US Patent 7742578 Location determination capabilities for emergency call services

A communication system comprising an access system configured to provide a plurality of end devices with access to a packet communication network, a first end device of the plurality of end devices configured to transmit a first query to the access system, receive a first response indicating a first identifier for the access system, transmit a registration message indicating the first identifier and a second identifier for the first end device, and transmit a first call request for a call wherein the first call request indicates the second identifier, and a call processing system in communication with the first end device and configured to receive the registration message, store the first identifier in association with the second identifier, receive the first call request, process the second identifier to determine the first identifier stored in association with the second identifier, and transmit a second call request indicating the first identifier.