Overlapping channels

Folks,
I have installed about 10 access-points in a company. Everything seems to be working fine, except fast roaming. I had a question about overlapping channels. Since the access-points have G radios, i presume that you can have 8 overlapping channels as appose to B radios which only have 3 overlapping channels. Am i right on this?
Also, would the access-points automatically select non overlapping channels so that they do not interfere with the adject AP frequency, or do i have to set that up manually??
Any advice would be highly appreciated!!!
Thanks

I think you are confusing G radio with A. G operates in the same frequenzy as B does (2,4Ghz) so you still have the same overlapping channels support.
That is 3. A radio however has the possibility of 8 channels and uses the 5Ghz spectrum.
Regarding the automatic. The AP searches for the least congested channel during startup. I´m not sure but I think they try to choose noneoverlapping channels. So in order to load-balance with overlapping channels you´d need to manually set them. However Cisco reccomends that you manually set the channels. That way you may always be sure it stays the same.
regards. Kristjan Edvardsson CCNP Wireless Lan support specialist.

Similar Messages

[svn] 4323: Bug: LCDS-544 - Scenario where two components have seperate channel sets with overlapping channels not working .

Revision: 4323
Author: [email protected]
Date: 2008-12-15 19:23:10 -0800 (Mon, 15 Dec 2008)
Log Message:
Bug: LCDS-544 - Scenario where two components have seperate channel sets with overlapping channels not working.
QA: Yes
Doc: No
Checkintests Pass: Yes
Details:
* Hunting to a new channel within a channelset never triggered a disconnect from the previous channel(s). This isn't a problem in general, but does becomes a problem when an app defines two distinct channelsets containing at least one shared channel at the head of the list. In this case, the first channelset hunts past it and connects on a later channel. But when the second channelset hunts through (triggering a connect fault when it hits that initial shared channel that can't connect), the fault is processed by the first channelset as well (incorrectly).
Ticket Links:
http://bugs.adobe.com/jira/browse/LCDS-544
Modified Paths:
flex/sdk/trunk/frameworks/projects/rpc/src/mx/messaging/ChannelSet.as

Running the script by python2 solves it for me:
su - mythtv -c "nice -n 19 python2 /usr/bin/tv_grab_nl_py --output ~/listings.xml"
Best regards,
Cedric

Aironet 1250 Overlapping Channels

Hi,
In my LAN, I have always been used an Aironet 1250 for internal use and always work fine. Now, I added a 3com AP but both AP are not correct. When I turned off the AIRONET 1250, the 3COM AP settings works fine. When both are turn on, the 3COM AP loses connectivity all the time.
I have heard about the overlapping channels in 802.11b/g networks.
Someone could tell me what I could do for solving this?
Note: Due to restrictions on my security lan, I could not use two SSID(using vlans) on my aironet 1250. This will be the best scenario, but it was not possible.
Thanks in Advance,
Fernando

yes. The Aironet 1250 connects to a DHCP server in the range 10.150.x.x and the 3com AP connects to a range 192.168.1.x. The DHCP servers are in different places and there is no any possibility that they could overlap one and another.
But I realized that the problem must be between the two access point because the 3 com AP got an IP Address from the range 10.150.x.x(it sounds crazyness but its true). Offcourse, soon the 3COM AP loses the connection.
Tks you very much,
Fernando

Non-Overlapping channels bleed over

I have multiple AP's in an arena enviornment. Now without violating the rule where an AP is assigned a non-overlapping channel, what is best practice if there are neighboring AP's within close proximity of each other and they are assigned the same channel?
For example, in our press level I have 2 AP's both on channel 11, the suite level below has a few more ap's where the signal bleeds over to the press level and even if some were on channel 1, 6, & 11 there would still be conflicting channels. I hope this questions makes sense.

Thanks for the points Rob! Things have been pretty busy the last couple months.
Planning RF fields is a three-dimensional thing, more or less dependent on the construction materials laterally and vertically.
Given that there are only the three channels (for 802.11g), you have no option other than stacking and staggering, like:
level3: 1--6--11--1--6--11--1--6--11
Level2: 6--11--1--6--11--1--6--11--1
Level1: 11--1--6--11--1--6--11--1--6
With the only real variation being the type of antennas you choose, the topology of the spaces, and the power levels of the APs. There's really no other way to do it (using only 802.11g).
NOW, what I'd recommend that you recommend is to add the additional capability for 802.11a. Many/most computer systems have dual band capability, most (Cisco) APs are rigged for dual band.
So light up that 802.11a channel and encourage the folks that can to move up there. It's an easy sell: more bandwidth ("sorta" ...but we're marketing here so outright lies are generally permitted), less interference, and better security (from the aspect of fewer hackers work this band because there's not enough "interesting" stuff on it, etc.).
The benefit to you is that you would have 40 non-overlapping channels ... much easier to plan.
I understand that you have some equipment and users that must remain on 802.11g (try to forbit B if you can, it's making the system slower and reducing your availability), but usually if you offer / encourage those with the capability to move to the better band, they'll take it.
Otherwise, start looking for places where you could say " You know, if I had an antenna with *this* kind of pattern, I could ..." because there probably is an antenna, somewhere, with that radiation pattern.
What you can't get in pattern, you can make up for with barriers, reflectors, etc.
Good Luck
Scott

Non-overlapping channels - 802.11a/n - need clarification

There seems to conflicting or inconclusive information the topics below. I have just been readying various docs using google searches. I am hoping to get some solid answers.
1) What channels for 802.11a are really non-overlapping? 8 or 12? I have read in some sources that it is 12 but the last 4 are for outdoor use(?).
2) in regards to 802.11a, channels 149 - 165 are considered for outdoor use so indoor availability is only 8 channels, correct?
3) What would be the non-overlapping channels for 802.11n? Indoor use only.
4) What happens when an 802.11n/a device and a traditional 802.11a device connect to the same network?
Thank you,

Hi Jacob,
Following diagram should helps you (Ref source )
Referencing this & if you look at your 4 queries you can find the proper answer. Here is my response
1) What channels for 802.11a are really non-overlapping? 8 or 12? I have read in some sources that it is 12 but the last 4 are for outdoor use(?).
As you can see, excluding UNII-2 extended there are 12 non overlapping channels (13 including CH165), depends on the different country regulations you can use those for indoor/outdoor deployments.
2) in regards to 802.11a, channels 149 - 165 are considered for outdoor use so indoor availability is only 8 channels, correct?
It depend on the courntry regulation. I think in US you can use that band(UNII-3) for both indoor/outdoor deployments. So in that case 12 CH availabel excluding UNII-2 extend band.
3) What would be the non-overlapping channels for 802.11n? Indoor use only.
802.11n in this band, you can aggregate two 20MHz channel, (effective 40MHz bandwidth). You can see 6 non-overlapping channels available with 40MHz width in those bands (80MHz & 160MHz option shown in the above diagram applicable to 802.11ac standard)
4) What happens when an 802.11n/a device and a traditional 802.11a device connect to the same network
802.11n device will communicate with 40MHz (if configured on you wireless network & client support channel bonding) & normal 802.11a client will connect using 20MHz channel without any CH bonding or aggregation
If that answers to your query pls mark this thread as "Answered"
HTH
Rasika
**** Pls rate all useful responses ****

Overlapping v's Non-overlapping channels...

I know it is bad practise to have more than one AP within the same cell area using the same channel, but wondered what the effects of this were. For example, if I had an AP in channel 6 and another AP ten yards from it in channel 6 also, what would be the repercussions?
Thinking about it logically, there would be radio collisions. Each AP could potentially try to transmit at the same time causing collisions. Therefore, you would see slow throughput and high error counts on the AP? Also, if a WLAN client transmitted a frame to a user on the wired network, each AP would receive it (regardless of association) and forward the frame on - resulting in the wired client receiving two copies of the same frame (one from each AP)???
Can anyone, explain why it is not good practise to have over-lapping channels (or any useful web links/documents)?
I will continue to use non-overlapping channels, but it would be nice to know why.
Thanks

Hi Darren,
That is a great question. Here are some links that have really good answers;
Channel Deployment Issues for 2.4-GHz 802.11 WLANs
From this doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00802846a2.html#wp134263
Assigning 802.11b Access Point Channels
An important concept to note regarding channel assignments is that the channel actually represents the center frequency that the transceiver within the radio and access point uses (e.g., 2.412 GHz for channel 1 and 2.417 GHz for channel 2). There is only 5 MHz separation between the center frequencies, and an 802.11b signal occupies approximately 30 MHz of the frequency spectrum. The signal falls within about 15 MHz of each side of the center frequency. As a result, an 802.11b signal overlaps with several adjacent channel frequencies. This leaves you with only three channels (channels 1, 6, and 11 for the U.S.) that you can use without causing interference between access points.
From this link;
http://www.wi-fiplanet.com/tutorials/article.php/972261
Channels and international compatibility
Although the statement that channels 1, 6, and 11 are "non-overlapping" is incomplete, the 1, 6, 11 guideline has merit. If transmitters are closer together than channels 1, 6, and 11 (e.g. 1, 4, 7, and 10), overlap between the channels will probably cause unacceptable degradation of signal quality and throughput.
http://en.wikipedia.org/wiki/IEEE_802.11
Hope this helps!
Rob
Please remember to rate helpful posts.........

Overlapping Channels Query

Hi,
I'm troubleshooting a wireless issue at one of our sites and had a query about the current setup. I've attached a diagram of the AP locations and the channels that are in use.
I notice that there are a few neighbouring APs using the same (overlapping) channel and wondered if this is of any concern. Wireless is not my speciality, but as far as I understand it, neighbouring APs are supposed to use non-overlapping channels.
For Info;
APs 2-3,9 -10, and 26 use omni-directional antennas
APs 4-8, 11-15, use directional antennas facing out of the building.
All APs are autonomous and use the same SSID
Should the channels be reconfigured so there are no overlapping channels?
Thanks,
Paul

Hi,
When working with wireless on the 2.4ghz we need to make sure that you distribut the 3 non overlapping channels between all your access points so that the access points with the same channel are the further apart and on the 5ghz we do not need to worry about this becasue all the channels are non overlapping vrs the 2.4ghz that the only non overlapping channels are 1-6-11.
Also we need to keep in mind that other access points close to you from another company will create interfirence to yours and yours to them the only way to fix this is distribut the non overlapping channels between your access points and the close access points.

Overlapping Channels and DVR issues

I wanted to report an issue or see if anyone else has experienced what has been happening to me. I live in the DC metro area and I go to the HD NBC (504) or HD CBS (509) stations with no problems. However multiple times I have gone to either station and what is showing is not correct. Sometimes when I go to channel 504, I'm getting programming produced by the local NBC channel, or when I go to channel 509, I get the weather radar. When this happens on either channel, I just turn the channel and then come back and the correct content is being broadcasted. I believe this is also causing DVR issues as well because sometimes when I got to watch a recording from either of these channels, I see the show recorded twice and only for 1 or 2 seconds. It's frustrating because I have lost out on shows that are not repeated nor on demand. Any ideas on what is gong on?

Jeddahdee wrote:
One of my DVR boxes has not been able to utilize any of the DVR functions since the second week I've had verizon. I have sent support emails with no response, chatted live with an agent to get help and they told me to call the support number because they can't help, and I have spoken to an agent over the phone so they could tell me to unplug and plug it back in or run around my house to fix cables outside my home; nothing has worked. Is this common? If i didn't like my internet speed I would have dropped this garbage service a long time ago !
I'd just bypass customer service and swap out the dvr for a different one. You can go to a fios store, do it through your account on verizon.net or the easiest way, do it on the dvr itself.
Go to menu, customer support, set top box exchange.

Multiple SSID channel question

I have 2 (for now) Aironet 1231g access points setup. They each have two SSIDs being broadcast on each one, both are the same two SSIDs. The question is, can can two different ssids from a single ap broadcast on the same channel. That means I would have both ssids broadcast on channel 6 on one of the APs then broadcast them both on channel 11 on the other? Or would each individual ssid have to be on its own non-overlapping channel? Both SSIDs are on seperate vlans. As of now it looks like it is working fine, I just want to make sure I have it configured the way it should be to work the best.

Hi Chris.
Channels are by radio, not SSID.
Exmaple
(AP#1) Channel 1
SSID - TEST1
SSID - TEST2
(AP#2) Channel 11
SSID - TEST1
SSID - TEST2
As you can see your TEST 1 will broacast on channel 1 and 11 ...
Make sense?

[svn] 4290: Bug: BLZ-288 - Consumer is only receiving first pushed message when Consumer and RemoteObject that is used to push the messages use different channel sets but same channel .

Revision: 4290
Author: [email protected]
Date: 2008-12-11 14:24:37 -0800 (Thu, 11 Dec 2008)
Log Message:
Bug: BLZ-288 - Consumer is only receiving first pushed message when Consumer and RemoteObject that is used to push the messages use different channel sets but same channel.
QA: Yes
Doc: No
Checkintests Pass: Yes
Details:
* The bug app was arguably generating bogus test data (messages with duplicate ids), and 99.9% of applications won't be configured this way (using multiple ChannelSets with overlapping Channels, pointing at the same server) but it's still worth making this work just right anyways.
Ticket Links:
http://bugs.adobe.com/jira/browse/BLZ-288
Modified Paths:
flex/sdk/trunk/frameworks/projects/rpc/src/mx/messaging/ConsumerMessageDispatcher.as

Remember that Arch Arm is a different distribution, but we try to bend the rules and provide limited support for them. This may or may not be unique to Arch Arm, so you might try asking on their forums as well.

How many 80Mhz wide channels?

I am getting ready to install some 3700 series AP's and then also configure the WLAN controller to support 802.11ac. I was reading on the net that there are basically 5 80Mhz channels you can use however when I look over Cisco documentation I do not see any reference to this and only see a DCA listing that would allow only 3 80Mhz wide channels. Here is the document I mentioned. - http://www.cisco.com/c/en/us/td/docs/wireless/technology/5760_deploy/CT5760_Controller_Deployment_Guide/802_11ac_support_on_WLC5760_and_Catalyst_3850.html
Here are the channel groupings for 5 channels that I want to setup:
36-48
52-64
100-112
132-149
153-165
Am I missing something or will this work?
Seth

80 MHz wide channels allow for five (5) non-overlapping channels in the U.S. and five (5) in the UK/EU (channels 149 and higher require light licensing for outdoor use only) when DFS is used, but only two (2) channels in the U.S. and one (1) in UK/EU without DFS.

Basic question about multiple AP's and channel selection

I have approximately 10 AP's (Aironet 1240G) which are to be deployed one of my office floors. We looked at a floor diagram and made sure that we ordered enough of them to completely saturate the floor with wireless coverage. There are some AP's which are probably only 50' from each other. It is a little overkill actually.
I have put a basic configuration on the switch so that there are two different SSID's on the AP (one for a production WLAN, and the other for a Guest WLAN). Each SSID is associated with a different VLAN.
What I would like to know is what do about channels for the AP's? Each AP will be independently configued and controlled.
I understand that there is a way to control which channels each AP uses, but I am not familiar with the commands or the best practices for how to configure the AP's
Should I do something like make sure each AP is using a different channel than its nearest adjacent neighbor? Would someone mind sharing what the command to do that is, and where it is applied?
I read through some of the archives and saw people mentioning to set "non overlapping channels", and to configure them to use channels 1,6,11. I guess I dont understand what is meant by that.
Do you manually set one AP on channel 1, then set its neighbor to use 6, and another neighbor to use 11, and then you keep that up?
What is the worst-case scenario on what happens when you do have AP's too close to each other set on the same channel?
I am happy to read through documentation if someone wouldnt mind pointing me to it. I am still trying to understand the concept, and then I should be able to understand the documentation that came with the AP.
Thank you for your help.

So your deploying autonomous access Points. If this was a Controller based deployment, it would actually manage the channels for you dynamically.
But what you really want to do is see you APs doing something like this:
(imagine each number represents an AP, and it channel)
1 6 11 1
6 11 1 6
11 1 6 11
1 6 11 1
This is an Autonmous configuration guide. I think it has a small section on channel assignment. If you're doing this manually, I think you specify the actual frequency to use in the CLI instead of channel number.
http://www.cisco.com/en/US/docs/wireless/access_point/12.4_3g_JA/configuration/guide/s43rf.html
So from the CLI under the Dot11Radio0 you'd do something like "channel 2412" for Channel 1... 2437 for 6, 2462
for 11....
If you have APs next to each other on the same channel, you are likely to have clients interferring with each other.

Using Wide Channel in draft-n routers

Hi all,
I've recently purchased the WRT310N router together with a WPC600N PCMCIA card for use in my notebook. I have other 802.11G devices at home (a SqueezeBox, another notebook with built-in G adapter and a BlackBerry Bold) which connect to the new router as well. Over the last 2 weeks, my wireless network has been practically unusable, requiring resets every couple of hours or twice daily at best. I've tried most of the recommendations from this forum - hard-resets; changing parameters like beacon interval etc..; changing to different channels (wide & standard), none of this really helped.
I then researched on the 802.11n standard and I think the firmware from Linksys seems to have some fundamental problem on the "wide channel" option. From various sources on the web, the "channel bonding" feature of 802.11n will utilise two ADJACENT and NON-OVERLAPPING 20MHz channels together to increase the overall bandwidth. As we all know, in the 2.4GHz band, if we start from channel 1, there could only be 3 non-overlapping channels altogether - CH1, CH6 and CH11. However, in the firmware of my WRT310N, if I choose CH6 as the wide channel, I'd be given the choice of either CH4 or CH8 as the standard channel. As each channel will need 20MHz but is only 5MHz apart from the adjacent channel, both CH4 or CH8 will directly interfere with CH6, causing unstable transmission/reception. I believe what the firmware should do when you choose CH6 as the wide channel is to give you only CH1 or CH11 as the standard channel.
With the above in mind, I disabled the wide channel option totally, my WPC600N now runs at a much lower bandwidth but the stability for my whole network has improved a lot (I haven't had a reboot since the last 24 hrs). Can someone confirm if my theory above is correct or not?
Regards,
Paul.

What all things which you wrote, its right but there are certain things which you need to adjust more on your Router, that will solve your problem.
Open an Internet Explorer browser page on your wired computer(desktop).In the address bar type - 192.168.1.1
Leave username blank & in password use admin in lower case...
For Wireless Settings, please do the following : -
Click on the Wireless tab
-Here select manual configuratioon...Wireless Network mode should be mixed...
-Provide a unique name in the Wireless Network Name (SSID) box in order to differentiate your network from your neighbours network...
- Set the Radio Band to Wide-40MHz and change the Wide channel to 9 and Standard Channel to 11-2.462GHz...Wireless SSID broadcast should be Enabled and then click on save settings...
Please make a note of Wireless Network Name (SSID) as this is the Network Identifier...
For Wireless Security : -
Click on the Sub tab under Wireless > Wireless Security...
Change the Wireless security mode to WEP, Encryption should be 64 bits.Leave the passphrase blank, don't type in anything...
Under WEP Key 1 type in any 10 numbers please(numbers only and no letters) and click on save settings...
Please make a note of WEP Key 1 as this is the Security Key for the Wireless Network.Now try if you could see the Wireless Network Name/SSID and try to connect...
Click on Advanced Wireless
settings>>Change the Beacon Interval to 75 >>Change the Fragmentation...
Threshold to 2304 Change the RTS Threshold to 2307 >>Click on "Save Settings"...
Now see if you can locate your Wireless Network and attempt to connect...

Channel configuration on dual SSID

I am installing a few aironet around a environment which requires dual SSID one for Guest and the other for business.
When configuring the channel for each SSID should I make both SSIDs on the same aironet the same channel and then ensure the closest aironet with the same dual SSIDs is both on the same but different (non-overlapping) channels ?
Or should both SSIDs on each aironet be on different channels?
Thank you.

Channel selection ... Hmmmm ... autonomous IOS ... Not a good combo.
I mean the issue here is your 802.11b radio. If you have neighborhood wifi around, smart money 802.11b is being used and Channels 1, 6 and 11 are used too. No issues with 802.11a since there are more channels to play with.
It's OK if you have a WLC because of the Dynamic Channel Assignment feature. But with autonomous WAP, you need to constantly monitor your neighbor.

Aiport Express - channels and muticast rate

Im using an airport express for my home network and wondered about the various settings to try out. Firstly does the channel make any difference to signal strength? I've noticed several neighbours have wireless networks on channel 1 so wanted to switch from that.
also regarding mutlicast rate. setup comes set as 5.5 and wondered what the various other options do, ie: which would be best for performance as oposed to furthest range.
11=best 2=furthest?
Cheers

kladzer welcome to the discussions.
See if this doesn't explain it for you.
Channels are important to understand because they affect the overall capacity of your WLAN. A channel represents a narrow band of radio frequency. Since radio frequency modulates within a band of frequencies, there is a limited amount of bandwidth within any given range to carry data. Therefore it is important that the frequencies do not overlap or else the throughput would be significantly lowered as the network sorts and reassembles the data packets sent over the air.
Knowing that the 802.11a specification operates at radio frequencies between 5.15 and 5.875 GHz, and that the 802.11b and 802.11g specification operates at radio frequencies in the 2.4 to 2.497 GHz range, we can see that the 802.11a has a wider frequency band, allowing more channels and more overall throughput. The wider frequency band allows 802.11a to support up to eight non-overlapping channels. However, 802.11b/g standards support only up to three non-overlapping channels.
Each channel is capable of carrying the maximum throughput for its standard. Therefore, the 802.11b and 802.11g standards have a maximum of three non-overlapping channels, each carrying 11 Mbps throughput (33 Mbps total) and 54 Mbps (162 Mbps total) throughput, respectively. The 802.11a standard has a maximum of eight non-overlapping channels carrying a maximum 54 Mbps throughput each (432 Mbps total). (For more on Wi-Fi standards, check out this Quick Reference guide.)
The frequency ranges and channels may vary by country. In the U.S., the 802.11b (2.4 GHz) standard operates on 11 channels. All but three of those channels are overlapping channels. Channels one, six, and eleven are the only non-overlapping channels.
Most manufactures set their default channel to one of the non-overlapping channels. D-Link products, for example, default to channel six. You have the option of selecting which channel your WLAN operates on in order to avoid interference from other wireless devices that operate in the 2.4 GHz frequency range. Examples of this would be 2.4 GHz cordless phones and X-10 wireless products.
The biggest advantage of 802.11b is that it's the most widely deployed wireless LAN technology and provides good wall penetration and indoor range. The advantage of 802.11a is that it provides increased network capacity and interferes with other wireless devices far less than 802.11b products do.
So to answer your question, unless you have a specific reason for changing it, I would suggest you keep your wireless channel configured for the manufacturer's default settings. If, however, you must change it, for the best performance I would suggest trying to use one of the other non-overlapping channels first: Channels one, six, and eleven. Other then interference issues, there really is no other reason or advantage to selecting another channel.
Cheers Don

Overlapping channels

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