From the initial experiments and literature survey, we
can imagine a way of classifying multi-directional walking
based on an array of PIR sensors, each of which (and thus
the motion plane of each PIR sensor) is well aligned with the
walking direction we want to detect. Therefore, the main result
of this paper is to demonstrate a novel way of recognizing
walking directions based on an array of PIR sensors, and
discuss the experimental results according to the number of
PIR sensors, the field of view of PIR sensors, and the reduced
feature sets.