The future of smart-home technology takes advantage of existing home infrastructure to transmit data with low-power sensors, uses electrical circuits as giant antennas.

Researchers at the University of Washington and the Georgia Institute of Technology have developed wireless sensors which use the electrical wiring in houses as an antenna to send and receive information almost anywhere in the home. These new low-power sensors only use a tiny fraction of the electricity of previous generation, and are capable of running for 50 years on a single watch battery.

One of the key components to conserving resources is the ability to measure their use (and misuse). Efficient use of electricity, water, and heat depends on proper operation of the individual pieces of the system, and any sort of leakage or heavy usage needs to be detected right away. That’s where these new sensors can really make a difference in transforming existing houses into smart-homes.

The current versions of wireless sensors tend to use large amounts of energy (and need battery replacement frequently) and/or only transmit their signal a small distance. But the team lead by Shwetak Patel, a UW professor, has designed a system using the copper wiring already in the walls of the house as a giant antenna - capable of transmitting data to a base station anywhere in the home.

"When you look at home sensing, and home automation in general, it hasn't really taken off. Existing technology is still power hungry, and not as easy to deploy as you would want it to be." - Shwetak Patel

The device developed by the team is called Sensor Nodes Utilizing Powerline Infrastructure, or SNUPI. The idea came about when Patel and co-author Erich Stuntebeck were doctoral students at Georgia Tech and worked to develop a method using electrical wiring to receive wireless signals in a home. They found that the wiring in a home is a remarkably efficient antenna at 27 megahertz.

While testing out the sensor in a 3,000-square-foot house, the team tried five locations in each room and found that only 5% of the house was out of range of the system, compared to 23% when using over-the-air communication at the same power level. They also found some surprising discoveries, such as the fact that a lamp cord plugged into an outlet acts as part of the antenna, that sensors can transmit near bathtubs because electrical grounding is usually connected to the copper plumbing pipes, and that wiring running outdoors can extend the range of the sensors outside the home.

According to the team, SNUPI uses less than 1% of the power for data transmission compared to the next most efficient model:

"Existing nodes consumed the vast majority of their power, more than 90 percent, in wireless communication. We've flipped that. Most of our power is consumed in the computation, because we made the power for wireless communication almost negligible." - Gabe Cohn, UW doctoral student

The existing prototype developed by the team uses custom electronics built by UW and consumes less than 1 milliwatt of power when transmitting, with less than 10% of that for communication. Depending on the configuration of the sensor, it could run continuously on one batter for 50 years, which is much longer than the battery’s decade-long shelf life.

"Basically, the battery will start to decompose before it runs out of power." - Patel

The team says the technology does not interfere with electricity flow or any other systems using electrical wiring to transmit Ethernet signals between devices plugged into two outlets.

Imagine the jump in energy efficiency if we could constantly monitor for lights left on, drafts, leaky pipes, high electrical usage, or humidity levels, all using low-cost, low-power sensors coupled with the existing wiring in our houses. This new sensor technology could let the average homeowner start to turn their home into an adaptive, energy-efficient home without breaking the bank. I can’t wait to see it on the shelves.