Stacked intelligent metasurfaces (SIMs) have recently gained significant interest since they enable precoding in the wave domain that comes with increased processing capability and reduced energy consumption. The study of SIMs and high frequency propagation make the study of the performance in the near field of crucial importance. Hence, in this work, we focus on SIM-assisted multiuser multiple-input multiple-output (MIMO) systems operating in the near field region. To this end, we formulate the weighted sum rate maximisation problem in terms of the transmit power and the phase shifts of the SIM. By applying a block coordinate descent (BCD)-relied algorithm, numerical results show the enhanced performance of the SIM in the near field with respect to the far field.

翻译：堆叠智能超表面（SIMs）因其能够在波域实现预编码，并具备更强的处理能力和更低的能耗，近来引起了广泛关注。对SIMs和高频传播的研究使得近场性能分析变得至关重要。因此，本研究聚焦于在近场区域运行的SIM辅助多用户多输入多输出（MIMO）系统。为此，我们基于发射功率和SIM的相移，构建了加权和速率最大化问题。通过应用基于块坐标下降（BCD）的算法，数值结果表明SIM在近场中的性能相较于远场得到了显著提升。