Rule of thumb for AP power.

[Ytrakas5]

Hey all, 

I'm just curious what your guyss process is when setting up powers for campus situations with many rooms back to back. We only have max 30 people per class with an mr56 per classroom, and it's currently in a spot where each classroom serves itself, not much overlap at all. Should I have AP overlap so that devices have options, or should I consolidate the power to so the each AP only serves each classroom to reduce interferance?

Also, what do you guys reccomend aiming for rssi wise? I'm under the impression that -55 to -65 is a good 5ghz signal strength for denser enviroments.

 

This picture is taken sitting in the center of one classroom with closest aps being in another classroom right next door, across the hall, and right above.

[alemabrahao]

Personally, I prefer to always overlap the signal in a triangular way to avoid roaming problems.

As for the signal, up to -65 is an excellent signal. So I would try to work at maximum up to that range.

[PhilipDAth]

Meraki provides a prebuilt radio profile called "Classroom Profile" for this exact use case. Start with that. You probably won't need to make any changes.

https://documentation.meraki.com/MR/Radio_Settings/RF_Profiles

[GIdenJoe]

If you don't expect high levels of traffic in the school you don't have to calculate bandwidth.  But if you do then it is very important to design for smaller cells having a cut off at higher levels than -65.

Aside from that try to have each classroom to have enough secondary coverage from an adjacent room so each client can roam if it deems necessary and have just enough that the experience in the hallways is fluent enough so roaming does not become an issue when walking there.

Try to shoot for having a solid -55 inside the classroom from the primary access point and the bleed through to the hallway down to -65 right next to the classroom.

Then have about -65 to lowest -70 signal from the adjacent classroom.  And also have that signal overlap a bit in the hallway once again for the roaming.

The AP power should never exceed 14 dBm and if the wall attenuation allows it you can even lower it a bit to keep to the values mentioned above.

[TBHPTL]

RSSI "are not the droids you are looking for" RSSI is a unitless integer from 0-250 and it is range varies from vendor to vendor and is a relative measurement. You always want to use RSS which is an absolute value expressed in dBm. What is important here is that you set a standard for what you use as your "yardstick" for dBm measurement/collection of the APs cell edge values in dBm.

As other have stated here, -65dBm is  considered a good RSS target, beyond this metric real time voice  and video will begin to erode after -67dBm. Iphones will start trying to roam at -70dBm. When you look at Apples doc you will note that they refer to RSSI in dBm...😐 

Also, just because you place an AP in the class room doesn't mean that the clients are exclusive to that AP. Clients and clients alone choose to which AP they will join.

https://www.metageek.com/training/resources/understanding-rssi/

https://support.apple.com/guide/deployment/wi-fi-roaming-support-dep98f116c0f/web

https://documentation.meraki.com/Architectures_and_Best_Practices/Cisco_Meraki_Best_Practice_Design/...