z-wave Tutorial

This page of tutorials section covers z-wave tutorial describing basic features,z-wave frequency bands,z-wave network, z-wave frame,z-wave protocol stack,z-wave physical layer,z-wave security,z-wave MAC layer and more. z-wave is a popular wireless technology in IoT(Internet of Things).

Z-wave technology based devices operates in ISM band. It is developed for low bandwidth data communication applications such as security sensors, home automation, alarms etc. The following section mentions frequencies used in z-wave. It uses 868.42 MHz in Europe and 908.42MHz in USA. Following table-1 mentions basic features of z-wave technology widely used in IoT(Internet of Things) due to low power and low data rate. Z-wave protocol is developed by Sigma Designs, Inc. including encryption. Open source implementation of Z-Wave protocol stack known as open-zwave is also available but it does not support security layer. Z-wave PHY and MAC layer specifications are defined in ITU-T G.9959 standard.

z-wave frequency bands

Following table mentions frequency bands, data rate and channel bandwidth supported by z-wave technology through out the world.

z-wave network

The z-wave network consists of controllers (one primary controller and more than one secondary controllers) and slaves. Controller devices are the nodes in a z-wave network which initiates control commands. It also sends out the commands to other nodes. The slave devices are the nodes which replies based on command received and also execute the commands. Slave nodes also forward the commands to other nodes in the network. This makes it possible for controller to establish communication with the nodes who are not in radio frequency region.

Controllers:
A controller device will have full routing table for this mesh network and it will host it. Hence controller can communicate with all the nodes of z-wave network. There are two types of controllers viz. primary and secondary.

The controller which creates new z-wave network initially will become primary controller. This primary controller is master controller in the network and there will be only one in each z-wave network. Primary controller will have capability to include and exclude the nodes in the network. Hence primary controller always keeps latest topology of the network. Primary controller also takes care of managing allocation of node IDs.

The controllers which are added to the z-wave network using the primary controller are known as secondary controllers. They do not have capability to include or exclude any nodes. They will get copies of the routing tables from primary controller.

Slaves:
The slave devices/nodes in z-wave network receive the commands and performs action based on the commands. These slave nodes are unable to transmit information directly to the other slave nodes or controllers unless they are instructed to do so in the commands. The slave nodes do not compute routing tables. They can store routing tables. They will act as a repeater.

Home ID:
The z-wave protocol uses Home ID field to separate the networks from each other. It is 32 bit unique identifier which will be pre-programmed in all the controller devices. At the start, all the slave nodes will have Home ID value as zero. All the slave devices need Home ID value in order to communicate in the z-wave network. This will be communicated to all by the controller. Controllers exchange Home ID which makes it possible for more than one controller to control slave nodes.

Node ID:
This node ID is 8 bit value. Similar to Home ID, they are also assigned to slave nodes by controller. Node ID's are used in order to address individual nodes in a z-wave network. These Node ID's are unique within a network defined by a unique Home ID.

z-wave frame structure

As shown in the fig-1, z-wave frame consists of a preamble part, SOF(Start of Frame), Frame data and EOF(End of Frame) symbol. The data part is manchester codes or NRZ coded based on data rate. MAC layer controls the RF spectrum. Data part comes from the upper layers and z-wave frame as mentioned in formed at the MAC/PHY layers. After this is done the z-wave frame as depicted is transmitted by the RF antenna after necessary radio frequency conversion as desired using RF Transceiver. For details on z-wave frame structure as well as various z-wave MAC layer frame types,
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z-wave protocol stack

The z-wave protocol stack consists of PHY layer, MAC layer, Transport layer, Network layer and application layer. Other than servicing their peers all the layers have their own tasks.
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z-wave Physical layer(zwave PHY)

The z-wave Physical layer takes care of preamble insertion in the z-wave frame. It takes care of modulation and demodulation as well as RF channel selection. It takes care of data frame transmission and reception.
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z-wave security

As z-wave open protocol architecture does not specify security layer specifications it is implementation specific. z-wave security layer provides secured communication between nodes as well as between controllers and nodes.
Read more.

Similar posts on z wave technology

z-wave tutorial
z-wave physical layer-PHY
z-wave MAC layer
z-wave protocol stack
z-wave security basics
z-wave device conformance testing

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