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Information Freshness in Semantic Communication Networks

Asvadi, Sepehr | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58753 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Ashtiani, Farid
  7. Abstract:
  8. In this Ph.D dissertation, we investigate the information freshness in semantic communication networks. Information freshness plays a fundamental role in networked control systems. In fact, controlling decisions in such networks should be based on information generated recently. The quality of information freshness can be represented by the Age of Information (AoI) function, from which two well-known metrics, i.e., average AoI and average peak AoI (PAoI), are derived. In the semantic approach to information freshness, an effort is made to redesign the network structure to improve these metrics. However, this approach complicates the analysis of communication networks. Previously, analytical approaches such as modeling the communication network with a Markovian stochastic hybrid system (SHS) were proposed for analyzing information freshness metrics. However, these approaches had several shortcomings. As a result, information freshness in many important communication structures has not been thoroughly analyzed. We pursue two objectives in this doctoral dissertation. The first goal is to introduce new approaches for analyzing information freshness metrics, and the second goal is to propose and analyze effective semantic structures for information freshness. The key contributions of this dissertation are as follows:
    1. Proposing a mathematical relation for calculating the average PAoI by modeling the communication network with Markovian SHSs.
    2. Presenting theorems for finding information freshness metrics after modeling the communication network with semi-Markovian SHSs.
    3. Introducing a novel approach for computing information freshness metrics in multi-path networks.
    4. Analyzing the average AoI in symmetric broadcast channels for several scheduling policies.
    5. Proposing and examining a multi-source semantic queueing structure with the concept of vacation times for the server.
    6. Presenting and analyzing a new prioritized structure to fairly regulate information freshness metrics for high-priority and low-priority classes.
    7. Analyzing the average AoI in multi-path multi-hop networks and providing a lower bound for it.
  9. Keywords:
  10. Information freshness ; Information Age ; Semantic Communication ; Stochastic Hybrid Systems

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