WO2025256735A1

WO2025256735A1 - Flexible signaling radio bearer termination

Info

Publication number: WO2025256735A1
Application number: PCT/EP2024/066160
Authority: WO
Inventors: Ethiraj Alwar; Janne Veikko Kaasalainen; Raghuram Reddy KRISHNAMURTHY
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2024-06-12
Filing date: 2024-06-12
Publication date: 2025-12-18
Anticipated expiration: 2026-12-12

Abstract

A method and apparatus are disclosed for enabling and implementing flexible signaling radio bearer (SRB) termination. As described herein, an SRB termination may be relocated to and/or from a centralized unit (CU) of a base station and a distributed unit (DU) of the base station. The relocation may be enabled and/or implemented based on one or more trigger conditions.

Description

FLEXIBLE SIGNALING RADIO BEARER TERMINATION

TECHNOLOGICAL FIELD

[0001] An example embodiment relates generally to flexible termination of signaling radio bearers (SRBs).

BACKGROUND

[0002] Some wireless technologies include floating radio resource control (RRC) mechanisms. A user device may be served by an RRC instance in a centralized unit (CU) and/or a distributed unit (DU) of a base station. Thus, there is a need to dynamically change a location (e.g., the CU and/or the DU) at which a signaling radio bearer (SRB) is terminated.

BRIEF SUMMARY

[0003] A method and apparatus are disclosed for enabling and implementing flexible signaling radio bearer (SRB) termination. As described herein, an SRB termination may be relocated to and/or from a centralized unit (CU) of a base station and a distributed unit (DU) of the base station. The relocation may be enabled and/or implemented based on one or more trigger conditions.

[0004] In an example embodiment, an apparatus is provided comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to perform transmitting, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU. In one example, the request comprises information identifying the at least one SRB and context information associated with the at least one SRB. In one example, the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

[0005] In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to receive, by the at least one CU from the at least one DU, a response to the relocation request. In one example, the response comprises radio resource control (RRC) context information and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted. In one example, the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted. In one example, the information further comprises one or more AS security keys and one or more security algorithms. In one example, the request is transmitted based on a location of an RRC protocol termination. In one example, the request is transmitted based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity. In one example, the request is transmitted based on an RRC state transition. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request such that one or more UL messages carried over the at least one SRB are decoded in the at least one DU. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request such that one or more DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to delay relocation of the at least one SRB from the at least one CU to the at least one DU until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the CU or DU hosting termination of the at least one SRB after the reallocation. In one example, the at least one CU is configured to buffer a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request by at least one of the following: two or more CU(s) or one or more network elements on the same level as the at least one CU.

[0006] In an example embodiment, a method is provided comprising transmitting, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU. In one example, the request comprises information identifying the at least one SRB and context information associated with the at least one SRB. In one example, the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

[0007] In one example, the method further comprises receiving, by the at least one CU from the at least one DU, a response to the relocation request. In one example, the response comprises radio resource control (RRC) context information and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted. In one example, the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms. In one example, the method further comprises transmitting, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted. In one example, the information further comprises one or more AS security keys and one or more security algorithms. In one example, the transmitting is based on a location of an RRC protocol termination. In one example, the transmitting is based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity. In one example, the transmitting is based on an RRC state transition. In one example, the method further comprises transmitting the request such that UL messages carried over the at least one SRB are decoded in the at least one DU. In one example, the method further comprises transmitting the request such that DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU. In one example, the method further comprises delaying the relocation until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages. In one example, the method further comprises transmitting one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the at least one CU or the at least one DU hosting the SRB termination after the reallocation. In one example, the method further comprises buffering, by the at least one CU, a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed. In one example, the method further comprises transmitting the request by at least one of the following: two or more CU(s) or one or more network elements on the same level as the at least one CU. [0008] In an example embodiment, an apparatus further comprises means for transmitting, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU. In one example, the request comprises information identifying the at least one SRB and context information associated with the at least one SRB. In one example, the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

[0009] In one example, the apparatus further comprises means for receiving, by the at least one CU from the at least one DU, a response to the relocation request. In one example, the response comprises radio resource control (RRC) context information and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted. In one example, the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms. In one example, the apparatus further comprises means for transmitting, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted. In one example, the information further comprises one or more AS security keys and one or more security algorithms. In one example, the transmitting is based on a location of an RRC protocol termination. In one example, the transmitting is based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity. In one example, the transmitting is based on an RRC state transition. In one example, the apparatus further comprises means for transmitting the request such that UL messages carried over the at least one SRB are decoded in the at least one DU. In one example, the apparatus further comprises means for transmitting the request such that DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU. In one example, the apparatus further comprises means for delaying the relocation until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages. In one example, the apparatus further comprises means for transmitting one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the at least one CU or the at least one DU hosting the SRB termination after the reallocation. In one example, the apparatus further comprises means for buffering, by the at least one CU, a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed. In one example, the apparatus further comprises means for transmitting the request by at least one of the following: two or more CU(s) or one or more network elements on the same level as the at least one CU.

[0010] In an example embodiment, a non-transitory computer readable storage medium comprising computer instructions that, when executed by an apparatus, cause the apparatus to transmit, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU. In one example, the request comprises information identifying the at least one SRB and context information associated with the at least one SRB. In one example, the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

[0011] In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to receive, by the at least one CU from the at least one DU, a response to the relocation request. In one example, the response comprises radio resource control (RRC) context information and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted. In one example, the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted. In one example, the information further comprises one or more AS security keys and one or more security algorithms. In one example, the transmitting is based on a location of an RRC protocol termination. In one example, the transmitting is based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity. In one example, the transmitting is based on an RRC state transition. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit the request such that UL messages carried over the at least one SRB are decoded in the at least one DU. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit the request such that DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to delay the relocation until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the at least one CU or the at least one DU hosting the SRB termination after the reallocation. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to buffer, by the at least one CU, a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit the request by at least one of the following: two or more CU(s) or one or more network elements on the same level as the at least one CU. [0012] In an example embodiment, an apparatus is provided comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, and relocating, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU. In one example, the request comprises an identifier identifying the at least one SRB, context information associated with the at least one SRB, and/or at least one SRB payload. In one example, the at least one SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the at least one DU. In one example, the context information comprises a most recent PDCP context information. In one example, the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived Access Stratum (AS) security keys. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to relocate, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU.

[0013] In an example embodiment, a method is provided comprising receiving, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, and relocating, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU. In one example, the request comprises an identifier identifying the at least one SRB, context information associated with the at least one SRB, and/or an SRB payload. In one example, the SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the DU. In one example, the context information comprises a most recent PDCP context information. In one example, the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived AS security keys. In one example, the method further comprises relocating, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU.

[0014] In an example embodiment, an apparatus further comprises means for receiving, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, and relocating, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU. In one example, the request comprises an identifier identifying the at least one SRB, context information associated with the at least one SRB, and/or an SRB payload. In one example, the SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the DU. In one example, the context information comprises a most recent PDCP context information. In one example, the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived Access Stratum (AS) security keys. In one example, the apparatus further comprises means for relocating, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU. [0015] In an example embodiment, a non-transitory computer readable storage medium comprising computer instructions that, when executed by an apparatus, cause the apparatus to receive, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, and relocate, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU. In one example, the request comprises an identifier identifying the at least one SRB, context information associated with the at least one SRB, and/or an SRB payload. In one example, the SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the DU. In one example, the context information comprises a most recent PDCP context information. In one example, the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived AS security keys. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to relocate, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU.

[0016] In an example embodiment, an apparatus is provided comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB), transmitting, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU, and decoding, based on the SRB being terminated in the at least one DU, the UL information in the at least one DU.

[0017] In an example embodiment, a method is provided comprising receiving, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB), and transmitting, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU, or decoding, based on the SRB being terminated in the DU, the UL information in the at least one DU.

[0018] In an example embodiment, an apparatus further comprises means for receiving, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB), and transmitting, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU, or decoding, based on the SRB being terminated in the DU, the UL information in the at least one DU.

[0019] In an example embodiment, a non-transitory computer readable storage medium comprising computer instructions that, when executed by an apparatus, cause the apparatus to receive, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB), and transmit, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU, or decode, based on the SRB being terminated in the DU, the UL information in the at least one DU.

[0020] In an example embodiment, an apparatus is provided comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: configuring a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station, receiving, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU, and identifying, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the at least one DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU.

[0021] In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB and receive, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB. In one example the at least one memory is further configured to, with the at least one processor, cause the apparatus to receive, by the at least one DU and from the UE, a UL information transfer. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit, from at least one DU to the at least one CU and based on receiving a UL message via the second SRB, a UL RRC message transfer. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to decode, based on receiving a UL message via the first SRB, the UL information transfer in the at least one DU. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to: receive, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement, transmit, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request, and receive, by the at least one CU from the at least one DU, an SRB termination relocation response. In one example, the context information associated with the first SRB comprises an SRB payload. In one example, the at least one memory is further configured to, with the at least one processor, cause the apparatus to receive, by the at least one DU from the UE, a UL information transfer via the first SRB and transmit, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, an UL message transfer. In one example, the at least one trigger condition further comprises at least one of a DL and UL PDCP Count rollover or an Access Stratum (AS) security key change.

[0022] In an example embodiment, a method is provided comprising configuring a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station, receiving, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU, and identifying, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU. [0023] In one example, the method further comprises transmitting, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB and receiving, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB. In one example, the method further comprises receiving, by the at least one DU and from the UE, a UL information transfer. In one example, the method further comprises transmitting, based on receiving a UL message via the second SRB and from the at least one DU to the at least one CU, a UL RRC message transfer. In one example, the method further comprises decoding, based on receiving a UL message via the first SRB, the UL information in the at least one DU. In one example, the method further comprises: receiving, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement, transmitting, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request, and receiving, by the at least one CU from the at least one DU, an SRB termination relocation response. In one example, the context information associated with the first SRB comprises an SRB payload. In one example, the method further comprises receiving, by the at least one DU from the UE, a UL information transfer via the first SRB, and transmitting, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, a UL message transfer. In one example, the at least one trigger condition further comprises at least one of a DL and UL PDCP Count rollover or an Access Stratum (AS) security key change.

[0024] In an example embodiment, an apparatus further comprises means for configuring a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station, receiving, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU, and identifying, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU. [0025] In one example, the apparatus further comprises means for transmitting, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB and receiving, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB. In one example, the apparatus further comprises means for receiving, by the at least one DU and from the UE, a UL information transfer. In one example, the apparatus further comprises means for transmitting, based on receiving a UL message via the second SRB and from the at least one DU to the at least one CU, a UL RRC message transfer. In one example, the apparatus further comprises means for decoding, based on receiving a UL message via the first SRB, the UL information in the at least one DU. In one example, the apparatus further comprises means for: receiving, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement, transmitting, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request, and receiving, by the at least one CU from the at least one DU, an SRB termination relocation response. In one example, the context information associated with the first SRB comprises an SRB payload. In one example, the apparatus further comprises means for receiving, by the at least one DU from the UE, a UL information transfer via the first SRB, and transmitting, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, a UL message transfer. In one example, the at least one trigger condition further comprises at least one of a DL and UL PDCP Count rollover or an Access Stratum (AS) security key change.

[0026] In an example embodiment, a non-transitory computer readable storage medium comprising computer instructions that, when executed by an apparatus, cause the apparatus to: configure a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station, receive, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU, and identify, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU.

[0027] In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB and receive, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to receive, by the at least one DU and from the UE, a UL information transfer. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to transmit, based on receiving a UL message via the second SRB and form the at least one DU to the at least one CU, a UL RRC message transfer. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to decode, based on receiving a UL message via the first SRB, the UL information in the at least one DU. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to receive, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement, transmit, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request, and receive, by the at least one CU from the at least one DU, an SRB termination relocation response. In one example, the context information associated with the first SRB comprises an SRB payload. In one example, the computer instructions further comprise computer instructions that, when executed by the apparatus, cause the apparatus to receive, by the at least one DU from the UE, a UL information transfer via the first SRB and transmit, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, a UL message transfer. In one example, the at least one trigger condition further comprises at least one of a DL and UL PDCP Count rollover or an Access Stratum (AS) security key change. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Having thus described certain example embodiments of the present disclosure in general terms, reference will hereinafter be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0029] FIG. 1 is a diagram of an example communication system;

[0030] FIG. 2 is a block diagram of an apparatus that may be specifically configured in accordance with an example embodiment of the present disclosure;

[0031] FIG. 3 is a representation of a dynamic change of termination points of signaling radio bearers (SRBs);

[0032] FIG. 4A is a representation of an SRB being terminated at a centralized unit (CU) of a base station;

[0033] FIG. 4B is a representation of an SRB being terminated at a distributed unit (DU) of a base station;

[0034] FIG. 5 is a representation of CU-initiated flexible SRB termination;

[0035] FIG. 6 is a representation of DU-initiated flexible SRB termination;

[0036] FIG. 7 is a representation of DU logic for selectively terminating or forwarding

SRB traffic;

[0037] FIG. 8 is a representation of a user equipment (UE) having a first SRB and a second SRB, wherein termination of the first SRB is switched from a CU to a DU and back to the CU;

[0038] FIG. 9 is a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2, in order to apply flexible SRB termination;

[0039] FIG. 10 is a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2, in order to apply flexible SRB termination;

[0040] FIG. 11 is a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2, in order to apply flexible SRB termination; and

[0041] FIG. 12 is a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2, in order to apply flexible SRB termination, in accordance with an example embodiment of the present disclosure.

DETAILED DESCRIPTION

[0042] Some embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the disclosure are shown. Indeed, various embodiments of the disclosure may be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein; rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. As used herein, the terms “data,” “content,” “information,” and similar terms may be used interchangeably to refer to data capable of being transmitted, received and/or stored in accordance with example embodiments of the present disclosure. Thus, use of any such terms should not be taken to limit the spirit and scope of example embodiments of the present disclosure.

[0043] Additionally, as used herein, the term ‘circuitry’ refers to (a) hardware-only circuit implementations (e.g., implementations in analog circuitry and/or digital circuitry); (b) combinations of circuits and computer program product(s) comprising software and/or firmware instructions stored on one or more computer readable memories that work together to cause an apparatus to perform one or more functions described herein; and (c) circuits, such as, for example, a microprocessor s) or a portion of a microprocessor s), that require software or firmware for operation even if the software or firmware is not physically present. This definition of ‘circuitry’ applies to all uses of this term herein, including in any claims. As a further example, as used herein, the term ‘circuitry’ also includes an implementation comprising one or more processors and/or portion(s) thereof and accompanying software and/or firmware. As another example, the term ‘circuitry’ as used herein also includes, for example, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, other network device (such as a core network apparatus), field programmable gate array, and/or other computing device.

[0044] One example of a communications system 10 in which an example embodiment may be deployed is depicted in FIG. 1. The system of FIG. 1 may be utilized for a variety of applications. For example, a communications system 10 may include at least one core network 12, at least one base station 14 (e.g., gNB, NodeB, etc.), and/or at least one user device 16 (16a, b,. . .N) (e.g., user equipment (UE), wireless device, user terminal, terminal device, etc.).

[0045] In FIG. 1, user devices 16a and 16b are configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as a NodeB) 14 providing the cell, such as a NodeB which is used hereinafter by way of example to represent an access node. The physical link from a user device to a NodeB is called the uplink or reverse link and the physical link from the NodeB to the user device is called the downlink or forward link. It should be appreciated that the NodeB s or their functionalities may be implemented by using any node, host, server, base station or access point (AP), and/or other entity suitable for such a usage.

[0046] A communications system typically comprises more than one NodeB, in which case the NodeB s may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signaling purposes. The NodeB is a computing device configured to control resources of the communication system to which the NodeB is coupled. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment.

[0047] The user device illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a user device may be implemented with a corresponding apparatus, such as the apparatus of FIG. 2.

[0048] The user device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A user device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The user device is configured to perform one or more of user equipment functionalities. The user device may also be called a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE) just to mention but a few names or apparatuses.

[0049] Although an example embodiment may be deployed in various types of communications systems, a 5G communications system will be described herein by way of example, but not of limitation, and the method and apparatus of an example embodiment may be utilized in conjunction with other communication systems, such as 5G-Advanced, 6G, and/or the like. A 5G system enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than a Long Term Evolution (LTE) system (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. A 5G system may have various radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integratable with existing legacy radio access technologies, such as LTE. Integration with an LTE system may be implemented, at least in the early phase, as a system, where macro coverage is provided by an LTE system and 5G radio interface access comes from small cells by aggregation to the LTE system. In other words, a 5G system is planned to support both inter-radio access technology (RAT) operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0050] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in a 5G system require bringing the content close to the radio which leads to local break out and multi-access edge computing (MEC). A 5G system enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self- healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), and critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, and healthcare applications).

[0051] The communication system 10 is also able to communicate with other networks, such as a public switched telephone network or the Internet, or utilize services provided by them. The communication network 10 may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service. The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0052] Edge cloud may be brought into radio access network (RAN) by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side and non-real time functions being carried out in a centralized manner).

[0053] It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of LTE or even be nonexistent. Some other technology advancements that may be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (e.g., gNB). It should be appreciated that MEC can be applied in 4G networks as well.

[0054] 5G systems may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board vehicles, or ensuring service availability for critical communications, and future railway/maritime/aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node or by a gNB located on-ground or in a satellite.

[0055] The depicted system is only an example of a part of a radio access system in which the system 10 of FIG. 1 may be deployed and in practice, the system may comprise a plurality of NodeBs, the user devices may have access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the NodeBs or may be a Home NodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The NodeBs of FIG. 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of NodeBs are required to provide such a network structure.

[0056] For fulfilling the need for improving the deployment and performance of communication systems, the concept of “plug-and-play” NodeBs has been introduced. Typically, a network which is able to use “plug-and-play” Node Bs, includes, in addition to Home NodeBs (HnodeBs), a home node B gateway, or HNB-GW. A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNB s back to a core network. Although FIG. 1 depicts one example communication system in which system 10 of an example embodiment may be deployed, the system of other example embodiments may be deployed in other types of systems, be they to support communications or otherwise.

[0057] One example of an apparatus 20 that may be configured to function as the core network 12, base station 14, and/or user device 16 is depicted in FIG. 2. As shown in FIG. 2, the apparatus includes, is associated with or is in communication with a processor 22, a memory 24 and a communication interface 26. The processor may be in communication with the memory device via a bus for passing information among components of the apparatus. The memory device may be non-transitory and may include, for example, one or more volatile and/or non-volatile memories. In other words, for example, the memory device may be an electronic storage device (e.g., a computer readable storage medium) comprising gates configured to store data (e.g., bits) that may be retrievable by a machine (e.g., a computing device like the processor). The memory device may be configured to store information, data, content, applications, instructions, or the like for enabling the apparatus to carry out various functions in accordance with an example embodiment of the present disclosure. For example, the memory device could be configured to buffer input data for processing by the processor. Additionally or alternatively, the memory device could be configured to store instructions for execution by the processor.

[0058] FIG. 2 depicts an example of a simplified block diagram of an apparatus according to various embodiments of the present disclosure, whose implementation may differ from what is shown. The connections shown in FIG. 2 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in FIG. 2.

[0059] The apparatus 20 may, in some embodiments, be embodied in various computing devices as described above. However, in some embodiments, the apparatus may be embodied as a chip or chip set. In other words, the apparatus may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus may therefore, in some cases, be configured to implement an embodiment of the present disclosure on a single chip or as a single “system on a chip.” As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

[0060] The processor 22 may be embodied in a number of different ways. For example, the processor 22 may be implemented by processing circuitry. For example, the processor may be embodied as one or more of various hardware processing means such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing element with or without an accompanying DSP, or various other circuitry including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like. As such, in some embodiments, the processor 22 may include one or more processing cores configured to perform independently. A multi-core processor may enable multiprocessing within a single physical package. Additionally or alternatively, the processor may include one or more processors configured in tandem via the bus to enable independent execution of instructions, pipelining and/or multithreading.

[0061] In an example embodiment, the processor 22 may be configured to execute instructions stored in the memory device 24 or otherwise accessible to the processor. Alternatively or additionally, the processor may be configured to execute hard coded functionality. As such, whether configured by hardware or software methods, or by a combination thereof, the processor may represent an entity (e.g., physically embodied in circuitry) capable of performing operations according to an embodiment of the present disclosure while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively or additionally, as another example, when the processor is embodied as an executor of instructions, the instructions may specifically configure the processor to perform the algorithms and/or operations described herein when the instructions are executed. However, in some cases, the processor 22 may be a processor of a specific device (e.g., an image or video processing system) configured to employ an embodiment of the present disclosure by further configuration of the processor by instructions for performing the algorithms and/or operations described herein. The processor 22 may include, among other things, a clock, an arithmetic logic unit (ALU) and logic gates configured to support operation of the processor.

[0062] The communication interface 26 may be any means such as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data, including media content in the form of video or image files, one or more audio tracks or the like. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network. Additionally or alternatively, the communication interface may include the circuitry for interacting with the antenna(s) to cause transmission of signals via the antenna(s) or to handle receipt of signals received via the antenna(s). In some environments, the communication interface may alternatively or also support wired communication. As such, for example, the communication interface may include a communication modem and/or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB) or other mechanisms.

[0063] In at least some technologies, flexible SRB termination may be enabled and/or implemented based on certain triggers, which may be specific to one UE or to a plurality of UEs. Such triggers may include a location of RRC protocol termination, a location of an AIML data collection entity, an RRC state transition, and/or the like. Depending on logical entity triggering radio resource control (RRC) reconfiguration, there may be multiple triggers (as described herein) based on which a user device (e.g., user equipment (UE)) may be reconfigured through an RRC reconfiguration procedure. Such scenarios may be broadly categorized into distributed unit (DU) centric scenarios and centralized unit (CU) centric scenarios, as described herein.

[0064] DU-centric scenarios may include intra-DU mobility, beam management, carrier aggregation, L2 -triggered transform precoder change, and/or other scenarios. For example, there may be multiple Fl application protocol (F1AP) transactions involving DU and CU coordination, including: an F1AP procedure from a DU to a CU to send encoded CellGroupConfig, an F1AP procedure from a CU to a DU to send the encoded RRC reconfiguration procedure, and/or an F1AP procedure from a DU to a CU to send the RRC reconfiguration complete. In some examples, L2 -triggered RRC reconfiguration may be a significant portion of the overall number of reconfigurations for a given UE.

[0065] CU-centric scenarios may include inter-DU mobility, inter-gNB mobility, next generation application protocol (NGAP) triggers (e.g., such as protocol data unit (PDU) session management), and/or other scenarios.

[0066] Handling DU-centric RRC processing in a DU of a base station and/or handling CU-centric RRC processing in a CU of a base station may rely on dynamically changing SRB termination between the CU and the DU. Such flexible SRB termination may provide various advantages, such as decreasing latency, improving central processing unit (CPU) usage, reducing Fl AP signaling overhead in DU-centric scenarios, enabling flexible SRB termination based on a UE’s RRC state (e.g., RRC -Inactive, RRC-Connected, etc.), and/or other advantages.

[0067] In at least some technologies, depending on a UE RRC state transition, SRB termination may be changed dynamically between a CU of a base station and a DU of a base station. For example, the CU may configure the DU to handle RRC messages when the UE is in an RRC-connected state. For example, when the CU identifies an inactivity trigger for the UE such that the UE may be moved to an RRC -inactive state, the CU may take control of the RRC so that it can store the latest context (e.g., the CU initiates a message to the DU that SRB termination is switched to the CU).

[0068] In at least some technologies SRB termination may be changed dynamically. In some examples, SRB termination may be changed dynamically based on artificial intelligence/machine learning (AIML) data collection and/or training. In 6G networks with AIML, there may be use cases (e.g., radio access network 1 (RANI) channel state information (CSI) prediction) which involve two-sided ML Models (e.g., UE and RAN). In a split architecture, for example, when an ML Model is hosted in a DU, data collected from UE (e.g., which may transported over a first SRB (e.g., SRB1)) may be relied on as input data and/or inference data to the ML Model in the DU. In some examples, such data may be transported from UE to the DU to the CU and then back to the DU, for example, if one or more of the SRB(s) (e.g., all of the SRB(s)) are terminated in the CU only.

[0069] Certain example embodiments of the present disclosure include various examples for flexible SRB termination.

[0070] In some examples, a first control-plane (CP) instance may be a primary owner of a UE context, the ownership may be assigned to a second CP instance, and the ownership may be reassigned back to the first CP instance. The assignment may be partial or full, for example, such as encoding and/or decoding of at least some (e.g., all) messages over a single SRB or a plurality of SRBs. The first CP instance may use a trigger to assign an RRC task to another CP instance (e.g., the second CP instance) or take it back. As used herein, the term “centralized unit’ 7“CU” may be used to describe central resources close to a cell site. As used herein, the term “distributed unit’ 7“DU” may be used to describe distributed resources close to a cell site.

[0071] In some examples, dynamic change of termination points of SRBs may be described. Such a dynamic change of termination points of SRBs may include dynamically changing SRB termination, for example, between a CU and a DU.

[0072] In some examples, a fallback to SRB termination at a CU may be described. For example, a predetermined mechanism may enable SRB termination at a DU such that at least some (e.g., all) DU-centric scenarios may be handled in the DU itself, which may optimize RRC processing. If CU-centric events occur, for example, the SRB termination point may be switched back to the CU, such that the CU may handle the RRC processing. In some CU-centric scenarios, there may be El interaction and/or CU-centric processing (e.g., admission control, bearer profile selection, etc.). Handling RRC processing in CU- centric scenarios at the CU may provide advantages such as ensuring consistent architecture (e.g., in CU-centric interactions with other network interfaces such as NGAP and/or Xn application protocol (XnAP) interfaces, etc.), allowing scenarios using more memory and/or CPU power, and/or other advantages. The SRB termination point may be subsequently switched back to the DU, for example, after processing of the CU-centric event(s) is complete. An example sequence of events may include: (i) executing an SRB termination change procedure to a DU, (ii) identifying by a CU and/or receiving notification from the DU of the DU encountering events that may not be DU-centric (e.g., inter-DU mobility, NGAP -triggered PDU session setup, etc.), (iii) executing the SRB termination change procedure to the CU, (iv) completing the procedure for the triggering event, and/or (v) executing the SRB termination change procedure to the DU. [0073] In some examples, UE selection may be a factor in flexible SRB termination. For example, one or more eligible UEs may be identified for which SRB termination at a DU may be preferable. Determining UE(s) for which SRB termination at the DU may be preferable may rely on various factors, such as stationarity and/or mobility pattem(s) of the UE(s), speed, services/5G quality of service (QoS) identifier (5QI) utilization pattern(s), etc. A CU may use deterministic algorithms and/or AIML methods to gain information indicating UE behavior and/or to select UE(s) which have limited mobility (e.g., within a cell or across a plurality of cells of a given DU), a limited number of data bearers, etc. [0074] In some examples, flexible SRB termination may rely on trigger conditions. For example, triggers may be specific to individual UEs and/or common across multiple UEs. SRB termination may rely on trigger conditions such as a location of RRC protocol termination. In at least some architectures (e.g., 6G RAN architecture, etc.), it may be possible to terminate an RRC protocol in either a DU or a CU, for example, depending on low latency signaling for different services/bearers. SRB termination may rely on trigger conditions such as a location of an AIML data collection entity. In at least some architectures (e.g., split-gNB architecture, etc.), an AIML model may be hosted in either a DU or a CU, for example, depending on use case. The AIML model may rely on data being collected from UE(s) as input parameters (e.g., L3 measurements), which may be reported using RRC procedures transported over a first SRB (e.g., SRB1). For example, depending on where the AIML model is hosted, information may be decoded (e.g., consumed) in either the DU or the CU. SRB termination may rely on trigger conditions such as an RRC state transition. For example, if a UE is in an RRC-connected state, traffic of a first SRB (e.g., SRB1) may be terminated at a DU. If the UE is in (and/or switches to) an RRC -inactive state, the traffic of the first SRB may be terminated at the CU.

[0075] In some examples, a DU or a CU may be triggered to terminate an SRB. For example, if a trigger condition is met, the CU may enable SRB termination in the DU. Trigger conditions may include, for example, a UE moving from an RRC -Inactive state to an RRC-Connected state. At least some of the messages (e.g., all messages) received via a given SRB from a UE may be terminated in the DU. Such termination and/or configuration thereof may be transparent the UE. The CU may reconfigure the SRB termination to forward traffic to the CU based on CU-identified trigger(s) and/or DU-identified trigger(s). The SRB termination may occur entirely in the CU and/or entirely in the DU.

[0076] Certain example embodiments of the present disclosure may be applied to any SRB. For example, one or more SRBs may be selected as candidates for flexible termination. The examples described herein may be applicable to any SRBs defined in any architectures.

[0077] Referring now to FIG. 3, a representation of a dynamic change of termination points of signaling radio bearers (SRBs) is provided. Termination of an SRB may be dynamically changed between a CU and a DU. The example of FIG. 3 shows a system 30 comprised of a user equipment (UE) 32, a distributed unit (DU) 34, and a centralized unit (CU) 36. The UE 32 may transmit data via SRBx, which may be terminated in the DU 34. The SRBx may be alternatively terminated in the CU 36.

[0078] Referring now to FIGS. 4A-4B, a representation of an SRB being terminated at a centralized unit (CU) of a base station and a representation of an SRB being terminated at a distributed unit (DU) of a base station, respectively, are provided. FIG. 4A illustrates a representation 40a, which comprises a user equipment (UE) 42a, a distributed unit (DU) 44a, a centralized unit (CU) 46a, and an SRBx 48a. The curved line in FIG. 4A represents end-to-end termination from the UE 42a to the DU 44a and/or the CU 46a. FIG. 4B illustrates a representation 40b, which comprises a user equipment (UE) 42b, a distributed unit (DU) 44b, a centralized unit (CU) 46b, and an SRBx 48b. The curved line in FIG. 4B represents end-to-end termination from the UE 42b to the DU 44b and/or the CU 46b.

[0079] For uplink (UL) SRB messages, if a termination point is set to be at a DU, UL messages carried over a designated SRB may be decoded (e.g., consumed) in the DU (e.g., not forwarded to a CU). If the termination point is switched to be at the CU, the DU may transparently forward the SRB messages to the CU. For downlink (DL) SRB messages, a terminating entity (e.g., a DU or a CU) may be responsible for encoding and sending an RRC reconfiguration to a UE. For example, if the SRB is terminated at the DU, the DU encodes RRC reconfigurations related to a beam configuration or intra-DU cell mobility. If triggers from the next generation application protocol (NGAP) (e.g., PDU session setup/modification, etc.) indicate that the CU should send the RRC messages over the SRB, the termination point may be switched to the CU.

[0080] Certain example embodiments of the present disclosure may include SRB- associated context transfer. The procedures described herein may be applicable for scenarios in which SRB termination is relocated from CU to DU or from DU to CU. For example, if an SRB termination point is moved, some of RRC context and PDCP context associated with the SRB may be re-initialized with other PDCP DL COUNT entities and/or PDCP UL COUNT entities such that the relocation procedure may be transparent to a UE. The PDCP DL COUNT entities and/or PDCP UL COUNT entities may be relied upon for PDCP data transfer protocol and/or security operations, among others. For example, in addition to (and/or independently of) the DL and UL PDCP Count, derived security keys (e.g., Access Stratum (AS) security keys) for the security operations (e.g., ciphering, integrity protection, etc.) may also be transferred. For example, during the relocation, the UE may send the UL PDCP PDU in parallel, which may rely on the PDCP context associated with the SRB at a CU coordinating with the PDCP context associated with the SRB at a DU. Such coordination may entail the CU processing and updating the DU of the DL and UL PDCP Count associated with the latest UL PDCP PDU. Advantages of the coordination may include that in-order delivery of the PDCP PDUs is maintained. A new message from the CU to the DU may be enhanced to carry information indicating the coordination. UE context modification may be enhanced to carry information indicating the coordination. The relocation may be delayed until there are no pending (e.g., missing) UL PDCP PDUs. If there are pending (e.g., missing) UL PDCP PDUs, missing sequence numbers (SNs) of the PDCP window may also be exchanged. If such missing SNs are received, the PDCP context at the DU may account of the received SNs for PDCP operation. The CU may be a primary owner (e.g., owning security -related aspects such as security key/algorithm selection, etc.). If the DU detects DL and UL PDCP Count rollover, it may notify the CU. [0081] Referring now to FIG. 5, a representation of CU-initiated flexible SRB termination is provided. The example of FIG. 5 shows a sequence diagram 50. The sequence diagram 50 includes a distributed unit (DU) 52 of a base station and a centralized unit (CU) 54 of a base station. The CU 54 may transmit an SRB termination relocation request 56 to a DU 52. The SRB termination relocation request 56 may include an SRB identifier (ID) and/or context information associated with the SRB. The CU 54 may initiate a procedure for changing a termination point of one or more SRBs to the DU 52. The SRB ID may indicate a specific SRB for which the termination point may be relocated to the CU 54. Context information (e.g., an information element (IE)) associated with the SRB may include a PDCP and/or other context information associated with the SRB being relocated. [0082] The CU-initiated flexible SRB termination may be achieved via enhancing F1AP with a UE context modification request procedure with new IE(s) (e.g., an SRB termination relocation indication). The new IE may indicate a logical endpoint at which the SRB may be terminated (e.g., the DU 52 or the CU 54). The IE may be set to a Boolean value, for example if the value is TRUE, UL SRB traffic on any indicated SRB may be terminated at the DU 52, and/or if the value is FALSE, UL SRB traffic on any indicated SRB (e.g., which may have been previously terminated at the DU 52) may be terminated in the CU 54.

[0083] The DU 52 may transmit an SRB termination relocation response 58 to the CU 54. The SRB termination relocation response may comprise RRC information and/or most recent PDCP PDU information. For example, if the CU 54 receives RRC messages between the SRB termination relocation request 56 and the SRB termination relocation response 58, the CU 54 may buffer the messages until the CU 54 receives the SRB termination relocation response 58 from the DU 52 such that messages are not lost (e.g., if the response is delayed). For example, if the DU 52 receives the SRB termination relocation request 56 during an ongoing RRC procedure, the DU 52 may include information indicating such circumstances in the RRC information IE. The RRC information may be used to reject the SRB termination relocation request 56 and/or request that the CU 54 continue the switching procedure.

[0084] Referring now to FIG. 6, a representation of DU-initiated flexible SRB termination is provided. The example of FIG. 6 shows a sequence diagram 60. The sequence diagram 60 includes a distributed unit (DU) 62 of a base station and a centralized unit (CU) 64 of the base station. The CU 64 may transmit an SRB termination relocation required message 66 to a DU 62. The SRB termination relocation required message 66 may include an SRB identifier (ID), context information associated with the SRB, and/or an SRB payload. The DU 62 may trigger a procedure to request a change of termination point of one or more SRBs to the CU 64. An IE may include context information associated with an SRB being terminated. The IE may include an RRC payload, for example, after PDCP processing at the DU 62. The CU 64 may bypass the PDCP processing at the CU 64 and/or may directly process the RRC message (e.g., if the PDCP processing occurs in the DU 62).

[0085] The DU-initiated flexible SRB termination may be achieved via enhancing F1AP with a UE context modification request procedure by including a new flag “SRB Termination Relocation Indication”. The IE of the SRB termination relocation required message 66 may indicate that termination of one or more SRBs should be switched from the DU 62 to the CU 64.

[0086] Referring now to FIG. 7, a representation of DU logic for selectively terminating or forwarding SRB traffic is provided. The example of FIG. 7 shows a sequence diagram 70. The sequence diagram 70 includes a user equipment (UE) 72a, a distributed unit (DU) 72b, and a centralized unit (CU) 72c. The UE 72a may transmit a UL information transfer 74 for an SRBx to the DU 72b. At least one of wo or more alternate scenarios 76 may be subsequently implemented. In one example, a determination 78a may be made that SRBx is being terminated in the CU 72c. In this example, the DU 72b may transmit a UL RRC message transfer 78b to the CU 72c. Alternatively, in another example, a determination 78c may be made that SRBx is being terminated in the DU 72b. In this example, the DU 72b may decode (e.g., consume) the data locally at 78d.

[0087] Referring now to FIG. 8, a representation of a user equipment (UE) having a first SRB (e.g., SRBx) and a second SRB (e.g., SRBy), wherein termination of the SRBx is switched from a CU to a DU and back to the CU is provided. The example of FIG. 8 shows a sequence diagram 800. The sequence diagram 800 includes a UE 802, a DU 804, and a CU 806. At 808, the UE 802 may be configured with one or more SRBs (e.g., SRBx, SRBy, etc.) with SRB termination at the CU 806. At 810, the UE 802 may transmit a UL information transfer via an SRB (e.g., any SRB) to the DU 804. At 812, a determination may be made that a UL message was received via any SRB. At 814, based on receiving a UL message on any SRB, the DU 804 may transmit a UL RRC message transfer to the CU 806. The CU 806 may identify a trigger condition for requesting a change of termination point of SRBx from the CU 806 to the DU 804.

[0088] At 816, the CU 806 may determine to relocate SRBx to the DU 804. At 818, the CU 806 may transmit an SRB termination relocation request for SRBx to the DU 804. The SRB termination relocation request may comprise an SRB ID of SRBx and/or context information associated with SRBx. Additionally or alternatively, at 818, the CU 806 may trigger an F1AP, comprising the SRB termination relocation request configuring the given SRB (e.g., SRBx) with a corresponding configuration indicating to the DU 804 that at least some (e.g., any) signaling received via SRBx should be decoded (e.g., consumed) locally in the DU 804 (e.g., not forwarded to the CU 806).

[0089] At 820, the DU 804 may transmit an SRB termination relocation response to the CU 806. Additionally or alternatively, at 820, the DU 804 may transmit an F1AP comprising an SRB termination relocation response to the CU 806. At 822, the UE 802 may transmit a UL information transfer to the DU 804.

[0090] At least one of two or more alternate scenarios 824 may be subsequently implemented. In one example, at 826, the DU 804 may determine that the UL message was received via SRBy. In this example, based on determining that the UL message was received via SRBy, at 828, the DU 804 may transmit a UL RRC message transfer to the CU 806. Alternatively, in another example, at 830, the DU 804 may determine that the UL message was received via SRBx. In this example, based on determining that the UL message was received via SRBx, at 832, the DU 804 may decode (e.g., consume) the data locally. The termination point of SRBx may be the DU 804. The termination point of the SRBy may be the CU 806.

[0091] At 834, The DU 804 may determine to relocate SRBx to the CU 806. The DU 804 may identify a trigger condition for requesting a change of termination point of SRBx from the CU 806 to the DU 804. At 836, the DU 804 may transmit an SRB termination relocation required message comprising an SRB ID, context information associated with the SRB, and/or an SRB payload to the CU 806. The DU 804 may transmit an F1AP comprising the SRB termination relocation required message and the corresponding SRB ID (e.g., SRBx).

[0092] At 838, The CU 806 may transmit an SRB termination relocation request comprising an SRB ID and/or context information associated with the SRB to the DU 804. The CU 806 may trigger an F1AP comprising an SRB termination relocation request configuring a given SRB (e.g., SRBx) and/or the corresponding configuration, changing the termination point of SRBx from the DU 804 to the CU 806. At 840, the DU 804 transmits an SRB termination relocation response to the CU 806.

[0093] At 842, the UE 802 transmits a UL information transfer to the DU 804. The UL information transfer may be transmitted via SRBx. At 844, the DU 804 may determine that an UL message was received via any SRB. At 846, The DU 804 may transmit a UL RRC message transfer to the CU 806. Based on receiving any UL message via any SRB (e.g., SRBx, SRBy, and/or any other SRB), the DU 804 may forward such traffic to the CU 806. [0094] FIGS. 9-12 are flow charts illustrating the operations performed in order to configure, apply, and make use of flexible SRB termination. Referring now to FIG. 9, a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2 (e.g., a CU, a DU, a UE, etc.), in order to enable and/or implement flexible SRB termination is provided. In the example flow chart, a user device (e.g., UE, wireless device, etc.) may be configured with one or more SRBs having one or more termination points.

[0095] As shown in block 90, at least one centralized unit (CU) of a base station may transmit to at least one distributed unit (DU) a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU. The request may comprise information identifying the at least one SRB (e.g., an SRB identifier (ID) and/or the like) and/or context information associated with the at least one SRB. The context information associated with the at least one SRB may comprise at least one packet data convergence protocol (PDCP) entity associated with the SRB being relocated. The apparatus of this example also includes means, such as the processor 22 and/or the like for transmitting the request. The flexible SRB termination configuration and/or transmission thereof may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[0096] As shown in block 92, the at least one CU may receive from the at least one DU a response to the relocation request. The response may comprise radio resource control (RRC) context information and/or information associated with a most recent PDCP context information. The most recent PDCP context information may comprise a PDCP downlink (DL) Count and/or a PDCP uplink (UL) Count received and/or transmitted. The information associated with the most recent PDCP context information may further comprise one or more security keys (e.g., Access Stratum (AS) security keys) and/or one or more security algorithms. The apparatus of this example also includes means, such as the processor 22 and/or the like for receiving the response to the relocation request. The flexible SRB termination configuration and/or reception thereof may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[0097] The operations of FIG. 9 may comprise further operations. For example, the at least one CU may transmit to the at least one DU information associated with the PDCP configuration and/or the most recent PDCP context information received and/or transmitted. The information associated with the PDCP configuration may further comprise one or more security keys (e.g., Access Stratum (AS) security keys) and/or one or more security algorithms. For example, the transmitting may be based on a location of an RRC protocol termination. For example, the transmitting may be based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity. For example, the transmitting may be based on an RRC state transition. For example, the at least one CU may transmit the request such that UL messages carried over the at least one SRB may be decoded in the at least one DU. For example, the at least one CU may transmit the request such that DL RRC reconfiguration messages to a user equipment (UE) may be encoded and/or transmitted by the at least one DU. For example, the relocation may be delayed until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages. For example, the at least one CU may transmit one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the at least one CU and/or the at least one DU hosting the SRB termination after the reallocation. For example, the at least one CU may buffer a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed. For example, the request may be transmitted by at least one of: two or more CU(s) and/or one or more network elements on the same level as the at least one CU. The apparatus of this example also includes means, such as the processor 22 and/or the like for performing these operations. These operations may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[0098] Referring now to FIG. 10, a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2 (e.g., a CU, a DU, a UE, etc.), in order to enable and/or implement flexible SRB termination is provided. In the example flow chart, a user device (e.g., UE, wireless device, etc.) may be configured with one or more SRBs having one or more termination points. [0099] As shown in block 100, at least one distributed unit (DU) of a base station may receive from at least one centralized unit (CU) of the base station, based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU. The request may comprise an identifier identifying the at least one SRB, context information associated with the at least one SRB, and/or an SRB payload. The SRB payload may comprise a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the at least one DU. The apparatus of this example also includes means, such as the processor 22 and/or the like for receiving the request. Receiving the request may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00100] As shown in block 102, at least one SRB termination may be relocated from the at least one DU to the at least one CU such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU. The apparatus of this example also includes means, such as the processor 22 and/or the like for relocating the at least one SRB termination. Relocating the at least one SRB termination may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00101] The operations of FIG. 10 may comprise further operations. For example, the context information may comprise a most recent PDCP context information. For example, the context information may comprise the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and/or derived security keys (e.g., Access Stratum (AS) security keys). For example, the at least one SRB termination may be relocated from the at least one CU to the at least one DU at a later point in time. The apparatus of this example also includes means, such as the processor 22 and/or the like for performing these operations. Performing these operations may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00102] Referring now to FIG. 11, a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2 (e.g., a CU, a DU, a UE, etc.), in order to enable and/or implement flexible SRB termination is provided. In the example flow chart, a user device (e.g., UE, wireless device, etc.) may be configured with one or more SRBs having one or more termination points.

[00103] As shown in block 110, at least one distributed unit (DU) may receive from a user equipment (UE) an uplink (UL) information transfer via a signaling radio bearer

(SRB). The apparatus of this example also includes means, such as the processor 22 and/or the like for receiving the UL information transfer. Receiving the UL information transfer may be as described with respect to FIGS. 3-7 and/or any other examples described herein. [00104] As shown in block 112, a determination may be made as to where the SRB will be terminated. The apparatus of this example also includes means, such as the processor 22 and/or the like for making this determination. Making this determination may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00105] As shown in block 114, based on the SRB being terminated in at least one centralized unit (CU) of the base station, the at least one DU may transmit a UL radio resource control (RRC) message to the at least one CU. The apparatus of this example also includes means, such as the processor 22 and/or the like for transmitting the RRC message. Transmitting the RRC message may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00106] As shown in block 116, based on the SRB being terminated in the at least one DU, the UL information may be decoded locally in the at least one DU. The apparatus of this example also includes means, such as the processor 22 and/or the like for decoding the UL information. Decoding the UL information may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00107] Referring now to FIG. 12, a flow chart illustrating the operations performed, such as by the apparatus of FIG. 2 (e.g., a CU, a DU, a UE, etc.), in order to enable and/or implement flexible SRB termination is provided. In the example flow chart, a user device (e.g., UE, wireless device, etc.) may be configured with one or more SRBs having one or more termination points.

[00108] As shown in block 120, a user equipment (UE) may be configured with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station. The apparatus of this example also includes means, such as the processor 22 and/or the like for configuring the UE. Configuring the UE may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00109] As shown in block 122, the at least one CU may receive an uplink (UL) radio resource control (RRC) message based on at least one distributed unit (DU) of the base station receiving the at least one UL message via the first SRB or the second SRB. The apparatus of this example also includes means, such as the processor 22, and/or the like for receiving the RRC message. Receiving the RRC message may be as described with respect to FIGS. 3-7 and/or any other examples described herein. [00110] As shown in block 124, the at least one CU may identify at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU based on the at least one CU determining to relocate a first SRB termination to the DU. The apparatus of this example also includes means, such as the processor 22 and/or the like for identifying the at least one trigger condition. Identifying the at least one trigger condition may be as described with respect to FIGS. 3-7 and/or any other examples described herein.

[00111] The operations of FIG. 12 may comprise further operations. For example, the at least one CU may transmit to the at least one DU, based on an SRB identifier and/or context information associated with the first SRB, an SRB termination relocation request for the first SRB. For example, the at least one CU may receive from the at least one CU an SRB termination relocation response for the first SRB. For example, the at least one DU may receive from the UE a UL information transfer. For example, the at least one DU may transmit to the at least one CU, based on receiving a UL message via the second SRB, a UL RRC message transfer. For example, the UL information may be decoded in the at least one DU based on receiving a UL message via the first SRB. For example, the at least one CU may receive from the at least one DU an SRB termination relocation requirement based on the at least one DU determining to relocate the first SRB termination to the at least one CU and based on an SRB identifier and context information associated with the first SRB. For example, the at least one CU may transmit to the at least one DU an SRB termination relocation request based on an SRB identifier and context information associated with the first SRB. For example, the at least one CU may receive from the at least one DU an SRB termination relocation response. For example, the context information associated with the first SRB may comprise an SRB payload. For example, the at least one DU may receive from the UE a UL information transfer via the first SRB. For example, the at least one DU may transmit to the at least one CU a UL message transfer based on the at least one DU receiving a UL message via the first SRB and/or the second SRB. For example, the at least one trigger condition may further comprise at least one of a DL and UL PDCP Count rollover and/or a security key change (e.g., an Access Stratum (AS) security key change). The apparatus of this example also includes means, such as the processor 22 and/or the like for performing these operations. Performing these operations may be as described with respect to FIGS. 3-7 and/or any other examples described herein. [00112] As described above, a method and apparatus are disclosed for enabling flexible SRB termination, for example, where the apparatus may be the device 20 and the method may be any one of the methods of FIGS. 9-12.

[00113] Figures 9-12 illustrate flowcharts depicting methods according to an example embodiment of the present disclosure. It will be understood that each block of the flowcharts and combination of blocks in the flowcharts may be implemented by various means, such as hardware, firmware, processor, circuitry, and/or other communication devices associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory device of an apparatus employing an embodiment of the present disclosure and executed by a processor. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (for example, hardware) to produce a machine, such that the resulting computer or other programmable apparatus implements the functions specified in the flowchart blocks. These computer program instructions may also be stored in a computer-readable memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks.

[00114] Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions. [00115] Many modifications and other embodiments set forth herein will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims.

[00116] Moreover, although the foregoing descriptions and the associated drawings describe certain example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

THAT WHICH IS CLAIMED:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU, wherein the request comprises: information identifying the at least one SRB; and context information associated with the at least one SRB, wherein the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

2. The apparatus according to Claim 1, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to receive, by the at least one CU from the at least one DU, a response to the relocation request, wherein the response comprises: radio resource control (RRC) context information; and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted, wherein the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms.

3. The apparatus according to Claim 1, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted, wherein the information further comprises one or more AS security keys and one or more security algorithms.

4. The apparatus according to Claim 1, wherein the request is transmitted based on a location of an RRC protocol termination.

5. The apparatus according to Claim 1, wherein the request is transmitted based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity.

6. The apparatus according to Claim 1, wherein the request is transmitted based on an RRC state transition.

7. The apparatus according to Claim 1, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request such that one or more UL messages carried over the at least one SRB are decoded in the at least one DU.

8. The apparatus according to Claim 7, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to delay relocation of the at least one SRB from the at least one CU to the at least one DU until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages.

9. The apparatus according to Claim 7, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the CU or DU hosting termination of the at least one SRB after the reallocation.

10. The apparatus according to Claim 9, wherein the at least one CU is configured to buffer a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed.

11. The apparatus according to Claim 1, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request such that one or more downlink DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU.

12. The apparatus according to Claim 1, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit the request by at least one of the following: two or more CUs; or one or more network elements on the same level as the at least one CU.

13. A method comprising: transmitting, by at least one centralized unit (CU) of a base station to at least one distributed unit (DU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one CU to the at least one DU, wherein the request comprises: information identifying the at least one SRB; and context information associated with the at least one SRB, wherein the context information comprises a packet data convergence protocol (PDCP) entity associated with the SRB being relocated.

14. The method according to Claim 13, further comprising receiving, by the at least one CU from the at least one DU, a response to the relocation request, wherein the response comprises: radio resource control (RRC) context information; and information associated with a most recent PDCP context information comprising PDCP downlink (DL) Count and PDCP uplink (UL) Count received or transmitted, wherein the information further comprises one or more Access Stratum (AS) security keys and one or more security algorithms.

15. The method according to Claim 13, further comprising transmitting, by the at least one CU to the at least one DU, information associated with the PDCP configuration and the most recent PDCP context information received or transmitted, wherein the information further comprises one or more AS security keys and one or more security algorithms.

16. The method according to Claim 13, wherein the transmitting is based on a location of an RRC protocol termination.

17. The method according to Claim 13, wherein the transmitting is based on a location of an artificial intelligence (Al) and/or machine learning (ML) data collection entity.

18. The method according to Claim 13, wherein the transmitting is based on an RRC state transition.

19. The method according to Claim 13, further comprising transmitting the request such that UL messages carried over the at least one SRB are decoded in the at least one DU.

20. The method according to Claim 19, further comprising delaying the relocation until there is no pending PDCP protocol data units (PDUs) in the one or more UL messages.

21. The method according to Claim 19, further comprising transmitting one or more sequence numbers (SNs) of PDCP context information received in the one or more UL messages during reallocation to the at least one CU or the at least one DU hosting the SRB termination after the reallocation.

22. The method according to Claim 21, further comprising buffering, by the at least one CU, a received RRC message while the reallocation from the at least one CU to the at least one DU has not yet been completed.

23. The method according to Claim 13, further comprising transmitting the request such that DL RRC reconfiguration messages to a user equipment (UE) are encoded and transmitted by the at least one DU.

24. The method according to Claim 13, further comprising transmitting the request by at least one of the following: two or more CUs; or one or more network elements on the same level as the at least one CU.

25. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, wherein the request comprises: an identifier identifying the at least one SRB; context information associated with the at least one SRB; and/or at least one SRB payload, wherein the at least one SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the at least one DU; and relocating, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU.

26. The apparatus according to Claim 25, wherein the context information comprises a most recent PDCP context information.

27. The apparatus according to Claim 25, wherein the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived Access Stratum (AS) security keys.

28. The apparatus according to Claim 25, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to relocate, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU.

29. A method comprising: receiving, by at least one distributed unit (DU) of a base station from at least one centralized unit (CU) of the base station and based on at least one trigger condition, a request to relocate at least one signaling radio bearer (SRB) termination from the at least one DU to the at least one CU, wherein the request comprises: an identifier identifying the at least one SRB; context information associated with the at least one SRB; and/or an SRB payload, wherein the at least one SRB payload comprises a radio resource control (RRC) payload after a packet data convergence protocol (PDCP) entity has been processed at the DU; and relocating, from the at least one DU to the at least one CU, the at least one SRB termination such that one or more uplink (UL) messages carried over the at least one SRB are decoded in the at least one DU.

30. The method according to Claim 29, wherein the context information comprises a most recent PDCP context information.

31. The method according to Claim 29, wherein the context information comprises the PDCP entity that is associated with the at least one SRB being relocated, including a DL and UL PDCP Count and derived Access Stratum (AS) security keys.

32. The method according to Claim 29, further comprising relocating, at a later point in time, the at least one SRB termination from the at least one CU to the at least one DU.

33. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB); transmitting, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU; and decoding, based on the SRB being terminated in the at least one DU, the UL information in the at least one DU.

34. A method comprising: receiving, by at least one distributed unit (DU) of a base station and from a user equipment (UE), an uplink (UL) information transfer via a signaling radio bearer (SRB); and transmitting, based on the SRB being terminated in at least one centralized unit (CU) of the base station, a UL radio resource control (RRC) message from the at least one DU to the at least one CU; or decoding, based on the SRB being terminated in the DU, the UL information in the at least one DU.

35. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: configuring a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station; receiving, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU; and identifying, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the at least one DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU.

36. The apparatus according to Claim 35, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to: transmit, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB; and receive, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB.

37. The apparatus according to Claim 35, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to receive, by the at least one DU and from the UE, a UL information transfer.

38. The apparatus according to Claim 37, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to transmit, from the at least one DU to the at least one CU and based on receiving a UL message via the second SRB, a UL RRC message transfer.

39. The apparatus according to Claim 38, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to decode, based on receiving a UL message via the first SRB, the UL information transfer in the at least one DU.

40. The apparatus according to Claim 35, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to: receive, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement; transmit, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request; and receive, by the at least one CU from the at least one DU, an SRB termination relocation response.

41. The apparatus according Claim 40, wherein the context information associated with the first SRB comprises an SRB payload.

42. The apparatus according to Claim 35, wherein the at least one memory is further configured to, with the at least one processor, cause the apparatus to: receive, by the at least one DU from the UE, a UL information transfer via the first SRB; and transmit, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, a UL message transfer.

43. The apparatus according to Claim 35, wherein the at least one trigger condition further comprises at least one of: a DL and UL PDCP Count rollover; or an Access Stratum (AS) security key change.

44. A method comprising: configuring a user equipment (UE) with a first signaling radio bearer (SRB) and a second SRB being terminated at at least one centralized unit (CU) of a base station; receiving, based on at least one distributed unit (DU) of the base station receiving at least one uplink (UL) message via the first SRB or the second SRB, a UL radio resource control (RRC) message by the at least one CU; and identifying, by the at least one CU and based on the at least one CU determining to relocate a first SRB termination to the DU, at least one trigger condition for requesting a change of termination point of the first SRB from the at least one CU to the at least one DU.

45. The method according to Claim 44, further comprising: transmitting, from the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request for the first SRB; and receiving, by the at least one CU and from the at least one DU, an SRB termination relocation response for the first SRB.

46. The method according to Claim 44, further comprising receiving, by the at least one DU and from the UE, a UL information transfer.

47. The method according to Claim 46, further comprising transmitting, based on receiving a UL message via the second SRB and from the at least one DU to the at least one CU, a UL RRC message transfer.

48. The method according to Claim 47, further comprising decoding, based on receiving a UL message via the first SRB, the UL information in the at least one DU.

49. The method according to Claim 44, further comprising: receiving, by the at least one CU from the at least one DU, based on the at least one DU determining to relocate the first SRB termination to the at least one CU, and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation requirement; transmitting, by the at least one CU to the at least one DU and based on an SRB identifier and context information associated with the first SRB, an SRB termination relocation request; and receiving, by the at least one CU from the at least one DU, an SRB termination relocation response.

50. The method according to Claim 49, wherein the context information associated with the first SRB comprises an SRB payload.

51. The method according to Claim 44, further comprising: receiving, by the at least one DU from the UE, a UL information transfer via the first SRB; and transmitting, by the at least one DU to the at least one CU and based on the at least one DU receiving a UL message via the first SRB or the second SRB, a UL message transfer.

52. The method according to Claim 44, wherein the at least one trigger condition further comprises at least one of: a DL and UL PDCP Count rollover; or an Access Stratum (AS) security key change.