RF Predictive Modeling for New Site

By | December 23, 2016

RF Predictive Modeling for New Site

Recently had a request to do an AP placement for an office floor which was under construction, client wanted to know the location of the Access Points before the walls / ceiling go up. Now only option left here was to do a predictive modeling to figure out the best placements.

First and most important thing is to understand the client, their requirements and the end devices used by the WLAN you are designing. I will not go into depth, for that best recommendation is to go through CWDP study guide.

Site Visit:

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Always go for a site walk to understand what the environment is and where the  WLAN will be deployed.Do a quick check on other WLAN’s in the vicinity, what  channels and bands are  being used.

Walk the parameter of the space to check if there is non WiFi interference that  might affect your WLAN, this will also give you the channel utilization caused by  other WLANs which further will help you get a starting point on what channels you  might want to avoid.

 

 

For example, in the below case the neighbor had his AP’s on Channel 7 with 40 MHz channel width in 2.4 Band.

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Site walk was done late in the evening. However, during the office hours, the interference is high. Another recommendation would be to visit the site during business hours to get a real snapshot of the surroundings during peak hours.

Proper Floor Plans:

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Generally, floor plans are very hard to get for an existing site, but if the site is under construction you will get the real deal, i.e. CAD files with all possible details. Also, the best part is that you have the construction team available on site to ask all kinds of questions.

I was able to get the furniture plan and Ceiling plan which had lots of details. Generally, the first thing I do at a site visit is to scale the floor plan.

Floor plans will have a scale on them but it will be shown in millimeters as highlighted by the red boxes in the below image.

Furniture plan is what I use to import in the predictive tool to draw my walls, furniture, cubical, Filing cabinets, printers, etc to input the attenuation.

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If it is a site that has not been constructed you can’t take any attenuation measurements.

pic3 In this case you can use your experience and then use the attenuation readings you  must have captured previously or just use the tool and its generic recommended  attenuation’s. Also pay very close attention to the legend provided in these drawings. For example, It will tell you that the meeting rooms have double dry wall, and then you can adjust the attenuation in the tool before you draw the walls for the meeting rooms.

 

Ceiling Plans: They are also as important as we will be mounting our access points on the ceiling. Different part of the floor might have different ceilings, T-Bar, dry wall, open, etc.

Ceiling plans will also indicate where are the light fixtures, sprinklers, exit signs and other obstructions which you want to avoid when placing you access points.

There might be some areas where you might not able mount you access point at all, good example for that would be Soundscape blades.

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Example of a Ceiling Plan

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Legend is your friend to understand the map. Below are some examples

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Mounting of the access points:

In this section you want to figure out what kind of mounting brackets you will be using. T-Bar, Wall mount, in some cases custom solutions.

In the below case, we had an open concrete ceiling so the idea was to use pipes as conduits and use suspension poles to lower the access points at same height or below (I requested them to have access point 3 inches below to avoid any interference) the light fixtures.

Here we decided to use an electrical box to be attached to the pole and use a wall mount bracket to the attached access point.

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I will Share some more information once the site is deployed in next year, till then Merry Xmas and Happy holidays to all reader.

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