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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
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
Fronthaul and C-RAN definition and drivers
Fronthaul interface and requirements
Conclusions
WDM passive solutions:
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
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 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
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 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
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
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)
20
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)
21
DWDM : a technology included in NGPON2
22
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
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