two questions a) stress testing b) really low gain antennas

another couple of questions.

stress tests

I've been able to find a couple of commercial systems built to
stress-test wi-fi networks, but are there any freeware products to do
it? You know, something that would allow a single laptop to behave like
a dozen (or a gross).

antennas

what can be done about getting a really low gain antenna? something
between an Access Point with the antenna removed, and the standard
single omni antenna the Access Point comes with?

thanks again

On 6 May 2005 06:19:00 -0700, (E-Mail Removed) wrote:

>stress tests
>
>I've been able to find a couple of commercial systems built to
>stress-test wi-fi networks, but are there any freeware products to do
>it? You know, something that would allow a single laptop to behave like
>a dozen (or a gross).

Simulating a client radio is simply a matter of generating MAC
addresses on the fly. A special program isn't really necessary as
simply using ifconfig to change the MAC address on the fly is
sufficient. See:
http://www.polarcove.com/whitepapers/detectwireless.pdf
or dig out "Wellenreiter" for the entire system.
http://www.wellenreiter.net
http://www.vanille.de/projects/wellenreiter.html
for sample code.

The Perl code fragment works but takes too long to change the MAC
address because it waits for the ARP table to expire. Send the inetd
process a kill -1 after each change and it will go faster. I do the
same thing with a simple shell script call to ifconfig in a loop
(beause I'm a rotten Perl and C++ programmist).

I also take great care not to run this on a live system with
potentially irate users. The limiting factor is the ability of the
access point(s) to build a large enough table of MAC addresses heard
and port numbers. Cheap junk will do 32 MAC addresses and crap out.
Proxim/Orinoco access points will go up to 2000. If dual radio, do
NOT assume that both radios share the same table.

I'm restricted by NDA from disclosing any results, but I would be very
interested in the results of your testing.

>antennas
>
>what can be done about getting a really low gain antenna? something
>between an Access Point with the antenna removed, and the standard
>single omni antenna the Access Point comes with?

Well, that's a new one. What are you trying to accomplish?

I just did a quick test with Netstumbler. Difference between an
alleged 2dBi rubber ducky antenna and with both antennas terminated by
50 ohms is only about 20dB. My WRT54Gv1.1 apparently leaks quite a
bit. 20dB would be a reduction in range to 1/10 of the normal (with
antennas) configuration.

Try:
- 50 ohm dummy load. With the antenna removed or terminated, the
circuit board leaks quite a bit. Few access points are properly
shielded.
- XX dB attenuator driving stock rubber ducky antenna. Finding an
attenuator with R-SMA or R-TNC connectors will be almost impossible.
I had to make my own or use adapters.
- Leaky coax cable (Radiax).
- Helical antenna (1/4 wave wound into a spiral).
- 1/4 wave radiator inside a sealed paint can. Punch some holes
in it to leak RF.
- Put access point inside an old microwave oven.



--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Jeff Liebermann wrote:

> Try:
> - 50 ohm dummy load. With the antenna removed or terminated, the
> circuit board leaks quite a bit. Few access points are properly
> shielded.
> - XX dB attenuator driving stock rubber ducky antenna. Finding an
> attenuator with R-SMA or R-TNC connectors will be almost impossible.
> I had to make my own or use adapters.
> - Leaky coax cable (Radiax).
> - Helical antenna (1/4 wave wound into a spiral).
> - 1/4 wave radiator inside a sealed paint can. Punch some holes
> in it to leak RF.
> - Put access point inside an old microwave oven.

I use a 1dbi paper clip sometimes. But that's an estimated gain figure.

On Fri, 06 May 2005 12:53:06 -0400, Rôgêr <(E-Mail Removed)> wrote:

>I use a 1dbi paper clip sometimes. But that's an estimated gain figure.

I still had my test setup together so I tried it. I juggled the
router for maximum signal strength to my laptop. The 3.8" paper clip
was about 3dB below the alleged 2dBi rubber ducky antenna. That gives
the paper clip a gain of about -1dBi or worse. However, the accuracy
of my desktop test range and sloppy measureing tools leaves much to be
desired.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Jeff Liebermann wrote:

> - Put access point inside an old microwave oven.

I seem to be getting some interference with this method. But it goes
away when I turn the microwave off. Coincidence?

Rôgêr <(E-Mail Removed)> wrote:
>Jeff Liebermann wrote:
>> - Put access point inside an old microwave oven.
>I seem to be getting some interference with this method. But it goes
>away when I turn the microwave off. Coincidence?

8*) It has to do with the RF-activated shielding in the microwave.
By using RF-activated shielding, they extend the useful lifetime of
the shielding, as it's only working when the microwave is on. Put a
2.4GHz portable phone in the microwave to keep the sheilding active
(note, you must keep the phone in an active call). 8*)