When you start to plan your smart home system without a doubt one of the first questions you are likely to face is should my system be built using Z-Wave or ZigBee based devices? To answer the question of which smart home protocol to use we must first get a basic understanding of each standard and how they compare to each other, so let’s get started.
Why not use a Wi-Fi network?
Most people unless living under a rock have heard of and probably use a Wi-Fi network in their home. Wi-Fi networks use what we call a star configuration to communicate with devices on its network. In the star network the hub or router is the central point and each device communicates directly with and only with the router or central hub. The problem with Wi-Fi and the star network configuration is that as the distance between devices and the router or hub increase the strength of the signal decrease.
If the distance of a device is out of the transmitting range of the router or central hub, that device will not be part of the network. The problem is only multiplied by the fact that when the signal travel through obstacles such as walls and ceilings the signal is weakened thus reducing its range capability’s. It is because of these limitations not to mention the fact that our internet and TV signals live on this network that Wi-Fi is an extremely poor choice for building our smart home network.
Using Z-Wave or ZigBee devices to build our smart home
Welcome to Z-Wave and ZigBee these two technologies use what we call a mesh network, both protocols like Wi-Fi use wireless signals but operate somewhat differently than the star type network. In the mesh type network the signal originates from the hub just like the star network, however some of the devices in system act as repeaters and pass the signal along or hop to other devices in the network.
The passing along of the signal between devices extends its effective travel distance while also greatly reducing signal loss due to obstacles such as walls and ceilings in turn greatly increasing the reliability and efficiency of the network. Okay so now that we know a little bit about the mesh protocol and how it works, lets take a closer look at both Z-Wave and ZigBee and how they differ from each other.
Z-Wave vs. ZigBee
We know that both Z-Wave and ZigBee use the mesh type network protocol but separates the two technologies? The big characteristic that set the mesh network apart from the star is its ability to have the signal be repeated or hopped between devices. Z-Wave networks support up to four hops between the controller or hub and the destination device and ZigBee networks are not limited to any specific number of hops.
The Z-wave network has the capability to support up to 232 devices whereas a ZigBee network can support up to 65,000. I think that it is worth noting that the specs are maximum ranges and you would likely run into serious bandwidth issues long before you were to reach any of these limits, further more unless you live in a 1,000,000+ sq ft mansion I doubt you would come close to the max number of devices for either protocol.
Both Z-Wave and ZigBee use very little power, as a matter of fact most devices that are battery-powered can run for several years without the need for a battery change. Devices in the network that are setup to act as repeaters need to be or should I say are suggested to be hardwired. Devices acting as a hop point or repeater draw a lot more power, so remember when designing your system, battery operated devices should not be programmed to act as repeaters.
Z-Wave and ZigBee and their level of compatibility
Both Z-Wave and ZigBee have a high degree of Interoperability meaning that when you go out to by devices to build your system those devices will be able to communicate and work together right out the box without any type of tweak or work around or to put into modern terms plug and play.
Z-Wave is a proprietary technology that was originally developed by the Danish company Zensys in 2001, in 2009 Z-Wave was sold to Sigma Designs and recently this year sold it to Silicon Labs. Z-Wave is run by the Z-Wave Alliance which controls the certification of all Z-Wave devices. In my opinion Z-Wave has a small advantage over ZigBee for its interoperability due to the exceptional certification process that is enforced by the Z-Wave Alliance.
The Z-Wave Alliance makes sure that every Z-Wave device complies to a strict set of standards and that every Z-Wave certified device will work with every Z-Wave certified controller. Z-Wave works with somewhere around 600 manufactures and between them produce around 2100 Z-Wave certified products. All of these products bear the Z-Wave or Z-Wave plus logo and are able to implemented seamlessly in any network that have Z-Wave devices installed.
ZigBee is an open standard controlled by the Zigbee Alliance established in 2002 that was originally created for commercial use before transitioning into the smart home market. ZigBee has a well-known stigma surrounding its technology that it has a lack of interoperability, this perception may be a little undeserved. In my opinion a large part of the stigma that surrounds ZigBee stems from its two levels of certification.
One level certifies the hardware and the other certifies the software, so it is possible that a manufacture may get their hardware certified but not their software. The result is devices that are broadcasting the ZigBee signal but using software that is not certified and the device in question fails to work even though it bears the ZigBee ready logo.
There are many ZigBee ready products on the market that are interoperable they just got a bad name because of their complicated certification process. In order to ensure a Zigbee product is in full compliance with the Zigbee protocol, you just have to make sure the product uses the ZigBee Home Automation certification.
ZigBee vs. Z-Wave signal range
We touched a bit on the range of mesh type networks as compared to star networks, however we did not take into account a few other factors that can effect this measurement. Any good smart home network needs to have the ability to reach the farthest corners of your home regardless of the obstacles that it may have to face.
When designing your system this is a fact that you will do well to remember because ignoring this can have a serious impact on your system performance. No one can tell you the effective range of a wireless signal in your home without doing a visual observation because the actual range in your home will depend on many factors. What I can tell you is that the power level and frequency of your controller or hub will determine the range capabilities of your signal.
ZigBee operates at 2.4 GHz compared to the 908 MHz of Z-Wave. The higher frequency allows ZigBee to transmit more data but reduces the range of the signal. A higher frequency is less effective at traveling through obstacles like walls than a lower frequency signal. A Z-Wave signal traveling between two devices can go up to 300 feet in an unobstructed setting with no electrical interference for ZigBee somewhere around 100 feet .
The same signal gets significantly reduced in your house when you consider obstructions like walls, ceilings and various sources of electrical interference that reduce the effective distance of your signal. A good rule of thumb to go by when comparing signal travel distance is ZigBee between 33 to 66 feet, and Z-Wave 100 feet.
ZigBee vs. Z-Wave reliability
Your smart home system needs to be reliable considering you can connect everything from your door locks to your security system. You want your system to be a source of freedom and ease of use not one of frustration because of a device working intermittently or failing to work all together.
Z-Wave operates in the 908 MHz frequency band which means it does not have to compete things operating on the 2.4 GHz band that ZigBee uses and believe me that frequency range can get pretty crowded. You may also experience poor reliability if your network is not making good use of repeaters around obstructions and corners. Since Z-Wave devices have a greater effective range than ZigBee, you can expect fewer design challenges and reliability problems stemming from range issues. In my opinion Z-Wave in the hands of a novice will typically yield better results in respect to reliability due to its greater range capabilities and operating frequency.
Z-Wave vs. ZigBee security
Your home automation system may very well consist of many sensitive components that may include but is not limited to security systems, door locks, surveillance cameras and maybe more, so having a secure system is a top priority. Both Z-Wave and ZigBee use the AES 128 encryption standard. This is the same encryption used by banks and government and is one of the most secure protocols on the market.
There is no one that can guarantee your system will be 100% hack proof no matter what type of encryption you use, however I would go out on a limb and say that it is HIGHLY unlikely that anyone is going to hack your Z-Wave or ZigBee based network.
There is one point that I would like to bring to your attention, back in early 2016, Z-wave got a reputation for being insecure, however the allegation was not really warranted. The security lapses that the allegations referred to were caused by implementation errors that were used by certain manufactures of Z-Wave products. Even though the high-level encryption standard was available, some companies chose not to use it so the fault was not with Z-Wave but with the companies that made a bad decision not to implement the security standard.
Well anyways on a good note The Z-Wave Alliance now requires AES 128 encryption on all Z-Wave powered devices in order to get it certified so this should never be problem again going forward. Moving forward to the present day as of April 2, 2017 The Z-Wave Alliance requires a mandatory implementation of their new Security 2 (S2) framework on all devices receiving the Z-Wave certification.
This latest security update enables manufacturers to offer best-in-class security without any compromises in terms of power consumption or latency by using a single command structure that replaces a previous three-step process, and, it helps to prevent your Z-Wave devices from being used in a DDOS attack. The details of how it accomplishes this are a little beyond the scope of this article, but if you’re interested in learning more, you can see the interview with Sigma Designs’ Vice President Bill Wong.
Both Z-Wave and ZigBee are very robust and capable smart home technologies and technically it’s not necessary to choose one protocol or the other, however sticking with one can be advantageous. A mesh network will become more reliable as you add more devices because of its unique functionality of having the transmitted signal hop from one device to another. A Z-Wave network with 20 devices will tend to be more reliable than a Z-Wave network that has 10 devices or a ZigBee network that has 10 devices.
My official opinion on which protocol is better
If I had to choose one technology over the other, my choice would be the Z-Wave platform. The novice that is installing his or her’s first home automation system will have a much easier time putting together a highly reliable Z-Wave powered network vs. a ZigBee powered network. The Z-Wave Alliance’s robust certification process coupled with Z-Waves longer transmit distance will make finding products that will plug right into your network a snap.
Adding to all the previous benefits, Z-Waves 908 MHz operating frequency keeps it away from the often crowded 2.4 GHz frequency that ZigBee runs on further reducing the chance of interference and causing unforeseen headaches.
If what I have told you is not convincing enough, like I mentioned above you don’t have to pick one technology over the other. You have many home automation hubs on the market such as the Samsung SmartThings and the Wink Hub 2 that support both platforms enabling you to build a hybrid system. So as you set out to build you home automation system you do not have to feel pressured into going with this platform or that one, just know that you have options and picking one over the other don’t have to be an over complicated process.
Well I know this has been a long article and I hope that after reading this you understand the fundamental differences between the two protocols and you are able to make an informed decision on which one you want to power your home automation system.
