A Model for 5G Cellular IoT Systems with Early Transmissions at the Random Access Phase

While the market for massive machine type communications (mMTC) is evolving at unprecedented pace, the standardization bodies including 3GPP are lagging behind with standardization of a truly 5G-grade cellular Internet-of-Things (CIoT) systems. As an intermediate solution, an early data transmission mechanisms encapsulating the data into the preambles has been recently proposed for 4G/5G Narrowband IoT (NB-IoT) technology. This mechanism is also expected to become a part of future CIoT systems. The aim of this paper is to propose a model for CIoT systems with early transmission functionality. The developed model captures both random access and data transmission phases as well as traffic in both downlink and uplink directions. Our numerical results demonstrate that the use of early transmission functionality allows to drastically decrease the delay of uplink packets by up to 40-50% even in presence of downlink traffic sharing the same set of resources. However, it also affects the optimal share of resources allocated for random access and data transmission phases. As a result, the optimal performance of 5G mMTC technologies with or without early transmission mode can only be attained if the dynamic resource allocation is implemented. © 2024 IEEE.