Z-Wave Communication Protocol Tutorial for Smart Homes

Z-Wave Communication Protocol Tutorial for Smart Homes

In this tutorial, you learn how the Z-Wave communication protocol for smart home work.

After the technical key facts we take a closer look at Z-Wave mesh networks and why they are used in smart homes.

If you want to include security devices in your home like security cameras, I explain in this tutorial why you should use the Z-Wave series 700 in the future.

Z-Wave Logo

Table of Contents

Z-Wave is a very popular Smart Home communication protocol that is not based on the WiFi protocol for the communication but use wireless radio frequency to build a network with smart devices.

In 1990 Z-Wave was developed by the Danish company Zensys because they created a consumer light-control system and needed a communication protocol. To promote the technology of Z-Wave, five companies formed the Z-Wave Alliance in 2005. Sigma Designs in 2008 and Silicon Labs in 2018 acquired Z-Wave later on. Since 2005 the Z-Wave Alliance grows up to 700 members.

Not only the number of companies in the alliance grows over the years, the number of Z-Wave products also explodes. In 2005 there were 6 products in the market and by 2012 the number raises to 600 because of the increasing popularity of smart home devices. Today there are more than 2400 interoperable Z-Wave products on the market.

The interoperability is one of the main advantages from Z-Wave compared to other smart home communication protocols like ZigBee. This interoperability is achieved through a 2 steps certification program:

  1. First all smart devices get a technical certification through Silicon Labs because all Z-Wave chips are produces only by Silicon Labs.
  2. In the second step only the products with a market certification from the Z-Wave Alliance can be sold. During this process it is tested that the device is compatible with other Z-Wave smart devices.

The following table shows the technical key facts for the Z-Wave smart home communication protocol:

 

Z-Wave

Operating Range

100 feet / 30 meters

Maximum number of devices theoretically

232

Data rate

9.6-100 kB/s

Frequency

850-916 MHz (US)

Network Type

Mesh

Need Hubs

Yes

Network Join Time

30 ms

Encryption and data authentication

Advanced Encryption Standard (AES-128)

Maximum hobs in mesh network

4

Technology

Radio Frequency

Number of interoperable products

3200

Z-Wave Mesh Network

The following picture shows an example of a Z-Wave mesh network that can have up to 232 devices and could be further extended with a network bridge. A network bridge is a computer networking device that bridges multiple networks like if they were a single network.

Z-Wave Mesh Network

In a mesh network all devices connect directly, dynamically and non-hierarchically to as many other nodes as possible. Therefore a mesh network can span much further then the range of a single unit which is about 100 feet / 30 meters. But note that the longer the distance, the longer will be the delay between the signals and for example a light turns on with a noticeable delay.

For example in the picture above, the slave in the bedroom is not in range of the controller, but a routing slave forwards and repeats messages from the client to the slave. These forwarding can taken place maximum 4 times. Generally all mesh networks are more robust against failing devices because it is possible that all messages take another route in the mesh network. Therefor adding new devices to the network that are able to route information between the nodes strengthens the whole network.

There are three different types of nodes in a Z-Wave network with different functions and permissions that are describes in the following table.

 

Neighbors

Route

Function

Controller

Knows all neighbors

Has access to complete routing table

Can communicate with every device in the network, if route exists

Slave

Knows all neighbors

Has no information about routing table

Can only reply to the node which it has received the message from.

Routing Slave

Knows all neighbors

Has partial knowledge of routing table

Can reply to the node which he has received the message from and can send unsolicited messages to a number of predefined nodes he has a route too

Battery powered devices are not designed to be routing slaves because to forward messages in the network, the routing slaves can not enter sleep mode. This would dramatically decrease the battery lifetime of the device.

A routing table shows the connections between the nodes in the mesh network. The following table shows the routing table for the example Z-Wave network.

 

1

2

3

4

5

6

1

x

  

x

  

2

 

x

x

x

  

3

 

x

x

x

x

 

4

x

x

x

x

x

x

5

  

x

x

x

x

6

   

x

x

x

Add a new smart device to the network

How are smart devices clearly assigned to a Z-Wave network? There are two different IDs for this purpose.

  1. Network ID: The Network ID, also called Home ID is a unique 32-bit identifier and identifies all nodes in one logical Z-Wave network and is assigned to each device by the primary controller during the paring. The Network ID is assigned to every controller during the factory process. Also if there is another controller that joins the network, the controller inherits the Home ID from the primary controller.
  2. Node ID: The second ID is the Node ID and assigned to each node by the primary controller. The Node ID is only assigned once within the network and has a length of 8-bit.

The following picture shows how a Z-Wave network is build by two controllers and two slaves.

Z-Wave add devices to network

Before the network is created, the controllers have different Home IDs and a the Node ID of 1. The Salves have no Home ID and also no Node ID.
After the primary controller is selected, the Home ID of the primary controller is written to all salves and also the secondary controller. The Node ID is set to a unique address for every slave and controller by the primary controller.

Before a new device is connected to the Z-Wave network, the device has to be pared once. Because the controller of the network measures the signal strength of the new device and optimizes the routing table for the network with the signal strength, the new device should be pared on the final place, where the device will be in the future. Otherwise the routing table will not be optimized and therefore the signal strength and reliability of the network could be decreased.

Z-Wave Radio Frequency

Another advantage of Z-Wave is the used radio frequency. Z-Wave uses different operating frequencies depending on the county or region. But independent of the country the operating frequency is not in the spectrum of WiFi (2.4 GHz / 5 GHz) and Bluetooth and therefore the signal is more reliable.

The following table shows the used Z-Wave radio frequency depending on the country. Also the table shows the residential voltage and the net frequency.

Country/Region

Z-Wave Frequency

Residential Voltage

Frequency

Brazil

919.8 MHz, 921.4 MHz

127 V, 220 V

60 Hz

Canada

908.4 MHz, 916 MHz

120 V

60 Hz

CEPT (EU)

868.4 MHz, 869.85 MHz

230 V, 240 V, 220 V

50 Hz

China

868.4 MHz

220 V

50 Hz

Hong Kong

919.8 MHz

220 V

50 Hz

India

865.2 MHz

230 V

50 Hz

Japan

922.5 MHz, 923.9 MHz, 926.3 MHz

100 V

50 Hz, 60 Hz

South Korea

920.9 MHz, 921.7 MHz, 923.1 MHz

230 V

60 Hz

USA

908.4 MHz, 916 MHz

120 V

60 Hz

Different Z-Wave Series

During all the years of development on the Z-Wave smart home communication protocol, different series of the hardware chip were released by Zensys (300 series), Sigma Designs (500 series) and later Silicon Labs (700 series).

The 700 series was released in April 2019 and improved the 500 series especially in power consumption and security. The wireless communication of the 700 series uses 64% less power so that the maximum battery live is increased to 10 years.

The 3 optional layers of security that the 500 series offered are now mandatory, making Z-Wave, in my opinion, to the best smart home communication protocol for security related devices.

Also the CPU, in the 700 series is an ARM Cortex and increases the CPU power by 18% compared to the 500 series.

If you want to buy a smart home device that includes the 700 series, make sure in the product specification the Z-Wave Gen7 is listed. One of the first companies that is series 700 certified is Aeotec. The first Gen7 devices from Aeotec are the Range Extender 7 and the Recessed Door Sensor 7.
If you are interested in the technical details of the different Z-Wave series, you find the specifications in the following table.

Hardware Platform

300 series

500 series

700 series

CPU / MCU

Optimized 8051 CPU Core

Optimized 8051 CPU Core

ARM® Cortex M4

CPU / MCU Speed

16 MHz

32 MHz

39 MHz

Memory

2 kB

16 kB

64 kB

Flash Memory

32 kB

128 kB

512 kB

Gecko

No

No

Yes

SAW Filter

No

Optional

Inbuilt

Number of GPIO pins

10

14

32

Operating ambient temperature

-15 to 85°C

-10 to 85°C

-40 to 85°C

Chipset dimensions (mm)

12.5 x 13.6 x 2.4

13.6 x 12.5 x 1.9

9 x 9 x 1.21

Power Use

 

 

 

Active power consumption

36 mA

35 mA

12.5 mA

Sleep-mode power consumption

2.5 uA

1 uA

1 uA

Security energy use

50% less

Coin cell compatible

No

No

Yes

Maximum battery life

1 year

1.5 years

10 years

Wireless Security

 

 

 

Network key

Optional

Yes

Yes

AES-128 bit encryption

No

Optional

Always

ECDH

No

Optional

Always

S2

No

Optional

Always

SmartStart

No

Optional

Always

Man in the middle attack prevention

No

Optional

Always

Wireless Performance

 

 

 

Output power DBM (TX)

-2.5 dBm

300 series +2.5dBM

up to +13 dBm

Range sensitivity (RX)

-102 dBm / -98 dBm

down to -103 dBm with saw filter

-97.5 dBm

Wireless speed

9.6 / 40 kbit/s

9.6 / 40 / 100 kbit/s

9.6 / 40 /100 kbit/s

Maximum wireless range outdoors (Direct)

up to 100 metres

up to 150 metres

more than 200 meters

Maximum wireless range outdoors (Max Hop/Repeat)

up to 400 metres

up to 600 metres

more than 800 meters

Maximum wireless range indoors (Direct)

more than 30 metres

up to 75 metres

up to 100 meters

Maximum wireless range indoors (Max Hop/Repeat)

more than 120 metres

up to 300 metres

up to 400 meters

Z-Wave Specific Features

 

 

 

Included in

N/A

Gen5

Gen7

Z-Wave Plus

No

Yes

Yes

Backwards compatibility

Yes, with 100 series

Yes, 100 to 300 series.

Yes, 100 to 500 series.

Network Wide Inclusion

No

Optional

Yes

Explorer Frames

No

Yes

Yes

Advanced route diversity calculation

No

Yes

Yes

Flirs (Beaming wakeup)

Optional

Optional

Always

OTA Z-Wave firmware updates

No

Optional

Always

Released

May 2005

March 2013

April 2019

If you have any questions regarding Z-Wave, smart home communication protocols in general or other questions, leave a comment and I will answer your questions as soon as possible.
And if you are interested in other smart home communication protocols, check out the tutorial for ZigBee and MQTT.

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