Z-Wave Technology: Tutorial on Features, Frequency, and Network

This tutorial provides an overview of Z-Wave technology, covering its basic features, frequency bands, network architecture, frame structure, protocol stack, physical layer, security aspects, and MAC layer functionalities.

Z-Wave is a prominent wireless technology in the realm of the Internet of Things (IoT). Devices utilizing Z-Wave operate within the ISM band, making it well-suited for low-bandwidth data communication applications such as security sensors, home automation systems, and alarms. In Europe, it uses 868.42 MHz, while in the USA, it operates at 908.42 MHz.

The following table outlines the key features of Z-Wave technology, which is widely adopted in IoT due to its low power consumption and low data rate capabilities. The Z-Wave protocol, including encryption, was developed by Sigma Designs, Inc. While an open-source implementation of the Z-Wave protocol stack, known as Open-ZWave, is available, it lacks support for the security layer. The PHY and MAC layer specifications for Z-Wave are defined in the ITU-T G.9959 standard.

Table-1: Z-Wave Features

Z-Wave Frequency Bands

The following table details the frequency bands, data rates, and channel bandwidths supported by Z-Wave technology across various regions of the world.

Table-2: Z-Wave Frequency Bands

Z-Wave Network

The Z-Wave network comprises controllers (one primary and potentially multiple secondary controllers) and slave devices.

Controllers are the nodes that initiate control commands and transmit them to other nodes within the network. Slave devices, on the other hand, respond to received commands and execute them. They can also forward commands to other nodes, facilitating communication with nodes outside the controller’s direct radio frequency range.

Controllers

A controller device maintains a full routing table for the mesh network, enabling it to communicate with all nodes. There are two types of controllers:

• Primary Controller: The first controller to create a new Z-Wave network becomes the primary controller. It serves as the master controller and is unique to each Z-Wave network. The primary controller can include and exclude nodes and manages the allocation of node IDs, thus maintaining the network’s topology.
• Secondary Controllers: These are added to the network via the primary controller. They lack the ability to include or exclude nodes but receive copies of the routing tables from the primary controller.

Slaves

Slave devices/nodes receive and execute commands. They cannot directly transmit information to other slave nodes or controllers unless instructed to do so within the received commands. Slave nodes do not compute routing tables but can store them and act as repeaters.

Home ID

The Z-Wave protocol utilizes a 32-bit Home ID to differentiate networks. This unique identifier is pre-programmed in all controller devices. Initially, all slave nodes have a Home ID value of zero, which they need to communicate within the network. The controller communicates this ID to the slaves. Controllers can exchange Home IDs, enabling multiple controllers to manage slave nodes.

Node ID

The Node ID is an 8-bit value assigned to slave nodes by the controller. These IDs are used to address individual nodes within a Z-Wave network and are unique within a network defined by a specific Home ID.

Z-Wave Frame Structure

As depicted in Figure 1, the Z-Wave frame consists of a preamble, SOF (Start of Frame), frame data, and EOF (End of Frame) symbol. The data portion is either Manchester coded or NRZ coded, depending on the data rate.

The MAC layer manages the RF spectrum. The data part originates from the upper layers, and the Z-Wave frame is formed at the MAC/PHY layers. Following this, the frame is transmitted via the RF antenna after appropriate radio frequency conversion using an RF transceiver.

Z-Wave Protocol Stack

The Z-Wave protocol stack includes the PHY layer, MAC layer, Transport layer, Network layer, and Application layer. Each layer performs specific tasks in addition to servicing its peers.

Z-Wave Physical Layer (ZWave PHY)

The Z-Wave Physical layer handles preamble insertion into the Z-Wave frame, manages modulation and demodulation, selects RF channels, and oversees data frame transmission and reception. Additional details can be found by reading more on the topic.

Z-Wave Security

The open protocol architecture of Z-Wave does not inherently specify security layer specifications, making it implementation-specific. The Z-Wave security layer ensures secure communication between nodes and between controllers and nodes.