Fig. 1.17 shows an example of logical architecture of network slicing in a radio access net- work. In this example, different NSIs2 28 can either share the same functions or have dedicated functions. The new RAT features flexible air interface design and a unified medium access control (MAC) scheduling to support different network slice types. Such a combination allows time-domain and frequency-domain resource isolation without compromising resource efficiency. The protocol stack can be tailored to meet the diverse service requirements from different NSIs. For instance, layer-3 RRC functions can be customized in network slice design phase. Layer-2 can have various configurations for different NSIs to meet specific require- ments for radio bearers. In addition, layer-1 uses flexible numerology to support different Sub-network blueprint: a description of the structure (and contained components) and configuration of the sub-network instances and the plans/workflows for how to instantiate it. A sub-network blueprint refers to physical and logical resources and may refer to other sub-network blueprints. Network slice instance is the realization of network slicing concept. It is an end-to-end logical network, which comprises a group of network functions, resources, and connections. A network slice instance typi- cally covers multiple technical domains, which includes terminal, access network, transport network, and core network, as well as dual-connectivity domain that hosts third-party applications from vertical industries. Different network slice instances may have different network functions and resources. They may also share some of the network functions and resources. 40 Chapter 1 NSI 1 (eMBB) NSI 2 (URLLC) NSI 3 (mMTC) LTE slice NR slice common RRC common RRC LTE RRC NR RRC NR RRC NR RRC/PDCP/ Common PDCP NR PDCP/RLC LTE RLC NR RLC LTE scheduler Unified NR scheduler LTE MAC/PHY NR MAC/PHY NR MAC/PHY NR MAC/PHY Flexible shared radio resource Signaling link Traffic link Figure 1.17 Example of RAN architecture with 