Protocol Violations in the WiFi Distributed Coordination Function of Raspberry Pi 4
Bjørn Ivar Teigen, Neil J. Davies, Kai Olav Ellefsen, Tor Skeie, Jim Tørresen · 2022
Low latency wireless communications is a growing research area with wide-ranging applications in many areas of technology. Modeling latency in the unlicensed wireless spectrum is challenging because many devices, different protocols, and both persistent and on-demand networks coexist using the same radio resources. Useful modeling depends on a detailed understanding of how each protocol works in order to capture and quantify interaction effects. While validating a model of WiFi latency, we discovered protocol violations in the WiFi implementation on the Raspberry Pi 4. In this work, we document how the WiFi protocol on Raspberry Pi 4B does not conform to the 802.11 WiFi standard. Our results have implications for researchers using the Raspberry Pi 4 to measure WiFi performance. These findings may be symptomatic of a blind spot in the WiFi certification process. If similar protocol violations are common in WiFi devices, this may be important to understand the performance of WiFi networks and their interactions with other wireless protocols.