WiFi CSI Fundamentals and Engineering
The WiFi Channel as a Distributed Sensor
What one CSI matrix actually looks like — OFDM structure, multipath superposition as a worked example, and why RSSI discards the degrees of freedom that make WiFi sensing possible.
Commodity CSI: Capture Limits and Calibration
What ESP32 CSI actually gives you — sampling rate, antenna count, phase noise floor, ESP-CSI API surface, and when cheap hardware is enough for real sensing.
Building an Activity Classifier on CSI
A practical path from variance thresholds to spectrogram CNNs for WiFi HAR — label collection, training, evaluation, and why transfer learning across rooms fails without adaptation.
Baselines, Drift, and Generalization
Empty-room CSI fingerprinting, furniture drift, cross-site domain shift, adaptive baselines, and when to re-baseline — the engineering behind reliable occupancy sensing.
RF Privacy Research Series
Wavey also publishes research on the adversarial mirror of WiFi sensing — detecting and mitigating unauthorized RF surveillance:1
RF Privacy: The Flip Side of WiFi Sensing
WiFi CSI sensing works both ways — the same physics that detects occupancy without cameras also lets an attacker observe a room without consent. What the research says and why RF privacy is an unserved problem.
2
WiFi Sensing Attacks: LeakyBeam, BFId, and the BFI Side Channel
NDSS 2025 and CCS 2025 proved passive WiFi surveillance is practical — occupancy detection at 20m through walls, identity inference across 197 subjects, all from plaintext beamforming feedback on commodity hardware.
3
Detecting Unauthorized RF Sensing: A Layered Approach
Five detection layers for unauthorized RF sensing — from emitter inventory to behavioral baselines. What works today on ESP32 mesh, what remains open research, and why passive sniffer detection is the hardest problem.
4
RF Privacy Defenses: Obfuscation, Metasurfaces, and Their Limits
How to prevent unauthorized WiFi sensing — CSI fuzzing, intelligent reflecting surfaces, BFI obfuscation, and anti-sensing shields. What each defense achieves, what it costs, and why detection and mitigation must work together.
5
IEEE 802.11bf and the WiFi Sensing Privacy Gap
802.11bf standardizes WiFi sensing but leaves privacy protection vendor-dependent. No mandatory secure-LTF for sensing NDPs, no opt-out mechanism, and BFI remains plaintext — what enterprise buyers and researchers need to know.