On Mon, 21 Jun 2004, Cliff Skolnick wrote: > > On Jun 21, 2004, at 5:19 PM, Daniel Dobkin wrote: > > I have begun doing some 802.11 interference surveys in public places > > (downtown San Jose and along El Camino in Burlingame so far); in no > > case have I yet found offered loads exceeding about 2% of the channel > > capacity: that is, there is no interference to speak of coming from > > 802.11 networks. My highest AP count was about 25. Anecdotal > > reports from my colleagues at Tropos Networks indicate that high-power > > cordless phones are the biggest interference offenders. However, it > > is worth noting that other published data shows that network speeds do > > slow down when about 7 simultaneous high-rate downloads are proceeding > > from 1 AP, and presumably similar result would be obtained from > > collocated AP's run by differing organizations (since the medium is > > common): if the airport networks were HEAVILY used they would indeed > > clash. > > Can you please give us more about how you got the first 6 high-rate > downloads from one AP to not interfere?
There's all in the same collison domain... The access point in ibss mode is decding when to transmit and it doesn't of course stomp on itself, so when the level of traffic from the clients to the ap exceedes a certain threshhold which will vary depnding on the speed at which they're connected, they stomp on each other... > I'd love to understand your test methodology here. I would *hope* that > one client talking to a server would see interference from a second > client otherwise the first client was not using the media to even half > of its potential. > > And yes, they would clash...and since the internet upstream to each AP > is usually a small number of single digit megabits there is little > issue, they will all get out pretty much there full upstream. If it is > local systems like security scanners or baggage stuff I will run in > terror. I do not want my personal safety or that of others to involve > the 2.4Ghz band. It's a dump, but sometimes it is really useful when > you don't *need* it to protect life or property, ie surfing the web > while waiting for a plane. The folk using homeland security grants to > buy wi-fi gear for monitoring are foolish and putting us all at risk to > attack by a leaky microwave oven. My neighbor had a microwave that > took out wifi for half a block, kinda scary. Part 15 devices are *not* > for public safety to use in anything even remotely critical. > > > The better question to ask is: why should the Federal government > > regulate what is essentially a local matter? The property owner, the > > airport authority, should have the right to specify what sort of > > equipment and activities are permitted on the airport, subject to > > contractual obligations to their tenants. If they are being > > unreasonably avaricious (as seems to be the case here), it is > > something to be taken up with the local political establishment, since > > airports are usually run by a port authority or related local > > jurisdiction. The folks who use the airport ought to be making the > > call about the benefits of additional revenues vs. the risks of losing > > service, rather than the FCC. This is actually an issue of some > > importance in the long run: the FCC and other regulatory agencies > > were born out of an environment in which most communications were very > > long-wave and high-power, with huge ranges so that interference was an > > inevitable issue and regulation needed to span borders. It is much > > less clear that such as assumption is valid for current and future > > short-range, low-power emitters, but if we can't develop alternative > > mechanisms to deal with disputes like this one, we might be stuck with > > the inefficient, awkward centralized regulatory model we use today. > > There is public space (a city park), private space (a home), and then > that uncomfortable mix of public access private space like a mall or an > airport. Now if it was a public airport, they should be able to > regulate for safety not to ensure a revenue stream. I could see the > airport setting standards for installations and that is about it, if > you use my tax dollars to build the thing it should be regulated as > public space. If it is a privately owned airport, well, then the > renters (airlines) are hosed. > > Think about how we treat free speech in malls, the government can't > tell us to stop saying stuff - but unfortunately the owner of the mall > can in some cases. It is one of those grey areas where lawyers make > lots of money. > > So is the airport in question a municipal or private airport? > > As for your comments on the FCC, while it may be improved I kinda like > the centralized model. I really don't want each city, county or state > allocating spectrum. Imagine needing a special specific radio for each > state or a pile of cell phones when you travel. Imagine hundreds of > flavors of wi-fi regulated differently and using different bands. > Cards would be enormously expensive. In fact I like the idea of an > even more centralized guiding body like the ITU, and I just lost a > bunch of my anarchist points writing this paragraph. > > Cheers, > Cliff > > -- > "If you love wealth more than liberty, the tranquility of servitude > better than the animating contest of freedom, depart from us in peace. > We ask not your counsel nor your arms. Crouch down and lick the hand > that feeds you. May your chains rest lightly upon you and may posterity > forget that you were our countrymen." > - Samuel Adams > > _______________________________________________ > BAWUG's general wireless chat mailing list > [unsubscribe] http://lists.bawug.org/mailman/listinfo/wireless > -- -------------------------------------------------------------------------- Joel Jaeggli Unix Consulting [EMAIL PROTECTED] GPG Key Fingerprint: 5C6E 0104 BAF0 40B0 5BD3 C38B F000 35AB B67F 56B2 _______________________________________________ BAWUG's general wireless chat mailing list [unsubscribe] http://lists.bawug.org/mailman/listinfo/wireless
