Delivery of low bit rate isochronous streams over the DOCSIS 1.0 cable television protocol

The Data Over Cable Systems Interface Specification (DOCSIS) 1.0 protocol e nables the delivery of Internet Protocol (IP) traffic over Cable TV network s with significantly higher data rates when compared to analogue modems and Integrated Services Digital Network (ISDN) links. The availability of grea ter bandwidth enables the delivery of high quality audio and video services . Such services require bounded delay characteristics. This paper evaluates the capacity and performance characteristics of the DOCSIS 1.0 protocol fo r the delivery of isochronous streams given the limited Quality Of Service (QOS) features of the protocol and a modem population of up to 500 nodes. S tream rates of up to 64Kbps with different packet size were considered, sui table for compressed audio, voice and low quality video. Packet concatenati on for upstream traffic was also considered. Simulation results indicated t hat such streams, within the given protocol limitations, can be supported f or a particular system population with trade offs in terms of system throug hput and channel utilisation of up to 50%. Network capacity, in terms of th e number of simultaneous streams supported and link utilisation, is signifi cantly affected by packet size. Support for concatenation has limited advan tages. Performance benefits from concatenation are more evident when delive ring higher rate bitstreams.