Read through any number of case studies recounting wireless sensor network deployments, from industrial applications to building automation, and the open question is often whether wireless will work. Reliability is always one of the primary issues.
A Case in Point
Recently, I read of an implementation where thousands of lives depend on the reliability of wireless communications and the operating parameters pushed the limits of the medium to the ends of the Earth-literally.
This month, the National Oceanic and Atmospheric Administration (NOAA) announced the deployment of the second-generation Deep Ocean Assessment and Reporting of Tsunamis (DART II) system. The goal of DART II is to detect and measure the seismic waves generated by a tsunami as it travels across the open ocean. With this data, the government hopes to provide enough warning to move U.S. coastal populations out of harm's way.
NOAA's system is based on 31 pressure recorders that have been strategically deployed on the seabed, at depths of about 3 to 4 miles, near regions with a history of tsunami generation. These devices transmit their data to surface buoys via acoustic modems (wireless communications). The buoys in turn transmit the pressure data to 66 Iridium low-Earth-orbiting satellites. The entire constellation of satellites operates as a mesh network, providing worldwide wireless communications. The satellites then relay the data to warning centers.
But the system provides for more than a one-way conversation. The satellite data link supports two-way communications, which allows technicians at warning centers to request pressure measurements from any specific buoy. For instance, to better understand a developing situation, acquire data critical to real-time forecasts, and avoid false alarms, a technician can request that one or more specific buoys transmit updates at a faster rate.
This application adds a whole new meaning to the phrase "remote monitoring" and demonstrates the reliability of wireless communications under the most demanding operational parameters. The system wirelessly transmits vital data from the seabed, up through 3 to 4 miles of water, and then a few hundred miles to the low-Earth-orbiting satellites and back to Earth and the tsunami warning centers. And the transmissions are fast enough to be called real-time links.
Granted we're talking about a $37.5 million system, but I'm thinking that if we can count on this technology to protect our coastal communities from disaster, we expect the same reliability in industrial, medical, and building automation applications.