Transmission Mask Analysis for Range-Doppler Sensing in Half-Duplex ISAC

TL;DR

This paper analyzes transmission masks in half-duplex ISAC systems, deriving their expected range-Doppler response and revealing Doppler-invariance of range sidelobes, along with optimal masking strategies for different dynamic regimes.

Contribution

It provides a closed-form analysis of transmission masks in ISAC, demonstrating Doppler-invariance of range sidelobes and identifying optimal masks for various mobility scenarios.

Findings

Range sidelobes are Doppler-invariant.

Cyclic difference sets are optimal in moderate dynamics.

Tradeoff exists between Doppler sidelobe energy and mainlobe fluctuation.

Abstract

In this paper, we analyze the periodic transmission masks for MASked Modulation (MASM) in half-duplex integrated sensing and communication (ISAC), and derive their closed-form expected range-Doppler response $\mathbb{E}\{r(k,l,\nu)\}$. We show that range sidelobes ($k\neq l$) are Doppler-invariant, extending the range-sidelobe optimality to the 2-D setting. For the range mainlobe ($k=l$), periodic masking yields sparse Doppler sidelobes: Cyclic difference sets (CDSs) (in particular Singer CDSs) are minimax-optimal in a moderately dynamic regime, while in a highly dynamic regime the Doppler-sidelobe energy is a concave function of the mask autocorrelation, revealing an inevitable tradeoff with mainlobe fluctuation.