# US 12,004,250 B2 · Packet data convergence protocol data recovery > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,004,250 B2 - Document ID: US12004250B2 - Status: Granted - Kind: B2 - Application number: 18/107,768 - Filed: 2023-02-09 - Published: 2023-06-15 - Granted: 2024-06-04 - Earliest claimed: 2018-07-02 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Matteo Fiorani; Panagiotis Saltsidis - Web page: https://patentgrep.com/patent/US12004250B2 ## CPC - H04W 76/19: Connection re-establishment - H04L 1/08: by repeating transmission, e.g. Verdan system {(H04L1/1858 and H04L1/189 take precedence)} - H04W 88/085: {Access point devices with remote components} - 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 Embodiments described herein provide methods and apparatuses for synchronizing radio link control re-establishment between a user equipment (UE) and a base station distributed unit (DU) with Packet Data Convergence Protocol (PDCP) data recovery. A method performed by a Control Plane data processing apparatus comprises: obtaining an indication that an uplink and/or downlink outage has occurred between the base station DU and the UE; and transmitting a request to a user plane (UP) data processing apparatus to instruct the UP data processing apparatus to retransmit any data protocol units previously transmitted to the UE which were unacknowledged by the UE. ## Claims ### Claim 1 A method performed by a central unit (CU) of a base station comprising the CU and one or more distributed units (DU), for synchronizing radio link control re-establishment between a user equipment (UE) and a DU, the method comprising: obtaining, in a control plane (CP) data processing apparatus of the CU, an indication that an uplink and/or downlink outage has occurred between the DU and the UE; sending a request from the CP data processing apparatus to a user plane (UP) data processing apparatus of the CU, to instruct the UP data processing apparatus to retransmit, via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE; and, responsive to the request, retransmitting, by the UP data processing apparatus and via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE. ### Claim 2 (depends on 1) The method of claim 1, wherein said obtaining comprises receiving the indication from the DU. ### Claim 3 (depends on 1) The method of claim 1, wherein the CP data processing apparatus is collocated with the base station DU. ### Claim 4 (depends on 1) The method of claim 1, wherein the indication comprises a UE Context Modification Required message. ### Claim 5 (depends on 1) The method of claim 1, further comprising, responsive to obtaining the indication, generating a radio resource control (RRC) reconfiguration message in the CP data processing apparatus and transmitting the RRC reconfiguration message to the UE. ### Claim 6 (depends on 1) The method of claim 1, wherein the request comprises a Bearer Context Modification Request comprising a Packet Data Convergence Protocol (PDCP) data recovery information element (IE) indicating that PDCP data recovery is requested. ### Claim 7 A method, in a base station comprising a central unit and one or more distributed units (DU), for synchronizing radio link control re-establishment between a user equipment (UE) and a DU, the method comprising: obtaining an indication that an uplink and/or downlink outage has occurred between the DU and the UE; requesting a user plane (UP) data processing apparatus of the CU to retransmit, via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE; and, responsive to the request, retransmitting, by the UP data processing apparatus and via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE. ### Claim 8 A base station comprising a control plane (CP) data processing apparatus and a user plane (UP) data processing apparatus, the CP data apparatus and the UP data processing apparatus comprising processing circuity configured to: obtain, in the CP data processing apparatus, an indication that an uplink and/or downlink outage has occurred between a distributed unit (DU) of the base station and a user equipment (UE); send a request from the CP data processing apparatus to the UP data processing apparatus, to instruct the UP data processing apparatus to retransmit, via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE; and, responsive to the request, retransmitting, by the UP data processing apparatus and via the DU, any data protocol units previously transmitted to the UE which were unacknowledged by the UE. ### Claim 9 (depends on 8) The base station of claim 8, wherein said obtaining comprises receiving the indication from the DU. ### Claim 10 (depends on 8) The base station of claim 8, wherein the CP data processing apparatus is collocated with the base station DU. ### Claim 11 (depends on 8) The base station of claim 8, wherein the indication comprises a UE Context Modification Required message. ### Claim 12 (depends on 8) The base station of claim 8, further comprising, responsive to obtaining the indication, generating a radio resource control (RRC) reconfiguration message in the CP data processing apparatus and transmitting the RRC reconfiguration message to the UE. ### Claim 13 (depends on 8) The base station of claim 8, wherein the request comprises a Bearer Context Modification Request comprising a Packet Data Convergence Protocol (PDCP) data recovery information element (IE) indicating that PDCP data recovery is requested.