Integrated Sensing and Communication Exploiting Prior Information: How Many Sensing Beams are Needed?

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This paper studies an integrated sensing and communication (ISAC) system where a multi-antenna base station (BS) aims to communicate with a single-antenna user in the downlink and sense the unknown and random angle parameter of a target via exploiting its prior distribution information.

• We consider a general transmit beamforming structure where the BS sends one communication beam and potentially one or multiple dedicated sensing beam(s).
• Firstly, motivated by the periodic feature of the angle parameter, we derive the periodic posterior Cram\'{e}r-Rao bound (PCRB) for quantifying a lower bound of the mean-cyclic error (MCE), which is more accurate than the conventional PCRB for bounding the mean-squared error (MSE).
• Then, note that more sensing beams enable higher flexibility in enhancing the sensing performance, while also generating extra interference to the communication user.