Along with the springing up of the semantics-empowered communication (SemCom)
research, it is now witnessing an unprecedentedly growing interest towards a
wide range of aspects (e.g., theories, applications, metrics and
implementations) in both academia and industry. In this work, we primarily aim
to provide a comprehensive survey on both the background and research taxonomy,
as well as a detailed technical tutorial. Specifically, we start by reviewing
the literature and answering the "what" and "why" questions in semantic
transmissions. Afterwards, we present the ecosystems of SemCom, including
history, theories, metrics, datasets and toolkits, on top of which the taxonomy
for research directions is presented. Furthermore, we propose to categorize the
critical enabling techniques by explicit and implicit reasoning-based methods,
and elaborate on how they evolve and contribute to modern content & channel
semantics-empowered communications. Besides reviewing and summarizing the
latest efforts in SemCom, we discuss the relations with other communication
levels (e.g., conventional communications) from a holistic and unified
viewpoint. Subsequently, in order to facilitate future developments and
industrial applications, we also highlight advanced practical techniques for
boosting semantic accuracy, robustness, and large-scale scalability, just to
mention a few. Finally, we discuss the technical challenges that shed light on
future research opportunities.Comment: Submitted to an IEEE journal. Copyright might be transferred without
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