Stacked Intelligent Metasurfaces for Integrated Sensing and Communications

• Published in: IEEE wireless communications letters Vol. 13; no. 10; pp. 2807 - 2811
• Main Authors: Niu, Haoxian, An, Jiancheng, Papazafeiropoulos, Anastasios, Gan, Lu, Chatzinotas, Symeon, Debbah, Merouane
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.10.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Array signal processing; Communications systems; Constraints; Data transmission; Downlink; Hardware; Integrated sensing and communication; integrated sensing and communications (ISAC); Metasurfaces; Optimization; Radar antennas; Radar targets; Radio frequency; Stacked intelligent metasurfaces (SIM); Target detection; User requirements; User satisfaction; wave-based beamforming
• ISSN: 2162-2337; 2162-2345
• DOI: 10.1109/LWC.2024.3447272

Stacked intelligent metasurfaces (SIM) have recently emerged as a promising technology, which can realize transmit precoding in the wave domain. In this letter, we investigate a SIM-aided integrated sensing and communications system, in which SIM is capable of generating a desired beam pattern for simultaneously communicating with multiple downlink users and detecting a radar target. Specifically, we formulate an optimization problem of maximizing the spectrum efficiency, while satisfying the power constraint of the desired direction. This requires jointly designing the phase shifts of the SIM and the power allocation at the base station. By incorporating the sensing power constraint into the objective functions as a penalty term, we further simplify the optimization problem and solve it by customizing an efficient gradient ascent algorithm. Finally, extensive numerical results demonstrate the effectiveness of the proposed wave-domain precoder for automatically mitigating the inter-user interference and generating a desired beampattern for the sensing task, as multiple separate data streams transmit through the SIM.