Wireless Access

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Improve this terrible network design

A few years ago, someone at my company with little to no experience with Aruba designed the following network for a chain of hotels we service.

 

  • Aruba3600 in our datacenter acting as a standalone master running 6.1.3.6
  • Controller terminates around ~400 RAPS
  • Each hotel having anywhere from 10-20 AP93s all configured as RAPs back to this same controller.
  • Forwarding mode bridge since we have a dhcp server onsite which acts as our gateway and delivers captive portal as well.
  • RAP operating mode is always (regardless of connectivity to the controller).
  • Default ARM profile maxing out TX rates.
  • All users receive the default ap-role on the controller
  • 1 AP group was created as the master and all the hotels have their own ap-group which was cloned from the original so changing a setting on 1 group changes them all.
  • The controller configuration is as basic as it gets, no special tweaks nothing .
  • Every 2 rooms there is an 8" cinder block wall
  • APs are inside the suspended ceiling

Hotels have 2 floors (some L-Shaped and some I-shaped) -- APs only on 1st floor.

Very low or non-existent RSSI levels on the 2nd floor

Poor RSSI levels on the 1st floors

APs are layed out like the following image (w/ RSSI levels)

Capture.PNG

 

How do you improve this without adding a local controller and not moving APs to the 2nd floor?

 

Pasquale Monardo | Senior Network Solutions Consultant
ACDX #420 | ACMP
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Re: Improve this terrible network design

I would attempt to put an AP93 in a room and determine how much horizontal and vertical coverage you would get from it.  Having access points in the halls is convenient in terms of maintenance, but has the drawback of creating RF interference, and not reaching into the rooms that they were designed to provide coverage to.

 

In general, measuring and possibly moving AP93s to the rooms will possibly provide coverage to the rooms where it is needed, and avoid crippling RF interference.  The VRD for Residence Halls here:  http://www.arubanetworks.com/wp-content/uploads/NextGenAppNote_2012-06_28.pdf explains the rationale.

 

The information in your post is detailed, but much more detail is required to determine if moving them into the rooms is indeed feasible.  The new design will probably require more access points, but you probably only have half as many as you will need to provide coverage to that location in the first place.  You could start adding access points to the rooms on the second floor, so that current coverage on the first floor is maintained....

 

edited.png



Colin Joseph
Aruba Customer Engineering

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Re: Improve this terrible network design

Thanks Colin, this is great information.

 

Definitely moving them into the rooms would help but I am not sure if it is feasible unfortunately.

The plan is to move them out of the ceiling and attach them to the T-bars (exposing them).
They also seem to be positioned in line with the cinder block walls, therefore moving them slightly like below would probably help. (rooms 143,144,146 would probably suffer -- green dot signifies a potential new AP)

Capture.PNG

 

Moving them into the rooms would be ideal and as the VRD pointed out, since the building has high attenuation walls/floors between rooms and between floors, microcells can come in handy.

Purchase of more APs and moving them to the 2nd floor with low transmit power can possibly solve the issue most likely only if budget allows unfortunately and if testing proves so.

 

What more detail is needed as I can provide more if needed..

Pasquale Monardo | Senior Network Solutions Consultant
ACDX #420 | ACMP
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Guru Elite

Re: Improve this terrible network design

You probably will not have to lower the transmit power at all, because the cinder block will provide natural attenuation that you will need to keep them from interfering with each other.  Because of the cinder block you might be able to run them close to full power, maximizing your coverage.  You can probably do nothing until you first put an AP in a room on the 1st floor and measure left-right-above-below to see the coverage.  Do the same thing with one access point on the second floor.

 



Colin Joseph
Aruba Customer Engineering

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Re: Improve this terrible network design

That's what I was thinking. We have someone going there Tuesday morning.
2nd Floor has no APs but we are allowed to run a temporary cable for the purpose of this exercise.

What do you think about all of these being RAPs?
Pasquale Monardo | Senior Network Solutions Consultant
ACDX #420 | ACMP
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Guru Elite

Re: Improve this terrible network design


pmonardo wrote:
That's what I was thinking. We have someone going there Tuesday morning.
2nd Floor has no APs but we are allowed to run a temporary cable for the purpose of this exercise.

What do you think about all of these being RAPs?

There should be no problem that these are RAPs, based on the limited information in this diagram.



Colin Joseph
Aruba Customer Engineering

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Re: Improve this terrible network design

The only issue I see with RAPs is ARM not working between APs to best choose TX and channels.

I have some APs with the same channels next to each other, e.g. AP7 and 2 (rooms 118-122). Client aware is enabled as well.

Pasquale Monardo | Senior Network Solutions Consultant
ACDX #420 | ACMP
[If you found my post helpful, please give kudos!]
Guru Elite

Re: Improve this terrible network design

ARM on RAPs should not function any differently as long as they terminate on the same controller.  If the AP is disconnected from the controller, channels and power will not change, of course.  It is quite possible that you have other RF that might be interfering.  Since these are AP93s, you have only 3 channels, but you will have more attenuation if they are in the rooms as opposed to if they are in the halls.  That will make two access points next to each other having the same channel less of an issue.



Colin Joseph
Aruba Customer Engineering

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Re: Improve this terrible network design

Interesting, was told otherwise.

The interesting thing is that there are barely any other wifi signals around the hotel.

Hopefully we will be able to move the APs to the rooms to test. More to come..

Pasquale Monardo | Senior Network Solutions Consultant
ACDX #420 | ACMP
[If you found my post helpful, please give kudos!]

Re: Improve this terrible network design

We had a similar challenge this past summer in our dorms with that type of wall material in between rooms.

A couple of things to take in consideration :

 

- We tested placing the APs (105's or 135's) ceiling mounted (inside the room) but there was no 802.11a signal on the other side (-82dBm) with the highest power level and with the 802.11g we received a (-70 - 75 dBm) and the signal quality wasn't good.

- Decided to place the APs wall mounted and noticed that the bleed between floors was much better and also would allow us to provide wireless coverage for 3 floors ( the room the AP is mounted plus the bottom and upper floors)

- We spreaded the APs across different floors

- ARM does a great job adjusting the power/channel changes but one of the things you have to take in consideration is that the 11g radios will hear each other too much because of the density of APs so you may want to lower the mix EIRP value to 6 and Max to 15 possibly even 12. We also added Air Monitors to help the ARM process 

 

Screenshot 2013-11-08 16.48.04.png

 

Screenshot 2013-11-08 18.57.37.png

 

Looking at the RF pattern on the 93H attenas you could wall mounted them and get good signal in between floors but of course you should test this to make sure the floor-ceiling distance and materials in between floors doesn't cause too much attenuation 

 

You could also do a virtual survey using Airwave Visual RF or the Standalone version and that also will give you an idea of how to approach it

Screenshot 2013-11-08 16.28.53.png

Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
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