When one sense is not enough
CSI answers "is someone there, are they moving?" Real problems often need more: Is that motion a person or a pump? Is the machine healthy? How far away? The answer is fusing cheap modalities — the Multi-Modal Sensor Hub in the catalog carries five.
The fusion vector
Our field configuration produces a 510-dimension feature vector per measurement:
- WiFi CSI — 56 subcarriers: presence, motion, through-wall reach.
- Microphone FFT — 256 bins: breathing band (0.2–0.5 Hz envelope), machine harmonics, glass-break transients.
- IMU FFT — 32 bins: structural vibration — bearing wear and cavitation have signatures long before failure.
- Ultrasonic — 128 bins: line-of-sight distance + motion, immune to radio interference.
Each modality covers another's blind spot: ultrasonic needs line of sight, CSI does not; CSI cannot hear a bearing, the IMU can.
Real deployments of this exact stack
- Data-center cages — CSI mesh detects wrong-cage and after-hours entry where cameras are contractually banned.
- Oil & gas hazardous zones — the full 510-D stack watches for people in H₂S areas and listens to rotating equipment, where electronics must be minimal and cameras are prohibited.
- RF-triggered evidence — CSI motion wakes a camera for a 10-second burst (CameraPlus): privacy-preserving and energy-saving.
Design rule
Start with the question, not the sensors. "Alert when someone enters after hours" is CSI alone. "Alert when the pump sounds wrong" is mic + IMU. Buy sensors for the question you actually asked — the hub is there when the question grows.