  With spectrum resources becoming congested and the emergence of
sensing-enabled wireless applications, conventional resource allocation methods
need a revamp to support communications-only, sensing-only, and integrated
sensing and communication (ISaC) services together. In this letter, we propose
two joint spectrum partitioning (SP) and power allocation (PA) schemes to
maximize the aggregate sensing and communication performance as well as
corresponding energy efficiency (EE) of a semi-ISaC system that supports all
three services in a unified manner. The proposed framework captures the
priority of the distinct services, impact of target clutters, power budget and
bandwidth constraints, and sensing and communication quality-of-service (QoS)
requirements. We reveal that the former problem is jointly convex and the
latter is a non-convex problem that can be solved optimally by exploiting
fractional and parametric programming techniques. Numerical results verify the
effectiveness of proposed schemes and extract novel insights related to the
impact of the priority and QoS requirements of distinct services on the
performance of semi-ISaC networks.
