The system had been designed to collect footfall data—the number of people who pass through an area—when we needed to be measuring viewable impressions: the number of opportunities for people to engage with Soofa Sign ad content.

The system had also been built under the assumption that the Wi-Fi sensor would be able to consistently identify unique Wi-Fi enabled devices, of which some set of those devices would represent people carrying Wi-Fi enabled smartphones. However, since the initial design of the system, the industry had shifted towards device identification randomization for the sake of privacy, making it difficult to track unique devices. My new system had to count devices without knowing exactly how many were unique.