Sum-rate Maximization for RIS-assisted Integrated Sensing and Communication Systems with Manifold Optimization

• Published in: IEEE transactions on communications Vol. 71; no. 8; p. 1
• Main Authors: Shtaiwi, Eyad, Zhang, Hongliang, Abdelhadi, Ahmed, Lee Swindlehurst, A., Han, Zhu, Vincent Poor, H.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Array signal processing; Beamforming; Communication systems; Communications systems; integrated sensing and communications; Interference; interference mitigation; manifold optimization; Manifolds; Mathematical programming; Optimization; Radar; reconfigurable intelligent surface; Sensors; sum-rate maximization; Wireless communication systems
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2023.3277872

Integrated sensing and communication (ISAC) is a key enabler for next-generation wireless communication systems to improve spectral efficiency. However, the coexistence of sensing and communication functionalities can cause harmful interference. In this paper, we propose to use a reconfigurable intelligent surface (RIS) in conjunction with ISAC to address this issue. The RIS is composed of a large number of low-cost elements that can adjust the amplitude and phase shift of impinging signals, thus providing a relatively high beamforming gain. To maximize the sum-rate of the communication system, we jointly optimize the beamformer at the base station (BS) and the phase shifts at the RIS, subject to a threshold on the interference power, the unit-norm constraint of the transmit power, and the unit modulus constraint of the RIS phase shifts. To efficiently tackle this NP-hard problem, we first reformulate the problem into a more tractable form using the fractional programming (FP) technique. Then, we exploit the geometrical properties of the constraints and adopt an alternating manifold-based optimization to compute the optimal active beamformer and the RIS phase shifts, respectively. Simulation results demonstrate that the proposed RIS-assisted design significantly reduces the mutual interference and improves the system sum-rate for the communication system.