The emerging 802.11ah specification for running low-power WiFi over 900 MHz at distances up to a kilometer is one of the most promising new radios. "We believe this new standard is a very strong candidate for IoT applications in smart homes and buildings where a WiFi router is nearby," says Kathleen Philips, who heads an ultra-low-power wireless research program at the Holst Center, a partner with Imec in the Netherlands.
Home and building automation has been a fragmented market served by a host of incompatible wireless protocols including EnOcean, 6LowPAN, WirelessHART, ANT, and RF4CE -- most requiring their own gateways. "The definition of this WiFi extension can be a major catalyst for these markets, because it will communicate with already available infrastructure, resolving interoperability issues," Philips told EE Times.
Her group is designing an 11ah chip now that aims to send 100 kbit/s distances of up to a kilometer with a peak transmit power consumption of 12 milliwatts and 5 mW for the receiver. "Since this is expected to be one of the new mass markets, vendors will differentiate on cost, battery life, robustness, and distance," she says.
Holst also is researching far-field RF wireless charging over a distance of five to 10 meters as an alternative to inductive approaches that require close alignment of coils. The approach is geared for IoT devices that cannot be easily moved to align with an inductive technique and do not have access to other energy sources.
"With a 3W EIRP source transmitting at 915 MHz, we can harvest 30 microwatts on a continuous basis from up to five meters away from the source," Phillips says, describing her group's current work.
In other efforts, the Holst team is developing a radio for personal area networks that consumes 5.1 mW, has a -95 dBm sensitivity and supports Bluetooth 4.0, IEEE 802.15.4, and Zigbee protocols. It is also working on a radio for smart buildings that consumes 4 mW in receive mode, has a -120 dBm sensitivity, and supports multiple protocols.