Data forwarding in low layer mobility

Abstract

There are provided measures for enabling / enabling efficient / advantageous data forwarding in / for a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2 centric mobility), in / for a mobile communication system, in low layer mobility. Such measures exemplarily comprise obtaining, by a low-layer entity in a radio access network of the mobile communication system, low-layer mobility and a configuration of data forwarding in the low-layer mobility from a high-layer control plane entity, initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration, and notifying a high layer user plane entity of initiation of data forwarding, wherein at least one target cell of low layer mobility is identified. The configuration may indicate punctual data forwarding in which data forwarding to the target cell is triggered when the serving cell change decision is completed, or may indicate early data forwarding in preparation of a candidate target cell for low-layer mobility in which data forwarding to the target cell is triggered when the candidate target cell is ready for low-layer mobility. Data forwarding to at least one of the one or more candidate target cells is triggered.

Description

Technical Field

[0001] The present disclosure relates to data forwarding in low-layer mobility in / for a mobile communication system. More specifically, the present disclosure relates to measures / mechanisms (including methods, apparatus (i.e., devices, entities, elements, instances and / or functions) and computer program products) for enabling / implementing data forwarding in a low-layer mobility in / for a wireless network of a mobile communication system, such as L1 / L2-centric mobility. Background Art

[0002] The present disclosure generally relates to low-layer mobility in / for a mobile communication system (e.g., a 3GPP standardized mobile / wireless communication system, such as a 5G / NR system and a next generation system beyond 5G) (radio access network of the system). Typically, low-layer mobility represents mobility implemented and / or performed by / via a lower layer of an applicable protocol stack (for example, a user equipment or a mobile terminal), such as the physical (L1) and data link (L2) layers of the OSI model.

[0003] Here, L1 / L2-centric mobility is exemplified as an implementation of low-layer mobility and can be considered as (an example of) low-layer mobility. In L1 / L2-centric mobility, the decision about cell change (i.e., handover) is based on L1 measurements and is made at the MAC layer (on L2) in a low-layer entity, such as a communication control entity like a gNB or more specifically, a distributed unit (DU) of a gNB. Therefore, L1 / L2-centric mobility can also be referred to or considered as L1 / L2-based inter-cell mobility / handover.

[0004] In the typical process of low-level mobility and associated delayed data forwarding (as explained below) Figure 4 As shown), the UE receives data from the source DU until the source DU decides that the UE should switch to another DU (i.e., the target DU) and thus triggers a cell / path switch. The UE then performs a switching procedure, such as, for example, RA-based switching, RACH-free switching, etc. Here, it is exemplarily assumed that the UE performs a random access (RA) to the target cell (i.e., the target DU). After the RA procedure, the UE sends an RRC reconfiguration completion to the target cell (i.e., the target DU), and the RRC reconfiguration completion is forwarded to the CU-CP. The CU-CP performs a bearer modification with the CU-UP to update the bearer establishment and causes the CU-UP to start forwarding data to the target DU (and stop forwarding data to the source DU). After this is completed, the UE starts receiving data from the target. In this case, the UE will experience a (service) interruption during the time required to perform a cell / path switch from the source DU to the target DU and to initiate data forwarding from the CU-UP to the target DU.

[0005] In another typical process of low-layer mobility and associated early data forwarding, the CU-UP may start forwarding data to all potential / candidate target cells, i.e., target DUs (and stop forwarding data to the source DU) when the preparation of all potential / candidate target cells (i.e., target DUs) is completed, i.e., even before the handover decision of the source DU. In this case, the data will be available in the target cell when the RA process (i.e., any handover process) to the finally selected target cell (i.e., the final target DU) is completed, resulting in a shorter (service) interruption. However, this will result in higher (signaling) overhead, because the data needs to be forwarded to all potential / candidate target cells, i.e., target DUs, before the final handover decision, which is a waste of network resources.

[0006] Although L1 / L2-centric mobility aims to reduce latency, (signaling) overhead, and (service) disruption time, it can be seen from the above that reducing (service) disruption time and reducing (signaling overhead) are conflicting goals.

[0007] As described above, for the available mechanisms for L1 / L2-centric mobility, the conflicting issues are as follows.

[0008] In just-in-time data forwarding, after a handover procedure (such as, for example, a RA procedure), i.e., after the reception of the associated RRC reconfiguration at the target DU is completed (see Figure 4 In step 17), data is forwarded to the target cell to confirm the handover execution. However, this may result in a long (service) interruption time.

[0009] In early data forwarding, after cell preparation, i.e., after the reception of the relevant RRC reconfiguration at the source DU is completed (see Figure 4 In step 10 of ), the data is forwarded to the prepared potential / candidate target cells to confirm the cell preparation. However, this will lead to higher (signaling) overhead (such as buffer space for storage, discarding sent PDUs, etc.) because the data will be forwarded to multiple potential / candidate target cells in advance. In particular, considering that the target cell can be prepared in advance, the data must be forwarded to the target cell in a longer time; considering the dynamic switching solution where the UE dynamically changes between target cells, the problem becomes more serious.

[0010] Therefore, there is room for improvement and a desire / need for techniques for (enabling / implementing) efficient / advantageous data forwarding in low-layer mobility in / for a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2-centric mobility). In particular, there is room for improvement and a desire / need for techniques for facilitating reducing (service) interruption time and / or reducing (signaling) overhead of data forwarding in low-layer mobility (such as L1 / L2-centric mobility). Summary of the invention

[0011] Various exemplary embodiments of the present disclosure are directed to addressing at least part of the above-mentioned problems and / or issues and disadvantages.

[0012] Various aspects of exemplary embodiments of the disclosure are set out in the appended claims.

[0013] According to an exemplary aspect of the present disclosure, a method is provided for a low-layer entity in a wireless access network of a mobile communication system (or, in other words, operable or used by it), the method comprising: obtaining a configuration of low-layer mobility and data forwarding in the low-layer mobility from a high-layer control plane entity, initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration, and notifying a high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of the low-layer mobility is identified.

[0014] According to an exemplary aspect of the present disclosure, there is provided an apparatus for a low-layer entity in a radio access network of a mobile communication system (or, in other words, operable or used by it), the apparatus comprising: at least one processor and at least one memory, the at least one memory comprising computer program code, wherein the processor together with the at least one memory and the computer program code is configured to cause the apparatus to execute: obtaining configuration of low-layer mobility and data forwarding in the low-layer mobility from a high-layer control plane entity, initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration, and notifying a high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of the low-layer mobility is identified.

[0015] According to an exemplary aspect of the present disclosure, there is provided an apparatus for a low-layer entity in a radio access network of a mobile communication system (or, in other words, operable or used by it), the apparatus comprising: a component for obtaining a configuration of low-layer mobility and data forwarding in the low-layer mobility from a high-layer control plane entity, a component for initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration, and a component for notifying a high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of the low-layer mobility is identified.

[0016] According to various developments / modifications, any of the above-mentioned method-related and / or apparatus-related example aspects of the present disclosure may include one or more of the following features:

[0017] The configuration indicates just-in-time data forwarding upon decision of serving cell change for low layer mobility,

[0018] The initiation includes: making a serving cell change decision for a target cell for low layer mobility, and triggering data forwarding to the target cell when the serving cell change decision is completed,

[0019] The notification includes: sending a notification to a higher-layer user plane entity, the notification including: an indication of a serving cell change decision, and an identifier for a target cell,

[0020] The notification comprises: issuing a notification to a higher layer control plane entity for informing a higher layer user plane entity, the notification comprising: an indication of a serving cell change decision, an indication of an attribute of the serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for a target cell,

[0021] This configuration indicates early data forwarding in the preparation of candidate target cells for low-layer mobility.

[0022] The initiating includes: performing candidate target cell preparation for one or more candidate target cells for low layer mobility, and triggering data forwarding to at least one candidate target cell of the one or more candidate target cells when the candidate target cell preparation is completed,

[0023] The proceeding includes making an upcoming serving cell change decision for a target cell for low layer mobility among the one or more candidate target cells, and when the upcoming serving cell change decision is completed, data forwarding is triggered.

[0024] The notification includes: issuing a notification to a higher layer user plane entity, the notification including: an indication of application of early data forwarding, and an identifier for at least one candidate target cell among the one or more candidate target cells,

[0025] The notification comprises: issuing a notification to a higher layer control plane entity for informing a higher layer user plane entity, the notification comprising: an indication of application of early data forwarding, an indication of attributes of an upcoming serving cell change as a change between serving cells associated with different lower layer entities, and an identifier for at least one candidate target cell of the one or more candidate target cells,

[0026] The method, functionality or operability comprises: making a serving cell change decision for a target cell among one or more candidate target cells for low layer mobility, and notifying a higher layer user plane entity of the serving cell change decision,

[0027] The notification of the serving cell change decision comprises: sending a notification to a higher-layer user plane entity, the notification comprising an indication of a downlink data delivery status, the indication indicating that the downlink data has been confirmed by a user equipment element or function as a destination,

[0028] The notification of the serving cell change decision further comprises: sending a notification to a higher layer user plane entity, the notification comprising: an indication of the serving cell change decision, and an identifier for the target cell,

[0029] The notification of the serving cell change decision further comprises: issuing a notification to a higher layer control plane entity for informing a higher layer user plane entity, the notification comprising: an indication of the serving cell change decision, an indication of an attribute of the serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for the target cell,

[0030] The method, functionality or operability comprises: making an early data forwarding cancellation decision for cancelling early data forwarding, and notifying a higher layer user plane entity of the early data forwarding cancellation decision,

[0031] The notification of the early data forwarding cancellation decision includes sending a notification to a higher-level user plane entity or to a higher-level control plane entity for informing the higher-level user plane entity, wherein the notification includes an indication of the cancellation of the early data forwarding,

[0032] Data forwarding is initiated based on low layer measurements, in particular layer 1 measurements, from user equipment elements or functions,

[0033] In the notification, at least one target cell for low layer mobility is identified using or based on its global cell identifier or its physical cell identifier,

[0034] The configuration includes an index for each potential target cell for low-layer mobility,

[0035] In the notification, at least one target cell for low layer mobility is identified using or based on its index in the configuration,

[0036] The low layer entity is or includes a functional unit that provides support for the lower layers (such as layer 1 and / or layer 2) of the protocol stack for communications in the radio access network and / or mobile communication system.

[0037] A low-level entity is or includes a distributed unit of communication control elements or functions in a radio access network, such as a base station or NodeB,

[0038] A high-layer control / user plane entity is or includes a functional unit that provides support for control / user plane functions of a high layer (such as layer 3) of a protocol stack for communications in a radio access network and / or a mobile communication system,

[0039] Low-layer mobility is or includes mobility controlled at or on a lower layer (such as layer 1 and / or layer 2) of a protocol stack for communications in a radio access network and / or mobile communication system, such as inter-cell handover,

[0040] The low layer entity is related to the cell currently serving the user equipment element or function and / or represents the source cell of the low layer mobility.

[0041] According to an exemplary aspect of the present disclosure, there is provided a method for a high-level control plane entity (or, in other words, operable or used by) in a wireless access network of a mobile communication system, the method comprising: establishing a configuration of low-level mobility and data forwarding in the low-level mobility, and providing the configuration to the low-level entity.

[0042] According to an exemplary aspect of the present disclosure, there is provided an apparatus for a high-layer control plane entity (or, in other words, operable or used by) in a radio access network of a mobile communication system, comprising: at least one processor and at least one memory, the at least one memory comprising computer program code, wherein the processor together with the at least one memory and the computer program code is configured to cause the apparatus to perform: establishing configuration of low-layer mobility and data forwarding in the low-layer mobility, and providing the configuration to the low-layer entity.

[0043] According to an exemplary aspect of the present disclosure, there is provided an apparatus for a high-level control plane entity (or, in other words, operable or used by) in a radio access network of a mobile communication system, comprising: a component for establishing a configuration of low-level mobility and data forwarding in the low-level mobility, and a component for providing the configuration to the low-level entity.

[0044] According to various developments / modifications, any of the above-mentioned method-related and / or apparatus-related example aspects of the present disclosure may include one or more of the following features:

[0045] This configuration indicates just-in-time data forwarding at serving cell change decision for low layer mobility,

[0046] The method, functionality or operability comprises: obtaining a notification of a bearer context modification from a higher layer user plane entity, the notification comprising: an indication of a serving cell change decision made by a lower layer entity, and an indication of initiation of data forwarding to a target cell for lower layer mobility,

[0047] The method, functionality or operability comprises: obtaining a notification from a lower layer entity, the notification comprising: an indication of a serving cell change decision made by the lower layer entity, an indication of an attribute of the serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for a target cell for low layer mobility, and based on the notification, informing a higher layer user plane entity of initiation of data forwarding to the target cell,

[0048] The notification includes: causing a bearer context modification at a higher-level user plane entity to enable the higher-level user plane entity to perform data forwarding to the target cell,

[0049] This configuration indicates early data forwarding in the preparation of candidate target cells for low-layer mobility.

[0050] The method, functionality or operability comprises: obtaining a notification of a bearer context modification from a higher layer user plane entity, the notification comprising: an indication of an upcoming serving cell change decision made by a lower layer entity and an indication of initiation of data forwarding to at least one of one or more candidate target cells for lower layer mobility,

[0051] The method, functionality or operability comprises: obtaining a notification from a lower layer entity, the notification comprising: an indication of application of early data forwarding by the lower layer entity, an indication of an attribute of an upcoming serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for at least one of the one or more candidate target cells, and based on the notification, informing a higher layer user plane entity of initiation of early data forwarding to at least one of the one or more candidate target cells,

[0052] The notifying includes: causing a bearer context modification at a higher-layer user plane entity to enable the higher-layer user plane entity to perform early data forwarding to at least one candidate target cell of the one or more candidate target cells,

[0053] The method, function or operability comprises: obtaining a bearer context modification notification from a higher layer user plane entity, the notification comprising: an indication of a serving cell change decision made by a lower layer entity, and an indication of initiation of data forwarding to a target cell for lower layer mobility,

[0054] The method, functionality or operability comprises: causing a bearer context modification at a higher layer user plane entity for enabling the higher layer user plane entity to perform data forwarding to a target cell,

[0055] the identifier for the target cell is or is based on its global cell identifier or its physical cell identifier,

[0056] The method, function or operability includes setting an index for each potential target cell for low layer mobility,

[0057] An index of each potential target cell for low layer mobility is provided to the lower layer entities in configuration and to the higher layer user plane entities,

[0058] The identifier for the target cell is or is based on its index,

[0059] A high-level control plane entity is or includes a functional unit that provides support for control plane functions of a high level (such as layer 3) of a protocol stack for communications in a radio access network and / or a mobile communication system,

[0060] The low layer entity is or includes a functional unit that provides support for the lower layers (such as layer 1 and / or layer 2) of the protocol stack for communications in the radio access network and / or mobile communication system.

[0061] A low-level entity is or includes a distributed unit of communication control elements or functions in a radio access network, such as a base station or NodeB,

[0062] Low-layer mobility is or includes mobility controlled at or on a lower layer (such as layer 1 and / or layer 2) of a protocol stack for communications in a radio access network and / or mobile communication system, such as inter-cell handover,

[0063] The low layer entity is related to the cell currently serving the user equipment element or function and / or represents the source cell of the low layer mobility.

[0064] According to an exemplary aspect of the present disclosure, a method is provided for a high-layer user plane entity (or, in other words, operable or used by) in a wireless access of a mobile communication system, the method comprising: obtaining notification information of initiation of data forwarding in low-layer mobility by a low-layer entity, and performing data forwarding according to the notification information.

[0065] According to an exemplary aspect of the present disclosure, there is provided a device for a high-layer user plane entity (or, in other words, operable or used by it) in a wireless access network of a mobile communication system, the device comprising: at least one processor and at least one memory, the at least one memory comprising computer program code, wherein the processor together with the at least one memory and the computer program code are configured to cause the device to execute: obtaining notification information of initiation of data forwarding by a low-layer entity in low-layer mobility, and performing data forwarding according to the notification information.

[0066] According to an exemplary aspect of the present disclosure, there is provided a device for a high-level user plane entity (or, in other words, operable or usable by it) in a wireless access network of a mobile communication system, the device comprising: a component for obtaining notification information of initiation of data forwarding in low-level mobility by a low-level entity, and a component for performing data forwarding according to the notification information.

[0067] According to various developments / modifications, any of the above-mentioned method-related and / or apparatus-related example aspects of the present disclosure may include one or more of the following features:

[0068] The notification information indicates on-time data forwarding upon decision of serving cell change for low layer mobility.

[0069] The obtaining includes obtaining a notification from a lower layer entity, the notification including an indication of a serving cell change decision made by the lower layer entity and an identifier for a target cell for low layer mobility,

[0070] The method, functionality or operability comprises: issuing a bearer context modification notification to a higher layer control plane entity, the notification comprising: an indication of a serving cell change decision made by a lower layer entity, and an indication of initiation of data forwarding to a target cell for lower layer mobility,

[0071] The obtaining includes: obtaining information about the initiation of data forwarding to the target cell from a high-level control plane entity, wherein the information is capable of performing the data forwarding to the target cell,

[0072] The information causes a bearer context modification at a higher layer user plane entity for enabling data forwarding to be performed towards the target cell,

[0073] The notification information indicates early data forwarding in preparation of candidate target cells for low layer mobility,

[0074] The obtaining includes obtaining a notification from a lower layer entity, the notification including an indication of application of early data forwarding to at least one of the one or more candidate target cells and an identifier of at least one of the one or more candidate target cells for low layer mobility,

[0075] The method, functionality or operability comprises issuing a notification of a bearer context modification to a higher layer control plane entity, the notification comprising an indication of an upcoming serving cell change decision made by a lower layer entity and an indication of initiation of data forwarding to at least one of one or more candidate target cells for lower layer mobility,

[0076] The obtaining includes: obtaining, from a higher layer control plane entity, information regarding initiation of early data forwarding to at least one of the one or more candidate target cells, the information enabling early data forwarding to be performed to at least one of the one or more candidate target cells,

[0077] The information causes a bearer context modification at a higher layer user plane entity for enabling early data forwarding to at least one of the one or more candidate target cells,

[0078] The method, function or operability comprises: obtaining a notification from a lower layer entity, the notification comprising an indication of a downlink data delivery status, the indication indicating that the downlink data has been acknowledged by a user equipment element or function as a destination,

[0079] The method, functionality or operability comprises: obtaining a notification from a lower layer entity, the notification comprising: an indication of a serving cell change decision and an identifier for a target cell for low layer mobility,

[0080] The method, functionality or operability comprises: obtaining information about a serving cell change decision from a higher layer control plane entity, the information comprising: an indication of the serving cell change decision, and an identifier for a target cell for low layer mobility,

[0081] The method, functionality or operability comprises: obtaining a notification from a lower layer entity or via a higher layer control plane entity, the notification comprising an indication of cancellation of early data forwarding,

[0082] the identifier for the target cell is or is based on its global cell identifier or its physical cell identifier, or its index is set or configured in the index of each potential target cell for low layer mobility,

[0083] A high-level user plane entity is or includes a functional unit that provides support for user plane functions of a high level (such as layer 3) of a protocol stack for communications in a radio access network and / or a mobile communication system,

[0084] The low layer entity is or includes a functional unit that provides support for the lower layers (such as layer 1 and / or layer 2) of the protocol stack for communications in the radio access network and / or mobile communication system.

[0085] A low-level entity is or includes a distributed unit of communication control elements or functions in a radio access network, such as a base station or NodeB,

[0086] Low-layer mobility is or includes mobility controlled at or on a lower layer (such as layer 1 and / or layer 2) of a protocol stack for communications in a radio access network and / or mobile communication system, such as inter-cell handover,

[0087] The low layer entity is related to the cell currently serving the user equipment element or function and / or represents the source cell of the low layer mobility.

[0088] According to an example aspect of the present disclosure, there is provided a computer program product comprising a (computer executable) computer program code, which, when the program code is executed (or run) on a computer or the program is run on a computer (e.g., a computer of a device according to any one of the aforementioned device-related example aspects of the present disclosure), is configured to cause the computer to execute a method according to any one of the aforementioned method-related example aspects of the present disclosure.

[0089] The computer program product may include or may be embodied as a (tangible / non-transitory) computer-readable (storage) medium etc. on which computer-executable computer program code is stored, and / or the program is directly loadable into the internal memory of a computer or its processor.

[0090] Listed below are further developments and / or modifications of the above-described example aspects of the present disclosure.

[0091] Through the exemplary embodiments of the present disclosure, a technology for (enabling / implementing) efficient / advantageous data forwarding in a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2-centric mobility) / for a mobile communication system in low-layer mobility can be enabled / implemented. In addition, a technology for facilitating reducing (service) interruption time and / or reducing (signaling) overhead of data forwarding in low-layer mobility (such as L1 / L2-centric mobility) can be enabled / implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] In the following, the present disclosure will be described in more detail by way of non-limiting examples with reference to the accompanying drawings, in which

[0093] Figure 1 A flowchart illustrating an example of a method or process according to at least one exemplary embodiment is shown,

[0094] Figure 2 A flowchart illustrating an example of a method or process according to at least one exemplary embodiment is shown,

[0095] Figure 3 A flowchart illustrating an example of a method or process according to at least one exemplary embodiment is shown,

[0096] Figure 4 shows a sequence diagram illustrating an example of a low-layer mobility and data forwarding process that is the basis of at least one exemplary embodiment,

[0097] Figure 5A sequence diagram illustrating an example of a low layer mobility and just-in-time data forwarding process according to at least one exemplary embodiment is shown,

[0098] Figure 6 A sequence diagram illustrating an example of a low layer mobility and early data forwarding procedure according to at least one exemplary embodiment is shown,

[0099] Figure 7 shows a schematic block diagram illustrating an example of a structure of an apparatus according to at least one exemplary embodiment, and

[0100] Figure 8 A schematic block diagram illustrating an example of a structure of an apparatus according to at least one exemplary embodiment is shown. DETAILED DESCRIPTION

[0101] The present disclosure is described herein with reference to specific non-limiting examples and what are presently considered to be conceivable (embodiments). It will be appreciated by those skilled in the art that the present disclosure is by no means limited to these examples and embodiments and can be applied more broadly.

[0102] It should be noted that the following description mainly relates to specifications used as non-limiting examples of certain exemplary network configurations and system deployments. That is, the following description mainly relates to 3GPP standards, which are used as non-limiting examples. Therefore, the description of the exemplary embodiments given herein specifically relates to terms directly related thereto. Such terms are used only in the context of the non-limiting examples and embodiments presented, and naturally do not limit the present disclosure in any way. On the contrary, any other system configuration or deployment can be equally utilized, as long as it is consistent with the content described herein and / or the exemplary embodiments described herein are applicable to these system configurations or deployments.

[0103] For example, the present disclosure is also applicable to any (mobile / wireless) communication system, such as 5G / NR system and next generation system beyond 5G. For example, the present disclosure is applicable to 3GPP standardized mobile / wireless communication systems starting from Release 18.

[0104] In the following, several variants and / or alternatives are used to describe various exemplary embodiments and implementations of the present disclosure and its various aspects. Generally, it should be noted that, according to certain needs and constraints, all described variants and / or alternatives can be provided individually or in any conceivable combination (also including combinations of individual features of various variants and / or alternatives). In this specification, the words "including" and "comprising" should be understood as not limiting the described exemplary embodiments and implementations to consist only of those features that have been mentioned, and such exemplary embodiments and implementations may also include features, structures, units, modules, etc. that are not specifically mentioned.

[0105] In the accompanying drawings, it should be noted that the lines / arrows interconnecting individual blocks or entities are generally intended to show the operational coupling between them, which can be a physical and / or logical coupling, which is independent of the implementation (e.g., wired or wireless) on the one hand, and can also include any number of intermediate functional blocks or entities not shown on the other hand. In the flowchart or sequence diagram, the order of operations or actions shown is generally illustrative / exemplary, and any other order of the corresponding operations or actions is also conceivable if feasible.

[0106] According to exemplary embodiments of the present disclosure, in general, measures / mechanisms for (enabling / implementing) efficient / advantageous data forwarding in low-layer mobility in a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2-centric mobility) are provided. In addition, measures / mechanisms for facilitating reducing (service) interruption time and / or reducing (signaling) overhead of data forwarding in low-layer mobility (such as L1 / L2-centric mobility) are also provided.

[0107] In the following, it is assumed that a specific configuration / architecture of a radio access network of a 3GPP-based system / 3GPP-related system, in particular, a communication control entity (such as a gNB) in / for a radio access network is used as a basis for illustrating exemplary embodiments (without limiting the present disclosure accordingly). That is, it is assumed that the radio access network or the communication control entity (such as a gNB) includes a plurality of lower-layer entities for controlling and / or supporting and / or implementing lower-layer operability (such as L1 / L2 operability), and a higher-layer entity for controlling and / or supporting and / or implementing higher-layer operability (such as L3 operability), wherein the higher-layer entity (logically and / or functionally and / or physically) is split into a higher-layer control plane entity for handling control plane (CP) operability and a higher-layer control plane entity for handling user plane (UP) operability. Each low-layer entity may be (implemented by / implemented in) a distributed unit DU (of / in gNB), a high-layer control plane entity may be (implemented by / implemented in) a central unit control plane CU-CP (implemented by / implemented in), and a high-layer user plane entity may be (implemented by / implemented in) a central unit user plane CU-UP (implemented by / implemented in).

[0108] Regarding L1 / L2-centric mobility (L1 / L2-based inter-cell mobility / handover), it is assumed that the user equipment (element or function) is initially served / controlled by a lower-layer entity, i.e., resides in a cell of the lower-layer entity, commonly referred to as a source cell or source DU, and will be handed over to another lower-layer entity, i.e., handed over to a cell of the other lower-layer entity, commonly referred to as a target cell or target DU. Therefore, L1 / L2-centric mobility (L1 / L2-based inter-cell mobility / handover) involves a service cell change, as a change between service cells associated with different lower-layer entities, also referred to as an inter-DU situation, for illustrating exemplary embodiments (but not limiting the present disclosure).

[0109] Figure 1 A flow chart illustrating an example of a method or process according to at least one exemplary embodiment is shown. Figure 1 The method or process is a method or process of a lower layer entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functionality or operability (such as a communication and / or communication control unit such as a distributed unit DU (of / in gNB) in / for a 3GPP network or system) (or, in other words, operable or used by it).

[0110] like Figure 1 As shown, the method or process includes: an operation of obtaining a configuration of low-layer mobility and data forwarding in the low-layer mobility from a high-layer control plane entity (S110), an operation of initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration (S120), and an operation of notifying a high-layer user plane entity of the initiation of data forwarding (S130), wherein at least one target cell of the low-layer mobility is identified.

[0111] like Figure 1 As shown by the dotted line in , the method or process may further include: making a decision (such as, for example, a serving cell change decision or an early data forwarding cancellation decision) and notifying a higher-level user plane entity of the decision (S140).

[0112] Figure 2 A flow chart illustrating an example of a method or process according to at least one exemplary embodiment is shown. Figure 2 The method or process is a method or process of a high-level control plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functionality or operability (such as a communication and / or communication control unit such as a central unit-control plane CU-CP (of / in gNB) in / for a 3GPP network or system) (or, in other words, operable or used by it).

[0113] like Figure 2 As shown, the method or process includes: an operation of establishing a configuration of low-layer mobility and data forwarding in the low-layer mobility (S210), and an operation of providing the configuration to a low-layer entity (S220).

[0114] like Figure 2 As shown by the dotted line in , the method or process may further include: obtaining a notification and / or informing a higher-level user plane entity of an operation in the notification (S230).

[0115] Figure 3 A flow chart illustrating an example of a method or process according to at least one exemplary embodiment is shown. Figure 3 The method or process is a method or process of a higher-level user plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functionality or operability (such as a communication and / or communication control unit such as a central unit-user plane CU-UP (of / in gNB) in / for a 3GPP network or system) (or, in other words, operable or used by it).

[0116] like Figure 3 As shown, the method or process includes: an operation of obtaining notification information of initiation of data forwarding by a lower layer entity in lower layer mobility (S310), and an operation of performing data forwarding according to the notification information (S320).

[0117] like Figure 3 As shown by the dotted line in , the method or process may also include: an operation of sending a notification of bearer context modification to a high-level control plane entity (S330).

[0118] like Figure 3 As shown by the dotted line in , the method or process may also include: an operation of obtaining a notification from a low-level entity and / or obtaining information from a high-level control plane entity (S340).

[0119] It should be noted that the steps / operations in the above process do not necessarily follow Figure 1 and Figure 3 The order shown is executed unless technically required (described as) such order. For example, Figure 3 The steps / operations S330 and S340 may be performed in a different order.

[0120] Here, the notification / providing / issuing operation should generally cover any way of causing / initiating / initiating the corresponding transmission and / or performing / realizing the actual transmission, and the acquisition operation should generally cover any way of performing / realizing the actual reception and / or acquiring / processing / accepting after the corresponding reception. Any data, information, notification, indication, etc. sent / obtained can be provided as is (e.g., in / as a dedicated element), as the content of some message / in some message (in any possible form / format), or provided in any other way, as long as it can be sent / obtained accordingly.

[0121] In the following, exemplary procedures for conceivable use cases are illustrated with respect to an example configuration / architecture (as described above) for illustrative purposes without limiting the present disclosure accordingly. Figure 4 The diagram shows the basics of low-level mobility and data forwarding, but Figure 5 and Figure 6 The details and / or implementation of the above-described operations are illustrated.

[0122] It should be noted that Figures 4 to 6 The message names given in are exemplary and represent a non-limiting example implementation, but do not limit the present disclosure.

[0123] Figure 4 A sequence diagram illustrating an example of a low-layer mobility and data forwarding procedure that is the basis of at least one exemplary embodiment is shown.

[0124] Figure 4 An exemplary process of low-layer mobility and subsequent data forwarding is as follows.

[0125] In step 1, the UE provides L3 measurements to the source DU, which are forwarded to the CU-CP in step 2. Based on these L3 measurements, the CU-CP decides on cell preparation (i.e., HO decision) in step 3 and proceeds with context establishment in the target DU in steps 4 and 5. The CU-CP then communicates with the CU-UP to perform bearer context establishment in steps 6 and 7.

[0126] In step 8, the CU-CP forwards the RRC Reconfiguration Request to the source DU using DL RRC messaging, and the source DU forwards the message to the UE in step 9. In steps 10 and 11, the UE responds with an RRC Reconfiguration Complete, which is then forwarded from the source DU to the CU-CP.

[0127] The UE provides periodic L1 reports to the source DU based on its configuration, such as in step 12 .

[0128] Once the source DU decides that the UE should switch to another DU (ie, target DU), ie after the source DU makes a cell switching decision, it triggers a cell / path switch using MAC CE in step 13. So far, the UE receives data from the serving DU, as shown in step 14.

[0129] The UE then applies the RRC configuration for the target cell (i.e., target DU), as indicated by the MAC CE, and performs a handover procedure, such as, for example, RA-based handover, RACH-free handover, etc. Here, it is exemplarily assumed that the UE performs random access (RA) on the target cell (i.e., target DU) in steps 15 and 16. After the RA procedure or any other (inter-DU) handover procedure, the UE sends an RRC reconfiguration complete to the target cell (i.e., target DU) in step 17, which is forwarded to the CU-CP in step 18.

[0130] The CU-CP performs a bearer modification with the CU-UP in steps 19 and 20 to update the bearer setup and cause the CU-UP to start forwarding data to the target DU (and stop forwarding data to the source DU). After this is completed, the UE starts receiving data from the target DU, as shown in step 21.

[0131] Finally, in the operations of steps 22 and 23, the CU-CP releases the UE context from the source DU through a UE context release request.

[0132] As described above, the UE will experience a (service) interruption during the time required to perform a cell / path switch from the source DU to the target DU and initiate data forwarding from the CU-UP to the target DU, because only Figure 4 After receiving the RRC reconfiguration completion in step 17, that is, after confirming the handover execution, the data will be forwarded. Figure 4 When the data is forwarded after receiving RRC reconfiguration completion in step 10 (i.e., after confirming cell preparation), the (service) interruption is shorter, but the (signaling) overhead is higher because the data needs to be forwarded to all potential / candidate target cells (i.e., target DU) before the final handover decision.

[0133] Figure 5 A sequence diagram illustrating an example of a low-layer mobility and just-in-time data forwarding process according to at least one exemplary embodiment is shown.

[0134] In the just-in-time data forwarding according to at least one exemplary embodiment, the source DU is enabled to inform the CU (i.e., CU-CP or CU-UP) of the serving cell change decision, i.e., the decision to change / switch to the target cell for low-layer mobility, or to transmit a serving cell change command (i.e., corresponding MAC CE) to the UE so as to initiate data forwarding to the target DU on time (i.e., within / at the time of the cell change decision / command).

[0135] Figure 5 An exemplary process of low-layer mobility and just-in-time data forwarding is as follows.

[0136] Steps 1 to 8 are the same as above Figure 4 Steps 1 to 8 in are equivalent, and therefore refer to Figure 4 Related description.

[0137] In step 9, the CU-CP configures L1 / L2-centric mobility and enables the data forwarding option. In this regard, the CU-CP establishes a configuration of L1 / L2-centric mobility and data forwarding, i.e., just-in-time data forwarding, and provides the configuration indicating just-in-time data forwarding to the source DU.

[0138] Steps 10 to 12 are equivalent to the above Figure 4 and therefore refer to steps 9 to 11 in detail. Figure 4 Related description.

[0139] In step 14 , the source DU decides whether a serving cell change (or, in other words, a cell / path switch) and initiation of data forwarding to the target DU is required, which may be achieved based on the UE L1 measurements received in step 13 .

[0140] In step 15, the source DU sends a corresponding MAC CE to the UE to trigger a serving cell change.

[0141] After triggering the serving cell change (in step 14 / 15), in one option / alternative denoted as "direct CU-UP notification", the source DU notifies the CU-UP of the serving cell change decision in step 16, where the identity of the target cell (i.e., target DU) is notified / informed. This can be implemented using a control PDU. As shown, the notification or message may include the NR-CGI of the target cell (as the target cell identity) to enable cell / path switching, as the NR-CGI helps the CU-UP identify the target cell, i.e., the target DU. In an alternative implementation, the notification or message may include the PCI of the target cell (as the target cell identity), where appropriate or sufficient.

[0142] Optionally, in step 17, the CU-UP may inform the CU-CP of the bearer context modification based on the notification of the source DU.

[0143] After triggering the serving cell change (in step 14 / 15), in step 18, in an option / alternative represented as "CU-UP notification by CU-CP", the source DU notifies the CU-CP of the serving cell change decision, wherein the identity of the target cell (i.e., the target DU) is notified / informed, and the serving cell change is notified / informed that it is an inter-DU cell change (i.e., the attribute of the serving cell change). This can be achieved using a corresponding notification or message. As shown in the figure, the notification or message may include the NR-CGI of the target cell (as the target cell identity) so that the CU-CP can perform a bearer context modification with the CU-UP, i.e., issue a bearer context modification request to notify the CU-UP (thereby enabling the CU-UP to perform a cell / path switch). In an alternative, the notification or message may include the PCI of the target cell (as the target cell identity), where appropriate or sufficient (as well as an inter-DU cell change indication).

[0144] The CU-CP performs a bearer modification with the CU-UP in steps 19 and 20 to update the bearer setup and cause the CU-UP to start forwarding data to the target DU (and stop forwarding data to the source DU). After this is completed, the data is forwarded to the target DU and is therefore available at the target DU, as shown in step 21.

[0145] Then (or at least partially in parallel with any of the above notification options / alternatives), as indicated by the MAC CE, the UE applies the RRC configuration for the target cell (i.e., target DU) and performs a handover procedure, such as, for example, RA-based handover, RACH-free handover, etc. Here, it is exemplarily assumed that the UE performs a random access (RA) to the target cell (i.e., target DU) in steps 22 and 23. After the RA procedure or any other (inter-DU) handover procedure, the UE sends an RRC reconfiguration complete to the target cell (i.e., target DU) in step 24, which is forwarded to the CU-CP in step 26. When the RRC reconfiguration in step 24 is completed, i.e., when the serving cell change to the target cell is performed / completed, the UE starts receiving data from the target DU, as shown in step 25.

[0146] Steps 27 and 28 are the same as above. Figure 4 Steps 22 and 23 in are equivalent, and therefore refer to Figure 4 Related description.

[0147] As can be seen from the above, according to the timely data forwarding provisions of at least one exemplary embodiment, when deciding to send a serving cell change command (related to cell / path switching) to the UE, the source DU informs the CU-CP or CU-UP that data forwarding should be initiated, and indicates the relevant target cell or target DU to which the switching will be performed. In this regard, the source DU transmits its decision / indication to the CU-UP directly or indirectly, that is, to the CU / UP (for example, using a control PDU) or to the CU-CP, and transmits it to the CU-UP via the CU-CP (via the E1 interface or a reference point therebetween).

[0148] Figure 6 A sequence diagram illustrating an example of a low layer mobility and early data forwarding procedure according to at least one exemplary embodiment is shown.

[0149] In early data forwarding according to at least one exemplary embodiment, the source DU is enabled to inform the CU (CU-CP or CU-UP) of candidate target cell preparation, i.e., the decision of one or more candidate target cells for low-layer mobility, or, therefore, the possible (upcoming) transmission of a serving cell change command (i.e., corresponding MAC CE) to the UE, so as to initiate data forwarding to a potential / candidate target cell or target DU as early as possible, i.e., earlier than the cell change decision / command.

[0150] Figure 6 An exemplary process of low-layer mobility and just-in-time data forwarding is as follows.

[0151] Steps 1 to 8 are the same as above Figure 4 Steps 1 to 8 in are equivalent, and therefore refer to Figure 4 Related description.

[0152] In step 9, the CU-CP configures L1 / L2-centric mobility and enables data forwarding options. In this regard, the CU-CP establishes a configuration of L1 / L2-centric mobility and data forwarding, i.e., early data forwarding, and provides the source DU with a configuration indicating early data forwarding. Optionally, the CU-CP may also provide the source DU with conditions for when to start and / or stop early data forwarding.

[0153] Steps 10 to 12 are equivalent to the above Figure 4 and therefore refer to steps 9 to 11 in detail. Figure 4 Related description.

[0154] In step 14, the source DU decides to initiate early data forwarding to the (one or more at least some relevant) candidate target cells or candidate target DUs determined as a result of the previous candidate target cell preparation, which can be implemented based on the UE L1 measurement received in step 13. In this regard, the source DU can also decide or determine the need or desire of the (one or more at least some relevant) candidate target cells or candidate target DUs for the upcoming serving cell change (or, in other words, future cell / path switch), and can initiate early data forwarding based on such decision or determination. Therefore, data forwarding to at least one target cell (i.e., a subset of the prepared target cells) is initiated, which can be based on the conditions for starting early data forwarding (when provided by the CU-CP).

[0155] After the triggering of early data forwarding (in step 14), in an option / alternative denoted as "direct CU-UP notification", the source DU notifies the CU-UP of the early data forwarding decision in step 15, wherein the identity of the candidate target cells (i.e., target DU) is notified / informed. This can be implemented using a control PDU. As shown, the notification or message may include (a list of) NR-CGI (as target cell identities) of the candidate target cells to enable (prepare or initiate) data forwarding, as the NR-CGI helps the CU-UP identify the candidate target cells, i.e., target DUs, as the destination for data forwarding. In an alternative implementation, where appropriate or sufficient, the notification or message may include (a list of) PCI (as target cell identities) of the candidate target cells.

[0156] Optionally, in step 16, the CU-UP may inform the CU-CP of the bearer context modification based on the notification of the source DU.

[0157] After triggering early data forwarding (in step 14), in step 17, in an option / alternative represented as "CU-UP notification by CU-CP", the source DU notifies the CU-CP of the early data forwarding decision, wherein the identity of the candidate target cell (i.e., the target DU) is notified / informed, and the upcoming serving cell change is notified / informed that it is an inter-DU cell change (i.e., the attribute of the upcoming serving cell change). This can be implemented using a corresponding notification or message. As shown in the figure, the notification or message may include (a list of) NR-CGIs (as target cell identities) of the candidate target cells so that the CU-CP can perform a bearer context modification with the CU-UP, i.e., issue a bearer context modification request to notify the CU-UP (thereby enabling the CU-UP to perform (prepare or initiate) data forwarding). In an alternative implementation, the notification or message may include (a list of) PCIs (as target cell identities) of the candidate target cells, where appropriate or sufficient (and an inter-DU cell change indication).

[0158] The CU-CP performs a bearer modification with the CU-UP in steps 18 and 19 to update the bearer setup and cause the CU-UP to start forwarding data to the candidate target DU. After this is completed, the data is forwarded to the candidate target DU and is therefore available at the candidate target DU, as shown in step 20 (for the actual target DU selected subsequently).

[0159] In step 22 , the source DU decides whether a serving cell change (or, in other words, a cell / path switch) is required, including initiation of data forwarding to the actual target DU selected thereby, which may be achieved based on the UE L1 measurements received in step 21 .

[0160] In step 23, the source DU sends a corresponding MAC CE to the UE to trigger a serving cell change.

[0161] After triggering the serving cell change (in step 22 / 23), the source DU notifies the CU-UP (decided by the serving cell change) of the downlink data delivery status, which indicates that the downlink data has been confirmed by the UE as the destination. For example, as shown in step 24, the source DU informs the CU-UP of the downlink data delivery status, i.e., the PDUs that have been confirmed by the UE, for example, using a control PDU. Then, in step 29, the CU-UP notifies / provides the downlink data delivery status to the target DU. Therefore, the target DU knows which PDUs have been confirmed (i.e., received by / via the source DU) and can therefore be released or discarded.

[0162] In one option / alternative denoted as "direct CU-UP notification", the source DU notifies the CU-UP of the downlink data delivery status in or together with an indication or message such as a control PDU, and the source DU also notifies the CU-UP of the serving cell change decision in the indication or message, wherein the identity of the target cell (i.e., the target DU) is notified / informed, as shown in step 24. As shown, the notification or message may include the NR-CGI of the target cell (as the target cell identity) to enable cell / path switching, because the NR-CGI helps the CU-UP identify the target cell, i.e., the target DU. In an alternative implementation, the notification or message may include the PCI of the target cell (as the target cell identity) where appropriate or sufficient.

[0163] Optionally, in step 25, the CU-UP may inform the CU-CP of the bearer context modification based on the notification of the source DU.

[0164] It should be noted that even in this option / alternative, the source DU may inform the CU-UP of the downlink data delivery status and the serving cell change decision in different / separate notifications or messages. For example, the DU may first (only) inform the CU-UP of the downlink data delivery status, such as in / with the control PDU shown in step 24, and the source DU may concurrently or thereafter (only) inform the CU-CP of the serving cell change decision, and the target cell identifier, such as in or with another control PDU not shown but which may occur at any time between steps 23 and 25.

[0165] In one option / alternative denoted as "CU-UP notification by CU-CP", the source DU notifies the CU-CP of the serving cell change decision using a corresponding notification or message (such as a control PDU) that is different / distinct from the indication or message, in which or together with the indication or message, the source DU notifies the CU-UP of the downlink data delivery status. In such notification or message, the identity of the target cell (i.e., the target DU) is notified / informed, and the serving cell change is notified / informed that it is an inter-DU cell change (i.e., an attribute of the serving cell change), as shown in step 26. As shown, the notification or message may include the NR-CGI of the target cell (as the target cell identity) so that the CU-CP can perform a bearer context modification with the CU-UP, i.e., issue a bearer context modification request to notify the CU-UP (thereby enabling the CU-UP to perform a cell / path switch). In an alternative implementation, the notification or message may include the PCI of the target cell (as the target cell identity), where appropriate or sufficient (as well as an inter-DU cell change indication).

[0166] The CU-CP performs a bearer modification with the CU-UP in steps 27 and 28 to update the bearer setup and cause the CU-UP to start forwarding data to the target DU (and stop forwarding data to the source DU). After this is completed, the data will be forwarded to the target DU and is therefore available at the target DU.

[0167] Then (or at least partially in parallel with any of the above notification options / alternatives regarding the serving cell change), as indicated by the MAC CE, the UE applies the RRC configuration for the target cell (i.e., target DU) and performs a handover procedure, such as, for example, RA-based handover, RACH-free handover, etc. Here, it is exemplarily assumed that the UE performs a random access (RA) to the target cell (i.e., target DU) in steps 30 and 31. After the RA procedure or any other (inter-DU) handover procedure, the UE sends an RRC reconfiguration complete to the target cell (i.e., target DU) in step 32, which is forwarded to the CU-CP in step 34. When the RRC reconfiguration in step 32 is completed, i.e., when the serving cell change to the target cell is performed / completed, the UE starts receiving data from the target DU, as shown in step 33.

[0168] Steps 35 and 36 are the same as above. Figure 4 Steps 22 and 23 in are equivalent, and therefore refer to Figure 4 Related description.

[0169] although Figure 6 , but the source DU may at some point (i.e., Figure 6 After deciding to initiate early data forwarding in step 14 of Figure 6 Before deciding to perform cell / path switching in step 22 of the process, the source DU may decide to stop / terminate early data forwarding, i.e., make an early data forwarding cancellation decision. Such a decision may be made based on a condition for stopping early data forwarding (when provided by the CU-CP). If so, the source DU may initiate the stop / termination of early data forwarding by sending a corresponding notification of the early data forwarding cancellation decision to the CU-CP or CU-UP (e.g., by sending a cancellation message).

[0170] As can be seen from the above, according to the early data forwarding provisions of at least one exemplary embodiment, the source DU decides when data forwarding should be initiated (regardless of or in particular before the serving cell change decision), and accordingly informs the CU-CP or CU-UP to indicate the (relevant) potential / candidate target cell or target DU to the CU-CP or CU-UP. The CU-UP may continue to forward data to / receive data from the source DU until further confirmation is received from the source DU to stop the source DU communication. In this regard, the source DU transmits its decision / indication to the CU-UP directly or indirectly, i.e., to the CU / UP (e.g., using a control PDU) or to the CU-CP, and to the CU-UP via the CU-CP (via the E1 interface or a reference point therebetween).

[0171] According to at least one exemplary embodiment, it is applicable to Figure 5 and Figure 6In any of the processes, the CU-CP may decide / determine the application of just-in-time data forwarding or early data forwarding, for example based on certain settings, requests, constraints, etc. Based on such a decision / determination, the CU-CP may establish the configuration of the low-layer mobility and the data forwarding in the low-layer mobility accordingly, i.e., configure the source DU accordingly.

[0172] According to at least one exemplary embodiment, a target cell index may be used to identify a (potential / candidate) target cell or a corresponding target DU. Figure 5 and Figure 6 any process in the process.

[0173] For the target cell index, the CU-CP may set an index for each potential target cell of the low-layer mobility, and the CU-CP may provide the index of each potential target cell of the low-layer mobility to the source DU and the CU-UP. The provisioning of the source DU may be done in, with, or in connection with the configuration of L1 / L2-centric mobility (such as Figure 5 and Figure 6 in step 9 of any one of the above), and the provisioning of CU-UP may be accomplished by any dedicated or any other indication or message.

[0174] For example, the CU-CP may provide the CU-UP with an index of each potential target (ie, prepared) cell with a bearer context establishment request (ie, Figure 5 and Figure 6 The same index for the potential target cell is also provided to the source DU. In this case, the source DU with the cell change trigger (i.e., Figure 5 Any of steps 16 and 18, or Figure 6 Any one of steps 15, 17, 24 and 26 of the target cell can only provide an index number of the target cell, but cannot provide another identifier such as NR-CGI with a corresponding indication or message (such as a control PDU). Therefore, the potential PCI duplication problem between the prepared target cells can be solved and signaling optimization can be achieved.

[0175] Through the exemplary embodiments of the present disclosure, as described above, measures / mechanisms for (enabling / implementing) efficient / favorable data forwarding in low-layer mobility in a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2-centric mobility) are provided. In addition, measures / mechanisms for facilitating reduction of (service) interruption time and / or reduction of (signaling) overhead of data forwarding in low-layer mobility (such as L1 / L2-centric mobility) are also provided.

[0176] Therefore, the goals of low-layer mobility, such as L1 / L2-centric mobility (L1 / L2-based inter-cell mobility / handover), such as reducing (service) interruption time and / or reducing (signaling) overhead in data forwarding can be advantageously achieved. More specifically, it can be achieved that the (to be forwarded) data is available in a timely manner at the target cell or target DU (i.e., before the UE requires it due to the completion of the handover execution), and the (to be forwarded) data is not unnecessarily forwarded to all prepared target cells or more prepared target cells than needed / convenient, thereby reducing the (excessive) overhead on the F1 interface or reference point between the CU-UP and the DU.

[0177] Therefore, achievable effects / advantages according to one or more exemplary embodiments include at least the following:

[0178] - Reduced (service) compared to delayed data forwarding triggered after a cell change

[0179] Interruption time,

[0180] - by (at least partially) executing the F1AP process in parallel (e.g. Figure 5 and Figure 6 those steps included in the various options / option boxes in any one of the above) and RRC procedures to reduce the (service) interruption time,

[0181] - Reduced (service) interruption time in case of early data forwarding, because CU-UP

[0182] Data is not forwarded to all prepared cells, but only to the relevant cells, - data forwarding is performed only for a short period of time, but not too long (as might happen with traditional mechanisms of early data forwarding),

[0183] -Signaling optimization utilizing direct DU to CU-UP communication.

[0184] Various other beneficial aspects that may be achieved according to one or more exemplary embodiments include the following:

[0185] Appropriate UE configuration may be specified to enable fast application of configuration (which will further enable low interruption) and dynamic switching between candidate cells. In order to enable these procedures to achieve low interruption time, it may be ensured that UE data is available in a timely manner in the node to which the UE will be handed over.

[0186] No full L2 (and L1) reset is required, thus avoiding longer delays, greater overhead and longer outage time than beam switch mobility. Instead, serving cell changes are enabled via L1 / L2 signaling, which reduces delays, overhead and outage time.

[0187] Configuration and maintenance for multiple candidate cells is enabled to allow rapid application of configurations for candidate cells.

[0188] A dynamic switching mechanism between candidate serving cells (including SpCell and SCell) for potential applicable scenarios based on L1 / L2 signaling is enabled.

[0189] CU-DU interface signaling is enabled to support L1 / L2 mobility.

[0190] The above functions and their related operations, procedures, methods and processes may be implemented by corresponding functional elements, entities, modules, units, processors, etc., as described below. These functional elements, entities, modules, units, processors, etc. (i.e., implementations of one or more exemplary embodiments) may be implemented in a cloud environment through SDN, NFV / NFVI, etc.

[0191] Although the aforementioned exemplary embodiments of the present disclosure are mainly described with reference to operations, procedures, methods and processes, the corresponding exemplary embodiments of the present disclosure also cover corresponding devices, entities, modules, units, network nodes and / or systems, including their software and / or hardware.

[0192] Reference below Figure 7 and Figure 8 Describe the corresponding exemplary embodiments of the present invention, while for the sake of brevity, refer to Figures 1 to 6 A detailed description of the corresponding configuration / settings, schemes, processes, sequences, methods, and functions, principles and operations.

[0193] exist Figure 7 and Figure 8 In the embodiment, the blocks are basically configured to perform the corresponding methods, procedures and / or functions as described above. The entire blocks are basically configured to perform the methods, procedures and / or functions as described above, respectively. Figure 7 and Figure 8 It should be noted that the individual blocks are intended to illustrate the corresponding functional blocks that implement the corresponding functions, processes or procedures. Such functional blocks are independent of implementation, that is, they can be implemented by any kind of hardware or software or a combination thereof.

[0194] In addition, Figure 7 and Figure 8 In the embodiment, only functional blocks related to any one of the above methods, procedures and / or functions are shown. Those skilled in the art will recognize that there are any other conventional functional blocks required to operate the corresponding structural arrangement, such as power supply, central processing unit, corresponding memory, etc. Among other things, one or more memories are provided for storing programs or program instructions for controlling or enabling individual functional entities or any combination thereof to operate as described herein with respect to the exemplary embodiments.

[0195] Figure 7 A schematic diagram illustrating an example of a structure of an apparatus according to at least one example embodiment is shown. Here, an apparatus may represent a physical entity or component, such as a structural device that implements a specific network element, entity or function or its function, or a functional or logical entity or component. For example, the apparatus shown may be implemented in or by a server or the like in a cloud environment, such as through a cloud-based implementation.

[0196] like Figure 7 As shown, according to at least one example embodiment, the apparatus 700 may include or implement at least one processor 710 and at least one memory 720 (and possibly at least one interface 730), which may be operatively connected or coupled via a bus 740 or the like.

[0197] The processor 710 and / or the interface 730 of the device 700 may also include a modem, etc., to facilitate communication via a (hardwired or wireless) link, respectively. The interface 730 of the device 700 may include a transmitter, a receiver, or a transceiver, which is connected or coupled to one or more antennas, antenna units (such as antenna arrays), or communication facilities or components for communicating with (multiple) linked, coupled or connected devices (hardwired or wireless), respectively. The interface 730 of the device 700 is generally configured to communicate with at least one other device, equipment, node or entity (particularly its interface).

[0198] The memory 720 of the device 700 may represent a (non-transitory / tangible) storage medium (e.g., RAM, ROM, EPROM, EEPROM, etc.), and stores corresponding software, programs, program products, macros or small applications, etc. or parts thereof, which may be assumed to include program instructions or computer program codes that, when executed by a corresponding processor, enable a corresponding electronic device or device to operate according to the example embodiments described herein. In addition, the memory 720 of the device 700 may store (including databases) any data, information, etc. used in the operation of the device.

[0199] According to various example embodiments, the corresponding apparatus (and / or part thereof) may represent a component for performing the corresponding operation and / or exhibiting the corresponding function, and / or the corresponding device (and / or part thereof) may have a function for performing the corresponding operation and / or exhibiting the corresponding function.

[0200] In view of the foregoing, the illustrated apparatus 700 may be used to practice one or more of the example embodiments described herein.

[0201] When in the subsequent description it is stated that a processor (or some other component) is configured to perform a certain function, this will be interpreted as being equivalent to or corresponding to a description stating that (i.e., at least one) processor or corresponding circuit system is configured to cause the device to perform at least the function mentioned so, the processor or corresponding circuit system potentially cooperating with computer program code stored in a memory of the corresponding device or otherwise available (it should be understood that the memory may also be an external memory or provided / implemented by a cloud service, etc.). It should be understood that in this document, a processor or more generally a processing portion should not only be considered to represent a physical portion of one or more processors, but can also be considered to be a logical division of the processing tasks performed by one or more processors.

[0202] According to at least one example embodiment, the illustrated apparatus 700 may represent or implement / embody a low-layer entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a distributed unit DU (of / in a gNB) in / for a 3GPP network or system. Therefore, the apparatus 700 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 1 and Figures 4 to 6 as described in any one of (for source DU).

[0203] Thus, the apparatus 700 may be caused or the apparatus 700 or its at least one processor 710 (possibly together with a computer program code stored in its at least one memory 720) may be configured to: obtain from a high-layer control plane entity a configuration of low-layer mobility and data forwarding in the low-layer mobility, initiate data forwarding to at least one target cell of the low-layer mobility according to the configuration, and notify a high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of the low-layer mobility is identified.

[0204] According to at least one example embodiment, the illustrated apparatus 700 may represent or implement / embody a high-level control plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a central unit control plane CU-CP (of / in a gNB) in / for a 3GPP network or system. Therefore, the apparatus 700 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 2 and Figures 4 to 6 as described in any one of (for CU-CP).

[0205] Thus, the apparatus 700 may be caused or the apparatus 700 or its at least one processor 710 (possibly together with computer program code stored in its at least one memory 720) may be configured to: establish a configuration of low-layer mobility and data forwarding in the low-layer mobility, and provide the configuration to the low-layer entity.

[0206] According to at least one example embodiment, the illustrated apparatus 700 may represent or implement / embody a high-level user plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a central unit user plane CU-UP (of / in a gNB) in / for a 3GPP network or system. Therefore, the apparatus 700 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 3 and Figures 4 to 6 as described in any one of (for CU-UP).

[0207] Therefore, the device 700 can be caused or the device 700 or its at least one processor 710 (possibly together with the computer program code stored in its at least one memory 720) is configured to: obtain notification information of the initiation of data forwarding in the low-layer mobility by the low-layer entity, and perform data forwarding according to the notification information.

[0208] As described above, the apparatus according to at least one example embodiment may be constructed by including one or more units or components or circuit systems for performing corresponding operations, processes and / or functions. For example, such one or more units or components or circuit systems may be based on Figure 7 The illustrated device structure is implemented / realized (eg, by one or more processors 710, one or more memories 720, one or more interfaces 730, or any combination thereof).

[0209] Figure 8 A schematic diagram illustrating an example of a structure of an apparatus according to at least one example embodiment is shown.

[0210] like Figure 8 As shown, the device 810 according to at least one example embodiment may represent or implement / embody a low-layer entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a distributed unit DU (of / in a gNB) in / for a 3GPP network or system. Therefore, the device 810 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 1 and Figures 4 to 6as described in any one of (for source DU).

[0211] Such an apparatus 810 may (at least) include: one or more units / components / circuitry systems represented by an acquisition portion 811, which represent any implementation for (or are configured to) acquire low-layer mobility and configuration of data forwarding in low-layer mobility from a high-layer control plane entity; one or more units / components / circuitry systems represented by an initiation portion 812, which represent any implementation for (or are configured to) initiate data forwarding to at least one target cell of low-layer mobility according to the configuration; and one or more units / components / circuitry systems represented by a notification portion 813, which represent any implementation for (or are configured to) notify a high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of low-layer mobility is identified.

[0212] In addition, such an apparatus 810 may additionally / optionally also include one or more units / components / circuitry systems represented by a decision portion 814, which represents any implementation for (or configured to) make a decision, such as a serving cell change decision for a target cell for low-layer mobility, a serving cell change decision for a target cell among one or more candidate target cells for low-layer mobility, an upcoming serving cell change decision for a target cell among one or more candidate target cells for low-layer mobility, or an early data forwarding cancellation decision for canceling early data forwarding.

[0213] like Figure 8 As shown, the device 820 according to at least one example embodiment may represent or implement / embody a high-level control plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a central unit control plane CU-CP (of / in a gNB) in / for a 3GPP network or system. Therefore, the device 820 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 2 and Figures 4 to 6 as described in any one of (for CU-CP).

[0214] Such an apparatus 820 may include (at least) one or more units / components / circuitry systems represented by an establishing portion 821, which represents any implementation of a configuration for (or configured to) establishing low-layer mobility and data forwarding in low-layer mobility; and one or more units / components / circuitry systems represented by a providing portion 822, which represents any implementation of a configuration for (or configured to) providing the configuration to a low-layer entity.

[0215] In addition, such an apparatus 820 may additionally / optionally also include one or more units / components / circuitry represented by an acquisition / notification portion 823, which represents any implementation for (or configured to) perform one or more of the various acquisition / notification operations or steps, as described above. Additionally or alternatively, such an apparatus 820 may additionally / optionally (at least) include one or more units / components / circuitry represented by a causing portion 824, which represents any implementation for (or configured to) causing a bearer context modification at a high-level user plane entity.

[0216] like Figure 8 As shown, the device 830 according to at least one example embodiment may represent or implement / embody a high-level user plane entity in / for a radio access network of a mobile communication system, or an element, function or entity with similar / comparable functions or operability, such as a communication and / or communication control unit such as a central unit user plane CU-UP (of / in a gNB) in / for a 3GPP network or system. Therefore, the device 830 may be configured to perform a process and / or display a function and / or implement a mechanism, such as Figure 3 and Figures 4 to 6 as described in any one of (for CU-UP).

[0217] Such an apparatus 830 may (at least) include: one or more units / components / circuit systems represented by an acquisition portion 831, which represent any implementation for (or are configured to) acquire notification information of initiation of data forwarding by a lower-layer entity in lower-layer mobility; and one or more units / components / circuit systems represented by an execution portion 832, which represent any implementation for (or are configured to) perform data forwarding based on the notification information.

[0218] In addition, such a device 830 may additionally / optionally also include one or more units / components / circuitry systems represented by the issue / acquisition portion 833, which represents any implementation for (or configured to) perform one or more of the various issue / acquisition operations or steps described above.

[0219] For further details on the operability / functionality of the apparatus (or its units / components) according to exemplary embodiments, reference is made to the respective Figures 1 to 6 Any of the above descriptions.

[0220] According to exemplary embodiments of the present disclosure, any one of (at least one) processor, (at least one) memory and (at least one) interface, and any one of the units / components shown may be implemented as individual modules, chips, chipsets, circuit systems, etc., or one or more of them may be respectively implemented as a common module, chip, chipset, circuit system, etc.

[0221] According to exemplary embodiments of the present disclosure, a system may include any conceivable combination of any depicted or described apparatuses and other network elements or functional entities, which are configured to cooperate as described above.

[0222] Generally, it should be noted that if the corresponding functional blocks or elements according to the above aspects are only suitable for performing the above functions of the corresponding parts, they can be implemented in hardware and / or software respectively in any known manner. The above method steps can be implemented in individual functional blocks or by individual devices, or one or more of the method steps can be implemented in a single functional block or by a single device.

[0223] In general, a basic system architecture of a (tele)communication network including a mobile communication system (where some examples of exemplary embodiments are applicable) may include an architecture of one or more communication networks including (multiple) radio access network sub / systems and (multiple) possible core networks. Such an architecture may include one or more communication network control elements or functions, such as, for example, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as base stations, access points, NodeBs (NBs), eNBs or gNBs, distributed or centralized units, which control the respective coverage areas or (multiple) cells, and one or more communication stations (such as communication elements or functions, such as user equipment or terminal equipment, such as UEs, or another device with similar functionality (such as modem chipsets, chips, modules, etc.), which may also be part of a station, element, function or application capable of communication, such as a UE, an element or function used in a machine-to-machine communication architecture, or attached as a separate element to an element, function or application capable of communication, etc.) capable of communicating with it via one or more communication beams for sending several types of data in multiple access domains via one or more channels. Furthermore, core network elements or network functions may be included, such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc.

[0224] The general functionality and interconnection of the described elements and functions (which also depends on the actual network type) are known to those skilled in the art and are described in the corresponding specification, so a detailed description thereof is omitted here. It should be understood that several additional network elements and signaling links, in addition to those described in detail below, may be used to communicate with elements, functions or applications, such as communication endpoints, communication network control elements (such as servers, gateways, radio network controllers), and other elements of the same or other communication networks.

[0225] The communication network architecture considered in the examples of exemplary embodiments may also be able to communicate with other networks, such as a public switched telephone network or the Internet, including the Internet of Things. The communication network may also be able to support the use of cloud services for virtual network elements or their functions, wherein it should be noted that the virtual network part of the (remote) communication network may also be provided by non-cloud resources, such as an internal network, etc. It should be understood that the network elements and / or corresponding functions of the access system, core network, etc. may be implemented using any node, host, server, access node or entity, etc. suitable for such use. In general, the network functions may be implemented as network elements on dedicated hardware, software instances running on dedicated hardware, or virtualized functions instantiated on an appropriate platform (e.g., a cloud infrastructure).

[0226] Without changing the idea of ​​the present disclosure, any method step is suitable for implementation as software or by hardware. Such software can be independent of the software code and can be specified using any known or future developed programming language, such as Java, C++, C and Assembler, as long as the functions defined by the method steps are retained. Such hardware can be independent of the hardware type and can be implemented using any known or future developed hardware technology or any mixture of these technologies, such as MOS (metal oxide semiconductor), CMOS (complementary MOS), BiMOS (bipolar MOS), BiCMOS (bipolar CMOS), ECL (emitter coupled logic), TTL (transistor transistor logic), etc., using, for example, ASIC (application specific IC (integrated circuit)) components, FPGA (field programmable gate array) components, CPLD (complex programmable logic device) components or DSP (digital signal processor) components. The device / apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such a chip or chipset; however, this does not exclude the possibility that the functionality of the device / apparatus or module (rather than being implemented by hardware) is implemented as software in a (software) module, such as a computer program or computer program product comprising executable software code portions for execution / running on a processor. For example, a device may be considered as a device / apparatus or a component of more than one device / apparatus, whether they cooperate in functionality or are functionally independent of each other but in the same device housing.

[0227] Means and / or units / components or parts thereof may be implemented as individual devices, but this does not exclude that they may be implemented in a distributed manner throughout the system, as long as the functionality of the device is preserved. Such and similar principles will be considered known to those skilled in the art.

[0228] Software in the sense of this specification comprises software code, which itself includes code components or parts or a computer program or computer program product for performing corresponding functions, as well as software (or computer program or computer program product) embodied on a tangible medium such as a computer-readable (storage) medium on which the corresponding data structures or code components / parts are stored, or embodied in a signal or chip (potentially during its processing).

[0229] The present disclosure also covers any conceivable combination of the above method steps and operations, and any conceivable combination of the above nodes, devices, modules, or elements, as long as the concepts of the above methods and structural arrangements are applicable.

[0230] In view of the above, measures are provided for enabling / implementing efficient / favorable data forwarding in low-layer mobility in / for a mobile communication system (i.e., a radio access network of a mobile communication system, such as L1 / L2-centric mobility). Such measures exemplarily include, a low-layer entity in the radio access network of the mobile communication system obtaining a configuration of low-layer mobility and data forwarding in the low-layer mobility from a high-layer control plane entity, initiating data forwarding to at least one target cell of the low-layer mobility according to the configuration, and notifying the high-layer user plane entity of the initiation of data forwarding, wherein at least one target cell of the low-layer mobility is identified. The configuration may indicate just-in-time data forwarding, wherein data forwarding to the target cell is triggered when a serving cell change decision is completed, or may indicate early data forwarding at the time of preparation of candidate target cells for low-layer mobility, wherein data forwarding to at least one of the one or more candidate target cells is triggered when candidate target cell preparation is completed.

[0231] Although the present disclosure is described above with reference to examples according to the accompanying drawings, it should be understood that the present disclosure is not limited thereto. On the contrary, it is clear to those skilled in the art that the present disclosure can be modified in many ways without departing from the scope of the inventive concept disclosed herein.

[0232] List of abbreviations and acronyms

[0233] 3GPP Third Generation Partnership Project

[0234] 5G Fifth Generation

[0235] CU-CP Central Unit - Control Plane

[0236] CU-UP Central Unit - User Plane

[0237] DL Downlink

[0238] DU Distributed Unit

[0239] gNB gNodeB (5G / NR base station)

[0240] HO Switchover

[0241] MAC Media Access Control

[0242] MAC CE Media Access Control Element

[0243] NFV Network Function Virtualization

[0244] NFVI Network Function Virtualization Infrastructure

[0245] NR New Radio

[0246] NR-CG New Radio Cell Global Identity / Identifier

[0247] OSI Open Systems Interconnection

[0248] PCI Physical Cell Identity / Identifier

[0249] PDU Packet Data Unit

[0250] RA Random Access

[0251] RACH Random Access Channel

[0252] RRC Radio Resource Control

[0253] SDN Software Defined Network

[0254] UE User Equipment

[0255] UL Uplink

Claims

1. A method for a low-level entity in a radio access network of a mobile communication system, comprising: Obtain configuration of low-layer mobility and data forwarding in low-layer mobility from high-layer control plane entities, initiating data forwarding to at least one target cell of lower layer mobility according to the configuration, and A higher layer user plane entity is informed of the initiation of data forwarding, wherein the at least one target cell for the lower layer mobility is identified.

2. The method according to claim 1, wherein The configuration indicates on-time data forwarding upon decision of serving cell change for low layer mobility.

3. The method of claim 2, wherein the initiating comprises: making a serving cell change decision for a target cell for low layer mobility, and When the serving cell change decision is completed, data forwarding to the target cell is triggered.

4. The method of claim 3, wherein the notification comprises: issuing a notification to the higher layer user plane entity, the notification comprising: an indication of the serving cell change decision and an identifier for the target cell, or A notification is issued to the upper layer control plane entity for informing the upper layer user plane entity, the notification comprising: an indication of the serving cell change decision, an indication of the attributes of the serving cell change as a change between serving cells associated with different lower layer entities, and an identifier for the target cell.

5. The method according to claim 1, wherein The configuration indicates early data forwarding in preparation of candidate target cells for low-layer mobility.

6. The method of claim 5, wherein the initiating comprises: performing candidate target cell preparation for one or more candidate target cells for low layer mobility, and When the candidate target cell preparation is completed, data forwarding to at least one of the one or more candidate target cells is triggered.

7. The method of claim 6, wherein the notification comprises: issuing a notification to the higher layer user plane entity, the notification comprising: an indication of the application of the early data forwarding and an identifier for the at least one candidate target cell of the one or more candidate target cells, or A notification is issued to the higher layer control plane entity for informing the higher layer user plane entity, the notification comprising: an indication of the application of the early data forwarding, an indication of the attributes of the upcoming serving cell change as a change between serving cells associated with different lower layer entities, and an identifier for the at least one candidate target cell among the one or more candidate target cells.

8. The method according to claim 6 or 7, further comprising: making a serving cell change decision for a target cell of the one or more candidate target cells for low layer mobility, and notifying the higher layer user plane entity of the serving cell change decision, The notification of the serving cell change decision comprises: issuing a notification to the higher layer user plane entity, the notification comprising an indication of a downlink data delivery status, the indication indicating that the downlink data has been confirmed by a user equipment element or function as a destination.

9. The method of claim 8, wherein the notification of the serving cell change decision further comprises: issuing a notification to the higher layer user plane entity, the notification comprising: an indication of the serving cell change decision and an identifier for the target cell, or A notification is issued to the higher layer control plane entity for informing the higher layer user plane entity, the notification comprising: an indication of the serving cell change decision, an indication of the attributes of the serving cell change as a change between serving cells associated with different lower layer entities, and an identifier for the target cell.

10. The method according to any one of claims 6 to 9, further comprising: making an early data forwarding cancellation decision for cancelling the early data forwarding, and notifying the higher layer user plane entity of the early data forwarding cancellation decision, The notification of the early data forwarding cancellation decision includes sending a notification to the higher-level user plane entity or to the higher-level control plane entity, so as to inform the higher-level user plane entity, and the notification includes an indication of the cancellation of the early data forwarding.

11. The method according to any one of claims 1 to 10, wherein The data forwarding is initiated based on low layer measurements, in particular layer 1 measurements, from user equipment elements or functions.

12. The method according to any one of claims 1 to 11, wherein The configuration includes an index of each potential target cell for low layer mobility, and In the notification, the at least one target cell for low layer mobility is identified using or based on its index in the configuration.

13. A method for a high-level control plane entity in a radio access network of a mobile communication system, comprising: Establishing low layer mobility and configuration of data forwarding in low layer mobility, and Provide the configuration to lower level entities.

14. The method according to claim 13, wherein The configuration indicates on-time data forwarding upon decision of serving cell change for low layer mobility.

15. The method according to claim 14, further comprising: A notification of a bearer context modification is obtained from a higher layer user plane entity, the notification comprising an indication of a serving cell change decision made by the lower layer entity and an indication of initiation of data forwarding to a target cell for lower layer mobility.

16. The method according to claim 14, further comprising: obtaining a notification from the lower layer entity, the notification comprising an indication of a serving cell change decision made by the lower layer entity, an indication of attributes of the serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for a target cell for low layer mobility, and Based on the notification, a higher layer user plane entity is informed of the initiation of data forwarding to the target cell.

17. The method according to claim 13, wherein The configuration indicates early data forwarding in preparation of candidate target cells for low-layer mobility.

18. The method according to claim 17, further comprising: Obtaining notification of a bearer context modification from a higher layer user plane entity, the notification comprising an indication of an upcoming serving cell change decision made by the lower layer entity and an indication of initiation of data forwarding to at least one of one or more candidate target cells for lower layer mobility.

19. The method according to claim 17, further comprising: obtaining a notification from the lower layer entity, the notification comprising: an indication of application of the early data forwarding by the lower layer entity, an indication of attributes of an upcoming serving cell change being a change between serving cells associated with different lower layer entities, and an identifier for the at least one of the one or more candidate target cells, and Based on the notification, a higher layer user plane entity is informed of the initiation of the early data forwarding to the at least one candidate target cell among the one or more candidate target cells.

20. The method according to any one of claims 13 to 19, further comprising: An index is set for each potential target cell for low-layer mobility, where The index of each potential target cell for low layer mobility is provided to the lower layer entity in the configuration and to a higher layer user plane entity.

21. A method for a high-level user plane entity in a wireless access network of a mobile communication system, comprising: Obtaining notification information of the initiation of data forwarding in lower layer mobility by lower layer entities, and Data forwarding is performed according to the notification information.

22. The method according to claim 21, wherein The notification information indicates on-time data forwarding upon decision of serving cell change for low layer mobility.

23. The method according to claim 21, wherein The notification information indicates early data forwarding in preparation of candidate target cells for low layer mobility.

24. An apparatus of a low-layer entity in a radio access network of a mobile communication system, the apparatus comprising at least one processor and at least one memory, the at least one memory comprising a computer program code, wherein the processor together with the at least one memory and the computer program code is configured to cause the apparatus to execute: Obtain configuration of low-layer mobility and data forwarding in low-layer mobility from high-layer control plane entities, initiating data forwarding to at least one target cell of lower layer mobility according to the configuration, and A higher layer user plane entity is informed of the initiation of data forwarding, wherein the at least one target cell for the lower layer mobility is identified.

25. An apparatus of a high-level control plane entity in a radio access network of a mobile communication system, the apparatus comprising at least one processor and at least one memory, the at least one memory comprising computer program code, wherein the processor together with the at least one memory and the computer program code is configured to cause the apparatus to execute: Establishing low layer mobility and configuration of data forwarding in low layer mobility, and Provide the configuration to lower level entities.

26. An apparatus of a high-layer user plane entity in a radio access network of a mobile communication system, the apparatus comprising at least one processor and at least one memory, the at least one memory comprising computer program code, wherein the processor together with the at least one memory and the computer program code is configured to cause the apparatus to execute: Obtaining notification information of the initiation of data forwarding in lower layer mobility by lower layer entities, and Data forwarding is performed according to the notification information.

27. A computer program product comprising computer program code, which, when executed on a computer, is configured to cause the computer to perform the method according to any one of claims 1 to 12, 13 to 20 or 21 to 23.

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