By H. Allen Ecker, Scientific-Atlanta, Inc.
Most of the participants who plan to build or use the "Information Superhighway” agree that INTEROPERABILITY is one of the most critical success factors. However, as in most cases in which agreement on broad general concepts is universal, we find that "the devil is in the details". It is hard to argue with the concept that Interoperability is required to have multiple equipment and system providers and to have access by the consumer to multiple programming and other service providers. However, the key questions are how to define Interoperability in the complex network structure of the "Information Superhighway" and how to implement Interoperability in the intensely competitive and highly political market History tells us that the only way to resolve Interoperability issues such as we find on the "Information Superhighway" is for all the players to understand accurately the technical and economic implications insufficient detail so that rational business decisions can be made. In the past year the Communications Industry has made significant progress in understanding the technical details in many segments of the “Information Superhighway". Although progress has been made in understanding the economic details, uncertainty still exists both in the area of cost of installation and operation and in the area of derived revenue from the variety of potential programs and services.
The large scale trials that are being implemented in 1994 by Time Warner, US West and others will address some of the unanswered technical and economic questions.
From a technical perspective it is useful to consider the Interoperability issues in the following categories:
- Digital video compression
- Digital audio compression
- Digital system multiplexing and transport
- Modulation and error correction
- Security and conditional access
- Network operating system
Of course, there are multiple sub-layers ineach one of the above categories that must be addressed in detail to achieve lnteroperability.
This paper attempts to address important sub-layers in each of the major categories in which agreement has been reached on details and to identify several critical Interoperability details on which the industry must still reach agreement to have a truly Interoperable "Information Superhighway".