Short Frame Structure Optimization for Industrial IoT with Heterogeneous Traffic and Shared Pilot

In this paper, we investigate the short frame structure optimization in terms of shared-pilot length and finite block length (FBL) for an industrial Internet-of-Things (IIoT) system with heterogeneous traffic requirements on latency, reliability and information size. Both dynamic and static optimization approaches are investigated to allow trade-offs between performance, complexity and signaling overhead. Effective throughput maximization problems are formulated based on statistical and instantaneous channel state information (CSI), respectively, and their monotonicities are proved. A statistical CSI based static joint block length and shared-pilot length (S-JBSPO) algorithm is proposed, which is conducted offline. With no spectral overhead and very low complexity, S-JBSPO outperforms the existing instantaneous CSI based approaches from medium to high SNR. An instantaneous CSI based dynamic JBSPO (D-JBSPO) algorithm is proposed, which maintains a near-optimal and robust throughput performance against a wide range of traffic requirements, and significantly outperforms the previous approaches, thanks to a much higher degree of freedom. D-JBSPO also demonstrates a significant performance gain over S-JBSPO, regardless of the Doppler frequency and the number of devices.