Channel Based Sampling in a Network Based Data Acquisition System

Abstract

Over the last few years, PCM based data acquisition systems have become known as "Traditional PCM" systems. This terminology modification is a sign of the evolution of the next generation of telemetry/data acquisition systems based on network topologies. This has come about due to users clamoring for functionality that has not been available in the traditional systems, such as supporting increased data rates, providing access to onboard archived data, supporting on-the-fly reconfiguration, and simplifying data distribution and delivery. The iNET standard is using standard network technology to improve device interoperability and data acquisition. To minimize impact on existing data acquisition system devices, the initial effort of this approach has included the transmission of "Traditional" fixed PCM frames within a network message based structure. This approach, however, squanders network bandwidth, as a PCM frame includes all samples of all channels, and requires significant processing power for even simple tasks. Delivering on the promise of a more flexible transmission method requires a change in how data is acquired in the data acquisition devices. The iNET standard defines such a packet based transport system, which supports channel based packet formats besides "Traditional PCM" to efficiently deliver data products. This paper will provide background on the benefits of these methods and an overview of methods by which these formats can be implemented.