3GPP functional splits Sample Clauses

3GPP functional splits. As a part of study item for 5G New Radio interface (5G NR – 3GPP Release 15), 3GPP started studying different functional splits between central and distributed units. For the initial phase, 3GPP has taken LTE protocol stack (E-UTRA) as a basis for the discussion, until RAN2 defines and freezes the protocol stack for New Radio (NR). They have proposed eight main split options [31] with lower layer splits requiring much larger transport data rates and shorter latency at the midhaul links than higher layer splits. On the other hand, fewer functions can be centralized with higher layer splits. The 3GPP functional split options between central and distributed units are elaborated below and shown in Figure 14.  Option 1 (RRC/PDCP): In this highest layer split, RRC (Radio Resource Control) is in CU while the lower layers are kept in DU. The entire user plane is in the distributed unit (close to the transmission point) while RRC/RRM functions are centralized in CU.  Option 2 (PDCP/RLC): RRC, PDCP (Packet Data Convergence Protocol) are centralized in CU while the lower layers are co-located in DU (ensuring tight synchronization between RLC, MAC, PHY layers). Option 2 was selected as the high layer split point and the interface between CU and DU was named as F1 Interface (carrying control signals and user plane data). The control and user plane functions inside CU were further separated into Control Plane Signalling (CU-CP) and one or more User Plane (CU-UP) logical entities. Consequently, the F1 interface was split into control (F1-C) and user plane (F1- U), and new interface E1 was opened between CU-CP and CU-UP entities. Option 2 has already been defined for LTE dual cell connectivity feature.  Option 3 (Intra RLC): RRC, PDCP and high RLC (partial function of RLC) are in CU while the lower layers are kept in DU.  Option 4 (RLC-MAC split): RRC, PDCP, and RLC (Radio Link Control) are in CU while the lower layers are kept in DU.  Option 5 (Intra MAC split): RRC, PDCP, RLC and higher part of the MAC layer (High MAC) are in CU while the lower layers are kept in DU. Time critical functions (e.g. HARQ, radio channel and signal measurements from PHY, random access control) are located in DU (Low-MAC sublayer). From Option 5 onwards, the scheduling of data transmission can be centralized. Having centralized scheduling can provide benefit for interference management and coordinated transmission in multiple cells.  Option 6 (MAC-PHY split): The MAC (Medium Access Cont...