From Information Freshness to Semantics of Information and Goal-oriented Communications

TL;DR

This paper reviews the evolution from traditional data transmission metrics to goal-oriented, semantics-aware communication paradigms, emphasizing task relevance and efficiency in future wireless networks.

Contribution

It unifies existing semantics-aware metrics and analytical tools, providing a comprehensive framework for designing goal-oriented communication systems.

Findings

Semantics-aware metrics better address task relevance than traditional measures.

Analytical tools like MDP and Lyapunov optimize semantic communication policies.

Framework bridges information theory, control, and networking for 6G design.

Abstract

Future wireless networks must support real-time, data-driven cyber-physical systems in which communication is tightly coupled with sensing, inference, control, and decision-making. Traditional communication paradigms centered on accuracy, throughput, and latency are increasingly inadequate for these systems, where the value of information depends on its semantic relevance to a specific task. This paper provides a unified exposition of the progression from classical distortion-based frameworks, through information freshness metrics such as the Age of Information (AoI) and its variants, to the emerging paradigm of goal-oriented semantics-aware communication. We organize and systematize existing semantics-aware metrics, including content- and version-aware measures, context-dependent distortion formulations, and history-dependent error persistence metrics that capture lasting impact and urgency. Within this framework, we highlight how these metrics address the limitations of purely accuracy- or freshness-centric designs, and how they collectively enable the selective generation and transmission of only task-relevant information. We further review analytical tools based on Markov decision process (MDP) and Lyapunov optimization methods that have been employed to characterize optimal or near-optimal timing and scheduling policies under semantic performance criteria and communication constraints. By synthesizing these developments into a coherent framework, the paper clarifies the design principles underlying goal-oriented, semantics-aware communication systems. It illustrates how they can significantly improve efficiency, reliability, and task performance. The presented perspective aims to serve as a bridge between information-theoretic, control-theoretic, and networking viewpoints, and to guide the design of semantic communication architectures for 6G and beyond.