Smart Home

Methods of Communication

Making Sense of Smart Home Protocols Now and in the Future

By Jay Basen

When I first started automating my home in the 1980s, X10 was the only protocol that enabled information to be communicated between smart home devices. Thankfully, there is now a wide range of modern smart home protocols and devices that incorporate them. Protocols used by today’s smart home devices include:

Zigbee, Z-Wave, Z-Wave Long Range, Bluetooth Low Energy (BLE), Wi-Fi, Thread, HomeKit, DotDot, and Sidewalk.

With much thanks to Johan Pederson, manager, product marketing – smart home & consumer IoT at Silicon Labs, this article will try to make sense of today’s smart home protocols and talk about the changes coming in the near future.

The Zigbee standard was developed by the Zigbee Alliance, which re-branded itself as the Connectivity Standards Alliance (CSA) in 2021. Today, the CSA is a consortium of more than 350 companies in more than 37 countries and is “on a mission to simplify and harmonize the IoT.”

Zigbee is an open standard wireless protocol designed to allow IoT devices to communicate with each other. Its devices primarily operate at 2.4 GHz, which is the same frequency range as Wi-Fi. Similar to Wi-Fi, Zigbee breaks down the 2.4 GHz frequency spectrum into a series of channels, so a channel can be chosen for devices to communicate on to minimize the amount of interference from Wi-Fi. Zigbee devices operate as a mesh network, which will route communications through other Zigbee devices in the home to work around interference.

Theoretically, up to 65,000 Zigbee devices can exist in a single Zigbee mesh network. However, the practical limit is more on the magnitude of a few hundred, which should be more than adequate for even a very large smart home.

The Zigbee protocol is designed to be very secure and also very reliable. It includes 128-bit AES encryption and offers features such as retries of lost messages and acknowledgements when messages are received.

Zigbee devices theoretically have a range of between 75 and 100 meters indoors, but a more practical limitation is around 40 feet. The mesh networking ability of Zigbee devices, for the most part, negates this limitation as communications can hop from one Zigbee device to another.

The data rate of communications between Zigbee devices is 250 Kbps. Wi-Fi speed, in comparison, is measured in Mbps (1 Mbps is 1000 times faster than 1 Kbps). So, while the speed of Zigbee is perfectly adequate for communications between, for example, a smart light switch and a Zigbee hub, it isn’t a protocol that you would want to use for streaming video

from a high definition security camera to a smart display.

Whereas Zigbee devices primarily operate in the 2.4GHz band overlapping the frequencies used by Wi-Fi, Z-Wave operates at 908/916MHz in the U.S. This lower frequency eliminates any interference with Wi-Fi. In addition, the lower frequency does a better job of penetrating through the walls in a home.

Z-Wave devices can reliably communicate at distances up to 100 meters, but the lower frequency range of the protocol means that data throughput is lower. Z-Wave only transfers data at 10-100kbps, which is still adequate for

Z-Wave

Wi-Fi

communications between a typical Z-Wave device, such as a light switch and a smart home hub. A Z-Wave network can include up to 232 devices.

Z-Wave uses 128-bit AES encryption and is also UL 1023 compliant for security applications.

It is also important to keep in mind that the SmartThings hub, Hubitat Elevation hub, and others include both Z-Wave and Zigbee radios, so a homeowner can include devices from both standards in their smart home.

The first thing to understand about Z-Wave Long Range is that it is no longer a mesh networking technology. Instead, it uses a star topology where each device connects independently to a hub.

At first glance, this would appear to be a significant step back. However, unlike traditional Z-Wave’s range of up to 100m per hop, a Z-Wave Long Range device can communicate with a hub that is up to a mile away. In addition, a Z-Wave Long Range network can consist of up to 4,000 devices.

Z-Wave Long Range devices operate at 912/920MHz so, like traditional Z-Wave devices, they will not interfere with Wi-Fi or Zigbee devices.

Z-Wave Long Range devices are backward compatible with existing Z-Wave installations, and each device can participate in a normal Z-Wave mesh network if there is no Long Range capability in the Z-Wave gateway/hub.

These devices require very little power. In fact, the estimated battery life for a basic coin-style battery that powers a Z-Wave Long Range device is 10 years. 128-bit AES encryption for security.

Bluetooth Low Energy (BLE) supports mesh networking and much lower power consumption than “classic” Bluetooth. In addition, a BLE mesh network can theoretically consist of up to 32,767 devices.

BLE does operate in the same 2.4GHz band as Wi-Fi, but it utilizes 40, narrow, 2MHz channels and “hops” among the available channels to avoid interference.

While classic Bluetooth has been subject to security exploits, BLE uses 128-Bit AES encryption to create a highly secure mesh network.

BLE devices typically have a range of only a few meters due to being battery-powered and the corresponding need to save energy by limiting transmitter power.

A typical use case is for a “beacon,” which is a small devices that transmit signals over the protocol in a home where a person’s location can be used to drive smart home automation.

Wi-Fi is the most ubiquitous network in homes with broadband internet access so, on one hand, it makes sense to use it as the basis for communications to smart home devices in a home.

With Wi-Fi, there’s no requirement to purchase a hub, no additional knowledge required to add smart home devices to the network, and a large number of smart home devices from which to choose. Wi-Fi-based smart home devices also tend to be less expensive than smart home devices that use other protocols, and Wi-Fi is a strict standard, so any Wi-Fi device can communicate with any Wi-Fi router, access point, or range extender. disadvantages of using Wi-Fi as the underlying protocol for your smart home. For instance, as the number of Wi-Fi devices grows, the amount of RF interference also grows. Additionally, most residential Wi-Fi networks use a single subnet, which limits the number of devices to 255, but many routers can’t even handle this number of simultaneously connected devices.

Another limitation worth noting is range. Wi-Fi also operates at 2.4GHz and 5 GHz. So, while devices connecting to a Wi-Fi network at 2.4GHz have a practical range of 150 feet, conversely devices connecting at 5GHz only have a practical range of 50 feet

Thread is an open source wireless mesh networking protocol based on industry standard IPv6 addressing. Thread mesh networks differ from Zigbee and Z-Wave networks in that there is no hub required that could fail and take down the entire network. Instead, all IoT devices on a Thread network can communicate on a peer-topeer basis, and the network uses one or more “border routers” that forward data to the remainder of the homeowner’s Ethernet/Wi-Fi network, the internet, and cloud services.

If a border router fails, another device with border router capabilities can take over the job of communicating between thread devices and the homeowner’s Ethernet/Wi-Fi network, the internet, and cloud services.

Thread is able to minimize the power requirements for its devices by leveraging IEEE 802.15.4 for the physical layer of the protocol. Utilizing 802.15.4 also means that Thread operates in the same 2.4GHz band as Zigbee and Wi-Fi. It also has a similar range and the same throughput of Zigbee. Finally, like Zigbee and Z-Wave, Thread utilizes AES encryption for security.

Amazon Sidewalk

that passes between a user taking an action, such as pressing a button to turn a light on, and the response of the light turning on.

While all the above sounds great, currently there are very few smart home devices that implement Thread. In coming years, this is expected to rapidly change as Thread becomes one of the core components of the Matter protocol (see below.)

HomeKit is a proprietary smart home framework that provides for control of HomeKit-compatible smart home devices by Apple products, including iPhones, HomePod smart speakers, etc.

HomePods and AppleTVs can act as hubs to perform automation when, for example, a homeowner is away from home with their iPhone. In addition, HomePods and AppleTVs can also participate in automation and scenes to, for example, start playing music when a motion detector senses that a person has entered a room. HomeKit-compatible devices communicate using Wi-Fi and Bluetooth.

DotDot is another standard under the CSA umbrella. It is a layer that is designed to sit on top of communications protocols and allows IoT devices to talk to each other. Two devices that implement DotDot will be able to communicate even if one device connects to a hub using Zigbee and the other connects to the hub using Wi-Fi. DotDot is part of the Zigbee 3.0 specification and helps solve the incompatibilities between different Zigbee devices.

Amazon Sidewalk extends a homeowner’s network through select Ring and Echo products (which can act as a Sidewalk bridge) to create a neighborhood-wide network. Sidewalk-enabled devices can then connect back to your smart home even when out of range of your network. Instead, the Sidewalk-enabled device will connect to a neighbor’s Sidewalk bridge, utilize a small portion of that homeowner’s internet connection and connect back to your smart home.

Sidewalk uses low-energy Bluetooth and 900MHz radio signals to allow Sidewalk devices to connect at distances up to one-half mile. It is also important to know that Amazon limits the amount of bandwidth a homeowner shares with their neighbors through the sidewalk to 500MB per month.

A potential use case for Sidewalk? A dog with a Sidewalk-enabled tracking collar escapes from its owner’s backyard. As the dog wanders around the neighborhood, its tracker connects back to the owner’s smart home by connecting to a neighbor’s Sidewalk bridge. In this way, the homeowner can locate their lost dog even though she has wandered out of range of the homeowner’s network.

Matter is the newest protocol for IoT wireless communications. It promises to be a unifying standard that will allow all IoT devices to work together. If you think that Matter will just be another competing standard that confuses consumers and complicates smart homes, you are probably wrong.

First, and foremost, you have to look at the companies behind Matter, which include Amazon, Apple, Google, and Samsung SmartThings. These companies have recognized that it is in their best interest to have IoT devices that are compatible with all of their platforms. Then they can differentiate themselves among competitors by building the best possible platform, but device makers only have to build IoT devices for one protocol specification, rather than four.

Matter is built on top of existing standards, including Thread and DotDot, so existing Thread and even Zigbee devices may be able to be upgraded to Matter with only a firmware update. Matter also leverages and builds upon the existing security layers within these standards.

Matter will be royalty-free, which keeps the price of IoT devices that use the Matter protocol low, and it’s being developed as an open-source project. The software is available for download on Github and licensed under the Apache open source license. The availability of a referencesoftware implementation of Matter should speed up development of the Matter-based IoT devices by manufacturers.

Adding Matter devices to an existing smart home doesn’t mean you have to throw away all your existing Z-Wave and Zigbee devices. First, you may be able to install a firmware update to some Zigbee devices that converts them to Matter. However, that won’t be the case for Z-Wave devices. Fortunately, the Matter consortium thought about this problem.

According to Johan Pederson, in the CSA and Z-Wave Alliance there is work on-going defining bridging specifications, meaning smart home hub manufacturers can update their systems to assign a Matter-compatible, virtual, IPv6 address to each Zigbee and Z-Wave device connected to the hub. Then Matter IoT devices will be able to communicate with these devices to create a cohesive ecosystem.

Since Samsung SmartThings is a member of the Matter Consortium, you can be sure they will implement this functionality in the SmartThings hub. It will be up to other smart home hub manufacturers to follow their lead.

I’m sure there will be missteps and problems as Matter devices become available in 2022, but those problems should be short lived. In the long run, having a unifying communications standard will be good for the smart home industry. x

DotDot Matter