Capacity-CRB Tradeoff in OFDM Integrated Sensing and Communication Systems

TL;DR

This paper investigates the fundamental tradeoff between sensing and communication in OFDM-based ISAC systems, deriving the Capacity-BCRB region and optimal power allocation strategies through theoretical analysis and simulations.

Contribution

It introduces a general framework for analyzing the sensing-communication tradeoff in OFDM ISAC systems and characterizes the optimal input distribution and power allocation.

Findings

Gaussian input distribution achieves Pareto boundary

Convex power allocation solves the tradeoff optimization

Numerical results verify theoretical insights

Abstract

Integrated sensing and communication (ISAC) has emerged as a key technology for future communication systems. In this paper, we provide a general framework to reveal the fundamental tradeoff between sensing and communication in OFDM systems, where a unified ISAC waveform is exploited to perform both tasks. In particular, we define the Capacity-Bayesian Cramer Rao Bound (BCRB) region in the asymptotically case when the number of subcarriers is large. Specifically, we show that the asymptotically optimal input distribution that achieves the Pareto boundary point of the Capacity-BCRB region is Gaussian and the entire Pareto boundary can be obtained by solving a convex power allocation problem. Moreover, we characterize the structure of the sensing-optimal power allocation in the asymptotically case. Finally, numerical simulations are conducted to verify the theoretical analysis and provide useful insights.