Z-Wave is a wireless protocol that uses radio waves to transmit information. It is primarily used in smart homes particularly for control, monitoring and status reading for household appliances having physical range of 100 meters. It operates in ISM band and is developed for low bandwidth data communication applications.
This technology, due to its interoperability can encompass a wide range of ecosystem of smart computing devices that can work efficiently with different brands and models. With its advanced technology, there is no interference from other wireless technologies like Wi-Fi or ZigBee which operate on similar band.
History of Z-Wave
It was first coined by a Danish company Zensys, and it began as a light-control system for consumers. Later it evolved as a home network mesh protocol implemented on a System-on-Chip (SoC). There was a considerable improvement provided by its 500 Series which provided 50% improvement in battery life, 67% improvement in range and 250% increase in bandwidth. Some Z-Wave technology were made open source in 2016 on which interoperability layer was added with the freedom to the manufacturers, hobbyists, developers and academics, the ability to read, use and comment on how Z-Wave works without actually joining the Z-Wave alliance.
Working of Z-Wave in IoT Network
Let us discuss the working of z-wave in IoT network. It is based on master-slave mesh type ad-hoc network that can connect numerous Z-Wave devices simultaneously which can communicate with each other. It consists of one primary controller, one or more than one secondary controller and many slave devices.
The controller is the one which can initiate communication or give commands to the slaves. The slave devices reply to these commands and can also communicate with the other slave devices in the network. The controller has the full routing table of the network.
The primary controller is the one which creates the Z-Wave network newly and becomes the master controller. They also have the capability to exclude or include the slave nodes. It also manages the allocation of node IDs.
The secondary controllers are added in the network by the primary controller and they do not have the capability to add or remove any node from the network. They get copies of the routing table from the primary controller.
The slave devices act based on the commands initiated by the controllers. They cannot communicate with other slave devices directly until they are explicitly asked to do so in the commands. The slaves can only store the routing table but cannot compute it.
All the slave devices need Home ID value to communicate in the Z-Wave network. This ID is a 32-bit unique identifier which will be communicated to the slaves by the controller. Similar to Home ID the slaves also need Node ID, an 8-bit identifier. This ID is used to distinguish the slave devices for a particular Home ID.
Z-Wave Protocol Stack
The architecture consists of the Physical layer, MAC layer, Transport layer, Network layer and the Application layer. The Z-Wave frame has preamble which is inserted by the Physical layer.
The Physical layer takes care of the channel selection, modulation and demodulation of the signals. It also takes care of data frame transmission and reception.
The MAC layer is responsible for the Home ID and the Node ID. It also controls the medium between nodes based on collision avoidance and back off algorithms.
The Transport layer takes care of transmission and reception of frames as well as re-transmission and acknowledgment of frames. It also takes care of insertion of checksum.
The Network layer is responsible for frame routing and routing table updates.
The Application layer controls the payload in the frame received or transmitted.
Z-Wave Vs ZigBee
Both the technologies are wireless short-range communication protocols which are based on mesh ad-hoc network topology. ZigBee provides higher data rate but in turn reduces the range. Zigbee provides a data rate of 40-250 kbps while Z-Wave’s data rate is 9.6-100 kbps. But Z-Wave data range is 98 feet which is much higher than the ZigBee 32 feet range. As ZigBee is an open source ZigBee chips are available from multiple vendors while Z-Wave chips are available only at silicon labs. A ZigBee network can support up to 65,000 devices whereas the Z-Wave network has the ability to support only 232 devices.
M.Tech (VLSI Design and Embedded system)
BS Abdur Rahman University