GreenNet Promises “Greener” IoT with Energy-Saving Wireless Sensor Nodes

May 09, 2016  |  Communications, Energy

Energy efficiency has long been touted as one of the benefits of the Internet of Things (IoT). Thanks to greater connectivity between devices, data analytics can lead to less waste and equipment can power down when it’s not needed. But what if the actual infrastructure that makes up the IoT—the “Internet” rather than the “Things”—was also designed to save energy?

One promising new development is GreenNet, a fully operational network of wireless sensor nodes developed by STMicroelectronics that’s far more energy-efficient than current state-of-the-art IoT platforms. If deployed, its capabilities could help companies reduce energy costs, increase productivity and boost profitability.

The most important aspect of this design is that it’s helping make the IoT self-sufficient by allowing it to gather energy from the environment. That’s true energy-efficiency.

Martin Heusse, one of the main academic partners of the project, says that the main objective was to operate sensors using as little energy as possible for long periods of time without requiring any maintenance (e.g., changing the battery). For the IoT, this would be a remarkable improvement as it makes the sensors more self-sustaining, eliminating the time and resources needed to make sure all sensors are working properly.

In his article in the IEEE Internet of Things Journal, Heusse and his team of researchers outline GreenNet’s significant advantages over current wireless sensor networks. First, they enhanced the beacon-enabled mode of the IEEE 802.15.4 standard by designing a “sleeping strategy”. Nodes communicate information back and forth, which requires energy, but only need to do so when there is information to share. Rather than have the nodes alert at all times, the team proposes an approach where nodes have periods of defined activity (exchanging data and signaling) and inactivity (with longer periods of sleep to save energy). The nodes only need to “wake up” every four minutes for about 10 milliseconds to send or retrieve data, keeping them primarily inactive and considerably reducing energy usage if the needs for data transfers are low.

Greennet
Incoming and outgoing superframe structure in IEEE 802.15.4.

 

 

In addition to sleep mode, the wireless nodes have an almost unlimited lifetime energy supply thanks to photovoltaic energy harvesting technology also developed by STMicroelectronics. Each node comes with a tiny solar panel which can gather light from both indoor and outdoor environments to charge their coin-size battery. This overcomes the major drawback of battery-powered modes and their limited lifetimes even for a larger footprint.

In addition to sleep mode, the wireless nodes have an almost unlimited lifetime energy supply thanks to photovoltaic energy harvesting technology also developed by STMicroelectronics. Each node comes with a tiny solar panel which can gather light from both indoor and outdoor environments to charge their coin-size battery. This overcomes the major drawback of battery-powered modes and their limited lifetimes even for a larger footprint.

Finally, the researchers designed a multichannel beacon train (MCBT) protocol which allows sensor nodes joining the network structure to do so quickly and energy efficiently. Typically, this joining procedure consumes a significant amount of energy since nodes must listen to 16 different channels at once until they gather enough information about their neighborhood to attach to the network. By joining quickly, the nodes avoid draining too much power and depleting the battery supply.

“The potential for these sensors are seemingly endless,” said Heusse, “and that’s what makes the Internet of Things so remarkable. But the most important aspect of this design is that it’s helping make the IoT self-sufficient by allowing it to gather energy from the environment. That’s true energy-efficiency.”

This current system allows nodes to communicate between each other up to distances of 50 feet, but the GreenNet team intends to look into experiments which could potentially increase the distance of communication.

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