Rate and Detection-Error Exponent Tradeoff for Joint Communication and Sensing of Fixed Channel States

TL;DR

This paper investigates the fundamental limits of joint communication and sensing for fixed channel states, characterizing the tradeoff between communication rate and sensing error exponent in mono-static and bi-static scenarios.

Contribution

It provides an exact tradeoff characterization for mono-static sensing without sensing assistance and introduces a new achievable region for bi-static sensing, highlighting the benefits of joint strategies.

Findings

Closed-loop sensing improves the tradeoff in mono-static scenarios.

Joint strategies outperform successive strategies in bi-static sensing.

The rate of communication significantly influences the tradeoff region.

Abstract

We study the information-theoretic limits of joint communication and sensing when the sensing task is modeled as the estimation of a discrete channel state fixed during the transmission of an entire codeword. This setting captures scenarios in which the time scale over which sensing happens is significantly slower than the time scale over which symbol transmission occurs. The tradeoff between communication and sensing then takes the form of a tradeoff region between the rate of reliable communication and the state detection-error exponent. We investigate such tradeoffs for both mono-static and bi-static scenarios, in which the sensing task is performed at the transmitter or receiver, respectively. In the mono-static case, we develop an exact characterization of the tradeoff in open-loop, when the sensing is not used to assist the communication. We also show the strict improvement brought by a closed-loop operation, in which the sensing informs the communication. In the bi-static case, we develop an achievable tradeoff region that highlights the fundamentally different nature of the bi-static scenario. Specifically, the rate of communication plays a key role in the characterization of the tradeoff and we show how joint strategies, which simultaneously estimate message and state, outperform successive strategies, which only estimate the state after decoding the transmitted message.