telecom italia wcdma ran ip backhauling - tim network architecture and synchronization aspects
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A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 1
WCDMA RAN
IP backhauling
TIM Network
Architecture and
Synchronization aspects
TIM - Telecom Italia
Alessandro Guerrieri
ITSF 09 - Time & Sync in Telecoms
3rd-5ft November 2009 - Rome
Rome 3-5 Nov 2009 2
Agenda
• Synchronization in 3G
Radio Access Network
• Iub interface evolution
from ATM to IP
• Iub over IP and
synchronization
solutions
A.Guerrieri – TIM WCDMA RAN IP Backhauling
A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 3
Synchronization in 3G Radio Access Network
RNC
MSC
SGSN
MGWRBS
Radio Access Network Core Network
UuIub Iu
Radio Interface
Synchronization
Frame
Synchronization
Node
Synchronization
Network
Synchronization
frequency error
< 50 ppb
A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 4
Network Synchronization is responsible for the distribution of clocks, and allows
the clocks to operate at the same frequency in different nodes. Note that clock
in this context does not deal with the time of day, but with frequency only.
Node Synchronization is the basis for the numbering of frames between the
RNC and RBS nodes, and for frame timing. The correct operation of Node
Synchronization is dependent on the proper operation of Network
Synchronization.
Frame Synchronization is responsible for the numbering of user frames, and for
the transmission and reception of frames to and from the RNC node at the
correct times, to compensate for transfer and processing delay in the RNC-RBS
path. The correct operation of Frame Synchronization in the Intra-RNS case is
dependent on the proper operation of the Node Synchronization.
Radio Interface Synchronization is responsible for the alignment of radio frames
between the RBS and the UE.
Synchronization in 3G Radio Access Network
Rome 3-5 Nov 2009 5
Iub interface
evolution
in TIM
Radio Access
Network
A.Guerrieri – TIM WCDMA RAN IP Backhauling
A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 6
Iub Interface over ATM: the 3GPP Standard
Node B
Application Part
(NBAP)
AAL Type 2
ALCAP
Transport
Layer
Physical Layer
Radio
Network
Layer
Radio Network
Control Plane
Transport
Network
Control Plane
DC
H F
P
RA
CH
FP
ATM
DS
CH
FP
AAL Type 5
User Plane
SSCF-UNI
SSCOP
AAL Type 5
SSCF-UNI
SSCOP
Q.2630.1
Q.2150.2
FA
CH
FP
PC
H F
P
US
CH
FP
CP
CH
FP
TF
CI2
FP
Radio Layer
Protocols
Transport Layer
Protocols (TNL)
ALCAP protocol stack: for AAL2 connections setup
Rome 3-5 Nov 2009 7
RAN Reference architecture – before 2005
BTS
BTS
MGW
MSC
SGSN
ATM SwBTS
BTS
Iub, Mub
Iub, Mub
UTRAN Core Network
RNCIu
Iub
ATM Sw
RNCIu
Iur
BTS
MGW
MSC
SGSN
BTS
BTS
Iub, Mub
BTS
Iub
ATM Sw
RNC
Iur
BTS
Iub
Iub
E1 Links
STM1 links
(local)
Iu
A.Guerrieri – TIM WCDMA RAN IP Backhauling
ATM Sw
ATM Sw
SDH
SDH
SDH
Rome 3-5 Nov 2009 8
Common ITU-T specifications used
Specified by 3GPP
ATM Adaptation
Layer
AAL2
AAL0
AAL5
Physical Layer
E1 - STM1 (PDH-SDH)
VP (Virtual Path)
ATM Layer
VC (Virtual Channel)
Radio Network Layer
Transport Network Layer
ATM Transport according to 3GPP R99
UTRAN Protocol layers - Iub over ATM
Radio Application
Layer
WCDMA Radio
Application Channels
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 9
Common ITU-T specifications used
Specified by 3GPP
ATM Adaptation
Layer
AAL2
AAL0
AAL5
Physical Layer Electrical / Optical - GbE
VP (Virtual Path)
ATM Layer
VC (Virtual Channel)
Radio Network Layer
Transport Network Layer
Radio Application
Layer
WCDMA Radio
Application Channels
Eth Layer PWE3 (Martini circuits) over Eth
UTRAN Protocol layers - ATM over Eth (generic)
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 10
RAN Reference architecture – after 2005
BTS
BTS
MGW
MSC
SGSN
ATM SwBTS
BTS
Iub, Mub
Iub, Mub
UTRAN Core Network
RNCIu
Iub
ATM Sw
RNCIu
IurOPM
GTW-A
GTW-A
BTS
GTW-B
MGW
MSC
SGSN
BTS
BTSIub, Mub
GTW-A
OPM GTW-B
BTS
Iub
ATM Sw
RNC
Iur
BTS
Iub
Iub
E1 Links
STM1 links
(local)
Iu
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 11
Iub over TI GbE backbone
OPM TI
(GbE)
RNC
E1
E1
GTW-A
E1
E1
GTW-A
GTW-B
RNC
Link E1
Link STM-1 VC 12
Link STM-1 VC 4
Ethernet
OSS
PWE3/Ethernet
ATM
ATMATM
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 12
Iub (ATM) over GbE
NodeB
SOL SDH
nxE1 GBE
DWDM Infr. GBE
nxSTM1
SDH
3G
SDH
RNC
feeder
metro
8630 8840
ADM
ADM
Rete ottica
metropolitana OPM
Circuito ATM
VLAN per UMTS
PWE3 (Martini circuits)
GTW_AGTW_B
Modem
SHDSL
Modem
SHDSL
Centrale di
attestazioneSOL
rame
metro
STM1CWDM CWDM
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 14
Common ITU-T specifications used
Specified by 3GPP
ATM Adaptation
Layer
AAL2
AAL0
AAL5
Physical Layer
Physical Connection (E1/E3/STM1)
VP (Virtual Path)
ATM Layer
VC (Virtual Channel)
Radio Network Layer
Transport Network Layer
ATM Transport according to 3GPP R99
UTRAN Iub over ATM
Radio Application
Layer
WCDMA Radio
Application Channels
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 15
Common ITU-T specifications used
Specified by 3GPP
Physical Layer
Electrical / Optical (GbE)
Radio Network Layer
Transport Network Layer
ATM Transport according to 3GPP R99
Radio Application
Layer
WCDMA Radio
Application Channels
IPTransport Layer
UTRAN Iub over IP
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 16
Iub over IP Protocol Stack
DCH, HS-DSCH, E-DCH FACH, PCH, RACH FPs
and Node Sync (over FACH)
NBAP
TransportNetworkLayer
RadioNetworkLayer
Radio Network
Control Plane
Network Synch Radio Network
User Plane
NW
Sync
Ethernet
UDPSCTP (*)
NTP (**)
(*) SCTP (Stream Control Transmission Protocol)
(**) NTP (Network Time Protocol )
Ethernet Ethernet
IPIP IP
UDP
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 17
OPM
RNC
Eth
Eth
Eth
Eth
RNC
Link E1
Link STM-1 VC 12
Link STM-1 VC 4
Ethernet
OSS
IP IPIP
Eth
Eth
Iub over IP
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 18
RNC
GE
NodeB
Metro
FEEDER1GE
1GE
SGU
Site
RemoteFeeder
Optical
Network
DWDM or
naked fiber
1GE
METROdi raccolta
GE SL
Site
GE
naked
fiber
Optical
Fiber
Ring
Iub over IP Architecture (FTTB)
A.Guerrieri – TIM WCDMA RAN IP Backhauling
1GE
10GE
10GE
10GE
10GEGE
OPM
METRO
Rome 3-5 Nov 2009 19
OPMOptical Packed Metro
Layer 2 NetworkRNC
Eth
Eth
Eth
Iub over IP - “Layer 3 Architecture”
DCN
(OSS)
RdG
MdR
MdR
Remote
Feeder
Remote
Feeder
RPS HSRP
HSRP
RSTP
Layer 3 connection Layer 3 connection
MdR = Def Gateway MdR = Def Gateway
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 21
Network Synchronization over IP
• Client - Server synchronization architecture.
A Network Synch NTP Server is integrated in
RNC and a client is in RBS
• Synch - Server connection is based on NTP
Protocol (Network Time Protocol) over UDP/IP
• Network synchronization for an IP connected
RBS is achieved by aligning the frequency of
the RBS to the frequency of an NTP server
with traceability to a G.811 source.
• RBSs are synchronized using ad hoc clock
recovery algorithm that uses NTP packets
(OCXO in RBS)
• No other synchronization functionalities
required (external devices, Synch nodes, GPS
etc.)
A.Guerrieri – TIM WCDMA RAN IP Backhauling
SASE
2 MHz GPS
Iu over IP/ETH Iu over ATM/SDH
SS
SC
Synchronization Server
Synchronization Client
SC SC
SS
NTP
IP/EthernetNetwork
A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 22
Network Sync details
RNC
Iub over IPSync
Client
Sync
Server
Timing
Unit
In order to meet performance requirements, the Synch Client sends an NTP request at regular intervals.
The regulator selects the NTP packet frequency based on its need. The range of 1-10 packets per second.
The higher request frequency is used at start-up or acquisition to make convergence time shorter, and then
when steady state is reached, the rate is decreased.
Iu over
ATM (SDH) Core
Network
In case Iu is connected only over IP, there will be no transmission interface available from which the RNC
can take its synchronization. In this case, the RNC must take its synchronization from the physical
synchronization port on its Timing Unit. The signal to this physical synchronization port can be e.g. a 2.044
MHz signal from a SASE, or from an SDH multiplexer on site
RNC
Iub over IPSync
Client
Sync
Server
Timing
Unit
Iu over IP
SASE
Core
Network
Rome 3-5 Nov 2009 23
Iub over IP – Network Synch Protocol Stack
DCH, HS-DSCH, E-DCH FACH, PCH, RACH FPs
and Node Sync (over FACH)
NBAP
TransportNetworkLayer
RadioNetworkLayer
Radio Network
Control Plane
Network Synch Radio Network
User Plane
NW
Sync
Ethernet
UDPSCTP (*)
NTP (**)
(*) SCTP (Stream Control Transmission Protocol)
(**) NTP (Network Time Protocol )
Ethernet Ethernet
IPIP IP
UDP
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 24
Backhauling requirements for Iub over IP
• Service requirements: no additional requirement for the backhauling IP
network compared to the "ATM over GbE" solution.
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 25
Backhauling requirements for Iub over IP
A.Guerrieri – TIM WCDMA RAN IP Backhauling
The max PDV is generally not a sufficient requirement for the
purpose of qualifying a packet network as able to carry timing
over packets.
This is especially true in the definition of the start up
conditions: in this case the PDV statistics is fundamental (e.g.
in order to select a suitable number of good packets)
• Current requirement in TIM network: when best 1% packets
have less than 20 microseconds delay variation, locking
happens quite fast (<16 minutes)
Lowest
delay
distribution
PDV
distribution
However when longer starting periods are acceptable, the
limits might be expressed in terms of PDV (i.e. 99% of the
packets below x ms depending on the actual acceptable start
up period).
The assumption is also that changes in the PDV disitribution
are detected.
After the clock has been locked, the PDV limits (e.g. 99% of
packets < 10 ms) can also be considered sufficient thanks to
OCXO stability (that can keep few ppb per day).
Note: an alternative approach often used is to specify the
requirements in terms of G.8261 (i,e, test cases 12 to 17 in
Appendix VI.5.2 with traffic model 2 according to Appendix
VI.2.2). However this is sometimes not practical.
PDV
distribution
x msec
Rome 3-5 Nov 2009 26
TI Optical Packet Metro
A.Guerrieri – TIM WCDMA RAN IP Backhauling
• 24 MdR (Metro di Raccolta)
• 60 Metro 30 sites
• 70 Metro Feeder
• 180 Remote Feeder (180 SGU sites)
• OPM Load between Feeder and Metro: 5%-10%
• Number of nodes between Node B and RNC: 4 (Remote Feeder, Metro Feeder,
Metro, MdR)
• OPM Traffic Handling: QoS priority (3 queues)
RNC
GE
NodeB
Metro
FEEDER1GE
1GE
SGU
Site
RemoteFeeder
Optical Network
DWDM or
naked fiber
1GE
METROdi raccolta
GE SL
Site
GE
naked
fiber
Optical
Fiber
Ring
1GE
10GE
10GE
10GE
10GEGE
OPM
METRO
• 100 Node Bs active today
using Iub over IP and optical
fiber
• FTTB with dedicated naked
fiber (no GPON)
• Project started in 1H 2008
• Hundreds of Nobe B over IP
planned for 2009-2010
• Very stable solution
• No synchronization
problems
Rome 3-5 Nov 2009 27
QoS for Iub over IP
• QoS separation at IP level, using DSCP (Differentiated Services Code
Points). [0...63].
• QoS separation at Ethernet level by using the Priority Bits (L2 Ethernet
priority 802.1p). P-bit [0..7]
Bearer X
Bearer Y
Bearer Z
DSCPX
DSCPY
DSCPZ
P-BitX
P-BitY
P-BitZ
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 28
QoS Mapping – TIM choices
3 QoS Priority Levels
• Maximum: Network Synchronization and Conversational/Streaming traffic
• Medium: PS R99 DCHs and NBAP signaling
• Best effort: HSDPA/HSUPA
Layer 3:
DSCP
Layer 2:
P-bit
High Priority46 Sync
18 CS & Stream
5
Sync, CS, Stream
Medium Priority22
PS R99, NBAP
3
PS R99, NBAP
Best Effort0
HSxPA
0
HSxPA
Our Optical Packed Metro is a Layer 2 network working with 3 P-bit values (5, 3, 0), so we
had to adapt the mapping of DSCP to P-bit to the existing situation.
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 29
QoS Mapping – TIM choices (2)
Layer 3:
DSCP
Layer 2:
P-bit
46 Sync
18 CS &
Stream
5
Sync, CS,
Stream
22
PS R99,
NBAP
3
PS R99,
NBAP
0
HSxPA
0
HSxPA
A.Guerrieri – TIM WCDMA RAN IP Backhauling
Rome 3-5 Nov 2009 30
Conclusions
• Iub over IP is the solution for:
─ the transport bottlenecks removal
─ the evolution of the network towards new services:
─ HSDPA Evolution 64QAM (up to 21 Mbps)
─ HSDPA Evolution MIMO (up to 28 Mbps)
─ HSDPA Evolution MultiCarrier (up to 42 Mbps)
─ LTE (150/300 Mbps)
• Live traffic shows good performance and no quality, reliability or
throughput variations.
• Iub over IP (optical fiber) deployment started in 1H 2008
• 100 Node Bs active today using Iub over IP and optical fiber
• Hundreds of Nobe B over IP planned for 2009-2010 in the TIM Radio
Access Network
A.Guerrieri – TIM WCDMA RAN IP Backhauling
• Iub over IP (with sync based on NTP over IP) is a very stable solution:
no synchronization problems in real network (18 months)
TIM A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 31
Acknowledgements:
Lorella Parmeggiani(TI Opical Packet Metro Engeniering)
A.Guerrieri – TIM WCDMA RAN IP BackhaulingRome 3-5 Nov 2009 32
Thanks for
Your Attention
Alessandro Guerrieri
TIM Telecom Italia
Wireless Access Engineering