Characteristics of the D-MAC data channel as a carrier for business data services

One area of great interest is in the potential use of D-MAC DBS TV systems to support data services for business users. Any discussion of the use of D-MAC to provide data services must begin by placing the hypothetical D-MAC network (using the D-MAC data channel) in the context of the well-known ISO/OSI reference model. The generalised communications model for a D-MAC network is shown. A central host system interacts with a hub. The hub transmits data via a D-MAC carrier to a large number of receivers. Each receiver then interacts with a terminal to deliver information. Note that while the hub to receiver link is a one way broadcast link, the interfaces between the hub and host and the receiver and terminal are not similarly restricted. It is the first three layers-the physical, link and network layers-that are the subject of the paper. A model of these layers has been developed which allows detailed examination of the performance of a D-MAC network carrying a fully-compliant ISO protocol at the network layer