Stacked Intelligent Metasurface Enabled Spatial Domain Index Modulation

Abstract

This paper investigates a stacked intelligent metasurface (SIM)-enabled spatial domain index modulation framework. We propose a phase-regulated SIM-enabled spatial domain index modulation (SIM-SDIM) scheme, where spatial bits are mapped onto programmable phase-state combinations of multiple SIM layers. The cascaded SIM propagation converts different spatial-bit sequences into distinguishable wave-domain transmission patterns, enabling wave-domain pattern indexing instead of physical antenna indexing. To characterize the proposed architecture, the proposed transmission model, power compensation mechanism, and maximum likelihood detector are developed. Furthermore, we derive a moment-generatingfunction (MGF) based union bound analysis for the average bit error probability (ABEP) with spatially correlated channel conditions. Monte Carlo simulation results demonstrate that the proposed SIM-SDIM scheme can outperform conventional transmit spatial modulation with properly configured layer numbers, meta-atom spacings, and meta-atom numbers, while revealing the conventional tradeoff between spatial bit load and detection reliability.