Introduction

The document provides guidelines on how to correctly dimension a Wirepas Positioning System in terms of the number of gateways and the number of anchors. The targeted audience is mainly System Integrators (SIs) who wish to deploy a project based on Wirepas Positioning system.

What you’ll learn

• How to use the Wirepas Positioning Dimensioning tool.
• The main dimensioning elements for a Wirepas Positioning system.

What you’ll need

An understanding of the Wirepas Positioning System and its components is required therefore please read the Wirepas Positioning System Overview [1].

Understanding the main dimensioning factors

The main advantage of the Wirepas Positioning system is its flexibility and ease of installation. This is all thanks to its battery-powered infrastructure (i.e. battery-powered Anchors). 

The picture below shows a typical system architecture.

To ensure correct system performance in a Wirepas Positioning project, you will need to install the right amount of Anchors and gateways.

A Wirepas Positioning project includes four elements:

• The infrastructure:
  • Anchors - these create the local mesh network and relay information from the Tags to a gateway.
  • Gateways - these connect the local mesh network to the cloud.
• The Wirepas Positioning Engine (WPE) backend: receives all traffic from the gateway(s) and computes the position of each Tag.
• The asset Tags: generate traffic (RSSI data) each time a localization is performed. This is the main data traffic.
• Sensors (optional): these can be either dedicated devices or be embedded into Tags and Anchors. These generate additional traffic.

To ensure a proper operation of a system in terms of reliability, scalability and power consumption, it is important to deploy the right amount of anchors and gateways..

The table below summarizes the main elements to take into account when dimensioning a project and their influence.

As shown in the above table, there are multiple elements to take into account to properly dimension a system for deployment. In order to ease the dimensioning, Wirepas has developed an Excel spreadsheet to help determine the required number of anchors and gateways for a given use case.

Wirepas Positioning Dimensioning tool

The Wirepas Position Dimensioning tool consists of an Excel spreadsheet which allows to determine the number of anchors and gateways required, based on the project requirements; it also provides indicative lifetime for the anchors. The tool is attached to this document: Wirepas Positioning Dimensioning Tool.

The dimensioning tool also provides an idea on the feasibility of the requirements (i.e. The tool will show an error if the precision requirement does not match or if the number of anchors required for the project is too high or if the throughput generated by the tags cannot be absorbed) 

The results always need to be fine tuned based on:

• Environment specificities.
• Final Power consumption and battery figures (which are provided by the Device supplier).

In the tool the following assumption are taken:

• Environment: typical Factory, Warehouse, Building. Please note that the tool is not designed to simulate chain topologies such as tunnels or mines.
• Tags are equally distributed in the environment in terms of density and traffic generated.

It also assumes that the system is properly installed as described in Wirepas Positioning Installation guidelines [2] document.

Input parameters

In this section we will describe the different input parameters to the tool. All parameters highlighted with colored cell can be changed.

Measurement System

From this dropdown, you can select if you want the measurement system to be in meter or feet.

Tags and Sensors input parameters

• Number of Mobile Tags: Corresponds to the total number of mobile Tags in the network. In case of a multisite configuration it is recommended to run the simulation for each building based on the maximum amount of tags in a given building.
• Average Position Update Rate per tag: (minutes): In case of a mixed network with Tags having different or dynamic localization interval, the average value is computed based on the use case targets.
• Number of Other Sensors: To identify other traffic generators in the network, typically sensors. In case you have dedicated sensors please add them here.
  In case of Sensors embedded in Tag(s) and/or Anchor(s):
  • An Anchor sending a sensor data (i.e. temperature) shall be counted as one sensor.
  • A Tag sending additional packets (i.e. button press) shall also be counted as one sensor.
• Average Sensors Update Rate per Sensors: (minutes): The average packets the sensors will send per minute.
• Diagnostics Update Rate: (minutes): The Diagnostic interval for the Wirepas Massive network diagnostics. Recommended value is 30 minutes for mass production rollout.

Site Information

• Area to cover: This is the total size of the area to cover. In case of multiple floors, you should input the total floor surface. In case of multi building deployment you shall input one building.
• Number of floors: Number of floors. Is only one floor then input 1.

Positioning Accuracy

• Targeted Accuracy: This parameter is used to compute the required Anchor density to achieve a certain level of accuracy. The Wirepas Positioning system is not designed to achieve a reliable and a stable accuracy. The accuracy in a real environment highly depends on the environment (i.e. with a lot of concrete or metal) and the number in this cell shall be taken as a ballpark number in a typical environment.
  Note: In the case of a Smart Building, where a per room accuracy is required, please count one Anchor per room.

Simulation Results

This table provides the simulation results, it includes the required quantity of Anchors and gateway(s) and an estimation of the worst case power consumption of Anchors.

• Recommended number of Anchors: Provides an estimation of the number of Anchors required to achieve the requirements in the input parameters.
• Needed Anchor density (area covered by 1 anchor): Provides an estimation of the area each Anchors shall cover (assuming a well distributed Tags density and Anchors density).
  • Note: The tool will tune the Anchors density based on: 
    • The Targeted accuracy 
    • The Tags density 
    • In case you see the message ‘Error, too high Anchors Density’ then it means your Tags density is too high. Please contact your Wirepas Sales or Support to further study your use case.
• Recommended number of Gateways: Gives an estimation based on the following assumptions:
  • To absorb the traffic generated by the Tags, Sensors and Anchors
  • 1 gateway to cover maximum 30000m²
  • 1 gateway per floor
• Anchors Battery lifetime estimate: The simulator computes here the Battery lifetime of Anchors for 2 battery capacity with the following assumptions / comments:
  • The estimation assumes that the Tags, Anchors and gateway(s) are equally distributed in the area and that the gateway is properly positioned (see Wirepas Positioning Installation guidelines [2]). 
  • The estimation computes the worst case Anchor power consumption, which is for the Anchors nearest the gateway (as they route more traffic because of the mesh topology).
  • You can also input a custom battery capacity to simulate the battery lifetime for another battery capacity.
  • Numbers are only for dimensioning purpose to size which Anchors capacity is needed. Final battery lifetime must come from the device manufacturer.

References

[1] Wirepas Positioning System Overview
[2] Wirepas Massive Tracking Installation guidelines

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