The WiFi Alliance has finally given a brand name to its sub-GHz WiFi standard, with 802.11ah now called HaLow. Operating in the unlicensed 900MHz ISM band, the primary goal of 802.11ah is to create a version of WiFi that enjoys better attenuation through physical barriers and a longer range.
Some advocate using the new standard as an ideal smart city technology, given its predicted potential max range of 1km. However, that range is entirely dependent on the RF regulations of the countries in which it will be deployed, and so it’s unlikely that we’ll see 802.11ah deployments achieving that speed.
Although it is still in its draft stages, due to be finalized this year, the protocol will use narrower channels than the more familiar 802.11 WiFi standards, with the 1MHz channel providing a data rate of around 100-150kbps – not great for streaming video, but plenty for backhauling sensor data or images. The largest 4MHz channels in the standard could manage video however, with an 18Mbps bandwidth – but again, that’s dependent on the RF regulation. It uses the 802.11a/g specification, which outlines a maximum of 26 channels.
This is a means of providing the main benefits of LPWAN protocols like Sigfox, LoRa or Weightless, using the familiar WiFi brand and ecosystem. For consumer oriented devices, the ability to utilize the same WiFi access point that serve the home would potentially allow utilities to backhaul their smart meter readings over the home’s broadband connection, and avoid paying an LPWAN vendor or cellular MNO for the same task. Other businesses could follow the same model, relying on the ubiquity of WiFi to provide a free route to the cloud for their data, and smart city WiFi deployments would revel in such a technology.
In this guise, HaLow is potentially a very disruptive technology, particularly as the WiFi Alliance envisions tri-band routers that provide the familiar 2.4GHz, the newer high-bandwidth 5.8GHz, and now the sub-GHz 802.11ah – all while retaining the familiar characteristics of the wireless protocol that has made it such a titan of networking. Similarly, WiFi devices could be built that utilized both 802.11ah and one of the higher bandwidth protocols.
“Wi-Fi HaLow is well suited to meet the unique needs of the smart home, smart city and industrial markets because of its ability to operate using very low power, penetrate through walls and operate at significantly longer ranges than Wi-Fi today,” said Edgar Figueroa, president and CEO of Wi-Fi Alliance. “Wi-Fi HaLow expands the unmatched versatility of Wi-Fi to enable applications from small, battery-operated wearable devices to large-scale industrial facility deployments – and everything in between.”
The main criticism of WiFi as an IoT protocol has always been its relatively high power consumption. For edge devices like environmental sensors, motion sensors, or actuators, WiFi wasn’t viable due to the physical requirements of transmitting. That same argument is leveled at 2G, 3G, and 4G, which led the industry to turn its attention to lower power consumption protocols.
Bluetooth is the most prominent alternative protocol in the market, but is only now catching up on the likes of ZigBee and Z-Wave in terms of power consumption. With a mesh implementation due to be released soon, Bluetooth might steal a march on the established mesh protocols – although the Google/Nest backed Thread is another challenger that lurks in the wings.
But there are other technologies out there that could remove or mitigate the issue of battery life entirely. Currently, batteries represent a significant proportion of the BOM cost of a small end-node like a doorbell or light switch, as well as requiring a fairly large footprint in the schematics to accommodate its physical size.
A wireless charging technology like Ossia’s Cota (see separate piece) that pushes power to devices at a range of up to 30-feet could allow designers to use whichever protocol they require – safe in the knowledge that their devices would be receiving regular wireless recharging. However, Ossia’s technology doesn’t have any customers yet, although it could be arriving on the market at around the same time as the first HaLow devices.