Abstract—This article describes a novel architecture for delivering personalized IPTV experiences to the end users. The frame work levera ges the IP Multimedia Subsys tem (IMS) framework to quickly enable new innovative, multi- media services . We describe the session flows for some important use cas es, suc h as access ing the elec tro nic service guide, Video On Demand (VoD) , fas t cha nne l changi ng, and enhanced parental co nt rol service s. A measurement study for each of these sessions is quantified. Index Terms — IPTV, IMS, handoffI. I NTRODUCTION P Mult imedia Subs yst em (I MS ) is a next generati on ne twor k (NGN) ar chit ec ture for mo bi le and fixed mul timedi a ser vic es, sta ndar dize d by the 3rd Ge ner ati on Partnership Project (3GPP ) [1]. IMS enables new services and ac ts as an integr ati on pl atform for the co mbinati on of tel ec ommunic ati ons and Int ernet ser vic es. So me of its attributes are as follows: I 1. Access Agn os tic Inf rastru ct ur e – ser vi ces are independent of underlying access network.. 2. Fu ll mob il it y - transparent co nnec ti vi ty ac ro ss heteroge ne ous networ ks, pr otocols and access mechanisms. 3. Alway s on, al way s her e capa bil ity v ia se ssi ons that cro ss net wor ks and devices, automaticall y and transparently. 4. Us er-centr ic cont ext, bo th de vi ce and co nt ext- sensitive. 5. Personali zed co nte xt-a war e appl ica tions catere d to the needs of an individual or a group of individuals. 6. Flexible user interface ena bli ng user s to ach ieve their goals efficiently . 7. Pr iva cy, saf et y an d secur it y of in forma ti on to saf egu ard bus ine ss and con sumer int egr ity and protect the digital rights of content creators. In this paper we focus on some of the items outlined above. The vision is to offer seamless, networked-based media overthree screens (TV, mobile device, and PC) enabled through IMS, int egr ating mult ime dia wi th rich co mmunic ati ons services to deli ver pers onalized, interactive televis ion no matter where the viewer is, when the content is requested, orwhat kind of dev ice is use d. In particular , several handof fscenar ios be twee n wi re li ne se t to p boxes and wi re less handsets wi ll be shown . We sho w the adv anta ges of this arc hite cture in fa st mar ket intr oducti on by red uci ng the dependence on proprietary v endor solutions. In addition this architecture introduces the f lexibility needed to cope with the emer gin g 3GPP re qui rement changes and deli vers advanc ed fe atu res in a timely fashi on. There are se ve ral reaso ns for using an IMS cor e. Some of the rea sons are as follows: 1. Core service ne twork wh ich is indepe nden t of access technology 2. Same appli cat ion is av ai la bl e from any acc ess method or device. 3. Abilit y to migra te and depl oy across fixed and mobile users 4. Stand ards all ow scal able depl oyment of new servi ces 5. Evol ut ion to combi ned se rvices for enhanced user experience (presence, messaging, address book) 6. Se curi ty in I MS is buil t- in - identi ty management , authentication, authorization and service access 7. Centralized user profiles shared between applications 8. Arc hit ect ure des igned for sc ala bil ity an d red unda ncy 9. Common solution to achieve Quality of Service 10. Fl exib le Char ging for mult imedia and co mbined services 11. Common Pr ovi sioning Section III discusses the specifics of the IPTV infrastructure using an IMS core. Section IV investigates in detail some typical session flow scenarios that we believe are novel in the cont ext of IP TV. Se ct ion V de sc ri be s a pr ot ot ypi ca l impl ementat ion of the above me nt ioned scenarios in a realistic environment. In addition, we provide protocol level me as ur ements to hi ghlight va lu ab le insi ghts in this fr amework and suggest possi bl e bott len ec ks and improvements from a service provider’s stand point. II.RELATED WORKBodzinga et al. discuss how IMS and IPTV service platforms can be interwor ked and inte gra ted to re duce networ kcomple xit y and pr ovide a flexib le networ k for novel diff eren tiated service s [2]. An impor tant aspect that IMS addresses is redundancy and scalability; these issues within IMS are addressed in [3]. This is particularly attractive foroper at or s that depl oy se rvic es whic h sc al e to a large subscriber base. Traditional telecommunications networks are opt imized to have ded ica ted net work fun ctions at cer tai n locations, taking cost, quality of service, reliability and othertechnical circumstances into account. Load sharing of spread net work functi ons hardly could be rea lize d. Wit h the IP Multimedia Sub sy stem (IMS), a tota lly diff erent approa ch will be realized. It is based on the IP protocol carrying bearerand signal ing/con trol traffi c. While bearer traff ic functi ons st il l to be opti mi zed wi th re spec t to be st lo ca ti on, the sig nall ing and control fun cti ons of the net work could be spr ead mor e or less arbitr aril y ove r the network be cau se relati ve ly lo w tr affic be twee n the functi ons does not sig nif ica ntly impa ct the opt imi zati on res ult of the tot al networ k. Thi s is an addi ti onal de gr ee of fr ee dom for assigning such kind of equipment to given locations. It opens up new possi bi lit ies for sca ling the equ ipment for total IMS-TV: An IMS based Architecture forInteractive, Personalized IPTV 180 Park Av e, Florha m Park, NJ 07932 1
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Abstract — This article describes a novel architecture for
delivering personalized IPTV experiences to the end users.The framework leverages the IP Multimedia Subsystem(IMS) framework to quickly enable new innovative, multi-media services. We describe the session flows for someimportant use cases, such as accessing the electronicservice guide, Video On Demand (VoD), fast channelchanging, and enhanced parental control services. Ameasurement study for each of these sessions is quantified.
Index Terms — IPTV, IMS, handoff
I. I NTRODUCTION
P Multimedia Subsystem (IMS) is a next generation
network (NGN) architecture for mobile and fixedmultimedia services, standardized by the 3rd GenerationPartnership Project (3GPP) [1]. IMS enables new services andacts as an integration platform for the combination of telecommunications and Internet services. Some of itsattributes are as follows:
2. Full mobility - transparent connectivity acrossheterogeneous networks, protocols and accessmechanisms.
3. Always on, always here capability via sessions thatcross networks and devices, automatically andtransparently.
4. User-centric context, both device and context-sensitive.
5. Personalized context-aware applications catered tothe needs of an individual or a group of individuals.
6. Flexible user interface enabling users to achievetheir goals efficiently.
7. Privacy, safety and security of information tosafeguard business and consumer integrity and
protect the digital rights of content creators.
In this paper we focus on some of the items outlined above.The vision is to offer seamless, networked-based media over three screens (TV, mobile device, and PC) enabled through
IMS, integrating multimedia with rich communicationsservices to deliver personalized, interactive television nomatter where the viewer is, when the content is requested, or what kind of device is used. In particular, several handoff scenarios between wireline set top boxes and wirelesshandsets will be shown. We show the advantages of thisarchitecture in fast market introduction by reducing thedependence on proprietary vendor solutions. In addition thisarchitecture introduces the flexibility needed to cope withthe emerging 3GPP requirement changes and deliversadvanced features in a timely fashion. There are several
reasons for using an IMS core. Some of the reasons are asfollows:
1. Core service network which is independent of accesstechnology2. Same application is available from any access
method or device.3. Ability to migrate and deploy across fixed and
mobile users4. Standards allow scalable deployment of new services5. Evolution to combined services for enhanced user
experience (presence, messaging, address book)6. Security in IMS is built-in - identity management,
authentication, authorization and service access7. Centralized user profiles shared between
applications8. Architecture designed for scalability and redundancy
9. Common solution to achieve Quality of Service10. Flexible Charging for multimedia and combined
services11. Common Provisioning
Section III discusses the specifics of the IPTV infrastructureusing an IMS core. Section IV investigates in detail sometypical session flow scenarios that we believe are novel in thecontext of IPTV. Section V describes a prototypicalimplementation of the above mentioned scenarios in arealistic environment. In addition, we provide protocol levelmeasurements to highlight valuable insights in thisframework and suggest possible bottlenecks andimprovements from a service provider’s stand point.
II.R ELATED WORK
Bodzinga et al. discuss how IMS and IPTV service platformscan be interworked and integrated to reduce network complexity and provide a flexible network for noveldifferentiated services [2]. An important aspect that IMSaddresses is redundancy and scalability; these issues withinIMS are addressed in [3]. This is particularly attractive for operators that deploy services which scale to a largesubscriber base. Traditional telecommunications networks areoptimized to have dedicated network functions at certainlocations, taking cost, quality of service, reliability and other technical circumstances into account. Load sharing of spread
network functions hardly could be realized. With the IPMultimedia Subsystem (IMS), a totally different approachwill be realized. It is based on the IP protocol carrying bearer and signaling/control traffic. While bearer traffic functionsstill to be optimized with respect to best location, thesignalling and control functions of the network could bespread more or less arbitrarily over the network becauserelatively low traffic between the functions does notsignificantly impact the optimization result of the totalnetwork. This is an additional degree of freedom for assigning such kind of equipment to given locations. It opensup new possibilities for scaling the equipment for total
IMS-TV: An IMS based Architecture for Interactive, Personalized IPTV
network capacity needs and gives a chance to distributeredundancy geographically, which influences network reliability in a positive way. Moreover, the distributed IMSarchitecture based on SIP proxy mechanisms provide better means for redundancy and scalability as compared to ”classicsoft switches” that still follow a nodal architecture.
III. SYSTEM ARCHITECTURE
Figure 1 shows a high-level IPTV network architecture beingsupported by an IMS infrastructure. Three functional layersare defined, namely, the Service layer, the Control layer andthe IPTV control layer. The layered architecture facilitatesinteroperability amongst different vendor solutions andmaintains ease of service creation. The IPTV service layer
provides multimedia services to the end user by means of theIPTV Application Platform (IAP). It implements the portalwith which a user interacts and includes functionalities likethe electronic service guide (ESG), VoD etc. The IAPinteracts with the IPTV Terminal Function (ITF) that handlesdisplay and interactivity functions for users. It also performsfunctions such as content encoding/decoding and bufferingfor both unicast and multicast streams.
Figure 1 - High level architecture
A more detailed implementation is described in Figure 2. The
system is divided into a number of logically separated parts
namely the home network, access network, aggregation
network and the service provider domain.
A. IPTV user profiles
In the IMS IPTV architecture, personalization is an
important feature. To achieve personalization at the
application level (i.e. with personalized EPG’s,
advertisements, or even personalized blended communication
services), every user has an IPTV profile. The relation
between the IPTV profile and the IMS profile depends on theavailability of a home IMS gateway (HIGA) [4]. The HIGA is
a functional block with an attached ISIM card reader, which
can be deployed in the residential gateway or any other
networked consumer equipment. The HIGA translates home
signaling, whether SIP, UPnP or perhaps pure HTTP to IMS
signaling. It also takes care of NAT traversal and secure
connectivity with the P-CSCF in the IMS domain, as well as
identity, device subscription, and management inside the
home domain and towards the IMS core.
In a home network domain without an IMS gateway, every
IPTV account needs to have IMS public/private ID pairings
for the users of the system; these are used to log into the IMS
domain. However, since the TV is a social device, in which
many users are quite often watching TV together, the IMS
IPTV STB contains a default user which represents the
triggering a special interactivity mode in the STB.
3. Firmware upgrades. The MDC can carry an order for
all STB’s to download an upgrade, immediately or
schedule to some appropriate time.
4. Alert or emergency messages, which should be
shown as immediate pop-ups in the STB; these may
not disappear until the user acknowledges them.
For each piece of information in the MDC, there is a tag witha timestamp, which marks the validity of the information;there is also a tag that marks whether the information isincluded in the XML content (i.e. the EPG goes inside theXML-wrapped content), or whether it should be obtained viasome other means (i.e. an HTTP GET to a particular server,or a file transfer of some type). The XML wrapper contains aset of tags to identify the desired receivers of the content. Inthis way, the MDC can contain information that it has taggedto be received by a subset of the STB population. Typical tagsthat can be used include the following:
1. Channel being watched: only STB’s currentlydisplaying that channel will react upon the
information.2. Age: only STB’s whose active user falls into the age
range will react.3. Region: only STB’s located in the specified region
will react.4. Gender: only STB’s whose active user has the
desired gender will react (if field is populated)The filtering of the received information according to the
XML tags happens in the STB. In this way, the user can
decide
how much personal information he or she wants to configure
in his/her personal profile in the STB.
C.IPTV control planeThe control plane of the IPTV architecture can be divided
into a set of functions, like session setup, media flow setup,
media flow control, and non-media related functions. The
choice of protocols for each function tries to re-use existing
de-facto standards or IETF standardized protocols when
possible. The key components of the IMS control layer are the
x-CSCFs and the HSS. The S-CSCF evaluates all originating
and terminating messages and may, based on information of
the service, link-in during session setup any number of IMS
Appliaction Servers (ASs) to perform wanted IPTV services.
In all IPTV related SIP messages originating from the ITF,
the IPC will be linked-in. For IPTV, the HSS keeps triggers
and filter information for the IPTV Public Service ID (PSI) or the service identifier. The information is stored and conveyed
on a per IMS Application Server basis. This means that IMS
ASs are allocated dynamically and that SIP messages will be
routed all the time to the same IMS Application Server. The
S-CSCF downloads rules and triggers, upon user registration,
from the HSS.
IV. SESSION FLOW SEQUENCE DIAGRAMS
The set top box (STB) in the IMS IPTV architecture is a
full back-to-back IMS user agent that performs the default
IMS registration upon startup. When the STB is switched on,
it first obtains IP connectivity, which can be statically
configured or obtained via DHCP. As part of the IP
configuration, the STB discovers the IP address or DNS name
of the P-CSCF, which is the entry point to the IMS layer.
Once the STB obtains IP connectivity, it performs an IMS
registration with the predefined default profile. The default profile can be a family user IMS public ID, common for the
house hold or a personalized public IMS ID. Figure 3 shows
the simplified steps of the IMS registration. The only
important aspect of the registration is that the S-CSCF
performs a 3rd party registration of the user in the IPTV AS,
trigered by the information on the IMS user profile stored in
the HSS. After having registered the user, the STB sends a
SIP SUBSCRIBE towards the IPTV AS. The body of the SIP
SUBSCRIBE contains the last setup information that the STB
has cached, with a timestamp on it, wrapped in the same
XML schema in which the information within the multicast
data channel was sent.
The information included contains the following:
1. IP address of the multicast data channel.2. URL to the valid electronic program guide (and
interactive program guide if not the same) for theuser.
3. The latest profile information of the user.4. Any other needed common setup information.
When the IPTV AS receives the SUBSCRIBE, it confirms
the SIP dialog and checks the validity of all the information
in the XML body. Then, the AS generates a SIP NOTIFY
with the updated information wrapped in the same schema,
with a tag indicating whether it is the same as the STB sent
The SUBSCRIBE/NOTIFY SIP session dialog is active as
long as the STB is actively watching/connected to IPTV. This
SIP session offers an extremely effective personalization
mechanism to reach a particular user (or a small group of
users) in the IPTV system. By having a homogeneous XML
to send metadata information over the MDC or over a SIP
NOTIFY, the IPTV AS has the ability to reach any single
user individually or in a bradcast distribution, without
changing the content of the metadata being sent. The same
type of filters that are applied in the client when receiving
information over the multicast data channel can be applied to
the received NOTIFY’s; so, the STB can filter out undersired
information without compromising the privacy of the
registered user.
The last step of the startup procedure is tuning in to the last
broadcast channel that the registered profile was watching.
Figure 5 describes the simplified flow. The STB triggers a
SIP INVITE towards the IPTV AS. This INVITE contains
simplified SDP information that refers to the type of TV
channel being received, in this case multicast in standard
definition. The goal of the SIP INVITE is setting up a ’media pipe’ to the STB to deliver the required set of channels. The
AS responds with a full SDP that describes the type of media
to be received. Finally, when the INVITE dialog is
completed, the STB joins the required multicast channel by
performing an IGMP join.
It is important to notice that an update to the SIP DIALOG
only occurs when the characteristics of the media pipe
change, but not when the channel changes. In this manner,
changing between multicast channels with the same
bandwidth characteristics happens via IGMP, without SIP
intervention. Figure 6 illustrates the procedure. This
behavior is required to achieve a fast channel changing
experience, which would be encumbered if the SIP sessionhad to be updated with every channel change.
Figure 5 - Tuning to a broadcast channel
When the user changes channel to a multicasted media
with different characteristics, the SIP dialog is updated via a
SIP UPDATE. This mechanism is important since it allows
the IMS system to know the proper QoS requirements
requested by the media flow being sent to the user. Of course,
updating the SIP dialog may introduce a small delay in the
channel changing experience, but this update provides for
assured media delivery of the requested standard or high
definition live channel.
Figure 6 - Channel Changing
Nevertheless, it is important for the IPTV provider to knowwhich channel the different STB’s are watching, to providetargeted advertisement or any type of media related addedvalue services. For this to happen, the STB has a channelchanging timeout, which triggers when the user has notchanged channel in the last ‘x’ seconds (for example, five
seconds). When the timeout triggers, the STB sends a SIPINFO towards the IPTV AS, which contains an XML bodywith the status information of the media. In the case of multicast live channels, this status information is simply thechannel being watched.
A. Accessing Video on Demand
As described in the previous section, the SIP INVITE
dialog remains unchanged as long as the media
characteristics do not change. In this way, when the user
decides to watch a Video on Demand movie, or any other on
demand media item, a new SIP session is created, after
This paper investigated an IMS based architecture for the
delivery of IPTV services. In particular, session flows for
linear TV, video on demand, remote parental authorization,
and interactive services were some of the use cases that were
discussed in this paper. This paper demonstrates the great
promise that IMS-TV has and its the potential to deliver
differentiated services, which offer attractive, interactive, rich
multimedia experiences for the end user.
R EFERENCES
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