Out of band, out of mind.(Multisystem Operator)

By Brian Santo, Senior Editor

MSOs are preparing to unlock the DOCSIS Set-top Gateway

The cable industry is on the verge of moving out-of-band (OOB) signaling from a proprietary channel to a DOCSIS channel. The primary means to achieve this is the DOCSIS Set-top Gateway, or DSG.

With DSG, cable is continuing to follow the way of all technology, the path toward specifications and standardization. It started three decades ago with agreements on connectors, hit a high note with DOCSIS, and continues with the gradual migration to IP transport and the imminent rollout of OpenCable Application Platform (OCAP) middleware--which DSG complements.

Motorola and Cisco Systems' recently acquired Scientific Atlanta operation each have their own proprietary approach to transmitting program guide information and other non-video program data to and from set-top boxes. Both use spectrum outside of the frequencies allocated for video, hence the term out-of-band (OOB).

OOB signaling has its upstream drawbacks. One is a susceptibility to interference. Another is a bandwidth limit of 256 kbps--fine for applications such as pay-per-view, where set-tops had to be occasionally polled, but certain to be inadequate for interactive, real-time services that operators are preparing to offer within the year.

Bandwidth limits affect things as simple as changing channels. A VOD stream, meanwhile, requires real-time, two-way communication, difficult if not impossible with traditional OOB signaling, but easily provided by a DOCSIS channel.