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Sub-GHz: An Essential Piece of the Smart Home Puzzle

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This article originally appeared in the October 2022 issue of Security Business Magazine. When sharing, don’t forget to mention Security Business Magazine on LinkedIn and @SecBusinessMag on Twitter.

As the diversity of smart home devices and solutions continues to grow – making our lives ever more convenient and connected – understanding the communication framework behind them is more important than ever.

I caught up with my longtime friend Mariusz Malkowski, Director of Customer Success and Integration for Building36 Technologies, to discuss why sub-GHz frequencies continue to be a critical aspect of smart home technology. , as well as future prospects for devices and solutions. using sub-GHz.

The genesis of the smart home

Ask Malkowski or any of us who have done this for our entire career how long smart home technology has relied on the sub-GHz layer to communicate, and we’ll tell you you have to First establish when the “smart home” really started.

“I think the breaking point for the smart home was the iPhone in 2007, when consumers started wanting to do more with their wearables,” Malkowski says. “You’ll find devices 20 to 30 years ago that were in a smart home space, but they probably weren’t called a smart home back then. Instead, ‘home automation’ was the big word. Back then, you could install a smart home system for a few hundred thousand dollars, but it has since become much more reliable and more affordable.”

Since the early days of home automation, a proliferation of proprietary and standards-based solutions has given consumers a variety of options at the 2.4 GHz and sub-GHz layers; however, only sub-GHz offers the fundamental benefits of longer range, longer battery life, better reliability, and smaller footprint.

Maximize range and battery life

“With the same power budget – the same amount of power used – you’ll get about twice the range of Z-Wave compared to 2.4GHz, and that just depends on the physics,” Malkowski says. “Now that’s thrown out the window with Z-Wave long range, where your typical range will be around a mile, and on 2.4 GHz you’re lucky to get 300 feet. The higher the frequency is low, the better the range, the better the penetration.

A white paper published by Texas-based Silicon Laboratories (www.silabs.com/documents/public/white-papers/Key-Priorities-for-Sub-GHz-Wireless-Deployments.pdf) developed this particular advantage of sub-GHz. It cites three main reasons for better range performance on 2.4 GHz applications: “As radio waves pass through walls and other obstructions, the signal weakens,” the report says. “Attenuation rates increase at higher frequencies, so the 2.4 GHz signal decays faster than a sub-GHz signal.”

Second, “2.4 GHz radio waves also fade faster than sub-GHz waves when reflected off dense surfaces. In very crowded environments, the 2.4 GHz transmission can fade quickly, negatively affecting signal quality.

And finally, “although radio waves travel in a straight line, they bend when they hit a solid edge. As frequencies decrease, the diffraction angle increases, allowing sub-GHz signals to bend more far around an obstacle, thus reducing the blocking effect.

When it comes to battery longevity, Malkowski says sub-GHz frequencies can support up to double those of comparable 2.4GHz devices, without replacement. “The same door lock from a given manufacturer with a 900 MHz radio frequency – you’ll probably have about 18-24 months before you need to replace it. For 2.4 GHz on the other hand, due to the nature of the communication, it will take about 12 to 16 months,” he explains.

At this point, the Silicon Laboratories white paper states, “Sensitivity is inversely proportional to channel bandwidth, so a narrower bandwidth creates higher receiver sensitivity and allows efficient operation at lower transmission rates. . In general, all radio circuits operating at higher frequencies…need more current to achieve the same performance as lower frequencies.

An open and reliable highway

Take a moment to count the number of Wi-Fi or Bluetooth enabled devices in your home. When you consider that your computer, smartphone, smart speaker, smart TV, game consoles, remote controls – and even, occasionally, your microwave oven – are all competing to run on 2.4 GHz, it’s easy to see how things can get a little crowded.

The sub-GHz layer, on the other hand, does not suffer from the same amount of traffic. “The more devices you have in the same 2.4GHz space, the less potential reliability there is,” Malkowski says. “That’s why it’s so important to be in the sub-GHz.”

This sentiment was echoed by the Silicon Laboratories white paper, which states: “Sub-GHz ISM [industrial, scientific, and medical] The bands are primarily used for proprietary low duty cycle links and are not as likely to interfere with each other. The quieter spectrum means easier transmissions and fewer retries, which is more efficient and saves battery power.

Another facet of greater sub-GHz reliability is reduced latency. “As far as latency — or how fast you can talk to devices — you can open a Z-Wave door lock in two seconds, and that’s the worst case scenario,” Malkowski says. “In ZigBee or OpenThread, on the other hand, it would be eight to 10 seconds. Does that difference really matter? Sometimes yes, sometimes no.”

Malkowski sums up the benefits of sub-GHz frequencies using an analogy: “On the sub-GHz layer, I have the experience of being on a six-lane highway full of cars, and I’m driving alone in the lane of left.” He points out that reliability, as well as freedom from interference with other devices, will ultimately be key to the future advancement of smart home solutions.

Different countries, different frequencies

The most often cited disadvantage of sub-GHz is that the frequencies have to be readjusted depending on the country you are in. “Companies that use technologies other than Z-Wave – they very often point out that it’s not a global solution,” Malkowski says. “With ZigBee or OpenThread, we can make a device and sell it around the world, but with Z-Wave this is not possible.”

Despite the hurdle that device makers face when it comes to making their products available in a global market, it’s important to note that for the average smart home consumer in the United States – for whom control Automated lighting and overseas usable garage door openers are not an entirely essential feature – this constraint on sub-GHz is of limited concern.

Time-tested

With the market for smart home technology rapidly evolving, one could be forgiven for worrying that the sub-GHz layer itself will eventually become too crowded – or simply become an unviable option for device manufacturers. devices, whether due to new FCC regulations or replacement by its high-frequency counterparts.

But Malkowski isn’t too worried: “We’re seeing new additions to the sub-GHz layer like Amazon Sidewalk, but we’re still a long way from where they are in terms of frequency,” he says. “They use what’s called spread spectrum, which allows them to hop on different frequencies. So the probability of it becoming overcrowded is much less than 2.4, which has fixed channels. This is the main difference. Also, it is usually the emergency services that dictate which frequencies are available or not. I anticipate that the same groups we have access to today will still be available 20+ years from now. Far from being eclipsed, sub-GHz frequencies provide a faster, more reliable and cost-effective device communication solution that will continue to benefit consumers of smart home technology for decades.

Mitchell Klein is executive director of strategic partnerships at Silicon Labs, as well as executive director of the Z-Wave Alliance (https://z-wavealliance.org).