Abstract
Received-signal-strength-based (RSS-based) device-free localization (DFL) is a promising technique since it is able to localize the person without attaching any electronic device. This technology requires measuring the RSS of all links in the network constituted by several radio frequency (RF) sensors. It is an energy-intensive task, especially when the RF sensors work in traditional work mode, in which the sensors directly send raw RSS measurements of all links to a base station (BS). The traditional work mode is unfavorable for the power constrained RF sensors because the amount of data delivery increases dramatically as the number of sensors grows. In this paper, we propose a binary work mode in which RF sensors send the link states instead of raw RSS measurements to the BS, which remarkably reduces the amount of data delivery. Moreover, we develop two localization methods for the binary work mode which corresponds to stationary and moving target, respectively. The first localization method is formulated based on grid-based maximum likelihood (GML), which is able to achieve global optimum with low online computational complexity. The second localization method, however, uses particle filter (PF) to track the target when constant snapshots of link stats are available. Real experiments in two different kinds of environments were conducted to evaluate the proposed methods. Experimental results show that the localization and tracking performance under the binary work mode is comparable to the those in traditional work mode while the energy efficiency improves considerably.
Highlights
When a target enters a monitored region surrounded by a network of radio frequency (RF) sensors, the target will influence the of radio signals emitted by sensors, e.g., shadow and reflect the radio signals [1]
The RF sensor network is comprised of CC2530 nodes, which are fully compatible with IEEE 802.15.4 standard and work at 2.4 GHz frequency band
The RF sensors were equipped with directional antennas [37] which have 110 degrees of horizontal beamwidth to mitigate the interference outside the monitored region
Summary
When a target (person) enters a monitored region surrounded by a network of radio frequency (RF) sensors, the target will influence the of radio signals emitted by sensors, e.g., shadow and reflect the radio signals [1]. We propose a new work mode in which the RF sensors only output two states of a link: obstructed and unobstructed. To localize the device-free target when the sensors work in the binary mode, it is necessary to develop new localization methods since previous localization methods [1,8,12,13,14] can only work in the traditional work mode. We perform target tracking in the binary work mode by employing PF which proves to be able to accurately estimate the position of the target.
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