ISAC in Scalable Cell-Free Massive MIMO Networks With Hardware Impairments

The convergence of integrated sensing and communication (ISAC) with cell-free massive MIMO (CF-mMIMO) is a promising enabler for next-generation wireless networks, offering simultaneous connectivity and environmental awareness. This paper introduces a scalable CF-mMIMO-based ISAC framework that explicitly accounts for transceiver hardware impairments and supports joint downlink data transmission and sensing. To balance sensing reliability and communication performance, scalable hardware impairments (HWIs)-aware communication and sensing precoders are designed in conjunction with a heuristic fractional power allocation strategy. Furthermore, building on a non-scalable ideal HWI-aware maximum a posteriori ratio test (MAPRT) detector, two novel scalable target detection algorithms, the partial pseudo-MAPRT (P-pMAPRT) and the improved partial pseudo-MAPRT (IP-pMAPRT) detectors, are proposed. Numerical results demonstrate that the proposed framework achieves competitive sensing accuracy, even in the presence of severe HWIs, while maintaining high spectral efficiency per user across a broad range of operating conditions.