> ## Documentation Index
> Fetch the complete documentation index at: https://docs.waveyhq.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# WiFi CSI Sensing vs mmWave Radar Compared

> Compare commodity WiFi reuse with dedicated 60 GHz radar for presence, motion, and vitals sensing across cost, scale, and precision.

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

|                    | mmWave radar module      | ESP32 CSI node                      |
| ------------------ | ------------------------ | ----------------------------------- |
| Unit cost          | $10 to $50+ per module   | $3 to $8 per module                 |
| Dedicated hardware | Yes: radar in every zone | Reuses existing WiFi infrastructure |
| OTA upgrade        | Module-specific          | Standard ESP32 firmware             |
| Ecosystem          | Smaller, vendor-specific | Huge (Home Assistant, MQTT, etc.)   |

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](/use-cases/presence-detection) for CSI micro-motion scope.