By any of several measures, switched digital video is hot. The list of vendors playing in the SDV arena is growing, with some products in their second or third generation. The body of peer-reviewed literature is expanding. Debates are live, and increasingly urgent. And the industry’s two largest MSOs are planning to invest in this category, heavily. The shift from trial to deployment has begun.

Two papers delivered at the NCTA Cable Show and four prepared for SCTE‘s Cable-Tec Expo focus upon switched. Moreover, because SDV cuts across several other categories and is assumed as part of the industry’s strategic roadmap, the topic now frequently shows up elsewhere – for instance, in papers covering bandwidth management and advanced advertising.

As SDV matures, there remain open questions. Exactly how many additional QAM devices are required to achieve the access network nirvana of one stream per tuner? What role can variable bit rate (VBR) encoding play within this architecture? How do you track and monitor the exponentially increasing number of streams? (The topic of one of this year’s Cable-Tec Expo papers.) And to borrow from the question that BigBand Networks Chief Cable Architect Doug Jones raised in these pages in May, what will it take to turn open protocols into open systems? Related to that last question is the possible standardization of separate digital video interfaces used, respectively, by Time Warner Cable and Comcast.

Whether and how that fraternal debate is resolved, the clock is ticking on deployments. The early champions of SDV, Time Warner execs talk of deploying it across half of their national footprint by the end of 2007. Comcast, which can drive markets by its sheer weight, expects to move into deployments in that same timeframe.

The bottom line is that, after years of sitting on the vine, switched digital is as ripe as ever. A topic that once engaged attendees at the SCTE Conference on Emerging Technologies has become an action item on the Cable-Tec Expo agenda. The case of Austin Three of this year’s Expo papers are framed to present SDV "lessons learned." Todd Bowen, director of digital systems at Time Warner’s Austin division, prepared one of these. It’s the more detailed and heavier of the two authored by operators, the other coming from Bob Clyne Sr., VP technology at Cablevision Systems. A team from BigBand wrote the third.

The Austin story, explains Bowen, goes back three years, to an initial trial that included 160 digital services switched into 10 edge QAMs. It resulted in a few two-way issues and signal problems, but was mostly notable for being "totally transparent to the customer."

The bulk of Bowen’s paper is a detailed explanation of Austin’s subsequent, system-wide SDV launch. Channel selection was "the major first decision." The wrong choice can lead to blocking, yet a decision here is not irrevocable, as channels can be moved in and out of switching. How to deal with the unidirectional CableCard host devices, which cannot receive switched channels, is a topic that Bowen singles out for special consideration.

The preparatory headend work in Austin entailed the wiring and routing of feeds through a Bigband Networks BMR1200 to encryption QAM devices and dovetailed with an upgrade of the system’s optical network to accommodate greater volumes of video traffic. Hub work involved rack space, powering, air conditioning and wiring for service groups and edge QAM devices. Factors behind Austin’s decision to use the upper-end spectrum between 705 and 747 MHz for SDV included channel viewing patterns, set-top signal levels and placement of VOD QAM frequencies.

To get the plant ready, Austin addressed non-responders and ingress. The non-responder rate began at 11 percent and improved after two years of SDV to 6.5-7 percent. But Bowen says that growing numbers of high-speed data and digital phone modems helped.

As for managing ingress in the plant or drop, SDV complicates matters. Specifically, it forced the Austin team to "change from troubleshooting channel impairment to troubleshooting the frequency spectrum the SDV QAMs operate in."

That adjustment is one example of the kind of training it takes to prepare for SDV operationally. In terms of other preparations, Bowen emphasizes the importance of system-wide communications, especially related to "trip wire" issues, such as those affecting CableCard subscribers.

That Bowen – and the Austin experience – has lessons to share is proved by his first rule of SDV: "Don’t assume anything!" That section, which comprises more than half of the paper, is well worth digesting in its entirety. (See sidebar for summary lessons.)

Austin completed its SDV launch in the spring of 2006. Since then, the system has added 90 additional channels to its initial 84 switched lineup, monitoring usage across its 350 service groups all the while. The benefits that resulted from this launch – an expanded international tier, additional standard and high definition services and support for analogy simulcast – are likely to be replicated elsewhere as Time Warner continues to deploy this technology.

Other systems will benefit from accelerated deployment cycles, but are also likely to face similar challenges. That puts a premium on studying all of these case studies carefully. Vendor partners As for what the vendor community has to say about this category, consider the following roundup of views:

BigBand Networks: How does this pioneering vendor of switched video, which claims to have 6.5 million homes passed with its switched offering, regard the current enthusiasm for the category?

"It’s a strong validation of the vision that we saw and we’re bringing to bear with next-generation technologies," says Biren Sood, vice president of the cable video business at BigBand.

BigBand planned to demo its third-generation edge QAM platform at Expo. It also is trumpeting its shipment of 70,000 Edge QAM units in 2006 and other successes, such as a deal to deliver international programming to Cablevision Systems and the ability to add HD channels to a programming lineup.

Sood emphasized BigBand’s adherence to standards and "continuing to bring technology to bear that supports open standards and, more importantly, open standards that drive open systems."

BigBand keenly underscores its market leadership in this video category. "We continue to believe we’re the only successfully commercially deployed switched digital video solution that’s out there – the key being switched – which means a solution which is actually oversubscribing the network and allowing operators to take advantage of the statistical gain that the technology affords," he said.

C-COR: In a paper delivered at the Cable Show, C-COR SVP Advanced Global Technology Joe Matarese leaned upon a more granular view of what viewers actually watch to introduce the concept of switched digital programming.

The upshot is an expanded business case. "What I really wanted to do was explore some of the ways that we can make SDV … more supportive of advanced advertising," he said.

Currently engaged in the development of dynamic VOD advertising playlists and in front of ad sales groups making "presentation after presentation" on basic SDV, Matarese says C-COR is anticipating the eventual convergence of on-demand, advertising and SDV. The enablers are shared QAMs and common resource management.

Matarese said C-COR had three consistent points at this year’s shows: 1) An SDV platform in the TV-Guide Motorola environment that could integrate with addressable advertising; 2) VOD advertising; and 3) optical access gear that enables opportunistic expansion of the network.

At Cable-Tec, C-COR also planned to demonstrate a 1 GHz Edge QAM device, the CHP eQAM, which works with the CHP Max5000 headend platform and supports 120 QAM channels in a two-rack unit configuration.

Harmonic: Having waited, like others, for the industry to engage, Harmonic believes its narrowcast service gateway (NSG) already is positioned as an EdgeQAM platform well-suited for SDV.

"We feel very comfortable with the NSG9000, the first universal EdgeQAM in the market," says Gil Katz, Harmonic director of cable solutions. "It was designed to support switched broadcast, modular CMTS (and) IPTV."

Harmonic is executing on a strategy that sees switched broadcast as an interim point along a longer continuum. "At the end, we’ll have the shape of switched unicast," Katz says.

Katz sees these two approaches coexisting, with long-tail programs on switched broadcast and more popular programs on switched unicast, where targeted advertisements can generate rapid returns on infrastructure investments.

At the ANGA cable show in Germany, where the NSG9000 was part of a Cisco Systems modular CMTS demonstration, Katz offered views on how best to deliver digital video over IP networks. "Bypass is the wrong term," he says. "Go direct to the QAM."

Motorola: The cornerstone of Motorola’s SDV strategy lies in last year’s pickup of Vertasent. Motorola’s edge resource manager (ERM), which was developed by Vertasent, allows cable operators to share bandwidth between services over narrowcast QAMs.

"One of the things that is unique about the Motorola solution is that it does marry two on-demand services, VOD and switched digital video, into a common network infrastructure, and that’s a bit different than the way some others have approached it," says Bruce Bradley, vice president, Motorola digital video solutions. "With separate QAM infrastructures for VOD and switched digital video, you occasionally have stranded bandwidth in the VOD silo while your switched digital video silo is starving for bandwidth."

Once modular M-CMTSs and their components become available, Motorola will also be able to share bandwidth across video and high-speed data.

Bradley says Motorola has integrated its ERM with VOD server vendors, who are the largest users of narrowcast QAMs, including Cisco/Arroyo and Concurrent, and with most of the widely deployed edge QAM manufacturers.

At the Cable Show, Motorola’s VOD demonstration used SeaChange‘s backoffice solution with the Motorola, formerly Broadbus, VOD pump. The company also demonstrated its ERM working in conjunction with SDV in Las Vegas and anticipated similar demonstrations at Cable-Tec Expo.

Scientific-Atlanta: At the Cable Show, this Cisco company had a two-fold demonstration. First, it showed off its existing SDV platform, which the company says switches actively to 100,000 set-top boxes.

Second, it showed SDV and VOD working off of its universal session and resource manager (USRM) platform, a product that it had introduced in January. "We’ve decoupled the session resource management functionality from the DNCS (digital network control system) completely," says Jeff Taylor, director, product strategy and management for S-A’s Subscriber Network Systems.

A software upgrade to the current platform enables this new functionality, facilitating its adoption by current customers, and the decoupling also allows the company to compete in systems that use Motorola’s digital addressable controller (DAC).

For Expo, S-A planned to demonstrate the USRM’s redundancy mechanisms and other functionality, as well as the SDV Collector tool set, which gathers data from all SDV servers for use across multiple departments.

"The operations piece allows for an operator to do all of their capacity planning," Taylor says, "to figure out when you’re potentially reaching blocking thresholds and when you might need to split a service group."

Tandberg Television: Building upon its OpenStream digital services platform, which is widely deployed in the VOD space, Tandberg launched its OpenStream SDV solution at the Cable Show in May.

The Tandberg SDV solution boasts massive scalability, full redundancy, and an open platform that allows cable operators to control and manage switched multi-rate (from 2 to 20 Mbps) and multi-format (SD/HD and MPEG-2/MPEG-4) digital TV services.

For Expo, Tandberg planned to demonstrate the SDV solution along with its DOCSIS 3.0 compliant, Universal EdgeQAM EQ8096. It also supports multi-rate, multi-format video content, advanced codec support and extended reporting capabilities.

Tandberg is one player poised not only to leverage its encoding expertise, but also to capitalize on the convergence of SDV, VOD and advanced advertising. "Our vision is a single campaign management system that connects with on-demand, linear, and switched digital video delivery platforms using emerging, industry-standard interfaces," says Michael Adams, Tandberg VP, systems architecture.

Vecima Networks: Active in QAM modulator technology since 2001, Vecima unveiled its HyperQAM Universal Edge QAM device at Cable-Tec Expo. "It’s targeted for switched digital video, as well as M-CMTS and, of course, video on demand," says Doug Fast, Vecima’s EVP and VP of R&D.

Able to support up to 128 QAM outputs in a two-rack unit configuration, the HyperQAM nearly triples the density of Vecima’s VistaLynx product. The design also supports up to 8 QAMs in a single block. "The more channels per block, the lower cost the hardware," Fast says. –Jonathan Tombes is editor of Communications Technology. Sidebar: Lessons Learned: Time Warner Cable (Summarized from paper prepared for SCTE Cable-Tec Expo by Todd Bowen, director digital systems, Time Warner Cable, Austin.)

Switched channel candidates: Bowen offers four candidates, with caveats. Channels without 24-hour programming, but excluding event pay per view (PPV). Channels with alternate time zones, but excluding any that are popular basic services. Analog simulcast low-power television (LPTV) channels, but with the understanding that any which are watched continuously will not yield bandwidth savings until service group sizes are reduced. Simulcast channels that serve multiple ad zones, because switching them enables increasing the number of ad zones while minimizing capital expenditures.

Service group size: During its SDV trial, Austin determined the "sweet spot" to be a group size of between 500 and 1,000 tuners. Peaks of unique channel usage occurred not only during prime time, but also (and surprisingly) during the midday. One takeaway on sizing involves limits on the efficiency of size reduction: the sum of utilization for split groups always exceeds 100 percent of the original group. Given the unique characteristics of service groups, operators should budget for monitoring tools.

Software and hardware: Although the trial allowed for some de-bugging, Bowen says that other problems appeared only after reaching critical mass. Examples include issues related to specific set-tops, to individual channels, or to specific series of events. Troubleshooting entails duplicating the issue in a lab setting, identifying the root cause, problem solving with vendors and testing the fix. Handled with care, Internet forums can be useful sources of problem reporting.

Non-responders: Bowen notes that a converter not in two-way is able to piggyback on a switched stream that another subscriber has requested, but only while that first subscriber continues to tune to it. Repairing two-way issues in Austin was mostly a matter of fixing a converter’s internal wiring. Deploying SDV hub-by-hub facilitates troubleshooting, which is standard and does not exceed a service technician’s competence.

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