Jim Salter

Jim Salter

Jim Salter

What's a Plume? For those of you who haven't been keeping score, For those of you who haven't been keeping score, Plume is one of our favorite Wi-Fi mesh kits. We don't really love its annual subscription fee, but it comes out firmly at the top of our complex, multiple-device performance tests every time. If you want nothing to do with ongoing subscriptions, we also love—and strongly recommend—the newer Amazon Eero three-piece kits.

At CES 2020, 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 IPQ4019 chipset used in the Superpods exposes the necessary RF data, but the older QCA9557 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 with 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 microwave-spectrum 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 didn't 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 since both devices use the microwave spectrum, problems ensued.

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 microwave spectrum (read: 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.

Note: Several readers have pointed out that Bosch sensors frequently use Zigbee—which operates at 2.4GHz, like 802.11n Wi-Fi—for communication between the sensors and their control panel. The alarm vendor said that the sensor itself was being triggered by the high 2.4GHz RF emission from the Nighthawk, but it's also possible a disruption in the Zigbee communication between sensor and panel was responsible for the false alarms.

Testing Plume Motion

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 doesn't build that functionality in themselves, some other vendor likely will—the company's 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

The combination of Live, one-day, and seven-day reporting is effective and intuitive

The Bad

No direct support from professional alarm or alarm monitoring companies—yet

The advanced settings can still use a little work—Plume reported using all four of our test Chromebooks as auxiliary sensors, but only one checkbox labeled "Debian computer" was in the optional device exclusion list

The Ugly

Consumers who are already paranoid about mesh telemetry really aren't going to love the addition of motion detection

Listing image by Plume