A new communication protocol for wireless sensor networks just released by the Viterbi School's Information Sciences Institute is the most efficient yet with more than a tenfold improvement on previous versions.
Sensornets – an emerging way to monitor inaccessible and unwired places – depend on placing numerous sensor units across a wide area. The units communicate with each other, sending the information they gather at intervals to the human operators.
In wilderness parks, for example, such networks are used to monitor activity by wildlife. Sensornets are also being explored for industrial applications such as oilfield monitoring and management.
Because the units are battery-powered, minimum power consumption is critical – but at the same time, continuing coverage is essential. Ordinary wireless methods such as WiFi won't work because of this limitation.
The activities of the units are orchestrated by special operating rules called Media Access Control protocols. More than three years of ISI research – supported by the National Science Foundation, Intel and other funders – produced a new protocol, SCP-MAC, which marked a dramatic improvement in energy efficiency.
The protocol combines two techniques: “low-power listening,” in which units switch on for only very brief periods; and “scheduled channel polling,” which synchronizes and schedules the listening.
“The basic approach of SCP-MAC is to let units alternate periods of sleeping with very brief periods of listening, as shown in the figure,” said ISI research scientist and project developer Wei Ye. “Such a sleep pattern is found on birds, who need to keep vigilance while sleeping. To minimize the listening cost, SCP-MAC utilizes ‘low-power listening,’ which detects channel activity very quickly.”
It further reduces the transmission cost, Ye explained, by synchronizing the listening schedules of nodes, so that a unit can wake up its neighbors by transmitting a short tone.
Previous protocols required individual units to be active for approximately 2 to 3 percent of monitoring time – that is, about 29-45 minutes of sensornet activity every day. SCP-MAC reduced the monitoring time to less than two minutes each day.
The system was developed by Ye, who worked with project leader John Heidemann and programmer Fabio Luis Silva in the ISI Laboratory for Embedded Networked Sensor Experimentation.
In February, the group made the new protocol available for download by sensornet users and developers at
http://www.isi.edu/ilense/software/scpmac/
Source: University of Southern California
Related stories:
2008 ozone hole larger than last year
The 2008 ozone hole – a thinning in the ozone layer over Antarctica – is larger both in size and ozone loss than 2007 but is not as large as 2006.
Energy Storage For Hybrid Vehicles
Hybrid technology combines the advantages of combustion engines and electric motors. Scientists are developing high-performance energy storage units, a prerequisite for effective hybrid motors.
Low vitamin D levels pose large threat to health
Researchers at Johns Hopkins are reporting what is believed to be the most conclusive evidence to date that inadequate levels of vitamin D, obtained from milk, fortified cereals and exposure to sunlight, lead to substantially increased risk of death.
Seizures in newborns can be detected with small, portable brain activity monitors
Compact, bedside brain-activity monitors detected most seizures in at-risk infants, researchers at Washington University School of Medicine in St. Louis showed. That means the compact units could assist clinicians in monitoring for electrical seizures until confirmation with conventional EEG (electroencephalography), the researchers assert in an article published in the June issue of
Pediatrics.
Ski Faster with Camera-less Fusion Motion Capture
Professional skiers can now learn how to ski faster with the aid of a new system used to capture 3D motion of athletic movements – Fusion Motion Capture (FMC). Featured in Wiley-Blackwell’s journal,
Sports Technology, this is the first time the study of FMC has been published in a journal.
Beyond chess: Deep green models rapid change for combat commanders
Can an artificial intelligence program anticipate military surprises? The USC Information Sciences Institute is playing a $7.6 million part in a DARPA research effort called Deep Green aimed at creating a system that can do so, one that might help future combat commanders in the field anticipate enemy moves.
Astronomers weigh the coldest brown dwarfs with astronomy's sharpest eyes
Astronomers have used ultrasharp images obtained with the Keck Telescope and Hubble Space Telescope to determine for the first time the masses of the coldest class of "failed stars," a.k.a. brown dwarfs. With masses as light as 3 percent the mass of the sun, these are the lowest mass free-floating objects ever weighed outside the solar system. The observations are a major step in testing the theoretical predictions of objects that cannot generate their own internal energy, both brown dwarfs and gas-giant planets. The new findings, which are being presented in a press conference today at the American Astronomical Society meeting in St. Louis, show that the predictions may have some problems.
Robots go Where Scientists Fear to Tread
Scientists are diligently working to understand how and why the world’s ice shelves are melting. While most of the data they need (temperatures, wind speed, humidity, radiation) can be obtained by satellite, it isn’t as accurate as good old-fashioned, on-site measurement and static ground-based weather stations don’t allow scientists to collect info from as many locations as they’d like.