Backup conditional switching configuration with single connection

Abstract

An apparatus comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed, cause the apparatus, together with the at least one processor, to: determine that a conditional switching condition is satisfied; and selecting a conditional handover configuration from the at least one conditional handover configuration to perform a conditional handover based on a determination that the conditional handover condition is satisfied and based at least in part on the priority information.

Description

Background Technical Field

[0001] Examples and non - limiting embodiments generally relate to wireless communication, and more particularly, to conditional handover. Brief Description of Prior Developments

[0002] For user equipment in a wireless network, the conditional handover process is generally known. Summary of the Invention

[0003] The following summary of the invention is for illustrative purposes only. The summary of the invention is not intended to limit the scope of the claims.

[0004] According to one aspect, an apparatus may be utilized to provide an example embodiment, the apparatus including: at least one processor; and at least one non - transitory memory storing instructions that, when executed in conjunction with the at least one processor, cause the apparatus to: determine that a conditional handover condition is met; and based on the determination that the conditional handover condition is met and at least in part based on priority information, select a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover.

[0005] According to another aspect, an example method may be provided, including: determining, by a user equipment, that a conditional handover condition is met; and based on the determination that the conditional handover condition is met and at least in part based on priority information, selecting, by the user equipment, a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover.

[0006] According to another aspect, a non - transitory program storage device may be utilized to provide an example embodiment, the non - transitory program storage device being readable by an apparatus and tangibly embodying a program of instructions that are executable by the apparatus to perform operations. The operations include: determining that a conditional handover condition is met; and based on the determination that the conditional handover condition is met and at least in part based on priority information, selecting a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover.

[0007] According to another aspect, an apparatus may be utilized to provide an example embodiment, the apparatus including: at least one processor; and at least one non - transitory memory storing instructions that, when executed in conjunction with the at least one processor, cause the apparatus to: receive handover information; and at least in part based on the reception of the handover information, send handover information with conditional handover priority information to a user equipment.

[0008] According to another aspect, an example method may be provided, including: receiving handover information including measurement configuration information; and at least in part based on the reception of the handover information, sending handover information with conditional handover priority information to a user equipment.

[0009] According to another aspect, an example embodiment can be provided using a non-transitory program storage device that can be read by a device and tangibly embodies a program of instructions that are executable by the device to perform operations including: receiving handover information including measurement configuration information; and sending, at least in part based on the reception of the handover information, handover information with conditional handover priority information to a user equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The foregoing aspects and other features are explained in the following description in conjunction with the accompanying drawings, in which:

[0011] Figure 1 is a block diagram of one possible and non-limiting example system in which an exemplary embodiment can be practiced;

[0012] Figure 2 is a diagram showing conditional handover;

[0013] Figure 3 is a message sequence diagram of an example of conditional handover and execution;

[0014] Figure 4 is a message sequence diagram of an example of conditional handover and execution;

[0015] Figure 5 is a diagram showing an example of a message sequence for an example conditional handover;

[0016] Figure 6 is a diagram showing an example of a message sequence for an example conditional handover;

[0017] Figure 7 is a diagram showing an example of a message sequence for an example conditional handover. DETAILED DESCRIPTION

[0018] The features described herein generally relate to an enhancement of conditional handover (CHO) using a secondary cell group (SCG) configuration.

[0019] The following abbreviations that can be found in the specification and / or the drawings are defined as follows: 3GPP Third Generation Partnership Project 5G Fifth Generation 5GC 5G Core Network AMF Access and Mobility Management Function CHO Conditional Handover CPA Conditional PSCell Addition CPAC Conditional PSCell Addition / Change CPA / CPA Conditional PSCell Change / Addition CPC Conditional PSCell Change CU Central Unit DC Dual Connectivity DU Distributed Unit eNB(or eNodeB) Evolved Node B (e.g., LTE base station) EN-DC E-UTRA-NR Dual Connectivity en-gNB or En-gNB Node that provides NR user plane and control plane protocol termination towards the UE and acts as secondary node in EN-DC E-UTRA Evolved Universal Terrestrial Radio Access, i.e., LTE radio access technology gNB(or gNodeB) Base station for 5G / NR, i.e., node that provides NR user plane and control plane protocol termination towards the UE and is connected to 5GC via the NG interface I / F Interface LTE Long Term Evolution MAC Medium Access Control MCG Master Cell Group MME Mobility Management Entity MN Master Node ng or NG New Generation ng-eNB or NG-eNB New Generation eNB NR New Radio N / W or NW Network PCell Primary Serving Cell PSCell Primary Secondary Cell PDCP Packet Data Convergence Protocol PHY Physical Layer RAN Radio Access Network Rel Release RLC Radio Link Control RLF Radio Link Failure RRH Remote Radio Head RRC Radio Resource Control RU Radio Unit Rx Receiver SCG Secondary Cell Group SDAP Service Data Adaptation Protocol SGW Serving Gateway SMF Session Management Function TS Technical Specification TTT Trigger Time Tx Transmitter UE User Equipment (e.g., wireless, typically a mobile device) UPF User Plane Function

[0020] Go to Figure 1 , which shows a block diagram of one possible and non - limiting example in which an example can be practiced. User Equipment (UE) 110, Radio Access Network (RAN) node 170, and (a) network element(s) 190 are shown. In Figure 1 example, User Equipment (UE) 110 communicates wirelessly with wireless network 100. The UE is a wireless device that can access wireless network 100. UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected by one or more buses 127. Each of the one or more transceivers 130 includes a receiver Rx132 and a transmitter Tx 133. The one or more buses 127 can be an address bus, a data bus, or a control bus, and can include any interconnecting mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber, or other optical communication equipment, etc. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. UE 110 includes module 140, which includes one or both of part 140 - 1 and / or part 140 - 2, and module 140 can be implemented in various ways. Module 140 can be implemented in hardware as module 140 - 1, for example, as part of one or more processors 120. Module 140 - 1 can also be implemented as an integrated circuit or by other hardware such as a programmable gate array. In another example, module 140 can be implemented as module 140 - 2, which is implemented as computer program code 123 and executed by one or more processors 120. For example, the one or more memories 125 and computer program code 123 can be configured to, together with one or more processors 120, cause user equipment 110 to perform one or more operations as described herein. UE 110 communicates with RAN node 170 via wireless link 111.

[0021] The RAN node 170 in this example is a base station that provides access to the wireless network 100 by a wireless device such as the UE 110. The RAN node 170 can be, for example, a base station for 5G, also known as New Radio (NR). In 5G, the RAN node 170 can be an NG-RAN node, which is defined as a gNB or an ng-eNB. A gNB is a node that provides NR user plane and control plane protocol termination towards the UE and is connected to the 5GC (such as, for example, (one or more) network elements 190) via the NG interface. An ng-eNB is a node that provides E-UTRA user plane and control plane protocol termination towards the UE and is connected to the 5GC via the NG interface. The NG-RAN node can include multiple gNBs, and a gNB can also include a Central Unit (CU) (gNB-CU) 196 and (one or more) Distributed Units (DU) (gNB-DU), where the DU 195 is shown. Note that the DU can include or be coupled to a Radio Unit (RU) and control the Radio Unit (RU). The gNB-CU is a logical node that hosts the RRC, SDAP, and PDCP protocols of the gNB or the RRC and PDCP protocols of the en-gNB, and these protocols control the operation of one or more gNB-DUs. The gNB-CU terminates at the F1 interface connected to the gNB-DU. The F1 interface is shown as reference numeral 198, although this reference numeral 198 also shows the link between the remote element and the centralized element of the RAN node 170 (such as between the gNB-CU 196 and the gNB-DU 195). The gNB-DU is a logical node that hosts the RLC, MAC, and PHY layers of the gNB or the en-gNB, and the operation of the gNB-DU 195 is partially controlled by the gNB-CU. One gNB-CU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates at the F1 interface 198 connected to the gNB-CU. Note that the DU 195 is considered to include the transceiver 160, for example, as part of the RU, but some examples that include the transceiver 160 can have the transceiver 160 as part of a separate RU, for example, under the control of the DU 195 and connected to the DU 195. The RAN node 170 can also be an eNB (evolved Node B) base station for LTE (Long Term Evolution) or any other suitable base station or node.

[0022] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces ((multiple) N / WI / F) 161, and one or more transceivers 160 interconnected by one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include (multiple) processors 152, memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memories and (multiple) processors and / or other hardware, but these are not shown.

[0023] The RAN node 170 includes a module 150, which includes one or both of part 150-1 and / or part 150-2, and the module 150 can be implemented in a variety of ways. The module 150 can be implemented in hardware as module 150-1, for example, as part of one or more processors 152. The module 150-1 can also be implemented as an integrated circuit or implemented by other hardware such as a programmable gate array. In another example, the module 150 can be implemented as module 150-2, which is implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and computer program code 153 are configured to cause the RAN node 170 to perform one or more operations as described herein together with one or more processors 152. Note that the functions of the module 150 can be distributed, such as being distributed between the DU 195 and the CU 196, or only implemented in the DU 195.

[0024] One or more network interfaces 161 communicate via a network (such as via link 176 and link 131). Two or more gNBs 170 can communicate using, for example, link 176. The link 176 can be wired or wireless or both, and can implement, for example, the Xn interface for 5G, the X2 interface for LTE, or other suitable interfaces for other standards.

[0025] One or more buses 157 can be an address bus, a data bus, or a control bus, and can include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fibers or other optical communication equipment, a wireless channel, etc. For example, one or more transceivers 160 can be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 implemented for a gNB in 5G, where other elements of the RAN node 170 may be physically located in a different position from the RRH / DU 195, and one or more buses 157 can be partially implemented as, for example, an optical fiber cable or other suitable network connection to connect other elements of the RAN node 170 (e.g., a central unit (CU), gNB-CU) to the RRH / DU 195. The reference numeral 198 also indicates those suitable (multiple) network links.

[0026] Note that the descriptions herein indicate that a "cell" performs functions, but it should be clear that the equipment forming the cell will perform the functions. A cell forms part of a base station. That is, each base station can have multiple cells. For example, for a single carrier frequency and associated bandwidth, there can be three cells, each cell covering one-third of a 360-degree area, such that the coverage area of a single base station covers an approximately elliptical or circular shape. In addition, each cell can correspond to a single carrier, and a base station can use multiple carriers. Thus, if there are three 120-degree cells for each carrier and there are two carriers, the base station has a total of 6 cells.

[0027] The wireless network 100 may include one or more network elements 190, which may include core network functions and provide connectivity via one or more links 181 using additional networks (e.g., a telephone network and / or a data communication network (e.g., the Internet)). Such core network functions for 5G may include one or more Access and Mobility Management Functions (AMF) and / or User Plane Functions (UPF) and / or one or more Session Management Functions (SMF). Such core network functions for LTE may include MME (Mobility Management Entity) / SGW (Serving Gateway) functions. These are merely example functions that may be supported by the one or more network elements 190, and note that both 5G and LTE functions may be supported. The RAN node 170 is coupled to the network element 190 via the link 131. The link 131 may be implemented as, for example, the NG interface for 5G, or the S1 interface for LTE, or other suitable interfaces for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / W I / F) 180 interconnected by one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to cause the network element 190 to perform one or more operations in conjunction with the one or more processors 175.

[0028] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functions into a single, software-based management entity or virtual network. Network virtualization involves platform virtualization, typically combined with resource virtualization. Network virtualization is classified as either external, which combines many networks or parts of networks into virtual units, or internal, which provides network-like functions to software containers on a single system. Note that the virtualized entities resulting from network virtualization still use hardware such as processors 152 or 175 and memories 155 and 171 at some level for implementation, and such virtualized entities also produce technical effects.

[0029] The computer-readable memories 125, 155, and 171 can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memories, magnetic memory devices and systems, optical memory devices and systems, fixed memories, and removable memories. The computer-readable memories 125, 155, and 171 can be components for performing storage functions. As non-limiting examples, the processors 120, 152, and 175 can be of any type suitable for the local technical environment and can include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. The processors 120, 152, and 175 can be components for performing functions such as controlling the UE 110, the RAN node 170, and other functions as described herein.

[0030] Generally, various embodiments of the user equipment 110 can include, but are not limited to, cellular phones (such as smart phones), tablet computers, personal digital assistants (PDAs) with wireless communication capabilities, portable computers with wireless communication capabilities, image capture devices (such as digital cameras with wireless communication capabilities), game devices with wireless communication capabilities, music storage and playback appliances with wireless communication capabilities, Internet appliances that allow wireless Internet access and browsing, tablet computers with wireless communication capabilities, and portable units or terminals that combine these functions.

[0031] Conditional handover (CHO) with secondary cell group (SCG) configurations is discussed in the mobility enhancement Rel.18 work item. The mobility enhancement WID objectives 3 and 4 are as follows [RP-213565]: 3. Specify CHO including the target MCG and the target SCG [RAN3, RAN2]. Note 5: For Rel-17, this objective has already been a target, so this objective will be considered at RAN#95-e. 4. Specify CHO including the target MCG and candidate SCGs for CPC / CPA [RAN3, RAN2] CHO including the target MCG and the target SCG is used as the baseline.

[0032] In the following, an overview of CHO in Rel.16 and the evolution of this CHO from Rel.17 towards Rel.18 is provided.

[0033] Conditional handover (Rel.16)

[0034] The CHO procedure has been introduced in 3GPP Rel.16 to improve mobility robustness. In the case of CHO, the network can prepare multiple target cells, where each conditional handover reconfiguration is associated with the CHO execution conditions evaluated by the UE. The CHO execution conditions refer to the measurement IDs that associate measurement objects with reporting configurations, and the CHO execution conditions are configured by the source gNB. The reporting configuration defines the measurement events (A3 or A5) that trigger the CHO execution. Whenever the CHO execution conditions are met, the corresponding target configuration is selected, and the handover towards the selected target cell is performed. As given in TS 38.300, the signaling procedures for conditional handover are provided in Figure 2 For conditional handover signaling procedures are provided in

[0035] In this CHO, the source gNB can send an RRC reconfiguration in step 6 or perform early data forwarding of the start user plane data to all prepared target cells after receiving the RRC reconfiguration complete in step 7. When the communication with the UE continues after step 6, the source gNB sends an early SN status transfer message (step 7a) to the target gNB, which indicates the packets that have been received by the UE and should be deleted from the buffer to be maintained for each prepared target PCell.

[0036] CHO with SCG (Rel.17)

[0037] In Rel.17, RAN3 has specified the signaling enhancements required to support CHO with SCG, where the target MN that receives the handover request from the source node can add and prepare the target SN, i.e., handover to a DC connection: · In this case, the CHO configuration provided by the target node back to the source node contains the master cell group (MCG) configuration to be applied to the target PCell and the secondary cell group (SCG) configuration to be applied to the target PSCell. · The CHO execution conditions are evaluated by the UE based on the measurements of the target PCell, i.e., the measurements of the target PSCell are not considered in the evaluation. · When the CHO execution conditions are met, the UE performs random access to the target PCell and the target PSCell.

[0038] Considering that there is a time between CHO preparation and execution, the radio signal quality of the target PSCell may be insufficient at the time of CHO execution, resulting in an SCG failure and an interruption of the SCG bearer, which may be up to 500 ms or more (depending on the T304 value that supervises the random access to the target PSCell). This issue will be addressed in Rel.18 by the following items: 1) Provide conditions (different from the CHO execution conditions) to determine whether to access the target PSCell / SN. For example, the conditions (e.g., CPAC conditions) are evaluated using the target PSCell measurements. 2) Allow the target MN to prepare more than one candidate target PSCell / SN.

[0039] As will be further understood from the following description, to overcome the foregoing problems, the UE may start evaluating the (multiple) conditions for the prepared target PSCell when the UE receives the (multiple) CHO configurations. In this way, the UE can perform simultaneously with the measurements for the prepared target PCell and target PSCell, and consider the radio link strength / quality of the target PCell and target PSCell when deciding on CHO execution.

[0040] When the PSCell access conditions for the prepared target PSCell are satisfied while evaluating the CHO conditions, the UE may wait and does not need to perform random access to the target PSCell until the CHO conditions for the corresponding target PCell are satisfied.

[0041] When the CHO conditions are satisfied, using the features described herein, it may still be useful to check whether the departure conditions for the target PSCell (the PSCell access conditions for which have been satisfied previously) are not satisfied to ensure that the radio signal of the target PSCell is still sufficient. If the departure conditions are not satisfied, the UE may perform CHO and perform random access to the target PCell and the selected target PSCell. When two execution events are configured, this is a principle similar to the principle applied to Rel-16 CHO.

[0042] Otherwise, in an example embodiment, if the departure conditions are satisfied (or if no prepared target PSCell has satisfied the PSCell access conditions when evaluating the CHO conditions), the UE may perform the DCCHO configuration including MCG configuration and SCG configuration, but only perform random access to the target MN. The UE may notify the MN that no prepared target PSCell has satisfied the PSCell access conditions, and using this information, the MN may immediately reconfigure the UE, e.g., remap the SN bearers to the MN. Note that delaying PCell access until one of the PSCell access conditions is satisfied is useless because delaying PCell access may cause RLF.

[0043] Also refer to Figure 3, which shows an example message sequence diagram for CHO configuration and execution for Hypothesis 1. For Hypothesis 1, the UE is configured with a CHO condition evaluated using PCell measurements and another PSCell access condition evaluated using PSCell measurements. As long as both conditions are not satisfied, the UE will not perform DC CHO configuration.

[0044] In one scenario, it is possible that the UE is only configured with a DC CHO configuration that includes both MCG configuration and SCG configuration. In this case, the UE will evaluate both the CHO and PSCell access conditions. Unless both conditions are satisfied, the UE will not apply the DC CHO configuration and will not perform random access to the target PSCell. Additionally, in the case where the PSCell condition for the target cell is not satisfied, this will limit the UE's access to the target PCell. However, there are problems / difficulties: Problem 1. In the case where the UE is configured with CHO and PSCell access conditions that work as described above, if neither the CPAC condition nor the CHO condition is satisfied, the UE may not be able to perform DC CHO configuration.

[0045] Also refer to Figure 4 , which shows an example message sequence diagram for CHO configuration and execution for Hypothesis 2. For Hypothesis 2, the UE is configured with a "hard" condition for the CHO condition and a "soft" condition for the CPAC condition. The soft condition means that even if the soft condition is not satisfied, the UE can still use the CHO configuration.

[0046] In one scenario, the UE is configured with a DC CHO configuration with SCG configuration and another CHO configuration (single - connection configuration) without SCG configuration. In this case, for the CHO with SCG configuration, the UE will receive a hard CHO execution condition and a soft PSCell access condition, and for the CHO configuration without SCG configuration, the UE will only receive a hard PCell access condition. Considering that the CHO configurations are for the same target PCell, such as 1 or 2, the same CHO condition is expected for all CHO configurations.

[0047] In the case where the hard PCell access condition is satisfied and the PSCell access condition is not satisfied, since the soft condition also allows the UE to use other CHO configurations, the UE can select from the available CHO configurations (e.g., CHO ID 1, CHO ID 2, or CHO ID 3). It is not clear whether the UE will select ID 1 or ID 2 or ID 3. There is no mandatory behavior to distinguish these three configurations, and the choice is left to the UE implementation. In the case where the UE selects ID1 or ID2 as the DC CHO configuration, there are the following problems / difficulties: Problem 2: The UE applies the MCG configuration, and some bearers are mapped to the SCG but not used. After a period of time, the target PCell must reconfigure the UE to remap the SCG bearers (which cannot be established because the UE has no connection to the SCG) to the MCG. This will cause an interruption regarding the SCG bearers at the same time.

[0048] In another case, a situation can occur where the CHO condition is met and the PSCell access condition is about to be met, but the PSCell access condition has not been met yet. Then, the UE can select ID 3, which is a single-connection configuration (only MCG, no SCG) that does not wait for the PSCell condition to be met. However, there will be the following problems / difficulties: Problem 3: Since the UE is under single connection (or due to the consumption of limited resources of the target PCell caused by overload on the single connection), the UE only applies the MCG configuration that provides fewer resources to the UE. The new PCell will reconfigure the UE shortly after the handover (because the PSCell has already been about to meet the CHO condition), and this reconfiguration requires the preparation of the PSCell from scratch (extra signaling both on the network and the air interface). This reconfiguration also causes the UE to suffer from reduced throughput until the DC is established.

[0049] With the features described herein, two methods are proposed to ensure that the UE does not experience an interruption regarding the SCG bearers in the CHO with a candidate SCG.

[0050] Method 1 (to solve the above Problem 1): The target MN is configured to provide a CHO configuration with a single connection whenever the target MN adds a CHO with an SCG configuration. This behavior is known to the source MN, or the source MN can request from the target MN to provide a CHO configuration without DC. The source MN only includes the PSCell access condition for the CHO with a single connection and the conditions for the PCell and the PSCell for the CHO with a dual connection. If the PSCell access condition is not met, the UE can select the CHO configuration without DC (only including the MCG) and execute this CHO configuration. Here, all bearers of the UE are served by the MN.

[0051] Method 2 (to solve the above Problem 2 and Problem 3): (For multiple CHO configurations) When the CHO execution condition is met, the UE is notified that the UE is provided with a method to prioritize the configurations among multiple CHO conditions with a single connection and a dual connection. · In an example embodiment, this behavior is specified as a mandatory UE behavior in the specification. General rules can define the priority of the CHO configurations, such as, for example, the sequence of the CHO configurations in the RRC message, or the lower ID of the CHO configuration has a higher priority. · In another exemplary embodiment, the source MN may indicate this (indicating the priority of the CHO configuration) to the UE during conditional handover configuration.

[0052] Using the features described herein, the connection can be maintained and one of the single / double configurations can be selected according to the priority after the measurement is determined. Also refer to Figure 5 , an example message sequence diagram for Method 1 is shown. Method 1 is developed for the above-mentioned Hypothesis 1, where there are only hard conditions. The UE behavior can be guaranteed by the hard conditions, where the network enforces to ensure that the UE is always provided with a CHO configuration with a single connection, and the CHO configuration has the correct execution conditions to enable PCell access.

[0053] Also refer to Figure 6 , an example message sequence diagram for Method 2a is shown. Method 2a is developed for the above-mentioned Hypothesis 2, where there are hard conditions for the PCell and soft conditions for the PSCell. The UE behavior is achieved by indicating the priority for a single connection, so that the UE can select the correct MCG configuration for PCell access without any bearer remapping.

[0054] Using the features described herein, the connection can be maintained at the cell boundary and one of the single configuration or the double configuration can be selected according to the priority after the measurement is determined. Using Method 2a / 2b, the serving MN of the UE can add a priority to the CHO configuration provided to the UE, and in the sense that the CHO configuration with a higher priority can be processed before the CHO configuration with a lower priority, the UE behavior can be changed. This means that the CHO conditions applied to the higher priority CHO configuration can be executed immediately, and the situation where some CHO conditions are applied simultaneously is avoided, which may otherwise result in two potential target cells and the selected cell is caused by random UE selection.

[0055] The source MN can provide the UE with a CHO configuration including a priority. The UE can process the CHO conditions according to the priority of the CHO configuration and can perform a cell change when the CHO conditions are applied. A new information element (IE) for allocating / associating a "priority" to the CHO configuration of the UE at the serving MN can be provided. The new IE "allocated priority" of the CHO configuration can be sent to the UE. In one example, this can be sent together with the CHO configuration or sent in relation to the identifier of the CHO configuration.

[0056] Using the features described herein, this can be used for: · In the case where the UE cannot apply the DC CHO configuration, for example, when the PSCell condition is not met, avoid interruptions regarding SCG bearers such as. · Avoided signaling overhead and latency caused by waiting for a new RRC reconfiguration from the target MN to remap the bearer to the MN and caused by the signaling overhead and latency.

[0057] Figure 6 , at step 6, Option 1 is shown, where in this exemplary embodiment, if only CHO condition 1 holds, then ID3 is preferred. This can be used at step 9, where if CHO condition 1 holds and none of the PSCell conditions hold, the UE can perform CHO ID3. Figure 6 Step 8 in shows Option 2, where if only the PCell condition holds, the UE can give priority to single connection. The preparation part of Option 1 can be incorporated into Option 2; the preparation part, in which the source MN interacts with the target SN. For Option 1, the source MN can indicate to the UE what to do via a message at step 6, for example. For Option 2, in one exemplary embodiment, the UE can be preconfigured to consider the priority accordingly. In one type of alternative embodiment, Option 2 can be signaled to the UE as a configuration setting. Based on the information from the source MN to the UE during step 6, step 9 (which uses Option 1 information) can be carried out after step 8 to perform CHO ID 3.

[0058] Also referring to Figure 7 , an example message sequence diagram for Method 2b is shown. In Method 2b, the network configures the UE such that if a DC handover may occur, the UE will consider DC. Here, the UE is configured with the condition that the UE will not immediately perform CHO ID1 after the CHO condition is met, but the UE checks whether one of the PSCell conditions is about to be met, such as, for example, whether the timer trigger time (TTT) for PSCell access is running. If the PSCell condition is about to be met, the UE can wait until the condition is fully met and then perform a DC handover. If the condition stops being met, for example, the TTT stops running, or the TTT is not running at all, the UE can consider CHO ID3 as proposed in Method 2a.

[0059] The trigger time (TTT) is a timer that starts running when the target PSCell power meets a specific condition. The condition can be, for example: 1) Comparison of the target PSCell power with a threshold, such as, for example, the PSCell is stronger than the threshold (A5 event); 2) Comparison of the target PSCell power and the serving PSCell power, with an offset in the comparison, such as, for example, the target PSCell is 3 dB (or more offset values) stronger than the serving PSCell power.

[0060] If the target PSCell power meets the configured condition (one of the above two conditions), the UE does not immediately perform a handover. Instead, the UE can observe whether the condition is met for a specific time period (TTT) to ensure that the observation is not an abnormal event (it is possible that the condition is temporarily met due to fluctuations in the measurement), and the cell change is actually reasonable, recommended, and will be executed.

[0061] Therefore, before the UE is reconfigured back to dual connection after a handover, the UE will not suffer from single connection. The serving MN does not need to reconfigure the UE to DC by immediately performing a secondary node (SN) addition procedure after CHO execution (the PSCell becomes good immediately after CHO execution).

[0062] The UE can provide a capability indication to the network node, which is used to indicate support for conditional handover including priority information. The priority information assigned to the conditional handover configuration can be followed at the UE, for example, by evaluating the conditional handover configuration according to the assigned priority. The UE can provide a capability indication to the network node, which is used to indicate support for the feature of waiting for the expiration of the ongoing TTT before the selection of the target cell regarding the handover configuration.

[0063] Reference Figure 7 , in this exemplary embodiment, the source MN 702 can send a handover request (CHO) to the target MN 704 in step 1, as shown at 706. The target MN 704 can send an SN addition request to the target SN 708 in step 2, as shown at 710. The target SN 708 can send an SN addition request ACK to the target MN 704 in step 3, as shown at 712. At step 4, the target MN 704 can form a CHO configuration; and the example is shown at 714. This example 714 has three (3) IDs; ID1, ID2, and ID3. In step 5, the target MN 704 can send a handover request (CHO) ACK to the source MN 702, as shown at 716. In this example, 716 includes CHO ID 1, CHO ID 2, and CHO ID 3. The target MN 702 can send an RRC reconfiguration to the UE 110 in step 6, as shown at 718. This can include the handover command with IDs 1, 2, and 3 described in detail in Figure 7 In this example, this includes: ID1: CHO configuration 1-1, CHO condition 1, PSCell condition 1-1 ID2: CHO Configuration 1-2, CHO Condition 1, PSCell Condition 1-2 ID3: CHO Configuration 1-3, CHO Condition 1, Option 1: If the PSCell access condition is about to be satisfied, then give priority to ID 1 or ID 2. Note that the three CHO IDs are only examples and should not be considered restrictive. UE 110 may send an RRC reconfiguration complete to the source MN 702 at step 7, as shown at 720. At step 8, as long as the PSCell access condition is in operation, for example when the PSCell condition has not been satisfied, UE 110 may use Option 2 to give priority to ID 1 or ID 2 722. However, when the PSCell access condition is satisfied, as shown at step 9, UE 110 may then execute 724 the prioritized ID; in Figure 7 the example of, this is CHO ID 1. In the event that the PSCell is not in operation at step 8, the process may proceed as Figure 6 shown.

[0064] In Figure 6 the example shown, at step 6, ID 3 may be indicated as ID 3: CHO Configuration 1-3, CHO Condition 1, Option 1: If only CHO Condition 1 holds, then give priority to ID 3. In Figure 6 at step 8 in, if only the PCell condition holds, UE 110 may execute the option to give priority to single connection 622. Then, at step 9, when UE 110 determines that CHO Condition 1 holds and no PSCell condition holds, UE 110 may use CHO ID 3 to execute 624 Option 1 in the RRC reconfiguration message 618.

[0065] Note that in one example embodiment, after the features of method 2b are executed, the features of method 2a may not be executed; after the features of method 2b are executed, the features of an alternative method may be executed. The features of method 2a may also be executed without using the features of method 2b.

[0066] As described above, in one type of example, single connection may be prioritized, for example, at Figure 6 step 8 in. Figure 5 Returning to reference Figure 5 shows another example method regarding single connection. Using the example shown in Figure 7Steps 2 and 3 are the same. At step 4, the target MN 704 can be configured to provide a CHO configuration with a single connection along with the DC configuration, as shown at 514. At step 5, the target MN can provide the CHO configuration, as shown in the example 513 shown. At step 6, a handover request (CHO) ACK can be sent by the target MN 704 at 516 to the source MN 702 with CHO ID 1, CHO ID 2, and CHO ID 3, where CHO ID 3 indicates a single connection. At step 7, the source MN 702 can be configured as shown at 517 to provide PSCell conditions for all CHO configurations with SCG, and provide PCell conditions only for CHO configurations with a single connection. At step 8, an RRC reconfiguration can be sent as indicated at 518 to include ID 1, ID 2, and ID 3, where ID 3 includes CHO configuration 1-3, CHO condition 1. Thus, at step 10, the UE 110 can be configured such that if CHO condition 1 holds and none of the PSCell conditions hold, the UE can perform 524 a CHO with a single connection, CHO ID 3. Figure 5 shown in the example 513 shown. At step 6, a handover request (CHO) ACK can be sent by the target MN 704 at 516 to the source MN 702 with CHO ID 1, CHO ID 2, and CHO ID 3, where CHO ID 3 indicates a single connection. At step 7, the source MN 702 can be configured as shown at 517 to provide PSCell conditions for all CHO configurations with SCG, and provide PCell conditions only for CHO configurations with a single connection. At step 8, an RRC reconfiguration can be sent as indicated at 518 to include ID 1, ID 2, and ID 3, where ID 3 includes CHO configuration 1-3, CHO condition 1. Thus, at step 10, the UE 110 can be configured such that if CHO condition 1 holds and none of the PSCell conditions hold, the UE can perform 524 a CHO with a single connection, CHO ID 3.

[0067] In one type of exemplary embodiment, at least some features from method 1 (see Figure 5 ) can be carried out using features from method 2 (see Figures 6 - 7 ). At least some features from method 1 can be used together with at least some features from method 2 to ensure that a single connection is prepared in certain cases. In one example, if the target node does not provide both a single connection configuration and a dual connection configuration, there is nothing to be prioritized on the serving cell side. On the other hand, as another different example, the target may have provided both a single connection configuration and a dual connection configuration even without a source gNB request. For this second different example, method 1 is of no help to method 2; where method 2 is an independent solution. However, for the first example, additional mechanisms may be required on top of at least some features from method 1 to have different configurations such that the features from method 1 can be prioritized over different configurations (single / dual). In some alternative embodiments, at least some features in method 1 and method 2 can be practiced separately or independently; at least some features in method 1 do not need to be carried out using at least some or all features in method 2, and at least some features in method 2 do not need to be carried out using at least some or all features in method 1.

[0068] The UE can select a conditional handover configuration according to the priority information. The UE can receive the priority information from a network entity. The UE can apply the priority; and the received priority can request the UE to wait for the ongoing TTT at the UE to expire before the UE performs a single-connection handover / PCell change. The UE can apply the priority to multiple conditional handovers. The UE can prioritize the PCell change. The UE can prioritize the PCell change only when the PSCell condition is not provided. The UE can prioritize the change to a single connection over the change to a dual connection. The received priority information can correspond to this behavior, and the UE can perform according to the received priority.

[0069] Figure 5 、 Figure 6 and Figure 7 Some examples of handover commands at the RRC reconfiguration signaling are shown. However, these examples should not be considered restrictive. The handover information in the handover command can include one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information as shown in the examples in the figure.

[0070] The MN can determine the priority between conditional handover configurations. The MN can prioritize the dual-connection cell change over the single-connection cell change, or otherwise. The UE may need to follow this priority.

[0071] The UE behavior can be caused by the priority assigned at the MN to the conditional handover configuration. Compared with a single handover configuration (which does not include the PSCell configuration), the MN can assign a higher priority to a dual-connection handover configuration (which includes conditions / measurements regarding the PCell and PSCell). But this is just one possible preference. The UE can be requested to delay the selection of the target cell / handover configuration until the ongoing TTT expires; this can increase the number of dual-connection cell changes and avoid subsequent reconfigurations. The priority information can trigger the UE to do so.

[0072] According to an example embodiment, a device is provided, including: at least one processor; and at least one non-transitory memory storing instructions that, when executed, together with the at least one processor cause the device to: determine that a conditional handover condition is satisfied; and based on the determination that the conditional handover condition is satisfied and at least partially based on the priority information, select a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover.

[0073] At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: receive handover information from a network entity, where the handover information includes one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information, and where the conditional handover priority information includes priority information. The conditional handover priority information can include information indicating that a first conditional handover configuration will be given priority relative to a second conditional handover configuration priority. The priority information can be indicated as depending on at least one parameter. The at least one parameter can include: when the PSCell access condition determination is running and the PSCell access condition has not been satisfied. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: when the PSCell access condition is running and not satisfied, prioritize different conditional handover configurations. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: after the PSCell condition is satisfied, perform a different conditional handover configuration. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: receive a plurality of conditional handover conditions from a network entity, and the determination that a conditional handover condition is satisfied is based on at least one of the received plurality of conditional handover conditions. The priority information can include priority information pre-configured in the apparatus. The at least one parameter can include when only CHO condition 1 holds. The at least one parameter can include when only the PCell condition holds. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: if the PCell condition exists, prioritize single connection. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: when the PSCell access condition is running in the apparatus, select a first conditional handover configuration from at least two conditional handover configurations, where the first conditional handover configuration has priority over one or more other conditional handover configurations among the at least two conditional handover configurations. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: based on the priority information and when the PSCell condition is satisfied, select and perform a first conditional handover or a different one of the at least two conditional handover configurations. At least one memory and instructions can be configured to, in conjunction with at least one processor, cause the apparatus to: provide a capability indication to a network node for indicating support for conditional handover including the priority information.

[0074] In an example embodiment, an example method can be provided, including: determining, by a user equipment, that a conditional handover condition is satisfied; and selecting, by the user equipment, a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is satisfied and at least partially based on priority information.

[0075] In an example embodiment, a non-transitory program storage device can be provided that is readable by a device and tangibly embodies a program of instructions that are executable by the device to perform operations. The operations can include: determining that a conditional handover condition is satisfied; and selecting a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is satisfied and at least in part based on priority information.

[0076] According to one example embodiment, a device is provided that includes: means for determining that a conditional handover condition is satisfied; and means for selecting a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is satisfied and at least in part based on priority information.

[0077] According to one example embodiment, a device is provided that includes: at least one processor; and at least one non-transitory memory storing instructions that, when executed with the at least one processor, cause the device to: receive handover information; and send handover information with conditional handover priority information to a user equipment at least in part based on the receipt of the handover information.

[0078] The at least one memory and the instructions can be configured to, with the at least one processor, cause the device to: form conditional handover priority information using at least one parameter for preferring a first conditional handover configuration over a second conditional handover configuration. The at least one parameter can include when a PSCell access condition is about to be satisfied. The at least one parameter can include whether a timer trigger time (TTT) of a PSCell access condition is running. The at least one parameter can include: waiting for a conditional handover configuration selection until the expiration or stop of the timer trigger time (TTT) of the PSCell. The at least one parameter can include: when a first conditional handover condition exists and at least one other conditional handover condition does not exist.

[0079] As described above, the UE may provide a network node with an indication of its ability to support conditional handover. The ability indicator may indicate, for example, support for including CHO priority information or support for features such as waiting for the expiration of an ongoing TTT before the selection of a target cell for handover configuration. Then, the network node may use the ability indicator to configure / indicate the UE subsequently as described above only if the network and / or the network node and / or the UE support this type of CHO. Thus, the instructions at the network node may be configured to cause the network node to receive an ability indicator from the user equipment to then configure or indicate the user equipment (but only if the UE supports this type of CHO) such as, for example, at least one of the following: CHO priority information, or waiting for the expiration of the trigger time of an ongoing timer. If no such ability information is received by the network node from the UE, the network node may be configured not to send information about CHO including priority information to the UE, or not to wait until the TTT expires.

[0080] In an example embodiment, an example method may be provided, including: receiving handover information including measurement configuration information; and, at least in part based on the reception of the handover information, sending handover information with conditional handover priority information to a user equipment.

[0081] In an example embodiment, a non-transitory program storage device may be provided, which can be read by a device and tangibly embodies a program of instructions that are executable by the device for performing operations. The operations include: receiving handover information including measurement configuration information; and, at least in part based on the reception of the handover information, sending handover information with conditional handover priority information to a user equipment.

[0082] According to an example embodiment, an apparatus is provided, including: means for receiving handover information; and means for, at least in part based on the reception of the handover information, sending handover information with conditional handover priority information to a user equipment.

[0083] It should be understood that the foregoing description is illustrative only. Those skilled in the art can design various alternatives and modifications. For example, the features recited in the various dependent claims may be combined with each other in any suitable combination. In addition, features from the different example embodiments above may be selectively combined into new example embodiments. Thus, this specification is intended to cover all such alternatives, modifications, and variations that fall within the scope of the appended claims.

Claims

1. A device, comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed, together with the at least one processor cause the device to: determine that a conditional handover condition is met; and select a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is met and at least in part based on priority information.

2. The device according to claim 1, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the device to: receive handover information from a network entity, wherein the handover information includes one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information, and wherein the conditional handover priority information includes the priority information.

3. The device according to claim 2, wherein the conditional handover priority information includes information indicating that a first conditional handover configuration will be given priority over a second conditional handover configuration.

4. The device according to claim 1, wherein the priority information is indicated to depend on at least one parameter.

5. The device according to claim 4, wherein the at least one parameter comprises: when the PSCell access condition determination is running and the PSCell access condition has not been met.

6. The device according to claim 5, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the device to: prioritize different conditional handover configurations when the PSCell access condition is running and has not been met.

7. The device according to claim 6, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the device to: execute the different conditional handover configurations after the PSCell condition is met.

8. The device according to claim 1, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the device to: receive a plurality of conditional handover conditions from a network entity, and the determination that the conditional handover condition is met is based on at least one of the received plurality of conditional handover conditions.

9. The device according to claim 8, wherein the priority information includes priority information pre-configured in the device.

10. The device according to claim 4, wherein the at least one parameter includes when only CHO condition 1 holds.

11. The device according to claim 4, wherein the at least one parameter includes when only the PCell condition holds.

12. The device according to claim 4, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the device to: prioritize single connection if the PCell condition exists.

13. The apparatus according to claim 4, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the apparatus to: when the PSCell access condition is in operation in the apparatus, select a first conditional handover configuration from at least two conditional handover configurations, wherein the first conditional handover configuration has a higher priority than one or more other conditional handover configurations among the at least two conditional handover configurations.

14. The apparatus according to claim 13, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the apparatus to: based on the priority information and when the PSCell condition is met, select and execute the first conditional handover or a different one of the at least two conditional handover configurations.

15. The apparatus according to claim 1, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the apparatus to: provide to a network node an indication of the ability to support conditional handover including priority information.

16. A method, comprising: determining, by a user equipment, that a conditional handover condition is met; and selecting, by the user equipment, a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is met and at least in part based on priority information.

17. A non-transitory program storage device readable by a device, tangibly embodying a program of instructions executable by the device for performing operations, the operations comprising: determining that a conditional handover condition is met; and selecting a conditional handover configuration from at least one conditional handover configuration to perform a conditional handover based on the determination that the conditional handover condition is met and at least in part based on priority information.

18. An apparatus, comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed, together with the at least one processor, cause the apparatus to: receive handover information; send, at least in part based on the reception of the handover information, the handover information with conditional handover priority information to a user equipment.

19. The apparatus according to claim 18, wherein the at least one memory and the instructions are configured to, together with the at least one processor, cause the apparatus to: form the conditional handover priority information using at least one parameter for making a first conditional handover configuration have a higher priority than a second conditional handover configuration.

20. The apparatus according to claim 19, wherein the at least one parameter includes when the PSCell access condition is about to be met.

21. The apparatus according to claim 20, wherein the at least one parameter includes whether a timer trigger time (TTT) of the PSCell access condition is in operation.

22. The apparatus according to claim 20, wherein the at least one parameter comprises: Wait for a conditional handover configuration selection until the expiration or stop of the timer trigger time (TTT) of the PSCell.

23. The apparatus according to claim 19, wherein the at least one parameter comprises: When a first conditional handover condition exists and at least one other conditional handover condition does not exist.

24. The apparatus according to claim 18, wherein the instructions are configured to, together with the at least one processor, cause the apparatus to receive a capability indicator from the user equipment to configure or indicate the user equipment with respect to at least one of: priority information, or waiting for the expiration of the trigger time of a running timer.

25. A method, comprising: receiving handover information including measurement configuration information; and at least partially based on the receiving of the handover information, sending the handover information with conditional handover priority information to a user equipment.

26. A non-transitory program storage device readable by an apparatus, tangibly embodying a program of instructions executable by the apparatus for performing operations, the operations comprising: receiving handover information including measurement configuration information; and at least partially based on the receiving of the handover information, sending the handover information with conditional handover priority information to a user equipment.

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