IoT gateways and hubs benefit from enabling multiple protocols such as Wi-Fi, Zigbee, Thread, and Bluetooth to support a diverse end node landscape. These protocols share the same 2.4 GHz ISM band and adopting Wi-Fi coexistence strategies can minimize the performance degradation that happens when one or more collocated radios operate simultaneously.
Wi-Fi coexistence allows multiple 2.4 GHz technologies including Wi-Fi, Zigbee, Thread, and Bluetooth to operate without signals from one radio interfering with adjacent radios. Interference degrades wireless performance through message failures, resulting in more message retries. These issues can lead to reduced device responsiveness and increased power consumption.
Coexistence historically was achieved through a combination of hardware design techniques and protocol features such as collision avoidance or message retries. Current gateways and hubs support increased throughput, often transmit at higher power levels, and may integrate up to four 2.4 GHz radios. These factors make coexistence more difficult to achieve and require designers to take additional steps to ensure advanced, reliable IoT wireless performance.
Managed Wi-Fi coexistence is an effective technique to reduce wireless interference when multiple radios operate in a single, small form-factor device such as an IoT gateway or hub. Wireless performance is improved with managed Wi-Fi coexistence by separating collocated radios through a signaling system that coordinates access to 2.4GHz for transmit and receive.
Silicon Labs’ managed Wi-Fi coexistence solution, based on IEEE 802.15.2 packet traffic arbitration (PTA), implements a coordination scheme that allows the EFR32 Mighty Gecko SoC to signal the Wi-Fi device before receiving or transmitting a message. Once the Wi-Fi device is aware of an EFR32 request, Wi-Fi transmit can be delayed, improving EFR32’s message reliability.
Figure 1: IoT Network without Managed Coexistence
Figure 2: IoT Network with Managed Coexistence PTA
Silicon Labs’ managed Wi-Fi coexistence supports one, two, and three wire PTA implementations. The solution is flexible and supports request, grant, and priority signals. Implemented at the MAC layer and tested with major Wi-Fi chip vendors, our managed Wi-Fi coexistence helps designers improve IoT wireless gateway and hub performance by improving responsiveness and reducing power consumption. Read our application note (AN1017) to learn more about Wi-Fi’s impact on Zigbee/Thread (IEEE 802.15.4) and methods to improve wireless IoT gateway and hub performance.
Managed coexistence is critical when using multiple 2.4 GHz radios in today’s small hubs and gateways. The Wi-Fi Coexistence Development Kit provides a simple, but flexible backplane which developers can connect a Wi-Fi solution and up to three (3) Silicon Labs radios including Zigbee, Thread and Bluetooth solutions using the flexible PTA (Packet Traffic Arbitration) implementation to help manage radio operation.
NOTE: Not all Wi-Fi solution are capable of supporting PTA. When choosing a Wi-Fi solution, be sure to select a vendor and a Wi-Fi solution that supports coexistence/PTA operation.
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