Apparatus, system and method for DC (dual connectivity)

A base station (eNodeB) in a mobile communication system for DC (Dual Connectivity) including at least a UE (User Equipment), a MeNB (Master eNodeB), a SeNB (Secondary eNodeB), a MME (Mobility Management Entity), and a S-GW (Serving Gateway), wherein the UE is connected to the MeNB and the SeNB, C-Plane (Control Plane) signaling is performed by interfaces between the MeNB and the SeNB and between the MeNB and the MME, and U-Plane (User Plane) data is transferred from the S-GW to the MeNB and the SeNB, upon a handover from a source MeNB to a target eNB, the source MeNB comprising:

• a sender configured to send a Handover Request message to the target eNB;
• a receiver configured to receive a Handover Request Acknowledge message from the target eNB;
• and
• a controller configured to release a source SeNB,
• wherein the UE receives a RRCConnectionReconfiguration message from the source MeNB, the RRCConnectionReconfiguration message informing the UE that the source MeNB has released the source SeNB, and sends a RRCConnectionReconfigurationComplete message to the target eNB,
• wherein the target eNB adds a new SeNB, from among the source SeNB or another SeNB, if a resource of the new SeNB is available;
• and
• wherein security context is deleted at the UE and the source SeNB.

A UE (User Equipment) in a mobile communication system for DC (Dual Connectivity) including at least a MeNB (Master eNodeB), a SeNB (Secondary eNodeB), a MME (Mobility Management Entity), and a S-GW (Serving Gateway), wherein the UE is connected to the MeNB and the SeNB, C-Plane (Control Plane) signaling is performed by interfaces between the MeNB and the SeNB and between the MeNB and the MME, and U-Plane (User Plane) data is transferred from the S-GW to the MeNB and the SeNB,

• the UE comprising:
• upon a handover from a source MeNB to a target eNB,
• a receiver that receives a RRCConnectionReconfiguration message from the source MeNB, the RRCConnectionReconfiguration message informing the UE that the source MeNB has released a source SeNB;
• and
• a transmitter that sends a RRCConnectionReconfigurationComplete message to the target eNB;
• wherein the source MeNB sends a Handover Request message to the target eNB,
• receives a Handover Request message Acknowledge from the target eNB, and
• releases the source SeNB,
• wherein the target eNB adds a new SeNB, from among the source SeNB or another SeNB, if a resource of the new SeNB is available, and
• wherein security context is deleted at the UE and the source SeNB.

A method of a mobile communication system for DC (Dual Connectivity) including a UE (User Equipment), a MeNB (Master eNodeB), a SeNB (Secondary eNodeB), a MME (Mobility Management Entity), and a S-GW (Serving Gateway), wherein the UE is connected to the MeNB and the SeNB, C-Plane (Control Plane) signaling is performed by interfaces between the MeNB and the SeNB and between the MeNB and the MME, and U-Plane (User Plane) data is transferred from the S-GW to the MeNB and the SeNB, the method comprising:

• upon a handover from a source MeNB to a target eNB,
• sending a Handover Request message to the target eNB;
• receiving a Handover Request Acknowledge message from the target eNB;
• releasing a source SeNB;
• receiving a RRCConnectionReconfiguration message from the source MeNB, the RRCConnectionReconfiguration message informing the UE of the releasing of the source SeNB;
• and
• sending a RRCConnectionReconfigurationComplete message to the target eNB,
• wherein the target eNB adds a new SeNB, from among the source SeNB or another SeNB, if a resource of the new SeNB is available, and
• wherein security context is deleted at the UE and the source SeNB.

A method of a base station (eNodeB) in a mobile communication system for DC (Dual Connectivity) including at least a UE (User Equipment), a MeNB (Master eNodeB), a SeNB (Secondary eNodeB), a MME (Mobility Management Entity), and a S-GW (Serving Gateway), wherein the UE is connected to the MeNB and the SeNB, C-Plane (Control Plane) signaling is performed by interfaces between the MeNB and the SeNB and between the MeNB and the MME, and U-Plane (User Plane) data is transferred from the S-GW to the MeNB and the SeNB, the method comprising:

• upon a handover from a source MeNB to a target eNB,
• sending a Handover Request message to the target eNB and;
• receiving a Handover Request Acknowledge message from the target eNB;
• and
• releasing a source SeNB,
• wherein the UE receives a RRCConnectionReconfiguration message from the source MeNB, the RRCConnectionReconfiguration message informing the UE that the source MeNB has released the source SeNB, and sends a RRCConnectionReconfigurationComplete message to the target eNB,
• wherein the target eNB adds a new SeNB, from among the source SeNB or another SeNB, if a resource of the new SeNB is available, and
• wherein security context is deleted at the UE and the source SeNB.

A method of a UE (User Equipment) in a mobile communication system for DC (Dual Connectivity) including at least a MeNB (Master eNodeB), a SeNB (Secondary eNodeB), a MME (Mobility Management Entity), and a S-GW (Serving Gateway), wherein the UE is connected to the MeNB and the SeNB, C-Plane (Control Plane) signaling is performed by interfaces between the MeNB and the SeNB and between the MeNB and the MME, and U-Plane (User Plane) data is transferred from the S-GW to the MeNB and the SeNB, the method comprising:

• upon a handover from a source MeNB to a target eNB,
• receiving a RRCConnectionReconfiguration message from the source MeNB, the RRCConnectionReconfiguration message informing the UE that the source MeNB has released a source SeNB;
• and
• sending a RRCConnectionReconfigurationComplete message to the target eNB;
• wherein the source MeNB sends a Handover Request message to the target eNB,
• receives a Handover Request message Acknowledge from the target eNB, and
• releases the source SeNB,
• wherein the target eNB adds a new SeNB, from among the source SeNB or another SeNB, if a resource of the new SeNB is available, and
• wherein security context is deleted at the UE and the source SeNB.