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AP setting: 40Mhz or 20Mhz Channel with?

Discussion in 'General Wireless Discussion' started by nikleb, Feb 6, 2016.

  1. nikleb

    nikleb Regular Contributor

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    Can somebody tell me more about the pros/cons of using 40Mhz or 20Mhz Channel on the 2.4Ghz radio?
     
  2. coxhaus

    coxhaus Part of the Furniture

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    40Mhz will have higher bandwidth. If your internet connection is fast enough it will make a difference. Now days with so many 2.4Ghz radios out there it is hard to use 40Mhz because your wireless device will down grade to 20Mhz automatically.
     
  3. nikleb

    nikleb Regular Contributor

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    What confuses me is that the selection of 20Mhz or 40Mhz in the setup of my WAC120 doesn't show any difference in insider. insider shows my radio to be double the length of all other present radios.
    Changing channel # does work...
     
  4. sfx2000

    sfx2000 Part of the Furniture

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    All the cool kids do the 20MHz thing in the 2.4GHz playground...
     
  5. Kal-EL

    Kal-EL Very Senior Member

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    Yes but with the faster speed tiers offered now sometimes you might not have a choice but to force 40mhz on 2.4 to get what your paying for. This is not a issue for me. ;) YET !!! In fact i have 2.4 ghz disabled it's really crowded and right now i dont need it, 5ghz works awesome here and covers my whole home. :D
     
  6. sfx2000

    sfx2000 Part of the Furniture

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    Again, all the cool kids use 20MHz channels in 2.4GHz - it's a shared medium...

    One isn't paying for airspace on the public channels... community commons, we all share...
     
    avtella likes this.
  7. sfx2000

    sfx2000 Part of the Furniture

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    Best case - standards compliant in 2.4GHz - 216 Mbps, which is is good enough for 20MHz channels...

    Going off the range - turboQAM for some AC1900 class routers - 289Mbps - I'd recommend not going there due to 802.11b/g/n interop...
     
  8. pete y testing

    pete y testing Very Senior Member

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    for a router to be certified it needs to have obss coexistence enabled and have the ability to reduce the bandwidth back to the neighborhood friendly 20mhz which means 150M max sync on 2.4 gig , forcing the router back to 40mhz will get you a max sync of 300M on 2.4 gig ( this is if the router is 300M on 2.4 gig ) and thus greater throughput

    20mhz can also help with client compatibility esp with apple type clients that can and do crack a wobbly when connecting to 40mhz 2.4 gig
     
  9. coxhaus

    coxhaus Part of the Furniture

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    I don't understand 216 Mbps. Back in the old Linksys days when people had 5 and 7 megabit connections you could tell a difference between 40mhz and 20mhz. What am I missing?

    PS
    You can't save 2.4GHz. It is lost.
     
    Last edited: Feb 6, 2016
  10. System Error Message

    System Error Message Part of the Furniture

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    40Mhz isnt always faster. When there is other traffic operating within the frequency range your wifi traffic can suffer and since it is a wider frequency range the chance of getting interference is high. If a device that supports only 20mhz and not 40mhz connects such as phones than all devices drop to 20mhz. If you force 40mhz than 20mhz only devices cant connect.

    If you have the airspace to use 40mhz than you can benefit from it but this is very rare in a residential area filled with wifi. Back than there wasnt much 2.4Ghz traffic so the higher bandwidth helped.

    In a densed wifi environment 20 mhz helps more than 40mhz. It is possible to apply 40mhz on channels 1 or 13 which will give less of a chance of interference.

    back than wifi practical rates were a lot lower than now. Now on 5Ghz with newer AC wifi chips you can get 50% practical bandwidth utilisation, last time was about 30% or a lot lower so for a slow connection it could be seen as wifi chips last time had higher latency and lower practical utilisation.
     
  11. sfx2000

    sfx2000 Part of the Furniture

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    2.4Ghz considerations on 20MHz channels...

    B11
    G54

    11N - 20MHz...

    N72 - single stream - N65 is typical here
    N144 - 2 streams - short GI give N150 - see comment below for N240
    N216 - three streams - short GI give N240, but I've never seen this in the real world

    Double things for 40MHz channels - but generally these days, wide channels don't work in the real world...
     
  12. sfx2000

    sfx2000 Part of the Furniture

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    OBSS these days for compliant 802.11n AP's generally results in narrow channels - 20/40Auto mode...

    There's still a few Draft N AP's that don't honor OBSS and down select, so they stay 40MHz, which contributes to the whole 2.4GHz mess...

    And then we have Turbo/NitroQAM - just makes the 2.4GHz mess that much worse...

    And then we have the whole 802.11N greenfield mess, that wrecks legacy networks (but at the same time, legacy crashes them)...

    Friendly neighbors basically should just run B/G/N auto with 20MHz channels if they can - really can't get much better than that... all clients and bridges work well there.
     
  13. sfx2000

    sfx2000 Part of the Furniture

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    Wide Channels in 2.4GHz, even in clear airspace - 3 dB less Tx/Rx - just a big loss all around...
     
  14. System Error Message

    System Error Message Part of the Furniture

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    I suppose it depends on range too with 3dB loss. I've tested 40mhz and 20mhz recently regarding watching a video through remote desktop. 40Mhz was only slightly better than 20Mhz since there was some wifi traffic in the area. Range was the same. In some cases 40Mhz performed even worse than 20Mhz when there was other traffic within the frequency region. I used channel 13 (the country i tested it in had channel 13 available legally) since most routers would use auto up to channel 11.

    I think experience would differ depending on your wifi router and surroundings. Some are capable of switching between automatically while some cant. The auto capability in wifi is usually very poor which is why for some weird reason some wifi routers like to use the same channel that i do even when i switch and there is free airspace.
     
    avtella likes this.
  15. RogerSC

    RogerSC Part of the Furniture

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    Have about 20 2.4GHz. wireless networks that I see around here, 40MHz. channel just isn't possible here. Well, it's possible, I suppose, but I want to be one of the cool kids. My next door neighbor, bless his soul, just got a 5GHz. router that really works. He's on the bottom of the higher (non-DFS) 5GHz. frequencies (149), I'm at the top of those (161) so we don't bother each other. There's also two very low-level 5GHz. networks on the lower frequency part of 5GHz. Those definitely aren't a problem.

    So, I use pretty much all 5GHz., since 2.4GHz. is just a mess. The signals are on all different channels, too, not just 1, 6, and 11. Kind of surprised when I hear of people able to use 40MHz. channels on 2.4GHz., they're always way out in sparsely populated areas these days.
     
  16. coxhaus

    coxhaus Part of the Furniture

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    There are 23 2.4GHz networks around me. I have given up on 2.4GHz also. I am all 5GHz 40MHz wide now.
     
  17. System Error Message

    System Error Message Part of the Furniture

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    I have almost no 5Ghz networks around me. 80Mhz for 3 5Ghz radios for me to use :). Back where i tested 2.4Ghz there were around 10 networks around.

    What really matters is how what wifi can the router see and what wifi can the client see. If the router and client could see each other and no other traffic around each other than they will perform well even if there is interference or traffic in between. Wireless traffic that are interfering but have low signal can be ignored however from all the wifi survey images ive seen on this site people seem to love setting their wifi signals to high rather than low since lower transmit helps in a densed environment for 2.4Ghz only if everyone does it. In the 5Ghz with its limited range there is less consequence for higher transmit power.
     
  18. sfx2000

    sfx2000 Part of the Furniture

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    One more note - if one wants to try 40MHz in 2.4 - 20/40 auto, and try to keep the Primary Channel (Asus calls this Control Channel) on 1 or 11 to minimize interference to other networks...

    If you're caught in a situation where there is an adjacent network running wide channels, your best bet is to discover which is the primary, and put your network there...

    Most AP's these days, in 20/40 auto will try to do 40, but as someone mentioned above, typically run in 20MHz due to OBSS scan results - also note that any Apple devices will send 40MHz Intolerant in their Probe Requests, which is supposed to put AP's into 20MHz mode anyways..

    Apple's 802.11n Airports, FWIW, set 40MHz intolerant in their beacon frames (AC models don't), so if you're tinkering about trying 40MHz, and an Airport or Apple device is near by...
     
  19. avtella

    avtella Very Senior Member

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    Even among 1/6/11 channels you may find one or the other gives you slightly better signal, I was going through FCC docs of some routers and found some really liked channel 6 (in terms of power output) for example, then again depending on nearby APs this may be nullified.
     
  20. coxhaus

    coxhaus Part of the Furniture

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    I have to say wide channels like 40MHz and 80MHz are great for home use where there are few users and you want to allocate all your internet bandwidth. If I was running a business using QOS then I would run 20MHz. Not running the wide bandwidth is just one step closer helping with QOS.