In previous articles we’ve looked at the problems of relying on the cloud and how manufacturers try to lock us into their ecosystems.
Now we’re going to drop down a level in the technology stack to talk about the physical and transport layers: how exactly do these devices communicate over the air.
To design a robust smart home network, we can’t simply connect a hundred devices to our home router and expect everything to work. Each wireless protocol has been designed to solve a different engineering problem, with its own trade-offs between bandwidth, energy consumption, and range.
Let’s dive into the technical details of the protocols we’ll encounter when setting up our system with Home Assistant: WiFi, Bluetooth, Zigbee, and the newer Thread and Matter 👇.
WiFi (IEEE 802.11): bandwidth at the cost of energy
WiFi is the protocol everyone knows and is the most widely used by cheap commercial devices (like the ESP8266/ESP32 modules we saw from Tuya or Sonoff).
At the network level, WiFi uses a star topology. This means that every plug, light bulb, or relay must connect directly to a central access point (our home router or a repeater).
WiFi is excellent for transmitting large volumes of data (like a video stream from an IP security camera), because it has high bandwidth and operates natively with the TCP/IP stack.
The question naturally arises: why don’t we use WiFi for everything? Because for general home automation it presents severe design problems:
- High energy consumption: Maintaining an active WiFi connection requires more power than Zigbee or Thread. Battery-powered WiFi sensors exist, but they often rely on long sleep periods and are not ideal for reporting frequently.
- Load on the access point: Adding dozens of clients increases management traffic and can overwhelm a modest home router. The actual limit depends heavily on the hardware, coverage, and network configuration.
- Limited range: If the router is in the living room, a WiFi relay in the garage will likely lose connection constantly.
Bluetooth Low Energy (BLE)
Bluetooth Low Energy is a Wireless Personal Area Network (WPAN) protocol that solves the energy consumption problem of WiFi.
In home automation, it is mainly used for battery-powered devices that transmit very little information, such as temperature sensors (the famous Xiaomi thermometers), smart scales, or smart locks.
Although a mesh version exists (Bluetooth Mesh), in the maker ecosystem and Home Assistant, BLE is typically used via Bluetooth Proxies.
We use ESP32 boards placed around the house that “listen” for BLE beacons from sensors and forward them to Home Assistant over WiFi.
Zigbee (IEEE 802.15.4): A Network Designed for Home Automation
Given WiFi’s inefficiency for the Internet of Things (IoT), the industry adopted Zigbee. Currently, it’s the go-to protocol if you want to build a fast, reliable local network in Home Assistant.
Zigbee operates in the 2.4 GHz band and is designed to transmit small packets with very low power consumption. Actual battery life depends on the device, the battery type, the reporting interval, and network quality.
A Practical Problem: The 2.4 GHz Band
Both WiFi and Zigbee share the 2.4 GHz band. This doesn’t mean they can’t coexist, but if we fill the house with devices and leave the router broadcasting on heavily overlapping channels, they can interfere with each other.
This usually isn’t a serious problem in small installations, but for a serious home network, it’s wise to think about channel distribution. Otherwise, you’ll run into the classic issues: “sometimes it responds,” “sometimes it drops out,” and “who knows why the hallway sensor is asleep today.”
Mesh Topology
The main architectural advantage of Zigbee is that it doesn’t use a star topology, but a mesh network.
In a Zigbee network, devices connected to mains power (like bulbs or plugs) act as router nodes. If a sensor in the garden can’t reach the main coordinator, the signal will hop from the living room bulb to the hallway plug, and finally reach its destination. The more mains-powered Zigbee devices you have, the stronger and more extensive your network will be.
We’ll discuss in more detail how to set up a Zigbee network, its coordinators (Dongles), and device types in a dedicated course entry.
Thread: An IP-Based Mesh
Thread is a relatively new protocol that solves one of Zigbee’s historical problems.
Although Zigbee is fantastic, it is not an IP-based protocol. That means a Zigbee device doesn’t have an IP address (like 192.168.1.50) and doesn’t speak the same “language” as our home network. It requires translation hardware (the USB coordinator we connect to Home Assistant).
Thread is essentially a low-power mesh network, similar to Zigbee, but designed for native IP integration.
Technically, it uses the 6LoWPAN standard (IPv6 over Low-Power Wireless Personal Area Networks). It retains all the advantages of Zigbee: very low power consumption, operation in the 2.4 GHz band, and mesh networking capability. The difference is that by using IPv6 natively, Thread devices can integrate into our local network much more naturally.
To connect a Thread network to our WiFi/Ethernet network, a Thread Border Router is used, such as specific HomePods, Google Nest Hubs, or a Home Assistant Connect ZBT-2 dedicated to Thread.
Matter: The Common Language, Not a Radio
Now we come to one of the biggest sources of confusion in the current market. People often ask: “Which is better, Zigbee or Matter?” This is a trick question, because Matter is not a radio transport protocol.
If we recall the OSI network model, WiFi and Thread operate at the lower layers (Physical / Link / Transport). Matter operates at the Application Layer.
Matter is a communication standard, a common language. Historically, a Tuya WiFi bulb spoke one language, and a Shelly WiFi bulb spoke another.
What Matter does is define a universal vocabulary. Matter works on top of WiFi, Ethernet, or Thread.
- If you plug in a TV (needing high bandwidth), it will use Matter over WiFi.
- If you install a battery-powered door sensor (needing low power), it will use Matter over Thread.
The goal of Matter is that you can buy any device with its logo, scan a QR code with your phone, and have it work immediately with HomeKit, Google Home, Alexa, or Home Assistant, with local control as a foundation of the standard.
This doesn’t mean all manufacturers will abandon their apps or cloud services. It means that, at least for basic device control, they shouldn’t force us to go through their server just to turn on a light. That’s already a big step forward.
Matter is already implemented in Home Assistant, and its catalog continues to grow. Nevertheless, Zigbee still boasts a huge catalog and very competitive prices, so it remains a very practical choice for sensors and actuators.
How to Choose a Protocol Without Going Crazy
The practical decision is usually much simpler than it seems. For cameras, display panels, or devices that move a lot of data, WiFi remains the natural choice. For battery-powered sensors, buttons, motion detectors, and door contacts, Zigbee or Thread make much more sense.
For older devices, garage door openers, or cheap sensors that already transmit in sub-GHz, RF 433/868 MHz can be a very inexpensive way to listen to the world, as long as we accept its limitations. And for future interoperability between commercial ecosystems, Matter will become increasingly important, although it’s still wise to look carefully and not buy based on the logo alone.
If you’re unsure, a fairly healthy architecture for a normal home is: WiFi for mains-powered devices needing high bandwidth, Zigbee for small sensors and actuators, and MQTT as the glue between systems.
