ts. Option 8: In this option, RF functionality is in the DU and the entire upper layer func- tions are located in the CU. Option 8 allows for separation of RF and the physical layer and further facilitates centralization of processes at all protocol layer levels, resulting in very tight coordination of the RAN and efficient support of features such as CoMP, MIMO, load balancing, and mobility. This option will allow traffic aggregation from NR and LTE transmission points to be centralized. Moreover, it can facilitate the man- agement of traffic load between NR and LTE transmission points, yielding high degree of centralization and coordination across the entire protocol stack, which enables more efficient resource management and radio performance. Separation between RF and physical layer decouples RF components from physical layer updates, which may improve their respective scalability. Separation of RF and physical layer allows reuse of the RF components to serve physical layers of different radio access technologies and allows pooling of physical layer resources, which may enable cost-efficient dimension- ing of the physical layer. It further allows operators to share RF components, which may reduce system and site development/maintenance costs. However, it results in more stringent requirements on fronthaul latency, which may cause constraints on net- work deployments with respect to network topology and available transport options, as 74 Chapter 1 well as rigorous requirements on fronthaul bandwidth, which may imply higher resource consumption and costs in transport mechanisms. There are strict timing, frequency, and synchronization requirements for the fronthaul links. In particular, 3GPP has imposed stringent latency requirements on transporting I/Q signals over the fronthaul, which pose certain challenges for system designers [11,14]. CPRI trans- port for fronthaul requires a low latency link and 200 us is a generally accepted value for the round-trip latency, which limits the length of the fronthaul links 