Re: [Acx100-devel] Some operational questions regarding the acx driver

[Analabha R. <har...@gm...>]

Can you give me a phenomenological relationship between signal
strength and operation range for the DWL card?


On Sat, 12 Feb 2005 23:12:49 +1100, Sean Dwyer <ew...@aa...> wrote:
> On Sat, Feb 12, 2005 at 04:44:49AM -0600, Analabha Roy wrote:
> 
> > 2. Do you have any data on the operational stability of these D-Link
> > DWL 520+ cards with your drivers? Are there any data-loss problems, or
> > do they connect sporadically? I have heard of such problems with other
> > wireless cards and I was wondering if you have some solid info
> > regarding this matter.
> 
> I can give you my anecdotal experience with the DWL-520+. I first attempted to
> create a wireless gateway between two debian linux boxes, one the router,
> another a linux bridging server, but the results weren't too good. I've been
> unable to track down the reasons for this, but I believe it to be a mixture of
> several factors: ad-hoc mode isn't quite stable, the cards are susceptible to
> overheating, and we've had quite a hot summer. To clarify further, the
> physical separation included the walls of a converted garage and house, and
> I believe signal strength was trickier for ad-hoc mode for that reason.
> Believe me, I tried _everything_ from swapping the cards around, to
> reinstalling identical software/hardware, it still wouldn't work reliably.
> 
> For some reason it was always the router in the house, not the server here in
> my flat which broke down. The driver does not behave with preemptive kernels
> (but I believe there is a sporadic bug with iptables in the 2.6.x series which
> may also be at fault), but seems currently most stable with version 2.6.7.
> 
> Then I got a DI-514 wireless router. At first I tried it at the router, which
> worked fine, but for operability reasons, I switched the arrangement around so
> it's now here in the flat. I tried keeping the signal strength at both ends to
> 10db but (again climatic conditions may well have had an influence) was forced
> to return to 18db. The link seems most fragile if the router is taken down and
> powered up again (ie the card doesn't settle and sporadically drops TX), but
> in general operation this is rare, and perhaps once in every three weeks (and
> only on hot days) does it drop the link for a few minutes.
> 
> My guess is that these kinds of issues are general wireless problems, and
> hopefully with better vendor support for 802.11n on linux, we're going to see
> this largely go away. I stuck with 802.11b because I've seen more problems
> with all 802.11g wireless cards under linux, and I'm not singling-out D-Link,
> ALL the vendors have been slapdash. I hope that helped in some way. The golden
> rule seems to be: keep your link simple, keep your cards cool, avoid a
> radio-noisy environment if possible.
> 
> 
> > 3. I have been toying with the idea of building my own wireless router
> > to connect with my cable modem. Since the acx driver has already
> > worked with mdk without problems, and I have an old box (P-II w 128 mb
> > ram + eth0) with a free pci slot, I was thinking of popping another
> > one of these DWL-520+ beasties into it, installing Mandrake MNF and
> > compiling your drivers in. However, I'm a tad worried about wireless
> > security, so I was wondering if it is possible to tell the driver to
> > reduce the transmission power for the wireless ESSID signal broadcast
> > to a few metres (so it stays inside the apt). This should be possible
> > in principle. Just wondering if it can been implemented in your code
> > and/or in the firmware of the card yet. Please do let me know and
> > point me to a HOWTO that shows the steps.
> 
> For the reasons I gave above, I advise against ad-hoc mode unless you have
> identical systems where you can prove that the hardware isn't at fault (and
> I'm not saying it is or not, just that I couldn't nail it down). So I have a
> spare 520+ hanging around that I know works, but won't work reliably in that
> manner. An 802.11b router won't set you back much at all (I only paid A$80 for
> mine), and you'll keep more hair than I do :) The best configuration if you're
> trying to set up a network router is to have the card in the linux box, and
> the router cabled into your local network, it avoids nasty things like proxy
> ARP bridging. You can (by use of iwconfig wlan0 txpower <number>) change your
> card's signal strength, but remember this is going to be affected by the
> quality of your link and how busy it will be. That's my $0.02 :)
> 
> --
> "You know your god is man-made when he hates all the same people you do."
> 
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