Low-PAPR OFDM-ISAC Waveform Design Based on Frequency-Domain Phase Differences

2025-03-17

AI Summary

High peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) waveforms severely limits full-spectrum integrated sensing and communication (ISAC) reuse. Method: This paper introduces, for the first time, frequency-domain phase difference (PD) as a novel degree of freedom to construct a PD-based OFDM-ISAC waveform architecture. A joint optimization model is formulated, incorporating time–frequency coupling constraints, unit-modulus constraints in the frequency domain, PD constraints, and a low-PAPR objective. An ADMM-based non-convex algorithm—ADMM-PLPOI—is designed to jointly optimize frequency-domain phase control, unit-modulus compliance, and time-domain PAPR reduction. Results: Simulations demonstrate that the proposed method reduces PAPR by 3.2 dB compared to conventional OFDM-ISAC, improves bit-error-rate (BER) performance by approximately 2 dB, and enhances sensing–communication synergy accuracy and hardware implementation feasibility.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Mixed Discrete/Continuous 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
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Low peak-to-average power ratio (PAPR) orthogonal frequency division multiplexing (OFDM) waveform design is a crucial issue in integrated sensing and communications (ISAC). This paper introduces an OFDM-ISAC waveform design that utilizes the entire spectrum simultaneously for both communication and sensing by leveraging a novel degree of freedom (DoF): the frequency-domain phase difference (PD). Based on this concept, we develop a novel PD-based OFDM-ISAC waveform structure and utilize it to design a PD-based Low-PAPR OFDM-ISAC (PLPOI) waveform. The design is formulated as an optimization problem incorporating four key constraints: the time-frequency relationship equation, frequency-domain unimodular constraints, PD constraints, and time-domain low PAPR requirements. To solve this challenging non-convex problem, we develop an efficient algorithm, ADMM-PLPOI, based on the alternating direction method of multipliers (ADMM) framework. Extensive simulation results demonstrate that the proposed PLPOI waveform achieves significant improvements in both PAPR and bit error rate (BER) performance compared to conventional OFDM-ISAC waveforms.

Problem

• Designs low-PAPR OFDM-ISAC waveform for integrated sensing and communications.
• Utilizes frequency-domain phase differences for simultaneous spectrum use.
• Develops ADMM-PLPOI algorithm to optimize waveform performance.

Innovation

• Utilizes frequency-domain phase differences for OFDM-ISAC
• Develops ADMM-PLPOI algorithm for non-convex optimization
• Improves PAPR and BER in OFDM-ISAC waveforms