Low-power, long-range WiFi; imec shows all-digital HaLow transmitter

February 04, 2016 // By Graham Prophet
Nanotech researchers Imec (Leuven, Belgium) and the associated Holst Centre have implemented a Wi-Fi HaLow low-power fully digital polar transmitter for IoT applications.

Wi-Fi HaLow is the designation created by the Wi-Fi Alliance for products incorporating IEEE 802.11ah technology. Wi-Fi HaLow operates in frequency bands below 1 GHz, and is configured to provide long range at low power for modest data rate traffic, and connectivity according to “Wi-Fi Certified” standards. It is intended for uses in areas such as smart home, connected car, and digital healthcare, as well as industrial, retail, agriculture, and smart city. WiFi Alliance says;

Wi-Fi HaLow extends Wi-Fi into the 900 MHz band, enabling the low power connectivity necessary for applications including sensor and wearables. Wi-Fi HaLow’s range is nearly twice that of today’s Wi-Fi, and will not only be capable of transmitting signals further, but also providing a more robust connection in challenging environments where the ability to more easily penetrate walls or other barriers is an important consideration. Wi-Fi HaLow will broadly adopt Wi-Fi protocols and deliver many of the benefits that consumers have come to expect from Wi-Fi today, including multi-vendor interoperability, strong government-grade security, and easy setup.

Imec/Holst’s presentation describes a transmitter with a ten-fold power reduction as compared to state-of-the-art OFDM transmitters; it is a 1.3nJ/b fully digital polar transmitter optimised for IoT applications and the IEEE 802.11ah Wi-Fi protocol,

Compared to other IoT standards, says Imec, the IEEE 802.11ah standard’s sub-GHz carrier frequency and mandatory modes with 1 MHz/2 MHz channel bandwidths allow devices to operate in a longer range with scalable data rates from 150 kb/s to 2.1 Mb/s. The standard uses OFDM to improve the link robustness against fading, which is important in urban environments, and to achieve a high spectral efficiency (data rate over a given bandwidth).

Imec and Holst Centre’s fully-digital polar transmitter meets the tight spectral mask and error-vector-magnitude (EVM) requirements of conventional Wi-Fi standards. The measured phase noise at 1.5 MHz offset is -115 dBc/Hz which is 15 dB lower than the spectral mask requirement