Conclusions#

Co-located, strong Wi-Fi can have a substantial impact on Bluetooth and 802.15.4 performance. It can be improved by using the following unmanaged coexistence techniques:

  1. Implement Frequency Separation

  2. Operate Wi-Fi with 20 MHz Bandwidth

  3. Increase Antenna Isolation

  4. Implement Protocol and Stack Retry Mechanisms

  5. Remove FEM (or Operate FEM LNA in Bypass)

With market trends toward higher Wi-Fi TX power, higher Wi-Fi throughput, and integration of Wi-Fi, Bluetooth, and other radios, into the same device, unmanaged techniques alone may prove insufficient, so a managed coexistence solution is required. Even with a managed coexistence solution, all unmanaged coexistence recommendations are still necessary.

Silicon Labs recommends the following managed coexistence strategies:

  • Wi-Fi/PTA devices providing 802.15.4-derived Packet Traffic Arbitration.

  • Silicon Labs’ EFR32 PTA solution:

    • Implement one to four GPIOs as a combination of REQUEST, GRANT, PRIORITY, and RHO (two additional GPIOs are required to implement the PWM with High-Duty Cycle Wi-Fi feature for multi-EFR32 configurations).

    • Supports both single-EFR32 and multi-EFR32 configurations with single Wi-Fi/PTA interface.

    • Silicon Labs’ coexistence library and coexistence-hal-config.h #define settings to configure EFR32 PTA support for available GPIO pins and for compatibility with the chosen Wi-Fi/PTA device.

    • Silicon Labs’ API, supporting run-time PTA reconfiguration. For more information, see Zigbee and OpenThread Coexistence with Wi-Fi or Bluetooth Coexistence with Wi-Fi.

Bluetooth#

Wi-Fi/Bluetooth coexistence test results show substantial Bluetooth performance improvements when PTA is utilized:

  • Connection stability

    • Prevent user frustration with unstable product function as Wi-Fi throughput varies.

  • Substantially reduced message failure with associated throughput improvement:

    • Improves end-node battery life.

    • Reduces message latency.

    • Bluetooth remains operational, even during high Wi-Fi duty cycles.

802.15.4#

Wi-Fi/802.15.4 coexistence test results show substantial 802.15.4 performance improvements when PTA is utilized:

  • Improved device join success:

    • However, device join utilizes broadcast messages, which are not retried.

    • If possible, device join success can be further improved by temporarily reducing Wi-Fi traffic during devices joining 802.15.4 network.

  • Substantially reduced MAC retries:

    • Reduces message latency.

    • Improves end-node battery life.

    • Frequency separation remains important, as best managed coexistence performance is for “far-away” channels.

  • Substantially reduced message failure:

    • 802.15.4 network remains operational, even during high Wi-Fi duty cycles.