C-RAN architecture and fronthaul challenges Philippe Chanclou, Anna Pizzinat, Yann Denis Orange Labs Networks Sebastien Randazzo Orange DTRS/DIRM RAN world 2015 Session : CLOUD RAN WORKING GROUP 20 January 2015, Dusseldorf, Germany
Contents 1. C-RAN Centralized and Cloud RAN drivers Local RAN Centralized RAN 2. Fronthaul Fiber fronthaul and wireless fronthaul 3. 5G Challenges 4. Conclusion 2
System module System module System module C-RAN: centralized Already deployed in some countries. Today one can already manage several. Next generation of products will support multiple sites (first level of pooling) and an internal interface to enable CoMP support. CoMP=Coordinated MultiPoint AAA, Active Antenna Arrays Wireless Central Office IP/MPLS network Optical Fiber S1 Digital-RoF Fronthaul : CPRI Backhaul C-RAN: intra & inter pooling + CoMP : DU: : : UE: BaseBand Unit or Digital Unit Unit or Remote Head User Equipment 3 4 Cs of C-RAN: Centralization, Cloud, Cooperation, Clean At research level: reach pooling at user equipment (UE) level
C-RAN drivers Interest coming from network operational teams: site engineering solution due to increased network rollout difficulties Antenna site simplification: footprint reduction, renting cost reduction, reduced time to install Contribute to RAN strategies on tower sharing Better radio performances: thanks to very low latency between s: Better performance in mobility Improved uplink coverage Higher capacity and improved cell edge performance with inter-site CoMP pooling and aggregation gains possible across a number of sites Energy efficiency Future proof for LTE-A and beyond In case of hetnets: improved interference control s are in a secured location: no need for IPSec Drivers = cost reductions & ease of deployment 4
How to build a fronthaul solution? 1. Technical requirements: CPRI: digitized radio signal high data rates 3 sectors LTE 20MHz 2x2 MIMO 3x2.457Gbit/s technical aspects Complete radio configuration LTE+ 3G+ 2G: up to 15 s Latency + synchronization + jitter also to be taken into account 2. Business aspects: low cost and scalability regulatory aspects * business aspects 3. Regulated countries: the fronthaul solution must be available for other operators wholesale offer Fronthaul must be monitored to provide SLA by dedicated fiber monitoring solution different levels of SLA are possible Antenna site demarcation point demarcation point Optical Fiber demarcation point Central Office outdoor compliant and as simple as possible 3. Non-Regulated countries: fronthaul provided by the RAN vendor demarcation point Wireless 5 Optical fiber is needed for the fronthaul Wireless fronthaul shall also be considered Mobile operator fiber / wireless provider Mobile operator
switch fabric Different levels of centralisation Wide C-RAN µ µ Macrocells + Hetnets centralised processing node (DU pool µ Micro-small cell µ µ µ Outdoor: Local C-RAN Indoor: Private C-RAN µ µ µ µ µ µ µ µ µ µ µ 6
Local C-RAN Micro/small cell Macro cell Micro/small cell Cell site cabinet Wireless or Optical Fiber coax Wireless or Optical Fiber R R R CSG Central office backhaul With wireless fronthaul, turn existing macro site into local C-RAN 7 Easier and faster deployment, same network architecture, better radio performance
Wireless fronthaul: a reality today! Antenna WFM WFM FrontLink 58 Product Digital Interfaces Antenna Antenna RF Interface Wireless fronthaul on Orange commercial network with FrontLink solution from Three sectors LTE 2600 MIMO 2x2 3x2.457Gbit/s CPRI on a wireless fronthaul link In less than 70 MHz bandwidth 30 cm 8
Wireless fronthaul: similar KPIs as fiber Fiber-based Fronthaul Wireless Fronthaul Fiber-based Fronthaul Wireless Fronthaul Network accessibility Network retainability Fiber-based Fronthaul Wireless Fronthaul Network mobility 9 Apple to apple comparison between fiber and wireless fronthaul over 3-months period
Wireless fronthaul: similar KPIs as fiber Fiber-based Fronthaul Wireless Fronthaul RTT ping 32 bytes RTT ping 1400 bytes Network integrity 10 Apple to apple comparison between fiber and wireless fronthaul over 3-months period
From local C-RAN to wide C-RAN Mobile coverage done by only s Central office Fronthaul 11 s Stack
How to build a fronthaul solution? Focus on fiber fronthaul R: Remote Unit : Remote Head : BaseBand Unit CSG: Cell-Site Gateway D-RoF: Digital over Fiber, CPRI or OAI Local RAN Wireless coax R R R Cell site cabinet CSG Mobile Backhaul (Carrier Ethernet, PON, MW) fibre Central Office Centralised RAN Wireless D-RoF Demarcation point Mobile Fronthaul fibre Optical Distribution Network Demarcation point IP/MPLS network Dark fiber Carrier Network (Eth., OTN, PON) D-RoF Carrier fronthaul D-RoF 12 Not enough fiber available? Challenges: latency, jitter, synchronization Too expensive for OTN
How to build a fronthaul solution? Focus on fiber fronthaul Dark fiber PRO S CON S D-RoF Carrier Network (Eth., OTN, PON) Native fronthaul solution Need fibers, lot of fibers No native monitoring and OAM D-RoF High efficiency fiber sharing Native OAM and demarcation Risk on performance (latency, synchro) needed for CPRI CPRI rate dependent Power supply required Foot print (cooling cabinet) Cost issue 13 D-RoF Passive WDM low footprint Carrier fronthaul Shared fiber Active WDM: -provide infrastructure monitoring and OAM -clear demarcation point -CPRI transparent (no framing, bit rate independent) -multiplexing low and high CPRI rate and other traffics (alarm, GPS ) -CWDM with colorized transceivers (outdoor compatible) already available -scalability to DWDM with colorless and outdoor transceivers under investigation
What is a passive fronthaul solution? - 1/2 FTTA & PTTA hybrid cable Hotel Data center area for a cells cluster Backhaul Low foot print cabinet Energy and passive fiber 14 Passive CWDM MUX & DeMUX optical fiber hotel 3G 4G interface fronthaul interface backhaul
DeMUX MUX System module System module System module What is a passive fronthaul solution? - 2/2 colorised SFP CWDM compatible with outdoor environment hotel DeMUX MUX PTx tap coupler Antenna site alarms Few fibers No active components on passive mux High reliability Suited for outdoor deployment Quick qualification process CWDM technology is low cost No introduction of transport latency Up to 16 (18) channels per fiber PTx alarms optical supervisory channel 15
Accumulation of antenna site number (%) Where is the optimal location? scenario based on France considering only high density area ( 9k antenna sites): 15 km limit to be compatible to LTE Adv & 5G Core Network Node IP Mobile Backbone node Metro node 16 NGMN limit Reach (km)
Energy consumption gain Calculation made on Rennes area France (one on 10 big cities) 15-km square coverage area, 86 cell sites, 13 intermediate central offices and one Core CO Based on average consumption of commercial equipments a-/ptp: Traditional + backhaul Cell Site (cabinet) Intermediate CO Core CO CS GW Aggr. 1 De- Aggr. 1 COGW CORE -40% -50% +10% d-/ptp: distributed + backhaul Cell Site (cabinet) CS GW Intermediate CO Aggr. 1 fronthaul only Core CO De- Aggr. 1 COGW CORE Cell Site (cab.) Aggr. 1 Intermediate CO Aggr. 2 Core CO De- Aggr. 1+2 COGW CORE 17 *PSVAC: Power Supplying, Ventilation and Air Conditioning CSGW: Cell Site GateWay
What will be 5G? LTE: Max DL 300Mbit/s LTE-A: Max DL 1Gbit/s improvements based on carrier aggregation, MIMO, enhanced interference coordination and coordinated MultiPoint 5G should support: 1000 times higher mobile data volume per area 10 100 times higher number of connected devices 10-100 times higher typical user data rate 10 times longer battery life 5 times reduced End-to-End latency 10x performance 10x spectrum 10x base stations 18 interne Orange
switch fabric 5G impact on fronthaul CPRI link-rate explosion: LTE-A 20MHz 8x8 MIMO CPRI 9.8Gbit/s 5G 100MHz CPRI 20Gbit/s, >> 100MHz at mm-waves CPRI? Massive MIMO Compression? new functional split between and DU? Fronthaul and backhaul coexistence? Adaptable fronthaul for dynamic network load? CRAN load balancer: CPRI switch? 5G End-to-End Latency: 5 times reduced? µ µ centralised processing node (DU pool µ µ µ µ
Fronthaul over Ethernet: the promise, but with some challenges A lot of work ongoing on fronthaul over Ethernet: possibility to reuse Ethernet connectivity inside the RAN but not on transport network (?) Ethernet includes natively OAM Linked with compression & functional split work However some challenges: CPRI: constant bit rate interface transporting also synchronization to Packetization delay and utilization of Eth packets Frequency and time/phase synchronization. Need standardization to define Ethernet mapping Switchs and gateways must be «transparent» and CPRI dedicated? To address an antenna site, several CPRI over Eth. links must be carried WDM is the must-have for fronthaul network for either native CPRI or CPRIoEth. Should this work be done in the framework of CPRI redefinition?
Conclusions and next steps C-RAN drivers and global perspective Wireless Fronthaul Fiber Fronthaul Standardization CPRI redefinition - Site engineering solution - performance improvements and future proof for LTE-A - Hybrid Fronthaul/Backhaul solution needed to address HetNets - C-RAN to co-exist with regular RAN architecture - Wireless fronthaul commercially available today for network densification and local C-RAN - Use of millimetric bands in future for massive small cells - CWDM ready: simple and cost effective with passive monitoring - DWDM tomorrow with colorless transceivers and high number of available wavelengths CPRI defined as a backplane extension coming from industry fora and not from a standardization group (ETSI Open Initiative) - CPRI transport: include natively the OAM of the medium - New functional split interface to reduce bandwidth? - Packetized fronthaul? - Reference configuration including demarcation point - Sleep mode for energy efficiency? 21
Acknowledgements: Trugarez Thank you Merci Danke Grazie Tack 谢谢감사합니다ありがとうございました Orange, the Orange mark and any other Orange product or service names referred to in this material are trade marks of Orange Brand Services Limited. Orange restricted.
Cloud-RAN compared to Distributed-RAN Co-Ax Conventional Architecture Cloud RAN Architectures Standard Remoted Centralised Intra Pooling + CoMP Inter Pooling + CoMP Possible future products Traditional Site Remote Head Site (R) 3 cells (1 site) per Phase 1 CRAN 3 cells (1 site) per Upto 30 cells per Phase 2 CRAN Upto 30 cells per Upto 30 cells per 30 or more cells per Future CRAN 30 or more cells per 30 or more cells per Site Site Site 1 Site 2 Backhaul Copper M-Wave Intra-site pooling (typ. 3 cells/sectors max and several Mobile Central Office 1 X2 2 Technologies: 2G, 3G,4G) 3 to 12 fronthaul links Backhaul Copper M-Wave Backhaul Copper M-Wave Backhaul Copper M-Wave Central Office Backhaul Copper M-Wave Inter-site pooling: 30 -?hundreds? Switching Layer Internal fronthaul links 1 2 3 Internal Backhaul Copper M-Wave Backhaul Copper M-Wave Central Office Backhaul Copper M-Wave 1 2 3 Internal Backhaul Copper M-Wave Internal Backhaul Copper M-Wave between remote and head known as Fronthaul CRAN = Cloud RAN = Base Band Unit = Base Station = Remote Head
Wireless fronthaul enables local C-RAN Macro site Remote macro sector Micro sector (3G and/or 4G) Wireless Fronthaul Remote macro sector Macro site «local C-RAN» Remote macro sector Remote Micro sector Remotre Micro sector Remote Micro sector 24 With wireless fronthaul, turn existing macro site into local C-RAN Easier and faster deployment, same network architecture, better radio performance