Using The "Oddball" Channels?

[DaveMcLain]

I have a question about using channels other than 1,6 and 11 with 802.11B/G. Everywhere I read I'm always told that those three are the best to use because they do not overlap each other at all. This is true but in the two environments where I have wireless implemented(work and home) I have about 6 or 7 other WLAN's already present. Right now here at home if I fire up Net Stumbler I find networks using channels 1,2 several on 6, 8(mine) and 11. It seems to me that using one of the weird channels with some overlap would be a lot better than one of the standard three. Am I thinking correctly? At work I'm using channel 4. Wireless performance is good in both locations with very good range, stability and throughput. Any thoughts? Why aren't we using more of the channels regularly? Or should we?

 

[thiggins]

There is a good diagram and discussion here of channel use.

The problem with using the overlapping channels is that your signal may be seen as noise by the APs and clients on the non-overlapping channels. If it is noise, then the AP and client will just try to communicate as if you were not there.

But if you are operating on an in-use channel, then the DCF mechanism built into 802.11 can operate properly to manage contention for bandwidth. You may not get as much bandwidth on a busy channel. But at least you should not suffer sporadic disconnects, etc.

Give the channels a try if you like. If it improves things, great. But don't count on it.

 

[DaveMcLain]

Thank you for the info. From my understanding then if two WLAN's are on the same channel and I would say strong enough relative to one another then they can actively avoid interference. It still causes a reduction in bandwidth but the signal at the clients and AP tend to remain robust(data can get through).

If the signal is weak enough that the clients and AP can't readily decipher it as an 802.11B or G signal weather that weakness comes from being far away or on another nearby channel it acts as noise from any other source and it can therefore contaminate the data and cause packet loss etc. VERY interesting.

Back when my wife was my girlfriend she lived in an apartment were there were around 20 wireless AP's visible at any given time. In her situation the use of an oddball channel worked wonders but her apartment was also rather small so that could be one of the reasons too. I think that out of the 20 I could see with my Engenius wireless card about 7 or 8 were named Linksys and running on channel 6. What was the their wireless experience like? Bad I'd say.

Thanks again for the great info.

 

[thiggins]

Thank you for the info. From my understanding then if two WLAN's are on the same channel and I would say strong enough relative to one another then they can actively avoid interference. It still causes a reduction in bandwidth but the signal at the clients and AP tend to remain robust(data can get through).

Yup. That's basically it.

 

[bobbodavis]

European channels

I live in Germany. Most of my neighbors are on either channels 1 or 6. I'm using DD-WRT v24 sp2's built in site survey application to scan around me. Since no one else seems to be on channel 11, I figured i'd take advantage, but I'm beginning to think no one is using that channel for a reason.

When I use channel 11 or any channel from 9-11, my laptop can never find my WRT54G or WRE54G even when they're right next to each other. Just the same, my WRE54G can't connect to the WRT54G. Change to any channel 8 and below and they immediately find each other and connect. It almost seems like everything above channel 8 is being blocked, but i can't find anywhere why this might be.

Is there some difference with European frequencies that would require a european verison of these routers to take advantage of the higher channels?

 

[thiggins]

Must be some other reason 1-11 are allowed worldwide. List of WLAN channels