As mentioned in the previous post, the protocols are the communication languages of your installation. So it is very important that your hub and your modules “speak” the same language.
There are quite a lot of protocols, each with their strengths and weaknesses. Some are old and all were not conceived for home automation. Some will be preferred for alarm systems which requires a higher security as others will be perfect for lighting and gardening.
So depending on your requirements, you may need an installation with multiple protocols for different purposes or one could also do the job.
Here is a short description of the most famous protocols on the market so that you know what’s out there :
Zigbee is a cousin of Wi-Fi as it coexists on the same frequencies. It requires very low power to work and it creates a mesh network so that every compatible module can route information and doing so extend the range of communication. Zigbee is for example used by the Philips Hue lighting system.
Z-wave is one of the most famous and used protocols. Like Zigbee, it creates a mesh network but it adds the ability for the modules to interact without requiring a controller. It also consumes low power so that modules can work on batteries (up to 2 years for some of them), ideal for upgrading an existing house.
Insteon uses a double-meshed network, meaning that this protocol can either transmit through the powerlines and radio-frequency at the same time. Each device work as a peer and can retransmit the messages. That way the range is extended and the reliability is improved. Insteon is also compatible with the X10 protocol.
Wi-Fi is also used for home automation, for example in the Harmony Hub system (designed to control your home cinema, tv, etc. with the same remote). One of its inconvenient for its use in home automation is that it requires some power to work.
The 4.0 version of Bluetooth protocol was focused on power consumption and is known as BLE (Bluetooth Low Energy). This norm is often used in all the wearable devices like smart bands and smart watches.
This protocol was created in 1999 from 3 previous standards. It works with several communication media : powerlines, radio frequency, infrared, Ethernet and twisted pair wiring. Each device in the network is independent and can communicate with the other devices. One of the strength of this protocol is that each device has to be approved by independent labs making sure that the protocol in correctly implemented and that all devices are able to communicate together with no compatibility issues.
Thread was designed for the IoT (Internet of Things) also called Home Automation or "Smart". It uses open standards and the IPv6 technology to create a mesh network. This protocol is quite new (2014) but makes tempting promises : secure, robust, self-healing, interoperable and battery friendly.