Use of MPLS in Mobile Backhaul Networks - Broadband Forum

Use of MPLS in
Mobile Backhaul Networks

Introduction
� Backhaul plays a vital role in mobile networks by acting as the link
between Radio Access Network (RAN) equipment (Eg: radio
basestation) and the mobile backbone network.
– This means that backhaul is able to transport mobile data from the end
user to the internet (or similar network), mobile networks and traditional
telephone networks.
� The rapidly evolving telecoms marketplace has meant that mobile
operators are facing a significant spike in bandwidth demands in the
backhaul due to-
– The proliferation of 3G-based data services and
– The emergence of high-speed air interface enhancements such as High
Speed Packet Access (HSPA).
� At the same time, backhaul network operators are being required to
significantly reduce operational costs in order to compensate for
declining Average Revenue Per User (ARPU) and to compete with a
host of new competitors and technologies.
� Operators are also required to protect (or sufficiently emulate) core
legacy services such as voice, which still account for a substantial
share of revenue.

Addressing the bottleneck
� 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 multipurpose
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, and for the use of future
technologies such as Long Term Evolution (LTE) and mobile
WiMAX.
� Ultimately, this fully consolidated network will be able to handle
many different types of traffic on a single cell site, enabling the
operator to offer many different services to many different types
of customer.

MPLS Mobile Backhaul Initiative
� MPLS Mobile Backhaul Initiative (MMBI) tackles
these backhaul challenges.
� 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.
� This presentation outlines the market dynamics that
are driving the need to deploy MPLS technology in
Radio Access Network (RAN) backhaul and provides
a brief overview of the MMBI.

Market Trends

Traffic Increasing but Revenues Shrinking
� The combination of rising traffic requirements coupled with declining
revenues is a key motivation for operators migrating RANs to a
converged, packed-based architecture
� MPLS has been globally deployed in these types of networks and has
been an important element in creating an environment for the delivery
of new data services
� As these packet-based networks grow in popularity, MPLS must now
also be extended into to the backhaul

Total Cell Sites & Mean Subscribers
per Cell Site (2003-2013)

Market Trends & Challenges
� Third-generation mobile networks have become a
reality.
– The total number of 3G subscribers stood at around 614
Million at the end of 2007 and the number is forecasted to
grow at a CAGR of 34% in near future.
– Growing at a CAGR of over 27%, 3G market for mobile
handsets will supersede 475 Million units (including HSDPA
handsets) by 2010.
– The growing 3G market is expected to fuel demand for 3Gbased
Mobile TV market with subscriber growth forecasted
at a CAGR of nearly 48% by 2012.
– Introduction of femtocells is expected to result in mass
adoption of 3G technology across the world.
“3G Market Forecasts to 2010”, Market and Research 2008

Issues:
Traditional Backhaul-Expensive
� Mobile operators are generating revenues from a range of new
“next generation” data services that are designed to generate
revenues in addition to those from legacy voice services.
� However, these new 3G-based services 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)
� If mobile operators were to expand the backhaul network to
meet these new bandwidth requirements in the traditional
manner, the move to 3G could represent a significant increase
in required bandwidth and associated opex.

Issues cont.
More sophisticated requirements
� Backhaul needs 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 backhaul networks must support many
different generations of technologies simultaneously.
– Must protect existing legacy technology investments for
some years.
– But 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.

Issues cont.
Access & Aggregation Diverse Traffic
� The access and aggregation networks are used for more than
just mobile backhaul and it increasingly being used to carry
traffic for more than one mobile operator.
� This requires methods of separating and securing multiple
operator traffic while maintaining service level agreements
(SLAs).
– We estimate that as many as three-quarters of 2G and 3G cell
sites are co-located.
� The access and aggregation networks can be used to host
multiple services as well as multiple operators.
� An ISP that has an IP/MPLS based network could provide
services such as-
– IPTV
– broadband access and enterprise VPN
– as well as mobile backhaul services, generating further value from
the network.

MMBI meets the needs
Flexible * Scalable * Cost Effective

Backhaul Infrastructure Requirements
� 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
– 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).

Overview
MPLS Mobile Backhaul Initiative
� In 2008, the IP/MPLS Forum, now part of the
Broadband Forum, launched it’s MPLS Mobile
Backhaul Initiative (MMBI).
� MMBI provides a framework for the use of MPLS
technology to bring solutions to transport RAN
backhaul traffic over access, aggregation and core
networks.
� The specification provides possible deployment
scenarios and recommendations on how to deploy
MPLS in each of these scenarios.
� This is a valuable reference guide that allows
vendors and operators to select the appropriate
feature sets for their specific scenario.

What does MMBI address?
� 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.
� 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 covered:
– 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.

Scope of MMBI
Access
Network
Backhaul Transport &
RAN
Access
Network
RAN
2 G
3 G
4 G
RNC
Aggregation
Network
Focus Area BSC
for BBF
backhaul a GW
Transport network &
Mobile Core Network
Core
Network
2G SGSN
3G PDSN/
SGSN
3G MSC
2G MSC
PSN
Internet
GGSN
PDN GW
CSN WiMAX

Business Benefits
� MMBI will directly impact mobile operators’ bottom line by-
– Simplifying operations,
– Reducing Operating Expenses (OPEX)
– Leveraging the cost benefits of backhaul technologies such as Ethernet.
– Enabling operators to support “next generation” services such as locationbased
services (LBS), mobile IPTV and mobile gaming, and
– Providing flexibility 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 track record 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,
mobile backhaul among others.

Why is MMBI uniquely qualified as the
Backhaul solution?
� Amazing flexibility
– Supports both 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.
� 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).
– Deploys on any layer 2 technology capable of supporting MPLS labeled
switching.
– 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 provide
differentiated services for this aggregate so that QoS requirements are met while
at the same time providing further improvements in scalability.
– Provides economies of scale.
� Leverages 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.
� This provides significant reduction of capital and operational costs.

Architectural Scenarios
EDGE (2.5G)
Network
GSM/GPRS (2G/2.5G)
UMTS /HSDPA/HSUPA
(3G)
CDMA 1x-RTT (2.5G)
CDMA 1x EV-DO (3G)
Mobile WiMAX
Long Term Evolution (4G)
R3, R99/R4
R99/R5, R6
IS-2000
IS-856
WiMAX Forum Network
Access Architecture R1.1
R7/R8
Specification
Transport Network
Layers (TNLs)
TDM
TDM
ATM
ATM
IP
HDLC or TDM
IP
IP
IP
Speed (approximate)
56 - 114 Kbps
236.8 Kbps – 473.6
Kbps
~384 Kbps (uplink) ~ 2
to 3.1 Mbps (downlink)
144 Kbps)
~ 1.8 Mbps (uplink), ~
3.1 Mbps (downlink)
50 Mbps
> 50 Mbps (uplink)
> 100 Mbps (downlink

Architectural Overview
� Network architectures for RAN backhaul in
the IP/MPLS Forum’s MPLS Mobile Backhaul
Initiative are defined for various Transport
Network Layers (TNL) and mobile network
generations.
� These scenarios are grouped as follows and
comprise two basic categories:
– Legacy (TDM, ATM, HDLC) and
– Future (IP/Ethernet).

Legacy Options
� In the legacy environment, RAN equipment-
– Communicates via either TDM or ATM TNLs and
– Are connected with a T1/E1 interface, or with an
Ethernet interface (Fast Ethernet) if TDM or ATM
is encapsulated over Ethernet via IP or MPLS.
– The functionality necessary to transport legacy
traffic over MPLS can be performed either at the
edge node, the access node, the access gateway
or directly in the RAN equipment.
– The HDLC layer features in CDMA 1x-RTT and
covers RAN equipment communicating by means
of HDLC-encoded bit streams.

IP/Ethernet Options
� IP/Ethernet scenarios include:
– In R5 3G, LTE and mobile WiMAX environments, the RAN
equipment interfaces use the IP TNL – either at the Iub
inter-face (for 3G) or on R7/R8 for LTE or mobile WIMAX.
– Mobile traffic over IP TNL can be transported either via
Ethernet pseudowires or regular IP/MPLS TE tunnels over
MMBI’s mobile backhaul network.
– IP termination can take place either at the edge node, the
access node, the access gateway or directly at the RAN
equipment.
� Various deployment scenarios arise depending on
the location (and the extent) of MPLS technology in
the mobile backhaul network and whether it
comprises both the access and aggregation sections
of the network or just the aggregation section.

RAN Equipment Synchronization
� RAN equipment needs to be fully synchronized to a common
reference timing signal to ensure-
– sufficient frequency stability,
– radio framing accuracy and
– handoff control for RF channels.
� Thus the mobile backhaul network needs to support distribution
of frequency from the Radio Network Controller (RNC) to the
RAN equipment.
– Example: in the case where the air-interface is based on Time
Division Duplexing (TDD), the base station clocks must be
synchronized to ensure no overlap of their transmissions within the
TDD frames.
� Ensuring synchronization allows for tighter accuracies and
reduced guard bands thereby ensuring higher capacity.

Clocking and Sync in RAN
1: Radio Framing
Accuracy
BTS
BTS
NodeB
NodeB
BSC
BSC
RNC
2 : Handoff
Control 3 : Backhaul
Transport Reliability
Mobile Core
Network(s)
� Synchronization is vital across many elements in the mobile
network
� In the Radio Access Network (RAN), the need is focused in three
principal areas

How does MMBI Address Timing?
� The MMBI outlines the following methods for clock distribution
over an IP/MPLS based backhaul network.
– In RAN equipment with IP TNL (including LTE)
� Packet based methods where the frequency reference is carried over
packets (e.g., based on Network Time Protocol (NTP)) may be used to
deliver frequency to address the frequency stability requirements of
the radio equipment.
– For legacy TNLs, such as TDM and ATM
� Dedicated timing stream implemented using a pseudowire may be
used to carry the reference timing signal from the RNCs to the RAN
equipment both for backhaul transport reliability as well as frequency
stability requirements of the radio equipment
� Other methods for distributing the reference timing signal to the
RAN equipment include:
– Synchronous Ethernet or IEEE 1588 v2
– PDH/SDH transmission mechanisms used in the mobile access
networks.
– GPS is also widely used to support the strict synchronization
requirements of TDD systems

OAM & Resiliency
� A key advantages of MPLS is that it provides a wide selection
of flexible troubleshooting and OAM tools that enable the
deployment of a truly carrier-grade backhaul network.
� These include-
– Fault detection methods to drive protection switching mechanisms
such as MPLS Fast Reroute.
– Fault diagnosis, fault isolation (eg: LSP Ping and LSP traceroute)
and performance monitoring.
– Loopback and connectivity check.
� Examples include VCCV for pseudowire-based MPLS backhaul
solutions and BFD for IP based MPLS backhaul solutions.
� These OAM tools will remain applicable for future LTE mobile
backhaul networks implemented as either IP based or Ethernet
pseudowire based solutions.
– Note: For legacy TNLs and Ethernet pseudowire based solutions,
the MMBI initiative leverages previous specifications by the
IP/MPLS Forum that support interworking between native
Layer1/Layer2 OAM and MPLS OAM.

Conclusion
� MPLS technology in backhaul is the solution to the bottleneck in today’s
mobile network.
– Offers benefits and cost efficiencies in both legacy mobile backhaul and for
future environments based on new technologies such as LTE.
– Protects existing technology investments
– Ensures that the technology will remain sufficiently “future proof” and
scalable.
– New services can be successfully rolled out, while mobile operators are able
to leverage further cost benefits by using an MPLS-based backhaul network
to deliver many non-backhaul services.
� MMBI provides 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).

For more information
Check out
http://www.broadband-forum.org/technical/ipmplstechspec.php