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Proposed Wi-Fi standard to use sub-1GHz band

Posted: 01 Sep 2015 ?? ?Print Version ?Bookmark and Share

Keywords:Wi-Fi Alliance? Wi-Fi? WLAN? 802.11ah? IoT?

The IEEE 802.11 working group is working on a new standard called 802.11ah that operates in sub-1GHz license-exempt bands. According to them, the planned standard offers a better transmission range and can also be used for large scale sensor networks with low power consumption targeting for billions of Internet of Things (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 programmes 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.

Use Cases

In general, there are three use case categories for 802.11ah: sensor networks, backhaul networks for sensors and metre 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; there are 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; 802.11ah sensor is native IP support; and up to 8,191 devices associated with an access point (AP) through a hierarchical identifier structure.

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 metres are deployed throughout the home, enabling home devices and appliance to be "smart."


802.11ah will cover a greater distance than 801.11ac in smart home environment.

The second use case is in backhaul networks for sensors and metre data. The backhaul networks provide the connection between sensors and data collectors. IEEE 802.15.4g provides a link for the lower sensor and 802.11ah provides a wireless backhaul link to forward the aggregated data generated by the sensors to the data centre. The image below illustrates a wireless backhaul network in which the 802.11ah AP and gateway collect and forward the data from sensor devices to the data centre.

802.11ah can provides access to backhaul networks

802.11ah can provides access to backhaul networks.

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