Prior to DBS, I used a fixed 40 Mhz plan across the board for eight plus years 
with no obvious problems attributed to channel width.

Jeff

From: "wireless-lan@listserv.educause.edu" <WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU> 
on behalf of Mike Atkins <matk...@nd.edu>
Reply-To: "wireless-lan@listserv.educause.edu" 
<WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>
Date: Thursday, December 1, 2016 at 4:35 AM
To: "wireless-lan@listserv.educause.edu" <WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>
Subject: Re: [WIRELESS-LAN] 5GHz Channel Width

For those with large deployments of 40 or 80 MHz channel use, have you heard 
any complaints from users having issues staying connected?  (specifically older 
laptops and android devices)  I mean issues not specific to coverage or roaming 
or anything like that.  I noticed some strange occurrences on a few test 
devices that are a bit older but that could be related to something I did to 
the devices at some point in time.  I have not done much investigation yet.  I 
was just curious if others had some experience/observations.




Mike Atkins
Network Engineer
Office of Information Technology
University of Notre Dame
Phone: 574-631-7210


     ----  .__o
   ----- _-\_<,
   ---  (*)/'(*)

From: The EDUCAUSE Wireless Issues Constituent Group Listserv 
[mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>]
 On Behalf Of Jeffrey D. Sessler
Sent: Thursday, December 01, 2016 3:12 AM
To: 
WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>
Subject: Re: [WIRELESS-LAN] 5GHz Channel Width

Our environment (residential) is about 80% Mac and I’ve not run into issues 
with DBS. With a dense deployment, it’s rare that there would be a reason to 
force a client to another AP as the number of clients per AP is very low i.e. a 
sticky client isn’t an issue. In less dense deployments it’s likely all radios 
will be at 80Mhz, making it a non-issue.

If the AP placement is done well from the start, it’s hard to fathom a 
situation where DBS is going to make a truly bad decision. If it sees an influx 
of 11g clients, it’s going to reduce width. If the environment is mostly all 
11n and 11ac (as it is at my university), it’s going to favor 80Mhz.

In general, I favor letting the software make the decisions and only change 
that if I can demonstrate that it’s causing harm.

From: The EDUCAUSE Wireless Issues Constituent Group Listserv 
[mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU] On Behalf Of Jake Snyder
Sent: Wednesday, November 30, 2016 4:40 PM
To: 
WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>
Subject: Re: [WIRELESS-LAN] 5GHz Channel Width

One things to keep in mind is that certain device manufacturers preference 
wider channels.  Apple in the Mac OS X products for instance, will always 
prefer an 80MHz channel over a 40MHz channel.  As well as a 40MHz channel over 
a 20MHz channel.  Things like DBS can lead to stickier clients, as you are now 
mixing channel widths.  This leads you to trying things like Opt-R in order to 
force now sticky clients to other APs, which will likely be less successful 
since OS X doesn’t support 802.11v.  This means DEAUTH, ironically which the OS 
X devices don’t handle as well as their PC brethren…


https://support.apple.com/en-us/HT206207

Selection criteria for band, network, and roam candidates
OS X always defaults to the 5GHz band over the 2.4GHz band, as long as the RSSI 
for a 5GHz network is -68 dBm or better.
If multiple 5GHz SSIDs meet this level, OS X chooses a network based on these 
criteria:
802.11ac is always preferred over 802.11n or 802.11a
802.11n is always preferred over 802.11a
80 MHz channel width is always preferred over 40 MHz or 20 MHz
40 MHz channel width is always preferred over 20 MHz

All in all, I would suggest not doing DBS in OS X heavy environments.  My 
preference is to take each building and decide whether it can be leveraged in 
20, 40 or 80, and configure the whole building that way.

For how to decide if you can get away with 20 vs 40 vs 80, my preference is to 
pick the channels you want to use, and start with a survey.  Let’s say you want 
to enable UNII 1 and UNII 3.  That’s 8x 20MHz Channels.  Could i go to 40MHz?  
If i can get away with 4 channels, then yes.  Or I could add channels until i 
get to the number of channels needed to maintain channels separation.   This 
varies wildly based on density of APs in a building.  Eventually you run out of 
channels that you can add and then must either deal with co-channel 
interference or drop down to a narrower width.

Start with 20MHz
How many channels do i need with my current design to maintain channel 
separation? (Survey may be necessary)
Do i have twice that many channels enabled at the current channel width?
If yes, increase channel width to 2x current channel width.
If no, do i feel comfortable adding channels to get to twice that?
If yes, add channels and increase channel width to 2x current channel width.

Hope this helps

Thanks
Jake Snyder



On Nov 30, 2016, at 12:03 PM, Jeffrey D. Sessler 
<j...@scrippscollege.edu<mailto:j...@scrippscollege.edu>> wrote:

Depending on the building construction, and assuming you are using DFS 
channels, running 40Mhz and even 80Mhz is very likely with no downside. 5GHz 
does not propagate very well, so a static 20Mhz plan in anything but big open 
spaces is IMHO unnecessary.

If you are a Cisco customer, enabling DFS (Dynamic Bandwidth Selection) is 
likely the best choice for maximizing the use of the 5Ghz space. DFS will 
dynamically adjust width based on the client make up and other factors, and 
I’ve found it to be far better than a human design since the environment is 
never static.

I have a newly completed 110-bed residential hall with a very dense deployment 
of APs (105 AP’s total), most are in-room/suite. With DFS enabled, a clear 
majority of the in-room APs run at 80MHz. In more public and/or open spaces, 
they tend to adjust to 20Mhz or 40Mhz. Most of the clients in this residence 
hall are 11.ac<http://11.ac> and report a 1300 or 1170 Mbps connection speed.

Jeff




From: 
"wireless-lan@listserv.educause.edu<mailto:wireless-lan@listserv.educause.edu>" 
<WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>> 
on behalf of "Trinklein, Jason R" 
<trinkle...@cofc.edu<mailto:trinkle...@cofc.edu>>
Reply-To: 
"wireless-lan@listserv.educause.edu<mailto:wireless-lan@listserv.educause.edu>" 
<WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>>
Date: Tuesday, November 29, 2016 at 1:35 PM
To: 
"wireless-lan@listserv.educause.edu<mailto:wireless-lan@listserv.educause.edu>" 
<WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU<mailto:WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU>>
Subject: [WIRELESS-LAN] 5GHz Channel Width

Hi All,

I was just reading a blog article that heavily recommends not to use 40Mhz 
channel width in multi-floor environments, particularly where many 5GHz radios 
are used (particularly in our case with Xirrus multi-radio APs). Our campus 
presently uses 20MHz channel width in all buildings. We are testing and 
considering 40MHz width because of the bandwidth benefits for clients. What do 
you use on your campus? Have you found that setting a 40MHz channel width on 
your 5GHz radios has caused too much interference?

Here is the article:
http://divdyn.com/dual-5ghz-radio-aps/

Your thoughts are appreciated.
--
Jason Trinklein
Wireless Engineering Manager
College of Charleston
81 St. Philip Street | Office 311D | Charleston, SC 29403
trinkle...@cofc.edu<mailto:trinkle...@cofc.edu> | (843) 300–8009
********** Participation and subscription information for this EDUCAUSE 
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********** Participation and subscription information for this EDUCAUSE 
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********** Participation and subscription information for this EDUCAUSE 
Constituent Group discussion list can be found at 
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********** Participation and subscription information for this EDUCAUSE 
Constituent Group discussion list can be found at 
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********** Participation and subscription information for this EDUCAUSE 
Constituent Group discussion list can be found at 
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