Transmit Power Minimization in Stacked Intelligent Metasurface-aided Multi-User Systems

Stacked Intelligent Metasurfaces (SIM), emerging as
a revolutionary programmable electromagnetic architecture, have
demonstrated unprecedented capabilities in manipulating wireless
propagation environments. However, the existing research
on SIM-aided downlink communication does not consider the
fairness between users. Therefore, this paper studies a SIMaided
digital-analog hybrid system, which aims to fairly guarantee
the communication quality of each user while minimizing
the transmission power. The hybrid system leverages SIM for
channel improvement with digital precoding further eliminating
the interference between users. To this end, we formulate a
transmit power minimization problem under quality-of-service
constraints, solved by an efficient alternating optimization algorithm.
Simulation results demonstrate that compared to conventional
fully digital MIMO systems, the proposed SIM-aided
hybrid system achieves 6.93 dBm lower transmit power under the
same signal-to-interference-plus-noise ratio (SINR) constraints
for users. This work reveals SIM’s powerful wave-based beamforming
capability in channel enhancement, providing effective
solutions for energy-efficient networks with low hardware costs.