Exploiting Semantic Communications for Ultra-Reliable Low-Latency Communications

Ultra-reliable low-latency communication (URLLC) has emerged as a key service class for enabling next-generation mission-critical applications. However, the increasingly stringent quality-of-service requirements pose significant challenges for URLLC under traditional bit-level communication (BitCom), especially in handling rare and extreme events that are likely to occur in low signal-to-noise ratio (SNR) conditions and resource-constrained wireless environments. Semantic communication (SemCom), by compressing source information toward task-relevant content, demonstrates clear advantages over BitCom in low SNR regimes and under limited resource availability. Furthermore, SemCom inherently conveys task-specific meanings, making it well-suited for mission-critical applications in machine-to-machine communications. Motivated by these observations, we investigate the performance of URLLC under the SemCom paradigm, and derive a closed-form upper bound on the delay violation probability (DVP) using stochastic network calculus. To further exploit the strengths of both SemCom and BitCom, we propose a hybrid semantic and bit communication paradigm (HSBP). To ensure URLLC performance under HSBP, we first conduct a theoretical performance analysis and, based on this analysis, propose a bisection-based bandwidth allocation algorithm to minimize the maximum DVP. Extensive simulation results validate the accuracy of the derived upper bound and demonstrate that the proposed HSBP paradigm outperforms pure SemCom and pure BitCom in terms of DVP.