How can backscatter communication improve wireless sensor networks?

As an integral part of the Internet of Things (IoT), wireless sensor networks (WSNs) are projected to have rapid growth. According to the “Wireless Sensor Network Markets” report, by 2023, there will be 3.4 billion annual WSN chipset shipments worldwide up from 1 billion in 2018.

If the WSNs only use batteries for their power, one of the major issues is the cost of changing the batteries. Energy harvesting, employing a variety of techniques, offers great potential for WSNs — if the energy budget can be met. In a WSN, the RF signal transmission is notorious for being the biggest power hog. For example, in one system, only 700 nA was consumed by the RF transmitter in the sleep mode. However, during the transmit/receive cycle that only lasted 7.5 ms, the current draw was 15 mA, which comprised over 90% of the total 33-nAH energy consumption.

Researchers at the University of Waterloo in Ontario, Canada may have the answer to greatly reduce the power required for signal transmission in a Wi-Fi network. In the design of a Wi-Fi-based backscatter system called WiTAG, they addressed the need for Wi-Fi compatibility, ability to work with encryption, avoid interference and consume extremely low power. In contrast with existing approaches, WiTAG does not require a high-frequency oscillator. They attribute the low power consumption to their system’s ability to use a 50-KHz clock which is highly accurate and very stable even with temperature changes, while consuming only a few microwatts of power. In the current configuration, the researchers demonstrated that with a client and an access point that are 8 meters apart, a tag can achieve data rates of 40 Kbps when it is located anywhere between the two devices.

For investigating how energy harvesting could avoid changing batteries in your next wireless sensor application, check out the Implementing Energy Harvesting & Higher Energy Efficiency Sensor Designs Symposium to be held June 22 at Sensors Expo in San Jose from June 22-24.