How do you handle BLE and WiFi coexistence on the same chip?

BLE and WiFi both operate in the 2.4 GHz ISM band (2.400-2.4835 GHz), which creates a fundamental coexistence challenge when both radios are active on the same chip or the same PCB. WiFi channels 1, 6, and 11 (the non-overlapping channels in 2.4 GHz, each 20 MHz wide) occupy most of the band, while BLE uses 40 channels of 2 MHz each across the same spectrum. When both radios attempt to transmit simultaneously, the WiFi signal (at 15-20 dBm TX power) overwhelms the BLE receiver (sensitivity around -95 dBm), and the BLE transmission interferes with WiFi reception. Without coexistence management, packet loss rates of 20-50% are common, leading to BLE connection drops and WiFi throughput degradation.

Combo chips like the ESP32, Nordic nRF7002 (WiFi companion to nRF5340 BLE), and CYW43455 (Cypress/Infineon) implement hardware-level coexistence arbitration. The most common mechanism is the Packet Traffic Arbitration (PTA) or coex grant/request protocol: when one radio needs to transmit, it asserts a request signal; the coexistence arbiter decides which radio gets access based on priority rules and timing. Time-critical BLE connection events (especially the anchor point where the first packet must be exchanged) get high priority to prevent connection drops, while WiFi bulk data transfers can tolerate brief pauses. On ESP32, the coexistence module uses a combination of time-division (alternating WiFi and BLE access in microsecond-granularity slots) and frequency-domain awareness (BLE's adaptive frequency hopping avoids the channels currently used by WiFi).

From a firmware perspective, you can improve coexistence by: (1) increasing the BLE connection interval so BLE needs fewer time slots, giving WiFi more airtime; (2) using BLE's adaptive frequency hopping to avoid the three WiFi channels in use; (3) scheduling WiFi data transfers (like firmware OTA) during periods when BLE activity is low; (4) reducing WiFi TX power if range permits, decreasing the desensitization of the BLE receiver; and (5) on dual-chip designs, using an external coexistence interface (3-wire or 4-wire PTA signals between the WiFi and BLE chips) to coordinate access. Testing coexistence requires measuring both WiFi throughput and BLE connection stability simultaneously under load — a common failure mode is that everything works during individual testing but breaks when both radios are active under realistic application conditions.