A Non-Orthogonal Waveform Enabled Spectrally Efficient Over-the-Air ISAC Transmission

This paper presents an experimental investigation into the feasibility of non-orthogonal waveform design for integrated sensing and communications (ISAC) systems. The integration of sensing and communication functionalities in wireless systems holds promise for enhancing spectral efficiency and enabling diverse applications. We propose a novel approach utilizing non-orthogonal waveforms, termed spectrally efficient frequency division multiplexing (SEFDM), to facilitate sensing and communication tasks. The system model encompasses multi-user MIMO-SEFDM communication and digital MIMO radar sensing, considering both omnidirectional and directional beamforming scenarios. We formulate an optimization problem to balance performance between communication and sensing functions. Moreover, communication performance trade-offs between orthogonal and non-orthogonal signal waveforms are studied. Through practical experiments conducted on an established over-the-air experimental platform, we evaluate the performance of the proposed ISAC waveform design and showcase the performance benefits of non-orthogonal waveform design in improving spectral efficiency, sensing beampattern accuracy, and communication quality.