Date: Wed, 06 Dec 2000 09:10:18 -0000 (GMT) From: Duncan Barclay <dmlb@dmlb.org> To: Warner Losh <imp@village.org> Cc: mobile@FreeBSD.ORG, Wesley Morgan <morganw@chemicals.tacorp.com>, Greg Lehey <grog@lemis.com>, Christopher Yeoh <cyeoh@linuxcare.com.au> Subject: Re: ray committed Message-ID: <XFMail.001206091018.dmlb@computer.my.domain> In-Reply-To: <200012060604.XAA76044@harmony.village.org>
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Hi
On 06-Dec-00 Warner Losh wrote:
> In message <14893.53324.616401.949125@rockhopper.linuxcare.com.au>
> Christopher Yeoh writes:
>: As far as range goes, for our situation the aviators worked better
>: than even wavelans with small antennas (yes this surprised us!). The
>: situation is fairly unusual though. We're on different floors and the
>: floor is made of reinforced concrete). Definitely no signal through
>: the floor (eg being directly above doesn't work). However, the way the
>: appartments are arranged there appears to be a path through a couple
>: of appartments, outside and then into his side window, that the
>: aviators can get a decent signal along.
>
> OK. I have two floors of my house. It is mostly wood based with the
> usual duct work and such. I was down stairs and the "base" was
> upstairs. I'd notice that sometimes things would just work, but that
> heavy load doesn't work too well (eg a simple FTP or scp would swamp
> the link). With the ZoomAir + Orinoco card (both with their default
> tiny anntennas) I can still get good interactive performance and 1.5mbps
> of ftp transfers.
1.5Mb/s data or about 160kB/s is about the theoretical limit for 802.11 at
2Mb/s and TCP/IP. I get 160kB/s ftp with my Libretto 50 over the raylink
driver.
> I see only slightly worse interactive performance
> during the ftp than when it isn't running. With the aviator, the ftp
> would just about shut down the link. Then after a while things would
> get worse and worse. I could then take the laptop with the aviator
> upstairs to 1' of the base station (which is just an intel box with an
> aviator card) and get 0 throughput (which sounds like a driver
> problem). The really strange part is that I can reboot both machines
> and still get horrible to zero throughput. This points to "enemy
> action" of some sort.
>
> I also have a wireless link with the older pre802.11 wavelan cards at
> 2.4GHz to a friends house. Maybe that is impacting things.
This could be a problem. Do you know if these are frequency hopping or
direct sequence? If frequency hopping they are likely to be interfering.
> It
> doesn't impact the 802.11b cards that I use. We've also noticed
> mysterious outages with the radio link for reasons that we still don't
> understand. We've theorized that it may be due to other users in the
> 2.4GHz band, which is also causing problems for the aviators.
How long is the link? 802.11 was designed for a couple of 100m - this is not
just Tx power/Rx sensitivity but stuff like
resiliance to fading channels
resiliance to mutli-path
timing parameters (remember 150m/microsecond)
...
> Or that
> could just be a red herring.
>
> I have also tried turning off the wireless link above and things
> didn't get better.
It might be direct sequence then if it's WaveLAN. This wouldn't affect the
Aviators.
I think you might have a half dead card.
> Warner
Duncan
---
________________________________________________________________________
Duncan Barclay | God smiles upon the little children,
dmlb@dmlb.org | the alcoholics, and the permanently stoned.
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