A Soft Metric for Assessing the Compliance of WLAN Devices

The goal of this paper is to derive a soft metric for assessing the compliance of the medium access mechanism of commercially available Wi-Fi
^TM
certified units with the IEEE 802.11 standard. The metric is used in conjunction with data collected through a practical testbed based on a Universal Software Radio Peripheral (USRP). The metric derived in this paper captures three compliance aspects: 1- the statistical distribution of the backoff random number that underlies the medium access protocol used by the WiFi Unit Under Test (UUT); 2- the accuracy of the length of the silence period between frames; and 3- the adherence to prescribed transmission opportunity limits set by the standard. The assessment of the first two aspects relies on the Kullback-Leibler distance between probability distributions, whereas the assessment of the third aspect relies on evaluating the probability with which transmission thresholds set by the standards are exceeded. The soft metric proposed in this work is in the form of a single scalar, which enables the UUTs to be ranked based on their level of compliance.