  Meta-surfaces, also known as Reconfigurable Intelligent Surfaces (RIS), have
emerged as a cost-effective, low power consumption, and flexible solution for
enabling multiple applications in Internet of Things (IoT). However, in the
context of meta-surface-assisted multi-pair IoT communications, significant
interference issues often arise amount multiple channels. This issue is
particularly pronounced in scenarios characterized by Line-of-Sight (LoS)
conditions, where the channels exhibit low rank due to the significant
correlation in propagation paths. These challenges pose a considerable threat
to the quality of communication when multiplexing data streams. In this paper,
we introduce a meta-surface-aided communication scheme for multi-pair
interactions in IoT environments. Inspired by holographic technology, a novel
compensation method on the whole meta-surface has been proposed, which allows
for independent multi-pair direct data streams transmission with low
interference. To further reduce correlation under LoS channel conditions, we
propose a vortex beam-based solution that leverages the low correlation
property between distinct topological modes. We use different vortex beams to
carry distinct data streams, thereby enabling distinct receivers to capture
their intended signal with low interference, aided by holographic
meta-surfaces. Moreover, a prototype has been performed successfully to
demonstrate two-pair multi-node communication scenario operating at 10 GHz with
QPSK/16-QAM modulation.
