Cyclic Prefix-Based Passive Sensing for 6G Integrated Sensing and Communication in Power-Constrained Optical Wireless Systems

Abstract

Integrated sensing and communication (ISAC) is a key technology for 6G networks. Optical wireless communication (OWC) offers high data rates and wide bandwidth, enabling efficient sensing and communication integration. This paper proposes a passive sensing scheme that exploits the cyclic prefix (CP) in a clipping-enhanced optical OFDM (CEO-OFDM) system without dedicated sensing signals. CEO-OFDM mitigates clipping distortion under peak power constraints while enabling target detection and time difference of arrival (TDOA) estimation. The Cramér-Rao lower bound (CRLB) is derived to analyze sensing performance. Simulation results show that the proposed system outperforms conventional DCO-OFDM and ACO-OFDM in both sensing accuracy and bit error rate (BER). In multiframe estimation, the TDOA error is about four and two times lower than those of DCO-OFDM and ACO-OFDM, respectively.