Page 2: The Control Plane

Page 3: Rate Clampers & Edge QAMs

Page 4: Who’s Doing What?

— Jeff Baumgartner, Site Editor, Cable Digital News

Page 2: The Control Plane

Much of the brains of any SDV deployment are contained in the "control plane" – where session management and edge resources are managed.

In the approach of BigBand Networks Inc. (Nasdaq: BBND), its Switched Broadcast Session Server (SBSS) serves as the control plane of the SDV system, according to Biren Sood, the company's VP of product marketing. It performs two major functions: session management (processing individual session and channel change requests from set-top boxes) and edge resource management (the dynamic setting up and tearing down of a session to individual QAMs). BigBand packages both of those functions together.

The Cisco Systems Inc. (Nasdaq: CSCO) Universal Session Resource Manager (USRM) is the second generation of the vendor's SDV server. It's capable of handling the edge and resource management functions together or separately. It's in beta testing now, with an expected commercial rollout this summer.

Motorola Inc. (NYSE: MOT)'s entry in this category today is the Switched Video Manager 1000 (SVM 1000), though a higher capacity model, dubbed the SVM 2000, is in the works. Those devices receive the channel change request, but work in conjunction with the company's ERM 1000, an edge resource manager Motorola obtained via its acquisition of Vertasent. (See Motorola Buys Vertasent.) The ERM 1000 is designed to control the narrowcast bandwidth being assigned to a given service group.

While those products are geared for cable networks based on Motorola's digital platform, Motorola is also working on a Global Session Resource Manager for Cisco-based digital cable environments. That product adds in a high-performance session manager for video-on-demand and for more advanced apps like "Start Over," according to Bruce Bradley, director of product marketing, digital video solutions, for Motorola's Home & Networks Mobility unit.

Vendors have also developed new centralized systems that govern and generate reports for the entire SDV system. For its part, Motorola has created what it calls the Switched Video Operations Manager 1000. Among its abilities, the system can determine if a service group is running low on bandwidth or send an alarm if an edge QAM should fail. BigBand introduced a product in this category, the Video Management System (VMS), in April 2008. (See BigBand Bows Video Manager.)

Table 1: SDV Servers & Resource Managers

Although Arris Group Inc. (Nasdaq: ARRS) isn't supporting the CHP eQAM it obtained from the acquisition of C-COR, it is continuing to offer another product that came via the C-COR deal: the nABLE Global Session and Resource Manager (GSRM), which originally cut its teeth on video-on-demand (VOD) deployments.

The current implementation of that product will apply to any SDV application, but it's initially applicable to Comcast's SDV architecture, says Mike Caldwell, Arris's senior director of product management.

Tandberg Television introduced a session manager of its own in May 2007, based on standard interfaces being defined by MSOs. However, Tandberg decided last summer to put product development on hold once it was clear that operators remained interested in supporting open interfaces for edge QAMs to hook into, but had backed away from wanting to develop similar interfaces for other elements of the SDV architecture, including edge resource managers and session managers.

"As a result, we had a standard tire, but there weren't any standard-sized wheels for us to mount the tires on," recalls Michael Adams, vice president of applications software strategy for Tandberg Television. "But we have the [session manager] nicely architected, just in case." In the meantime, Tandberg has transferred that work into other products in its video technology portfolio.

Page 3: Rate Clampers & Edge QAMs

SDV Clampers
Another important component of SDV systems are the rate clampers, which set the bit-rate of the standard-definition or high-definition switched digital video stream. Although suppliers such as Imagine Communications and BigBand are developing more efficient variable bit rate (VBR) technology for switched digital video, all deployments today use constant bit rate (CBR) systems.

BigBand outputs clamped CBR streams via its Broadband Multimedia-Services Router (BMR). The bit rate at which SDV streams are clamped can vary, based on how much "action" is expected from the video source. On the high end, HD SDV streams are clamped at 19.4 Mbit/s, while standard-def is clamped in the range of 3 Mbit/s, Sood says.

Table 2: SDV Bit Rate Clampers/Re-Encoding Systems

"Depending upon the source of the MPEG stream (whether it's being re-encoded or from a satellite receiver) will determine whether the MPEG stream needs to be rate-clamped to a CBR. So, on some streams it may be needed, while on others, it may not," Motorola noted in a follow-up email on the subject.

Edge QAMs
The edge QAM terminates IP-based multicasts and then translates those feeds as MPEG-based transport packets via RF (radio frequency) down the cable plant. From a vendor and product standpoint, the edge QAM element of the SDV architecture is certainly the most crowded, with more than 10 vendors vying for what's sure to be limited market share. As we'll show later, it's also the most expensive component of the SDV platform.

To support SDV, edge QAMs must be able to replicate the video streams delivered in the switched tier and support a signaling mechanism that talks to the session management system, which governs which specific service group needs a stream of the channel in the switched tier. However, many of the newest edge QAMs are considered "universal," meaning they can share resources among multiple cable applications, including SDV, VOD, digital broadcast video, and even IP-based Docsis traffic.

Among other vendors, Arris's flagship edge QAM device is the D5, a product that Comcast Corp. (Nasdaq: CMCSA, CMCSK) has selected for its SDV effort. Comcast has also picked Harmonic Inc. (Nasdaq: HLIT)'s edge QAMs for SDV. And the D5 is Arris's only active edge QAM product, as it turns out. C-COR, which was acquired by Arris late last year, was working on an edge QAM of its own, the CHP eQAM. That product has been put on "indefinite hold" so Arris can focus its attention on one edge QAM product, says Arris's Caldwell.

Table 3: Edge QAMS

Although the edge QAM market is littered with big and small players alike, one of the most intriguing newcomers is LiquidxStream Systems Inc. (See our company profile). LiquidxStream, which had its coming-out party in January, is banking on the density of its entry, the LxS-3216, which is equipped with 32 QAM channels per RF port and 512 QAMs per device. (See LiquidxStream Enters E-QAM Race .)

The SDV Tuning Adapter/Tuning Resolver
A new product on the SDV scene is the "tuning adapter," which used to be referred to as the "tuning resolver."

As designed, the tuning adapter will turn inherently "one-way" digital TVs, set-tops, and even some stand-alone TiVo Inc. (Nasdaq: TIVO) DVRs equipped with CableCARD slots, into two-way devices capable of viewing channels an operator offers in the "switched" tier. Without these adapters, so-called Unidirectional Digital Cable Products (UDCPs) are incapable of viewing those channels -- or using any "interactive" cable application, for that matter.

The adapters will update firmware and communicate channel change requests via a USB interface. CableLabs issued the specs last November. It's expected that product should start showing up by mid-2008. (See CableLabs Spec Brings SDV to the Masses and NCTA Sees Solution to Switching Snag.)

Table 4: SDV Tuning Resolvers/Adapters

So far, Motorola and Cisco are the only vendors to formally announce tuning adapter products. Motorola's MTR700 tuning adapter is a mirror image of its all-digital DCT700. (See As the 'Tuning Resolver' Turns.) Cisco's STA-1520 is a dedicated SDV tuning adapter that looks much like the RNG 100, a new, standard-def, digital set-top with on-board MPEG-4 capabilities. (See Cisco Intros SDV Tuning Adapter .) Both vendors have submitted their tuning adapters for certification at CableLabs.

Other SDV Elements
SDV systems also use bulk encryption systems that apply security one time, rather than to each SDV session. In the U.S., most bulk encrypters are supplied by Motorola and Cisco, which also happen to make up the industry's conditional access "duopoly."

Set-tops in any SDV deployment also require a special client software application that talks to the various control mechanisms on the system for channel changing functions. Cisco, for example, has added such an enhancement to SARA (Scientific Atlanta Resident Application). Time Warner Cable and Comcast are also developing their own SDV set-top clients. Gemstar-TV Guide International Inc. (Nasdaq: GMST), which owns a piece of the GuideWorks LLC joint venture with Comcast, also supplies this element.

Page 4: Who’s Doing What?

SDV system costs
Vendors typically do not publicize pricing on the different components of an SDV system, but the edge QAM is well known to be the most expensive piece of any switched digital video deployment. A recent research note from ThinkPanmure LLC confirms this, and offers a thumbnail sketch of how SDV deployment costs break down.

Table 5: Estimated SDV System Cost Breakdown

A recent SDV reportfrom Heavy Reading indicates "it will cost MSOs no more than about $35 per home passed to deploy SDV throughout their markets." That could drop to as low as $10 per home passed depending on the number of streams that are being switched and the size of the SDV service groups, the report adds.

Who's doing what: SDV
In the U.S., Time Warner Cable and Cablevision have SDV deployed the most broadly. Cablevision uses it pretty much across the board for some in-language programming as well as some high-definition television fare. At last check, Time Warner Cable will have SDV up and running in most of its major systems by year's end.

Comcast, which also has a trial going in Denver, has said it plans to install SDV in up to 15 percent of its footprint by year's end. (See Comcast Spreads the Love .)

BigBand says its SDV systems are deployed, or are being deployed, across 25 different cable systems, with commitments for more than 14 million homes passed. "This isn't a science experiment," Sood says. "But we are seeing a dramatic shift to new Motorola system awards. A year ago, it was very focused on SA [Cisco/Scientific Atlanta]."

Last year, Cisco said its SDV technology had received "commitments" for deployments exceeding 7 million homes passed, and the firm has not updated that number since. (See SA Touts SDV Milestone.) Cisco, however, has also been linked to Comcast's SDV tech trial in Cherry Hill, N.J. (See Comcast Reveals SDV Test Beds.)

Motorola has claimed to have SDV commitments for 24 million homes passed, though that number has increased, Bradley says, with the addition of another North American cable company that has committed its SDV footprint to Motorola. (See SDV Turf Battle Heating Up.) Those commitments include wins for Motorola's switched digital video management equipment, and not necessarily the company's edge QAMs, Bradley says.

But, as Harmonic and Arris suggested recently, Motorola has also seen SDV activity slow down from what was projected at the end of 2007. (See Arris Settles Down and Harmonic: Waiting on SDV.)

Table 6: Deployment Snapshot

While some may view slower capital spending by MSOs as a root cause of that decline, getting interactive program guides ready for SDV deployments "is certainly an issue," Bradley says. "You can't get away with deploying switched digital until all the set-tops [in a given cable] system are capable of doing switched digital. It becomes an all-or-nothing type of solution. We have to make sure we cover every combination and permutation that's out there."

One possible permutation that operators might consider is the Digeo Inc. Moxi box. Not only does it use an IP-based upstream path, it also uses a different navigation system than other set-tops that are typically on most U.S. cable systems.

Given those situations, operators tend to start kicking off SDV in sites that use more uniform set-tops and interactive programming guides.

Outside the U.S., according to Tandberg Television's Adams, MSOs in Europe and the Asia/Pacific region that are already built out to 860 MHz don't see a need for SDV. "They don't have the same bandwidth crunch," he says.

However, operators with plant with 450 MHz or less will likely look at it. A "classic market" for SDV would be Eastern Europe, where cable plant was initially built "on a budget," Adams explains. "The only demand for [SDV] is in those systems with limited bandwidth," those that don't have much interest in upgrading to 860 MHz or higher.

Seeking the Holy Grail
Although SDV deployments today use the multicast model, it's quite clear that operators would eventually like to migrate to a unicast model that enables individual streams to be delivered to each customer and opens the door to targeted advertising – one that can be applied to "live" program feeds, such as what Time Warner Cable has championed with its Start Over service, as well as movies, TV shows, and other titles being served from video-on-demand (VOD) libraries. That, of course, sets the path toward the so-called network-based DVR.

With video server prices set to drop dramatically again, and better ingest capabilities, it might be more cost-effective to replicate the stream in the server.

"In five years time everything you get off your cable system will probably be unicast to you," Adams predicts.

But before cable reaches the point of unicast, BigBand is starting to talk up an interim step called "virtual infinite linear."

That point is reached when the number of set-top tuners in a service group is matched by the number of available SDV streams. In a sample scenario, a service group with 250 tuners would have access to 250 streams.

The multicast model would still exist, but the incremental impact on the streams required in that service group starts to approach zero, Sood says.