Enhancing Communication Capacity in Urban Hotspot Areas: Optimal Deployment Study of RIS-Assisted THz Communication Systems

With the evolution of 5G-Advanced and 6G, the terahertz (THz) band-with ultra-large bandwidth potential-has become a core candidate for 100 Gbps-level high-speed communications. However, THz base stations on high-rise buildings, while advantageous for emergency communications and large-scale event broadcasting, face insufficient capacity in dense urban hotspots due to THz waves’ inherent strong directivity, high path loss, and obstacle sensitivity. To solve this, this paper proposes an optimal reconfigurable intelligent surface (RIS) deployment strategy for high-rise scenarios. It enhances hotspot communication by expanding signal coverage, using intelligent reflection for multipath gains, and jointly optimizing RIS spatial position, base station precoding matrix, and RIS precoding matrix. Simulation results show the proposed strategy outperforms random RIS deployment significantly: in 0–20 GHz ultra-wideband, it maintains a stable 4.5–4.6 bit/s/Hz subcarrier achievable rate; at 50 dBm base station transmit power, its hotspot capacity is over 2.5 times that of random deployment.