IRS-Assisted Green Communication Systems: Provable Convergence and Robust Optimization

Abstract

Intelligent reflecting surfaces (IRSs) are regarded as a key enabler of green wireless communication, due to their capability of customizing favorable wireless propagation environments. In this paper, we investigate resource allocation for IRS-assisted green multiuser multiple-input single-output (MISO) systems. To minimize the total transmit power, both the beamforming vectors at the access point (AP) and the phase shifts at multiple IRSs are jointly optimized, while taking into account the minimum required quality-of-service (QoS) of multiple users. First, two novel algorithms, namely a penalty-based alternating minimization (AltMin) algorithm and an inner approximation (IA) algorithm, are developed to tackle the non-convexity of the formulated optimization problem when perfect channel state information (CSI) is available. Unlike existing designs that cannot ensure convergence, the proposed penalty-based AltMin and IA algorithms are guaranteed to converge to a stationary point and a Karush-Kuhn-Tucker (KKT) solution of the design problem, respectively. Second, the impact of imperfect knowledge of the CSI of the channels between the AP and the users is investigated. To this end, a non-convex robust optimization problem is formulated and the penalty-based AltMin algorithm is extended to obtain a stationary solution. Simulation results reveal a key trade-off between the speed of convergence and the achievable total transmit power for the two proposed algorithms. In addition, we show that the proposed algorithms can significantly reduce the total transmit power at the AP compared to various baseline schemes and that the optimal numbers of transmit antennas and IRS reflecting elements, which minimize the total power consumption of the considered system, are finite.

arXiv comment30 pages, 12 figures, submitted to IEEE Transactions on Communications

References in corpus (3)

• A Framework of Robust Transmission Design for IRS-aided MISO Communications with Imperfect Cascaded Channels
• Robust Beamforming Design for Intelligent Reflecting Surface Aided Cognitive Radio Systems with Imperfect Cascaded CSI
• Robust Transmission Design for Intelligent Reflecting Surface Aided Secure Communication Systems with Imperfect Cascaded CSI

Cited by in corpus (4)

• A Novel Wireless Communication Paradigm for Intelligent Reflecting Surface Based Symbiotic Radio Systems
• Secure Wireless Communication in RIS-Aided MISO Systems with Hardware Impairments
• Multi-Objective Resource Allocation for IRS-Aided SWIPT
• Angle-Domain Intelligent Reflecting Surface Systems: Design and Analysis