| dc.description.abstract | ITU-R officially specifies the fifth generation mobile communication technology (5G) as IMT-2020. 5G has three application scenarios, namely enhanced mobile broadband (eMBB), massive machine type communications (mMTC), ultra-high reliability and low latency communications (URLLC). In order to achieve the above three application scenarios, the IMT-2020 has defined several key requirements, such as peak data rate, mobility, spectrum efficiency, regional transmission traffic, etc. The key requirements of different application scenarios are quite different. According to the characteristics of requirements, the suitable spectrum resources can be identified. The main features of URLLC are high reliability and low delay, which are used in special environments (such as factory automation, automatic driving, etc.). Nowadays, the mainstream discussion on the implementation of URLLC services is based on the authorized spectrum. Due to the high price of licensed spectrum and the increasing demand under the development of commercial applications, the use of unlicensed band (UB) is expected to become a solution for small-scale factories to implement the Industrial Internet of Things. Therefore, the goal of this research is to realize the technology of URLLC over UB.
In our previous research, we proposed the single channel reservation mechanism and the multi-channel reservation mechanism to ensure that there is a channel reserved for real-time transmission at any time through channel detection and dynamic frequency hopping. With such mechanisms, the base station (gNB) and user equipment (UE) need to detect one or more idle channels at the same time to successfully reserve the channel(s). Our subsequent research proposed a progressive single channel reservation (P-SCR) in order to further improve the ability of channel reservation. The P-SCR lets gNB first select an idle channel, and then informs all UEs to detect and occupy that channel within a period of time. P-SCR mechanism can greatly improve the success probability of channel reservation and occupy only two channels at most at any time. It indeed improves the spectrum utilization efficiency, reduces the impact on heterogeneous systems, and satisfies the URLLC requirement. In this thesis, we analyze the P-SCR mechanism through mathematical analysis. We analyze the relationship between a pair of nodes to prove that P-SCR can indeed improve the success probability of channel reservation. According to the analysis results, we further propose two grouping methods. Simulation results show that, for the outer UE, the grouping methods can indeed reduce the required time slots for reservation meanwhile improving the success probability of channel reservation. | en_US |