Switching

Abstract

The invention relates to switching. An apparatus (DU) comprises: means for receiving an identification of a serving network access node; and means for associating a subset of contention-free random access (CFRA) resources with the identified serving network access node. An apparatus (CU) comprises: means for sending a first message comprising an identification of a serving network access node (sDU) to enable an association of a contention-free random access (CFRA) resource subset with the identified serving network access node (sDU); and means for, in a reply, receiving a second message specifying an association of the subset of contention-free random access (CFRA) resources with the identified serving network access node (sDU).

Description

Technical Field

[0001] Examples of the present disclosure relate to contention-free random access. Some examples relate to using contention-free random access to switch between cells controlled by different distributed units. Background Art

[0002] Handover transfers an ongoing communication session of a user equipment (UE) from one cell to another cell in a connected state. Handover is used to provide continuity of service to a user, especially when the user is mobile.

[0003] Historically, cell level mobility has been configured at Layer 3 (e.g., Radio Resource Control, RRC). The network controls UE mobility based on UE measurement reports. The trigger for completing the handover can be the network, or the user equipment in the case of conditional handover. The user equipment performs a conditional handover only if the execution conditions configured by the network are met. The handover decision is made based on Layer 3 measurements.

[0004] Dual Active Protocol Stack (DAPS) handover allows the user equipment to initiate a handover to a target cell while maintaining a connection with the source cell by activating two protocol stacks, one for the source cell and the other for the target cell.

[0005] Low Layer Triggered Mobility (LTM) enables handover via L1 / L2 signaling while preserving the configuration of the upper layers and / or minimizing configuration changes of the lower layers. The network triggers LTM cell handover by sending a MAC Control Element (CE) to the UE.

[0006] In contention-free random access (CFRA), dedicated CFRA resources are configured per UE and are unique, i.e. other UEs cannot use the resource. This has the advantage that when a preamble is sent on PRACH based on dedicated CFRA resources, no collision is possible. The need to configure CFRA resources uniquely per UE (i.e. multiple UEs cannot share resources) can lead to resource scarcity, especially in dense urban deployments. Summary of the invention

[0007] Examples are provided as claimed in the following claims according to various, but not necessarily all, examples.

[0008] Although the above examples and optional features of the present disclosure are described separately, it will be understood that their provision in all possible combinations and arrangements is included in the present disclosure. It will be understood that various examples of the present disclosure may include any or all of the features described for other examples of the present disclosure, and vice versa. In addition, it will be understood that any one or more or all of the features (in any combination) can be implemented / included in / executable by devices, methods and / or computer program instructions as needed and appropriately. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Some examples will now be described with reference to the accompanying drawings, in which:

[0010] Figures 1 to 13 An example of the subject matter described herein is shown.

[0011] The drawings are not necessarily to scale. Certain features and views of the drawings may be shown schematically or exaggerated in scale for the sake of clarity and conciseness. For example, the dimensions of some elements in the drawings may be exaggerated relative to other elements to aid in illustration. Similar reference numerals are used in the drawings to indicate similar features. For the sake of clarity, not all reference numerals may be shown in all drawings.

[0012] In the following description, reference numbers without subscripts (e.g., 10) may be used to refer to a class (or collection), reference numbers with numeric-type subscripts (e.g., 10_1) may be used to refer to a specific instance of a class (a member of a collection), and reference numbers with variable-type subscripts (e.g., 10_i) may be used to refer to a non-specific instance of a class (a member of a collection). DETAILED DESCRIPTION

[0013] The following relates to a device, comprising:

[0014] Component 305 for receiving an identification 304 of a serving network access node; and

[0015] A component 306 for associating a subset 604 of contention-free random access (CFRA) resources 602 with the identified serving network access node. In some but not necessarily all examples, the device is a network access node, such as a network node that is not serving a user equipment (UE) served by the serving network access node. In some but not necessarily all examples, the device is a distributed unit, such as a target distributed unit (tDU) 204_2, which is the target of the UE handover from the serving network access node to the target distributed unit. The serving network access node can be a distributed unit.

[0016] The following relates to a device, comprising:

[0017] Component 303 for sending a first message 302 comprising an identification 304 of a serving network access node to enable association of a subset 604 of contention-free random access (CFRA) resources 602 with the identified serving network access node; and

[0018] Component 307 for receiving, in reply, a second message 321 specifying an association of a subset 604 of contention-free random access (CFRA) resources 602 with the identified serving network access node. In some but not necessarily all examples, the apparatus is a central unit (CU). For example, a central unit controlling a serving network access node (sDU) as a distributed unit and / or controlling a target distributed unit (tDU) (which is the target of a UE handover from a serving network access node (sDU) to a target distributed unit (tDU)).

[0019] The terms "target" and "candidate" as applied to a distributed unit or network access node are interchangeable.

[0020] Figure 1 An example of a network 100 is shown that includes multiple network nodes, including terminal nodes 110, access nodes 120, and one or more core nodes 129. Terminal nodes 110 and access nodes 120 communicate with each other. One or more core nodes 129 communicate with access nodes 120.

[0021] In this example, the network 100 is a radio telecommunication network in which at least some of the terminal nodes 110 and the access nodes 120 communicate with each other using transmission / reception of radio waves.

[0022] In some examples, one or more core nodes 129 can communicate with each other. In some examples, one or more access nodes 120 can communicate with each other.

[0023] The network 100 may be a cellular network comprising a plurality of cells 122, each cell 122 being served by an access node 120. The interface between the terminal node 110 and the access nodes 120 defining the cells 122 is a wireless interface 124 in this example.

[0024] The access node 120 is a cellular radio transceiver. The terminal node 110 is a cellular radio transceiver.

[0025] In the example shown, the cellular network 100 is a 3rd Generation Partnership Project (3GPP) network, where the terminal nodes 110 are user equipments (UEs) and the access nodes 120 are base stations.

[0026] In the example shown, the network 100 is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN includes E-UTRAN NodeBs (eNBs) 120, which provide E-UTRA user plane and control plane (RRC) protocol terminations towards the UE 110. The eNBs 120 are interconnected to each other by means of an X2 interface 126. The eNBs are also connected to a Mobility Management Entity (MME) 129 by means of an S1 interface 128.

[0027] In another example, the network 100 is a Next Generation (or New Radio NR) Radio Access Network (NG-RAN). The NG-RAN includes gNodeBs (gNBs) 120, which provide user plane and control plane (RRC) protocol terminations towards the UE 110. The gNBs 120 are interconnected to each other by means of an X2 / Xn interface 126. The gNBs are also connected to an Access and Mobility Management Function (AMF) by means of an N2 interface 128.

[0028] User equipment includes mobile devices. When referring to user equipment, whenever possible, the reference includes and encompasses reference to mobile devices.

[0029] Figure 2 A network according to current 3GPP specifications is shown. The network is hierarchical. It comprises a core 129 and a radio access node 120. The core 129 is connected to the radio access node 120 via an interface 128 (NG interface). The radio access node 120 is connected to a user equipment via an air interface 124 (Uu). The radio access node 120 is connected to other radio access nodes 120 via an interface 126 (Xn interface).

[0030] In this example, one or more radio access nodes 120 are logically divided into a central unit (CU) 202 and one or more distributed units (DU) 204. The DU 204 uses one or more transmit receive points (TRP) 126.

[0031] The CU 202 controls the operation of one or more DUs 204. The CU 202 terminates the F1 interface connected with the DUs 204. The CU 202 hosts higher layer protocols, such as at least a Radio Resource Control (RRC) protocol layer and a Packet Data Convergence Protocol (PDCP) protocol layer.

[0032] The DU 204 is partially controlled by the CU 202. One DU 204 supports one or more radio transmission points 126. One TRP 126 is supported by only one DU 204. The DU 204 terminates the F1 interface connected to the CU 202. The DU 204 hosts the lower layer protocols, such as the radio link control (RLC) protocol layer, the media access control (MAC) protocol layer, and the physical (PHY) protocol layer. The DU 204 can communicate with the RRC layer hosted by the CU 302 via a dedicated interface (e.g., the F1 interface).

[0033] The interface 127 supports information exchange between the CUs 202 of two different radio access nodes 120. The interface 127 enables interconnection of radio access nodes 120 provided by different manufacturers. In at least some examples, data exchange through the interface 127 is between two radio access nodes 120 belonging to the same operator or between operators with an agreement.

[0034] Figure 3 An example of an apparatus 204 is shown, the apparatus 204 comprising:

[0035] Component 305 for receiving an identification 304 of a serving network access node; and

[0036] Component 306 for associating a subset of contention-free random access (CFRA) resources with the identified serving network access node.

[0037] refer to Figure 4 In some but not necessarily all examples, the apparatus 204 is a network access node, such as a network node that is not currently serving a user equipment (UE) served by a serving network access node. In some but not necessarily all examples, the apparatus 204 is a distributed unit (DU), such as a target distributed unit (tDU), which is a target for a UE to be handed over from a serving network access node to a target distributed unit (tDU). The serving network access node may be a distributed unit (sDU).

[0038] Figure 3 Also shown is an example of an apparatus 202 comprising:

[0039] A component 303 for sending a first message 302, the first message comprising an identification 304 of a serving network access node, so as to associate a subset of contention-free random access (CFRA) resources with the identified serving network access node; and

[0040] Means 307 for receiving, in reply, a second message 321 specifying an association of a subset of contention free random access (CFRA) resources with the identified serving network access node.

[0041] refer to Figure 4 In some but not necessarily all examples, the device 202 is a central unit (CU). For example, a central unit that controls a serving network access node (sDU) as a distributed unit and / or controls a target distributed unit (tDU) (which is the target of a UE handover from a serving network access node (sDU) to a target distributed unit (tDU)).

[0042] The CFRA resources may, for example, include a random access preamble that the UE uses to perform random access to a target network access node that does not serve the user equipment. The CFRA resources may, for example, be constrained in time. The CFRA resources may, for example, include a random access preamble at one or more occasions for performing random access to the target network access node. Additionally or alternatively, the CFRA resources may, for example, be constrained in space. The CFRA resources may, for example, include a random access preamble for a specific beam (e.g., a receive beam at the target network access node).

[0043] In some examples, the CFRA resource is a random access preamble at a specific random access channel (RACH) opportunity for a specific beam. The CFRA resource can be determined, for example, by a combination of a preamble index, a physical random access channel (PRACH) mask index indicating a RACH opportunity, and / or a synchronization signal (SS) / physical broadcast channel (PBCH) index.

[0044] Figure 4 An example of a distributed unit 204_2 operating as a target distributed unit (tDU) is shown. A target distributed unit (tDU) is a target of a handover of a user equipment.

[0045] The distributed unit 204_2 operates as a serving distributed unit (sDU) of the user equipment 110 and is serving the user equipment (UE) 110. The UE 110 is connected to a cell controlled by the serving distributed unit (sDU) 204_1.

[0046] Distributed unit 204_2 does not operate as a serving distributed unit (sDU) for UE 110 and is not serving user equipment (UE) 110. UE 110 is not connected to a cell controlled by serving distributed unit (sDU) 204_1.

[0047] UE 110 may change serving cells. For example, UE 110 may change from being connected to a cell controlled by distributed unit 204_1 to being connected to a cell controlled by distributed unit 204_2. This may be referred to as a handover between distributed units 204_1, 204_2. The serving distributed unit (sDU) for UE 110 changes from DU 204_1 to DU 204_2.

[0048] To connect to a cell controlled by distributed unit 204_1 (through handover or otherwise), UE 110 performs a random access to the target allocation unit (tDU), which in this case is distributed unit 204_1. Such a random access requires the use of CFRA resources if it is to be contention-free.

[0049] The distribution unit (DU) may, for example, comprise components for enabling it to operate as a target distribution unit (tDU) for one UE and as a serving distribution unit for another UE.

[0050] The allocation unit 204 may, for example, include components for enabling it to operate as a target allocation unit (tDU). Figure 4 The target allocation unit (tDU) in FIG. 1 is used to operate and includes:

[0051] Component 305 for receiving an identification 304 of the serving network access node 204_1; and

[0052] Component 306 for associating a subset of contention-free random access (CFRA) resources with the identified serving network access node 204_1.

[0053] The serving network access node 204_1 is a service distribution unit (sDU).

[0054] In this example, the means for receiving an identification of a serving network access node 305 is configured to receive an identification of the serving network access node 204_1 from a central unit (CU) 202 of the radio access network.

[0055] The central unit (CU) 202 includes:

[0056] A component 303 for sending a first message 302, the first message comprising an identification 304 of a serving network access node, so as to associate a subset of contention-free random access (CFRA) resources with the identified serving network access node 204_1; and

[0057] Means 307 for receiving, in reply, a second message 321 specifying an association of a subset of contention-free random access (CFRA) resources with the identified serving network access node 204_1.

[0058] In this example, the means 303 for sending a first message and the means 307 for receiving a second message in response are configured to communicate with the target network access node (tDU) 204_2.

[0059] CU 202 sends the identification of serving DU 204_1 (sDU) of UE 110 to target DU 204_2 (tDU) of UE 110 to enable selection of a CFRA resource subset at target DU 204_2 based on the received identification 304 of serving DU 204_1. The selection associates the selected contention-free random access (CFRA) resource subset with the identified serving network access node (serving DU 204_1).

[0060] The CFRA resource subset may be, for example, DU-specific and specific to the identified serving DU 204_1 (sDU).

[0061] A subset of contention-free random access (CFRA) resources for a serving network access node (sDU) is contention-free with respect to other different network access nodes (DUs).

[0062] The first message 302 is configured to prepare the non-serving network access node 204_2 (tDU) to become the serving network access node (sDU) of the UE 110 via a contention-free random access (CFRA) connection using a contention-free random access (CFRA) resource selected from a subset of contention-free random access (CFRA) resources associated with the UE's serving access node.

[0063] It will be understood that the means for sending the first message 302 and the means for receiving the second message 321 in response are configured to communicate with the target network access node (tDU) to enable the target network access node (tDU) to become the serving network access node of UE 110 via a contention free random access (CFRA) connection using contention free random access (CFRA) resources selected from a subset of contention free random access (CFRA) resources associated with the serving access node of UE 110.

[0064] A subset of contention-free random access (CFRA) resources is reserved for connection of any UE currently served by the identified serving access node (sDU) to the target network access node 204_2 (tDU) as the serving network access node.

[0065] Association of a subset of contention-free random access CFRA resources for connecting a UE served by a different serving access node to a target network access node as a serving network access node with the different serving network access node is prevented.

[0066] One way to maintain contention-free random access is to identify a subset of contention-free random access (CFRA) resources only to the identified serving network access node (sDU) and not to other network access nodes.

[0067] refer to Figure 4 , the UE 110 communicates 311 with its serving DU 204_1 (sDU). The UE 110 may, for example, send a measurement report to the serving DU 204_1 (sDU), and the serving DU 204_1 sends a trigger 313 to the CU 202. The CU 202 sends 321 a CFRA resource subset 604 to the source DU 204_1. The source DU 204_1 (sDU) selects a CFRA resource from the received CFRA resource subset 604. The source DU 204_1 (sDU) identifies 300 the selected CFRA resource 602 to the UE 110. The UE 110 performs random access 910 on a connection to the target DU 204_2 (tDU) using the received selected CFRA resource 602 to enable a handover of the UE 110 from the serving DU 204_1 (sDU) to the target DU 204_2 (tDU).

[0068] The CFRA resource subset 604 sent to the source DU 204_1 (sDU) is specific to that DU. It is obtained by:

[0069] The central unit (CU) 202 sends a first message 302 including an identification 304 of the serving DU 204_1 (sDU) of the UE 110 to the target DU 204_2 (tDU).

[0070] The target DU 204_2 (tDU) uses the received identification 304 of the serving DU 204_1 (sDU) to associate a contention-free random access (CFRA) resource subset 604 with the identified serving DU (sDU) 204_1.

[0071] In reply to the first message 302 , the target DU 204_2 (tDU) sends a second message 321 to the CU 202 specifying an association of a contention free random access (CFRA) resource subset 604 with the identified serving DU 204_1 (sDU).

[0072] Thus, in reply to sending the first message 302, the CU 202 obtains a second message 321 specifying an association of a contention free random access (CFRA) resource subset 604 with the identified serving DU 204_1 (sDU).

[0073] Different CFRA resource subsets for random access target DU (tDU) may be associated with different corresponding service DUs. Figure 5 , the first UE 110_1 (UE1) is served by the service DU 204-1 (sDU1) and uses the CFRA resources from the first CFRA resource subset 604_1 to randomly access the target DU 204_2 (tDU), while the second UE 110_3 (UE2) is served by the service DU 204-3 (sDU2) and uses the CFRA resources from the second CFRA resource subset 604_2 to randomly access the target DU 204_2 (tDU).

[0074] refer to Figure 5 , 6 7A, the first UE 110_1 (UE1) communicates 311_1 with its serving DU 204_1 (sDU1). The UE 110_1 may, for example, send a measurement report to the serving DU 204_1 (sDU1), and the serving DU 204_1 sends a trigger 313_1 to the CU 202.

[0075] The central unit (CU) 202 sends a first message 302_1 including an identification 304 of the serving DU 204_1 (sDU1) of the UE 110_1 to the target DU 204_2 (tDU).

[0076] The target DU 204_2 (tDU) uses the received identification of the serving DU 204_1 (sDU) to associate a first contention-free random access (CFRA) resource subset 604_1 with the identified serving DU 204_1 (sDU).

[0077] The target DU 204_2 (tDU) selects a first subset of contention-free random access (CFRA) resources 604_1 ( Figure 6 ).

[0078] In reply to the first message 302_1 , the target DU 204_2 (tDU) sends a second message 321_1 to the CU 202 specifying an association of a first contention-free random access (CFRA) resource 602 subset 604_1 with the identified serving DU 204_1 (sDU).

[0079] Therefore, in reply to sending the first message 302_1 to the target DU 204_2 (tDU), the CU 202 obtains the first CFRA resource 602 subset 604_1 specific to the serving DU 204_1 (sDU) of the UE 110_1 from the target DU 204_2 (tDU).

[0080] The CU 202 sends a first subset 604_1 of CFRA resources 602 to the source DU 204_1 (sDU1).

[0081] The source DU 204_1 (sDU1) selects a CFRA resource 602 ( Fig. 7A ).

[0082] The source DU 204_1 (sDU1) identifies 330 the selected CFRA resource 602 to the UE 110_1.

[0083] The UE 110_1 makes a random access connection 910_1 to the target DU 204_2 (tDU) using the received selected CFRA resource 602 to implement the handover of the UE 110_1 from the serving DU 204_1 (sDU1) to the target DU 204_2 (tDU).

[0084] refer to Figure 5 , 6 7B, the second UE 110_3 (UE2) communicates 311_3 with its serving DU 204_3 (sDU2). The UE 110_3 may, for example, send a measurement report to the serving DU 204_3 (sDU2), and the serving DU 204_3 sends a trigger 313_3 to the CU 202.

[0085] The central unit (CU) 202 sends a first message 302_3 including an identification 304 of the serving DU 204_3 (sDU2) of the UE 110_3 to the target DU 204_2 (tDU).

[0086] The target DU 204_2 (tDU) uses the received identification of the serving DU 204_3 (sDU2) to associate the second contention-free random access (CFRA) resource subset 604_2 with the identified serving DU 204_3 (sDU2).

[0087] The target DU 204_2 (tDU) selects a second subset of contention-free random access (CFRA) resources 604_2 ( Figure 6 ).

[0088] In reply to the first message 302_3, the target DU 204_2 (tDU) sends a second message 321_3 to the CU 202 specifying an association of a second contention-free random access (CFRA) resource 602 subset 604_2 with the identified serving DU 204_3 (sDU2).

[0089] Therefore, in reply to sending the first message 302_3 to the target DU 204_2 (tDU), the CU 202 obtains the second CFRA resource 602 subset 604_2 specific to the serving DU 204_3 (sDU2) of the UE 110_3 from the target DU 204_2 (tDU).

[0090] CU 202 sends a second subset 604_2 of CFRA resources 602 to source DU 204_3 (sDU2). Source DU 204_3 (sDU2) selects CFRA resources 602 ( Figure 7B The source DU 204_3 (sDU2) identifies 330 the selected CFRA resource 602 to the UE 110_3. The UE 110_3 uses the received selected CFRA resource 602 to make a random access connection 910_3 to the target DU 204_2 (tDU) to implement the handover of the UE 110_3 from the serving DU 204_3 (sDU2) to the target DU 204_2 (tDU).

[0091] The first subset 604_1 for serving DU 204_1 ( sDU1 ) and the second subset 604_2 for serving DU 204_3 ( sDU2 ) are different subsets that include or contain different CFRA resources 602 .

[0092] The first subset 604_1 for serving DU 204_1 (sDU1) and the second subset 604_2 for serving DU 204_3 (sDU2) may be, for example, non-overlapping subsets, where a CFRA resource 602 that is a member of the first subset 604_1 is not a member of the second subset 604_2.

[0093] The first subset 604_1 for serving DU 204_1 (sDU1) and the second subset 604_2 for serving DU 204_3 (sDU2) may be, for example, orthogonal subsets. If the transmissions on the two resources do not interfere with each other, the two resources are orthogonal. For example, different timings or different frequency domain resources or different spatial resources (e.g., beams) or different sequences that satisfy orthogonality.

[0094] In the example shown, the first message 302_1 includes an identification of the DU 204_1 (sDU1) that enables association of the first subset 604_1 of contention-free random access (CFRA) resources 602 with the identified DU 204_1, and the separate first message 302_2 includes an identification of the DU 204_3 (sDU2) that enables association of the second subset 604_2 of contention-free random access (CFRA) resources 602 with the identified DU 204_3. However, in other examples, the single first message 302 may include: an identification of the DU 204_1 (sDU1) that enables association of the first subset 604_1 of contention-free random access (CFRA) resources 602 with the identified DU 204_1; and an identification of the DU 204_3 (sDU2) that enables association of the second subset 604_2 of contention-free random access (CFRA) resources 602 with the identified DU 204_3.

[0095] In the example shown, the target DU 204_2 (tDU) sends a second message 321_1 specifying an association of a first subset 604_1 of contention-free random access (CFRA) resources 602 with an identified serving DU 204_1 (sDU1) to the CU 202, and separately sends a second message 321_3 specifying an association of a second subset 604_2 of contention-free random access (CFRA) resources 602 with an identified serving DU 204_3 (sDU2) to the CU 202. However, in other examples, the target DU 204_2 (tDU) sends a second message 321 specifying an association of a first subset 604_1 of contention-free random access (CFRA) resources 602 with an identified serving DU 204_1 (sDU1) and specifying an association of a second subset 604_2 of contention-free random access (CFRA) resources 602 with an identified serving DU 204_3 (sDU2) to the CU 202.

[0096] In the example shown, the CU 202 identifies the subsets 604_1 , 604_2 of CFRA resources 602 to the respective serving network access nodes (sDu1 , sDU2) based on the replies 321_1 , 321_3 to the transmitted identifications of the serving network access nodes (sDu1 , sDU2).

[0097] The first contention-free random access (CFRA) resource 602 subset 604_1 is used to connect the UE 110_1 served by the DU 204_1 (sDU1) to the target DU 204_2 (tDU) which is a serving network access node.

[0098] The second contention-free random access (CFRA) resource 602 subset 604_2 is used to connect the UE 110_2 served by the DU 204_3 (sDU2) to the target DU 204_2 (tDU) which is the serving network access node.

[0099] The first contention-free random access (CFRA) resource 602 subset 604_1 is not used to connect the UE 110_2 served by the DU 204_3 (sDU2) to the target DU 204_2 (tDU) which is the serving network access node.

[0100] The second contention-free random access (CFRA) resource 602 subset 604_2 is not used to connect the UE 110_1 served by the DU 204_1 (sDU1) to the target DU 204_2 (tDU) which is a serving network access node.

[0101] The target DU 204_2 (tDU) includes components for allocating subsets 604_1, 604_2 of CFRA resources 602 to corresponding serving network access nodes (sDU1, sDU2). Such allocation by the target DU 204_2 (tDU) associates the subsets 604 of CFRA resources 602 with corresponding serving network access points (DUs) based on the received identification of the serving network access node (DU). The first subset 604_1 of CFRA resources 602 is associated with DU 204_1 (sDU1). The second subset 604_2 of CFRA resources 602 is associated with DU 204_3 (sDU2).

[0102] The target DU 204_2 (tDU) includes means for storing a subset 604 of CFRA resources 602 associated with a corresponding serving network access node (sDU).

[0103] The target DU 204_2 (tDU) comprises means for informing the network (CU 202) of the allocation of the CFRA resource 602 subsets 604_1, 604_2 to the respective serving network access nodes (sDU1, sDU2).

[0104] The target DU 204_2 (tDU) includes a component for implementing contention-free random access by reserving a first subset 604_1 of contention-free random access (CFRA) resources 602 for association with only DU 204_1 (sDU1) and not with other DUs, and reserving a second subset 604_2 of contention-free random access (CFRA) resources 602 for association with only DU 204_3 (sDu2) and not with other DUs.

[0105] The reservation may be temporary. In this example, the target DU 204_2 (tDU) includes a component for temporarily reserving a first non-contention random access (CFRA) resource 602 subset 604_1 for connecting any UE currently served by the identified service access node 204_1 (sDU1) to the target DU 204_2 (tDU) as a serving network access node. The association of the first non-contention random access (CFRA) resource 602 subset 604_1 with a different serving network access node (sDU2 or other node) is blocked. The target DU 204_2 (tDU) also includes a component for temporarily reserving a second non-contention random access (CFRA) resource 602 subset 604_2 for connecting any UE currently served by the identified service access node 204_3 (sDU2) to the target DU 204_2 (tDU) as a serving network access node. Association of the second contention-free random access (CFRA) resource 602 subset 604_2 with a different serving network access node (sDU1 or other node) is blocked.

[0106] Figure 8 An example of a message 302 for providing an identification 304 of a serving network access node is shown.

[0107] Message 302 is a standardized message including standardized information elements 802 .

[0108] The message 302 is processed by the target DU 204_2 to obtain the identification 304 of the serving network access node (eg, sDU1 or sDU2) from the standardized information element 802_1.

[0109] In at least some examples, the message is a UE CONTEXT SETUP REQUEST message.

[0110] In at least some examples, the message is received by the target DU 204_2 (tDU) from the CU 202 via the F1 interface.

[0111] Although the previous examples used a split architecture utilizing a central unit CU 202 and distributed units 204, other examples may use other architectures.

[0112] Although the previous examples use a split architecture utilizing a central unit CU 202 and distributed units 204 (where there is no direct DU to DU communication), other examples may use other architectures (where there is direct DU to DU communication). The identity of the serving DU may then be provided directly to the target DU (without going through the CU). The CFRA resource subset may then be provided directly by the target DU to the serving DU (without going through the CU).

[0113] Although the following examples use contention-free random access as part of a low layer triggered mobility (LTM) handover (HO), CFRA resources may be used for any random access procedure.

[0114] Low Layer Triggered Mobility (LTM) is a low layer procedure (ie, below Layer 3) and is performed by the DU 204 .

[0115] The user equipment 110 may for example implement low latency triggered mobility (LTM) which implements serving cell change (handover) via low latency signaling (eg below layer 3). Once the handover is triggered, the handover delay may for example be less than 10 ms (milliseconds).

[0116] LTM is a process in which a network node (e.g., DU 202) receives measurement reports from UE 110, and based on these measurement reports, the network node controls the change of the serving cell of the UE through a MAC CE. The network node prepares one or more candidate cells and provides the cell change configuration of the prepared candidate cells to the UE. Then, by selecting one of the cell change configurations as the target configuration of the LTM, the LTM cell switch is triggered. The trigger for the selection can be at the network node (normal switch) or at the user equipment (conditional switch). The cell change configuration can, for example, define information used to connect to a new cell in the random access procedure 910. The cell change configuration can be provided as an incremental configuration (i.e., a change relative to a reference configuration) or as a complete explicit cell change configuration.

[0117] The distributed unit 204_2 (tDU) is configured to perform a low layer triggered mobility (LTM) handover (HO) of the user equipment 110_1 (UE1) served by the serving DU 204_1 (sDU1) to the distributed unit 204_2 (tDU) using a random access procedure 910_1 based on a contention free random access (CFRA) resource from a first subset 604_1 of contention free random access (CFRA) resources 602 associated with the serving DU 204_1 (sDU1).

[0118] The distributed unit 204_2 (tDU) is configured to perform a low layer triggered mobility (LTM) handover (HO) of the user equipment 110_2 (UE2) served by the serving DU 204_3 (sDU2) to the distributed unit 204_2 (tDU) based on a contention free random access (CFRA) resource using a random access procedure 910_3 from a second contention free random access (CFRA) resource 602 subset 604_2 associated with the serving DU 204_3 (sDU2).

[0119] exist Fig. 9AIn FIG. 9 , a random access 910 using a CFRA resource 602 selected from a subset of CFRA resources is during a preparation phase 902 of the LTM 900, which precedes an execution phase 906. The execution phase is triggered 904. This is an early synchronization for early timing advance acquisition.

[0120] exist Fig. 9B In FIG. 9 , random access 910 using CFRA resources 602 selected from the subset of CFRA resources is during an execution phase 906 of the LTM 900, which is subsequent to the preparation phase 902 of the LTM 900. The execution phase is triggered 904.

[0121] Fig. 10A An example of method 500 is shown. Method 500 may be performed, for example, by distributed unit 204 (DU) operating as a target distributed unit (tDU).

[0122] The method 500 includes, at block 502, receiving an identification of a serving network access node (sDU).

[0123] The method 500 includes, at block 504, associating a subset 604 of contention free random access (CFRA) resources 602 with an identified serving network access node (sDU).

[0124] Fig. 10B An example of a method 510 is shown. The method 510 may be performed, for example, by a central unit 202 (CU) in communication with a target distributed unit (tDU).

[0125] The method 510 includes, at block 512, sending a first message including an identification of a serving network access node (sDU) to associate a subset 604 of contention-free random access (CFRA) resources 602 with the identified serving network access node (sDU).

[0126] The method 510 includes, at block 514, receiving in reply a second message specifying an association of a subset 604 of contention free random access (CFRA) resources 602 with the identified serving network access node (sDU).

[0127] Fig.11 An example of a controller 400 suitable for use with devices such as network devices 202, 204 is shown. Controller 400 may be implemented as a controller circuit. Controller 400 may be implemented solely in hardware, with certain aspects in software (including only firmware), or may be a combination of hardware and software (including firmware).

[0128] like Fig.11As shown in , the controller 400 can be implemented using instructions that implement the hardware functions, such as by using executable instructions of a computer program 406 in a general or special purpose processor 402, which can be stored on a computer-readable storage medium (disk, memory, etc.) for execution by such processor 402.

[0129] The processor 402 is configured to read from and write to the memory 404. The processor 402 may also include an output interface via which the processor 402 outputs data and / or commands, and an input interface via which data and / or commands are input to the processor 402.

[0130] The memory 404 stores a computer program 406 including computer program instructions (computer program code) that, when loaded into the processor 402, controls the operation of the apparatus 202, 204. The computer program instructions of the computer program 406 provide logic and routines that enable the apparatus to perform the methods shown in the figures. The processor 402 can load and execute the computer program 406 by reading the memory 404.

[0131] The device 202 comprises:

[0132] at least one processor 402; and

[0133] at least one memory 404 including computer program code,

[0134] The at least one memory stores instructions that, when executed by the at least one processor 402, cause the apparatus 202 to at least:

[0135] Sending a first message, the first message including an identification of a serving network access node (sDU) to associate a contention-free random access (CFRA) resource subset with the identified serving network access node (sDU); and

[0136] In reply, a second message is received specifying an association of a subset of contention free random access (CFRA) resources with the identified serving network access node (sDU).

[0137] The device 204 comprises:

[0138] at least one processor 402; and

[0139] at least one memory 404 including computer program code,

[0140] The at least one memory stores instructions that, when executed by the at least one processor 402, cause the apparatus 204 to at least:

[0141] receiving an identification of a serving network access node; and

[0142] A subset of contention free random access (CFRA) resources is associated with the identified serving network access node.

[0143] like Fig.12 As shown in , the computer program 406 may arrive at the apparatus 202, 204 via any suitable delivery mechanism 408. The delivery mechanism 408 may be, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a storage device, a recording medium (e.g., a compact disk read-only memory (CD-ROM) or a digital versatile disk (DVD) or a solid-state memory), an article of manufacture including or tangibly embodying the computer program 406. The delivery mechanism may be a signal configured to reliably transmit the computer program 406. The apparatus 202, 204 may propagate or send the computer program 406 as a computer data signal.

[0144] Computer program instructions for causing the apparatus 202 to perform at least the following items or for performing at least the following items:

[0145] A first message is sent, the first message including an identification of a serving network access node (SDU) to enable an association of a subset of contention-free random access (CFRA) resources with the identified serving network access node (SDU), so as to receive in reply a second message specifying an association of a subset of contention-free random access (CFRA) resources with the identified serving network access node (SDU).

[0146] Computer program instructions for causing the device 204 to perform at least the following items or for performing at least the following items:

[0147] obtaining an identification of the serving network access node from the received message; and

[0148] A subset of contention-free random access (CFRA) resources is associated with the obtained identity of the serving network access node.

[0149] The computer program instructions may be included in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over multiple computer programs.

[0150] Although memory 404 is shown as a single component / circuit, it may be implemented as one or more separate components / circuits, some or all of which may be integrated / removable, and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0151] Although processor 402 is shown as a single component / circuit, it may be implemented as one or more separate components / circuit, some or all of which may be integrated / removable.Processor 402 may be a single-core or multi-core processor.

[0152] Fig.13 is using early synchronization LTM ( Fig. 9A )of Figure 5 examples, and similar references are used for similar features.

[0153] UE1 110_1 is served by a cell under source DU1 204_1. UE2 110_3 is served by a cell under source DU2 204_3. The target cell is under target DU 204_2 (tDU).

[0154] The target DU and the source DU can be the same entity (i.e., both the serving cell and the target cell can be under the same DU). The target DU and the source DU can be different entities (i.e., the serving cell and the target cell can be under different DUs). In the latter inter-DU scenario, the target DU and the source DU can be under the control of the same CU, or the target DU and the source DU can be under the control of different CUs.

[0155] The LTM process 900 shown has a preparation phase 902 and an execution phase 906. The execution phase is caused by a trigger 904.

[0156] Random access 910 using a CFRA resource 602 selected from a subset of CFRA resources occurs during the preparation phase 902 of the LTM 900, which precedes the execution phase 904. This is early synchronization for early timing advance acquisition.

[0157] UE1 110_1 sends L3 measurement report messages 311_1, 313_1 to CU 202 via source DU 204_1 (sDU1) (sDU1 204_1 sends UL RRC message transmission message 313_1 including L3 measurement report to CU 202). CU 202 decides to use LTM and initiates LTM candidate cell preparation 702_1.

[0158] CU 202 sends UE context establishment request 302_1 to target DU 204_2 (tDU) to prepare the target cell. Message 302_1 includes the identification of serving DU 204_1 (sDU1) to associate a subset 604 of contention-free random access (CFRA) resources 602 with the identified serving DU 204_1 (sDU1).

[0159] The target DU 204_2 (tDU) receives a message 302_1 including an identification of the serving DU 204_1 (sDU1). In this example, the message 302_1 is a UE context establishment request 302_1 including a gNB-DU ID of the serving cell (e.g., the ID of the source DU 204_1 (sDU1)).

[0160] The target DU 204_2 (tDU) associates 306_1 a first contention-free random access (CFRA) resource 602 subset 604_1 with the identified serving DU 204_1 (sDU1). The target DU 204_2 (tDU) may generate 306_1 a CFRA resource subset 604_1, for example, for sDU1, and the first CFRA resource 602 subset 604_1 is allocated to the source sDU1 204_1.

[0161] The target DU 204_2 (tDU) then sends a message 321_1 specifying an association of a first contention free random access (CFRA) resource 602 subset 604_1 with the identified serving DU 204_1 (sDU1). In this example, the message 321_1 is a UE context setup response message 321_1 including the first CFRA resource 602 subset 604_1.

[0162] The CU 202 receives a message 321_1 specifying an association of a first contention-free random access (CFRA) resource 602 subset 604_1 with the identified serving DU 204_1 (sDU1).

[0163] CU 202 prepares 704 the RRC configuration and provides 323_1, 330_1 the RRC configuration to UE 110_1 (UE1) via source DU 204_1 (sDU1). In this example, the message 323_1 from CU 202 to sDU1 204_1 is a DL RRC message transmission message 323_1 including the first CFRA resource 602 subset 604_1. The message 330_1 from sDU1 204_1 to UE1 110_1 is an RRC reconfiguration message 330_1 including the first CFRA resource 602 subset 604_1.

[0164] UE 110_1 (UE1) stores the configuration of the LTM candidate target cell and sends RRC reconfiguration complete messages 706_1, 708_1 to CU 202 via source DU 204_1 (sDU1). Message 706_1 from UE1 110_1 to sDU1 204_1 is an RRC reconfiguration complete message. Message 708_1 from sDU1 204_1 to CU 202 is an UL RRC message transmission message 708_1.

[0165] Prior to receiving the LTM cell handover command 724_1, UE 110_1 (UE1) may perform DL early synchronization and early TA acquisition with the candidate target cell.

[0166] The early timing advance (TA) acquisition steps are:

[0167] Once the source DU 204_1 (sDU1) decides to trigger PRACH signal transmission from the UE1 110_1 to the target DU 204_2 (tDU), the source DU 204_1 (sDU1) selects 712_1 a CFRA resource 602 from the first subset 604_1 of CFRA resources 602 .

[0168] Then, the source DU 204_1 (sDU1) sends a PDCCH order 714_1 to the UE1 110_1. The PDCCH order 714_1 contains relevant configuration information (eg, preamble ID, SS / PBCH index, RACH timing, etc.), including the selected UE-specific CFRA resource 602.

[0169] The source DU 204_1 (sDU1) marks the UE-specific CFRA resources 602 as “reserved” until the UE 110_1 (UE1) completes random access using the UE-specific CFRA resources 602 or there is a release of the UE-specific CFRA resources.

[0170] Based on the received information, the UE 110_1 (UE1) triggers a random access procedure 910_1 to the target DU 204_2 (tDU), ie, a preamble transmission 716_1 through a PRACH (ie, physical random access channel) of the target DU 204_2 (tDU).

[0171] After acquiring the timing advance (TA) associated with the UE 110_1 (UE1), the target DU 204_2 (tDU) provides 718_1, 720_1 the TA value for LTM switching of the target cell and other relevant information (e.g., preamble ID, SS / PBCH index, RACH timing, etc.) to the source DU 204_1 (sDU1) via the CU 202. Now, the source DU 204_1 (sDU1) can associate the received TA value with the specific UE 110_1 (UE1).

[0172] In this example, the message 720_1 is a UE context modification request 720_1 indicating the acquired TA value of the target cell. sDU1 204_1 responds with a UE context modification response 722_1.

[0173] The execution phase 904_1 is triggered by a low layer measurement report 720_1 sent from UE1 110_1 to serving DU 204_1 (sDU1). UE 110_1 (UE1) performs L1 measurements on the configured LTM candidate target cells and sends a low layer measurement report 904_1 to source DU 204_1 (sDU1).

[0174] The source DU 204_1 (sDU1) decides 722_1 to perform an LTM cell handover to the target cell (tDU 204_2) and sends an LTM command 724_1 (MAC CE) to the UE 110_1 (UE1) triggering the LTM cell handover at the UE 110_1 (UE1).

[0175] UE 110_1 (UE1) switches to the configuration of the LTM candidate target cell (tDU 204_2) and accesses 726_1 the target cell. If necessary (ie, if timing advance is not available / invalid), UE 110_1 (UE1) performs a random access (not shown).

[0176] UE 110_1 (UE1) may use RRC Reconfiguration Complete to indicate successful completion of the LTM cell handover to the target cell.

[0177] UE2 110_3 sends L3 measurement report messages 311_3, 313_3 to CU 202 via source DU 204_3 (sDU2) (sDU2 204_3 sends UL RRC message transmission message 313_3 including L3 measurement report to CU 202). CU 202 decides to use LTM and initiates LTM candidate cell preparation 702_3.

[0178] CU 202 sends UE context establishment request 302_3 to target DU 204_2 (tDU) to prepare the target cell. Message 302_3 includes the identification of serving DU 204_3 (sDU2) to associate a subset of contention-free random access (CFRA) resources 602 with the identified serving DU 204_3 (sDU2).

[0179] The target DU 204_2 (tDU) receives a message 302_3 including an identification of the serving DU 204_3 (sDU2). In this example, the message 302_3 is a UE context establishment request 302_3 including a gNB-DU ID of the serving cell (e.g., the ID of the source DU 204_3 (sDU2)).

[0180] The target DU 204_2 (tDU) associates 306_3 a second subset 604_2 of contention-free random access (CFRA) resources 602 with the identified serving DU 204_3 (sDU2). The target DU 204_2 (tDU) may generate 306_3 a subset 604_2 of CFRA resources, for example, for sDU2, and the second subset 604_2 of CFRA resources 602 is allocated to the source DU 204_3 (sDU2).

[0181] The target DU 204_2 (tDU) then sends a message 321_3 specifying an association of a second contention-free random access (CFRA) resource 602 subset 604_2 with the identified serving DU 204_3 (sDU2). In this example, the message 321_3 is a UE context establishment response message 321_3 including the second CFRA resource 602 subset 604_2.

[0182] The CU 202 receives a message 321_3 specifying an association of a second contention-free random access (CFRA) resource 602 subset 604_2 with the identified serving DU 204_3 (sDU2).

[0183] CU 202 prepares 704 the RRC configuration and provides 323_3, 330_3 the RRC configuration to UE 110_3 (UE2) via source DU 204_3 (sDU2). In this example, the message 323_3 from CU 202 to sDU2 204_3 is a DL RRC message transmission message 323_3 including the second CFRA resource 602 subset 604_2. The message 330_3 from sDU2 204_3 to UE2 110_3 is an RRC reconfiguration message 330_3 including the second CFRA resource 602 subset 604_2.

[0184] UE 110_3 (UE2) stores the configuration of the LTM candidate target cell and sends RRC reconfiguration complete messages 706_3, 708_3 to CU202 via source DU 204_3 (sDU2). Message 706_3 from UE2 110_3 to sDU2 204_3 is an RRC reconfiguration complete message. Message 708_3 from sDU2 204_3 to CU 202 is an UL RRC message transmission message 708_3.

[0185] Before receiving the LTM cell switch command 724_3, UE 110_3 (UE2) may perform DL early synchronization and early TA acquisition with the candidate target cell.

[0186] The early timing advance (TA) acquisition steps are:

[0187] Once the source DU 204_3 (sDU2) decides to trigger PRACH signal transmission from the UE2 110_3 to the target DU 204_2 (tDU), the source DU 204_3 (sDU2) selects 712_3 a CFRA resource 602 from the second CFRA resource 602 subset 604_2.

[0188] Then, the source DU 204_3 (sDU2) sends a PDCCH order 714_3 to the UE2 110_3. The PDCCH order 714_3 contains relevant configuration information (eg, preamble ID, SS / PBCH index, RACH timing, etc.), including the selected UE-specific CFRA resource 602.

[0189] The source DU 204_3 (sDU2) marks the UE-specific CFRA resources as “reserved” until the UE 110_3 (UE2) completes random access using the UE-specific CFRA resources 602 or there is a release of the UE-specific CFRA resources 602.

[0190] Based on the received information, the UE 110_3 (UE2) triggers a random access procedure 910_3 to the target DU 204_2 (tDU), ie, a preamble transmission 716_3 through a PRACH (ie, physical random access channel) of the target DU 204_2 (tDU).

[0191] After acquiring the timing advance (TA) associated with UE 110_3 (UE2), the target DU 204_2 (tDU) provides 718_3, 720_3 the TA value for LTM switching of the target cell and other relevant information (e.g., preamble ID, SS / PBCH index, RACH timing, etc.) to the source DU 204_3 (sDU2) via CU202. Now, the source DU 204_3 (sDU2) can associate the received TA value with the specific UE 110_3 (UE2). In this example, the message 720_3 is a UE context modification request 720_3 indicating the acquired TA value for the target cell. sDU2 204_3 responds with a UE context modification response 722_3.

[0192] The execution phase 904_3 is triggered by a low layer measurement report 720_3 sent from UE2 110_3 to serving DU 204_3 (sDU2). UE 110_3 (UE2) performs L1 measurements on the configured LTM candidate target cells and sends a low layer measurement report 904_3 to source DU 204_3 (sDU2).

[0193] The source DU 204_3 (sDU2) decides 722_3 to perform an LTM cell handover to the target cell (tDU 204_2) and sends an LTM command 724_3 (MAC CE) to the UE 110_3 (UE2) triggering the LTM cell handover at the UE 110_3 (UE2).

[0194] UE 110_3 (UE2) switches to the configuration of the LTM candidate target cell (tDU 204_2) and accesses 726_3 the target cell. If required (ie, if timing advance is not available / invalid), UE 110_3 (UE2) performs a random access (not shown).

[0195] UE 110_3 (UE2) may use RRC Reconfiguration Complete to indicate successful completion of the LTM cell handover to the target cell.

[0196] The above process avoids PRACH collisions in the case where CFRA resources are shared between UEs connected to different DUs. It prevents the source DU from using the same CFRA resources for different UEs (which may cause PRACH collisions).

[0197] The CFRA resource pool is configured per DU (subset 604). This prevents CFRA resources from being shared by UEs belonging to different source DUs.

[0198] This process avoids the CFRA resource starvation problem in dense environments, enables low-latency handover by avoiding RACH collisions (HO failures), and implements shared CFRA resources for early TA acquisition.

[0199] According to one example, a first subset 604_1 of CFRA resources 602 of the target cell belonging to the target DU 204_2 (tDU) is shared among all UEs 110 in the source cell belonging to the first source DU 204_1 (sDU1), and a second subset 604_2 of CFRA resources of the target cell belonging to the target DU 204_2 (tDU) is shared among all UEs in the source cell belonging to the second source DU 204_3 (sDU2).

[0200] In some examples, the first subset 604_1 of CFRA resources 602 of the target cell is orthogonal to the second subset 604_2 of CFRA resources 602 of the target cell. In other words, the orthogonal subsets of CFRA resources 602 of the target cell are configured to UEs in the source cell belonging to different source DUs 204.

[0201] According to some examples, CU 202 provides identification of first source DU 204_1 (sDU1) and / or second source DU 204_3 (sDU2) to target DU 204_2 (tDU).

[0202] According to some examples, CU 202 provides the identification of the first source DU 204_1 (sDU1) and / or the second source DU 204_3 (sDU2) to the target DU 204_2 (tDU) as part of the UE context establishment request message.

[0203] According to an example, the CU 202 provides the identification of the first source DU 204_1 (sDU1) and / or the second source DU 204_3 (sDU2) to the target DU 204_2 (tDU) as part of the UE context modification request message.

[0204] According to an example, the CU 202 provides the identification of the first source DU 204_1 (sDU1) and / or the second source DU 204_3 (sDU2) as part of a new message to the target DU 204_2 (tDU) through the F1 interface.

[0205] According to an example, the target DU 204_2 (tDU) allocates the first CFRA resource subset 604_1 to the first source DU 204_1 (sDU1) and allocates the second CFRA resource subset 604_2 to the second source DU 204_3 (sDU2).

[0206] According to an example, the first subset of CFRA resources 604_1 is completely or partially orthogonal to the second subset of CFRA resources.

[0207] According to an example, the first CFRA resource subset 604_1 is identical to the second CFRA resource subset 604_2, but the first and second CFRA resource subsets 604_2 are orthogonal to a third CFRA resource subset, which is shared among all UEs in the source cell belonging to the third source DU.

[0208] According to an example, the CU 202 allocates the first subset of CFRA resources 604_1 to the first source DU 204_1 (sDU1), and allocates the second subset of CFRA resources 604_2 to the second source DU 204_3 (sDU2).

[0209] According to an example, both the first and second CFRA resource subsets 604_2 are subsets of the total amount of CFRA resources provided by the target DU 204_2 (tDU) for the target cell.

[0210] According to the example, if another UE of the first source DU 204_1 (sDU1) needs to perform LTM preparation for a cell belonging to the same target DU 204_2 (tDU), the target DU 204_2 (tDU) provides a first subset of CFRA resources 604_1. Similarly, if another UE of the second source DU 204_3 (sDU2) needs to perform LTM preparation for a cell belonging to the same target DU 204_2 (tDU), the target DU 204_2 (tDU) provides a second subset of CFRA resources.

[0211] According to the example, as long as at least one UE has prepared for LTM (where the candidate target cell belongs to the target DU 204_2 (tDU)), the target DU 204_2 (tDU) retains the CFRA resource set.

[0212] According to the example, if UE context release is performed for all UEs of the source DU in the target DU 204_2 (tDU), the target DU 204_2 (tDU) will release the CFRA resources reserved for the source DU.

[0213] According to the example, if an explicit indication is received from the CU 202, the target DU 204_2 (tDU) will release the CFRA resources.

[0214] According to the example, a new procedure is introduced, which allows efficient signaling by requesting a CFRA resource pool from the target DU 204_2 (tDU) for multiple source DUs respectively. In this case, a list of source DUs is indicated in the CFRA resource request message, and a set list of CFRA resource pools is indicated in the CFRA response message.

[0215] Reference Figure 8 and 13 , Message 302 can be a UE context establishment message. Exemplary structure of the UE context establishment request message in 3GPP TS 38.473:

[0216]

[0217] This message includes a new information element <LTM source DU information>.

[0218] The new information element <LTM source DU information> includes a new information element <gNB-DU ID>.

[0219] The new information element <gNB-DU ID> is the identification 304 of the serving network access node (sDU). It can be the gNB-DU ID of the serving cell, such as the ID of the source DU 204 (sDU).

[0220] The gNB-CU sends a UE CONTEXT SETUP REQUEST message to the gNB-DU to request the establishment of a UE context.

[0221] References to "computer-readable storage medium," "computer program product," "tangibly embodied computer program," etc., or "controller," "computer," "processor," etc., should be understood to include not only computers having different architectures (e.g., single / multi-processor architectures and sequential (von Neumann) / parallel architectures), but also special-purpose circuits, such as field-programmable gate arrays (FPGAs), application-specific circuits (ASICs), signal processing devices, and other processing circuits. References to computer programs, instructions, code, etc., should be understood to include software for a programmable processor or firmware, such as the programmable content of a hardware device, whether instructions for a processor or configuration settings for a fixed-function device, gate array, or programmable logic device, etc.

[0222] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0223] (a) only hardware circuit implementation (e.g., implementation in analog and / or digital circuits only), and

[0224] (b) a combination of hardware circuitry and software, such as (where applicable):

[0225] (i) a combination of analog and / or digital hardware circuits with software / firmware, and

[0226] (ii) any portion of a hardware processor (including a digital signal processor) with software, software and memory that work together to enable a device (such as a mobile phone or server) to perform various functions, and

[0227] (c) Hardware circuits and / or processors, such as a microprocessor or portion of a microprocessor, that require software (such as firmware) in order to operate, but where the software may not be present, the operation may not require it.

[0228] This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" also covers an implementation of a hardware-only circuit or processor and its accompanying software and / or firmware. The term "circuitry" also covers (for example and if applicable to a particular claim element) a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0229] The blocks shown in the accompanying drawings may represent steps in a method and / or code sections in a computer program 406. The particular sequence diagram of the blocks does not necessarily imply that the blocks have a required or preferred order, and the order and arrangement of the blocks may be changed. In addition, some blocks may be omitted.

[0230] Where a structural feature has been described, it may be replaced by a means for performing one or more functions of the structural feature, whether that function or functions are described explicitly or implicitly.

[0231] As used herein, a "module" refers to a unit or device that does not include certain parts / components to be added by an end manufacturer or user. The devices 202, 204 may be modules.

[0232] The above examples are for components that are enabled by:

[0233] Automotive systems; telecommunications systems; electronic systems, including consumer electronics; distributed computing systems; media systems for generating or rendering media content, including audio, visual and audiovisual content and mixed, mediated, virtual and / or augmented reality; personal systems, including personal health systems or personal fitness systems; navigation systems; user interfaces, also known as human-machine interfaces; networks, including cellular, non-cellular and optical networks; ad hoc networks; the Internet; the Internet of Things; virtualized networks; and related software and services.

[0234] According to examples of the present disclosure, the device may be provided in an electronic device (e.g., a mobile terminal). However, it should be understood that the mobile terminal is only an example of an electronic device that will benefit from the implementation examples of the present disclosure, and therefore should not be considered to limit the scope of the present disclosure to this. Although in a specific implementation example, the device may be provided in a mobile terminal, other types of electronic devices may easily adopt examples of the present disclosure, such as but not limited to: mobile communication devices, handheld portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices, and other types of electrical systems. In addition, devices may easily adopt examples of the present disclosure regardless of their intent to provide mobility.

[0235] The term "comprising" is used in this document in an inclusive sense rather than an exclusive sense. That is, any reference to X comprising Y indicates that X may include only one Y or may include multiple Ys. If the exclusive sense of "comprising" is intended, it will be made clear from the context by reference to "comprising only one" or by use of "consisting of."

[0236] In this specification, the terms "connected", "coupled" and "in communication" and their derivatives refer to being operationally connected / coupled / in communication. It should be understood that any number or combination of intermediate components (including no intermediate components) may be present to provide direct or indirect connection / coupling / communication. Any such intermediate components may include hardware and / or software components.

[0237] As used herein, the term "determine" (and its grammatical variations) may include, but is not limited to, calculating, estimating, processing, deriving, measuring, investigating, identifying, looking up (e.g., looking up in a table, a database, or another data structure), ascertaining, etc. Furthermore, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), obtaining, etc. Furthermore, "determining" may include resolving, selecting, choosing, establishing, etc.

[0238] In this specification, reference has been made to various examples. The description of a feature or function relative to an example indicates that these features or functions are present in the example. The use of the term "example" or "for example" or "may" or "might" herein (whether explicitly stated or not) means that such features or functions are present in at least the described example (whether described as an example or not), and they may but not necessarily be present in some or all other examples. Therefore, "example", "for example", "may" or "might" refers to a specific instance in a class of examples. The characteristics of an instance may be characteristics of only the instance or characteristics of the class or characteristics of a subclass of the class (which includes some but not all instances in the class). It is therefore implicitly disclosed that a feature described with reference to one example without reference to another example may (if possible) be used in the other example as part of a working combination, but does not necessarily have to be used in the other example.

[0239] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0240] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0241] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0242] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0243] The terms "a", "an" or "the" used in this document have an inclusive rather than an exclusive meaning. That is, any reference to X that includes one / the Y indicates that X may include only one Y or may include multiple Ys, unless the context clearly indicates otherwise. If "a" or "the" is intended to be used in an exclusive sense, it will be made clear from the context. In some cases, "at least one" or "one or more" may be used to emphasize the inclusive meaning, but it should not be considered that any exclusive meaning can be inferred without these terms.

[0244] The feature (or feature combination) in the claims refers to the feature (or feature combination) itself, and also refers to the feature (equivalent feature) that achieves substantially the same technical effect. Equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0245] In this specification, reference has been made to various examples where adjectives or adjective phrases are used to describe characteristics of the examples. Such description of characteristics relative to the examples indicates that the characteristics exist in some examples exactly as described, and in other examples substantially as described.

[0246] The above description describes some examples of the present disclosure, but those skilled in the art will be aware of possible alternative structures and method features that provide equivalent functions to the specific examples of such structures and features described above, and for the sake of brevity and clarity, they have been omitted from the above description. However, the above description should be understood to implicitly include references to such alternative structures and method features that provide equivalent functions, unless such alternative structures or method features are explicitly excluded in the above description of examples of the present disclosure.

[0247] While attention has been paid in the foregoing description to those features regarded as being of importance, it should be understood that the applicant may seek protection through the claims for any patentable feature or combination of features mentioned above and / or shown in the drawings, whether or not such features are emphasized.

Claims

1. A device for wireless communication, comprising: at least one processor; as well as at least one memory including computer program code, The at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to at least: receiving an identification of a serving network access node; as well as A subset of contention free random access (CFRA) resources is associated with the identified serving network access node.

2. The device according to claim 1, wherein: The at least one memory also stores instructions that, when executed by the at least one processor, cause the apparatus to implement contention-free random access by reserving the subset of contention-free random access CFRA resources for association only with the identified serving network access node and not with other network access nodes.

3. The device according to claim 1 or 2, wherein: The at least one memory also stores instructions that, when executed by the at least one processor, cause the device to: temporarily reserve the contention-free random access CFRA resource subset for connecting any UE currently served by the identified serving access node to the device as a serving network access node, wherein association of the contention-free random access CFRA resource subset with different serving network access nodes is blocked.

4. The device according to any one of claims 1 to 3, wherein: The subset of contention-free random access (CFRA) resources for the serving network access node is contention-free with respect to other different network access nodes.

5. The device according to any one of claims 1 to 4, wherein: The at least one memory also stores instructions that, when executed by the at least one processor, cause the apparatus to: associate a subset of CFRA resources with a corresponding serving network access node based on the received identification of the serving network access node.

6. The device according to any one of claims 1 to 5, wherein: The at least one memory further stores instructions that, when executed by the at least one processor, cause the apparatus to: Allocate the CFRA resource subset to the corresponding service network access node; as well as The network is informed of the allocation of the CFRA resource subsets to the corresponding serving network access nodes.

7. The device according to any one of claims 5 or 6, wherein: The CFRA resource subset includes: different subsets for different network access nodes; or non-overlapping subsets for different network access nodes; or Orthogonal subsets for different network access nodes.

8. The apparatus according to any one of claims 1 to 7, configured to operate as a distributed unit DU of a radio access network.

9. The device according to claim 8, wherein: The at least one memory further stores instructions which, when executed by the at least one processor, cause the apparatus to receive the identification of the serving network access node configured to: receive the identification of the serving network access node from a central unit CU of the radio access network.

10. The apparatus according to any one of claims 1 to 9, configured to process a standardized message comprising a standardized information element to obtain the identification of the serving network access node from the standardized information element.

11. The apparatus according to any one of claims 1 to 10, configured as a network access node, and configured to perform a low layer triggered mobility (LTM) handover (HO) of a user equipment served by the serving network access node to the apparatus based on a random access procedure using contention-free random access (CFRA) resources from the contention-free random access (CFRA) resource subset associated with the serving network access node.

12. A method for wireless communication, comprising: receiving an identification of a serving network access node; as well as A subset of contention free random access (CFRA) resources is associated with the identified serving network access node.

13. A computer readable medium storing instructions which, when executed by one or more processors of a device, enable the device to: obtaining an identification of the serving network access node from the received message; and The contention-free random access CFRA resource subset is associated with the obtained identifier of the serving network access node.

14. An apparatus for wireless communication, comprising: at least one processor; as well as at least one memory including computer program code, The at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to at least: Sending a first message, wherein the first message includes an identifier of a serving network access node, so as to associate a contention-free random access CFRA resource subset with the identified serving network access node; as well as In response, a second message is received specifying an association of the subset of contention free random access (CFRA) resources with the identified serving network access node.

15. The device according to claim 14, wherein: The first message is configured to prepare a non-serving network access node to become the serving network access node of the UE via a contention free random access CFRA connection using contention free random access CFRA resources selected from the contention free random access CFRA resource subset associated with the serving access node of the UE.

16. The device according to claim 14 or 15, wherein: The at least one memory further stores instructions that, when executed by the at least one processor, cause the apparatus to: send one or more first messages comprising: an identifier of the first serving network access node, so as to associate the first contention-free random access CFRA resource subset with the identified first serving network access node; as well as The identifier of the second serving network access node is used to associate the second contention-free random access CFRA resource subset with the identified second serving network access node.

17. The device according to claim 14, 15 or 16, wherein: The at least one memory also stores instructions that, when executed by the at least one processor, cause the apparatus to identify the subset of contention-free random access (CFRA) resources only to the identified serving network access node and not to other network access nodes.

18. The device according to any one of claims 14 to 17, wherein: The at least one memory also stores instructions which, when executed by the at least one processor, cause the apparatus to: enable temporary reservation of the contention-free random access CFRA resource subset for connecting any UE currently served by the identified serving access node to a target network access node as a serving network access node, wherein association of the contention-free random access CFRA resource subset for connecting a UE served by a different serving access node to the target network access node as a serving network access node with the different serving network access node is blocked.

19. The device according to any one of claims 14 to 17, wherein: The at least one memory also stores instructions that, when executed by the at least one processor, cause the apparatus to: identify a subset of CFRA resources to a corresponding serving network access node based on a reply to the transmitted identification of the serving network access node.

20. The apparatus according to claim 14, configured as a central unit CU of a radio access network, wherein: Sending the identification of the serving network access node comprises: sending the identification of the serving network access node to a distributed unit DU of the radio access network.

21. A method for wireless communication, comprising: Sending a first message, wherein the first message includes an identifier of a serving network access node, so as to associate a contention-free random access CFRA resource subset with the identified serving network access node; as well as In response, a second message is received specifying an association of the subset of contention free random access (CFRA) resources with the identified serving network access node.

22. A computer readable medium storing instructions which, when executed by one or more processors of a device, enable the device to: A first message is sent, the first message including an identification of a serving network access node to associate a subset of contention-free random access CFRA resources with the identified serving network access node, and a second message is received in reply specifying the association of the subset of contention-free random access CFRA resources with the identified serving network access node.

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