IMS White Paper
Transcript of IMS White Paper
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IP multimedia a new era in communications
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Contents
Executive summary 3
The renewal of person-to-person communications 4
IP multimedia and its benefits will generate new business 5
Examples of applications 6
IMS will build operators revenues and cut their costs 7
Open service creation 7
The essentials of IMS and SIP 8
IMS A major building block in convergent core networks 9
One network experience 9
IMS and voice 9
Conclusions 10
Glossary of terms and abbreviations 11
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Executive summary
Person-to-person mobile communication
is undergoing a transformation that
will see users sharing rich content like
never before.
Based on the technologies of IP
Multimedia Subsystem (IMS) and Session
Initiation Protocol (SIP), the mobile and
Internet domains will merge, allowing
users to access, create, consume and
share digital content using interoperable
devices.
With an IMS-based network, operators
will be able to set up and introducenew services much more quickly than
before, achieving a fast time to market
to meet changing customer demands.
New functionalities can be added easily,
lowering the cost of new services by
avoiding the need to build and run a
completely separate, parallel network to
support each feature.
Using IMS in their networks, operators
will be able to offer users a wide range
of applications that can reside in theterminal, in a server, or both. These
applications can interact with each
other to provide the user with rich
communications capabilities. Users will
be able to mix and match a variety of
IP-based services in any way they
choose during a single communications
session, integrating for example voice,
video, text, content sharing and presence
information.
Because IMS supports open service
creation and third party applications
and application servers, operators have
the chance to customize services and
applications for their own customers.
The importance of open service creation
is highlighted by a recent market study
on IP multimedia services, revealing
that different countries prefer different
service sets. Open service creation will
give operators the tools to optimize
IP multimedia services for local
requirements. It will also allow them
to develop their service concepts in
co-operation with external applicationdevelopers.
The use of IP in core networks makes
possible new service concepts and
convergence between fixed and mobile
networks. Being access agnostic and
supporting both fixed and mobile clients
and access, the IMS is a central building
block for convergent communications.
The coming world of converged
networks and services holds greatopportunities for operators and IMS will
be a major factor in making these
opportunities a success.
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The renewal of person-to-personcommunications
The phenomenal success of mobile
telephony has so far been built on a
modest set of services dominated by the
basic person-to-person voice call.
However, the building blocks of a
communications future that will offer
users far more options are now falling
into place.
Connectivity is more diverse than ever
with wireless and wire line access
technologies such as GPRS, EDGE,
WCDMA, DSL and WLAN becomingcommonplace and providing broadband
on the move.
Now it is the turn of the core network to
be developed by implementing the IMS.
Defined by the 3GPP, the IMS will form
the heart of a converged network and
will provide authentication, roaming
and network interconnectivity to allow
IP-enabled terminals to network fully.
With these elements in place,IP convergence, which will merge the
mobile and fixed network domains,
will become a reality. Packet-based
networks of all types will give users the
ability to access, create, consume and
share digital content using interoperable
devices that are connected with each
other anytime, anywhere.
Content-to-person services have
advanced in recent years with the
advent of applications such as browsing,
downloading and Internet access
coming to the fore. Mobile operators are
following this up now by placing an
increasingly high priority on renewing
person-to-person communications.
Richer person-to-person applications
demand a mechanism that can establish
a peer-to-peer connection between
IP-enabled devices. IMS is the network
technology to achieve this.
Research done by Nokia in cooperation
with the UK based research agency
Market and Opinion Research
International (MORI), indicates a clear
demand for IP multimedia services.
Between 33% and 43%, or 90 million
main mobile phone users in Great
Britain, Germany, Singapore and the USA
consider they would be likely to use
these services in the next two years.
The top three services in terms of likely
adoption are push to talk, video sharing
and instant messaging while content
sharing is also appealing to consumers
across countries.
Figure 1. Mixing and matching services in a single communication session
Push totalk
MessagingRich
messaging
Presence
VoiceInteractive
gaming
Videosharing
ChatContentsharing
Packet-switchednetwork
(GPRS or 3G)
IP Multimedia channelbetween terminals
The demand is there and users are
interested in the benefits that IP
multimedia services can bring. A clear
proof of this is already shown in the
market. The push to talk service has
been launched commercially by several
operators world wide. The importance
of presence has been recognized and
more and more operators are combining
presence with their other services.
The first operators are moving into the
phase of commercial deployment of IMS.
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IP multimedia and its benefits willgenerate new business
User interfaces and services will be
independent of time and place, but at thesame time customized for the terminal
used. For example, a videoconference
could be held with different participants
using a fixed line connected to a PC,
a mobile phone connected via WCDMA
network, and a laptop connected via
WLAN. With IMS co-ordinating these
services, this is an example of true fixed
and mobile convergence.
Furthermore, users will gain easy access
to new applications because the same
SIP client in their terminal can be used
for all services. SIP capable phones are
becoming more widely available and
SIP clients are already available for
downloading into Nokia Series 60
Platform terminals.
Using IMS in their networks enables
operators to offer users a wide range of
applications that can reside in the
terminal, in a server, or both.
Additionally, these applications can
interact with each other to provide the
user with rich communications
capabilities.
There are two main benefits to users of
adopting IP-based peer-to-peer
communications.
First, users will be able to mix and
match a variety of IP-based services in
any way they choose during a single
communications session. Users can
integrate voice, video, text, content
sharing and presence as part of their
communication and can add or drop
services as and when they choose.
This is what is often referred to as a
rich call and is not possible without
peer-to-peer connection.
For example, two people can play an
interactive game directly between
terminals, make comments during the
game using voice and share files or
video with each other.
Second, these services and the way they
can be used will be available regardless
of the access network. Users will be
able to choose the access network that
gives them the best price, bandwidth or
availability at a particular time and
location.
Figure 2. SIP applications implemented in two domains.
Packet-switchednetwork
SIP SIP
IP MultimediaSubsystem (IMS)
Application serversServices, applications
Presence
PoC
SIP/ISC
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Examples of applications
The key applications emerging for the
IP-converged world include:
Push to talkAlready implemented over GPRS
networks, push to talk provides direct
one-to-one or one-to-many voice
communication over the mobile
network, emulating the traditionalwalkie-talkie service. Calls are started
with the push of one key and connected
directly, thus enabling a conversational
voice service. Push to talk calls are half
duplex while one person speaks,
the others can only listen.
Video sharingVideo sharing enables mobile users to
share one-way video in real time while
they are already active in a voice session.
This is a great way to gain additional
revenue from voice calls and differentiate
within 3G services. Wideband operators
can offer one-way video sharing as an
enhancement to existing voice calls.
Content sharingA SIP-based peer-to-peer connection will
enable two or more users to share all
types of content. As an example, a user
could send the best photo as a MMS
(content push) and share the rest of
the photos with her friends (content
pull) by using content sharing. Direct
file sharing is possible not only
between mobile terminals but also
between mobiles and PCs or any other
IP connected device.
PresencePresence will add a new dimension to
personal communication. Widely used
in the Internet to support instant
messaging, presence enables mobileusers to allow their terminals to provide
dynamic status information about
subscribers, including their call/
connection status, identities, terminal
capabilities and availability. Presence is
an application in itself, but is also an
enabler and enhancement to other
applications such as rich call, push to
talk and messaging.
MessagingMessaging will evolve building on the
existing SMS, MMS and e-mail. From the
users perspective, messaging services
can converge into a single messaging
service using different messaging
technologies enabled by the network.
Messaging will be driven by user services
rather than enabling technologies as is
the case today. Key messaging services
are expected to include text messaging,
chat, multimedia messaging, voice and
video messaging, business messaging
and application messaging.
Figure 3. Video sharing between two devices.
Voice over IPThe importance of Voice over IP (VoIP)
is increasing all the time. It is already
widely used in fixed networks, using
VoIP capable fixed phones or PC VoIP
clients. The emergence of mobile
terminals capable of supporting both
cellular and WLAN access, allows mobile
terminals to use an IP-based connection
for voice within a WLAN access zone,
increasing the need for a VoIP solutionfor mobile operators. IMS is a central
element in an operators VoIP solution,
supporting both fixed and mobile SIP
clients, as well as working with PSTN.
VoIP to PSTN interworking is discussed
in more detail in the section on
convergence.
Rich callA rich call integrates voice, video and
text, supported with parallel sharing of
content (image, data, or other value-
added information) into a seamless and
coherent user experience. SIP provides
the essential elements for a rich call.
Third party SIP applicationsIMS and SIP enable open service creation,
bringing advantages to both application
developers and operators. Developers
can create applications that are used
directly by SIP-capable terminals, taking
advantage of the peer-to-peer capability
of IMS, although operators will remain in
control. More versatile services based onapplication servers are also possible.
CS-voice call
Invite
Video stream
Kate Lucy
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Open service creation
IMS supports open service creation and
third party applications and application
servers, enabling operators to tailor
services and applications for their
customers. Operators can develop the
new services themselves, outsource the
development work, or purchase the
applications from external sources.
IMS also allows operators to take
advantage of applications from third
party service providers and application
developers and hosted on external
servers.
More than thousand developer
companies worldwide are currentlyestimated to be working on SIP
applications bringing innovation far
beyond most previous expectations.
Some of these companies are already
developing and testing their applications
on Nokia terminals using SIP APIs and
SDKs.
The use of standard open specifications
based systems such as IMS is important
to application developers because it
enables them to create applications thatcan be used across networks and on
terminals of all types with minimal
customization.
The true potential of the IP converged
future will only be realized with the
involvement of this developer
community. Its creativity will be
harnessed by providing developers
with the open APIs and SDKs they need
to create SIP-based applications.
Applications can be quickly developed
due to the reuse of common IP protocols,
and quickly deployed by using the
common connectivity features of SIP to
establish connections.
This short time-to-market will make it
possible for services to be profitable in
a very short time. Services made
available only for the duration of a
football tournament or the Olympics,
for example, will be feasible.
In IP converged networks, the operator
has just one network to manage, while
SIP remains the enabling protocol. This
will lower the cost of new services by
avoiding the need to build and run a
completely separate, parallel network
to support each feature. Without IMS,
each time a new application needs to
be implemented, the operator must
re-engineer many of the same
functionalities that have been used
before in previous applications. Thisconstant replication of critical functions
is both costly and time consuming.
Additionally, because each service will be
built on separate servers as stand-alone
services they will inevitably work
slightly differently and the user will not
get a true seamless experience. In the
longer term, introducing more and more
services in this way will result in a core
network that is so complex it becomes
almost unmanageable and will
inevitably increase operationalexpenditure (OPEX).
Implementing new services on existing
infrastructure will also reduce the
equipment costs themselves. The cost
advantage will increase for every new
SIP service that is subsequently
implemented. OPEX will also be lower in
the longer run.
System capacity can also be improved,
because resources can be shared across
many services. Infrastructure
investments in firewalls, mobility
services and so on, which have been put
in place for SIP, can also be reused.
IMS will build operators
revenues and cut their
costs
It will be vital for operators to implement
IMS in their core network, not only to
maintain their competitiveness as other
operators move towards IP convergence,
but also to achieve cost savings and
allow smooth evolution of services.
New revenue streams will be created by
providing subscribers with multimedia
services that can be mixed and matched
in a controlled, secure and chargeable
way. Additionally, new services can be
implemented that were not previously
possible or were too complex or costly tobe practical, such as sharing video clips
between users.
Wider availability of an operators
services will also be achievable,
encouraging greater use. Services can be
created in one platform and made
available over multi-access networks,
broadening their reach and increasing
customer loyalty to reduce churn.
In addition, the same SIP based
architecture will support both person-to-person and content-to-person services.
Historically, service integration has been
time consuming in mobile networks,
because each service often required its
own protocols, standards and service
domains. With an IMS-based network,
operators will be able to set up and
introduce new services much more
quickly than before, achieving fast time
to market to meet changing customer
demand. With IP multimedia, service
integration is easy, since services are
created on top of a single IP-based
platform. Voice-based applications can
be integrated easily with content
sharing applications, mobile terminal
applications with PC applications,
and so on.
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essential for the success of any service
scenario.
All these mobile network specific
functionalities have been implemented
in the Nokia IMS. It provides a complete
service delivery for SIP services in both
mobile and fixed domains.
SIP has already been implemented in
2G GPRS networks. 3G networks are notessential for SIP-based sessions, although
the greater bandwidth of technologies
such as EDGE and 3G will greatly benefit
capacity-intensive applications such as
video sharing.
The essentialsof IMS and SIP
The major element needed for the
renewal of the core network to enable
IP-based peer-to-peer connectivity is the
IMS (IP Multimedia Subsystem), which
uses SIP (Session Initiation Protocol).
When a SIP client issues a find and
connect request, the IMS finds the relevant
terminals and connects them via IP.
SIP enables clients to invite other clients
into a session and negotiate control
information about the media channels
needed for the session. The IMS providesa full suite of network capabilities for
authentication of clients, network-to-
network interfaces and administrative
functions such as charging. The IMS
establishes packet data connections
between end points in a carrier-class,
chargeable way. Once established, the IP
connection can be used to exchange all
types of communication media,
including voice, video, content and more.
SIP is defined by the IETF and has beenwidely used throughout the Internet.
It shares much with Internet protocols
such as HTTP and SMTP (protocol header
formats). Like HTTP, SIP is a text-based
client-to-server protocol. SIP has been
adopted by the 3GPP as the session
management protocol and is the basis
for IMS.
First defined in the 3GPP Release 5
standard (and being further developed
in subsequent releases), IMS provides
mobile operators with a common and
tightly standardized platform for
deploying SIP applications. These can
reside directly in SIP-capable terminals,
in an application server, or both.
The IMS supports a standardized IMS
Service Control (ISC) interface, which
allows open connectivity towards SIP
application servers.
Like SIP, IMS is access independent,
working with existing voice and datanetworks in both the fixed domain (for
example PSTN, ISDN, WLAN and Internet)
and the mobile domain (for example
GSM, CDMA and WCDMA). However,
implementing SIP applications in mobile
networks have some key differences
compared to the fixed domain. The most
essential ones are related to mobility
management, security architecture and
customer care and billing.
A major area of mobility management
is optimizing the resources of radio air
interface based on Quality of Service
(QoS) parameters for different services.For example, video sharing service can
be deployed using streaming traffic class,
guaranteeing the right user experience.
Another important area of mobility
management is handling the abnormal
traffic cases typical for radio networks,
such as handset battery running out or
terminal moving out of network
coverage during an active session.
IMS security architecture consists of
access security and network domain
security. For access security, IMS supports
IETF authentication typical for fixed
SIP clients, as well as SIM-based
authentication, which is the most
favoured one for mobile terminals.
Network domain security provides
security between network domains
and nodes within one domain. In a
typical case, this means a well-defined
security architecture between
operators core networks.
Regarding customer care and billing,the most important features are support
for both prepaid and postpaid mobile
subscriptions. Also easy-to-use auto-
provisioning for the new services is
Figure 4. Session establishment with IMS
Packet-switchednetwork
Any IP connection(e.g. GPRS, EDGE,
WCDMA, WLAN, ADSL)
IP-based servicespossible between
terminals
SIP capableterminal
SIP
Find andconnect
IP Multimedia Subsystemfinds the other terminal and
connects the terminals with IP
SIP
IMS
The main functions of the IMS for
providing complete service delivery
include:
Authentication and authorization of
both mobile and fixed SIP clients
Control over sessions for person-to-
person, person-to-group and
content-to-person multimedia
communication
Charging functionality that allows
the operator to apply time-based,
event-based or volume-based
charging to subscribers
Implementation of the relevant QoS
mechanism for the IP services being
used in the communications session
Functionality to connect roaming
users to the home domain for IPmultimedia services
Access and network domain
security functions
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WLAN devices. IMS also provides the
necessary interworking with other
SIP-based networks such as enterprise
intranets.
IMS and voice
Voice over IP is having a significant
impact on traditional telephony, with the
growing adoption of VoIP using the
Internet, and the introduction of VoIP
services by fixed operators using their
own IP networks. VoIP over WLAN is
becoming common within enterprises
and at homes as a natural extension of
WLAN data access. The introduction of
WLAN capable multiradio terminals
allows the mobile to be used as an IP
phone when in the WLAN coverage area.
Crucially for the evolution of VoIP
services, the IMS works with PSTN and
mobile networks via signalling and
media gateways. The samesupplementary services are provided
for VoIP calls as we have today for
circuit switched calls.
IMS A major building blockin convergent core networks
interworking to existing voice networks.
Both fixed and mobile networks are
enhanced to enable IP multimedia
person-to-person services and bring
mobility to media consumption and
business services. This means that
service delivery will be access network
agnostic. The ability to employ all
services all the time is the automatic
result of ubiquitous access and Internet
technologies, such as SIP and HTTP.
Overall, the user experience will be
seamless: the same voice and
multimedia services are used in the
same way, independent of the access
network and the terminal, providing
people with both mobility and
personalization. Nokia can help to make
this simple both for the consumer and
network operator.
IMS is the technology that will link all
the many aspects of communications
into a converged whole. IMS supportsboth 3GPP and IETF SIP clients and can
be connected to several types of devices,
whether mobile terminals, fixed PCs or
Convergence of fixed and mobile
communications is happening today.
There are five significant enablers of
this trend:
Wide spread use of IP and SIP
Range of complementary radio access
Development of devices with a
number of functions
Digitization of content
Multi-radio handsets
Operators are considering how to launch
innovative service bundles over manyaccess types, whilst looking to reduce
costs by consolidating their core
network. Consumers and business users
want to access a wider variety of
networks and services with a smaller
number of devices.
Three prime trends clearly demonstrate
this:
Voice is going mobile: an increasing
proportion of all voice calls are being
made over mobile networks. The rapid development of new IP
multimedia services in both the fixed
and mobile domains. SIP will help
converge the two.
The growing popularity of VoIP
telephony over fixed networks, with
SIP as a major enabler.
These trends show that communication
is moving from the circuit-switched
domain towards open IP-based
networks. In this evolution IMS plays a
crucial role. The use of IP in the core
networks makes possible new service
concepts and convergence between
fixed and mobile networks.
One network experience
The individual perception of fixed-
mobile convergence will be that of a
common service experience, regardless
of network type. Mobile phones will
increasingly be able to use IP-basedcommunication services. The PSTN is
migrating to IP, which brings VoIP
telephony services and smooth
Figure 5. People want mobility and personalization
My phonebook
My agendaMy messages
My presence info
My applications
My ringing tones
On the move Home
Office
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Conclusions
Person-to-person (both one-to-one and
one-to-many) IP-based multimedia
services are universally recognized as
being the future direction for the mobile
communications industry. Operators
around the world will undoubtedly
move towards IP convergence over the
next few years, with IMS being one of
the major enablers.
An IP-based service architecture, capable
of supporting multimedia and service
integration, will be a key element of
future cellular networks. SIP will be the
standard signaling protocol/mechanismto support multimedia sessions in 3GPP
Release 5 networks and beyond. This
choice ensures that future multimedia
services will be truly IP based.
By implementing SIP, the operator gets
the whole array of IP based services in
the same network that is easy to
implement, manage and control.
Developing and introducing new
services are simplified compared to the
conventional networks.
All the key components for IP convergence
are available today. IMS infrastructure
equipment is commercially available,
service development tools are widely
available from sources such as Forum
Nokia, and IP-capable terminals are
becoming available. SIP applications,such as push to talk, are already being
deployed.
Operators benefit from taking
advantage of the opportunity today and
implementing the necessary IMS
machinery in their core network.
The winners in IP multimedia will be
those that are proactive and take the
early initiative.
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The contents of this document are copyright 2004 Nokia. All rights reserved. A license is hereby granted to download and print a copy of this document for personal use only.
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Glossary of terms and abbreviations
3GPP
3rd Generation Partnership Project
API
Application Program Interface
CDMA
Code Division Multiple Access
DSL
Digital Subscriber Line
EDGE
Enhanced Data Rates for GSM Evolution
GPRS
General Packet Radio Services
GSM
Global System for Mobile communications
HTTP
Hyper Text Transfer Protocol
IETF
Internet Engineering Task Force
IMS
IP Multimedia Subsystem
IP
Internet Protocol
ISC
IMS Service Control
ISDN
Integrated Services Digital Network
MMS
Multimedia Messaging Service
PoC
Push to Talk over Cellular
PSTN
Public Switched Telephone Network
QoS
Quality of Service
SDK
Software Development Kit
SIP
Session Initiation Protocol
SMS
Short Message Service
SMTP
Simple Mail Transfer Protocol
UMTS
Universal Mobile Telecommunications
System
VoIP
Voice over Internet Protocol
WCDMA
Wideband Code Division Multiple Access
WLAN
Wireless Local Area Network
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