The Wi-Fi Alliance's relatively new Wi-Fi HaLow (802.11ah) specification seems to be ideal in some characteristics for IoT devices:
Wi-Fi HaLow will enable a variety of new power-efficient use cases in the Smart Home, connected car, and digital healthcare, as well as industrial, retail, agriculture, and Smart City environments.
Wi-Fi HaLow extends Wi-Fi into the 900 MHz band, enabling the low power connectivity necessary for applications including sensor and wearables. Wi-Fi HaLow’s range is nearly twice that of today’s Wi-Fi, and will not only be capable of transmitting signals further, but also providing a more robust connection in challenging environments where the ability to more easily penetrate walls or other barriers is an important consideration.
However, as mentioned in the linked source, HaLow operates in the 900MHz frequency, which, according to eWeek, is an unlicensed frequency:
Unfortunately, the new HaLow standard doesn't have its frequencies to itself. Because the 900MHz band is shared with other licensed services, the new WiFi band is subject to interference from other users and there is no remedy when that interference happens.
For example, if a ham radio operator next door goes on the air with a powerful signal that wipes out your smart thermostat, you're out of luck. Because you're an unlicensed service, you're required to accept that interference.
However, if your smart thermostat happens to cause interference to that ham radio operator next door, then you're required to stop doing it. As an unlicensed user, you have few rights to the spectrum if someone else wants to use it.
Presumably this is related to the FCC rules which are commonly seen on RF products:
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
Does this make HaLow too problematic for use as a communication method, since my transmissions could easily be forced to stop if someone else was transmitting in that frequency? If I wished to design a device using HaLow, how could I avoid interference which would require me to stop broadcasting?