June 23, 2017 | By Navnit Goel
802.11ah or Wi-Fi HaLow standard has been endorsed for IoT by Wi-Fi Alliance about 18 months back. It operates in unlicensed sub 1 GHz frequency range, supports channel bandwidth of 1 and 2 MHz for IoT, Data throughput support ranges for 350 Kbps to few Gbps, Consumes low power with support of longer sleep time, has lower design complexity and supports upto 1 km range.
With all these features HaLow appeared to be an attractive solution for IoT in LAN range. However the uptake for HaLow has been slow. Following are the reason slow uptake:
HaLow’s Frequency of operation is different than 2.4 GHz and 5 GHz, necessitating use of different Radio at Access Point than used for normal Wi-Fi network. It increases cost of Access Points.
HaLow Spectrum is not harmonized across the world. It operates in 900 MHz in USA, 850 MHz in Europe and 700 MHz. It does not have operating spectrum in several countries.
The new Wi-Fi standard 802.11ax which will also support IoT overcomes some of these major shortcomings. Following are the advantages in new standard:
It supports 2.4GHz and 5GHz bands, so no separate radio needed for access point.
Client can operate in 20 MHz channel bandwidth only mode
With support of OFDMA Resource blocks of 2MHz can be allocated to a single client. HaLow and other previous variants of Wi-Fi use OFDM.
The 2 MHz transmission can also use a Dual sub-Carrier Modulation (DCM), which repeats the same information on two tones to improve signal quality.
- Lower Data rate of 375 Kbps is supported
Since HaLow operates in Sub 1 GHz frequency, so penetration and range is better in HaLow compared to 802.11ax
HaLow meets the criterion for wide area IoT as in Cellular networks , However there are competitive Low Power WAN ( LPWAN) technologies such as LTE-M, LoRA and Sigfox are gaining momentum in long range. In t future HaLow may not uptake much. 802.11ax along with BLE and ZigBee may be used for home, enterprise and other indoor applications while LTE-M, LoRA and Sigfox may be technologies for LPWAN applications.
References: For IoT Over Wi-Fi, 802.11ax Is the New HaLow Network Computing 22/06/17