The IEEE 802.11 working group is defining an additional Wi-Fi standard that operates in sub-1GHz license-exempt bands. According to the group, the called 802.11ah delivers a much improved transmission range and can also be used for large scale sensor networks with low power consumption targeting for billions of IoT or M2M device connections.

802.11ah is based on down-clocking of the 802.11ac standard and adds some enhancements in PHY and MAC layers such as power saving, large number of station support, better coverage and mobile reception. This standard is still in the draft status, with a final version expected in 2016. The Wi-Fi Alliance has also begun to define certification programs based on 802.11ah.

IEEE 802.11 WLAN is mainly operated in the 2.4GHz and 5GHz frequency bands. However, these high-frequency bands limit the transmission range of 802.11n and 802.11ac for outdoor environments. Learn the basics of 802.11ah and about some of the test challenges.

In general, there are three use case categories for 802.11ah: sensor networks, backhaul networks for sensors and meter data, and Wi-Fi extended range networks. Large coverage, low power consumption, native IP support and large numbers of device support are the main advantages for 802.11ah. It's characteristics include: 802.11ah can extend the range with 1MHz and 2MHz mandatory modes; 802.11ah sensor is native IP support; up to 8,191 devices associated with an access point (AP) through a hierarchical identifier structure; and some enhancements in 802.11ah PHY and MAC layers designed to achieve ultra-low power consumption and multi-year battery life for large scale sensor networks, optimised for small packet size and long sleep time.

The image below shows an example of sensor networks in a future smart home. In this application, an AP with 802.11ah technology is placed indoors. A large number of devices such as temperature sensors, light sensors, and smart meters are deployed throughout the home, enabling home devices and appliance to be "smart."

By: DocMemory
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