Wireless Local Area Networks, or Wi-Fi networks (e.g., IEEE 802.11b), are ideal for extending the reach of local area networks to accommodate the increased mobility of users. Using a WLAN, users throughout the WLAN coverage area can connect to the corporate data network using a Personal Computer (PC) incorporating a wireless LAN card. Furthermore, WLANs allow users to make and receive voice calls using WLAN enabled Personal Digital Assistance (PDAs) or other Wi-Fi enabled devices. The use of WLAN or Wi-Fi networks to carry Voice over Internet Protocol (VoIP) traffic is gaining popularity such that some WLANs are being installed as dedicated networks for voice traffic. This capability is appealing since it allows users to make and receive wireless calls within the coverage area of the WLAN without incurring cellular telephone charges. Campuses, airports, hotels, for example, and other public places are well suited to WLAN implementations.
The benefit of a WLAN is limited by the constraints of the coverage area of that WLAN. As users leave the coverage area, WLAN calls are disconnected. This limitation has been addressed previously by Siemens' HiPath CorporateConnect feature, in which users may, on-demand, hand-over (i.e. transfer) a WLAN call from the wireless device to a cellular device. According to know methods, when a user decides to hand-over a call to a target device, the user enters a hand-over access code followed by the telephone number of the target device. Consequently, the target device is dialed and the call is connected to that target device upon answering the incoming call.
However, know techniques require the user to actively request the hand-over and determine when the hand-over should occur. Typically it is difficult for the user to accurately evaluate the received WLAN signal strength or the quality of the IP connection in order to determine the optimal time and physical location for handing over the call.