Wi-Fi Radar (KrakenSDR)

Active Development

Concept

Wi-Fi signals penetrate walls and reflect off human bodies, creating detectable Doppler shifts and signal disruptions. By processing these reflections with coherent multi-channel receivers, we can detect and localize human presence through walls — a signal processing challenge that relies entirely on existing Wi-Fi infrastructure.

Quick Facts


Status	Active
Language	N/A
Started	2026

What This Is

An experimental signal processing system that analyzes reflections of ambient Wi-Fi signals (2.4 GHz / 5 GHz) for through-wall human detection and localization. The system uses coherent multi-channel RF receivers to process reflected Wi-Fi signals, extracting micro-Doppler signatures and bistatic range information to detect and localize human movement.

Core Principles

Wi-Fi as Illumination Source:

Ubiquitous Coverage: Wi-Fi access points provide dense, continuous illumination in urban/indoor environments
Wall Penetration: 2.4 GHz signals penetrate common building materials (drywall, wood, brick)
Reflection Characteristics: Human bodies create measurable reflections at Wi-Fi frequencies
Micro-Doppler Signatures: Breathing, walking, and limb motion create characteristic Doppler patterns

Bistatic Geometry:

Wi-Fi AP as Transmitter: Existing access points serve as non-cooperative illuminators
Target Reflection: Human bodies reflect Wi-Fi signals toward receiver array
Coherent Processing: Multiple receiver channels enable angle-of-arrival estimation and beamforming
Range-Doppler Mapping: Cross-correlation extracts bistatic range; FFT reveals Doppler shifts from motion

Signal Processing Challenges:

Direct Signal Cancellation: Remove strong direct path from AP to receiver (adaptive filtering)
Multipath Suppression: Indoor environments create complex multipath reflections
Clutter Rejection: Static objects (furniture, walls) must be filtered from moving targets
Low SNR Operation: Human reflections are weak compared to direct signal and clutter

Technical Approach

The system processes coherent multi-channel Wi-Fi signals using:

Reference Signal Extraction: Capture direct Wi-Fi signal from AP
Surveillance Channel Processing: Receive reflected signals from multiple antennas
Adaptive Interference Cancellation: Remove direct signal and static multipath
Beamforming: Spatial filtering to enhance target signals
Range-Doppler Processing: Extract target range and velocity
Micro-Doppler Analysis: Classify human activity patterns
Tracking: Maintain target tracks over time