Generalized Adaptive Spreading Modulation: A Novel Waveform for Integrated Sensing and Communication Oriented Vehicular Applications

This study aims to present a comparative analysis of existing waveforms for Integrated sensing and communication (ISAC) in vehicular environments. A novel multi-carrier framework based on Generalized Adaptive Spreading Modulation (GASM) is proposed for ISAC-enabled vehicular environments. The GASM waveform offers symbol spreading in both time and frequency domains with tunable spreading parameters, which allows the proposed GASM-based waveform to adapt according to the rapid time-frequency variations of the fading channel and combat the most common system impairments such as carrier frequency offset (CFO) and symbol timing offset (STO). The GASM scheme is the generalization of various existing waveforms such as Orthogonal frequency-division multiplexing (OFDM), Fractional Fourier Transform based OFDM (FrFT-based OFDM), and Orthogonal Chirp Division Multiplexing (OCDM). The proposed GASM-based ISAC system is evaluated in terms of average bit error rate (ABER) for communication and ambiguity function (AF) for range and Doppler capabilities. The performance of GASM-based ISAC system is found superior when compared with existing waveforms, i.e., OFDM, FrFT-based OFDM, OCDM, Generalized Frequency Division Multiplexing (GFDM), and Orthogonal Time Frequency Space (OTFS) modulation.