Question

We have 9 AP's 250s within close proximity of one another some only 20-30ft apart


I am wondering when the option "High Density Configuration" is required, and what affect this has on the AP reach and configuration . As the AP's sit on Auto power allocation I am wondering if they should be allowed to transmit at 16db in almost open space on their 5Ghz radio.

 

Also as 250's have been around for a while what benefits could we see on slightly higher models.


26 replies

This guide reviews when to use High Density settings: https://thehivecommunity.aerohive.com/s/article/When-to-Use-High-Density-Settings

Briefly, you only want high density settings enabled if the APs are in the same room (no walls between them) and you are processing a large amount of client data.

 

I would highly recommend dropping the power to 5dBm or less, given how close the APs are to each other. With APs that are too close, with the power set too high, you'll get overlapping signals which causes packet damage, which causes slow wireless and possibly client disconnections. To see if the APs are too loud, you can run the command "show acsp neighbor" and check the RSSI values. This guide goes in to detail on how to read the output of that command (it's the first command discussed in the Solution section): https://thehivecommunity.aerohive.com/s/article/Radio-Frequency-Interference-NG

 

Finally, this page compares our AP models so you can see the differences in later models compared to your AP250: https://www.aerohive.com/wp-content/uploads/Aerohive_Datasheet_AP-Portfolio.pdf

 

Ah thanks for this > It seems our AP's have the config which allows them to choose up to 19db, im thinking to reduce this marginally as I am think this will help roaming also , and this may be why our clients pin to one AP for quite some time

In the first article Sam has linked it says about disabling the lower data rates, this can also help with clients roaming between APs.

For 5Ghz , I have 6 N/A, 9 N/A, 12 Basic, 18 Optional, 24 Basic and all other optional, I am a little purplexed if you normally have 1 basic or not ..

For 5GHz there shouldn't be a 1 option, it should start with 6. For the 2.4GHz section, I usually recommend 1-9 be set to N/A.

Sorry might have been how I wrote above our 5ghz ..For 5Ghz , I have 6 N/A, 9 N/A, 12 Basic, 18 Optional, 24 Basic and all other optional is this a recommended configuration

Yes, thank you for clarifying, that is a recommended configuration.

Thanks Sam for this , as I am fairly new to Aerohive , I always thought you had only 1 of the speeds set to Basic, what is the relevance of the 2 .. ie 12 being set to Basic and 24 set to Basic.

Hi All I see this on one of my AP's for example which is between two other APs literally 20ft either side of it in clear view

#show acsp neighbor

wifi0(7) ACSP neighbor list (0/384):

 

 

wifi1(8) ACSP neighbor list (0/384):

 

 

 

#show interface wifi1

AC=access category; be=best-effort; bg=background; vi=video; vo=voice;

AIFS=Arbitration Inter-Frame Space; Txoplimit=transmission opportunity limit;

IDP=Intrusion detection and prevention; BGSCAN=background scan; PS=Power save;

HT=High throughput; A-MPDU=Aggregate MAC protocol data unit;

DFS=Dynamic Frequency Selection; CU=Channel Utilization;

EIRP=Effective Isotropic Radiated Power (Transmit Power + Max Antenna Gain + Max TX Chains Gain);

 

Summary state=High collision;

 

This is on power 9, whereas two adjacent AP's either side 20ft away of it in an Open office are on 15/16 , I suspect this is being drowned ?

The neighbor list isn't populating which is odd, can you see neighbors from any of the other APs? Have you got either DFS or UNII-3 channels enabled? With many APs in a small area if you don't have one of these enabled you may be getting co-channel interference.

Could you screenshot the hivemanager page with the channels/tx powers the APs are using?

Hi , these are the AP's (The one with the power 9 is the detail I shared, the adjacent AP's are the bottom entry (power 16) and the 3rd line showing (power 15), we use 40Mhz,



Capture2Capture1

On review a few AP's show lack of ACSP, neighbors also I guess could this be why the AP's are all quite high possibly, I am wondering if it could be the code which I am due to update soon maybe ?

The neighbor list won't populate if we aren't getting background scans through. If you can send me tech data from an AP, I can tell you if we're getting background scans through or not.

 

Basic is a minimum requirement that the device needs to meet, Optional is a speed that is available but not required. Setting 12 and 24 to basic means a device will need to either meet 12Mbps or 24Mbps at minimum in order to connect/roam to this AP. Obviously if a device can meet 24Mbps, it can meet 12Mbps, but having the 12Mbps enabled as well gives slower devices the option to connect.

 

With your APs that close to each other I would strongly recommend a static power and channel plan and I would lower the power on the APs significantly so we can avoid overlapping signals.

HI Sam, how do I send you this direct for evaluation, as we also use MAC books 95% of the time Skip Background Scan When: Select from the following options:

Clients are connected: Clear to prevent an AP with connected clients from scanning channels. Disabled by default.

Connected clients are in power save mode: Select to allow an AP to scan channels when connected clients are in power save mode. You might want to disable this option if some clients (for example, MacBook 10.4.11), are experiencing intermittent connection issues when in power save mode. Enabled by default. (should we disable this, esp if clients stay on in the night)

 

I have that tech Let me know where i can send it to regards

 

You can send that directly to me at communityhelp@aerohive.com. I would recommend allowing background scans in all situations if you have power or channel selection set to Auto on the APs. The APs need the background scan in order to determine the best channel and power setting for the environment. If you have a static channel and power plan, you would be fine leaving background scans disabled.

Thank you for that data. We are missing a majority of the background scans requested by the AP, which would explain the blank neighbor list. It also means most of the other data I would check is most likely out of date. I would recommend enabling background scans in as many situations as possible to get this data to populate.

Hi Sam, so I guess here do we want Scans to happen when people are connected would this cause loss of service, what would help us ensure accurate data on the AP given the below is currently used , kind regards

Capture1

There is a small chance that a background scan would cause a client disconnection, but this won't be a problem for the majority of clients on the market today. I would recommend unchecking the box next to "Connected clients are in power save mode" to start with, pushing that change out as a delta configuration update, waiting an hour, then sending me new tech data so I can see if we've improved.

So I am thinking it should Scan now when clients are connected, but is not scanning if it see's Power save mode clients or Voice traffic

That is correct with the settings you have now, but we'll want to try running scans with clients in power save mode too since we're not getting enough scans through to populate the data we need.

I have since updated this do you want me to send over detail today

Thanks Craig, I took a look at the new data and emailed you with my recommendations. Please let me know if I can clarify anything.

HI Sam, I have just sent you the details on your response , hopefully this might highlight the next steps , and how the AP determines what Power it chooses.

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