Stacked Intelligent Metasurfaces for Task-Oriented Semantic Communications

TL;DR

This paper introduces a novel SIM-aided semantic communication system that uses electromagnetic neural networks for direct image recognition, achieving over 90% accuracy by encoding semantic information through electromagnetic wave propagation.

Contribution

It proposes a new SIM-based EMNN architecture for task-oriented semantic communication, enabling direct semantic encoding via electromagnetic waves, which is a significant departure from traditional signal transmission methods.

Findings

Achieves over 90% image recognition accuracy.

Demonstrates effective semantic encoding through electromagnetic wave propagation.

Validates the system's efficiency with extensive numerical results.

Abstract

Semantic communication (SemCom) leveraging advanced deep learning (DL) technologies enhances the efficiency and reliability of information transmission. Emerging stacked intelligent metasurface (SIM) with an electromagnetic neural network (EMNN) architecture enables complex computations at the speed of light. In this letter, we introduce an innovative SIM-aided SemCom system for image recognition tasks, where a SIM is positioned in front of the transmitting antenna. In contrast to conventional communication systems that transmit modulated signals carrying the image information or compressed semantic information, the carrier EM wave is directly transmitted from the source. The input layer of the SIM performs source encoding, while the remaining multi-layer architecture constitutes an EMNN for semantic encoding, transforming signals into a unique beam towards a receiving antenna corresponding to the image class. Remarkably, both the source and semantic encoding occur naturally as the EM waves propagate through the SIM. At the receiver, the image is recognized by probing the received signal magnitude across the receiving array. To this end, we utilize an efficient mini-batch gradient descent algorithm to train the transmission coefficients of SIM's meta-atoms to learn the semantic representation of the image. Extensive numerical results verify the effectiveness of utilizing the SIM-based EMNN for image recognition task-oriented SemComs, achieving more than 90\% recognition accuracy.