Z-Wave Home Automation Technology Explained

Z-Wave is a form of wireless communications standard aimed at home automation and small office automation for everything from lighting control to smart locks and much more.


Z-Wave Tutorial Includes:
Z-Wave basics     Z-Wave LR    


The concept of Z-Wave technology is to use low-power RF radio circuitry embedded into home electronics devices and systems to provide easy automation and control, primarily for home usage.

Z-Wave technology is aimed at a number of wireless home automation areas including lighting, residential access control, entertainment systems and all forms of household appliances.

Z-Wave home and office automation networking

Z-Wave can be set up as a mesh network, and can therefore be used to control all areas of home automation, possibly controlled by a single controller.

The International Telecommunications Union, ITU has included the Z-Wave PHY and MAC layers as an option in its G.9959 standard. This defines a set of guidelines for sub-1-GHz narrowband wireless devices.

Z-Wave Alliance

To support and promote Z-Wave technology, and organisation known as the Z-Wave Alliance was founded.

This is a consortium of manufacturers who have products in this sector. By having a common standard, the market share is increased as users are able to select products from different manufacturers to more exactly suit their needs.

The Alliance also provides certification of products, thereby enabling standards to be maintained and user to select products they know will operate alongside each other.

Advantages of using Z-Wave technology

It's worth considering the benefits and advantages of using Z-Wave as a solution when considering installing a home or office automation system:

  • Ease Of Installation:   The installation of Z-Wave devices is very straightforward like many other wireless systems. The wireless connectivity means that no wires are required for the communication.

  • Range of devices:   There are many different manufacturers involved in designing, manufacturing and marketing Z-Wave products and currently there are many thousands of devices available, so it is possible tog et what is needed for virtually all requirements.

  • Affordability:   The Z-Wave system is expandable allowing a system to be built up as required. The mesh network means that devices can link together to provide reliable communication.

  • Security:   Security is a major issue for any wireless automation system and the security has been built into the standard from the outset and improved over time to meet the latest requirements. It actually uses the same encryption scheme as online banking.

  • Reliability:   Z-Wave protocol has been established for many years and it has evolved to meet the requirements of modern automation systems. This evolution has incorporated may improvements to ensure that any Z-Wave network remains reliable and stable.

  • Trustworthy:   Z-Wave has been adopted by some of the major companies and this has ensured that they have taken the standard to a point where they can put their name it it and the resulting smart home products.

Z-Wave capabilities

It is important to understand what a Z-Wave network is able to achieve - what are its capabilities:

  • Bidirectional communication:   The standard allows for bidirectional communication and this allows for status as well as control. IT also means that all messages are acknowledged to provide reliable communications.

  • Status monitoring:   The bi-directional communication means that nodes are able to provide status information back to the controller or hub, enabling all the devices to be monitored giving their state, and sensor readings, etc where applicable.

  • Mesh network:   Having a mesh network means that dead-spots can be covered and the range to be increased.

  • Easy of control and management:   There are many ways in which a network can be controlled and there are plenty of Apps to enable this, either using a smartphone, laptop, etc and the network can even be controlled remotely over the Internet.

  • Upgrades   With home and office automation requirements developing as the technologies become more widespread, the Z-Wave standard has been developed to provide additional capabilities. Z-Wave LR - long range is one example.

Z-Wave technology basics

A simple overview of Z-Wave technology is given in the table below:


Z-Wave Technology Overview
 
Parameter Details
Frequency range 800 - 900MHz
Original developer Zensys
Applications Home and office automation
Range Standard: 100-800 metres, Z-wave LR: 1.6km+
Modulation FSK although GFSK and DSSS-OQPSK supported
Output power 0dBm
Max number of network nodes 232 nodes

Z-Wave uses a mesh network topology and accordingly any non battery powered device acts as a signal repeater, enabling reliable connections from one node to the next.

Battery powered devices do not act as repeaters as this would result in high levels of battery drain and hence a shorter lifetime.

The mesh network approach means that, the more devices in the network, the more resilient it becomes. This is because it may not be possible for the controller to reach outlying nodes, or those in areas where the controller signal cannot reach.

The frequencies used for Z-Wave are below that of the normal 2.4 GHz Wi-Fi band and this enables better penetration of walls and other items found in all homes, but in addition to this, the mesh network means that data to be transferred can intelligently routed by the network to get around obstacles and thereby obtaining robust whole-home coverage.

Z-Wave typically has a range of about 100 metres or 328 feet in open air. However walls and other items in the home will considerably reduce this and therefore it is recommended that the maximum device spacing Z-Wave network is around 10 metres of 30 feet. Anything closer will provide better communications.

The Z-Wave signal can hop roughly 600 feet, and Z-Wave networks can be linked together for even larger deployments. Each Z-Wave network can support up to 232 Z-Wave devices allowing the flexibility to provide sufficient devices for a complete automated home.

Understanding Z-Wave devices - under the hood

The Z-Wave technology uses three layers to provide the functionality and capabilities that are used. These three layers are contained within the device and intercommunicate in an ordered fashion.

Having layers like this conforms to the OSI model and is the way that many systems using hardware, firmware and software are structured.

  • Radio Layer:   The radio layer or RF interface may also be referred to as the physical layer, or PHY. It controls and manages the way a signal is exchanged between network and the physical radio hardware. The elements of this include aspects such as frequencies used, encoding, hardware access, and the like.

  • Network Layer:   The network layer controls how control data is exchanged between two devices or nodes. It includes aspects like the addressing, network organisation, routing, etc.

  • Application Layer:   This is particularly specific tot he type of device in question. This layer manages which messages need to be handled by specific applications including tasks like switching a light or altering the temperature of a heating device, monitoring a sensor, etc.

Radio layer

The Z-Wave technology uses a simple RF interface to ensure that encode and decode functions are able to be achieved with a minimum level of processing, and hence power consumption. It also ensures that the RF signal can be transmitted with the maximum efficiency.

Some of the key parameters of the Z-Wave RF interface are summarised in the table below:


Z-Wave Technology Summary
 
Parameter Details
Data rate 9.6 or 40 kbit/s; speeds are fully interoperable.
Modulation scheme FSK Manchester channel encoding and GFSK and DSSS-OQPSK supported
Approximate max range Around 50 metres line of sight indoors and 200 metres line of site outdoors
Frequency bands 868.42 MHz SRD Band (Europe)
900 MHz ISM band: 908.42 MHz (United States)
916 MHz (Israel)
919.82 MHz (Hong Kong)
921.42 MHz (Australian/New Zealand)
Duty cycle In Europe, the 868 MHz band has a 1% duty cycle limitation
Power save Z-Wave units are only be active 0.1% of the time to reduce power consumption

Z-Wave Network layer

The Z-Wave network layer is the area of the protocol stack that controls the data exchange between the different devices, sending data over the RF or radio layer.

The network layer consists of three layers:

  • Media Access Layer:   Referred to as the MAC, this layer controls the basic usage of the wireless hardware. It does this in a manner that is not visible to the end user.
  • Transport Layer:   The transport layer within the Z-Wave technology protocol stack controls message transfer between two wireless nodes and ensures error free transmission.
  • Routing Layer:   The routing layer manages the Z-Wave wireless mesh capabilities. It enables the various nodes to link together and route messages from one node to another if one node is out of range of another..

Z-Wave devices

In order to have a hierarchy within a wireless network, various types of Z-Wave device are specified:

  • Controller:   As the name implies, these devices are those that control other Z-Wave devices. Controller devices are factory programmed with what is termed a Home ID. This cannot be changed by the user.
  • Slave:   Slave devices are those that are controlled by controllers. Slave devices do not have a pre-programmed Home ID, but instead they take the Home ID assigned to them by the Z-Wave network controller.
  • Routing slave:   This form of Z-Wave slave is one that knows its neighbours and has partial knowledge of routing table. It can reply to the node from which it has received the message. It can also send unsolicited messages to a number of predefined nodes to which it has routes.

Z-Wave software & firmware

The Z-Wave system was originally a proprietary system, but as its popualrity has increased, the software has become internationally standardised and much of the applicationware is open source.

The Z-Wave MAC/PHY is globally standardized by the International Telecommunication Union as ITU 9959 radio. In addition to this the Z-Wave Interoperability, Security (S2), Middleware and Z-Wave over IP specifications were released into the public domain in 2016.

In this way Z-Wave has become a fully-ratified open-source protocol for development. This has been a very good move for many other systems where releasing the standard has enabled the number of manufacturers and hencve the market to increase.

In addition to the basic Z-Wave software itself, OpenZWave has been created. This is a library of C++ and wrappers and supporting projects, to interface different languages and protocols. This provides gthe basis for anyone to generate applications to control devices on a Z-Wave network, without requiring in-depth knowledge of the Z-Wave protocol.

OpenZWave is intended for use by application developers to enable them to include Z-Wave functionality in their applications. This too, increases the use and attractiveness of Z-Wave for an increasing number of projects and developments.

Z-Wave vs other standards

Apart from Z-Wave, there are many standards available that can be used for home and office automation, and it is worth looking at the advantages and disadvantages of each.

It's worth looking at how Z-Wave compares with the other standards.

  • Frequency bands:   Z-Wave uses the 800-900 MHz band whereas Zigbee, Thread and Bluetooth LE all use the 2.4 GHz band where there is much more interference. The lower frequency band also suffers slightly less attenuation giving a slightly greater range for the same power.

  • Bandwidth:   Z-Wave uses a low bandwidth as this is what the 800-900MHz unlicensed band can support, whereas Bluetooth LE, Thread and Zigbee have access to a much higher bandwidth should this be needed. That said, most automation applications only require a relatively low bandwidth.

  • Networking:   Z-Wave, Zigbee and Bluetooth LE all support mesh networking to give a resilient network and longer range.

  • Interoperability:   Z-Wave offers a better level of interoperability when compared to Zigbee.

  • Data rate:   Z-Wave has a lower data rate than Zigbee or Bluetooth LE. This may or may not be an issue if only switching and control is required.

Z-Wave updates

In order to keep pace with the increasing requirements for remote monitoring and control, Z-Wave has been updated and other variants are available.

  • Z-Wave Plus :   Z-Wave Plus improves on the basic Z-Wave standard while keeping backward compatibility with older versions. Z-Wave Plus gives increased range, increased battery life, greater bandwidth, Oer-The-Air updates and several other improvements.

  • Z-Wave S2:   This provides a significant improvement in the security available within Z-Wave without impacting battery life.

  • Z-Wave LR Long Range :   A version of Z-Wave has been developed to enable long range links to be established - typically distances of over a mile line of sight. This opens up many more possibilities for the use of Z-Wave technology.



In order to cater for a wide variety of applications, the assignment of IDs is regulated and allows for a variety of scenarios. A primary controller has the function of including other nodes into the network. It does this by assigning them its own Home ID. If a node accepts the Home ID of the primary controller this slave node then becomes part of the network. The primary controller also assigns an individual Node ID to each new device that is added to the network - this is called Inclusion.

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