1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

WiFi N-only mode Tx rate stuck at 7 when transmitting

Discussion in 'Tomato Firmware' started by matthewchng, Dec 12, 2012.

  1. matthewchng

    matthewchng Serious Server Member

    I'm not sure if I'm the only noticing this but here's my issue. It seems that the router's Tx rate when connected via 802.11n is "stuck" at 7 when it tries to transmit data to its WiFi clients. Note that the test results below were obtained with WiFi set to N-only mode or G-only mode.

    I'm running shibby's Tomato Firmware 1.28.0000 MIPSR2-104 K26 Max on my Asus RT-N12 C1.

    In N-only mode, when the router isn't uploading to the client, the Tx rate looks fine and matches the Rx rate with the client about 2 metres away in direct line of sight. Once I force a transmission from router to client with iperf server running on the client, the Tx rate fluctuates and stays at 7 at most times until the transfer is complete and then return to a value matching that of the Rx rate.

    The iperf results also reflects the "bad performance" with values between 5-12mbps in N-only mode when router is uploading to the client while showing a more consistent 20-22mbps in G-only mode. Note that G-only is performing better than N-only when downloading on a WiFi client which makes using wireless N quite pointless.

    The following values were observed by me on the "Device Listing" link in the admin area.

    WiFi is running in N-only mode
    [​IMG]

    WiFi running in G-only mode
    [​IMG]

    Here's a graph for clarity in N-only mode running iperf upload from client then download
    [​IMG]

    Is this a bug in the firmware or is this a problem with the hardware? The other features that I'm using seem to be functioning alright though.
     
  2. benson

    benson Serious Server Member

    I found same problem. it's only appear if the client is using Atheros chipset.
    Set 802.11n Preamble to GF-BRCM will solve this problem. it will appear full tx Rate.
     
  3. matthewchng

    matthewchng Serious Server Member

    Thanks for the suggestion, changed the 802.11n Preamble from Mixed Mode to GF-BRCM. No difference for me though. :(

    The Tx still keeps fluctuating down to 7 more often than desired.
    [​IMG]

    The upload rate is still way better than the download rate with my Macbook as the WiFi client at about 3 metres away from the router in direct line of sight. Download rate is averaged under 20Mbps while upload is closer to 65Mbps.
    [​IMG]
     
  4. benson

    benson Serious Server Member

    this is client to router transmit speed. may be just power save function. if transfer data to the client, the data rate will be higher as possible.

    [​IMG]
    this is the list in my ASUS RT-N12 B1 Router, I like to set Preamble to GreenFlied, it will be to 65 if I set Preamble to GF-BRCM. otherwise it always be 6 or 7,never higher or lower.
    your RX is my TX, so not same reason.
    by some document ar9285 is draft 802.11n, so may be this reason lead the problem.
    just for your reference.
     
  5. matthewchng

    matthewchng Serious Server Member

    Oh, OK.

    By the way, can your other non Atheros clients both download/upload at max N-only speeds? Can you provide a similar screen grab like the real time graph above for the eth1 interface during the transfers?

    What firmware are you using and which version? I really hope it's just a problem with the software instead of hardware.
     
  6. benson

    benson Serious Server Member

    [​IMG]
    [​IMG]
    [​IMG]
    for reference... :)
     
  7. benson

    benson Serious Server Member

    I found a bug(maybe), if I set wireless mode to G only and press save, then set wireless mode back to N only and press save. this will be only 802.11n client can connect. where old client (b/g) can't connect. I think this is real N only mode. other found, the wireless performance will be better, my RX rate always at 72.
    after reboot the router, in the router information page still appear N only, but 802.11b/g client still can connect it. I think this isn't N only mode.
     
  8. matthewchng

    matthewchng Serious Server Member

    We're on the same version of shibby build but my Tx rate just can't get past 30Mbps. Rx rate get well above 75Mbps.

    Tested twice again from my Macbook Pro with 60 seconds of upload/download each after a full NVRAM erase with the default WiFi settings. Sigh...

    [​IMG]

    [​IMG]
     
  9. benson

    benson Serious Server Member

    it's strange, Do you had tested using ASUS official firmware ?
     
  10. matthewchng

    matthewchng Serious Server Member

    Just did. Reverted to latest Asus stock firmware but got the same results. Now flashed Toastman's 1.28.0500.5 build and still the same with the Tx maxing out at about 30mbps.

    Could it be that when there are a mixture of 65mbps N clients and 130mbps N clients, the router will only transmit at 65mbps rates? And would I be correct to assume that a 65mbps client's transfer speeds will be in the range of 32mbps up/down just like how a 54mbps G client's transfer speeds is about 27mbps up/down?

    Edit:
    Nevermind, I isolated the network to only having a single 130mbps N client but still the same 30mbps/70+mbps Tx/Rx rates from the router. Only logical explanation I can come up with now is that the router decides to not transmit at higher rates due to there being many other APs within range. The client, on the other hand, doesn't consider this but just pushes data back to the router as fast as is possible.
     
  11. benson

    benson Serious Server Member

Share This Page