IEEE 802.11ah
The IEEE working group802.11ah, also known as Low Power WiFi or WiFi HaLow, is concerned with the standardization of a Low Power WAN( LPWAN). In order to extend the expansion range compared to WiFi, 802.11ah operates in the sub- GHz range below 1 GHz, but excludes the white spaces of previously used TV channels.
ISM bands at 868 MHz (Europe) and 915 MHz (U.S.) are used, which is related to range and wall penetration. As a result, low- power WANs based on 802.11ah can provide wireless coverage for complete single-family homes.
In the approach taken by the IEEE working group, the physical layer and MAC layer are modified so that it can be used in the Internet of Things( IoT).
For the Internet of Things (IoT), there are various low-power network concepts such as ZigBee 3.0 according to 802.15.4, Bluetooth Low Energy( BLE), Random Phase Multiple Access( RPMA) or Long Range WANs( LoRaWAN). In addition, there are some proprietary network concepts such as Ingenu, SigFox, Dash7, nWave and Weightless.
802.11ah can be configured in star or tree topology. It has a different physical layer and MAC layer implementation than WLANs. The radio link uses Orthogonal Frequency Division Multiplex( OFDM) with 32 or 64 tones and is essentially a variant of 802.11ac. The OFDM approach supports a wide variety of modulation schemes, including biphase shift keying(BPSK), quadrature phase shift keying( QPSK), and quadrature amplitude modulation 16QAM to 256QAM. Channel widths are variable and are 1, 2, 4, 8 and 16 MHz, with resulting data rates ranging from 1 Mbit/s to 357 Mbit/s. The WiFi Alliance has developed WiFi HaLow as an LPWAN concept based on 802.11ah.