Double-Active-IRS Aided Wireless Communication: Deployment Optimization and Capacity Scaling

• Published in: IEEE wireless communications letters Vol. 12; no. 11; p. 1
• Main Authors: Kang, Zhenyu, You, Changsheng, Zhang, Rui
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.11.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: active IRS; Algorithms; Amplification; Array signal processing; Asymptotic properties; Azimuth; Beamforming; capacity scaling order; double IRS; Intelligent reflecting surface (IRS); Optimization; Placement; Reflection; Resource management; Signal to noise ratio; Wireless communication; Wireless communication systems; Wireless communications
• ISSN: 2162-2337; 2162-2345
• DOI: 10.1109/LWC.2023.3294258

In this letter, we consider a double-active-intelligent reflecting surface (IRS) aided wireless communication system, where two active IRSs are properly deployed to assist the communication from a base station (BS) to multiple users located in a given zone via the double-reflection links. Under the assumption of fixed per-element amplification power for each active-IRS element, we formulate a rate maximization problem subject to practical constraints on the reflection design, elements allocation, and placement of active IRSs. To solve this non-convex problem, we first obtain the optimal active-IRS reflections and BS beamforming, based on which we then jointly optimize the active-IRS elements allocation and placement by using the alternating optimization (AO) method. Moreover, we show that given the fixed per-element amplification power, the received signal-to-noise ratio (SNR) at the user increases asymptotically with the square of the number of reflecting elements; while given the fixed number of reflecting elements, the SNR does not increase with the per-element amplification power when it is asymptotically large. Last, numerical results are presented to validate the effectiveness of the proposed AO-based algorithm and compare the rate performance of the considered double-active-IRS aided wireless system with various benchmark systems.