Deploying Video Over DSL As a Universal Service
July 1, 2003
America's Network
By Malcolm Loro and Mike Drew of Catena Networks
Within today's evolving telecommunications landscape, the delivery of advanced video services over DSL has emerged as a significant opportunity area for many service providers. The widespread reach of copper loop infrastructures and the long-standing relationships with POTS customers offer fertile ground for deploying video as a bundled offering with voice and broadband data services. However, the successful deployment of video-over-DSL requires a well-planned approach that is both economically viable and addresses the full scope of the market opportunity.
Video-over-DSL offers an excellent way for carriers to reverse revenue erosion and to compete effectively against cable providers. Not only can video provide significant new incremental revenue for carriers; the bundling of voice, data and video can be a powerful factor in reducing subscriber churn. Subscribers can get a complete spectrum of advanced services from a single source. In some areas ― such as rural environments, where cable has not yet been deployed ― video-over-DSL even provides an opportunity for telco carriers to leapfrog potential cable competitors and build a significant barrier to entry.
Having learned from the difficulties with first-generation DSL deployment, which treated broadband as an overlay to the voice network and resulted in disjointed pockets of service availability, the industry needs to view video-over-DSL as a universally deployable service from the outset. This doesn't necessarily imply the immediate, wholesale conversion of existing networks. However, carriers must make careful, up-front architectural decisions, so that they can smoothly roll out video services and avoid technology roadblocks along the way.
Key considerations for the success of video-over-DSL deployments include:
Seamless architecture for deployment in both Central Offices and Remote Terminals
Standards-based delivery of existing and emerging video services (broadcast services, video-on-demand, interactive video, etc.)
Technological and economic scalability to allow for smooth expansion, universal availability and manageable operating costs
Creating a seamless architecture is critical because it lays the foundation for both universal service delivery and economic scalability. While many Central Offices (COs) now house DSL equipment, deploying such equipment at remote terminal (RT) sites has been more challenging because of operational and physical-space issues. Further, carriers continue to rely on Digital Loop Carriers (DLCs), originally designed for narrowband services, to reach subscribers served from RTs. It has been prohibitively expensive for carriers to deliver broadband services from RTs, because they must absorb the capital costs of collocating remote DSL equipment and/or the operational costs of sending technicians to install DSL linecards in Next Generation DLCs (NGDLCs). This overlay approach simply cannot provide the flexibility or sustainable economics needed for delivering consumer-oriented video services. Using a new Broadband Loop Carrier (BLC) architecture, which combines POTS and DSL on every line, service providers are now deploying networks that treat voice and broadband as universally available services. This lays the foundation for delivering video-over-DSL services quickly and cost-effectively. Because BLCs provide POTS and DSL on every line, carriers can software-provision services to any subscriber - remotely, without manual intervention.
As carriers move toward including video as an integrated service offering, advanced capabilities within the access network equipment will play a critical role. For example, carriers using BLCs that have integrated IGMP and multicasting capabilities will have much more flexibility in delivering video services over their network infrastructures. By driving multicasting functionality as close to end users as possible, service providers can minimize the need for high bandwidth consumption on their video transport networks. Carriers also can use distributed multicasting intelligence, rather than dedicated servers, to eliminate potential bottlenecks and single points of failure within the video delivery infrastructure.
By moving video service provisioning and multicasting to BLCs near the subscribers, carriers have more flexibility to use a variety of standards-based technologies in the transport network. Remote BLCs can interface with a wide range of transport technologies including, ATM, IP, Gigabit Ethernet, Packet over SONET (PoS), and DWDM. Therefore, carriers can seamlessly deliver video-over-DSL services at the edge of their existing networks, without having to make forklift technology changes to the core.
Besides simplifying technology choices, the ability to deploy integrated voice, data and video services over BLCs also enables carriers to leverage the standards-based, multi-vendor marketplace. Instead of being locked into a broadband video delivery architecture that dictates equipment choices at various points throughout the network, the BLC-based approach is independent of both transport and CPE choices (set top boxes, etc.). This open-standards approach is equally applicable to broadcast environments, where a common video stream is served to many subscribers via multicasting, and to video-on-demand environments, where the video content is delivered point-to-point from the video headend server.
Carriers also must determine what "flavor" of DSL is needed for effective delivery of video services. Some industry experts contend that VDSL will be necessary to provide the bandwidth for supporting different, simultaneous channels on a large number of televisions within each home. However, the reach of VDSL is so small that it typically doesn't fit well within most existing telco networks. Carriers must undertake expensive redesign efforts, which prevents them from cost-effectively deploying video to the majority of their current subscribers. In reality, the "sweet spot" for serving most residential customers is the need to support two simultaneous TV users. ADSL can adequately address this requirement, while still supporting concurrent Internet usage. Choosing a BLC with support for optional parameters in the ADSL standard that enable downstream data rates of more than 10 Mbps provides even more headroom on the ADSL link. Carriers also can consider the emerging ADSL2+ standard, which will boost ADSL carrying capacities even further. At the same time, advances in digital video encoding technologies are opening the potential for more channels to be carried over any given bandwidth level.
The bottom line is that by deploying highly integrated POTS+DSL architectures and standards-based BLCs, carriers can immediately generate new revenue from video services ― without sacrificing current POTS densities or compromising on rate/reach performance. At the same time, they can create highly scalable, broadband video delivery networks, while avoiding major forklift upgrades and excessive, ongoing operational costs. In addition, the scalability of BLC architectures will enable carriers to offer new, on-demand and interactive services using their existing network infrastructures.
