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.........

Similar Messages

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 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

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.

[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

Possible to make non-HD channel switch to HD channel? (like 7 to 507)

Hey, just got Fios installed this week and am liking it so far.
Quick question... I had Cablevision before this, and they had it set up so that if you put on an non-HD channel using an HD set top box, it automatically switched to the HD version of that channel.
Is there any way to make this happen with Fios? So like... if I put on 7, it would automtically change to 507.
Thanks in advance for any help.
Solved!
Go to Solution.

Welcome to FiOS, and welcome to the forums!
Unfortunately no. But if you will take the time to set up a Favorites list, if you haven't already done so, then you can at least somewhat minimize accidentally surfing to the SD channel by mistake. If you are interested in setting up a Favorites list, here is a link to a thread which should help you get started:
http://forums.verizon.com/t5/FiOS-TV-Technical-Assistance/Exploiting-FiOS-TV-Favorites/td-p/9935
With my Favorites list I have all of the HD channels I care about included, and only those SD channels I am interested in that are not duplicated by HD channels. And I must admit, it is pretty rare that I ever watch any SD channel any more.....
Justin
Verizon FiOS TV, Internet, and phone
QIP6416-P1, IMG 1.7.1, Build 09.97
Keller, TX 76248

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.

How do I AI config for SCXI multiple non-contiguous channels

I need to configure a measurement of with multiple groups of thermocouple channels.
Using LV 5.1.1 (could use 6, but I am supporting lots of code built with 5.1.1), DAQ 6.8.1 (can up to 6.9.1 if it matters), PXI-6052E, SCXI-1102, SCXI-1303 (or TC-2095).(using SCXI addressing).
The problem occurs when I try to configure multiple scan lists with gaps between channels.
(see LV DAQ SCXI example SCXI-1102/1127/1101 Thermocouple)
example channel list:
ob1 ! sc1 ! md1 ! cjtemp
ob1 ! sc1 ! md1 ! 0:3
ob1 ! sc1 ! md1 ! 5:9
This gives an error: -10370 in AI Group Config.
Likewise if I use an individual channel in each address string. like:
...md1 ! 0
...md1 ! 1
...md1 ! 3
But, I can skip channels betwe
en cjtemp and the first channel of the next scanlist without error.
Also, I can add scan lists for other modules, like:
...md1 ! 0:3
...md1 ! 4:8
...md3 ! 12:14
without error!
What I really want to do is to do AI Config first for all channels, then start, then loop on AI Read and some processing & storage.
When I loop through the channel address lists (strings with contiguous channel sets e.g. 3:6) I get the same task # for all config calls. Then when I loop through the AI Start's for each , I get an error -10609 in AI Clock Config.
The thing is that I cannot necessarily have all contiguous channels, and I don't want to go through a sequence of {AIConfig, AIStart, AIRead, AI CLear} for each scanlist each time through. That takes too much time and resources.
Eventually I want to configure multiple non-contiguous scanlists in multiple SCXI modules.
But, for right now I need to do this for one SCXI module.
Anyone have any ideas?
How can I approach this.
Thanks
Dave

Dave
Check the following link into the NI Knowledgebase (if you haven't already)
which I think explains your situation.
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/02a55e1f39
e8bd15862567e700577877?OpenDocument
Bottom line is you will not be able to skip channels on any SCXI module
other than the SCXI-1112. You will need to include the channels in your scan
list then discard the data later.
Either that or as the Knowledgebase suggests, use Virtual Channels. You can
then miss channels out in the scan list as you require. They actually get
scanned but NI-DAQ discards the data for you.
Ian Bell
NI UK
"Dave Karon" wrote in message
news:[email protected]...
> I need to configure a measurement of with multiple groups of
> thermocouple channels.
> Using LV 5.1.1 (could use 6, but I am supporting lots of code built
> with 5.1.1), DAQ 6.8.1 (can up to 6.9.1 if it matters), PXI-6052E,
> SCXI-1102, SCXI-1303 (or TC-2095).(using SCXI addressing).
>
> The problem occurs when I try to configure multiple scan lists with
> gaps between channels.
> (see LV DAQ SCXI example SCXI-1102/1127/1101 Thermocouple)
> example channel list:
> ob1 ! sc1 ! md1 ! cjtemp
> ob1 ! sc1 ! md1 ! 0:3
> ob1 ! sc1 ! md1 ! 5:9
> This gives an error: -10370 in AI Group Config.
> Likewise if I use an individual channel in each address string. like:
> ..md1 ! 0
> ..md1 ! 1
> ..md1 ! 3
>
> But, I can skip channels between cjtemp and the first channel of the
> next scanlist without error.
> Also, I can add scan lists for other modules, like:
> ..md1 ! 0:3
> ..md1 ! 4:8
> ..md3 ! 12:14
> without error!
>
> What I really want to do is to do AI Config first for all channels,
> then start, then loop on AI Read and some processing & storage.
> When I loop through the channel address lists (strings with contiguous
> channel sets e.g. 3:6) I get the same task # for all config calls.
> Then when I loop through the AI Start's for each , I get an error
> -10609 in AI Clock Config.
>
> The thing is that I cannot necessarily have all contiguous channels,
> and I don't want to go through a sequence of {AIConfig, AIStart,
> AIRead, AI CLear} for each scanlist each time through. That takes too
> much time and resources.
>
> Eventually I want to configure multiple non-contiguous scanlists in
> multiple SCXI modules.
> But, for right now I need to do this for one SCXI module.
>
> Anyone have any ideas?
> How can I approach this.
> Thanks
> Dave

Loss of non internet channels

Hi everyone looking for some advice where possible. I returned home from work yesterday and i had a pop up on the general freeview channels advising Low signal but the internet channels were all ok so i reset and retuned but still only have the 60 or so internet channels and the others are no longer there.
Now the landlord has since put scaffolding round the property could this be the issue as i am not sure how the connection runs with it obviously not being your run of the mill tv ariel.
Thanks

Hi indierick,
Are you sure you the cable that is connected to the TV has the channels being broadcast ?
Any loose connections, etc ?
Just to make sure, can you plug the aerial into the TV (most TVs have an RF in) and see if the TV is picking up the channels ?

SocketChannel problems reading from a non-blocking channel

why when I read a "big" message from the channel (SocketChannel.read(ByteBuffer)) I receive it cutted in more parts?

up

Dynex DX-24L150A11 adding non-existing channels

I bought this Dynex TV (DX-24L150A11) for my mother last summer, and it's been pretty good. She has the most basic cable plan with Comcast (gets a few unscrambled channels with no cable box). She gets local over-the-air HD channels just fine by having the cable hooked up. It's her first HDTV, and she's loving the clarity.
She didn't want all the channels she could receive (home shopping, foreign language, etc), so I programmed the TV with just the channels she wants so that she can channel surf with the Channel +/- buttons.
The problem is that the TV randomly adds channels with no signal to the programmed list. No one has programmed them in. They just appear on the list. So now when she uses the Channel +/- buttons, she is frustrated with all of the channels that have no picture. There are probably 10-20 channels added to the list.
I have reprogrammed this TV at least 10 times over the last few months to remove the offending channels. I updated the firmware. We thought it would work better, but then the channels started appearing again.
I know she doesn't know how to program the TV, so she's not adding the channels herself (and why would she?).
What's wrong with this TV's firmware? Is there something else that could be causing this (like maybe she's hitting some weird button combination on the remote)?

I saw this a long time ago. The User *was* adding channels unkowingly when using the channel +/- buttons. It seemed to occur when the button was pressed repeatedly very fast succession, instead of slowly or being held down. It seems as if the controller thought the key presses were meaning to add channels...
If you find my post useful or informative, please click the icon below with the plus sign and star to give kudos. Thank you!

I just bought a Samsung S22B310B computer monitor and hooked up to my Mac Mini. I have my mac set to the 1920X1080 resolution but the entire screen (21.5") is not filled. It looks like non HD channels do on an HD TV. Used regular hook up not DVI.

Just bought Samsung S22B310B computer monitor and hooked it up to my mac mini. I have my mac set to the 1920X1080 resolution but the entire screen (21.5") is not filled. How do fill the screen? it fills the screen on other resolution settings. I have it hooked up regularly and not to the DVI hook up. I'm not a computer savvy person please help!

That monitor supports both (digital) DVI and (analog) VGA connections, so you should not need a converter or use a different adapter.
You should use the Apple Supplied HDMI to DVI Adapter and a (digital) DVI cable to the monitor.

Using Multiple non-successive Analog DAQ Channels

Hi,
I need to use multiple analog channels from my DAQ Device in a particular application. Is it necessary to use continuous range of analog channels (e.g. 0,1,2,3,...) or can i use channels in any order (e.g. 2,4,6...)? My DAQ Device has 16 AIOs. What are advantages/Disadvantages of using non-successive channels ?.
Thanks.

Hello,
It is perfectly acceptable to sample on multiple channels that are not in a continuous range, nor do the channels have to be increasing order. In most applications, there are little to no advantages/disadvantages of doing this, other than ease of use for the programmer.
-Alan A.

Overlapping v's Non-overlapping channels...

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