Transcript CY2009 Interlock Process Bell Labs

PON Architecture for Wireless
Backhaul
Paul Wilford
October 28, 2009
-
1
The mobile backhaul problem
2 | PON Architecture for Wireless Backhaul
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The mobile backhaul problem
Current Wireless Carrier Environment
 Increased bandwidth demands
 Due to more advanced users and handsets
 Mobile broadband (killer app)
 TDM Backhaul is not efficient for packet data
 Doesn’t fit well in traditional T1 Architecture
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The mobile backhaul problem
Data is becoming the primary use of the network
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The mobile backhaul problem
New mobile data services require exponentially increasing bandwidth but
generate less revenue per bit transported than voice services.
 100 Kb/s for GSM GPRS (downlink)
 ≥100 Mb/s for LTE (downlink)
This will break the traditional voice-optimized TDM Mobile Backhaul (MBH) network
 Legacy leased line capex and opex scale linearly with bandwidth
Traffic
ARPU
2000-2005
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2005-2010
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2010-2020
2
Landscape of today
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Landscape of today
Voice Channels
GSM
UMTS
IP Channel
Base
Station
NodeB
•SGSN – Serving GPRS Support Node
•GGSN – Gateway GPRS Support Node
•PDSN – Packet Data Support Node
•HSGW – HRPD Serving Gateway
Separate Core Networks
for different
Radio Access Networks
•RNC – Radio Network Controller
•DoRNC – Data Optimized RNC
•BSC – Base Station Controller
•MSC – Mobile Switching Center
•HRPD – High Rate Packet Data (1xEV-DO)
DoRNC
Voice Channels
3G1X
HRPD
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PDSN/HSGW
BTS
IP Channel
BTS
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Landscape of today
Examples of customer deployments – Customer ‘X’
Customer ‘X’ primarily uses ATM for backhaul. The overall strategy is to seek
higher-capacity, lower-cost solutions as the more data-centric technologies
such as HSDPA drive capacity requirements.
The target state architecture is one that is flexible and can scale as capacity
demand increases. Some solutions being considered include fiber to the cell
site and bonded copper.
Customer ‘X’ has a combination of GSM/UMTS networks and will need to
integrate backhaul for all networks as it migrates from GSM to UMTS to LTE.
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Landscape of today
Examples of customer deployments – Customer ‘Y’
Customer ‘Y’s backhaul strategy consists of delivering Ethernet over the
existing copper infrastructure with a migration to fiber-based Ethernet
backhaul services.
Customer ‘Y’ plans to leverage its Fiber to the Premise (FTTP) network with
pseudowire to provide backhaul services.
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3
Landscape of Tomorrow
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Landscape of tomorrow – Evolution to a common core
GSM and CDMA voice and data networks converge into an IP-based evolved packet core (EPC)
For LTE, IP data from the eNodeB connects directly to the EPC
Voice Channels
GSM
UMTS
IP Channel
Base
Station
RNC
NodeB
MME
LTE
PCRF
SGW
PDN GW
HSGW
DoRNC
Voice Channels
3G1X
HRPD
BTS
IP Channel
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BTS
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Landscape of tomorrow - 4G/LTE Mission
High Peak Data Rates
100 Mbps DL (20 MHz, 2x2 MIMO)
50 Mbps UL (20 MHz, 1x2)
Improved Spectrum
Efficiency
3-4x HSPA Rel’6 in DL*
2-3x HSPA Rel’6 in UL
1 bps/Hz broadcast
Full Broadband Coverage
Network Co-existence
UMTS, GSM, HRPD, CDMA
Core Network
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for DL in LTE,
but 1x2 for
HSPA Rel’ 6
Improved Cell
Edge Rates
3-4x HSPA Rel’6 in DL*
2-3x HSPA Rel’6 in UL
Scalable Bandwidth
1.4, 3, 5,
10, 15, 20 MHz
Radio Access Network
*Assumes 2x2
Packet Domain Only
Simplified Network
Architecture
Low Latency
< 5ms User Plane (UE to RAN edge)
< 100ms camped to active
< 50ms dormant to active
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Landscape of tomorrow – Technology Innovation
With increased spectral efficiency, reduced latency and increased bandwidth,
LTE enables innovations to improve performance at the handset.
An example of this is CoMP.
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4
What is CoMP?
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What is CoMP? – Cooperative Multi-Point
Overcome inter-cell interference by coordinating Tx/Rx at several base
stations, thereby greatly increasing user rates and system capacity.
Controller
Today’s network
High-speed
backhaul
Interference
Desired
signal
Desired
signal
Each user is
connected to
a single base
Each user is
connected to
several bases
Data rates limited by interference
All signals are potentially
useful – no interference!
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What is CoMP? - System Outline
Backhaul that conveys both uplink
and downlink baseband signal.
Handset
Base
Station
Base
Station
CoMP
Processor
Base
Station
Performs downlink and uplink CoMP
beamforming.
Base
Station
Handset
Handset
Handset
Base stations communicate with a centralized CoMP processor. The backhaul
network conveys both uplink and downlink signals.
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What is CoMP? – Coherent vs. Non-Coherent
 Coherent
 Uses I/Q samples for CoMP processing in time or frequency domain
 Requires the highest bandwidth from the backhaul network
 Potential for greatest gain at the handset
 Non-coherent
 Uses soft bits for CoMP processing
 Requires less backhaul bandwidth than coherent scheme
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What is CoMP? – Uplink and Downlink
 Uplink
 To perform uplink CoMP, I/Q samples or soft bits must be transmitted to
the CoMP processor
 Downlink
 To perform downlink CoMP there are two options:
 Data and beam forming coefficients sent to each base station
 I/Q samples or soft bits sent to each base station
 After CoMP processing performed at CoMP processor
 The backhaul network must support the required data distribution
to all nodes
 Channel State Information is required for beam forming
 Different base stations adjust the amplitude and phase of the
transmission of the signals to the handsets to achieve improved handset
performance
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What is CoMP? - Requirements
CoMP schemes demand for
 High bandwidth
 multiple Gbit/s (DL &UL coherent, time domain)
 <1 Gbit/s (DL & UL coherent, frequency domain)
 about 100 Mbit/s (non-coherent)
 Low latency
 about 1 ms (all schemes, optimal case)
 high backhaul latency may become a show stopper for CoMP
– Need for a backhaul solution that is low latency
The Technical challenge is to meet the latency requirement under fully loaded
conditions. This requires sophisticated scheduling and MAC Layer processing.
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5
Different PON technologies
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Different PON technologies
PON technologies:
 APON – ATM PON
 First PON standard – used primarily for business applications
 622 Mbps/155 Mbps
 BPON – Broadband PON
 Extension of APON – added OMCI (OAM Management Control Interface) and WDM capability
 622 Mbps/155 Mbps
 GEPON/EPON – Ethernet PON
 IEEE 802.3ah Standard
 1Gbps/1Gbps
 GPON – Gigabit PON
 ITU-T G.984 Standard
 Evolution of BPON
 2.5Gbps/1.25Gbps
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Different PON technologies
PON technologies:
 10G EPON – 10G Ethernet PON
 Extension of GE/EPON
 10 Gbps/1 Gbps
 XGPON – 10G GPON
 Extension of GPON
 XGPON1 – 10 Gbps/2.5 Gbps
 XGPON2 – 10 Gbps/10 Gbps
 GPON is a suitable backhaul technology for packet-based services
 For increased capacity and to support applications like CoMP, XGPON2 is the best
backhaul solution
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6
Synchronization
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Synchronization: Problems with synchronization
 Base station radio interface typically requires some level of synchronization
 Frequency accuracy
 Time/phase accuracy
 Base station backhaul interface (typically legacy base stations) may be
synchronous (T1/E1)
 Synchronization considerations
 Relative phase stability
 Mobile hand-off between base stations
 Coherent CoMP
 Core network may or may not be synchronous
 (Traditional) Ethernet, Synchronous Ethernet, SONET, etc.
 Separate timing distribution network may or may not exist
 GPS, NTR, etc.
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Synchronization: GPON Mobile Backhaul End-to-End Synchronization
E1/Sync E
GPON PHY 8 kHz clock
IEEE 1588v2 (when PRC not avail. at OLT)
PRC
PRC
E1, GPON-fed cell site
Eth gateway (ONU)
GPON
IP/ Ethernet
Network
Cell site
OLT
E1,
Eth
RNC/BSC
Gateway
RNC
BSC
 The GPON Transmission Convergence (GTC) layer supports the transport of an 8 kHz clock via 125
microsecond framing
 Therefore GPON provides deterministic synchronization like TDM
 However, CoMP requires something better
 To achieve more precise timing synchronization, provisions must be made to compensate for the
OLT-ONU delay variations
GPON frame
ONU
t
OLT
ONU
ONU
GPON frame
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GPON frame
GPON frame
t
t
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t
7
The MAC Layer
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The MAC Layer: GPON
 GPON QoS is maintained through transmission containers (T-CONTs)
 T-CONT classes
 Type 1 – fixed bandwidth
 Type 2 – assured bandwidth
 Type 3 – allocated bandwidth + non-assured bandwidth
 Type 4 – best effort
 Type 5 – superset of all of the above
 Scheduling algorithm at the GEM Layer guarantees that transmission
container bandwidth and latency guarantees are satisfied under fully
loaded conditions
 Dynamic Bandwidth Allocation
 Maximum fiber bandwidth utilization
 Based on queue status from ONUs
 Security (via AES)
 FEC
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The MAC Layer: Backhaul challenges
 CoMP data processed and sent to downstream path for
scheduling/reflection to ONUs
 Very low latency requirement of 1 ms
 Handoff between eNodeBs requires tighter synchronization at base stations
 OLT must send additional information to ONUs so they know neighboring
ONU timing for handoffs
 FEC at 10 Gbps
 Completing R-S computations for 10 Gbps within 125 us is challenging
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The MAC Layer:
CoMP timing messages
I/O Macro
Scheduling for QoS and CoMP reflection
North
Bound
I/F
GEM Layer
Downstream
(encapsulation)
AES
Encryption
I/O Macro
TC Layer
Downstream
I/O Macro
PHY Layer
Downstream
PLOAM
Downstream
BWMap
(Dual Port)
10G FEC encode
FEC
Encode
Processor I/F
Regs
I/O Macro
S1/X2 translation
South
Bound
I/F
DBR
Upstream
GEM Layer
Upstream
PLS
Upstream
PLOAM
Upstream
TC Layer
Upstream
FEC
Decode
PHY Layer
Upstream
MAC CORE
I/O
CoMP processing. Data fed to
downstream GEM Layer for
reflection to ONUs
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S1/X2 translation
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I/O Macro
I/O
10G FEC decode
8
Conclusions
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Conclusions
XGPON2:
 Is a backhaul solution that can accommodate growth in bandwidth demand
 Is a backhaul solution that connects to the simplified network architecture
 Is a backhaul solution that can integrate data from 2G,3G and LTE networks
 Is a backhaul solution that can handle the uplink and downlink data distribution
requirements for applications like CoMP
 Is a backhaul solution that is synchronous and is compatible with IEEE 1588v2
synchronization through packet networks
 Is a backhaul solution that contains efficient scheduling in the MAC layer for
maintaining QoS under fully loaded conditions
31 | PON Architecture for Wireless Backhaul
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Thank You!
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Backup Slides
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The MAC Layer: ONU block diagram
I/O Macro
10G
PHY Layer
Downstream
FEC
Decode
TC Layer
Downstream
PLOAM
FIFO
DS
GEM Layer
Downstream
BWMap
(Dual Port)
USER I/F
Translation
I/O
Macro(s)
AES
Decryption
I/O Macro
FEC
Encode
I/O Macro
PHY Layer
Upstream
I/O
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Processor I/F
PLOAM
FIFO
US
TC Layer
Upstream
GEM Layer
Upstream
MAC CORE
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Regs
USER I/F
Translation
I/O Macro
I/O
Conclusions: Broadband Access Networks can support 3G/LTE Bandwidth
Requirements
GPON satisfies LTE bandwidth needs
XGPON2 satisfies LTE
bandwidth needs
• 2.5G DS/1.25G US shared
• Optical split adjusted as required.
DL Speed [Mbps]
>
1000
500
100
• Future evolution to 10G PON (λ
overlay on same PON)
GPON
Wireline
10
ADSL2+
ADSL2
8
4
• 10G DS/10G US
shared
Bonded VDSL2 supports
HSPA+ and early LTE
LTE
VDSL2
24
10G
PON
SHDSL.bis
ADSL
1
0,512
HSPA
GPRS
2000
35 | PON Architecture for Wireless Backhaul
HSPA+
2002
UMTS
2004
2006
2008
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Wireless
2010
2012
ADSL2+ and
SHDSL.bis are
tactical solutions
for 2G  3G