What are some important topics related to WLAN troubleshooting and design?

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  • Updated 4 years ago
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OK, David, I know I'm opening a HUGE topic here that really should be an event in and of itself; but we have to talk about it. What are the important topics, considerations, issues, etc. that you see around WLAN troubleshooting and design?

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Tom Carpenter

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Posted 4 years ago

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David Coleman, Official Rep

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Even though there are numerous resources available to learn about proper WLAN design, deployment and troubleshooting, many WLAN deployments are simply not planned properly. That was been the purpose of today’s community event... “How to become a Wi-Fi Expert”  Take the time to learn about WLAN design and troubleshooting.
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Rasika Nayanajith

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If you know well your CWAP topics, you know what to looking for.

Also taking wireless captures & wifi packet analyzing skills go long way here.

HTH
Rasika
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David Coleman, Official Rep

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We decide to release a booklet on this topic which is excerpted from the CWNA Study Guide. Everyone gets a free copy if you pst a question or reply in this last hour. 
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David Coleman, Official Rep

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From a design standpoint, everyone needs to learn about BOTH coverage planning and capacity planning.
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David Coleman, Official Rep

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At a minimum you need -70 dBM received signal strength to provide coverage for high data rates and provide for a Signal-to-Noise ratio of 20 dB or greater.  Voice and video grade WLANs require -67 dBM or higher
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Tom Carpenter

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I call that capability :) - when you have coverage AND capacity AND the right features, you have capability.


coverage + features - capacity = no capability

capacity + features - coverage = no capability

coverage + capacity - features = no capability


You gotta have 'em all.

Tom


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David Coleman, Official Rep

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As for capacity..... I bet somebody is going to ask me the million-dollar question. 
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autumn pitts

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I think this is something interesting.  Most of the management I have engaged on the subject only understands coverage.
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Manoah Coenraad, Champ

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What I see in the ' field' is a lot of Wifi deployments not planned properly. A wrong design, No site survey, Not enough coverage.. etc..etc.. There is not enough knowhow about wifi designing.
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Tom Carpenter

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OK, David, you asked for it. How many client devices should you plan to support per radio? or per AP?
(Edited)
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Rasika Nayanajith

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My rule of thumb,

if it is general deployment I would go with avg 25.

if it is for video ~10

Always prefer 5GHz

Rasika
(Edited)
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David Coleman, Official Rep

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Manoah, if everyone would take the time to perform a proper WLAN site survey... our lives would be so much easier.  Please everyone....   SITE SURVEYS are important
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lowkey

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Ok, but how to tell this to client buying WLAN equipment ? :)
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Manoah Coenraad, Champ

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Did you ever buy a car, without a test drive? So the same for the site surveys. You have to do it to be sure the're no issues with the ' car'(wifi).
(Edited)
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Norman M

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I, think we have to explain this to the client.
Without a proper site survey there wouldn't be any garanties.
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Manoah Coenraad, Champ

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I agree with Norman, no garanties without a Site survey.
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David Coleman, Official Rep

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The answer to the million-dollar question is:  IT DEPENDS!
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Raymond Hendrix

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on?... ;)
(Edited)
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Jay

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Probably won't get a book but this has been some great reading for the past few hours plus bonus links, great job everyone.
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David Coleman, Official Rep

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Hey that is a post.... Amanda... send Jay a book!
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Gustavo Gomez Jr.

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I see a lot of generalists that do not have the time or resources to learn wireless technologies. If you have the knowledge you also need the proper tools to perform layer 1 troubleshooting = spectrum analysis and L2 packet capture. Software to verify coverage and capacity = air magnet or ekahau.
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Manoah Coenraad, Champ

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Most of the wifi problems starts with a wrong design
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lowkey

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seen too many projects with no design at all :)
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David Coleman, Official Rep

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Nobody likes the answer of "It depends" on how many client devices per radio. But the bottom line is that there are too many variables.  WLAN vendors will tell you their APs can handle 100- 400 devices at the same time... but that is marketing nonsense.
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Raymond Hendrix

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it can be done with Ruchus outdoor ap's no extra's and no security... seen it work.
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autumn pitts

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The marketing nonsense, makes the job harder.  I still get to explain why we should not hide SSIDs.
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Matthew Gast

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It may be more true if we have more lower-bandwidth devices.  The iPad I use at home clearly demands more of the Wi-Fi than my Nest devices do.  But it will be a long time before I need to think about lots of little devices on the network as much as the big devices I already have.
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Jukka Kettunen

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For troubleshooting, check the basics first. People often assume that things are OK and forget to check the basics.
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Manoah Coenraad, Champ

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Yes, they can connect 100-400 devices, but none of them can send or receive any packet ;)
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Gustavo Gomez Jr.

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Keith R. Parsons Professionals Are Defined By Their Tools -> highly recommended!

http://www.wlanpros.com/ten-talks-keith-r-parsons-professionals-defined-tools/
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Nicolas Maton

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A very important thing most wi-fi designers forget about in the 2.4Ghz is what i call the ripple effect.. Eventually you will receive frames from another ap that is using the same channel as your ap. This wil lower the airtime available for this specific ap.Co-channel interference even with low rssi.  
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David Coleman, Official Rep

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The first variable is what type of devices are being used. Are they 3x3:3 laptops or are they 1x1:1 tablets.   With normal application bandwidth such as web browsing, low-definition video streaming, email, etc.....   35-50 laptops (3x3:3) connecting to a single 802.11n or 802/11ac radio is certainly doable.
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David Coleman, Official Rep

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However if all of the devices are 1x1:1 tablets communicating at much lower data rates, they will consume more airtime and thus a number of 20-25 tablet connections per radio with average bandwidth usage is a better plan
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David Coleman, Official Rep

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The other big variable is bandwidth intensive applications.  You will not have 50 happy clients connecting to the same AP radio if they are all using High-Definition video streaming.
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David Coleman, Official Rep

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Aerohive's white paper on High-Density Design has some fantastic formulas for planning on capacity using all of these variables.  Kudos to Mr. Andrew vonNagy - Wi-Fi Boy Genius that wrote this paper.
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rsm1080

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Is it better to survey for 5GHz first using the aforementioned -67rssi and 20dB SNR since the cells are usually smaller and then go back and survey for 2.4GHz?
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David Coleman, Official Rep

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Always survey for 5 GHz first...  absolutely.   In many cases you will be turning off a lot of the 2.4 GHz radios to avoid co-channel inetrefrence
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Jay

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In a lot of schools in the district I work for I have setup access points in every other room could I still turn off the 2.4 radio or is that enough space to avoid co-channel interference?
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David Coleman, Official Rep

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Hopefully. If you have APs in every other classroom and you are turning off every other 2.4 GHz radio and the walls are made of cinder block or concrete, you should be good.
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J. Goodnough, Champ

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What can be tricky too are applications with tons of small packets...