  We propose a probabilistic shaping approach for region-of-interest signaling,
where a low-rate signal controls the desired probabilistic ranges of a
high-rate data stream using a flexible distribution controller. In addition, we
introduce run-length-aware values for frozen bit indices in systematic polar
code to minimize the run-length without using run-length-limited code. Our
compact system can support soft-decision forward-error-correction decoding with
excellent spectral efficiency compared with related work based on hybrid
modulation schemes.
