What can Wi-Fi radars do and how do they detect motion through walls?

Most people associate Wi-Fi with wireless internet access, but few are aware that this technology is capable of more than just data transmission. Thanks to recent advancements, Wi-Fi can now detect motion, presence, even breathing—and it can do so through walls.

This is not science fiction: Wi-Fi radar is already available today, and it is being used across various fields—from smart homes and security systems to medical remote monitoring.

In this article, we’ll explore:

• what Wi-Fi radar is and how it works,

• how it can detect through walls,

• what devices, algorithms, and standards power it,

• and the benefits and privacy concerns it raises.

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What is Wi-Fi radar?

Wi-Fi radar (or Wi-Fi sensing) is a technology that analyzes the reflections of Wi-Fi radio waves to gather information about what’s happening in the environment.

Basic principle:

• The Wi-Fi device constantly emits signals (e.g. at 2.4 GHz or 5 GHz).

• These signals are reflected off walls, objects, and people.

• The radar analyzes changes in the signal—such as delay, phase, amplitude.

• From these variations, it can determine:

  • if someone moved,

  • how fast they moved,

  • the spatial extent of motion,

  • whether someone is present,

  • or even whether they’re breathing (!).

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How can it see through walls?

Radio waves—especially those in the 2.4 GHz and 5 GHz Wi-Fi bands—can penetrate certain materials, especially if they’re:

• non-metallic,

• unshielded (e.g., drywall, wood, brick).

The transmitted signal passes through the obstacle, reflects off the target on the other side, and returns to the sensor, which analyzes the altered waveform.

The key: Channel State Information (CSI)

CSI provides detailed information about the radio channel:

• propagation paths,

• multipath reflections,

• variations in phase and amplitude.

Motion modifies this “signature,” which the radar then interprets.

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What signals does Wi-Fi radar use?

The best part? No additional sensor is required—even a standard router or IoT device may be suitable for sensing.

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What can Wi-Fi radar detect?

• General presence (whether someone is in the room)

• Fine movements – such as breathing, gestures

• Walking, sitting, lying down

• Sudden movement, falls

• Motion-based identification

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Use cases

1. Smart homes

• Automatic lighting, HVAC control

• Triggering events based on presence

2. Elder care / medical monitoring

• Breathing monitoring, sleep tracking

• Fall detection with real-time alerts

• Fully contactless, no wearables needed

3. Security systems

• Hidden presence detection (e.g., behind a wall)

• Safeguarding critical infrastructure (data centers, vaults)

• Motion-triggered lighting or alarms

4. Office environments

• Automatic room occupancy tracking

• Presence-based energy optimization

• Analytics on movement in shared spaces

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Real-world examples

Google – Project Soli

• A miniature mmWave radar that detects finger gestures in the air

• Also featured in some Pixel phones

Amazon – Echo & Sidewalk Radar

• Wi-Fi radar for presence detection

• Automatically responds as a user enters or exits a room

Origin Wireless

• Turns standard Wi-Fi routers into breathing monitors for infants or seniors

• Commercialized as of 2023

Aura WiFi Motion by Cognitive Systems

• Uses compatible routers to act as motion sensors

• Already in use in apartment buildings and offices

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Advantages

• ✅ No need for extra sensors

• ✅ Works through walls

• ✅ Invisible and discreet – non-invasive

• ✅ Offline capable (with local processing)

• ✅ More privacy-friendly than cameras

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Challenges and limitations

• ❗ Accuracy can vary with environment (metal surfaces, clutter)

• ❗ Interference from other Wi-Fi sources

• ❗ Requires refined algorithms for reliable detection

• ❗ Privacy concerns – motion data can be sensitive

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Privacy concerns

• While no video or audio is recorded, movement patterns may still identify individuals

• Under GDPR and similar regulations, presence data is considered personal data

• Ethical consideration: if users are unaware of being monitored, it could violate their rights

It is essential to inform users and offer opt-out options whenever such systems are used.

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Future trends

• 802.11bf standard (“Wi-Fi Sensing”): the official sensing standard set to launch 2024–25

• Edge AI integration: on-device learning for gesture and presence recognition

• Motion-based identity – new biometric layer based on how people move

• Healthcare: wireless lung function, apnea detection

• Self-organizing radar networks: mesh Wi-Fi forming distributed sensor systems

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Conclusion

Wi-Fi radar opens up new possibilities in motion detection and presence awareness. Its ability to “see” through walls and sense without touch is especially valuable for healthcare, security, and smart living.

As the technology evolves and the 802.11bf standard becomes widely adopted, we’ll see this “invisible radar” embedded in everyday devices—making our homes and environments not just connected, but aware.