Softspeak: Making VoIP Play Well in Existing 802.11 Deployments
Source: University of California
Voice over IP (VoIP) in 802.11 Wireless Networks (WiFi) is an attractive alternative to cellular wireless telephony. Unfortunately, VoIP traffic is well known to make inefficient use of such networks. Indeed, the author demonstrates that increasing handset deployment has the potential to cripple existing hotspot and enterprise WiFi networks. The experiments show that VoIP halves the available TCP capacity of an 802.11b hotspot when six to eight VoIP stations share the medium, and effectively extinguishes TCP connectivity when ten VoIP stations are present. Further, the paper shows that neither the higher data rates of 802.11a/g nor the 802.11 standard for quality of service, 802.11e, fully ameliorate the problem. Instead, the problem is rooted in WiFi's contention-based medium-access control mechanism and considerable framing overhead.