# US 2018/0324651 A1 · System and Method for Handovers in a Dual Connectivity Communications System > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0324651 A1 - Document ID: US20180324651A1 - Status: Published application - Kind: A1 - Application number: 15/655,994 - Filed: 2017-07-21 - Published: 2018-11-08 - Earliest claimed: 2017-05-05 - Assignees: Futurewei Technologies, Inc. - Applicants: Futurewei Technologies, Inc. - Inventors: Nathan Edward Tenny; Xuelong Wang - Web page: https://patentgrep.com/patent/US20180324651A1 ## CPC - H04W 36/0016: {Hand-off preparation specially adapted for end-to-end data sessions} - H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload} - H04W 36/0027: {for a plurality of data sessions of end-to-end connections, e.g. multi-call or multi-bearer end-to-end data connections} - H04W 36/0033: {with transfer of context information} - H04W 36/0038: {of security context information} - H04W 36/0069: {in case of dual connectivity, e.g. decoupled uplink/downlink} - H04W 12/04: Key management, e.g. using generic bootstrapping architecture [GBA] - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method for operating a first access node in a dual connectivity (DuCo) handover includes receiving an event trigger for a combined event from a user equipment (UE), sending to a second access node, a combined instruction for primary secondary cell (PSCell) addition and a role change with the second access node in accordance with the event trigger, adding as the second access node as a PSCell, and indicating to the UE, a role change between the first access node and the second access node. ## Claims ### Claim 1 A method for operating a first access node in a dual connectivity (DuCo) handover, the method comprising: receiving, by the first access node, an event trigger for a combined event from a user equipment (UE); sending, by the first access node, to a second access node, a combined instruction for primary secondary cell (PSCell) addition and a role change with the second access node in accordance with the event trigger; adding, by the first access node, as the second access node as a PSCell; and indicating, by the first access node, to the UE, a role change between the first access node and the second access node. ### Claim 2 (depends on 1) The method of claim 1, further comprising: receiving, by the first access node, a UE context release instruction from the second access node; and releasing, by the first access node, a UE context associated with the UE. ### Claim 3 (depends on 2) The method of claim 2, further comprising: forwarding, by the first access node, at least one data packet to the second access node prior to receiving the UE context release instruction. ### Claim 4 (depends on 1) The method of claim 1, further comprising: receiving, by the first access node, an acknowledgement for both the PSCell addition and the role change from the second access node. ### Claim 5 (depends on 1) The method of claim 1, wherein the event trigger reflects a combination of a first quality indicator associated with the first access node falling below a first threshold and a second quality indicator associated with the second access node rising above a second threshold relative to a third quality indicator associated with the first access node. ### Claim 6 A method for operating a first access node in a dual connectivity (DuCo) handover, the method comprising: receiving, by the first access node, a combined event trigger for a combined event from a user equipment (UE); sending, by the first access node, to a second access node, a combined instruction for a role change with the second access node and a primary secondary cell (PSCell) release in accordance with the combined event trigger; indicating, by the first access node, to the UE, a role change between the first access node and the second access node; receiving, by the first access node, a UE context release instruction from the second access node; and releasing, by the first access node, a UE context associated with the UE. ### Claim 7 (depends on 6) The method of claim 6, further comprising: forwarding, by the first access node, at least one data packet to the second access node prior to receiving the UE context release instruction. ### Claim 8 (depends on 6) The method of claim 6, further comprising: receiving, by the first access node, an event trigger for a PSCell addition; and adding, by the first access node, the second access node as a PSCell in accordance with the event trigger. ### Claim 9 (depends on 8) The method of claim 8, wherein receiving the event trigger and adding the second access node occur prior to receiving the combined event trigger. ### Claim 10 (depends on 6) The method of claim 6, wherein the combined event trigger reflects a combination of a first quality indicator associated with the first access node falling below a first threshold and a second quality indicator associated with the second access node rising above a second threshold relative to a third quality indicator associated with the first access node. ### Claim 11 A method for operating a second access node in a dual connectivity (DuCo) handover, the method comprising: receiving, by the second access node, from a first access node, a combined instruction for a role change with the second access node and a primary secondary cell (PSCell) release; changing, by the second access node, to operating as a primary cell (PCell); and sending, by the second access node, a user equipment (UE) context release instruction to the first access node. ### Claim 12 (depends on 11) The method of claim 11, further comprising: establishing, by the second access node, a UE context for a UE as a PSCell. ### Claim 13 (depends on 11) The method of claim 11, further comprising: operating, by the second access node, as a PSCell prior to sending the UE context release instruction. ### Claim 14 A method for processing packets during a role change between a first access node and a second access node, the method comprising: applying, by a user equipment (UE), to a first set of packets, a first set of packet data convergence protocol (PDCP) functions associated with the first access node prior to a processing of a switch indicator, wherein the first set of PDCP functions associated with the first access node includes sequence number assignment and header compression; applying, by the UE, to a second set of packets, a first set of PDCP functions associated with the second access node after the processing of the switch indicator, wherein the first set of PDCP functions associated with the second access node includes sequence number assignment and header compression; applying, by the UE, to a third set of packets, a second set of PDCP functions associated with the first access node when communicating with the first access node, wherein the second set of PDCP functions associated with the first access node includes header addition and/or removal and deciphering and/or ciphering; and applying, by the UE, to a fourth set of packets, a second set of PDCP functions associated with the second access node when communicating with the second access node, wherein the second set of PDCP functions associated with the second access node includes header addition and/or removal and deciphering and/or ciphering. ### Claim 15 (depends on 14) The method of claim 14, wherein the switch indicator is an activation time, and wherein applying the second set of PDCP functions associated with the first access node and applying the second set of PDCP functions associated with the second access node occur both prior to and subsequent to the activation time. ### Claim 16 (depends on 15) The method of claim 15, wherein the activation time comprises a time when the role change occurs. ### Claim 17 (depends on 15) The method of claim 15, wherein the first set of packets comprises packets exchanged prior to the activation time, and wherein the third set of packets comprises packets exchanged with the first access node. ### Claim 18 (depends on 15) The method of claim 15, wherein the second set of packets comprises packets exchanged after the activation time, and wherein the fourth set of packets comprises packets exchanged with the second access node. ### Claim 19 (depends on 14) The method of claim 14, wherein the switch indicator is a PDCP protocol data unit (PDU) indicating the role change, and wherein applying the second set of PDCP functions associated with the first access node and applying the second set of PDCP functions associated with the second access node occur both prior to and subsequent to the processing of the PDCP PDU. ### Claim 20 (depends on 19) The method of claim 19, wherein the first set of packets comprises packets exchanged prior to the processing of the PDCP PDU, and wherein the third set of packets comprises packets exchanged with the first access node. ### Claim 21 (depends on 19) The method of claim 19, wherein the second set of packets comprises packets exchanged after the processing of the PDCP PDU, and wherein the fourth set of packets comprises packets exchanged with the second access node. ### Claim 22 (depends on 19) The method of claim 19, wherein the PDCP PDU is one of a PDCP control PDU indicating the role change or a PDCP data PDU including an end marker.