I. Conclusion

Although both Bluetooth and Wi-Fi use the 2.4 GHz ISM band, their physical layer (PHY), link layer/MAC, uses, and design goals are completely different, resulting in drastically different performance characteristics (throughput, power consumption, latency, interference immunity, coverage, etc.).

II. Differences in Physical Layer (PHY)

Modulation and Multiplexing: Wi-Fi mostly uses DSSS/OFDM (802.11b/g/n/ac/ax), suitable for high data rates and bandwidth; Bluetooth Classic uses GFSK/Frequency Hopping (FHSS), and **Bluetooth Low Energy (BLE)** primarily uses narrow-channel GFSK (or a coding extension of BLE 5), favoring low speed and low power consumption.

Channel Bandwidth: Wi-Fi commonly uses 20/40/80/160 MHz channels, occupying a wide spectrum per transmission; BLE uses only 2 MHz per channel (traditional), and Bluetooth Classic uses even narrower channels or frequency hopping.

Spectrum Usage Strategies: Bluetooth commonly uses Frequency Hopping Service (FHSS) or Adaptive Frequency Hopping (AFH) to quickly switch channels and avoid interference; Wi-Fi transmits continuously within a wide frequency band, making it more susceptible to narrowband interference for longer periods.

III. Link Layer/MAC Differences

Access Methods: Wi-Fi uses CSMA/CA (Carrier Sense and Random Backoff), with multiple devices competing for the same channel, suitable for bursty high-bandwidth transmission; Bluetooth (especially BLE) primarily uses connection events/master-slave scheduling, with transmission characterized by short packets and timing, resulting in controllable latency and higher energy efficiency.

Topology and Applications: Wi-Fi is primarily used in infrastructure mode (AP/router), supporting multiple users and high throughput; Bluetooth is primarily used in point-to-point/piconet networks, targeting low-power applications such as device pairing, sensors, and audio.

Latency and Throughput: Wi-Fi supports tens of Mbps to Gbps (depending on the standard); BLE typically ranges from hundreds of kbps to a few Mbps (BLE 5's 2 Mbps). In terms of latency and power consumption, Bluetooth is better suited for short, frequent packets.

IV. Differences in Power Consumption and Device Design Goals

Bluetooth is designed with extremely low power consumption (battery-powered devices/sensors), allowing for extended periods of sleep when idle and only briefly waking up to transmit during connection events.
Wi-Fi is designed for high-speed data paths, resulting in higher transmit power, higher wake-up frequency, and higher overhead, thus consuming more power.

V. Anti-interference and Coexistence Mechanisms

Bluetooth's frequency hopping/AFH (Average Frequency Hopping) has a natural frequency avoidance capability, partially mitigating narrowband interference or short-term Wi-Fi occupancy.

Wi-Fi occupies bandwidth and lasts for extended periods, easily interfering with nearby Bluetooth. Conversely, Bluetooth's short-term frequency hopping usually has a smaller impact on Wi-Fi.

Modern SoCs implement hardware-level coexistence mechanisms to coordinate the TX/RX times of Bluetooth and Wi-Fi to reduce mutual interference.

VI. Security and Pairing/Authentication Models

Wi-Fi (WPA2/3) is geared towards network-level security, complex authentication, and encryption; Bluetooth offers pairing/bonding, optional encryption, and privacy features (but with different implementations and uses).

VII. Regulatory and Implementation Differences

Although both operate in the ISM band, they follow different spectrum occupancy rules and transmission characteristics (transmission bandwidth, power limits, spectrum masks, etc.). Their device antenna designs and RF links also differ, affecting coverage and performance.

VIII. Actual Impact / Why the "Feeling" is Different

Throughput, Latency: Wi-Fi has high throughput and variable latency; Bluetooth has lower throughput but controllable latency and timely response.

Power Consumption and Battery Life: Bluetooth is far superior to Wi-Fi (especially BLE).

Stability/Coverage: Wi-Fi (higher transmit power and more complex signal processing) generally outperforms Bluetooth in coverage and wall penetration (depending on antenna and power).

Mutual Interference: In congested 2.4GHz environments, Wi-Fi's long bandwidth packets are more likely to "crush" Bluetooth, causing connection/audio stuttering; proper configuration can mitigate this.

IX. Practical Suggestions (Coexistence and Optimization)

Prioritize switching to 5GHz Wi-Fi (if available) to move out of the 2.4GHz congestion zone.

Reducing Wi-Fi channel bandwidth (from 40/80MHz back to 20MHz) can reduce the probability of interference with Bluetooth.

Enable Bluetooth AFH/Power Saving mode and turn on the BT/Wi-Fi coexistence switch in the firmware/driver (if the SoC supports it).

Physical isolation and antenna orientation: Increase distance or adjust antenna orientation to reduce interference coupling.

QoS and timing: Use time windows/priorities for critical traffic (Bluetooth audio or low-latency links), or retry/buffer at the application layer for a smoother experience.