Skip to main content
Both WiFi CSI and mmWave radar are non-visual RF sensors. The tradeoff is dedicated ranging hardware versus commodity WiFi reuse. Choose based on whether you need centimeter precision or building-scale economics.

​
RF front-end

mmWave radar uses a purpose-built transceiver (typically 60 GHz) with chirp modulation designed for range-Doppler processing. Resolution reaches centimeter-range distance and sub-Hz Doppler for micro-motion. WiFi CSI uses the existing 2.4/5 GHz WiFi PHY. Resolution is limited by wavelength (~6 cm at 5 GHz) and packet-rate sampling. Fine-ranging is not the design goal.

​
Fine-motion SNR

Radar front-ends are optimized for detecting sub-millimeter chest displacement: breathing and heartbeat are first-class signals. ESP32 CSI can detect breathing after phase sanitization, but the hardware noise floor is higher and SNR is placement-dependent. For clinical-grade vitals, radar wins. For presence awareness (“someone is still in the room”), CSI is often sufficient.

​
Cost and scale

Covering a 10-room office with radar means 10+ dedicated modules. With CSI, a few nodes per room on hardware you may already have deployed for other purposes.

​
When to choose which

mmWave radar: per-zone ranging, fall detection with low false-alarm requirements, vital signs in a clinical-adjacent setting, single-room precision. WiFi CSI: whole-building occupancy at scale, multi-room analytics, smart-home presence holds, security zone detection. Anywhere economics and ubiquity matter more than centimeter ranging. See presence detection for CSI micro-motion scope.