Ultra-low power radios: key enablers in wireless sensor systems

September 02, 2013 // By Harmke de Groot and Kathleen Philips, imec, Leuven (Belgium) and Holst Centre, Eindhoven (the Netherlands)
Wireless sensor systems with ultra-small and low-power sensors that operate autonomously for a long period have a lot to offer. Their application can range from new patient-centric health care, a healthier lifestyle, context-aware support for business and entertainment purposes, future vehicles, monitoring of machines and processes, buildings and smart constructions, and the environment. However, their practical usefulness (functionalities, autonomy, form factor...) largely depends on how much power they consume.

Since most of the power is consumed by the wireless communication, the development of ultra-low power radio technologies is a key requisite. Equally important is the standardisation of the devices, reducing the cost of system integration, realising the connection to personal computing platforms and enabling device interoperability. We have developed a multi-standard transceiver for wireless sensor networks, that, by careful selection of its architecture and circuit design trade-offs, achieves ultra-low power consumption.

Autonomous wireless sensor systems can be deployed for continuous monitoring: chronically-ill patients can be followed during their daily routine, machines and industrial processes can be monitored, smart buildings can be controlled. When compliant to wireless standards, the sensor systems can talk to each other and have plug and play functionalities with e.g. mobile phones and personal computing platforms. But today’s commercially available short-range radios, compliant to wireless standards such as Bluetooth or Zigbee, consume too much power for small devices running on small batteries (20 to 50 mW). New, ultra-low power radio techniques are needed, which will also enhance the practical application and usefulness of the devices for reliable long-term monitoring.

Today’s wireless sensor systems operate on commercially available low-power radios such as Bluetooth Low Energy (BLE). The sensors themselves consume relatively little energy when functioning, as a result of power optimisations. However, the power consumption of the radio chip in the system is the weak factor. Although a BLE radio chip’s power consumption is highly dependent on the data rate of the application, around 50-85% of the power consumption of the total system is typically consumed in the BLE radio communication.

Imec and Holst Centre develop radio chips with significantly reduced power consumption compared to the off-the-shelf alternatives. The power consumption of our novel wireless communication chipsets is 10 to 100 times lower than the commercial equivalents. Such ultra-low power radio chips would decrease the overall power consumption of the complete sensor system and open up opportunities