Fronthaul Challenges & Opportunities Anna Pizzinat, Philippe Chanclou – Orange Labs Networks

LTE world summit 2014

Session : backhaul summit

23-25 June 2014, Amsterdam RAI, Netherlands

2

Contents

1. Cloud RAN Cloud RAN drivers

Local RAN

Centralized RAN

2. Fronthaul Fiber fronthaul and wireless fronthaul

3. Conclusion Centralize if you can, distribute if you must

Phase 1 CRAN

BBU1

Fibr

e

BBU2

Fibr

e

BackhaulCopperM-Wave

Fibre

BackhaulCopperM-Wave

Fibre

Central Office

Radio

Site 1

BS

Radio

Site 2

BS

3 cells (1 site) per

BBU

3 cells (1 site) per

BBU

X2

Switching Layer

BackhaulCopperM-Wave

Fibre

BackhaulCopperM-Wave

Fibre

BackhaulCopperM-Wave

Fibre

Central Office

Future CRAN

Possible future products

Fibre Fibre Fibre

BBU1 BBU2 BBU3

30 or more cells per BBU

30 or more cells per BBU

30 or more cells per BBU

Internal Internal

Phase 2 CRAN

BackhaulCopperM-Wave

Fibre

BackhaulCopperM-Wave

Fibre

BackhaulCopperM-Wave

Fibre

Central Office

BBU1 BBU2 BBU3

Fibre Fibre Fibre

Upto 30 cells per

BBU

Upto 30 cells per

BBU

Upto 30 cells per

BBU

Internal Internal

Radio

BBU

BS

Fibr

e

Site

BackhaulCopperM-Wave

Fibre

Remote HeadSite (RRU)

Radio

BBU

BS

Co-

Ax

Site

BackhaulCopperM-Wave

Fibre

TraditionalSite

Cloud-RAN compared to Distributed-RAN

Fibre between remote BBU and Radio head known as “Fronthaul” CRAN = Cloud RAN BBU = Base Band Unit BS = Base Station RRH = Remote Radio Head

Inter-site BBU pooling: 30 - ?hundreds? fronthaul links

Standard BS BBU Remoted BBU Centralised Intra BBU Pooling + CoMP Inter BBU Pooling + CoMP

Conventional Architecture Cloud RAN Architectures

Intra-site BBU pooling (typ . 3 cells/sectors max

and several Mobile Technologies: 2G, 3G,4G)

3 to 12 fronthaul links

4

C-RAN: centralized BBU

RRH RRH

RRH

IP/MPLS network

S1

Central Office

BBU Sys

tem

m

odul

e

BBU Sys

tem

m

odul

e

BBU

Sys

tem

m

odul

e

Backhaul

Digital-RoF

Fronthaul : CPRI

Already deployed in some countries.

Today one BBU can already manage 6 RRH. Next generation of BBU products will support multiple sites (first level of pooling) and an internal interface to enable CoMP support. CoMP=Coordinated MultiPoint

4 Cs of C-RAN: Centralization, Cloud, Cooperation, Clean At research level: reach BBU pooling at user equipment (UE) level

C-RAN: intra & inter BBU pooling + CoMP

RRH → AAA, Active Antenna Arrays

RRH RRH

RRH

Wireless

Optical Fiber

5

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

– Antennas sites with negotiation problems – Adding new radio access technologies on existing sites with very

limited space – Find new locations to replace sites that have to be switched off or

solution for failed negotiation sites – Reducing building cost (crane, metallic structure, etc.) and renting cost – Reducing the electrical consumption, maintenance on site – Less or not any cooling cabinets and shelters – Decrease antenna site time to build and time to repair

Contribute to RAN strategies about

– Tower sharing – Solar powered antenna site – Simplification of operational installation procedures at antenna sites

C-RAN drivers

Drivers = cost reductions & ease of deployment

6

C-RAN drivers Radio performances, very low latency between BBUs enables:

– Better performance in mobility – Improved uplink coverage – Higher capacity and improved cell edge performance with inter-site CoMP

When BBU’s are centralized (e.g. with C-RAN), it means pooling and aggregation gains possible across a number of sites and energy efficient (see slide in annex)

C-RAN is future proof for LTE-A and beyond In case of hetnets, higher interference is expected

– The same BBU shared between small cells and parent macrocell could provide even higher gains than in a macrocell scenario.

BBUs are in a secured location: no need for IPSec The new fronthaul segment is the key to assess the TCO (total cost of ownership)

RRH

Central Office

BBU

Sys

tem

m

odul

e

RRH RRH

RRHRRH

RRH

RRH

RRH

RRH

7

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 → Complete radio configuration LTE+ 3G+ 2G: up to 15 RRHs

Latency + synchronization + jitter also to be taken into account

2. Business aspects: low cost and scalability

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

→ outdoor compliant and as simple as possible

3. Non-Regulated countries: fronthaul provided by the RAN vendor

technical aspects

business aspects

regulatory aspects *

Optical fiber is needed for the fronthaul

Wireless fronthaul shall also be considered

RRH

RRH

RRH

Central Office

BBU

BBU

BBU

fiber / wireless provider Mobile operator

Mobile operator

demarcation point

demarcation point

Wireless

Optical Fiber

RRH RRH

RRH

demarcation point

8

Local C-RAN

RRU

RRU

RRU

coax

Cell site cabinet

CSG BBU

Wireless or

Optical Fiber

BBU

RRH

RRH

RRH

BBU

Wireless or

Optical Fiber

BBU

RRH

RRH

RRH

Central office

backhaul

Macro cell Micro/small cell

Micro/small cell

9

Wireless fronthaul: a reality today !

30 cm

BBU WFM WFM RRH

RRHDigital Interfaces

Antenna

Antenna

RF Interface

FrontLink™ 58 Product

RRH

Antenna

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

10

Wireless fronthaul: similar KPIs as fiber

Network accessibility

Network mobility

Network retainability

Fiber-based Fronthaul

Wireless Fronthaul Fiber-based Fronthaul Wireless Fronthaul

Fiber-based Fronthaul Wireless Fronthaul

Apple to apple comparison between fiber and wireless fronthaul over 3-months period

11

Wireless fronthaul: similar KPIs as fiber

Apple to apple comparison between fiber and wireless fronthaul over 3-months period

Network integrity

RTT ping 32 bytes RTT ping 1400 bytes

12

Wireless fronthaul enables local C-RAN

Remote macro sector

Macro site « local C-RAN »

Remote macro sector

Remote Micro sector

Macro site Remote macro sector Micro sector (3G and/or 4G) Wireless Fronthaul

Remotre Micro sector

Remote Micro sector

With wireless fronthaul, turn existing macro site into local C-RAN

Easier and faster deployment, same network architecture, better radio performance

13

From local C-RAN to centralized RAN

Central office

BBU

BBU

BBU

BBU

BBU

BBU

BBU

BBU

BBU

BBU

BBU

BBU

Fronthaul

BBUs Stack

Mobile coverage done by only RRHs

14

RRU: Remote Radio Unit RRH: Remote Radio Head BBU: BaseBand Unit CSG: Cell-Site Gateway D-RoF: Digital Radio over Fiber, CPRI or OBSAI

Optical Distribution Network

RRU

RRU

RRU

coax Cell site cabinet

RRH

RRH

RRH

D-RoF

IP/MPLS network

fibre

Central Office

CSG

Mobile Backhaul (Carrier Ethernet, PON, MW)

fibre BBU

BBU

BBU

BBU

Mobile Fronthaul

RRH

RRH

RRH

D-RoF BBU

BBU

BBU

Dark fiber

RRH

RRH

RRH

D-RoF BBU

BBU

BBU

Carrier Network (Eth., OTN, PON)

Carrier fronthaul

How to build a fronthaul solution? Focus on fiber fronthaul

Demarcation point

Demarcation point

Wireless

RRH RRH

RRH

BBU

Wireless RRH

RRH

RRH

Not enough fiber available? Challenges: latency, jitter, synchronization Too expensive for OTN

Local RAN

Centralised RAN

15

RRH

RRH

RRH

D-RoF BBU

BBU

BBU

Dark fiber

RRH

RRH

RRH

D-RoF

BBU

BBU

BBU

Carrier Network (Eth., OTN, PON)

• Native fronthaul solution

PRO’S

• Risk on performance (latency, synchro) needed for CPRI

• CPRI rate dependent • Power supply required • Foot print (cooling cabinet) • Cost issue

CON’S

• Need fibers, lot of fibers • No native monitoring and OAM

• High efficiency fiber sharing • Native OAM and demarcation

How to build a fronthaul solution? Focus on fiber fronthaul

RRH

D-RoF

RRH RRH

BBU

BBU

BBU

Carrier fronthaul

Shared fiber

Passive WDM low footprint

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

16

Conclusions and next steps

C-RAN drivers and global perspective

- Radio Site engineering solution (footprint reduced, energy efficiency, less operations on site, etc.)

- Radio 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 - BBU in secured place and existing location

Fiber Fronthaul - CWDM ready: good, simple, cost effective option with additional “passive” fiber monitoring - DWDM tomorrow with colorless transceivers and high number of available wavelengths

Centralize if you can, distribute if you must

Wireless Fronthaul

- Wireless fronthaul commercially available today (up to 7.3Gpbs): enabling network densification and local C-RAN

- Use of millimetric bands in future for massive small cells (mRRU) deployment (Nx10Gbps fronthaul links in dense urban areas)

17

Is it time to rethink CPRI?

Energy efficiency - No sleep mode? - Constant rate

Standardisation -CPRI is coming from industry forums and not from a standardization group (cf. ETSI Open Radio Innitiative) -CPRI is defined as a “backplane extension” and not a network interface

CPRI redefinition

- CPRI transport: include natively the OAM (Operations, Administration and Maintenance) of the medium: Fiber, wireless, etc… - New function splitting interface to reduce bandwidth? - Packetized fronthaul? - Network architecture of Fronthaul (PtP, MPtoMP) - Reference configuration including demarcation point

merci

19

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

Energy consumption gain

Based on average consumption of commercial equipments

60

80

100

120

140

160

180

200

220

240 To

tal E

nerg

y C

onsu

mpt

ion

[ kW

]

PSVAC * OTN CSGW ˟ Optical transceiver BBU RRH

*PSVAC: Power Supplying, Ventilation and Air Conditioning ˟CSGW: Cell Site GateWay