n Mountaser et al. 2017 [6]. Table 11.2 Experimentation parameters. Parameters Values Carrier frequency 2.68 GHz System bandwidth 5 MHz (25 RBs) Frame type Tx/Rx antennas 1 Tx antenna/1 Rx antenna Modulation schemes 16 QAM and 64 QAM IP packet size (bytes) 1500 eMBB, 500 URLLC, and 300 mMTC The OAI eNodeB is modified and divided into two entities, the DU and the CU, to support Cloud-RAN. They run on separate servers, each with an 8 GB RAM with Xeon 1220 and 4 cores. The DU and CU are connected with Ethernet link with a capacity of 1 gigabit. Focus- ing on the DL direction, the IP packets are injected in the eNodeB PDCP layer and are then processed by the whole protocol stack in CU. Afterwards, the PDU in the CU is packe- tized. The Ethernet packet is then transmitted to the DU via Ethernet. Upon arrival, the DU depacketizes the Ethernet packet into PDU, which undergoes further baseband processing. The configuration parameters are listed in Table 11.2. 11.3.2 Evaluation and Discussion of the Results Figure 11.4 evaluates the total latency from PDCP to PHY for user plane packets. The aim is to compare the latency added by the different functionality splits in addition to the legacy protocol stack processing latency. We can note from this analysis that enhanced mobile broadband (eMBB) is the most affected service. This is due to the large packet size, which introduces higher computation load and hence delay. The massive machine type commu- nications (mMTC) and ultra-reliable low-latency communications (URLLC) services are impacted by the splits in almost the same way. The only difference is that URLLC has latency of 10 us higher than mMTC due to the larger packet size. From this analysis we can observe that intra-PHY split adds a larger latency than PDCP-RLC and MAC-PHY splits. 11 Flexible Function Split Over Ethernet Enabling RAN Slicing No split PDCP-RLC MAC-PHY Intra-PHY URLLC Figure 11.4 Latency for an IP Packet from when it is injected to PDCP layer to when it is transmitted to the UE. Source: © 2017, IEEE Repr