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Get data frame when it is expecting ACK (802.11a) RRS feed

  • Question

  • Hello,

    We have two Sora machines and both of them use SDRMiniport driver (under 802.11a mode).
    Then we get the chance see this strange behaviour when we test them with iperf. Here is how we setup the Sora machines.
    Machine A's IP: 192.168.0.100 
    Machine B's IP: 192.168.0.200

    ARP setting on both machines:
    arp -s 192.168.0.100 02-50-F2-8C-FF-00
    arp -s 192.168.0.200 02-50-F2-5F-DD-00

    Machine A runs: iperf -c 192.168.0.200 -i 1 -t 100000 -l 1000 -u -b 6m
    Machine B runs: iperf -c 192.168.0.100 -i 1 -t 100000 -l 1000 -u -b 6m
    Then both machine run: iperf -s -i 1 -u
    Data rate: 6Mbps, sample rate 44MHz.

    We only added several print out statement to the source code "sdr_mac_tx.c" and "sdr_mac_rx.c".
    Finally, we realized the sender could occasionally get data frame when it finishes the transmission and is waiting for ACK come back.
    Not sure if we have done something wrong. Any suggestions will be appreciated.

    Thanks
    Muye


    • Edited by MUYE20 Tuesday, November 5, 2013 4:01 PM Revision
    Tuesday, November 5, 2013 1:59 AM

All replies

  • Hi MUYE20,
    From your description I understand the environment of your experiment, and all the steps seems reasonable to me. But what behavior is strange exactly?

    Please also note:
    1. Sample rate 44MHz is not a good optional, normally you should use 40MHz to confirm to 802.11a standard
    2. You should be careful when adding debug output, if they are added to the crtical code, such as demodulating a frame or sending ACK, you will probably influence the ACK response time, which is strictly limited by the standard.
    3. As before, we recommend you use user mode 'umxsdrbrick.exe' / 'umxsdra.exe' instead of old 'SDRMiniport' driver.

    Thursday, November 7, 2013 3:00 AM
    Answerer