On the Impact of Phase Noise on Monostatic Sensing in OFDM ISAC Systems

TL;DR

This paper analyzes how phase noise from oscillator imperfections affects monostatic sensing in OFDM-based ISAC systems, providing insights for hardware and algorithm design in future 6G networks.

Contribution

It introduces a misspecified Cramér-Rao bound analysis to evaluate phase noise impact on sensing performance in OFDM ISAC systems with various oscillator types and conditions.

Findings

Phase noise significantly degrades range and velocity accuracy under certain conditions.

Oscillator type and bandwidth critically influence sensing performance.

Guidelines for hardware and algorithm design in 6G ISAC systems are established.

Abstract

Phase noise (PN) can become a major bottleneck for integrated sensing and communications (ISAC) systems towards 6G wireless networks. In this paper, we consider an OFDM ISAC system with oscillator imperfections and investigate the impact of PN on monostatic sensing performance by performing a misspecified Cram\'er-Rao bound (MCRB) analysis. Simulations are carried out under a wide variety of operating conditions with regard to SNR, oscillator type (free-running oscillators (FROs) and phase-locked loops (PLLs)), 3-dB bandwidth of the oscillator spectrum, PLL loop bandwidth and target range. The results provide valuable insights on when PN leads to a significant degradation in range and/or velocity accuracy, establishing important guidelines for hardware and algorithm design in 6G ISAC systems.