[Soekris] problem using multiple wireless cards

[Emilio Ancillotti]

Hi there,

I have a problem using my soekris 4801 with two miniPCI wireless cards (R52H High Power Mikrotik 802.11a/b/g mPCI). 

The problem is the following. When each wireless card works alone I have not problem, and I obtain a throughput of about 24-25Mbps.
However, when both cards work simultaneously, the per flow throughput of each cards is reduce of about 40%, even if the two wireless cards use different channels (1 and 11).

My testbed consisted of a soekris 4801 (runnig Debian with linux kernel 2.6.22 ) with two R52H High Power Mikrotik 802.11a/b/g mPCI adapter. I installed one miniPCI card into the Mini-PCI socket, and I put the second one into the PCI slot using a miniPCI to PCI single Slot Adapter. As wireless driver I used the madwifi driver version 0.9.4. 

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).

I repeated the same experiment using a PC equipped with an Athlon 64 processor (2043.086 MHz processor with 1GB of memory). I put both the wireless cards into two PCI slots using two miniPCI to PCI single Slot Adapter. In this case both the wireless cards are able to work simultaneously and I obtained a per flow throughput of about 24-25Mbps.
 
Has anyone experienced the same problem?

I would be really grateful if anyone shared his experience relative to
my question.

Regards,
Emilio Ancillotti


-- 
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Emilio Ancillotti, PhD
   Pervasive Computing & Networking Lab. (PerLab)
   Institute for Informatics and Telematics (IIT)
   National Research Council (CNR)
      Via G. Moruzzi, 1    ||    voice:    +39 050 315 2437
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