Conditional handover (CHO) deconfiguration and failure handling in wireless communication

Abstract

To provide conditional handover (CHO) deconfiguration and failure handling in wireless communications.SOLUTION: Methods, systems, and devices for wireless communications are described for management of conditional handover (CHO) configurations. A source base station may configure user equipment (UE) with one or more CHO configurations for multiple target base stations. The CHO configurations may provide, for each target base station, one or more associated conditions that may trigger the UE to initiate a handover to a particular target base station, or to deconfigure a CHO configuration, such as based on a measurement threshold of one or more target base station measurements, one or more source base station measurements, or combinations thereof. The CHO configurations may also include failure handling information for initiating one or more subsequent handovers responsive to a failure of an initial handover attempt.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] cross reference This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 842,330, filed May 2, 2019, by Purkayastha et al., entitled “Conditional Handover (CHO) Deconfiguration and Failure Handling in Wireless Communications,” and U.S. Patent Application No. 16 / 805,347, filed February 28, 2020, by Purkayastha et al., entitled “Conditional Handover (CHO) Deconfiguration and Failure Handling in Wireless Communications,” each of which is assigned to the assignee of the present application.

[0002] The following relates generally to wireless communications, and more particularly to conditional handover (CHO) deconfiguration and failure handling in wireless communications. [Background technology]

[0003] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcasts, and the like. These systems may be capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth generation (4G) systems, such as Long Term Evolution (LTE), LTE Advanced (LTE-A), or LTE-A Pro systems, and fifth generation (5G) systems, sometimes referred to as New Radio (NR) systems. These systems may employ technologies such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include several base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, sometimes referred to as user equipment (UE).

[0004] In some cases, the UE may be moving with respect to one or more base stations, which may result in the UE undergoing a handover procedure from a base station to which the UE is currently connected (e.g., a source base station) to a new base station (e.g., a target base station). The handover procedure may be initiated by the source and target base stations exchanging information related to the UE and the source base station sending a handover command to the UE. In some cases, the UE may reduce a connection with the source base station 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 a handover, and the UE may initiate the handover upon detecting a condition indicated in the configuration, and such a handover may be referred to as a conditional handover (CHO). However, the conditional handover configuration presents challenges related to managing the CHO configuration for the target base station. Summary of the Invention [Means for solving the problem]

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses supporting conditional handover (CHO) deconfiguration and failure handling in wireless communications. Various aspects of the present disclosure describe techniques for managing CHO configurations. In some cases, a source base station may configure a user equipment (UE) with one or more CHO configurations for multiple target base stations. For each target base station, the CHO configuration may provide one or more associated conditions that may trigger the UE to initiate a handover to a particular 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 configuration may include failure handling information, deconfiguration criteria, or a combination thereof.

[0006] In some cases, the failure processing information may include one or more CHO timer values, and upon sending the random access request to the target base station, the UE may start a 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 there was a handover failure to the target base station. In some cases, in response to the failure identification, the UE may determine whether any other target base stations have a CHO configuration, and may send a random access request to the second target base station if a CHO configuration exists for the second 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 a CHO configuration, at which point the UE may declare a radio link failure and may initiate a connection re-establishment 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 measurements or channel quality measurements) on the source base station, one or more target base stations, or a combination thereof. If one or more of the measurements for a particular target base station satisfy the deconfiguration criteria, the UE may deconfigure the CHO configuration associated with that particular target base station. In some cases, the UE may send a measurement report to the source base station, which may include measurements associated with the deconfigured target base station that the source base station may use to release the handover configuration. In some cases, the UE may send a deconfiguration indication with the measurement report (e.g., cell ID of the deconfigured target base station).

[0008] A method of wireless communications in a UE is described. The method may include 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 the one or more target base stations, and one or more timers related to the handover to the 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 met, transmitting a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, in response to transmitting the first random access request, starting a first conditional handover timer for completing the first random access procedure, and determining a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure.

[0009] An apparatus for wireless communications in a UE is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to 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 the one or more target base stations, and one or more timers related to the handover to the one or more target base stations, determine based on the conditional handover configuration that a first measurement threshold for initiating a handover to a first target base station is met, transmit a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, start a first conditional handover timer to complete the first random access procedure in response to transmitting the first random access request, and determine a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure.

[0010] Another apparatus for wireless communications in a UE is described. The apparatus may include means for 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 the one or more target base stations, and one or more timers related to the handover to the 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 met, transmitting a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, starting a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request, and determining a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure.

[0011] A non-transitory computer-readable medium storing code for wireless communications in a UE is described. The code may include instructions executable by a processor to 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 the one or more target base stations, and one or more timers related to the handover to the one or more target base stations, determine based on the conditional handover configuration that a first measurement threshold for initiating a handover to a first target base station is met, transmit a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, start a first conditional handover timer to complete the first random access procedure in response to transmitting the first random access request, and determine a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure.

[0012] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the 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, apparatus, and non-transitory computer-readable media described herein, the conditional handover configuration includes 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.

[0013] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for determining, in response to expiration of the first conditional handover timer, that a second measurement threshold for initiating a handover to a second target base station is met, sending a second random access request to the second target base station based on the conditional handover configuration to initiate a second random access procedure for the handover to the second target base station, initiating a second conditional handover timer to complete the second random access procedure, and repeating the determining, sending, and initiating for any other target base stations configured for conditional handover upon further conditional handover failures. Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for initiating a connection re-establishment procedure upon determining that no other target base stations are configured for conditional handover.

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

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

[0016] A method of wireless communications in a UE is described. The method may include receiving a conditional handover configuration from a source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met, 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 in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a conditional handover configuration from a source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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, determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met, and release the first conditional handover configuration of the first target base station.

[0018] Another apparatus for wireless communications in a UE is described. The apparatus may include means for receiving a conditional handover configuration from a source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met, and releasing the first conditional handover configuration of the first target base station.

[0019] A non-transitory computer-readable medium storing code for wireless communications 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, where each of the one or more conditional handover configurations includes a trigger 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, determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met, and release the first conditional handover configuration of the first target base station.

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

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

[0022] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include an operation, feature, means, or instruction for transmitting a measurement report to the source base station indicating that the first conditional handover configuration of the first target base station is to be released. In some examples of the methods, apparatus, and non-transitory 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, apparatus, and non-transitory computer-readable media described herein, the first deconfiguration measurement threshold may be a channel quality threshold associated with the first target base station, where 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, apparatus, and non-transitory computer-readable media described herein, the first deconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold associated with the first target base station, where 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, apparatus, and non-transitory computer-readable media described herein, the first deconfiguration measurement threshold may be a differential threshold, where the first conditional handover configuration is released in response to a difference in a channel quality measurement between the source base station and the first target base station exceeding the differential threshold.

[0024] A method of wireless communication in a source base station is described. The method may include: establishing, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a UE from the source base station to one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of a conditional handover of the UE from the source base station to the respective target base station; and transmitting, to the UE, the one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for activation of handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

[0025] An apparatus for wireless communication in a source base station is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of the conditional handover of the UE from the source base station to the respective target base station, and transmit to the UE the one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for activation of handover of the UE from the source base station to the associated target base station, and the conditional handover time period of the associated target base station.

[0026] Another apparatus for wireless communication in a source base station is described. The apparatus may include means for establishing, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of the conditional handover of the UE from the source base station to the respective target base station, and transmitting the one or more conditional handover configurations to the UE, each indicating an associated target base station, one or more measurement thresholds for activation of handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

[0027] A non-transitory computer-readable medium storing code for wireless communications at a source base station is described. The code may include instructions executable by a processor to: establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of the conditional handover of the UE from the source base station to the respective target base station; and transmit, to the UE, the one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for activation of handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

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

[0029] A method of wireless communication in a source base station is described. The method may include: establishing, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger 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 the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station; and transmitting to the UE the one or more conditional handover configurations, each indicating the associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, the conditional handover timer value for completing a conditional handover of the UE to the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station.

[0030] An apparatus for wireless communication in a source base station is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating a conditional handover of the UE to the associated target base station, a conditional handover timer value for completing the 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 to transmit to the UE the one or more conditional handover configurations, each indicating the associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, the conditional handover timer value for completing the 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.

[0031] Another apparatus for wireless communications in a source base station is described. The apparatus may include means for establishing, by a source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger 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 the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station, and transmitting to the UE the one or more conditional handover configurations, each indicating an associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, the conditional handover timer value for completing a conditional handover of the UE to the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station.

[0032] A non-transitory computer-readable medium storing code for wireless communications at a source base station is described. The code may include instructions executable by a processor to: establish, by a source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger 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 the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station; and transmit, to the UE, the one or more conditional handover configurations, each indicating an associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, the conditional handover timer value for completing a conditional handover of the UE to the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station.

[0033] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for determining at the UE that at least one first conditional handover configuration should be deconfigured, and in response to the determination to deconfigure, transmitting deconfiguration information to the UE indicating that the UE should delete one or more of the radio resource control configuration, or the first measurement value, and reporting 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, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for receiving a measurement report from the UE indicating that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met, and releasing the first conditional handover configuration of the first target base station in response to the measurement report. In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, releasing the first conditional handover configuration may include operations, features, means, or instructions for deleting one or more of a radio resource control configuration, a first deconfiguration measurement threshold, a first trigger measurement threshold, or one or more timers associated with the first target base station included in the first conditional handover configuration.

[0035] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, releasing the first conditional handover configuration may further include an operation, feature, means, or instruction for providing an indication to the first target base station that the first conditional handover configuration is released.

[0036] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the deconfiguration measurement threshold may be a channel quality threshold associated with each respective target base station, where 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, apparatus, and non-transitory computer-readable media described herein, the deconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold for each respective target base station, where 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, apparatus, and non-transitory computer-readable media described herein, the deconfiguration measurement threshold may be a differential threshold, where the conditional handover configuration associated with the first target base station is released in response to a difference in a channel quality measurement between the source base station and the first target base station exceeding the differential threshold. [Brief description of the drawings]

[0037] [Figure 1] FIG. 1 illustrates an example of a system for wireless communication supporting conditional handover (CHO) deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Diagram 2] FIG. 2 illustrates an example of a portion of a wireless communication system having a source base station and a target base station supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Diagram 3] FIG. 1 illustrates an example process flow supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. [Figure 4]FIG. 1 illustrates an example process flow supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. [Diagram 5] FIG. 1 illustrates an example process flow supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. [Figure 6] FIG. 1 illustrates an example process flow supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. [Figure 7] FIG. 1 illustrates an example process flow supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. [Figure 8] FIG. 1 is a block diagram of a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 9] FIG. 1 is a block diagram of a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 10] FIG. 13 is a block diagram of a communications manager supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the present disclosure. [Figure 11] FIG. 1 is a diagram of a system including a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 12] FIG. 1 is a block diagram of a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 13] FIG. 1 is a block diagram of a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 14] FIG. 13 is a block diagram of a communications manager supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the present disclosure. [Figure 15] FIG. 1 is a diagram of a system including a device supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 16] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 17] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 18] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 19] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 20] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 21] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. [Figure 22] 1 is a flowchart illustrating a method for supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Various aspects of the present disclosure provide techniques for user equipment (UE) handover in a wireless communication system. A UE may undergo a handover procedure from a source cell to a target cell, in which the UE may release or reduce 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 and target base stations exchanging information related to the UE, and the source base station sending a handover command to the UE. In some cases, the UE may reduce 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 upon detecting a condition indicated in the configuration, and such a handover may be referred to as a conditional handover (CHO).

[0039] In some aspects of the disclosure, a source base station may configure a UE with one or more CHO configurations for multiple target base stations. For each target base station, the CHO configuration may provide one or more associated conditions that may trigger the UE to initiate a handover to a particular 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 configuration may include failure handling information, deconfiguration criteria, or a combination thereof.

[0040] In some cases, the CHO configuration 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, the source base station, or a combination thereof, and if the measurements satisfy the handover criteria, the UE may initiate a handover with the target base station that satisfied the handover criteria (e.g., by sending a random access request to the target base station). Although the CHO configuration may enable the UE to autonomously initiate a handover if the handover criteria is satisfied (e.g., if the source base station measurements are below a threshold and the target base station measurements are above a threshold), maintaining such a configuration may consume resources at the base station and the UE, may constrain the flexibility of one or more target base stations, may consume overhead associated with target base station measurements, etc.

[0041] For example, the source base station may configure a CHO with the first target base station, which may result in the source base station periodically providing information related to the UE to the first target base station, the first target base station reserving a contention-free random access preamble for the UE (which may constrain the first target base station from allocating contention-free preambles to other devices), the UE performing measurements to the first target base station, the UE sending a measurement report with the first target base station measurements, etc. Thus, if the first target base station is no longer a suitable candidate for handover of the UE, it may be beneficial for the UE, the source base station, and the target base station to deconfigure the CHO of the first target base station. Furthermore, if a random access procedure initiated as part of the CHO fails or there is a radio link failure, service interruption or increased latency may occur.

[0042] According to various techniques described 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 measurements or channel quality measurements) on the source base station, one or more target base stations, or a combination thereof. If 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 autonomously deconfigure the CHO configuration. In some cases, the UE may send a measurement report to the source base station that may include measurements associated with the first target base station to be deconfigured that the source base station may use to release the handover configuration. In some cases, the UE may send a deconfiguration indication with the measurement report (e.g., a cell ID of the target base station to be deconfigured). In other cases, the UE may maintain the CHO configuration until the source base station sends a 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 enable the first target base station to release resources reserved for the UE.

[0043] Additionally or alternatively, in some cases, the CHO configuration may include one or more CHO timer values, and upon sending the random access request to the target base station, the UE may start a 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 expiration of the CHO timer, the UE may identify that there has been a handover failure to the target base station. In some cases, in response to the failure identification, the UE may determine whether any other target base stations have a CHO configuration, and may send a random access request to the second target base station if a CHO configuration exists for the second 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 a CHO configuration, at which point the UE may declare a radio link failure and may initiate a connection re-establishment procedure.

[0044] Such techniques may enable efficient management of CHO configurations and failure handling for failed CHO handovers. Deconfiguration of CHO configurations may enable more efficient management of CHO configurations by deconfiguring CHO configurations based on UE measurements, which may enable ensuring that a relatively recent set of CHO configurations can be used for handover if handover criteria are satisfied. Additionally, failure handling techniques described herein may reduce latency and service interruptions associated with failed random access procedures of handover attempts.

[0045] Aspects of the present disclosure are first described in the context of a wireless communication system. Various example process flows illustrating CHO configuration management and failure handling are then described. Aspects of the present disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flow charts relating to CHO deconfiguration and failure handling in wireless communication.

[0046] 1 illustrates an example of a wireless communication system 100 supporting CHO deconfiguration and failure handling in wireless communication according to an aspect of the disclosure. The wireless communication system 100 includes a base station 105, a UE 115, and a core network 130. In some examples, the wireless communication system 100 may be a Long Term Evolution (LTE) network, a LTE-Advanced (LTE-A) network, a 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.

[0047] The base station 105 may wirelessly communicate with the UE 115 via one or more base station antennas. The base station 105 described herein may include or may be referred to by those skilled in the art as a transceiver base station, a radio base station, an access point, a radio transceiver, a Node B, an eNode B (eNB), a next generation Node B or a giga Node B (any of which may be referred to as a gNB), a Home Node B, a Home eNode B, or some other suitable terminology. The wireless communication system 100 may include different types of base stations 105 (e.g., macro base stations or small cell base stations). The UE 115 described herein may be able to communicate with various types of base stations 105 and network equipment, including macro eNBs, small cell eNBs, gNBs, relay base stations, etc.

[0048] Each base station 105 may be associated with a particular geographic coverage area 110 in which communication with various UEs 115 is supported. Each base station 105 may provide communication coverage to the respective geographic coverage area 110 via a communication link 125, where the communication link 125 between the base station 105 and the UE 115 may utilize one or more carriers. The communication link 125 shown 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 and uplink transmissions may also be referred to as reverse link transmissions.

[0049] A geographic coverage area 110 for a base station 105 may be divided into sectors constituting a portion of the geographic 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 type of cell, or various combinations thereof. In some examples, the base station 105 may be mobile and thus provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and the overlapping geographic 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 a heterogeneous LTE / LTE-A / LTE-A Pro network or NR network, for example, where different types of base stations 105 provide coverage for various geographic coverage areas 110.

[0050] The term "cell" refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier) and may be associated with an identifier (e.g., physical cell identifier (PCID), virtual cell identifier (VCID)) to distinguish adjacent cells operating over the same or different carriers. In some examples, a 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 may provide access for different types of devices. In some cases, the term "cell" may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which a logical entity operates.

[0051] The UEs 115 may be distributed throughout the wireless communication system 100, and each UE 115 may be fixed or mobile. The UEs 115 may also be referred to as mobile devices, wireless devices, remote devices, handheld devices, or subscriber devices, or some other suitable terminology, where a "device" may also be referred to as a unit, station, terminal, or client. The UEs 115 may also be personal electronic devices, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, the UEs 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, etc., which may be implemented in various items, such as an appliance, a vehicle, a meter, etc.

[0052] Some UEs 115, such as MTC or IoT devices, may be low-cost or low-complexity devices and may provide automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC may refer to data communication technologies that allow devices to communicate with each other or with the base station 105 without human intervention. In some examples, M2M communication or MTC may include communication from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can utilize the information or present the information to a human interacting 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.

[0053] Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communication (e.g., a mode that supports one-way communication via transmit or receive, but not transmit and receive simultaneously). In some examples, half-duplex communication may be performed at a reduced peak rate. Other power conservation techniques for the UE 115 include entering a power-saving "deep sleep" mode when not engaged in active communication, or operating over a limited bandwidth (e.g., pursuant to narrowband communication). In some cases, the UE 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.

[0054] In some cases, the UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) protocol or a device-to-device (D2D) protocol). One or more of the groups of UEs 115 utilizing D2D communication may be within the geographic coverage area 110 of the base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of the base station 105 or may not be able to receive transmissions from the base station 105 in some cases. In some cases, a group of UEs 115 communicating via D2D communication may utilize a one-to-many (1:M) system in which each UE 115 transmits to all other UEs 115 in the group. In some cases, the base station 105 facilitates scheduling of resources for D2D communication. In other cases, D2D communication is performed between UEs 115 without the involvement of the base station 105.

[0055] The base stations 105 may communicate with the core network 130 and with each other. For example, the base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1, N2, N3, or other interface). The base stations 105 may communicate with each other via backhaul links 134 (e.g., via an X2, Xn, or other interface), either directly (e.g., directly between the base stations 105) or indirectly (e.g., via the core network 130).

[0056] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC), which 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 (e.g., control plane) functions such as mobility, authentication, and bearer management for the UEs 115 served by the base stations 105 associated with the EPC. User IP packets may be forwarded through the S-GW, which may itself be connected to a P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to network operator IP services. The operator IP services may include access to the Internet, an intranet, an IP multimedia subsystem (IMS), or packet-switched (PS) streaming services.

[0057] At least some of the network devices, such as the base stations 105, may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with the UE 115 through some other access network transmission entity, which may be referred to as a radio head, a smart radio head, or a transmit / receive point (TRP). In some configurations, 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., the base station 105).

[0058] The wireless communication system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). The 300 MHz to 3 GHz region is commonly referred to as the ultra-high frequency (UHF) region or decimeter band, because the wavelengths span approximately one decimeter to one meter. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves may penetrate structures sufficiently for a macrocell to serve UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter distances (e.g., less than 100 km) compared to transmissions using lower frequencies and longer waves in the short wave (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz.

[0059] The wireless communication system 100 may also operate in the very high frequency (SHF) region, also referred to as the centimeter band, using the frequency band from 3 GHz to 30 GHz. The SHF region includes bands such as the 5 GHz Industrial, Scientific and Medical (ISM) band that may be used opportunistically by devices that may be able to tolerate interference from other users.

[0060] The wireless communication system 100 may also operate in the extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz), also referred to as the millimeter band. In some examples, the wireless communication system 100 may support millimeter wave (mmW) communications between the UE 115 and the base station 105, and the EHF antennas of the respective devices may be smaller and more closely spaced than the UHF antennas. In some cases, this may facilitate the use of antenna arrays in the UE 115. However, propagation of EHF transmissions may be subject to greater atmospheric attenuation and shorter distances than SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions using one or more different frequency regions, and the designated use of the bands across these frequency regions may vary by country or regulatory body.

[0061] 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 employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U), or NR technology in an unlicensed band, such as the 5 GHz ISM band. When operating in an unlicensed radio frequency spectrum band, wireless devices, such as the base station 105 and the UE 115, may employ a listen-before-talk (LBT) procedure to ensure that the frequency channel is clear before transmitting data. In some cases, operation in an unlicensed band may be based on a carrier aggregation configuration in conjunction with component carriers operating in the licensed band (e.g., LAA). Operation in an unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination thereof. Duplexing in an unlicensed spectrum may be based on Frequency Division Duplexing (FDD), Time Division Duplexing (TDD), or a combination of both.

[0062] In some examples, the base station 105 or the UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, the wireless communications system 100 may use a transmission scheme between a transmitting device (e.g., the base station 105) and a receiving device (e.g., the UE 115), where the transmitting device is equipped with multiple antennas and the receiving device is equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may be transmitted by the transmitting device, for example, via different antennas or different combinations of antennas. Similarly, the multiple signals may be received by the receiving device via 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. The different spatial layers may be associated with different antenna ports used for channel measurements and channel reporting. MIMO techniques include Single-User MIMO (SU-MIMO), in which multiple spatial layers are transmitted to the same receiving device, and Multi-User MIMO (MU-MIMO), in which multiple spatial layers are transmitted to multiple devices.

[0063] Beamforming, sometimes referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting or receiving device (e.g., base station 105 or UE 115) to shape or steer an antenna beam (e.g., a transmit beam or a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining signals communicated through antenna elements of an antenna array such that signals propagating at a particular orientation relative to the antenna array are subject to constructive interference, while other signals are subject to destructive interference. Adjustment of signals communicated through antenna elements may include the transmitting or receiving device applying some amplitude and phase offset to 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 beamforming weight set associated with a particular orientation (e.g., relative to the antenna array of the transmitting or receiving device, or relative to some other orientation).

[0064] In one example, the base station 105 may use multiple antennas or antenna arrays to direct beamforming operations for directional communication with the UE 115. For example, some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by the base station 105 multiple times in different directions, which may include transmitting the signals according to different beamforming weight sets associated with different directions of transmission. The transmissions in different beam directions may be used (e.g., by the base station 105, or a receiving device such as the UE 115) to identify beam directions for subsequent transmissions and / or receptions by the base station 105.

[0065] In some cases, the antennas of the base station 105 or the UE 115 may be arranged in one or more antenna arrays that may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be located together in an antenna assembly such as an antenna tower. In some cases, antennas or antenna arrays associated with the base station 105 may be located in various geographic locations. The base station 105 may have an antenna array with several rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with the UE 115. Similarly, the UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

[0066] In some cases, the wireless communication system 100 may be a packet-based network that operates according to a layered protocol stack. In the user plane, communication at the bearer or packet data convergence protocol (PDCP) layer may be IP-based. The radio link control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. The media access control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to perform retransmissions at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may establish, configure, and maintain an RRC connection between the UE 115 and the base station 105 or core network 130, which supports radio bearers for user plane data. In the physical layer, transport channels may be mapped to physical channels.

[0067] A time interval in LTE or NR is, for example, T sThe time intervals of the communication resources may be organized according to radio frames, each having a duration of 10 milliseconds (ms), where the frame period is T f =307,200T s A radio frame may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, each subframe may have a duration of 1 ms. A subframe may be further divided into two slots each having a duration of 0.5 ms, each slot may include 6 or 7 modulation symbol periods (e.g., depending on the length of a cyclic prefix prepended to each symbol period). Excluding the cyclic prefix, each symbol period may include 2048 sampling periods. In some cases, a subframe may be the smallest scheduling unit of the wireless communication system 100 and may be referred to as a transmission time interval (TTI). In other cases, the smallest scheduling unit of the wireless communication system 100 may be smaller than a subframe or may be dynamically selected (e.g., in a burst of shortened TTIs (sTTIs) or in a selected component carrier using sTTIs).

[0068] In some wireless communication systems, a slot may be further divided into multiple minislots that contain one or more symbols. In some instances, a symbol or a minislot of a minislot may be the smallest unit of scheduling. Each symbol may vary in duration depending, for example, on the subcarrier spacing or the frequency band of operation. Additionally, some wireless communication systems may implement slot aggregation, in which multiple slots or minislots are aggregated together and used for communication between the UE 115 and the base station 105.

[0069] The term "carrier" refers to a set of radio frequency spectrum resources having a defined physical layer structure to support communications over the communication link 125. For example, a carrier of the communication link 125 may include a portion of a radio frequency spectrum band that operates according to a physical layer channel 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., the Evolved Universal Mobile Telecommunications System Terrestrial Radio Access (E-UTRA) Absolute Radio Frequency Channel Number (EARFCN)) and may be arranged according to a channel raster for discovery by the UE 115. A carrier 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, a signal waveform transmitted over a carrier may be composed of multiple subcarriers (e.g., using a multi-carrier modulation (MCM) technique, such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)).

[0070] The organizational structure of carriers may differ for various radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR). For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or control signaling to support decoding of the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc.) and control signaling that coordinates operations on the carrier. In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations on other carriers.

[0071] In some cases, the base station 105 may be a source base station 105 and may configure one or more UEs 115 with one or more CHO configurations for one or more target base stations 105. For each target base station 105, the CHO configuration may provide one or more associated conditions that may trigger the UE 115 to initiate a handover to the particular target base station 105 (e.g., based on one or more target base station 105 measurements, one or more source base station 105 measurements, a measurement threshold, or a combination thereof). In some cases, the CHO configuration may include failure handling information, deconfiguration criteria, or a combination thereof.

[0072] FIG. 2 illustrates an example of a wireless communication system 200 having a source base station and a target base station supporting CHO deconfiguration and failure handling in wireless communication according to aspects of the 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 stations 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. The wireless communication system 200 illustrates an example of a conditional handover procedure in which a communication connection between the UE 115-a and a source cell served by the source base station 105-a (e.g., a first base station) is handed over to one of the first target base station 105-b or the second target base station 105-c.

[0073] Initially, the UE 115-a and the source base station 105-a may be in a connected state and may be exchanging information over the first communication connection 205. In some cases, the UE 115-a may transmit one or more measurement reports in which the UE 115-a may provide one or more measurements to several neighboring base stations, including the source base station 105-a and the first and second target base stations 105-b and 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 good candidates for handover of the UE 115-a (e.g., based on signal strength measurements being above a threshold). In this example, the source base station 105-a may identify that the first and second target base stations 105-b and 105-c are handover candidates and may communicate a handover request to each identified candidate (e.g., via the backhaul link 134). In this example, the first target base station 105-b may perform admission control based on the received handover request, may reserve some resources (e.g., contention-free random access preamble, random access resources, etc.) for the UE 115-a, and may provide information for random access to the source base station 105-a, which may be used to configure the first CHO configuration 215-a. Similarly, the second target base station 105-c may perform admission control based on the received handover request, may reserve some resources for the UE 115-a, and may provide information for random access to the source base station 105-a, which may be used to configure the second CHO configuration 215-b.

[0074] The source base station 105-a may provide the UE 115-a with a CHO configuration, which may be used by the UE 115-a to autonomously initiate a handover to the second communication connection 210. In some cases, the CHO configuration may be provided in RRC signaling (e.g., in an RRC reconfiguration message) transmitted to the UE 115-a. The CHO configuration may provide, for example, a 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, cell-specific radio network temporary identifier (C-RNTI), etc.), and one or more measurement thresholds (e.g., RRM thresholds, channel quality metric thresholds, signal strength metric thresholds, etc.) to be used to trigger a handover to the associated target base station 105. According to various techniques provided herein, the CHO configuration provided to the UE 115-a may also include one or more deconfiguration parameters, one or more failure handling parameters, or any combination thereof.

[0075] In some cases, the deconfiguration parameters in the CHO configuration may provide for event-based deconfiguration and may include one or more timers, one or more deconfiguration thresholds for each CHO target base station 105-b and 105-c or any combination thereof. Optionally, in some cases, the one or more timers may include a validity timer that starts when the handover request is acknowledged by the source base station 105-a. In some cases, a 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 for the duration of the validity timer. In other cases, the UE 115-a may also receive an indication of a validity timer associated with each target base station 105-b and 105-c having a CHO configuration and may deconfigure the associated CHO configuration upon expiration of the associated validity timer. In other cases, the source base station 105-a may send an explicit release of the CHO configuration to the target base station 105-b or 105-c whose validity timer has expired, and in such cases the UE 115-a need not maintain a validity timer or multiple validity timers 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, which may be based on an estimate of the UE 115-a movement, the signal strength of the target measured at the UE 115-a, changes in the measurements at the UE 115-a over time, an estimate of the traffic load of the source base station 105-a or the target base station 105-b or 105-c (e.g., as tracked by the respective base station 105), or any combination thereof.

[0076] In some cases, the CHO configuration may include one or more deconfiguration thresholds that provide criteria for deconfiguring the CHO. In such a case, if the UE 115-a measurements meet the threshold-based criteria for deconfiguration for the CHO target base station 105-b or 105-c, the UE 115-a may release the CHO configuration without waiting for an explicit instruction 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 and the associated measurement report configuration corresponding to the handover trigger and the CHO deconfiguration trigger. In some cases, the UE 115-a may send measurement reports 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 the reserved resources for the UE 115-a. In some cases, the measurement report (e.g., an RRC measurement report message) may include a deconfiguration indication (e.g., a cell ID of the target base station 105-b or 105-c to be deconfigured). Upon deconfiguring the CHO configuration for the target base station 105-b or 105-c, the UE 115-a may stop performing and evaluating measurements for whether the target base station 105-b or 105-c satisfies 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 a neighbor cell measurement (e.g., signal strength, channel quality metric, etc.) falls below a threshold, event 2 where the source base station 105-a (e.g., source primary cell (SpCell)) measurement becomes better than a first threshold and the target base station 105-b or 105-c measurement becomes worse than a second threshold, event 3 where the measurement offset between the target base station 105-b or 105-c 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 an associated CHO configuration and may provide a measurement report (e.g., including an indication of deconfiguration) to the source base station 105-a.In some cases, the measurement thresholds configured in each CHO may be different for each target base station 105-b and 105-c.

[0077] In some cases, the CHO configuration may additionally or alternatively include one or more timers for use in detecting handover failure. In some cases, the one or more timers may include a conditional handover timer (e.g., CHO_timer_TgNB) that is initiated by the UE 115-a upon transmission of a random access request of the handover procedure. In such a case, the UE 115-a may determine that the CHO criteria for handover from the source base station 105-a to the first target base station 105-b are met, may transmit a random access request to the first target base station 105-a, and may 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 may initiate failure processing. If 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 upon sending the random access request. In some cases, the failure process may include selecting a second target base station 105-c (e.g., or another base station having a CHO configuration for which the UE 115-a satisfies the CHO criteria for initiating handover) and sending a random access request to the second target base station 105-c. The UE 115-c may start a second conditional access timer associated with the second target base station 105-c, and the process may continue until the random access procedure is successfully executed or the UE 115-a runs out of CHO targets that satisfy the CHO criteria, at which point the base station 105-b may declare a radio link failure and may initiate an RRC re-establishment procedure. In some cases, the conditional handover timer may be different for each of the different target base stations. Table 1 below includes an example of conditional handover timer start criteria, stop criteria, and failure actions to be taken in case of conditional handover timer expiration.

[0078] [Table 1]

[0079] 3 illustrates an example of a general process flow 300 for a CHO supporting CHO deconfiguration and failure handling in wireless communication according to aspects of the disclosure. In some examples, the process flow 300 may implement aspects of the 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 FIG. 2, a source base station 105-d, which may be an example of a base station described with reference to FIG. 1 and FIG. 2, a first target base station 105-e, and a second target base station 105-f. The process flow 300 includes functions and communications performed by the UE 115-b and the base stations 105-d, 105-e, and 105-f in the context of a conditional handover procedure.

[0080] In the following description of process flow 300, operations between UE 115-b and base stations 105-d, 105-e, and 105-f may be transmitted in an order different from that shown, or the operations may be performed in a different order or at different times. Some operations may also be omitted from process flow 300, or other operations may be added to process flow 300. Although base station 105 and UE 115-b are shown as performing some of the operations of process flow 300, it should be understood that any wireless device may perform the illustrated operations.

[0081] At 305, the UE 115-b may send 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 multiple neighboring base stations, which may include the first target base station 105-e and the second target base station 105-f. The measurement report may be a “low” threshold measurement report, which may indicate that the channel measurements associated with the source base station 105-d are below a threshold used to indicate that the source base station 105-d should configure CHO for the UE 115-b.

[0082] At 310, the source base station 105-d may transmit a handover request to the first target base station 105-e. Additionally, at 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 the handover request based on relevant measurements from a measurement report of the UE 115-b (e.g., based on neighbor base station measurements that are above a threshold or better than others of the neighbor base station measurements). Although this example shows two target base stations 105, more or fewer target base stations 105 may be identified for the CHO configuration. In some cases, the handover request may include handover information related to the UE 115-b, as well as a duration for a validity timer as described herein.

[0083] At 320, the first target base station 105-e may perform admission control in response to receiving the handover request. Similarly, at 325, the second target base station 105-f may perform admission control in response to receiving the handover request. The admission 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.

[0084] At 330, the first target base station 105-e may send a handover request recognition response to the source base station 105-d. Additionally, in this example, at 335, the second target base station 105-f may send a handover request recognition response to the source base station 105-d. The handover request recognition response may include information (e.g., random access preamble, C-RNTI, etc.) for use by the UE 115-b to establish a connection. The source base station 105-d may receive the handover request recognition response and may determine CHO criteria for each target cell for use by the UE 115-b to trigger a 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.

[0085] At 340, the source base station 105-d may send 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.

[0086] At 345, the UE 115-b may determine that conditions for handover to the first target base station 105-d are satisfied. Such a determination may be made based on one or more channel quality measurements of the UE 115-b compared to a CHO configuration provided by the source base station 105-d, for example. At 350, the UE 115-b may initiate a random access channel (RACH) procedure with the first target base station 105-e and may perform the handover procedure.

[0087] 4 illustrates an example of a process flow 400 for configuring and then releasing a CHO configuration in wireless communication according to aspects of the disclosure. In some examples, the process flow 400 may implement aspects of the 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 FIGs. 1 and 2, a source base station 105-g, which may be an example of a base station described with reference to FIGs. 1 and 2, and a target base station 105-h. The process flow 400 includes functions and communications performed by the UE 115-c and the base stations 105-g and 105-h in the context of a conditional handover procedure.

[0088] In the following description of process flow 400, operations between the UE 115-c and the base stations 105-g and 105-h may be transmitted in an order different from that shown, or the operations may be performed in a different order or at different times. Some operations may also be omitted from process flow 400, or other operations may be added to process flow 400. Although the base station 105 and the UE 115-c are shown as performing some of the operations of process flow 400, it should be understood that any wireless device may perform the illustrated operations.

[0089] At 405, the UE 115-c may send 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 multiple 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 measurements associated with the source base station 105-g are below a threshold used to indicate that the source base station 105-g should configure CHO for the UE 115-c.

[0090] At 410, the source base station 105-g may transmit a handover request to the target base station 105-h. Although the example of FIG. 4 shows a single target base station 105-h, in other cases, multiple different target base stations may be configured for 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 the handover request based on relevant measurements from a measurement report of the UE 115-c (e.g., based on a neighbor base station measurement that is above a threshold or better than others of the neighbor base station measurements). In some cases, the handover request may include handover information related to the UE 115-c, as well as a duration for a validity timer as described herein.

[0091] At 415, the target base station 105-h may perform admission control in response to receiving the handover request. The admission control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preambles, etc.) may be reserved for the UE 115-c.

[0092] At 420, the target base station 105-h may send a handover request acknowledgement response to the source base station 105-g. The handover request acknowledgement response may include information (e.g., a random access preamble, a 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 acknowledgement response and may determine CHO criteria for the target cell for use by the UE 115-c to trigger a CHO. The CHO criteria may include, for example, one or more measurement thresholds (e.g., measThreshHO_TgNB) for the target base station 105-h (and for any other configured target base stations), the source base station 105-g, or any combination thereof.

[0093] At 425, the source base station 105-g may send the 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 stations 105-h 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-h.

[0094] At 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 a determination may be made based on one or more measurement reports provided by the UE 115-c, based on signal strength measurements of the UE 115-c, positioning information of the UE 115-c, etc.

[0095] At 435, the source base station 105-g may send another RRC reconfiguration to the UE 115-c to release the CHO configuration for the target base station 105-h. At 440, the source base station 105-g may send a handover cancel to the target base station 105-h to cancel the CHO configuration. The UE 115-c and the target base station 105-h may remove the CHO configuration based on the signaling from the source base station 105-g.

[0096] 5 illustrates an example of a process flow 500 supporting CHO deconfiguration and failure handling in wireless communication according to aspects of the disclosure. In some examples, the process flow 500 may implement aspects of the 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 FIGS. 1 and 2, a source base station 105-i, which may be an example of a base station described with reference to FIGS. 1 and 2, and a target base station 105-j. The process flow 500 includes functions and communications performed by the UE 115-d and the base stations 105-i and 105-j in the context of a conditional handover procedure.

[0097] In the following description of process flow 500, operations between UE 115-d and base stations 105-i and 105-j may be transmitted in an order different from that shown, or the operations may be performed in a different order or at different times. Some operations may also be omitted from process flow 500, or other operations may be added to process flow 500. Although base station 105 and UE 115-d are shown as performing some of the operations of process flow 500, it should be understood that any wireless device may perform the illustrated operations.

[0098] At 505, the UE 115-d may send 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 multiple 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 a channel measurement associated with the source base station 105-i is below a threshold used to indicate that the source base station 105-i should configure CHO for the UE 115-d.

[0099] At 510, the source base station 105-i may send a handover request to the target base station 105-j. Although the example of FIG. 5 shows a single target base station 105-j, in other cases, multiple different target base stations may be configured for 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 the handover request based on relevant measurements from a measurement report of the UE 115-d (e.g., based on a neighbor base station measurement that is above a threshold or better than others of the neighbor base station measurements). In some cases, the handover request may include handover information related to the UE 115-d, as well as optionally a duration for the validity timer 540. If multiple CHO configurations for multiple target base stations are configured, there may be multiple different validity timers for the different target base stations.

[0100] At 515, the target base station 105-j may perform admission control in response to receiving the handover request. The admission control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preambles, etc.) may be reserved for the UE 115-d.

[0101] At 520, the target base station 105-j may send a handover request acknowledgement response to the source base station 105-i. The handover request acknowledgement response 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 acknowledgement response and may determine CHO criteria for the target cell for use by the UE 115-d to trigger a CHO. The CHO criteria may include, for example, one or more measurement thresholds (e.g., measThreshHO_TgNB) for the target base station 105-j (and for any other configured target base stations), the source base station 105-i, or any combination thereof. In this example, the CHO criteria may also include a validity duration (e.g., calTimer_TgNB) for the target base station 105-j.

[0102] At 525, the source base station 105-i may send 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 CHO, may provide information for accessing the associated base station 105 (e.g., random access information, C-RNTI, etc.), and may provide a handover threshold associated with each target base station 105-j. If the CHO configuration provided to the UE 115-d includes a validity timer, the UE 115-d may start a 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 a validity timer, and the UE 115-d may not maintain a validity timer 540, which may simplify the implementation at the UE 115-d. In such a case, upon expiration of the validity timer, the source base station 105-i may explicitly release the CHO through another RRC reconfiguration message. If the UE 115-d maintains a validity timer 540, the UE 115-d may autonomously release the CHO configuration upon expiration of the validity timer 540, and the base station 105 may also release the CHO configuration based on the validity timer maintained in the base station 105.

[0103] At 530, the UE 115-d may determine that a condition for handover is satisfied while the validity timer is valid. Such a determination may be made, for example, based on one or more channel quality measurements of the UE 115-d compared to a CHO configuration provided by the source base station 105-i. At 535, the UE 115-d may initiate a RACH procedure with the first target base station 105-j and may perform a handover procedure with the target base station 105-j.

[0104] 6 illustrates an example of a process flow 600 supporting CHO deconfiguration and failure handling in wireless communication according to aspects of the disclosure. In some examples, the process flow 600 may implement aspects of the 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 FIG. 2, a source base station 105-k, which may be an example of a base station described with reference to FIG. 1 and FIG. 2, a first target base station 105-l, and a second target base station 105-m. The process flow 600 includes functions and communications performed by the UE 115-e and the base stations 105-k, 105-l, and 105-m in the context of a conditional handover procedure.

[0105] In the following description of process flow 600, operations between the UE 115-e and the base stations 105-k, 105-l, and 105-m may be transmitted in an order different from that shown, or the operations may be performed in a different order or at different times. Some operations may also be omitted from process flow 600, or other operations may be added to process flow 600. Although the base station 105 and the UE 115-e are shown as performing some of the operations of process flow 600, it should be understood that any wireless device may perform the illustrated operations.

[0106] At 605, the UE 115-e may send 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 multiple neighboring base stations, which may include the first target base station 105-l and the second target base station 105-m. The measurement report may be a “low” threshold measurement report, which may indicate that the channel measurements associated with the source base station 105-k are below a threshold used to indicate that the source base station 105-k should configure CHO for the UE 115-e.

[0107] At 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 the handover request, the admission control, and the handover request acknowledgement response). The handover preparation may include determining information (e.g., random access preamble, C-RNTI, 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 a 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, the base station 105 may maintain a validity timer 620 and may release the CHO configuration of the target cell upon expiration of the associated validity timer.

[0108] At 615, the source base station 105-k may send the CHO configuration information in an RRC reconfiguration message to the UE 115-e. 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.

[0109] At 625, the UE 115-e may determine that conditions for handover to the first target base station 105-l are satisfied. Such a determination may be made, for example, based on one or more channel quality measurements of the UE 115-e compared to a CHO configuration 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 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 the random access request while the CHO timer 635 is valid.

[0110] At 645, the UE 115-e may determine that conditions for handover to the second target base station 105-m are satisfied. Such a determination may be made, for example, based on one or more channel quality measurements of the UE 115-e compared to a CHO configuration provided by the source base station 105-k while the CHO configuration of the second target base station 105-m is active. At 655, 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 650 associated with the second target base station 105-m upon transmission of the 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. If the CHO timer 650 expires before completing the random access procedure with the second target base station 105-m, the UE 115-e may repeat the process for any other target base station that has an active CHO configuration. If multiple target base stations have CHO configurations 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 time remaining in the validity timer, the earliest configured CHO, etc.). If there is a CHO failure and no other target base station is configured for CHO, the UE 115-e may assert a radio link failure and may initiate an RRC connection re-establishment procedure.

[0111] 7 illustrates an example of a process flow 700 supporting CHO deconfiguration and failure handling in wireless communication according to aspects of the disclosure. In some examples, the process flow 700 may implement aspects of the 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 FIGs. 1 and 2, a source base station 105-n, which may be an example of a base station described with reference to FIGs. 1 and 2, and a target base station 105-o. The process flow 700 includes functions and communications performed by the UE 115-f and the base stations 105-n and 105-o in the context of a conditional handover procedure.

[0112] In the following description of process flow 700, operations between the UE 115-f and the base stations 105-n and 105-o may be transmitted in an order different from that shown, or the operations may be performed in a different order or at different times. Some operations may also be omitted from the process flow 700, or other operations may be added to the process flow 700. Although the base station 105 and the UE 115-f are shown as performing some of the operations of the process flow 700, it should be understood that any wireless device may perform the illustrated operations.

[0113] At 705, the UE 115-f may send 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 multiple 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 a channel measurement associated with the source base station 105-n is below a threshold used to indicate that the source base station 105-n should configure CHO for the UE 115-f.

[0114] At 710, the source base station 105-n may send a handover request to the target base station 105-o. Although the example of FIG. 7 shows a single target base station 105-o, in other cases, multiple different target base stations may be configured for 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 the handover request based on relevant measurements from a measurement report of the UE 115-f (e.g., based on a neighbor base station measurement value that is above a threshold or better than others of the neighbor base station measurements). In some cases, the handover request may include handover information related to the UE 115-f.

[0115] At 715, the target base station 105-o may perform admission control in response to receiving the handover request. The admission control may determine that resources (e.g., C-RNTI, contention-free random access resources, random access preambles, etc.) may be reserved for the UE 115-f.

[0116] At 720, the target base station 105-o may send a handover request acknowledgement response to the source base station 105-n. The handover request acknowledgement response 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 acknowledgement response and may determine CHO criteria for the target cell for use by the UE 115-f to trigger a CHO. The CHO criteria may include, for example, one or more measurement thresholds (e.g., measThreshHO_TgNB) for the target base station 105-o (and for 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, if satisfied, trigger a deconfiguration of the CHO. In some cases, the CHO criteria may also include a duration for one or more timers (eg, a validity timer, a CHO timer, or both).

[0117] At 725, the source base station 105-n may send the 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 stations 105-o 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 and deconfiguration thresholds associated with each target base station 105-o.

[0118] At 730, the UE 115-f may determine that a condition for target base station 105-o deconfiguration is satisfied. Such a determination may be made, for example, based on one or more channel quality measurements of the UE 115-f compared to a CHO configuration provided by the source base station 105-n. At 735, the UE 115-f may send 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. The CHO deconfiguration may include releasing the RRC configuration of the target base station 105-o, and the UE 115-f may cease performing and evaluating measurements for whether the target base station 105-o satisfies handover or CHO deconfiguration criteria. In some cases, the measurement report (e.g., an RRC measurement report message) may include a deconfiguration indication.

[0119] The source base station 105-n may send a handover cancel indication to the target base station 105-o, at 740. The target base station 105-o may release 745 the reserved resources for the UE 115-f in response to the handover cancel indication.

[0120] 8 illustrates a block diagram 800 of a device 805 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 805 may be an example of an aspect of a UE 115 as described herein. The device 805 may include a receiver 810, a communications manager 815, and a transmitter 820. The device 805 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0121] 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 deconfiguration and failure handling in wireless communications, etc.). The information may be conveyed to other components of the device 805. The receiver 810 may be an example of an aspect of the transceiver 1120 described with reference to FIG. 11. The receiver 810 may utilize a single antenna or a set of antennas.

[0122] The communications manager 815 may receive a conditional handover configuration from the 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 the one or more target base stations, and one or more timers related to the handover to the one or more target base stations, may determine a first conditional handover failure in response to expiration of the first conditional handover timer before completing the first random access procedure, may determine based on the conditional handover configuration that the first measurement threshold for initiating a handover to the first target base station is met, may send a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, and may start a first conditional handover timer for completing the first random access procedure in response to sending the first random access request.

[0123] The communications manager 815 may also receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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, release a first conditional handover configuration of the first target base station, and determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is satisfied. The communications manager 815 may be an example of an aspect of the communications manager 1110 described herein.

[0124] Communications manager 815, or its subcomponents, may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functions of communications manager 815, or its subcomponents, may be performed by a general purpose processor, a DSP, an application specific integrated circuit (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 in this disclosure.

[0125] The communications manager 815 or its subcomponents may be physically located in various locations, including distributed such that portions of the functionality are implemented by one or more physical components at different physical locations. In some examples, the communications manager 815 or its subcomponents may be separate and distinct components according to various aspects of the disclosure. In some examples, the communications manager 815 or its subcomponents may be combined with one or more other hardware components, including, but not limited to, an input / output (I / O) component, a transceiver, a network server, another computing device, one or more other components described in this disclosure, or combinations thereof according to various aspects of the disclosure.

[0126] The transmitter 820 may transmit signals generated by other components of the device 805. In some examples, the transmitter 820 may be collocated with the receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of an embodiment of the transceiver 1120 described with reference to FIG. 11. The transmitter 820 may utilize a single antenna or a set of antennas.

[0127] 9 illustrates a block diagram 900 of a device 905 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 905 may be an example of an aspect of the device 805 or a UE 115 as described herein. The device 905 may include a receiver 910, a communications manager 915, and a transmitter 940. The device 905 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0128] 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 deconfiguration and failure handling in wireless communications, etc.). The information may be conveyed to other components of the device 905. The receiver 910 may be an example of an aspect of the transceiver 1120 described with reference to FIG. 11. The receiver 910 may utilize a single antenna or a set of antennas.

[0129] The communications manager 915 may be an example of an aspect of the communications manager 815 as described herein. The communications 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 communications manager 915 may be an example of an aspect of the communications manager 1110 as described herein.

[0130] The handover configuration manager 920 may receive a conditional handover configuration from the 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 the one or more target base stations, and one or more timers associated with the handover to the one or more target base stations, and may determine a first conditional handover failure in response to expiration of the first conditional handover timer before completing the first random access procedure.

[0131] The measurement manager 925 may determine, based on the conditional handover configuration, that a first measurement threshold for triggering a handover to the first target base station is met.

[0132] The random access manager 930 may send a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for handover to the first target base station.

[0133] The conditional handover timer 935 may start a first conditional handover timer for completing the first random access procedure in response to sending the first random access request.

[0134] In some cases, the handover configuration manager 920 may receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 release a first conditional handover configuration of the first target base station.

[0135] The measurement manager 925 may determine, based on the conditional handover configuration, that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met.

[0136] The transmitter 940 may transmit signals generated by other components of the device 905. In some examples, the transmitter 940 may be collocated with the receiver 910 in a transceiver module. For example, the transmitter 940 may be an example of an aspect of the transceiver 1120 described with reference to FIG. 11. The transmitter 940 may utilize a single antenna or a set of antennas.

[0137] 10 illustrates a block diagram 1000 of a communications manager 1005 supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The communications manager 1005 may be an example of an aspect of the communications manager 815, communications manager 915, or communications manager 1110 described herein. The communications 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 establishment component 1035. Each of these modules may communicate directly or indirectly with each other (e.g., via one or more buses).

[0138] The handover configuration manager 1010 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 the one or more target base stations, and one or more timers associated with the handover to the one or more target base stations.

[0139] In some examples, the handover configuration manager 1010 may determine the first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure.

[0140] In some examples, the handover configuration manager 1010 may receive a conditional handover configuration from a source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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. In some examples, the handover configuration manager 1010 may release a first conditional handover configuration for a first target base station.

[0141] In some examples, the handover configuration manager 1010 may repeat the determining, sending, and starting the timer for any other target base stations configured for conditional handover upon further conditional handover failures.

[0142] In some examples, in response to expiration of the first conditional handover timer, the handover configuration manager 1010 may select a second target base station from the set of available target base stations based on one or more of a channel quality measurement associated with each of the set of available target base stations, an amount of time remaining in a validity timer associated with each of the set of available target base stations, or any combination thereof.

[0143] In some examples, the handover configuration manager 1010 may delete one or more of the radio resource control configuration, the first measurement value, and the reporting configurations for the conditional handover trigger and the conditional handover deconfiguration trigger provided in the first conditional handover configuration, or one or more timers associated with the first target base station.

[0144] In some examples, the handover configuration manager 1010 may cease 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, the one or more timers include at least a first conditional handover timer for completing a first random access procedure with the first target base station.

[0145] In some cases, the first deconfiguration measurement threshold is a channel quality threshold associated with the first target base station, where 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 deconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold associated with the first target base station, where 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 deconfiguration measurement threshold is a differential threshold, where the first conditional handover configuration is released in response to a difference in channel quality measurements between the source base station and the first target base station exceeding the differential threshold.

[0146] The measurement manager 1015 may determine, based on the conditional handover configuration, that a first measurement threshold for triggering a handover to the first target base station is met.

[0147] In some examples, the measurement manager 1015 may determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met.

[0148] In some examples, the measurement manager 1015 may determine that a second measurement threshold for triggering a handover to a second target base station is met in response to expiration of the first conditional handover timer.

[0149] In some examples, the measurement manager 1015 may determine based on the conditional handover configuration that a second trigger measurement threshold for initiating a handover to the second target base station is met.

[0150] In some examples, the measurement manager 1015 may send 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.

[0151] The random access manager 1020 may send a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for handover to the first target base station.

[0152] In some examples, the random access manager 1020 may send a second random access request to the second target base station based on the conditional handover configuration to initiate a second random access procedure for handover to the second target base station.

[0153] The conditional handover timer 1025 may start a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request. In some examples, the conditional handover timer 1025 may start a second conditional handover timer for completing the 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.

[0154] The validity timer 1030 may start the first validity timer and the second validity timer, if present, in response to receiving the conditional handover configuration. In some examples, the validity timer 1030 may delete the second conditional handover configuration in response to expiration of the second validity timer. In some examples, the validity timer 1030 may stop the first validity timer upon transmitting the first random access request to the first target base station.

[0155] If the RRC connection establishment component 1035 determines that the other target base station is not configured for conditional handover, it may initiate a connection re-establishment procedure.

[0156] 11 illustrates a diagram of a system 1100 including a device 1105 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 1105 may be an example of or may include components of a device 805, a device 905, or a UE 115 as described herein. The device 1105 may include components for two-way voice and data communications, including components for transmitting and receiving communications, including a communications manager 1110, an I / O controller 1115, a transceiver 1120, an antenna 1125, a memory 1130, and a processor 1140. These components may be in electronic communication over one or more buses (e.g., bus 1145).

[0157] The communications manager 1110 may receive a conditional handover configuration from the 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 the one or more target base stations, and one or more timers related to the handover to the one or more target base stations, may determine a first conditional handover failure in response to expiration of the first conditional handover timer before completing the first random access procedure, may determine based on the conditional handover configuration that the first measurement threshold for initiating a handover to the first target base station is met, may send a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station, and may start a first conditional handover timer for completing the first random access procedure in response to sending the first random access request.

[0158] The communications manager 1110 may also receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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; release a first conditional handover configuration of a first target base station; and determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is satisfied.

[0159] The I / O controller 1115 may manage input and output signals for the device 1105. The I / O controller 1115 may also manage peripherals that are not integrated into the device 1105. In some cases, the I / O controller 1115 may represent a physical connection or port to an external peripheral. In some cases, the I / O controller 1115 may utilize an operating system, such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS / 2®, UNIX®, LINUX®, or another known operating system. In other cases, the I / O controller 1115 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I / O controller 1115 may be implemented as part of a processor. In some cases, a user may interact with the device 1105 through the I / O controller 1115 or through hardware components controlled by the I / O controller 1115.

[0160] The transceiver 1120 may communicate bidirectionally via one or more antennas, wired links, or wireless links, as described above. For example, the transceiver 1120 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 1120 may also include a modem for modulating packets for transmission and providing modulated packets to an antenna, and for demodulating packets received from the antenna.

[0161] In some cases, a wireless device may include a single antenna 1125. In some cases, however, a device may have two or more antennas 1125 that may be capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0162] The memory 1130 may include RAM and ROM. The memory 1130 may store computer-readable computer-executable code 1135 that includes instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1130 may include a BIOS that may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0163] The processor 1140 may include intelligent hardware devices (e.g., general purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, 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 a memory (e.g., memory 1130) to cause the device 1105 to perform various functions (e.g., functions or tasks supporting CHO deconfiguration and failure handling in wireless communications).

[0164] Code 1135 may include instructions for implementing aspects of the disclosure, including instructions for supporting wireless communications. Code 1135 may be stored in a non-transitory computer-readable medium, such as a system memory or other type of memory. In some cases, code 1135 may not be directly executable by processor 1140, but may (e.g., when compiled and executed) cause a computer to perform functions described herein.

[0165] 12 illustrates a block diagram 1200 of a device 1205 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 1205 may be an example of an aspect of a base station 105 as described herein. The device 1205 may include a receiver 1210, a communications manager 1215, and a transmitter 1220. The device 1205 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0166] 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 deconfiguration and failure handling in wireless communications, etc.). The information may be conveyed to other components of the device 1205. The receiver 1210 may be an example of an aspect of the transceiver 1520 described with reference to FIG. 15. The receiver 1210 may utilize a single antenna or a set of antennas.

[0167] The communications manager 1215 may: establish, by the source base station, one or more conditional handover configurations with the respective target base stations for a conditional handover of the UE from the source base station to the one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon initiation of the conditional handover of the UE from the source base station to the respective target base station; and transmit to the UE the one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for initiating handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

[0168] The communications manager 1215 may also establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating the conditional handover of the UE to the associated target base station and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station, and transmit the one or more conditional handover configurations to the UE, each indicating the associated target base station, the trigger measurement threshold for initiating the conditional handover to the associated target base station, and the conditional handover timer value for completing the conditional handover of the UE to the associated target base station. The communications manager 1215 may be an example of an aspect of the communications manager 1510 described herein.

[0169] The communications manager 1215 or its subcomponents may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 1215 or its subcomponents may be performed by a general purpose processor, a DSP, an application specific integrated circuit (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 in this disclosure.

[0170] The communications manager 1215 or its subcomponents may be physically located in various locations, including distributed such that portions of the functionality are implemented by one or more physical components at different physical locations. In some examples, the communications manager 1215 or its subcomponents may be separate and distinct components according to various aspects of the disclosure. In some examples, the communications manager 1215 or its subcomponents may be combined with one or more other hardware components, including, but not limited to, an input / output (I / O) component, a transceiver, a network server, another computing device, one or more other components described in this disclosure, or combinations thereof according to various aspects of the disclosure.

[0171] The transmitter 1220 may transmit signals generated by other components of the device 1205. In some examples, the transmitter 1220 may be collocated with the receiver 1210 in a transceiver module. For example, the transmitter 1220 may be an example of an aspect of the transceiver 1520 described with reference to FIG. 15. The transmitter 1220 may utilize a single antenna or a set of antennas.

[0172] 13 illustrates a block diagram 1300 of a device 1305 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 1305 may be an example of the device 1205 or an aspect of a base station 105 as described herein. The device 1305 may include a receiver 1310, a communications manager 1315, and a transmitter 1330. The device 1305 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0173] 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 deconfiguration and failure handling in wireless communications, etc.). The information may be conveyed to other components of the device 1305. The receiver 1310 may be an example of an aspect of the transceiver 1520 described with reference to FIG. 15. The receiver 1310 may utilize a single antenna or a set of antennas.

[0174] The communications manager 1315 may be an example of an aspect of the communications manager 1215 as described herein. The communications manager 1315 may include a handover configuration manager 1320 and a UE handover manager 1325. The communications manager 1315 may be an example of an aspect of the communications manager 1510 as described herein.

[0175] The handover configuration manager 1320 may establish, by the source base station, one or more conditional handover configurations with the respective target base stations for a conditional handover of the UE from the source base station to the one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of the conditional handover of the UE from the source base station to the respective target base station.

[0176] The UE handover manager 1325 may send one or more conditional handover configurations to the UE, each indicating an associated target base station, one or more measurement thresholds for triggering a handover of the UE from the source base station to the associated target base station, and a conditional handover time period for the associated target base station.

[0177] The handover configuration manager 1320 may establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating a conditional handover of the UE to the associated target base station and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station.

[0178] The UE handover manager 1325 may send one or more conditional handover configurations to the UE, each indicating an associated target base station, a trigger measurement threshold for initiating a conditional handover to the associated target base station, and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station.

[0179] The transmitter 1330 may transmit signals generated by other components of the device 1305. In some examples, the transmitter 1330 may be collocated with the receiver 1310 in a transceiver module. For example, the transmitter 1330 may be an example of an aspect of the transceiver 1520 described with reference to FIG. 15. The transmitter 1330 may utilize a single antenna or a set of antennas.

[0180] 14 illustrates a block diagram 1400 of a communications manager 1405 supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The communications manager 1405 may be an example of an aspect of the communications manager 1215, the communications manager 1315, or the communications manager 1510 described herein. The communications 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 directly or indirectly with each other (e.g., via one or more buses).

[0181] The handover configuration manager 1410 may establish, by the source base station, one or more conditional handover configurations with the respective target base stations for a conditional handover of the UE from the source base station to the one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon activation of the conditional handover of the UE from the source base station to the respective target base station.

[0182] In some examples, the handover configuration manager 1410 may establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating 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.

[0183] In some examples, the handover configuration manager 1410 may release the first conditional handover configuration of the first target base station in response to the measurement report. In some examples, the handover configuration manager 1410 may delete one or more of the radio resource control configuration, the first deconfiguration measurement threshold, the first trigger measurement threshold, or the one or more timers associated with the first target base station that are included in the first conditional handover configuration. In some examples, the handover configuration manager 1410 may provide an indication to the first target base station that the first conditional handover configuration is released.

[0184] In some cases, the deconfiguration measurement threshold is a channel quality threshold associated with each respective target base station, where 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 deconfiguration measurement threshold includes a first threshold associated with the source base station and a second threshold for each respective target base station, where 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 deconfiguration measurement threshold is a differential threshold, where the conditional handover configuration of the first target base station is released in response to a difference in channel quality measurements between the source base station and the first target base station exceeding the differential threshold.

[0185] The UE handover manager 1415 may send one or more conditional handover configurations to the UE, each indicating an associated target base station, one or more measurement thresholds for triggering a handover of the UE from the source base station to the associated target base station, and a conditional handover time period for the associated target base station.

[0186] In some examples, the UE handover manager 1415 may send one or more conditional handover configurations to the UE, each indicating an associated target base station, a trigger 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. In some cases, the UE autonomously deconfigures the first conditional handover configuration of the first target base station based on expiration of a first validity time period.

[0187] The timer manager 1420 may 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 an estimate of the UE's movement to each respective target base station, a traffic load of the source base station or each respective target base station, a channel quality measurement provided by the UE to each respective target base station, or any combination thereof.

[0188] The measurement manager 1425 may receive a measurement report from the UE indicating that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met.

[0189] 15 illustrates a diagram of a system 1500 including a device 1505 supporting CHO deconfiguration and failure handling in wireless communications according to an aspect of the disclosure. The device 1505 may be an example of or may include components of a device 1205, a device 1305, or a base station 105 as described herein. The device 1505 may include components for two-way voice and data communications, including components for transmitting and receiving communications, including a communications manager 1510, a network communications manager 1515, a transceiver 1520, an antenna 1525, a memory 1530, a processor 1540, and an inter-station communications manager 1545. These components may be in electronic communication over one or more buses (e.g., a bus 1550).

[0190] The communications manager 1510 may establish, by the source base station, one or more conditional handover configurations with the respective target base stations for a conditional handover of the UE from the source base station to the one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon initiation of the conditional handover of the UE from the source base station to the respective target base station, and transmit to the UE the one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for initiating handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

[0191] The communications manager 1510 may also establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating a conditional handover of the UE to the associated target base station and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station, and transmit the one or more conditional handover configurations to the UE, each indicating the associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, and the conditional handover timer value for completing the conditional handover of the UE to the associated target base station.

[0192] The network communications manager 1515 may manage communications with a core network (e.g., via one or more wired backhaul links). For example, the network communications manager 1515 may manage the transfer of data communications for client devices, such as one or more UEs 115.

[0193] The transceiver 1520 may communicate bidirectionally via one or more antennas, wired links, or wireless links, as described above. For example, the transceiver 1520 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 1520 may also include a modem for modulating packets for transmission and providing modulated packets to an antenna, and for demodulating packets received from the antenna.

[0194] In some cases, a wireless device may include a single antenna 1525. In some cases, however, the device may have two or more antennas 1525 that may be capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0195] The memory 1530 may include RAM, ROM, or a combination thereof. The memory 1530 may store computer-readable code 1535 including instructions that, when executed by a processor (e.g., processor 1540), cause the device to perform various functions described herein. In some cases, the memory 1530 may include a BIOS, which may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0196] The processor 1540 may include intelligent hardware devices (e.g., general purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, 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 within the processor 1540. The processor 1540 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 1530) to cause the device 1505 to perform various functions (e.g., functions or tasks supporting CHO deconfiguration and fault handling in wireless communications).

[0197] The inter-station communications manager 1545 may manage communications with other base stations 105 and may include a controller or scheduler for controlling communications with the UE 115 in cooperation with the other base stations 105. For example, the inter-station communications manager 1545 may coordinate scheduling for transmissions to the UE 115 for various interference mitigation techniques, such as beamforming or joint transmission. In some examples, the inter-station communications manager 1545 may provide an X2 interface in LTE / LTE-A wireless communications network technology to communicate between the base stations 105.

[0198] The code 1535 may include instructions for implementing aspects of the disclosure, including instructions for supporting wireless communication. The code 1535 may be stored in a non-transitory computer-readable medium, such as a system memory or other type of memory. In some cases, the code 1535 may not be directly executable by the processor 1540, but may (e.g., when compiled and executed) cause a computer to perform functions described herein.

[0199] FIG. 16 illustrates a flow chart illustrating a method 1600 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of the method 1600 may be performed by the UE 115 or components thereof as described herein. For example, the operations of the method 1600 may be performed by a communications manager as described with reference to FIGS. 8-11. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

[0200] At 1605, the UE may receive a conditional handover configuration from the 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 the one or more target base stations, and one or more timers associated with the handover to the one or more target base stations. The operations of 1605 may be performed according to 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. 8-11.

[0201] At 1610, the UE may determine based on the conditional handover configuration that a first measurement threshold for triggering a handover to the first target base station is met. The operations of 1610 may be performed in accordance with 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. 8-11.

[0202] At 1615, the UE may transmit a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for handover to the first target base station. The operations of 1615 may be performed according to 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. 8-11.

[0203] At 1620, the UE may start a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request. The operations of 1620 may be performed according to 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. 8-11.

[0204] At 1625, the UE may determine a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure. The operations of 1625 may be performed according to 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. 8-11.

[0205] FIG. 17 illustrates a flow chart illustrating a method 1700 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of the method 1700 may be performed by the UE 115 or components thereof as described herein. For example, the operations of the method 1700 may be performed by a communications manager as described with reference to FIGS. 8-11. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

[0206] At 1705, the UE may receive a conditional handover configuration from the 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 the one or more target base stations, and one or more timers associated with the handover to the one or more target base stations. The operations of 1705 may be performed according to 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. 8-11.

[0207] At 1710, the UE may determine based on the conditional handover configuration that a first measurement threshold for triggering a handover to the first target base station is met. The operations of 1710 may be performed in accordance with 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. 8-11.

[0208] At 1715, the UE may transmit a first random access request to the first target base station based on the conditional handover configuration to initiate a first random access procedure for handover to the first target base station. The operations of 1715 may be performed according to 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. 8-11.

[0209] At 1720, the UE may start a first conditional handover timer for completing the first random access procedure in response to transmitting the first random access request. The operations of 1720 may be performed according to 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. 8-11.

[0210] At 1725, the UE may determine a first conditional handover failure in response to expiration of the first conditional handover timer prior to completing the first random access procedure. The operations of 1725 may be performed according to 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. 8-11.

[0211] At 1730, the UE may determine that a second measurement threshold for triggering a handover to the second target base station is met in response to expiration of the first conditional handover timer. The operations of 1730 may be performed in accordance with 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. 8-11.

[0212] At 1735, the UE may transmit a second random access request to the second target base station based on the conditional handover configuration to initiate a second random access procedure for handover to the second target base station. The operations of 1735 may be performed according to 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. 8-11.

[0213] At 1740, the UE may start a second conditional handover timer for completing the second random access procedure. The operations of 1740 may be performed according to 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. 8-11.

[0214] At 1745, the UE may repeat the determining, sending, and initiating upon further conditional handover failures to any other target base stations configured for conditional handover. The operations of 1745 may be performed according to 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. 8-11.

[0215] At 1750, the UE may initiate a connection re-establishment procedure upon determining that no other target base stations are configured for conditional handover. The operations of 1750 may be performed according to methods described herein. In some examples, aspects of the operations of 1750 may be performed by an RRC connection establishment component such as those described with reference to FIGS. 8-11.

[0216] FIG. 18 illustrates a flow chart illustrating a method 1800 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of the method 1800 may be performed by the UE 115 or components thereof as described herein. For example, the operations of the method 1800 may be performed by a communications manager as described with reference to FIGS. 8-11. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

[0217] At 1805, the UE may receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 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. 8-11.

[0218] At 1810, the UE may determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met. The operations of 1810 may be performed according to 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. 8-11.

[0219] At 1815, the UE may release the first conditional handover configuration of the first target base station. The operations of 1815 may be performed according to methods described herein. In some examples, aspects of the operations of 1815 may be performed by a handover configuration manager such as described with reference to FIGS. 8-11.

[0220] FIG. 19 illustrates a flow chart illustrating a method 1900 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of the method 1900 may be performed by the UE 115 or components thereof as described herein. For example, the operations of the method 1900 may be performed by a communications manager as described with reference to FIGS. 8-11. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

[0221] At 1905, the UE may receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 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. 8-11.

[0222] At 1910, the UE may determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met. The operations of 1910 may be performed according to 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. 8-11.

[0223] At 1915, the UE may release the first conditional handover configuration of the first target base station. The operations of 1915 may be performed according to methods described herein. In some examples, aspects of the operations of 1915 may be performed by a handover configuration manager such as those described with reference to FIGS. 8-11.

[0224] At 1920, the UE may determine based on the conditional handover configuration that a second trigger measurement threshold for initiating a handover to the second target base station is satisfied. The operations of 1920 may be performed in accordance with 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. 8-11.

[0225] At 1925, the UE may send a random access request to the second target base station based on the second conditional handover configuration of the second target base station to initiate a random access procedure for handover to the second target base station. The operations of 1925 may be performed according to 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. 8-11.

[0226] FIG. 20 illustrates a flow chart illustrating a method 2000 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of method 2000 may be performed by the UE 115 or components thereof as described herein. For example, the operations of method 2000 may be performed by a communications manager as described with reference to FIGS. 8-11. In some examples, the UE may execute a set of instructions to control functional elements of the UE to perform functions described below. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the functions described below.

[0227] At 2005, the UE may receive a conditional handover configuration from the source base station indicating one or more conditional handover configurations associated with one or more target base stations, where each of the one or more conditional handover configurations includes a trigger 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 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. 8-11.

[0228] At 2010, the UE may determine based on the conditional handover configuration that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met. The operations of 2010 may be performed according to 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. 8-11.

[0229] At 2015, the UE may release the first conditional handover configuration of the first target base station. The operations of 2015 may be performed according to methods described herein. In some examples, aspects of the operations of 2015 may be performed by a handover configuration manager such as described with reference to FIGS. 8-11.

[0230] At 2020, the UE may send 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 in accordance with 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. 8-11.

[0231] At 2025, the measurement report includes a deconfiguration instruction for the first target base station. The operations of 2025 may be performed in accordance with 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. 8-11.

[0232] FIG. 21 illustrates a flow chart illustrating a method 2100 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of method 2100 may be performed by a base station 105 or components thereof as described herein. For example, the operations of method 2100 may be performed by a communications manager as described with reference to FIGS. 12-15. In some examples, the base station may execute a set of instructions to control functional elements of the base station to perform functions described below. Additionally or alternatively, the base station may use dedicated hardware to perform aspects of the functions described below.

[0233] At 2105, the base station may establish, by the source base station, one or more conditional handover configurations with the respective target base stations for conditional handover of the UE from the source base station to the one or more target base stations, where each conditional handover configuration includes a conditional handover time period for completing a random access procedure upon initiation of the conditional handover of the UE from the source base station to the respective target base station. The operations of 2105 may be performed according to 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. 12-15.

[0234] At 2110, the base station may transmit one or more conditional handover configurations to the UE, each indicating an associated target base station, one or more measurement thresholds for triggering handover of the UE from the source base station to the associated target base station, and a conditional handover time period for the associated target base station. The operations of 2110 may be performed according to 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. 12-15.

[0235] FIG. 22 illustrates a flow chart illustrating a method 2200 for supporting CHO deconfiguration and failure handling in wireless communications according to aspects of the disclosure. The operations of method 2200 may be performed by a base station 105 or components thereof as described herein. For example, the operations of method 2200 may be performed by a communications manager as described with reference to FIGS. 12-15. In some examples, the base station may execute a set of instructions to control functional elements of the base station to perform functions described below. Additionally or alternatively, the base station may use dedicated hardware to perform aspects of the functions described below.

[0236] At 2205, the base station may establish, by the source base station, one or more conditional handover configurations with respective target base stations for conditional handover of the UE from the source base station to one or more target base stations, where each conditional handover configuration includes a trigger measurement threshold for initiating a conditional handover of the UE to the associated target base station and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station. The operations of 2205 may be performed according to 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. 12-15.

[0237] At 2210, the base station may send one or more conditional handover configurations to the UE, each indicating an associated target base station, a trigger measurement threshold for initiating a conditional handover to the associated target base station, and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station. The operations of 2210 may be performed according to 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. 12-15.

[0238] It should be noted that the methods described herein describe possible implementations, that the operations and steps may be rearranged or otherwise modified, and that other implementations are possible. Furthermore, aspects from two or more of the methods may be combined.

[0239] Embodiment 1: A method of wireless communication in a UE, comprising: 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 the one or more target base stations, and one or more timers related to the handover to the one or more target base stations; determining, based at least in part on the conditional handover configuration, that a first measurement threshold for initiating a handover to a first target base station is met; transmitting a first random access request to the first target base station, based at least in part on the conditional handover configuration, to initiate a first random access procedure for the handover to the first target base station; in response to transmitting the first random access request, starting a first conditional handover timer for completing the first random access procedure; and in response to expiration of the first conditional handover timer prior to completing the first random access procedure, determining a first conditional handover failure.

[0240] Embodiment 2: The method of embodiment 1, wherein the one or more timers include at least a first conditional handover timer for completing a first random access procedure with the first target base station.

[0241] Embodiment 3: The method of embodiment 1 or 2, wherein the conditional handover configuration includes at least a first conditional handover configuration to a first target base station and a second conditional handover configuration to a second target base station.

[0242] Embodiment 4: The method of any of embodiments 1-3, further comprising starting a first validity timer and a second validity timer in response to receiving the conditional handover configuration, and deleting the second conditional handover configuration in response to expiration of the second validity timer.

[0243]

[0023] Embodiment 5: The method of embodiment 4, further comprising stopping the first validity timer upon sending the first random access request to the first target base station.

[0244] Embodiment 6: The method of any of embodiments 1 to 5, further comprising: determining, in response to expiration of the first conditional handover timer, that a second measurement threshold for initiating a handover to a second target base station is met; sending a second random access request to the second target base station based at least in part on the conditional handover configuration to initiate a second random access procedure for the handover to the second target base station; and starting a second conditional handover timer for completing the second random access procedure.

[0245]

[0023] Embodiment 7: The method of embodiment 6, further comprising initiating a connection re-establishment procedure upon determining that the other target base station is not configured for the conditional handover.

[0246]

[0023] Embodiment 8: The method of embodiment 6 or 7, wherein the first duration of the first conditional handover timer is different from the second duration of the second conditional handover timer.

[0247] Embodiment 9: The method of any of embodiments 6-8, further comprising: in response to expiration of the first conditional handover timer, selecting a second target base station from the plurality of available target base stations based at least in part on a channel quality measurement associated with each of the plurality of available target base stations.

[0248] Embodiment 10: The method of any of embodiments 6 to 9, wherein the second target base station is selected based at least in part on the second target base station having a shorter remaining validity timer duration than other of the available plurality of target base stations.

[0249] Embodiment 11: The method of any of embodiments 1 to 10, further comprising receiving a deconfiguration message from a source base station that deconfigures one or more conditional handover configurations, and deconfiguring the one or more conditional handover configurations based at least in part on the deconfiguration message.

[0250]

[0023] Embodiment 12: The method of embodiment 11, wherein the deconfiguration message is received in radio resource control signaling from the source base station.

[0251] Embodiment 13: The method of embodiment 11 or 12, further comprising deleting one or more of the radio resource control configuration, or the first measurement, and the reporting configuration for the conditional handover trigger, provided in the first conditional handover configuration, and discontinuing evaluation of conditional handover measurements associated with the conditional handover configuration and whether the measurements satisfy the conditional handover criteria.

[0252] Embodiment 14: An apparatus comprising at least one means for carrying out the method of any of embodiments 1 to 13.

[0253] Embodiment 15: An apparatus for wireless communication comprising a processor, a memory in electronic communication with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any of embodiments 1 to 13.

[0254] Embodiment 16: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the method of any of embodiments 1 to 13.

[0255] Embodiment 17: A method of wireless communication in a user equipment (UE), comprising: receiving a conditional handover configuration from a source base station 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 trigger 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, based at least in part on the conditional handover configuration, that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met; and releasing the first conditional handover configuration of the first target base station.

[0256] Embodiment 18: The method of embodiment 17, further comprising: determining, based at least in part on the conditional handover configuration, that a second trigger measurement threshold for initiating a handover to the second target base station is met; and sending a random access request to the second target base station, based at least in part on the second conditional handover configuration of the second target base station, to initiate a random access procedure for the handover to the second target base station.

[0257] Embodiment 19: The method of embodiment 17 or 18, wherein releasing the first conditional handover configuration comprises deleting one or more of the radio resource control configuration, the first measurement value, and the reporting configuration for the conditional handover trigger and the conditional handover deconfiguration trigger, or one or more timers associated with the first target base station, 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 the conditional handover criteria or the conditional handover deconfiguration criteria.

[0258]

[0046] Embodiment 20: The method of any of embodiments 17 to 19, further comprising: sending a measurement report to the source base station indicating that the first conditional handover configuration of the first target base station is released.

[0259]

[0046] Embodiment 21: The method of any of embodiments 17 to 20, wherein the measurement report further includes a deconfiguration instruction for the first target base station.

[0260] Embodiment 22: The method of any of embodiments 17 to 21, wherein the first deconfiguration measurement threshold is a channel quality threshold associated with a first target base station, and the first conditional handover configuration is released in response to a channel quality measurement value of the first target base station being less than the channel quality threshold.

[0261] Embodiment 23: The method of any of embodiments 17-22, wherein the first deconfiguration measurement threshold comprises 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.

[0262] Embodiment 24: The method of any of embodiments 17 to 23, wherein the first deconfiguration measurement threshold is a differential threshold, and the first conditional handover configuration is released in response to a difference in a channel quality measurement between the source base station and the first target base station exceeding the differential threshold.

[0263] Embodiment 25: An apparatus comprising at least one means for carrying out the method of any of embodiments 17 to 24.

[0264] Embodiment 26: An apparatus for wireless communication comprising a processor, a memory in electronic communication with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform any of the methods of embodiments 17 to 24.

[0265] Embodiment 27: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the method of any of embodiments 17 to 24.

[0266] Embodiment 28: A method for wireless communication in a source base station comprising: establishing, by a source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a user equipment (UE) from the source base station to the one or more target base stations, each conditional handover configuration including a validity time period during which the conditional handover configuration is valid and a conditional handover time period for completing a random access procedure upon activation of a conditional handover of the UE from the source base station to the respective target base station; and transmitting to the UE one or more conditional handover configurations, each indicating an associated target base station, one or more measurement thresholds for activation of a handover of the UE from the source base station to the associated target base station, and the conditional handover time period for the associated target base station.

[0267]

[0081] Embodiment 29: The method of embodiment 28, further comprising: deconfiguring the first conditional handover configuration of the first target base station in response to expiration of a first validity time period associated with the first target base station.

[0268]

[0081] Embodiment 30: The method of embodiment 28 or 29, wherein the UE autonomously deconfigures the first conditional handover configuration of the first target base station based on expiration of the first validity time period.

[0269]

[0081] Embodiment 31: The method of any of embodiments 28-30, wherein each of the one or more target base stations has a different value for one or more of the validity time period or the conditional handover time period.

[0270] Embodiment 32: The method of any of embodiments 28 to 31, wherein one or more of the validity time period or the conditional handover time period is determined based at least in part on one or more of an estimate of the UE's movement to each respective target base station, a traffic load of the source base station or each respective target base station, a channel quality measurement to each respective target base station provided by the UE, or any combination thereof.

[0271] Embodiment 33: An apparatus comprising at least one means for carrying out the method of any of embodiments 28 to 32.

[0272] Embodiment 34: An apparatus for wireless communication comprising a processor, a memory in electronic communication with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform any of the methods of embodiments 28 to 32.

[0273] Embodiment 35: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the method of any of embodiments 28 to 32.

[0274] Embodiment 36: A method for wireless communication in a source base station comprising: establishing, by a source base station, one or more conditional handover configurations with respective target base stations for conditional handover of a user equipment (UE) from the source base station to the one or more target base stations, each conditional handover configuration including a trigger measurement threshold for initiating a conditional handover of the UE to an associated target base station and a conditional handover timer value for completing the conditional handover of the UE to the associated target base station; and transmitting to the UE the one or more conditional handover configurations, each indicating an associated target base station, the trigger measurement threshold for initiating a conditional handover to the associated target base station, and the conditional handover timer value for completing the conditional handover of the UE to the associated target base station.

[0275] Embodiment 37: The method of embodiment 36, further comprising: determining in the UE that at least one first conditional handover configuration should be deconfigured; in response to the determination to deconfigure, transmitting deconfiguration information to the UE indicating that the UE should delete one or more of the radio resource control configuration, or the first measurement value, and the reporting configuration for the first conditional handover configuration; receiving a measurement report from the UE indicating that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of the first target base station is met; and releasing the first conditional handover configuration of the first target base station in response to the measurement report.

[0276] Embodiment 38: The method of embodiment 36 or 37, wherein releasing the first conditional handover configuration comprises deleting one or more of a radio resource control configuration, a first deconfiguration measurement threshold, a first trigger measurement threshold, or one or more timers associated with the first target base station, the radio resource control configuration, the first deconfiguration measurement threshold, the first trigger measurement threshold, or one or more timers associated with the first target base station, the radio resource control configuration, the first deconfiguration measurement threshold, the first trigger measurement threshold, or the ...

[0277]

[0081] Embodiment 39: The method of any of embodiments 36-38, wherein releasing the first conditional handover configuration further comprises providing an indication to the first target base station that the first conditional handover configuration is released.

[0278] Embodiment 40: The method of any of embodiments 36-39, wherein the deconfiguration measurement threshold is a channel quality threshold associated with each respective target base station, and the conditional handover configuration of the first target base station is released in response to the channel quality measurement value of the first target base station being less than the channel quality threshold of the first target base station.

[0279] Embodiment 41: The method of any of embodiments 36-40, wherein the deconfiguration measurement thresholds comprise a first threshold associated with the source base station and a second threshold for each respective target base station, and the conditional handover configuration of the first target base station is deconfigured 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 for the first target base station.

[0280] Embodiment 42: The method of any of embodiments 36 to 41, wherein the deconfiguration measurement threshold is a differential threshold, and the conditional handover configuration associated with the first target base station is deconfigured in response to a difference in channel quality measurements between the source base station and the first target base station exceeding the differential threshold.

[0281] Embodiment 43: An apparatus comprising at least one means for carrying out the method of any of embodiments 36 to 42.

[0282] Embodiment 44: An apparatus for wireless communication comprising a processor, a memory in electronic communication with the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform any of the methods of embodiments 36 to 42.

[0283] Embodiment 45: A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to perform the method of any of embodiments 36 to 42.

[0284] The techniques described herein may be used for various wireless communication systems, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and other systems. A CDMA system may implement a radio technology, such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 releases are sometimes commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA), and other variants of CDMA. A TDMA system may implement a radio technology, such as Global System for Mobile Communications (GSM).

[0285] An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are parts of the Universal Mobile Telecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP®). CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned herein as well as other systems and radio technologies. Aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described as examples, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used throughout much of the description, although the techniques described herein are applicable to other than LTE, LTE-A, LTE-A Pro, or NR applications.

[0286] A macro cell may generally cover a relatively large geographic area (e.g., a radius of several kilometers) and allow unrestricted access by UEs subscribing to the network provider's service. A small cell may be associated with a lower power base station compared to a macro cell, and the small cell may operate in the same or a different frequency band (e.g., licensed frequency band, unlicensed frequency band, etc.) as the macro cell. Small cells may include pico cells, femto cells, and micro cells, according to various examples. A pico cell may, for example, cover a small geographic area and allow unrestricted access by UEs subscribing to the network provider's service. A femto cell may also cover a small geographic area (e.g., a home) and provide restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for users in the 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, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or more (eg, two, three, four, etc.) cells and may also support communication using one or more component carriers.

[0287] The wireless communications systems described herein may support synchronous or asynchronous operation. For synchronous operation, base stations may have similar frame timing and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, base stations may have different frame timing 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.

[0288] The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout this description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0289] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed using 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. A 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 in conjunction with a DSP core, or any other such configuration).

[0290] 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 on or transmitted via a computer-readable medium as one or more instructions or codes. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of 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 physically located in various locations, including being distributed such that portions of the functions are implemented in different physical locations.

[0291] Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory 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-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general purpose or special purpose computer or a general purpose or special purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of media. As used herein, disk and disc include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically using lasers. Combinations of the above are also included within the scope of computer-readable media.

[0292] As used herein, including within the claims, "or" as used in a list of items (e.g., a list of items ending with a phrase such as "at least one of" or "one or more of") indicates an inclusive list, such as, 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 and B and C). Also, the phrase "based on" as used herein should not be construed 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 present disclosure. In other words, the phrase "based on" as used herein is to be interpreted similarly to the phrase "based at least in part on."

[0293] In the accompanying figures, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes the similar components. If only a first reference label is used herein, the description is applicable to any of the similar components having the same first reference label, regardless of the second reference label, or any other subsequent reference label.

[0294] The description set forth herein with respect to the accompanying drawings describes exemplary configurations and does not necessarily represent all examples that may be implemented or fall within the scope of the claims. As used herein, the term "exemplary" means "serving as an example, instance, or illustration" and does not mean "preferred" or "advantageous over other examples." The detailed description includes specific details for the purposes of providing an understanding of the described techniques. However, these techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0295] The description herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications of 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. Thus, the present disclosure is not limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. [Explanation of symbols]

[0296] 100 Wireless communication system 105 Base station 110 Geographic Coverage Areas 115 User Equipment (UE) 125 Communication Links 130 Core Network 132, 134 backhaul links 200 Wireless Communication System 205 First communication connection 210 Second communication connection 215-a First CHO configuration 215-b Second CHO construct 805 Devices 810 Receiver 815 Communications Manager 820 Transmitter 905 Devices 910 Receiver 915 Communications Manager 920 Handover Configuration Manager 925 Measurement Manager 930 Random Access Manager 935 Conditional Handover Timer 940 Transmitter 1005 Communications Manager 1010 Handover Configuration Manager 1015 Measurement Manager 1020 Random Access Manager 1025 Conditional Handover Timer 1030 Validity Timer 1035 RRC connection establishment component 1105 Devices 1110 Communications Manager 1115 I / O Controller 1120 Transceiver 1125 Antenna 1130 Memory 1135 Code 1140 Processor 1145 Bus 1205 Devices 1210 Receiver 1215 Communications Manager 1220 Transmitter 1305 Devices 1310 Receiver 1315 Communications Manager 1320 Handover Configuration Manager 1325 UE Handover Manager 1330 Transmitter 1405 Communications Manager 1410 Handover Configuration Manager 1415 UE Handover Manager 1420 Timer Manager 1425 Measurement Manager 1505 Devices 1510 Communications Manager 1515 Network Communications Manager 1520 Transceiver 1525 Antenna 1530 Memory 1535 Computer readable code, code 1540 Processor 1545 Inter-Station Communication Manager 1550 Bus

Claims

1. 1. A method for wireless communication in a user equipment (UE), comprising: receiving a conditional handover configuration from the source base station indicating one or more target base stations, one or more measurement thresholds for triggering a handover from a 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; determining, based at least in part on the conditional handover configuration, that a first measurement threshold for triggering the handover to a first target base station is met; sending a first random access request to the first target base station based at least in part on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station; in response to the sending of the first random access request, starting a first conditional handover timer for completing the first random access procedure; determining a first conditional handover failure in response to expiration of the first conditional handover timer before completing the first random access procedure; A method for providing the above.

2. The method of claim 1 , 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.

3. The method of claim 1 , wherein the conditional handover configurations include at least a first conditional handover configuration to the first target base station and a second conditional handover configuration to a second target base station.

4. sending a second random access request to the second target base station in response to expiration of the first conditional handover timer to initiate a second random access procedure for the handover to the second target base station; starting a second conditional handover timer for completing the second random access procedure; The method of claim 1 , further comprising:

5. initiating a connection re-establishment procedure upon determining that no other target base stations are configured for the conditional handover. The method of claim 4 , further comprising:

6. 5. The method of claim 4, wherein a first duration of the first conditional handover timer is different from a second duration of the second conditional handover timer.

7. selecting the second target base station from a plurality of available target base stations based at least in part on a channel quality measurement associated with each of the plurality of available target base stations in response to expiration of the first conditional handover timer. The method of claim 4 , further comprising:

8. initiating a connection re-establishment procedure in response to expiration of the first conditional handover timer. The method of claim 1 , further comprising:

9. receiving a deconfiguration message from the source base station to deconfigure one or more conditional handover configurations; deconfiguring the one or more conditional handover configurations based at least in part on the deconfiguration message; The method of claim 1 , further comprising:

10. The method of claim 9, wherein the deconfiguration message is received in radio resource control signaling from the source base station.

11. - deleting one or more of the radio resource control configuration or the first measurement value and the reporting configuration for the conditional handover trigger provided in the first conditional handover configuration; discontinuing conditional handover measurements associated with the conditional handover configuration and evaluating whether the measurements satisfy conditional handover criteria; The method of claim 9 , further comprising:

12. 1. A method for wireless communication in a user equipment (UE), comprising: receiving a conditional handover configuration from a source base station 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 trigger measurement threshold for initiating a conditional handover to an associated target base station and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station; determining, based at least in part on a first conditional handover configuration, that a first deconfiguration measurement threshold for deconfiguring a first conditional handover configuration of a first target base station is met; Releasing the first conditional handover configuration of the first target base station; A method for providing the above.

13. determining, based at least in part on the conditional handover configuration, that a second trigger measurement threshold for initiating a handover to a second target base station is met; sending a random access request to the second target base station based at least in part on a second conditional handover configuration of the second target base station to initiate a random access procedure for the handover to the second target base station; The method of claim 12, further comprising:

14. sending a measurement report to the source base station indicating that the first conditional handover configuration of the first target base station is released; The method of claim 12, further comprising:

15. The method of claim 14 , wherein the measurement report includes a deconfiguration indication for the first target base station.

16. 13. The method of claim 12, wherein the first deconfiguration 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 a channel quality measurement of the first target base station being less than the channel quality threshold.

17. 13. The method of claim 12, wherein the first deconfiguration measurement threshold comprises 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 a first channel quality measurement of the source base station exceeding the first threshold and a second channel quality measurement of the first target base station being less than the second threshold.

18. 13. The method of claim 12, wherein the first deconfiguration measurement threshold is a difference threshold, and the first conditional handover configuration is released in response to a difference in a channel quality measurement between the source base station and the first target base station exceeding the difference threshold.

19. 1. A method for wireless communication in a source base station, comprising: establishing, by the source base station, one or more conditional handover configurations with respective target base stations for a conditional handover of a user equipment (UE) from the source base station to the one or more target base stations, each conditional handover configuration including a trigger measurement threshold for initiating the conditional handover of the UE to an associated target base station, a conditional handover timer value for completing the conditional handover of the UE to the associated target base station, and a de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station; transmitting the one or more conditional handover configurations to the UE, each indicating the associated target base station, the trigger measurement threshold for initiating the conditional handover to the associated target base station, the conditional handover timer value for completing the conditional handover of the UE to the associated target base station, and the de-configuration measurement threshold for de-configuring the conditional handover configuration of the associated target base station; A method for providing the above.

20. determining at least a first conditional handover configuration to be deconfigured in the UE, the determining being performed at least in part based on a signal at the source base station or from the associated target base station; in response to the determination to deconfigure, transmitting deconfiguration information to the UE indicating that the UE should delete one or more of a radio resource control configuration, or a first measurement value, and a reporting configuration for the first conditional handover configuration; receiving a measurement report from the UE indicating that a first deconfiguration measurement threshold for deconfiguring the first conditional handover configuration of a first target base station is met; releasing the first conditional handover configuration of the first target base station in response to the measurement report; 20. The method of claim 19, further comprising:

21. the step of releasing the first conditional handover configuration further comprising: providing an indication to the first target base station that the first conditional handover configuration is released. The method of claim 20.

22. 20. The method of claim 19, wherein the deconfiguration measurement threshold is a channel quality threshold associated with each respective target base station, and the conditional handover configuration of a first target base station is released in response to a channel quality measurement value of the first target base station being less than the channel quality threshold for the first target base station.

23. 20. The method of claim 19, wherein the deconfiguration measurement thresholds comprise a first threshold associated with the source base station and a second threshold for each respective target base station, and the conditional handover configuration of a first target base station is released in response to a first channel quality measurement of the source base station exceeding the first threshold and a second channel quality measurement of the first target base station being less than the second threshold for the first target base station.

24. 20. The method of claim 19, wherein the conditional handover configuration associated with a first target base station is released in response to a difference in a channel quality measurement between the source base station and the first target base station exceeding a difference threshold.

25. An apparatus for wireless communication in a user equipment (UE), comprising: means for receiving a conditional handover configuration from a source base station indicating one or more target base stations, one or more measurement thresholds for triggering a handover from a 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, based at least in part on the conditional handover configuration, that a first measurement threshold for triggering the handover to a first target base station is met; means for transmitting a first random access request to the first target base station based at least in part on the conditional handover configuration to initiate a first random access procedure for the handover to the first target base station; means for starting, in response to the sending of the first random access request, a first conditional handover timer for completing the first random access procedure; means for determining a first conditional handover failure in response to expiration of the first conditional handover timer before completing the first random access procedure; An apparatus comprising:

26. 26. The apparatus of claim 25, 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.

27. means for transmitting a second random access request to the second target base station in response to expiration of the first conditional handover timer to initiate a second random access procedure for the handover to the second target base station; means for starting a second conditional handover timer for completing the second random access procedure; 26. The apparatus of claim 25, further comprising:

28. means for initiating a connection re-establishment procedure in response to expiration of the first conditional handover timer.

26. The apparatus of claim 25, further comprising:

29. means for receiving a deconfiguration message from the source base station to deconfigure one or more conditional handover configurations; means for deconfiguring the one or more conditional handover configurations based at least in part on the deconfiguration message; 26. The apparatus of claim 25, further comprising:

30. The deconfiguration message is received in radio resource control signaling from the source base station, and the device: means for deleting one or more of a radio resource control configuration, or a first measurement value, and a reporting configuration for a conditional handover trigger, provided in a first conditional handover configuration; and means for discontinuing evaluation of conditional handover measurements associated with the conditional handover configuration and whether the measurements satisfy a conditional handover criterion.

30. The apparatus of claim 29.

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