Method and apparatus for signalling radio link failure

Abstract

To provide an apparatus, a method, and a computer program for signalling radio link failure during conditional handover in a dual connectivity mode.SOLUTION: A communication system includes an apparatus 601 for performing a step of operating in a dual connectivity mode; a step of detecting a radio link failure (S-RLF) between the apparatus and a primary cell of a secondary cell group; and a step of providing information to a primary cell 603 of a master cell group on the basis of the radio link failure, the information being that the radio link failure occurred on the secondary cell group while waiting for a prepared conditional cell change from the primary cell of the secondary cell group to be fulfilled.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to an apparatus, method and computer program, particularly but not exclusively to an apparatus, method and computer program for signaling radio link failure, especially when master cell group fast recovery is configured. [Background technology]

[0002] A communication system may be viewed as a facility that enables a communication session between two or more entities, such as communication devices, base stations / access points, and / or other nodes, by providing a carrier between the various entities involved in the communication path. A communication system may be provided, for example, by a communication network and one or more compatible communication devices.

[0003] Access to the communication system may be via a suitable communication device or terminal. The communication device is provided with suitable signal transmission and reception equipment to enable communication, e.g. to enable access to the communication network or direct communication with other communication devices. The communication device may access a carrier provided by a station or access point and transmit and / or receive communications on the carrier.

[0004] A communication system and associated devices typically operate according to a given standard or specification that defines what the various entities associated with the system are permitted to do and how it should be accomplished. The communication protocols and / or parameters used for the connection are also typically defined. An example of a communication system is UTRAN (3G wireless). Another example of an architecture known as Long Term Evolution (LTE) or Universal Mobile Telecommunications System (UMTS) radio access technology. Another exemplary communication system is the so-called 5G wireless or New Radio (NR) access technology. Summary of the Invention

[0005] According to one aspect, there is provided an apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code, together with the at least one processor, causing the apparatus to operate in a dual connectivity mode, wherein the apparatus communicates with a master cell group comprising a primary cell and at least one secondary cell, and the apparatus communicates with a secondary cell group comprising a primary cell and at least one secondary cell; detecting a radio link failure between the apparatus and the primary cell of the secondary cell group; and providing information to the primary cell of the master cell group based on the radio link failure, the information being information that the radio link failure occurred on the secondary cell group while waiting for a ready condition cell change from the primary cell of the secondary cell group to be satisfied.

[0006] The at least one memory and the computer program code, together with the at least one processor, cause the device to at least transmit the information configured by the primary cell of the secondary cell group via its own wireless link or a wireless link of the primary cell of the master cell group.

[0007] The information may be further configured to inform the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration.

[0008] The information further configured to inform the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration may be a bitmap configured to indicate the at least one candidate cell in a measured cell list.

[0009] The information may be further configured to inform the primary cell of the master cell group of a condition change execution condition associated with at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0010] The information may be further configured to inform the primary cell of the master cell group of the signal measurement value of the primary cell of the secondary cell group, and the at least one candidate cell from the secondary cell group may be a difference between the primary cell and the at least one candidate cell of the secondary cell group, and an execution condition for each condition change for the condition cell change associated with the cell.

[0011] The at least one memory and the computer program code, together with the at least one processor, may be configured to cause the device to receive a radio resource control message from the primary cell of the master cell group, the radio resource control message comprising a cell identity of a prepared cell from the secondary cell group to change to, and to perform a cell change from the primary cell of the secondary cell group to the prepared cell of the secondary cell group based on the cell identity.

[0012] The at least one memory and the computer program code, together with the at least one processor, may be configured to cause the device to receive a radio resource control reconfiguration message from the primary cell of the master group, the radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell from the secondary cell group to be changed to, and to make a cell change from the primary cell of the secondary cell group to an unprepared cell of the secondary cell group based on the cell identity.

[0013] The device may be a user equipment.

[0014] According to a second aspect, there is provided an apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code, together with the processor, causing the apparatus to perform at least the steps of: communicating with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising the device and at least one secondary cell as a primary cell and communicating with a secondary cell group comprising the primary cell and at least one secondary cell; and receiving information from the further device based on a radio link failure between the at least one further device and the primary cell of the secondary cell group, the information being information that the radio link failure has occurred on the secondary cell group while waiting for a ready condition cell change from the primary cell of the secondary cell group to be fulfilled.

[0015] The information may be further configured to inform the device of an identity associated with at least one candidate cell from the secondary cell group for which the at least one further device has a valid condition modification configuration.

[0016] The information configured to inform the device of the identification value associated with the at least one candidate cell from the secondary cell group for which the at least one further device has a valid condition change configuration may be a bitmap configured to indicate the at least one candidate cell in a measurement cell list.

[0017] The information may be further configured to inform the device of a condition change execution condition associated with at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0018] The information may be further configured to inform the device of the signal measurement value of the primary cell of the secondary cell group, the at least one candidate cell from the secondary cell group, a difference between the primary cell and the at least one candidate cell of the secondary cell group, and an execution condition for each condition change for the condition cell change associated with the cell.

[0019] The at least one memory and the computer program code, together with the at least one processor, cause the device to at least: generate, based on the information, a radio resource control message comprising a cell identity of a prepared cell to change from the secondary cell group; and provide the radio resource control message to the at least one further device, wherein the at least one further device performs a cell change from the primary cell of the secondary cell group to the prepared cell from the secondary cell group based on the cell identity.

[0020] The at least one memory and the computer program code, together with the at least one processor, cause the device to: generate, based on the information, a radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell to change from the secondary cell group; and provide the radio resource control message to the at least one further device, wherein the at least one further device performs a cell change from the primary cell of the secondary cell group to an unprepared cell from the secondary cell group based on the cell identity.

[0021] The device may be a master node.

[0022] According to a third aspect, there is provided an apparatus comprising at least one processor and at least one memory including computer program code, the at least one memory and the computer program code, together with the at least one processor, causing the apparatus to: communicate with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising a primary cell and at least one secondary cell and communicating with a secondary cell group comprising the device as a primary cell and a secondary cell; and receiving information from the at least one further device for a cell change from the primary cell in the secondary cell group.

[0023] The at least one memory and the computer program code, together with the processor, cause the device to at least perform a step of receiving a message from the primary cell of the master cell group, the message comprising information based on a radio link failure between the primary cell of the secondary cell group and the at least one further device while waiting for a ready condition cell change from the primary cell of the secondary cell group to be met.

[0024] According to a fourth aspect, there is provided a method for an apparatus, comprising the steps of operating the apparatus in a dual connectivity mode, wherein the apparatus communicates with a master cell group comprising a primary cell and at least one cell, and the apparatus communicates with a secondary cell group comprising a primary cell and at least one secondary cell, and providing an indication based on a radio link failure between the apparatus and the primary cell of the secondary cell group, the information being that the radio link failure occurs on the secondary cell group while waiting for a ready condition cell change from the primary cell of the secondary cell group to be satisfied.

[0025] The method may further comprise the step of sending information configured by the primary cell of the secondary cell group via its own radio link or via a radio link of the primary cell of the master cell group.

[0026] The information may be further configured to inform the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration.

[0027] The information configured to inform the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration may be a bitmap configured to indicate the at least one candidate cell in a measured cell list.

[0028] The information may be further configured to inform the primary cell of the master cell group of a condition change execution condition associated with at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0029] The information may be further configured to inform the primary cell of the master cell group of the signal measurement value of the primary cell of the secondary cell group, and the at least one candidate cell from the secondary cell group may be a difference between the primary cell and the at least one candidate cell of the secondary cell group and respective condition change execution conditions for a condition cell change associated with the cell.

[0030] The method may comprise the steps of receiving a radio resource control message comprising a cell identity of a prepared cell from the secondary cell group to be changed, and performing a cell change from the primary cell of the secondary cell group to the prepared cell from the secondary cell group based on the cell identity.

[0031] The method may comprise the steps of receiving a radio resource control reconfiguration message from the primary cell of the master group comprising a cell identity of a cell other than a prepared cell from the secondary cell group to be changed to, and performing a change from the primary cell of the secondary cell group to a non-prepared cell from the secondary cell group based on the cell identity.

[0032] The device may be a user equipment.

[0033] According to a fifth aspect, there is provided a method for an apparatus, wherein the at least one memory and the computer program code together with the processor comprise: a step of communicating with at least one further device, wherein the further device operates in a dual connectivity mode communicating with a master cell group comprising the device and at least one secondary cell as a primary cell and communicating with a secondary cell group comprising the primary cell and at least one secondary cell; and a step of receiving information from the further device based on a radio link failure between the at least one further device and the primary cell of the secondary cell group, wherein the information is information that the radio link failure has occurred on the secondary cell group while waiting for a ready condition cell change from the primary cell of the secondary cell group to be fulfilled.

[0034] The information may further be configured to inform the device of an identification value associated with at least one candidate cell from the secondary cell group for which the at least one further device has a valid condition modification configuration.

[0035] The information configured to inform the device of the identification value associated with at least one candidate cell from the secondary cell group for which the at least one further device has a valid condition change configuration may be a bitmap configured to indicate the at least one candidate cell in a measured cell list.

[0036] The information may be further configured to inform the device of a condition change execution condition associated with at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0037] The information may be further configured to inform the device of the signal measurement value of the primary cell of the cell group, the at least one candidate cell from the secondary cell group, a difference between the primary cell and the at least one candidate cell of the secondary cell group and respective condition change execution conditions for a condition cell change associated with the cell.

[0038] The method comprises the steps of generating, based on the information, a radio resource control message comprising a cell identity of a prepared cell to change to from the secondary cell group, and providing the radio resource control message to the at least one further device, where the at least one further device performs a cell change from the secondary cell group to the prepared cell based on the cell identity.

[0039] The method may comprise the steps of generating, based on the information, a radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell to change from the secondary cell group, and providing the radio resource control message to the at least one further device, where the at least one further device performs a cell change from the primary cell of the secondary cell group to an unprepared cell from the secondary cell group based on the cell identity.

[0040] The device may be a master node.

[0041] According to a sixth aspect, a method for an apparatus is provided, the method comprising the steps of communicating with at least one further apparatus, the further apparatus operating in a dual connectivity mode communicating with a master cell group comprising a primary cell and at least one secondary cell and communicating with a secondary cell group comprising the apparatus as a primary cell and a secondary cell, and receiving information regarding a cell change from the primary cell of the secondary cell group from the at least one further apparatus.

[0042] The method may comprise a step of receiving a message from the primary cell of the master cell group, the message comprising information based on a radio link failure between the primary cell of the secondary cell group and the at least one further device while waiting for a ready condition cell change from the primary cell of the secondary cell group to be satisfied.

[0043] According to a seventh aspect, an apparatus is provided, comprising means for operating the apparatus in a dual connectivity mode, wherein the apparatus communicates with a master cell group having a primary cell and at least one secondary cell, and the apparatus communicates with a secondary cell group having a primary cell and at least one secondary cell, detecting a radio link failure between the apparatus and the primary cell of the secondary cell group, and providing information based on the radio link failure to the primary cell of the master cell group, the information being information that the radio link failure has occurred in the secondary cell group while waiting for a prepared condition cell change to be satisfied from the primary cell of the secondary cell group.

[0044] The means may be adapted to transmit information configured by the primary cell of the secondary cell group via its own radio link or via a radio link of the primary cell of the master cell group.

[0045] The information may be further configured to inform the primary cell of the master cell group of an identification value for at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration.

[0046] The information configured to inform the primary cell of the master cell group of an identification value for at least one candidate cell from the secondary cell group for which the device has a valid condition change configuration may be a bitmap configured to indicate the at least one candidate cell in a measured cell list.

[0047] The information may be further configured to inform the primary cell of the master cell group of a condition change execution condition related to at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0048] The information may be further configured to inform the primary cell of the master cell group of the signal measurement value of the primary cell of the secondary cell group, and the at least one candidate cell from the secondary cell group may be a difference between the primary cell and the at least one candidate cell of the secondary cell group and respective condition change execution conditions for a condition cell change associated with the cell.

[0049] The means comprises the steps of receiving a radio resource message from the primary cell of the master group comprising a prepared cell from the secondary cell group to be changed, and performing a cell change from the primary cell of the secondary cell group to the prepared cell of the secondary cell group based on the cell identification.

[0050] The means comprises the steps of receiving a radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell from the secondary cell group to change from the primary cell of the master group, and performing a cell change from the primary cell of the secondary cell group to a non-prepared cell from the secondary cell group based on the cell identity.

[0051] The device may be a user equipment.

[0052] According to an eighth aspect, the method comprises the steps of: communicating with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising the device and at least one secondary cell as a primary cell and communicating with a secondary cell group comprising the primary cell and at least one secondary cell; and receiving information from the at least one further device based on a radio link failure between the at least one further device and the primary cell of the secondary cell group, the information being information that the radio link failure has occurred on the secondary cell group while waiting for a ready condition cell change from the primary cell of the secondary cell group to be met.

[0053] The information may further be configured to inform the device of an identification value associated with at least one candidate cell from the secondary cell group for which the at least one further device has a valid condition modification configuration.

[0054] The at least one further device may be further configured to inform the device of the identification value associated with at least one candidate cell from the secondary cell group having a valid condition change configuration. The information may be a bitmap configured to indicate the at least one candidate cell in a measured cell list.

[0055] The information may be further configured to inform the device of a condition change execution condition related to at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

[0056] The information may be further configured to inform the device of the signal measurement value of the primary cell of the secondary cell group, the at least one candidate cell from the secondary cell group, a difference between the primary cell and the at least one candidate cell of the secondary cell group and respective condition change execution conditions for the condition cell change associated with the cell.

[0057] The means comprises the steps of generating, based on the information, a radio resource control message comprising a cell identity of a prepared cell from the secondary cell group to change to, and providing the radio resource control message to the at least one further device, the at least one further device performing a cell change from the primary cell of the secondary cell group to a non-prepared cell from the secondary cell group based on the cell identity.

[0058] The means comprises the steps of generating, based on the information, a radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell from the secondary cell group to be changed to, and providing the radio resource control message to the at least one further device, wherein the at least one further device performs a cell change from the primary cell of the secondary cell group to a non-prepared cell of the secondary cell group based on the cell identity.

[0059] The device may be a master node.

[0060] According to a ninth aspect, an apparatus is provided comprising means for communicating with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising a primary cell and at least one secondary cell and with a secondary cell group comprising the device as a primary cell and a secondary cell, and receiving information regarding a cell change from the primary cell of the secondary cell group from the at least one further device.

[0061] The means comprises a step of receiving a message from the primary cell of the master cell group, the message comprising information based on a radio link failure between the primary cell of the secondary cell group and the at least one further device while waiting for a ready condition cell change from the primary cell of the secondary cell group to be met.

[0062] According to a tenth aspect, there is provided a non-transitory computer-readable storage medium comprising computer-readable instructions which, when executed by at least one processor, cause the device to operate in a dual connectivity mode, wherein the device communicates with a master cell group comprising a primary cell and at least one secondary cell, and the device communicates with a secondary cell group comprising a primary cell and at least one secondary cell; detect a radio link failure between the device and the primary cell of the secondary cell group; and provide information based on the primary cell of the master cell group, wherein the information is information that the radio link failure occurs on the secondary cell group while waiting for a prepared condition cell change to be satisfied from the primary cell of the secondary cell group.

[0063] According to an eleventh aspect, there is provided a non-transitory computer storage medium comprising computer-readable instructions which, when executed by at least one processor, cause an apparatus to: communicate with at least one further apparatus, the further apparatus operating in a dual connectivity mode communicating with a master cell group comprising the apparatus and at least one secondary cell as a primary cell and communicating with a secondary cell group comprising the primary cell and at least one secondary cell; and receiving information from the at least one further apparatus based on a radio link failure between the at least one further apparatus and the primary cell of the secondary cell group, the information being information that the radio link failure occurs on the secondary cell group while waiting for a prepared cell change to be fulfilled from the primary cell of the secondary cell group.

[0064] According to a twelfth aspect, there is provided a non-transitory computer-readable storage medium comprising computer-readable instructions which, when executed by at least one processor, cause the device to communicate with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising a primary cell and at least one secondary cell and with a secondary cell group comprising the device as a primary cell and a secondary cell, and receiving from the at least one device information regarding a cell change from the primary cell of the secondary cell group.

[0065] According to a thirteenth aspect, there is provided a computer program comprising instructions causing the device to perform at least the steps of: operating the device in a dual connectivity mode, wherein the device communicates with a master cell group having a primary cell and at least one secondary cell, and the device communicates with a secondary cell group having the primary cell and at least one secondary cell group; detecting a radio link failure between the device and the primary cell of the secondary cell group; and providing information based on the radio link failure to the primary cell of the master cell group, wherein the information is information that the radio link failure occurs on the secondary cell group while waiting for a prepared condition cell change to be satisfied from the primary cell of the secondary cell group.

[0066] According to a fourteenth aspect, there is provided a computer program comprising instructions causing an apparatus to perform at least the following steps: communicate with at least one further apparatus, the further apparatus operating in a dual connectivity mode communicating with a master cell group comprising the apparatus and at least one secondary cell as a primary cell and communicating with a secondary cell group comprising the primary cell and at least one secondary cell; and receive information from the at least one further apparatus based on a radio link failure between the at least one further apparatus and the primary cell of the secondary cell group, the information being information that the radio link failure has occurred on the secondary cell group while waiting for a prepared condition cell change to be satisfied from the primary cell of the secondary cell group.

[0067] According to a fifteenth aspect, a computer program comprising instructions, comprising at least the steps of: communicating with at least one further device, the further device operating in a dual connectivity mode communicating with a master cell group comprising a primary cell and at least one secondary cell, and communicating with a secondary cell group comprising the device as a primary cell and a secondary cell, and receiving from the at least one further device information regarding a cell change from the primary cell of the secondary cell group. In the above, many different aspects have been described. It should be understood that further aspects may be provided by a combination of any two or more of the above-mentioned aspects.

[0068] Various other aspects are also described in the following detailed description and the appended claims.

[0069] Some illustrative embodiments will now be described in further detail, by way of example only, with reference to the following examples and the accompanying drawings. [Brief description of the drawings]

[0070] [Figure 1] FIG. 1 shows a schematic diagram of a 5G system (5GS). [Diagram 2] FIG. 2 shows a schematic diagram of the control device. [Diagram 3] FIG. 3 shows a schematic diagram of a terminal. [Figure 4] FIG. 4 shows a signaling diagram of a process for performing a conditional handover. [Diagram 5] FIG. 5 shows a signaling diagram of a process for performing a conditional PS cell change triggered by an SN. [Figure 6] FIG. 6 illustrates a signaling diagram of a process for secondary cell group failure messaging in accordance with some embodiments. [Figure 7] FIG. 7 shows a schematic diagram of a non-volatile memory medium storing instructions that, when executed by a processor, enable the processor to perform one or more of the steps of the process or method of any of FIGS. 4-6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] In the following, some embodiments are described with reference to a mobile communication device capable of communicating via a wireless cellular system, and a mobile communication system serving such a mobile communication device. Before describing the exemplary embodiments in detail, some general principles of wireless communication systems, their access systems, and mobile communication devices are briefly described with reference to Figures 1, 2, and 3 to aid in understanding the technology underlying the described examples.

[0072] Figure 1 shows a schematic diagram of a 5G system (5GS). The 5GS may be composed of a terminal or user equipment (UE), a 5G radio access network (5GRAN) or a next-generation radio access network (NG-RAN), a 5G core network (5GC), one or more application functions (AFs), and one or more data networks (DNs).

[0073] A 5G-RAN may comprise one or more gNodeBs (GNBs) or one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) centralized unit functions.

[0074] 5GC may include the following entities: Network Slice Selection Function (NSSF), Network Exposure Function, Network Repository Function (NRF), Policy Control Function (PCF), Unified Data Management (UDM), Application Function (AF), Authentication Server Function (AUSF), Access and Mobility Management Function (AMF), and Session Management Function (SMF).

[0075] FIG. 2 shows an example of a control device 200 that controls the functions of the 5GRAN or 5GC shown in FIG. 1. The control device may include at least one random access memory (RAM) 211a, at least one read-only memory (ROM) 211b, at least one processor 212, 213, and an input / output interface 214. The at least one processor 212, 213 may be coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute appropriate software code 215. The software code 215 may, for example, enable execution of one or more steps for executing one or more of the present aspects. The software code 215 may be stored in the ROM 211b. The control device 200 may be interconnected with other control devices 200 that control other functions of the 5GRAN or 5GC. In some embodiments, each function of the 5GRAN or 5GC includes a control device 200. In alternative embodiments, two or more functions of the 5GRAN or 5GC may share a control device.

[0076] FIG. 3 illustrates an example of a terminal 300, such as the terminal illustrated in FIG. 1. The terminal 300 may be provided by any device capable of transmitting and receiving wireless signals. Non-limiting examples include user equipment, mobile stations (MS) or mobile devices, such as mobile phones or what are known as "smartphones", computers with wireless interface cards or other wireless interface facilities (e.g., USB dongles), personal digital assistants (PDAs) or tablets with wireless communication capabilities, machine type communication (MTC) devices, Internet of Things (IoT) type communication devices, or any combination thereof. The terminal 300 may provide, for example, communication of data for carrying out the communication. The communication may be one or more of voice, electronic mail (email), text messages, multimedia, data, machine data, and the like.

[0077] The terminal 300 may receive signals via a radio or wireless interface 307 via a suitable device for receiving and may transmit signals via a suitable device for transmitting radio signals. In Fig. 3, a transceiver device is indicated diagrammatically by a block 306. The transceiver device 306 may be provided for example by a radio part and an associated antenna device. The antenna device may be located inside or outside the mobile device.

[0078] The terminal 300 comprises at least one processor 301, at least one memory ROM 302a, at least one RAM 302b, and possible other components 303 for use in software and hardware-assisted execution of tasks designed to perform operations including control of access to and communication with the access system and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute appropriate software code 308. The software code 308 may, for example, enable one or more of the present aspects to be performed. The software code 308 may be stored in the ROM 302a.

[0079] The processor, memory and other associated controls may be provided on a suitable circuit board and / or within a chipset. This feature is indicated by reference numeral 304. The device may optionally have a user interface such as a keypad 305, a touch-sensitive screen or pad, or a combination thereof. Optionally, one or more of a display, a speaker and a microphone may be provided depending on the type of device.

[0080] One or more of the following aspects relate to mobility in a cellular / mobile communication network, such as an LTE network or an NR network.

[0081] Conditional Handover (CHO) is a feature defined in two separate Work Items (WIs) on mobility enhancements for both LTE and NR in Release 16. Conditional Handover is similar to Baseline Handover (BHO) and an example is shown in Figure 4.

[0082] In this example, a system is shown that includes a UE 401, a source node (SN) 403, a target node (TN) 405, other potential target nodes 407, a serving gateway / user plane function (S-GW / UPF) 409, and a mobile management entity / access and mobility management function (MME / AMF) 411. In this example, the user equipment 401 is configured to be handed over to the target node 405 by the source node 403 as part of a conditional handover.

[0083] The first action is to trigger the UE 401 (based on an event) to send a measurement report from the UE 401 to a source node 403, as shown in step 400 of FIG.

[0084] The source node receiving the measurement report may then be configured to perform a conditional handover decision based on the measurement report, as shown in FIG. 4 by step 402, where the source node hands over to another node (either the target node 405 or another potential target node 407).

[0085] The source node is then configured to prepare one or more potential target nodes, which may be performed by sending a CHO request to the potential target nodes, as illustrated in FIG. 4 by steps 404 (CHO request to target node) and 406 (CHO request to other potential target nodes).

[0086] The message is received and admission control is performed as shown in FIG. 4 by step 408 (admission control in the target node) and step 410 (admission control in other potential target nodes).

[0087] Additionally, the potential target node may be configured to send an acknowledgement message back to the source node 403, as shown in FIG. 4 by step 412 (CHO request acknowledgement from target node) and step 414 (CHO request acknowledgement from other potential target nodes).

[0088] Upon receiving the acknowledgement message, the source node 403 is then configured to generate and send a radio resource control (RRC) reconfiguration message, or handover command, to the UE 401, as shown in FIG.

[0089] In contrast to Baseline Handover (BHO), where the UE immediately accesses the target cell to complete the handover, in the case of Conditional Handover (CHO), the UE 401 is configured to only access the target cell once an additional CHO execution condition expires. In other words, the HO preparation and execution phases are decoupled. The condition is set in the HO command, for example by the source node. Thus, for example, the UE is configured to evaluate the CHO condition as shown in FIG. 4 by step 418.

[0090] While the CHO condition is being evaluated by the UE, data may still be exchanged between the UE 401 and the source node 403, as shown in step 420 of FIG.

[0091] Once the CHO condition is met for the target node, the transmission and reception of user data between the UE 401 and the source node 403 is stopped, as shown in step 422 of FIG.

[0092] Further, the UE 401 is configured to transmit a Physical Random Access Channel (PRACH) preamble to the target node 405, as shown in step 424 of FIG.

[0093] A random access channel (RACH) response from the target node 405 is then sent back to the UE 401, as shown in FIG.

[0094] A radio resource control (RRC) reconfiguration complete message is then sent from the UE 401 to the target node 405, as shown in FIG.

[0095] A handover success message is sent from the target node 405 to the source node 403, as shown in step 430 of FIG.

[0096] The source node 403 is then configured to stop transmitting / receiving data to / from the UE 401 and initiate a data forwarding operation for any received data, as shown in FIG. 4 by step 432.

[0097] Next, a sequence number (SN) status transfer message is transferred from the source node 403 to the target node 405 as shown in FIG.

[0098] Further, data transfer between the source node 403 and the target node 405 is performed as shown in step 436 of FIG.

[0099] The source node 403 further releases the CHO preparations of other potential target nodes 407 as shown in FIG.

[0100] The path switch information is then passed to the core network as shown in FIG.

[0101] In this way, CHO allows the HO command to be sent very early when the UE is still safe in the source cell, without jeopardizing the access in the target cell and the stability of its radio link, i.e., conditional handover provides mobility robustness.

[0102] CHO can also be extended for dual connectivity situations, where there is a Master Cell Group (MCG) with a Primary Cell (PCell) and one or more Secondary Cells (SCells), and a Secondary Cell Group (SCG) with a Primary Cell (PSCell) and one or more Secondary Cells (PSCells).

[0103] In these situations, the conditional handover functionality may be extended for the primary cell in the secondary group (PSCell) addition / modification procedure related to the Multi-RAT Dual Connectivity (MR-DC) (non-standalone) scenario, which may be defined as Conditional PSCell Change (CPC).

[0104] The functionality of CPC is similar to CHO in standalone architecture as shown in Figure 4, except that a conditional execution is applied for the change of PSCell based on measurements on a secondary cell group (SCG). The radio link between the UE and the master node (MN) is available during the execution of the conditional PSCell change, which in this case can be used by the UE for radio resource control (RRC) signaling, whereas in the case of CHO in standalone architecture, the radio link between the UE and the network is completely interrupted from the start of the CHO execution until its completion. Furthermore, in case of a failure scenario during the conditional PSCell change, the failure can be communicated to the master node in this case.

[0105] For example, with respect to FIG. 5, an exemplary Condition PSCell Change (CPC) is triggered by a secondary node using Signaling Radio Bearer 3 (SRB3).

[0106] Thus, for example, the UE 501 is configured to transmit a measurement report to a source primary cell in a secondary group (S-PSCell) 505, as illustrated in FIG.

[0107] An RRC connection reconfiguration message is then sent back from the S-PSCell 505 to the UE 501, as shown in FIG. 5 by step 502.

[0108] The UE is then configured to evaluate the CPC conditions, as shown in Figure 5 by step 504. While the evaluation is performed, data may be transferred between the UE 501 and the master node 503. In this case, data transmission via the source secondary node is also possible.

[0109] The CPC condition is satisfied for T-PSCell 507, as shown in step 506 of FIG.

[0110] Once the CPC condition is met, a random access procedure (similar to the CHO condition being met as shown in Figure 4) is performed between the UE 501 and the target primary cell in the secondary group (T-PSCell) 507, as shown in step 508 of Figure 5. During this procedure, data transfer between the UE and the master node is still possible.

[0111] Once complete, the UE 501 is then configured to send an RRC Connection Reconfiguration Complete message to the T-PSCell 507, as shown in FIG. 5 by step 510.

[0112] The basic PSCell change scenario initiated by the secondary node (SN) without the involvement of the master node (MN), when the UE experiences a secondary group-radio link failure (S-RLF) due to various reasons including timer failure (T310 expiry), the steps of the signaling procedure are as follows:

[0113] The UE suspends the Secondary Cell Group (SCG) radio bearers and resets the Secondary Cell Group-Medium Access Control (SCG-MAC).

[0114] The UE sends the SCG-Failure information in a radio resource control (RRC) message to the master node (MN) over the MN radio link, which comprises the failure cause and the latest measurement report per source node (SN) measurement configuration.

[0115] The MN may forward the SCG-Failure Information to the SN via a SN-Modify Request message to inform the SN of the failure scenario so that the SN can stop scheduling to the UE.

[0116] Then, when the master node (MN) receives the SCG-Failure Indication message from the UE, two actions are possible at the MN.

[0117] If the measurement results include cells served by the same secondary node (SN), the master node (MN) may be configured to send an SN-Modify Request to inform the SN of the SCG failure and enable the SN to take further actions which will be signaled via the MN.

[0118] And if the measurement result includes cells served by other secondary nodes (SNs), the master node (MN) can initiate the SN cell change procedure by triggering an SN addition procedure without forwarding the SCG failure information to the source SN, where the MN has already decided to take action to address the failure.

[0119] In case an SCG failure occurs after the UE receives a Conditional PSCell Change (CPC) command from the SN, the SCG failure information indication needs to be improved to allow the MN to take appropriate actions for the failure, taking into account also the condition of the conditional PSCell change and the prepared cell information. Even if the MN decides to trigger an immediate PSCell change to the prepared cell, the MN needs to know this additional information.

[0120] As mentioned above, the SCG failure information used to provide information about the failure of the SCG does not include any indication about the prepared PSCells, in other words, there is no information about the PSCells that were prepared by the SN without the involvement of the MN and for which the UE received its condition PSCell change configuration.

[0121] For example, an SCG failure information message is shown below for NR SCG failure, and a similar message exists for LTE SCG failure.

[0122] --ASN1START --TAG-SCGFAILUREINFORMATION-START SCGFailureInformation::= SEQUENCE{ criticalExtensions CHOICE scgFailureInformation SCGFailureInformation-IEs, criticalExtensionsFuture SEQUENCE {} } } SCGFailureInformation-IEs::= SEQUENCE{ failureReportSCG FailureReportSCG OPTIONAL, nonCriticalExtension SEQUENCE{} OPTIONAL } FailureReportSCG::= SEQUENCE { failureType ENUMERATED t310-Expiry, randomAccessProblem, rlc-MaxNumRetx, synchReconfigFailureSCG,scg-ReconfigFailure, srb3-IntegrityFailure,spare2,spare1}, measResultFreqList MeasResultFreqList OPTIONAL, measResultSCG-Failure OCTET STRING(CONTAINING MeasResultSCG- Failure) OPTIONAL, … } MeasResultFreqList::= SEQUENCE (SIZE (1..maxFreq)) OF MeasResult2NR -- TAG-SCGFAILUREINFORMATION-STOP -- ASN1STOP [Table 1]

[0123] The concept discussed in some embodiments is a signaling procedure for Secondary Cell-Radio Link Failure (S-RLF) reporting when the UE has a condition Primary Cell-in-Secondary Group (PSCell) change already configured by a Secondary Node (SN) without the involvement of a Master Node (MN).

[0124] Thus, in some embodiments, detecting an S-RLF when there is a valid pending condition PSCell change execution command, the UE sends an SCG failure indication message to the MN with the following changes:

[0125] The SCG-Failure Indication message includes additional information to inform the MN that a conditional change of the PSCell is already prepared. This information may be represented in some embodiments by a parameter / flag called the conditional PSCell-Change-pending parameter / flag. In other words, the UE has received a conditional PSCell change configuration but has not yet executed the change (e.g., an S-RLF occurred while waiting for the PSCell change execution condition to be met).

[0126] The SCG failure indication message may also be configured to indicate cell identities of prepared candidate PSCells for which the UE has a valid change condition configuration. In some embodiments, this may be provided as a bitmap indicating the prepared cells in the measurement cell list. In some embodiments, the MN uses this information to decide whether to trigger a SN change to a non-prepared cell or perform a PSCell change to a prepared cell. Herein, the MN may also use the signal strength difference between the prepared and non-prepared cells.

[0127] The UE may also be configured to include additional information regarding the condition PSCell change execution condition for each prepared PSCell along with the measurements of the source PSCell and the prepared PSCell. Alternatively, in some embodiments, to simplify signaling, the SCG failure information may include a delta between the measurement results and the execution condition for each of the measured cells. This information may be used by the MN to select a new PSCell within the prepared cells.

[0128] In some embodiments, upon receipt of this information, the MN may be configured to decide to send an RRC message including the cell identity of the prepared cell for which an immediate PSCell change should be triggered and to inform the SN that a conditional cell change execution has been triggered.

[0129] Additionally, in some embodiments, the MN may initiate a PSCell change towards an unprepared target cell and send a new RRC reconfiguration message, in which case the MN informs the SN to cancel the conditional PSCell preparation as part of an inter-node message carrying SCG failure information.

[0130] In some embodiments, the modified SCG failure indication reporting can be controlled by the SN via RRC signaling, which is applicable only if the condition cell change is not known to the MN, otherwise the legacy SCG failure indication can continue.

[0131] A message sequence illustrating a modified SCG fault indication procedure triggered on the S-RLF when a condition PSCell change is pending is shown with respect to FIG.

[0132] Thus, for example, a UE 601, a master node (MN) 603, and a secondary node (SN) 605 are configured to operate in dual connectivity mode, as illustrated in FIG.

[0133] Then, as part of the condition PSCell change with the intra-SN target cell, the secondary node 605 is configured to send an RRC reconfiguration message to the UE, as shown in FIG. 6 by step 602.

[0134] At some point, the UE is configured to detect a Secondary Cell Radio Link Failure (S-RLF), as shown in FIG.

[0135] This causes the UE 601 to generate and send a secondary cell group failure message (SCG failure message) to the master node 603, as shown in step 608 of Figure 6. The SCG failure message contains information (and is implemented as the following parameters):

[0136] Information indicating whether a conditional PSCell change is pending (CPC pending), in other words, whether the UE has a valid conditional PSCell change configuration (or the execution condition is not yet met) while S-RLF is detected.

[0137] This is information (prepared cell information) indicating the cell identity (physical or global cell identity, PCI) of a PSCell prepared for executing a conditional PSCell change.

[0138] This is information (Cpsc-condition) that indicates the condition PSCell execution condition of each target cell prepared in the UE.

[0139] And information (measurement results) that may include measurement values ​​of the source PSCell and the prepared target PSCell.

[0140] In some embodiments (and may be implemented as an alternative to the parameter Cpsc-condition), the message may further comprise information (Cpsc-condition-diff) including a difference between the measurement result and the execution condition of each of the measured cells. For example, the UE may be configured to indicate whether the condition was met at all (at least temporarily, not necessarily for the duration of time until the trigger). In some embodiments, if an A3 event is configured for condition PSCell change (A3 event is when the target PSCell is offset better than the source PSCell), the UE may include information in the message indicating the difference between the measurement value of the source PSCell and the measurement value of the target PSCell. Furthermore, in some embodiments, if an A5 event is configured for condition PSCell change (A5 event is when the source PSCell becomes worse than threshold 1 and the target PSCell becomes better than threshold 2), the UE may be configured to include information in the message indicating the difference between the measurement value of the target PSCell and threshold 2.

[0141] The MN that receives the SCG failure information message is configured to determine a target cell based on the prepared cells in the measurement results. In some embodiments, the MN is configured to use the prepared cell information and the Cpsc-condition-diff for target cell selection. This is illustrated in FIG. 6 by step 608.

[0142] In some embodiments, the master node is configured to generate and send an RRC reconfiguration message to the UE 601. The RRC reconfiguration message may comprise controls to perform an immediate PSCell change for a prepared cell identification, as shown in Figure 6 by step 610. In some further embodiments, the RRC reconfiguration message may comprise controls to perform a PSCell change to an unprepared inter-SN target cell, as shown in Figure 6 by step 612.

[0143] In some embodiments, where the RRC reconfiguration message may include controls to perform a PSCell change to an unprepared inter-SN target cell, the master node (MN) 603 is further configured to generate and send an SN modification request message to the secondary node (SN) 605, as shown in Figure 6 by step 614. In some embodiments, the SN modification request message comprises an SCG failure indicator and further a flag or parameter indicating that a PSCell change is triggered.

[0144] In such an embodiment, the failure message can provide the MN with additional information regarding the prepared target PSCells when an S-RLF is detected. Furthermore, using the extended information in the SCG failure report, the MN can react immediately by triggering the execution of the conditional PSCell change without waiting for the SN to respond back using the MN radio link, which saves additional signaling over the Xn interface and reduces the delay in handling the S-RLF. Furthermore, in some embodiments, due to the extended SCG failure information, the NW can release pre-reserved resources in candidate PSCells that are no longer considered (e.g., based on reported measurements of prepared PSCells).

[0145] FIG. 7 shows a schematic diagram of non-volatile memory media 1300a (e.g., a computer disk (CD) or digital versatile disk (DVD)) and 1300b (e.g., a universal serial bus (USB) memory stick) that store instructions and / or parameters 1302 that, when executed by a processor, enable the processor to perform one or more of the steps of the processes or methods of FIGS. 4-6.

[0146] It should be noted that embodiments of the present invention may be implemented as a circuit, software, hardware, application logic, or a combination of software, hardware, and application logic. In an exemplary embodiment, the application logic, software, or instruction set is maintained on any one of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any medium or means that can contain, store, communicate, propagate, or carry instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer or smartphone, or user equipment.

[0147] As used in this application, the term "circuit" refers to all of the following: (a) a hardware-only circuit implementation (such as an implementation in analog and / or digital circuitry only); (b) a combination of circuitry and software (and / or firmware), including (where applicable): (i) a processor or (ii) portions of a processor / software (including digital signal processors), software, and memory(s) that cooperate to cause a device such as a mobile phone or server to perform various functions; and (c) a circuit such as a microprocessor or portion of a microprocessor that requires software or firmware for operation, even if the software or firmware is not physically present. This definition of "circuit" applies to all uses of the term in this application, including any claims. As a further example, the term "circuit" as used in this application also encompasses merely a processor (or processors) or portion of a processor and its (their) associated software and / or firmware implementation. The term "circuit" would also cover, for example, a baseband integrated circuit or an application processor integrated circuit for a mobile phone, or similar integrated circuits in a server, cellular network device, or other network device, if applicable to a particular claim element.

[0148] The described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. Those skilled in the art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in an embodiment that may not be present in all embodiments of the invention. Those skilled in the art will readily appreciate that the above-described invention may be implemented in a different sequence of steps and / or with hardware elements in different configurations than those disclosed. Thus, while the invention has been described based on these preferred embodiments, it will be apparent to those skilled in the art that certain modifications, variations, and alternative constructions will become apparent while remaining within the spirit and scope of the invention.

Claims

1. operating a user equipment in a dual connectivity mode, wherein the user equipment communicates with a master cell group comprising a primary cell and at least one secondary cell, and the user equipment communicates with a secondary cell group comprising the primary cell and at least one secondary cell; detecting a radio link failure between the user equipment and the primary cell of the secondary cell group; providing information based on the radio link failure to the primary cell of the master cell group; 1. A user equipment comprising: means configured to: When there is a pending valid conditional primary cell, PSCell, change execution command for the secondary cell group, the information indicates that the radio link failure occurred on the secondary cell group while waiting for the conditional primary cell, PSCell, change execution command for the secondary cell group to be satisfied.

2. 2. The user equipment of claim 1, wherein the information is configured by the primary cell of the secondary cell group, and the means is configured to at least cause the user equipment to transmit the information via a radio link of the primary cell of the master cell group.

3. 3. The user equipment of claim 1, wherein the information is further configured to notify the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the user equipment has a valid condition change configuration.

4. 4. The user equipment of claim 3, wherein the information configured to notify the primary cell of the master cell group of an identification value associated with at least one candidate cell from the secondary cell group for which the user equipment has a valid condition change configuration is a bitmap configured to indicate the at least one candidate cell in a measured cell list.

5. The user equipment according to any one of claims 1 to 4, wherein the information is further configured to notify the primary cell of the master cell group of a condition change execution condition related to at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

6. 6. The user equipment of claim 5, wherein the information is further configured to notify the primary cell of the master cell group of a difference between the signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group and the condition change execution condition related to the at least one candidate cell from the secondary cell group.

7. The means comprises: receiving, from the primary cell of the master cell group, a radio resource control message comprising a cell identity of a prepared cell from the secondary cell group for which the user equipment has a valid modification condition configuration; performing a cell change from the primary cell of the secondary cell group to the prepared cell from the secondary cell group based on the cell identification; The user equipment according to any one of claims 1 to 6, configured to cause the user equipment to at least:

8. The means comprises: receiving, from the primary cell of the master group, a radio resource control reconfiguration message comprising a cell identity of a cell other than a prepared cell from the secondary cell group for which the user equipment has a valid modification condition configuration; performing a cell change from the primary cell of the secondary cell group to an unprepared cell from the secondary cell group for which the user equipment does not have a valid condition change configuration based on the cell identity; The user equipment according to any one of claims 1 to 6, wherein the user equipment is configured to at least:

9. communicating with a user equipment, the user equipment being configured to operate in a dual connectivity mode and communicating with a master cell group provided by a base station, the master cell group comprising a primary cell and at least one secondary cell, and with a secondary cell group comprising the primary cell and at least one secondary cell; receiving information from the user equipment based on a radio link failure between the user equipment and the primary cell of the secondary cell group; 1. A base station comprising: means configured to: When there is a pending valid conditional primary cell, PSCell, change execution command for the secondary cell group, the information indicates that the radio link failure occurred on the secondary cell group while waiting for the conditional primary cell, PSCell, change execution command for the secondary cell group to be satisfied.

10. 10. The base station of claim 9, wherein the information is further configured to inform the base station of an identification value associated with at least one candidate cell from the secondary cell group for which the user equipment has a valid condition change configuration.

11. 11. The base station according to claim 9 or 10, wherein the information is further configured to inform the base station of a condition change execution condition relating to at least one candidate cell from the secondary cell group and signal measurement values ​​of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group.

12. 12. The base station of claim 11, wherein the information is further configured to inform the base station of a difference between the signal measurements of the primary cell of the secondary cell group and the at least one candidate cell from the secondary cell group and respective condition change execution conditions for the condition cell change associated with the at least one candidate cell from the secondary cell group.

13. The means comprises: generating, based on the information, a radio resource control message comprising a cell identity of a prepared cell from the secondary cell group for which the user equipment has an effective condition change configuration; providing the radio resource control message to the user equipment such that the user equipment is configured to perform a cell change from the primary cell of the secondary cell group to the prepared cell from the secondary cell group based on the cell identity; The base station according to any one of claims 9 to 12, wherein the base station at least:

14. The base station according to any one of claims 9 to 13, wherein the base station is a master node.

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