What makes one channel better than another?

~ I'm using Wifi Analyzer on my android phone. It has a screen that shows ~ channels and their ratings, but never says how they determine the rating. ~ ~ Usually they suggest 1 or more "better" channels but I have no idea ~ whether I should switch or not. ~ ~ Right now, I'm using 9. ~ ~ Thanks.

Hi Juan,

In general, in 2.4GHz 802.11, you want to use a chunk of bandwidth that is least occupied by by anything else.

Do be aware that, in general, 802.11 carriers in 2.4GHz use about

20MHz of bandwidth (or a bit more), while a nominal "channel" is 5MHz. Or in other words, your carrier uses about 4 channels.

I.e. when you're using channel 9 (center frequency 2452 MHz), transmissions in your cell will spread from about 2440 - 2465 MHz. So you're occupying (parts of) channels 7, 8, 9, 10, 11.

Now, here's the thing. In most places, most well behaved 2.4GHz Wi-Fi uses will stick to channels 1, 6 and 11. This is because they are the 3 "non-overlapping" channels in the FCC domain. So, if you are using channel 9, you are actually interfering with (and being interfered by) cells on channels 6 and 11. So, if there are nearby APs on 6 and 11, you're actually doing WORSE than you would have had you stuck to 6 or 11.

If you want to read more, here's an article on the subject - an oldie but still valid:

So to summarize ... if you want a better channel ... use 5GHz ;-)

Aaron Leonard has written on 7/17/2013 5:47 PM:

Wow! Great info. I'm headed for channel 1.

The 2.4/5.8G wifi adapters don't seem to work all that well. Certainly for range, you want a single band 2.4G adapter.

miso has written on 7/18/2013 3:34 AM:

I have what I have. :-)

You notice this is war driving. The dual band adapters are pretty deaf. I think the task is harder than it sounds on paper. You have about an octave to do the duplexing. Sounds like a lot of room, but lets meditate on the filter requirement. Say TX power is 20dbm. Put the antenna gain at 6db on 5.8 and say 3 db on 2.4. [Just making up easy numbers here. Linear 4 and 2.] Then the 20dbm 5.8G signal at the duplexer is 14dbm. You want the 2.4G signal to be detectable to about -80dbm (and that isn't a great receiver). Figure on 20db margin, so you need 104db of filtering. That isn't cheap. I can see why dual band units suck.

Jeff can check my numbers since it is late at night here.

I don't see how war driving relates to my question. Sorry.

My comment about war driving was more related to not jumping to 5.8G wifi just to get a clear channel. That is, the dual band boxes don't work very well.

Well unless they make single band 5.8G routers/clients.

~ > So to summarize ... if you want a better channel ... use 5GHz ;-)

~ The 2.4/5.8G wifi adapters don't seem to work all that well. Certainly ~ for range, you want a single band 2.4G adapter.

Hey I said the 5GHz *channels* were better (because cleaner). Not that the *adapters* are better.

2.4/5GHz integrated laptop adapters tend to be quite good.

For range, of course shorter frequency/long wavelength is better. Not clear from the original posting however that range was a goal.

If you live on a desert island, by all means stick to 2.4. If you live in a dorm room: another story.

Me, I live on a 1/6 acre lot in an old 2100 sq. ft. house with all neighbors using 2.4GHz Wi-Fi. I admit that 5GHz from a single AP (even a nice Cisco Aironet brand AP) is insufficient to cover my house, and that the interference from my neighbors is insufficient to give me personally any reason to avoid 2.4GHz.

Aaron

Aaron Leonard has written on 7/22/2013 6:48 PM:

My situation is similar.

Thanks.

I think frequency can only be higher or lower. ;-)

The lower frequency signals in general tend to go further in practice. In theory, for the same aperture, the results would be the same except for loss through walls. [By same aperture, that means the antenna size is the same. You can have a higher gain antenna at 5.8GHz in the same physical size as 2.4GHz using a colinear design. But in practice, the antenna on a dual band adapter is a compromise to cover two bands, so they do neither band well.]

The dual band adapters on 2.4GHz are not as good as the single band

2.4GHz adapters. Do a little war driving to convince yourself of this.

I'm not in a dorm room, but I can "see" 4 to 5 wifi adapters with my phone from my house. The deal is I maintain a worse case signal around

-55dbm RSSI, while they are in the -80dbm range. Not a problem.

I think frequency can only be higher or lower. ;-)

The lower frequency signals in general tend to go further in practice. In theory, for the same aperture, the results would be the same except for loss through walls. [By same aperture, that means the antenna size is the same. You can have a higher gain antenna at 5.8GHz in the same physical size as 2.4GHz using a colinear design. But in practice, the antenna on a dual band adapter is a compromise to cover two bands, so they do neither band well.]

The dual band adapters on 2.4GHz are not as good as the single band

2.4GHz adapters. Do a little war driving to convince yourself of this.

I'm not in a dorm room, but I can "see" 4 to 5 wifi adapters with my phone from my house. The deal is I maintain a worse case signal around

-55dbm RSSI, while they are in the -80dbm range. Not a problem.