Subject: Re: multiple wireless cards
Newsgroups: gmane.linux.drivers.madwifi.devel
Date: 2008-07-19 23:10:22 GMT (24 weeks, 6 days, 5 hours and 27 minutes ago)
Hi Emilio, You may just be experiencing plain old-fashioned interference. Two WiFi devices operating that close to each other at the same time are pretty much guaranteed to step on each other. Even with the channel separation between 1 and 11, the amount of power bleeding over is probably enough to induce packet loss. That's an issue even when both cards are purely transmitting because of backoff and/or lost ACKs. Try it with different cards and/or different drivers and see what happens. Eric Thus spake emilio ancillotti (emilio.ancillotti <at> iit.cnr.it): > Hi there, > > I have a problem using 2 Atheros based wireless cards at the same time. > Secifically, when each card works alone the driver works fine. However, > when both cards work simultaneously, the per flow throughput of each > cards is reduce of about 30-40%, even if the two wireless cards use > different channels (1 and 11). > My testbed consisted of a soekris 4801 with 2 R52H High Power Mikrotik > 802.11a/b/g mPCI adapter runnig the madwifi 0.9.4 and the linux kernel > 2.6.22. > To see the throughput reduction I opened two outgoing asimptotic UDP > flows (using the iperf tool) between the soekris board and two laptop. > The two wireless cards worked in ad-hoc mode and I used 54Mbps as the > wireless transmission rate (I disable the autorate alghoritm). > > Has anyone experienced the same problem? > > I would be really grateful if anyone shared his experience relative to > my question. > > Regards, > Emilio Ancillotti > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Madwifi-devel mailing list > Madwifi-devel <at> lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/madwifi-devel -- Eric W. Anderson University of Colorado eric.anderson <at> colorado.edu Dept. of Computer Science phone: +1-720-984-8864 Systems Research Lab - ECCR 1B54 PGP key fingerprints: personal: 1BD4 CFCE 8B59 8D6E EA3E EBD5 4DC9 3E61 656C 462B academic: D3C5 D6FF EDED 9F1F C36D 53A3 74B7 53A6 3C74 5F12
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