Enhancing Information Freshness via Knowledge Graph-Aided Semantic Communication

This paper investigates semantic communication to enhance the information freshness of status update systems, using time division multiple access (TDMA) as an example. Age of information (AoI) is used to characterize information freshness, defined as the time elapsed since the generation of the last successfully received status update. Prior works on analyzing and optimizing AoI have focused on the conventional bit-oriented communication paradigm, aiming to efficiently and reliably deliver each bit of the update message. When a large number of users take turns transmitting their update messages over a wireless channel to a common access point (AP), conventional bit-oriented TDMA systems may result in a high average AoI because users have to wait a long time for the next update opportunity. To address this problem, we propose a knowledge graph-aided semantic communication for TDMA systems, referred to as KGSC-TDMA, to achieve higher information freshness. With the aid of the shared knowledge graph, KGSC-TDMA transmits the meaning of update messages in the form of triplets instead of exact bits, thus reducing the amount of information transmitted and the time to receive update messages. Furthermore, an update in KGSC-TDMA is successful, even with bit errors, as long as the AP can recover the meaning of the message received. Experimental results indicate that KGSC-TDMA outperforms conventional bit-oriented TDMA in average AoI, thanks to shorter packet durations and robust semantic recovery.