From Wi-Fi to Spy-Fi — we test Plume’s new motion detection feature, Ars Technica

my ally is the Force, and a powerful ally it is –

Superpods can now sense disturbances in the Force — er, the RF spectrum, that is.

Jim Salter – Mar 3, : am UTC

In the live view of Plume motion, you can get a rapidly updating idea of how much movement the kit sees. You’re looking at my kids wandering around the living room right now.

Jim Salter

Plume Motion has a log area where you can see history of motion in the house. See that blip at 2AM? That’s when the movie I was watching finished, and I got up and went to bed.

Jim Salter

There’s a “last seven days” version of the Plume motion log as well. There’s still enough granularity here to figure out what time of day motion tends to occur.

Jim Salter

At CES , Wi-Fi mesh kit manufacturer Plume announced the addition of motion-sensing capability to its newer Superpod devices. Before we go any further, let’s be clear about what we’re talking about — this is not

detection of a device you ‘re holding, like a phone or tablet. Instead, Plume is doing real-time analysis of extremely low-level RF data pulled from the Superpods’ radios. This is real motion detection, with no gimmicks involved. (Plume Motion requires Superpods — at least for now. The Superpods can also use stationary devices — including any original generation pods, or computers or IoT devices connected to the Wi-Fi — to further refine their detection.

Plume co-founder Adam Hotchkiss explained to us that, although any Wi-Fi device could theoretically be used to sense the data necessary to analyze motion, not all Wi-Fi chipsets actually expose that data. The Qualcomm IPQ

chipset used in the Superpods exposes the necessary RF data, but the older QCA chipset used in the first-generation pods does not.

Hotchkiss told us that most (if not all) Wi-Fi 6 chipsets provide sufficient low-level RF data access for Plume Motion, so we may start seeing similar features from competing vendors in the next year or two.

How it works

Although the idea of sensing motion using Wi-Fi seems novel, the underlying physics is well established. Both 2.4GHz and 5GHz spectra have high absorption factors for water, so human (or animal) bodies present measurable interference to signals on those frequencies. Devices which have multiple antennas can therefore spot changes in the RF noise floor with some directionality and, with sufficient analysis, can isolate patterns corresponding to movement.

Professional security devices have been using 2.4GHz RF to sense motion for quite some time. I found that out the hard way a year or so ago. A small business had trouble getting reliable service in the rear of its building and did not want to invest in multiple access points — so I moved its router up above head height.

Moving the router solved the business’ Wi-Fi problems, but it caused a new one — the security alarm started going off for no apparent reason. After much head-scratching, I discovered that a Bosch intrusion

sensor was just on the other side of an interior wall, at the same height — and it also operated on 2.4GHz.

When a device at the back of the office requested data, the return transmission from the router — a Netgear Nighthawk — would Swamp the sensor, which would report motion detected. So the concept of motion detection with Wi-Fi frequencies isn’t novel at all — just the idea of using your actual Wi-Fi gear to do it, rather than separate, dedicated devices.

Testing Plume Motion

In this clip, I open the Plume app on my phone, toggle into the motion detection, then put the phone down and walk around the house. Jim Salter The Plume firmware necessary to enable the feature — along with the update to the Plume smartphone app — went live Friday night, and we tested it over the weekend.

Plume Motion can be tuned to “low,” “medium,” or “high” sensitivity. If set on “high,” an optional checkbox to ignore pet detection is available. The default setting was high sensitivity, without the special pet-detection feature enabled; we found that those defaults worked well. You can’t necessarily tell the exact room in which motion is occurring — sometimes the Superpod downstairs would be the first one to trigger on me moving around in the living room upstairs — but you can get a pretty good idea, since the strength of detection at each Superpod is visible and correlates well to distance.

You can also set Plume Motion to send alerts to your phone when motion is detected. You can also set the system to automatically disable alerts when key devices are present on the Wi-Fi and enable them again when those devices disappear.

There aren’t any tie-ins — for now — with other security systems. We suspect that, if Plume does not build that functionality in themselves, some other vendor likely will — the company free and open source (OpenSync) (protocol makes such integration simple.) Conclusions

There’s no doubt at all that Plume Motion works. It detects me and my kids without a problem, and — even without the pet exceptions enabled — it doesn’t present false positives for the cats or dogs moving around.

Without tie-ins to “real” alarm systems or monitoring companies, it’s probably best — for now — to view Plume Motion as a neat extra feature rather than a serious security system. But the underlying technological concept is sound, and we would not be surprised to see support for using Plume’s motion detection in more serious alarm monitoring packages in the future.

The Good

Human detection is reliable, with solid detection rates and no false positives that we witnessed Families that don’t have large pets probably won’t even need to mess with the pet exception setting

It’s possible to get a decent, if not perfect, idea of where movement is occurring by seeing which Superpods trigger most strongly