Analysis of High-Reliable and Low-Latency Communication Enablers for New Radio Unlicensed

In this paper, the performance impact of several high-reliable and low-latency communications technology enablers in the unlicensed spectrum for standalone operation is evaluated. Firstly, a comparison between MulteFire (MF) and New Radio-Unlicensed (NR-U) is established. It is shown that higher sub-carrier spacings and shorter processing times provide clear latency reduction benefits. Additionally, different transmission time intervals (TTI) durations are evaluated. Shortening the TTI duration decreases the latency by a factor of 5.75 at 99.99% reliability and reduces the uplink Listen Before Talk (LBT) blocking probability by 18%. The possibility of having multiple switching points during the frame is also evaluated. It is concluded that having multiple switching points provides a latency reduction mainly due to the reduction of the number of channel accesses and the reduced gaps within the frame. A time-diversity technique to cope with high uplink LBT blocking probability is also evaluated. By combining the aforementioned features, a latency reduction factor of 31 is achieved when optimized NR-U and MulteFire performances are compared.