An Explanation for Unexpected 802.11 Outdoor Link-Level Measurement Results

This paper provides experimental evidence that "Weird"/poor outdoor link-level performance measurements may be caused by driver/card-specific antenna diversity algorithms unexpectedly supported/activated at the WLAN transmitter side. The authors focus the analysis on the Atheros/MADWiFi card/driver case, and they observe that the transmit antenna diversity mechanisms remain by default enabled when the available antennas are not homogeneous in terms of gain or, even worse, when only a single antenna is connected. This may cause considerable performance impairments (large frame loss ratio), in conditions frequently encountered in outdoor link deployments.