Handover configuration with fallback conditions using a single connection

Abstract

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

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION One example and non-limiting embodiment relates generally to wireless communications, and more particularly to conditional handover. [Background technology]

[0002] Conditional handover procedures are commonly known for user equipment in wireless networks. Summary of the Invention [Problem to be solved by the invention]

[0003] The following summary is intended to be merely an example and is not intended to limit the scope of the claims. [Means for solving the problem]

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

[0005] According to another aspect, an example method may be provided that includes determining, by 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 for performing the conditional handover based on determining that the conditional handover condition is met and based at least in part on priority information.

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

[0007] According to another aspect, an example embodiment may provide an apparatus comprising at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus to: receive handover information; and, based at least in part on the receipt of the handover information, transmit the handover information along with conditional handover priority information to user equipment.

[0008] According to another aspect, an example method may be provided that includes receiving handover information that includes measurement configuration information, and transmitting the handover information along with conditional handover priority information to user equipment based at least in part on the receipt of the handover information.

[0009] According to another aspect, an exemplary embodiment may provide a non-transitory program storage device readable by an apparatus that tangibly embodies a program of instructions executable by the apparatus to perform operations, the operations including: receiving handover information including measurement configuration information; and based at least in part on receiving the handover information, transmitting the handover information along with conditional handover priority information to user equipment.

[0010] The foregoing aspects and other features are explained in the following description, taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram of one possible, non-limiting example system in which the example embodiments may be practiced. [Figure 2] FIG. 1 illustrates a conditional handover. [Figure 3] 10 is a message sequence chart for an exemplary conditional handover and execution. [Figure 4] 10 is a message sequence chart for an exemplary conditional handover and execution. [Figure 5] FIG. 1 illustrates one example of a message sequence for an exemplary conditional handover. [Figure 6] FIG. 1 illustrates one example of a message sequence for an exemplary conditional handover. [Figure 7] FIG. 1 illustrates one example of a message sequence for an exemplary conditional handover. DETAILED DESCRIPTION OF THE INVENTION

[0012] The features described herein primarily relate to improving conditional handover (CHO) functionality in a Secondary Cell Group (SCG) configuration.

[0013] The following abbreviations that may appear in the specification and / or drawings are defined as follows: 3GPP 3rd Generation Partnership Project 5G (5th Generation) 5GC 5G Core Network AMF Access and Mobility Management Functions 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 Connection DU distribution device eNB (or eNodeB) evolved Node B (e.g., LTE base station) EN-DC E-UTRA-NR dual connection en-gNB or En-gNB A node that provides NR user plane and control plane protocol termination for UEs and acts as a secondary node within the EN-DC E-UTRA Evolved Terrestrial Radio Access, i.e., LTE radio access technology gNB (or gNodeB) A base station for 5G / NR, i.e., a node that provides NR user plane and control plane protocol termination for UEs and is connected to 5G via the NG interface. I / F interface LTE Long Term Evolution MAC Media Access Control MCG Master Cell Group MME Mobility Management Entity MN Master Node ng or NG Next Generation ng-eNB or NG-eNB Next 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 equipment Rx Receiver SCG Secondary Cell Group SDAP Service Data Adaptation Protocol SGW Serving Gateway SMF Session Management Facility TS Technical Specifications TTT Trigger Time Tx transmitter UE User Equipment (e.g., wireless, typically mobile device) UPF User Plane Function

[0014] Turning to FIG. 1 , this figure shows a block diagram of one possible, non-limiting example in which an example may be practiced. Illustrated are a user equipment (UE) 110, a radio access network (RAN) node 170, and a network element 190. In the example of FIG. 1 , the user equipment (UE) 110 is in wireless communication with a wireless network 100. The UE is a wireless device capable of accessing the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected via one or more buses 127. Each of the one or more transceivers 130 includes a receiver (Rx) 132 and a transmitter (Tx) 133. The one or more buses 127 may be address, data, or control buses and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber or other optical communication facilities, and the like. 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. The UE 110 includes a module 140 comprising one or both of components 140-1 and / or 140-2, which may be implemented in several ways. The module 140 may be implemented in hardware as module 140-1, such as implemented as part of one or more processors 120. The module 140-1 may also be implemented as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 140 may 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 the computer program code 123 may be configured, by the one or more processors 120, to cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with the RAN node 170 via a wireless link 111.

[0015] The RAN node 170 in this example is a base station that provides access to the wireless network 100 by wireless devices such as the UE 110. The RAN node 170 may be, for example, a base station for 5G, also known as New Radio (NR). In 5G, the RAN node 170 may be an NG-RAN node, defined as either a gNB or an ng-eNB. A gNB is a node that provides NR user plane and control plane protocol termination for the UE and is connected to the 5GC (e.g., network element 190) via an NG interface. An ng-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed units (DUs) (gNB-DUs), of which DU 195 is shown. It should be noted that a DU may include or be coupled to a radio unit (RU) to control the radio unit (RU). The gNB-CU is a logical node that hosts the RRC, SDAP, and PDCP protocols of a gNB or the RRC and PDCP protocols of an en-gNB, controlling the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface that connects with the gNB-DU. The F1 interface is illustrated as reference 198, which also illustrates a link between a remote element of the RAN node 170 and a 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 a gNB or en-gNB, and its operation 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 the F1 interface 198 that connects with the gNB-CU.It should be noted that the DU 195 is considered to include the transceiver 160, e.g., as part of an RU, although some instances of this may have the transceiver 160, e.g., as part of a separate RU under the control of or connected to the DU 195. The RAN node 170 may also be an evolved NodeB (eNB) base station in the case of Long Term Evolution (LTE), or any other suitable base station or node.

[0016] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / WI / F) 161, and one or more transceivers 160, interconnected through 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 the processor 152, the memory 155, and the network interface 161. Note that the DU 195 may also include its own one or more memories and processors, and / or other hardware, although these are not shown.

[0017] The RAN node 170 includes a module 150 comprising one or both of components 150-1 and / or 150-2, which may be implemented in several ways. The module 150 may be implemented in hardware as module 150-1, such as implemented as part of one or more processors 152. The module 150-1 may also be implemented as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and the computer program code 153 are configured by the one or more processors 152 to cause the RAN node 170 to perform one or more of the operations as described herein. It should be noted that the functionality of the module 150 may be distributed, such as distributed between the DU 195 and the CU 196, or may be implemented solely within the DU 195.

[0018] One or more network interfaces 161 communicate over a network, such as via links 176 and 131. Two or more gNBs 170 may communicate, for example, using link 176. Link 176 may be wired or wireless or both, and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interfaces for other standards.

[0019] The one or more buses 157 may be address, data, or control buses and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, optical fiber or other optical communications facilities, wireless channels, and the like. For example, one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 in the case of LTE, or a distributed unit (DU) 195 for a gNB implementation in the case of 5G, with other elements of the RAN node 170 possibly physically located at a different location from the RRH / DU, and the one or more buses 157 may be implemented in part, for example, as optical fiber cables or other suitable network connections, to connect the other elements of the RAN node 170 (e.g., central unit (CU), gNB-CU) to the RRH / DU 195. Reference 198 also indicates those suitable network links.

[0020] It should be noted that the description herein indicates that a "cell" performs a function, but it should be clear that the equipment forming the cell performs the function. A cell constitutes part of a base station; that is, there may be multiple cells per base station. For example, there may be three cells for a single carrier frequency and associated bandwidth, with each cell covering one-third of a 360-degree area, such that the coverage area of ​​a single base station covers an approximately oval or circle. Furthermore, each cell may correspond to a single carrier, and the base station may use multiple carriers. Thus, if there are three 120-degree cells per carrier, and there are two carriers, the base station has a total of six cells.

[0021] The wireless network 100 may include network element(s) 190, which may include core network functions, providing connectivity via link(s) 181 with additional networks, such as a telephone network and / or a data communication network (e.g., the Internet). Such core network functions for 5G may include an Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF) and / or a Session Management Function (SMF). For LTE, such core network functions may include Mobility Management Entity (MME) / Serving Gateway (SGW) functionality. Note that these are merely example functions that may be supported by the network element 190; both 5G and LTE functions may be supported. The RAN node 170 is coupled to the network element 190 via link 131. The link 131 may be implemented, for example, as an NG interface for 5G, an S1 interface for LTE, or another suitable interface for other standards. Network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / WI / F) 180 interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and computer program code 173 are configured, by the one or more processors 175, to cause network element 190 to perform one or more operations.

[0022] 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: a virtual network. Network virtualization is often accompanied by platform virtualization, which is combined with resource virtualization. Network virtualization is categorized as either external virtualization, which combines many networks or portions of networks into virtual devices, or internal virtualization, which provides network-like functionality in software containers on a single system. It should be noted that the virtualized entities resulting from network virtualization are still implemented at some level using hardware, such as processor 152 or 175 and memory 155 and 171, and that it is such virtualized entities that provide the technical effect.

[0023] The computer-readable memories 125, 155, and 171 may be of any type suitable for the local technology environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The computer-readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable for the local technology environment and may include, by way of non-limiting example, 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 may be means for performing functions such as control of the UE 110, the RAN node 170, and other functions described herein.

[0024] In general, various embodiments of user equipment 110 may include, but are not limited to, mobile phones such as smartphones, tablets, 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, gaming devices with wireless communication capabilities, music storage and playback devices with wireless communication capabilities, internet appliances that allow wireless internet access and browsing, tablets with wireless communication capabilities, and portable devices or terminals incorporating combinations of such functionality.

[0025] Conditional Handover (CHO) with Secondary Cell Group (SCG) configuration is discussed in the Mobility Enhancement Rel. 18 work item. Mobility Enhancement WID Goals 3 and 4 are as follows [RP-213565]: 3. Identifying CHOs containing target MCGs and target SCGs [RAN3, RAN2]. Note 5: This goal will be reported in RAN#95-e as this is already targeted in Rel-17. 4. To identify CHOs containing target MCGs and candidate SCGs [RAN3, RAN2] for CPC / CPA. The CHO containing the target MCG and target SCG is used as the baseline.

[0026] In the following, an overview of CHO in Rel. 16 and its evolution in Rel. 17 towards Rel. 18 is provided.

[0027] Conditional Handover (Rel.16)

[0028] The CHO procedure is introduced in 3GPP Rel. 16 to improve mobility robustness. For CHO, the network may prepare multiple target cells, where each conditional handover reconfiguration is associated with a CHO execution condition that is evaluated by the UE. The CHO execution condition refers to a measurement ID that associates a measurement object with a reporting configuration and is configured by the source gNB. The reporting configuration specifies the measurement event (A3 or A5) that triggers CHO execution. Whenever the CHO execution condition is met, the corresponding target configuration is selected and handover is performed to the selected target cell. The signaling procedure for conditional handover is provided in Figure 2 as described in TS 38.300.

[0029] In this CHO, the source gNB may start early data transfer of user plane data to all prepared target cells after sending RRC Reconfiguration in step 6 or after receiving RRC Reconfiguration Complete in step 7. As communication with the UE continues after step 6, the source gNB sends to the target gNB an Early SN Status Transfer message indicating packets that have been received by the UE and that are considered to be deleted from the buffers maintained for each prepared target PCell (step 7a).

[0030] CHO with SCG (Rel.17)

[0031] In Rel.17, RAN3 specifies the signaling enhancements required to support CHO with SCG, where a target MN receiving a handover request from a source node can add and prepare a target SN, i.e., handover to DC connection: The CHO configuration returned by the target node to the source node in this case includes 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 condition is evaluated by the UE based on measurements of the target PCell, i.e. measurements of the target PSCell are not taken into account in the evaluation. The UE performs random access to the target PCell and target PSCell when the CHO execution conditions are met.

[0032] Assuming there is a time between CHO preparation and execution, the radio signal quality of the target PSCell may not be sufficient at the time of CHO execution, resulting in SCG failure and interruptions in the SCG bearers that can be up to 500 ms or more (depending on the T304 value supervising the random access to the target PSCell). 1) Providing a condition (different from the CHO execution condition) to determine whether to access the target PSCell / SN, for example, the condition (e.g., CPAC condition) is evaluated using the target PSCell measurement; 2) Enabling a target MN to prepare two or more candidate target PSCells / SNs This will be addressed in Rel.18.

[0033] As will be further understood from the following description, to overcome the above-mentioned problems, the UE may start evaluating the conditions for the prepared target PSCell already at the time the UE receives the CHO configuration, so that the UE may simultaneously perform measurements for the prepared target PCell and the target PSCell and take their radio link strength / quality into account when deciding on CHO execution.

[0034] If the PSCell access conditions for the prepared target PSCell are met 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 of the corresponding target PCell are met.

[0035] Once the CHO condition is met, it may still be useful to check whether the exit condition of the target PSCell (whose PSCell access condition was previously met) is not met, to ensure that the radio signal of the target PSCell is still sufficient, due to the features as described herein. If the exit condition is not met, the UE may perform CHO and implement random access to the target PCell and the selected target PSCell. This is the same principle as that applied to Rel-16 CHO when two execution events are configured.

[0036] On the other hand, in one exemplary embodiment, if the exit condition is met (or if none of the prepared target PSCells meet the PSCell access condition while evaluating the CHO condition), the UE may perform DC CHO configuration consisting of MCG and SCG configuration, but perform random access only to the target MN. The UE may inform the MN that none of the prepared target PSCells meet the PSCell access condition, and using this information, the MN may immediately reconfigure the UE, e.g., remap SN bearers to the MN. Note that delaying PCell access until one of the PSCell access conditions is met is not useful as it may lead to RLF.

[0037] Referring also to Figure 3, an exemplary message sequence chart for CHO configuration and execution is shown for scenario 1. For scenario 1, the UE is configured with a CHO condition evaluated using PCell measurements and another PSCell access condition evaluated using PSCell measurements. The UE will not perform DC CHO configuration unless both conditions are met.

[0038] In one scenario, it may happen that a UE is configured with only a DC CHO configuration, which includes both MCG and SCG configurations. In that case, the UE evaluates both the CHO and PSCell access conditions. Unless both conditions are met, the UE will neither apply the DC CHO configuration nor perform random access to the target PSCell. Furthermore, this restricts the UE from accessing the target PCell if the PSCell conditions are not satisfied in the target cell. However, this presents problems / challenges: Issue 1. When a UE is configured with CHO and PSCell access conditions functioning as described above, the UE may not be able to perform DC CHO configuration if both CPAC and CHO conditions are not met.

[0039] 4, an exemplary message sequence chart for CHO configuration and execution for scenario 2 is shown. For scenario 2, the UE is configured with "hard" conditions for CHO conditions and "soft" conditions for CPAC conditions. Soft conditions mean that the UE can use the CHO configuration even if the soft conditions are not satisfied.

[0040] In one scenario, a UE is configured with a DC CHO configuration with an SCG configuration and another CHO configuration without an SCG configuration (single connection configuration). In that case, the UE receives hard CHO execution conditions and soft PSCell access conditions for the CHO configuration with an SCG configuration, and only hard PCell access conditions for the CHO configuration without an SCG configuration. Assuming the CHO configurations are for the same target PCell, e.g., 1 or 2, the same CHO conditions are expected for all CHO configurations.

[0041] If the hard PCell access condition is met and the PSCell access condition is not met, the UE can select from the available CHO configurations (e.g., CHO ID1, 2, or 3) because the soft condition allows the UE to use other CHO configurations as well. It is not obvious whether the UE should select ID1, ID2, or ID3. There is no mandatory behavior to distinguish between these three configurations, and the selection is left to the UE implementation. If the UE selects ID1 or ID2, which are DC CHO configurations, the following issues / challenges exist: Problem 2: The UE applies an MCG configuration, in which some of the bearers are mapped to the SCG but are not used. The target PCell then has to reconfigure the UE to remap to the MCG the SCG bearers that could not be set up because the UE did not establish a connection with the SCG. This causes a communication interruption for the SCG bearers in the meantime.

[0042] In another case, the CHO condition is satisfied and the PSCell access condition is close to being satisfied, but the PSCell access condition is not yet satisfied. In this case, the UE may select ID3, which is a single connection configuration (MCG only, no SCG), without waiting for the PSCell condition to be satisfied. However, the following problems / issues exist: Issue 3: The UE only applies the MCG configuration that provides fewer resources to the UE because the UE is in a single connection (or because the overload in the single connection leads to exhaustion of the limited resources of the target PCell). The new PCell reconfigures the UE immediately after handover (because the PSCell was already close to satisfying the HO condition), which requires preparation of the PSCell from the beginning (additional signaling both in the network and on the air interface). This also means that the UE suffers from reduced throughput until the DC is configured.

[0043] With the features as described herein, two methods are proposed to ensure that the UE does not experience interruptions to SCG bearers in a CHO with SCG candidates.

[0044] Method 1 (to address issue 1 above): The target MN is configured to provide a CHO configuration with single connectivity every time it adds an SCG configuration to the CHO. This behavior is recognized by the source MN, or the source MN may request the target MN to provide a CHO configuration without DC. The source MN includes only a PCell access condition for CHO with single connectivity, and a condition for the PCell and a condition for the PSCell for CHO with dual connectivity. If the PSCell access condition is not satisfied, the UE may select and execute a CHO configuration without DC (including only an MCG). Here, all bearers of the UE are served by the MN.

[0045] Method 2 (to address issues 2 and 3 above): The UE is informed that if the CHO execution conditions (for multiple CHO configurations) are met, the UE is provided with a method to prioritize configurations among multiple CHO conditions using single and dual connections. In one example embodiment, this behavior is recorded as mandatory UE behavior in the specification. General rules may specify the priority of the CHO configurations, for example the sequence of the CHO configurations in the RRC message, or a 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.

[0046] By the features described herein, connectivity can be maintained, and one of the single / dual configurations can be selected according to priority after measurements are determined. Also referring to FIG. 5, an example message sequence chart for Method 1 is shown. Method 1 was developed for Assumption 1 described above, where only difficult conditions exist. Under difficult conditions, the network-mandated implementation always provides a single-connection CHO configuration that allows the UE to access the PCell under suitable execution conditions, so that UE behavior can be guaranteed.

[0047] Referring also to Figure 6, an exemplary message sequence chart for Method 2a is shown. Method 2a is developed for Scenarios 2 as described above, where there are hard conditions for the PCell and soft conditions for the PSCell. UE behavior is achieved by specifying a priority for a single connection, so that the UE can select an appropriate MCG configuration for PCell access without requiring any bearer remapping.

[0048] By the features as described herein, connectivity at cell borders can be maintained, and one of the single or dual configurations is selected according to priority after measurements are determined. By Method 2a / 2b, the UE's serving MN can add a priority to the CHO configurations provided to the UE, and the UE behavior can be changed in the sense that a CHO configuration with a higher priority can be processed before a CHO configuration with a lower priority. This means that a CHO condition that applies to a higher priority CHO configuration can be executed immediately, avoiding a situation where multiple CHO conditions apply simultaneously, which would otherwise result in two potential target cells and the selected cell resulting from random UE selection.

[0049] The source MN may provide the UE with a CHO configuration including a priority. The UE may process the CHO conditions according to the priority of the CHO configuration and may perform a cell change when the CHO conditions apply. A new information element (IE) may be provided to assign / associate a "priority" to the UE's CHO configuration in the serving MN. The new IE "assigned priority" of the CHO configuration may be sent to the UE. In one example, it may be sent together with the CHO configuration or may be sent in association with an identifier of the CHO configuration.

[0050] With the features as described herein, it can be used to: · Avoiding communication interruption of SCG bearers when the UE is unable to apply the DC CHO configuration, e.g. when PSCell conditions are not met. · Avoids signaling overhead and delay caused by waiting for a new RRC Reconfiguration to remap bearers from the target MN to the MN.

[0051] FIG. 6 illustrates Option 1 in step 6, where, in this exemplary embodiment, ID3 is prioritized if only CHO Condition 1 is valid. This may be used in step 9, where the UE may execute CHO ID3 if CHO Condition 1 is valid and none of the PSCell conditions are valid. Step 8 in FIG. 6 illustrates Option 2, where the UE may prioritize single connection only if the PCell condition is valid. The preparation portion of Option 1 may be integrated into Option 2, where the source MN interacts with the target SN. In Option 1, the source MN may indicate to the UE what to do, for example, via messaging in step 6. In Option 2, in one exemplary embodiment, the UE may be pre-configured to appropriately consider priorities. In one type of alternative embodiment, Option 2 may be signaled to the UE as a configuration setting. Step 9, which may use Option 1 information, may be executed after step 8, based on information from the source MN to the UE during step 6, to assign CHO ID3.

[0052] 7, an exemplary message sequence chart for Method 2b is shown. In Method 2b, the network configures the UE to consider DC if DC handover is likely. Here, the UE is conditionally configured so that the UE does not execute CHO ID1 immediately after the CHO condition is met, but the UE checks whether one of the PSCell conditions is likely to be met, such as whether the time-to-trigger (TTT) timer for PSCell access is running. If the PSCell condition is likely to be met, the UE may wait until the condition is fully met and then execute DC handover. If the condition is no longer met, for example, if the TTT is stopped or not executed at all, the UE considers CHO ID3 as proposed in Method 2a.

[0053] Time-To-Trigger (TTT) is a timer that starts running when the target PSCell power meets certain conditions, such as: 1) Comparison of the target PSCell power with a threshold, e.g., when a PSCell is more powerful than the threshold (A5 event); 2) Comparison of the target PSCell power with the serving PSCell with an offset, for example, the target PSCell being 3 dB more powerful than the serving PSCell power (or a larger offset value). It could be.

[0054] If the target PSCell power satisfies the set condition (one of the two above), the UE will not perform handover immediately. Instead, the UE may observe whether this condition is satisfied for a certain time period (TTT) to ensure that the observation was not an outlier event (it may happen that the condition is satisfied temporarily due to measurement fluctuations) and that a cell change is indeed valid and is recommended and should be performed.

[0055] Therefore, the UE does not encounter the single connectivity issue until it is reconfigured back to dual connectivity after handover. The serving MN does not need to reconfigure the UE with the DC by proceeding with the secondary node (SN) addition procedure immediately after CHO execution (PSCell is in good state immediately after CHO execution).

[0056] The UE may provide a capability indication to the network node indicating that it supports conditional handover, including priority information. The priority information assigned to the conditional handover configuration may be examined at the UE side, for example, by evaluating the conditional handover configuration according to the assigned priority. The UE may provide a capability indication to the network node indicating that it supports the function of waiting until the expiration of an ongoing TTT before selecting a target cell for the handover configuration.

[0057] Referring to FIG. 7, in this exemplary embodiment, the source MN 702 may send a handover request (CHO) to the target MN 704 as indicated by 706 in step 1. The target MN 704 may send an SN addition request to the target SN 708 as indicated by 710 in step 2. The target SN 708 may send an SN addition request ACK to the target MN 704 as indicated by 712 in step 3. In step 4, the target MN 704 may form a CHO configuration, an example of which is shown at 714. This example 714 includes three IDs: ID1, ID2, and ID3. The target MN 704 may send a handover request (CHO) ACK to the source MN 702 as indicated by 716 in step 5. In this example, 716 includes CHO ID1, CHO ID2, and CHO ID3. The target MN 702 may send an RRCReconfiguration to the UE 110 as indicated by 718 in step 6. This may include a handover command as detailed in Figure 7 with ID1, ID2, and ID3. In this example, this is: 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 met, prioritize ID1 or ID2 Includes:

[0058] Note that these three CHO IDs are merely exemplary and should not be considered limiting. UE 110 may send an RRCReconfiguration Complete to source MN 702 in step 7, as indicated by 720. In step 8, UE 110 may prioritize ID1 or ID2 using option 2 722 as long as the PSCell access condition is active, e.g., when the PSCell condition is not yet satisfied. However, as indicated in step 9, once the PSCell access condition is satisfied, UE 110 may implement 724 the preferred ID, which in the example of FIG. 7 is CHO ID1. If a PSCell is not active in step 8, the process may proceed as shown in FIG. 6.

[0059] 6, in step 6, ID3 may be indicated as ID3:CHO Config 1-3, CHO Condition 1, Option 1:Prefer ID3 only if CHO Condition 1 is valid. In step 8 in FIG. 6, UE 110 may implement 622 the option to prioritize single connection only if Pcell conditions are valid. Then, in step 9, UE 110 may execute 624 option 1 in RRCReconfiguration message 618 using CHO ID3 when it is determined that CHO Condition 1 is valid and no PSCell conditions are valid.

[0060] It should be noted that in one exemplary embodiment, the features of Method 2a may not be performed after the features of Method 2b are performed, and another alternative method may be performed after the features of Method 2b are performed. The features of Method 2a may also be performed without using the features of Method 2b.

[0061] As described above, in one type of example, single connectivity may be preferred, such as in step 8 in FIG. 6. Referring back to FIG. 5, another exemplary method is shown regarding single connectivity. In the example shown in FIG. 5, the source MN 702 in step 1 may send a handover request (CHO) as indicated by 506, which may optionally request single connectivity. Steps 2 and 3 may be the same as those in FIG. 7. In step 4, the target MN 704 may be configured to provide a CHO configuration using single connectivity together with a DC configuration as indicated by 514. In step 5, the target MN may provide a CHO configuration as indicated by example 513 as shown in FIG. 5. In step 6, a handover request (CHO) ACK may be sent 516 by the target MN 704 to the source MN 702 with CHO ID1, CHO ID2, and CHO ID3, where CHO ID3 indicates single connectivity. In step 7, the source MN 702 may be configured, as indicated by 517, to provide a PSCell condition for all CHO configurations with SCG and a PCell condition only for CHO configurations with single connection. In step 8, an RRCReconfiguration may be sent, as indicated by 518, to include ID1, ID2, and ID3, where ID3 includes CHO configurations 1-3, CHO condition 1. Thus, in step 10, the UE 110 may be configured, as indicated by 524, such that if CHO condition 1 is valid and none of the PSCell conditions are valid, the UE may perform CHO with single connection ID3.

[0062] In one type of exemplary embodiment, at least some of the features of Method 1 (see FIG. 5) may be implemented together with the features of Method 2 (see FIGS. 6-7). At least some of the features of Method 1 may be used together with at least some of the features of Method 2 to ensure that single connectivity is prepared in a particular case. In one example, if the target node does not offer both single connectivity and dual connectivity configurations, there is no preference on the serving cell side. Meanwhile, in another different example, the target may already offer both single connectivity and dual connectivity configurations without a request from the source gNB. In this second different example, Method 1 does not contribute to Method 2, which is a standalone solution. However, in the first example, having diverse configurations may require additional mechanisms in addition to at least some of the features of Method 1, and as a result, the features of Method 1 can prioritize diverse configurations (single / dual). In some alternative embodiments, at least some of the features of Method 1 and Method 2 may be practiced separately or independently, and at least some of the features of Method 1 need not be implemented together with at least some or all of the features of Method 2, and at least some of the features of Method 2 need not be implemented together with at least some or all of the features of Method 1.

[0063] The UE may select a conditional handover configuration according to priority information. The UE may receive priority information from a network entity. The UE may apply the priority, and the received priority may require the UE to wait for an ongoing TTT of the PSCell to expire at the UE side before performing a single connection handover / PCell cell change. The UE may apply a priority for multiple conditional handovers. The UE may prioritize a PCell change. The UE may prioritize a PCell change only if a PSCell condition is not provided. The UE may prioritize a change to single connectivity over a change to dual connectivity. The received priority information may support this behavior, and the UE may act according to the received priority.

[0064] 5, 6, and 7 show some examples of handover commands in RRC Reconfiguration signaling. However, these examples should not be considered limiting. The handover information in the handover command may include one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information, as illustrated by the examples in the figures.

[0065] The MN may decide on a priority between conditional handover configurations. The MN may prioritize a dual-connection cell change over a single-connection cell change, or vice versa. The UE must follow this priority.

[0066] The UE behavior may be due to the priority assigned to the conditional handover configuration at the MN. The MN may assign a higher priority to the dual connectivity handover configuration (including conditions / measurements on the PCell and PSCell) than to the single handover configuration (not including the PSCell configuration). However, this is just one example. The UE may be required to delay the selection of the target cell / handover configuration until the ongoing TTT expires, which may increase the number of dual connectivity cell changes and avoid subsequent reconfigurations. The priority information may trigger the UE to perform this action.

[0067] According to one exemplary embodiment, an apparatus is provided that includes at least one processor and at least one non-transitory memory that stores instructions that, when executed by the at least one processor, cause the apparatus to: determine that a conditional handover condition is met; and select a conditional handover configuration from the at least one conditional handover configuration to perform the conditional handover based on determining that the conditional handover condition is met and based at least in part on priority information.

[0068] The at least one memory and instructions may be configured by the at least one processor to cause the device to receive handover information from a network entity, the handover information including one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information, the conditional handover priority information including priority information. The conditional handover priority information may include information indicating that a first conditional handover configuration is prioritized over a second conditional handover configuration. The priority information may be indicated as dependent on at least one parameter. The at least one parameter may include: when a PSCell access condition determination is ongoing, and when the PSCell access condition is not satisfied. The at least one memory and instructions may be configured by the at least one processor to cause the device to prioritize a different conditional handover configuration while the PSCell access condition is ongoing and not satisfied. The at least one memory and instructions may be configured by the at least one processor to cause the device to execute a different conditional handover configuration after the PSCell condition is satisfied. The at least one memory and instructions may be configured by the at least one processor to cause the device to receive a plurality of conditional handover conditions from a network entity, and determining that the conditional handover condition is met is based on at least one of the received plurality of conditional handover conditions. The priority information may include priority information pre-configured in the device. The at least one parameter may include when only CHO condition 1 is valid. The at least one parameter may include when only PCell condition is valid. The at least one memory and instructions may be configured by the at least one processor to cause the device to prioritize single connection when a PCell condition exists.The at least one memory and instructions may be configured, by the at least one processor, to cause the device to select a first of the at least two conditional handover configurations when a PSCell access condition is running in the device, with the first conditional handover configuration taking priority over other of the at least two conditional handover configurations. The at least one memory and instructions may be configured, by the at least one processor, to cause the device to select and perform the first conditional handover or a different one of the at least two conditional handover configurations based on the priority information and when the PSCell condition is satisfied. The at least one memory and instructions may be configured, by the at least one processor, to cause the device to provide a capability indication to a network node indicating support for conditional handover, the capability indication including the priority information.

[0069] In an example embodiment, an example method may be provided that includes determining, by the 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 for performing the conditional handover based on determining that the conditional handover condition is met and based at least in part on the priority information.

[0070] In an exemplary embodiment, a non-transitory program storage device readable by an apparatus may be provided that tangibly embodies a program of instructions executable by the apparatus to perform operations. The operations may include: determining that a conditional handover condition is met, and selecting a conditional handover configuration from the at least one conditional handover configuration to perform the conditional handover based on determining that the conditional handover condition is met and based at least in part on the priority information.

[0071] According to one exemplary embodiment, an apparatus is provided that includes means for determining that a conditional handover condition is met, and means for selecting a conditional handover configuration from at least one conditional handover configuration for performing a conditional handover based on determining that the conditional handover condition is met and based at least in part on priority information.

[0072] According to one exemplary embodiment, an apparatus is provided that includes at least one processor and at least one non-transitory memory that stores instructions that, when executed by the at least one processor, cause the apparatus to receive handover information and, based at least in part on the receipt of the handover information, transmit the handover information along with conditional handover priority information to user equipment.

[0073] The at least one memory and instructions may be configured, by the at least one processor, to cause the device to form conditional handover priority information with at least one parameter for use in prioritizing a first conditional handover configuration over a second conditional handover configuration. The at least one parameter may include a timing when a PSCell access condition is about to be satisfied. The at least one parameter may include whether a time-to-trigger (TTT) timer for the PSCell access condition is running. The at least one parameter may include waiting to select the conditional handover configuration until the expiration or stop of the PSCell time-to-trigger (TTT) timer. The at least one parameter may include a case when a first conditional handover condition exists and at least one other conditional handover condition does not exist.

[0074] As described above, the UE may provide a capability indication to a network node indicating that it supports conditional handover. Such a capability indicator may indicate, for example, whether it supports functionality including CHO priority information or whether it supports functionality including waiting until an ongoing TTT expires before selecting a target cell for handover configuration. The network node may then use the capability indicator to configure / instruct the UE, as described above, only if the network and / or network node and / or UE supports this type of CHO. Thus, instructions in the network node may be configured to cause the network node to receive a capability indicator from the user equipment, and then configure or instruct the user equipment, e.g., at least one of CHO priority information or waiting for expiration of a running trigger duration timer, only when the UE supports this type of CHO. If such capability information is not received by the network node from the UE, the network node may be configured not to send information to the UE regarding priority information or CHO including waiting until expiration of the TTT.

[0075] In an example embodiment, an example method may be provided that includes receiving handover information that includes measurement configuration information, and transmitting the handover information along with conditional handover priority information to user equipment based at least in part on the receipt of the handover information.

[0076] In an exemplary embodiment, a non-transitory program storage device readable by the device may be provided that tangibly embodies a program of instructions executable by the device to perform operations. The operations may include: receiving handover information that includes measurement configuration information; and transmitting the handover information, along with conditional handover priority information, to user equipment based at least in part on receiving the handover information.

[0077] According to one exemplary embodiment, an apparatus is provided that includes means for receiving handover information and means for transmitting the handover information along with conditional handover priority information to user equipment based at least in part on the receipt of the handover information.

[0078] It should be understood that the foregoing description is merely illustrative. Various alternatives and modifications may be devised by those skilled in the art. For example, the features recited in the various independent claims may be combined with each other in any suitable combination. In addition, features of different embodiments described above may be selectively combined into new embodiments. Accordingly, the present description is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

Claims

1. at least one processor; and 1. An apparatus comprising at least one non-transitory memory that stores instructions, the instructions, when executed by at least one processor, causing the apparatus to: determining that a conditional handover condition is met; and selecting a conditional handover configuration from the at least one conditional handover configuration for implementing the conditional handover based on determining that a conditional handover condition is met and based at least in part on the priority information.

2. 10. The apparatus of claim 1, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to receive handover information from a network entity, the handover information including one or more of conditional handover configuration information, measurement configuration information, and conditional handover priority information, and the conditional handover priority information includes priority information.

3. The apparatus of claim 2 , wherein the conditional handover priority information includes information indicating that a first conditional handover configuration is prioritized over a second conditional handover configuration.

4. The apparatus of claim 1 , wherein the priority information is indicated as being dependent on at least one parameter.

5. The apparatus of claim 4 , wherein the at least one parameter includes when a determination of a PSCell access condition is in progress and when a PSCell access condition is not satisfied.

6. 6. The apparatus of claim 5, wherein the at least one memory and instructions are configured by the at least one processor to cause the apparatus to prioritize different conditional handover configurations while a PSCell access condition is active and not satisfied.

7. 7. The apparatus of claim 6, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to perform different conditional handover configurations after a PSCell condition is met.

8. 10. The apparatus of claim 1, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to receive a plurality of conditional handover conditions from a network entity, and wherein determining that a conditional handover condition is met is based on at least one of the received plurality of conditional handover conditions.

9. The device of claim 8 , wherein the priority information includes priority information that is preset within the device.

10. The apparatus of claim 4 , wherein at least one parameter includes when only CHO Condition 1 is in effect.

11. The apparatus of claim 4 , wherein the at least one parameter includes when only PCell conditions are valid.

12. The device of claim 4 , wherein the at least one memory and instructions are configured by the at least one processor to cause the device to prioritize a single connection when a PCell condition exists.

13. 5. The apparatus of claim 4, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to select a first of the at least two conditional handover configurations when a PSCell access condition is running in the apparatus, with the first conditional handover configuration taking priority over one or more other of the at least two conditional handover configurations.

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

15. 10. The apparatus of claim 1, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to provide a capability indication to a network node indicating that the apparatus supports a conditional handover, the capability indication including priority information.

16. determining that a conditional handover condition is met by the user equipment; and 11. The method of claim 10, further comprising: selecting, by user equipment, a conditional handover configuration from at least one conditional handover configuration for performing the conditional handover based on determining that a conditional handover condition is met and based at least in part on priority information.

17. 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: determining that a conditional handover condition is met; and and selecting a conditional handover configuration from the at least one conditional handover configuration to implement the conditional handover based on determining that a conditional handover condition is met and based at least in part on the priority information.

18. at least one processor; and 1. An apparatus comprising at least one non-transitory memory that stores instructions, the instructions, when executed by at least one processor, causing the apparatus to: Receive handover information, An apparatus that causes handover information along with conditional handover priority information to be transmitted to user equipment based at least in part on receiving the handover information.

19. 20. The apparatus of claim 18, wherein the at least one memory and instructions are configured, by the at least one processor, to cause the apparatus to form conditional handover priority information with at least one parameter used to prioritize a first conditional handover configuration over a second conditional handover configuration.

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

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

22. 21. The apparatus of claim 20, wherein the at least one parameter includes waiting to select a conditional handover configuration until expiration or stopping of a time-to-trigger (TTT) timer of the PSCell.

23. 20. The apparatus of claim 19, wherein the at least one parameter includes a first conditional handover condition being present and at least one other conditional handover condition being absent.

24. The instructions are transmitted by at least one processor to the apparatus: Priority information, or and waiting for expiration of a running trigger period timer.

25. receiving handover information including measurement configuration information; and A method comprising: transmitting handover information along with conditional handover priority information to user equipment based at least in part on receiving the handover information.

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 A non-transitory program storage device that includes transmitting handover information along with conditional handover priority information to user equipment based at least in part on receiving the handover information.

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