TECHNICAL WHITE PAPER Delivering on demand Video services in cable environment over the DVB-C path By Simeon Bajec, Product Manager, BeeSmart d.o.o., simeon.bajec at beesmart.tv Abstract Cable networks have a long history in delivering broadcast channels to customers and in the past they were the main channel for delivering a wide range of content to the home. In the past years their share is undermined by IPTV technology and internet service providers. The main reason for this is the interactivity that can easily be added in the IPTV environment. Not to fall behind, the cable operators need to add interactivity alongside the digital signal to the customer. The easiest way to achieve interactivity is to upgrade the IP bandwidth with DOCSIS 3.0 technology and provide the interactive content which means a huge investment in the network. The other way is to use the video headend reference architecture from Cable Labs which is described in the modular headend architecture specification and delivers IP MPEG packets over QAM channels. In this model the interactive content is delivered over QAM channels and only signalling is going thru the IP path which can be any DOCSIS technology. This document contains description of the MHA architecture and its elements. The concept is described and explained in detail to show the feasibility of such solution. 2011 BeeSmart d.o.o. All Rights Reserved. 1
Contents Abstract... 1 Definition and goals... 2 Modular Headend Architecture... 2 Technique comparison... 4 Conclusion... 5 Abbreviations... 5 References... 5 About the Author... 5 Definition and goals Cable operators are facing the problem to upgrade their network to interactivity. Interactivity means delivering on demand video content to the customers CPE which is mostly a STB. There are different approaches to achieve this functionality on cable networks. Cable providers can upgrade the DOCSIS data network to get enough bandwidth to the customers for interactive content. This is mostly achieved as an upgrade of their CMTS equipment to the DOCSIS 3.0 standard. Second approach is to use the DOCSIS data path as a control channel and the DVB-C infrastructure as the content path. This approach is specified within the modular headend architecture (MHA) document issued by Cable Labs. This document describes the MHA approach in more detail. Modular Headend Architecture The Modular Headend Architecture (MHA) described by Cable Labs allows delivering interactive video content over E-QAM devices. The MHA describes two reference architectures - video headend reference architecture and the M-CMTS reference architecture. In both architectures the main component is the Edge QAM (EQAM) device, for which all necessary interfaces are described. The other architecture entities are described in the components and the functionalities which they cover. This white paper focuses on the video headend reference architecture. The M-CMTS reference architecture is an extension of the video headend reference architecture and adds channel bundling, which is possible in DOCSIS 3.0, to the CMTS system and increases downstream bandwidth to deliver on demand content. For this architecture also a DOCSIS 3.0 capable CMTS device is needed. This is the all IP approach for on demand content delivery. The Video headend reference architecture defined by Cable Labs provides the mechanism to transport IP MPEG-2 TS on demand streams over QAM channels (DVB-C standard) to the user STB. The entities in such a system are the E-QAM, edge resource 2011 BeeSmart d.o.o. All Rights Reserved. 2
manager (ERM), Video Session Manager (Video SM), Video server and Hybrid Set Top Box (STB). Picture 1: Video headend reference architecture The E-QAM is responsible to map the MPEG-2 TS stream from the input IP/UDP port pair to the appropriate output QAM channel, transport stream and program. Interfaces on the E- QAM are the Edge Resource Manager Interface (ERMI) I and II, Downstream Radio Frequency Interface (DRFI), EQAM-VSI (input interface) and the management interface. The ERM is the entity that manages the EQAM resources and communicates it to the Video SM. The Video SM sets up the Video streaming session between the Video Server and EQAM and maintains it. We can combine the ERM and Video SM and call it Session Resource Manager (SRM). The Video server streams the content toward the EQAM input interface. The hybrid STB is the user interface and communicates with the ERM to setup and play the on demand video content. The client software enables the use of the Video headend architecture. Theory of operation or how does it work in steps (illustrated in Picture 2): 1. The STB initiates a RTSP session and contacts the SRM 2. The SRM check the STB rights, location and resources 3. The SRM initiates the RTSP session towards the VOD server 4. The VOD server starts streaming the content towards the E-QAM with the defined IP and port combination 5. The SRM sends the DVB-C content information towards the STB back over the RTSP protocol 6. The STB tunes to the stream and shows it 2011 BeeSmart d.o.o. All Rights Reserved. 3
Picture 2: SRM session initiation and streaming Technique comparison The Table 1 gives a short technique comparison between the MOHA and DOCSIC architectures. Architecture Property Video Headend reference architecture M-CMTS reference architecture Video on Demand DVB-C IP IP delivery path Upgrade costs Low High High Complexity Medium Medium Low All IP Headend Yes Yes Yes Interoperable with other architectures DOCSIC 3.0 deployment Yes With additions With additions Table 1: Architecture comparisons From the headend point of view the same elements are used in both solutions. For the Video Headend reference architecture additional SRM is necessary. The main difference are the costs of a Video Headend reference architecture deployment which are probably half of a DOCSIS 3.0 deployment and the video on demand delivery path which is only in the Video Headend reference architecture the DVB-C network. 2011 BeeSmart d.o.o. All Rights Reserved. 4
Conclusion The Video Headend reference architecture is mostly viewed as a step towards a cable network which will have enough bandwidth to deliver interactive services thru the IP path. The solution is cost effective and supports all advanced interactive TV features. It can be setup without big investments in the network and the headend equipment stays almost the same when the upgrade to all IP is done. Abbreviations ERM Edge resource manager E-QAM Edge QAM QAM quadrature amplitude modulation, the format with which TV programs are provided in cable networks MHA Modular Headend architecture, a reference architecture described by Cable Labs VOD- Video on Demand HFC Hybrid Fibre Coax, cable provider network SM- Session Manager STB Set Top Box, user equipment SDV Switched Digital Video IP Internet Protocol DVB-C Digitav Video Broadcast Cable References More information about Cable Labs and their specifications visit http://www.cablelabs.com/ More information about RFC standards visit RFC Editor http://www.rfc-editor.org About the Author Simeon Bajec works as a Product Manager at BeeSmart d.o.o. He graduated at the University of Ljubljana. Simeon has a broad work experience in network and IPTV technologies and worked in many projects as a consultant and a solution manager. 2011 BeeSmart d.o.o. All Rights Reserved. 5