Zero-Padding 2D-DFT Scheme for Photonics-Assisted W-Band Fiber-Wireless ISAC System with Orthogonal Time Frequency Space Modulation

In this paper, an orthogonal time frequency space (OTFS) waveform based on photonics-assisted is proposed in a W-band fiber-wireless integrated sensing and communication (ISAC) system. The OTFS signal is modulated in the delay-Doppler (DD) domain, which enhances the robustness of the signal against frequency-selective fading. And a zero-padding two-dimensional discrete Fourier transform (ZP-2D-DFT) scheme is proposed for the OTFS-based photonics-assisted W-band fiber-wireless ISAC system. Compared with the traditional 2D-DFT scheme, the proposed ZP-2D-DFT scheme can significantly improve the sensing accuracy and theoretical resolution of ISAC systems. In addition, a proof-of-concept experiment of the OTFS-based photonics-assisted W-band fiber-wireless ISAC system is demonstrated using the optical heterodyne up-conversion technique. The experimental results show that, after transmission over a 50 km standard single mode fiber (SSMF) and a 3.2 m wireless link, a communication data rate of 5.44 Gbit/s and a theoretical ranging resolution of 1.58 cm are achieved simultaneously. Moreover, by using the OTFS waveform, it can obtain a receiver sensitivity gain of 1.18 dB compared to the OFDM signal in the W-band fiber-wireless ISAC system.