Fundamental Trade-offs in Quantized Hybrid Radar Fusion: A CRB-Rate Perspective

Abstract

Hybrid radar fusion (HRF), which combines monostatic and bistatic sensing in a common spectrum, offers enhanced spatial diversity, but is particularly vulnerable to quantization error effects due to the large power imbalance between the direct and reflected uplink signals. Although finite-resolution analog-to-digital converters (ADCs) have been considered in the existing literature on integrated sensing and communication (ISAC), their role in HRF architectures has not yet been characterized. This paper develops a finite-resolution quantized sensing-communication framework for HRF systems by deriving a Cramer-Rao bound (CRB) and achievable uplink rate. Tight lower bounds on the Fisher information matrix and the communication rate are obtained, enabling a tractable characterization of finite-resolution quantized HRF. The fundamental sensing-communication trade-off is then characterized through two complementary constrained formulations: CRB minimization subject to per-user uplink rate requirements, and sum-rate maximization subject to a CRB constraint, whose solutions trace the CRB-rate trade-offs in HRF. Numerical results reveal how ADC resolution, dynamic range, and system configuration jointly shape this boundary and show that HRF performance can degrade sharply under coarse quantization due to the weak bistatic component, providing design guidelines for selecting ADC architectures and operating regimes in future HRF-enabled ISAC systems.