These are my personal notes on Z-Wave that I made while trying to understand how Z-Wave networks work. They may be helpful if you are new to the protocol.
What is Z-Wave? -Z-Wave is a low power wireless communications protocol using low-energy radio waves.
It is used primarily for home automation for wireless control of home appliances e.g. lighting , security systems, thermostats, garage door openers etc .. wiki
Z-Wave uses a mesh networking topology and has a range of around 30 metres. between nodes.
![Tutorial Tutorial](/uploads/1/1/3/6/113686231/871660963.jpg)
Z-Wave Components
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- In the continuous-wave modulation, a high frequency sine wave is used as a carrier wave. This is further divided into amplitude and angle modulation. If the amplitude of the high frequency carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal, then such a technique is called as Amplitude Modulation.
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There are two main components
- Controllers
- Slaves
Controllers – All Z-Wave networks require a controller. The first controller on the network is the primary controller and is responsible for including and excluding nodes, assigning node IDs to nodes and maintaining a network routing table.
A controller is assigned a factory Network Id which it assign to all nodes that are included on the network.
A USB controller stick that you plug into a computer is a common type of controller.
Slaves- These are nodes like lights,switches etc. Nodes can be mains powered or battery. Mains powered nodes (always on) can be used as repeaters.
Network Topology
A mesh topology allows any node to connect to any other node and allows multiple connections.
The diagram below compares a Wi-Fi network with a Z-Wave network
![Z noise free Z noise free](https://www.sonicscoop.com/wp-content/uploads/2013/05/DeNoise_RX2-300x168.jpg)
In a Wi-Fi network all nodes must be in wireless range of the Wireless Access point, and they can only communicate through the access point.
In Z-Wave a node must be in range of another node and can communicate with adjacent nodes. A packet can hop over 4 nodes which means effectively limits the distance between a controller and the farthest node.
Forwarding Nodes or Repeaters
A node can forward packets to adjacent node as shown in the diagram above.
However to act as a forwarding node the node must be mains powered.
Battery powered nodes cannot forward packets.
Sending Messages and Responses
Messages follow a command response format.
Generally all messages are sent from the controller to the slave nodes.
The node acknowledges the message.
Slave nodes cannot initiate messages i.e. then can only respond. However forwarding nodes can send predetermined messages to assigned (associated) nodes.
This type of behaviour is useful with devices like motion sensors,light switches etc which need to send motion data immediately to a controlling device.
Polling
Polling is used between the controller and slave nodes to request updated status information and for sending control commands.
Th controller will at a predetermined interval send commands and request data to each node.
Adding Nodes to a Network
To become part of a Z-Wave network a node needs to be included into the network.
Z Noise Free
This can only be done on the primary controller. Before inclusion a slave node has a network ID of 0 and Node ID of 0.
After inclusion the node has network ID of the controller and a unique Node ID between 2 and 232.
Note 8 bits are used for the node ID and the primary controller has the node ID of 1. Some IDs are reserved
Some nodes are always
Removing Nodes from a Network
Any Controller can remove a node from a network. When a node is removed it’s network ID and node ID are set to zero.
Neighbour Lists
Each node maintains a list of adjacent nodes that it can communicate with.
They communicate this list back to the controller when requested and the controller uses it to build a routing table.
Routing Table
The primary controller creates and maintains the router table. The controller uses this table to route packets across the network using source routing.
Controllers
A Z-Wave network requires at east one controller. This controller is the primary controller.
Other controllers can be added to the network and can be used for issuing commands to nodes.
Controllers are divided into two types:
- Static
- Portable
Static Controller are mains powered and should not be moved.
Portable controllers are usually battery powered and as such cannot route messages. A portable controller can be the primary controller and that is often the case in very small networks.
All controllers have a copy of the routing table.
Resources:
Popularity ZigBee vs Z-Wave
Related Tutorials
- Principles of Communication
- Useful Resources
- Selected Reading
The other type of modulation in continuous-wave modulation is the Angle Modulation. Angle Modulation is the process in which the frequency or the phase of the carrier varies according to the message signal. This is further divided into frequency and phase modulation.
- Frequency Modulation is the process of varying the frequency of the carrier signal linearly with the message signal.
- Phase Modulation is the process of varying the phase of the carrier signal linearly with the message signal.
Let us now discuss these topics in greater detail.
Frequency Modulation
Waves Z-noise Tutorial
In amplitude modulation, the amplitude of the carrier varies. But in Frequency Modulation (FM), the frequency of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.
The amplitude and the phase of the carrier signal remains constant whereas the frequency of the carrier changes. This can be better understood by observing the following figures.
The frequency of the modulated wave remains constant as the carrier wave frequency when the message signal is at zero. The frequency increases when the message signal reaches its maximum amplitude.
Which means, with the increase in amplitude of the modulating or message signal, the carrier frequency increases. Likewise, with the decrease in the amplitude of the modulating signal, the frequency also decreases.
Mathematical Representation
Let the carrier frequency be fc
The frequency at maximum amplitude of the message signal = fc + Δf
The frequency at minimum amplitude of the message signal = fc − Δf
The difference between FM modulated frequency and normal frequency is termed as Frequency Deviation and is denoted by Δf.
The deviation of the frequency of the carrier signal from high to low or low to high can be termed as the Carrier Swing.
Carrier Swing = 2 × frequency deviation
= 2 × Δf
Equation for FM WAVE
The equation for FM wave is −
$$s(t) = A_ccos[W_ct + 2pi k_fm(t)]$$
Where,
Ac = the amplitude of the carrier
wc = angular frequency of the carrier = 2πfc
m(t) = message signal
FM can be divided into Narrowband FM and Wideband FM.
Narrowband FM
The features of Narrowband FM are as follows −
- This frequency modulation has a small bandwidth.
- The modulation index is small.
- Its spectrum consists of carrier, USB, and LSB.
- This is used in mobile communications such as police wireless, ambulances, taxicabs, etc.
Wideband FM
The features of Wideband FM are as follows −
X Noise Vs Z Noise
- This frequency modulation has infinite bandwidth.
- The modulation index is large, i.e., higher than 1.
- Its spectrum consists of a carrier and infinite number of sidebands, which are located around it.
- This is used in entertainment broadcasting applications such as FM radio, TV, etc.
Phase Modulation
In frequency modulation, the frequency of the carrier varies. But in Phase Modulation (PM), the phase of the carrier signal varies in accordance with the instantaneous amplitude of the modulating signal.
The amplitude and the frequency of the carrier signal remains constant whereas the phase of the carrier changes. This can be better understood by observing the following figures.
The phase of the modulated wave has got infinite points where the phase shift in a wave can take place. The instantaneous amplitude of the modulating signal, changes the phase of the carrier. When the amplitude is positive, the phase changes in one direction and if the amplitude is negative, the phase changes in the opposite direction.
Relation between PM and FM
The change in phase, changes the frequency of the modulated wave. The frequency of the wave also changes the phase of the wave. Though they are related, their relationship is not linear. Phase modulation is an indirect method of producing FM. The amount of frequency shift, produced by a phase modulator increases with the modulating frequency. An audio equalizer is employed to compensate this.
Equation for PM Wave
The equation for PM wave is −
$$s(t) = A_ccos[W_ct + k_pm(t)]$$
Where,
Ac = the amplitude of the carrier
Waves Z Noise
wc = angular frequency of the carrier = 2πfc
m(t) = message signal
Phase modulation is used in mobile communication systems, while frequency modulation is used mainly for FM broadcasting.