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[Ham-80211] OT??? High power 2.4 GHz rules change

Tim Gorman ab0wr at ab0wr.net
Fri May 19 22:38:27 UTC 2006


I hate to rain on your parade but DSSS *is* most definitely considered by the 
FCC to be spread spectrum. I quote from Part 2.

"Direct Sequence Systems. A spread spectrum system in which the carrier has 
been modulated by a high speed spreading code and an information data 
stream. ....."

OFDM, if the frequency span occupied is much, much greater than the modulating 
bandwidth, will probably also be considered spread spectrum based on my 
reading of the FCC rules and regulations under CFR 47. 

802.11h has been specifically designed to work in conjunction with 802.11a (an 
OFDM system) to provide APC functions. And it works! So saying that it is a 
"Practical Impossibility" has already been proved wrong. 

My opinion is that APC, of exactly the sort specified by the FCC, is also 
possible with DSS. It is merely a matter of implementation. That isn't to say 
it won't be complex and won't be a pain in the butt but that doesn't make it 
a "Practical Impossibility". Heck, if nothing else, a scanning narrow band 
receiver operating in conjuction with the spread spectrum receiver can be 
used to provide the necessary feedback for the APC loop. There isn't anything 
very complicated or "impossible" about doing that. 

It doesn't matter how federal judges will rule on "Practical Impossiblity" 
cases if "Practical Impossibility" doesn't apply. Sounds to me like perhaps 
you've been taking the ARRL statements about how hard APC is to do too much 
to heart. In the case of OFDM and FHSS it is easy to do - it has already been 
done as a matter of fact. It is just an implementation decision for DSSS - 
not an impossibility.

tim ab0wr


On Friday 19 May 2006 11:12, DuBose Walt Civ AETC CONS/LGCA wrote:
> A couple of quick comments...
>
> 1) The FCC has defined what is means by spread spectrum and how to obtain
> APC under Part 97.
>
> 2) DSSS (802.11b) and OFDM (802.11g) do not fit the FCC diffinition of
> spread spectrum.
>
> 3) Accomplishing APC on DSSS and OFDM types of modulation using the method
> of APC that the FCC has defined in Part 97 is a "Practical Impossibility"
> (a legal term) and I can assure you that no knowledgable federal attorney
> is going to get the government involved in Practical Impossibility
> litigation. There is too much case law at stake if they lose and judges
> almost always rule against practical impossibility.
>
> Walt/K5YFW
>
> PS, just this week finished a contract law seminar from the Defense
> Acquisition University (continuing educations requirement for procurement
> professionals) that shows just how federal judges are ruling.  IMHO they
> would not rule in favor of the government where there is a question of
> Practical Impossibility.
>
> -----Original Message-----
> From: ham-80211-bounces at lists.tapr.org
> [mailto:ham-80211-bounces at lists.tapr.org]On Behalf Of Tim Gorman
> Sent: Thursday, May 18, 2006 12:06 PM
> To: TAPR Mailing List for Ham Radio Use of 802.11
> Subject: Re: [Ham-80211] OT??? High power 2.4 GHz rules change
>
>
> Contrary to other posts, I can find nothing in any FCC documentation that
> shows they approaced the ARRL about dropping the APC requirement. And since
> this is a public proceeding, it will cost you little to add your comments
> to
>
> the proceeding at this time. If you do not comment on it and it becomes
> reality *then* you could incur significant legal costs trying to fight the
> isse as a seconcdary user of the spectrum.
>
> I an an amateur radio operator with two Linksys wrt54g wireless routers I
> have
> modified the firmware on. I have been looking at purchasing amplifiers to
> up
>
> their output to establish an omni-directional hubbed network. Amplifiers
> with
> moderate power levels are not that expensive. Dropping the APC requirement
> *would* make it easier to implement the current FCC requirements. Meeting
> current requirements would require applications to make use of the 802.11h
> modules in the modified firmware I am using. It *will* require additional
> work over just buying off-the-shelf stuff and using it.
>
> Having said that, I have to tell you I have already posted comments against
> the proposal. After thinking about it a lot I came to the conclusion that
> APC
> *is* the technological path to follow to limit spectrum pollution, be it
> pollution in the Part 15 or Part 97 arena. Hams are supposed to engineer
> their equipment based on sound engineering practice and judgment.
> Implementing APC *is* exhibiting sound engineering practice and judgment.
> While you can argue that philosophically amateurs will implement APC on
> their
> own without it being in the rules, pragmatically that is not the case. The
> ARRL in their proposal admits this by basically saying APC, as formulated
> by
>
> the FCC, is too hard for amateurs to do. Basically, that is a crock.
> Conceptually, it is easy to do in any FHSS system. It is hard to do in a
> DSSS
> system because trying to identify signal strengths of narrow band signals
> is
>
> difficult in a DSSS system. But I'm sure some DSP processing could handle
> this.
>
> Anyway, as you can see there are probably lots of varying views on this
> subject. You need to think your position through and put in your comments,
> while I think it is past the comment date, I think the FCC will still
> accept
>
> comments as long as they aren't actively in the process of analyzing them.
>
> tim ab0wr
>
> On Wednesday 17 May 2006 11:03, Marlon K. Schafer (509) 982-2181 wrote:
> > Hi All,
> >
> > As I'm sure you guys are aware, HAMs are primary users in about half of
>
> the
>
> > 2.4 gig band.  When using APC you can run very high wattage.  I can't
> > remember if it's 100 or 1000.  This is for video as I recall.
> >
> > There's a proposal to drop the APC requirement.  As a board member of the
> > Wireless Internet Provider's Association (www.wispa.org) I've been asked
>
> to
>
> > ask for your input on the issue.
> >
> > WISPs, and other license exempt users, are limited (for all practical
> > purposes) to 4 watts for our broadcast sites.  And much of the gear is
> > contention based, so anything that's always on tends to cause great
> > headaches and gnashing of teeth.
> >
> > We will likely fight this new proposal but wanted input from the HAM
> > community first.
> >
> > Are there people using this ability today?
> >
> > What's it used for?
> >
> > Any plans for more high power 2.4 gig use?
> >
> > Are there any reasons that we shouldn't come out against the proposal to
> > drop the APC requirement?
> >
> > Am I missing anything?  Asking the wrong questions etc?
> >
> > Thanks all!
> > Marlon
> > (509) 982-2181                                   Equipment sales
> > (408) 907-6910 (Vonage)                    Consulting services
> > 42846865 (icq)                                    And I run my own wisp!
> > 64.146.146.12 (net meeting)
> > www.odessaoffice.com/wireless
> > www.odessaoffice.com/marlon/cam
> >
> >
> >
> >
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> > https://lists.tapr.org/cgi-bin/mailman/listinfo/ham-80211
>
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