3 -5 November 2009 - Rome Italia - WCDMA... · BTS BTS MGW MSC SGSN ATM Sw BTS BTS Iub, Mub Iub,...

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


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


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



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


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


Rome 3-5 Nov 2009 9


Specified by 3GPP

ATM Adaptation

Layer

AAL2

AAL0

AAL5

Physical Layer Electrical / Optical - GbE

VP (Virtual Path)

ATM Layer


Radio Network Layer


Radio Application

Layer

WCDMA Radio


Eth Layer PWE3 (Martini circuits) over Eth

UTRAN Protocol layers - ATM over Eth (generic)


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


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


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


Rome 3-5 Nov 2009 13

Iub over IP


Rome 3-5 Nov 2009 14


Specified by 3GPP

ATM Adaptation

Layer

AAL2

AAL0

AAL5

Physical Layer

Physical Connection (E1/E3/STM1)

VP (Virtual Path)

ATM Layer


Radio Network Layer



UTRAN Iub over ATM

Radio Application

Layer

WCDMA Radio



Rome 3-5 Nov 2009 15


Specified by 3GPP

Physical Layer

Electrical / Optical (GbE)

Radio Network Layer



Radio Application

Layer

WCDMA Radio


IPTransport Layer

UTRAN Iub over IP


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


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


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)


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


Rome 3-5 Nov 2009 20

Synchronization

over IP

solution


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.)


SASE

2 MHz GPS

Iu over IP/ETH Iu over ATM/SDH

SS

SC

Synchronization Server

Synchronization Client

SC SC

SS

NTP

IP/EthernetNetwork


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


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.


Rome 3-5 Nov 2009 25

Backhauling requirements for Iub over IP


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


• 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


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.


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


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


• 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)


Thanks for

Your Attention

Alessandro Guerrieri

TIM Telecom Italia

Wireless Access Engineering

[email protected]

3 -5 November 2009 - Rome Italia - WCDMA... · BTS BTS MGW MSC SGSN ATM Sw BTS BTS Iub, Mub Iub,...

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