Overview
Designated as a fourth-generation (4G)
mobile specification, LTE is designed to provide multi-megabit bandwidth, more
efficient use of the radio network, latency reduction, and improved mobility.
This combination aims to enhance the subscriber's interaction with the network
and further drive the demand for mobile multimedia services. With wireless
broadband, users can more readily access their Internet services, such as
online television, blogging, social networking, and interactive gaming - all on
the go.
Changes in mobile communications have
always been evolutionary, and the deployment of LTE will be the same. It will
be a transition from 3G to 4G over a period of several years, as is the case
still with the transition from 2G to 3G. As a result, mobile operators must
look for strategies and solutions that will enhance their existing 3G networks,
while addressing their 4G deployment requirements without requiring a
"forklift" upgrade.
Specifically, mobile operators need
the multimedia core network to be readily upgradeable to meet the requirements
of the System Architecture Evolution (SAE), the 4G core network architecture of
the LTE standard.
Solutions already deployed in the market
may include many of the elements required of the 4G network, including
integrated intelligence, simplified network architecture, high bandwidth
performance capabilities, and enhanced mobility. Only solutions capable of
supporting multiple functions in a single node through a software upgrade will
protect today's investment for tomorrow's network, and avoid a costly
replacement of the existing systems.
Radio access solutions are a primary
consideration of the LTE deployment strategy, as LTE impacts the mobile
operators' most valued asset, spectrum. As an equally important part of this
equation, the multimedia core network will play a central role in enhancing
mobility, service control, efficient use of network resources, and a smooth
migration from 2G/3G to 4G. As a result, SAE calls for a transition to a
"flat," all-IP core network, called the Evolved Packet Core (EPC),
which features a simplified architecture and open interfaces as defined by the
3GPP standards body. A key EPC goal is to enhance service provisioning while
simplifying interworking with non-3GPP mobile networks. The standards promise
an all-IP core network with a simplified and flattened architecture that
supports higher throughput, lower latency, and mobility between 3GPP (GSM,
UMTS, and LTE) and non-3GPP radio access technologies, including CDMA, WiMAX,
Wi-Fi, High Rate Packet Data (HRPD), evolved HRPD (eHRPD), and ETSI-defined
TISPAN networks.
As a result, mobile operators are
looking for the best multimedia core solutions to deliver an optimum user
experience and build an efficient network. Key considerations for the
multimedia core network include:
Figure 1. Migration to Wireless
Broadband
• Integration of intelligence at
the access edge: As a greater variety of services and user types cross the
mobile network, it is critical to increase network and subscriber intelligence.
Through this intelligence, including quality of service (QoS) and policy
enforcement, mobile operators will better understand individual users and their
transactions and be able to shape the service experience and optimize network
efficiency.
• Simplified network topology: In
order to effectively deliver the enhanced performance of LTE, the network will
need to be simplified and flattened with a reduction of elements involved in
data processing and transport.
• Optimized backhaul: With the
introduction of 4G, the transport backhaul is a key consideration that many are
realizing after the fact. It is very important to deploy a core network
solution that is flexible enough to offer smooth migration from centralized
(longer backhaul) to distributed (shorter backhaul) core network nodes.
• Converged mobility and policy:
Maintaining the subscriber session is an important consideration during 4G to
2G/3G mobility events. Additionally, unified policy management in the network
is critical for efficient service delivery over mixed 4G and 2G/3G networks. It
is therefore important to deploy a core network based on a single mobility and
policy control paradigm.
• Increased performance
characteristics: Clearly the intent of LTE is to improve the performance and
efficiency of the network. To realize the full potential of LTE, mobile
operators must deploy core solutions that can meet the demands generated by
increased mobile multimedia services and a growing subscriber base, including
increased network capacity requirements, thousands of call transactions per
second, and significant throughput.
• 2G/3G to 4G migration: As
mobile operators migrate their networks to LTE, they will seek to minimize
costs and maximize subscriber usage. This will require core solutions that can
address 2G/3G network requirements, while at the same time be utilized for 4G
network introductions. Operators will want to avoid a "forklift"
upgrade, while deploying best-in-class solutions based on open standards.
Additionally, mobile users will expect a uniform service experience across both
networks, with consideration to the bandwidth differences.
While it is likely the evolution to 4G
technologies will take many years, it is imperative for mobile operators to
identify the multimedia core elements now that will most effectively migrate
them to a 4G network in the future.
Solutions designed for the specific
requirements of the next-generation multimedia core network include the
capability to support both 2G/3G and 4G functionality in a single platform and
will provide major benefits to mobile operators that want to smoothly migrate
their networks, maximize their investments, and offer an exceptional experience
to their customers.
Figure 2. Integrated Multimedia
Core for 2G/3G and 4G
Standard
Interfaces and Protocols
EPC also supports standard interfaces
and open protocols aimed at enabling operators to launch services and
applications with Internet speed, while also reducing the overall cost-per-packet
through the inherent advantages of going all-IP.
Standardized interfaces and protocols
also enable operators to achieve a best-in-class approach with their network
infrastructure. By eliminating proprietary protocols, operators can operate an
open network that empowers them to select the vendors they deem most qualified
to deliver a specific network function without having to worry about
interoperability issues.
Converged
Mobility and Policy Management
In 2G/3G networks, diverse schemes
were used for mobility management within and across the access technology
boundary. So, an operator choosing to deploy 2G access technology of one kind
and 3G access technology of a different kind had to deploy two divergent
mobility management schemes in the same network. This caused serious issues,
and more importantly impeded rapid deployment of some access technologies. EPC
is an attempt to address this divergent mobility management issue.
With a single comprehensive
architecture, EPC supports all access technologies, including 2G/3G and 4G from
all standards-defining organizations. The basis of this convergence is the use
of an IETF-defined mobility management protocol such as Proxy Mobile IPv6
(PMIPv6). If an operator wants to deploy any access technology with an EPC,
a single mobility management protocol such as PMIPv6 is all that's
required. This is a significant step toward building a single common IP core
for future access technologies with seamless mobility. This gives operators the
freedom to choose any access technology without having to worry about a
complete overhaul of their existing IP core or an IP core overlay.
Common Core
Platform
The benefits of an EPC highlight the
growing importance of a common packet core across multiple access technologies.
As many operators transition from disparate 3G specifications (UMTS and
CDMA2000) to LTE and EPC, there is the potential for significant network
simplification and cost savings, as well as greater efficiencies within the
core network.
Integrating EPC Network Functions
The EPC specifications call out the
Mobility Management Entity (MME), Serving Gateway (SGW), and Packet Data
Network Gateway (PGW) as specific network functions, but do not define them as
separate nodes in the network. In keeping with the simpler and flatter
architecture intentions, these three functions can logically be integrated into
one node. However, this will require a solution that is capable of this
integration and can deliver the benefits of such integration.
Figure 3. Combining Network
Functions into a Single Carrier-Class Platform
For instance, the MME, SGW, and PGW
can be combined into one carrier-class platform. By collapsing these functions,
operators could reduce the signaling overhead, distribute session management,
and utilize the control and user plane capabilities of the carrier-class node.
Alternatively, an operator could
deploy the MME separate from the combined SGW and PGW, resulting in reduced
signaling overhead (S5 and S8 would be internal), fewer hops on the bearer
path, less backhaul, reduced signaling on the S7 interface, and lower session
requirement for the PGW. This also provides for a single location for policy
enforcement and charging data generation.
Additionally, colocation of 2G/3G
SGSNs with the MME will significantly reduce signaling and context transfer
overhead. This colocation will also be key to 2G/3G and 4G mobility and session
management. The advantage of integrating or collapsing functional elements into
one carrier-class node is paramount to the goals of simplifying and flattening
the network while also reducing latency.
Convergence
of 3G and 4G Core Networks
The concept of collapsing EPC
functions can be taken a step further. The move to LTE will be an evolution,
meaning many 3G, 2.5G, even 2G networks - whether 3GPP or 3GPP2 - will remain
operational for many years to come. Mobile operators can seize this opportunity
to combine EPC functions with GPRS and UMTS functions (3GPP GGSN, and SGSN),
easing network migration, reducing signaling overhead, enhancing resource
utilization by sharing common session data storage, and improving mobility
between 2G/3G and 4G access systems. Most importantly, operators have the potential
to achieve this without a "forklift" upgrade by leveraging their
existing 3G deployed base. This results in dramatic capital and operational
savings and reduces risk involved in adding new, unproven access technology.
Innovative solutions currently
deployed around the globe already meet many of the requirements of LTE and EPC,
such as integrated intelligence, simplified network architecture, high
bandwidth performance capabilities, and enhanced mobility. Some solutions are
capable of supporting 2G/3G today on a single platform, and through software
upgrades can support 4G functionality when LTE networks are deployed.
Mobile operators will benefit from
solutions that can provide 2G/3G functionality now and evolve to 4G functionality
later without replacing costly systems and equipment that will still be needed
to support legacy networks while subscribers transition to the new network.
Whether existing systems are deployed
as SGSN, GGSN, PDSN, Home Agent, or other gateway functions, they must be
designed to be integrated with or upgraded to the 4G functional elements - MME,
SGW, PGW, and ePDG - through a simple software upgrade.
Intelligence in
the Network
Key to creating and delivering
high-bandwidth multimedia services in 2G/3G and 4G networks - and meeting
subscriber demand - is the capability to recognize different traffic flows,
which allows functional elements to shape and manage bandwidth, while
interacting with applications to a very fine degree and delivering the quality
of service required. This is done through session intelligence that utilizes
deep packet inspection technology, service steering, and intelligent traffic
control to dynamically monitor and control sessions on a
per-subscriber/per-flow basis.
The interaction with and understanding
of key elements within the multimedia call - devices, applications, transport
mechanisms, and policies - require:
• Sharing information with external
application servers that perform value-added processing
• Exploiting user-specific attributes
to launch unique applications on a per-subscriber basis
• Extending mobility management
information to non-mobility-aware applications
• Enabling policy, charging, and QoS
features
