Measuring the Impact of Slow User Motion on Packet Loss and Delay over IEEE 802.11b Wireless Links

IEEE 802.11b compliant WLAN technology is increasingly used for cordless telephone services. Often, a WLAN phone is moved during a call. In the present paper we explore to what extent slow user motion influences the wireless link quality. We conducted extensive measurements with speech over commercial WLAN equipment using an experimental environment enforcing controlled motion. Our experiments show that – in contrast to the common assumption – an increase of motion speed can result in a better link quality: The packet loss rate and variance, measured after link-layer retransmissions, decreases. In addition, our measurements demonstrate that the modulation type, the maximal number of retransmissions, the experimental setting, and even the quality of power supply are the dominant influences on link quality.