, which will enable the kind of
coexistence analysis we're used to doing (provide separation distance, tx
power, antenna characteristics, etc). Which then can lead to concrete
recommendations. Makes sense to
me.
Hope that helps.
-Ben
----- Original Message -----
Sent: Tuesday, June 09, 2009 1:35 PM
Subject: Re: [802.19] WhiteSpace Coexistence Use
Cases
> Richard, Mark, Alex,
>
> I
propose the following wording for the third paragraph of Section 1.
Introduction:
>
> The purpose of this document is to
identify and examine potential limitations on operation and use of the
White Space spectrum when more than one radio technology is attempting to use a
band.
Only going to examine limitations?
seems very negative...perhaps I've missed the point.
A goal is to lay the foundation for further
investigations into the feasibility and effort required to operate devices more
efficiently in such coexistence situations in the White Space. Such future
work enabled by this document may include investigation of modifications to base standards to achieve (acheive
or enhance?) efficient White Space use, or development of mechanisms that
can be used by industry in White Space spectrum to improve efficiency.
By "develop machanisms" do you
mean the result will be a recommended practices or some other kind of standards
document? Might as well be specific as there is a finite number of
things an 802 WG can produce.
>
> As reference, the current wording in Document 26r1
IS:
>
> The purpose of this document is to lay the foundation for
developing mechanisms that can be used by industry in White Space spectrum to
prevent the type of problems suffered by the Citizen Band (CB). In the CB
bands, interference became such an issue that wide spread use ceased and low
cost widely available equipment became uneconomic.
>
> --- ---
---
>
> DISCUSSION
>
> Firstly, the proposed wording
change addresses correctly (I believe) what the purpose and goals of this
document are as decided by the Study Group decisions/polls. I believe this
proposed wording is not contentious, but time will determine that.
>
> Secondly, I would like more discussion before the group sets in stone
the reference to "the type of problems suffered by the Citizen Band (CB)."
I believe the CB reference is a very effective statement for use informally
within our Study Group, as we try to explain concepts and get at the heart of
problems as we grapple with them, but upon reflection I am questioning this
wording and analogy in an official document from our Study Group. The CB
reference misses the mark for our study, in my opinion, on several key
points:
>
> 1) CBs are entirely one technology attempting to share
bands, and the CB technology is not separate technologies attempting to coexist,
which is what we are dealing with in TV Whitespace.
>
> 2)
The "type of problem encountered" by CBs in the '70s, which is what I believe is
being referenced in the existing text, has a name in networking --- "congestion
collapse." This happened with CBs, owing to CBs' own brief, boom for a
period of a few years. This exact problem has occurred with many different
technologies in their early generations. However, CB technology has not
addressed pushing a higher point of efficiency for onset of "congestion
collapse", whereas other technologies have. CB technology "has chosen" ---
in a sense --- to remain what it was. CBs are still in use today, serving
their core users; the technology is what it is. The core CB users are
probably very glad that the bulk of the fad users have moved on to other
technologies, and that their CB technology has remained simple. The
economy of the technology may not be suitable to the fad users, but it very well
may be suitable to the core users. If not, something will change.
That is the market.
>
> 3) This exact same issue of "congestion
collapse" which occured with CB also occurred with Ethernet, and Aloha, and
perhaps other technologies --- the simplicity of the technology led to a
limitation --- a threshold of "congestion collapse" which was lower than could
be provided by more advanced (and more complicated) sharing techniques.
However, in these technologies, unlike with CB, more advanced sharing techniques
were developed. For example, Ethernet and ultimately 802.11 and many other
technologies, eventually developed techniques that pushed up to higher
efficiency (throughput as a fraction of dedicated channel capacity) the onset of
"congestion collapse" in their networks. These are better examples to use
in our report, since these are examples where techniques were developed and
adopted to push up the onset of "congestion collapse," enabling higher
efficiency on their networks.
>
> 4) CBs are still in use
today. Although the advancement in other technologies over the last 30
years has almost certainly had an impact on the CB business, it is not correct
(I believe) to characterize the CB business as a failure, which is a "take away"
I get from the existing wording. It serves its core users and it is what
it is. It may eventually be "mothballed", as is probably the fate of all
technology. Bottom line, citing a technology which had its heyday over 30
years ago, but is still serving a purpose today, does not deliver our message
most effectively (my opinion). I think we can make the same point but with
more fitting examples or references.
>
> I hope this isn't overkill
for making the case for my simple suggestion.
>
> Later,
tjk
>
> -----Original Message-----
> From: Gerald Chouinard
[mailto:gerald.chouinard@xxxxxx]
> Sent: Tuesday, June 09, 2009 5:59
AM
> To:
STDS-802-19@xxxxxxxxxxxxxxxxx> Subject: [802.19] WhiteSpace Coexistence Use Cases
>
>
Richard, Mark, Alex,
>
> Thank's for the effort in putting this
white paper together. See my
> comments in 'track change' in the
attached copy. I guess this could be
> discussed on the
teleconference calls if time permits.
>
> Gerald
>