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Abstract: Mobile backhaul is a critical part of the mobile network that links the Radio Access Network (RAN) and the mobile core networks. Service providers are rapidly moving to next generation wireless technologies like 3G, Mobile WiMAX and LTE to satisfy the growing demand of bandwidth and marginal overall growth in average revenue per user. In this new situation, backhaul networks with many cell sites have become the “bottleneck” offering insufficient capacity to support higher bandwidths and often expensive to upgrade. To address the problem, operators are migrating from existing separate, legacy ATM and TDM backhauling networks to a more cost-effective, converged, MPLS-enabled, and multi-purpose infrastructure. In addition to reducing operational costs, MPLS-based networks will also lay the foundations for the delivery of next generation mobile services such as location-based services, mobile gaming and Mobile TV. This paper provides an overview of IP/MPLS Forum‟s Mobile Backhaul Initiative, the challenges which operators are facing in current situation, proposed reference architecture and business benefits of using MPLS in the Mobile Backhaul. MPLS Mobile Backhaul Initiative (MMBI) for 3G/WiMAX/LTE Authors: Ankur Rawat and Sasindran M. Prabhu

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Page 1: Whitepaper mpls mobile_backhaul_initiative

Abstract:

Mobile backhaul is a critical part of the mobile network that links the Radio Access Network (RAN) and the mobile core networks. Service providers are rapidly moving to next generation wireless technologies like 3G, Mobile WiMAX and LTE to satisfy the growing demand of bandwidth and marginal overall growth in average revenue per user. In this new situation, backhaul networks with many cell sites have become the “bottleneck” offering insufficient capacity to support higher bandwidths and often expensive to upgrade. To address the problem, operators are migrating from existing separate, legacy ATM and TDM backhauling networks to a more cost-effective, converged, MPLS-enabled, and multi-purpose infrastructure. In addition to reducing operational costs, MPLS-based networks will also lay the foundations for the delivery of next generation mobile services such as location-based services, mobile gaming and Mobile TV.

This paper provides an overview of IP/MPLS Forum‟s Mobile Backhaul Initiative, the challenges which operators are facing in current situation, proposed reference architecture and business benefits of using MPLS in the Mobile Backhaul.

MPLS Mobile Backhaul Initiative

(MMBI) for 3G/WiMAX/LTE

Authors:

Ankur Rawat and

Sasindran M. Prabhu

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Table of Contents

Introduction to Mobile Backhaul.................................................3

Market trends and Challenges……………………………………………..4

IP/MPLS Forum‟s MPLS Mobile Backhaul Initiative (MMBI)…………6

MMBI Architecture Overview……………………………………………….9

Business Benefits of IP/MPLS Forum‟s MMBI………………………..11

Market Prospects and Vendor Offerings………………………………..12

Conclusion…………………………………………………………………….14

Tech Mahindra‟s Plan………………………………………………..........15

References......................................................................................16

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Acronyms and Abbreviations

ATM Asynchronous Transfer Mode

BS Base Station

BSC Base Station Controller

BTS Base Transceiver Station

IP Internet Protocol

LTE Long Term Evolution

MMBI MPLS Mobile Backhaul Initiative

MPLS Multiprotocol Label Switching

MSC Mobile Switching Center

QoS Quality Of Service

RNC Radio Network Controller

RTP Real Time Protocols

SDH Synchronous Digital Hierarchy

SONET Synchronous Optical Network

TDM Time Division Multiplexing

TNL Transport Network Layer

WIMAX Worldwide Interoperability for Microwave Access

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Introduction to Mobile Backhaul

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.

Fig 1: Mobile Backhaul Network Overview

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 Table 1.

Table 1: Interfaces and Services

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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.

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.

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.

Market Trends and Challenges

The mobile communications industry continues to grow at a significant pace.

Industry sources report the following facts and figures:

The number of worldwide mobile subscribers hit 3.3 billion in 2007 and

will grow to 5.2 billion by 2011*

2.9 million Backhaul connections worldwide in 2006, grown to 4.8

million by 2009*

Two out of every three towers already have more than one mobile

operator on it.

Evolving backhaul requirements per cell site: 2-16 T1/E1s in 2006; 2-8

T1/E1s and 10-30 Mbps Ethernet in 2010

Mobile operators pay incremental charges for 2x to 10x bandwidth*

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Legacy backhaul networks are prohibitively expensive. In the U.S. alone,

mobile operators‟ transport costs have increased from $2 billion in 2006

to $16 billion in 2009

Fierce competition is squeezing margins while new data and video

appliances such as Apple‟s iPhone, Samsung‟s Instinct and LG‟s

Voyager are driving demand for more bandwidth

Growing dependence on mobile connectivity

Exponential traffic growth in parallel to flat or low growth of average

revenue per user (ARPU)

The bandwidth increase will primarily be on Best Effort data user

services and driven by „flat fee business models‟**

More technologies need to be supported: 2G/GSM, 2G/CDMA,

3G/UMTS, 3G/EVDO, HSDPA, WiMAX and LTE

Evolution towards Ethernet and IP-based backhaul solutions.

* Infonetics Research Mobile Backhaul Equipment, Installed Base and

Services,

** Lightreading.

The new 3G-based services will require a substantial increase in bandwidth,

which will in turn lead to greater mobile backhaul costs. It is estimated that

backhaul can account for as much as 30% of a mobile operator‟s operating

costs (Opex) (source: Yankee Group, 2005).

The cost of backhaul is not the only consideration in the migration to 3G. As

well as extra traffic, backhaul will need to be able to handle a range of new

functionality, including Quality of Service (QoS) and resiliency management.

These new elements will become increasingly important as mobile operators

migrate towards packet-based backhaul networks.

Mobile operators will also be required to protect existing legacy technology

investments for some years. At the same time operators will need a backhaul

strategy that is “future proof” and will be able to support a new generation of

networks and access technologies such as LTE. This requires the mobile

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backhaul network to support many different generations of technologies

simultaneously.

The new backhaul infrastructure must therefore meet three main criteria: it

must be flexible (to support both legacy and IP services), scalable (to support

emerging future technologies) and cost-effective (to compensate for rising

levels of backhaul traffic). It also needs to be a converged network, which

means the operator does not need to run two separate networks (leased lines

and IP).

These market trends have made backhaul a strategic asset for mobile

operators and one that is currently a major area of investment; these trends

will grow as further air interface enhancements (HSPA, EV-DO, Rev C, mobile

WiMAX etc.) are rolled-out. However, global ARPU trends remain only flat or

negative, despite uplift in the proportion of revenues relating to higher-

bandwidth data services. This creates a major business challenge with

backhaul as a significant bottleneck

IP/MPLS Forum’s MPLS Mobile Backhaul Initiative (MMBI)

The IP/MPLS Forum is tackling the backhaul challenges via its MPLS Mobile

Backhaul Initiative (MMBI). The initiative aims to leverage the benefits of

MPLS technology in the backhaul by providing a framework for a single MPLS

aggregation/backhaul network that is flexible, scalable and economical.

The IP/MPLS Forum‟s MPLS Mobile Backhaul Initiative (MMBI) proposes a

framework for the use of MPLS technology to bring solutions to transport RAN

backhaul traffic over access, aggregation and core networks.

The framework describes possible deployment scenarios and provides

recommendations on how to deploy MPLS in each of these scenarios. This will

create a reference guide that will allow vendors and operators to select the

appropriate feature sets for their specific scenario. The focus is on a shared

network infrastructure that is able to support (emulate) existing legacy

services (2G, 2.5G) as well as new services based on 3G and beyond (Eg:

HSPA, LTE). This will enable a migration path between existing legacy ATM

and TDM backhaul networks to a more cost-effective, converged, MPLS-

enabled, and multi-purpose network.

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The work is independent from the air interface technology wherever possible

but allows for the possibility that some specific backhaul requirements related

to the air interface may need to be considered.

Areas within the scope of the initiative include: QoS considerations (Eg; to

support specific service types), resiliency capabilities, clocking and

synchronization, Operations and Maintenance (OAM), and support for various

Transport Network Layers (TNLs), LTE and mobile WiMAX.

Fig 2: Scope of MMBI

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Also IP/MPLS forum has described the key requirements for mobile backhaul

in the following table.

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:

Table 3: Network Clock and Time Sync Requirements

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MMBI Architecture Overview The Broadband Forum has published the following technical specification:

MPLS in Mobile Backhaul Networks Framework and Requirements

Technical Specification

The Broadband Forum is currently working on the following technical

specifications

Mobile backhaul network for LTE

Mobile backhaul network for 2G and 3G

Figure 3 shows Broadband Forum‟s proposed reference architecture applied to

centralized mobile networks, depicting the Access, Aggregation and Core parts

of the mobile backhaul network according to the type of TNL used over the

Abis/Iub interface. This reference architecture corresponds to current and

near-term mobile 3G technologies (3GPP and 3GPP2).

Fig 3: Reference Architecture for centralized mobile networks with MPLS for transport

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This reference architecture shows various MPLS use cases that are based

upon the type of the Transport network layer (TNL) carried over the MPLS

network. This reference architecture gives an overview of the functional

architecture without dealing with network node architecture. Four types of

TNL are considered in the work item (TDM TNL, ATM TNL, HDLC TNL and IP

TNL) according to the mobile network generation. TDM TNL is used for

2G/2.5G networks (GSM/GPRS, TDMA, and CDMA). HDLC TNL may be used

for CDMA networks. ATM TNL is used for UMTS-R99, R4 networks, and IP

TNL is used for UMTS R5, R6, R7, CDMA 2000, 3GPP2 networks. A detailed

listing of different TNL is provided in Table 4.

Table 4: Different RANs of Centralized Mobile Networks with Corresponding TNL

In the context of this work, the scenarios arising out of these TNLs are

hereafter referred to as TNL Scenarios since they refer to the transport service

provided by the MPLS network to the mobile network. Thus we have 4 TNL

scenarios, TDM TNL, ATM TNL, IP TNL and HDLC TNL.

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Business Benefit of IP/MPLS MPLS Mobile Backhaul Initiative

This architecture will directly impact mobile operators‟ by simplifying

operations, reducing Opex and leveraging the cost benefits of backhaul

technologies such as Ethernet. It will also enable operators to support “next

generation” services such as location-based services (LBS), mobile IPTV and

mobile gaming, and will be sufficiently flexible to protect investments in new

and emerging technologies.

This flexibility works in two ways: it will protect radio equipment investment

legacy 2G/3G and it will be able to be re-used again as mobile operators

migrate to future technologies such as LTE and mobile WiMAX.

MPLS is an established technology with proven support for providing QoS,

traffic engineering (TE), legacy layer 1 and layer 2 emulation (via pseudowires)

and resiliency features. These advantages can be leveraged for use in a wide

variety of network architectures and applications such as Enterprise VPN,

IPTV, and mobile backhaul among others.

The same flexibility that lets MPLS be applied to these various applications

allows it to be applied to legacy mobile backhaul networks as well as future

technologies such as LTE. For example, the same MPLS network

infrastructure can be used to carry the legacy traffic pseudowires may also be

used to carry and provide QoS guarantees to next generation LTE traffic.

Additionally, MPLS can be deployed on any layer 2 technologies capable of

supporting MPLS labelled switching.

IP/MPLS - with its packet-switching advantages and pseudowire technology -

is ideally suited to overcome the scalability limitations of traditional circuit

based technologies such as ATM and TDM. MPLS permits support of these

technologies using pseudowires to protect existing investments in legacy

equipment. For future IP and Ethernet based interfaces, it is possible to

aggregate traffic over single TE tunnels and provides differentiated services for

this aggregate so that QoS requirements are met while at the same time

providing further improvements in scalability.

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Because a single service provider can leverage the MPLS network to meet the

requirements of not only the diverse set of mobile backhaul technologies but

also to those of other applications, the MPLS network also provides economies

of scale. This has a significant impact in reducing both a service provider‟s

capital and operational costs. Furthermore, investments in MPLS technologies

benefit the service provider by making it “future proof” and still applicable in

the fast evolving mobile technology scenarios (eg: LTE and beyond).

Market Prospects and Vendor Offerings in MMBI space

In the fixed-line network, the successful application of ADSL technology has

brought a 2Mbps bandwidth to the end user‟s home. The increasing growth of

broadband subscriber base results in huge demands for large bandwidth.

Data traffic transferred through the provincial backbone transport network

accounts for 90% of the total traffic. This indicates that the IP-based service

bearing has become the development trend in the industry. The future service

transport network tends to be intelligent, highly integrated and broadband-

enabled, which can be achieved by using the MPLS technology.

Leading network operators such as British Telecom (BT), France Telecom (FT)

and China Mobile have been actively participating in standardization of latest

flavors of MPLS like MPLS-TP and have planned to use the MPLS-TP

technology for service transport and mobile data backhaul. They have been

actively participating in and paying much attention to the development and

testing of related products by telecom equipment manufacturers.

Leading telecom equipment manufacturers, such as Alcatel-Lucent, Cisco,

Nortel, Nokia-Siemens, Ericsson, ZTE, Huawei, FiberHome, UTStarcom, etc.,

have been actively involved in the R&D of the MPLS-TP technology and related

standardization work. For example, ZTE has implemented MPLS-TP related

OAM and protection functions on its ZXR10 9000 and ZXCTN

6100/6200/6300 product series and successfully trialed them over the

networks of operators such as China Mobile and Telecom Malaysia. Huawei

has launched the PTN 912/OSN 3900/1900 series, FiberHome the CiTRANS

660/620 series, UTStarcom the TN 725/705 series, Alcatel-Lucent the 1850

TSS 320/40/5 series and Ericsson the OMS 2430/2450 series.

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On all accounts, both telecom equipment manufacturers and network

operators have been actively engaged in the research and planning of the use

MPLS technology in Mobile Backhaul environment. This indicates that MPLS

has promising prospects and will play a key role in the future mobile backhaul

network.

Companies like Alcatel-Lucent, Cisco, Huawei and Juniper are offering

IP/MPLS forum certified MMBI products. Table shown below gives the details

of vendors, products and certified functionality.

Vendor Product Certified Services

ALU

7750 Service Router,

7705 Service Aggregation Router

TDM over MPLS (T1 and E1)

Cisco

7600 series Edge Router,

2941 Mobile Wireless Router

TDM over MPLS (T1 and E1)

Huawei

CX600 Series Metro Service

Platform

TDM over MPLS (E1)

Juniper BX7000 Multi-Access

Gateway TDM over MPLS (T1)

Axerra AXN1600/AXN800,

AXN10/AXN1 TDM over MPLS (T1 and E1)

Table 5: IP/MPLS Forum Certified Products

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Conclusion

Wireless traffic volume is growing at a staggering pace, driven by new highspeed mobile services such as mobile video, multimedia messaging and web browsing. This traffic growth is made possible by new 3G deployments

such as CDMA EV-DO and UMTS HSDPA, and with 4G technologies like WiMAX and LTE on the horizon this trend is set to continue. The pressure for mobile operators to leverage their networks further, while at the same time

creating a cohesive and logical transformation path towards the next generation is at an all time high. Creativity and effective thinking "outside the

box" will be what distinguishes operators from one another. MPLS technology in the backhaul is the solution to this problem for a series of

reasons. The flexibility of the technology means it will offer benefits and cost efficiencies in both legacy mobile backhaul and for future environments based on new technologies such as LTE. This means existing technology investments

are protected and at the same time ensures that the technology will remain sufficiently “future proof” and scalable.

The goal of the IP/MPLS Forum is to provide guidelines on the architecture, scenarios and technology choices for IP/MPLS RAN backhaul within the

various network environments (legacy, IP, converged).

The MMBI framework is based on the mobile network definitions outlined by the industry standards organizations (3GPP, 3GPP2, WiMAX Forum etc.) The solution is based on MPLS specifications and protocols developed at the IETF.

The MMBI initiative is also being coordinated with other mobile backhaul activities underway at industry organizations such as the Metro Ethernet Forum (MEF) and the DSL Forum.

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Tech Mahindra’s Plan

Based on the Capabilities in MPLS, WiMAX, 3G, LTE and other data-

communication technologies, Tech Mahindra will be able to contribute in the following areas.

Data plane module

Control plane module

OAM module

MPLS, 3G, Wimax and LTE specific features

EMS/NMS module

Based on the opportunity from the vendors, we will be able to select among these activities:

Requirement Analysis

Product Design and Development

Testing and Validation

Interoperability Testing

Network Design, Deployment and Maintenance for Telecom Service Providers.

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References

IP/MPLS Forum MMBI Framework and Requirements Technical

Specifications

http://www.broadband-forum.org/downloads/MPLS-

MobileBackhaul.pdf

http://www.highbeam.com/doc/1G1-193324910.html

http://www.currentanalysis.com

http://www.lightreading.com

http://www.heavyreading.com

http://www.wikipedia.org

About Tech Mahindra

Tech Mahindra is part of the multi-billion (USD) Mahindra Group, in

partnership with British Telecommunications plc (BT), the world‟s leading

communications service provider. Focused primarily on the

telecommunications industry, Tech Mahindra is a leading global systems

integrator, Business Process Outsourcing provider as well as Business

transformation consulting organization. Tech Mahindra has recently expanded

its IT portfolio by acquiring the leading global business and information

technology services company, Mahindra Satyam (earlier known as Satyam

Computer Services).