Multipath Exploitation for Human Activity Recognition Using a Radar Network
Ronny G. Guendel, Nicolas C. Kruse, Francesco Fioranelli, Alexander Yarovoy
Abstract
In this study, the problem of multipath in radar sensor networks for human activity recognition (HAR) has been examined. Traditionally considered as a source of additional clutter, the multipath is being investigated for its potential to be exploited through the creation of virtual radar nodes. These virtual nodes are conceptualized to observe targets from aspect angles that differ from those of physically existing radars. To realize this idea, an innovative processing pipeline is proposed that extracts information from multipath signals to improve HAR. The pipeline isolates and tracks the line-of-sight (LOS) and multipath components of a moving human target performing continuous sequences of activities observed by a network of 3 radar sensors. Furthermore, the method has been verified with experimental data consisting of 6 activities and 14 volunteers by comparing classification metrics with the use of a single radar as well as only the LOS components of the 3 radars in the network. A 12-layer convolutional neural network (CNN) classifier has been designed to operate on range-Doppler (RD) images derived from the LOS and multipath components, extracted by the proposed method. A substantial performance improvement using the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">leave-one-person-out</i> test set is demonstrated in the order of + 11% by exploiting a multi-radar network with its LOS and multipath components.