Optimum bandwidth utilization in a shared cable system data channel

Abstract

A full service network (FSN) provides three communication channels that end between a headend and each set-top within the FSN, namely (1) forward-application-transport (FAT) channels that supply data from the headend to all or to only addressed ones of the set-tops, (2) a forward-data-channel (FDC) that supplies data from the headend to all or to only addressed set-tops, and (3) a reverse-data-channel (RDC) that supplies data from the set-tops to the headend. The FDC carries eight types of traffic, namely (1) conditional access message; (2) entitlement management messages; (3) broadcast data; (4) network management services messages or information; (5) general massaging; (6) application downloading; (7) Internet Protocol external device data services, and (8) VBR downloading. A fixed bandwidth FDC provides a first bandwidth portion for the high priority transmission of items (1), (2) and (3) at a continuous bit rate (CBR). All other items are transmitted over the FDC using at an available bit rate (ABR). A priority system for the selective transmission of these other items is based upon (1) how full a data buffer for an item is, as compared to a fullness reference, (2) how old the oldest data in the data buffer for the item is, as compared to an age reference. The fullness reference and the age reference are usually different for each of these other data items.