Low-power, long-range WiFi; imec shows all-digital HaLow transmitter
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 for the IEEE 802.11ah standard. At 1 MHz/2 MHz with 64-QAM OFDM data packets, both the far-out and close-in spectrum pass the mask with at least 4.8 dB margin. The EVM is below 4.4%. The power consumption of the transmitter is as low as 7.1 mW, when delivering 0 dBm output power and operating from a 1V supply. This represents a 10x power reduction compared to state-of-the-art OFDM transceivers, and consequently, the prototype transmitter chip meets the stringent requirements for IoT applications.
The work is presented as part of Imec’s Intuitive internet-of-things R&D programme, that aims at developing the building blocks for the future internet-of-things, an intuitive IoT, with sensor systems that are aware of us, our perspective and our environment and react exactly as we need or want, assisting us in an unobtrusive way. Imec’s research activities focus on the development of ultra-small, low-cost, intelligent, and ultra–low power sensors, radio chips and heterogeneous sensor networks.
Imec; www.imec.be
Holst Centre is an independent open-innovation R&D centre that develops generic technologies for Wireless Autonomous Transducer Solutions and for Systems-in-Foil; www.holstcentre.com
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