Importance

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Abstract

A novel and improved method and apparatus for switching the radio interface layer of a wireless telephone call from code division multiple access (CDMA) cellular to GSM time division multiple access (TDMA) cellular during the course of that telephone call or other communication is described. In accordance with one embodiment of the invention, a set of base stations operating in accordance with the GSM standard generate pilot beacons signals in accordance with CDMA technology. During a phone call, a subscriber unit detects CDMA pilot signals, and notifies a base station controller when CDMA pilot signals are detected and the strength at which they are received. The base station controller identifies CDMA pilot signals from CDMA pilot beacon, and initiates a CDMA to GSM handover via the generation of a set of signaling messages which instruct the subscriber unit and receiving GSM infrastructure equipment to prepare for the switching of the radio interface layer. The subscriber unit responds by acquiring the GSM synchronization information and establishing a RF interface with the GSM base station without interrupting the telephone call being conducted.

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First Claim