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Introductory Guide to Z-Wave Technology

Z-Wave communicates using wireless technology designed specifically for remote control applications. Z-Wave operates in the sub-gigahertz frequency range, around 800 - 900MHz. This band competes with some cordless telephones and other consumer electronics devices, but avoids interference with Wi-Fi and other systems.









Z-Wave Technology Quick Overview


  • Uses a “Network ID” and a “Node” ID (Similar to an IP Address)

  • Uses RF technology to transmit between Nodes (Phases do not matter)

  • Uses a Mesh Network configuration

  • Each A/C Powered node can act as repeaters, for extending the distance (Battery operated nodes do not repeat)

  • Must have a “Primary Controller” to learn in the modules

  • Can have a maximum of 232 devices



Radio Specifications


  • Bandwidth: 9,600 bit/s or 40 kbit/s, fully interoperable

  • Modulation: GFSK

  • Range: 75 feet assuming a non-intrusive environment (non interference), with an optimum range of 30 feet.

  • Frequency band: uses the 800 to 900 MHz ISM band: 868.42MHz ( UAE )

  • Power limit: 1mW transmission



Network and Topology


Z-Wave is a low powered mesh networking technology where each node or device on the network is capable of sending and receiving control commands through walls or floors and use intermediate nodes to route around household obstacles or radio dead spots that might occur.



Z-Wave uses a source-routed mesh network topology and has one master (primary) controllers that control routing and security. Devices can communicate to another by using intermediate nodes to actively route around and circumvent household obstacles or radio dead spots that might occur. The following example assumes that other devices exist on the network to create the mesh.


Example: A message from node A to node C can be successfully delivered even if the two nodes are not within range, providing that a third node B can communicate with nodes A and C.


If the preferred route is unavailable, the message originator will attempt other routes until a path is found to the "C" node.



This allows a Z-Wave network to span much farther than the radio range of a single unit; however, with the use of several hops a delay could occur between the control command and the desired result. (Z-Wave, 2011)


For more information on the Z-Wave:




Z-Wave Components and Terminology


Controllers


A controller is defined as a unit that has the ability to compile a routing table of the network and can calculate routes to the different nodes. There are different roles for each controller. Some of the most common are Primary and Secondary roles, also known as static controllers.



Primary Controller is the device that contains a description of the Z-Wave network and controls the outputs. It assigns the “Network or Home ID” and “Node ID” to the Z-Wave node during the enrollment process.



Secondary Controller contains the same “Network ID” as the primary and is required to remain stationary to maintain the routing table.



Notes:

  • Any controller can be primary, but only one primary controller can exist on a network at a time.

  • The primary controller manages the allotment of node IDs and gathers information about which nodes can reach each other.

  • The secondary controllers can obtain the network routing information gathered by the primary controller.


Slave Nodes


Slave nodes are nodes that do not contain routing tables, but may contain a network map. This map contains information about routes to different nodes if assigned to it by the controller.


  • Slave Nodes has the ability to receive frames and respond to them if necessary

  • Routing Slave have the ability to host a number of routes for talking to other slaves and controllers

  • Frequently Listening Routing Slave (FLiRS) is configured to listen to a wake up beam during every wake up interval. → See “Beaming” for more information.



Notes:

  • Any slave node can act as a repeater if the nodes state is set to “listen” mode. However, it is important to note that some Z-Wave manufacturers require software to enable the repeating option in the node

  • If the Routing Slave is A/C powered they can be used as repeaters, battery powered devices do not repeat in an effort to control the battery life



Home ID


To separate networks from one another the Z-Wave network uses a unique identifier called the Home ID. It refers to the ID that the Primary Controller assigns the node during the inclusion process.


  • This is a 32-bit code established by the primary controller

  • Additional controllers will be assigned the same Home ID during the inclusion process

  • All slave nodes in the network will initially have a Home ID that is set to zero (0)

  • Once the slave node contains a Home ID it must be excluded before you can assign it to a different network





Node ID


A node is the Z-Wave module itself. A Node ID is the identification number or address that each device is assigned during the inclusion process. The logic works very similar to that of an IP Address.


  • The primary controller assigns the ID to each node

  • There are a total of 232 nodes available on each network

  • Important Note: the Primary Controller is considered part of the network and must be subtracted from the overall node count. Therefore, the total numbers of slave nodes available are 231.


In the example below, you can see where the primary controller has a home ID of 16 (0x00001111) and each node has an id of 02 and 03. Note the primary controller will always contain the Node ID of 01.






Routing


All controllers have a routing table that enables the controller to calculate the routes in the Z-Wave network. It keeps track of these routes and knows which ‘path’ to take to communicate with the destination node.


In the following example, the controller knows to reach the second slave node it must pass through the first node so the path would be as follows:









When slave 1 receives the message it will look at the destination node ID then cross-reference that with its own ID. If it does not match it will forward (repeat) the signal along. See “Hopping” and “Beaming” for more information.


Note: Battery powered devices, such as door locks and battery-powered thermostats, will not repeat.



Z-Wave also determines the most efficient path to take to get to the correct node. The example below describes how the Z-Wave mesh routing network decided to get to node 6. In this example we can see how the primary controller decides to use the path of “Slave 1 → Slave 4 → Slave 6” (highlighted in green) versus the path “Slave 2 → Slave 3 → Slave 5 → Slave 6” (highlighted in red). It knows that it has fewer nodes to go through so the message will be delivered more efficiently.






Z-Wave also has an intuitive intelligence where it uses its two-way communication to determine the position of each node, hence may determine the most efficient path is direct communication versus hopping through other nodes.



Beaming


Battery powered nodes (FLiRS) have a battery saver feature in which the node will be awake for 1.5 seconds then sleep for 1.5 seconds. The Beam is a carrier that is transmitted for a preset period. The 2-way battery devices operate as follows: the radio turns off (to conserve battery) for 1.5 seconds and then wakes up for 1.5 seconds. If a carrier 'Beam' is detected the battery device will fully wake up, checks into the network with a broadcast to all the surrounding nodes. When the FLiRS device receives this broadcast, it responds with an “I do” and beams the command to that particular slave node. If it does not hear the beam command, it falls back to sleep and 1.5 seconds later starts the cycle over.



The key is that the Beam Command is issued from devices that use a permanent power source (like AC). In addition, the repeating device must have recent firmware that have the ability to transmit the Beam Command.



How Does The Beam Command Effect My Installation?


  • If there are no battery powered 2-way Z-wave devices in your network then the Beaming Command is not needed.

  • If your Z-Wave installation includes a lock, battery powered thermostat, or any other Z-Wave battery powered device, read on.

  • Not all repeating devices can issue a beam command. If a controller tries to send a signal to a 2-way battery powered device it will depend on another Z-wave module to repeat the command, that repeating module must support the Beam Command.

  • Z-Wave nodes not capable of receiving or sending beams will disregard the data and drop the packet.

  • Without a Z-Wave device that supports Beaming, the destination node may not receive the message because it was “Sleeping”



How Does Beaming Differ From Repeating?


A slave node that simply repeats the signal grabs the message, understands that it is not intended for itself and sends the packet a long. A module that support beaming will recognizes that there is a battery powered device nearby and will hold the message in a buffer until the node wakes up with the broadcast request mentioned above.


Note: In a multi-hop situation, only the last node before the destination node needs to be a module that supports beaming.



Hopping


Hopping is the number of times a message can be repeated before the message is dropped. The maximum number of hops a Z-Wave device can perform is five, however the optimum number of hops is two. While designing a system the installer or applications engineer must realize that the more hops a message takes the more susceptible it is to incorrect translations of the message.





Inclusion


Including a node into a network is the process of assigning the Home ID and Node ID to the slave unit. The inclusion process is initiated on the Primary Controller first then activating the function button or command on the node itself. When an un-initialized node is activated, the Primary Controller will assign it the Home ID and Node ID.

Notes:

• If the node will not include it may have been assigned to a different Home ID.

• A possible solution to this issue is to send it an Exclusion command or perhaps factory default the unit.



Exclusion


Excluding a node from the network is the process of removing the assigned Home ID and Node ID. The exclusion process resets the Home ID and Node ID to zero. The only exception is a controller, if you exclude a controller the Home ID reverts to the ID programmed during manufacturing.

Notes:

• Any Primary Controller can exclude a node.

• The node does not have to exist on the controller’s network to send it an exclusion command.



Network Wide Inclusion (NWI)




NWI is the process in which you can include devices into the primary controller that are outside the controllers range. Before NWI, all devices had to be included within close proximity to the primary controller and then the routing table reconfigured after installing. NWI allows the installer to start at the controller and include the devices that are within its range. Once those have been included in the network, then the installer can include the next level of devices that are not within direct range of the primary controller. The image below represents an ideal installation using NWI. The key is nodes 1-4 must support NWI in order to pass the inclusion message on to the primary controller during the inclusion process.


As depicted by the following figure, using NWI the installer will include in Slave Nodes 1-4 (red circle) first, then proceed to include nodes 5-12 (green circle). The nodes within range of the primary controller marked with a red circle and those that not within range are marked with the green circle. The red circle has a diameter of 30’ from the primary controller and the green circle has a diameter of > 75’ from the primary controller.


Example would be Node 7 is out of the range of the primary controller, so using the NWI feature of node two we will “bounce” the enrollment process off Node 2 to get a successful inclusion into the network.












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