This article is excerpted from a Burton Group research report. The report, "Voice over Wireless: Can You Hear Me...
Now?" is available with a license to Burton Group's Network and Telecom Strategies Service. Details about Burton Group's research and services are on www.burtongroup.com, or e-mail information requests to firstname.lastname@example.org.
Voice over wireless local area network (VoWLAN) solutions exist today and, in certain industries, are already widely implemented. The current solutions rely on proprietary protocols to provide the high priority required for voice traffic. With the soon-to-be-implemented Wi-Fi Multimedia Extensions (WME) and 802.11e quality of service (QoS) standards, the need for proprietary packaging of the voice traffic on the wireless local area network (WLAN) will be removed. The result is that VoWLAN systems will be more compatible with existing voice over Internet Protocol (VoIP) implementations in the enterprise LAN. While VoWLAN will be a useful adjunct to wired VoIP, the density and performance considerations will generally prevent VoWLAN from becoming the VoIP infrastructure for an enterprise.
VoIP running over the wired local area network (LAN) has begun to take hold in the enterprise. The benefits of using a single set of cabling for both data and voice traffic are now widely accepted. At the same time, enterprises have begun serious deployments of wireless LANs (WLANs) based on the 802.11 standards of the Institute of Electrical and Electronics Engineers (IEEE). Mobile workers within the enterprise are beginning to expect to be able to use the enterprise wireless network for phone service just as they use the wireless network for their other mobile applications. The issues surrounding the use of wireless networks for VoIP, or any time- or latency-sensitive traffic, are significantly different than those for a wired LAN. A certain level of performance expectations, normally provided by dedicated ports, switched connections, and the available quality of service (QoS) mechanisms of a wired LAN, are not available from wireless LANs.
Even in the absence of formal QoS standards, vendors have successfully instituted Voice over WLAN (VoWLAN) products. While there are alternatives to VoWLAN devices, such as wireless private branch exchange (PBX) and cellular phones, the use of VoWLAN can provide benefits to the enterprise.
Some of the issues that are more important with wireless LANs, as compared with wired LANs, include:
- Latency and throughput restrictions
- Number of simultaneous users supported
- Security issues
- Location tracking (E911)
- Handset battery life
- Roaming within the enterprise WLAN
- Roaming between the enterprise LAN and cellular networks
The enterprise acceptance of voice over wireless networks is growing quickly, driven in part by the rapid deployment of VoIP on the wired network. Manufacturing and retail environments have been using the VoWLAN technology for several years, while hospitals and other medical enterprises have quickly implemented the technology in areas where cellular phones are simply not permitted. In addition, there is now a growing push for consumer implementations of VoIP over wireless so that home users can use their broadband network connections for inexpensive, wire-free phone calls. This effort will drive commoditization of many of the VoWLAN components in the long term and make VoWLAN just one more option for making phone calls. As part of this drive, several handset manufacturers will be introducing "converged" handsets that support both cellular and VoWLAN connectivity. These products, along with the eventual and inevitable support for roaming between WLAN and cellular networks, will further drive the movement toward VoWLAN in the enterprise.