Joint Beamforming Design for Active RIS-Assisted ISAC Systems with Transmitter Hardware Impairments

Area of Science:

• Wireless communication
• Signal processing
• Metamaterials

Background:

• Active reconfigurable intelligent surfaces (RIS) offer enhanced signal control compared to passive RIS.
• Integrated sensing and communication (ISAC) systems face challenges from base station (BS) hardware impairments (HWIs).
• Active RIS can mitigate fading and establish virtual line-of-sight (LoS) links in ISAC.

Purpose of the Study:

• To maximize radar output signal-to-noise ratio (SNR) in an active RIS-assisted ISAC system with BS HWIs.
• To jointly design radar receive filters, BS transmit beamforming, and active RIS reflection coefficients.
• To address the non-convex optimization problem considering system constraints and coupling effects.

Main Methods:

• Formulated a radar output SNR maximization problem under BS HWIs and active RIS constraints.
• Developed an alternating optimization (AO)-based iterative framework.
• Employed generalized Rayleigh quotient, semidefinite relaxation, Charnes-Cooper transformation, Dinkelbach transformation, and majorization-minimization.

Main Results:

• Achieved stable convergence of the proposed iterative algorithm.
• Demonstrated significant improvement in radar output SNR under BS transmitter HWIs.
• Validated the effectiveness of joint design for radar and communication performance.

Conclusions:

• The proposed active RIS-assisted ISAC design effectively mitigates BS HWIs.
• Joint optimization of system parameters enhances radar performance in ISAC.
• The developed AO framework provides a robust solution for complex ISAC optimization problems.