z wave basics
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.
| Specification | z-wave support |
|---|---|
| Standard | ITU-T G.9959 (PHY and MAC) |
| RF Frequency Range | 868.42 MHz in Europe, 908.42 MHz in US |
| Data rate | 9.6, 40, 100 Kbps |
| Maximum Nodes | 232 |
| Architecture | Master and slave in mesh mode |
| MAC layer | CSMA/CA |
| RF PHY modulation | FSK (for 9.6kbps and 40 kbps), GFSK with BT=0.6 (for 100 kbps) |
| Coding | Manchester(for 9.6kbps), NRZ(for 40 and 100 kbps) |
| Distance | 30 meter in indoors, 100 meters in outdoors |
Table-1: z-wave features
z-wave frequency bands
Following table mentions frequency bands, data rate and channel bandwidth supported by z-wave technology through out the world.
| Region | RF Center Frequency (G.9959/MHz) | Data Rate | Channel Width |
|---|---|---|---|
| Australia | fANZ1/919.80,fANZ2/921.40, | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| Brazil | Same as Australia | ||
| Canada | Same as USA | ||
| Chile | Same as USA | ||
| China | fCN1/868.40, | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| European Union | fEU1/869.85, fEU2/868.40 | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| Hong Kong | fHK1/919.80 | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| India | fIN1/865.20 | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| Israel | fIL1/916.00 | 100/ 40/9.6Kbps | 400/ 300/300KHz |
| Japan | fJP1/922.50, fJP2/923.90,fJP3/926.30 | 100/100/ 100 kbps for all bands | 400/400/ 400 KHz for all bands |
| Korea | fKR1/920.90,fKR2/921.70,fKR3/923.10 | 100/100/ 100 kbps for all bands | 400/400/ 400 KHz for all bands |
| Malaysia | fMY1/868.10 | 100/40/ 9.6Kbps | 400/300/ 300KHz |
| Mexico | Same as USA | ||
| New Zealand | Same as Australia | ||
| Russia | fRU1/869.00 | 100/40/ 9.6Kbps | 400/300/ 300KHz |
| Singapore | Same as EU | ||
| South Africa | Same as EU | ||
| Taiwan | Same as Japan | ||
| UAE | Same as EU | ||
| USA | fUS1/916.00, fUS2/908.40 | 100/40/ 9.6Kbps | 400/300/ 300KHz |
Table-2: z-wave frequency bands
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.
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.
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.
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