Multi-Device Low-Latency IoT Networks With Blind Retransmissions in the Finite Blocklength Regime

In future wireless communications, the Internet of Things (IoT) is a promising paradigm which is expected to connect massive number of devices while satisfying ultra-reliable and low latency communications (URLLC). In this article, we consider a multi-device IoT network supporting URLLC, where the data transmission process from the devices perform blind Automatic Repeat-reQuest (ARQ) or Hybrid ARQ (HARQ) via shared radio resources. We leverage recent advances in the characterization of coding rates and error probability in the finite blocklength regime to investigate the reliability and goodput performances of such network with both ARQ and HARQ schemes. Furthermore, both reliability-oriented and goodput-oriented designs are proposed for ARQ and HARQ schemes, respectively. In particular, we provide the optimal solutions for the error probability minimization problem, while efficient sub-optimal solutions for the goodput maximization problem are introduced, which show a tight performance in comparison to exhaustive search. Via simulation, the analytical results are validated and the system performance for both schemes are evaluated under variant setups with respect to total resources, packet sizes and SNR.