A protocol for efficient transfer of data over hybrid fiber/coax systems

The cable TV plant is a broad bandwidth channel into the home and community that has been used primarily for the distribution of television. As the plant is upgraded, there is an opportunity to use it for the transport of high-speed digital signals. While the downstream channel is relatively easy to exploit, the topology and physical characteristics of the upstream channel present new challenges at both the physical and the media access layers. We present a media access protocol that efficiently transfers data on this channel. A primary goal of the design is to keep that portion of the protocol resident in the station as simple as possible. Thus, we use centralized control located in the cable head-end. A station wishing to transmit sends a request to the head-end using a contention channel. The head-end acknowledges the request and then schedules the request, informing the station, by means of a grant message, exactly when to transmit. The protocol performs efficiently under a wide range of conditions, and is robust in the presence of channel errors