Handover method and apparatus between different systems
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.
1. A method for performing handover from an orthogonal frequency division modulation (OFDM) mobile communication system to a code division multiple access (CDMA)-based UMTS system, the method comprising the steps of:
measuring, by a user equipment (UE) in communication with a packet data network (PDN) via the OFDM mobile communication system, signal strength of the UMTS system, and sending a measurement report message indicating the measured signal strength to the OFDM mobile communication system;
determining, by a radio access network (E-RAN) of the OFDM mobile communication system, to perform handover from the OFDM mobile communication system to the UMTS system based on the measured signal strength;
sending, by the E-RAN, to a Enhanced-Core Network (E-CN) of the OFDM mobile communication a handover required message including a ‘source radio network controller (RNC) to target RNC transparent container’;
sending, by the E-CN, to a target serving GPRS support node (SGSN) a forward relocation request message;
sending, by the target SGSN, to a target radio network controller (RNC) a relocation request message;
allocating, by the target RNC, a radio bearer (RB) information, and sending the RB information to the E-CN via the target SGSN;
sending, by the E-CN, to the UE a handover command message including the RB information; and
accessing, by the UE, the UMTS system using the RB information.
2. The method of claim 1 , wherein the forward relocation request message comprises mobility management (MM) context.
3. The method of claim 1 , wherein handover command message includes the ‘target RNC to source RNC transparent container’.
4. A system for performing handover from an orthogonal frequency division modulation (OFDM) mobile communication system to a code division multiple access (CDMA)-based UMTS system, the method comprising the steps of:
a user equipment (UE) for measuring in communication with a packet data network (PDN) via the OFDM mobile communication system, signal strength of the UMTS system, and sending a measurement report message indicating the measured signal strength to the OFDM mobile communication system;
an Enhanced-radio access network (E-RAN) of the OFDM mobile communication system for determining the E-RAN performs handover from the OFDM mobile communication system to the UMTS system based on the measured signal strength, and sending to a Enhanced-Core Network (E-CN) of the OFDM mobile communication a handover required message including a ‘source radio network controller (RNC) to target RNC transparent container’;
the E-CN for sending to a target serving GPRS support node (SGSN) a forward relocation request message, and sending to the UE a handover command message including the RB information;
the target SGSN for sending to a target radio network controller (RNC) a relocation request message;
the target RNC for allocating a radio bearer (RB) information, and sending the RB information to the E-CN via the target SGSN;
wherein the UE accesses the UMTS system using the RB information.
5. The system of claim 4 , wherein the forward relocation request message comprises mobility management (MM) context.
6. The system of claim 4 , wherein handover command message includes the ‘target RNC to source RNC transparent container’.