Sub-GHz frequencies are frequencies below 1 GHz that are used for wireless technology. While various WLANs, such as 802.11, Bluetooth and ZigBee, operate in the license-free ISM bands in the gigahertz range at 2.4 GHz and 5 GHz, other radio technologies take advantage of radio transmission in frequency ranges below 1 GHz.
The decisive factor for the use of sub-GHz frequencies is the radio advantages offered by the certified White Spaces Devices(WSD). Frequencies below 1 GHz have lower free- space attenuation compared with microwaves and are therefore suitable for data transmission at low data rates over long distances. For example, a frequency of 900 MHz has a level advantage of 8.5 dB over microwaves of 2.4 GHz at the same distance. Since sub-GHz frequencies thus have low power consumption, these frequency ranges are used for low-power WANs, but also for sensor networks, smart metering and alarm systems.
The disadvantage is that the usable channels in the sub-gigahertz range are narrow and the frequency bands can be different in different regions.