Strand: scalable trilateration with Node.js

This work reports on the development details and results of an experimental setup for the localization of the attendants of a music festival. The application had to be reporting in real-time the asymmetric crowd density based on the Received Signal Strength Indicator (RSSI) between the attendants’ smartphones and an experimental installation of 24 WiFi access points. The impermanent nature of the application led to the implementation of a cloud-based solution, called “STRAND”. STRAND is based on Node.js components, which communicate through websockets, collect, process and exchange data and continuously report the produced information to the end-user. To cope with the near real-time requirements, and the volatility of the crowd concentration density, STRAND horizontally scales the trilateration component, i.e. the component that estimates the user location based on distance measurements. STRAND was tested during the festival days in July 2018 and the results show a system that copes with very high loads and achieves the temporal and accuracy requirements the were set.