y to be more dense, compared with 4G, at least when mmWave frequency bands are used. This is because in these bands the cell radius is significantly smaller (sometimes 0.1x) compared with lower frequency bands currently used in 4G. Therefore, to provide coverage in certain areas in the nWave band, 5G may need 100 times more base stations than 4G. Furthermore, the 5G network, including NG-RAN and 5GC, should provide support for a variety of network services with extremely challenging QoS properties. For example, 3GPP TS 23.501 specifies 10 ms latency for low latency eMBB applications such as AR and 5 ms for electricity distribution high voltage. Another example is real-time control for discrete automation with requirement of <1 ms E2E latency. To satisfy such stringent requirements, 3GPP selected significantly more complex radio technology compared with 4G (e.g. dynamic numerology and slot structure, massive multiple-input multiple-output (MIMO), beamforming, etc.). For details about NR physical layer refer to Section 3.5. New features requiring SON enhancements are not limited to the physical layer. For example, the following NG-RAN and 5GC functionalities have SON impacts as well: Network slicing, which allows an operator to serve multiple tenants (with potentially very different QoS requirements) on the same NG-RAN and 5GC infrastructure. NG-RAN centralization with various split deployment options (described in Chapter 4) and virtualization (described in Section 6.2). 6.5.9.2 "Legacy" SON Use Cases The E-UTRAN SON functionalities introduced in Release-8 to Release-11 are still applicable to NG-RAN, as shown in Table 6.5.6. Furthermore, the following "legacy" D-RAN SON functionalities remain relevant in 5G: Automatic Neighbor Relations (ANR) management (including automatic X2 and Xn interfaces setup); Physical cell ID (PCI) configuration and PCI conflict resolution; Load balancing; Inter-cell interference coordination; Random access optimization; Centralized capacity and coverage optimization; Self-healing; 6 En