arating the RRC and PDCP for the control-plane stack and the PDCP for the user-plane stack into different central entities. This option enables centralization of the PDCP sublayer, which may be predominantly affected by user-plane process and may scale with user-plane traffic load. Option 3: In this option, the lower RLC functions, MAC sublayer, physical layer, and RF functions are located in the DU, whereas PDCP and higher RLC functions are Centralized (cloud) Distributed F1 interface To/from vEPC/5GC Central unit (CU) Distributed unit (DU) To/from RRH Upper Lower Upper Lower Upper Lower Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8 Upper Lower Upper Lower Upper Lower Figure 1.26 Functional split between the CU and the DU [ 34 Data channel/Control channel/PBCH Data channel/Control channel Option 6 Option 6 Coding Decoding Rate matching Rate de-matching Cell specific signals(e.g., SS, CSI-RS) UE specific signals(e.g., DMRS) PRACH Scrambling De-scrambling Option 7-3 Option 7-3 downlink only downlink only Modulation Signal generation Demodulation Channel estimation Layer mapping Layer mapping Channel estimation PRACH detection /equlization & IDFT Option 7-2 Option 7-2 Precoding Precoding RE mapping RE de-mapping Option 7-2a Option 7-2a Digital BF Digital BF Option 7-1 Option 7-1 IFFT/CP insertion FFT/CP removal PRACH filtering Digital to analog conversion Analog to digital conversion Analog BF Analog BF Figure 1.27 Variants of option 7 functional split 34 5G Network Architecture 71 implemented in the CU. Depending on real-time/non-real-time RLC processing require- ments, the lower RLC may include segmentation functions and the higher RLC may include ARQ and other RLC functions. In this case, the centralized RLC functions will segment the RLC PDUs based on the status reports, while the distributed RLC functions will segment the RLC PDUs into the available MAC PDU resources. This option will allow traffic aggregation from NR and LTE transmission points to be centralized. It can further facil