ECOC 2014 Market Focus

WDM introduction in

access networks for

fronthaul application

Anna Pizzinat and Fabienne Saliou

Orange Labs, Lannion, France

[email protected], [email protected]

Market Focus, September 23rd, 2014

mailto:[email protected]

mailto:[email protected]

2

Agenda

section 1

section 2

section 3

section 4

Fronthaul and C-RAN definition and drivers

Fronthaul interface and requirements

Conclusions

WDM passive solutions:

From CWDM to DWDM

3

RU

RU

RU

Syste

m

mo

du

le

coax

DU

D-RoF

RU: Radio Unit, RRH: Remote Radio Head

DU or BBU: BaseBand Unit

CSG: Cell-Site Gateway

Step 1: Macro base station

Step 2: Distributed base station

RRH

RRH

RRH

Syste

m

mo

du

le

D-RoF

DU

RRH

~15kg

CSG

D-RoF interface stretched to a few tens of meters

RU close to the antenna

Energy savings

Deployed

Space constraints in cell site cabinet

IP/MPLS

network

fibreS1

X2

Central OfficeCSG

Backhaul: from CSG to first node of

mobile core network

for LTE macro site 200 to 800 Mbit/s

fibre

4

C-RAN: centralized BBU

RRH

RRH

RRH

IP/MPLS

network

S1

Central Office

BBU

Syste

m

module

BBU

Syste

m

module

BBU

Syste

m

module

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 provides 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

Syste

m

mo

du

le

RRH RRH

RRHRRH

RRH

RRH

RRH

RRH

7

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

240T

ota

l E

nerg

y C

on

su

mp

tio

n [

kW

]PSVAC *

OTN

CSGW ˟

Optical transceiver

BBU

RRH

*PSVAC: Power Supplying, Ventilation and Air Conditioning

˟CSGW: Cell Site GateWay

- 50%

- 10%

8

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 providerMobileoperator

Mobileoperator

demarcationpoint

demarcationpoint

Wireless

Optical Fiber

RRH

RRH

RRH

demarcationpoint

9 France Telecom Group confidential Orange Group confidential

Topology: point to point between antenna site and CO

Distance: 96% Orange France links shorter than 10km

Up to 15 RRHs on the same site but limited number of fibers

Fronthaul: network requirements

Multiplexing + monitoring are needed

10

Local C-RAN

RRU

RRU

RRU

coax

Cell site

cabinet

CSGBBU

Wireless

or

Optical Fiber

BBU

RRH

RRH

RRH

BBU

Wireless

or

Optical Fiber

BBU

RRH

RRH

RRH

Central

office

backhaul

Macro cellMicro/small cell

Micro/small cell

11

Fronthaul : Active or Passive solution?

RRH

RRH

RRH

RRH

RRH

RRH

Central

Office

BBU

Syste

m

mo

du

le

BBU

Syste

m

mo

du

le

BBU

Syste

m

mo

du

le

Fibre provider

or Mobile operator

Mobile

operatorMobile

operator

Active solution means CPRI traffic encapsulation

by means of OTN or Eth+compression. Power

supply needed at radio site demarcation point.

Passive solution means fibre with monitoring

without CPRI encapsulation. No need of power

supply at radio site demarcation point.

12

Agenda

section 1

section 2

section 3

section 4



Conclusions


From CWDM to DWDM

13

Dual fibre CWDM for fronthaul

Rx

Rx λ’1, λ’1,... λ’N

λ’N

Central Office RRH

RRH

RRH

Rx

Tx

Rx

Tx

Tx

Rx

Base Station

Syste

m

mo

du

le

BBU

BBU

BBU

- CWDM : channel spacing 20nm (16 channels from 1270 to 1610nm)

based on Dual fibre optical distribution network

λ’1

Tx

λ1

MU

X/D

EM

UX

λ1, λ1,... λN

MU

X/D

E

Tx

TxRx

λN

For 2G,

3G, LTE

Min

15 RRH

/site

1270

-15 CWDM channels used to cover a full antenna site

- the 16th channel used for link monitoring

- commercial transceivers available with CPRI bitrates up to 10Gbit/s, and I-Temp class (outdoor)

14

Evolution of CWDM : single fiber ODN

Several emerging solutions to realize CWDM with a single fibre

ODN : CWDM SFPs “bidi” to insert in BBUs and RRHs

SFP Single Wavelength Single Fiber (SWSF):

same CWDM wavelength used for transmission

and reception on the same fiber thanks to an

optical splitter.

Drawback: performances suffer in the presence of

optical reflections (depending on connectors type)

Products available with bit rates up to 2.5Gbit/s

Solution 1

15




SFP SWSF with Reflection Immune Operation (RIO):

this SWSF transceiver can recognize reflected signals

thus reduces signal reflection impact.

Products available with bit rates up to 1.25Gbit/s

Solution 2

16




SFP Cooled Single Channel (CSC): each 20nm

CWDM channel is divided in two sub-channels

that are used for transmission and reception,

respectively.

Products available with bit rates at 2.5Gbit/s,

5Gbit/s and 10Gbit/s in roadmap.

Solution 3

17




CSC provides higher optical budgets

Simplified architecture , reduced number of components involved

(MUX, fiber, transceivers + sparing ones)

What about semi-passive monitoring with a single fiber ODN ?

- Rayleigh Back Scattering issue

18

From CWDM single fiber to DWDM

CWDM

CH1610CWDM

CH1610

CW

DM

MU

X / D

MU

X CW

DM

MU

X / D

MU

X

λ1, λ1,... λN

λ’1, λ’1,... λ’N

λ1

λ’1

CWDM

CH1610DW

DM

CWDM

CH1610

DW

DM

DWDM offers better spectral efficiency than CWDM :

typically 100GHz spacing (0.8nm) or 200GHz (1.6nm)

Possibility to insert DWDM channels in a CWDM infrastructure

(smooth migration for higher density cases)

DWDM Sub-channels

(in the 13nm bandwidth of the CWDM)

Alternatively : Pure DWDM network but need for low cost transmitters

19

Low cost colorless DWDM transmitters

To reduce the cost of DWDM transmitters, an identical transmitter in each

network termination is needed whatever the targeted wavelength (permits

mass production)

Colorless Technologies:

Several commercial systems available at 1.25Gbit/s

– Tunable lasers : 10Gbit/s transmissions achieved but control and management of the

wavelength can be costly and complex (OutdoorTemperature variation…)

– Externally seeded sources : based on RSOA or Injection locked Fabry-Perot. A

Broadband Light Source at CO shared to remotely “pump” users with a multiple channel

Tx. (BLS drawbacks :high power, energy, not pay as grow)

– Wavelength re-use : studied in early 2000’s. Re-use of the downstream

wavelength for the upstream with re-amplification and re-modulation. Limited

bitrates evolution and optical budget

– External cavity lasers :

– Short cavity lasers with Bragg Gratings but difficult tunability mechanism

– Long cavity with self seeded sources based on RSOA : still in the

research domain (upgrade of the bitrate can be difficult)

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DWDM : a technology included in NGPON2

NGPON2 : TWDM PON + WDM PON with optional overlay on the

same ODN

evolution towards WDM only for P2P links (FTTA and FTTO)

including CPRI links for mobile fronthaul

NGPON 2 Standard G989.x FSAN (ITU-T in 2015)

TWDM-PON WDM P2P

For Residential Users (FTTH*) For NON Residential Users

(FTTA*, FTTO*)

+

*Fiber To The Home

CPRI considered with framingCPRI considered with framing or transparent

21

Requirements for fronthaul are under discussion at FSAN

and ITU-T(G989.1 amd 1 ) :

Bitrates :

• symmetrical for upstream and downstream

• all CPRI bitrates under discussion with mainly CPRI3(2.4G), CPRI5 (5G),

CPRI6 (6G), CPRI8 (10G)

Latency

• 500µs from SNI to UNI, symmetrical

Synchronization:

• Radio Frequency deviation limited to 2ppb counting only the CPRI link

Jitter

• jitter mask defined in NGPON2

Temperature range

• I-Temp for outdoor environment (antenna site)

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DWDM : a technology included in NGPON2

22

Agenda

section 1

section 2

section 3

section 4



Conclusions


From CWDM to DWDM

23

WDM introduction in access networks …

Conclusions

P2P

FTTA

FTTO

CWDMCWDM

bidiDWDM

FTTH TDM PONs

1260

1280

1300

1320

1340

1360

1380

1400

1420

1440

1460

1480

1500

1520

1540

1560

1580

1600

1620

1640

Wavelength (nm)

O-Band E-Band S-Band C-Band L-Band U-Band

10GE/XG-PON U/S

GPON U/S

(Narrow/Reduced)B/GPON

GE-PON U/S

B/GPON

GE-PON D/S RF-Video

10GE/XG-PON D/S

Co existence of TDM and WDM technologies possible with wavelength overlay

NGPON2 NGPON2

Co-existing on the

same ODN ?

NGPON2

NGPON2

Acknowledgements:

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.

ECOC 2014 Market Focus

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