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what happens when wireless channels interfere

We are having an issue when our wireless users get really slow to no throughput while web browsing and I wanted to really troubleshoot this.

We have our wireless network 'competing' with our neighbors wireless on Channel 11, even though our channels are mixed (channel 1, 6, 11 throughout our officespace) Some of our users intermittently experience a down network, where they can't hit any websites.

What I'm wondering is, what exactly happens when you are on a wireless network that is getting interference from a nearby wireless network? Should the user be notified in Windows that he/she has disconnected/reconnected to the network? Or are there zero Windows notifications.

Additionally, I also suspect that we ran out of DHCP addresses, but am not sure. If this is the case, what does the user notice on their end? Does the behavior I described sound like any of these issues?

Thanks in advance and sorry for all the questions...
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jumpassociates
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jumpassociates
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1 Solution
 
John HurstBusiness Consultant (Owner)Commented:
Most times (it seems to me) you would not get connected on Channel 11 if a nearby Channel 11 is connected and in use. So for starters, why do you not just avoid Channel 11 (since your neighbour is using it). Stick to Channel 6 and avoid the interference problem. ... Thinkpads_User
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jumpassociatesAuthor Commented:
Thanks for the response!

Let me clarify..

so our officespace requires us to have multiple WAPS..because of this, I have the WAPS on alternating channels for our network, using 1, 6 and 11 to get the least interference. I figure that is better than just doing 1 and 6 since our local WAPS would interfere if they were all just 1 and 6..isn't that right?
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John HurstBusiness Consultant (Owner)Commented:
I would be inclined to try just 1 and 6 and see if you have a problem. It might be easier than getting your neighbour to change. If it doesn't work for you, you can always go back to the three channels.

... Thinkpads_User
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Don S.Commented:
when a computer connects to a chanel, it will try to stay on that chanel until the signal drops too far and there is another chanel with the same SSID that is greater strength.  So what you will see with interference is a big drop off in throughput - it's like having a bad wire in a wired lan.  There are a lot of errors and dropped packets that causes the througput to go to heck.  The end user probably won't see much on his end except maybe intermittant dropping of the connection for no apparent reason.  You don't neccissarily have to stay with just the three channels.  Many higher end WAPs have automatic chanel selection that will sense nearby conflicting channels and select the best one to use.  Also, you can use MetaGeek's Inssider to see what channels are being used in any area.  They also make a product called Wi-Spy which is a relatively cheap spectrum analyzer that would for sure pin point any interference issues.
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profgeekCommented:
Rule of thumb is to avoid any overlap of same channels.  I generally do a survey (as suggested by dons6718) before installing any WAPs to see what channels are already in use in the environment and then I set things up to avoid any channel conflicts.  Channel conflicts will yield strange and unpredictable results, such as those you are experiencing.
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jumpassociatesAuthor Commented:
profgeek,

I understand how you would want to avoid channel overlap, but what happens when you're setting up an office space, where all the other tenants in your building are using up most of the channel?

In my office, I've set up 1 6 and 11, and a lot of people that are connecting to the 11, I think, are getting interference from our neighbor who also set up as 11.
Would it be better or worse if we set up a 1, 6 and 10 network? Would the 6 and 10 channels be better than the 11 conflicting with our neighbor?
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John HurstBusiness Consultant (Owner)Commented:
How many wireless access points do you have. If each access point is secure, secure clients won't interfere with each other. That is, you can have a single wireless router and several people can use it all on the same channel and not interfere.

So if you have 3 access points, set them up securely on channels 1, 6 and 9 or 10 and avoid your neighbour.

.... Thinkpads_User
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jumpassociatesAuthor Commented:
I have 7 access points covering two floors of office, all alternating on channels 1 6 and 11.


You think I should set it up as 1,6 and 10? Having a WAP set up on 10 would avoid the interference with our neighbor on channel 11, but would also have some overlap from our WAP on 6, right?
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John HurstBusiness Consultant (Owner)Commented:
I cannot say with any precision. You need to do some experimenting. ... Thinkpads_User
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profgeekCommented:
In the U.S., if you need 3 channels, they need to be 1, 6, and 11.  Using 1, 6, and 10 will give you some overlap.  For non-overlap, there must be 25mhz of separation between the channels you are using.  For 3 channels, that can only occur on 1, 6, and 11.  Is channel 11 interfering on your entire site, or just some areas?  If just some areas, then you could use 11 in the non-conflicting areas, and use 1 and 6 in the conflicting areas.  That's why a site survey is important.  As thinkpads_users says, though, your mileage will vary, as it depends on a lot of things, including wall materials, metal (which absorbs signals, etc..  So it's difficult to say how it will work in a particular place.  I'd start with a site survey to see where the conflicting signals are worst, and which channels they are on in those areas.  
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jumpassociatesAuthor Commented:
Thanks for the info!
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