What makes one channel better than another?

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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.

Re: 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:

http://www.cisco.com/en/US/docs/wireless/technology/channel/deployment/guide/Channel.html

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



Re: What makes one channel better than another?
Aaron Leonard has written on 7/17/2013 5:47 PM:
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Wow! Great info. I'm headed for channel 1.

Re: What makes one channel better than another?
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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.



Re: What makes one channel better than another?
miso has written on 7/18/2013 3:34 AM:
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I have what I have. :-)

Re: What makes one channel better than another?
On 7/18/2013 12:39 AM, Juan Wei wrote:
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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.


Re: What makes one channel better than another?
miso has written on 7/18/2013 4:10 AM:
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I don't see how war driving relates to my question. Sorry.

Re: What makes one channel better than another?
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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.


Re: What makes one channel better than another?

~ > 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

Re: What makes one channel better than another?
Aaron Leonard has written on 7/22/2013 6:48 PM:
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My situation is similar.

Thanks.

Re: What makes one channel better than another?
On 7/22/2013 3:48 PM, Aaron Leonard wrote:
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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.


Re: What makes one channel better than another?
On 7/22/2013 3:48 PM, Aaron Leonard wrote:
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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.


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