It's almost universally accepted that to support the rich applications that are the real promise of interactive TV, something in the network must get "thicker." Early odds were on the advanced set-top — a client chock-full of added memory, fast processing and a DOCSIS cable modem. But as advanced models have been delayed, expectations have shifted toward leveraging the capabilities of the current generation of thin client set-tops by supporting them with thick headend servers.
In delaying the rollout of advanced set-tops, operators haven't just lost local processing and storage capability but also the fat, always-connected Data Over Cable Service Interface Specification data pipe to and from the set-top. The ability of new data-intensive applications — such as addressable advertising and walled gardens — to co-exist with functions such as the interactive program guide will clearly be limited by the need to share the same old data infrastructure. Whether the client is fat, or the server is fat, the pipe between them remains decidedly skinny.
Application developers and original equipment manufacturers have done an admirable job trimming applications to run in the processing and memory footprints of existing set-tops. But little attention has been paid to adapting existing data connectivity to provide the capacity, efficiency and flexibility necessary to enable easy, cost effective deployment of multiple data-intensive interactive applications.
It is vital for operators in the near term to devise innovative ways to work around the bottlenecks of existing set-top data infrastructure to handle the data connectivity demands of interactive application deployment.
The out-of-band (OOB) channel is a logical target for improving data infrastructure. It already serves as the data link to the set-top, and every set-top box, regardless of vendor or generation, has it. Its always-on connectivity offers the most viewer-friendly means of delivering data to the set-top. (Like DOCSIS, data is always available without requiring the user to tune a particular video channel.) But its capacity is pitiful compared to DOCSIS, and already packed with code objects, access control and program guide data. Further, the OOB channel is bound by legacy to the access control system, making it about as flexible as month-old taffy.
Probably the biggest weakness of the OOB channel is that it is carousel based — data is transmitted in repeating cycles with no particular sensitivity to when different pieces of data need to be delivered to different destinations. The more data to be transmitted, the longer it takes for the whole cycle to complete. Drop it in and it gets there — eventually. But interactive applications require a data-delivery mechanism with some notion of time — sensitivity and more predictable delivery, something more like Federal Express than the U.S. Postal Service.
Operators who can't afford to wait for DOCSIS and its increased capacity must consider three key improvements to maximize the capacity of the existing OOB pipe.
Improve OOB 'intelligence'
With its broadcast carousel transmission and limited bandwidth, contention in the OOB channel is an inevitable problem as operators try to add more data for more applications. Legacy systems offer few tools to cope with the needs of transmitting data for multiple applications.
Technology that enables intelligent management of the OOB channel by supporting dynamic mixing of data from different sources is critical for existing set-tops to support interactive applications. An example of this type of intelligent arbitration of OOB bandwidth would be slowing delivery of program guide data for next week's line-up to make room for burst data for an addressable advertising overlay that must run with a commercial in the next 15 minutes. Such an example must take into account time-sensitivity requirements for different application data, typical network distribution latency, and available storage on the set-top to be able to prioritize and package data from different applications for distribution through a highly contended pipe.
Historically, the OOB channel has functioned as an extension of the access control system carrying access control and code download data that enable basic set-top functionality and tiered video services. Obviously, such functionality is closely bound to the subscriber management and billing systems. In that capacity, control of the OOB channel has been very well adapted to batch-based data transmissions driven by a single source. But it is not easily extended to manage dynamic prioritization of data from different sources or to support the needs of interactive applications. To support multiple applications whose data transmission needs are more time-sensitive and complex, operators will need to manage the OOB channel using a much more flexible tool built to protect the critical path of data for core video services while enabling dynamic data-transmission scenarios.
Many operators already have mixed set-top deployments, often as a result of acquisition and consolidation; and going forward, many expect to continue mixed deployments as a means of fostering competition among their suppliers. Though all set-tops use an OOB channel for data distribution, the tools and means available to access that channel for inserting application data differ from vendor to vendor. This leaves an operator who has a mixed deployment of set-tops with no centralized, standardized way to manage data connectivity for the deployed set-tops, and no single point of access for integration with interactive applications. Standardized access to the set-top data path through a common access point, regardless of what set-top manufacturer, memory configuration, operating system, middleware or application, enables easier integration of applications and greater control of the OOB channel.
Vendors today are focusing their efforts on developing and testing these technologies and services. Results so far have been impressive in three key areas:
- Optimized data transfer efficiency through use of data-centric tools.
- Comprehensive set-top data-connectivity services that simplify data transmission by providing a standardized platform for data transfer.
- Reduced congestion and contention enabling multiple applications to share the OOB pipe.
By examining and managing the OOB data path properly and utilizing data-centric tools and technologies, operators can maximize their current legacy systems to enable applications once thought to be deployable only in next generation set-tops.
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