Speeds and Power for High Density

[JasoLest]

We're working on a project in a K-12 school system to expand wireless coverage.  We currently have roughly 1 AP per every 2 classrooms.  Some schools have AP1020's and some have AP832's.  We will soon have 1 AP per classroom and several in the common areas (libraries, cafeterias, etc).  We are 1:1 with Chromebooks, so classrooms could have 20-25 Chromebooks along with personal devices on our guest network.

What are some general recommendations for setting the power for both 2.4 and 5 radios, assuming that any device will be within 20-30 feet and line-of-site of an AP?  Also, since we no longer have "B" clients, what speeds should we look at shutting down now?  Should we also start shutting down some of the lower "G" speeds since any client should be capable of hitting the higher speeds if an AP is nearby?

[mswanson_FTNT · Accepted solution]

Hello Jason,

Here are some recommendations for you based on your design requirements:  

• Align power to provide symmetrical coverage in 2.4GHz and 5GHz.  17dbm for 5GHz and 12dbm for 2.4GHz is a good place to start.  
• Set the Probe Response Threshold to 20
• Set the Adequate Signal Threshold to -55
• Remove low Base and Supported Transmit Rates
• Remove 1mbps, 2mbps, 5.5mbps, 6mbps, 9mbps, MCS0, MCS8, and MCS16

You could also consider segregating traffic per band.  For instance, have school issued Chromebooks and Staff devices on 5GHz and have guest devices on 2.4GHz.  If you have any further questions please let us know.

Matt Swanson

System Engineer

Fortinet

720-509-9868 | c: 763-639-3185

[JasoLest]

So, to disable the slow speeds, I just go in on each ESS and uncheck 1, 2, 5.5, 6, 9, MCS0, MCS8, and MCS16 anywhere they appear under Advanced?  I wish it was a little simpler like some other brands.  It would be nice if the RF Band setting would let you just select 802.11gn instead of 802.11bgn and do it for you.

[markdr_FTNT]

Hi Jason,

Yes, you need to trim the lower MCS base rates on a per ESS basis if you don't want client connections at the lower speeds. The Beacons for each ESS are sent out at the lowest rate and therefore clients can only connect at the advertised rate or higher.

Note that if this is done, any clients sitting on the edge of the WLAN's range will not be able to rate adapt down any lower than the minimum you set and therefore you will likely see an increase in the retries for unacknowledged frames.

[bandersen_FTNT]

Just adding that you "only" need to modify the section that corrosponds to the setting of the radio, that's using the ESS profile.

Meaning that if only have radios for 2,4 set to bgn mode, then no need to change settings for b and g sections only for bgn section of the rates.

Thanks

Brian

[JasoLest]

Thanks guys.  I made the change last night at one site and no complaints today.

[AlanRuss]

Hello Jason,
If you’d like, we can have an SE contact you directly for some deeper dive. You can reach out to me directly and I can get you in touch with the closest Wireless Specialist.


Alan Russell
SE Manager
Secure Wireless and Access Technologies

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From: "Jason Lester via secure.802.xx.pub"
Reply-To: "secure.802.xx.pub@fuse-lists.fortinet.com"
Date: Thursday, March 30, 2017 at 4:52 PM
To: "secure.802.xx.pub@fuse-lists.fortinet.com"
Subject: [secure.802.xx.pub] - Speeds and Power for High Density
Resent-From:
Resent-Date: Thursday, March 30, 2017 at 4:52 PM


We're working on a project in a K-12 school system to expand wireless coverage. We currently have roughly 1 AP per every 2 classrooms. Some schools have AP1020's and some have AP832's. We will soon have 1 AP per classroom and several in the common areas (libraries, cafeterias, etc). We are 1:1 with Chromebooks, so classrooms could have 20-25 Chromebooks along with personal devices on our guest network.

What are some general recommendations for setting the power for both 2.4 and 5 radios, assuming that any device will be within 20-30 feet and line-of-site of an AP? Also, since we no longer have "B" clients, what speeds should we look at shutting down now? Should we also start shutting down some of the lower "G" speeds since any client should be capable of hitting the higher speeds if an AP is nearby?

-----End Original Message-----

[JasoLest]

Thanks for the info.  I also sent Alan an e-mail.

[markdr_FTNT]

Hi Jason,

Just to add another point, if you have a mixture of AP1020's and AP832's  then you should try and physically group them together so that site/area A has the AP1020's and site/area B has the AP832's. 

The reason for this is that the Virtual Cell technology which creates a common BSSID has a requirement that the radio hardware matches. If it doesn't and different radios (or radio settings) do not match inside a given ESS profile, then you will end up with broken/multiple BSSID's in the air; resulting sub optimal performance (for a number of reasons).

Best Regards,

Mark

[JasoLest]

The models are at different locations.