Detecting outdoor coexistence as a proxy of infectious contact through magnetometer traces

Abstract

If epidemic contact detection using smartphones can be done with sufficiently fine resolution in outdoor environments, so that those who were within the transmissible distance from an infected person may be identified as a potential infected is explored. The smartphone GPS, at least in its current capacity, is not useful to determine the coexistence within a couple meters that is critical for infectious disease transmission is shown. As an alternative, the usage of magnetometers is proposed, which enables the coexistence determination with the required precision, with much less energy consumption than GPS, and with an added bonus of indoor usability.

Empirical Determination of Efficient Sensing Frequencies for Magnetometer-Based Continuous Human Contact Monitoring

“…The employed technologies range from similar Global Positioning System (GPS) positions [ 4 ], similar Wi-Fi fingerprints [ 5 ], Bluetooth peer discovery [ 6 ], and identical cells in mobile communication [ 7 ]. Unfortunately, they either provide position information too coarse to be used for infectious contact detection [ 8 ] (GPS, cellular/Wi-Fi fingerprinting), require infrastructure (cellular/Wi-Fi), cannot be used indoors (GPS), consumes high power (GPS) [ 9 ], or could compromise privacy (Bluetooth beacons). Some recent works [ 8 , 10 ], however, present a new possibility by demonstrating that magnetometer trace analysis can detect the coexistence in close proximity, works both indoors and outdoors, and offers better privacy protection by not revealing any identity.…”

“…Unfortunately, they either provide position information too coarse to be used for infectious contact detection [ 8 ] (GPS, cellular/Wi-Fi fingerprinting), require infrastructure (cellular/Wi-Fi), cannot be used indoors (GPS), consumes high power (GPS) [ 9 ], or could compromise privacy (Bluetooth beacons). Some recent works [ 8 , 10 ], however, present a new possibility by demonstrating that magnetometer trace analysis can detect the coexistence in close proximity, works both indoors and outdoors, and offers better privacy protection by not revealing any identity. In particular, Kuk et al [ 8 ] exploit that the magnetometer readings show high cross-correlation when two smartphones coexist in close distances that could enable disease transmission such as a couple of meters [ 11 ].…”

“…Some recent works [ 8 , 10 ], however, present a new possibility by demonstrating that magnetometer trace analysis can detect the coexistence in close proximity, works both indoors and outdoors, and offers better privacy protection by not revealing any identity. In particular, Kuk et al [ 8 ] exploit that the magnetometer readings show high cross-correlation when two smartphones coexist in close distances that could enable disease transmission such as a couple of meters [ 11 ]. Figure 1 shows example traces generated by two phones held by the people walking side-by-side through a corridor in a university campus.…”

“…To illustrate this point, Table 1 shows the actual energy consumption as we vary the sensing frequency. All high sensing frequencies in the table have been used in the existing magnetometer-based applications such as indoor location and navigation: 10 Hz [ 8 , 12 ], 25 Hz [ 13 , 14 ], 49.65 Hz [ 10 ], 50 Hz [ 15 ], 100 Hz [ 16 , 17 ], and 200 Hz [ 18 ]. Assuming a typical smartphone battery capacity of 2800 mAh (e.g., on Galaxy S5), our measurement using the Monsoon power monitor [ 19 ] shows that the operating duration of a fully charged device is approximately 24 h without sensing anything or running any application (`baseline’ in Table 1 ).…”

“…Kuk et al. [ 8 ] showed that even in outdoors the magnetometer traces can be compared to detect contacts within a few meters where the current GPS can have an order-of-magnitude larger errors. It showed that two closely located smartphones generate highly correlated magnetometer traces, which can be exploited to detect coexistence.…”