VoIP Over Multiple IEEE 802.11 Wireless LANs

IEEE 802.11 WLAN has high data rate (e.g., 11Mbps for 802.11b and 54Mbps for 802.11g) while voice stream of VoIP has low data rate requirement (e.g., 29.2Kbps). One may therefore expect WLAN to be able to support a large number of VoIP sessions (e.g., 200 and 900 sessions in 802.11b and 802.11g, respectively). Prior work by one of the authors, however, indicated that 802.11 is extremely inefficient for VoIP transport. Only 12 and 60 VoIP sessions can be supported in an 802.11b and an 802.11g WLAN, respectively. This paper shows that the bad news does not stop there. When there are multiple WLANs in the vicinity of each other a common situation these days the already-low VoIP capacity can be further eroded in a significant manner.