  In this work, we take the initiative in studying the fundamental tradeoff
between communication and quickest change detection (QCD) under an integrated
sensing and communication setting. We formally establish a joint communication
and sensing problem for quickest change detection. Then, by utilizing constant
subblock-composition codes and a modified QuSum detection rule, which we call
subblock QuSum (SQS), we provide an inner bound on the fundamental tradeoff
between communication rate and change point detection delay in the asymptotic
regime of vanishing false alarm rate. We further provide a partial converse
that matches our inner bound for a certain class of codes. This implies that
the SQS detection strategy is asymptotically optimal for our codes as the false
alarm rate constraint vanishes. We also present some canonical examples of the
tradeoff region for a binary channel, a scalar Gaussian channel, and a MIMO
Gaussian channel.
