Description
The ESP32 is a low-cost ($2–$5) Wi-Fi + Bluetooth/BLE SoC by Espressif. Its appeal for CSI research is that it is the cheapest commodity device that exposes 802.11n CSI out of the box via Espressif's esp_wifi_set_csi_rx_cb API — no firmware patching needed. The ESP32 CSI Tool (Hernandez & Bulut, 2020) and follow-up ESP32-CSI-Tool made this practical for distributed sensor deployments. ESP32-S3 and -C3 variants extend this to 802.11n on cheaper / lower-power silicon. Variants also speak BLE 4.2/5.0, making the ESP32 a natural carrier for the BLE-calibrated CSI deployment proposed in the thesis.
Specs / capabilities
- 802.11b/g/n at 2.4 GHz (single antenna; no 5 GHz on baseline ESP32)
- 64 subcarriers reported (legacy 20 MHz HT)
- Bluetooth 4.2 BR/EDR + BLE on baseline ESP32; BLE 5.0 on S3/C3
- Tensilica Xtensa LX6 dual-core (240 MHz) on ESP32; RISC-V on C3
- Operates as STA, AP, or sniffer; CSI export via callback in user firmware
- ~$2-5 per board, USB-C dev kits widely available
Tooling
- ESP-IDF (Espressif's official SDK): https://github.com/espressif/esp-idf
- ESP32 CSI Tool (Hernandez & Bulut): https://stevenmhernandez.github.io/ESP32-CSI-Tool/
- Arduino + PlatformIO for rapid prototyping
Used by (papers)
- hernandez2020 — ESP32 CSI Tool release paper
- Increasingly common in 2021+ papers that need many cheap distributed CSI nodes