IEEE 802.11ah: sub GHz Wi-Fi
IEEE 802.11ah is a sub GHz Wi-Fi standard that utilizes the license exempt ISM bands below 1 GHz & provides longer range connectivity.
- IEEE 802.11ah is a wireless networking protocol published in 2017 called Wi-Fi HaLow as an amendment of the IEEE 802.11-2007 wireless networking standard.
- It uses 900 MHz license-exempt bands to provide extended-range Wi-Fi networks, compared to conventional Wi-Fi networks operating in the 2.4 GHz, 5 GHz and 6 GHz bands. It also benefits from lower energy consumption, allowing the creation of large groups of stations or sensors that cooperate to share signals, supporting the concept of the Internet of things (IoT).
- The protocol's low power consumption competes with Bluetooth, LoRa, and Zigbee, and has the added benefit of higher data rates and wider coverage range.
Key Parameters of Wi-Fi Halow
| Parameter | Value |
| Frequency Range | Sub-1 GHz (See table below for details) |
| Data Rate | 150 kbps to 15 Mbps |
| Range | More than 1 km (official claim), the Range can go up for lower datarate applications |
| Low Power Operation | Has multiple power saving modes and can operate on coin cell batteries for months or years |
| Security | Supports Wi-Fi level Security (WPA3) |
| Interoperability | No proprietary hubs or gateways are required. |
| Channels & Modulation | Narrow band OFDM channels |
In addition to gaining access to additional spectrum, the use of 802.11ah will provide improved coverage range because of the propagating characteristics of these frequencies. This will open the applications of available to IEEE 802.11ah users to new opportunities including wide area based sensor networks, sensor backhaul systems and potential Wi-Fi off-loading.
ISM bands available
There are several ISM bands that are available for use by IEEE 802.11ah that exist below 1GHz. These are not globally available, but suitable bands do appear in most areas of the globe.
Wi-Fi HaLow Frequency Bands by Country
| Country | Frequency Band |
| China | 755 - 787 MHz |
| Europe | 863 - 868 MHz |
| Japan | 916.5 - 927.5 MHz |
| Korea | 917.5 - 923.5 MHz |
| Singapore | 866 - 869 & 920 - 925 MHz |
| USA | 902 - 928 MHz |
IEEE 802.11ah sub GHz Wi-Fi defines the channels based upon the spectrum that is available in a given country.
The basic channel width is 1MHz, although it is possible to bond two adjacent channels together to form a 2 MHz channel to provide higher data throughput capability. Wider channels are available, the widest in the US being 16 MHz for the 902 - 928 MHz ISM band. Again this uses the same channel bonding method adopted for 802.11n and 11ac. Channel widths of 1, 2, 4, 8, and 16 MHz can be used.
802.11ah uses orthogonal frequency division multiplexing, OFDM to provide the modulation scheme for the signal.
The Media Access Control or MAC layer features a number of enhanced elements to provide support for large numbers of stations, power saving, and the like that.
- Support for large number of stations: 802.11 access point allocate identifiers, called Association IDentifiers, AID, to stations that associate with the AP.
Use Cases for Wi-Fi HaLow
Home and building automation: Wi-Fi Halow is low-power solution to connect door locks, cameras, appliances, and heating, ventilation, and air conditioning components.
Agriculture: The range and ability of Wi-Fi HaLow to connect multiple sensors across a network over vast areas allows this technology to be used to track and monitor crops and livestock. Sensors based on coin cell batteries can operate on the farm for years.
Industrial: Wi-Fi HaLow enables the connection of sensor devices and actuators across large distances in factories and refineries. It offers robust WPA3 security and built-in support for IPv6.
Logistics and transportation: The sub-1 GHz radio frequency offers significant advantages that enhance planning and efficiency in the logistics of moving goods from suppliers to factories, warehouses, and points of sale.
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