RF sensing is big news, so here are the other options

I just spent a few hundred words explaining how Wi-Fi sensing would become the next big thing, but it’s not the only sensing technology coming out that will take advantage of radio waves to determine where people and things are in space. Two other technologies deserve a mention as well: radar and ultra-wideband.

Ultra-wideband, or UWB, is probably the most familiar to people thanks to Apple placing a UWB chip inside many of its devices. Apple is using the technology for fine-range sensing at short distances. This allows Apple to use its AirTag with a UWB chip to locate your lost keys within a couple of inches.

When combined with other radios, it can ensure that a person is physically close to a lock before it opens. Or it can be used to determine which person’s handset is near a HomePod Mini device so the smart speaker can pull music playing on that handset and play it in the room.

We’ve written before how we think UWB is the beginning of ambient computing since it helps devices in a smart home understand who a person is and where they are in relation to other devices in the room. But Apple’s UWB isn’t the only option out there.

UWB communication refers to how the radio signal is transmitted. UWB radios transmit data in short pulses across huge swaths of spectrum that measure more than 500 megahertz. Instead of a conventional radio signal, which you can think of more as a continuous stream of data over a specific channel of spectrum, UWB radios transmit pulses of information over a wide channel of spectrum.

Thus UWB radios are great for figuring out where things are in time and space. They are less good for measuring velocity or where something is moving. In addition to UWB in phones for consumer applications, the FiRa Consortium is using UWB for fine range positioning in industrial and enterprise applications.

These UWB applications often use spectrum in the 60 GHz range, which is pretty empty and has really bad propagation properties, so the signals can’t go very far. This means UWB is a close-range technology.

Another close-range RF technology deployed in smart home sensing is radar. For example, Google’s Soli radar, which is used on its second-generation Nest display, leverages a Soli radar sensor to track a person’s breathing rate to figure out how well the person is sleeping. The device also uses the radar for gesture-based interactions at close range.

Soli uses spectrum in the 60 GHz range, too, but instead of UWB it uses a waveform modulation scheme called frequency modulated continuous wave (FMCW). (Fun fact: The aforementioned Wi-Fi sensing uses the OFDM waveform.) Radar’s waveform is optimized for detecting where things are in space and figuring out their velocity.

That is why Google’s Soli can figure out breathing patterns at a close distance. The Soli radar also uses multiple antennas to get an even more detailed picture of what’s happening at close range because each antenna is essentially taking a picture and using that data to process the movements. The more antennas, the finer the resolution.

Other companies, such as Texas Instruments, use 60GHz radar for building sensors as well. In TI’s case, customers use the radar on co-bots in factory settings so they can work safely with humans in the nearby vicinity.

So in the next few years, we’re going to see a lot of new capabilities thanks to new sensors and radios on devices. I can’t wait.