802.11ah – the one they called HaLow

IEEE Std 802.11ah-2016, Amendment 2 to the 2016 revision, brought Wi-Fi into **uncharted territory**: the **sub-1 GHz spectrum**. no official "Task Group ah" mentioned in the sources, but this one gave us **Wi-Fi HaLow** – a low-power, long-range version of Wi-Fi built for the **Internet of Things (IoT)**.

the idea was clear: 2.4 and 5 GHz Wi-Fi are great for speed, but not ideal for **battery-powered sensors** or **devices spread across long distances**. 802.11ah solved that by operating in **license-exempt sub-1 GHz bands** – like 900 MHz – which meant better penetration through walls, greater range, and way less power draw.

on the PHY side, it introduced the **S1G PHY – Sub 1 GHz Physical Layer**, plus support for **1 MHz PPDU masks**, designed to fit narrowband use while staying compatible with Wi-Fi logic. it wasn’t about gigabits – it was about **reliability, reach, and efficiency**.

MAC-layer enhancements included support for things like **NDP Ack**, **NDP BlockAck**, and **NDP CTS** – short, efficient control frames with minimal overhead. it also allowed for features like **ADE (Association Identifier with Differential Encoding)** and flexible AID Response handling to manage the thousands of small devices IoT networks need.

and of course, it was all about **low power consumption**. everything in the MAC was tuned to reduce active time, sleep faster, and avoid unnecessary transmissions – perfect for devices that need to run on a coin cell for years.

802.11ah became part of **802.11-2020**, and while it didn’t dominate the consumer market, it found a niche in **agriculture, smart cities, industrial IoT**, and other places where range and efficiency mattered more than speed.

802.11ah gave Wi-Fi a quiet side. less power, more distance, and a place in the growing IoT world.