Voice over wireless LAN via wireless distribution system

A multiplex-multicast (M.-M) scheme previously proposed by us (W. Wang et al, IEEE ISCC´04, 2004) can improve the VoIP capacity in a WLAN operating as an infrastructure basic service set (BSS) by close to 100%. This paper extends the M-M scheme for WLAN connected via a wireless distribution system (WDS). Specifically, we show that given a fixed delay requirement, the M-M scheme can increase the number of supportable VoIP sessions by ten times as compared to ordinary VoIP transmission over the WDS. In addition, with 22 VoIP sessions (max limit in an 802.11b infrastructure BSS connected via a wired distribution system), the M-M scheme can achieve acceptable packet delays, (average of 27.1 ms and standard deviation of 7.5 ms) in a 10-hop WDS. Last but not least, we show that the use of packet scheduling in conjunction with the M-M scheme can further double the VoIP capacity while extending voice-service coverage at the same time.