Z-Wave's mesh networking capabilities are one of its most powerful features, but blindly throwing together a bunch of devices in an effort to achieve smart home greatness is not a very realistic expectation. Knowing a little about how Z-Wave mesh networks work, and the ways you can assist the technology in performing its magic, can bring significant speed and reliability improvements to your whole smart home solution.
In this article, we want to explore some common mistakes we see people make when setting up their Z-Wave networks, and the simple steps you can take to avoid them in your setup.
In this article, we want to explore some common mistakes we see people make when setting up their Z-Wave networks, and the simple steps you can take to avoid them in your setup.
Controller Placement
We all know the Z-Wave controller is the brain of your smart home system, and while sticking it in a corner of the house, enclosed in a metal server rack with 50 other devices may be convenient, this is often the worst idea when it comes to a wireless technology like Z-Wave. Big, heavy objects like server racks, fridges, washing machines, metal doors/gates, TV's and other electrical components will usually have an adverse effect on RF transmission, so make sure your controller is positioned as far away as possible from these kinds of objects.
When data is sent from one Z-Wave node to another, this is called a hop. Despite all the benefits of mesh networking, too many hops can cause significant transmission delays and can choke the network with excessive traffic. You will always get the best reliability and performance when your controller is capable of reaching a good proportion of the network directly. The simplest way of achieving this is to physically position your hub in the most central location in your home, relative to the other nodes on the network.
When data is sent from one Z-Wave node to another, this is called a hop. Despite all the benefits of mesh networking, too many hops can cause significant transmission delays and can choke the network with excessive traffic. You will always get the best reliability and performance when your controller is capable of reaching a good proportion of the network directly. The simplest way of achieving this is to physically position your hub in the most central location in your home, relative to the other nodes on the network.
Here's a simple, real-life example of what can occur when the controller is poorly positioned:
The Hourglass Effect
In this mesh configuration, node #2 is the only device in direct range of the controller. This kind of arrangement, where just a single or small number of nodes are capable of communicating between the controller and the rest of the mesh, is often referred to as the hourglass effect as it introduces a potential bottleneck in the network. If node #2 becomes overloaded, slow response times and potential failures can occur. If it fails completely or becomes unresponsive, the entire system will break down.
By simply moving the controller closer to the centre of the network resulted in this configuration:
By simply moving the controller closer to the centre of the network resulted in this configuration:
The Advantages of Better Controller Placement
Now, nodes #2, #4 and #9 all have a direct connection with the controller. The mesh has multiple paths it can take to route messages and there is no longer a single point of failure in the system.
Bonus tip: To make controller placement easier, most hubs will feature a Wi-Fi bridging option to allow connecting the controller to your local network wirelessly. This is ideal in situations where a wired ethernet point is not available at your target location. Check for this setting under your controller's network configuration.
Bonus tip: To make controller placement easier, most hubs will feature a Wi-Fi bridging option to allow connecting the controller to your local network wirelessly. This is ideal in situations where a wired ethernet point is not available at your target location. Check for this setting under your controller's network configuration.
More is More
Z-Wave relies on always-on (240VAC powered) nodes to build a mesh network. This means, every mains powered node will act as a signal repeater. The mesh is the key to Z-Wave reliability and the more powered nodes there are, the more pathways Z-Wave has for routing messages between them. Notice we said mains powered! Battery powered devices play no role in improving the range or performance of the mesh because they spend the majority of their time switched off to conserve battery life. Therefore, a mesh network comprising mostly of battery powered devices, is unlikely to yield good results.
For a Z-Wave Plus network, it's usually recommended to have at least one powered Z-Wave device roughly every 20 meters for maximum efficiency, but in our experience, reducing this to 10 meters is preferred. If it's not possible to add additional nodes at a particular location due to wiring constraints etc, consider using a dedicated Z-Wave range extender or a simple Z-Wave wall plug which can achieve the same outcome.
Distance between nodes is not always the main criteria for adding more. Z-Wave radio signals may reflect off walls, furniture and other obstacles and cause two nodes that are just a few meters apart to be completely invisible to one another. By adding more powered devices and/or repeaters in the mesh avoids Z-Wave “dead zones” due to these reflections.
For a Z-Wave Plus network, it's usually recommended to have at least one powered Z-Wave device roughly every 20 meters for maximum efficiency, but in our experience, reducing this to 10 meters is preferred. If it's not possible to add additional nodes at a particular location due to wiring constraints etc, consider using a dedicated Z-Wave range extender or a simple Z-Wave wall plug which can achieve the same outcome.
Distance between nodes is not always the main criteria for adding more. Z-Wave radio signals may reflect off walls, furniture and other obstacles and cause two nodes that are just a few meters apart to be completely invisible to one another. By adding more powered devices and/or repeaters in the mesh avoids Z-Wave “dead zones” due to these reflections.
The Proper way to Pair
When establishing a new network, start by pairing your closest mains powered nodes first, and working your way out in a roughly circular or spherical fashion relative to the controller. This helps solidify the structure of the mesh as you go, while giving the controller the best options for seeing the furthest devices in the home during the pairing process. This is thanks to a feature known as Network Wide Inclusion (NWI) where intermediate nodes can be used to route information about the device being added back to the controller.
After all your the mains powered nodes have been added, this is the right time to add all your battery operated devices.
Bonus tip: Unless it's absolutely crucial to your setup, we'd recommend not using secure inclusion. This is an option set on the controller when pairing which ensures all traffic between the controller and the device is encrypted. Secure Inclusion adds considerable overhead on the Z-Wave network so it should be used sparingly. It is strongly advised to only use it for devices that really need this extra level of protection. A door lock would be one such example.
After all your the mains powered nodes have been added, this is the right time to add all your battery operated devices.
Bonus tip: Unless it's absolutely crucial to your setup, we'd recommend not using secure inclusion. This is an option set on the controller when pairing which ensures all traffic between the controller and the device is encrypted. Secure Inclusion adds considerable overhead on the Z-Wave network so it should be used sparingly. It is strongly advised to only use it for devices that really need this extra level of protection. A door lock would be one such example.
Polling is the Enemy
With some older (pre-2016) Z-Wave devices, it used to be necessary for the controller to frequently query nodes in order to maintain current state (e.g., on or off?). This process is called polling. For most new devices on the market today however, polling is not required as these will now support instant status notifications.
Z-Wave is a low-bandwidth network protocol and is not designed to be highly utilised. Polling is considered bad practice because it can quickly flood your network with polling traffic, resulting in slow transmission times and failures. Unfortunately, polling is still enabled by default in some controllers so please check your system settings to confirm it is off. If you really have to poll a device, make sure you increase the polling interval to the maximum time possible for your application.
Bonus tip: While you're poking around under the hood, make sure your devices are not broadcasting too often as well. For example, we sometimes see power metering (on devices which support this) cranked to crazy levels which can generate frequent updates back to the controller. Do a quick check of any per-device Z-Wave configurations that might cause this kind of unnecessary traffic.
Z-Wave is a low-bandwidth network protocol and is not designed to be highly utilised. Polling is considered bad practice because it can quickly flood your network with polling traffic, resulting in slow transmission times and failures. Unfortunately, polling is still enabled by default in some controllers so please check your system settings to confirm it is off. If you really have to poll a device, make sure you increase the polling interval to the maximum time possible for your application.
Bonus tip: While you're poking around under the hood, make sure your devices are not broadcasting too often as well. For example, we sometimes see power metering (on devices which support this) cranked to crazy levels which can generate frequent updates back to the controller. Do a quick check of any per-device Z-Wave configurations that might cause this kind of unnecessary traffic.
Understanding Network Healing
The process of pairing a new device with the controller involves (in part) a discovery of any neighbouring nodes that should be used when relaying messages. As a result, each node is aware of its closest neighbours and can remember its last working route for the next request. If there's a change in the network topology, the nodes have no way of knowing what routes to try - unless the network is healed.
Network healing is a feature built into most Z-Wave controllers and it forces a re-discovery of neighbouring nodes. The controller can self-heal the network to an extent - automatically searching for alternative routes when required - but it may take a while before a better route is discovered. Fortunately, a heal can be performed on demand and can be done at a network-wide level or at a node level. The feature is sometimes referred to as a network repair but regardless of the name, the underlying task performed is the same. You will usually find the option in your controller's Z-Wave configuration settings.
Healing your network is highly recommended whenever a new device is removed without following the proper Z-Wave exclusion process, or, when a device is physically relocated to a different part of the house. Every time you add a new node to an existing network, it is good practice to heal at least a few surrounding nodes as well.
Network healing is a feature built into most Z-Wave controllers and it forces a re-discovery of neighbouring nodes. The controller can self-heal the network to an extent - automatically searching for alternative routes when required - but it may take a while before a better route is discovered. Fortunately, a heal can be performed on demand and can be done at a network-wide level or at a node level. The feature is sometimes referred to as a network repair but regardless of the name, the underlying task performed is the same. You will usually find the option in your controller's Z-Wave configuration settings.
Healing your network is highly recommended whenever a new device is removed without following the proper Z-Wave exclusion process, or, when a device is physically relocated to a different part of the house. Every time you add a new node to an existing network, it is good practice to heal at least a few surrounding nodes as well.
And Finally...
This may sound obvious and not strictly a Z-Wave mesh thing but we feel compelled to mention it... Always, ALWAYS make regular backups of your controller! Automated backups saved onto an external drive or in the cloud is the best option (if your controller software supports it). That way, if something ever goes wrong, and your Z-Wave or hub configuration takes a turn for the worse, you can always restore to your last known working state.
And there you have it! We've covered a lot of ground but hopefully this info helps set you on a path of mesh networking bliss. As always, feel free to drop us a note if you need any further details on anything discussed here.
And there you have it! We've covered a lot of ground but hopefully this info helps set you on a path of mesh networking bliss. As always, feel free to drop us a note if you need any further details on anything discussed here.
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