Fundamental Limits of 1-bit ISAC Systems: Capacity Region and Optimal Power Control

TL;DR

This paper explores the capacity limits of 1-bit ISAC systems, revealing that simultaneous optimal communication and sensing are achievable with specific input distributions, and derives optimal power control policies.

Contribution

It characterizes the capacity region of 1-bit ISAC channels with CSI, showing no trade-off between sensing and communication, and develops optimal power control strategies.

Findings

Both capacities can be achieved simultaneously with constant-amplitude inputs.

Optimal power control policies depend on the weighting between sensing and communication.

No trade-off exists between sensing and communication capacities with CSI at the receiver.

Abstract

This paper investigates the fundamental limits of integrated sensing and communication (ISAC) systems with 1-bit receiver quantization. We analyze a Gaussian fading ISAC channel with separate communication and monostatic sensing links, where both communication and sensing receivers are equipped with 1-bit quantizers. When the communication channel state information (CSI) is available at the receiver, we characterize the communication-sensing capacity region of 1-bit ISAC channel and show that no trade-off exists between communication and sensing performance. In particular, both communication and sensing capacities can be simultaneously achieved by a constant-amplitude input distribution with a specific rotational symmetry. For the scenario where communication CSI is also available at the transmitter, we formulate a weighted optimization problem that balances communication and sensing rates in 1-bit ISAC channel under an average power constraint and then derive the corresponding optimal power control policy. The results demonstrate how the optimal power control policy evolves with the weighting parameter, transitioning from a communication-centric, opportunistic transmission to a more uniform allocation as sensing becomes increasingly prioritized.