Research On NR-U Channel Access Mechanism

With the rapid development of mobile communication technology,the global mobile data traffic and the number of mobile devices are increasing doubly.The licensed spectrum can no longer meet the future demand,and the unlicensed spectrum is considered as a supplementary solution by operators.With the development and application of 5G NR,3GPP puts forward the concept of NR-U,aiming at extending NR technology in unlicensed frequency band.The research and standardization of NR-U in 3GPP are still in progress.One of the key problems of NR-U operating in unlicensed frequency band is to ensure fair coexistence with other systems,such as Wi-Fi.In order to make NR-U and Wi Fi coexist more fairly,this paper introduces the muting period into the NR-U channel access mechanism,and establishes the simulation model of coexistence of NR-U and Wi-Fi.According to the optimal muting period search algorithm,the optimal muting period corresponding to the specific transmission time of NR-U is simulated,and the discrete mapping relationship is formed into a function expression by polynomial fitting.The optimal muting period corresponding to any NR-U transmission time is generated by using the fitting function.The simulation verifies that the optimal muting period can make NR-U and Wi-Fi basically achieve fairness.In this thesis,according to the scalable subcarrier spacing of NR-U and the characteristics of mini-slot,the multiple granularity of slot synchronization supported by NR-U is calculated.Under the premise of NR-U slot synchronization,the mini-slot based NR-U channel access mechanism is simulated in the coexistence scenario.According to the simulation results,the NR-U subcarrier spacing configuration and the corresponding synchronization slot size are given under different scenarios and different NR-U channel access priorities,which can make NR-U and Wi-Fi achieve basic fairness.