Delivery of low rate isochronous streams over the digital video broadcasting/Digital Audio-Visual Council cable television protocol

This paper examines the capacity and performance characteristics of the digital video broadcasting (DVB)/Digital Audio-Visual Council (DAVIC) cable television protocol for the delivery of low rate isochronous streams for a cable population of up to 700 nodes. Streams (ranging from 8 to 128 kbps) suitable for timing critical services such as compressed/uncompressed voice (e.g., VoIP: G711 and G.7231), audio and low quality video, were considered in order to study the effects on channel capacity when using reservation and fixed access for the delivery of timing critical services. The analysis focuses on the,performance of the upstream channel, which is the limiting factor of community antenna television (CATV) networks and is critical in the delivery of services to individual subscribers on demand. Simulation results indicated that such streams, within the given protocol limitations, can be supported for a particular system population with trade-offs in terms of system throughput and channel utilization. Network capacity, in terms of the number of simultaneous streams supported and link utilization, is significantly affected by packet size. Analysis of the results indicated that for different streams, packet sizes and combined with header suppression, the benefits from the use of fixed access is essential for the support of timing critical services.