Utilizing 900 MHz For Low Power Long Range Sensors
In the last 15 years, Wi-Fi has evolved to a robust and versatile technology; it is being improved almost constantly. The 802.11ah standard provides two things important for IoT sensor systems: range and low power consumption, expanding Wi-Fi’s integral role in collecting data from large amounts of sensors.
In healthcare, for example, the demand for Wi-Fi technology is exploding as doctors, nurses and other medical professionals use Wi-Fi-enabled devices, ranging from smartphones to patient monitors. Wi-Fi access helps medical professionals’ access real-time information and patient records.
In 1997, the IEEE released the base standard 802.11 for wireless local area network (WLAN) communications. In the years following, amendments were made to this standard and have been treated as their own standards. 802.11ah (Wi-Fi Alliance brand name : HaLow-pronounced Halo), was published in 2017 for low to moderate data rate, long-range sensors and controllers. Wi-Fi HaLow runs on frequencies below one gigahertz.
With its low power consumption and use of 900 MHz license exempt bands, Wi-Fi HaLow is ideal for applications that require many sensors at better link budgets and increased data packet size. HaLow nearly doubles the range of standard Wi-Fi connections, 2.4 GHz and 5 GHz bands, providing a more robust connection in challenging environments where the ability to easily penetrate walls or other barriers is an important consideration. For example, healthcare facilities like hospitals, are trying to reduce traffic in the 2.4 GHz and 5 GHz Wi-Fi spectrum. HaLow 802.11ah, using the 900 MHz spectrum, could be an ideal solution, allowing large amounts of data to be kept out of the 2.4 GHz and 5 GHz networks.
It also benefits from lower energy consumption, allowing the creation of large groups of stations or sensors that cooperate to share signals, supporting the concept of the Internet of Things (IoT). The protocol's low power consumption competes with Bluetooth and has the added benefit of higher data rates and wider coverage range. For example, HaLow uses target wake time to reduce the amount of energy a device needs to stay connected to the network. It does this by having devices wake up for very short times at defined intervals—say, for milliseconds every 15 seconds—to accept messages.
Wi-Fi HaLow will enable a variety of new power-efficient use cases in the Smart Home, connected car, and digital healthcare, as well as industrial, retail, agriculture, and Smart City environments. It’s ideal for short, burst-y data that has low-power consumption and is required to travel long distances. One of the issues in Wi-Fi networks in the 2.4 GHz and 5 GHz spectrum is that they are getting very crowded, adding hundreds or thousands of sensors to those networks is not ideal.
802.11ah is highly suitable for low-power sensor networks over moderate distances, as well as sensor and meter backhaul, aggregating multiple separate sensor networks via gateways. Its long range and ability to get through walls, makes for a simple aggregation network.
Although 802.11ah was released in 2017, there has been an unusual delay, given the size of the Wi-Fi ecosystem, in pushing commercial silicon into 802.11ah. Numerous factors may explain the delay, including that HaLow will not be as low cost and low power as LoRA or Sigfox, though it is likely to be cheaper and lower power than NB-IoT and LTE Cat-M.
However, commercial silicon for 802.11ah has picked up this year; potentially bringing the first applications in healthcare and agriculture. The HaLow specs including its ultra-low power performance is ideal for these kinds of use cases. Expectantly, once the concepts have been proven, HaLow applications will expand from there. Five start-ups are releasing chipsets and established market manufacturers.
The five start-ups aiming to launch HaLow chips this year:
Newracom of Korea, the only company with a commercial HaLow chip (used in a Korea Telecom gateway).
Morse Micro of Australia, considered the most developed of the pre-commercial start-ups, aiming to sample silicon around mid-year.
Methods2Business of The Netherlands, which has IP for a HaLow media access controller (MAC) based on a Tensilica digital signal processor.
Adapt-IP of the USA, which has developed an FPGA version of a HaLow baseband and is considering a partnership to design a complete HaLow chip this year.
Palma Ceia SemiDesign (PCS), which has IP blocks for NB-IoT and HaLow transceivers and aims to raise funds to create its first chip level product for HaLow this year.
