Design Con 2015

The future of home automation – ZigBee or Z-Wave?

-December 14, 2013

Introduction

 

There has been an ongoing debate between which technology is the best overall solution for Home Automation: ZigBee or Z-Wave? Obviously one will win but can we predict which one?

                                                              

According to the ZigBee Alliance, ZigBee Home Automation offers a global standard for interoperable products. Standardization enables smart homes that can control appliances, lighting, environment, energy management and security as well as the expandability to connect with other ZigBee networks.


On the other hand, Sigma Designs explains Z-Wave as a wireless RF-based communications technology designed for control and status reading applications in residential and light commercial environments. Target applications for Z-Wave are home entertainment, lighting and appliances control, HVAC systems and security.


So what is the difference then?

 

Comparison

 

As one can read in the introduction, both technologies address similar environments and applications. Let’s dive into the details in order to find out the differences, as well as the pros and cons of using each technology.

 

PHY and RF

The first obvious difference is in the physical layer. Z-Wave took the Sub-1GHz approach, which has superior range versus the 2.4GHz approach of ZigBee. However, Sub-1GHz home automation requires different SKUs for different regions. How many? Well it depends – for Australia and Brazil this is 921.4MHz, China and Singapore at 868.4MHz, Russia at 869MHz, India at 865.2MHz, U.S. at 908.4MHz and Japan at 2 other bands. So there is no “one product fits the whole world” solution as there is with the ZigBee Home Automation.

 

Z-Wave uses frequency-shift keying (FSK) modulation and I believe this is good enough for the Sub-1GHz environment. ZigBee is based on direct sequence spread spectrum (DSSS) which is a more advanced and robust modulation.

 

Here are two very practical notes:

  • ‒    Both ZigBee and Z-Wave are mesh networks, so usually you can rely on the mesh to connect remote devices which do not connect directly.
  • ‒     Due to the use of the Sub-1GHz range for Z-Wave, there is a need for a larger antenna. Usually 2.5 times larger. As we all want to have smaller products, it actually limits the range advantage of the Sub-1GHz technology.
 

Available Silicon and SW

When it comes to availability of silicon and software, there is a huge difference between ZigBee and Z-Wave.

 

ZigBee chipsets are developed and manufactured by multiple silicon vendors including Texas Instruments, Atmel, Silcon Labs, Freescale, STMicroelectronics and more. Whereas, Z-Wave products are only manufactured and sold by Sigma Designs.

 

If we compare packaged modules – the picture is the same, multiple ZigBee module makers vs. very few of Z-Wave (I found only the Digi-Sigma Designs collaboration).

 

When it comes to software, there is even a bigger gap. ZigBee software has multiple vendors. Larger silicon manufactures will develop their own software and provide that to their customers. (Texas Instruments, Silicon Labs, etc.)

 

Protocol aspects

Both ZigBee and Z-Wave are supporting mesh network topology, which is a strong requirement towards the revolution of “internet of things”.

 

The number of nodes you may support with a single Z-Wave product is limited to 232 (theoretically), however practical use cases will support a 10 nodes network. The number of nodes you may support with a single ZigBee network is 65,000 (theoretically), however practical use cases support a 500 nodes network (on a single channel, single PAN ID). IEEE 802.15.4 networks (the foundation layer of ZigBee) can practically support thousands of devices. Perhaps more than the network capability to run a specific number of nodes, it’s important to look at the memory capabilities of the devices. ZigBee devices has wider set of memory options, up to 512KB of Flash and 32KB RAM from certain silicon providers, hence they can for sure handle more nodes in their networks.

 

Interoperability is a big issue. The Z-Wave protocol is not open, and can be provided only under licensing with Sigma Designs and can only run on their silicon receivers. The Z-Wave devices will interoperate well with similar Z-Wave devices. The challenge is the limited set of devices and architectures you can support. ZigBee on the other hand, as an open industry standard, will allow interoperability with any ZigBee certified device. ZigBee has defined several profiles per market segments. The ZigBee Home Automation standard is fully interoperable with a variety of devices such as door locks, sensors, alarms, smoke detectors, blinds, motor control etc.


The same device can also interoperate with other profiles such as ZigBee Light Link (LEDs, CFLs, light sensors, light switches, etc.). There are a few silicon vendors that are providing a complete interoperable solution today. One example is Texas Instruments who is providing the CC2538 device, which can fully interoperate between ZigBee Home Automation, ZigBee Light Link and ZigBee Smart Energy networks.

 
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