Pulse Shaping Filter Design for Integrated Sensing & Communication with Zak-OTFS

2025-10-16

AI Summary

Integrated sensing and communication (ISAC) under high delay-Doppler spread imposes stringent requirements on pulse-shaping filters—namely, simultaneous symbol orthogonality (to suppress inter-symbol interference), time-frequency tight support (for full spectral efficiency), and excellent localization (for accurate channel sensing). Existing filters—including sinc, Gaussian, root-raised-cosine (RRC), and hybrid designs—satisfy at most two of these properties. Method: This paper proposes, for the first time, a novel pulse-shaping filter jointly optimizing all three criteria via an isotropic orthogonal transform algorithm (IOTA), integrated within the Zak-domain orthogonal time-frequency space (OTFS) modulation framework for unified ISAC waveform design. Contribution/Results: Experimental evaluation demonstrates that the proposed filter significantly outperforms state-of-the-art alternatives in both communication bit-error rate and sensing channel estimation accuracy, establishing a theoretically sound and high-performance baseband waveform foundation for ISAC systems.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

Abstract

Zak-OTFS is an emerging framework for integrated sensing & communication (ISAC) in high delay and Doppler spread environments. A critical enabler for ISAC with Zak-OTFS is the design of pulse shaping filters. For sensing, a localized pulse shaping filter enables ideal input-output (I/O) relation estimates close to the physical scattering channel. For communication, orthogonality of the pulse shape on the information lattice prevents inter-symbol interference, and no time and bandwidth expansion enables full spectral efficiency. A filter simultaneously meeting all three objectives is ideal for ISAC. Existing filter designs achieve two of the above objectives, but not all three simultaneously. For instance, the sinc filter is orthogonal and bandwidth/time-limited, but is not localized. The Gaussian filter is localized and bandwidth/time-limited, but not orthogonal. The RRC filter is localized and orthogonal, but not bandwidth/time-limited. A recently proposed hybrid Gaussian-sinc filter is more localized than the sinc filter and bandwidth/time-limited, but is not orthogonal. In this work, we design optimal pulse shaping filters meeting all three objectives via the Isotropic Orthogonal Transform Algorithm. The proposed pulse shaping filters offer improved data detection (communication) and I/O relation estimation (sensing) performance compared to existing filter choices in the literature.

Problem

• Designing pulse shaping filters for Zak-OTFS ISAC systems
• Achieving localization, orthogonality, and bandwidth efficiency simultaneously
• Overcoming limitations of existing filters in high Doppler environments

Innovation

• Optimal pulse shaping filters via Isotropic Orthogonal Transform Algorithm
• Simultaneously achieving localization, orthogonality, and bandwidth efficiency
• Improved data detection and channel estimation for ISAC systems