Uplink Ultra-Reliable Low Latency Communications Assessment in Unlicensed Spectrum

Through this paper, the performance of uplink transmissions in terms of latency and reliability in unlicensed spectrum is addressed. Our goal is to provide insights into how ultra-reliable and low latency communications behave over the unlicensed spectrum in standalone mode. Our system model is based on the MulteFire radio access technology and operates in the 5 GHz unlicensed band. Grant-free is an alternative to scheduled uplink scheme aiming at reducing the latency of uplink transmissions. With grant-free uplink, the users can transmit their uplink data without needing a specific grant. In this paper, both grant-free and scheduled uplink are analyzed with a focus on their performance in unlicensed spectrum. Based on extensive system-level simulations, we show that the grant-free approach is also suitable for latency reduction in the unlicensed spectrum under certain load conditions. Nevertheless, scheduled uplink presents some advantages when the number of grant-free users transmitting simultaneously increases.