Advanced Spatial Modulation-Aided Integrated Sensing and Backscatter Communication: System Design and Performance Analysis

This paper proposes an innovative framework that integrates electromagnetic inverse scattering with improved quadrature spatial modulation (IQSM) to simultaneously accomplish sensing, identification, and backscatter communication. Specifically tailored for energy- and spectrum-efficient wireless operations in highly cluttered environments, the proposed system employs distinct load impedance modulation at the tags to effectively separate structural and antenna mode signatures. Structural mode signals are processed using inverse scattering combined with compressive sensing techniques, enabling precise localization of both tags and surrounding clutter. Concurrently, antenna mode signals are utilized for accurate tag identification. In addition, the antenna mode enables the acquisition of the reliable channel state information (CSI), facilitating the integration of IQSM schemes into the backscatter communication module. Furthermore, we present a theoretical analysis by deriving the bit error probability (BEP) for the proposed system. The proposed system is validated through a proof-of-concept experimental setup consisting of transmit and receive arrays, each configured as a 3×3 uniform linear antenna array (ULA). Both simulation and experimental results confirm that the inverse scattering-based approach achieves high-precision sensing and accurate identification of tags individually or in combination. Additionally, the integration of IQSM significantly enhances spectral efficiency (SE) and data throughput, compared with the state-of-the-art systems that do not incorporate spatial modulation (SM) techniques. These findings highlight the effectiveness and practical viability of the proposed integrated sensing and communication system for challenging clutter-rich scenarios.