  The industrial point of view towards integrated sensing and communication
(ISAC), the preference is to leverage existing resources and fifth-generation
(5G) infrastructure to minimize deployment costs and complexity. In this
context, we explore the utilization of current 5G new radio (NR) signals
aligned with 3rd generation partnership project (3GPP) standards. Positioning
reference signals (PRS) for sensing and physical downlink shared channel
(PDSCH) for communication have been chosen to form an ISAC framework. However,
PRS-based sensing suffers from Doppler ambiguity when the Doppler frequency
shift is severe. To address this challenge, we introduce a novel method within
the ISAC system that leverages the demodulation reference signal (DMRS) present
in PDSCH to eliminate Doppler ambiguity. Furthermore, we formulate a resource
allocation problem between PRS and PDSCH to achieve a Pareto optimal point
between communication and sensing without Doppler ambiguity. Through
simulations and analysis, we demonstrate the effectiveness of our proposed
method on joint DMRS-PRS exploitation in mitigating Doppler ambiguity and the
efficiency of the resource allocation scheme in achieving Pareto optimality for
ISAC within a 5G NR framework.
