Adjacent APs using overlapping 2.4 GHz channels (honeycomb pattern)?

[chiseledst]

I have 15 APs on the same floor of a building. Model of AP is AIR-AP1815W-A-K9. 

I have 2.4ghz and 5ghz devices that connect to them. Each AP is in a room. The rooms are all adjacent to each other. The placement of the APs vary depending on the room. Please see the picture I am going to upload as a visual of where the APs are, which direction they face and what channels (1,6,11) the APs are currently. 

I have two questions: 

1. The 1815w AP is a small AP that is usually mounted sideways upright where the white cover is facing the direction of choice. Does this mean the radio waves are only going that direction? Nothing is going behind it? 

2. In my picture, you can see that certain rooms have overlapping channels where both APs are on the same channel. Is this affecting performance? I have noticed that we have inconsistent performance across our 2.4 ghz devices - where the device is literally in the room but gets 1 bar. Is it necessary to apply the honeycomb pattern in this kind of layout where you ensure channels 1,6, or 11 are not next to each other? Right now the channels are being selected automatically with "Global" as the assignment method. You can flip it to custom and manually choose on the WLC. 

I am going to experiment with this. Thought I'd ask on here. I am the farthest thing from a wireless expert so please let me know what you think. 

[marce1000]

        - For safety have a Wireless Site Survey done too.

 M.

[Leo Laohoo]

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@chiseledst wrote:
1. The 1815w AP is a small AP that is usually mounted sideways upright where the white cover is facing the direction of choice. Does this mean the radio waves are only going that direction? Nothing is going behind it? 

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IF each room has an AP, then it does not matter what antenna pattern it has. 

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@chiseledst wrote:

2. In my picture, you can see that certain rooms have overlapping channels where both APs are on the same channel. Is this affecting performance? I have noticed that we have inconsistent performance across our 2.4 ghz devices - where the device is literally in the room but gets 1 bar. Is it necessary to apply the honeycomb pattern in this kind of layout where you ensure channels 1,6, or 11 are not next to each other? Right now the channels are being selected automatically with "Global" as the assignment method. You can flip it to custom and manually choose on the WLC. 

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Why 2.4 Ghz?  What is so important about it?  Nobody designs WiFi with 2.4 Ghz in mind.  Every design is 5.0 Ghz because there are more channels to use (vs 2.4 Ghz).  

[chiseledst]

Where exactly is the antenna? So the the little AP is basically shooting waves 360 degrees? 2.4 because I have devices that are older and use 2.4 specifically otherwise they do not work well. So do you think I should manually make the APs follow the honeycomb pattern where APs close to eachother do not have overlapping channels? Can you look at the picture I provided as reference?

[Leo Laohoo]

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@chiseledst wrote:
Where exactly is the antenna? So the the little AP is basically shooting waves 360 degrees? 2.4 because I have devices that are older and use 2.4 specifically otherwise they do not work well. So do you think I should manually make the APs follow the honeycomb pattern where APs close to eachother do not have overlapping channels? Can you look at the picture I provided as reference?

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1815W Antenna Patterns

[ammahend]

figure 5 and 6 in this document show radiation pattern of antenna here

you will notice, azimuth plan (looking at radiation patter standing say 30 feet right on  top of the AP) or elevation plane (looking at radiation pattern say 30 feet away from the AP standing in front) is almost a circle, which mean the radiation is a almost sphere.  With AP vertically mounted.

so it doesn't matter much if you point left or right, if the AP is verticle then you will see a spherical coverage pattern. 

one additional thing you can do it download ekahau, and use it to perform a survey with one AP and verify coverage, you wont be able to save it without license but you will still be able to see coverage pattern, there are several tutorials available on youtube.

regarding channel problems you may consider to tone down power all the way to make sure there is no more than 20-30% overlap between rooms, assign channels manually and disable DCA. If this doesn't work then turn off 2.4 on every alternate AP.  clients are seeing one bar most likely because of sticky client issue, they are not able to roam efficiently and keep shifting to lower datarate and stick to far away AP, make sure datarate is high along with other adjustments. 

[chiseledst]

Thanks, I will look into everything you mentioned. Is it worth manually changing the channels so there are no two close APs with the same channel? I am studying wireless fundamentals and one point I came across was that adjacent APs and their 2.4 channels should not overlap, hence alternating 1,6, and 11 between adjacent APs.

[Scott Fella]

Like what the others have mentioned, you should use some tool to check signals like WiFI Explorer or something else. You need to see what the signals are to really determine what you need to do. Also you need to check the power levels the controller is setting the radios to. Can you manually hard set the channels, sure you can, but why. Power and attenuation also can make a difference since amp’s have to have 3 adjacent ap’s to hear each other for rrm to work. That might not be your issue but who knows.

[Rich R]

You don't mention what model of WLC or software version you're using but if you have FRA enabled then some of the 2.4 radios may be turned off so check that too.
https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_RRM_White_Paper/fra.html
https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/802-11ac-solution/at-a-glance-c45-737165.html
https://www.cisco.com/c/en/us/td/docs/wireless/controller/ewc/17-12/config-guide/ewc_cg_17_12/cisco_flexible_radio_assignment.html
https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-10/config-guide/b_cg810/radio_resource_management.html#info_fra

[JPavonM]

Regarding channel overlap and performance, Wi-Fi standard is developed to support that scenario and all devices using the same channel will contend for the access, so no destructive interference will happen (unless there would be any hidden node).

The real problem with performance is that 2.4 GHz band is too crowded, not only from your network devices and endpoints using them, but also from neighbour networks and non Wi-Fi devices that, in this case, cause real interference and transmission disruption thus impacting quality of experience.

As some colleagues are telling you, configure the network with both 2.4- and 5-GHz bands enable and let the devices decide which one to use, or use something like "Your-SSID" in 5 GHZ band and "Your-SSID-legacy" in 2.4 GHz band, and tell users with legacy devices to connect to the only one they see.