Constant Modulus Waveforms for IoT-Centric Integrated Sensing and Communications

2025-06-26

AI Summary

In resource-constrained Internet-of-Things (IoT) scenarios, orthogonal frequency-division multiplexing (OFDM)-based integrated sensing and communication (ISAC) systems suffer from high peak-to-average power ratio (PAPR), leading to excessive power consumption, elevated hardware cost, and increased receiver complexity. To address this, we propose a low-complexity single-carrier constant-envelope waveform achieving strict unit PAPR. The waveform jointly employs frequency and phase modulation, preserving communication data rate while significantly enhancing radar ambiguity function performance and range–velocity resolution. By co-optimizing bandwidth efficiency, sensing accuracy, and receiver implementation complexity, our design simultaneously ensures high-reliability communication and high-precision sensing—without compromising the low-power, compact-size, and low-cost advantages essential for IoT endpoints. The resulting physical-layer ISAC solution is hardware-efficient and practically deployable in resource-limited IoT terminals.

Technology Category

• Application Domains: Internet of Things, Sensor Networks & Smart Cities
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Security and Privacy: Applications of cryptography
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Integrated sensing and communications (ISAC) is considered a key enabler to support application scenarios such as the Internet-of-Things (IoT) in which both communications and sensing play significant roles. Multi-carrier waveforms, such as orthogonal frequency division multiplexing (OFDM), have been considered as good candidates for ISAC due to their high communications data rate and good time bandwidth property for sensing. Nevertheless, their high peak-to-average-power-ratio (PAPR) values lead to either performance degradation or an increase in system complexity. This can make OFDM unsuitable for IoT applications with insufficient resources in terms of power, system complexity, hardware size or cost. This article provides IoT-centric constant modulus waveform designs that leverage the advantage of unit PAPR and thus are more suitable in resource-limited scenarios. More specifically, several single-carrier frequency and/or phase-modulated waveforms are considered. A comprehensive discussion on their radar sensing and communications performance is conducted based on performance metrics, including the radar ambiguity function, the bandwidth property, the data rate, and the communications receiver complexity.

Problem

• High PAPR in OFDM limits IoT ISAC performance
• Resource constraints challenge IoT sensing and communication
• Designing constant modulus waveforms for efficient IoT ISAC

Innovation

• IoT-centric constant modulus waveform designs
• Leverage unit PAPR for resource-limited scenarios
• Single-carrier frequency and phase-modulated waveforms