Sensing-as-a-service is anticipated to be the core feature of 6G perceptive
mobile networks (PMN), where high-precision real-time sensing will become an
inherent capability rather than being an auxiliary function as before. With the
proliferation of wireless connected devices, resource allocation in terms of
the users' specific quality-of-service (QoS) requirements plays a pivotal role
to enhance the interference management ability and resource utilization
efficiency. In this article, we comprehensively introduce the concept of
sensing service in PMN, including the types of tasks, the
distinctions/advantages compared to conventional networks, and the definitions
of sensing QoS. Subsequently, we provide a unified RA framework in
sensing-centric PMN and elaborate on the unique challenges. Furthermore, we
present a typical case study named "communication-assisted sensing" and
evaluate the performance trade-off between sensing and communication procedure.
Finally, we shed light on several open problems and opportunities deserving
further investigation in the future