Radio waves has different behaviors at different frequencies, and these differences in radio waves affect how a person use a smart home that contains many device. Radio waves of low frequencies can travel long distance, pass through walls and water very easily, but they provide very little space to transmit data. Radio waves of high frequencies provides a large amount of space to transmit data, but they have a rapid loss of strength and have difficulties passing through obstacles.
An understanding of the relationship between the frequency of radio waves and there behavior is essential to use a frequency chart according to the need of the smart home devices. The frequency chart map out the radio spectrum from the lowest radio frequencies to the highest radio frequencies, such as the millimeter waves used in 5G. The frequency chart divide the radio spectrum into twelve band. The chart also demonstrate the behavior of each of these band.
How Radio Waves Work in a Smart Home
While it is not necessary to memorize the frequencies of each band on the chart, it is important to recognize that as the frequency of the radio waves increases, the bandwidth and limitation of those radio frequencies increases as well. Many of the protocol for smart homes are in the middle portion of the radio spectrum. Many smart home protocols use the 2.4 GHz band.
This frequency band offer an ideal balance between range and data capacity. However, the 2.4 GHz band is very crowded with many device in the home that use this band, including Wi-Fi, Bluetooth, Zigbee, Thread, microwave oven, and cordless phone. Because many device use the 2.4 GHz band, there is interference between those device, which can impact the smart home device’s commands.
The sub-gigahertz protocol use frequencies that are much lower than the 2.4 GHz band. Because these frequency are lower, they do not compete with the device that use the 2.4 GHz band. The sub-gigahertz protocol have lower data transfer rate than many of the other protocols, and region limits their power.
However, many use these protocol for smart lock and security sensor for the home. These device do not require high data transfer rate but must remain reliably. The 5 GHz band allow device to transfer data at a faster rate.
It feature wider channel for data transfer, which allow data to stream at a higher rate. However, 5 GHz signal lose strength much more rapidly than the 2.4 GHz band. The 5 GHz band struggle with passing through walls and furniture in the home.
Additionally, the 5 GHz band does not have the range of the 2.4 GHz band. Device that work with the 2.4 GHz band will not work as well with the 5 GHz band, especially if the device is locate in another part of the home. Many of the source of interference include the smart device in the home.
However, interference can come from the neighbor’s Wi-Fi signal as much as the microwave oven in the home. In the 2.4 GHz band, only three channel for Wi-Fi do not overlap with each other. You must take care to choose these channel to minimize the interference between these band.
The channel for Zigbee device can be placed between the channel for the Wi-Fi band to minimize the interference between the two type of device. However, the Zigbee device and the router for the Zigbee device must be placed in separate area of the home. Adding device to a smart home network does not necessarily improve the coverage of the network.
Battery-powered smart sensor do not relay radio signal to other smart device. They will not help expand the coverage of a smart home network. Mains-powered device will relay the network’s signal and can expand the coverage of a mesh network.
However, the device have to be placed in strategic location in the smart home because the physics of radio wave and their range to device in the smart home will not change, no matter how many device are added to the network. Choosing which radio frequency to use in a smart home depend on the physics of the radio band. High frequency will be used for device that require high data transfer rate, such as for streaming video.
Low frequency will be used for device with low data requirement, such as smart lock, as they will have less interference between device and have the ability to pass through wall to the device in the smart home. The frequency chart for smart home illustrates these relationship between task for smart device and the physics of the radio frequency to make decision about the radio frequency for the smart home device.