This information presented here is intended to represent the issues and considerations of small venue location specific installations.
Large scale installations can be considered as a composite of many smaller scale units. The same methods apply to installations of many hundreds of Access Points (APs) and the principles discussed herein should be considered as macro scale within these large deploys.
At this scale the macro blocks here may overlap and the principles deployed should be best effort approach given the specific environment.
Optimisations in AP placement
Encapsulation
The object of encapsulation is to wrap the location area in coverage so that the sensitive area is best contained within the bounds of the polygon prescribed by the APs.
Placement of APs for location deployments are different than that of coverage maps.
APs spread to boundaries of physical building
Avoid APs contained inside other APs
Obliquing
The aim of oblique placement is to stagger the APs to avoid obvious symmetry in the placement. Improved opportunity for differentiated triangulation.
The following four AP example with oblique placement shows how unsymmetrical placement can:
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Provide wider selection of angles in triangulation models
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Improve coverage
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Increase channelling
Alignment
When you place APs, you should avoid as much as possible having APs hidden behind other APs.
Avoiding lines of three or more APs can assist with calibration data between APs, and give additional triangulation for which to interpolate results.
Avoiding lines of three, in common square six/square configurations, allows calibration data to flow unhampered through APs.
Typical faults are placements down a single side of a long corridor, APs are better alternatively offset in these scenarios.
Channelling
By channelling we mean placing APs longitudinally along lines of major traffic.
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Placement of APs where traffic occurs, and not over dead zones.
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Avoid where possible heavy barriers like walls/retail shelving.
Deployment density
The density of APs required for location tracking is greater than a typical hotspot scenario.
Where a single hotspot may need only one access point for coverage, with location analytics we need at least three APs to perform triangulation.
The aim is to have as many of the APs in a given zone able to detect the signal as possible.
Where a single hotspot may need only one access point for coverage
Four APs are more typical for location tracking as this gives the required containment pattern
Density
At the fundamental level we are trying to achieve opportunities of triangulation from our source to the APs.
Overpopulating the zone can cause additional noise/interference levels that lessen the accuracy, but may give more fluid/wider coverage results.
We require a minimum of three APs, four is a very typical basic deployment, to achieve good levels of encapsulation. Interference limits the effectiveness from five/six APs upwards.
Orientation
Physical placement of APs should be made to give them the cleanest path both to the expected data points and to each other. AP-AP communication is important for dynamic calibration of the system. APs should face the locality zone and avoid obstacles and obstructions.
As the beam pattern from typical access points is bulb shaped, placement with enough height to focus the direction of coverage is best. Ceiling APs should face downwards to the recipients.
Occlusions
The real world environment is often not a simple box. We may have a number of obstacles to overcome.
In general we want to exclude these interferers from our inclusion zone, and so we can adjust the encapsulation to factor them out.
Typical examples are:
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An awkward shaped corner in an room.
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A fire escape
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Lighting structures in ceiling spaces
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Electrical obstacles (microwave ovens)
The following figure shows good placement strategy to avoid such obstacles.
Sample Deployments
Basic floor plan
Using the principles outlined we present some example configurations for small venue deployments (sub 50m scale) and consider an arbitrary un-square space.
We have a number of options to improve coverage keeping install and hardware costs down and to keep location quality in check.
Office
Real world solutions rarely fall into simple square box shapes.
The following deployment makes some compromises in terms of full coverage to increase general accuracy and make installation easier.
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Lower left meeting rooms are excluded from encapsulation as movement inside is understood (AP close association can provide meeting room stats regardless)
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AP 1-6 obliquing
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AP1, AP2, AP4, AP5 channelling
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No alignment issues
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AP5, avoid occlusion
Retail
Retail spaces are often more uniform in nature. Box shaped venues and knowledge of common patterns of shelving can be leveraged to give best approach to placements.
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Encapsulation
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Channelling
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Obliquing
