In the 3GPP context, service interactivity refers to a class of features that enables user engagement during the consumption of a streaming or downloaded service/content on the UE, distributed over broadcast or unicast bearers. Examples of services/contents which may offer interactivity capabilities include linear/live TV services, video-on-demand programs, and pre-downloaded media content which a user can consume later on, in a time-shifted manner. For video content, for example a TV program or an advertisement, service interactivity facilitates active watching (as opposed to passive viewing) by allowing the end-user to actively interact and participate with the presented content. In the context of services delivered over PSS or MBMS, different forms of service interactivity may be possible, for example:

• Voting for a favourite performer,
• Dynamic quizzes, surveys, elections,
• Rating of a live event during a program,
• Web access to additional information related to main content,
• Online chats about actors in TV episode or movie,
• Interactive advertisements,
• eCommerce and online shopping,

and many others. Personalized and interactive service capabilities in 3GPP streaming and download services, via unicast and/or broadcast delivery, can drive higher end-user satisfaction and loyalty to the service operator, i.e., create greater "stickiness" of the operator's service offerings such as linear TV programs, live sports events and downloadable multimedia content. It could also enable the operator to further monetize streaming services (especially when distributed over MBMS) by, for example:

• Increasing the subscriber base through premium contextual service offerings.
• Supporting on-demand information or targeted advertising via simple user interaction such as click-to-call, click-to-SMS, or click-to-Web access.
• Driving greater cellular airtime or data volume usage associated with end-user initiated traffic pertaining to interactivity, the fees for which may be borne by a 3rd-party entity such as an advertiser or content provider, as opposed to the subscriber.

Service interactivity in 3GPP streaming and download service comprises application/presentation layer functionality, pertaining to user interface and user experience afforded by the interactivity feature, as well as a transport/signaling component, responsible for the discovery, synchronization and delivery of application and media content that define the interactivity experience. While the definition of the former, application/presentation layer aspects is largely outside the scope of 3GPP specification, delivery and signaling functions for enabling interactivity are fully within 3GPP's domain. Many of the tools required to signal and deliver functional components of interactive services may already exist in 3GPP PSS and MBMS specifications, but need to be clearly understood, leveraged, and possibly extended to fully support service interactivity. The present document examines major use cases for service interactivity in 3GPP streaming and download services, and associated requirements and potential gaps in existing PSS and MBMS service layer specifications for interactivity support. It surveys service interactivity functionality specified in broadcast TV standards, as a reference point for potential emulation by, or differentiation from, 3GPP-defined mechanisms. It concludes by identifying functional gaps in MBMS and PSS specifications to support the identified recommended requirements regarding interactivity, and summarizes the necessary capabilities to fulfill those gaps.

The present document covers the study of interactivity support for 3GPP-based streaming and download services, in the context of services delivery over MBMS and PSS. Topical areas addressed include the following:

• Use cases and associated assumptions, recommended requirements and gap analyses on the operation of and means to support interactivity capabilities in streaming and download services.
• End-to-end architecture and functional component models, with emphasis on unicast and broadcast DASH services.
• Differentiation between application/presentation level and transport/service layer functions in support of interactive services.
• Overview of service interactivity mechanisms in terrestrial broadcast TV services, as defined in DVB and ATSC specifications.
• Notification mechanisms to activate interactive events, either pre-scheduled or to occur dynamically and unpredictably, at precise times during consumption of a main service or program.
• Functional gaps in current MBMS and PSS application/service layer specifications to support desired interactivity functions.
• Measurement and reporting of the consumption of interactive features.