Low-Complexity Single-Chain ISAC Receiver via Beat-Signal Domain FRFT

Abstract

This letter introduces a single-chain Fractional Fourier Transform (FRFT)-based receiver for integrated sensing and communication (ISAC) that eliminates the need for matched-filter banks. While Slope-Shift Keying (SSK) is a promising modulation technique for automotive FMCW radar, conventional coherent receivers require a bank of matched filters, making the receiver processing complexity scale linearly with the modulation order. To overcome this limitation, we apply the FRFT in the beat-signal domain. By exploiting the chirp-rate-dependent energy focusing property, this approach converts slope discrimination into a fractional-domain peak detection problem. Consequently, it enables efficient high-order symbol detection using only a single standard receive processing chain. Simulation results demonstrate that the proposed scheme reduces the modulation-order-dependent digital processing burden while maintaining stable bit error rate (BER) performance and radar sensing performance under high-mobility Rician multipath V2V conditions.