Study of Generic Stream Encapsulation (GSE) Application to the DVB-Family Standards

Status

Completed
Status date

2011-04-05
Activity Code

1D.004

Objectives

This project addresses a range of issues relating to the continued evolution of the Generic Stream Encapsulation (GSE) protocol (ETSI TS 102 606) as a common transmission method for the second generation of DVB physical layer waveforms. It envisions a world where IP is the dominant network technology and is used to support audio-visual and multimedia services as well as to provide a seamless IP network (Internet) service to the end user.

In both cases, the DVB transmission network can be the only transmission network between the sending and receiving equipment, or alternatively it could form only one part of the end to end path (i.e. where a heterogeneous network path comprises a set of links/sub networks employing different network technologies and the DVB transmission network is just one technology used).

The key objectives of this project are:

To identify the technical issues raised by the use of GSE over the DVB-family standards and the possible optimizations of this protocol, and to define accordingly technical solutions, i.e. adaptations of the GSE protocol or DVB physical layers, definition of new mechanisms and functionalities. For this objective, the activity shall seek to harmonize the proposed technical solutions across the different DVB standards.
To assess the performances of GSE (through semi-analytic evaluations), to identify its features of interest and to highlight its benefits compared to MPE/MPEG-TS in terms of overhead and functional support.
To study the design of a signalling system suitable for GSE-only systems. The work will identify the requirements for different use cases, and then propose a suitable signaling scheme, seeking to harmonize the proposed solutions across the different use cases.
To prepare technical contributions for the relevant DVB standardization groups (e.g. DVB-GBS , DVB-RCS), reflecting the outcomes of the project (e.g. recommendations for the design of technical solutions to support GSE, dissemination of the results from performance assessments, technical recommendations intended to help define appropriate signalling for generic stream only systems).

Challenges

The main objective of the project is the analysis of GSE only systems over DVB family standards including protocol encapsulation specification and GSE only systems signalling specification.

Benefits

The project main benefits will be:

Standardization support for a full specification of a GSE-like return link encapsulation for RCS-NG systems.
Contributions to the specification of GSE only system signalling applicable to all DVB families.

Features

The Generic Stream Encapsulation (GSE) protocol allows efficient encapsulation of IP and other network layer packets over a “generic” physical layer. Such a “generic” physical layer is intended as a transport mode that carries a sequence of data bits or data packets, possibly organized in frames, but with no specific timing constraints. These are referred to as Generic Streams (GS). Convergence has become a key concept in broadcasting, communications and related domains over the past few years – and it is IP, or the Internet Protocol, that has become the key “convergence layer”.

Conceptually, the Generic Stream is at the same level in DVB systems as the Transport Stream, offering an alternative means of carrying whatever audio, video and data is being broadcast. All DVB second-generation physical layer standards (e.g. DVB-S2, DVB-T2, etc…) will be “multi-mode”, offering the option of using either the traditional MPEG Transport Stream or DVB-GSE.

Plan

The work to be done will be covered in 10 months. The organization of the work is divided in five different tasks:

Task 1 provides a state of the art reference of the different DVB standards. This study takes into account the classification provided by 3 different use cases:

Fixed DVB broadcasting systems to reception -only systems (DVB-S2,T2,C2),
Mobile DVB broadcasting systems (DVB-SH,T2),
Fixed DVB broadcast/interactive systems (DVB-RCS, NG, DVB-S2).

Each use case is analyzed taking into account the following aspects:

Architecture,
Application and services,
Physical and link layer,
Observed GSE impact.

As a result of this study, the consortium has identified for each use case the technical requirements to support GSE, in TN1 entitled “DVB standards wrt. GSE: current status and technical requirements”.

Task 2 concentrates on GSE only systems signalling aspects, starting by a current status analysis and finally providing what would be the technical high-level requirements for signalling and metadata over GSE only systems. A starting point for this work is what has been already provided in the DVB TM-GBS CMT group. This group intends to define the general DVB signalling over IP for any DVB systems. If DVB signalling already runs over IP, DVB signalling over GSE should be straight forward except for specific signalling aspects relating to the transmission and bearer. Certain considerations should be taken per use case, as for example:

Description of available physical pipes and support for network topology discovery (e.g. PSI/NIT),
Support of service mapping to physical layer transmission pipes (e.g. PSI/SI INT style table),
Satellite interactive network organization (e.g. RCS generic SI tables),
Other issues: signalling information portioning, timeouts in signalling tables, synchronization issues, etc.,
Backward compatibility issues, recognising that DVB GS and TS systems will probably need to coexist for some time.

The deliverable TN2 “GSE-only system signalling: status and requirements” contains the results of this work:

Current status definition: work achieved in DVB (objectives, planning, achievements, summary of the performed technical work),
High level architecture of a DVB reference system based on GSE generic stream(s) only,
Signalling Requirements, general and per -use case.

Task 3 will be divided in two work packages:

WP3100 - Detailed Specification (for the use of GSE) - will consider 3 different subtasks, one per use case, but now trying to concentrate on the detail specification and implementation issues. Possible protocol adaptations or new mechanisms or features in the GSE or physical layer standards should be considered.
WP3200 - Analysis of Performance - will provide a performance assessment to clarify and highlight the qualitative and quantitative benefits provided by GSE compared to MPE/MPEG-TS for the transport of IP data in the considered use case.

Here the focus will be on finding out whether (hopefully always), how (that should have been answered by the respective standard) and at what „cost“ (through semi-analytical means) GSE can be operated (with and without MPE and PSI/SI) over the various DVB carriers The output will be TN3 “Detailed Specification and performance assessment”.

Task 4 will propose and specify the signalling mechanisms to satisfy the detailed technical requirements arising from Task 2. This specification shall cover the definition of the signalling formatting and parameters, how the signalling is carried within DVB systems, and how receiver can identify and locate this signalling in the generic stream. The output of WP4000 will be TN4 “GSE-only system signalling specification”.

Task 4 is divided in 3 sub-tasks:

WP4100 for the proposal of a GSE-only signalling architecture, identification of the signalling mechanisms and signalling information, protocol messages and parameters.
WP4200 for the definition of GSE-only Signalling protocol, checking the different methods for mapping services carried by a DVB multiplex and provide the specification according to the signalling architecture defined in WP4100 and the requirements established in WP2000.
WP4300 will specify the design and operation of a DVB-RCS system using GSE-only signalling specification.

Task 5 shall address the preparation of technical contributions for the relevant DVB standardization groups. These contributions shall be based on the technical results obtained in the four previous tasks.

A CCN was agreed for the realisation of additional simulation activities, with the purpose to validate crucial parts of the specified signalling framework, i.e. the IP/UDP header suppression and the bootstrapping methods.

Current status

The project was completed in February 2011.

The project finished task 1 and task 2 in Dec 2009. The main achievements have been:

State of the art reference of the different DVB standards and GSE implementation requirements per use case,
GSE only systems signalling status and requirements per use case.

Task 3 was reviewed end of April 2010. The main results provided were:

Adaptations of DVB Standards for GSE Support,
GSE Protocol and Signalling Adaptations for DVB Standards,
Analysis of GSE-Like Protocols suitable for DVB-RCS: GSEalt, GSEng, RLE,
Error Control Checks analysis (Frame/Packet Integrity Checks, Reassembly Protection),
Performance analysis (based on functional advantages and overhead comparison).

Task 4 was completed in July 2010. As a result of the work, a signalling architecture for GSE-only broadcast and interactive satellite systems was specified, dealing with aspects such as:

GSE PSI/SI packets identification
IP Addressing
GSSTP encapsulation of DVB tables
IP/UDP header suppression for efficiency improvement
Synchronization through GSE-based NCR
Signalling security (encryption) and protection
RCST logon, addressing and routing
Connection Control Protocol

Task 5 activities were completed in February 2011. The outputs of the project have provided support to DVB standardization groups, such as TM-RCS, TM-GBS, TM-SSP and TM-T2. Several papers were published as result of the performed work.

In the frame of the CCN activities, completed in February 2011, the IP/UDP header suppression method and the bootstrapping method were simulated. The simulation showed their feasibility and efficiency. The IP/UDP header suppression method provides a better efficiency than the transmission of signalling tables with complete headers. The gain is especially significant for IPv6.
Thus the IP/UDP header suppression technique allows to provide an efficient IP-based GSE-only signalling architecture, without the overhead penalty.