Vendors Look for VOD Improvements


Executives from MSOs and equipment vendors are looking at a number of new technology strategies to handle the increasing amounts of video-on-demand and streaming content, and some of the latest solutions — greater use of dense wave division multiplexing and scaled distributed storage — were on display last month at the Society of Cable Telecommunications Engineers’ annual Cable-Tec Expo in Orlando Fla.


As operators look to expand their storage capability from 1,000 hours to perhaps as much as 10,000 hours, better distribution storage architecture may be needed, said Broadbus Technologies Inc. vice president of engineering George Kajos.

One option is for operators to place “near-term” storage in hub or in node locations for the popular and frequently viewed content. Longer-term storage, including library content, could reside at the headend, while an archive for niche content could be located further back on the network. “A hierarchical storage architecture delivers the best economics,” Kajos said.

That setup allows MSOs to minimize the total number of copies of any one title, cutting down on storage costs. Separating content and streaming storage also increases system efficiency, according to Kajos.

He also compared the costs and benefits of using small computer system interface (SCSI) hard drives versus serial advanced technology attachment (ATA) technology for storage. The SCSI drives are faster and have quicker transfer rates, but the ATA drives are denser with a cheaper per gigabit cost. “Serial ATA technology will potentially offer more storage at lower prices and much easier maintenance and upgrade for great improvement in total cost of ownership,” Kajos said.

Arris Group Inc. engineer Rajive Dhar believes operators should look at putting in coarse wave division multiplexing in hub rings to save costs on VOD transport. He said MSOs are quickly moving to GigaBit Ethernet transport from VOD servers to quadrature amplitude modulations because of the lower cost of GigE. But as digital grows and VOD usage climbs, such a network is expensive to scale.


Switching has to be introduced to enable operators to take advantage of multiplexing gains in the network. That requires a combination of dense wavelength division multiplexing (DWDM) and condensed DWM technology, Dhar said.

“Using CWDM in the hub rings has huge cost advantages,” Dhar said. “The hub rings are typically in the 20 kilometer range, which makes them suitable for CWDM. And CWDM-based rings have the potential to reduce costs by 60% to 80% over DWDM networks. Use DWDM for the rings connecting headends and use CWDM for the smaller hub rings.”