ies supporting HPF, MPF, and LPF in strict order. It maintains <100 us delay through the complete network with all hops included. 94 Open Radio Access Network (O-RAN) Systems Architecture and Design It defines no fronthaul packet loss through network configuration (so no oversubscription), thus maintaining packet loss the 10 7 FLR requirement. Profile B may be supported by the bridges in a fronthaul network and adds frame- preemption feature. Given that nonfronthaul traffic is preemptable, no maximum frame size is defined for it in Profile B. Fronthaul gateway In an indoor "small-cell" aggregation use case, multiple (say, 8. 16) RUs are connected to a sin- gle logical DU. All RUs combined support a single logical cell across a larger geographical area. The definition of a logical cell here is that it is a single set of time and frequency resources that can be shared across multiple physical cells. The same signal is broadcasted in downlink (trans- mit) direction across multiple cells and the receive direction is implemented by Cooperative Multipoint (CoMP)-like combining (IQ summing). In addition, the fronthaul gateway (FHGW) (Fig. 2-44) reduces wiring as it combines the connectivity from multiple RUs (shown on the right-hand side in the figure) to a single interface toward the DU. In this (enterprise networking) example, the physical connection to the DU is 25 GbE or 2 X 10 GbE (typically, optical), which implies that (given a 2R2T or 4R4T/100 MHz deploy- ment) IQ samples can be transported in uncompressed (16b I/Q) form. The connectivity to the RU is 10 GbE (optical or PoE) and as such would be required to support compression in the case of 4R4T/100 MHz deployment. Connectivity (Fig. 2-45), functionality, and timing requirement at "box" level are summarized as: 1 X 10/25 Gbps toward DU Optical 1 X 10/25 Gbps toward second FHGW/AU Optical < 8 X 10 Gbps toward RU Electrical, PoE support Optional optical Uplink eCPRI Ethernet eCPRI eCPRI De- eCPRI De- Ethernet Compress IQ Combining Time/Offset Uplink Framing Compr