Resource-efficient l1 / l2 handover execution in a wireless communications network

Abstract

A method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device (521), such as a UE, in a wireless communications network, performed by a source radio access node (511), such as a source gNB-DU5 The method comprises triggering (501) LTM of the wireless communications device (521) towards a candidate cell served by a candidate radio access node (512), such as a candidate gNB-DU. The method further comprises requesting (502) the candidate radio access node (512) to send a cell Scheduling Request, SR, configuration for the wireless 10 communications device (521). The method further comprises receiving (502) the SR configuration from the candidate radio access node (512). The method further comprises transmitting (505) an indication of the SR configuration to the wireless communications device (521).

Description

[0001] RESOURCE-EFFICIENT L1 / L2 HANDOVER EXECUTION IN A WIRELESS

[0002] COMMUNICATIONS NETWORK

[0003] TECHNICAL FIELD

[0004] Embodiments disclosed herein relate to methods and apparatuses for resourceefficient L1 / L2 handover execution in a wireless communications network. A corresponding computer program and a computer program carrier are also disclosed.

[0005] BACKGROUND

[0006] In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and / or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio access node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio access node. The radio access node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio access node.

[0007] Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E- UTRAN / LTE is a variant of a 3GPP radio access network wherein the radio access nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN / LTE the functions of a 3G RNC are distributed between the radio access nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio access nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio access nodes, this interface being denoted the X2 interface.

[0008] Wireless communication systems in 3GPP

[0009] Figure 1 illustrates a simplified wireless communication system. Consider the simplified wireless communication system in Figure 1, with a UE 12, which communicates with one or multiple access nodes 103-104, which in turn is connected to a network node 106. The access nodes 103-104 are part of the radio access network 10.

[0010] For wireless communication systems pursuant to 3GPP Evolved Packet System, (EPS), also referred to as Long Term Evolution, LTE, or 4G, standard specifications, such as specified in 3GPP TS 36.300 and related specifications, the access nodes 103-104 corresponds typically to a Evolved NodeBs (eNBs) and the network node 106 corresponds typically to either a Mobility Management Entity (MME) and / or a Serving Gateway (SGW). The eNB is part of the radio access network 10, which in this case is the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), while the MME and SGW are both part of the EPC (Evolved Packet Core network). The eNBs are interconnected via the X2 interface, and connected to EPC via the S1 interface, more specifically via S1-C to the MME and S1-U to the SGW.

[0011] For wireless communication systems pursuant to 3GPP 5G System, 5GS (also referred to as New Radio, NR, or 5G) standard specifications, such as specified in 3GPP TS 38.300 and related specifications, on the other hand, the access nodes 103-104 corresponds typically to an 5G NodeB (gNB) and the network node 106 corresponds typically to either a Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF). The gNB is part of the radio access network 10, which in this case is the NG-RAN (Next Generation Radio Access Network), while the AMF and UPF are both part of the 5G Core Network (5GC). The gNBs are inter-connected via the Xn interface, and connected to 5GC via the NG interface, more specifically via NG-C to the AMF and NG-U to the UPF.

[0012] To support fast mobility between NR and LTE and avoid change of core network, LTE eNBs may also be connected to the 5G-CN via NG-U / NG-C and support the Xn interface. An eNB connected to 5GC is called a next generation eNB (ng-eNB) and is considered part of the NG-RAN. LTE connected to 5GC will not be discussed further in this document; however, it should be noted that most of the solutions / features described for LTE and NR in this document also apply to LTE connected to 5GC. In this document, when the term LTE is used without further specification it refers to LTE-EPC.

[0013] 5G (or NR) is the fifth-generation technology standard for broadband cellular networks, which cellular phone companies began deploying worldwide in 2019. The 5G standard is specified by the industry consortium 3GPP. In cellular networks the service area is divided into small geographical areas called cells. All 5G wireless devices (UEs) in a cell communicate by radio waves with a cellular base station via antennas, over frequency channels assigned by the base station. The base stations, called gNBs, are connected to routers for Internet access.

[0014] In 3GPP NR, the terms CU (Centralised Unit) and DU (Distributed Unit) are used to a functional split within a 5G base station (gNB). The DU is a unit that sits close to the radio and runs the RLC, MAC layers. Its operation is controlled by the CU. CU is the centralized unit that runs the RRC and PDCP layers. The gNB consists of a CU and one DU connected to the CU via F1-AP. A CU with multiple DUs will support multiple gNBs. CUs are connected with other CUs through the Xn-AP as shown in Figure 2. The CU is a logical node that includes the gNB functions like transfer of user data, mobility control, session management, etc.

[0015] In cellular systems like 5G, handover procedures are used to allow UEs to change serving cell when e.g. the UE has moved from the coverage area of a current serving cell (source serving cell) to that of another cell (target or candidate serving cell). The existing mechanisms are controlled by the CU and rely on L3 measurements and involve RRC signalling and requires that the UE performs a complete random access procedure to the target cell. In addition all L2 contexts are reset. The procedure leads to data interruptions which may disturb latency critical services.

[0016] 3GPP Rel-18 approved to study methods to decrease handover interruption time and latency by defining handover based on L1 / L2 mechanisms controlled by the DU. The methods include

[0017] • Configuring multiple candidate cells to allow fast application of the configurations after handover

[0018] • Switch mechanisms among candidate cells, including L1 measurements and reporting,

[0019] Synchronization mechanisms, i.e. handling of Timing Advance in the target cell. New signalling between CU and DU to support L1 / L2 mobility (F1 interface changes)

[0020] In the following, the term L1 / L2 Triggered Mobility (LTM) will be used for the new handover mechanisms. A high-level diagram of a working assumption for an LTM handover solution is shown in Figure 3. The LTM handover solution of Figure 3 is for inter DU intra CU LTM. That is, there is a change of DU but not of CU.

[0021] In action 1 , a decision is made in the gNB-CU to configure LTM for a UE. In action 2, a request is sent to candidate gNB-DUs to set up a UE context. The candidate gNB-DU responds with the RRC configuration to be transferred to the UE in action 3. The UE is configured to perform L1 measurements on the candidate cells and reports them to the source gNB-DU in action 4.

[0022] In action 5, the CU decides based on L1 measurements to perform an LTM handover to a candidate cell. It is optional whether the candidate gNB-DU is involved at this stage. Two options exist. In option 1 , the serving DU informs the CU only after sending the LTM cell switch command to the UE and it can therefore not retrieve any dynamic information just before the execution. In option 2, dynamic information (including e.g. Timing Advance (TA), TCI states and / or active Bandwidth Part (BWP)) can be exchanged.

[0023] In action 6, a cell switch command is sent to the UE. This command includes a MAC CE element which may include any dynamic information exchanged in action 5. At action 7 the candidate gNB-DU may be informed of the triggered cell switch.

[0024] In action 8, the UE accesses the candidate cell and the access is detected by the candidate gNB-DU. One option for this action is to provide the UE with a configured UL grant as part of the cell switch command. The gNB-DU can then detect that the UE has accessed the cell by decoding an uplink message from the UE. An alternative is that the candidate cell dynamically schedules the UE with Physical Downlink Control Channel (PDCCH) and any response (UL message or acknowledgement of DL message) counts as a cell access detection. When the UE has been detected, the CU is notified in action 9, and the source DU may drop the UE context and user data may now be sent through the candidate DU instead. In Figure 3, the action 5 includes an optional signalling exchange with the candidate gNB-Dll where the candidate gNB-Dll provides dynamic resources, e.g. a configured UL grant or search space information for a PDCCH in the candidate cell. Depending on the signalling delays and delays in the Cell switch command execution, the time when the UE is ready to receive PDCCH in the candidate cell is not precisely known. The candidate cell may therefore need to transmit many PDCCH UL grants before the UE has ability to monitor PDCCH. Alternatively, if a configured grant is used, the candidate gNB-DU may be configured to listen to Physical Uplink Shared Channel (PUSCH) unnecessarily long time. This means that PDCCH and PUSCH capacity is wasted in the candidate cell.

[0025] SUMMARY

[0026] Thus, a new mechanism is needed to support LTM.

[0027] An object of embodiments herein may be to obviate some of the problems related to LTM.

[0028] Embodiments herein address the above-described problem by dynamically assigning a Scheduling Request configuration at the time LTM execution has been decided.

[0029] According to an aspect, the object is achieved by a method for LTM of a wireless communications device, such as a UE, in a wireless communications network, performed by a source radio access node, such as a source gNB-DU.

[0030] The method comprises triggering LTM of the wireless communications device towards a candidate cell served by a candidate radio access node, such as a candidate gNB-DU.

[0031] The method further comprises requesting the candidate radio access node to send a cell Scheduling Request, SR, configuration for the wireless communications device.

[0032] The method further comprises receiving the SR configuration from the candidate radio access node.

[0033] The method further comprises transmitting an indication of the SR configuration to the wireless communications device.

[0034] According to a further aspect, the object is achieved by a source radio access node, such as a gNB-DU, adapted for L1 / L2 Triggered Mobility, LTM, of a wireless communications device in a wireless communications network. The source radio access node is adapted to perform the method of the aspect above.

[0035] According to a third aspect, the object is achieved by a method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device in a wireless communications network, performed by a candidate radio access node.

[0036] The method comprises receiving a request to send a cell Scheduling Request, SR, configuration for the wireless communications device from a source radio access node.

[0037] The method further comprises transmitting the SR configuration to the source radio access node.

[0038] According to a fourth aspect, the object is achieved by a candidate radio access node, adapted for L1 / L2 Triggered Mobility, LTM, of a wireless communications device in a wireless communications network.

[0039] The candidate radio access node is adapted to receive a request to send a cell Scheduling Request, SR, configuration for the wireless communications device from a source radio access node.

[0040] The candidate radio access node is further adapted to transmit the SR configuration to the source radio access node.

[0041] According to a fifth aspect, the object is achieved by a method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device in a wireless communications network, performed by the wireless communications device.

[0042] The method comprises receiving, from a source radio access node, an indication of a cell Scheduling Request, SR, configuration for a candidate cell served by a candidate radio access node.

[0043] The method further comprises using an SR configured by the SR configuration for requesting UpLink-Shared Channel, UL-SCH, resources for a new transmission in the candidate cell.

[0044] According to a sixth aspect, the object is achieved by a wireless communications device, adapted for L1 / L2 Triggered Mobility, LTM, in a wireless communications network. The wireless communications device is adapted to receive, from a source radio access node, an indication of a cell Scheduling Request, SR, configuration for a candidate cell served by a candidate radio access node. The wireless communications device is further adapted to use an SR configured by the SR configuration for requesting UpLink-Shared Channel, LIL-SCH, resources for a new transmission in the candidate cell.

[0045] According to a further aspect, the object is achieved by a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the aspects above.

[0046] According to a further aspect, the object is achieved by a carrier comprising the computer program of the aspect above, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

[0047] Embodiments herein enable efficient LTM by more efficient resource usage in the candidate cells since the effects of the uncertainty in the arrival time of the UE is reduced. For example, the use of the SR instead of configured grants or dynamic scheduling from candidate cells is more resource-efficient with respect to PDCCH and PLISCH usage. The UE is provided an UL grant only when it has requested one by transmitting an SR.

[0048] BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In the figures, features that appear in some embodiments are indicated by dashed lines.

[0050] The various aspects of embodiments disclosed herein, including particular features and advantages thereof, will be readily understood from the following detailed description and the accompanying drawings, in which:

[0051] Figure 1 illustrates a simplified wireless communication system,

[0052] Figure 2 is a block diagram illustrating gNBs and interfaces between units of the gNBs,

[0053] Figure 3 is a combined flow chart and signalling diagram for an inter DU intra CU LTM handover,

[0054] Figure 4 is a block diagram schematically illustrating a wireless communications network in which embodiments herein may be implemented,

[0055] Figure 5 is a combined flow chart and signalling diagram for LTM handover according to some embodiments herein, Figure 6 is a block diagram schematically illustrating a centralised radio access node according to some embodiments herein,

[0056] Figure 7 is a block diagram schematically illustrating a source distributed radio access node according to some embodiments herein,

[0057] Figure 8 is a block diagram schematically illustrating a candidate distributed radio access node according to some embodiments herein,

[0058] Figure 9 is a block diagram schematically illustrating a UE according to some embodiments herein,

[0059] Figure 10 schematically illustrates a telecommunication network connected via an intermediate network to a host computer.

[0060] Figure 11 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection.

[0061] Figures 12 to 15 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station and a user equipment.

[0062] DETAILED DESCRIPTION

[0063] Embodiments herein relate to wireless communication networks in general. Figure 4 is a schematic overview depicting a wireless communications network 100 wherein embodiments herein may be implemented. The wireless communications network 100 comprises one or more RANs and one or more CNs. The wireless communications network 100 may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications / enhanced Data rate for GSM Evolution (GSM / EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE.

[0064] Access nodes operate in the wireless communications network 100 such as a source radio access node 111. The source radio access node 111 provides radio coverage over a geographical area, a service area referred to as a cell 115, which may also be referred to as a beam or a beam group of a first radio access technology (RAT), such as 5G, LTE, Wi-Fi or similar. There may also be further cells served by the source radio access node 111 , such as a second cell 116. The cell 115 and the second cell 116 may be referred to as source cells.

[0065] There may also be further radio access nodes, such as a candidate radio access node 112. The candidate radio access node 112 provides radio coverage over candidate cells, such as a third cell 125 and a fourth cell 126.

[0066] The source radio access node 111 and the candidate radio access node 112 may each be a NR-RAN node, transmission and reception point e.g. a base station, a radio access node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area depending e.g. on the radio access technology and terminology used. The respective first and second radio access node 111 , 112 may be referred to as a serving radio access node and communicates with a UE with Downlink (DL) transmissions to the UE and Uplink (UL) transmissions from the UE.

[0067] In particular, each of the source radio access node 111 and the candidate radio access node 112 may be a 5G base station (gNB) according to Figure 2 with a DU and a CU. Thus each of the source radio access node 111 and the candidate radio access node 112 may consist of a CU and one DU connected to the CU via F1-AP.

[0068] A number of wireless communications devices operate in the wireless communication network 100, such as a UE 121.

[0069] The UE 121 may be a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and / or a wireless terminals, that communicate via one or more Access Networks (AN), e.g. RAN, e.g. via the source radio access node 111 to one or more core networks (CN) e.g. comprising a CN node 130, for example comprising an Access Management Function (AMF). It should be understood by the skilled in the art that “UE” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell. Methods herein may in a first aspect be performed by the source radio access node 111 and in a second aspect by the candidate radio access node 112, or more specifically by the respective DU and CU of the source radio access node 111 and the candidate radio access node 112, in a third aspect by a wireless communications device, such as the UE 121. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in a cloud 140 as shown in Figure 4, may be used for performing or partly performing the methods.

[0070] Embodiments herein will now be described in more detail. As mentioned above, embodiments disclosed herein address a problem of achieving efficient LTM.

[0071] Embodiments herein disclose a procedure to achieve efficient LTM by the source gNB-DU requesting a new Scheduling Request (SR) configuration from the candidate gNB-DU (through the gNB-CU). The SR is used for requesting UpLink-Shared Channel (UL-SCH) resources for a new transmission. The MAC entity may be configured with zero, one, or more SR configurations. An SR configuration may comprise a set of Physical Uplink Control Channel (PUCCH) resources for SR across different BWPs and cells. For a logical channel, one PUCCH resource for SR may be configured per BWP. Each SR configuration may correspond to one or more logical channels. Each logical channel may be mapped to zero or one SR configuration, which is configured by RRC. The SR configuration of the logical channel that triggered a Buffer Status Report (BSR) (if such a configuration exists) may be considered as corresponding SR configuration for the triggered SR.

[0072] RRC may configure the following parameters for the scheduling request procedure:

[0073] - sr-ProhibitTimer (per SR configuration);

[0074] - sr-TransMax (per SR configuration);

[0075] - sr-Configlndex.

[0076] The choice how to allocate SRs to different UEs is base station proprietary, but in order to support many connected UEs all of them cannot be allocated with the shortest periodicity. In some embodiments herein a certain number of SRs with shorter periodicity may be defined, for example for high priority users, and then a second number of SRs with longer periodicity may be defined, for example for normal priority users.

[0077] In embodiments herein the candidate gNB-DU may try to find the shortest periodicity SR that is not yet allocated (or reserved for possible new users with high priority). If all SRs with shortest periodicity are occupied it needs to select a larger periodicity from for example a resource pool. In general it is a good idea that the scheduling request configuration should have the shortest possible periodicity so that any delays in accessing the candidate cell is minimized. The SR configuration may be transmitted to the UE in the cell switch command and the UE may use an SR configured by the SR configuration to establish the connection with the candidate cell associated with the candidate gNB-Dll.

[0078] In embodiments disclosed herein the Scheduling Request configuration is dynamically assigned at the time LTM execution has been decided. The scheduling request configuration is transferred over the standardized F1AP interfaces (or F1AP + XnAP interfaces in case the candidate gNB-Dll is connected to a different gNB-Cll than the source gNB-Dll) as part of a UE Context Modification Procedure. As mentioned above, the SR configuration may also be transferred to the UE in the cell switch command.

[0079] An advantage of embodiments herein is more efficient resource usage in the candidate cells since the effects of the uncertainty in the arrival time of the UE is reduced. For example, the use of the SR instead of configured grants or dynamic scheduling from candidate cells is more resource-efficient with respect to PDCCH and PUSCH usage. The UE is provided an UL grant only when it has requested one by transmitting an SR.

[0080] Figure 5 is a combined signalling diagram and flow chart and illustrates example methods to achieve efficient LTM execution. Specifically, Figure 5 illustrates methods for LTM of a wireless communications device 521 , exemplified in Figure 5 as a UE, in the wireless communications network 100. The actions of Figure 5 are performed by the wireless communications device 521, a source radio access node 511, exemplified in Figure 5 as a source gNB-DU, a candidate radio access node 512, exemplified in Figure 5 as a candidate gNB-DU and a centralised radio access node 510, exemplified in Figure 5 as a gNB-CU.

[0081] A first method may be performed by the source radio access node 511. A second method may be performed by the candidate radio access node 512. A third method may be performed by the wireless communications device 521.

[0082] Figure 5 assumes inter DU intra CU LTM, that is that the source gNB-DU 511 is connected to the same centralised radio access node 510 as candidate gNB-DU 512, is connected to. Thus, the source radio access node 511 and the candidate radio access node 512 may each be a gNB-DU. However, the actions are also valid for inter DU inter CU LTM. In that case signalling between the source DU 511 and the candidate DU 512 is forwarded on the Xn-AP interface between a first gNB-CU connected to the source gNB-DU 511 and a further gNB-CU connected to the candidate gNB-DU 512.

[0083] The actions are also valid when the source gNB-DU 511 and the candidate gNB-DU 512 are the same gNB-DU. That is when the source and candidate cells are served by the same DU.

[0084] The signalling of Figure 5 is between the source radio access node 511 , the centralised radio access node 510, the candidate radio access node 512 and the UE 521.

[0085] The actions may be performed in any suitable order, for example in another order than given below. Specifically, the sub-actions may be performed in another order than given below.

[0086] Action 5 in Figure 3 (LTM execution decision) corresponds to actions 501-504 in Figure 5.

[0087] Action 8 in Figure 3 (Access detection) corresponds to actions 507-509 in Figure 5.

[0088] Action 501:

[0089] In action 501 a decision is made by the source radio access node 511 to execute LTM towards a candidate cell, i.e. to trigger handover of the UE 521 from a source cell, served by the source radio access node 511 , to the candidate cell, served by the candidate radio access node 512, based on LTM. Thus, the source radio access node 511 triggers LTM of the wireless communications device 521 towards the candidate cell served by the candidate radio access node 512.

[0090] Action 502:

[0091] In action 502 the source radio access node 511 requests the candidate radio access node 512 to send a cell SR configuration for the wireless communications device 521. Correspondingly the candidate radio access node 512 receives the request to send the SR configuration for the wireless communications device 521 from the source radio access node 511.

[0092] The candidate radio access node 512 transmits the SR configuration to the source radio access node 511 and the source radio access node 511 receives the cell SR configuration from the candidate radio access node 512. The SR may be used by the wireless communications device 521 for requesting UL- SCH resources for a new transmission in the candidate cell.

[0093] For example, in action 502 the source radio access node 511 requests and retrieves the SR configuration of the candidate cell and, if necessary, random access preamble id for Contention free random access towards the candidate cell. The preamble id is needed if UE is not able to determine timing advance TA towards the candidate cell before the handover. Requesting the candidate radio access node 512 to send the cell SR configuration may be performed by sending an LTM cell switch request to the centralised radio access node 510 associated with the source radio access node 511. For example, the source radio access node 511 may request the SR configuration of the candidate cell from the candidate radio access node 512 by sending an LTM cell switch request to the centralised radio access node 510. The LTM cell switch request comprises the SR configuration request.

[0094] Receiving the cell SR configuration from the candidate radio access node 512 may comprise receiving the cell SR configuration in an LTM cell switch response from the centralised radio access node 510.

[0095] In some embodiments herein the candidate radio access node 512 selects, for the cell SR configuration, a shortest periodicity SR which is available for the wireless communications device 521.

[0096] Selecting the shortest periodicity SR available for the wireless communications device 521 may be based on a priority of the wireless communications device 521.

[0097] In some embodiments herein selecting the shortest periodicity SR comprises selecting an SR with a shortest periodicity that is not yet allocated or reserved for wireless communications devices with higher priority.

[0098] In some embodiments herein requesting the candidate radio access node 512 to send the cell SR configuration and receiving the cell SR configuration from the candidate radio access node 512 is performed as part of a UE Context Modification Procedure.

[0099] Action 502 may be performed in response to Action 501 , i.e. in response to triggering LTM of the wireless communications device 521 towards the candidate cell.

[0100] Action 503:

[0101] If TA determination is needed, the source radio access node 511 orders the UE 521 to transmit a random access preamble towards the candidate cell in action 503. In response to the order the UE 521 transmits the random access preamble towards the candidate cell.

[0102] Action 504:

[0103] The candidate radio access node 512 detects the preamble, calculates the TA and signals the TA value to the source radio access node 511 in action 504. The TA value is signaled via the gNB- CU 510.

[0104] Action 505:

[0105] In action 505, the source radio access node 511 transmits an indication of the cell SR configuration to the wireless communications device 521. For example, the source radio access node 512 sends a cell switch command to the UE 521 , including the earlier retrieved SR configuration.

[0106] Thus, the wireless communications device 521 receives, from the source radio access node 511, the indication of the cell SR configuration for the candidate cell served by the candidate radio access node 512.

[0107] The wireless communications device 521 may use an SR configured by the SR configuration for requesting UL-SCH resources for a new transmission in the candidate cell.

[0108] The indication of the cell SR configuration may be the cell SR configuration or an identifier of the SR configuration. In some embodiments herein the source radio access node 511 transmits a cell switch command including the indication of the cell SR configuration to the wireless communications device 521. In some embodiments herein the wireless communications device 521 receives the cell switch command including the indication of the cell SR configuration.

[0109] In some alternative embodiments, instead of signalling the actual scheduling request configuration to the UE 521, the source radio access node may send an indication of the SR configuration, such as an identifier of the SR configuration. For example, a scheduling request configuration Id and the logical channel Id may be sent in the cell switch command to reduce the amount of information to be signalled.

[0110] Action 506:

[0111] In action 506, the source radio access node 511 may inform the candidate radio access node 512 of the triggered cell switch. Action 507:

[0112] After the UE 521 acknowledges the cell switch command in action 505, it waits for the next SR opportunity in the candidate cell, and transmits the SR.

[0113] Action 508:

[0114] The candidate radio access node 512 detects the SR and provides the UE 521 with a UL grant on the PDCCH channel.

[0115] Action 509:

[0116] In action 509, the UE 521 transmits the RRC reconfiguration complete message in the granted PUSCH channel.

[0117] Action 5010:

[0118] The candidate radio access node 512 notifies the centralized radio access node 510 and the source radio access node 511 about the completion of the LTM procedure in action 5010.

[0119] To save the cell switch command size, as one alternative, it may be considered to provide the intended scheduling request configuration (with short periodicity) as part of a candidate cell configuration to the UE during a candidate cell preparation (see Figure 3 during actions 2 and 3). This scheduling request configuration may be identified with a scheduling request configuration Id but not connected to any logical channel group and logical channels. Then in cell switch command (Figure 5 message 505) the target DU may signal the scheduling request configuration Id together with the logical channel Id for the bearer where the scheduling request configuration should be used.

[0120] Figure 6 shows an example of the centralized radio access node 510.

[0121] Figure 7 shows an example of the source distributed radio access node 511.

[0122] The source radio access node 511 is adapted for LTM of the wireless communications device 521 in the wireless communications network 100. The source radio access node 511 is further adapted to trigger LTM of the wireless communications device 521 towards the candidate cell served by the candidate radio access node 512.

[0123] The source radio access node 511 is further adapted to, in response to triggering LTM of the wireless communications device 521 towards the candidate cell, request the candidate radio access node 512 to send the cell Scheduling Request, SR, configuration for the wireless communications device 121.

[0124] The source radio access node 511 is further adapted to receive the SR configuration from the candidate radio access node 112.

[0125] The source radio access node 511 is further adapted to transmit an indication of the SR configuration to the wireless communications device 121.

[0126] When the transmitted indication of the cell SR configuration is the cell SR configuration or the identifier of the SR configuration then the source radio access node 511 may be further adapted to transmit the cell switch command including the indication of the cell SR configuration to the wireless communications device 521.

[0127] In some embodiments herein the source radio access node 511 is further adapted to request the candidate radio access node 512 to send the cell SR configuration and receive the cell SR configuration from the candidate radio access node 512 as part of thellE Context Modification Procedure.

[0128] The source radio access node 511 may be further adapted to request the candidate radio access node 512 to send the cell SR configuration by sending the LTM cell switch request to the centralised radio access node 510 associated with the source radio access node 511 and further adapted to receive the cell SR configuration from the candidate radio access node 512 by receiving the cell SR configuration in the LTM cell switch response from the centralised radio access node 510.

[0129] In some embodiments herein the source radio access node 511 is further adapted to request the candidate radio access node 512 to send the SR configuration in response to triggering LTM of the wireless communications device 521 towards the candidate cell.

[0130] Figure 8 shows an example of the candidate distributed radio access node 512.

[0131] The candidate radio access node 512 is adapted for LTM of the wireless communications device 521 in the wireless communications network 100.

[0132] The candidate radio access node 511 is further adapted to receive the request to send the cell Scheduling Request, SR, configuration for the wireless communications device 521 from the source radio access node 511.

[0133] The candidate radio access node 511 is further adapted to transmit the SR configuration to the source radio access node 511. The candidate radio access node 511 may be further adapted to select, for the cell SR configuration, the shortest periodicity SR which is available for the wireless communications device 521.

[0134] In some embodiments herein the candidate radio access node 511 is adapted to select the shortest periodicity SR available for the wireless communications device 521 based on the priority of the wireless communications device 521.

[0135] In some embodiments herein the candidate radio access node 511 is adapted to select the shortest periodicity SR by selecting an SR with the shortest periodicity that is not yet allocated or reserved for wireless communications devices with higher priority.

[0136] Figure 9 shows an example of the UE 521.

[0137] The wireless communications device 521 is adapted for LTM in the wireless communications network. The wireless communications device 521 is further adapted to receive, from the source radio access node 511, an indication of the cell Scheduling Request, SR, configuration for the candidate cell served by the candidate radio access node 512.

[0138] The wireless communications device 521 is further adapted to use the SR configured by the SR configuration for requesting LIL-SCH resources for the new transmission in the candidate cell.

[0139] In some embodiments herein the indication of the cell SR configuration is the cell SR configuration or an identifier of the SR configuration. Then the wireless communications device 521 may be further adapted to receive the cell switch command including the indication of the cell SR configuration.

[0140] The centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, the UE 521 may comprise a respective input and output interface, IF, 606, 706, 806, 906 configured to communicate with each other, see Figures 6-9. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

[0141] The embodiments herein may be implemented through a respective processor or one or more processors, such as the respective processor 604, 704, 804, 904, of a processing circuitry in the centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, the UE 521 and depicted in Figures 6-9 together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the respective centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, and the UE 521. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the respective centralised radio access node 510, the source distributed radio access node 511, the candidate distributed radio access node 512, and the UE 521.

[0142] The centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, and the UE 521 may further comprise a respective memory 602, 702, 802, 902 comprising one or more memory units. The memory comprises instructions executable by the processor in the centralised radio access node 510, the source distributed radio access node 511, the candidate distributed radio access node 512, and the UE 521.

[0143] Each respective memory 602, 702, 802, 902 is arranged to be used to store e.g. information, data, configurations, and applications to perform the methods herein when being executed in the respective centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, and the UE 521.

[0144] In some embodiments, a respective computer program 603, 703, 803 and 903 comprises instructions, which when executed by the at least one processor, cause the at least one processor of the respective centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, and the UE 521 to perform the respective actions above.

[0145] In some embodiments, a respective carrier 605, 705, 805, 905 comprises the respective computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. Those skilled in the art will also appreciate that the units in the units described above may refer to a combination of analog and digital circuits, and / or one or more processors configured with software and / or firmware, e.g. stored in the respective centralised radio access node 510, the source distributed radio access node 511 , the candidate distributed radio access node 512, and the UE 521 described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

[0146] With reference to Figure 10, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211, such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, such as the source and target access node 111 , 112, AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first user equipment (UE) such as a Non-AP STA 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 such as a Non-AP STA in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

[0147] The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and / or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more subnetworks (not shown).

[0148] The communication system of Figure 9 as a whole enables connectivity between one of the connected UEs 3291, 3292 such as e.g. the UE 121, and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291 , 3292 are configured to communicate data and / or signaling via the OTT connection 3250, using the access network 3211, the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230. Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 11. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and / or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311 , which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

[0149] The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Figure 11) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Figure 11) of the telecommunication system and / or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

[0150] The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, applicationspecific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides. It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Figure 11 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291 , 3292 of Figure 10, respectively. This is to say, the inner workings of these entities may be as shown in Figure 11 and independently, the surrounding network topology may be that of Figure 10.

[0151] In Figure 11, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

[0152] The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the data rate, latency, power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime.

[0153] A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and / or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 3311 , 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

[0154] Figure 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 10 and Figure 11. For simplicity of the present disclosure, only drawing references to Figure 12 will be included in this section. In a first action 3410 of the method, the host computer provides user data. In an optional subaction 3411 of the first action 3410, the host computer provides the user data by executing a host application. In a second action 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third action 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth action 3440, the UE executes a client application associated with the host application executed by the host computer.

[0155] FIGURE 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 10 and Figure 11. For simplicity of the present disclosure, only drawing references to Figure 13 will be included in this section. In a first action 3510 of the method, the host computer provides user data. In an optional subaction (not shown) the host computer provides the user data by executing a host application. In a second action 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third action 3530, the UE receives the user data carried in the transmission.

[0156] FIGURE 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 10 and Figure 11. For simplicity of the present disclosure, only drawing references to Figure 14 will be included in this section. In an optional first action 3610 of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second action 3620, the UE provides user data. In an optional subaction 3621 of the second action 3620, the UE provides the user data by executing a client application. In a further optional subaction 3611 of the first action 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third subaction 3630, transmission of the user data to the host computer. In a fourth action 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

[0157] FIGURE 15 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figures 9 and 10. For simplicity of the present disclosure, only drawing references to Figure 15 will be included in this section. In an optional first action 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second action 3720, the base station initiates transmission of the received user data to the host computer. In a third action 3730, the host computer receives the user data carried in the transmission initiated by the base station.

[0158] In embodiments disclosed herein the non-limiting term UE refers to any type of wireless device communicating with a network node and / or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, vehicular to vehicular (V2V), machine type UE, MTC UE or UE capable of machine to machine (M2M) communication, PDA, tablet, mobile terminals, smart phone, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles etc.

[0159] The term radio access technology, or RAT, may refer to any RAT e.g. UTRA, E- UTRA, narrow band internet of things (NB-loT), WiFi, Bluetooth, next generation RAT, New Radio (NR), 4G, 5G, 6G, future generation RAT etc. Any of the equipment denoted by the term node, network node or radio network node may be capable of supporting a single or multiple RATs.

[0160] The term signal or radio signal used herein may be any physical signal or physical channel. Examples of DL physical signals are reference signal (RS) such as PSS, SSS, CSI-RS, DM RS signals in SS / PBCH block (SSB), discovery reference signal (DRS), CRS, PRS etc. RS may be periodic e.g. RS occasion carrying one or more RSs may occur with certain periodicity e.g. 20 ms, 40 ms etc. The RS may also be aperiodic. Each SSB carries NR-PSS, NR-SSS and NR-PBCH in 4 successive symbols. One or multiple SSBs are transmit in one SSB burst which is repeated with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms. The UE is configured with information about SSB on cells of certain carrier frequency by one or more SS / PBCH block measurement timing configuration (SMTC) configurations. The SMTC configuration comprising parameters such as SMTC periodicity, SMTC occasion length in time or duration, SMTC time offset wrt reference time (e.g. serving cell’s SFN) etc. Therefore, SMTC occasion may also occur with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms. Examples of UL physical signals are reference signal such as SRS, DM RS etc. The term physical channel refers to any channel carrying higher layer information e.g. data, control etc. Examples of physical channels are PBCH, NPBCH, PDCCH, PDSCH, sPUCCH, sPDSCH. sPUCCH. sPUSCH, MPDCCH, NPDCCH, NPDSCH, E-PDCCH, PUSCH, PUCCH, NPUSCH etc.

[0161] The term time resource used herein may correspond to any type of physical resource or radio resource expressed in terms of length of time. Examples of time resources are: symbol, time slot, subframe, radio frame, TTI, interleaving time, slot, subslot, mini-slot, etc. When using the word "comprise" or “comprising” it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

[0162] The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used.

[0163] NUMBERED EMBODIMENTS

[0164] 1. A method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device 521 , such as a UE, in a wireless communications network 100, performed by a source radio access node 511 , such as a source gNB-DU, the method comprises:

[0165] Triggering (501) LTM of the wireless communications device 521 towards a candidate cell served by a candidate radio access node 512, such as a candidate gNB-DU; requesting (502) the candidate radio access node 512 to send a cell Scheduling Request, SR, configuration for the wireless communications device 521 ; receiving (502) the SR configuration from the candidate radio access node 512; and transmitting (505) an indication of the SR configuration to the wireless communications device 521.

[0166] 2. A source radio access node 511, such as a gNB-DU, adapted for L1 / L2 Triggered Mobility, LTM, of a wireless communications device 521 in a wireless communications network. The source radio access node 511 is adapted to perform the method of embodiment 1.

Claims

CLAIMS1. A method for L1 / L2 T riggered Mobility, LTM, of a wireless communications device (521), in a wireless communications network (100), performed by a source radio access node (511), the method comprises: triggering (501) LTM of the wireless communications device (521) towards a candidate cell served by a candidate radio access node (512); requesting (502) the candidate radio access node (512) to send a cell Scheduling Request, SR, configuration for the wireless communications device (521); receiving (502) the cell SR configuration from the candidate radio access node (512); and transmitting (505) an indication of the cell SR configuration to the wireless communications device (521).

2. The method according to claim 1, wherein the transmitted indication of the cell SR configuration is the cell SR configuration or an identifier of the SR configuration and wherein the method further comprises transmitting (505) a cell switch command including the indication of the cell SR configuration to the wireless communications device (521).

3. The method according to claim 1 or 2, wherein requesting (502) the candidate radio access node (512) to send the cell SR configuration and receiving (502) the cell SR configuration from the candidate radio access node (512) is performed as part of a UE Context Modification Procedure.

4. The method according to any of the claims 1-3, wherein requesting (502) the candidate radio access node (512) to send the cell SR configuration is performed by sending an LTM cell switch request to a centralised radio access node (510) associated with the source radio access node (511) and wherein receiving (502) the cell SR configuration from the candidate radio access node (512) comprises receiving the cell SR configuration in an LTM cell switch response from the centralised radio access node (510).

5. The method according to any of the claims 1-4, wherein the source radio access node (511) and the candidate radio access node (512) each is a gNB-DU.

6. The method according to any of the claims 1-5, wherein requesting (502) the candidate radio access node (512) to send the SR configuration is performed in response to triggering LTM of the wireless communications device (521) towards the candidate cell.

7. The method according to any of the claims 1-6, wherein the SR is used by the wireless communications device (521) for requesting UpLink-Shared Channel, UL- SCH, resources for a new transmission in the candidate cell.

8. A source radio access node (511), adapted for L1 / L2 Triggered Mobility, LTM, of a wireless communications device 521 in a wireless communications network (100), wherein the source radio access node (511) is adapted to: trigger LTM of the wireless communications device (521) towards a candidate cell served by a candidate radio access node (512); in response to triggering LTM of the wireless communications device (521) towards the candidate cell, request the candidate radio access node (512) to send a cell Scheduling Request, SR, configuration for the wireless communications device (121); receive the SR configuration from the candidate radio access node (112); and transmit an indication of the SR configuration to the wireless communications device (121).

9. The source radio access node (511) according to claim 8, further configured to perform the method according to any of the claims 2-7.

10. A method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device (521) in a wireless communications network (100), performed by a candidate radio access node (512), the method comprises: receiving (502) a request to send a cell Scheduling Request, SR, configuration for the wireless communications device (521) from a source radio access node (511); transmitting (502) the SR configuration to the source radio access node (511).

11. The method according to claim 10, further comprising selecting, for the cell SR configuration, a shortest periodicity SR which is available for the wireless communications device (521).

12. The method according to claim 11 , wherein selecting the shortest periodicity SR available for the wireless communications device (521) is based on a priority of the wireless communications device (521).

13. The method according to claim 11 or 12, wherein selecting the shortest periodicity SR comprises selecting an SR with a shortest periodicity that is not yet allocated or reserved for wireless communications devices with higher priority.

14. A candidate radio access node (512), adapted for L1 / L2 Triggered Mobility, LTM, of a wireless communications device (521) in a wireless communications network (100), wherein the candidate radio access node (511) is adapted to: receive a request to send a cell Scheduling Request, SR, configuration for the wireless communications device (521) from a source radio access node (511); and transmit the SR configuration to the source radio access node (511).

15. The candidate radio access node (512) according to claim 14, further configured to perform the method according to any of the claims 11-13.

16. A method for L1 / L2 Triggered Mobility, LTM, of a wireless communications device (521) in a wireless communications network (100), performed by the wireless communications device (521), the method comprises: receiving (505), from a source radio access node (511), an indication of a cell Scheduling Request, SR, configuration for a candidate cell served by a candidate radio access node (512); and using an SR configured by the SR configuration for requesting UpLink-Shared Channel, LIL-SCH, resources for a new transmission in the candidate cell.

17. The method according to claim 16, wherein the indication of the cell SR configuration is the cell SR configuration or an identifier of the SR configuration and wherein the method further comprises receiving a cell switch command including the indication of the cell SR configuration.

18. A wireless communications device (521), adapted for L1 / L2 Triggered Mobility, LTM, in a wireless communications network, wherein the wireless communications device (521) is adapted to:receive, from a source radio access node (511), an indication of a cell Scheduling Request, SR, configuration for a candidate cell served by a candidate radio access node (512); and use an SR configured by the SR configuration for requesting UpLink-Shared Channel, LIL-SCH, resources for a new transmission in the candidate cell.

19. The wireless communications device (521) according to claim 18, wherein the indication of the cell SR configuration is the cell SR configuration or an identifier of the SR configuration and wherein the wireless communications device (521) is further adapted to receive a cell switch command including the indication of the cell SR configuration.

20. A computer program (703), comprising computer readable code units which when executed on a processor causes the computer to perform the method according to any one of claims 1-7.

21. A computer program (803), comprising computer readable code units which when executed on a processor causes the computer to perform the method according to any one of claims 10-13.

22. A computer program (903), comprising computer readable code units which when executed on a processor causes the computer to perform the method according to any one of claims 16-17.

23. A carrier (705, 805, 905) comprising the computer program according to any one of claims 20 to 22, wherein the carrier (705, 805, 905) is one of an electronic signal, an optical signal, a radio signal and a computer readable medium.

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