Secure OFDM-IM ISAC With Artificial-Noise-Aided Index Deception

2026-07-21

AI Summary

This work addresses the challenge in integrated sensing and communication (ISAC) where sensing targets may also act as eavesdroppers, making it difficult for conventional approaches to simultaneously ensure secure communication and effective sensing. To overcome this, the paper proposes an artificial noise (AN)-aided secure OFDM with index modulation (OFDM-IM) ISAC framework. Specifically, AN is injected into inactive subcarriers to safeguard communication confidentiality, while spatial precoding is employed at the legitimate receiver to cancel the AN. Concurrently, sensing energy is concentrated on active subcarriers to perform index spoofing against the target, thereby enhancing directional transmit power. By innovatively exploiting the inherent sparsity of OFDM-IM, the proposed scheme jointly achieves physical-layer security and improved sensing performance. Simulations demonstrate that, compared to conventional OFDM, the approach significantly boosts signal power at the target while maintaining high communication security.

Abstract

We propose an artificial noise (AN)-aided, secure OFDM with index modulation (OFDM-IM) framework for integrated sensing and communication (ISAC). Consider a security-critical scenario, where the sensing target is also a potential eavesdropper. Instead of suppressing the signal power toward the target, the proposed method injects AN into inactive OFDM-IM subcarriers. The precoder spatially nulls the AN at the legitimate receiver, while projecting active-subcarrier energy levels toward the target to deceive its index detector. Since the monostatic ISAC transmitter knows the AN waveform, the same inactive subcarriers also contribute to sensing. We formulate this scenario as an optimization problem that maximizes transmit power toward the target while providing secure communication with a legitimate receiver. Numerical results show that the proposed scheme improves targeted transmit power compared to classical OFDM.

Problem

• ISAC
• physical layer security
• index modulation
• eavesdropping target
• secure communication

Innovation

• Artificial Noise
• Index Modulation
• Integrated Sensing and Communication
• Secure Transmission
• OFDM-IM