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Five Strategies for Successful SDV Deployment

By Jennifer Whalen, editor, special projects Pressure to add new high-definition programming, expand channel lineups, and offer advanced DOCSIS services in the face of satellite and telco competition is causing cable operators to explore new bandwidth reclamation technologies. Switched digital video (SDV) is one such technology gaining traction this year with commercial launches and trials at many cable operators. SDV has the potential to reclaim large chunks of bandwidth. Vendors claim they have deployed SDV solutions for cable operators that achieve anywhere from 2-to-1 up to nearly 4-to-1 oversubscription rates. But, the technology adds new levels of complexity to cable networks, requiring careful planning, design, rollout, monitoring, and future proofing to achieve success. Broadband Gear Report talked to several vendors and one operator, as they were largely mum, about their strategies for success. Here's what they had to say.

Plan Early Early and careful planning is essential to a successful SDV deployment. One of the first things to do, said Greg Hardy, vice president of business development, transmission network systems, for Scientific-Atlanta, is to clearly define your objectives. "What do you want to accomplish when you're done?" he asked. "That helps drive the planning, which helps drive design, and the ultimate execution." Operators need to consider how much bandwidth they want to recover, what new services they want to launch, how much they can afford to spend, and how they will scale the system for future growth. Then, keep those objectives firmly in mind as they design their solution. Once you've defined your objectives, you need to know how the current network is being used, which means monitoring all the channel activity, said Mark McKelvey, Motorola's senior product manager for SDV. "You want to have a good sense for what channels are low-popularity or long-tail channels that make sense to switch," McKelvey explained. He added that modeling network traffic also will help you to size the network appropriately. At a minimum, McKelvey suggested that operators monitor traffic and viewing habits for four to six weeks. "Our feeling is that operators will want to drop [monitoring equipment] in even further out… maybe six months before you ever roll out switched digital." SDV will not be successful unless you clearly understand your subscriber's viewership patterns. "You can spend money and put SDV in, and six months from now look at the data and say, 'Did I really free up bandwidth?' Maybe you didn't. The reason you didn't is you didn't pick the right programs to switch, or you didn't pick enough of them," said Ramin Farassat, vice president of product marketing for RGB Networks. He added that programs in the switched tier need to reflect the viewing habits of the subscribers in that particular service group. For example, while ethnic channels may be good to switch in many neighborhoods, in certain locations subscribers will be watching them all the time, making them unsuitable for switching in that area. Facility readiness is an essential component of SDV, and one that operators may unintentionally underestimate. "The sheer number of edge QAMs that you need to fit into your headend and hub sites is a fairly daunting number," said Ron Wolfe, senior product marketing manager for BigBand Networks. He noted that a hub serving 50,000 households, with 100 service groups of 500 tuners each, and requiring eight QAMs per group would need to add 800 QAMs. "They consume a lot of power and dissipate a lot of heat." Most operators will need to add rack space, power capacity, and HVAC systems to support those QAMs. Return path readiness and elimination of ingress is also critical. "If operators haven't already fully qualified the reverse capabilities for all the segments that will go switched, they will have to do that now," said Mike Caldwell, senior director of product management for ARRIS. "The set-tops have to have real-time communication back to the headend." Nonresponsive set-tops are also a problem, said Doug Ike, vice president of advanced video engineering for Charter Communications. A nonresponsive set-top may not be able to send and process a switched channel request. Keys to SDV success include, "aggressively cleaning up the network and chasing nonresponders," Ike said. Finally, in the planning arena, it's never too early to start training your CSRs, system engineers, and technicians, said Eric Conley, CEO of Mixed Signals. "Get your CSRs and engineers up to speed early so your operations are prepared for the rollout when it happens," Conley suggested. To see the Enhanced Switched Digital Video Architecture with VBR & Bulk Encryption, click here.

Design Carefully During the design stage, operators must consider service group size, transport capacity, forward and return bandwidth, redundancy, IP assets, and other issues. Charter has two trials underway: one with Motorola's SDV solution in a system with Motorola set-tops and another using BigBand's SDV solution in a system with S-A set tops. "For Charter, getting the right service group sizing has been the largest amount of work," Ike said. "We are currently aligning our VOD service groups with our SDV service groups to simplify the operational management of the network." The operator is reducing its service group size to between 500 and 1,200 tuners, and SDV is driving that reduction. Counting tuners, rather than households, is a key distinction between VOD and SDV service groups, Ike noted. "With switched digital video, we have to account for a second tuner in a DVR or account for additional set-tops in the home," he explained. Vendors generally agree that smaller service groups are better. "We are trying to target in the 500 range," said Motorola's McKelvey. The notion of aligning VOD and SDV service groups is also important, especially if operators want to take advantage of the efficiency gains expected from QAM sharing, said S-A's Hardy. "Flat service groups are needed if you want to do QAM sharing." SDV also adds traffic to an operator's regional Gigabit Ethernet transport network. "You typically need to drop 1 Gigabit per second of video at any given hub site," said BigBand's Wolfe. "If you have hub sites that are bandwidth constrained, the regional network might need to be updated." SDV also has intensive IP addressing requirements, Wolfe added. Operators will need to include in the design process an IP addressing plan to tie SDV system components together. Sizing the return network correctly is also important, said Charter's Ike. "We have to make sure we have ample overhead to account for the additional control traffic on the network." Redundancy is another a design consideration. "Running redundancy on both the SDV components and sources is key," said Motorola's McKelvey. "You don't want any failures to produce outages for your customers."

Rollout Slowly Everyone agreed that a slow trial rollout to friendlies combined with strong project management and thorough testing to examine video quality, integration issues, and viewership patterns is essential to successful SDV deployment. A slow rollout applies to content as well as subscribers. Charter, for instance, is not yet oversubscribing the content in its switched tier, but rather offering the same programming as its linear broadcast lineup. This strategy allows the operator to "ensure that you have the communications network in place and that you are getting the channel change requests into the network correctly," Ike explained, adding that it also gives operators the chance to thoroughly test the two-way plant and continue to collect viewership data. A strong onsite project manager is a key component of a smooth SDV rollout, said S-A's Hardy. "You need a person who is responsible for making sure schedules get hit on time and has the ability to escalate problems to the MSO or vendor," Hardy explained. He also recommended having MSO IP networking expertise onsite or readily available, otherwise your rollout may stall as vendors wait for IP addresses, installation of router cards, and other needed changes to the MSO's IP network. Vendor testing is a crucial piece of the trial experience. Before selecting an SDV system, RGB's Farassat recommends that operators closely scrutinize the system's video quality, as clamping the broadcast VBR streams into CBR streams for SDV can cause problems. "It takes some good video processing to make sure you haven't degraded the video quality," Farassat said. "If you don't do a good job on the original video, setting the cap rate, etc., you end up with pretty bad video quality." To achieve the most robust performance and best quality, operators may want to consider a multivendor solution, said Mixed Signals' Conley. "Do an extended trial of different vendors and combinations of them," suggested Conley. "A single vendor solution is simpler for the MSO, but not necessarily the best." RGB echoed that sentiment, noting that the ability of QAMs to scale to support hundreds of simultaneous channel change requests expected in a commercial deployment varies by vendor. It goes without saying that integration testing is potentially the most important element of an SDV trial. "Even with open standards, there are issues that arise," said ARRIS's Caldwell. Potential glitches include touch points between the switched digital server and edge resource manager, QAM and edge resource manager, and the set-top and SDV session manager. To overcome this difficulty, Caldwell suggested that operators "over communicate." "They need to make sure all these vendors are talking to each other and that there is an open dialog during integration." Mixed Signals' Conley also urged operators to implement a robust monitoring solution with the SDV rollout. "SDV adds a huge amount of complexity to the network. When you do that, you introduce a lot problems," he said. These problems occur not only with the new equipment, but also in the existing core video infrastructure. "You get a spike in trouble calls, and not all are directly related to the new SDV equipment." Monitoring from the beginning will enable operators to identify and fix problems during the trial, facilitating a quicker rollout with less impact on the subscriber, he said.

Monitor Post Launch The importance of monitoring continues after launch. Operators will need to ask: "Is video quality up to the standard of the digital broadcast signal? Is it consistent across the channels in the switched digital tier, or are some better quality than others?" said Marc Tayer, senior vice president of marketing and business development for Imagine Communications. Tayer noted that operators can pursue two strategies when it comes to SDV quality: achieving consistent quality across the switched tier and broadcast, or assigning higher quality to specific assets, such as an HD pay-per-view event. Today's solutions enable operators to "calibrate and maintain different quality levels depending on the content asset," Tayer said. Operators also need to continue monitoring subscriber viewership patterns, after launch. "You may need to fine tune your list of switched channels," said ARRIS' Caldwell. He noted that some programs that originally stayed in the broadcast tier may need to be switched and vise versa as viewership in commercial rollouts may differ from friendly trials. Time of day also impacts viewership, said Imagine's Tayer. "Some content may be popular during prime time, but not during other hours," he said, adding that the ability to change whether a program is switched or broadcast depending on time of day, is important to gaining the most bandwidth savings from the switched tier. Tayer added that there may be other content that operators can add to the switched tier post launch. He suggested that some HD content might appropriate.

Plan for the Future SDV, like everything else in broadband cable, is not a static service that you can deploy and forget. When implementing your solution, it's important to plan for the future. "You need a road map to get to VBR stat mux for best video quality and bandwidth efficiency," said Tayer. RGB's Farassat agreed, adding that delivering SDV in variable bit rate "gives you potentially better use of the architecture and better video quality." Switched unicast services, where every subscriber receives a unique stream, is another future consideration. "The unicast advantage is that you can go to a more personalized TV environment, which includes addressable advertising," Tayer said. Planning for QAM sharing between VOD and SDV services also is critical because it offers operators additional ways to optimize bandwidth efficiency. Even if QAM sharing isn't on your immediate horizon, S-A's Hardy says to "plan for it now" as designing your current service groups to support future QAM sharing will save you labor later. Finally, plan for the "ability to move video to an IP endpoint," such as a cable modem or personal digital assistant, says ARRIS's Caldwell. Be sure that your SDV solutions supports delivery to IP devices as well as MPEG set-tops. Switched digital video is a complex technology with enormous potential to help operators reclaim bandwidth for long-tail content, high-definition channels, advanced DOCSIS data and other yet-to-be discovered broadband services, all necessary to keep in front of competitors. With careful planning, design, rollout, monitoring, and future proofing, operators can reap the bandwidth, efficiency, and personalized advertising potential that SDV offers.

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