Patent attributes
A method and apparatus performs handover from an OFDM-based E-UMTS system to a CDMA-based UMTS system. A UE in communication with a PDN via the E-UMTS system, measures signal strength of the UMTS system, and sends a measurement report message indicating the measured signal strength to the E-UMTS system. A radio access network (E-RAN) of the E-UMTS system, determines whether to perform handover from the E-UMTS system to the UMTS system based on the measured signal strength. If the handover is to be performed, a core network (E-CN) of the E-UMTS system generates a PDP context and an MM context for the UE in response to a handover request from the E-RAN. The E-CN sets up a data tunnel for the UE to a GGSN of the UMTS system using the PDP/MM context. After setting up the data tunnel, the E-CN sends to the UE a handover command message including information on a radio bearer (RB) to be used by the UE to access the UMTS system. The UE accesses the UMTS system using the RB information. After accessing the UMTS system, the UE forwards user data for the UE via a data transmission path composed of the E-CN, the data tunnel, a SGSN, and a RAN of the UMTS system, between the PDN and the UE.
