the data rate of the FH scales with user traffic. The latency requirement is relaxed compared to CPRI. In [6], the latency is found to be, on average, within 60 us. Option 7: This is an intra-PHY split whereby parts of the PHY functions are in CU. The other parts of PHY and RF are in DU. The key advantage of this option is the high degree of centralization with a significant reduction on the FH data rate requirement compared to CPRI by moving antenna-related operations to the CU (e.g. DL antenna mapping, fast Fourier transform). However, the DU in this option is more complex than the one in option 8. Option 8: This corresponds to a fully centralized RAN architecture. FH transports IQ data in time domain. While this option benefits from the advantages of full centralization, it has very high data rate requirement. Nevertheless, each of these envisioned splits has its own requirement. Depending on the split point, the latency and bandwidth requirements change as shown in Table 11.1 [7]. In general, the lower the split point, the greater the level of centralization, the higher is the required interface data rate, and the more stringent is the latency requirement. 11 Flexible Function Split Over Ethernet Enabling RAN Slicing Table 11.1 Bandwidth and latency requirements for different split points. One-way DL bandwidth UL bandwidth Split point latency (Mbps) (Mbps) RRC-PDCP 30 ms PDCP-RLC 30 ms Split MAC MAC-PHY PHY Split III 250 us to 2 ms Slice 1 Slice 2 Slice 3 IP packets IP packets IP packets High PHY Ethernet fronthaul network Slice 3 Slice 1 Slice 2 LowPHY Intra-PHY split MAC-PHY split PDCP-RLC split Figure 11.2 Example of the envisioned architecture of RAN functional split supporting RAN slicing. 11.2 Fronthaul Reliability and Slicing by Deploying Multipath at the Fronthaul 11.1.3 Flexible Functional Split as RAN Slicing Enabler The 5G network aims at supporting a wide range of services and applications with diverse key performance indicator (KPI) requirements. As such, there is no optimal split point that can 