ZigBee, Zwave or Wifi: The best protocol for Home Automation
By: Yelekal Mengistu
ZigBee, Zwave and Wifi are three of the most commonly used 'standards' or wireless communication language to try and make two or more devices talk to each other. While Wifi is more household name, ZigBee and Zwave are relatively to the wireless world. In fact, they have come into prominence in the very consumer driven industry of the smart home. Indeed, the popularity of the IoT revolution has opened the door to some other form of wireless communication medium.
It is noteworthy to mention that these protocols are no different then the usual electromagnetic waves that that come out of the radio. Their composition is the same and so are some of the characteristics. The latter are pivotal in differentiating the benefits and the drawbacks of the protocols in this article.
We intend to simplify it to the basic t and offer a greater hold on the understand of these wireless communication standard protocols. So what better way then to start from the actual science where the magic happens: Radio Frequency.
What is Radio Frequency?
Are you confused with all these names: ZigBee, Zwave, Bluetooth and HTTPS? If you're into smart automation, understanding these principals is essential. You see, all wireless devices connect with each other using a radio frequency, which is essentially a measurement of the oscillation of an alternating electromagnetic current in the range of 20 kHz to 300 GHz, where a Hz is identified as a cycle per second.
This type of traveling current creates a spectrum that is spaced out in different frequencies. Frequencies are one of the two distinct characteristics that define a radiation spectrum. They represent a single oscillation in the spectrum. The second attribute is wavelength, this represents the length of a wave in one frequency. By multiplying the Frequency by the wavelength, it is possible to calculate the speed at which the wave is traveling. However, nature dictates that any wave on the electromagnetic spectrum travels at the same speed which is the speed of light.
The Frequency and Wavelength are two inversely proportional attributes
Taking into consideration that the speed is constant, we can try to analyze these two characteristics, we can deduce that they are conversely proportional, this is to say that if the frequency is high, then the wavelength is short and if the frequency is low, then the wavelength is long. This is all nice, but what does this mean for the actions incurred by the waves?
Well, it is all down to the electromagnetic radiation energy. This is existent on all ends of the spectrum but it becomes considerably dangerous when it reaches the ultraviolet stage so at around 10^19 Hz. Starting at this stage, the radiation waves produce enough energy to disassemble electrons in chemical bonds, effectively destroying the principle atomic structure which could trigger a genetic change of any DNA. Radio frequency waves that we are exposed to are not harmful, the most common wave type being the 2.45 GHz commonly enjoyed by smart home device protocols.
So these protocols are the main event: ZigBee, Zwave and Wifi are similar but different in a lot of ways. By defining the wave frequency in an electromagnetic spectrum, we can say that Zwave has the lower frequency rate than the other two. Now, this translates to better attenuation or 'reachability' for other Zwave compatible devices: low frequency, higher wavelength (remember). But this also means that its bandwidth is sacrificed due to the converse being true.
Impact on Smart Homes
These three main wireless protocols have opened the door to consumers for their choice of smart home products. The most traditional protocol is 'Wifi'. And that in itself is not very self explanatory because what is Wifi other than another protocol powered by electromagnetic waves? Well, unlike Zwave and ZigBee, Wifi processes the most standardized protocol of them all. AS mentioned, Wifi protocol has a frequency of around 2.45 GHz, same as the ZigBee network. However, Wifi is more disruption proof thanks to its 802.11N, an open protocol, which is to say open to any manufacturer to implement using one common software language.
The 802.11 open protocol comes in different frequencies
With that in mind, there will never be an incompatible Wifi device because the protocol is the same. If there is Wifi, you're device, be it your smart phone, tablet, laptop or smart thermostat, will connect to an access point (your wireless router) and talk to each other to send and receive information over the internet. Such is the convenience attributed by this specific protocol. This also means that even if you have your day to day devices tuned in on your existing Wifi network (laptops, phones etc..), there is no need to add/create another network to accommodate your other set of devices, let's say your smart home devices.
Working off one access point can seem to be tricky in concept but this set up is actually very fitting as all devices connected to the Wifi network operate in an orderly fashion, whereby using the access point to let one operation finish so it is possible to move on to the next, reducing interference in the network. This capacity is supported by a special protocol that is called TCP/IP protocol. TCP/IP which stands for Transmission Control Protocol/Internet Protocol, is "a set of standardized rules that allow computers to communicate on a network such as the internet". The folks over AvastAcademy go further into detail by explaining that the TCP/IP protocol is indispensable in order for computers to communicate via the internet.
That being said, the IP "is the part that obtains the address to which data is sent. TCP is responsible for data delivery once that IP address has been found". So their collaboration is important for the communication of devices such as IoT devices for instance. Another aspect of this protocol is that it organizes the fragmented data sent by one device, creating what's called packets, and placing them in the right layer of data on the receiving end. This ensures that each segment of the data is received without any loss. The process of which requires validation to insure the transmission.
So getting back to our smart home devices, this type of back and forth might seem ideal for the safe travel of wireless commands. And it is very ideal but what this does is require more data transmission so more power consequently. Devices which use the other networks so ZigBee or Zwave are less power consuming then those dependent of Wifi protocols.
ZigBee, Zwave and Wifi powered devices and their secure storage
Zwave compatible devices
Fibaro Flood Sensor
Kwikset Obsidian Smart Lock
Ring Door/Window Sensor
Oomi Dual In-Wall Switch
Logitech Home Harmony Hub Extender
August Smart Lock
Zipato Bulb 2
Yale Keyfree Connected
D-Link mydlink sensors
Somfy ILT Series blinds
ADT Security Hub
GE Lighting Control
The list contains home security devices, a logical ascertainment given Zwave’s long range connectivity and unique protocol.
Speaking of security, data over a wireless protocol is also prone to breaches. Some protocols are more robust than others and that's the case here. Interestingly, Wifi is considered as the least safe protocol and it all has to do with cloud storage. You see, most smart home devices that connect through Wifi (uniquely through) don't need a hub to work. And even if they do, they are powered through the Wifi network using a lot of power to stay working. This set up increases vulnerability even more.
Zwave devices interconnected by a mesh
A lot of proprietary brands are ZigBee friendly. After all, next to Zwave, it is the only non-internet power standard protocol that is hovering over the 2.4 GHz frequency. According to the SHN or the Smart Home News team some examples include:
Amazon Echo Plus
Hive Active Heating and Accessories
Yale Smart Locks
Bosch Security Systems
SAMSUNG Comcast xfinity Box
With ZigBee, the options are more broader: best part if you can get yourself a hub like SmartThings or Wink, you can easily set all devices up on one go. Despite this convenience, it’s worth nothing that not all ZigBee powered devices will communicate with each other. And this is down to the manufacturers you choose.
A display showing some key ZigBee and Zwave devices
Choosing the best Network Protocol
Well we've seen how these protocols work and what kind of infrastructure they bring to the home automation process. Going through the different set of bandwidth, attenuation and security efficiencies give us an idea of which is best to choose from. However, this particular choice might rest on what you're looking of doing with your smart devices.
Zwave is distinctive in that it offers a lower frequency protocol, meaning it has greater 'non line of sight' range compared to its counterparts. But the Trade-off here is that it will compromise in bandwidth, running data slower than ZigBee or Wifi. In addition, Zwave is a trademarked brand that is solely manufactured by one company Sigma Designs. This enables it to license the Zwave protocol for smart device manufacturers to incorporate. The positive here is that if two devices are Zwave compatible, then no matter what the brand, they can communicate with one another.
However, since there is no leeway on other licensees, Sigma has control over market pricing. Thus, most of the times, Zwave products are slightly pricier. On the other hand, ZigBee is less restricted, with its protocol free to be programmed as manufacturers see fit. That being said, this flexibility means that not all ZigBee powered devices will understand each other, although the main tools of communications might be the same (keywords, prompts etc…but not enough words to format a sentence).
There is a specific behavior that is visible when trying to connect two ZigBee powered devices. There will be an acknowledgement but no action will be made. Which leads us to understand how mesh networks work. A mesh is simply a collection of devices that are tied together through radio frequency waves. It works by relaying a signal from one device to another, doing so until it hits the central nervous system, a hub. The hub is, like the access point, responsible of ordering the commands of specific devices according to the inputs received. Zwave and ZigBee devices mostly use hubs to tie in all their devices. The hub is responsible for relaying the message to that specific device so it can do its job.
It does so by doing 'hops' from one device to another, relaying information to the hub. With more hops, it puts a strain on the speed of the data that is flowing. In an effort to mitigate this effect, Zwave limits the number of hops to 4 while ZigBee has no restrictions. Theoretically, increasing the number of devices to relay to increases that the hub is reached to perform the desired command. They will act just like nodes that exist in the lymphatic system of the body, being intermediates when needed to. This is fitting for Zwave devices as they speak the same language but for ZigBee, setting up two different brands working with their own mesh networks might create interference.
Since they work on the same frequency, chances are there will be disruptions. Be that as it may, ZigBee is more likely be more prominent with branded proprietary networks like PHILIPS Hue. As such, they open the door to more compatibility even if they would have to create separate meshes for each brand of products.
(source: IoT Industrial Devices)
The ZigBee mesh: tying together all the devices on its network
Something is brewing…
Recently, some of the big players of the Tech industry: Amazon, Apple, Google, ZigBee and other prominent companies, announced that they were working on an encompassing system to allow multiple protocol power devices to be managed and controlled centrally. They called it 'Connected Home over Internet Protocol' or C.H.I.P. The premise of this project is to allow consumers to choose from an array of smart home products that are compatible with each other. This applies for functionality, storage, applications and more.
This is a big step for home automation since one of the biggest hurdles that is preventing new comers into the automated home world is the lack of consistency between products, leaving potential users to question whether or not they should buy one device over another.
A recent article by howtogeek.com has highlighted the upcoming steps to be taken. Josh Hendrickson in his article What is "Project Connected Home over IP" for Smart Home, cites the difficulties that led to the inception of the project. He also adds that although this might seem like a big and revolutionary change, the idea behind it is very simple and incrementally innovative than the standards we use today.
Companies already established in the smart home sector are developing an open source , royalty free home automation standard
"They (manufacturers) rely on Internet Protocol or IP as unifying standard to tie everything together. IP has been around for ages, and manufacturers understand its benefits and security needs". Josh makes the argument that since IP is already widely accepted in the smart home device community, it's easier to build on it a create a platform that will be seamlessly adopted by "Manufacturers (who), in turn, would need fewer resources to create smart home products and to maintain them".
Due to the project being in its infancy, even the C.H.I.P website doesn't offer much in terms of detail. Yet the idea is very clear: define a common language for smart devices without compromising the existing hardware. The work is deemed to be done on the back end, focusing on protocol rather than enhancing chip models. This is a relief amongst the current and (future) smart home enthusiasts.
One peculiar thing to mention is the absence of the Zwave brand from the project. Zwave being sometimes the stubbornly option from the other two protocols, this might signal the beginning of the end of a highly standardized protocol. The truth to this will be revealed in the near future.
ZigBee users can also take comfort by the fact that the centralized all encompassing protocol will solve their interfering meshes that we talked about earlier.
Whatever your need in the quest for home automation, the ZigBee, Zwave and Wifi protocols will always be ever present. Although they are similar in many ways, they do posses different attributes that might be dismissive when it comes to picking out the best smart devices or systems to implement.
The first point of comparison is the frequency of the electromagnetic wave. ZigBee, Wifi and even Bluetooth use the more conventional 2.45 GHz band. While Zwave is usually around the 0.9 GHz range. Now the relationship between the frequency and the speed at which the data can travel, otherwise known as the bandwidth, is a proportionally inverse relationship. The higher the frequency so the faster the bandwidth, the less ability the signal is able to travel. Similarly, when the frequency is low, the bandwidth is low but the signal has a better non line of sight range. Therefore it’s a matter of sacrificing bandwidth speed for better range or vice versa.
Depending on what kind of a sophisticated smart home ecosystem you want to set up, there are numerous options to consider. ZigBee and Zwave are identified as light weight protocols, meaning that they don't carry the amount of data that heavier protocols do, in a sense, they carry the essentials and leave out all the 'extra weight' like process validation, lowered data redundancy and also less fault tolerance (Additional setup or configuration that prevents a computer or network device from loosing connection in the event of an unexpected complication).
With that in mind, ZigBee products are cheaper by comparison and offer variety. Yet they might be hard to gel with other propitiatory ZigBee powered devices due to the specific manufacturers using around the 2.45GHz ballpark frequencies. Zwave products are much more robust when it comes to connectivity: they only understand each other and won’t interfere with each other even if you wish to set up more than one Zwave mesh in your home. However pricing and a lack of local storage capability might deter potential users (unless you HomeAssitant or Hubitat). As for Wifi, data privacy is an even bigger issue, your router will have direct communication with your devices, throwing the notion of a closed network out of the window. A way around this is MQTT, a light standard protocol that uses the internet to send messages to devices. Basically creating a local Wifi network. Wifi’s direct communication has regardless outfoxed ZigBee’s and Zwave’s approach to connectivity.
Bottom line, with announcement of the C.H.I.P program, the smart home infrastructure is going to significantly change. That is not to say that your ZigBee, Zwave or Wifi devices will become obsolete far from that. On the contrary, should a unified protocol come about, it will tie together the existing hardware, clearing up any compatibility issues. Based on that promise, it is safe to say everything you just leaned about the wireless protocols has just been acquired for your general knowledge. Because, if C.H.I.P comes into fruition, preferential treatment will be dropped and everything will talk the same language. It might just be a matter of when rather than how?