Conditional Handover (CHO) Deconfiguration and Failure Handling in Wireless Communications

Abstract

Methods, systems, and devices for wireless communications are described for the management of conditional handover (CHO) configurations. A source base station may configure user equipment (UE) using one or more CHO configurations for multiple target base stations. The CHO configurations may provide one or more associated conditions that can trigger the UE to initiate a handover to a specific target base station or to deconfigure the CHO configuration for each target base station, for example, based on measurement thresholds of one or more target base station measurements, one or more source base station measurements, or a combination thereof. The CHO configurations may also include failure handling information for initiating one or more subsequent handovers in response to the failure of an initial handover attempt.

Description

Technology Field

[0001] The present patent application claims priority to U.S. Provisional Application No. 62 / 842,330 filed by Purkayastha et al. on May 2, 2019, under the title "Conditional Handover (CHO) Deconfiguration and Failure Handling in Wireless Communications"; and U.S. Patent Application No. 16 / 805,347 filed by Purkayastha et al. on February 28, 2020, under the title "Conditional Handover (CHO) Deconfiguration and Failure Handling in Wireless Communications"; each of these applications is assigned to the assignee of the present application. Background Technology

[0002] The following concerns wireless communications in general, and more specifically, conditional handover (CHO) deconfiguration and failure handling in wireless communications.

[0003] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, and broadcast. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include 4G (fourth generation) systems, such as LTE (Long Term Evolution) systems, LTE-A (LTE-Advanced) systems, or LTE-A Pro systems, and 5G (fifth generation) systems, which may be referred to as NR (New Radio) systems. These systems may use technologies such as CDMA (code division multiple access), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDMA (orthogonal frequency division multiple access), or DFT-S-OFDM (discrete Fourier transform spread orthogonal frequency division multiplexing). A wireless multiple access communication system may include multiple base stations or network access nodes, and each of these multiple base stations or network access nodes simultaneously supports communication with multiple communication devices, which may be otherwise known as user equipment (UE).

[0004] In some cases, the UE may be moving between one or more base stations, which may cause the UE to experience a handover procedure from the base station currently connected to the UE (e.g., source base station) to a new base station (e.g., target base station). The handover procedure may be initiated by the source base station and the target base station exchanging information related to the UE, and by the source base station transmitting a handover command to the UE. In some cases, the UE may drop the connection with the source base station and initiate a random access procedure with the target base station to establish a connection with the target base station. In some cases, one or more handover configurations may be provided to the UE before the UE initiates the handover, and the UE may initiate the handover when it detects a condition indicated in the configuration, which may be referred to as a conditional handover (CHO). However, conditional handover configurations present challenges related to the management of CHO configurations for target base stations.

[0005] The techniques described relate to improved methods, systems, devices, and apparatus that support conditional handover (CHO) deconfiguration and failure handling in wireless communications. Various aspects of the present disclosure describe techniques that provide for the management of CHO configurations. In some cases, a source base station may configure user equipment (UE) using one or more CHO configurations for a plurality of target base stations. The CHO configurations may provide one or more associated conditions that can trigger the UE to initiate a handover to a specific target base station for each target base station (e.g., based on measurement thresholds of one or more target base station measurements, one or more source base station measurements, or a combination thereof). In some cases, the CHO configurations may include failure handling information, deconfiguration criteria, or a combination thereof.

[0006] In some cases, failure handling information may include one or more CHO timer values, and when transmitting a random access request to a target base station, the UE may initiate the CHO timer associated with the target base station. If the UE and the target base station are unable to complete the random access procedure before the expiration of the CHO timer, the UE may identify that the handover to the target base station has failed. In some cases, in response to failure identification, the UE may determine whether any other target base stations have CHO configurations, and if a CHO configuration exists for a second target base station, the UE may transmit a random access request to that second target base station. The UE may repeat the handover attempt and failure identification until the handover is successful or until there are no additional target base stations with CHO configurations—at this point, the UE may declare a radio link failure and initiate a connection reset procedure.

[0007] In some cases, one or more CHO configurations may include deconfiguration criteria. In such cases, the UE may perform one or more measurements (e.g., signal strength or channel quality measurements) on a source base station, one or more target base stations, or a combination thereof. In cases where one or more of the measurements of a specific target base station meet the deconfiguration criteria, the UE may deconfigure the CHO configuration associated with that specific target base station. In some cases, the UE may transmit a measurement report to the source base station that may include measurements associated with the deconfigured target base station, which the source base station can use to release the handover configuration. In some cases, the UE may transmit a deconfiguration indication (e.g., the cell ID of the target base station being deconfigured) along with the measurement report.

[0008] A wireless communication method in a UE is described. The method may include receiving a conditional handover configuration from a source base station, one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations; determining, based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; transmitting a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration; starting a first conditional handover timer for completing the first random access procedure in response to the step of transmitting the first random access request; and determining a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed.

[0009] An apparatus for wireless communication in a UE is described. The apparatus may include a processor, a memory that communicates electronically with the processor, and instructions stored in the memory. Instructions may be executable by the processor such that the apparatus receives a conditional handover configuration indicating one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations; determines, based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; transmits a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration; starts a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request; and determines a first conditional handover failure in response to the first conditional handover timer expiring before completing the first random access procedure.

[0010] Another device for wireless communication in a UE is described. The device may include means for receiving a conditional handover configuration indicating one or more target base stations from a source base station, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations; means for determining, based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; means for transmitting a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration; means for starting a first conditional handover timer to complete the first random access procedure in response to transmitting the first random access request; and means for determining a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed.

[0011] A non-transient computer-readable medium for storing code for wireless communication in a UE is described. The code may include instructions executable by a processor to receive a conditional handover configuration indicating one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations; to determine, based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; to transmit a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration; to start a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request; and to determine a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed.

[0012] In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, one or more timers include at least a first conditional handover timer for completing a first random access procedure with a first target base station. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the conditional handover configuration includes at least a first conditional handover configuration for a first target base station and a second conditional handover configuration for a second target base station.

[0013] Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include actions, features, means, or instructions for determining that a second measurement threshold for initiating a handover to a second target base station is satisfied in response to the expiration of a first conditional handover timer, transmitting a second random access request to a second target base station to initiate a second random access procedure for a handover to a second target base station based on the conditional handover configuration, starting a second conditional handover timer to complete the second random access procedure, and repeating the determining, transmitting, and initiating for any other target base stations configured for conditional handover in the event of additional conditional handover failures. Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include actions, features, means, or instructions for initiating a connection reset procedure when it is determined that other target base stations are not configured for conditional handover.

[0014] In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the first duration of the first conditional handover timer may differ from the second duration of the second conditional handover timer. Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include operations, features, means, or instructions for selecting a second target base station from a set of available target base stations based on one or more of channel quality measurements or any combination thereof associated with each of a set of available target base stations in response to the expiration of the first conditional handover timer.

[0015] Some examples of the methods, apparatuses, and non-transient computer-readable media described herein receive a deconfiguration message from a source base station for deconfiguring one or more conditional handover configurations, and may further include actions, features, means, or instructions for deconfiguring one or more conditional handover configurations based at least partially on the deconfiguration message. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the deconfiguration message is received in radio resource control signaling from a source base station. Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include actions, features, means, or instructions for deleting one or more of a first measurement and reporting configuration or a radio resource control configuration for a conditional handover trigger provided in a first conditional handover configuration, and for discontinuing the evaluation of conditional handover measurements associated with the conditional handover configuration and whether the measurements satisfy conditional handover criteria.

[0016] A wireless communication method in a UE is described. The method may include receiving from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—determining that, based on the conditional handover configuration, a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is satisfied, and releasing the first conditional handover configuration of the first target base station.

[0017] An apparatus for wireless communication in a UE is described. The apparatus may include a processor, a memory that communicates electronically with the processor, and instructions stored in the memory. Instructions may be executable by the processor to cause the apparatus to receive from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a release measurement threshold for releasing the conditional handover configuration of the associated target base station—and to determine, based on the conditional handover configuration, that a first release measurement threshold for releasing the first conditional handover configuration of the first target base station is satisfied, and to release the first conditional handover configuration of the first target base station.

[0018] Another device for wireless communication in a UE is described. The device may include means for receiving from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—means for determining that, based on the conditional handover configuration, a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is satisfied, and means for releasing the first conditional handover configuration of the first target base station.

[0019] A non-transient computer-readable medium for storing code for wireless communication in a UE is described. The code may include instructions executable by a processor to receive, from a source base station, a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a release measurement threshold for releasing the conditional handover configuration of the associated target base station—determine that a first release measurement threshold for releasing the first conditional handover configuration of the first target base station is satisfied based on the conditional handover configuration, and release the first conditional handover configuration of the first target base station.

[0020] Some examples of the methods, apparatuses and non-transient computer-readable media described herein may further include operations, features, means, or instructions for determining, based on a conditional handover configuration, that a second triggering measurement threshold for initiating a handover to a second target base station is satisfied, and based on a second conditional handover configuration of the second target base station, for transmitting a random access request to the second target base station to initiate a random access procedure for a handover to the second target base station.

[0021] In some examples of the methods, apparatuses and non-transient computer-readable media described herein, releasing the first conditional handover configuration may include actions, features, means, or instructions for deleting one or more of the first measurement and reporting configuration or radio resource control configuration for the conditional handover trigger and conditional handover unconfiguration trigger provided in the first conditional handover configuration, and discontinuing the conditional handover measurements associated with the first target base station, and the evaluations of whether the measurements satisfy conditional handover criteria or conditional handover unconfiguration conditions.

[0022] Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include operations, features, means, or instructions for transmitting a measurement report to a source base station indicating that a first conditional handover configuration of a first target base station is released. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the measurement report includes a deconfiguration indication for the first target base station.

[0023] In some examples of the methods, devices, and non-transient computer-readable media described herein, the first unconfiguration measurement threshold may be a channel quality threshold associated with the first target base station, and the first conditional handover configuration is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold. In some examples of the methods, devices, and non-transient computer-readable media described herein, the first unconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold associated with the first target base station, and the first conditional handover configuration is released in response to the first channel quality measurement of the source base station exceeding the first threshold and the second channel quality measurement of the first target base station being less than the second threshold. In some examples of the methods, devices, and non-transient computer-readable media described herein, the first unconfiguration measurement threshold may be a difference threshold, and the first conditional handover configuration is released in response to the difference between channel quality measurements of the source base station and the first target base station exceeding the difference threshold.

[0024] A wireless communication method at a source base station is described. The method may include the steps of: establishing one or more target base stations and one or more conditional handover configurations by the source base station for a conditional handover of a UE from the source base station to an individual target base station—each conditional handover configuration including a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of a UE from the source base station to an individual target base station—and transmitting one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from the source base station to the associated target base station, and a conditional handover time period of the associated target base station.

[0025] An apparatus for wireless communication at a source base station is described. The apparatus may include a processor, a memory communicating electronically with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from the source base station to an individual target base station by the source base station—each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of a UE from the source base station to an individual target base station—and to transmit one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from the source base station to the associated target base station, and a conditional handover time period of the associated target base station.

[0026] Another device for wireless communication at a source base station is described. The device may include means for establishing one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by the source base station—each conditional handover configuration including a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of a UE from a source base station to an individual target base station—and means for transmitting one or more conditional handover configurations to a UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0027] A non-transient computer-readable medium is described for storing code for wireless communication at a source base station. The code may include instructions executable by a processor to set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by the source base station—each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of a UE from a source base station to an individual target base station—and to transmit one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0028] In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, each of one or more target base stations may have a different value for a conditional handover time period. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the conditional handover time period may be determined based on one or more of the UE’s movement estimate for each individual target base station, the traffic load of the source base station or each individual target base station, channel quality measurements for each individual target base station provided by the UE, or any combination thereof.

[0029] A wireless communication method at a source base station is described. The method may include the step of, by the source base station, setting up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from the source base station to an individual target base station—each conditional handover configuration comprising a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—and the step of transmitting one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations represents an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station.

[0030] A device for wireless communication at a source base station is described. The device may include a processor, a memory that communicates electronically with the processor, and instructions stored in the memory. Commands may be executable by a processor to cause the device to set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station—each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—and to transmit one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station.

[0031] Another device for wireless communication at a source base station is described. The device may include means for setting up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from the source base station to an individual target base station by the source base station—each conditional handover configuration comprising a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—and means for transmitting one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations represents an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, a conditional handover timer value for completing a conditional handover of the UE to an associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station.

[0032] A non-transient computer-readable medium for storing code for wireless communication at a source base station is described. The code may include instructions executable by a processor to transmit one or more conditional handover configurations to the UE, wherein the source base station sets up one or more target base stations and one or more conditional handover configurations for a conditional handover of the UE from the source base station to individual target base stations—each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of the UE to the associated target base station, a conditional handover timer value for completing a conditional handover of the UE to the associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—and transmit one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, a conditional handover timer value for completing a conditional handover of the UE to the associated target base station, and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station.

[0033] Some examples of the methods, apparatuses and non-transient computer-readable media described herein may further include actions, features, means or commands for deciding to unconfigure at least one first conditional handover configuration in a UE, and in response to the decision to unconfigure, transmitting unconfiguration information to the UE indicating that the UE must delete one or more of the first measurement and reporting configuration or radio resource control configuration for the first conditional handover configuration, and releasing the first conditional handover configuration of the first target base station.

[0034] Some examples of the methods, apparatuses, and non-transient computer-readable media described herein may further include actions, features, means, or instructions for receiving a measurement report from a UE indicating that a first unconfiguration measurement threshold for unconfiguring a first conditional handover configuration of a first target base station is satisfied, and for releasing the first conditional handover configuration of the first target base station in response to the measurement report. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, releasing the first conditional handover configuration may include actions, features, means, or instructions for deleting one or more of one or more timers associated with the first target base station, a first triggering measurement threshold, a first unconfiguration measurement threshold, or a radio resource control configuration included in the first conditional handover configuration.

[0035] In some examples of the methods, devices, and non-transient computer-readable media described herein, releasing the first conditional handover configuration may further include operations, features, means, or instructions for providing a first target base station with an indication that the first conditional handover configuration is released.

[0036] In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the unconfiguration measurement threshold may be a channel quality threshold associated with each individual target base station, and the conditional handover configuration of the first target base station is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold of the first target base station. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the unconfiguration measurement threshold includes a first threshold associated with a source base station and a second threshold for each individual target base station, and the conditional handover configuration of the first target base station is released in response to the first channel quality measurement of the source base station exceeding the first threshold and the second channel quality measurement of the first target base station being less than the second threshold of the first target base station. In some examples of the methods, apparatuses, and non-transient computer-readable media described herein, the release measurement threshold may be a difference threshold, and a conditional handover configuration associated with the first target base station is released in response to the difference between the channel quality measurements of the source base station and the first target base station exceeding the difference threshold. Brief explanation of the drawing

[0037] FIG. 1 illustrates an example of a system for wireless communications that supports conditional handover (CHO) configuration release and failure handling in wireless communications according to aspects of the present disclosure.

[0038] FIG. 2 illustrates an example of a part of a wireless communication system having source and target base stations that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0039] FIGS. 3 through 7 illustrate exemplary process flows that support CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0040] FIGS. 8 and 9 illustrate block diagrams of devices supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0041] FIG. 10 illustrates a block diagram of a communication manager that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0042] FIG. 11 illustrates a diagram of a system including a device that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0043] FIGS. 12 and 13 illustrate block diagrams of devices supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0044] FIG. 14 illustrates a block diagram of a communication manager that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0045] FIG. 15 illustrates a diagram of a system including a device that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure.

[0046] FIGS. 16 through 22 illustrate flowcharts illustrating methods for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Specific details for implementing the invention

[0047] Various aspects of the present disclosure provide techniques for user equipment (UE) handover in a wireless communication system. A UE may experience a handover procedure from a source cell to a target cell, wherein the UE may release or drop an existing connection with the source cell to establish a new connection with the target cell. The handover procedure may be initiated by the source base station and the target base station exchanging information related to the UE, and the source base station transmitting a handover command to the UE. In some cases, the UE may drop an existing connection with the source base station upon receiving the handover command and may initiate a random access procedure with the target base station to establish a connection with the target base station. In some cases, one or more handover configurations may be provided to the UE before the UE initiates the handover, and the UE may initiate the handover when it detects a condition indicated in the configuration, which may be referred to as a conditional handover (CHO).

[0048] In some aspects of the present disclosure, a source base station may configure a UE using one or more CHO configurations for a plurality of target base stations. The CHO configurations may provide, for each target base station, one or more associated conditions that can trigger the UE to initiate a handover to a specific target base station (e.g., based on measurement thresholds of one or more target base station measurements, one or more source base station measurements, or a combination thereof), and one or more associated conditions for deconfiguring the CHO configuration. In some cases, the CHO configurations may include failure handling information, deconfiguration criteria, or a combination thereof.

[0049] In some cases, CHO configurations may provide one or more handover criteria for one or more target base stations. The UE may perform one or more measurements of the target base station(s), the source base station, or a combination thereof, and if the measurements satisfy the handover criteria, the UE may initiate a handover with this target base station (e.g., by sending a random access request to the target base station that satisfies the handover criteria). CHO configurations may allow the UE to autonomously initiate a handover when the handover criteria are satisfied (e.g., when the source base station measurement is below a threshold and the target base station measurement exceeds a threshold), but maintaining such configurations may consume resources in the base stations and the UE, limit the flexibility of one or more target base stations, and consume overhead associated with the target base station measurements.

[0050] For example, a source base station may form a CHO with a first target base station, which may cause the source base station to periodically provide information associated with the UE to the first target base station, cause the first target base station to reserve contention-free random access preambles for the UE (which may restrict the first target base station from allocating contention-free preambles to other devices), cause the UE to perform measurements on the first target base station, and cause the UE to transmit measurement reports containing the first target base station measurements. Accordingly, if the first target base station is no longer a suitable candidate for the UE's handover, deconfiguring the CHO of the first target base station may be beneficial to the UE, the source base station, and the target base station. Additionally, if a random access procedure initiated as part of the CHO is unsuccessful or there is a radio link failure, service interruptions or latency may increase.

[0051] According to the various techniques discussed herein, in some cases, one or more CHO configurations may include deconfiguration criteria. In such cases, the UE may perform one or more measurements (e.g., signal strength or channel quality measurements) on a source base station, one or more target base stations, or a combination thereof. In cases where one or more of the measurements of the first target base station satisfy the deconfiguration criteria, the UE may deconfigure the CHO configuration associated with the first target base station. In some cases, the UE may deconfigure the CHO configuration autonomously. In some cases, the UE may transmit a measurement report to the source base station that may include measurements associated with the deconfigured first target base station, which the source base station may use to release the handover configuration. In some cases, the UE may transmit a deconfiguration indication (e.g., the cell ID of the target base station being deconfigured) along with the measurement report. In other cases, the UE may retain the CHO configuration until the source base station transmits the deconfiguration to the UE in response to the measurement report. The source base station may also provide a cancellation indication to the first target base station, which may cause the first target base station to release resources reserved for the UE.

[0052] Additionally or alternatively, in some cases, CHO configurations may include one or more CHO timer values, and when transmitting a random access request to a target base station, the UE may initiate the CHO timer associated with the target base station. If the UE and the target base station are unable to complete the random access procedure before the expiration of the CHO timer, the UE may identify that the handover to the target base station has failed. In some cases, in response to the failure identification, the UE may determine whether any other target base stations have CHO configurations, and if a CHO configuration exists for a second target base station, the UE may transmit a random access request to that second target base station. The UE may repeat the handover attempt and failure identification until the handover is successful or until there are no additional target base stations with CHO configurations—at this point, the UE may declare a radio link failure and initiate a connection reset procedure.

[0053] Such techniques can enable failure handling for failed CHO handovers and efficient management of CHO configurations. Deconfiguring CHO configurations based on UE measurements can enable more efficient management of CHO configurations, which can enable a relatively current set of CHO configurations that can be reliably used for handovers when handover criteria are met. Additionally, the failure handling techniques discussed herein can reduce service interruptions and latency associated with failed random access procedures of handover attempts.

[0054] Aspects of the present disclosure are first described in the context of a wireless communication system. Subsequently, various exemplary process flows describing CHO configuration management and failure handling are discussed. Aspects of the present disclosure are further described and illustrated with reference to device diagrams, system diagrams, and flowcharts relating to CHO deconfiguration and failure handling in wireless communications.

[0055] FIG. 1 illustrates an example of a wireless communication system (100) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The wireless communication system (100) includes base stations (105), UEs (115), and a core network (130). In some examples, the wireless communication system (100) may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, the wireless communication system (100) may support enhanced broadband communications, ultra-reliable (e.g., mission-critical) communications, low-latency communications, or communications with low-cost and low-complexity devices.

[0056] Base stations (105) can communicate wirelessly with UEs (115) through one or more base station antennas. The base stations (105) described herein may include a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or a giga-NodeB (any of which may be referred to as a gNB), a home NodeB, a home eNodeB, or any other suitable term, or may be referred to by those skilled in the art by these. A wireless communication system (100) may include different types of base stations (105) (e.g., macro or small cell base stations). The UEs (115) described herein may communicate with various types of base stations (105) and network equipment, including macro eNBs, small cell eNBs, gNBs, relay base stations, etc.

[0057] Each base station (105) may be associated with a specific geographical coverage area (110) where communications with various UEs (115) are supported. Each base station (105) may provide communication coverage for individual geographical coverage areas (110) via communication links (125), and the communication links (125) between the base station (105) and the UE (115) may utilize one or more carriers. The communication links (125) illustrated in the wireless communication system (100) may include uplink transmissions from the UE (115) to the base station (105), or downlink transmissions from the base station (105) to the UE (115). Downlink transmissions may also be referred to as forward link transmissions, while uplink transmissions may also be referred to as reverse link transmissions.

[0058] A geographical coverage area (110) for a base station (105) may be divided into sectors that constitute a part of the geographical coverage area (110), and each sector may be associated with a cell. For example, each base station (105) may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, the base station (105) may be mobile and thus may provide communication coverage for a mobile geographical coverage area (110). In some examples, different geographical coverage areas (110) associated with different technologies may overlap, and overlapping geographical coverage areas (110) associated with different technologies may be supported by the same base station (105) or by different base stations (105). The wireless communication system (100) may include, for example, a heterogeneous LTE / LTE-A / LTE-A Pro or NR network in which base stations (105) of different types provide coverage for various geographical coverage areas (110).

[0059] The term “cell” refers to a logical communication entity used for communication with a base station (105) (e.g., via a carrier) and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) to distinguish neighboring cells operating via the same or different carriers. In some examples, the carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC), narrowband Internet-of-Things (NB-IoT), enhanced mobile broadband (eMBB), or others) that can provide access to different types of devices. In some cases, the term “cell” may refer to a part (e.g., a sector) of the geographical coverage area (110) where the logical entity operates.

[0060] UEs (115) may be distributed throughout the wireless communication system (100), and each UE (115) may be stationary or mobile. A UE (115) may also be referred to as a mobile device, wireless device, remote device, handheld device, or subscriber device or any other suitable term, wherein "device" may also be referred to as a unit, station, terminal, or client. A UE (115) may also be a personal electronic device such as a cellular phone, PDA (personal digital assistant), tablet computer, laptop computer, or personal computer. In some examples, a UE (115) may also refer to a WLL (wireless local loop) station, IoT (Internet of Things) device, IoE (Internet of Everything) device, or MTC device, etc., which may be implemented in various items such as devices, vehicles, meters, etc.

[0061] Some UEs (115), such as MTCs or IoT devices, may be low-cost or low-complexity devices and may provide automated communication between machines (e.g., via M2M (Machine-to-Machine) communication). M2M communication or MTC may refer to data communication technologies that enable devices to communicate with each other or with a base station (105) without human intervention. In some examples, M2M communication or MTC may include communications from devices that incorporate sensors or meters to measure or capture information and relay that information to a central server or application program, which may provide information to humans who can use the information or interact with the program or application. Some UEs (115) may be designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business billing.

[0062] Some UEs (115) may be configured to use operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports unidirectional communication through transmission or reception but does not support transmission and reception simultaneously). In some examples, half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for the UEs (115) include entering a power-saving "deep sleep" mode when not engaged in active communications, or operating over a limited bandwidth (e.g., depending on narrowband communications). In some cases, the UEs (115) may be designed to support critical functions (e.g., mission-critical functions), and the wireless communication system (100) may be configured to provide ultra-reliable communications for these functions.

[0063] In some cases, the UE (115) may also communicate directly with other UEs (115) (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol). One or more of a group of UEs (115) utilizing D2D communications may be within the geographical coverage area (110) of the base station (105). Other UEs (115) within such a group may be outside the geographical coverage area (110) of the base station (105) or may not receive transmissions from the base station (105). In some cases, groups of UEs (115) communicating via D2D communications may utilize a one-to-many (1:M) system in which each UE (115) transmits to each other UE (115) within the group. In some cases, the base station (105) enables the scheduling of resources for D2D communications. In other cases, D2D communications are performed between UEs (115) without the involvement of a base station (105).

[0064] Base stations (105) can communicate with each other and with the core network (130). For example, base stations (105) can interface with the core network (130) through backhaul links (132) (e.g., through S1, N2, N3 or other interfaces). Base stations (105) can communicate with each other directly (e.g., directly between base stations (105)) or indirectly (e.g., through the core network (130)) through backhaul links (134) (e.g., through X2, Xn or other interfaces).

[0065] The core network (130) may provide user authentication, access authorization, tracking, IP (Internet Protocol) connectivity, and other access, routing, or mobility functions. The core network (130) may be an evolved packet core (EPC) that may include at least one mobility management entity (MME), at least one serving gateway (S-GW), and at least one Packet Data Network (PDN) gateway (P-GW). The MME may manage non-access stratum functions (e.g., control plane), such as mobility, authentication, and bearer management for UEs (115) served by base stations (105) associated with the EPC. User IP packets may be transmitted through the S-GW, and the S-GW itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the IP services of network operators. The operators' IP services may include access to the Internet, intranet(s), IMS (IP Multimedia Subsystem), or PS (Packet-Switched) streaming services.

[0066] At least some of the network devices, such as base stations (105), may include subcomponents such as access network entities, which may be examples of access node controllers (ANCs). Each access network entity may communicate with UEs (115) through a number of other access network transmission entities, which may be referred to as radio heads, smart radio heads, or transmission / reception points (TRPs). In some configurations, the various functions of each access network entity or base station (105) may be distributed across various network devices (e.g., radio heads and access network controllers) or integrated into a single network device (e.g., base station (105)).

[0067] A wireless communication system (100) can operate using one or more frequency bands in the range of typically 300 MHz (megahertz) to 300 GHz (gigahertz). Generally, the 300 MHz to 3 GHz range is known as the ultra-high frequency (UHF) range or decimeter band because the wavelengths are in the range of lengths from approximately 1 decimeter to 1 meter. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves can penetrate structures sufficiently to provide service to UEs (115) located indoors by macro cells. Transmission of UHF waves may be associated with smaller antennas and shorter ranges (e.g., less than 100 km) compared to transmission using smaller frequencies and longer waves in the HF (high frequency) or VHF (very high frequency) portions of the spectrum below 300 MHz.

[0068] The wireless communication system (100) may also operate in the super high frequency (SHF) zone using frequency bands of 3 GHz to 30 GHz, also known as centimeter bands. The SHF zone includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be opportunistically used by devices that can tolerate interference from other users.

[0069] The wireless communication system (100) may also operate in the extremely high frequency (EHF) band of the spectrum, also known as the millimeter band (e.g., 30 GHz to 300 GHz). In some examples, the wireless communication system (100) may support millimeter wave (mmW) communications between UEs (115) and base stations (105), and the EHF antennas of individual devices may be much smaller and more closely spaced than UHF antennas. In some cases, this may enable the use of antenna arrays within the UE (115). However, propagation of EHF transmissions may experience much greater atmospheric attenuation and shorter range than SHF or UHF transmissions. The techniques disclosed herein may be used across transmissions using one or more different frequency bands, and the designated use of bands across these frequency bands may vary by country or regulatory body.

[0070] In some cases, the wireless communication system (100) may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communication system (100) may use License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band, such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations (105) and UEs (115) may use listen-before-talk (LBT) procedures to ensure that the frequency channel is cleared before transmitting data. In some cases, operations in unlicensed bands may be based on carrier aggregation configurations with component carriers operating in a licensed band (e.g., LAA). Operations in the unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination thereof. Duplication in the unlicensed spectrum can be based on frequency division duplexing (FDD), time division duplexing (TDD), or a combination of both.

[0071] In some examples, a base station (105) or a UE (115) may have multiple antennas that can be used to utilize techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, a wireless communication system (100) may use a transmit method between a transmit device (e.g., base station (105)) and a receive device (e.g., UE (115)), wherein the transmit device has multiple antennas and the receive device has one or more antennas. MIMO communications may use multipath signal propagation to increase spectral efficiency by transmitting or receiving multiple signals through different spatial layers, which may be referred to as spatial multiplexing. Multiple signals may be transmitted by the transmit device, for example, through different antennas or different combinations of antennas. Likewise, multiple signals may be received by the receive device through different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include SU-MIMO (single-user MIMO), in which multiple spatial layers are transmitted to the same receiving device, and MU-MIMO (multiple-user MIMO), in which multiple spatial layers are transmitted to multiple devices.

[0072] Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that can be used at a transmitting device or a receiving device (e.g., base station (105) or UE (115)) to steer or shape an antenna beam (e.g., a transmitting beam or a receiving beam) along a spatial path between a transmitting device and a receiving device. Beamforming can be achieved by combining signals transmitted through antenna elements of an antenna array such that signals propagating with specific orientations for the antenna array experience constructive interference, while other signals experience destructive interference. The adjustment of signals transmitted through antenna elements may include the transmitting device or the receiving device applying specific amplitude and phase offsets to the signals carried through each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a set of beamforming weights associated with a specific orientation (e.g., for the antenna array of the transmitting device or the receiving device, or for any other orientation).

[0073] In one example, the base station (105) may use multiple antennas or antenna arrays to perform beamforming operations for directional communications with the UE (115). For example, some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted multiple times by the base station (105) in different directions, which may include the transmission of signals according to different beamforming weight sets associated with different transmission directions. Transmissions in different beam directions may be used to identify the beam direction for subsequent transmission and / or reception by the base station (105) (e.g., by the base station (105) or a receiving device, such as the UE (115)).

[0074] In some cases, the antennas of the base station (105) or the UE (115) may be located within one or more antenna arrays capable of supporting MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located in an antenna assembly such as an antenna tower. In some cases, the antennas or antenna arrays associated with the base station (105) may be located at various geographical locations. The base station (105) may have an antenna array having multiple rows and columns of antenna ports that the base station (105) can use to support beamforming of communications with the UE (115). Likewise, the UE (115) may have one or more antenna arrays capable of supporting various MIMO or beamforming operations.

[0075] In some cases, the wireless communication system (100) may be a packet-based network operating according to a layered protocol stack. In the user plane, communications at the bearer or PDCP (Packet Data Convergence Protocol) layer may be IP-based. The RLC (Radio Link Control) layer may perform packet segmentation and reassembly to communicate over logical channels. The MAC (Medium Access Control) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use HARQ (hybrid automatic repeat request) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the RRC (Radio Resource Control) protocol layer may provide setup, configuration, and maintenance of the RRC connection between the core network (130) or base station (105) supporting radio bearers for user plane data and the UE (115). In the physical layer, transport channels may be mapped to physical channels.

[0076] Time intervals in LTE or NR are, for example, T s = can be expressed as multiples of a basic time unit that can refer to a sampling period of 1 / 30,720,000 seconds. The time intervals of communication resources can be organized according to radio frames each having a duration of 10 ms (milliseconds), where the frame duration is T f = 307,200 T sIt can be expressed as. Radio frames can be identified by a system frame number (SFN) in the range of 0 to 1023. Each frame may contain 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. Subframes may be further divided into two slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix added to each symbol period). Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases, a subframe may be a minimum scheduling unit of the wireless communication system (100) and may be referred to as a transmission time interval (TTI). In other cases, the minimum scheduling unit of the wireless communication system (100) may be shorter than a subframe or may be dynamically selected (e.g., in bursts of sTTIs (shortened TTIs) or in selected component carriers using sTTIs).

[0077] In some wireless communication systems, a slot may be further subdivided into a number of mini-slots containing one or more symbols. In some cases, a mini-slot or a symbol of a mini-slot may be the minimum unit of scheduling. Each symbol may have a duration that varies, for example, depending on the subcarrier interval or frequency band of the operation. Additionally, some wireless communication systems may implement slot aggregation in which a number of slots or mini-slots are aggregated together and used for communication between the UE (115) and the base station (105).

[0078] The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure to support communications over a communication link (125). For example, a carrier of a communication link (125) may include a portion of a radio frequency spectrum band that operates according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a predefined frequency channel (e.g., E-UTRA (evolved universal mobile telecommunication system terrestrial radio access) EARFCN (absolute radio frequency channel number)) and may be positioned according to a channel raster for discovery by UEs (115). Carriers may be downlink or uplink (e.g., in FDD mode) or may be configured to carry downlink and uplink communications (e.g., in TDD mode). In some examples, signal waveforms transmitted through a carrier may be composed of multiple sub-carriers (using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)).

[0079] The organizational structure of carriers may differ for different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR). For example, communications through a carrier may be organized according to TTIs or slots, each of which may include control information or signaling to support decoding user data as well as user data. A carrier may also include dedicated capture signaling (e.g., synchronization signals or system information, etc.) and control signaling to coordinate operations for the carrier. In some examples (e.g., in a carrier aggregation configuration), a carrier may also have control signaling or capture signaling to coordinate operations for other carriers.

[0080] In some cases, the base station (105) may be a source base station (105) and may configure one or more UEs (115) using one or more CHO configurations for one or more target base stations (105). The CHO configurations may provide one or more associated conditions that can trigger the UE (115) to initiate a handover to a specific target base station (105) for each target base station (105) (e.g., based on measurement thresholds of one or more target base station (105) measurements, one or more source base station (105) measurements, or a combination thereof). In some cases, the CHO configurations may include failure handling information, deconfiguration criteria, or a combination thereof.

[0081] FIG. 2 illustrates an example of a wireless communication system (200) having source and target base stations that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. In some examples, the wireless communication system (200) may implement aspects of the wireless communication system (100). The wireless communication system (200) may include a source base station (105-a), a first target base station (105-b), and a second target base station (105-c), which may be examples of the base station (105) described with reference to FIG. 1; and a UE (115-a), which may be an example of the UE (115) described with reference to FIG. 1. A wireless communication system (200) exemplifies a conditional handover procedure in which a communication connection between a source cell and a UE (115-a), served by a source base station (105-a) (e.g., a first base station), is handed over to either a first target base station (105-b) or a second target base station (105-c).

[0082] Initially, the UE (115-a) and the source base station (105-a) may be in a connected state and may be exchanging information through the first communication connection (205). In some cases, the UE (115-a) may transmit one or more measurement reports, and in these one or more measurement reports, the UE (115-a) may provide one or more measurements for a number of neighboring base stations, including the source base station (105-a), the first target base station (105-b), and the second target base station (105-c). Based on the measurements in the measurement reports, the source base station (105-a) may identify one or more neighboring base stations (105) that are excellent candidates for the handover of the UE (115-a) (e.g., based on signal strength measurements exceeding a threshold value). In this example, the source base station (105-a) can identify that the first target base station (105-b) and the second target base station (105-c) are handover candidates, and can communicate handover requests to each identified candidate (e.g., via backhaul links (134)). In this example, the first target base station (105-b) can perform acknowledgment control based on the received handover request, reserve specific resources (e.g., contention-free random access preamble, random access resources, etc.) for the UE (115-a), and provide the source base station (105-a) with information for random access that can be used to configure the first CHO configuration (215-a). Likewise, the second target base station (105-c) can perform acknowledgment control based on a received handover request, reserve specific resources for the UE (115-a), and provide the source base station (105-a) with information for random access that can be used to configure the second CHO configuration (215-b).

[0083] The source base station (105-a) may provide CHO configurations to the UE (115-a) that can be used by the UE (115-a) to autonomously initiate a handover to the second communication connection (210). In some cases, the CHO configurations may be provided in RRC signaling transmitted to the UE (115-a) (e.g., in an RRC reconfiguration message). The CHO configurations may provide, for example, the cell ID of the associated target base station (105), information for random access to the target base station (105) (e.g., contention-free random access resources, random access preamble, C-RNTI (cell-specific radio network temporary identifier)), and one or more measurement thresholds to be used to trigger a handover to the associated target base station (105) (e.g., RRM thresholds, channel quality metric thresholds, signal strength metric thresholds, etc.). According to the various techniques provided herein, the CHO configurations provided to the UE (115-a) may also include one or more deconfiguration parameters, one or more failure handling parameters, or any combination thereof.

[0084] In some cases, unconfiguration parameters within the CHO configurations may provide event-based unconfiguration and may include one or more timers, one or more unconfiguration thresholds for each CHO target base station (105-b and 105-c), or any combination thereof. Optionally, in some cases, one or more timers may include a validity timer that starts when a handover request is acknowledged by the source base station (105-a). In some cases, the validity timer (e.g., valTimer_TgNB) may be maintained by the source base station (105-a) and the target base stations (105-b and 105-c), and each target base station (105-b and 105-c) may reserve resources for the UE (115-a) during the duration of the validity timer. In other cases, the UE (115-a) may also receive indication of a validity timer associated with each target base station (105-b and 105-c) along with CHO configurations, and may unconfigure the associated CHO configuration upon the expiration of the associated validity timer. In other cases, the source base station (105-a) may transmit an explicit release of the CHO configuration for the target base station (105-b or 105-c) as the validity timer expires, and in such cases, the UE (115-a) does not need to maintain multiple validity timers or a validity timer for each target base station (105-b and 105-c). In some cases, the source base station (105-a) may determine the duration of the validity timer, and the duration of the validity timer may be based on estimates of movement of the UE (115-a), the signal strength of the target measured at the UE (115-a), changes in measurements at the UE (115-a) over time, estimates of the traffic load of the source base station (105-a) or the target base stations (105-b or 105-c) (e.g., tracked by individual base stations (105)), or any combination thereof.

[0085] In some cases, CHO configurations may include one or more deconfiguration thresholds that provide criteria for deconfiguring the CHO. In such cases, if UE (115-a) measurements satisfy threshold-based criteria for deconfiguration for the CHO target base station (105-b or 105-c), UE (115-a) may release the CHO configuration without waiting for an explicit indication from the source base station (105-a). The release of the CHO configuration may include releasing the RRC configuration of the target base station (105-b or 105-c), as well as the associated measurement reporting configurations corresponding to the handover trigger and the CHO deconfiguration trigger. In some cases, UE (115-a) may transmit a measurement report to the source base station (105-a) so that the network is notified of the deconfiguration, and the target base station (105-b or 105-c) may release resources reserved for UE (115-a). In some cases, the measurement report (e.g., RRC measurement report message) may include a deconfiguration indication (e.g., cell ID of the deconfigured target base station (105-b or 105-c)). When deconfiguring the CHO for the target base station (105-b or 105-c), the UE (115-a) may stop performing measurements on the target base station (105-b or 105-c) and stop evaluating whether the target base station (105-b or 105-c) meets the handover or CHO deconfiguration criteria. In some cases, one or more measurement events may be defined for CHO deconfiguration.In some examples, such measurement events may include: Event 1, where neighbor cell measurements (e.g., signal strength, channel quality metric, etc.) fall below a threshold; Event 2, where the measurement of the source base station (105-a) (e.g., SpCell (source primary cell)) becomes better than the first threshold and the measurement of the target base station (105-b or 105-c) becomes worse than the second threshold; Event 3, where the measurement offset between the target base station (105-b or 105-s) measurement and the source base station (105-a) exceeds an offset threshold; or any combination thereof. Upon detection of one or more of the measurement events, the UE (115-a) may release the associated CHO configuration (e.g., including an indication of unconfiguration) and provide a measurement report to the source base station (105-a). In some cases, the measurement thresholds configured in each CHO may differ for each target base station (105-b and 105-c).

[0086] Additionally or alternatively, in some cases, CHO configurations may include one or more timers for use in detecting a handover failure. In some cases, one or more timers may include a conditional handover timer (e.g., CHO_timer_TgNB) initiated by the UE (115-a) upon transmission of a random access request for the handover procedure. In such cases, the UE (115-a) may determine, for example, that CHO criteria for a handover from a source base station (105-a) to a first target base station (105-b) are satisfied, transmit a random access request to the first target base station (105-a), and start the conditional handover timer. If the conditional handover timer expires before the UE (115-a) establishes a connection with the first target base station (105-b), the UE (115-a) may assume that the random access procedure has failed and initiate failure handling. In cases where the UE (115-a) maintains a validity timer for the first target base station (105-b), the UE (115-a) may stop the validity timer when transmitting a random access request. In some cases, failure handling may include selecting a second target base station (105-c) (e.g., or another base station having a CHO configuration that satisfies the CHO criteria for the UE (115-a) to initiate a handover) and transmitting a random access request to the second target base station (105-c). The UE (115-c) may initiate a second conditional access timer associated with the second target base station (105-c), and the process may continue until a successful random access procedure is performed or until the UE (115-a) exhausts the CHO targets that satisfy the CHO criteria—at which point the base station (105-b) may declare a radio link failure and initiate an RRC reset procedure. In some cases, the conditional handover timer may differ for each of the different target base stations.Table 1 below includes examples of conditional handover timer start criteria, stop criteria, and failure actions to take in the case of conditional handover timer expiration. Table 1 - CHO Failure Handling Timer

[0087] FIG. 3 illustrates an example of a general process flow (300) for a CHO that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. In some examples, the process flow (300) may implement aspects of a wireless communication system (100 or 200). The process flow in this example includes a UE (115-b), which may be an example of a UE described with reference to FIG. 1 and 2; a source base station (105-d), a first target base station (105-e), and a second target base station (105-f), which may be examples of base stations described with reference to FIG. 1 and 2. The process flow (300) includes functions and communications implemented by the UE (115-b) and base stations (105-d, 105-e, and 105-f) in the context of conditional handover procedures.

[0088] In the following description of the process flow (300), operations between the UE (115-b) and the base stations (105-d, 105-e, and 105-f) may be transmitted in a different order than the illustrated order, or operations may be performed in different orders or at different times. Certain operations may also be excluded from the process flow (300), or other operations may be added to the process flow (300). Although the base stations (105) and the UE (115-b) are illustrated as performing a number of operations of the process flow (300), it should be understood that any wireless device may perform the illustrated operations.

[0089] In 305, the UE (115-b) may transmit a measurement report to the source base station (105-d). The measurement report may include one or more channel measurements for the source base station (105-d), as well as measurements for a number of neighboring base stations, which may include a first target base station (105-e) and a second target base station (105-f). The measurement report may be a "low" threshold measurement report, which may indicate that the channel measurement associated with the source base station (105-d) is below a threshold used to indicate that the source base station (105-d) must configure a CHO for the UE (115-b).

[0090] In 310, the source base station (105-d) may transmit a handover request to the first target base station (105-e). Additionally, in 315, the source base station (105-d) may transmit a handover request to the second target base station (105-f). In some cases, the source base station (105-d) may select the first target base station (105-e) and the second target base station (105-f) for handover requests based on associated measurements from the measurement report of the UE (115-b) (e.g., based on neighbor base station measurements that exceed a threshold or are superior to other neighbor base station measurements). This example illustrates two target base stations (105), but more or fewer target base stations (105) may be identified for the CHO configuration. In some cases, handover requests may include handover information associated with the UE (115-b) and may also include a time duration for a validity timer as discussed herein.

[0091] In 320, the first target base station (105-e) may perform acknowledgment control in response to receiving a handover request. Likewise, in 325, the second target base station (105-f) may perform acknowledgment control in response to receiving a handover request. The acknowledgment control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preamble, etc.) may be reserved for the UE (115-c).

[0092] In 330, the first target base station (105-e) may transmit a handover request acknowledgment to the source base station (105-d). Additionally, in this example, in 335, the second target base station (105-f) may transmit a handover request acknowledgment to the source base station (105-d). The handover request acknowledgments may include information for use by the UE (115-b) to establish a connection (e.g., random access preamble, C-RNTI, etc.). The source base station (105-d) may receive the handover request acknowledgments and determine CHO criteria for each target cell for use by the UE (115-b) to trigger the CHO. The CHO criteria may include, for example, one or more measurement thresholds of the associated target base station (105), source base station (105-d), or any combination thereof.

[0093] In 340, the source base station (105-d) may transmit CHO configuration information to the UE (115-b) in an RRC reconfiguration message. In some cases, the RRC reconfiguration message may indicate that the first target base station (105-e) and the second target base station (105-f) are configured for CHO, may provide information for accessing the associated base stations (105) (e.g., random access information, C-RNTI, etc.), and may provide handover thresholds associated with each target base station (105).

[0094] In 345, the UE (115-b) may determine that conditions for a handover to the first target base station (105-d) are met. Such determination may be made based on one or more channel quality measurements of the UE (115-b), for example, compared with the CHO configurations provided by the source base station (105-d). In 350, the UE (115-b) may initiate a random access channel (RACH) procedure with the first target base station (105-e) and perform a handover procedure.

[0095] FIG. 4 illustrates an example of a process flow (400) for configuring and subsequently releasing a CHO configuration in wireless communications according to aspects of the present disclosure. In some examples, the process flow (400) may implement aspects of a wireless communication system (100 or 200). The process flow in this example includes a UE (115-c), which may be an example of a UE described with reference to FIG. 1 and 2; a source base station (105-g) and a target base station (105-h), which may be examples of base stations described with reference to FIG. 1 and 2. The process flow (400) includes functions and communications implemented by the UE (115-c) and base stations (105-g and 105-h) in the context of conditional handover procedures.

[0096] In the following description of the process flow (400), operations between the UE (115-c) and the base stations (105-g and 105-h) may be transmitted in a different order than the illustrated order, or operations may be performed in different orders or at different times. Certain operations may also be excluded from the process flow (400), or other operations may be added to the process flow (400). Although the base stations (105) and the UE (115-c) are illustrated as performing a number of operations of the process flow (400), it should be understood that any wireless device may perform the illustrated operations.

[0097] In 405, the UE (115-c) may transmit a measurement report to the source base station (105-g). The measurement report may include one or more channel measurements for the source base station (105-g), as well as measurements for a number of neighboring base stations, which may include the target base station (105-h). The measurement report may be a "low" threshold measurement report, which may indicate that the channel measurement associated with the source base station (105-g) is below a threshold used to indicate that the source base station (105-g) must configure a CHO for the UE (115-c).

[0098] In 410, the source base station (105-g) may transmit a handover request to the target base station (105-h). While the example in FIG. 4 illustrates a single target base station (105-h), in other cases, a number of different target base stations may be configured for the CHO, and the operations of FIG. 4 may be used for any number of target base stations. In some cases, the source base station (105-g) may select the target base station (105-h) for handover requests based on associated measurements from the measurement report of the UE (115-c) (e.g., based on neighbor base station measurements that exceed a threshold or are superior to other neighbor base station measurements). In some cases, the handover request may include handover information associated with the UE (115-c) and may also include a time duration for a validity timer as discussed herein.

[0099] In 415, the target base station (105-h) may perform acknowledgment control in response to receiving a handover request. The acknowledgment control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preamble, etc.) may be reserved for the UE (115-c).

[0100] In 420, the target base station (105-h) may transmit a handover request acknowledgment to the source base station (105-g). The handover request acknowledgment may include information (e.g., random access preamble, C-RNTI, etc.) for use by the UE (115-c) to establish a connection with the target base station (105-h). The source base station (105-g) may receive the handover request acknowledgment and determine CHO criteria for the target cell for use by the UE (115-c) to trigger the CHO. The CHO criteria may include one or more measurement thresholds (e.g., measThreshHO_TgNB) of, for example, the target base station (105-h) (and any other configured target base stations), the source base station (105-g), or any combination thereof.

[0101] In 425, the source base station (105-g) may transmit CHO configuration information to the UE (115-c) in an RRC reconfiguration message. In some cases, the RRC reconfiguration message may indicate that the target base station (105-h) is configured for CHO, provide information for accessing the associated base stations (105) (e.g., random access information, C-RNTI, etc.), and provide handover thresholds associated with each target base station (105-h).

[0102] In 430, the source base station may determine that the UE (115-c) is moving away from the target base station (105-h). In some cases, such determination may be made based on one or more measurement reports provided by the UE (115-c), signal strength measurements of the UE (115-c), positioning information of the UE (115-c), etc.

[0103] In 435, the source base station (105-g) may transmit another RRC reconfiguration to the UE (115-c) to release the CHO configuration for the target base station (105-h). In 440, the source base station (105-g) may transmit a handover cancellation to the target base station (105-h) to cancel the CHO configuration. The UE (115-c) and the target base station (105-h) may delete the CHO configuration based on the signaling from the source base station (105-g).

[0104] FIG. 5 illustrates an example of a process flow (500) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. In some examples, the process flow (500) may implement aspects of a wireless communication system (100 or 200). The process flow in this example includes a UE (115-d), which may be an example of a UE described with reference to FIG. 1 and 2; and a source base station (105-i) and a target base station (105-j), which may be examples of base stations described with reference to FIG. 1 and 2. The process flow (500) includes functions and communications implemented by the UE (115-d) and base stations (105-i and 105-j) in the context of conditional handover procedures.

[0105] In the following description of the process flow (500), operations between the UE (115-d) and the base stations (105-i and 105-j) may be transmitted in a different order than the illustrated order, or operations may be performed in different orders or at different times. Certain operations may also be excluded from the process flow (500), or other operations may be added to the process flow (500). Although the base stations (105) and the UE (115-d) are illustrated as performing a number of operations of the process flow (500), it should be understood that any wireless device may perform the illustrated operations.

[0106] In 505, the UE (115-d) may transmit a measurement report to the source base station (105-i). The measurement report may include one or more channel measurements for the source base station (105-i), as well as measurements for a number of neighboring base stations, which may include the target base station (105-j). The measurement report may be a "low" threshold measurement report, which may indicate that the channel measurement associated with the source base station (105-i) is below a threshold used to indicate that the source base station (105-i) must configure a CHO for the UE (115-d).

[0107] In 510, the source base station (105-i) may transmit a handover request to the target base station (105-j). While the example in FIG. 5 illustrates a single target base station (105-j), in other cases, multiple different target base stations may be configured for the CHO, and the operations of FIG. 5 may be used for any number of target base stations. In some cases, the source base station (105-i) may select the target base station (105-j) for handover requests based on associated measurements from the measurement report of the UE (115-d) (e.g., based on neighbor base station measurements that exceed a threshold or are superior to other neighbor base station measurements). In some cases, the handover request may include handover information associated with the UE (115-d) and may also optionally include a time duration for the validity timer (540). In cases where multiple CHO configurations are configured for multiple target base stations, multiple different validity timers may exist for different target base stations.

[0108] In 515, the target base station (105-j) may perform acknowledgment control in response to receiving a handover request. The acknowledgment control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preamble, etc.) may be reserved for the UE (115-d).

[0109] In 520, the target base station (105-j) may transmit a handover request acknowledgment to the source base station (105-i). The handover request acknowledgment may include information (e.g., random access preamble, C-RNTI, etc.) for use by the UE (115-d) to establish a connection with the target base station (105-j). The source base station (105-i) may receive the handover request acknowledgment and determine CHO criteria for the target cell for use by the UE (115-d) to trigger the CHO. The CHO criteria may include one or more measurement thresholds (e.g., measThreshHO_TgNB) of the target base station (105-j) (and any other configured target base stations), of the source base station (105-i), or any combination thereof. In this example, the CHO criteria may also include a validity time duration (e.g., calTimer_TgNB) for the target base station (105-j).

[0110] In 525, the source base station (105-i) may transmit CHO configuration information to the UE (115-d) in an RRC reconfiguration message. In some cases, the RRC reconfiguration message may indicate that the target base station (105-j) is configured for the CHO, provide information for accessing the associated base stations (105) (e.g., random access information, C-RNTI, etc.), and provide handover thresholds associated with each target base station (105-j). In cases where the CHO configuration provided to the UE (115-d) includes a validity timer, the UE (115-d) may start the validity timer (540) associated with the target base station (105-j). In some cases, the source base station (105-i) and the target base station (105-j) may maintain validity timers, and the UE (115-d) may not maintain the validity timer (540), which can simplify the implementation in the UE (115-d). In such cases, upon the expiration of the validity timer, the source base station (105-i) may explicitly release the CHO through another RRC reconfiguration message. In cases where the UE (115-d) maintains the validity timer (540), the UE (115-d) may autonomously release the CHO configuration upon the expiration of the validity timer (540), and the base stations (105) may also release the CHO configuration based on the validity timers maintained in the base stations (105).

[0111] In 530, the UE (115-d) may determine that conditions for a handover are met while the validity timer is valid. Such determination may be made based on one or more channel quality measurements of the UE (115-d), for example, compared with the CHO configuration provided by the source base station (105-i). In 535, the UE (115-d) may initiate a RACH procedure with the first target base station (105-e) and perform a handover procedure with the target base station (105-j).

[0112] FIG. 6 illustrates an example of a process flow (600) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. In some examples, the process flow (600) may implement aspects of a wireless communication system (100 or 200). The process flow in this example includes a UE (115-e), which may be an example of a UE described with reference to FIG. 1 and 2; a source base station (105-k), a first target base station (105-l), and a second target base station (105-m), which may be examples of base stations described with reference to FIG. 1 and 2. The process flow (600) includes functions and communications implemented by the UE (115-e) and base stations (105-k, 105-l, and 105-m) in the context of conditional handover procedures.

[0113] In the following description of the process flow (600), operations between the UE (115-e) and the base stations (105-k, 105-l, and 105-m) may be transmitted in a different order than the illustrated order, or operations may be performed in different orders or at different times. Certain operations may also be excluded from the process flow (600), or other operations may be added to the process flow (600). Although the base stations (105) and the UE (115-e) are illustrated as performing a number of operations of the process flow (600), it should be understood that any wireless device may perform the illustrated operations.

[0114] In 605, the UE (115-e) may transmit a measurement report to the source base station (105-k). The measurement report may include one or more channel measurements for the source base station (105-k), as well as measurements for a number of neighboring base stations, which may include a first target base station (105-l) and a second target base station (105-m). The measurement report may be a "low" threshold measurement report, which may indicate that the channel measurement associated with the source base station (105-k) is below a threshold used to indicate that the source base station (105-k) must configure a CHO for the UE (115-e).

[0115] In 610, the source base station (105-k), the first target base station (105-l), and the second target base station (105-m) may perform target handover preparation (e.g., based on handover requests, acknowledgment control, and handover request acknowledgments). Handover preparation may include determining information (e.g., random access preambles, C-RNTIs, etc.) for use by the UE (115-e) to establish a connection. The source base station (105-k) may determine CHO criteria for each target cell for use by the UE (115-e) to trigger the CHO. The CHO criteria may include, for example, one or more measurement thresholds of the associated target base station (105), the source base station (105-k), or any combination thereof. In this example, the CHO configuration may also include a CHO timer for each target base station (105-l and 105-m). In some cases, base stations (105) may maintain validity timers (620) and release the CHO configurations of target cells upon the expiration of the associated validity timer.

[0116] In 615, the source base station (105-k) may transmit CHO configuration information to the UE (115-e) in an RRC reconfiguration message. In some cases, the RRC reconfiguration message may indicate that the first target base station (105-l) and the second target base station (105-m) are configured for CHO, may provide information for accessing the associated base stations (105) (e.g., random access information, C-RNTI, etc.), and may provide handover thresholds associated with each target base station (105).

[0117] At 625, the UE (115-e) may determine that conditions for a handover to the first target base station (105-l) are met. Such determination may be made based on one or more channel quality measurements of the UE (115-e), for example, compared with the CHO configurations provided by the source base station (105-k). At 630, the UE (115-e) may initiate a random access channel (RACH) procedure with the first target base station (105-l) and may start a CHO timer (635) associated with the first target base station (105-l) upon transmission of an initial random access request message. In this example, at 640, the UE (115-e) may determine a CHO failure based on the expiration of the CHO timer (635) before completing the random access procedure with the first target base station (105-l). For example, the UE (115-e) may not receive a random access response after one or more retransmissions of a random access request while the CHO timer (635) is valid.

[0118] In 645, the UE (115-e) may determine that conditions for a handover to the second target base station (105-m) are met. Such determination may be based on one or more channel quality measurements of the UE (115-e), which are compared with the CHO configurations provided by the source base station (105-k) while, for example, the CHO configuration of the second target base station (105-m) is active. In 655, the UE (115-e) may initiate a random access channel (RACH) procedure with the second target base station (105-m) and may start a CHO timer (650) associated with the second target base station (105-m) upon transmission of an initial random access request message. In this example, the random access procedure with the second target base station (105-m) may be successful, and the UE (115-e) may complete the handover. In cases where the CHO timer (650) expires before the random access procedure with the second target base station (105-m) is completed, the UE (115-e) may repeat the process for any other target base station having an active CHO configuration. In cases where multiple target base stations have a CHO configuration and satisfy the conditions for handover, the UE (115-e) may select one based on one or more predetermined criteria (e.g., the target base station with the best channel quality, the target base station with the shortest remaining time for the validity timer, the earliest configured CHO, etc.). In cases where there is a CHO failure and other target base stations are not configured for the CHO, the UE (115-e) may declare a radio link failure and initiate an RRC connection reset procedure.

[0119] FIG. 7 illustrates an example of a process flow (700) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. In some examples, the process flow (700) may implement aspects of a wireless communication system (100 or 200). The process flow in this example includes a UE (115-f), which may be an example of a UE described with reference to FIG. 1 and 2; a source base station (105-n) and a target base station (105-o), which may be examples of base stations described with reference to FIG. 1 and 2. The process flow (700) includes functions and communications implemented by the UE (115-f) and base stations (105-n and 105-o) in the context of conditional handover procedures.

[0120] In the following description of the process flow (700), operations between the UE (115-f) and the base stations (105-n and 105-o) may be transmitted in a different order than the illustrated order, or operations may be performed in different orders or at different times. Certain operations may also be excluded from the process flow (700), or other operations may be added to the process flow (700). Although the base stations (105) and the UE (115-f) are illustrated as performing a number of operations of the process flow (700), it should be understood that any wireless device may perform the illustrated operations.

[0121] In 705, the UE (115-f) may transmit a measurement report to the source base station (105-n). The measurement report may include one or more channel measurements for the source base station (105-n), as well as measurements for a number of neighboring base stations, which may include the target base station (105-o). The measurement report may be a "low" threshold measurement report, which may indicate that the channel measurement associated with the source base station (105-n) is below a threshold used to indicate that the source base station (105-n) must configure a CHO for the UE (115-f).

[0122] In 710, the source base station (105-n) may transmit a handover request to the target base station (105-o). Although the example in FIG. 7 illustrates a single target base station (105-o), in other cases, a number of different target base stations may be configured for the CHO, and the operations of FIG. 7 may be used for any number of target base stations. In some cases, the source base station (105-n) may select the target base station (105-o) for handover requests based on associated measurements from the measurement report of the UE (115-f) (e.g., based on neighbor base station measurements that exceed a threshold or are superior to other neighbor base station measurements). In some cases, the handover request may include handover information associated with the UE (115-f).

[0123] In 715, the target base station (105-o) may perform acknowledgment control in response to receiving a handover request. The acknowledgment control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preamble, etc.) may be reserved for the UE (115-f).

[0124] In 720, the target base station (105-o) may transmit a handover request acknowledgment to the source base station (105-n). The handover request acknowledgment may include information (e.g., random access preamble, C-RNTI, etc.) for use by the UE (115-f) to establish a connection with the target base station (105-o). The source base station (105-n) may receive the handover request acknowledgment and determine CHO criteria for the target cell for use by the UE (115-f) to trigger the CHO. The CHO criteria may include one or more measurement thresholds (e.g., measThreshHO_TgNB) of, for example, the target base station (105-o) (and any other configured target base stations), the source base station (105-n), or any combination thereof. In this example, the CHO criteria may also include one or more deconfiguration criteria (e.g., measThreshDeconfig_TgNB) that trigger the deconfiguration of the CHO when satisfied. In some cases, the CHO criteria may also include a time duration for one or more timers (e.g., a validity timer, a CHO timer, or both).

[0125] In 725, the source base station (105-n) may transmit CHO configuration information to the UE (115-f) in an RRC reconfiguration message. In some cases, the RRC reconfiguration message may indicate that the target base station (105-o) is configured for CHO, provide information for accessing the associated base stations (105) (e.g., random access information, C-RNTI, etc.), and provide handover thresholds and unconfiguration thresholds associated with each target base station (105-o).

[0126] In 730, the UE (115-f) may determine that conditions for deconfiguring the target base station (105-o) are met. Such determination may be made based on one or more channel quality measurements of the UE (115-f), for example, compared with the CHO configuration provided by the source base station (105-n). In 735, the UE (115-f) may transmit a measurement report to the source base station (105-n). In some cases, the measurement report may indicate that the CHO configuration for the target base station (105-o) is deconfigured. Deconfiguring the CHO may include releasing the RRC configuration of the target base station (105-o), and the UE (115-f) may stop performing measurements on the target base station (105-o) and evaluating whether the target base station (105-o) meets the handover or CHO deconfiguration criteria. In some cases, the measurement report (e.g., RRC measurement report message) may include an unconfiguration indication.

[0127] In 740, the source base station (105-n) may transmit a handover cancellation indication to the target base station (105-o). In 745, the target base station (105-o) may release resources reserved for the UE (115-f) in response to the handover cancellation indication.

[0128] FIG. 8 illustrates a block diagram (800) of a device (805) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (805) may be an example of aspects of a UE (115) as described herein. The device (805) may include a receiver (810), a communication manager (815), and a transmitter (820). The device (805) may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0129] The receiver (810) may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to CHO unconfiguration and failure handling in wireless communications). The information may be transmitted to other components of the device (805). The receiver (810) may be an example of aspects of the transceiver (1120) described with reference to FIG. 11. The receiver (810) may utilize a single antenna or a set of antennas.

[0130] A communication manager (815) receives a conditional handover configuration from a source base station, one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations, and determines a first conditional handover failure in response to the first conditional handover timer expiring before completing a first random access procedure, determines that a first measurement threshold for initiating a handover to a first target base station is satisfied based on the conditional handover configuration, transmits a first random access request to the first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration, and can start a first conditional handover timer to complete the first random access procedure in response to transmitting the first random access request.

[0131] The communication manager (815) may also receive from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to the associated target base station and a release measurement threshold for releasing the conditional handover configuration of the associated target base station—release a first conditional handover configuration of the first target base station, and determine that, based on the conditional handover configuration, the first release measurement threshold for releasing the first conditional handover configuration of the first target base station is satisfied. The communication manager (815) may be an example of aspects of the communication manager (1110) described herein.

[0132] The communication manager (815) or the subcomponents of the communication manager (815) may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. When implemented in code executed by a processor, the functions of the communication manager (815) or the subcomponents of the communication manager (815) may be performed by a general-purpose processor, a DSP, an ASIC (application-specific integrated circuit), an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this disclosure.

[0133] The communication manager (815) or the subcomponents of the communication manager (815) may be located in various physical positions, including being distributed so that parts of the functions are implemented at different physical locations by one or more physical components. In some examples, the communication manager (815) or the subcomponents of the communication manager (815) may be separate and distinct components according to various aspects of the present disclosure. In some examples, the communication manager (815) or the subcomponents of the communication manager (815) may be combined with one or more other hardware components, including (but not limited to) an I / O (input / output) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof, according to various aspects of the present disclosure.

[0134] The transmitter (820) can transmit signals generated by other components of the device (805). In some examples, the transmitter (820) may be colocated with the receiver (810) in a transceiver module. For instance, the transmitter (820) may be an example of aspects of the transceiver (1120) described with reference to FIG. 11. The transmitter (820) may utilize a single antenna or a set of antennas.

[0135] FIG. 9 illustrates a block diagram (900) of a device (905) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (905) may be an example of aspects of the device (805) or UE (115) as described herein. The device (905) may include a receiver (910), a communication manager (915), and a transmitter (940). The device (905) may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0136] The receiver (910) may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to CHO unconfiguration and failure handling in wireless communications). The information may be transmitted to other components of the device (905). The receiver (910) may be an example of aspects of the transceiver (1120) described with reference to FIG. 11. The receiver (910) may utilize a single antenna or a set of antennas.

[0137] The communication manager (915) may be an example of aspects of the communication manager (815) as described herein. The communication manager (915) may include a handover configuration manager (920), a measurement manager (925), a random access manager (930), and a conditional handover timer (935). The communication manager (915) may be an example of aspects of the communication manager (1110) described herein.

[0138] A handover configuration manager (920) may receive a conditional handover configuration from a source base station that indicates one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations, and may determine a first conditional handover failure in response to the first conditional handover timer expiring before completing a first random access procedure.

[0139] The measurement manager (925) can determine that a first measurement threshold for initiating a handover to a first target base station is satisfied based on a conditional handover configuration.

[0140] The random access manager (930) can transmit a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station based on a conditional handover configuration.

[0141] The conditional handover timer (935) can start the first conditional handover timer to complete the first random access procedure in response to transmitting the first random access request.

[0142] In some cases, the handover configuration manager (920) receives from the source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to the associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—and can release the first conditional handover configuration of the first target base station.

[0143] The measurement manager (925) can determine that, based on the conditional handover configuration, the first unconfiguration measurement threshold for unconfiguring the first conditional handover configuration of the first target base station is satisfied.

[0144] The transmitter (940) can transmit signals generated by other components of the device (905). In some examples, the transmitter (940) may be colocated with the receiver (910) in a transceiver module. For instance, the transmitter (940) may be an example of aspects of the transceiver (1120) described with reference to FIG. 11. The transmitter (940) may utilize a single antenna or a set of antennas.

[0145] FIG. 10 illustrates a block diagram (1000) of a communication manager (1005) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The communication manager (1005) may be an example of aspects of the communication manager (815), communication manager (915), or communication manager (1110) described herein. The communication manager (1005) may include a handover configuration manager (1010), a measurement manager (1015), a random access manager (1020), a conditional handover timer (1025), an optional validity timer (1030), and an RRC connection setup component (1035). Each of these modules may communicate indirectly or directly with one another (e.g., through one or more buses).

[0146] A handover configuration manager (1010) may receive a conditional handover configuration from a source base station, one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations.

[0147] In some examples, the handover configuration manager (1010) may determine a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed.

[0148] In some examples, the handover configuration manager (1010) may receive a conditional handover configuration from a source base station that indicates one or more conditional handover configurations associated with one or more target base stations, and each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to the associated target base station and a release measurement threshold for releasing the conditional handover configuration of the associated target base station. In some examples, the handover configuration manager (1010) may release the first conditional handover configuration of the first target base station.

[0149] In some examples, the handover configuration manager (1010) may repeat determining, transmitting, and starting timers for any other target base stations configured for conditional handover in the event of additional conditional handover failures.

[0150] In some examples, the handover configuration manager (1010) may select a second target base station from a set of available target base stations in response to the expiration of a first conditional handover timer, based on one or more of the channel quality measurement associated with each of a set of available target base stations, the amount of time remaining for a validity timer associated with each of a set of available target base stations, or any combination thereof.

[0151] In some examples, the handover configuration manager (1010) may delete one or more of the radio resource control configuration, the first measurement and reporting configuration for the conditional handover trigger and the conditional handover unconfiguration trigger, or one or more timers associated with the first target base station, provided in the first conditional handover configuration.

[0152] In some examples, the handover configuration manager (1010) may stop evaluating conditional handover measurements associated with the first target base station, and whether the measurements satisfy conditional handover criteria or conditional handover deconfiguration criteria. In some cases, one or more timers include at least a first conditional handover timer for completing the first random access procedure with the first target base station.

[0153]

[0154] In some cases, the first unconfiguration measurement threshold is a channel quality threshold associated with the first target base station, and the first conditional handover configuration is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold. In some cases, the first unconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold associated with the first target base station, and the first conditional handover configuration is released in response to the first channel quality measurement of the source base station exceeding the first threshold and the second channel quality measurement of the first target base station being less than the second threshold. In some cases, the first unconfiguration measurement threshold is a difference threshold, and the first conditional handover configuration is released in response to the difference between the channel quality measurements of the first target base station and the source base station exceeding the difference threshold.

[0155] The measurement manager (1015) can determine that a first measurement threshold for initiating a handover to a first target base station is satisfied based on a conditional handover configuration.

[0156] In some examples, the measurement manager (1015) may determine that a first disabling measurement threshold for disabling the first conditional handover configuration of the first target base station is satisfied based on the conditional handover configuration.

[0157] In some examples, the measurement manager (1015) may determine that a second measurement threshold for initiating a handover to a second target base station is satisfied in response to the expiration of the first conditional handover timer.

[0158] In some examples, the measurement manager (1015) may determine that a second triggering measurement threshold for initiating a handover to a second target base station is satisfied based on a conditional handover configuration.

[0159] In some examples, the measurement manager (1015) may transmit a measurement report to the source base station indicating that the first conditional handover configuration of the first target base station is released. In some cases, the measurement report includes a deconfiguration indication for the first target base station.

[0160] The random access manager (1020) can transmit a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station based on a conditional handover configuration.

[0161] In some examples, the random access manager (1020) may transmit a second random access request to the second target base station to initiate a second random access procedure for a handover to the second target base station based on a conditional handover configuration.

[0162] The conditional handover timer (1025) may start a first conditional handover timer to complete a first random access procedure in response to transmitting a first random access request. In some examples, the conditional handover timer (1025) may start a second conditional handover timer to complete a second random access procedure. In some cases, the first duration of the first conditional handover timer is different from the second duration of the second conditional handover timer.

[0163] The validity timer (1030) may initiate a first validity timer and a second validity timer in response to receiving a conditional handover configuration, if present. In some examples, the validity timer (1030) may delete the second conditional handover configuration in response to the expiration of the second validity timer. In some examples, the validity timer (1030) may stop the first validity timer when transmitting a first random access request to a first target base station.

[0164] The RRC connection setup component (1035) can initiate a connection reset procedure when it determines that other target base stations are not configured for conditional handover.

[0165] FIG. 11 illustrates a diagram of a system (1100) including a device (1105) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (1105) may be an example of components of a device (805), a device (905), or a UE (115) as described herein, or may include such components. The device (1105) may include components for bidirectional voice and data communications, including a communication manager (1110), an I / O controller (1115), a transceiver (1120), an antenna (1125), a memory (1130), and a processor (1140), as well as components for transmitting and receiving communications. These components may communicate electronically through one or more buses (e.g., a bus (1145)).

[0166] A communication manager (1110) receives a conditional handover configuration from a source base station, one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations, and determines a first conditional handover failure in response to the expiration of a first conditional handover timer before completing a first random access procedure, determines that a first measurement threshold for initiating a handover to a first target base station is satisfied based on the conditional handover configuration, transmits a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station based on the conditional handover configuration, and can start a first conditional handover timer to complete a first random access procedure in response to transmitting the first random access request.

[0167] The communication manager (1110) may also receive a conditional handover configuration from a source base station that indicates one or more conditional handover configurations associated with one or more target base stations—each of which includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a release measurement threshold for releasing the conditional handover configuration of the associated target base station—release a first conditional handover configuration of the first target base station, and determine that, based on the conditional handover configuration, the first release measurement threshold for releasing the first conditional handover configuration of the first target base station is satisfied.

[0168] The I / O controller (1115) can manage input and output signals for the device (1105). The I / O controller (1115) can also manage peripherals that are not integrated into the device (1105). In some cases, the I / O controller (1115) can represent physical connections or ports to external peripherals. In some cases, the I / O controller (1115) can utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS / 2®, UNIX®, LINUX®, or other known operating systems. In other cases, the I / O controller (1115) can represent or interact with a modem, keyboard, mouse, touchscreen, or similar device. In some cases, the I / O controller (1115) can be implemented as part of a processor. In some cases, the user can interact with the device (1105) through the I / O controller (1115) or through hardware components controlled by the I / O controller (1115).

[0169] The transceiver (1120) can communicate bidirectionally through one or more antennas, wired or wireless links, as described above. For example, the transceiver (1120) can represent a wireless transceiver and can communicate bidirectionally with another wireless transceiver. The transceiver (1120) may also include a modem for modulating packets, providing the modulated packets to the antennas for transmission, and demodulating packets received from the antennas.

[0170] In some cases, the wireless device may include a single antenna (1125). However, in some cases, the device may have more than one antenna (1125) capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0171] Memory (1130) may include RAM and ROM. Memory (1130) may store computer-readable computer-executable code (1135) containing instructions that, when executed, cause a processor to perform the various functions described herein. In some cases, memory (1130) may include a BIOS that can control basic hardware or software operations, such as interactions with peripheral components or devices, among other things.

[0172] The processor (1140) may include intelligent hardware devices (e.g., general-purpose processor, DSP, CPU, microcontroller, ASIC, FPGA, programmable logic device, discrete gate or transistor logic component, discrete hardware component, or any combination thereof). In some cases, the processor (1140) may be configured to operate a memory array using a memory controller. In other cases, the memory controller may be integrated into the processor (1140). The processor (1140) may be configured to execute computer-readable instructions stored in memory (e.g., memory (1130)) to enable the device (1105) to perform various functions (e.g., functions or tasks supporting CHO deconfiguration and failure handling in wireless communications).

[0173] The code (1135) may include instructions for implementing aspects of the present disclosure, including instructions for supporting wireless communications. The code (1135) may be stored in a non-transient computer-readable medium, such as system memory or other types of memory. In some cases, the code (1135) may not be directly executable by the processor (1140), but may enable the computer to perform the functions described herein (e.g., when compiled and executed).

[0174] FIG. 12 illustrates a block diagram (1200) of a device (1205) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (1205) may be an example of aspects of a base station (105) as described herein. The device (1205) may include a receiver (1210), a communication manager (1215), and a transmitter (1220). The device (1205) may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0175] The receiver (1210) may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to CHO unconfiguration and failure handling in wireless communications). The information may be transmitted to other components of the device (1205). The receiver (1210) may be an example of aspects of the transceiver (1520) described with reference to FIG. 15. The receiver (1210) may utilize a single antenna or a set of antennas.

[0176] A communication manager (1215) may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station—each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the start of a conditional handover of a UE from a source base station to an individual target base station—and transmit one or more conditional handover configurations to a UE, each of which indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0177] The communication manager (1215) may also set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by the source base station—each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station—and transmit one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to an associated target base station, and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station. The communication manager (1215) may be an example of aspects of the communication manager (1510) described herein.

[0178] The communication manager (1215) or the subcomponents of the communication manager (1215) may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. When implemented in code executed by a processor, the functions of the communication manager (1215) or the subcomponents of the communication manager (1215) may be performed by a general-purpose processor, a DSP, an ASIC (application-specific integrated circuit), an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this disclosure.

[0179] The communication manager (1215) or the subcomponents of the communication manager (1215) may be located in various physical positions, including distributed so that parts of the functions are implemented at different physical locations by one or more physical components. In some examples, the communication manager (1215) or the subcomponents of the communication manager (1215) may be separate and distinct components according to various aspects of the present disclosure. In some examples, the communication manager (1215) or the subcomponents of the communication manager (1215) may be combined with one or more other hardware components, including (but not limited to) an I / O (input / output) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof, according to various aspects of the present disclosure.

[0180] The transmitter (1220) can transmit signals generated by other components of the device (1205). In some examples, the transmitter (1220) may be colocated with the receiver (1210) in a transceiver module. For instance, the transmitter (1220) may be an example of aspects of the transceiver (1520) described with reference to FIG. 15. The transmitter (1220) may utilize a single antenna or a set of antennas.

[0181] FIG. 13 illustrates a block diagram (1300) of a device (1305) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (1305) may be an example of aspects of the device (1205) or base station (105) as described herein. The device (1305) may include a receiver (1310), a communication manager (1315), and a transmitter (1330). The device (1305) may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0182] The receiver (1310) may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to CHO unconfiguration and failure handling in wireless communications). The information may be transmitted to other components of the device (1305). The receiver (1310) may be an example of aspects of the transceiver (1520) described with reference to FIG. 15. The receiver (1310) may utilize a single antenna or a set of antennas.

[0183] The communication manager (1315) may be an example of aspects of the communication manager (1215) as described herein. The communication manager (1315) may include a handover configuration manager (1320) and a UE handover manager (1325). The communication manager (1315) may be an example of aspects of the communication manager (1510) described herein.

[0184] A handover configuration manager (1320) may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station, wherein each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the start of a conditional handover of a UE from a source base station to an individual target base station.

[0185] A UE handover manager (1325) may transmit one or more conditional handover configurations to a UE, and each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of the UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0186] A handover configuration manager (1320) can set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station, and each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of a UE to an associated target base station and a conditional handover timer value for completing a conditional handover of a UE to an associated target base station.

[0187] A UE handover manager (1325) can transmit one or more conditional handover configurations to a UE, and each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, and a conditional handover timer value for completing the UE's conditional handover to the associated target base station.

[0188] The transmitter (1330) can transmit signals generated by other components of the device (1305). In some examples, the transmitter (1330) may be colocated with the receiver (1310) in a transceiver module. For example, the transmitter (1330) may be an example of aspects of the transceiver (1520) described with reference to FIG. 15. The transmitter (1330) may utilize a single antenna or a set of antennas.

[0189] FIG. 14 illustrates a block diagram (1400) of a communication manager (1405) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The communication manager (1405) may be an example of aspects of the communication manager (1215), communication manager (1315), or communication manager (1510) described herein. The communication manager (1405) may include a handover configuration manager (1410), a UE handover manager (1415), a timer manager (1420), and a measurement manager (1425). Each of these modules may communicate indirectly or directly with one another (e.g., through one or more buses).

[0190] A handover configuration manager (1410) may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station, wherein each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the start of a conditional handover of a UE from a source base station to an individual target base station.

[0191] In some examples, the handover configuration manager (1410) may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station, and each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of a UE to an associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station.

[0192] In some examples, the handover configuration manager (1410) may release the first conditional handover configuration of the first target base station in response to a measurement report. In some examples, the handover configuration manager (1410) may delete one or more of the timers associated with the first target base station, the first triggering measurement threshold, the first unconfiguration measurement threshold, or the radio resource control configuration included in the first conditional handover configuration. In some examples, the handover configuration manager (1410) may provide the first target base station with an indication that the first conditional handover configuration is released.

[0193] In some cases, the unconfiguration measurement threshold is a channel quality threshold associated with each individual target base station, and the conditional handover configuration of the first target base station is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold of the first target base station. In some cases, the unconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold for each individual target base station, and the conditional handover configuration of the first target base station is released in response to the first channel quality measurement of the source base station exceeding the first threshold and the second channel quality measurement of the first target base station being less than the second threshold of the first target base station. In some cases, the unconfiguration measurement threshold is a difference threshold, and the conditional handover configuration associated with the first target base station is released in response to the difference between the channel quality measurements of the first target base station and the source base station exceeding the difference threshold.

[0194] A UE handover manager (1415) can transmit one or more conditional handover configurations to a UE, and each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of the UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0195] In some examples, the UE handover manager (1415) may transmit one or more conditional handover configurations to the UE, and each of the one or more conditional handover configurations indicates an associated target base station, a triggering threshold for initiating a conditional handover to the associated target base station, and a deconfiguration threshold for deconfiguring the conditional handover configuration of the associated target base station. In some cases, the UE autonomously deconfigures the first conditional handover configuration of the first target base station based on the expiration of a first validity period.

[0196] The timer manager (1420) can manage one or more times associated with the CHO. In some cases, the conditional handover time period is determined based on one or more of the UE’s movement estimate for each individual target base station, the traffic load of the source base station or each individual target base station, channel quality measurements for each individual target base station provided by the UE, or any combination thereof.

[0197] The measurement manager (1425) can receive a measurement report from the UE indicating that a first unconfiguration measurement threshold for unconfiguring the first conditional handover configuration of the first target base station is satisfied.

[0198] FIG. 15 illustrates a diagram of a system (1500) including a device (1505) that supports CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. The device (1505) may be an example of components of a device (1205), a device (1305), or a base station (105) as described herein, or may include such components. The device (1505) may include components for bidirectional voice and data communications, including a communication manager (1510), a network communication manager (1515), a transceiver (1520), an antenna (1525), a memory (1530), a processor (1540), and an inter-station communication manager (1545), as well as components for transmitting and receiving communications. These components may communicate electronically through one or more buses (e.g., a bus (1550)).

[0199] A communication manager (1510) may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by a source base station—each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the start of a conditional handover of a UE from a source base station to an individual target base station—and transmit one or more conditional handover configurations to a UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of a UE from a source base station to an associated target base station, and a conditional handover time period of the associated target base station.

[0200] The communication manager (1510) may also set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from a source base station to an individual target base station by the source base station—each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station—and transmit one or more conditional handover configurations to the UE, and each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to an associated target base station, and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station.

[0201] A network communication manager (1515) can manage communications with a core network (e.g., through one or more wired backhaul links). For example, the network communication manager (1515) can manage the delivery of data communications to client devices such as one or more UEs (115).

[0202] The transceiver (1520) can communicate bidirectionally through one or more antennas, wired or wireless links, as described above. For example, the transceiver (1520) can represent a wireless transceiver and can communicate bidirectionally with another wireless transceiver. The transceiver (1520) may also include a modem for modulating packets, providing the modulated packets to the antennas for transmission, and demodulating packets received from the antennas.

[0203] In some cases, the wireless device may include a single antenna (1525). However, in some cases, the device may have more than one antenna (1525) capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0204] Memory (1530) may include RAM, ROM, or a combination thereof. Memory (1530) may store computer-readable code (1535) containing instructions that, when executed by a processor (e.g., processor (1540)), cause the device to perform the various functions described herein. In some cases, memory (1530) may include a BIOS that, among others, can control basic hardware or software operations such as interaction with peripheral components or devices.

[0205] The processor (1540) may include intelligent hardware devices (e.g., general-purpose processor, DSP, CPU, microcontroller, ASIC, FPGA, programmable logic device, discrete gate or transistor logic component, discrete hardware component, or any combination thereof). In some cases, the processor (1540) may be configured to operate a memory array using a memory controller. In some cases, the memory controller may be integrated into the processor (1540). The processor (1540) may be configured to execute computer-readable instructions stored in memory (e.g., memory (1530)) to enable the device (1505) to perform various functions (e.g., functions or tasks supporting CHO deconfiguration and failure handling in wireless communications).

[0206] The inter-station communication manager (1545) may manage communications with other base stations (105) and may include a controller or scheduler for controlling communications with UEs (115) in cooperation with other base stations (105). For example, the inter-station communication manager (1545) may coordinate scheduling for transmissions to UEs (115) for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communication manager (1545) may provide an X2 interface within LTE / LTE-A wireless communication network technology to provide communication between base stations (105).

[0207] The code (1535) may include instructions for implementing aspects of the present disclosure, including instructions for supporting wireless communications. The code (1535) may be stored in a non-transient computer-readable medium, such as system memory or other types of memory. In some cases, the code (1535) may not be directly executable by the processor (1540), but may enable the computer to perform the functions described herein (e.g., when compiled and executed).

[0208] FIG. 16 illustrates a flowchart illustrating a method (1600) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (1600) may be implemented by a UE (115) or components of the UE (115) as described herein. For example, operations of the method (1600) may be performed by a communications manager as described with reference to FIGS. 8 through 11. In some examples, the UE may execute a set of commands to control functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use special-purpose hardware to perform aspects of the functions described below.

[0209] In 1605, the UE may receive a conditional handover configuration from a source base station indicating one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations. The operations of 1605 may be performed according to the methods described herein. In some examples, aspects of the operations of 1605 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0210] In 1610, the UE may determine, based on a conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied. The operations of 1610 may be performed according to the methods described herein. In some examples, aspects of the operations of 1610 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0211] In 1615, the UE may transmit a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station based on a conditional handover configuration. The operations of 1615 may be performed according to the methods described herein. In some examples, aspects of the operations of 1615 may be performed by a random access manager as described with reference to FIGS. 8 through 11.

[0212] In 1620, the UE may start a first conditional handover timer to complete the first random access procedure in response to transmitting a first random access request. The operations of 1620 may be performed according to the methods described herein. In some examples, aspects of the operations of 1620 may be performed by a conditional handover timer as described with reference to FIGS. 8 through 11.

[0213] In 1625, the UE may determine a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed. The operations of 1625 may be performed according to the methods described herein. In some examples, aspects of the operations of 1625 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0214] FIG. 17 illustrates a flowchart illustrating a method (1700) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (1700) may be implemented by a UE (115) or components of the UE (115) as described herein. For example, operations of the method (1700) may be performed by a communications manager as described with reference to FIGS. 8 through 11. In some examples, the UE may execute a set of commands to control functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use special-purpose hardware to perform aspects of the functions described below.

[0215] In 1705, the UE may receive a conditional handover configuration from a source base station indicating one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations. The operations of 1705 may be performed according to the methods described herein. In some examples, aspects of the operations of 1705 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0216] In 1710, the UE may determine, based on a conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied. The operations of 1710 may be performed according to the methods described herein. In some examples, aspects of the operations of 1710 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0217] In 1715, the UE may transmit a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station based on a conditional handover configuration. The operations of 1715 may be performed according to the methods described herein. In some examples, aspects of the operations of 1715 may be performed by a random access manager as described with reference to FIGS. 8 through 11.

[0218] In 1720, the UE may start a first conditional handover timer to complete the first random access procedure in response to transmitting a first random access request. The operations of 1720 may be performed according to the methods described herein. In some examples, aspects of the operations of 1720 may be performed by a conditional handover timer as described with reference to FIGS. 8 through 11.

[0219] In 1725, the UE may determine a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed. The operations of 1725 may be performed according to the methods described herein. In some examples, aspects of the operations of 1725 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0220] In 1730, the UE may determine that a second measurement threshold for initiating a handover to a second target base station is satisfied in response to the expiration of a first conditional handover timer. The operations of 1730 may be performed according to the methods described herein. In some examples, aspects of the operations of 1730 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0221] In 1735, the UE may transmit a second random access request to the second target base station to initiate a second random access procedure for a handover to the second target base station based on a conditional handover configuration. The operations of 1735 may be performed according to the methods described herein. In some examples, aspects of the operations of 1735 may be performed by a random access manager as described with reference to FIGS. 8 through 11.

[0222] In 1740, the UE may start a second conditional handover timer to complete a second random access procedure. The operations of 1740 may be performed according to the methods described herein. In some examples, aspects of the operations of 1740 may be performed by a conditional handover timer as described with reference to FIGS. 8 through 11.

[0223] In 1745, the UE may repeat determining, transmitting, and initiating for any other target base stations configured for conditional handover in the event of additional conditional handover failures. The operations of 1745 may be performed according to the methods described herein. In some examples, aspects of the operations of 1745 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0224] In 1750, the UE may initiate a connection reset procedure when it determines that other target base stations are not configured for conditional handover. The operations of 1750 may be performed according to the methods described herein. In some examples, aspects of the operations of 1750 may be performed by an RRC connection setup component as described with reference to FIGS. 8 through 11.

[0225] FIG. 18 illustrates a flowchart illustrating a method (1800) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (1800) may be implemented by a UE (115) or components of the UE (115) as described herein. For example, operations of the method (1800) may be performed by a communications manager as described with reference to FIGS. 8 through 11. In some examples, the UE may execute a set of commands to control functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use special-purpose hardware to perform aspects of the functions described below.

[0226] In 1805, the UE may receive from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations, each of the one or more conditional handover configurations including a triggering measurement threshold for initiating a conditional handover to the associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station. The operations of 1805 may be performed according to the methods described herein. In some examples, aspects of the operations of 1805 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0227] In 1810, the UE may determine, based on the conditional handover configuration, that a first disconfiguration measurement threshold for disconfiguring the first conditional handover configuration of the first target base station is satisfied. The operations of 1810 may be performed according to the methods described herein. In some examples, aspects of the operations of 1810 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0228] In 1815, the UE may release a first conditional handover configuration of a first target base station. The operations of 1815 may be performed according to the methods described herein. In some examples, aspects of the operations of 1815 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0229] FIG. 19 illustrates a flowchart illustrating a method (1900) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (1900) may be implemented by a UE (115) or components of the UE (115) as described herein. For example, operations of the method (1900) may be performed by a communications manager as described with reference to FIGS. 8 through 11. In some examples, the UE may execute a set of commands to control functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use special-purpose hardware to perform aspects of the functions described below.

[0230] In 1905, the UE may receive from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations, each of the one or more conditional handover configurations including a triggering measurement threshold for initiating a conditional handover to the associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station. The operations of 1905 may be performed according to the methods described herein. In some examples, aspects of the operations of 1905 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0231] In 1910, the UE may determine, based on the conditional handover configuration, that a first disconfiguration measurement threshold for disconfiguring the first conditional handover configuration of the first target base station is satisfied. The operations of 1910 may be performed according to the methods described herein. In some examples, aspects of the operations of 1910 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0232] In 1915, the UE may release a first conditional handover configuration of a first target base station. The operations of 1915 may be performed according to the methods described herein. In some examples, aspects of the operations of 1915 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0233] In 1920, the UE may determine, based on the conditional handover configuration, that a second triggering measurement threshold for initiating a handover to a second target base station is satisfied. The operations of 1920 may be performed according to the methods described herein. In some examples, aspects of the operations of 1920 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0234] In 1925, the UE may transmit a random access request to the second target base station to initiate a random access procedure for a handover to the second target base station based on the second conditional handover configuration of the second target base station. The operations of 1925 may be performed according to the methods described herein. In some examples, aspects of the operations of 1925 may be performed by a random access manager as described with reference to FIGS. 8 through 11.

[0235] FIG. 20 illustrates a flowchart illustrating a method (2000) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (2000) may be implemented by a UE (115) or components of the UE (115) as described herein. For example, operations of the method (2000) may be performed by a communications manager as described with reference to FIGS. 8 through 11. In some examples, the UE may execute a set of commands to control functional elements of the UE to perform the functions described below. Additionally or alternatively, the UE may use special-purpose hardware to perform aspects of the functions described below.

[0236] In 2005, the UE may receive from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations, each of the one or more conditional handover configurations including a triggering measurement threshold for initiating a conditional handover to the associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station. The operations of 2005 may be performed according to the methods described herein. In some examples, aspects of the operations of 2005 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0237] In 2010, the UE may determine, based on the conditional handover configuration, that a first disconfiguration measurement threshold for disconfiguring the first conditional handover configuration of the first target base station is satisfied. The operations of 2010 may be performed according to the methods described herein. In some examples, aspects of the operations of 2010 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0238] In 2015, the UE may release a first conditional handover configuration of a first target base station. The operations of 2015 may be performed according to the methods described herein. In some examples, aspects of the operations of 2015 may be performed by a handover configuration manager as described with reference to FIGS. 8 through 11.

[0239] In 2020, the UE may transmit a measurement report to the source base station indicating that the first conditional handover configuration of the first target base station is released. The operations of 2020 may be performed according to the methods described herein. In some examples, aspects of the operations of 2020 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0240] In 2025, the measurement report includes a deconfiguration indication for the first target base station. The operations of 2025 may be performed according to the methods described herein. In some examples, aspects of the operations of 2025 may be performed by a measurement manager as described with reference to FIGS. 8 through 11.

[0241] FIG. 21 illustrates a flowchart illustrating a method (2100) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (2100) may be implemented by a base station (105) or components of the base station (105) as described herein. For example, operations of the method (2100) may be performed by a communication manager as described with reference to FIGS. 12 through 15. In some examples, the base station may execute a set of commands to control functional elements of the base station to perform the functions described below. Additionally or alternatively, the base station may use special-purpose hardware to perform aspects of the functions described below.

[0242] In 2105, the base station may set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from the source base station to an individual target base station, wherein each conditional handover configuration includes a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of a UE from the source base station to an individual target base station. The operations of 2105 may be performed according to the methods described herein. In some examples, aspects of the operations of 2105 may be performed by a handover configuration manager as described with reference to FIGS. 12 through 15.

[0243] In 2110, the base station may transmit one or more conditional handover configurations to the UE, and each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of the UE from the source base station to the associated target base station, and a conditional handover time period of the associated target base station. The operations of 2110 may be performed according to the methods described herein. In some examples, aspects of the operations of 2110 may be performed by a UE handover manager as described with reference to FIGS. 12 through 15.

[0244] FIG. 22 illustrates a flowchart illustrating a method (2200) for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the present disclosure. Operations of the method (2200) may be implemented by a base station (105) or components of the base station (105) as described herein. For example, operations of the method (2200) may be performed by a communication manager as described with reference to FIGS. 12 through 15. In some examples, the base station may execute a set of commands to control functional elements of the base station to perform the functions described below. Additionally or alternatively, the base station may use special-purpose hardware to perform aspects of the functions described below.

[0245] In 2205, the base station may, by the source base station, set up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE from the source base station to an individual target base station, and each conditional handover configuration includes a triggering measurement threshold for initiating a conditional handover of the UE to the associated target base station and a conditional handover timer value for completing a conditional handover of the UE to the associated target base station. The operations of 2205 may be performed according to the methods described herein. In some examples, aspects of the operations of 2205 may be performed by a handover configuration manager as described with reference to FIGS. 12 through 15.

[0246] In 2210, the base station may transmit one or more conditional handover configurations to the UE, and each of the one or more conditional handover configurations indicates an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, and a conditional handover timer value for completing the UE's conditional handover to the associated target base station. The operations of 2210 may be performed according to the methods described herein. In some examples, aspects of the operations of 2210 may be performed by a UE handover manager as described with reference to FIGS. 12 through 15.

[0247] It should be noted that the methods described herein describe possible implementations, and that operations and steps may be rearranged or otherwise modified, and that other implementations are possible. Additionally, aspects from two or more of the methods may be combined.

[0248] Example 1: A wireless communication method in a UE comprises: receiving a conditional handover configuration from a source base station, indicating one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to one or more target base stations, and one or more timers associated with a handover to one or more target base stations; determining, at least partially based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; transmitting a first random access request to a first target base station to initiate a first random access procedure for a handover to a first target base station, at least partially based on the conditional handover configuration; starting a first conditional handover timer for completing the first random access procedure in response to the step of transmitting the first random access request; and determining a first conditional handover failure in response to the first conditional handover timer expiring before completing the first random access procedure.

[0249] Example 2: In the method of Example 1, one or more timers include at least a first conditional handover timer for completing a first random access procedure with a first target base station.

[0250] Example 3: In the method of Example 1 or Example 2, the conditional handover configuration includes at least a first conditional handover configuration for a first target base station and a second conditional handover configuration for a second target base station.

[0251] Example 4: The method of any one of Examples 1 to 3 further comprises the step of initiating a first validity timer and a second validity timer in response to receiving a conditional handover configuration; and the step of deleting the second conditional handover configuration in response to the expiration of the second validity timer.

[0252] Example 5: The method of Example 4 further includes the step of stopping a first validity timer when transmitting a first random access request to a first target base station.

[0253] Example 6: A method of any one of Examples 1 to 5 further comprises the steps of: determining that a second measurement threshold for initiating a handover to a second target base station is satisfied in response to the expiration of a first conditional handover timer; transmitting a second random access request to a second target base station to initiate a second random access procedure for a handover to a second target base station based at least partially on a conditional handover configuration; and starting a second conditional handover timer to complete the second random access procedure.

[0254] Example 7: The method of Example 6 further includes the step of initiating a connection reset procedure when it is determined that other target base stations are not configured for conditional handover.

[0255] Example 8: In the method of Example 6 or Example 7, the first duration of the first conditional handover timer is different from the second duration of the second conditional handover timer.

[0256] Example 9: The method of any one of Examples 6 to 8 further comprises the step of selecting a second target base station from a plurality of available target base stations in response to the expiration of a first conditional handover timer, based at least partially on a channel quality measurement associated with each of the plurality of available target base stations.

[0257] Example 10: In the method of any one of Examples 6 to 9, the second target base station is selected at least partially based on the fact that the second target base station has a shorter remaining effective timer duration than other target base stations among a plurality of available target base stations.

[0258] Example 11: A method of any one of Examples 1 to 10 further comprises the steps of: receiving a deconfiguration message from a source base station for deconfiguring one or more conditional handover configurations; and deconfiguring one or more conditional handover configurations at least partially based on the deconfiguration message.

[0259] Example 12: In the method of Example 11, the unconfiguration message is received from radio resource control signaling from the source base station.

[0260] Example 13: The method of Example 11 or Example 12 further comprises the step of deleting one or more of the first measurement and reporting configuration or radio resource control configuration for a conditional handover trigger provided in the first conditional handover configuration; and the step of discontinuing the evaluation of conditional handover measurements associated with the conditional handover configuration and whether the measurements satisfy conditional handover criteria.

[0261] Example 14: An apparatus comprising at least one means for performing the method of any one of Examples 1 to 13.

[0262] Example 15: A device for wireless communications comprising: a processor; a memory that communicates electronically with the processor; and instructions stored in the memory and executable by the processor to enable the device to perform the method of any one of Examples 1 to 13.

[0263] Example 16: A non-transient computer-readable medium for storing code for wireless communications, wherein the code comprises instructions executable by a processor to perform the method of any one of Examples 1 to 13.

[0264] Example 17: A wireless communication method in a UE (user equipment), comprising the steps of: receiving from a source base station a conditional handover configuration indicating one or more conditional handover configurations associated with one or more target base stations—each of the one or more conditional handover configurations includes a triggering measurement threshold for initiating a conditional handover to an associated target base station and a deconfiguration measurement threshold for deconfiguring the conditional handover configuration of the associated target base station—; determining that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is satisfied based at least partially on the conditional handover configuration; and releasing the first conditional handover configuration of the first target base station.

[0265] Example 18: The method of Example 17 further comprises the steps of: determining that a second triggering measurement threshold for initiating a handover to a second target base station is satisfied, at least partially based on a conditional handover configuration; and transmitting a random access request to a second target base station to initiate a random access procedure for a handover to a second target base station, at least partially based on a second conditional handover configuration of the second target base station.

[0266] Example 19: In the method of Example 17 or Example 18, the step of releasing the first conditional handover configuration comprises: deleting one or more of the first measurement and reporting configuration or radio resource control configuration for the conditional handover trigger and the conditional handover unconfiguration trigger provided in the first conditional handover configuration; and ceasing to evaluate the conditional handover measurements associated with the first target base station, and whether the measurements satisfy conditional handover criteria or conditional handover unconfiguration conditions.

[0267] Example 20: The method of any one of Examples 17 to 19 further comprises the step of transmitting a measurement report to a source base station indicating that the first conditional handover configuration of the first target base station is released.

[0268] Example 21: In the method of any one of Examples 17 to 20, the measurement report includes a deconfiguration indication for the first target base station.

[0269] Example 22: In the method of any one of Examples 17 to 21, the first release measurement threshold is a channel quality threshold associated with the first target base station, and the first conditional handover configuration is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold.

[0270] Example 23: In the method of any one of Examples 17 to 22, the first release measurement threshold includes a first threshold value associated with a source base station and a second threshold value associated with a first target base station, and the first conditional handover configuration is released in response to the first channel quality measurement of the source base station exceeding the first threshold value and the second channel quality measurement of the first target base station being less than the second threshold value.

[0271] Example 24: In the method of any one of Examples 17 to 23, the first release measurement threshold is a difference threshold, and the first conditional handover configuration is released in response to the difference between the channel quality measurements of the first target base station and the source base station exceeding the difference threshold.

[0272] Example 25: An apparatus comprising at least one means for performing the method of any one of Examples 17 to 24.

[0273] Example 26: A device for wireless communications comprising: a processor; a memory that communicates electronically with the processor; and instructions stored in the memory and executable by the processor to enable the device to perform the method of any one of Examples 17 to 24.

[0274] Example 27: A non-transient computer-readable medium for storing code for wireless communications, wherein the code comprises instructions executable by a processor to perform the method of any one of Examples 17 to 24.

[0275] Example 28: A method for wireless communication at a source base station, comprising the step of setting one or more target base stations and one or more conditional handover configurations by the source base station for a conditional handover of a UE (user equipment) from the source base station to an individual target base station — each conditional handover configuration includes a valid time period during which the conditional handover configuration is valid, and a conditional handover time period for completing a random access procedure at the initiation of a conditional handover of the UE from the source base station to an individual target base station — and transmitting one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations indicates an associated target base station, one or more measurement thresholds for initiating a handover of the UE from the source base station to the associated target base station, and a conditional handover time period of the associated target base station.

[0276] Example 29: The method of Example 28 further includes the step of deconfiguring the first conditional handover configuration of the first target base station in response to the expiration of the first validity period associated with the first target base station.

[0277] Example 30: In the method of Example 28 or Example 29, the UE autonomously deconfigures the first conditional handover configuration of the first target base station based on the expiration of the first validity period.

[0278] Example 31: In the method of any one of Examples 28 to 30, each of one or more target base stations has a different value for one or more of the valid time period or the conditional handover time period.

[0279] Example 32: In the method of any one of Examples 28 to 31, one or more of the valid time period or the conditional handover time period is determined at least partially based on one or more of the UE’s movement estimate for each individual target base station, the traffic load of the source base station or each individual target base station, channel quality measurements for each individual target base station provided by the UE, or any combination thereof.

[0280] Example 33: An apparatus comprising at least one means for performing the method of any one of Examples 28 to 32.

[0281] Example 34: A device for wireless communications comprising: a processor; a memory that communicates electronically with the processor; and instructions stored in the memory and executable by the processor to enable the device to perform the method of any one of Examples 28 to 32.

[0282] Example 35: A non-transient computer-readable medium for storing code for wireless communications, wherein the code comprises instructions executable by a processor to perform the method of any one of Examples 28 to 32.

[0283] Example 36: A method for wireless communication at a source base station, comprising the steps of: setting up one or more target base stations and one or more conditional handover configurations for a conditional handover of a UE (user equipment) from the source base station to an individual target base station by the source base station—each conditional handover configuration comprising a triggering measurement threshold for initiating a conditional handover of the UE to an associated target base station and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station—; and transmitting one or more conditional handover configurations to the UE, wherein each of the one or more conditional handover configurations represents an associated target base station, a triggering measurement threshold for initiating a conditional handover to the associated target base station, and a conditional handover timer value for completing a conditional handover of the UE to an associated target base station.

[0284] Example 37: The method of Example 36 comprises the steps of: deciding to unconfigure at least one first conditional handover configuration in the UE; transmitting unconfiguration information to the UE in response to the step of deciding to unconfigure, indicating that the UE must delete one or more of the first measurement and reporting configuration or radio resource control configuration for the first conditional handover configuration; receiving a measurement report from the UE indicating that a first unconfiguration measurement threshold for unconfiguring the first conditional handover configuration of the first target base station is satisfied; and releasing the first conditional handover configuration of the first target base station in response to the measurement report.

[0285] Example 38: In the method of Example 36 or Example 37, the step of releasing the first conditional handover configuration includes the step of deleting one or more of the one or more timers associated with the first target base station, the first triggering measurement threshold, the first unconfiguration measurement threshold, or the radio resource control configuration included in the first conditional handover configuration.

[0286] Example 39: In the method of any one of Examples 36 to 38, the step of releasing the first conditional handover configuration further comprises the step of providing an indication to the first target base station that the first conditional handover configuration is released.

[0287] Example 40: In the method of any one of Examples 36 to 39, the release measurement threshold is a channel quality threshold associated with each individual target base station, and the conditional handover configuration of the first target base station is released in response to the channel quality measurement of the first target base station being less than the channel quality threshold of the first target base station.

[0288] Example 41: In the method of any one of Examples 36 to 40, the release measurement threshold includes a first threshold associated with a source base station and a second threshold for each individual target base station, and in response to the first channel quality measurement of the source base station exceeding the first threshold and the second channel quality measurement of the first target base station being less than the second threshold of the first target base station, the conditional handover configuration of the first target base station is released.

[0289] Example 42: In the method of any one of Examples 36 to 41, the release measurement threshold is a difference threshold, and in response to the difference between the channel quality measurements of the first target base station and the source base station exceeding the difference threshold, the conditional handover configuration associated with the first target base station is released.

[0290] Example 43: An apparatus comprising at least one means for performing the method of any one of Examples 36 to 42.

[0291] Example 44: A device for wireless communications comprising: a processor; a memory that communicates electronically with the processor; and instructions stored in the memory and executable by the processor to enable the device to perform the method of any one of Examples 36 to 42.

[0292] Example 45: A non-transient computer-readable medium for storing code for wireless communications, wherein the code comprises instructions executable by a processor to perform the method of any one of Examples 36 to 42.

[0293] The techniques described herein can be used in various wireless communication systems such as CDMA (code division multiple access), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDMA (orthogonal frequency division multiple access), SC-FDMA (single carrier frequency division multiple access), and other systems. CDMA systems can implement radio technologies such as CDMA2000 and UTRA (Universal Terrestrial Radio Access). CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 releases may commonly be referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, HRPD (High Rate Packet Data), etc. UTRA includes WCDMA (Wideband CDMA) and other variations of CDMA. The TDMA system can implement radio technologies such as GSM (Global System for Mobile Communications).

[0294] OFDMA systems can implement radio technologies such as UMB (Ultra Mobile Broadband), E-UTRA (Evolved UTRA), IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM. UTRA and E-UTRA are part of the UMTS (Universal Mobile Telecommunications System). LTE, LTE-A, and LTE-A Pro are UMTS releases that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in documents from the organization named "3rd Generation Partnership Project" (3GPP). CDMA2000 and UMB are described in documents from the organization named "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein may be used in other systems and radio technologies as well as the systems and radio technologies mentioned herein. Aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for the purposes of example, and the terms LTE, LTE-A, LTE-A Pro, or NR may be used in most of the description, but the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR applications.

[0295] Macro cells generally cover a relatively large geographical area (e.g., a radius of several kilometers) and can allow unrestricted access by UEs subscribed to a network provider. Small cells may be associated with low-power base stations compared to macro cells, and small cells may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells depending on various examples. For instance, pico cells can cover a small geographical area and allow unrestricted access by UEs subscribed to a network provider. Femto cells can also cover a small geographical area (e.g., a home) and provide restricted access by UEs associated with the femto cell (e.g., UEs within a closed subscriber group (CSG), UEs for users within a home, etc.). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, pico eNB, femto eNB, or home eNB. The eNB may support one or more cells (e.g., two, three, four, etc.) and may also support communications using one or more component carriers.

[0296] The wireless communication systems described herein may support synchronous or asynchronous operation. In the case of synchronous operation, base stations may have similar frame timings, and transmissions from different base stations may be nearly aligned in time. In the case of asynchronous operation, base stations may have different frame timings, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operation.

[0297] The information and signals described herein may be represented using any of the various different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be mentioned throughout the description may be represented as voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0298] The various exemplary blocks and modules described in connection with the disclosure herein may be implemented or performed by a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration).

[0299] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. When implemented in software executed by a processor, the functions may be stored as one or more instructions or code on a computer-readable medium or transmitted through them. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of the software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Features implementing the functions may also be located in various physical positions, including distributed so that parts of the functions are implemented in different physical locations.

[0300] Computer-readable media include both communication media and non-transient computer storage media, comprising any medium that enables the transfer of a computer program from one place to another. Non-transient storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer. By example, but not by limitation, non-transient computer-readable media may include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transient medium that can be used to carry or store desired means of program code in the form of instructions or data structures and can be accessed by a general-purpose or special-purpose computer or a general-purpose or special-purpose processor. Additionally, any connection is appropriately referred to as a computer-readable medium. For example, where software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, DSL (digital subscriber line), or wireless technologies such as infrared, radio, and microwave, coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. Disks and discs as used herein include CDs, laser discs, optical discs, DVDs (digital versatile discs), floppy disks, and Blu-ray discs, wherein disks typically reproduce data magnetically, while discs reproduce data optically using lasers.The above combinations are also included within the scope of computer-readable media.

[0301] Including the claims, as used herein, the word “or” as used in a list of items (e.g., a list of items followed by phrases such as “at least one of” or “one or more of”) indicates a comprehensive list; thus, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A, B, and C). Furthermore, as used herein, the phrase “based on” shall not be interpreted as a reference to a closed set of conditions. For example, an exemplary step described as “based on condition A” may be based on both condition A and condition B without departing from the scope of the disclosure. In other words, as used herein, the phrase “based on” shall be interpreted in the same way as the phrase “at least partially based on”.

[0302] In the attached drawings, similar components or features may have the same reference label. Additionally, various components of the same type may be distinguished by a dash following the reference label and a second label distinguishing between similar components. Where only the first reference label is used in this specification, the description is applicable to any component among similar components having the same first reference label, regardless of the second reference label or other subsequent reference labels.

[0303] The description provided herein in connection with the attached drawings describes exemplary configurations and does not represent all examples that are within the scope of the claims or that may be implemented. As used herein, the term “exemplary” means “serving as an example, case, or example,” rather than “advantageous over other examples” or “desirable.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. However, these techniques may be practiced without these specific details. In some cases, well-known structures and devices are illustrated in block diagram form to avoid obscuring the concepts of the described examples.

[0304] The description herein is provided to enable those skilled in the art to manufacture or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Accordingly, the present disclosure is not limited to the examples and designs described herein, but should conform to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

Claim 1 A method for wireless communication in user equipment (UE), comprising: receiving a conditional handover configuration from a source base station, wherein the source base station indicates one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to the one or more target base stations, and one or more timers associated with a handover to the one or more target base stations; determining, at least partially based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; transmitting a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station, at least partially based on the conditional handover configuration; starting a first conditional handover timer for completing the first random access procedure in response to the step of transmitting the first random access request; and determining a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed. Claim 2 A method for wireless communication in user equipment (UE), wherein, in claim 1, the one or more timers include at least the first conditional handover timer for completing the first random access procedure with the first target base station. Claim 3 A method for wireless communication in user equipment (UE), wherein, in claim 1, the conditional handover configuration comprises at least a first conditional handover configuration for the first target base station and a second conditional handover configuration for the second target base station. Claim 4 A method for wireless communication in user equipment (UE) according to claim 1, further comprising: transmitting a second random access request to a second target base station to initiate a second random access procedure for handover to a second target base station in response to the expiration of the first conditional handover timer; and starting a second conditional handover timer to complete the second random access procedure. Claim 5 A method for wireless communication in user equipment (UE) according to claim 4, further comprising the step of initiating a connection reset procedure when it is determined that other target base stations are not configured for conditional handover. Claim 6 A method for wireless communication in UE (user equipment), wherein, in claim 4, the first duration of the first conditional handover timer is different from the second duration of the second conditional handover timer. Claim 7 A method for wireless communication in user equipment (UE) according to claim 4, further comprising the step of selecting a second target base station from a plurality of available target base stations in response to the expiration of the first conditional handover timer, at least partially based on a channel quality measurement associated with each of the plurality of available target base stations. Claim 8 A method for wireless communication in user equipment (UE) according to claim 1, further comprising the step of initiating a connection reset procedure in response to the expiration of the first conditional handover timer. Claim 9 A method for wireless communication in user equipment (UE) according to claim 1, further comprising: receiving a deconfiguration message from the source base station for deconfiguring one or more conditional handover configurations; and deconfiguring the one or more conditional handover configurations based at least partially on the deconfiguration message. Claim 10 In claim 9, the above-mentioned deconfiguration message is received from radio resource control signaling from the source base station, a method for wireless communication in user equipment (UE). Claim 11 A method for wireless communication in user equipment (UE) according to claim 9, further comprising: a step of deleting one or more of a first measurement and reporting configuration or a radio resource control configuration for a conditional handover trigger provided in a first conditional handover configuration; and a step of ceasing evaluation of conditional handover measurements associated with said conditional handover configuration and whether said measurements satisfy conditional handover criteria. Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 delete Claim 22 delete Claim 23 delete Claim 24 delete Claim 25 A device for wireless communication in a UE (user equipment), comprising: means for receiving a conditional handover configuration from a source base station, one or more target base stations, one or more measurement thresholds for initiating a handover from the source base station to the one or more target base stations, and one or more timers associated with the handover to the one or more target base stations; means for determining, at least partially based on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is satisfied; means for transmitting a first random access request to the first target base station to initiate a first random access procedure for a handover to the first target base station, at least partially based on the conditional handover configuration; means for starting a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request; and means for determining a first conditional handover failure in response to the first conditional handover timer expiring before the first random access procedure is completed. Claim 26 In claim 25, the device for wireless communication in user equipment (UE), wherein the one or more timers include at least the first conditional handover timer for completing the first random access procedure with the first target base station. Claim 27 An apparatus for wireless communication in user equipment (UE) according to claim 25, further comprising: means for transmitting a second random access request to a second target base station to initiate a second random access procedure for handover to a second target base station in response to the expiration of the first conditional handover timer; and means for starting a second conditional handover timer to complete the second random access procedure. Claim 28 An apparatus for wireless communication in user equipment (UE) according to claim 25, further comprising means for initiating a connection reset procedure in response to the expiration of the first conditional handover timer. Claim 29 An apparatus for wireless communication in user equipment (UE) according to claim 25, further comprising: means for receiving a deconfiguration message from the source base station for deconfiguring one or more conditional handover configurations; and means for deconfiguring the one or more conditional handover configurations based at least partially on the deconfiguration message. Claim 30 An apparatus for wireless communication in user equipment (UE), wherein, in claim 29, the deconfiguration message is received in radio resource control signaling from the source base station, and the apparatus further comprises: means for deleting one or more of the first measurement and reporting configuration or radio resource control configuration for a conditional handover trigger provided in the first conditional handover configuration; and means for stopping the evaluation of conditional handover measurements associated with the conditional handover configuration and whether said measurements satisfy conditional handover criteria.

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