Underlying causes of receiver-specific WiFi frame loss during CSI acquisition

Identify the underlying reasons why one or more ESP32 receivers in the ESPARGOS multi-antenna WiFi channel sounder intermittently miss WiFi frames and therefore fail to provide channel state information for particular frames. Analyze the internal operation of the ESP32 WiFi subsystem to ascertain the mechanisms responsible for these losses so that their impact on covariance estimation and subsequent processing can be understood and mitigated.

Background

In the ESPARGOS system, channel state information (CSI) from multiple ESP32-based receivers is clustered per transmitted WiFi frame. The authors note that some receivers sometimes miss frames, leading to incomplete CSI vectors and making standard sample covariance estimation unsuitable. Although they propose an alternative covariance estimation from incomplete data, the root causes of the frame losses remain unclarified.

Understanding the internal behavior of the ESP32 WiFi subsystem (e.g., buffering, timing, synchronization interactions) is necessary to diagnose and potentially prevent these frame losses. Resolving this unknown would improve the reliability of CSI acquisition and the robustness of downstream algorithms relying on multi-antenna coherence.