Wireless Channel selection DDWRT

[elliott35]

Ive got a TEW818 setup as a wireless AP as per this video. Im trying to change the wireless channel for each the 5 and 2.4Ghz frequencies as I have 2 other AP's in the house and would like them to each have their own channel. The issue is that if I have the channel width set to anything other than 20MHz it will not do anything but auto channel selection. Its my understanding that for the router to operate at full speed it needs to be set to a width of 40MHz on the 2.4Ghz band and 80MHz on the 5.0 GHz band. Does anyone know why DDWRT would be limiting me in this? ill attach a picture of what the wireless config page looks like below. Also, what is an extension channel? its an option that comes up when i select a higher channel width. 

 

Thanks,

 

Elliott

 

 

[elliott35]

I think I answered my own question. For anyone else who is interested in this issue, I found this article helpful. But I still dont know what the extension channel is. Anyone have an idea? 

[AMICLG]

As per spec of the FCC the router must drop to 20MHz mode to avoid interference.

 

When you run in 40MHz mode your using two non overlapping channels closest to each other (ie: 1 and 6 or 6 and 11. The only non overlapping channels on 2.4 GHz are 1/6/11. So to run all APs in 40MHz you need to have then far enough away from each other. 

 

But you don't actually need 40MHz unless you actually have a 2.4GHz 802.11 N device that does 600 Mbps, which is quiet uncommon unless you bough an aftermarket PCI-E card. 

 

Thus set all three APs on the 2.4GHz side to 1/6/11 @ 20MHz.  

 

Such is the same for 80MHz on 5.2GHz-5.8GHz for AC but with AC @ 80MHz their are only two non overlapping channels.

 

[beavo451]

6 minutes ago, elliott35 said:

I think I answered my own question. For anyone else who is interested in this issue, I found this article helpful. But I still dont know what the extension channel is. Anyone have an idea? 

 

Just a wild stab in the dark here, but I would guess that it controls the channel width "direction". As has been mentioned, the signal overlaps adjacent channels. My guess is that it controls whether the signal overlaps more on higher channels or more on lower channels. Or balanced with the choose not channel in the middle with the "lower upper" choice.

[elliott35]

If I set the Tx power low enough in DDWRT would I be able to keep the 5GHz band to 80MHz on each router?

[elliott35]

Also, its strange to me that on my new EA7500 i can specify 80MHz width as well as a channel. Whereas on the DDWRT router I cannot specify both

[AMICLG]

Just now, elliott35 said:

If I set the Tx power low enough in DDWRT would I be able to keep the 5GHz band to 80MHz on each router?

5GHz only has a wavelength of ~ 60mm vs 2.4GHz at ~ 120mm which is why 2.4GHz goes farther through walls.

 

So try setting the two the farthest away from each other or with the most walls between them on the same channel.

[elliott35]

I set the DDWRT to 80MHz low low CH36 and I set the EA7500 to 80MHz CH161. I have another TEW818 with no DDWRT that is set to AUTO 20/40/80 CH48. So theoretically if it were to begin having interference issues it would fall back to 20MHz. Does that make sense?