This article gives a brief overview of the future IEEE 802.11ah standard, which is stamped by the Wi-Fi alliance as Wi-Fi Halow, there are many main features as low energy consumption, the operation frequency in the 900MHz to reach more coverage range, the support of more than 8000 devices belonging to the same Access Point. Showing IEEE 802.11ah as one of the principal candidates to enable the Internet of Things (IoT) communications.
Now we present the Development line in Table I.
Tabla I. Development line of IEEE 802.11ah
|Status of the specification
||Percentage advance of the standard|
Figure 1. Highlights the comparison in coverage range between distinct technologies
The use cases mentioned by the IEEE 802.11 ah Task Group are:
- Smart sensor and meters.
- Backhaul aggregation and extended range hotspot.
- Extended range hotspot and cellular offloading.
The most relevant changes of IEEE 802.11ah in respect to the legacy standards, as usual, are made in the PHY and MAC layers of the OSI (Open System Interconnection) model.
PHY layer features.
This near future standard operates at 900MHz frequency as an average data, is well know that each country has its own regulations in the frequency spectrum, Table II illustrate the specific operation frequency of IEEE 802.11ah in the world.
Tabla II. Operational frequency of IEEE 802.11ah around the world
|614-787 & 779-787||China|
IEEE 802.11ah standard works with different channel bandwidth for transmissions as 1,2,4,8,16 MHz and similar as the frequency the number of channels are regulated by each country as show Table III.
Tabla III. Number of channels available in different countries for IEEE 802.11ah.
MAC layer features.
The principal MAC layer features developed in IEEE 802.11ah are:
- Increase on the supported number of devices linked to an access point, from 2007 to 8191 devices.
- MAC headers reduction, from 30Bytes to 14Bytes
- Frame control shortening.
- The development of a new contention mechanism call Restricted Access Window (RAW).
- The development of power saving mechanisms allowing an station stay in doze mode up to 7 days.
All of the above features are being developed focused on covering the IoT requirements, making probably to find in the market IEEE 802.11ah hardware in the end of the 2016 or in the start of the 2017.