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Thread: 20mhz vs. 40mhz and 270mbps? Relation?

  1. #1

    20mhz vs. 40mhz and 270mbps? Relation?

    I have a few different N devices working in my home and am kind of confused about the differences. Some run only 20mhz, some multiplex between 20 and 40mhz, and some operate at 144Mb, 270, and 300mbps.... what's the relationship between those 3 speeds and the 2 channels?

    And also, in my gigabit wifi-n router (Netgear WNR854T), I have two settings in the wireless panel that I'm not sure about. For wifi channel, it has the manual selection for 1 thru 12 but also an "auto" channel. Is there a benefit to using auto over the manual selection? And given that all my computers are wifi-n enabled, is there a difference between using 802.11n only mode or mixed mode bgn?
    Last edited by singularity2006; 12-16-07 at 07:30 PM.

  2. #2
    singularity2006 wrote:
    for some reason, the centrino pro driver will not let me get past 144Mbps.....

    The Intel 4965AGN card is properly 802.11n Draft 2 compliant and requires a 5GHz band channel to achieve 270Mbps link connectivity speed. This means the access point must support a 5Ghz channel, which few do as yet.

    If you have other "pre-N" cards running at 270Mbps link connectivity speed on the 2.4GHz band only at present, they will be doing that through pre-Draft 2 channel aggregation, which is basically unsustainable on a middle to long term basis in urban areas, where it s prone to interference from 802.11g networks.

    Cheers,

    Bill
    That just blew a huge door open for me. So basically, if I am using the Netgear WNR854T and a buffalo N-finiti usb adapter that is achieving 300Mbps, it is using a pre-N aggregation or is this N? I'm not even sure anymore.... it's so confusing!! and to top it off, I do notice that my wifi network seems to die suddenly - I'm guessing this is caused by the interference Bill was talking to above...

    can someone help explain this for me? It's so confusing.

  3. #3
    Elite Member TonyT's Avatar
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    Quote Originally Posted by singularity2006 View Post
    And also, in my gigabit wifi-n router (Netgear WNR854T), I have two settings in the wireless panel that I'm not sure about. For wifi channel, it has the manual selection for 1 thru 12 but also an "auto" channel. Is there a benefit to using auto over the manual selection? And given that all my computers are wifi-n enabled, is there a difference between using 802.11n only mode or mixed mode bgn?
    Channels:
    The usual defaul channel for soho wifi APs is channel 6. However, you can get interference from other 80211 devices or wifi devices such as cordless phones, baby monitors, microwave ovens, etc. Thus to avoid overlapping signals from other devices set the AP to use a channel at either end of the spectrum such as 1 or 11.

    Modes:
    Setting the AP to N Only prohibits non-N clients from using the AP. Setting to A-B-G will prohibit N clients from connecting. Setting to Auto will allow all clients to connect, however if you are using N clients and an A-B-G clients connects then the AP will automatically drop back to A-B-G mode and your N clienst will operate in that mode. The AP cannot use both N and A-B-G at the same time, it will auto use one or the other.
    No one has any right to force data on you
    and command you to believe it or else.
    If it is not true for you, it isn't true.

    LRH

  4. #4
    Thanks for the info, Tony. But I'm still at a loss to the channel bonding thing. currently, my router operates only in the 2.4GHz spectrum and also channel bonds to that spectrum. That said, how do I know which NIC will not only work on my Thinkpad T61 (unless someone has a BIOS hack to let me use an "unauthorized card") and will also channel bond in the 2.4GHz spectrum?

    It's really irritating that it's sooo poorly documented. I've been looking around and can only find the Atheros AR5008-3NX as being the only one that could possibly bond in 2.4GHz. But because of a BIOS lock Lenovo uses, I have no guarantee that an Atheros card from ebay would work. So I ultimately went to order the Thinkpad ABGN mini PCI-E NIC from Lenovo's website.

    My concern with that Thinkpad ABGN card is that the website has absolutely no documentation on what chipset it uses or additional specifications. Although some users did not that the prior generation of the Thinkpad ABGN card did use the Atheros 5008 chipset.... there are hopes that the new line will handle the 9000 chipset. But then - will that one also prevent me from channel bonding in 2.4GHz like the Intel Centrino Pro chipset? Or was the lack of ability to bond in the 2.4GHz spectrum only forced by Intel?

    Absolute confusion...!

    It's just really irritating that my dad's system and brother's system are both getting 300Mbps with their cards, which can bond to 2.4GHz. Mine on the other hand, stupid centrino pro, just has to force itself to use some other variation of the draft-N standard....

  5. #5
    Elite Member TonyT's Avatar
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    There are a few hacks that will disable the ibm bios lock for the mini-pciE slot so you can use any brand.
    http://www.google.com/search?hl=en&q...=Google+Search
    http://www.command-tab.com/2006/02/2...ireless-cards/
    or search the Think forums at ibm for "1802 error".
    No one has any right to force data on you
    and command you to believe it or else.
    If it is not true for you, it isn't true.

    LRH

  6. #6
    yeeeaaahhh....!

    I saw that 2nd link last night and have my boot CD ready... I'll be hacking it after my final tonight - gotta make sure I have my mission critical infrastructure idle before I can do it.

    But man, such a pain, I finally realized that my environment will not take channel bonding in the 2.4GHz. It works relatively well when my neighbors are not doing their thing. I've had to since disable the channel bonding entirely to at least maintain stable connections throughout the day.

    Really sucks - I had no idea channel bonding in 2.4GHz could have caused so much trouble lately! Holding out for those dual band routers... need channel bonding in 5GHz....

  7. #7
    Elite Member TonyT's Avatar
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    Note, the bios hack changes a bit or 2 in a line in the bios code. If have troubles after the hack you can fix by powering down comp, remove battery, remove cmos battery for 10 mminutes.
    No one has any right to force data on you
    and command you to believe it or else.
    If it is not true for you, it isn't true.

    LRH

  8. #8

    An Update

    SUPER... so I finally got myself the Apple Airport Extreme Gigabit edition that supports 5GHz channel bonding and some dual band adapters (Linksys WPC600N) and got really poor results anyway!

    For some odd reason, even in full N 5GHz bonded mode, the Linksys adapters can only get 270Mbps - baffling. However, my Intel Centrino Pro chipset gets full 300Mbps and gives me 10MB/sec FTP to my home NAS.

    But that is besides the point ...

    Turns out that 5GHz has only 1/2 of the range of 2.4GHz which absolutely defeats the purpose of me being able to use the capabilities of N. I had to drop my wireless N back to single channel 2.4GHz mode for me to get the reach I need (higher frequency transmissions have much lower propagation properties). So now, I get better range than my old 802.11g via use of a monitor arm mount to mount my router, got 20MB/sec on my gigabit line, but just cannot take advantage of the 802.11n speeds I was hoping for.

    *sigh*

  9. #9
    Junior Member gewone's Avatar
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    Cool

    Quote Originally Posted by TonyT View Post
    There are a few hacks that will disable the ibm bios lock for the mini-pciE slot so you can use any brand.
    http://www.google.com/search?hl=en&q...=Google+Search
    http://www.command-tab.com/2006/02/2...ireless-cards/
    or search the Think forums at ibm for "1802 error".
    I can dodge for this solution.
    I've successfully performed the "hack" on Thinkpad X30.
    I used the Linux bootup ISO.

  10. #10
    Elite Member BaLa's Avatar
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    so where does the mhz come in?

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