RAN Functional Decomposition the options and interfaces… RAN Functional Decomposition the options and interfaces… Andy Sutton Principal Network Architect Architecture & Strategy BT Technology 19th November 2018

Contents RAN architecture evolution RAN functional decomposition Access network connectivity 5G network deployment 5G demo update Summary

GSM - fully distributed RAN GSM BTS is a fully distributed radio base station All radio related protocols terminate in the BTS Radio interface encryption terminates in the BTS Distributed intelligence with centralised BSC BTS BSC Abis interface Core network NOTE: IP Sec GW used between BTS and BSC with IP Abis implementation Nokia GSM Ultrasite BTS

UMTS - many centralised functions UMTS is a simple L2 radio base station (known as Node B) All radio related protocols terminate in the RNC Radio interface encryption terminates in the RNC Distributed radio with centralised intelligence NodeB RNC Iub interface Core network Nokia UMTS Ultrasite BTS

LTE - distribution wins again… 2600 MHz RRU LTE eNB is a fully distributed radio base station All radio related protocols terminate in the eNB Radio interface encryption terminates in the eNB X2 interface between adjacent eNBs, no centralised network controller eNB EPC S1 interface eNB SecGW S1 interface Core network Huawei 3900 eNB (+GSM BTS)

LTE - RAN options CPRI S1 interface CPRI S1 interface 2600 MHz RRU LTE eNB is a fully distributed radio base station However, this radio (eNB) is made up of two components which can be geographically separated RRU/RRH and BBU - separated by CPRI interface RRU BBU CPRI S1 interface RRU BBU CPRI S1 interface Huawei 3900 eNB (+GSM BTS)

Base station architecture - LTE Note: a site may support one or more base station architectures for different radio channels/bands RRU BBU D-RAN with cabinet RFU S1 interface RRU BBU D-RAN with external RRU CPRI S1 interface RRU BBU CPRI C-RAN with centralised BBU S1 interface

RAN functional splits - protocol architecture Higher layer splits Lower layer splits S 1 RRC PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8 RRC PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data CPRI End to end latency Relaxed Very low Capacity requirement Traffic/capacity related Very high Reference 3GPP TR 38.801

RAN functional decomposition gNB RU* DU CU NR (air) interface CPRI eCPRI F1 interface S1 interface (EPC+) N2/N3 interfaces (NGC) * RU could be integrated within AAU (mMIMO) or standalone RU (RRU/RRH) with coaxial connections to passive antenna (typically 8T8R)

RAN functional decomposition - E1 interface Additional work is on-going on: DU-CU split for LTE (W1 interface) E2 interface between CU and RAN Intelligent Controller (RIC) A1/O1 interface between RIC and NMS & Orchestration layer gNB CU-c N2 F1-c RU* DU NR (air) interface CPRI eCPRI E1 F1-u CU-u N3 * RU could be integrated within AAU (mMIMO) or standalone RU (RRU/RRH) with coaxial connections to passive antenna (typically 8T8R)

Base station architecture - 5G - EN-DC (Option 3x) Note: a site may support one or more base station architectures for different radio channels/bands RU DU CU CPRI eCPRI D-RAN with AAU/RRU S1 interface RU DU CU C-RAN with option 2 split CPRI eCPRI F1 S1 interface RU DU CU CPRI eCPRI F1 C-RAN with option 7/8 split and further CU centralisation S1 interface Note: In full C-RAN configuration the DU and CU may be co-located or on separate sites

RAN functional splits - protocol architecture Higher layer splits Lower layer splits S 1 RRC SDAP/PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8 RRC SDAP/PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data F1 eCPRI CPRI Note: Service Data Adaptation Protocol (SDAP), has been introduced to the NR user plane to handle flow-based Quality of Service (QoS) framework in RAN, such as mapping between QoS flow and a data radio bearer, and QoS flow ID marking. End to end latency Relaxed Very low Capacity requirement Traffic/capacity related Very high Reference 3GPP TR 38.801

Base station architecture - 5G - Next Generation Core (NGC) Note: a site may support one or more base station architectures for different radio channels/bands RU DU CU CPRI eCPRI D-RAN with AAU/RRU N2/N3 interface RU DU CU C-RAN with option 2 split CPRI eCPRI F1 N2/N3 interface RU DU CU CPRI eCPRI F1 C-RAN with option 7/8 split and further CU centralisation N2/N3 interface Note: In full C-RAN configuration the DU and CU may be co-located or on separate sites (as illustrated)

RAN functional splits - protocol architecture Higher layer splits Lower layer splits N2-N3 RRC SDAP/PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data Option 1 Option 2 Option 3 Option 4 Option 5 Option 6 Option 7 Option 8 RRC SDAP/PDCP High-RLC Low-RLC High-MAC Low-MAC High-PHY Low-PHY RF Data F1 eCPRI CPRI End to end latency Relaxed Very low Capacity requirement Traffic/capacity related Very high

RAN access network connectivity RU DU CU CPRI eCPRI F1 S1 or N2/ N3 interface Fronthaul Mid-haul Backhaul CPRI, eCPRI or Non-ideal fronthaul Backhaul (in common use) Terms; Fronthaul, mid-haul and backhaul as defined by MEF (Metro Ethernet Forum)

5G within a multi-RAT network deployment - DRAN scenario PRTC sync source Openreach Point to point DWDM solution 21C IP/MPLS network (P routers not illustrated) 3G CSG OSA-FC OSA-FC 21CMSE D W M D W M 21CMSE Mobile core networks2 4G1 n x λ (can bypass CSG) 5G Future-proofed for network sharing and RAN evolution 1 - 2G is supported on the same base station as 4G (SRAN/Multi-RAT) 2 - Includes RNC for 3G and IP Sec GW for 4G and 5G

5G within a multi-RAT network deployment - DRAN scenario PRTC sync source Openreach Point to point DWDM solution 21C IP/MPLS network (P routers not illustrated) 3G CSG OSA-FC OSA-FC 21CMSE D W M D W M 21CMSE Mobile core networks2 4G1 n x λ (can bypass CSG) 5G E-Band 1 - 2G is supported on the same base station as 4G (SRAN/Multi-RAT) 2 - Includes RNC for 3G and IP Sec GW for 4G and 5G

5G within a multi-RAT network deployment - DRAN scenario PRTC sync source Openreach Point to point DWDM solution 21C IP/MPLS network (P routers not illustrated) 3G CSG OSA-FC OSA-FC 21CMSE D W M D W M 21CMSE Mobile core networks2 4G1 n x λ (can bypass CSG) 5G E-Band E-band link(s) could connect directly to a wavelength on OSA-FC product 1 - 2G is supported on the same base station as 4G (SRAN/Multi-RAT) 2 - Includes RNC for 3G and IP Sec GW for 4G and 5G

5G demo at Canary Wharf Highlights 1.3Gbps to test equipment (30 MHz LTE + 40 MHz NR) 600Mbps to Huawei 5G CPE (5 MHz LTE + 40 MHz NR) 4T4R LTE (15 MHz 2100 + 15 MHz 2600) with 64T64R NR

Summary The functional decomposition of the RAN is at an advanced stage in standards, industry fora and implementation (XRAN/ORAN, 3GPP, ONAP) Traditional 4G centric CRAN (CPRI based) is popular in Asia due to availability of dark fibre, this brings radio optimisation benefits through centralised scheduling etc. CPRI doesn’t scale for 5G due to amount of spectrum and antennas therefore eCPRI was developed by the same industry partners who developed CPRI Several industry groups are working towards a virtualised RAN to disaggregate the hardware from software for many functions, also enables innovative new entrants to market Major RAN vendors offer a range of different RAN architectures to meet various deployment scenarios BT is currently rolling out the radio, backhaul and core network infrastructure necessary to be a leader in 5G and converged networks https://www.ngmn.org/fileadmin/ngmn/content/downloads/Technical/2018/180226_NGMN_RANFSX_D1_V20_Final.pdf

Thank You Any questions?