Realtime detection of degradation in WiFi network´s goodput due to probe traffic

IEEE 802.11 WLAN (Wireless or WiFi LAN) clients discover neighboring APs (Access Points) by active or passive scanning. Such an active scan of WLAN injects probe frames in the network. Network conditions like packet losses, roaming, etc. result in increased active scanning and hence, an excessive increase of the probe traffic. Of the several causes inherent to WLANs like interference, we find an excessive probe traffic also has a potential of hampering goodput of a WiFi network. We confirm this behavior in a controlled home environment as well as in an uncontrolled enterprise environment. Our analysis of 36 hours of wireless traffic collected over a period of 5 months with approximately 45 million wireless frames reveals that goodput of a WLAN drops exponentially with increase in the probe traffic. Therefore, realtime detection of increase in probe traffic and knowledge of a threshold for acceptable probing is crucial for WLAN´s performance. In this paper, we formulate a metric to measure the increase in probe traffic in realtime and evaluate its functioning empirically. The metric not only reflects increase in probe traffic correctly, it is even simple enough to allow its realtime measurement.