Photonics-assisted integrated sensing and communication with ranging resolution improvement by multiple signal classification

The combination of orthogonal frequency-division multiplexing (OFDM) with photonics-assisted millimeter-wave (MMW) technology serves as an effective solution for realizing integrated sensing and communication (ISAC) systems. In this paper, we experimentally demonstrate a low-cost and simple photonics-assisted OFDM ISAC system using intensity modulation and envelope detection. Nonlinear distortion in the communication function of this ISAC system is compensated using decision feedback frequency domain Volterra nonlinear equalization (DF-FD-VNLE). Furthermore, the multiple signal classification (MUSIC) algorithm, implemented through subspace decomposition, is employed to enhance the low ranging resolution in radar function with limited waveform bandwidth. Experimental results indicate that the DF-FD-VNLE can achieve a 1.8 dB receiver sensitivity improvement at the hard-decision forward error correction (HD-FEC) threshold for the 4 Gbps OFDM signal over 1 m wireless transmission compared to linear equalization and 0.9 dB receiver sensitivity compared to conventional frequency domain Volterra nonlinear equalization (FD-VNLE). By utilizing the MUSIC algorithm, the radar performance is significantly improved compared to fast Fourier transform (FFT), resulting in an enhancement from 15 cm to 1 cm for single target detection and from 21 cm to 10 cm for dual target detection. Additionally, there is a significant improvement in PSLR by 18.6 dB.