The signal strength is measured in decibels relative to a milliwatt and is represented in –dBm format (0 to -100). The closer the value is to 0, the higher the signal strength. See figure below.
Signal strength | Radio condition |
| Near maximum Thread signal strength. |
Good radio conditions for high bandwidth applications. | |
Minimum signal strength for reliable packet delivery. | |
Minimum signal strength for connectivity. Packet delivery may be unreliable. | |
Signal too weak to be useful – considered as noise. |
The required signal strength depends on the application. Building automation networks use a narrow bandwidth so that signal strength normally suffices.
Typically, the signal strength for Thread systems ranges from -30 dBm to -100 dBm.
The signal strength of Thread radio communication is most accurately expressed in milliwatts (mW). However, as the transmision power of Thread and other wireless communication technologies, such as Zigbee, WLAN and others, is rather low, it would be difficult to read signal strength in mW. Therefore, the signal strength is measured in –dBm.