June 24, 2004

Advances in Real-Time Sensor Data Distribution across HPWREN

With the need for real-time sensor data distribution to various simultaneous recipients, HPWREN recently embraced the notion of multicast technology for such objectives. Multicast is a distribution method where many applications and users can receive the same data stream without replicating the data into individual streams per recipient. In addition, more of the data is now stored on a permanent data server to support enhanced data integration and presentation.

multicast data distribution

The individual sensors are able to asynchronously inject data into the common multicast stream. Alternatively, their data may be collected by a local or centralized data server, stored, and re-exported from the server into the multicast stream. The central server also provides a web interface for the archived data, while at the same time HPWREN users have immediate access to the real-time data via multicast. This real-time telemetry traffic is typically fairly low volume, and the multicast technology allows for an efficient distribution to a virtually unlimited number of machines and users on the network.

real-time data display

Real-time data access to a prototype sensor platform on Mount Laguna is available at http://hpwren.ucsd.edu/Sensors/MtLaguna. The text-based output, based on data the server receives via the multicast stream, is optimized for fast display and automatic refresh every minute. A graphical representation for the last two days can be obtained from the individual sensor lines being displayed. The web site is under development and is expected to evolve over time, and should accomodate more sensors soon.

real-time sensors

The Mount Laguna sensor setup is provided by the San Diego State University Field Station Programs. It provides telemetry data for air temperature, relative humidity, wind speed and direction, rain, solar radiation, fuel temperature, and fuel moisture. It also includes a solid-state 3D anemometer which generates data ten times per second.

ROADNet technology is being utilized for some of the data collection and presentation components within this new HPWREN real-time sensor data distribution system.

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