A system for providing voice communications between an end terminal in a packet data network and a wireless communication device includes a packet communication supporting subsystem, a base station subsystem, and a Voice-over-Internet-Protocol Mobile Switching Center ("VMSC"). The packet communication supporting subsystem communicates with the packet data network and also operates to locate the wireless communication device. The base station subsystem communicates with the wireless communication device, and also communicates the packet data network through the packet communication supporting subsystem in the form of data packets. The VMSC communicates with the packet communication supporting subsystem through a packet-switched network and communicating with the base station subsystem through a circuit-switched network. In addition, registration, call-making, call-releasing, and call-receiving methods are provided for a wireless communication device to provide voice communications between the wireless communication device and an end terminal in a packet data network.