Frame based equipment channel access enhancements in NR unlicensed spectrum for the URLLC transmissions

Ultra-reliable low-latency communication (URLLC) in 5G New Radio has been originally defined only for licensed spectrum. However, due to new use cases in the Industry 4.0 scenarios, URLLC operation is currently being extended to unlicensed spectrum in the ongoing Release 17 of the 3rd Generation Partnership Project. Although in such controlled environments we can guarantee the absence of any other technology sharing the channel on a long-term basis, the uncertainty of obtaining channel access through load based equipment (LBE) or frame based equipment (FBE) can impede with the latency requirements of URLLC. In FBE, the transmitters can be prioritized to support data with different requirements and have lower energy consumption and latency compared to LBE with a big contention window size. In this paper we analyze the performance of FBE in an unlicensed controlled environment through a Markov chain. Based on this analysis, we propose two schemes to improve the URLLC performance in FBE: The first scheme allows the transmitters to use multiple fixed frame period (FFP) configurations while the second scheme configures the FFP's starting point of each transmitter based on its priority. The simulations show the benefits of these schemes compared to the URLLC transmission of existing schemes.