Link-Level Evaluation of Reliability in 5G NR Modulation and Transport Block Configurations for Low-Latency Industrial IoT

The Industrial Internet of Things (IIoT) and robotic systems require ultra-reliable low-latency communication (URLLC) to support real-time automation. This paper investigates the impact of modulation order and transport block size (TBS) on the reliability of 5G New Radio (5G NR) link-level communication. Reliability is evaluated using the Block Error Rate (BLER) metric. Using MATLAB-based simulations, we analyze BLER performance across modulation schemes (QPSK to 256-QAM) and TBS configurations under varying Signal-to-Interference-plus-Noise Ratio (SINR) conditions. Results show that while higher-order modulation increases spectral efficiency, it requires significantly higher SINR to maintain acceptable BLER (⩾0.1). Likewise, larger TBS values degrade reliability, especially for complex modulation. These findings underscore the need for joint modulation-TBS adaptation to ensure robust communication in latency-sensitive industrial applications.