Telecom Italia - WCDMA RAN IP Back Hauling - TIM Network Architecture and Synchronization Aspects

ITSF 09 - Time & Sync in Telecoms 3rd-5ft Nov Novemb ember er 2009 2009 - Rom Rome e

WCDMA RAN IP backhauling TIM Network Architecture and Synchronization aspects TIM - Tele elecom com Italia Italia

Alessandro Guerrieri 

Agenda •

Synchron Synch roniza izatio tion n in 3G Radio Access Access Network

•

Iub int interfa erface ce evolut evolution ion from fro m ATM to IP

•

Iub ov Iub over er IP IP an and d synchronization solutions

Agenda •

Synchron Synch roniza izatio tion n in 3G Radio Access Access Network

•

Iub int interfa erface ce evolut evolution ion from fro m ATM to IP

•

Iub ov Iub over er IP IP an and d synchronization solutions

Synchronization in 3G Radio Ra dio Access Network

Radio Access Network

Core Network

MSC

Uu

RBS

Iub

RNC

Iu

MGW SGSN

Radio Interface Synchronization frequency error < 50 ppb

Frame Synchronization Node Synchronization Network Synchronization

Synchronization in 3G Radio Access Network

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.

Iub interface evolution in TIM Radio Access Network

Iub Interface over ATM: the 3GPP Standard Radio Network  Control Plane

Radio Network  Layer

Transport Network  Control Plane

User Plane

P

R F

D

Node B Application Part (NBAP)

C

P

H P

F

H P

F

F P

C

T H

I2

U S

F

S

H

C H F

D C

A A

C

C

P C

C H P

F

H

C F P

P

F

F P

Radio Layer Protocols

ALCAP

Q.2630.1 Q.2150.2

Transport Layer

SSCF-UNI

SSCF-UNI

SSCOP

SSCOP

AAL Type 5

AAL Type 5

Transport Layer Protocols (TNL) AAL Type 2 ATM

Physical Layer

ALCAP protocol stack: for AAL2 connections setup

RAN Reference architecture – before 2005 UTRAN

Core Network Iub

BTS BTS

MSC

SDH

ATM Sw

RNC Iub

Iu

MGW

Iur Iu

SDH

BTS

SGSN

RNC

Iub, Mub

BTS

ATM Sw

BTS

Iub, Mub

Iub

BTS

ATM Sw

E1 Links

BTS

Iub

ATM Sw

BTS BTS

MSC

Iur

STM1 links (local)

MGW Iu

Iub, Mub

SDH

ATM Sw

RNC

SGSN

UTRAN Protocol layers - Iub over ATM

Radio Application Layer ATM Adaptation Layer

Radio Network Layer

WCDMA Radio Application Channels

Specified by 3GPP 

Transport Network Layer

      2      5      0       L       L       L       A      A      A       A      A      A

VC

Common ITU-T specifications used 

(Virtual Channel)

ATM Layer

VP (Virtual Path) Physical Layer

E1 - STM1 (PDH-SDH) ATM Transport according to 3GPP R99 

UTRAN Protocol layers - ATM over Eth (generic) Radio Application Layer ATM Adaptation Layer

Radio Network Layer

WCDMA Radio Application Channels       2      5      0       L       L       L       A      A      A       A      A      A

Specified by 3GPP 

Transport Network Layer

VC

(Virtual Channel)

VP

(Virtual Path)

Common ITU-T specifications used 

ATM Layer

Eth Layer Physical Layer

PWE3 (Martini circuits) over Eth Electrical / Optical - GbE

RAN Reference architecture – after 2005 UTRAN

Core Network Iub ATM Sw

BTS

BTS

MSC

Iub, Mub

BTS

RNC

GTW-A GTW-B

OPM

Iub

Iu

MGW

Iur Iu

BTS

Iub, Mub

SGSN

RNC

GTW-A

BTS

Iub

BTS

ATM Sw

E1 Links

BTS

Iub

ATM Sw

BTS BTS

MSC

Iur

STM1 links (local)

MGW Iu

Iub, Mub

GTW-A

OPM

GTW-B

RNC

SGSN

Iub over TI GbE backbone

E1 RNC GTW-A GTW-B

E1

OPM TI

RNC

(GbE) E1 Link E1 Link STM-1 VC 12

OSS

GTW-A

Link STM-1 VC 4 Ethernet

E1

ATM

ATM PWE3/Ethernet

ATM

Iub (ATM) over GbE 3G

metro SOL rame

Centrale di attestazione

Rete ottica metropolitana

SDH NodeB

Modem SHDSL

feeder

GTW_A

ADM

Modem SHDSL

ADM

8630

CWDM

RNC

GTW_B

OPM CWDM

8840

STM1

metro Circuito ATM PWE3 (Martini circuits) VLAN per UMTS nxE1 SOL

nxSTM1

GBE SDH

DWDM

Infr. GBE

SDH

Iub over IP

UTRAN Iub over ATM Radio Application Layer ATM Adaptation Layer

Radio Network Layer

WCDMA Radio Application Channels

Specified by 3GPP 

Transport Network Layer

      2      5      0       L       L       L       A      A      A       A      A      A

VC

Common ITU-T specifications used 

(Virtual Channel)

ATM Layer

VP (Virtual Path) Physical Layer

Physical Connection (E1/E3/STM1)

ATM Transport according to 3GPP R99 

UTRAN Iub over IP Radio Application Layer

WCDMA Radio Application Channels

Radio Network Layer Specified by 3GPP 

Transport Network Layer Common ITU-T specifications used 

Transport Layer

Physical Layer

IP

Electrical / Optical (GbE)

ATM Transport according to 3GPP R99 

Iub over IP Protocol Stack

Radio Network  Control Plane  Radio  Network  Layer 

NBAP

Transport  Network  Layer 

Network Synch 

NW Sync

Radio Network  User Plane 

DCH, HS-DSCH, E-DCH FACH, PCH, RACH FPs and Node Sync (over FACH)

NTP (**) SCTP (*)

UDP

UDP

IP

IP

IP

Ethernet

Ethernet

Ethernet

(*) SCTP (Stream Control Transmission Protocol) (**) NTP (Network Time Protocol )

Iub over IP

Eth RNC

Eth

Eth RNC

Eth

OPM

Eth OSS

Link E1 Link STM-1 VC 12 Link STM-1 VC 4

Eth

Ethernet

IP

IP

IP

Iub over IP Architecture (FTTB)

NodeB GE

naked fiber

Optical Fiber Ring

SL Site 

GE

Remote Feeder

OPM

SGU  Site  1GE

Metro FEEDER 1GE 1GE

METRO

10GE

METRO di raccolta

10GE

GE

Optical Network DWDM or naked fiber

RNC 1GE 10GE

10GE

GE

Iub over IP - “Layer 3 Architecture” RPS

HSRP

Layer 3 connection

Layer 3 connection  

MdR = Def Gateway

MdR = Def Gateway  

MdR

Eth

OPM

Eth

Optical Packed Metro Layer 2 Network

RNC RSTP

Remote Feeder

MdR Remote Feeder

RdG

DCN (OSS)

HSRP

Eth

Synchronization over IP solution

Network Synchronization over IP Iu over IP/ETH

Iu over ATM/SDH

2 MHz

GPS

SS SASE

• 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

NTP

• Network synchronization for an IP connected IP/Ethernet Network

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) SC

SC

• No other synchronization functionalities SS

Synchronization Server

SC

Synchronization Client

required (external devices, Synch nodes, GPS etc.)

Network Sync details

RNC Sync Client

Iub over IP

Sync Server

Iu over ATM (SDH)

Timing Unit

Core Network

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.

RNC Sync Client

Iub over IP

Sync Server

Iu over IP

Timing Unit

Core Network

SASE 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

Iub over IP – Network Synch Protocol Stack

Radio Network  Control Plane  Radio  Network  Layer 

NBAP

Transport  Network  Layer 

Network Synch 

NW Sync

Radio Network  User Plane 

DCH, HS-DSCH, E-DCH FACH, PCH, RACH FPs and Node Sync (over FACH)

NTP (**) SCTP (*)

UDP

UDP

IP

IP

IP

Ethernet

Ethernet

Ethernet

(*) SCTP (Stream Control Transmission Protocol) (**) NTP (Network Time Protocol )

Backhauling requirements for Iub over IP

• Service requirements: no additional requirement for the backhauling IP network compared to the "ATM over GbE" solution.

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

PDV distribution

Lowest delay distribution

have less than 20 microseconds delay variation, locking happens quite fast (