  The sixth-generation (6G) network is expected to provide both communication
and sensing (C&S) services. However, spectrum scarcity poses a major challenge
to the harmonious coexistence of C&S systems. Without effective cooperation,
the interference resulting from spectrum sharing impairs the performance of
both systems. This paper addresses C&S interference within a distributed
network. Different from traditional schemes that require pilot-based
high-frequency interactions between C&S systems, we introduce a third party
named the radio map to provide the large-scale channel state information (CSI).
With large-scale CSI, we optimize the transmit power of C&S systems to maximize
the signal-to-interference-plus-noise ratio (SINR) for the radar detection,
while meeting the ergodic rate requirement of the interfered user. Given the
non-convexity of both the objective and constraint, we employ the techniques of
auxiliary-function-based scaling and fractional programming for simplification.
Subsequently, we propose an iterative algorithm to solve this problem.
Simulation results corroborate our idea that the extrinsic information, i.e.,
positions and surroundings, is effective to decouple C&S interference.
