Method and device for supporting handover
The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. According to an aspect of the embodiments of the present disclosure, a method for supporting handover is provided, comprising: receiving a message from a central unit control plane entity of a target base station; receiving a data packet from a source base station; and discarding a packet data convergence protocol (PDCP) service data unit (SDU) including the PDCP sequence number (SN) in the received data packet according to the indication of the message.
1. A method performed by a central unit (CU)-control plane (CP) of a source base station in a communication system, the method comprising:
receiving, from a core network, a handover command message for a handover to a target base station, wherein the source base station operates based on a first radio access technology (RAT) and the target base station operates based on a second RAT, and wherein the handover command message includes information on a tunnel associated with the second RAT for direct data forwarding from a CU-user plane (UP) of the source base station to the target base station; and
transmitting, to the CU-UP of the source base station, a bearer context modification request message, the bearer context modification request message including data forwarding information for the handover,
wherein the data forwarding information includes information on a quality of service (QOS) flow to be forwarded on the tunnel.
2. The method of claim 1 ,
wherein the data forwarding information further includes information on a transport layer address and information on an identifier (ID) of the tunnel, and
wherein the direct data forwarding is performed based on the data forwarding information.
3. The method of claim 2 ,
wherein the first RAT is a new radio (NR) and the second RAT is an evolved-universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN), and
wherein data is forwarded to the target base station without a service data adaptation protocol (SDAP) header.
4. The method of claim 3 ,
wherein the handover command message further includes information on an E-UTRAN-radio access bearer (E-RAB) ID corresponding to the tunnel.
5. The method of claim 4 , further comprising:
receiving, from the core network, a message for protocol data unit (PDU) session resource setup including information on a mapping between at least one QoS flow and the E-RAB ID.
6. A method performed by a central unit (CU)-user plane (UP) of a source base station in a communication system, the method comprising:
receiving, from a CU-control plane (CP) of the source base station, a bearer context modification request message, the bearer context modification request message including data forwarding information for a handover to a target base station, wherein the source base station operates based on a first radio access technology (RAT) and the target base station operates based on a second RAT;
identifying information on a quality of service (QOS) flow to be forwarded on a tunnel associated with the second RAT included in the data forwarding information; and
forwarding, to the target base station, data for the QoS flow using the tunnel.
7. The method of claim 6 ,
wherein the data forwarding information further includes information on a transport layer address and information on an identifier (ID) of the tunnel.
8. The method of claim 7 ,
wherein the first RAT is a new radio (NR) and the second RAT is an evolved-universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN), and
wherein the data is forwarded without a service data adaptation protocol (SDAP) header.
9. The method of claim 8 ,
wherein the QoS flow is mapped to an E-UTRAN-radio access bearer (E-RAB) ID.
10. A central unit (CU)-control plane (CP) of a source base station in a communication system, the CU-CP of the source base station comprising:
a transceiver; and
a processor configured to:
control the transceiver to receive, from a core network, a handover command message for a handover to a target base station, wherein the source base station operates based on a first radio access technology (RAT) and the target base station operates based on a second RAT, and wherein the handover command message includes information on a tunnel associated with the second RAT for direct data forwarding from a CU-user plane (UP) of the source base station to the target base station, and
control the transceiver to transmit, to the CU-UP of the source base station, a bearer context modification request message, the bearer context modification request message including data forwarding information for the handover,
wherein the data forwarding information includes information on a quality of service (QOS) flow to be forwarded on the tunnel.
11. The CU-CP of the source base station of claim 10 ,
wherein the data forwarding information further includes information on a transport layer address and information on an identifier (ID) of the tunnel, and
wherein the direct data forwarding is performed based on the data forwarding information.
12. The CU-CP of the source base station of claim 11 ,
wherein the first RAT is a new radio (NR) and the second RAT is an evolved-universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN), and
wherein data is forwarded to the target base station without a service data adaptation protocol (SDAP) header.
13. The CU-CP of the source base station of claim 12 ,
wherein the handover command message further includes information on an E-UTRAN-radio access bearer (E-RAB) ID corresponding to the tunnel.
14. The CU-CP of the source base station of claim 13 ,
herein the processor is further configured to control the transceiver to receive, from the core network, a message for protocol data unit (PDU) session resource setup including information on a mapping between at least one QoS flow and the E-RAB ID.
15. A central unit (CU)-user plane (UP) of a source base station in a communication system, the CU-UP of the source base station comprising:
a transceiver; and
a processor configured to:
control the transceiver to receive, from a CU-control plane (CP) of the source base station, a bearer context modification request message, the bearer context modification request message including data forwarding information for a handover to a target base station, wherein the source base station operates based on a first radio access technology (RAT) and the target base station operates based on a second RAT,
identify information on a quality of service (QOS) flow to be forwarded on a tunnel associated with the second RAT included in the data forwarding information, and
control the transceiver to forward, to the target base station, data for the QoS flow using the tunnel.
16. The CU-UP of the source base station of claim 15 ,
wherein the data forwarding information further includes information on a transport layer address and information on an identifier (ID) of the tunnel.
17. The CU-UP of the source base station of claim 16 ,
wherein the first RAT is a new radio (NR) and the second RAT is an evolved-universal mobile telecommunications system (UMTS) terrestrial radio access network (E-UTRAN), and
wherein the data is forwarded without a service data adaptation protocol (SDAP) header.
18. The CU-UP of the source base station of claim 17 ,
wherein the QoS flow is mapped to an E-UTRAN-radio access bearer (E-RAB) ID.