Wireless Access

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Occasional Contributor II
Posts: 16
Registered: ‎11-22-2013

2.4 Ghz, 1x1 Client Help

Hi all,

 

I'm trying to get up to speed with a challenging situation for a school. The client has 20 new Lenovo, Windows 7 laptops which came configured with Broadcom 2.4 Ghz, 1x1 WiFi cards installed. I have a single IAP-135 AP. These are the only clients attached to this AP.

 

I am having difficulty in being able to deliver an acceptable experience with these laptops starting with logging into a Server 2008 Domain, with Roaming Profiles/Folder Redirection. The Roaming Profiles have been checked and they are in the 2-15 MB size range. Problems start at logging in with a group of 15-18 users in the same room as the AP. Signal is great, noise is clean. I do see a number of retries being shown in the console, but I don't have the number available to me, as I write this message.

 

From someone elses experience, would you expect this because of the WiFi cards capabilities?

 

Everyones help is immensley appreciated. Thanks.

 

Kurt

MVP
Posts: 4,238
Registered: ‎07-20-2011

Re: 2.4 Ghz, 1x1 Client Help

[ Edited ]

 

If can verify the following to make sure that you are not experiencing slow performance because of RF issues :

 

ARM history will show you if there's a lot of channel/power changes and why

2014-01-22 21_30_11-Instant.png

 

ARM RF summary will show you the RF quality of the channels

2014-01-22 21_30_11-Instant.png

 

You should enable to Drop broadcast/multicast :

2014-01-22 21_38_13-Instant.png

2014-01-22 21_39_42-Instant.png

 

What type of wireless authentication are you using ?

 

Do you experience this issue only when you have several users ? or it also happens even with just one ?

 

Make sure there's not packet loss between the IAP and your server ?

 

After the user  is able to login are you still experiencing wireless performance ?

 

Have you tried updating the wireless drivers ?

 

Do you have another laptop that has another wireless chipset to test with ?

 

Have try this :

http://support.microsoft.com/kb/981830

http://social.technet.microsoft.com/Forums/en-US/20983681-6470-4e71-895c-394b34da4e2d/slow-logon-and-roaming-profile-issues 

 

 

 

Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4 Ghz, 1x1 Client Help

[ Edited ]

Try checking the channle utilization.

You can put the IAP in spectrum analysis(but you wont be able to serve any client)

If you got a fluke airchecker or something similar that would be great also.

 

The other important point.

2.4ghz and 1x1 :(

 

Even if you got an AP 135 the client with his 1x1 will take more air time than a client which could be 3x3 on 5ghz

 

your max speed per client would be 65mpbs and 30Mbps tcp/ip througput

 

Anywyas  the thing is that you are needing a lot of airtime in here, and its beacuse of the slow clients.

Let supppose that you need 7Mbs constantly for a few of minutes to download the profiles 

Assuming that you just got client capable of 65Mbps which is a tcp/ip throughput of 30 Mbps  and 20 clients at the same time logging in.

 

This means around 466% of airtime which means that yhou would need around  5 Radios to transmit 7Mbps constantly

 

I bealive that one AP is not enough with this slow clients  and the BW you needing and thats why you are getting those kind of trouble...


This would improve if you get more APs or you get the client to use better antenas for their laptops... for example if they would be running on 5ghz  3x3 client you would need just one AP.

 

The problem here could be your slow clients and the lack of APS in this specific scenario.(and even if you add more APS as you can just work on 2.4ghz as your client are just 2.4ghz which could be troublesome! as your just can work with 3 Channels and yhou would need to reuse)

 

In yhour sceneario it doesnt matter if it a AP 135 or AP 105 and so on. your problem  are the slow clients.

 

The first thing i advice my clients when they buy the solution to us

PLEASE buy 2x2:2 laptops abgn do NOT purshase 1x1 laptops bgn, this really impact your wifi performance...

 

Cheers

Carlos

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
Occasional Contributor II
Posts: 16
Registered: ‎11-22-2013

Re: 2.4 Ghz, 1x1 Client Help

Hi Carlos,

 

Thanks so much for your response. Would you be kind enough to explain in more detail:

 

  1. The calculation to get 466% Airtime
  2. The use of 7Mbs per client for downloading the profile to the client
  3. If on 5Ghz, using 2x2 what values am I using for the claculation of Airtime
  4. At this moment, there is only 1 AP that I've installed in the location, Am I able to do Spectrum Analysis and check the channel utilization?

Hopefully my questions aren't too dumb.

 

Thanks again,

 

Kurt

MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4 Ghz, 1x1 Client Help

Dont worry, there arent dumb questions!

 

Question number 1

 

To calculate this you must know

The minimum BW you needing for your clients = which i took for instance 7mbs, it would be 1mpbs, you need to ttell me that.  At least you said you had roaming profiles from 2mbs to 15mbs.


You need to know the antenna and speed of your clients which in your case is 1x1:1 Which equal to 65Mbps theorically which equal to 30 Mbps tcp/ip real througput.

 

You need to know how many clients will be using the minimum BW  which in your case its 20.

 

Now you know all these numbers the formula goes like this

 

Minimum BW = MBW

Real BW of your clients =RBW

Numbers of clients =NCL

Porcentage of airtime =%Airtime

Forumula:

 

(MBW/RBW)*100 = %Airtime

 

(%Airtime*NCL)/80 = Real airtime for all the clients

 

So lets use your values

(7Mbps/30Mbps)*100 =  23.3%

 

23.3% * 20 =  466%

 

455%/80 = 5.8 Radios Which is around 6 radios.

 

 

Question Number 2

 

Thats a number i though it would be a minimum, if you can tell me the Minimum BW that its needed then i can recalculate with it.

 

 

Question Number3

 


If you were able to use 5ghz in your scenario and you had 2x2 Client antenas the real Tcp/ip throughput would be 150Mbps.

You can calculate the real tcp/ip trhougput  by just cutting the theorical BW by half.

 

Question Number 4

 


You are able to do that, but you wont be able to serve clietns if you change it to spectrum monitor!.

What im not sure how much info you can get from Instant spectrum analisys... but with a controller based scenario it would give you that information!

 

 

If you ever wondered the source for the formula i just used

http://www.aerohive.com/330000/docs/help/english/documentation/Aerohive_High-Density_Wi-Fi-Design-Config-Guide_330073-02.pdf

Yes its from another vendor but the formula its pretty handy.

There is another one from Motorola High Density guide, which is a bit different but at the end it give you the same numbers...

 

http://www.revolutionwifi.net/

 

Cheers

Carlos

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4 Ghz, 1x1 Client Help

[ Edited ]

If you did the same formula but instead of using 1x1 clients using 2x2 clients you would see a big differnece in radios that you would need! much lessTry it

It is possible to do the same test but with clients with 2x2 antenas? and 5ghz capable?

 

 

Cheers

Carlos

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
Occasional Contributor II
Posts: 16
Registered: ‎11-22-2013

Re: 2.4 Ghz, 1x1 Client Help

Hi Carlos,

 

I'll be able to spend some time with this client tomorrow, as well as absorb your answers. I'll get a meassage up here with progress results. I do have 20 USB based A/B/G/N 2x2 addapters coming to add to the testing.

 

When things start to fall apart, I do see a number of retries on all of the clients, but I don't have a point of reference to know what's tolerable or disasterous. What would be the best report/s to run, and what how much duration of time do the IAP-135s keep in their log? Am I able to post them back here for you experienced folks to look at?

 

Thanks,

 

Kurt

Occasional Contributor II
Posts: 16
Registered: ‎11-22-2013

Re: 2.4 Ghz, 1x1 Client Help

Hi Victor,

 

Thanks so much for the input. Very good stuff. I'll be able to spend some time with this tomorrow. I've replied to Carlos, as well with a couple of additional questions so please chime in. I can't tell you how much I appreciate it, and how beneficial it is in understanding a good approach to troubleshooting, and design.

 

Thanks,

 

Kurt

MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4 Ghz, 1x1 Client Help

[ Edited ]

Hello Kurt

Be sure you got band steering on and that those clients are connecting to 5ghz :)  and have cahnnel bounding on(which is on for default on 5ghz)  Also have airtime fairness on(not on by default on controllers, but its on by default on instantsAP)

 

Well to see if something is not tolerable for me i use some rudimentary tools like ping. 

If i see to many ping drops 

Let say that you are logging on with your latops with the roaming profile and you got one laptop pinging to let say the swtich core? and you see a lot of ping drops, like 3 times out of 5  all the way, or  4 out of 10 pings this is really bad....

if i see 2 ping drop every 10  pings its bad but not that bad...

I would expect fo rexample out  of 100 pings 1% to 4% to be aceptable  more than that is not good...

 

Like i said its rudimentary, but it has been working for me just fine.

 

Maybe someone else can give you some MUCH better reference to know if its dissasterous or torable.

 

Hope victor can input you with more additional information.

 

Yeah forgot

GOOD LUCK Tomorrow!

 

Cheers

Carlos

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
Occasional Contributor II
Posts: 16
Registered: ‎11-22-2013

Re: 2.4 Ghz, 1x1 Client Help

Hi Carlos,

 

I've taken a look at the references you provided. Great!!!

 

I'm working through the training at Aruba, but real world business and opportunities are creating a trial by fire scenario. Thanks again.

 

Kurt

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