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Strong Wireless Signal but Slow Connectivity

Posted on 2013-11-16
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Last Modified: 2013-12-25
Hello Experts,

We have Cisco 1300 Series AP's distributed through out building. Building have 6 six floors.
Each AP's access point installed at the corridor and they are 30 meters from each other.

The AP has 2 SSID's Guest and Staff

Wireless is not my specialty, but as far as I understand it, neighboring APs are supposed to use non-overlapping channels.
 
I am not quite sure with configuration. So I need help
Also, I am also looking for free tool that can help me redesign the WLAN, if needed.

I would highly appreciate any help.

Thanks

Samir
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Question by:cciedreamer
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Expert Comment

by:Craig Beck
ID: 39653250
Can I ask why you're using the 1300, instead of say an 1131?  The 1300 is an outdoor bridge which 'can' be used as an access point.  It's not usually installed as an internal AP.

Depending on the antenna you use, 30m will probably be too far apart to offer any kind of decent overlap for clients to roam between APs successfully.  This will probably mean that they struggle to move from one AP to the other and will likely suffer drop-outs between APs.

Channels of neighbouring APs should be different, so you don't cause interference with eachother.  If you don't get this right you'll see very poor results.
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by:cciedreamer
ID: 39653453
Sorry its AP1131

ok. How do I configure the channel on the AP's

For example I have 10 on each floor. How I can accomplish that.

Thanks
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Expert Comment

by:Craig Beck
ID: 39653510
To configure the channel you can select a specific channel via the GUI.

Browse to the AP, then on the front screen you should see a section which shows the Network Interfaces.  Click on Radio0-802.11g, then click Settings.

There you will be able to change the channel to whichever you want to use.

You have 3 non-overlapping channels at 2.4GHz.  Therefore you should really only use channels 1, 6 and 11 if you're in the US.  In Europe or Japan you could also use 1,7 and 13 if you really wanted to although some kit from other countries might not work if you use channel 13.

At 5GHz (the Radio1-802.11a) interface, just leave it alone.  DFS (dynamic frequency selection) is a requirement in certain regions, on certain parts of the 5GHz frequency so it's easier to just let it do its thing.  There are also a lot more non-overlapping channels so you'll see less of an issue with co-channel interference anyway.
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by:cciedreamer
ID: 39667887
How are far should be the AP's from each other ?
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by:Craig Beck
ID: 39668161
In an open space it would be a fairly specific distance between each AP, but it would depend on the deployment type.  If you only need to provide coverage for data only (so no voice over wireless) your AP locations would be different to where you'd put them to fully support voice services.

Saying that, in an open space you'd typically see around 15-20m is absolutely as far as you would want to space the APs apart in order to provide seamless roaming support at higher data-rates.
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by:cciedreamer
ID: 39671205
We are a hospital and we giving internet access to guest and data access to staff.

Lets say we have 60 meters corridor and I kept 3 AP's and hey have 20meters distance from each other.

How the channel configuration will be in this case

Thanks for your great help.
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Craig Beck earned 500 total points
ID: 39671293
So at 2.4GHz you could use ch1, ch6, ch11 (one for each AP) with no issues at all.

At 5GHz, don't worry about setting channels over that distance - just let the APs choose their own channel using DFS.  Just make sure you boot the APs 5 minutes apart so each one can select a channel while there are other channels in use.
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by:cciedreamer
ID: 39685255
Hi,

How do I get the channel confgiration from cli ?
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by:cciedreamer
ID: 39685258
sh dot11 adjacent-ap gives me the following output. Please can you shed some light on channels Are they correct ? Is there any need to make any change

Thanks
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Expert Comment

by:Craig Beck
ID: 39685262
There's nothing attached?
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Author Comment

by:cciedreamer
ID: 39685266
Oops !!

AP100#sh dot11 adjacent-ap
         Fast Secure Adjacent AP List
     Radio          Address              Channel Age ( Hours) SSID
--------------- -------------- ------- ---------- ----------
Dot11Radio0     001a.e3d1.4710       1          0 Internet
Dot11Radio0     001a.e3d9.3730      64          2 Internet
Dot11Radio1     001a.e3d9.7850      48          3 Internet
Dot11Radio0     001a.e3d1.8830       4          1 Internet
Dot11Radio0     001a.e3d1.8831       4          7 Internet
Dot11Radio1     001a.e3d1.4710       1         15 Internet
Dot11Radio0     001a.e3d1.a6b1      13          9 Internet
Dot11Radio0     001d.70f3.d671       5         20 Internet
Dot11Radio0     001a.e3d1.8830       4          2 Staff
Dot11Radio0     001a.e3d1.9271      13          0 Internet
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Expert Comment

by:Craig Beck
ID: 39685271
Can you do a carrier busy test and post the results?

dot11 interface-number carrier busy

For interface-number, enter dot11radio 0 to run the test on the 2.4-GHz radio, or enter dot11radio 1 to run the test on the 5-GHz radio.

Use the show dot11 carrier busy command to re-display the carrier busy test results.
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by:cciedreamer
ID: 39685278
Frequency  Carrier Busy %
---------  --------------
   2412          2
   2417         12
   2422          5
   2427          7
   2432         11
   2437         10
   2442         10
   2447          1
   2452          0
   2457          0
   2462         11
   2467         29
   2472         31
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by:Craig Beck
ID: 39685283
That's not too bad.

I'd manually configure the 2.4GHz radio to use channel 9 based on that...

int dot 0
 channel 2452
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by:cciedreamer
ID: 39688034
Hi,

I am attaching the our floor diagram so you can help me to design the wireless with channel configuration.

I would really appreciate your big help.

Thanks
New-Doc.pdf
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Expert Comment

by:Craig Beck
ID: 39688183
Ok I'll be honest with you - that's not going to be the best design.

There are 4 radios all within earshot of each-other, so you'll have to use some overlapping channels to achieve this.  The good news is that you have 13 channels instead of 11, so that gives us the ability to get away with using 4 channels and not cause too much of an issue.

So, I would go with something this...

          1


          9
   5           13
          1


          13
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Author Comment

by:cciedreamer
ID: 39700763
Sir,

Earlier you have asked me to configure channel 9 on Dot11Radio 0 ? Can I ask the reason to understand more
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Author Comment

by:cciedreamer
ID: 39700768
Is there any good utility to make survey and understand which AP is running on what channels?

Thanks
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Expert Comment

by:Craig Beck
ID: 39700787
Sure...

Based on the channel utilization which you provided, Channel9 looks to be the best channel to use on that AP.  It is unused and would suffer from the least interference from surrounding channels.

There are plenty of tools you can use to perform a survey.  Industry standard software includes Fluke's AirMagnet and Ekahau's Site Survey tools.  These are expensive packages if you only want to survey a relatively small number of APs, but you could use something like Metageek's InSSIDer to get an idea of what channels/signals you're getting.
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by:cciedreamer
ID: 39710629
Sir,

I ran several carrier busy tests on 1 AP and in the result the % value changes everytime I run the test. In this case how to select the best channel for the AP.

Thanks
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Expert Comment

by:Craig Beck
ID: 39711464
Unfortunately that's the nature of wireless.  The utilization is based on how busy the channel is.  It could be that when you scan no-one is actually using the channel, but the next time you scan there are lots of users using the channel.

You need to look at the channel usage over a period of time and decide which seems to be the least congested based on the figures.  It's not an exact science by any means.
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by:cciedreamer
ID: 39739705
Thanks
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