  Advances in wireless communication and signal processing facilitate
integrated sensing and communication a compelling technology that intrinsically
combines sensing and communication functionalities for the dual purpose
exploitation of wireless hardware resources and pursues mutual benefits.
Consequently, the next generation communications network will be perceptive. In
this article, we provide a review of human related sensing in the context of
ISAC. We first present a general ISAC receiver signal processing framework,
with a focus on human activity recognition. Based on its specific spatial
deployments, we then categorize ISAC HAR into monostatic, bistatic, and
distributed deployments, and discuss their properties, critical research
problems and solutions. To facilitate the system's realization and improve its
recognition performance, we then explore the inherent connections between the
physical layer system parameters and HAR performance metrics. Experimental
results are presented for characterizing the sensing potentials of different
ISAC systems. Finally, we review the technical challenges and identify the open
research problems.
