Tomato for pure wireless N ?

Discussion in 'Tomato Firmware' started by ulyan, Sep 28, 2012.

  1. ulyan

    ulyan Networkin' Nut Member

    Hi there everyone,

    Long time since my noobish posts, I have a question related to wifi and tomato. Does anyone has a guide for configuring tomato, regardless the band, for full N only connection ?

    I mean greenfield, and all the advanced options on the wifi advanced settings page that even if I somehow find info about, I think some of them are related to lower modes like a,b,g etc , or maybe they should not be activated (CTS protection, afterburner etc).

    Thank you. :oops:

    PD: I don't know if the thread title is a bit exagerated or confused.
    PD2: I have an asus rt-n66u.
  2. koitsu

    koitsu Network Guru Member

    I was under the impression the option was under Basic -> Network, Wireless Network Mode -> N Only. Attached is a screenshot from my RT-N16 running tomato-K26USB-1.28.0500.5MIPSR2Toastman-RT-N-Ext.trx.

    Attached Files:

  3. ulyan

    ulyan Networkin' Nut Member

    But is this the only required thing to do ? From what I read there are several optimisations like I was saying, like greenfiled 802.11n Preamble. I want to squize the maximum troughtput ... :confused: (I don't know if I explain myself right). Thanks.
  4. koitsu

    koitsu Network Guru Member

    Your post subject is "Tomato for pure wireless N" and you asked for how to configure wireless to be "full N connection only". Performance tuning/tweaking is a separate (thus unrelated thing). Two separate (unrelated) subjects. :)

    I tend to recommend people not change any wireless settings under Advanced -> Wireless since most people I've seen online don't have any real understanding of what the variable/adjustment does (meaning they have no familiarity with the 802.11 protocol and driver behaviours in general). I know for actually improving signal strength (not the same thing as throughput) there is really great advice and logical science involved, but other things are usually a mystery to everyone except for Broadcom or Atheros (depending on what wifi chip is in your router).

    The Greenfield 802.11n thing, at least on Wikipedia, has a reference PDF from Broadcom that returns 404 at Buffalo's site. I did find the PDF over on Broadcom's site. Greenfield is also known as 802.11n Preamble Mode. But here's a more useful article, which says, and I quote: "802.11a/b/g devices cannot communicate with a Greenfield AP. Instead, their transmissions are likely to collide, causing errors and retransmissions for both parties". Given that there are always packets flying around for all 802.11 protocol types (b, g, and n) from neighbours/etc. I imagine there is no way to filter out those transmissions.

    What's a little confusing for me (using my Asus RT-N16) is that there are two options in the 802.11n Preamble pulldown: GreenField and GF-BRCM. BRCM is shorthand for Broadcom (it's their stock ticker, for example), so it seems to me that Broadcom invented their own preamble mode. I'm not surprised -- why not? Because the aforementioned PDF was written in April 2006, which is when 802.11n was still in Draft specification. See what happens when vendors do this crap? The only people who suffer are the customers. See, like I said, nobody knows. From looking at one of the Broadcom Linux drivers, I can see that GF-BRCM is completely unique/separate from the standard Greenfield stuff. It's referred to as, and I quote: 802.11 BCRM "Compromise" Pre-N. Hur hur hur... Broadcom.
  5. pharma

    pharma Network Guru Member


    Trial and error along with google is your best friend for performance tuning! :)
  6. Toastman

    Toastman Super Moderator Staff Member Member

    Spot On, Koitsu!
  7. chrcoluk

    chrcoluk Reformed Router Member

    I been running some tests.

    initially was lan side, but started using as easier.

    with greenfield preamble selected on my laptop with wireless N speeds seem capped to around 5mbit/sec TO the laptop, it flatlines at that speed regardless of channel, power etc.
    mixed mode (default) speeds are normal.
    GF-BRCM speeds are much better than normal greenfield but are slower than mixed mode, about 10-20% slower (varies).

    sadly I found no way to set preamble using the wl telnet tool so my tests are annoyingly dropping my internet connection everytime I make a change.

    An update.

    doing speedtests on the net was hiding the difference between gf-brcm and mixed mode.

    so normal greenfield is extremely slow and I think quite possibly is a bug, flatlines at 5mbit/sec.
    gf-brcm approx 50-70mbit sec, moves up and down in waves.
    mixed mode around 110mbit/sec.

    since my net is around 70mbit/sec it did hide most of difference between gf-bcrm and mixed mode but the greenfied was very clear on it.

    the tests were between my desktop pc which is gigabit ethernet and my laptop wireless N on 40mhz channel 2.4ghz. so wireless was only one side.
    Last edited: Dec 3, 2013
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