Media Visions - iTV | Warner's Qube
Rohit Khare stashed this in potpourri
The Eclipse system assigned a digital address (like a modern IP address) to each set-top box, controlled through its "BGC" (bridge gate controller). These field status monitors were controlled from the headend, again drawing on databases for direction, performing such actions as routinely polling the boxes on its section of the cable plant to retrieve any pay-per-view selections, for proper billing on the next account statement. By polling periodically instead of constantly, the upstream return path carried limited traffic. This simplified the job of the BGC as a plant gatekeeper, enabling the headend to open one distribution amplifier at a time to communication with any tendril of the cable plant, further reducing upstream noise, helping Qube cut signal errors, perhaps averting a subscriber having complaints about mistakes on the bill.
Qube data traffic on the 8-bit system traveled downstream and upstream between the headend and each set-top box at 256 Kilobits per second (Kbps) , five times faster than today's 56 Kbps modems. The Downstream bandwidth at 250 MHz (within the EM spectrum from 50 to 300 MHz) featured a single 6 MHz data carrier channel centered at 121 MHz, like the core thread in a rope. The remaining 244 MHz of downstream bandwidth transported 30 video channels and 30 audio channels, including 10 Columbus FM radio stations (regenerated from off-air reception of tower broadcasts). Upstream responses from the polled set-tops were returned to the headend at 256 Kbps within a 24-MHz carrier signal (5 to 30 MHz on the spectrum), further assuring subscriber data was reliably received and billed. "Keep the customers satisfied" was a guiding design element for MSOs during the franchise wars.
"The beauty of the design is that we only had to open the data distribution system when the network was polled", said Dempsey, "and each set-top would answer briefly, if only to say 'I'm here.' or perhaps send back tokens from any transactions. The network used bandwidth very efficiently. The entire system of 50,000 subscribers in Columbus could be polled in six second. All the information we needed could be collected from the set-top boxes in six seconds." .