3glte Mobile Backhaul Network Mplstp Based Solution 3499

8/6/2019 3glte Mobile Backhaul Network Mplstp Based Solution 3499

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3G/LTE Mobi le Bac k haul Net w ork

MPLS-TP based Solu t ion

Whit e Paper

2009 UTStarcom, Inc. All rights reserved. The information contained in this document

represents the current view of UTStarcom on the issues discussed as of the date of

publication. Please note the foregoing may not be a comprehensive treatment of the

subject matter covered and is intended for informational purposes only. Because

UTStarcom must respond to changing market conditions, the information herein should

not be interpreted to be a commitment on the part of UTStarcomand the specifications

are subject to change without notice. UTStarcom makes no warranties, express or

implied, on the information contained in this document.


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3G/LTE Backhaul Using MPLS-TP 1

Proprietary & Confidential

Introduction

Over the last 10 years, the progress of mobile service has been one of the biggest industry

successes in history. 4 billion connections to mobile devices worldwide were achieved for thewireless industry in December 2008 as a historic milestone (Souring: 3G Americas). This

estimate by Informa Telecoms & Media represents 60% of the entire global population today.

In some countries, millions of people are now experiencing connectivity to the world for the

first time through wireless and changing their economic, social and political fortunes forever.

The number of wireless users on 3G services continues to rise. Informa estimates that there

are nearly 415 million 3G subscriptions to date, with 77% share of the 3G market on

UMTS/HSPA networks or 320 million connections, and the remaining 95 million on CDMA EV-

DO. The number of commercial UMTS/HSPA networks has risen to 258 in more than 100

countries, including 41 networks in 20 countries in the Latin America and Caribbean region.

As many emerging markets are achieving a new level of communication, wireless technology

continues its rapid advancement into next generation mobile networks. Currently, more than

100 operators worldwide, including most industry leaders, have announced expectations to

migrate networks to LTE from 2010 and beyond. LTE is the next evolution of mobile

broadband technology that utilizes OFDM-based technology and a flat-IP core network

allowing an enhanced Internet experience on mobile devices.

However, these trends have created challenges for mobile operators, including fierce

competition and margin pressure. In order to improve both their profit margins and more

market share, mobile operators are rapidly developing new applications and services toattract and maintain customers. Now increasing mobile users are going broadband

applications, such as email, text messaging, web access, and live video, benefitting from

more and more portable handset devices.

The mobile backhaul network is the critical link between the broadband subscribers and the

network. Mobile backhaul networks link the remote base stations and cell towards to the

mobile operators core networks and provide access to both the voice network and the

internet. Mobile operators increasingly are focused on mobile backhaul transport, largely

because its costs represent up to 25 percent of their leased-line OPEX according to a March

2006 report by Heavy Reading, an independent analyst firm. One way to minimize transport

costs while increasing network flexibility is migrate to a packet-based architecture, which

achieves bandwidth savings through statistical aggregation of non-voice data services. A key

concern of the migration to 3G network is that any steps towards supporting future demands

must be not at the expense of existing revenue generating voice services. One solution is to

base the mobile backhaul network on packet based technology, which inherently supports

mobile data services and can scale to meet demand, while at the same time support TDM

and other legacy services such as ATM via circuit emulation services and pseudo-wires.
http://www.3gamericas.org/documents/Global_3G_Status_Update1.pdfhttp://www.3gamericas.org/index.cfm?fuseaction=page&pageid=324%20http://www.3gamericas.org/index.cfm?fuseaction=page&pageid=324%20http://www.3gamericas.org/documents/Global_3G_Status_Update1.pdf


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Nevertheless, mobile operators are reluctant to base their mobile backhaul network on

connection-less packet networks. The concern is that connection-less networks will not be

capable of providing the levels of quality and reliability necessary to support voice services.

Connection-less packet networks also demand new operational procedures and re-training of

staff.

Hence the dilemma facing mobile operators: the demands of future services are best met

using a packet based network, but connection-less packet networks could affect existing

revenue-generating voice services. However with the introduction of connection-oriented

packet networks, there is a possibility of solving this dilemma.

In this paper, we will present a migration plan using UTStarcom connection-oriented packet

transport MPLS-TP solution, which provides a path to a fully packet based network with the

levels of quality and reliability that can support both existing and future services.

Mobile Network Evolution & Backhaul

The terrain of mobile backhaul network spreads from the first transport equipment

connecting cell sites (e.g., BTSs/Node Bs/eNBs sites) to the transport aggregation

equipment connecting central sites (e.g., BSCs/RNCs/aGWs sites). The mobile backhaul is

considered to be consisting of three segments, i.e., access network, aggregation network

and metro/regional network (see Figure 2).

The mobile backhaul must be capable of transporting diverse mobile services including 2G,

3G and future LTE services. The logical interfaces and the services transported through the

mobile backhaul are summarized in (not limited to) Table 1.

Standards Inter faces Underlying Transport

2G Abis between BTS and BSC TDM

ATM IMA over E1/T1, ATM over SDH3G Iub between NodeB and RNC

IP over Ethernet

S1 between eNB and aGWLTE

X2 between pair of eNB

IP over Ethernet

Table 1: Interfaces and Services

The 2G Abis interface between BTS and BSC can be based on TDM. The 3G Iub interface

between Node B and RNC can be based on ATM/IMA and IP over Ethernet. From a logical

perspective, the Abis and Iub interfaces are purely static point-to-point connections.


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In the LTE network, the eNB has S1 and X2 interfaces. The S1 interface terminates on the

aGW. The X2 interface runs between eNBs and is used for neighbor discovery, handovers

and cell optimization. Each eNB needs to be able to communicate with its direct neighbors.

Based on LTE ongoing standardization and implementation, most likely, the S1 and X2

interfaces will be based on IP over Ethernet.

Figure 1: Mobile Backhaul Network Overview

Two types of fundamental connections must be established in the mobile backhaul. One is

the point-to-point connection between the transport equipment connecting the cell sites

and the transport equipment connecting the central sites for transporting Abis, Iub and S1.

The other is the point-to-point connection between the transport equipments/interfaces

connecting two eNBs for transporting X2.

To enable the richness of potential applications, unicast and multicast should be supported

by transport equipments in mobile backhaul with efficient utilization of network bandwidth.

Also, IP/MPLS Forum has described the key requirements for mobile backhaul in the

following table:

Mobile Operator Requirements Solutions / Test Areas

Support bandwidth growth and a

competitive cost model

Packet services in the radio access (RAN)

networks

Support a diverse set of interface

types at cell site

MPLS ATM and TDM pseudowires, Ethernet,

and IP

Implement network-based clock

synchronization

IEEE 1588v2, Real Time Protocol (RTP),

Synchronous Ethernet, Network Time Protocol

Version 3 (NTPv3), external clock reference



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Mobile Operator Requirements Solutions / Test Areas

Resiliency on par with TDM network MPLS, PBB-TE, MPLS-TP/T-MPLS, and native

Ethernet resiliency mechanisms

Table 2: Mobile Backhaul Requirements

In addition, network clock and time synchronization plays a critical role when making

technology/vendor choice for mobile backhaul. It has particular relevance for LTE, because

this technology requires not only highly accurate clock frequency synchronization, it needs

time sync as well. The following table depicts the requirement for frequency and time sync

for each of the major mobile technology:

Mob ile Technology Clock Frequency Timing Phase

GSM 0.05ppm NA

WCDMA 0.05ppm NA

CDMA2000 0.05ppm 3s

TD-SCDMA 0.05ppm 1.5s

WiMAX 0.05ppm 1 s

LTE 0.05ppm Time sync is required

Table 3: Network Clock and Time Sync Requirements

TN700 Based Solution

UTStarcom TN700 series products represent the latest generation of equipment supporting

Carrier Ethernet. Each product in this series is fully MEF9 and MEF14 certified and can

therefore be used for offering Carrier Ethernet Services. All of the TN700 products use

high-speed backplane buses and high capacity packet switch fabrics which greatly enhance

efficiency and reduce the overall size and power requirements of the systems.

With its support for MPLS-TP, the TN700 products not only support Carrier Ethernet but the

transport of other legacy traffic including ATM, Frame Relay, and TDM providing carriers

with the option of offering those services as well. This allows an enterprise to migrate to

Carrier Ethernet as they gradually retire their legacy equipment.


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Support for multi-protocol transport enables the TN700 to offer packet based mobile-

backhaul solution. As depicted in the diagram below, all different types of base stations e.g.,

2G, 2.5G, 3G, HSPA, or LTE can be connected to TN700 products and generated traffic can

be aggregated over 10G POS (packet over SDH/SONET) or Ethernet links. The solution also

is capable of handling the inter eNodeB (X2 interface) communication for LTE in a veryefficient and cost-effective manner using L2VPN mechanism. We will discuss this topic in

more detail later in this document.

BTSBTS

Node BNode B

eNB/Node B

Node BNode B

TN725

TN705

TDM n*E1 (copper)

ATM IMA n*E1/ T1 (copper)

STM-1 ATM (Fiber)

FE/GE (Fiber/ Copper)

10G/2.5G/155MPOS

10GE/GE

Cell SiteNetwork CO (Access)

SAToP (RFC 4553)

ATM over MPLS (RFC 4717)

CEP (RFC 4842)

EoMPLS (RFC 4448)

TN Solution Set

TN703E

Figure 2: Connecting Various Types of Base Stations to TN700

Using TN700 Solution, carriers can deploy next generation future-proof network that isbased on simple, easy-to-operate, and cost-efficient MPLS-TP technology. Use of this

technology drives down the OPEX significantly, because it uses less power, less space, and

makes use of existing personnel and their skill set. MPLS-TP supports deterministic-data

plane (This means that the forward and return path for a LSP traverses through the same

set of nodes) enabling it for predictable performance for all different traffic types.

Furthermore, its enhanced OAM capabilities make the trouble-shooting and fault localization

much more predictable and reliable. With TN700 solution, a mobile operator can provide

complete end-to-end backhaul solution while maintaining the connectivity to existing

IP/MPLS core and TDM/SDH/Microwave backhaul network. TN700 solution also meets the

stringent clock synchronization requirements for3G/4G backhaul. It supports Sync Ethernet

and 1588v2. It also has very high clock accuracy of 0.05ppm holdover over 24 hour time-

period. Clock synchronization capability will eliminate the need for local GPS or primary clock

source reducing the OPEX further.



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Cell Site Mobile Backhaul Mobile Core Network

2G BTS

3G Node B

3G Node B

3G NodeB orLTE eNodeB

BS C

aW G

RN C GGSNGGSN

MG WMG W

MS CMS C GMSCGMSC

SGSNSGSN

Operators Circuit SwitchingBackbone Network

Operators P acket Switching

Backbone Network

SGSNSGSN

T1/E1 (Copper)

ATM(IMA/STM-1)


Ethernet(Fiber, GPON, xDSL)

A-bis

E1/T1

AAL2/5

ATM

E1/T1

IMA

AAL2/5

ATM

STM-1

IP

MLPPP

E1/T1

LTE

UDP/IP

Ethernet

STM-

1

ATM

STM-1chGbE/10G

bE

Any traffic overMPLS-TP

TN705

TN705

TN703

TN725

Unified Backhaul Networknified Backhaul Network

Figure 3: End-to-End Mobile Backhaul Solution using TN700

LTE Mobile Backhaul

TN700 provides full support for LTE mobile backhaul using L2 based VPLS and VPWS. L2

Reference model can be found in [1]. As shown in the diagram below, the mobile backhaul

network can be created using TN703 for edge, TN705 for aggregation and TN725 for

distribution function. This network enables both S1 connectivity (eNodeB to aGW) and X2

connectivity (eNodeB to eNodeB). To provide high availability, the aggregation switches can

be connected in a mesh topology. Combined with 0.05 ppm clock holdover accuracy,

synchronous Ethernet, 1588v2, and comprehensive OAM, the TN700 offers a highly reliable,future-proof, cost-effective and low maintenance backhaul solution.


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EPC (Evolved Packet Core)

P-GW P-GWS5 Connectivity

MME/S-GW MME/S-GWAge

o

Ac

Pool Area 1Pool Area 2

U-PE

N- P EN- P E

U-PEU-PE

U-PE

eN B

T N703

eN B

T N703

eN B

T N703

eN B

T N703

eN B

T N703

eN B

T N703eN B

T N703

eN B

T N703

TN 72 5 TN 72 5

TN 7 05 TN 70 5

Figure 4: LTE Mobile Backhaul Solution

Connectivity between the base-stations is a unique function of LTE, it is known as X2

interface. X2 connectivity is achieved by implementing H-VPLS, where the edge nodes TN703 performs the U-PE function and aggregation nodes TN705/TN725 perform N-PE

function. A PW/LSP (VPWS) is setup from each eNodeB to other within a pool area via the

aggregation node serving the pool area, so that each eNodeB can reach its pool area

neighbor directly as needed. Moreover the N-PE or aggregation nodes are connected via

VPLS. If an eNodeB needs to communicate with another eNodeB under different aggregation

node, the communication will occur via the VPLS setup between the aggregation nodes.

Please note that physical link for both X2 and S1 connectivity will be the same between

eNodeB and aggregation node.



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aGWeNodeBeNodeB

eNodeBeNodeB

eNodeBeNodeB

eNodeBeNodeB

U-PE

U-PE

U-PE

U-PE

N-PE

N-PE

U-PE

U-PE

V PLS

aGW

Inter-pool X2

Intra-pool X2

S1 Connectivity

Pool Area 1

Pool Area 2

V P W S

Figure 5: S1 and X2 Connectivi ty

As stated earlier, TN700 is based on MPLS-TP technology. By design, MPLS-TP doesnt

depend upon IP layer (or addresses) for packet forwarding or OAM. The VPWS and VPLS

service setup doesnt require IP address information. This characteristic further simplifies

network planning. It also important to note that according to recent study, in LTE, the traffic

of S1 I/F will occupy more than 95% of network traffic (X2 will be less than 5%). So S1

interface will contribute to majority of traffic. And in such scenario, transport technology

such as MPLS-TP with static provisioning support is the best mobile backhaul solution for

LTE.

Multicast Support

TN700 uses combination of H-VPLS and IGMP proxy/snooping to achieve the multicast

function. In the following an example network is depicted. The TN700 form the H-VPLS

network the distribution layer performs N-PE function and aggregation/access layer

performs U-PE function



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IPTV Feed

IP/MPLSN-PE

U-PE

IGMP Proxy

eNodeBeNodeB

eNodeBeNodeB

eNodeBeNodeB

eNodeBeNodeB Figure 6: Multicast Support

Network Clock Synchronization

Highly accurate clock resiliency at par with TDM networks is one of the key requirements for

mobile backhaul application. Clock accuracy is critical for packet based services offered by

3G, HSPA, and LTE. TN700 has implemented several functions and mechanisms to ensure

that all the requirements related to network clock and time synchronization are met. The

following diagram depicts the synchronization architecture for TN700 based network

1588v2 Eliminates theneed for GPS sync at eachcell-site1588v2 Eliminates theneed for GPS sync at eachcell-site

TDM BasedTiming

Distribution

~

PRCIEEE 1588

Grandmaster

SyncEthernet&1588v2

POSPOS

Ethernet

Node B

Node B

1

2

Scenarios:

RNC

TN703E

Figure 7: Network Synchronization Architecture

With TN700 solution, the mobile operator has a choice of using traditional TDM clock, if

Packet over SDH backhaul (using SSM/S1 byte) is deployed. For 10GE/GE backhaul, the



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clock synchronization can be offered using Sync Ethernet (sync Ethernet is PHY point-to-

point level interface for carrying network clock; resembles SDH/SONET clock distribution

model).

For these applications, carrying time (time of the day) information accurately is equallycritical. Sync Ethernet cant carry time of the day information. For carrying this

information, TN700 has implemented a time over packet (ToP) protocol IEEE 1588v2. The

ToP Server transmits timing packets over asynchronous data path; the ToP slave recovers

timing from these packets. ToP doesnt only requires end nodes to support 1588v2, the

intermediate nodes are transparent to this protocol

Interoperabil ity with IP/ MPLS Netw ork

As mentioned earlier in this paper, TN700 is based MPLS-TP. Since MPLS-TP data plane is

based on MPLS, the TN700 offer full compatibility with existing IP/MPLS core network.

TN700 may be deployed in each metro network and connectivity can be provided betweenthese networks via the IP/MPLS core. It is also possible to interconnect mobile-backhaul

Metro to mobile core network via the same IP/MPLS core. The following diagram depicts

some of these IOP scenarios. TN700 has proven IOP with leading vendors products such

Alcatel-Lucent, Cisco, and Juniper Networks.

Core Network(IP/MPLS)

Metro Network Mobile

(MPLS-TP)Metro Network

Enterprise(MPLS-TP)

Metro Network Enterprise

(MPLS-TP)

Mobile Core

Network

PERNC

TN703

TN703

TN703TN703

TN703

TN703

TN705TN705TN725

TN705TN705

TN703

TN725TN725

TN725

(A)

(A)

(B)

(B)

Internet

Figure 8: TN700 IOP w ith IP.MPLS based core

Enhanced OAM

One of the key strengths of MPLS-TP based TN700 is the standard based enhanced OAM

support. The MPLS-TP working group continues to put significant effort on the integrated



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OAM for MPLS-TP based networks. These networks will support both Ethernet OAM (ITU

Y.1731, 802.1ag, and 802.3ah) and MPLS/PW OAM (Y.1711). The working group has

proposed a new framework for the OAM and has defined brand new functions such as

Tandem Connection Monitoring (TCM) getting direct inspiration from SDH/SONET space.

Moreover the MPLS-TP makes it mandatory to support OAM irrespective of operationalcondition of control plane (optional for MPLS-TP). The following diagram depicts the OAM

framework for TN700 solution:

B1

MPLS-TPMetro

MPLS-TPMetro B2

IP/MPLSCore

Access Link OAMIEEE 802.3ah


end to end LSP OAM ITU-T Y.1711

SegmentLSP OAM

SegmentLSP OAM

end to end ETH OAM IEEE 802.3ag/ITU-T Y.1731

MIP


MEP MEP

MEPMEP

MIP MIP

TN-ATN-B TN-Y TN-Z

P1 P2


MIP

MIP MIP

Figure 9: TN700 OAM Architecture

End to end Service Provisioning

UTStarcom TN700 solution comes with powerful e2e service provisioning NMS system

Netman 6000. Netman 6000 supports all classical functions of a network management

system including topology management, device management, fault management,

performance monitoring, security management, and network provisioning. Netman 6000

implements geographical redundancy (carriers choice) to support business continuity and

high availability. One of the key strengths of this NMS is service provisioning. The service

provisioning layer hides the complexity of MPLS-TP and presents the network in a simplified

manner to the operator. In addition, it is possible to create LSP and PW (as part of

VPWS/VPLS service) with batch commands for efficiency, speed, and accuracy. Operator is

also offered a built-in network capacity planner that empowers them to plan the network in

a timely manner with much less effort.



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Primary OMC-O Server

DCN

OMC-O Clients

NM S

Proxy

NM S

Proxy

OMC-O Clients

TN705/TN725 TN705/TN725

Backup OMC-O ServerPrimary OMC-O Server

DCN

OMC-O Clients

NM S

Proxy

NM S

Proxy

OMC-O Clients

TN705/TN725 TN705/TN725

Backup OMC-O Server

Figure 10: Netman 6000 OMC-O Redundancy Architecture

Advantages over IP/MPLS Switch/Router

Connection Oriented and Deterministic Data Plane:

Unlike IP/MPLS, the Label Switched Paths (LSP) and Pseudo Wire (PW) are established via

NMS using static provisioning. Such characteristic hide the complexity of underlying complex

MPLS protocol. Also, since the path is setup statically, it is much easier to plan the network,

because at any given time operator can view the overall network usage and based on this

information can expand the network in much more predictable and efficient manner. Inaddition, every LSP/PW connection is co-directional (also known as bi-directional), which

means both forward and return path will traverse through the same set of MPLS-TP nodes.

This function is also referred to as deterministic data plane. This function allows operators to

not only troubleshoot the network with confidence; operators can identify the troublesome

parts of the network before the actual problem really happens.

Enhanced standards based OAM:

MPLS-TP working group is putting tremendous effort in the OAM enhancement. Although is

OAM is based on existing standards such as Y.7131 (Ethernet OAM), IEEE 802.1ag and

802.3ah (Ethernet OAM), and Y.1711 (MPLS) OAM, the key differentiator is the frameworkitself. In MPLS-TP, more emphasis is on identifying each LSP/PW uniquely and then applying

various OAM functions to each MPLS-TP which participates in this path. The MPLS-TP OAM

frame derives several concepts such as Tandem Connection Monitoring (TCM), which is used

for inter-provider LSP OAM



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Lower OPEX:

MPLS-TP is based on L2VPN model of MPLS. The L3 implementation is in-general complex

and requires lot more processing power in IP/MPLS switch/router. As a result, IP/MPLS

router/switch consumes lot more power than MPLS-TP. Additionally the MPLS-TP basedproducts can be made available in much smaller factor. Both power and real-estate savings

drive the overall OPEX down. Also, since MPLS-TP is based on simple L2 architecture, these

systems are much easy to operate compared to IP/MPLS router. In fact, any operations

team who is currently handling SDH networks can easily trained on UTStarcoms MPLS-TP

product, because we offer unique end-to-end service (LSP) provisioning via our NMS

platform

Summary

Now mobile carriers are facing great challenges moving to an all-IP based network to getmore efficient bandwidth with a much lower cost per bit. Carriers must ensure to full utilize

their old network for invest protection, and also want to make seamlessly and economically

migration to the new network.

The TN700 Solution provides operators with the flexibility to implement a smooth, cost-

effective migration from 2G, 3G to future LTE in their mobile backhaul network. It combines

the pros of MPLS, pseudowire, and Ethernet technologies to provide not only legacy TDM

and ATM services with guaranteed SLAs, but also Ethernet service to ensure scalability for

unpredictable bandwidth requirement and packet economics for a compelling business case.

So TN700 solution empowers mobile carriers to expand the scope of their network while

reducing the number and complexity of network elements and the corresponding OPEX andCAPEX that negatively impact profits. The TN700 solution also lets operators leverage

UTStarcom industry leadership in the development of MPLS-TP network technology, as well

as the carrier network design, implementation and support experience.

References

[1] MPLS in Mobile Backhaul Networks Framework and Requirements IP/MPLS 20.0.0

Oct 2008

[2] MPLS Architectural Considerations for a Transport Profile April 2008

[3] MPLS-TP Framework draft-blb-mpls-tp-framework-01.rtf (www.ietf.org)
http://www.ietf.org/http://www.ietf.org/

3glte Mobile Backhaul Network Mplstp Based Solution 3499

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