Most homes, offices, and shops already hum with Wi‑Fi. Those radio waves don’t just carry data; they bounce off walls, furniture, and people. Subtle changes in those reflections can reveal when someone walks by, sits down, or even breathes. That’s the idea behind Wi‑Fi sensing, a feature set that turns access points into presence and motion sensors. A new IEEE standard, 802.11bf, is formalizing how networks do it reliably and safely.
This article explains how Wi‑Fi sensing works in plain language, what you can do today, what changes with 802.11bf, and how to set up practical deployments. We’ll cover accuracy, privacy, useful automations, and pitfalls to avoid. If you manage a home, a small business, or a larger building, you can get a lot of sensing power from the radios you already own.
What Wi‑Fi Sensing Actually Measures
Every Wi‑Fi packet ripples through your space. It bounces, bends, and arrives at the receiver from many directions with tiny delays. Engineers call this pattern the channel. A modern Wi‑Fi radio can estimate the channel using a measurement called Channel State Information (CSI)—phase and amplitude values across subcarriers and antennas.
When a person moves, they disturb that channel. Your body reflects radio energy; a footstep shifts phases and amplitudes in a way that looks like a wave moving across time. If someone is still but breathing, their chest motion causes rhythmic micro-changes. Wi‑Fi sensing algorithms watch these changes to infer events such as:
- Presence: Is anyone in this zone?
- Motion: Did something move? How strongly?
- Direction: Which way did movement flow?
- Breathing rate: At rest, can we see a periodic pattern?
- Occupancy changes: Did the room go from empty to occupied?
Key ingredients that make this possible:
- MIMO antennas: Multiple antennas provide spatial diversity to separate reflections.
- Wide channels: 80 or 160 MHz offer better time resolution than 20 MHz.
- Stable clocks and calibration: To track subtle phase changes without drift.
- Frequent snapshots: The receiver needs channel samples at tens of Hz or more for smooth signals.
Important limitation: Wi‑Fi sensing doesn’t produce images. It’s more like a “motion barometer” that detects disturbances in the radio field. That makes it inherently privacy-preserving compared to cameras, but it still needs guardrails (we’ll get to that).
Where 802.11bf Fits
Today’s commercial Wi‑Fi sensing systems exist, but many are proprietary. They rely on vendor-specific CSI access or clever tricks with packet timing. The IEEE 802.11bf effort is creating a common framework inside Wi‑Fi so that access points, clients, and software can coordinate sensing without hacks.
What 802.11bf adds
- Standardized sounding: Access points can schedule channel sounding packets specifically for sensing, including null data packets that carry no payload but reveal the channel.
- Coordination across APs: Multi‑AP systems can take synchronized measurements to improve coverage and reduce blind spots.
- Defined APIs: Software can request sensing sessions and retrieve processed metrics (for example, motion energy in zones) rather than raw CSI.
- Coexistence rules: Sensing traffic must not degrade data performance; 802.11bf defines duty cycles and fairness.
- Security and privacy expectations: The standard clarifies who can trigger sensing, how data is exposed, and how to prevent misuse.
Think of 802.11bf as the step that makes “Wi‑Fi sensing” a first‑class citizen in routers, smart home hubs, and enterprise controllers—so you can mix vendors more safely and integrate with automation platforms without bespoke drivers.
What You Can Do Today
You don’t have to wait for 802.11bf to try Wi‑Fi sensing. Vendors already ship products and features that use existing radios. You also can experiment at home with off‑the‑shelf hardware.
Consumer systems
- Mesh routers with motion: Some mesh systems repurpose their nodes to detect motion by observing changes in signal across the mesh backhaul. For example, Plume offers “Motion” services on certain hardware; other vendors have similar features partnered with sensing specialists.
- Subscription services: Motion alerts, occupancy dashboards, and basic automations often come as optional add‑ons through the router’s app.
DIY and research
- CSI extraction: A handful of chipsets let you access CSI. Enthusiasts use older Intel adapters, some Qualcomm/Atheros cards, or Broadcom chips on Raspberry Pi with community firmware to collect data. Tools like “CSIKit” help you parse and analyze it.
- Simple experiments: You can plot motion energy from CSI variance to build an entryway detector, or low‑pass filter signals to observe breathing when someone sits still near an AP.
These non‑standard paths require patience and may be brittle, but they demonstrate what’s possible. As 802.11bf lands in mainstream silicon, the same ideas will be available without hacks, and you’ll configure it from your router dashboard instead of a terminal.
How Accurate Is It?
Accuracy depends on frequency band, channel bandwidth, antenna geometry, and how you process the data. Here are practical expectations drawn from published research and vendor demos:
- Presence detection: Reliable within a typical room, often through interior walls. Sensitivity can reach “pet vs. person” levels if tuned.
- Motion direction: With multiple APs and decent geometry, you can infer pathways across zones (for example, “hall to kitchen”).
- Occupancy counting: Counting exact people is hard; changes (0 to 1+ or “few vs. many”) are more robust than absolute counts.
- Breathing rate: Possible at rest within a few meters of an AP when the environment is quiet and the subject is stationary; useful in bedrooms or clinics, not busy halls.
- Range and resolution: 5 and 6 GHz strike a good balance for home/office; 2.4 GHz penetrates further but gives coarser timing; 6 GHz can offer finer resolution with wide channels.
Limitations to plan for:
- Multipath sensitivity: Furniture moves, doors open, fans spin; the environment itself changes the baseline.
- Non‑stationary interference: Microwaves, vacuum cleaners, and neighboring networks can spike false positives.
- AP placement: Clustering APs in one corner reduces coverage and directionality. Spreading nodes yields better geometry.
- Pet confusion: A large dog can look like a person if thresholds aren’t tuned per zone.
With responsible tuning and at least two nodes per zone of interest, you can expect low‑latency presence detection that’s good enough for lights, HVAC, and basic security, plus calmer “breathing‑aware” rooms where the AP sits close to the bed and noise is minimal.
Practical Deployment Recipes
Home: make rooms responsive without cameras
If your mesh supports motion sensing, start there. Enable the feature, select rooms to monitor, and set sensitivity. Otherwise, place at least two APs so that their coverage overlaps the paths you care about—hallways, entries, and main living areas. Avoid placing both APs on the same wall; aim for overlapping triangles that “cut across” walking paths.
Steps
- Map your zones: Identify rooms you want to automate, places where lights should respond, or spots where you want “no‑motion” triggers to save energy.
- Place APs with intent: Cover each zone with at least two lines of sight. Shelf height often works better than ceiling for home gear.
- Baseline: Run a calibration while the house is quiet. Many systems ask you to leave for 2–5 minutes so they can learn “stillness.”
- Tune thresholds: Start conservative to avoid false alarms. Increase sensitivity only for rooms that need snappy lights.
- Integrate with automations: Use your router app or link it to Home Assistant via the vendor’s integration or a webhook/HTTP action.
Good first automations include stair lights at night, auto‑off for rooms after 10 minutes of stillness, and “sleep mode” when the bedroom shows low, steady motion for an hour.
Small business: make HVAC and lighting smarter
For offices and retail, sense occupancy at zone level. Place APs near entrances and across open areas; cover meeting rooms with at least two APs. Tie the sensing output to building systems through a gateway or BMS adapter.
Steps
- Define zones: Entrances, open office, meeting rooms, break areas, restrooms.
- Install or re‑aim APs: Favor cross‑coverage of each zone rather than maximum signal bars everywhere.
- Collect baseline data: Observe a week of motion heatmaps before acting.
- Automate: Set lighting scenes on presence; lower HVAC setback when zones are empty; send reminder if a meeting room is “ghost booked.”
- Review privacy notices: Post clear signs that you use non‑imaging occupancy sensors; offer an email for questions.
Expect energy savings and better comfort from matching conditioning to actual presence patterns rather than fixed schedules.
Privacy and Trust by Design
Wi‑Fi sensing can be done in a way that improves safety and comfort without feeling creepy. Follow these principles:
- Minimize data: Store derived events, not raw CSI. “Motion in room A at 18:42” is enough for automations.
- Keep it local: Prefer on‑device processing. If cloud features are optional, leave them off unless you truly need remote alerts.
- Make it visible: Offer a dashboard that shows exactly what the system knows (presence, motion levels) and nothing more.
- Set retention: Delete motion logs on a schedule; keep aggregate statistics only.
- Offer opt‑out: Allow room‑level disablement or “privacy hours.”
Because there are no images, misuse risks are lower than with cameras. But transparency still matters, especially in workplaces. 802.11bf’s standardized controls should help administrators enforce policies consistently across vendors.
Integrations That Make It Useful
Wi‑Fi sensing is most valuable when it triggers systems you already rely on. A few practical patterns:
- Lighting scenes: “Walk‑in turns on low‑blue light after 10pm; bright light during work hours.”
- HVAC setback: “If a floor is idle, let the temperature drift 2 degrees.”
- Security: “When away mode is on, any motion after a door sensor event is an alert.”
- Elder care: “If the bedroom shows no motion by 10am, check in.”
- Meeting rooms: “If the room is booked but empty for 10 minutes, release the booking.”
To wire this up, many systems expose Webhooks, MQTT, or vendor applets. As 802.11bf matures, expect mainstream support in platforms like Home Assistant, openHAB, and major building controllers.
Troubleshooting: Make It Calm and Reliable
Wi‑Fi sensing is sensitive—and that’s the point. But you want the sensitivity to be useful, not noisy. Common issues and fixes:
- False positives from fans or pets: Lower sensitivity, set a minimum motion duration, or exclude certain zones at night.
- Signal dead zones: Add another AP or re‑aim antennas to cross‑cover the space with better geometry.
- Slow or jittery triggers: Increase sample rate if supported, or shorten the smoothing window used by your automation.
- Baseline drift: Recalibrate after furniture moves or seasonal changes (open/closed windows alter airflow and reflections).
- Neighbor network interference: If possible, move to 5 or 6 GHz channels, or enable automatic channel selection.
Keep one zone as a testbed where you intentionally adjust thresholds and observe weekly performance before rolling changes to the rest of the site.
Under the Hood: A Gentle Technical Dive
Curious about the signals? Here’s a simplified view of techniques you’ll see in papers and products:
- Variance‑based detection: Compute short‑term variance of CSI amplitude; spikes imply motion.
- Doppler signatures: Movement induces small frequency shifts (Doppler) visible in time‑frequency plots, helping separate walking from hand gestures.
- Phase unwrapping: Careful filtering and unwrapping can reveal sub‑centimeter displacements useful for breathing detection.
- Multi‑AP fusion: Combining measurements across APs improves confidence and can infer direction via time differences and relative amplitude changes.
- Learning models: Classifiers or small neural nets can map signal features to events like “person entered” vs. “pet moved tail.”
802.11bf helps by giving algorithms better, cleaner inputs on a predictable schedule, so they don’t fight the data plane for airtime.
How 802.11bf Changes the Market
Standardization usually unlocks scale. Expect a few shifts as 802.11bf ships in chipsets and routers:
- Multi‑vendor interoperability: You’ll buy APs from vendor A and automation from vendor B, and they’ll cooperate for sensing.
- Better battery story for clients: Devices that volunteer for sensing can do so efficiently and safely, with duty cycle limits.
- Clear admin controls: Enterprise controllers will expose sensing policies alongside QoS and security.
- New apps: Retail traffic analytics, space utilization for hot‑desking, safer elder care monitoring without cameras, gym occupancy dashboards.
Crucially, sensing becomes a feature of the network rather than a bolt‑on. That reduces cost and complexity for anyone who already runs Wi‑Fi—which is nearly everyone.
Safety, Compliance, and Etiquette
Even with privacy advantages, treat sensing with care:
- Consent: In workplaces and public venues, inform people and respect local laws.
- Security: Restrict who can start sensing sessions and who can access event streams. Use strong admin passwords and MFA for controllers.
- Data hygiene: Retain only the minimum needed for automations; purge historical logs regularly.
- Testing: Validate “fall alerts” or other safety features periodically so you don’t over‑trust them.
Because 802.11bf defines who can control sensing and how data is shared, it gives IT teams better levers to enforce these practices.
Choosing Hardware and Planning Upgrades
If you’re buying new gear, look for these indicators:
- Multi‑band support: 5 and 6 GHz with 80/160 MHz channels.
- MIMO antenna arrays: More spatial streams help.
- Vendor mentions of sensing: Even before 802.11bf, some vendors advertise motion features.
- Open APIs: Check if the vendor provides webhooks or protocol integrations for events.
For enterprises planning lifecycle upgrades, ask your vendor about 802.11bf roadmaps, firmware timelines, and license models. Ensure you can keep sensing computations at the edge where latency is low and data stays local.
Real‑World Scenarios
Apartment living
One AP in the hallway and one in the living room give enough coverage to automate foyer lights, provide night‑light paths, and detect if a stranger slips inside while you’re away (powered by motion plus door sensor).
Clinic rooms
A single AP near the bed serves breathing‑aware monitoring at night without cameras or wearables. Staff get a gentle nudge if motion goes quiet longer than expected after a procedure.
Open office
APs above the main aisles and meeting rooms generate zone occupancy maps that inform cleaning rounds and auto‑release no‑show meetings, saving time and energy.
Common Myths
- “Wi‑Fi sensing sees through walls like X‑ray.” It doesn’t see; it detects motion through changes in reflections. Interior walls attenuate but don’t block all signals.
- “It’s as invasive as a camera.” No. Outputs are numeric motion metrics and simple events, not images or audio recordings.
- “I need special beacons in every room.” No extra beacons are required; existing APs and clients suffice, especially with 802.11bf.
- “It kills network performance.” Properly scheduled sensing, especially under 802.11bf rules, keeps air‑time impact tiny.
Getting Started Checklist
- Confirm your router or mesh supports motion sensing, or plan to add one AP for overlap in key rooms.
- Decide on a first automation (for example, hallway night lights or HVAC set‑back).
- Place APs to cross‑cover the space; aim for two lines of sight per zone.
- Baseline and tune sensitivity for a week; watch for pet or fan‑induced noise.
- Set privacy defaults: local processing, short retention, visible status.
- Iterate slowly: roll successful settings from one zone to the rest.
Summary:
- Wi‑Fi sensing uses channel changes to detect presence, motion, and even breathing without cameras.
- IEEE 802.11bf standardizes sounding, coordination, APIs, and safeguards so vendors can interoperate.
- You can try it today via certain mesh systems or DIY CSI experiments; 802.11bf will make it mainstream.
- Expect reliable room‑level presence, directional motion across zones, and careful setups for breathing detection.
- Place APs for cross‑coverage, baseline regularly, and tune thresholds to minimize false positives.
- Keep processing local, store only events, and communicate clearly to earn user trust.
- Integrate with lighting, HVAC, security, and scheduling to turn signal changes into useful actions.
