ESP-WIFI-CSI detects humans with WiFi signals only, no sensor needed

Espressif ESP-WIFI-CSI software relies on the disturbance in the force WiFi signals between one or more ESP32 boards and a router to detect whether humans are present in a room, or even indoor positioning, providing a cost-effective solution since no sensors are needed.

Channel state information (CSI) leverages carrier signal strength, amplitude, phase, and signal delay indicators to reveal the signal scattering, reflection, and power attenuation phenomena that occur with the carrier as the transmission distance changes. This is typically used to measure the channel status of the wireless network in Wi-Fi communication, but it’s also possible to analyze and study the changes in CSI to detect movements such as walking and running of people or animals, and Espressif claims it can also capture subtle movements caused by small movements such as breathing and chewing of people or animals in a static environment.


ESP-WIFI-CSI implementation works with all ESP32 series microcontrollers including ESP32, ESP32-S2, and ESP32-C3, and does not require any changes to the hardware, although an external IPEX antenna is better than a PCB antenna which has directivity. The company also explains Bluetooth LE can also be leveraged for presence detection by scanning surrounding devices to assist with the detection.

ESP32 WIFI CSI indoor positioning
ESP-WIFI-CSI with multiple ESP32 lightbulbs

Typical CSI applications include intruder detection, positioning and ranging, as well as human activity detection and gesture recognition. You’ll find more details on Github with the source code, sample, and a more detailed explanation showing how this all works. More details on ESP32 WiFI CSI indicators can be found on the documentation website. The video below from 2021 also shows a demo of ESP-WIFI-CSI for human detection only (no indoor location).

I could not find details about indoor location range, accuracy, and features like breathing detection when multiple ESP32 boards are in use, so it’s unclear whether ESP-WIFI-CSI will be able to provide the same type of solutions such as ToF sensors, for example, the VL53L5CP used in laptops for human detection and gesture recognition, as well as UWB sensors like Novelda UWB x4 which can detect submillimeter movements for applications such as heating or air conditioner control in a hotel room, where human detection must work even if the guest sleeps.

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