EMZETT.Z-Wave
In short: Z-Wave is a radio standard for smart-home devices that transmits at around 868 MHz (Europe) instead of 2.4 GHz and forms a mesh network.
In more detail: Because Wi-Fi, Bluetooth and Zigbee share the 2.4 GHz band, Z-Wave gets by with less interference. Data rates are low (up to about 100 kbit/s), which is plenty for switches and sensors.
In Depth
- Mesh: Mains-powered devices relay messages. A message may take up to four hops.
- Controller: A controller (hub) manages the network. Up to 232 devices per network.
- Certification: All devices are interoperability-tested. The Z-Wave Alliance defines command classes.
- Security: Encryption (S2) with key exchange during inclusion.
- Comparison: Zigbee is more open and cheaper, but uses 2.4 GHz. Matter aims to unite the worlds over IP.
- Regions: Frequencies differ (Europe 868 MHz, USA 908 MHz), devices are not cross-compatible.
- Hubs: Home Assistant talks Z-Wave through a USB stick.