Isella, L. et al. Close encounters in a pediatric ward: measuring face-to-face proximity and mixing patterns with wearable sensors.
Since the radiofrequency used to sense proximity cannot propagate through a human body, this enabled detection of face-to-face proximity relations.
The weight (w_{ij}) of an edge i-j represents the total cumulative time spent in face-to-face proximity by individuals i and j during the whole study duration.
In this paper, we have investigated whether low resolution co-presence information can be used as a substitute for detailed face-to-face proximity data, both from the point of view of extracting large-scale structural and statistical features of the temporal contact network in a population and in data-driven models of epidemic processes in a population.
Optimally, data collection with wearable sensors should thus contain both high resolution data about relative positions of individuals, in order to detect face-to-face proximity, and coarser co-presence information to inform for instance on mobility patterns within buildings or complement potential data losses.
Exchange of these low-power packets thus becomes a proxy for face-to-face proximity of individuals.
When a relation of face-to-face proximity is detected, it is relayed from the RFID devices to the RFID readers installed in the hospital ward.
Specifically, we use active Radio-Frequency Identification Devices RFIDD) as wearable sensors to measure face-to-face proximity with a high spatial and temporal resolution [24] [26].
In these networks, a node represents an individual, and an edge is drawn between two individuals whenever a face-to-face proximity event involving them was recorded.
For the ISI and SFHH deployments the devices were configured for a shortest spatial range of about 1 meter (for packets emitted at the lowest power), which affords the detection of face-to-face proximity.
The weakest power levels are used to assess face-to-face proximity as packets can only be detected when persons are facing one another (no shielding of the RFID tags) within about 1 m.
