A Seminar ReportOn

Introduction to IP ManagementSubsystem (IMS)

SubmittedIn Partial Fulfillment of B.E. (Computer Engineering)

By

Jaiswal PrateekTE Computer

(Roll No. 3126)

Under The Guidance of

Mr. Nilesh Patni

Department of Computer EngineeringModern College Of Engineering, Pune-05

(2009-2010)

Abstract

The IP Multimedia Subsystem (IMS) is an architectural framework for delivering

Internet Protocol (IP) multimedia services. It was originally designed by the

wireless standards body 3rd Generation Partnership Project (3GPP), as a part of

the vision for evolving mobile networks beyond GSM. Its original formulation

(3GPP R5) represented an approach to delivering "Internet services" over GPRS.

This vision was later updated by 3GPP, 3GPP2 and TISPAN by requiring support

of networks other than GPRS, such as Wireless LAN, CDMA2000 and fixed line.

According to the 3GPP, IMS is not intended to standardize applications but rather

to aid the access of multimedia and voice applications from wireless and wireline

terminals, i.e. create a form of fixed-mobile convergence (FMC). This is done by

having a horizontal control layer that isolates the access network from the service

layer. From a logical architecture perspective, services need not have their own

control functions, as the control layer is a common horizontal layer.

For operators, IMS takes the concept of layered architecture one step

further by defining a horizontal architecture, where service enablers and common

functions can be reused for multiple applications. The horizontal architecture in

IMS also specifies interoperability and roaming, and provides bearer control,

charging and security. What is more, it is well integrated with existing voice and

data networks, while adopting many of the key benefits of the IT domain. This

makes IMS a key enabler for fixed-mobile convergence. For these reasons, IMS

will become preferred solution for fixed and mobile operators’ multimedia

business.

The IMS terminal must perform three major tasks: access the IMS home or

visited network via the IP connectivity access network (IP-CAN), discover the P-

CSCF address and perform IMS level registration.

IMS network operation includes IMS User Authentication and Security

Associations, MS Level Registration, MS Session Setup, IMS Security, IMS Service

Delivery, IMS Roaming and IMS Charging

IMS advantages include separation of transport layer from session control layer -

Access Agnostic , convergence of Wire line and Wireless Services, session

management across multiple real-time services, compatibility with AIN services

(for PLMN), single Public Identity for user, consistency in Billing, Authentication

across various services, service Delivery Platform for new services. MS find a

variety of applications in every field of data communication.

References

The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the

Cellular Worlds" by Gonzalo Camarillo, Miguel-Angel Garcia-Martín.

Multimedia over Mobile IP By Chang Wen Chen and Jiebo Luo

http://www.3gpp.org 3GPP home page.

http://en.wikipedia.org

1. Welcome to IMS

It’s happening again. The telecom world is changing. What will it be this time? More

competition as we saw with the divestiture of the Bell System? Greater mobility that the launch

of cellular mobile networks gave us? Or perhaps a wider variety of information to suit our

personal preferences which the growth of the Internet has provided?

Considering the prevalent view, this change in telecom can bring us all three: more competition

for services, greater mobility, and more personalized services and content. The drivers behind

this change are derived from large and permanent shifts in the economics of today s telecom

market, dynamic new technologies that offer more capabilities, and more subtle shifts in our

information age lifestyle that fuels greater demand.

The changes that are underway are best described using the theme of Convergence:

Convergence of technologies: IP is the common network protocol

Convergence of networks: wireless and wireline networks sharing nodes

Convergence of access: handsets that access more than one network

Convergence of services: features that follow the user across networks

Convergence of content: access the same content across multiple networks

Convergence of revenue: user s demand is divided across fixed and mobile

Convergence of control: customer control over service provider features

1.1 IMS: The Open Architecture Reference Model for Convergence:

The mobile industry, through the Third Generation Partnership Project (3GPP)1, has defined a

model architecture and set of standards that create the framework to support these many forms of

convergence. The open-architecture model is referred to as the IP Multimedia Subsystem or IMS

in reference to the appearance of new services platforms added to mobile networks to deliver an

enriched set of services. Inherent in this new model architecture are definitions for Session

Initiated Protocol (SIP) and Quality of Service (QoS). Adaptations to the model extend the IMS

concept to fixed-line networks as well and define interfaces to traditional networks through

TISPAN2. TISPAN (Telecoms & Internet converged Services & Protocols for Advanced

Networks) includes new subsystems for the simulation and emulation of traditional POTS style

phone services on IP-based wireline networks. IMS technology will have great impact for both

fixed-line carriers and wireless carriers.

Considering convergence from the point of view of a large enterprise, there are a common set of

requirements that the new technology is ready to address. Within enterprises, work is produced

from a variety of different locations, using applications that are mission-critical to the

organization, and through a variety of different devices. There is also an expectation for carrier-

grade service reliability and network capabilities. These enterprises need more than voice

services over an IP network; they need applications that deliver business value over the IP

network.

IMS is an intelligent services platform which supports the delivery of multimedia applications

and content across both wireless and wireline networks. IMS also provides for multiple,

simultaneous sessions across one or more devices enabling greater user control over access to

information. As defined by the 3GPP, the objective of IMS is:

“The IM CN subsystem should enable the convergence of, and access to, voice,

video, messaging, data and web-based technologies for the wireless user, and combine

the growth of the Internet with the growth in mobile communications.”

1.2 Let your Imagination run Wild:

With the concept that a broader range of services can be available across any network quickly

paints an image of the telecom Golden Future:

Any user can obtain any information, at any time, over any device, anywhere they are.

IMS feeds the any information on any device promise and this ultimate view of information and

communication freedom is so appealing it rapidly generates a level of hype that reflects the

vision more than the reality. There are, however, many legitimate new opportunities made

possible by IMS and the changing economic drivers do support some level of convergence.

Many see this shift in the industry to be the most significant change since the emergence of

national wireless carriers from the patchwork of regional players in the U.S. market. National

digital networks offering national price plans and national roaming established a set of six

national operators to re-define the mobile market in the U.S. By looking at the present set of

dynamics some call for the demise of wireline revenue as more usage migrates to wireless. Add

to that the possibilities around a whole new set of service capabilities from IMS oriented to

wireless multimedia and the result is a pretty heady view of a new telecom landscape.

Some predict wireless and wireline networks merging their core networks into one mixed-access

network with shared IMS nodes. Others see large numbers of new virtual network operators who

enter the market with no network assets but offer value-added services through IMS platforms

hosted by others. There are some who predict a growing tilt in the balance of customer control

away from carriers and into the hands of the content providers.

1.3 Not so fast:

In my view, we will not see the fulfillment of the telecom Golden Future in the IMS or

Convergence model. There are many business restraints, competitive forces and technology

limitations that will guide the industry in slightly different directions. This industry will not stand

still waiting for IMS deployment and neither will the technology development at work to favor

one participant over another. The industry is dynamic and this is one of the inflection points

where it is not possible to see all the ramifications of where these changes will lead. Two years is

a long time in the mobile industry and 5 years is a lifetime.

The hype can easily distract us from the potential near-term value and practical considerations

constrained by today s network and today s legacy of invested capital in yesterday s

infrastructure. The technology promises new revenue and the reduction of churn but not until the

services and content applications catch up with the development of the technology. Business will

focus first on the operational aspects over which they have the greatest control operational

expenses. The analysis that reflects future savings in operating expenses will justify the

investments needed today.

1.4 Some New Business Opportunities are real:

Convergence is part of the evolution of wireless mobile that enables the technology to deliver

greater value and drives greater overlap into environments which had been the sole domain of

fixed-wire networks. Convergence together with IMS positions a new paradigm for telecom

providers. No longer defined by their place as either a local access provider, an internet service

provider, or a wireless mobile provider, telecommunications providers can offer some services in

each domain. The progression of the wireless mobile industry has carried it straight into an

intersection with Internet technology and also into an overlap with related industries offering

content and features that will fundamentally alter the business models of the wireless industry

players. The intersection of wireless mobility with the Internet creates new space for new players

with new business models that blur the traditional definition of a telecommunications carrier.

New models for distributing content and for establishing relationships with customers will enable

new entrants to expand the scope of their value and challenge the revenue streams of established

telecom providers.

There are new business models to be explored since new technologies will enable new entrants

to offer robust data and content services to end users with little or no infrastructure investment by

serving as Virtual Network Operators (VNOs). New business models based on the effective

distribution of content across multiple networks and integrated with personal, customized

services generates many varieties of VNOs with more range and scope than traditional Resellers

or MVNOs presently in the industry.

In this paper, the impact of IMS technology on service creation and delivery within the telecom

sector will be reviewed. And how the technology meets the evolving needs of users and the

resulting impact to wireless platforms and wireline networks will be looked. As a result, business

models will change for carriers as well as content providers due to the enhanced access IMS

platforms will provide for directly reaching end users across a variety of applications and

networks.

2. IMS Standards and Definitions

Before looking further at the drivers for these changes in the industry, it is important to define

the IMS model to form the basis of our comparisons with today s telecom architectures.

2.1 Who came up with this Architecture?

The efforts to define a new set of standards for mobile network architectures arose initially from

the Third Generation Partnership Project (3GPP) which was concerned with the definition of

standards for third-generation wireless networks. The 3GPP standards organization was

established in 1998 and largely represents the GSM set of technologies requirements in Europe.

3GPP first proposed IMS and SIP-based multimedia services as part of the evolution from 2G

networks to 3G networks for UMTS. In later versions, interfaces and inter-working were defined

for WLAN.

North American and Asian technologies that differ from the GSM set of standards are addressed

in the counterpart standards group called 3GPP25. The organization structure of 3GPP2 closely

resembles the 3GPP. There are certain differences, some which are significant, between the

standards adopted by each group for IMS.

2.2 Traditional Vertically-Integrated Networks:

Both wireless and wireline networks throughout the telecom industry have traditionally been

highly vertically integrated. Each network contained all the required network nodes and support

systems for billing and services separate from other networks. This level of network separation

was often repeated geographically within each network as well, with separate networks built in

adjacent geographic markets.

In each case, each vertically integrated network contained its own access network elements (base

stations, cell sites), switches (TDM circuit switching), gateways and customer authentication and

control nodes (HLR). The various support systems used for provisioning, billing and vertical

features (voice mail) were also dedicated separately to wireline and wireless networks.

Figure 2-1:

Traditional Wireless and Wireline Vertically-Integrated Networks:

Within the traditional networks there is significant duplication of network elements and multiple

access points to multiple Billing, Provisioning, and OSS systems. Further, the customer

authentication and subscription database is distributed across each wireline End Office switch

but more centrally housed in the Home Location Register (HLR of the wireless networks.

Figure 2-2:

Integrated Elements of the IMS Model Architecture:

IMS is defined for access independence. Services that originate through IP networks can serve

customers across mobile, landline, circuit-switched or WLAN networks. It was originally

intended for any packet-switched network including WLAN, UMTS, GRPS/EDGE,

CDMA2000, and DSL. Circuit-switched networks can be accessed through Circuit Switched

Gateways.

The common use of the Session Initiation Protocol (SIP) across all networks in IMS allows

services to be mixed across different networks, even networks with different architectures.

Roaming mobility is supported by anchoring services through a home network while the user is

accessing a roaming network. Ultimately, the goal is to make it easier and less expensive for any

network operator to offer a wider range of services including Voice over IP and multimedia.

The IMS architecture is organized into three functional planes:

Figure 2-3:

IMS Architecture Planes:

The significant integration of network functions to common control elements and common

interfaces occurs within the Control Plane. There are two major central functions at the core of

the IMS control architecture:

Home Subscriber Server (HSS):

The HSS is the central repository of all subscriber-specific authorizations and service

profiles and preferences. The HSS integrates several functions, some of which exist already in

the functions of the Home Location Register of mobile networks:

Subscriber Profile Database

Subscriber Service Permissions

Subscriber Preference Settings

Mobile Authentication Server

Home Location Register (HLR) for mobile roaming

Subscriber Presence Function

Subscriber Location Function

Call Session Control Function (CSCF):

The CSCF is the primary SIP signaling function in the network. It may likely be manifest

in multiple nodes and redundant and diverse to enhance reliability. The CSCF consists of several

types of SIP servers and process all the SIP signaling in the network. The three most common

SIP servers in the CSCF are:

Proxy-CSCF: First point of contact for device and controls authentication

Interrogating-CSCF: Entry point of all SIP messages

Serving-CSCF: Manages all session control functions

In addition, there the Application Servers and OSS and Billing platform servers those are

aggregated and assembled in the Service Plane. This leaves the network nodes, which are a

mixture of IP nodes and circuit switched modes in the Network Plane. The result is that all the

interfaces for Billing, Provisioning, and Maintenance systems are now aggregated into the

Services Plane eliminating a significant amount of duplication and offering significant expense

savings for service providers.

2.3 Session Initiation Protocol (SIP):

The Glue binding IMS functions and applications.

There are clear interface specifications for the OSS and Billing system interfaces and all call

control and application interfaces to the CSCF function are controlled through the Session

Initiation Protocol (SIP). SIP, together with the aggregation of all subscriber authentication,

service preferences and subscriber details in the HSS comprise the heart of the new IMS

architecture.

SIP works in conjunction with the Session Description Protocol (SDP) to initiate multimedia

sessions. SDP describes multimedia session functions such as session initiation and session

announcement. SIP is used to establish sessions according to the following general steps:

Session Initiation: The user s device signals the need for a session and the user s network

location is identified and a unique session identifier (SIP URI) is assigned.

Session Description: Delivers a description of the session to the user device. The SDP

protocol is used for this function.

Session Management: Once the session is accepted by the user device, media streams or

other content are then directly exchanged between the end points. Real Time Protocol (RTP)

or Real Time Streaming Protocol (RTSP) is commonly used.

Session Termination: Either party in the session can request session termination once the data

or media exchange is complete.

2.4 A Likely Mix of the Old and New:

The migration to the Model IMS architecture will be gradual.

In the end-state diagram of Figure 2-2 the network is portrayed as a tightly integrated set of

access technologies that consolidate their traffic through a single integrated core set of Control

and Service functions. In reality, the practicality of capital investments in existing networks and

the concerns over crossing network boundaries among differing corporate entities will lead to the

continuation of many multiple networks. The opportunity through IMS protocols is to simplify

network boundaries and gradually consolidate redundant network elements in areas where

common corporate control allows.

A significant cost saving opportunity comes eventually with the consolidation of Billing and

Operational Support Systems. Today, these systems tend to be dedicated to specific voice or data

networks and rarely combine the two. Multiple interfaces for each system and the replication of

subscriber data which must be coordinated generate large operating costs that can slowly be

reduced.

2.5 Linking the Subscriber to their Services:

One of the cornerstone concepts in IMS is the ability to locate a user across interconnected

networks and link that user to their services on which ever network the services are located. In

the case where services are distributed across multiple networks, the IMS single session control

concept would link the user back to the network hosting the services while using whichever

network the user is presently on to deliver the service.

2.6 The Present Status of IMS Standards:

The 3GPP has defined IMS standards as they apply to two types of networks, mobile (GSM-

based) and Wireless LAN or WiFi networks.

The 3GPP organizes and releases their standards in the form of Technical Specifications (TS).

The controlling specification for IMS is TS 23.228 for IP Multimedia Subsystem (IMS), Stage 2.

The current Version level is Version 7.1.0 dated October 4, 2005.

Some of the relevant IMS specifications prepared by 3GPP2 can be found under group TSG-X

and in technical specification X.S0013-0028.

HOW IMS UNITE THE CONVERGING TELECOM SECTORS

3. How IMS Unite the Converging Telecom Sectors

It’s not like Telecom hasn’t already been changing…

Technology has already led us far from the Bell System.

We are now at the turning point in the telecommunications industry where the distributed

intelligence and lower cost of the worldwide IP network has finally overtaken the dominance of

the circuit switched world. Further, the flexibility of digital protocols has led to the breakdown of

network barriers as services are carried in packet form across wireline, wireless, Ethernet and

cable networks. We were already well on the way to convergence before the IMS architecture

came along.

Figure 3-1 compares some of the changes driving towards this disruption:

Figure 3-1:

What IMS offers is a standards-based, open architecture with defined protocols to ensure service

quality levels to allow for the broadest range of services across networks. It provides the

roadmap for the convergence journey that digital economics were already driving.

Through these convergence technologies, features and services will extend across network

boundaries. Basic voice services or VoIP can now be found in wireline, wireless, internet, and

cable networks. Instant Messaging also crosses networks and some wireless multimedia

applications also are now beginning to.

Service providers will be under pressure to reduce the cost of providing these services to

improve margins. As they do, they will be looking for the most cost effective means to deliver

services and the IMS model architecture will eventually help move carriers to a lower cost

structure by centralizing features and services into the Services Plane. In some cases, a common

set of Application Servers or Service Delivery Platforms may be able to host services for

multiple networks under one service provider corporate umbrella. This is most practical where

the carrier has sole ownership of the networks rather than through jointly owned subsidiaries

where asset separation may be a corporate requirement.

Overlapping industries tend to become integrated industries. The benefits of a lower

cost structure through the IMS architecture may drive service providers to integrate parts of

their wholly owned networks to deliver services at lower cost.

3.1 It’s all about Connectivity, Control and Customization:

IMS offers many new choices.

Digital technology and the impact it has on the business models of service providers has created

a series of new choices for the subscriber to customize their service usage, gain greater control

over access to information across a broader range of connectivity and devices than before. This

shift in demand patterns will, in turn, cause shifts in the strategies of service providers to meet

these changing patterns in demand.

Usage shifts have already shown significant displacement of revenue from one network to

another. Wireless usage first eroded pay-phone revenue, then it eliminated the need for some

second-wireline uses. Wireless has also been shown to eliminate customer s primary wireline

dial-tone line in certain cases as well. As wireless network access extends indoor through WiFi

networks, and greater web-based and multimedia content is available across greater wireless

bandwidth, these trends already underway will continue.

Convergence is alive and well in wireless and wireline networks. It is further pushed by the

expanding competition focused between networks and also from new service provider models

such as the national Mobile Virtual Network Operators (MVNO) who are competing using

national brand names.

Another economic factor driving convergence is the depreciation of older, circuit switched

technology. Once it reaches the conclusion of its service life, the logical choice for replacement

capital assets is the same lower-cost packet nodes which are the heart of the converged network.

A carrier faced with future growth capacity planning will choose to adopt the convergence path

for the most effective use of their capital budget.

Declining top-line revenue, earnings pressure from higher expenses maintaining older, less

efficient equipment that is expanding as capacity continues to grow, all result in downward

pressure on the stock price of traditional wireline carriers. They must develop new sources of

revenue through new service offerings, improve their operating cost structure and increase their

competitiveness. Developing new features and delivering those features at a lower cost per

subscriber are keys to more effective competition for Wireline carriers. Wireline companies must

innovate new services or other differentiating features in order to stem the tide of eroding

revenues. Convergence is the most compelling plan to improve results on each of these counts,

not only for Wireline carriers but wireless as well. Figure 3-2 summarizes some of the major

drivers pushing wireless and Wireline convergence.

Figure 3-2:

Forces driving wireline and wireless carriers to convergence:

3.2 Connectivity: the first push to Convergence:

Drive for mobility un-tethers the user.

The drive for mobility led to a series of adaptations in the control of the customer s connection to

the network. Not only did the access medium change from copper to an air interface, there also

needed to be a completely different method to authenticate the identity of the user who no longer

had a fixed association to a fixed line. It took the wireless industry a few years to overcome the

struggle of counterfeiting customer identities in the Number Administration Module (NAM) chip

and solve the theft of service through service “cloning”. Second-generation authentication

procedures now safeguard the unauthorized access to a valid customer s identity on the network

and have shifted the fraud focus to subscription fraud in the provisioning process.

Figure 3-3 outlines some of the major user authentication steps through which the industry has

progressed from local loop fixed access to mobility. It also shows the impact of the next step in

the convergence sequence.

Figure 3-3:

Evolution of customer authentication in telecom networks:

3.3 Quality of Service and Resource Allocation are critical.

IMS requires the carrier to have greater control over their network resources:

Offering multimedia services on fixed-line networks and mirroring the fixed-line experience

through mobile networks requires several capabilities not yet present in either network. Chief

among these is the regulation of QoS (Quality of Service) to maintain sufficient throughput

within minimum delay limits appropriate to each session.

In the context of packet networks, Quality of Service (QoS) refers to the ability of the

connection to meet certain specified service commitments. Different types of traffic and different

services require different QoS levels due to their sensitivity to various transmission errors. The

major impairments experienced on packet networks include:

dropped packets -- routers may drop some packets when buffers are full

out-of-sequence packets -- packets arrive out of order and must be re-sequenced

latency (delay) -- packet transit time is delayed due to excessive retransmissions

jitter -- signal variations that can introduce timing errors or bit errors

bit errors -- bit corruption that can accumulate and degrade message integrity

The quality of certain services is much more susceptible to some types of errors than others. The

real-time nature of voice communications over packet, including VoIP, makes the speech quality

very susceptible to latency (delay) more so than to bit errors. Dropped packets may not affect

some services, such as voice, but would ruin the integrity of a file transfer. Therefore, the

network must identify the different types of traffic on the network and ensure that adequate

resources are available to meet the different needs of the different types of traffic.

To control QoS, networks must establish a set of traffic classes for services based on the type of

impairment that is most important to control. These traffic classes can then be prioritized across

the network to ensure the required resources are devoted to the service to preserve the quality

needed. In general, QoS traffic classes prioritize the following two types of services:

Time Sensitive Services -- Services such as Voice or Streaming Media which are very delay

sensitive but are able to tolerate some packet loss and not lose their value.

Content Sensitive Services -- Services such as file transfers and interactive services which

are not as time sensitive but are very sensitive to bit errors and packet loss.

UMTS specifications define four traffic classes for the management of QoS:

Conversational -- VoIP, voice

Streaming -- Video and Multimedia Content

Interactive -- Web browsing

Background -- Email and file transfers

The major distinguishing factor among these four classes is whether they are time-sensitive or

content-sensitive. Conversational and Streaming classes are real-time transfers of data and are

most time sensitive while Interactive and Background must preserve the accuracy of the bearer

channel payload content.

In the Internet, five traffic classes have been defined to control QoS characteristics of traffic

compared with the four classes defined for UMTS:

Premium Constant Bit Rate (PCBR) -- VoIP, voice

Premium Variable Bit Rate (PVBR) -- Video and teleconferencing

Premium Multimedia (PMM) -- Audio/Video downloads, adaptive video

Premium Mission Critical (PMC) -- Transactions, database queries

Best Effort (BE) -- Email, all else.

It is very important to note that it is not enough to allocate resources to ensure that the bearer

(data) channel can achieve the prescribed Quality of Service requirements. The control signals

passing among the nodes in the Transport Plane and the Control Plane must also be QoS

managed to ensure that the entire session quality is achieved.

There are two primary means for providing enough network resources to meet all the QoS needs

present in the demand on the network. One way is through gross over-provisioning where large

amounts of resources (queue size, bandwidth, diverse routes) are provided to ensure that the peak

traffic experiences maximum quality. Obviously very uneconomic in large scale networks and

requires forecasting of peak demand.

The other approach is to control quality and allocate resources through a reservation process by

which the initiation of each session includes a request for the required resources needed based on

the application of the session. Resource requests can then be accepted or rejected based on

available resources at the time. Premium services requiring premium resources can be charged at

a premium as well. The concept of Differentiated Service (DiffServ) for the internet is favored

as the means to regulate resources on a QoS basis. DiffServ routers would prioritize traffic based

on QoS requirements and the available bandwidth of the network. At times of congestion, lower

priority services would be dropped in favor of higher priority or premium services. An

abundance of dropped or denied services due to inadequate resources is a clear sign that capacity

growth is required in the network.

Premium Services will require Quality of Service (QoS) guarantees and resource

allocation of network assets and bandwidth. In the IMS model, these Premium Services create

opportunities for the service provider for service differentiation and premium revenue.

Since the definitions of QoS traffic classes differ between UMTS mobile networks and the

internet, it is necessary to coordinate QoS across the network boundaries. An agreed mapping

arrangement is needed to translate the mobile traffic classes to the internet traffic classes to

match as closely as possible the QoS prioritizations to preserve overall session quality across

both networks. In some ways, the ability to support QoS criteria defines the boundaries between

overlapping networks. Wireline and wireless networks must negotiate the boundaries of QoS

metrics to deliver services with an end-to-end quality commitment.

Also of significant concern in mobile networks is the continuation of active sessions as the users

moves between nodes on the present network or moves from one network to another; even from

the mobile network to a fixed-line network. The seamless continuation of their active sessions

with no user action required and with QoS maintained will require new standards for inter-

network cooperation and hand-off.

In a mobile context, the user s communications will likely be divided across multiple devices,

operating at different speeds and with different computing capabilities. Further, their information

may take multiple forms including voice, data, video, each with different requirements for QoS,

security and throughput. Finally, the entire state-of-the-art in wireless and fixed-line networks

continues to evolve making the specification of requirements and protocols very much a moving

target. Whatever techniques are introduced to meet this suite of needs must also be as dynamic

and adaptable as the evolution of the networks they will depend on.

3.4 Customization: The User gets greater control

Service customization allows the user to create personalized services.

One of the great benefits of locating all subscriber data in one Home Subscriber Server (HSS) is

that the same subscriber database can also record a wide range of customer-specific data. Service

preferences for each subscriber can be maintained to personalized their features and add greater

value to the suite of services for the subscriber.

New service applications and features can be created to leverage the use of individual

preferences. Examples such as time-of-day routing, or device preferences for the download of

media content can provide the user greater control over their subscription and the greater degree

of customization enhances customer retention.

Existing network services for enterprise customers already allow for some degree of

Service Configuration Management (SCM) such as centrex services where the enterprise can

manage their own service moves and changes. The IMS model allows for an expansion of this

concept into management of calling services between networks as well. Another example is a

feature for the simultaneous ringing of two (or more) phones at once, one Wireline and the other

wireless.

Combining customization and preferences with Presence and Location information extends the

concept further into community-based features such instant messaging and locating other users

within user groups based on each customer s opt-in choices. Media control is also possible such

that the user selects audio or music content when they are present on their wireless handset but

prefers video when connected on their notebook computer through a WiFi network.

There is a rich variety of possibilities that new feature applications can exploit based on

customer preferences established through the common HSS database and managed by the

customer to suit their immediate needs.

Service customization through subscriber preferences offers a wide range of new

revenue opportunities. Feature applications can be written that offer greater customer control

thereby enhancing customer retention.

IMS ARCHITECTURE

4. IMS Architecture

4.1 The 3 Network Planes:

Reshaping multiple networks into a common architecture:

The functional elements of the next-generation network (any kind of network, wireless, Wireline,

IP) are grouped in the 3GPP model architecture into one of three planes:

Network Plane: fundamental transport of network traffic

Control Plane: authorization, session management, and call connection functions

Services Plane: multimedia content, gaming content, interactive data services

4.2 The Network Plane:

The Network Plane contains all the traditional network switching and transport nodes found in

today’s Wireline and wireless networks. Given the continuous deployment of packet switching,

SONET fiber systems, ATM and an enormous volume of circuit switch nodes in the legacy voice

network, there are several overlapping access technologies. As a result, the next-generation

network will remain a mixture of circuit switched and packet switched matrices for many years.

In the IMS architecture all these different forms of access are supported. Gateways are used to

interface with non IMS-compatible systems including early VOIP networks. As an example, the

IMS architecture specifies a Breakout Gateway Control Function (BGCF) as a SIP server to

provide routing functionality to phone numbers when an IMS user calls to a phone in the PSTN

or PLMN circuit switched networks. The BGCF function may frequently be housed at the

PSTN/CS (Circuit Switch) Gateway which interfaces with the PSTN or PLMN circuit switched

networks.

The common thread of the Transport Plane is that is contains the traffic-bearing transport nodes

with a mixture of pre- and post-IMS functionality. Most of the past un-depreciated capital

investment is retained and these assets continue to generate revenue and meet capacity demands

while services gradually migrate to newer all-IP networks.

4.3 The Control Plane:

The Control Plane contains all the call control and authentication functions for call setup,

handoffs, and billing recording. The two most important Control Plane functions are the HSS

(Home Subscriber Server) and the CSCF (Call Session Control Function). The focus here is on

network elements and functions which can authenticate customer access establish and manage

voice and data sessions, record billing data and provide all customer-specific functions. Major

functional blocks are shown in Figure 4-2:

Figure 4-2:

Control Plane

As the sole location in the network of customer-specific data and functions, the Control Plane is

the critical point of authentication and customer billing control. All customer authorizations and

preferences on services are housed in the Home Subscriber Server (HSS) which is a database

similar to the Home Location Register (HLR) of the mobile GSM networks. This database

controls all subscriber access functions for authentication and policy decisions for using network

resources. In many networks, multiple HSS are used and another function called the Subscriber

Location Function (SLF) is needed for tracking which network the subscriber is presently located

on. Another possible companion function records Presence information which indicates whether

specific subscribers are present somewhere in the network. Taken together, Location and

Presence information offers valuable functions for service developers to create new location-

based services and community-driven functions among subscriber self-aligned groups such as

instant messaging.

Since the HSS contains the HLR functions from mobile networks, roaming across networks,

even between wireline and wireless networks, continues. The HSS manages all authorizations

and tracking of where the subscriber can be found. Further, the IMS concept defines that the

Home HSS retains control of the session for subscribers even as they roam onto other networks.

The Call Session Control Function (CSCF) is the primary SIP signaling function in the network.

It may likely be manifest in multiple nodes and redundant and diverse to enhance reliability. The

CSCF consists of several types of SIP servers and process all the SIP signaling in the network.

The three most common SIP servers in the CSCF are:

P-CSCF (Proxy-CSCF): This is the first point of contact for the user’s device and can occur

either in the Home network or a Roam network. In the case where the roaming network is not

yet IMS-compliant, the P-CSCF function will be in the home network. The P-CSCF remains

assigned to the IMS terminal throughout the session and inspects every SIP message,

authenticates the user and establishes an IPsec security association with the IMS device.

Once authenticated by the P-CSCF, other nodes respect the trust and multiple authentications

are not required in a session. The P-CSCF also manages the Quality of Service (QoS) for the

session and manages network resource allocation. The P-CSCF also controls the charging

function for billing.

I-CSCF (Interrogating-CSCF): The I-CSCF is the entry point for all SIP messages into the

administrative domain. It retrieves the subscriber location from the HSS and then routes the

SIP request to the appropriate Serving-CSCF.

S-CSCF (Serving-CSCF): The S-CSCF manages all session control for the Control Plane. As

such, it controls Session Initiation, Session Description, Session Management and Session

Termination functions.

Due to the extreme sensitivity of network integrity and security, there are no third-party control

elements in IMS networks. Third-party systems are present only in the Services Plane where

administration of Trusted and Non-Trusted platforms can be controlled.

4.4 Services Plane:

The Services Plane contains the content and administrative platforms including media servers

with media content, billing systems and application servers. There can be a mixture of carrier-

provided and third-party platforms in the Services Plane. Where carriers have allowed access

from trusted third-parties or managed service providers hosting applications, there will be

additional security and isolation controls. Third-party platforms and other non-trusted servers

will be strictly managed behind firewalls and DMZ zones.

One of the major benefits of the IMS architecture is that all administrative servers, including

provisioning, billing, and maintenance systems, are collectively accessed through uniform, open

interfaces in this plane. This removes much of the duplication and proliferation of these systems

across multiple networks. As we will see with IMS in general, this uniform interface is a target

goal and carriers will likely migrate to this structure over time. Since traffic bearing and revenue

bearing nodes tend to be deployed before administrative systems, we will likely see the

consolidation of support systems lag somewhat. Major functional blocks are shown in Figure 4-

3:

Figure 4-3:

Service Plane

4.5 IMS remains Model Architecture:

That is to say, it is not a firm blueprint.

Through the 3GPP standards process, the industry has created an entire series of specifications to

define architecture for the handling of new multimedia services on wireless networks as well as

across network boundaries. IMS is model architecture, meaning that it defines an end-point to the

integration of common multi-network functions in an abstract model. It does not define exact

descriptions of network nodes and the IMS functions can be split, combines, or duplicated for

network redundancy and reliability.

Due to the enormous capital investment already made in the multiple wireline and wireless

networks and the ongoing investment for 3G wireless services, IPTV and Triple Play wireline

services, there is a need for the industry to adopt IMS in a gradual manner to retain the

depreciation of existing assets and generate revenue and return on that investment.

IMS does offer savings in capital and expense but only once further investments of both are

made. Capital savings derived from consolidated feature, billing, and support platforms only

comes after further capital investments in IMS nodes to provide the core infrastructure.

Similarly, expense savings will accrue after the basic IMS functions are eventually deployed. It

is a clear case where capital must be invested in the short-term for expense savings in the long-

term. IMS can move carriers to a new, lower cost structure.

The presence of Gateways and Inter-working functions and other bridge technologies will extend

the life of existing network assets. Some of these deployments may not be fully SIP and IMS

compliant but may gradually move the industry closer to the model architecture. In later years,

these temporary nodes can be eliminated as the core elements they have protected eventually

merit replacement. In the end, the networks incrementally creep closer to the IMS model of

integrated functions along open interfaces all using a common set of protocols.

IMS - BASED SERVICES

5. IMS-Based Services

Faster, Smaller, Cheaper:

Drive new features more quickly to smaller groups with less risk.

In its optimum deployment, the IMS architecture allows carriers to deploy services at lower cost

per subscriber than the present more distributed services architecture. As result, carriers can take

greater risks to deploy trial services to a smaller, narrower segment of the market without having

to provide dedicated support processes and systems for each new service deployed. Since IMS

centralizes and standardizes all operational support system interfaces in the Services Plane, the

amount of incremental resources for billing, provisioning, and support for each new service is

minimized.

Faster, Smaller, Cheaper - Integrated systems support in IMS helps to reduce the

incremental cost to launch new services. Carriers can rapidly bring new features targeted to

smaller segments of the market at lower cost.

In present networks, many of the features are administered and delivered through dedicated

systems to control provisioning, customer care and billing. Voice provisioning and data

provisioning are normally separate with separate billing and customer care systems as well. This

triggers greater down-stream costs such as integrated voice and data billing and increases the

costs of offering bundles since it is more difficult to align the disparate billing systems.

In the final form, IMS provides standard interfaces between Application Servers, Service

Delivery Platforms and the billing and operational support systems. There are also standard

interfaces defined between the billing and provisioning systems and the Home Subscriber Server

(HSS). All of this simplifies the complexity of providing multiple systems to cover multiple

services.

The motivations for convergence for Wireline carriers are somewhat different than for wireless

carriers. Wireline carriers have seen their revenues erode as huge volumes of voice minutes have

migrated to wireless. As a result, they tend to prioritize IMS solutions that will first enable

mobility with their networks, such as linking WiFi coverage with mobile phones as in

Unlicensed Mobile Access (UMA).

A wireless provider see their voice revenue growth beginning to slow and are prioritizing

applications such as multimedia streaming or downloads, as a way to enhance total revenue and

improve on Average Revenue per User (ARPU). Many services fit into one of three categories:

Wireline, Wireless, or a Hybrid of both. Early IMS services will likely stay within either the

Wireline or Wireless categories and more complex hybrid services that cross network boundaries

are likely to follow later.

5.1 Early Targets in the Evolution towards IMS:

New services and new ways to implement existing services.

There are plenty of new service ideas that have never been practical before but can be more

easily devised using IMS technology on SIP-based platforms. There are also many existing

services which can be enhanced through the addition of new features that IMS makes possible.

There are also existing services which can be emulated or converted to a SIP-based IMS service

to integrate with the rest of the network. It is important to base the development of IMS on

services that produce increased revenue.

IMS is not economically viable if the goal is simply to replicate existing services in a

new architecture. The payoff of IMS is to develop and introduce new value-added services for

incremental revenue at a lower cost per subscriber.

In recent surveys of carriers asked what applications were driving the deployment of

IMS in the industry, the top 3 choices typically included Fixed-Mobile Convergence, Online

Gaming, and Music or Media Streaming. Much lower on the lists are existing services such as

Text Messaging and Ringtone Downloads. This supports the point that deployment of IMS must

be led by services that offer new sources of revenue, not by new ways to implement existing

services.

Some of the service categories discussed in the industry today include a mix of single-user

service enhancements, multi-party services, and enhanced media services. In each case, the focus

is on adding revenue generating functionality. Some current examples of service ideas for early

adoption include:

5.2 Early Adoption Features and Services:

Single-user Features:

Push to “x” (talk, read, view, browse)

Dynamic or Smart address book

Multi-user Features:

Instant Messaging plus chat

On-line gaming and sharing content

Point to multi-point broadcast

Enhanced Services:

Personalization of services

Presence and Location enhancements

Smart Address Book provides one conceptual example of a single-user feature improvement.

Consider how most mobile handsets organize their menu functions today. Typically, the address

book contains the phone numbers of your contacts, but text messaging is accessed through a

different menu function and sending an email requires an email client application accessed

though yet another menu. This follows from the separation of voice and data sessions as well as

the need for a more complex handset client to organize email.

A more user-focused design approach would organize the address book by contact with one-

button choices to select whether you want to use voice, text, or email as your medium. The

service can then be IMS-enhanced by adding Presence information and customer preferences

such that the network can tell you if the person you want to reach is presently on the network and

how they prefer to be contacted. Other context-based connections can offer the user more

choices in how they communicate.

5.3 Start with Today’s network; keep it Small and Simple:

Let the market help drive the path of development

It s not hard to dream up plenty of enticing, flashy, unique feature ideas. Ultimately, these new

services must be relevant to the marketplace and hit the magic formula for timing, value, pricing,

need and luck. In the end, all features, whether IMS or otherwise, must deliver compelling value

to the right market segment, with great performance at the right price and at the right time. In

addition, the IMS architecture introduces several new functions which require some adaptation

and integration into the existing business processes before more complex services can be

successfully introduced.

Carriers will want to start with small, simple single-user services to build up the necessary

experience base to progress to more complex offerings. Initial service offerings will not likely be

fully IMS compliant from the start. Phased implementation of IMS functions will focus on

gaining maximum utilization of existing network assets and will make use of existing

provisioning and billing platforms. Inter-working gateways will translate existing network

protocols into SIP rather than native SIP applications extending throughout the network.

Consider the breadth of the scope of changes that IMS eventually will drive into the network and

all the supporting billing, provisioning and maintenance systems. Ultimately, the network

changes are dramatic and the architecture will allow for a lower cost structure for the carrier but

between now and then there will be temporary and hybrid solutions at all levels of the network.

Figure 5-1 identifies some major areas of the network where the implementation of IMS

functionality will emerge gradually.

Figure 5-1:

Staged Introduction of IMS functionality in the network.

Early convergence services must also start out simple and fit within the confines of the network

capabilities. Single network services will dominate for wireless providers who will target

multimedia applications as the initial step towards improving revenue. It is the wireline providers

who will make the first step to providing a cross-network service offering in order to add some

basic mobility functions.

Service providers must carefully watch how the marketplace signals acceptance of these new

services. Once some early concepts are trialed, it is wise to let the market acceptance drive the

direction of feature deployment. Partnerships between carriers and device manufacturers are

needed to coordinate the priority of features that require handset software clients, SIP

compatibility, QoS functionality and other functions that divide between the network and the

device. Many services will simply stay as they are for a time. Email is the major enterprise data

application on mobile networks today. As a simple data application that is not very bandwidth or

QoS demanding, it can continue as a strong money-maker and even expand to more general

consumer use with a simple handset client. Similarly, SMS text messaging is a quick application

that is not likely to be a high priority for overhaul.

5.4 An Early IMS Example: Handoffs between Mobile and WiFi:

Unlicensed Mobile Access refers to WiFi 802.11 access by mobiles

One of the first wireline IMS-like services to be developed is called Unlicensed Mobile Access

(UMA) which targets 3G mobile phone access onto 802.11 WiFi networks. Some wireless

providers may also consider introducing this service early as well.

Particularly, wireless companies that are owned or joint owned by larger Wireline carriers will

see this as a way to leverage the cross-ownership to the benefit of the

Wireline carrier. At the same time, it serves the wireless carrier through defensively guarding

against the threat of VoIP providers taking voice minutes of use away from mobile networks

through WiFi hotspots. This service would allow for uninterrupted voice handoffs between the

mobile network and the WiFi network. It should also provide for continuous data sessions

between the networks without the need to establish a new data session when you cross from one

network to the other.

As a hybrid, this service will require an additional network platform to manage the interaction

between the two networks and to perform session management as the user switches between

networks. This platform will initially have interfaces to the mobile carrier s HLR and the also the

SS7 network of the wireline carrier. It may use a SIP client to help determine where the mobile

user s availability and to determine whether it will be a voice call or a data session. It is a special

purpose service platform that eventually can be eliminated under full IMS compliance when such

cross-network functions become an IMS application running from a Service Delivery Platform

with SIP access to the HSS platforms of both carriers.

Figure 5-2 shows a basic diagram of one example of how the UMA access model can be

implemented in a pre-IMS network using a separate service platform.

Figure 5-2:

One implementation example of pre-IMS Fixed Mobile Convergence.

There are some very early trials of providing VoIP voice service on a WiFi 802.11 compliant

network. Most of these provided independent voice services on each network with no handoff

between the networks at all. Essentially, there were two independent radios within one mobile

handset, one for 3G mobile and one for WiFi 802.11 VoIP. When the user entered a WiFi area,

the mobile would stay one the wireless network until it lost signal, then drop the voice call. The

user could then re-initiate their voice call using VoIP through the 802.11 WiFi network.

Although this provided limited service appeal, it has helped drive technology innovations to

integrate 802.11 technologies into handsets and meet the many size, software and battery drain

problems that became apparent. Most see this as an early evolutionary step towards convergence.

5.5 The Adolescence of the Next-Gen Network will have Turmoil:

Lots of trial and error and extra expenses before it settles out.

As attractive as the IMS model architecture is, and in spite of the simplicity and improved

operating economics it offers, there is not a straight-line path to get there.

Service providers will need to add more equipment, tolerate new autonomous interworking

platforms, and take on extra costs until the critical mass of SIP-compliant nodes and

functionality enters the network.

Service variety, complexity and innovation will grow in proportion to the integration of

IMS standards and functions in the network. Early on, service providers may have to add new,

independent platforms to emulate IMS-like services on autonomous platforms.

For example, one-number services that can simultaneously ring a wireless phone and a wireline

phone will require a dedicated inter-working function in a separate node to interface to both

networks. This new function becomes another new box to manage, maintain, and support with

new technician training and capacity management. While a carrier will choose to implement a

few of these to offer early convergence services, there is a limit to how many such temporary,

autonomous platforms they will tolerate for operational and economic reasons.

The network is destined to become more complex and more expensive before it gets

simpler and cheaper. Carrier focus should be on ensuring it does not become less reliable at

the same time.

A new set of features will emerge in this transition period as each type of equipment provider

moves to implement IMS-like versions of their systems. Some may be more

IMS and SIP compliant than others and each one is looking to add feature functionality to their

systems. Voice mail and messaging vendors will introduce unified messaging services based on

IMS standard interfaces but will surely have ways to support legacy SS7 and messaging formats.

A hybrid system that has an IMS-compliant engine but pre-IMS interfaces will be a common

choice. Since many vendors will offer such hybrids for their systems, the carrier networks can

become cluttered with hybrids that do not aggregate to any consistent IMS architecture.

The capital investment choices by carriers in the transition to IMS are critical to how

quickly they ultimately reach a lower cost network structure. Choosing too many hybrid

solutions too early will waste investment or delay the migration to a heterogeneous IMS

environment.

The competing pressures of driving early revenue gains through new service offerings positioned

against wanting to wait to deploy full IMS-compliant solutions will create a difficult balance for

decision makers. A certain amount of hybrid, adjunct pre-IMS solutions can be reasonably

tolerated if they target high-revenue service opportunities but the real economic gains of

consolidating to an IMS architecture only come once a critical mass of IMS-compliant nodes are

adopted. Aggressive early adopters of pre-IMS platforms with little or no SIP capability must

have a long-term strategy to evolve their investment choices to an end-state model for their

network that provides a fundamentally lower cost structure.

Once the advancement of new features gets underway, there will be richer, more media-inclusive

features introduced. These may still be single-user or multi-user focused but they will involve

both voice and data for full implementation. Some examples include:

5.6 Emerging Features in the Growth and Spread of IMS:

Single-user Features:

Voice with Audio Streaming

Vertical applications for enterprise

Multi-user Features:

Content Sharing among user groups

Entertainment content and sharing

Multi-party voice conferencing

Personal Assistant to manage contacts

Enhanced Services:

Group calling and management

Synchronizing address book with network

Many of these features remain confined to a single network. Cross-network features will

gradually develop in later stages. Instead, the trend in this stage of development is to mix some

media-rich features with more basic high-usage voice features. It is interesting to note that

significant vertical applications for enterprise are also possible with the IMS model. To execute

many enterprise applications with SIP capability end- to end will require extending SIP protocols

into the middleware platforms of the enterprise as well. In fact, imagining the development of a

content-rich enterprise vertical solution could develop into an enterprise essentially hosting their

own Service Delivery Platform or Application Server to take the place of the middleware

solutions present in enterprise networks today.

5.7 Are we there yet?

The IMS future is a moving target.

As time moves on, the industry will evolve to a market-based vision of what IMS will really look

like. Service offerings will mold to reflect what the marketplace accepts and new service

development will follow demand. It is too soon to really know what that might look like. There

are some general expectations to outline the types of service that will likely develop once full

IMS and SIP-compliant systems are widely deployed but the specific service and content blends

will be shaped by the market. Here are some of the types of multi-network and multi-service

features in the vision:

5.8 Long-Term Features in the Mainstream of IMS Offerings:

Single-user Features:

Voice with any kind of multimedia content

Mixed-media vertical applications for enterprise

Video telephony or video messaging

Multi-user Features:

Interactive gaming

Multi-party work collaboration

Multi-party video conferencing

Sharing of applications among users

Enhanced Services:

Context-driven applications

Mixed mode audio-video connections

There are many visions for how the IMS architecture will play out in the long run.

Different vendors will offer different interpretations of the IMS model architecture.

Different carriers will mix SIP-compliant applications and services in different blends.

Carrier will also have different amounts of hybrid pre-IMS platforms that will shape the suite of

services they can offer. Putting the technology choices aside, Marketing will have a huge

influence on the shape of IMS services. Consumer services will take shape around demand for

multimedia and content which will start to shift the balance of customer control away from the

carriers and more towards content providers as the focus on Content increases and Distribution is

seen as more of a commodity.

Enterprise services will also see many changes with the introduction of IMS services.

Specific vertical solutions can be more customized and more tightly integrated to an enterprises

whole IT work flow. Enterprises that adopt SIP-based applications in their middleware systems

can interface to IMS networks through the Services Plane and host their own applications for

corporate users with full content and configuration control over the end user device. Security is a

paramount concern for enterprise applications extended over wireless and IMS gives the

enterprise more control over the total end-to-end application to control end user security to their

own requirements. Handset and PDA devices have already evolved to the point where they have

enough processing power to support complex encryption clients that enterprise applications can

direct. Further, handset development is moving to integrate flash memory removable media cards

into handsets which sharply increases available memory. There are also development

opportunities to embed security and authentication functions directly onto the removable

memory card which would offer a more robust security solution than is possible on the more

limited SIM cards used in GSM devices today.

There are differing views of the degree to which mixed wireline and wireless networks will

integrate and there are many opinions about who wins and loses as the value chain adjusts to

accommodate the new Virtual Network Operators and the third-party service creators. The most

likely outcome, however, is that we will never quite reach the complete vision of the IMS model

architecture. There are many moving parts in the technology, in the standards, in the unknown

market demand. The picture will continue to evolve as it is implemented. We many never see the

full seamlessness of roaming, or the full richness of multimedia, or the full integration of multi-

network nodes. This massive industry exercise will have been successful, however, if it succeeds

in establishing a lower operating cost structure to offer a wider variety of services.

The changes in IP technology have permanently invaded the telecom arena. Telecom will follow

the path of SIP protocols towards IMS. The impact is enormous for service providers and brings

new opportunity to other service creators and content providers. In the end, it is all about

becoming more efficient as an industry. Whatever the services ultimately shape up to be, the

clear indication is that economic inertia will win as the total cost to develop, offer and support

new services will decrease.

CHANGING THE SERVICE DELIVERY PARADIGM

6. Changing the Service Delivery Paradigm

IMS standards and systems enable the flexible implementation of features and services across

multiple devices and networks using open architectures and standards. A major element in this

architecture is the Service Delivery Platform (SDP), also known as Application Servers and

Media Servers, which are used to host a wide range of services across multiple networks.

The gradual emergence of IMS platforms is really the migration to a series of parallel, standards-

based, open architecture platforms including Application Servers and Home Subscriber Servers

(HSS). Each function of the IMS architecture addresses specific interfaces in a more abstract

manner in order to apply across a broader range of the network and between networks. The result

of this generalization of repeated network tasks and services is to more effectively integrate

related services together and reduce the operating cost by interfacing with a common set of

support functions such as billing and provisioning. Services can be more tightly connected and

combine features into value-generating sets. It is another step in removing previously proprietary

functions which had been embedded in network nodes and allowing for more open access to

these common network functions. The services and feature applications are becoming decoupled

from the network infrastructure.

Using an open architecture model, Service Delivery Platforms perform the following:

Deliver and manage services across a wide variety of end user devices.

Support SIP-based applications and services across multiple networks.

Separate services and features from the Transport Plane network nodes.

Provide single point of access and an open platform for developers.

Provide defined interfaces to billing, provisioning and support systems

Provide a unified means to manage growing numbers of developers.

6.1 Where the Service Delivery Platforms reside in the Network:

Two new layers of functionality are created above the Transport Plane.

The IMS architecture separates the network by adding new layers of functionality separate from

the Transport Plane. The Control Plane contains the critical Call Session Control Function

(CSCF) and the Home Subscriber Server (HSS) functions (among others). The Service Plane

contains the Service Delivery Platforms (SDP) and the Application Servers (AS). The new

services and integrated features across multiple networks are hosted by the SDP and AS in the

Service Plane.

Figure 6-1:

6.2 How this New Model of Service Delivery is Different:

Feature Silos in the good ole days.

In voice networks, in particular, the implementation of enhanced services and features can

readily be seen in separate but similar manifestations throughout separate network nodes.

Examples include call waiting, conference calling, and voice mail services which had broad

application and customer acceptance.

Simple, Single-Node Features:

Certain of these features, such as call waiting and 3-way conference calling were relatively

simple applications that were incorporated directly into the network switching nodes at a local

Class-5 level at the edge of the PSTN voice network. These services had a high degree of

uniformity and generally worked in a similar, if not identical manner across manufacturers. They

did not, however, operate the same way in wireless networks as in wireline networks. Without

the physical signaling mechanism of onhook and off-hook , wireless networks required a

different operational process to implement features that perform the same function as their

wireline counterparts.

Since ubiquitous availability of these features was desired, it required that capital investment be

made at every network node across the network. It also required that the traffic-variable features

resources, such as conference calling bridges needed traffic management attention and periodic

capacity augmentation. This distributive method of feature deployment allowed for choices in

feature availability in some geographic areas preferentially. Capital investment could be made on

a geographic but not necessarily on an economic basis.

Complex, Systems-based Features:

Other more complex features, such as voice mail and larger multi-party conferencing systems,

required separate processing and storage resources and were commonly deployed as standalone

systems through specialized product vendors. Many of these systems incorporated prompt-driven

menus as the typical user interface which could be customized by the service provider. The result

was a patchwork of variation in feature compatibility and operational consistency. Menu choices

were often different between vendors and sometimes even between two implementations of the

same vendors system. Some service providers deployed voice mail systems dedicated to

individual network nodes while others aggregated voice mail resources into pooled locations

serving clusters of switches or across a geographic region. Upgrades, for feature enhancement or

for capacity augmentation, had to be applied repeatedly across multiple locations.

As with node-specific features, geographic deployment was based on the geographic footprint of

the network nodes which subtend the pooled resources. Cluster or regional deployments required

parallel, redundant operations functions which may differ based on the vendor chosen for each

regional deployment. The net effect is that many voiceoriented services were implemented

repeatedly at a local service level close to the edge of the network and sometimes inconsistently.

In contrast, standards-based IP Service Delivery Platforms occupy a position above the

individual network nodes in the hierarchy and apply features across not only multiple network

nodes but even across network boundaries. Using a per-customer, per-feature control structure,

services are controlled in a more network agnostic manner with the opportunity to offer a

broader array of services across a broader array of customers than previous models of distributed

service functions provided. SDPs become open architecture IP platforms which host abstracted

network functions and controlled through the policies and subscription permissions of the

separate Policy Administration Servers and Home Services Systems in the Control Plane. The

SDPs work in conjunction with these other new elements in the telecom architecture to form a

new model of multi-network control and operation.

6.3 Benefits of a New Service Delivery Model:

New Service Delivery models make the playing field more level.

One common, high-level aspect of SDP systems and Application Servers is that they create

abstract elements from the many functional elements that occur repeatedly throughout separate

networks. By their location in the higher service planes of the network architecture, they have

greater reach across networks and can be shared among multiple applications at a lower total

cost.

A generalized portfolio of functions has distinct advantages over dedicated node or distributed

service functions, including:

Ubiquity of feature availability

Consistency of operation and maintenance

Efficient maintenance and monitoring

Per-user subscription of individual services through policy control

Lower per-user capital and per-user operating expenditures

Access-to and distribution-of third-party services from new service creators

Ability to host equivalent services across multiple networks

Cost point is low enough to target smaller market segments

More of a supply and demand services model

Service features are more virtual and not network-specific

Uniform interface to back-office provisioning and billing systems

Provides a common User Interface that is more intuitive

Can be made to simulate or emulate traditional services

Eliminates duplication of common functionality

It is the fact that these services are separated from the network nodes and aggregated at a higher

functional level in the architecture that creates new service model possibilities for new content

and application players in the industry.

The Service Plane helps to level the playing field among network-based carriers and

other non-infrastructure service creators. Separating and standardizing the control and

delivery of service features acts to remove the walled garden of proprietary features and opens

access to new content.

Several new market dynamics are created in the process of making the networks more efficient.

Costs are reduced for the service providers and greater access is achieved for the service creators.

Incumbent service providers can make available a broad array of differentiating service features

very efficiently. The distinguishing element of their offering shifts from being based solely on

the features offered but also on the exclusive partnering with unique service creators and content

providers.

6.4 The Door Opens for Alternative Service Providers

The Emergence of the Virtual Network Operator.

These direct benefits from the promotion of Service Delivery Platforms to a higher position in

the network hierarchy open the door for an increasing role of alternate service providers.

Characteristic of these alternate providers is their role in the customer relationship with no

formal network infrastructure. Virtual Network Operators (VNOs) create business value on the

merits of a collection of services and features offered to customers on a subscription basis and

offered through the distribution of the wireless and wireline network infrastructure providers.

With service creation and delivery functions abstracted to separate open-architecture IP

platforms, there exists a balance between the expanded capability of new features on the one

hand, and the consistent control and policy administration of the interfaces on the other hand.

Although there is greater room for new service providers to enter the market, incumbent carriers

will retain the ability to differentiate themselves from competitors through distinctive exclusive

content and feature offerings they provide. The carriers continue to control the Transport Plane

and the Control Plane.

6.5 The Impact on Wireless and Wireline Carriers:

Open architectures and standards-based services create opportunities for the incumbent wireless

and wireline carriers as well. As cost advantages of IP networks begin to displace the traditional

TDM and circuit switched networks, incumbent carriers will migrate their infrastructure to an IP-

based architecture. This evolution with drive many other changes in Authentication, Policy

Administration, Digital Rights Management, Billing and Provisioning system interfaces, some of

which are not as yet thoroughly defined.

By adopting IMS-based systems and SIP-based applications, carriers not only achieve the

benefits of a lower cost structure, they also gain a more flexible platform for offering competitive

and targeted service offerings and content to a more targeted market segment. Through

Application Servers linked with Policy Servers and Home Subscriber Servers, carriers can offer

customized service packages to increase customer retention and lock in revenue streams with

more ways to meet customer service needs.

Carriers also gain the opportunity to host third party applications on their service platforms and

negotiate access to their customer s presence information and HSS functionality. A third-party

developer can launch innovative services in a hosted environment through a variety of

relationships with the hosting carrier. At one end of the spectrum is an application developer who

produces features under a services contract with the carrier and delivers turnkey software

applications with no claim on customer presence of any kind.

A further step might be a developer who develops an application and enters a comarketing

agreement with a carrier and has a brand presence in front of the customer. A third possibility is

a developer who simply enters a hosting agreement with the carrier, negotiating access to the

HSS, Application Servers, and perhaps other servers offering Presence or Location-Based

information. The developer then freely markets their features independently from the carrier. All

of these models exist in the industry today, but IMS technology provides a standard, defined

interface and platform to host applications allowing for a broader range of feature possibilities

and faster access for developers and content providers to enter the game.

The following chart diagrams this range of relationships and shows how IMS technology drives

expansion in this opportunity to engage with third party application developers.

Figure 6-3:

The improved interfaces with billing and OSS platforms along with SIP-based applications will

enlarge the overall services market allowing greater entry for new independent developers.

Multi-network service providers and VNOs will have new distribution channels for their content

and services.

SIP-based applications development expands the size of the feature market for

everyone. The position of independent developers and VNOs using emerging service-hosting

arrangements expands more than others.

6.6 Rapid early deployment will likely involve Partnerships.

Carriers and Developers cannot move forward alone yet.

Although these new technologies provide new resources and improved access to the network for

third party developers, we will initially see Carrier-Developer partnerships as the dominant

model for launching new services. The technology offers the ability to rapidly create and deploy

new features but rapidly bringing those services to market in the near-term will continue to result

from cooperation between carriers and close partnerships with specific developers. Enhancing a

carrier s ability to quickly bring new services to market will be a key strategy for developers to

create practical partnerships.

Carriers will quickly realize that they are not well positioned to re-invent the application

development process in-house to create innovative new services. This would remove many of the

cost-saving benefits of the new architecture to bring new services to market more quickly and at

a lower cost per subscriber. Not only would it be more expensive, but as already discussed in

terms of the crumbling walled garden, carriers realize that extensive application development is

not a core competency.

For their part, third-party application developers offer great innovation for a wide variety of

compelling features and services but as yet, lack direct market access to deliver those solutions.

For the near-term, the balance between application content and feature distribution must be

struck through Carrier-Developer partnerships. For now, the rapid deployment of new features

using third-party developers on IMS-based platforms will likely emerge from the middle Co-

Marketing portion of the Feature Deployment spectrum in Figure 6-3.

In time, new business models of service hosting similar to web-hosting will likely emerge where

third-party developers can host their applications on carrier networks with more independent

relationships.

Partnerships and Co-Marketing will dominate in the near-term. Service-hosting

arrangements similar to web-hosting will emerge as the concept matures.

6.7 Significant Challenges for Billing and Service Configuration Management:

As carriers strike new partnerships with developers for multimedia content there will be strong

focus on the management of these new services in the present environment of disparate billing

systems and provisioning processes. Although IMS defines interfaces for support systems with

third parties, it is likely that deployment of these enhanced processes will lag the desire to

quickly launch new revenue generating services through high-vale partnering agreements. The

result is that current billing and administrative processes will prevail over the long-term view of

simplified interfaces.

The back-office operations to provide service fulfillment, configuration, maintenance and billing

often provide the carrier with the greatest sticker shock in terms of the costs of deploying new

services. The complex weave of customer care access, billing data streams, provisioning and

service audits often result in significant administrative costs, IT development time and

operational expense. In the long term, the increased revenue from launching more targeted

applications to smaller target customer segments will only produce positive incremental cash

flow when back-office support systems are also consolidated through standard interfaces so that

each new offering is not a duplicative effort for the support systems.

By defining standard interfaces for support systems, the IMS model architecture seeks to reduce

the total cost of providing new services. More rapid implementation of services by leveraging

existing standard interfaces with billing and support systems allows for more narrowly targeting

services while maintaining profitable operating margins.

Leveraging a common set of billing and support systems through IMS open interfaces

is a critical element to reducing operating costs to launch services more quickly and maintain

operating margins.

HOW IT ALL FITS TOGETHER

7. How it all fits together

The telecom industry has been continuously re-shaped since the AT&T Divestiture of 1984.

Many of the changes have been gradual and evolutionary. A few have been revolutionary or

disruptive and have had major impact. IMS technology will be one of those large changes that

impacts on the existing service providers, allows entry for new service providers, and also

changes the business plans for the network equipment vendors.

The impact of these changes, however, will develop over the next 3 or 4 years and will not

change the face of telecom overnight. There are billions of dollars of invested capital in plant and

infrastructure that carriers must continue to operate to generate returns. The existing

infrastructure will need to inter-operate with the gradual introduction of new systems that

prioritize the opportunity for new revenue sources. This mixed environment will continue for the

next several years.

This change in the direction of telecom cannot be ignored by any carrier. Wireline and wireless

carriers are faced with permanent shifts of their revenue composition, cable providers see

wireline providers invading the video distribution market. Convergence brings more mobile

functionality to fixed networks and multimedia is now feasible acrossmobile networks. Content

owners and distributors are now seeing whole new media outlets for their property and some are

entering the telecom space as VNO s.

7.1 Changes affecting the Wireline Carriers:

Losing voice revenue to wireless networks.

Stagnant stock prices under perception of commodity service.

Introduction of DSL technologies positions them as broadband internet access

providers.

Building out fiber and Ethernet networks to offer multimedia and video on

demand.

Supporting convergence and IMS to offer voice mobility on WiFi networks.

Broadband and Ethernet offers enterprises with VPN and vertical solutions.

IMS offers the ability to support multi-network services with wireless affiliates.

Changes affecting the Wireless Carriers:

Growth in voice service revenues is slowing.

Need to supplement voice revenue with new, innovative data applications.

Rapid expansion of network throughput through 3G technologies (EV-DO,

UMTS, HSDPA)

Younger, more flexible infrastructure that can more quickly adopt IMS

technologies.

Supporting convergence as a way to defensively increase customer retention.

New revenue sources through multimedia streaming and download content.

IMS offers the ability to support multi-network services with wireline affiliates.

New partnerships with private-brand Virtual Network Operators and service

creators.

The advancements in the technology and the shifts in the flow of revenue among service

providers will drive service providers to extend beyond their traditional network boundaries and

this can lead to changes in the ownership of the customer relationship as well.

7.2 The big drivers are Lower Cost and New Revenue Sources:

The greatest challenges for any telecom service provider are to operate their networks at the

lowest unit cost structure possible and open new sources for subscriber revenue. IMS systems

offer the opportunity to do both in the long term. In the short term, carriers must expect to invest

more capital and make the network a little more complex before it gets simpler. The search for

new sources of revenue will lead carriers to introduce multimedia content and innovative new

services over networks that have dramatically improved throughput as compared with just 3 to 5

years ago. IMS technology will help carriers experiment with new services and bring them to

market more quickly and at a lower cost. Ultimately, the marketplace will determine the

successful mix of features and carriers will continuously innovate to follow where the market

leads them.

7.3 IMS brings a lower cost structure to carriers:

Overlapping networks tend to become integrated networks. The benefits of a lower cost structure

through the IMS architecture may drive service providers to integrate parts of their wholly

owned networks to deliver services at lower cost. IMS offers a lower cost structure for both the

Expense Budget and the Capital Budget.

Operational expense savings:

Since IMS platforms integrate common billing, support and maintenance interfaces through open

standards, the carrier can simplify their operations and reduce expense costs. IMS platforms offer

an open architecture for new service creation and delivery without having to replicate

provisioning and billing support for each application, the time to market and cost to introduce

new features are also reduced. IMS platforms are not economically viable if the goal is simply to

replicate existing

services in a new architecture. The payoff of adopting IMS-based systems is to develop and

introduce new value-added services for incremental revenue at a lower cost per subscriber.

Leveraging a common set of billing and support systems through IMS open interfaces is a

critical element to reducing operating costs to launch new services more quickly and maintain

operating margins.5

Capital budget savings:

Under the IMS framework, all major network functions comply with open standard interfaces.

Further, all services whether voice, data, or multimedia, are IP packet-based and carried over a

common core infrastructure. Only the access technology is specific to the transmission medium

used (wireless 3G, WiFi, Ethernet, etc.). Reducing the core network to an all-IP technology

simplifies the architecture and capitalizes on the economies of scale of computing platform

technology to lower equipment costs. The open standardized interfaces between nodes allows

carriers to source their network equipment from multiple vendors supporting overall lower

capital costs.

Even though the IMS framework supports lower costs, the network is destined to become more

complex and more expensive before it gets simpler and cheaper. The reality is that today s

networks are already loaded with infrastructure with long depreciation cycles are still earning a

return on their original investment. Even wireless networks, which have the lower average age of

plant, still have large volumes of imbedded investment with some recent high investments for 3G

that have yet to provide their full return. The result is that carriers will want to continue to use

existing infrastructure to provide new services. In the short-term, this will introduce new

dedicated-purpose autonomous platforms to offer some specific pre-IMS features using the

imbedded infrastructure. Also, carriers will implement special purpose inter-working platforms

to link existing pre-IMS networks together.

The capital investment choices by carriers in the transition to IMS are critical to how quickly

they ultimately reach a lower cost network structure. Choosing too many hybrid solutions too

early will waste investment or delay the migration to a heterogeneous IMS environment. Carrier

focus should be on ensuring it does not become less reliable at the same time.

7.4 The IMS model architecture brings New Revenue Opportunity:

The theme of IMS-based services will be Faster, Smaller, and Cheaper. Carriers must develop

new revenue sources quickly and improve operating margins. IMS platforms are designed to

integrate the required support functions of any new feature such as methods for provisioning the

new service, billing for the new service, and administering the services. By leveraging the same

set of OAM&P functions for all services rather than having dedicated OAM&P systems for each

service, the carrier can streamline the deployment of new features. Using the integrated IMS-

based Service Delivery Platforms, carriers can introduce services more quickly by not having to

establish the dedicated OAM&P systems and processes to support each new service. A new

feature can be more quickly trialed and deployed while the administration of the new feature

flows to existing systems. The carrier gains a time to market advantage.

New Revenue through more Targeting Service Offerings:

Similarly, with the ability to launch new service more quickly without the parallel launch of new

support processes, the carrier can also take a chance on launching more targeting niche services.

Each offering does not have to be a blockbuster, but new revenue growth can be nurtured among

an extensive set of niche offerings completed at lower cost. Carriers can more easily justify the

smaller incremental investment to target a new feature idea towards a smaller, perhaps more non-

traditional market group.

New Revenue through Premium Services Offerings:

Some of the most significant benefits from the IMS model architecture come from the wide

range of new services that can be created. Multimedia, video, streaming applications, downloads,

and vertical solutions for enterprise are all enhanced through the availability of greater

bandwidth and unified control. Premium services will require Quality of Service (QoS)

guarantees and resource allocation of network assets and bandwidth. In the IMS model, these

premium services create opportunities for the service provider to differentiation their services

and charge premium revenue. The carrier with the greatest unified control over their service

quality can segregate services with assured quality metrics and create classes of service quality at

premium prices.

Service customization through subscriber preferences offers another wide range of new revenue

opportunities. Feature applications can be written that offer greater customer control thereby

enhancing customer retention. Using the capabilities of the Home Subscriber Server and the

Presence and Location Server, carriers can develop innovative new features that customers can

tweak to their own preferences. This offers the combined benefit of higher retention and the

creation of premium revenue services.

7.5 Service Creation and Delivery create new Service Partnerships:

The IMS model architecture defines standard interfaces for the Service Delivery Platforms in the

Services Plane of the network. New platforms with standard tool kits to create new services

allow for the uniform delivery of new features through open standard interfaces to the Control

and Network Planes. This established a clear line of demarcation for the creation and delivery of

services where new entrants can create services and carriers can control access to the network

from the services environment. The Service Plane helps to level the playing field among

network-based carriers and other non-infrastructure service creators. Separating and

standardizing the control and delivery of service features will act to remove the walled garden

of proprietary features and enables access to new content. New service creators can also include

owners of media content looking for new outlets of distribution for their content. New models of

alternate service providers can be defined based on how carriers look to fill the need for the

creation of new services.

SIP-based applications development expands the size of the feature market for everyone. The

position of independent developers and VNOs using emerging servicehosting arrangements

expands more than others. There are several major roles that new service creators can take on

with carriers:

7.6 Application Developer and Service Creator Roles:

Contracted Developers:

Create private-label services on behalf of the carrier as a contractor.

Adhere to the carrier s service creation environment and integration testing.

No direct market brand name or presence.

Feature development according to selection and prioritization of carrier.

Co-Marketing Developers:

Create service priorities through joint market research of demand with carrier.

Create new services in conformance to the requirements of carrier s network.

Co-marketing and distribution with joint funding from carrier and developer.

Developer gets brand name exposure and identification in the marketplace.

Independent Developers:

Define their own development priorities based on their own market research.

Create features based on their own toolkit and specifications.

All features must conform to SIP and IMS based standard open interfaces.

Features may be multi-network capable.

Creator may want a simple hosting arrangement with the carrier.

Creator accepts complete marketplace risk exposure.

Partnerships and co-Marketing arrangements with carriers will dominate in the near-term.

Service-hosting arrangements similar to web-hosting will emerge as the concept matures. Rapid

early deployment of features will favor more partnerships and co marketing arrangements with

service creators. To successfully integrate independent feature development, the industry

requires the recognition of a Security Certification and Interoperability Testing Certification to

ensure service integrity of new features and feature platforms without compromising network

security integrity. Carriers will not allow independent service creators and application developers

to connect to the Control Plane without high security policies for trusted and non-trusted

platforms.

7.7 The role of the Network Service Provider is permanently changing:

New models of feature and service delivery are changing the role of the network service provider

and shifting the balance in the battle for customer ownership. Independent platforms for service

creation and new partnerships for application development bring new players into the

marketplace. Service creators and those who want to offer new services without network assets

(VNO s) will broaden the spectrum of provider choices for consumers.

The balance is shifting away from the mobile network being the focus of the business plan to a

model where mobile networks are just one element of a broader media distribution strategy,

which is likely to span across multiple networks mobile, internet and video. This is a more

integrated, cross-industry view of telecom showing the inevitable linkages to the content of the

medium and not just the medium itself.

In an industry where the term commodity seems to define the inevitable press of the

marketplace, the creative application of content through many devices and across multiple

networks builds real value for carriers. To carve a larger role in the value chain, carriers must

move out of their traditional roles as modes of transport and increase their partnerships with

content and solution providers.

7.8 Control of the Customer may show interesting shifts:

Customer control is another key emerging battle for carriers. Fought on many fronts, this battle

pits one carrier against another and together it will pit existing carriers against new VNO entrants

who stand to win much new ground. New VNO entrants have a broader agenda than simply to

re-distribute voice at incremental margins. They will cleverly combine content with national

brand names and new services to create their own direct relationship to the customer. The inter-

network nature of IMS services supports their ability to generate a content-based customer

relationship that extends across wireline and wirless networks.

The path of government deregulation, IP technology, and open industry standards has led the

telecom industry towards the intersection with the media industry. In part, the battle to control

the customer will be one of several forces working to drive the overlap between content owners

and the carriers that help distribute the content.

7.9 In the end it is still about Cost and Revenue:

There are many visions for the ultimate role of IMS in the telecom industry. The technology and

architecture are compelling enough to draw rich views of the future of telecom that is just over

the horizon. The hype is powerful and helps to define the vision but the true path of the telecom

industry over the short term will be more modest steps targeted for the near term increase in

revenues and the operational cost savings that will follow. The time from now through 2008 will

see dramatic opportunity for very new and innovative services and players. The rest of the IMS

revolution will wait out there until the new services win market success and carriers can see the

cost savings and increased revenue materialize. We may never reach the true IMS vision but this

time the telecom industry has a more well-defined path for each carrier to plan its future.

Conclusion

References

Books

[1]Gonzalo Camarillo, Miguel-Angel Garcia-Martín. “The 3G IP Multimedia Subsystem (IMS): Merging the

Internet and the Cellular Worlds”

[2]Chang Wen Chen and Jiebo Luo, Multimedia over Mobile IP

Websites

[1]http://www.3gpp.org/

[2] http://www.3gpp2.org/

[3] http://www.3gpp.org/ftp/Specs/html-info/23228.htm

[4] http://www.3gpp2.org/Public_html/specs/tsgx.cfm

[5] www.wikipedia.org.