Pulse Shaping for Random ISAC Signals: The Ambiguity Function Between Symbols Matters

TL;DR

This paper explores pulse shaping for ISAC signals, focusing on the ambiguity function's role, and proposes an optimization framework to improve signal design by minimizing sidelobes while managing interference and spectral constraints.

Contribution

It introduces a novel pulse shaping design for ISAC, linking the ambiguity functions of data symbols and pulses, and develops algorithms for optimized signal performance.

Findings

Significant reduction in sidelobe levels compared to RRC pulses

Enhanced ISAC signal performance through optimized pulse shaping

Validated theoretical analysis with numerical simulations

Abstract

Integrated sensing and communications (ISAC) has emerged as a pivotal enabling technology for next-generation wireless networks. Despite the distinct signal design requirements of sensing and communication (S&C) systems, shifting the symbol-wise pulse shaping (SWiPS) framework from communication-only systems to ISAC poses significant challenges in signal design and processing This paper addresses these challenges by examining the ambiguity function (AF) of the SWiPS ISAC signal and introducing a novel pulse shaping design for single-carrier ISAC transmission. We formulate optimization problems to minimize the average integrated sidelobe level (ISL) of the AF, as well as the weighted ISL (WISL) while satisfying inter-symbol interference (ISI), out-of-band emission (OOBE), and power constraints. Our contributions include establishing the relationship between the AFs of both the random data symbols and signaling pulses, analyzing the statistical characteristics of the AF, and developing algorithmic frameworks for pulse shaping optimization using successive convex approximation (SCA) and alternating direction method of multipliers (ADMM) approaches. Numerical results are provided to validate our theoretical analysis, which demonstrate significant performance improvements in the proposed SWiPS design compared to the root-raised cosine (RRC) pulse shaping for conventional communication systems.