[kwlug disc.] detecting wireless

[Cedric Puddy]

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No, the problem with phones not being seen by iwlist is because  
mobile phones don't speak the 802.11b/g Wireless LAN protocol.  They  
use the same radio frequency bands, but they don't even speak a  
similar language.    Imagine the difference like this:
	- we speak in an audible range between 3kHz and 9kHz, in english
	- we might hear someone speaking, say, Chinese, and know that we  
were hearing language, but not understand it (eg: "encrypted")
	- birds may make noise between 3-9kHz, but we wouldn't probably  
think of that as being a "people talking"
	- we wouldn't mistake the noise of a jack-hammer as "human language"

The iwlist tool is only interested in "people talking" in the area,  
and it will only pay attention to things that it recognizes as  
"people" -- it will completely ignore birds, jack-hammers and jet  
engines (even if they are making a lot of noise, and making it hard  
to hear people talk).

It's not interested in telling you about why you might have trouble  
talking -- it's just interested in who *is* talking.

(There are a few WLAN cordless phones that speak SIP VOIP protocol,  
but you probably don't have one .)

The problem with your access point is probably *not* another access  
point -- Access Points recognize each others traffic, and do their  
best to respect each others use of the radio spectrum -- for example,  
they will recognize when another access point is talking, and choose  
to *NOT* transmit potentially interfering signal at the same time.   
Non-access points (cordless phones, microwave ovens, 2.4 Ghz video  
cameras, etc.) don't give hoot (they can't even know) if you are  
using WLAN at any given microsecond and will happily do their thing  
regardless of whether or not it blocks your signal.

- -Cedric

On 6-Mar-07, at 1:41 PM, Oksana Goertzen wrote:

> Good idea.. I'll start with this because it comes with the distro  
> and I can easily use it.   It won't show cordless phones  
> because... ?  they're not transmitting IP or UDP?  [this is  
> probably a stupid question but ...]
>
> On 3/5/07, John Van Ostrand <john at netdirect.ca> wrote: On Mon,  
> 2007-03-05 at 11:14 -0500, Oksana Goertzen wrote:
> > In my neighbourhood someone has setup their wireless to operate  
> on the
> > same frequency as my home network.  I can see the other wireless
> > network (and occasionally one other) if if I do a scan of available
> > networks from a workstation.  We also have cordless phones in the
> > house set up on a different channel than our wireless.  I'm trying a
> > number of channels to see what's available in order to get our
> > wireless working consistently.  How can I tell what's available?   
> I'm
> > thinking someone else might also have cordless phones that are
> > interfering with our signal.
>
> You could use the iwlist tool. This will show other networks, signal
> strengths, etc. It will not show the cordless phones.
>
> --
> John Van Ostrand                       Net Direct Inc.
> CTO, co-CEO                   564 Weber St. N. Unit 12
>                                   Waterloo, ON N2L 5C6
> john at netdirect.ca                     ph: 518-883-1172 x5102
> Linux Solutions / IBM Hardware        fx: 519-883-8533
>
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|  CCj/ClearLine - Unix/NT Administration and TCP/IP Network Services
|  118 Louisa Street, Kitchener, Ontario, N2H 5M3, 519-489-0478
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    Cedric Puddy, IS Director            cedric at thinkers.org
      PGP Key Available at:              http://www.thinkers.org/cedric


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