What is VoWLAN (Voice over Wireless Local Area Network)
VoWLAN (Voice over WLAN) is a method of sending voice information in digital form over a wireless broadband network. Essentially, VoWLAN is VoIP delivered through wireless technology. The technology is sometimes called "VoWi-Fi" or "Wi-Fi VoIP" because it uses the IEEE 802.11 set of specifications (informally known collectively as Wi-Fi) for transporting data over wireless local area networks and the Internet.
VoWLAN is primarily a business application designed to provide economical voice communication over an Internet backbone. Because calls are routed internally or over the Internet, this system can decrease or even eliminate mobile telephony costs. VoWLAN uses the same IEEE 802.11 wireless networking standards as Wi-Fi to build a supporting infrastructure.
VoWLAN is similar to VoIP communications except that with VoWLAN, communication takes place within an organization’s geographic perimeter, such as in a hospital, factory or warehouse. VoWLAN works over a Wi-Fi network and software utilities installed on each client device such as a PDA, Wi-Fi handset or Wi-Fi enabled laptop. The client software provides the logical interface for communication, whereas the back-end wireless infrastructure serves as the communication medium.
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The WLAN must be built to provide coverage in any area where users might need to place or receive calls. As with cellular phones, users will expect coverage wherever they happen to be. Companies used to "hotspot" AP deployments will have to expand them to provide continuous coverage in stairwells, hallways, and other common spaces as well as in offices and conference rooms. Most WLAN systems can provide such coverage, but many require costly and time-consuming RF engineering for optimum AP placement. This engineering must be repeated whenever the space is reconfigured, or even when key pieces of furniture are moved. When deploying a WLAN for pervasive coverage, IT engineers should consider not just whether a particular system will provide such coverage, but how much hassle and cost will be required both initially, and as the covered space changes.
Seamless roaming
Wireless users must be handed off as quickly as possible as they roam from one AP coverage area to another. Most VoIP calls will disconnect if they encounter a handoff delay of more than one second, but even delays as short as 50 milliseconds will cause audible clicks or pops in the call. For optimum call quality, delays from the wireless infrastructure should be 5 milliseconds or less. Remember, VoIP packets are delayed at several points during the transmission; if the WLAN infrastructure delays packets beyond a few milliseconds, this can be all it takes to cause problems.
Quality of Service
Each wireless handset user must have guaranteed access to the wireless network to ensure consistent packet delivery, even when many other users are connected through the same AP. The WLAN infrastructure must be able to distinguish between users making voice calls and users checking e-mail or accessing web sites, and it must be able to prioritize the traffic and provide dedicated bandwidth for the call. This type of QoS requires WLAN APs and a WLAN controller that can recognize each user and reserve bi-directional, client-specific bandwidth depending on each user's QoS requirements at the time. Many WLAN systems can't deliver QoS to individual users, or can prioritize packets only from the AP up to the WLAN controller rather than over the wireless link from the AP to the client.
VoWi-Fi = Voice over wireless field
Wi-Fi VoIP = Wireless Field Voice over Internet Protocol**