What is Z-Wave

Z-Wave refers to a wireless communications protocol used primarily for intelligent home networks, allowing smart devices to connect with each other and thus exchange control commands and data. As a mesh network, Z-Wave achieves two-way communication through message confirmation. Z-Wave protocol applies to battery-powered devices and introduces the wireless connection at low cost into home/industry automation, providing a longer-term working alternative to Wi-Fi and Bluetooth with low power consumption.

Specification

Frequency

Z-Wave has a radio frequency range of 800-900 MHz, which varies from country/region to country/region.

Frequency in MHzUsed in
908.4; 908.42; 916USA, Canada, Argentina, Guatemala, The Bahamas, Jamaica, Barbados, Mexico, Bermuda, Nicaragua, Bolivia, Panama, British Virgin Islands, Suriname, Cayman Islands, Trinidad & Tobago, Colombia, Turks & Caicos, Ecuador, and Uruguay
868.40;868.42; 869.85CEPT Countries (Europe and other countries in region), and French Guiana
868.4China, Singapore, and South Africa
869Russia
865.2India
916Israel
919.8Hong Kong
919.8; 921.4Australia, New Zealand, Malaysia, Brazil, Chile, El Salvador, and Peru
919 – 923South Korea
920 – 923Thailand
920 – 925Taiwan
922 – 926Japan, and Taiwan

Chip series – SoC (systems on a chip)

Z-Wave is based on a proprietary design, and supported by Sigma Designs as its primary chip vendor. Sigma Designs bought Z-Wave from Zensys back in 2009, and then Silicon Labs acquired the business for a cool $240 million in 2018. Therefore, Silicon Labs is currently responsible for signing off on the software and hardware of Z-Wave Certified devices. In 2014, Mitsumi became a licensed second source for Z-Wave 500 series chips.

2019 – 700 series SoC released, come with new standard: Z-Wave Plus V2

2013 – 500 series SoC released, come with new standard: Z-Wave Plus

2008 – 400 series SoC released

2006 – 300 series SoC released

2005 – 200 series SoC released

2003 – 100 series SoC released

Z-Wave has had some difficult along the way, after all, no one is perfect. Much like the Star Trek Movies, all the even series chips were flawed and quickly obsoleted. The developers became so fearful of the curse of the even series that they skipped the 600 series and jumped straight to 700. The 200 series chips were simply buggy, they had some significant power issues, making them difficult to be used on battery powered devices. The flaws were quickly fixed, and the series replaced with the largely firmware compatible 300 series which had a long and plentiful life. Many 300 series chip-based devices are still in the market, though the chips have reached the end of their lives so there are limited inventories left. A small number of 300 series chip-based devices are Z-Wave Plus – but that number is quite small and there are probably none left on the shelf though you could have one installed in your home. Fortunately, as we’ve seen they are all completely interoperable, so there is no problem.

The 400 series suffered from a marketing mistake early on – the memory that holds the firmware is One-Time-Programmable (OTP), which means the firmware cannot be updated – EVER. You burn it once, and pray it is good. This is a nightmare for developers as they have to replace the chip every time and make a new firmware build, which they typically do hundreds of times per day. While the OTP saves a fraction of cent in the cost of the chip, the drawbacks it brought far outweigh that tiny cost. Fortunately, we developers didn’t have long to wait and the 400 series was replaced by the 500 series. The 500 series had plenty of FLASH with the ability to update the firmware in the device, even after it is installed in the field using a technique called Over-The-Air (OTA) firmware update.

The 700 series solution is a next-generation upgrade on Z-Wave 500 series. The new series has come up with added features to improve the efficiency, in addition to the existing features of the 500 series. It is leveraging the effective combination of low power and long-range communication, and designed to meet the future context-aware smart home applications.

https://z-wavealliance.org/z-wave-public-specifications/

Range & speed

To achieve the maximum efficiency, it is recommended to have a Z-Wave device roughly every 30 feet or even closer. While Z-Wave (300 series) has a range of 100 meters or 328 feet in open air, building materials reduce that range. The more line-powered devices in your Z-Wave network, the better, as they also act as repeaters to extend Z-Wave signals. Z-Wave’s mesh networking allows a Z-Wave signal to “hop” through other Z-Wave products to reach the destination device to be controlled. If there is a wall interfering with this signal, all you need is to install a simple Z-Wave repeater or other line-powered device to work around the wall, so the signal can continue to reach its destination. Z-Wave supports up to 4 hops, so the total home coverage will grow depending on the number of Z-Wave products in the network. The maximum range with 4 hops is roughly 600 feet or 400 meters.

On September 8, 2020, the Z-Wave Alliance announces the Z-Wave Long Range (Z-Wave LR) specification, which provides significantly extended wireless range (more than 1,000 meters) and supports star networks. It also increases scalability on a single smart home network to over 2,000 nodes – a 10x increase from Z-Wave.

 300 series500 series700 series
Wireless speed9.6 / 40 kbit/s9.6 / 40 / 100 kbit/s9.6 / 40 /100 kbit/s
Maximum wireless range outdoors (Direct)up to 100 metersup to 150 metersmore than 200 meters
Maximum wireless range outdoors (Max Hop/Repeat)up to 400 metersup to 600 metersmore than 800 meters
Maximum wireless range indoors (Direct)more than 30 metersup to 75 metersup to 100 meters
Maximum wireless range indoors (Max Hop/Repeat)more than 120 metersup to 300 meters 

Security

It’s fair to say that Z-Wave has not had the security that would be expected of its lifetime in the tech industry. This is perhaps a result of it being a closed system that has only become more available to security researchers in the past few years. However, it has begun to attract some more attention, and a few high-profile exploits have now been published. Two of these are caused by the device makers — the result of implementation errors by the device maker, and a failure to use the security features provided by the protocol. More seriously, in the case of the 2018 discovery dubbed Z-shave, a potential design issue in Z-Wave’s backwards compatibility allows for the forced downgrade of security measures between two devices.

2013 – Z-force packet interception and injection

2016 – EZ-Wave pentest tool abuse

2018 – Z-shave security downgrade attack

These discoveries led Sigma Designs to enhance the security model of the protocol in 2015 by adding what was called Security 2 (or S2) to enable certification of Z-Wave systems for security applications. These enhancements added mitigation for a number of attack scenarios including key interception, jamming, and rogue nodes, and were made mandatory for device certification in 2016.

As a result, newer devices, and older ones that support S2, can only be added to a controller that supports the new security requirements. Meanwhile, though non-secure devices (like some remotes) and older controllers may be able to work with other secure devices, they cannot send commands to secure ones.

All newly certified devices are now required to use AES-128 encryption. Security keys are exchanged on every message, except for a couple of Command Classes that have a certified exemption. These make things like remote controls so simple enough that they are not considered security threats.

Features

Z-Wave networks are composed of Internet of Things (IoT) devices and a master controller (commonly known as a gateway), which is the only device that Z-Wave connects to the Internet. When the Z-Wave gateway receives commands from the smart home Apps on a user’s smartphone, tablet PC or computer, it routes the commands to its target devices, with the number up to 232 devices (not verified).

Through the source-routed mesh network technology, Z-Wave signals can be sent to the devices that users need to control through other Z-Wave devices. Each Z-Wave network has a maximum of 4 hops.

Z-Wave provides small-packet transmission rates with a throughput of 9.6kbps, 40kbps, or 100kbps. Z-WavePHY and MAC layers are based on the ITU-T G.9959 global radio standard, which adopts GFSK modulation and Manchester coding. It also contains AES 128 encryption, IPv6, and multichannel operations.

In terms of battery life, Z-Wave-based devices can operate up to 10 years with a coin battery, while other battery-powered devices can theoretically operate for only one year or more.

All Z-Wave technologies are backward compatible.

Device type

Z-Wave accommodates three basic types of devices:

Controllers – these are the basis of the Z-Wave network and manage security and control of the devices on that network.

Routers – These are continuously powered devices like light bulbs that can act as relays for control signals to more distant devices on the network.

Slaves – Typically battery powered, these devices are those like wireless sensors which need to be able to last long periods on small batteries alone. They send and receive data as required, but don’t act as relays to conserve battery life.

Certification

To use the Z-Wave brand logo, intelligent home products must be certified by Z-Wave Alliance first, which puts forward many requirements. Above all, these products can interoperate with all other Z-Wave certified devices if certified. (Similar to Zigbee, intelligent home products without certification can also be put on the shelf.)

Certification of devices to Z-Wave standards is required as part of the Trademark and Distribution License agreement, and every device must pass a series of tests to ensure that it is compliant to Z-Wave standards prior to the device being marketed or sold commercially. The Z-Wave Plus logo on a product or package assures customers, consumers, dealers, integrators and service providers that the product will be reliably compatible with all Z-Wave certified products designed for the same region.

Resources

Difference between Z-Wave and Z-Wave Plus

https://www.z-wave.com/

https://www.z-wave.com/learn

https://en.wikipedia.org/wiki/Z-Wave

https://z-wavealliance.org/

https://www.silabs.com/

https://www.silabs.com/products/wireless/learning-center/mesh-networking/z-wave