Error handling in dual active link handover - Patents.com

Abstract

Methods, systems, and devices for wireless communications are described. In some systems, a user equipment (UE) may perform a dual active link handover procedure from a source base station to a target base station. During the dual active link handover procedure, the UE may have connections to both base stations simultaneously. In such cases, transmission opportunities for communicating with the base stations may conflict. To handle the competing transmission opportunities, the UE may drop monitoring opportunities or packet reception for the base station based on a prioritization rule. In some cases, to reduce packet loss, the base station may configure retransmissions or slot aggregation to provide the UE with additional opportunities to receive packets. Additionally or alternatively, the UE may send a notification message to the base station indicating the dropped monitoring opportunities or packets.

Description

[Technical field]

[0001] cross reference This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 899,114, entitled "Error Handling in Make-Before-Break Handover," filed September 11, 2019, and U.S. Provisional Patent Application No. 17 / 012,911, entitled "Error Handling in Dual Active Link Handover," filed September 4, 2020, by Awoniyi-Oteri et al., each of which is assigned to the assignee of the present application.

[0002] The following relates generally to wireless communications, and more particularly to error handling in dual active link handovers. [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 one or more base stations or one or more network access nodes, each simultaneously supporting communication for multiple communication devices, which may be known as user equipment (UE), in some cases.

[0004] In some wireless communication systems, a UE may communicate with a base station using beamforming techniques. A UE may have multiple panels (e.g., antenna modules, antenna arrays, etc.) each capable of forming a communication beam (e.g., a receive beam) for receiving messages from a base station. The UE may operate one panel at a time and form a receive beam in one direction at a time. When a UE is simultaneously connected to multiple base stations, the UE may drop a data packet in a transmission from a first base station when the UE is using a communication beam to receive a data packet in a transmission from a second base station. For example, the UE may not be able to switch in a timely manner to receive a data packet from a first base station at a scheduled transmit opportunity due to communication with the second base station in an overlapping or adjacent transmit opportunity. Dropping packets when connected to multiple base stations may result in packet loss at the UE and significant latency associated with the UE successfully receiving the dropped packet. Summary of the Invention [Means for solving the problem]

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support error handling in dual active link handover. Generally, the described techniques provide for a reduction in packet error rate, packet loss rate, or both during a dual active link handover. For example, a UE may perform a dual active link handover procedure from a source base station to a target base station to reduce or eliminate interruption time. In some cases, a dual active link handover may be referred to as a make-before-break (MBB) handover or a dual active protocol stack handover. During a dual active link handover procedure, a UE may have connections to both a source base station and a target base station simultaneously. In such a case, transmission opportunities to communicate with these base stations may compete (e.g., based on a time for a UE to switch from a first beam, bandwidth, and cell corresponding to the first base station to a second beam, bandwidth, and cell corresponding to the second base station). To handle competing transmission opportunities, a UE may, for example, drop monitoring opportunities or packet reception to a base station based on a prioritization rule to communicate to other competing transmission opportunities with other base stations. In some cases, to reduce packet loss, the base station may configure retransmission or slot aggregation to provide the UE with additional opportunities to receive packets. Additionally or alternatively, the UE may send a notification message to the base station indicating any dropped monitoring opportunities or packets, and if the UE misses a packet due to its dropping, the base station may decide to resend the missed packet to the UE (e.g., directly or via another base station) based on the notification message.

[0006] A method for wireless communications in a UE is described that may include simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, selecting to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time, and monitoring a third transmission opportunity for a message from the second base station based on execution of the dual active link handover.

[0007] An apparatus for wireless communication in a UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, select the first transmission opportunity to communicate with the first base station instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time, and monitor a third transmission opportunity for a message from the second base station based on execution of the dual active link handover.

[0008] Another apparatus for wireless communications in a UE is described that may include means for simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, means for identifying a time between a first transmit opportunity associated with the first base station and a second transmit opportunity associated with the second base station, means for selecting to communicate with the first base station at the first transmit opportunity instead of monitoring the second transmit opportunity for a message from the second base station based on the identified time, and means for monitoring a third transmit opportunity for a message from the second base station based on execution of the dual active link handover.

[0009] A non-transitory computer-readable medium storing code for wireless communications in a UE is described, which may include instructions executable by a processor to simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time, and monitor a third transmission opportunity for a message from the second base station based on execution of the dual active link handover.

[0010] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for identifying a configuration associated with performing a dual active link handover and determining, based on the configuration, a time relationship between the second transmission opportunity and the third transmission opportunity.

[0011] 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 configuration from one or both of the first base station and the second base station.

[0012] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the time relationship between the second transmission opportunity and the third transmission opportunity includes a retransmission timer for retransmission of a message missed during the second transmission opportunity when the UE may be performing a dual active link handover, and the retransmission timer may be shorter than a default retransmission timer.

[0013] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for identifying a slot aggregation configuration associated with performing a dual active link handover, where monitoring for a third transmission opportunity for the message may be based on the slot aggregation configuration.

[0014] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the slot aggregation configuration includes one or both of a number of repetitions of a message within a set of slots and a periodicity for the repetition of a message within a set of slots.

[0015] 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 configuration for one or both of a first communication link with a first base station and a second communication link with a second base station, and transmitting an indication of the selected configuration to one or both of the first base station and the second base station, where monitoring for a third transmission opportunity for the message may be based on the selected configuration.

[0016] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for transmitting a notification message indicating that the UE did not monitor the second transmission opportunity, where monitoring for a third transmission opportunity may be further based on transmitting the notification message.

[0017] 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 first transmission opportunity and a first communications beam for communicating with a first base station in a first bandwidth, where the UE may be configured to communicate using a single communications beam at a time, and determining that the identified time may be less than a threshold time for switching from the first communications beam for communicating with the first base station in the first bandwidth to a second communications beam for communicating with a second base station in the second bandwidth, where selecting to communicate on the first transmission opportunity instead of monitoring the second transmission opportunity may be further based on determining.

[0018] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first transmission opportunity and the second transmission opportunity at least partially overlap in time.

[0019] A method for wireless communication in a first base station is described that may include identifying that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, transmitting a message to the UE at a first transmission opportunity, and transmitting a message to the UE at a second transmission opportunity following the first transmission opportunity based on the UE performing the dual active link handover.

[0020] An apparatus for wireless communication in a first base station is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to identify that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, transmit a message to the UE at a first transmit opportunity, and transmit a message to the UE at a second transmit opportunity following the first transmit opportunity based on the UE performing the dual active link handover.

[0021] Another apparatus for wireless communication at a first base station is described that may include means for identifying that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, means for transmitting a message to the UE at a first transmit opportunity, and means for transmitting a message to the UE at a second transmit opportunity following the first transmit opportunity based on performance of the dual active link handover by the UE.

[0022] A non-transitory computer-readable medium storing code for wireless communication at a first base station is described, which may include instructions executable by a processor to identify that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, transmit a message to the UE at a first transmit opportunity, and transmit a message to the UE at a second transmit opportunity following the first transmit opportunity based on the UE performing the dual active link handover.

[0023] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for configuring a UE with a configuration related to the UE performing a dual active link handover, the configuration indicating a time relationship between a first transmission opportunity and a second transmission opportunity.

[0024] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, configuring the UE may include an operation, feature, means, or instruction for sending one or both of a configuration message and a dual active link handover command to the UE indicating the configuration.

[0025] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the time relationship between the first transmission opportunity and the second transmission opportunity includes a retransmission timer for retransmission of a message missed during the first transmission opportunity when the UE may be performing a dual active link handover, and the retransmission timer for the retransmission may be shorter than a default retransmission timer.

[0026] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for configuring a UE with a slot aggregation configuration associated with the UE performing a dual active link handover, where transmitting a message at the first transmission opportunity and the second transmission opportunity may be based on the slot aggregation configuration.

[0027] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, configuring the UE may include operations, features, means, or instructions for sending one or both of a configuration message and a dual active link handover command to the UE indicating a slot aggregation configuration, where the slot aggregation configuration includes one or more of a number of repetitions of the message within the set of slots and a periodicity for the repetition of the message within the set of slots.

[0028] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for determining that the UE did not receive a message at a first transmit opportunity, and transmitting the message at a second transmit opportunity, including retransmitting the message at the second transmit opportunity based on the determining.

[0029] 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 notification message from the UE indicating that the UE did not monitor the first transmission opportunity, where determining may be based on the notification message.

[0030] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for performing slot aggregation, where a message may be transmitted at a first transmission opportunity and at a second transmission opportunity based on the slot aggregation.

[0031] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first base station includes a source base station of a dual active link handover or a target base station of a dual active link handover.

[0032] A method for wireless communications in a UE is described that may include simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on performing a dual active link handover, identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, selecting to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a first message from the second base station based on the identified time, and sending a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0033] An apparatus for wireless communication in a UE is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, select the first transmission opportunity to communicate with the first base station instead of monitoring the second transmission opportunity for a first message from the second base station based on the identified time, and transmit a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0034] Another apparatus for wireless communications in a UE is described that may include means for simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on performing a dual active link handover, means for identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, means for selecting to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a first message from the second base station based on the identified time, and means for sending a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0035] A non-transitory computer-readable medium storing code for wireless communications in a UE is described, which may include instructions executable by a processor to simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a first message from the second base station based on the identified time, and send a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0036] 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 first message from one or both of the first base station and the second base station at the third transmission opportunity based on the notification message.

[0037] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for receiving from the second base station a configuration related to performing a dual active link handover, where the configuration may be received based on a notification message.

[0038] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the configuration includes one or both of a retransmission timer for retransmission of a first message missed during the second transmission opportunity when the UE may be performing a dual active link handover indicating a time relationship between the second transmission opportunity and the third transmission opportunity, and a slot aggregation configuration including one or both of a number of repetitions of the first message within the set of slots and a periodicity for the repetitions of the first message within the set of slots.

[0039] 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 slot aggregation configuration associated with performing a dual active link handover, where the slot aggregation configuration includes a number of repetitions of the first message in a set of slots and the notification message includes an indication of one or both of which repetitions were missed and how many repetitions were missed.

[0040] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the second transmission opportunity may correspond to a monitoring opportunity for a control channel message or a downlink grant for a data channel message.

[0041] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the notification message further indicates one or both of a search space schedule for the first base station and a periodic data transmission schedule for the first base station.

[0042] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, transmitting the notification message may include acts, features, means, or instructions for transmitting a scheduled uplink message to the second base station, where the scheduled uplink message includes the notification message.

[0043] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, transmitting the notification message may include operations, features, means, or instructions for transmitting the notification message within grant-free uplink resources.

[0044] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the notification message indicates a type of channel associated with the second transmission opportunity, a search configuration for the second transmission opportunity, a timing opportunity for the second transmission opportunity, or a combination thereof.

[0045] 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 first transmission opportunity and a first communications beam for communicating with a first base station in a first bandwidth, where the UE may be configured to communicate using a single communications beam at a time, and determining that the identified time may be less than a threshold time for switching from the first communications beam for communicating with the first base station in the first bandwidth to a second communications beam for communicating with a second base station in the second bandwidth, where selecting to communicate on the first transmission opportunity instead of monitoring the second transmission opportunity may be further based on determining.

[0046] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first transmission opportunity and the second transmission opportunity at least partially overlap in time.

[0047] A method for wireless communication in a first base station is described that may include identifying that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, receiving a notification message from the UE indicating that the UE did not monitor a first transmission opportunity based on the performing of the dual active link handover, and determining whether to retransmit a message to one or both of the UE and the second base station based on the notification message.

[0048] An apparatus for wireless communication in a first base station is described. The apparatus may include a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to: identify that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover; receive a notification message from the UE indicating that the UE did not monitor a first transmission opportunity based on the performance of the dual active link handover; and determine whether to retransmit a message to one or both of the UE and the second base station based on the notification message.

[0049] Another apparatus for wireless communication at a first base station is described that may include means for identifying that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, means for receiving a notification message from the UE indicating that the UE did not monitor a first transmission opportunity based on the performing of the dual active link handover, and means for determining whether to retransmit a message to one or both of the UE and the second base station based on the notification message.

[0050] A non-transitory computer-readable medium storing code for wireless communication at a first base station is described, which may include instructions executable by a processor to identify that a UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, receive a notification message from the UE indicating that the UE did not monitor a first transmission opportunity based on the performing of the dual active link handover, and determine whether to retransmit a message to one or both of the UE and the second base station based on the notification message.

[0051] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for transmitting a message to the UE at a first transmission opportunity and, based on the determining, retransmitting the message to the UE at a second transmission opportunity.

[0052] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for transmitting a configuration to the UE related to the UE performing a dual active link handover based on the notification message, where retransmitting the message at the second transmission opportunity may be based on the configuration.

[0053] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the configuration includes one or both of: a retransmission timer for retransmission of a message missed during the first transmission opportunity when the UE may be performing a dual active link handover indicating a time relationship between the first transmission opportunity and the second transmission opportunity; and a slot aggregation configuration including one or both of a number of repetitions of a message within the set of slots and a periodicity for the repetition of the message within the set of slots.

[0054] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the notification message further indicates one or both of a search space schedule for the second base station and a periodic data transmission schedule for the second base station, and the second transmission opportunity may be based on one or both of the search space schedule and the periodic data transmission schedule for the second base station.

[0055] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for transmitting a slot aggregation configuration to the UE related to the UE performing a dual active link handover, the slot aggregation configuration including a number of repetitions of a message in a set of slots, and the notification message including an indication of one or both of which repetitions were missed and how many repetitions were missed by the UE.

[0056] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for transmitting a message to the UE at the first transmission opportunity and forwarding the message to a second base station based on the notification message.

[0057] Some examples of the methods, apparatus, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for identifying that the first transmission opportunity is unused.

[0058] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first transmission opportunity may correspond to a monitoring opportunity for a control channel message or a downlink grant for a data channel message.

[0059] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, receiving a notification message may include operations, features, means, or instructions for receiving a scheduled uplink message from the UE, where the scheduled uplink message includes the notification message.

[0060] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, receiving the notification message may include operations, features, means, or instructions for receiving the notification message within grant-free uplink resources.

[0061] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the notification message indicates a type of channel associated with the first transmission opportunity, a search configuration for the first transmission opportunity, a timing opportunity for the first transmission opportunity, or a combination thereof.

[0062] In some examples of the methods, apparatus, and non-transitory computer-readable media described herein, the first base station includes a source base station of a dual active link handover or a target base station of a dual active link handover. [Brief description of the drawings]

[0063] [Figure 1] FIG. 1 illustrates an example of a wireless communication system that supports error handling in dual active link handover in accordance with an aspect of the present disclosure. [Diagram 2] FIG. 1 illustrates an example of a wireless communication system that supports error handling in dual active link handover in accordance with an aspect of the present disclosure. [Diagram 3] FIG. 1 illustrates an example of a process flow for supporting error handling in dual active link handover, according to an aspect of the disclosure. [Figure 4]FIG. 1 illustrates an example of a process flow for supporting error handling in dual active link handover, according to an aspect of the disclosure. [Diagram 5] FIG. 1 is a diagram of a device supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 6] FIG. 1 is a diagram of a device supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 7] FIG. 1 is a diagram of a communications manager supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 8] FIG. 1 is a diagram of a system including a device that supports error handling in dual active link handover, according to an aspect of the disclosure. [Figure 9] FIG. 1 is a diagram of a device supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 10] FIG. 1 is a diagram of a device supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 11] FIG. 1 is a diagram of a communications manager supporting error handling in dual active link handover according to an aspect of the disclosure. [Figure 12] FIG. 1 is a diagram of a system including a device that supports error handling in dual active link handover, according to an aspect of the disclosure. [Figure 13] 1 is a flowchart illustrating a method for supporting error handling in a dual active link handover according to an aspect of the disclosure. [Figure 14] 1 is a flowchart illustrating a method for supporting error handling in a dual active link handover according to an aspect of the disclosure. [Figure 15] 1 is a flowchart illustrating a method for supporting error handling in a dual active link handover according to an aspect of the disclosure. [Figure 16] 1 is a flowchart illustrating a method for supporting error handling in a dual active link handover according to an aspect of the disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] In some wireless communication systems, a base station may handoff one or more UEs using a dual active link handover procedure (e.g., for reduced interruption time). In some cases, a dual active link handover may be referred to as an MBB handover or a dual active protocol stack handover. A UE performing a dual active link handover may communicate with multiple base stations when transitioning between cells. For example, during a dual active link handover process, the UE may maintain an established connection with a source base station supporting a source cell while establishing a new connection with a target base station supporting a target cell. The source and target base stations may not coordinate scheduling, potentially causing the UE to compete for transmission opportunities. For example, the UE may form a receive beam in one direction at a time (e.g., based on UE capabilities or configuration). Thus, the UE may not be able to simultaneously receive transmissions from both the source and target base stations. If the source and target base stations schedule the UE reception with resources too close to each other (e.g., in overlapping time resources or in non-overlapping time resources that do not allow the UE enough time to switch between communication configurations for different base stations), the UE may choose to communicate with one of these base stations and drop communication with the other base station. These communications may include downlink transmissions, uplink transmissions, or a combination thereof.

[0065] If the UE drops a transmission opportunity for a base station (e.g., refrains from monitoring a monitoring opportunity or refrains from receiving a scheduled packet), the UE may introduce packet loss, latency, or both into the system. To reduce packet loss and latency, the UE, the base station, or both may implement one or more techniques for handling dual active link handover operations. In some cases, to reduce packet loss, the base station (e.g., the source base station, the target base station, or both) may configure retransmission or slot aggregation to provide the UE with additional opportunities to receive the packet. For example, the base station may implement a shortened retransmission timer for the packet during a dual active link handover. Additionally or alternatively, the base station may implement slot aggregation such that the base station transmits multiple repetitions of a packet to the UE (e.g., without waiting for a response from the UE). If the UE drops a transmission opportunity, the UE may perform slot aggregation on non-dropped transmission opportunities (e.g., for other repetitions) to successfully receive the packet.

[0066] In some cases, the UE may send a notification message to the base station indicating any dropped monitoring opportunities or packets. For example, the UE may indicate a transmission opportunity that the UE did not monitor (e.g., in the notification message or as part of another uplink message), and the base station may determine whether a packet was missed at this transmission opportunity. If so, the base station may retransmit the packet to the UE based on the notification message (e.g., directly or via another connected base station). This notification message may reduce the latency associated with the UE receiving the dropped packet. In some examples, the base station may implement slot aggregation, low latency retransmission, or both in addition to UE-assisted recovery using notification messaging.

[0067] Aspects of the present disclosure are first described in the context of a wireless communication system. Aspects of the present disclosure are further illustrated by and described with reference to process flows, diagrams and flowcharts relating to message processing in dual active link handover.

[0068] 1 illustrates an example of a wireless communication manager 100 supporting error handling in dual active link handover according to aspects of the disclosure. The wireless communication system 100 may include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be an LTE network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or an NR network. In some examples, the wireless communication system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission-critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

[0069] The base stations 105 may be distributed throughout a geographic area and may be devices in different forms or with different capabilities to form a wireless communication system 100. The base stations 105 and the UEs 115 may communicate wirelessly via one or more communication links 125. Each base station 105 may provide a coverage area 110 over which the UEs 115 and the base stations 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area over which the base stations 105 and the UEs 115 may support communication of signals according to one or more radio access technologies.

[0070] The UEs 115 may be distributed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be fixed, or mobile, or both at different times. The UEs 115 may be devices in different forms or with different capabilities. Some example UEs 115 are shown in FIG. 1. The UEs 115 described herein may be capable of communicating with various types of devices, such as other UEs 115, base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment) as shown in FIG. 1.

[0071] The base stations 105 may communicate with the core network 130, with each other, or both. For example, the base stations 105 may interface with the core network 130 through one or more backhaul links 120 (e.g., via an S1, N2, N3, or other interface). The base stations 105 may communicate with each other over the backhaul links 120 (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), or both. In some examples, the backhaul links 120 may be or include one or more wireless links.

[0072] One or more of the base stations 105 described herein may include or be referred to as a base transceiver station, radio base station, access point, radio transceiver, Node B, eNode B (eNB), Next Generation Node B or Giga Node B (any of which may be referred to as a gNB), Home Node B, Home eNode B, or other suitable terminology by those skilled in the art.

[0073] The UE 115 may include or be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where a "device" may also be referred to as a unit, a station, a terminal, or a client, among others. The UE 115 may also include or be referred to as a personal electronic device, such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, the UE 115 may include or be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, among others, which may be implemented in various articles, such as an appliance, a vehicle, a meter, and the like.

[0074] The UEs 115 described herein may be capable of communicating with various types of devices, such as other UEs 115, which may act as relays, as shown in FIG. 1, as well as base stations 105, and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, among others.

[0075] The UE 115 and the base station 105 may wirelessly communicate with each other over one or more communication links 125 on one or more carriers. The term “carrier” may refer to a set of radio frequency spectrum resources having a defined physical layer structure for supporting the communication link 125. For example, a carrier used for the communication link 125 may include a portion (e.g., a bandwidth part (BWP)) of a radio frequency spectrum band operated according to one or more physical layer channels for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer channel may carry collection signaling (e.g., synchronization signals, system information), control signaling coordinating operation for the carrier, user data, or other signaling. The wireless communication system 100 may support communication with the UE 115 using carrier aggregation or multi-carrier operation. The UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both frequency division duplex (FDD) and time division duplex (TDD) component carriers.

[0076] In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition or control signaling to coordinate operation with respect to other carriers. A carrier may be associated with a frequency channel (e.g., evolved universal mobile telecommunication 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 operated in a standalone mode where initial acquisition and connection may be made by the UE 115 via the carrier, or the carrier may be operated in a non-standalone mode where a connection is anchored using a different carrier (e.g., of the same or different radio access technology).

[0077] The communication links 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. A carrier may carry downlink or uplink communications (e.g., in an FDD mode) or may be configured to carry downlink and uplink communications (e.g., in a TDD mode).

[0078] A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples, the carrier bandwidth may be referred to as the carrier or the “system bandwidth” of the wireless communication system 100. For example, the carrier bandwidth may be one of several determined bandwidths for a particular radio access technology carrier (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 Megahertz (MHz)). The devices of the wireless communication system 100 (e.g., the base station 105, the UE 115, or both) may have a hardware configuration that supports communication on a particular carrier bandwidth or may be configurable to support communication on one of a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a base station 105 or a UE 115 that supports simultaneous communication via a carrier associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured to operate on a portion (e.g., a sub-band, BWP), or all, of the carrier bandwidth.

[0079] A signal waveform transmitted on 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)). In a system utilizing MCM techniques, a resource element may include one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely proportional. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the coding rate of the modulation scheme, or both). Thus, the more resource elements the UE 115 receives and the higher the order of the modulation scheme, the higher the data rate of the UE 115 may be. Wireless communication resources may refer to a combination of radio frequency spectrum resources, time resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial layers may further increase the data rate or data integrity for communication with the UE 115.

[0080] One or more numerologies for a carrier may be supported, where the numerology may include a subcarrier spacing (Δf) and a cyclic prefix. A carrier may be divided into one or more BWPs having the same or different numerologies. In some examples, a UE 115 may be configured with multiple BWPs. In some examples, a single BWP for a carrier may be active at a given time, and communication for the UE 115 may be limited to one or more active BWPs.

[0081] The time interval for the base station 105 or the UE 115 may be, for example, T s =1 / (Δf max N f ) seconds, where Δf max may represent the maximum supported subcarrier spacing, and N f may represent the maximum supported discrete Fourier transform (DFT) size. The communication resource time intervals may be organized according to radio frames, each having a specified duration (e.g., 10 milliseconds (ms)). Each radio frame may be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0082] Each frame may include multiple consecutively numbered subframes or slots, and each subframe or slot may have the same duration. In some examples, a frame may be divided (e.g., in the time domain) into subframes, and each subframe may be further divided into several slots. Alternatively, each frame may include a variable number of slots, and the number of slots may depend on the subcarrier spacing. Each slot may include several symbol periods (e.g., depending on the length of a cyclic prefix prepended to each symbol period). In some wireless communications systems 100, a slot may be further divided into multiple minislots containing one or more symbols. Excluding the cyclic prefix, each symbol period may include one or more (e.g., N f The duration of a symbol period may depend on the subcarrier spacing or the frequency band of operation.

[0083] A subframe, slot, minislot, or symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and may be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) may be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 may be dynamically selected (e.g., in a burst of shortened TTIs (sTTIs)).

[0084] The physical channels may be multiplexed on the carriers according to various techniques. The physical control channels and the physical data channels may be multiplexed on the downlink carriers, for example, using one or more of a time division multiplexing (TDM), a frequency division multiplexing (FDM), or a hybrid TDM-FDM technique. A control region (e.g., a control resource set (CORESET)) for the physical control channel may be defined by a number of symbol periods and may span the system bandwidth of the carrier, or a subset of the system bandwidth. One or more control regions (e.g., CORESET) may be configured for a set of UEs 115. For example, one or more of the UEs 115 may monitor or search the control region for control information according to one or more search space sets, and each search space set may include one or more control channel candidates at one or more aggregation levels arranged in a cascade. The aggregation level for the control channel candidates may refer to the number of control channel resources (e.g., control channel elements (CCEs)) associated with the coded information for a control information format having a given payload size. The search space sets may include a common search space set configured for sending control information to multiple UEs 115 and a UE-specific search space set for sending control information to a particular UE 115.

[0085] Each base station 105 may provide communication coverage via one or more cells, e.g., macro cells, small cells, hot spots, or other types of cells, or various combinations thereof. The term "cell" may refer to a logical communication entity used for communication with the base station 105 (e.g., over a carrier) and may be associated with an identifier (e.g., a physical cell identifier (PCID) or a virtual cell identifier (VCID), etc.) to distinguish neighboring cells. In some examples, a cell may also refer to a geographic coverage area 110, or a portion (e.g., a sector) of the geographic coverage area 110 (e.g., a sector) on which the logical communication entity operates. Such a cell may range from a smaller area (e.g., a structure, a subset of a structure) to a larger area depending on various factors, such as the capabilities of the base station 105. For example, a cell may be or include, among others, a building, a subset of a building, or an exterior between or overlapping with the geographic coverage area 110.

[0086] A macro cell generally covers a relatively large geographic area (e.g., a radius of several kilometers) and may allow unrestricted access by UEs 115 with a service subscription with a network provider that supports the macro cell. A small cell may be associated with a lower power base station 105 compared to a macro cell, and the small cell may operate in the same or different (e.g., licensed, unlicensed) frequency band as the macro cell. A small cell may provide unrestricted access to UEs 115 with a service subscription with a network provider or provide unrestricted access to UEs 115 that have an association with the small cell (e.g., UEs 115 in a closed subscriber group (CSG), UEs 115 associated with a user in a home or office). A base station 105 may support one or more cells and may also support communication via one or more cells using one or more component carriers.

[0087] In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) that may provide access to different types of devices.

[0088] In some examples, the base stations 105 may be mobile and thus provide communication coverage to moving geographic coverage areas 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, but the different geographic coverage areas 110 may be supported by the same base station 105. In other examples, overlapping geographic coverage areas 110 associated with different technologies may be supported by different base stations 105. The wireless communication system 100 may include a heterogeneous network, for example, where different types of base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

[0089] The wireless communication system 100 may be configured to support ultra-reliable communications, or low latency communications, or various combinations thereof. For example, the wireless communication system 100 may be configured to support ultra-reliable low latency communications (URLLC) or mission-critical communications. The UE 115 may be designed to support ultra-reliable, low latency, or critical functions (e.g., mission-critical functionality). Ultra-reliable communications may include private or group communications and may be supported by one or more mission-critical services, such as mission-critical push-to-talk (MCPTT), mission-critical video (MCVideo), or mission-critical data (MCData). Support for mission-critical functions may include service prioritization, and the mission-critical services may be used for public safety or general commercial applications. The terms ultra-reliable, low latency, mission-critical, and ultra-reliable low latency may be used interchangeably herein.

[0090] In some examples, the UE 115 may also be able to communicate directly with other UEs 115 over a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more 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 otherwise be able to receive transmissions from the base station 105. In some examples, 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 examples, 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.

[0091] 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) or a 5G core (5GC), which may include at least one control plane entity (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) that manages access and mobility, and at least one user plane entity (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), a user plane function (UPF)) that routes packets or interconnects with external networks. The control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the core network 130. User IP packets may be forwarded through a user plane entity, which may provide IP address allocation as well as other functions. The user plane entity may be connected to network operator IP services 150. Operator IP services 150 may include access to the Internet, an intranet, an IP Multimedia Subsystem (IMS), or packet-switched streaming services.

[0092] Some of the network devices, such as the base station 105, may include subcomponents, such as an access network entity 140, which may be an example of an access node controller (ANC). Each access network entity 140 may communicate with the UE 115 through one or more other access network transmitting entities 145, which may be referred to as a radio head, a smart radio head, or a transmit / receive point (TRP). Each access network transmitting entity 145 may include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 may be distributed across various network devices (e.g., radio heads and ANCs) or integrated within a single network device (e.g., the base station 105).

[0093] The wireless communication system 100 may operate using one or more frequency bands, typically ranging from 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the 300 MHz to 3 GHz region is known as the ultra-high frequency (UHF) region or decimeter band because the wavelengths span lengths of approximately 1 decimeter to 1 meter. Although UHF waves may be blocked or redirected by buildings and environmental features, these 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 kilometers) compared to transmissions using lower frequencies and longer waves in the shortwave (HF: high frequency) or very high frequency (VHF: very high frequency) portions of the spectrum below 300 MHz.

[0094] The wireless communication system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communication system 100 may employ Licensed Assisted Access (LAA), LTE Unlicensed (LTE U) radio access technology, or NR technology in an unlicensed band, such as the 5 GHz Industrial, Scientific, and Medical (ISM) band. When operating in an unlicensed radio frequency spectrum band, devices such as the base station 105 and the UE 115 may employ carrier sensing for collision detection and avoidance. In some examples, operation in an unlicensed band may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operation in an unlicensed spectrum may include downlink transmissions, uplink transmissions, P2P transmissions, or D2D transmissions, among others.

[0095] The base station 105 or 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. The antennas of the base station 105 or UE 115 may be located in one or more antenna arrays or antenna panels that may support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be collocated in an antenna assembly, such as an antenna tower. In some examples, the antennas or antenna arrays associated with the base station 105 may be located in diverse 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 can support various MIMO or beamforming operations. Additionally or alternatively, the antenna panels may support radio frequency beamforming for signals transmitted through the antenna ports.

[0096] Beamforming, sometimes referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used in a transmitting or receiving device (e.g., base station 105, UE 115) to shape or steer an antenna beam (e.g., transmit beam, 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 some signals propagating at a particular orientation relative to the antenna array are subject to constructive interference and other signals are subject to destructive interference. Adjustment of signals communicated through antenna elements may include the transmitting or receiving device applying an amplitude offset, a phase offset, or both to signals conveyed through an antenna element associated with the device. The adjustment 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 transmitting or receiving device's antenna array or to some other orientation).

[0097] The base station 105 or the UE 115 may use beam sweeping techniques as part of a beamforming operation. For example, the base station 105 may use multiple antennas or antenna arrays (e.g., antenna panels) to perform a beamforming operation for directional communication with the UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted multiple times in different directions by the base station 105. For example, the base station 105 may transmit signals according to different beamforming weight sets associated with different transmission directions. The transmissions in different beam directions may be used (e.g., by a transmitting device such as the base station 105 or by a receiving device such as the UE 115) to identify beam directions for subsequent transmission or reception by the base station 105.

[0098] Some signals, such as data signals associated with a particular receiving device, may be transmitted by the base station 105 in a single beam direction (e.g., a direction associated with a receiving device, such as the UE 115). In some examples, a beam direction associated with a transmission along a single beam direction may be determined based on signals transmitted in one or more beam directions. For example, the UE 115 may receive one or more of the signals transmitted in different directions by the base station 105 and may report to the base station 105 an indication of the signal received by the UE 115 that has the highest signal quality or a otherwise acceptable signal quality.

[0099] In some examples, transmission by a device (e.g., by the base station 105 or the UE 115) may be performed using multiple beam directions, and the device may use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from the base station 105 to the UE 115). The UE 115 may report feedback indicating precoding weights for one or more beam directions, where the feedback may correspond to the number of beams configured across the system bandwidth or one or more subbands. The base station 105 may transmit a reference signal (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)) that may be precoded or amplicoded. The UE 115 may provide feedback for beam selection, where the feedback may be a precoding matrix indicator (PMI) or a codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted by the base station 105 in one or more directions, the UE 115 may employ similar techniques for transmitting a signal multiple times in different directions (e.g., to identify a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., to transmit data to a receiving device).

[0100] A receiving device (e.g., UE 115) may attempt multiple receiving configurations (e.g., directional listening) when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may attempt multiple receiving directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at multiple antenna elements of an antenna array, any of which may be referred to as "listening" according to different receiving configurations or receiving directions. In some examples, a receiving device may use a single receiving configuration to receive along a single beam direction (e.g., when receiving a data signal). A single receiving configuration may be aligned to a beam direction determined based on listening through different receiving configuration directions (e.g., a beam direction determined to have the greatest signal strength, greatest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening through multiple beam directions).

[0101] In some examples, the base station 105 may use a transmission configuration indicator (TCI) state (e.g., corresponding to a beamformed transmission) to transmit a data transmission (e.g., a Physical Downlink Shared Channel (PDSCH) transmission), a control transmission (a Physical Downlink Control Channel (PDCCH) transmission), etc. to the UE 115. The UE 115 may use information about the TCI state to configure a receiver of the UE 115 to receive the beamformed transmission.

[0102] The UE 115 may communicate with multiple base stations 105 when transitioning between cells supported by different base stations 105. For example, during a dual active link handover process, the UE 115 may communicate with both the target base station 105 supporting the target cell and the source base station 105 supporting the source cell (e.g., simultaneously operating using a first active communication link to the source base station 105 and a second active communication link to the target base station 105 such that the UE 115 operates with dual active communication links). In some cases, transmissions from the source base station and the target base station to the UE 115 may overlap in time (e.g., simultaneous transmissions). In some examples, the UE 115 may perform TDM techniques on a physical control channel, a physical data channel, or a combination thereof to communicate with the source base station and the target base station. The source base station and the target base station may schedule transmission and search space independently of each other (e.g., without physical layer coordination), which may result in transmissions that overlap in time or are close in time. The UE 115 may form a receive beam in one direction at a time (e.g., based on UE capabilities or UE configuration). In some cases, the UE 115 may select a receive beam to utilize based on a default beam selection procedure. The UE 115 may determine a default beam to use based on various prioritization criteria (e.g., target base station priority vs. source base station priority, control channel priority vs. data channel priority, quality of service (QoS) thresholds for traffic carried on the channel, etc.). Choosing a default beam may cause the UE 115 to drop transmissions from the source base station or the target base station 105 depending on which beam was not selected. For example, when the UE 115 selects a default beam for communicating with the target base station 105, the UE 115 may drop monitoring opportunities or packet reception opportunities for the source base station 105 if the UE 115 does not have enough time to switch beams, cells, bandwidths, or some combination thereof.

[0103] In some examples, transmissions from the target base station and the source base station 105 may not overlap in time. However, the UE 115 may not be able to switch from receiving data packets from one base station 105 to receiving additional data packets from another base station 105 in time to receive the additional data packets (e.g., based on a process involving configuration of a communication beam, bandwidth, cell, radio frequency (RF) configuration, etc.). The UE 115 may drop monitoring for and receiving packets during a dual active link handover process based on overlapping or adjacent transmission opportunities to different base stations 105. For example, if the UE 115 is communicating with a first base station 105 in a first cell, on a first frequency, on a first bandwidth, using a first communication beam, according to a first RF configuration, etc., the UE 115 may drop a transmission opportunity associated with a second base station 105 based on not having enough time to switch to a second cell, a second frequency, a second bandwidth, a second communication beam, a second RF configuration, or some combination thereof.

[0104] To reduce packet loss or packet error rate at the UE 115, the base station 105 may implement one or more techniques for handling dropping of communication in a dual active link handover process. The base station 105 (e.g., the source base station or the target base station 105) may instruct the UE 115 to trigger a dual active link handover process or may detect that the UE 115 is performing a dual active link handover process. Thus, the base station 105 may identify when the UE 115 starts and ends the dual active link handover process (i.e., when the UE 115 may be connected to multiple base stations 105). The target base station and the source base station 105 may not coordinate on the scheduling and timing of communication with the UE 115. The dual active link handover process may be triggered when the UE 115 is moving into the coverage area 110 of another cell (e.g., a cell supported by the target base station 105), when the channel quality between the UE 115 and the source base station 105 falls below a threshold, etc.

[0105] In some examples, the base station 105 may configure the UE 115 so that the UE 115 can effectively handle packet dropping when the UE 115 is in a dual active link handover process and is connected to both base stations 105. In a first example, the base station 105 may indicate a timeline for retransmission (e.g., by defining a retransmission timer for packets during a dual active link handover operation). In a second example, the base station 105 may indicate a slot aggregation configuration for the UE 115.

[0106] In some examples, the source base station 105 may send a configuration message (e.g., a handover command, a handover message, or any other configuration message indicating a dual active link handover operation) to the UE 115. The configuration message may indicate to the UE 115 that the source base station 105, the target base station 105, or both are implementing slot aggregation during dual active link handover. If the UE 115 identifies a configuration for slot aggregation from the source base station 105, the UE 115 may prioritize transmissions from the target base station 105 (e.g., because the slot aggregation configuration at the source base station 105 may provide additional redundancy to transmissions from the source base station 105). In some examples, the base station 105 may configure a configuration message with a configuration for slot aggregation and retransmissions, and the UE 115 may select a configuration. The UE 115 may transmit an indication of the selected configuration back to the base station 105.

[0107] In some cases, the base station 105 may maintain a timer to determine when to retransmit a packet. The base station 105 may activate a retransmission timer following a packet transmission (e.g., following activation and expiration of a round-trip time (RTT) timer). After the base station 105 transmits a packet (e.g., a control channel message, a data message, etc.), if the base station 105 does not receive a response from the UE 115 within a threshold amount of time, the retransmission timer may expire and the base station 105 may retransmit the packet (e.g., at the next available transmission opportunity). The base station 105 may implement a retransmission timer during a dual active link handover operation that is different from a default retransmission timer (e.g., a retransmission timer used when the UE 115 is not performing a dual active link handover process). The retransmission timer for packet retransmission during a dual active link handover may have a shorter timer length than the default retransmission timer (e.g., to account for a higher probability of a missed packet at the UE 115).

[0108] Additionally or alternatively, the base station 105 may transmit packets using slot aggregation. During the dual active link handover process, the base station 105 may reduce search space periodicity, enable slot aggregation, or both. This may ensure that the UE 115 has multiple opportunities to receive transmissions (e.g., PDCCH messages, PDSCH messages, etc.) from the source base station 105, the target base station 105, or both. The base station 105 may indicate to the UE 115 that the slot aggregation configuration includes a certain number, N, of data transmissions to be sent in consecutive slots or a specific number of slots. Because the UE 115 may identify the amount and location of data in the indicated number of slots, the UE 115 may aggregate data within the slots for better performance. If the UE 115 drops a transmission opportunity during the dual active link handover, the UE 115 may aggregate received packets into non-dropped transmission opportunities of the slot aggregation configuration. The implementation of slot aggregation may improve the probability that the UE 115 may receive simultaneous or nearby transmissions from the source and target base stations 105 .

[0109] In some examples, the UE 115 may inform the source or target base station 105 of any transmissions that the UE 115 did not detect or receive from the source or target base station 105. For example, based on a configuration (e.g., a search space configuration, a CORESET configuration, etc.), the UE 115 may monitor certain resources of a control channel for PDCCH candidates (e.g., monitoring opportunities). In some cases, the monitoring may follow a periodicity of the PDCCH candidates. The base station 105 may or may not transmit a downlink control information (DCI) message at each control channel monitoring opportunity. However, in some cases, the UE 115 operating in a dual active link handover may refrain from monitoring one or more monitoring opportunities (e.g., based on competing transmission opportunities to different base stations 105). If the UE 115 did not monitor a monitoring opportunity for a transmission, the UE 115 may inform the corresponding base station 105. In some examples, not monitoring a transmission may be referred to as "dropping" a transmission or packet. Additionally or alternatively, if the UE 115 receives a downlink grant with a slot indication from the base station 105, the UE 115 may monitor the indicated slot for downlink data. If the UE 115 drops monitoring of the indicated slot (e.g., based on a competing transmission opportunity to another base station 105), the UE 115 may send a notification message to the base station 105 indicating that the UE 115 did not monitor the slot (or failed to receive the downlink data). The notification message may be an example of or similar to a negative acknowledgement (NACK) message. The notification message may include the type of channel (e.g., PDCCH, PDSCH, etc.), a search configuration, timing information (e.g., the number of slots for the scheduled PDSCH), frequency information, or some combination of these, or other identifying information for the dropped opportunity.

[0110] In some cases, the UE 115 may identify the schedule of a prioritized cell with which the UE 115 is communicating. For example, the UE 115 may be connected to a target base station 105 (which may be prioritized, for example) and may receive scheduling information for the target cell. The UE 115 may send this information to the source base station 105 (e.g., in a notification message) so that the source base station 105 may adjust scheduling based on the target cell.

[0111] In some examples, the UE 115 may inform the target base station or the source base station 105 that the UE 115 did not monitor during a transmission opportunity. This information may trigger the base station 105 to implement slot aggregation for the packet or packet retransmission (e.g., if the control channel is dropped). In some cases, the UE 115 may implement UE-assisted recovery in conjunction with base station triggering techniques. For example, if the base station 105 implements slot aggregation, the UE 115 may inform the base station 105 which slots the UE 115 did not monitor or receive. For example, if the UE 115 receives three out of four slots in a slot aggregation configuration, the base station 105 may not have to retransmit (as this may include enough information for the UE 115 to aggregate the information and make a successful decision). However, if the UE 115 informs the base station 105 that the UE 115 received one slot out of four slots, the base station 105 may retransmit the packet.

[0112] In some examples, the UE 115 may send notification information about the dropped transmission opportunity to the base station 105 by piggybacking the notification on a subsequent scheduled uplink message (e.g., a physical uplink shared channel (PUSCH) transmission, a physical uplink control channel (PUCCH) transmission, or both) to the source or target base station 105. In some other examples, the source or target base station 105 may configure the UE 115 with a dedicated grant-free PUSCH resource during the dual active link handover process. The target or source base station 105 may indicate to the UE 115 that the UE 115 may use this grant-free PUSCH to transmit a notification message indicating whether any packets were dropped.

[0113] 2 illustrates an example of a wireless communication manager 200 supporting error handling in dual active link handover according to aspects of the disclosure. In some examples, the wireless communication system 200 may implement aspects of the wireless communication system 100. For example, the wireless communication system 200 may include base stations 105-a and 105-b and a UE 115-a, which may be examples of corresponding devices described with reference to FIG. 1. The UE 115-a may communicate with the base stations 105-a and 105-b in a beamforming communication system.

[0114] In the wireless communication system 200, the base station 105-a, the base station 105-b, and the UE 115-a may operate using a dual active link handover technique. The source base station 105-a (e.g., a source base station for the UE 115-a) may communicate with the UE 115-a within the coverage area 110-a via a communication channel 205. The coverage area 110-a may correspond to a first cell (e.g., a source cell) for the UE 115-a. The UE 115-a may receive downlink messages (e.g., PDCCH / PDSCH information) from the base station 105-a on a receive beam 215 (e.g., an active communication beam in the UE 115-a). A target base station 105-b (e.g., a target base station for the UE 115-a during dual active link handover) may communicate with the UE 115-a within a coverage area 110-b in which the target base station 105-b serves a second cell (e.g., a target cell) for the UE 115-a over a communication channel 210. The UE 115-a may receive a PDCCH / PDSCH from the base station 105-b over a receive beam 220.

[0115] The wireless device may select a default beam for communication based on a set of rules. The beam used for communication (e.g., of PDCCH / PDSCH information) may be derived from measurements generated from a synchronization signal block (SSB), a CSI-RS, or both. In the case of a control transmission, the TCI state of a medium access control (MAC) indication for a CORESET associated with the PDCCH may indicate the associated spatial filter (i.e., beam) to be used for the PDCCH transmission. The first CORESET (e.g., CORESET0) may use the identified beam during the initial access procedure.

[0116] For data transmission, the PDSCH TCI state may follow CORESET0 if no other CORESET is configured, except for CORESET0. In some examples, the PDCCH for scheduling may carry a non-fallback DCI. The associated TCI state for the PDSCH may be indicated by a three-bit indicator. In some cases, when the K0 value for the PDSCH transmission (e.g., a value indicating the timing for the granted data transmission for a DCI message granting data transmission resources) is above a threshold, the PDSCH default beam may be based on the indicated TCI state. In other cases, when the K0 value is equal to or less than the threshold, the PDSCH default beam follows the TCI state of the scheduling PDCCH.

[0117] In some cases, the PDSCH TCI state may not be indicated in the scheduling PDCCH (e.g., if no non-fallback DCI is present). In some cases, when the K0 value for the PDSCH transmission is above a threshold, the PDSCH default beam may be based on the TCI state of the CORESET as monitored in the most recently scheduled search space with the lowest index. In other cases, when the K0 value is equal to or less than the threshold, the PDSCH default beam follows the TCI state of the scheduling PDCCH.

[0118] The UE 115-a may select a default beam for communication using similar rules when operating in a dual active link handover. In some cases, based on the prioritization rules, the UE 115-a may select a default beam corresponding to either the base station 105-a or the base station 105-b. The base station 105-a may transmit a first data packet to the UE 115-a at the same time (or in close proximity) that the base station 105-b transmits a second data packet to the UE 115-a. The UE 115-a may not be able to simultaneously form the receive beam 215 and the receive beam 220 to receive simultaneous or close transmissions. The UE 115-a may form the receive beam 215 (e.g., a default beam for reception from the base station 105-a based on the prioritization rules), which may cause the transmission from the target base station 105-b to be dropped. A transmission may also be dropped if the UE 115-a does not have enough time to switch between receive beams 215 and 220 to receive transmissions from the source base station 105-a and the target base station 105-b. For example, switching between these beams may involve switching beams, bandwidths, cells, etc.

[0119] The source base station 105-a or the target base station 105-b may configure the UE 115-a to handle dropping of data packets when the UE 115-a is in a dual active link handover process. In some examples, the target base station 105-b may include instructions for retransmission or configuration for slot aggregation to handle dropped transmissions in a dual active link handover message (or another downlink message). The UE 115-a may send instructions to the target base station 105-b to retransmit or may send configuration for slot aggregation to handle dropped transmissions according to a particular retransmission schedule or timer. In some other examples, the source base station 105-a may include configuration for the UE 115-a in a dual active link handover command, or the source base station 105-a, the target base station 105-b, or both may include configuration for the UE 115-a in a configuration message (e.g., prior to or during a dual active link handover).

[0120] In some cases, the target base station 105-b may maintain one or more retransmission timers. If the target base station 105-b transmits a packet to the UE 115-a and does not receive a response from the UE 115-a before the retransmission timer expires (or the base station 105-b receives a NACK while the timer is running from the UE 115-a), the target base station 105-b may retransmit the packet. In some other cases, the target base station 105-b may transmit data using slot aggregation. During a dual active link handover process, the target base station 105-b may reduce the search space periodicity, enable slot aggregation, or both, to ensure that the UE 115-a has additional opportunities to receive dropped packets. The target base station 105-b may indicate a slot aggregation configuration to the UE 115-a. The slot aggregation configuration may indicate the number of repetitions, N, a particular number of slots, a slot periodicity, or a combination thereof, to be sent in consecutive slots. The UE 115-a may receive the transmitted information (e.g., data) within the indicated slots and may aggregate the information for better decoding performance. During overlapping or non-overlapping, competing transmissions from the source base station 105-a and the target base station 105-b, the UE 115-a may be able to receive the transmissions by aggregating data from non-dropped opportunities in a slot aggregation configuration. The implementation of slot aggregation may improve the probability that the UE 115-a may receive simultaneous or closely spaced transmissions from the source base station 105-a and the target base station 105-b.

[0121] In some examples, the UE 115-a may notify the target base station 105-b that the UE 115-a dropped a transmission. For example, the UE 115-a may monitor a control channel for PDCCH candidates based on a configuration (including, for example, periodicity). In some cases, the UE 115-a may further monitor resources for grant-free PDSCH transmissions (e.g., where K0=0). In addition, if the UE 115-a receives a slot indication from the target base station 105-b for a PDSCH grant (e.g., the UE 115-a successfully decodes a scheduling PDCCH including K0>0 for the corresponding PDSCH grant), the UE 115-a may monitor the indicated slot for downlink data. In some examples, the UE 115-a may "drop" a transmission. For example, the UE 115-a may not monitor a PDCCH message or a PDSCH message based on competing transmission opportunities for a different base station 105. In some such examples, the UE 115-a may transmit a message to the base station 105 (e.g., during a UE assisted recovery procedure) indicating the dropped transmission. The message may include the type of channel (e.g., PDCCH configuration, PDSCH configuration, etc.), timing opportunity (e.g., the slot number in which the PDSCH is located), or other identifying information regarding the dropped transmission so that the base station 105 receiving the message can determine which monitoring opportunity was missed at the UE 115-a. In some examples, the UE 115-a may identify a schedule (e.g., a periodic schedule) for each of the connected base stations 105. The UE 115-a may send scheduling information regarding one base station (e.g., target base station 105-b) to the other base station (e.g., source base station 105-a) so that the source base station 105-a may avoid scheduling the target cell to limit dropping of transmissions. Additionally or alternatively, the wireless device may implement a dual active link handover technique for uplink transmissions (e.g., PUSCH / PUCCH).

[0122] In some examples, the UE 115-a may inform the target base station 105-b or the source base station 105-a that the UE 115-a did not monitor the data or that the UE 115-a dropped the data. This information may trigger the source base station 105-a or the target base station 105-b to implement slot aggregation for the data or retransmission (e.g., if the control channel is dropped). The UE 115-a may send this information by piggybacking this notification on the next scheduled PUSCH or PUCCH transmission to the source base station 105-a or the target base station 105-b. For example, the notification may be included as a header of a scheduled uplink message. In some examples, the source base station 105-a or the target base station 105-b may configure the UE 115-a with periodic, dedicated, grant-free PUSCH resources during dual active link handover. The UE 115-a may send a notification message indicating any dropped monitoring opportunities or packets in the grant-free PUSCH resources.

[0123] In some cases, if a non-prioritized base station 105 receives a notification message indicating that reception of a packet has been dropped at the UE 115-a, the non-prioritized base station 105 may send the packet to a prioritized base station for more reliable transmission. For example, a base station (e.g., a source base station 105-a) may forward a data packet to another base station (e.g., a target base station 105-b) via a backhaul connection for transmission to the UE 115-a. The target base station 105-b may transmit the data packet to the UE 115-a. The UE 115-a may not drop the data packet due to the UE 115-a receiving the data packet from the target base station 105-b (e.g., not from the source base station 105-a).

[0124] FIG. 3 illustrates an example of a process flow 300 supporting error handling in a dual active link handover according to aspects of the disclosure. In some examples, the process flow 300 may implement aspects of the wireless communication system 100 or 200 described with reference to FIG. 1 and FIG. 2. The process flow 300 may include a UE 115-b and base stations 105-c and 105-d, which may be examples of corresponding devices described with reference to FIG. 1 and FIG. 2. The UE 115-b may perform a dual active link handover procedure to transition a connection from a source base station (e.g., base station 105-c) to a target base station (e.g., base station 105-d). During the dual active link handover procedure, based on a lack of coordination (e.g., scheduling coordination at the physical layer) between the base stations 105-c and 105-d, the UE 115-b may not have enough time to switch beams, bandwidths, cells, etc., to communicate with both base stations 105 at the scheduled opportunity. Thus, the UE 115-b, the base station 105-c, the base station 105-d, or a combination thereof may implement techniques to reduce packet loss when the UE 115-b drops a scheduled communication opportunity with one of the base stations 105. The following alternative examples may be implemented, in which some steps are performed in a different order than described or are not performed at all. In some cases, the steps may include additional features not described below or further steps may be added.

[0125] At 305, the base station 105-c and the UE 115-b may establish a first connection link. At 310, the base station 105-c may send a handover command (e.g., a dual active link handover command) to the UE 115-b indicating a handover of the UE 115-b from a source base station (e.g., the base station 105-c) to a target base station (e.g., the base station 105-d). For example, the base station 105-c may determine to handover the UE 115-b based on a link quality between the base station 105-c and the UE 115-b, a distance from the UE 115-b to the base station 105-c, a distance from the UE 115-b to the base station 105-d, a mobility pattern of the UE 115-b, or some combination of these, or other handover triggers. Based on the dual active link handover command, the UE 115-b may establish a second communication link with the base station 105-d at 315. By performing a dual active link handover operation, the UE 115-b may simultaneously maintain a first communication link with the base station 105-c and a second communication link with the second base station 105-d (e.g., for a transition period before the UE 115-b loses connection with the source base station).

[0126] At 320, the UE 115-b may identify a time between a first transmission opportunity associated with a first base station (e.g., also corresponding to the first cell) and a second transmission opportunity associated with a second base station (e.g., also corresponding to the second cell). As described herein, the first base station may be either a target base station or a source base station, and the second base station may be either a source base station or a target base station. Based on the identified time, the UE 115-b may determine that the first transmission opportunity and the second transmission opportunity conflict (e.g., in an overlapping or non-overlapping scenario). For example, the transmission opportunities may fully overlap, partially overlap, or be separated in time by less than a threshold time. This threshold time may correspond to an amount of time for the UE 115-b to switch from a first communication beam for communication with the first base station in the first band to a second communication beam for communication with the second base station in the second bandwidth.

[0127] Based on the competing transmission opportunity, the UE 115-b may select to communicate with the first base station in the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station. In some examples, the UE 115-b may select a default beam for either the source base station or the target base station (e.g., based on a prioritization rule) and use the default beam for communication. As shown, the UE 115-b may prioritize communication with the target base station (e.g., base station 105-d) and receive a first message from the base station 105-d at 325 (e.g., based on selecting to communicate in the first transmission opportunity). However, based on this selection, the UE 115-b may refrain from receiving a second message from the source base station (e.g., base station 105-c. For example, the UE 115-b may drop monitoring opportunities from a search space associated with the base station 105-c or may drop a scheduled downlink grant for the base station 105-c. In some cases, based on dropping the second transmission opportunity at 330, the UE 115-b may miss a packet (e.g., the second message) from the base station 105-c.

[0128] However, the UE 115-b may monitor a third transmission opportunity for a second message from the base station 105-c based on the execution of a dual active link handover. For example, the UE 115-b may be configured with an additional opportunity to receive a packet from the base station 105-c based on the UE 115-b operating in a dual active link handover.

[0129] In a first example, the base station 105-c may determine that the UE 115-b missed the second message at 330 (e.g., based on a retransmission timer at the base station 105-c) and may retransmit the second message at 335. In some cases, the base station 105-c may implement a shorter retransmission timer when the UE 115-b is performing a dual active link handover than when the UE 115-b is simply connected to the base station 105-c (e.g., due to a higher likelihood that the UE 115-b will drop packets). The base station 105-c may indicate this retransmission timer for message retransmissions when the UE is performing a dual active link handover to the UE 115-b, or the UE 115-b may select the base station 105-c to implement the shorter timer.

[0130] In a second example, the base station 105-c may perform slot aggregation associated with the UE 115-b performing a dual active link handover. For example, the base station 105-c may reduce search space periodicity, implement slot aggregation for data transmission, or both during a dual active link handover operation. In some cases, the base station 105-c may configure the UE 115-b with a slot aggregation configuration (e.g., using a handover command or another configuration message at 310). The slot aggregation configuration may include a number of repetitions of the second message in a set of slots, a periodicity of the repetitions across slots, or both. Based on the slot aggregation configuration, the base station 105-c may transmit the second message multiple times (e.g., on multiple transmission opportunities, such as consecutive slots) to the UE 115-b, and the UE 115-b may receive the second message based on the aggregation repetitions on non-dropped transmission opportunities. For example, based on slot aggregation, even if the UE 115-b misses the second message at 330 (e.g., based on a dropped monitoring opportunity or packet reception), the UE 115-b may receive the second message at 335. In some cases, the UE 115-b may send a notification message to the base station 105-c indicating which repetitions of the slot aggregation data (e.g., the second message transmitted using slot aggregation) were dropped at the UE 115-b, how many repetitions were dropped, or both. The base station 105-c may determine whether to retransmit the slot aggregation data based on information regarding which repetitions were dropped, how many repetitions were dropped, or both at the UE 115-b.

[0131] Although the UE 115-b is described herein with respect to dropping data reception from a source base station, it should be understood that the UE 115-b may alternatively drop packet reception from a target base station (e.g., based on prioritization of communications with the source base station). Additionally, although described herein with respect to downlink transmissions (e.g., PDCCH messages, PDSCH messages, etc.), similar techniques may be implemented in the uplink. For example, the UE 115-b may drop downlink monitoring or reception based on prioritization of uplink transmissions (e.g., PUCCH messages, PUSCH messages, etc.), or may drop uplink transmissions for one cell based on communications with a different cell. The UE 115-b may implement slot aggregation, shortened retransmission timers, or both in the uplink (e.g., in addition to or instead of the base station 105 implementing these techniques in the downlink).

[0132] FIG. 4 illustrates an example of a process flow 400 supporting error handling in a dual active link handover according to aspects of the disclosure. In some examples, the process flow 400 may implement aspects of the wireless communication system 100 or 200 described with reference to FIG. 1 and FIG. 2. The process flow 400 may include a UE 115-c and base stations 105-e and 105-f, which may be examples of corresponding devices described with reference to FIG. 1-FIG. 3. As described with reference to FIG. 3, the UE 115-c may perform a dual active link handover procedure to transition a connection from a source base station (e.g., base station 105-e) to a target base station (e.g., base station 105-f). The UE 115-c, base station 105-e, base station 105-f, or a combination thereof, may implement techniques to reduce packet loss when the UE 115-c drops a scheduled communication opportunity with one of the base stations 105. The following alternative examples may be implemented, where some steps are performed in a different order than described or not performed at all. In some cases, the steps may include additional features not mentioned below or further steps may be added. For example, the UE 115, the base station 105, or both may interchangeably implement steps from process flows 300 and 400. For example, the system may support both base station-triggered and UE-assisted approaches to reduce packet loss during dual active link handover.

[0133] As described with reference to FIG. 3, at 405, the base station 105-e and the UE 115-c may establish a first connection link. At 410, the base station 105-e may send a handover command (e.g., a dual active link handover command) to the UE 115-c indicating a handover of the UE 115-c from a source base station (e.g., base station 105-e) to a target base station (e.g., base station 105-f). Based on the dual active link handover command, at 415, the UE 115-c may establish a second communication link with the base station 105-f. By performing the dual active link handover operation, the UE 115-c may simultaneously maintain a first communication link with the base station 105-e and a second communication link with the base station 105-f.

[0134] At 420, the UE 115-c may identify a time between a first transmission opportunity associated with a first base station (e.g., also corresponding to the first cell) and a second transmission opportunity associated with a second base station (e.g., also corresponding to the second cell). As described herein, the first base station may be either a target base station or a source base station, and the second base station may be either a source base station or a target base station. Based on the identified time, the UE 115-c may determine that the first transmission opportunity and the second transmission opportunity conflict (e.g., as described in more detail with reference to FIG. 3).

[0135] Based on the competing transmission opportunity, the UE 115-c may select to communicate with the first base station in the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station. In some examples, the UE 115-c may select a default beam for either the source base station or the target base station (e.g., based on a prioritization rule) and use the default beam for communication. As shown, the UE 115-c may prioritize communication with the target base station (e.g., base station 105-f) and may receive a first message from the base station 105-f at 425 (e.g., based on selecting to communicate in the first transmission opportunity). However, based on this selection, the UE 115-c may refrain from receiving a second message from the source base station (e.g., base station 105-e). For example, the UE 115-c may drop a monitoring opportunity from a search space associated with the base station 105-e or may drop a scheduled downlink grant for the base station 105-e. In some cases, based on dropping the second transmission opportunity at 430, the UE 115-c may miss a packet (eg, the second message) from the base station 105-e.

[0136] At 435, the UE 115-c may send a notification message to the base station 105-e (i.e., the base station 105 for which the UE 115-c dropped a monitoring opportunity or packet reception) indicating that the UE 115-c did not monitor the second transmission opportunity. If the UE 115-c dropped a PDCCH candidate or an unscheduled PDSCH monitoring opportunity, the notification message may indicate the particular dropped monitoring opportunity. The base station 105-e may identify whether the dropped monitoring opportunity included a message transmission (e.g., from the base station 105-e) and may determine whether to retransmit the message based on the identification. If the UE 115-c dropped a scheduled PDSCH transmission opportunity, the notification message may include a NACK for the scheduled PDSCH message. The UE 115-c may transmit the notification message within a ground free uplink resource or may piggyback the notification message on a subsequent uplink transmission (e.g., the next scheduled uplink message, such as a scheduled PUCCH or PUSCH message).

[0137] If the UE 115-c misses a packet from the base station 105-e (e.g., based on prioritizing transmission opportunities for the base station 105-f, at 425), the base station 105-e may determine to retransmit the packet. In some examples, the base station 105-e may retransmit the packet (e.g., the second message) to the UE 115-c at the third transmission opportunity, at 440, based on the notification message. In some other examples, the base station 105- may retransmit the packet to the base station 105-f at 445 (e.g., instead of or in addition to retransmitting to the UE 115-c). For example, the base station 105-e may forward the packet (e.g., the second message) to the base station 105-f over a wired backhaul, over a wireless backhaul link, via a network entity, or over some combination of these or other interfaces. At 450, the base station 105-f may transmit the second message to the UE 115-c at the third transmission opportunity. For example, if the UE 115-c prioritizes communication with the base station 105-f, this forwarding technique may improve the transmission reliability of the second message.

[0138] Although the UE 115-c is described herein with respect to dropping packet reception from a source base station, it should be understood that the UE 115-c may alternatively drop packet reception from a target base station (e.g., based on prioritization of communications with the source base station). Additionally, although described herein with respect to downlink transmission, similar techniques may be implemented in the uplink. For example, the UE 115-c may drop downlink monitoring or reception based on prioritization of uplink transmission, or may drop uplink transmission for one cell based on communications with a different cell. The UE 115-c may implement UE-assisted recovery for dropped uplink opportunities (e.g., in addition to or instead of implementing these techniques for dropped downlink opportunities).

[0139] 5 illustrates a diagram 500 of a device 505 supporting error handling in dual active link handover according to an aspect of the disclosure. The device 505 may be an example of an aspect of a UE 115 as described herein. The device 505 may include a receiver 510, a communications manager 515, and a transmitter 520. The device 505 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0140] The receiver 510 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 message processing in dual active link handover, etc.). The information may be passed to other components of the device 505. The receiver 510 may be an example of an aspect of a transceiver 820 described with reference to FIG. 8. The receiver 510 may utilize a single antenna or a set of antennas.

[0141] The communications manager 515 may simultaneously maintain a first communication link with the first base station and a second communication link with the second base station based on the execution of the dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, and select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time. In some cases, the communications manager 515 may monitor a third transmission opportunity for a message from the second base station based on the execution of the dual active link handover. Additionally or alternatively, the communications manager 515 may send a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0142] Activities performed by the communications manager 515 described herein may be implemented to realize one or more potential advantages. For example, monitoring additional opportunities for messages, sending a notification message indicating that the UE did not monitor the second transmission opportunity, or both may reduce packet loss at the UE (e.g., device 505). In some cases, configuring slot aggregation or a shorter retransmission timer for packet retransmission during dual active link handover operation may reduce latency associated with the UE receiving packets (e.g., from a non-prioritized base station). Additionally or alternatively, notifying the base station that the UE has dropped a monitoring opportunity may reduce latency associated with the base station retransmitting a packet that was originally transmitted on the dropped monitoring opportunity.

[0143] Communications manager 515 may be an example of an aspect of communications manager 810 described herein. Communications manager 515, or subcomponents thereof, may be implemented in hardware, code executed by a processor (e.g., software or firmware), or any combination thereof. When implemented in code executed by a processor, the functions of communications manager 515, or subcomponents thereof, may be performed by a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (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.

[0144] The communications manager 515 or its subcomponents may be physically located in various locations, including being distributed such that portions of the functionality are implemented at different physical locations by one or more physical components. In some examples, the communications manager 515 or its subcomponents may be separate and distinct components according to various aspects of the present disclosure. In some examples, the communications manager 515 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 present disclosure.

[0145] The transmitter 520 may transmit signals generated by other components of the device 505. In some examples, the transmitter 520 may be collocated with the receiver 510 in a transceiver module. For example, the transmitter 520 may be an example of an embodiment of a transceiver 820 described with reference to FIG. 8. The transmitter 520 may utilize a single antenna or a set of antennas.

[0146] In some examples, the communications manager 515 may be implemented as an integrated circuit or chipset for a mobile device modem, and the receiver 510 and the transmitter 520 may be implemented as analog components (e.g., amplifiers, filters, antennas, or any other analog components) coupled to the mobile device modem to enable wireless transmission and reception over one or more bands.

[0147] The communications manager 515 as described herein may be implemented to realize one or more potential advantages. One implementation may enable the device 505 to provide assistance to reduce packet error rates, packet loss rates, or both during a dual active link handover. Based on techniques for dual active link handover, the device may support error handling in a dual active link handover, thus potentially reducing latency associated with receiving dropped packets.

[0148] Thus, the device 505 may reduce the number of dropped packets or reduce the latency associated with receiving dropped packets during dual active link handover, and therefore may communicate on the channel with a higher probability of successful communication. In some examples, based on the higher probability of successful communication, the device 505 may more efficiently power up a processor or one or more processing units associated with dual active link handover, which may allow the device to conserve power and enhance battery life. For example, the processor of the device 505 (e.g., a processor controlling the receiver 510, the communications manager 515, the transmitter 520, or some combination thereof) may reduce processing resources used for retransmissions. That is, using error handling for dual active link handover to improve transmission reliability may potentially reduce the number of retransmissions performed in the system, allowing the UE 115 to reduce the number of times the processor ramps up processing power and turns on a processing unit to handle retransmissions.

[0149] 6 illustrates a diagram 600 of a device 605 supporting error handling in dual active link handover according to an aspect of the disclosure. The device 605 may be an example of an aspect of a device 505 or a UE 115 as described herein. The device 605 may include a receiver 610, a communications manager 615, and a transmitter 645. The device 605 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0150] The receiver 610 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 message processing in dual active link handover, etc.). The information may be passed to other components of the device 605. The receiver 610 may be an example of an aspect of a transceiver 820 described with reference to FIG. 8. The receiver 610 may utilize a single antenna or a set of antennas.

[0151] Communications manager 615 may be an example of an aspect of communications manager 515 as described herein. Communications manager 615 may include a communications link component 620, a competing transmission opportunity identifier 625, a prioritization component 630, a monitoring component 635, a notification component 640, or a combination thereof. Communications manager 615 may be an example of an aspect of communications manager 810 as described herein.

[0152] The communication link component 620 can simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on performing a dual active link handover.

[0153] The competing transmission opportunity identifier 625 may identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station. Based on the identified time, the prioritization component 630 may select to communicate with the first base station in the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station.

[0154] In a first example, the monitoring component 635 may monitor the third transmission opportunity for a message from the second base station based on the execution of a dual active link handover. In a second example, the notification component 640 may send a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0155] The transmitter 645 may transmit signals generated by other components of the device 605. In some examples, the transmitter 645 may be collocated with the receiver 610 in a transceiver module. For example, the transmitter 645 may be an example of an embodiment of the transceiver 820 described with reference to FIG. 8. The transmitter 645 may utilize a single antenna or a set of antennas.

[0156] FIG. 7 illustrates a diagram 700 of a communications manager 705 supporting error handling in dual active link handover according to an aspect of the disclosure. The communications manager 705 may be an example of an aspect of the communications manager 515, communications manager 615, or communications manager 810 described herein. The communications manager 705 may include a communications link component 710, a contention transmission opportunity identifier 715, a prioritization component 720, a monitoring component 725, a configuration component 730, a dual active link handover command component 735, a retransmission timer component 740, a slot aggregation component 745, a notification component 750, a message reception component 755, or a combination thereof. Each of these modules may be in direct or indirect communication with one another (e.g., via one or more buses). The communications manager 705 may be implemented in the UE 115 to handle wireless communications.

[0157] In some cases, the communication link component 710 may simultaneously maintain a first communication link with a first base station and a second communication link with a second base station based on the execution of a dual active link handover. The contention transmission opportunity identifier 715 may identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station. The prioritization component 720 may select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time. The monitoring component 725 may monitor a third transmission opportunity for a message from the second base station based on the execution of a dual active link handover.

[0158] In some examples, the competing transmission opportunity identifier 715 may select a first communications beam for communicating with a first base station in a first bandwidth and the UE is configured to communicate using a single communications beam at a time. The competing transmission opportunity identifier 715 may determine that the identified time is less than a threshold time for switching from the first communications beam for communicating with the first base station in the first bandwidth to a second communications beam for communicating with a second base station in the second bandwidth, and selecting to communicate on the first transmission opportunity instead of monitoring the second transmission opportunity may be further based on determining. In some cases, a first communication beam for communicating with a first base station at a first transmission opportunity and a first bandwidth is selected based on the first base station, the second base station, a first channel associated with the first transmission opportunity, a second channel associated with the second transmission opportunity, a first QoS associated with traffic for the first channel, a second QoS associated with traffic for the second channel, a first timing resource for the first transmission opportunity, a second timing resource for the second transmission opportunity, or a combination thereof.

[0159] In some cases, a threshold time for switching from a first communications beam for communicating with a first base station in a first bandwidth to a second communications beam for communicating with a second base station in a second bandwidth exceeds a threshold for switching from the first communications beam for communicating with the first base station to a third communications beam for communicating with the first base station. In some cases, the first transmission opportunity and the second transmission opportunity at least partially overlap in time.

[0160] The configuration component 730 may identify a configuration associated with performing a dual active link handover and may determine a time relationship between the second and third transmission opportunities based on the configuration. The configuration associated with performing a dual active link handover may be a configuration for the UE to implement when the UE is performing a dual active link handover that differs from a configuration the UE implements when the UE is not performing a dual active link handover. The dual active link handover command component 735 may receive a configuration from one or both of the first base station and the second base station. For example, the configuration component 730 may receive a configuration from a source base station for communicating with a source base station, a configuration from a target base station for communicating with a target base station, or both.

[0161] In some cases, the time relationship between the second and third transmission opportunities is based on a retransmission timer for retransmission of a missed message during the second transmission opportunity when the UE is performing a dual active link handover. The transmission timer component 740 may configure a retransmission timer, where the retransmission timer is shorter than a default retransmission timer (e.g., used when the UE is not performing a dual active link handover).

[0162] The slot aggregation component 745 may identify a slot aggregation configuration associated with performing a dual active link handover, and monitoring for a third transmission opportunity for the message is based on the slot aggregation configuration. In some cases, the slot aggregation configuration includes one or both of a number of repetitions of the message within the set of slots and a periodicity for the repetitions of the message within the set of slots.

[0163] In some examples, the configuration component 730 may select a configuration for one or both of the first communication link with the first base station and the second communication link with the second base station and may send an indication of the selected configuration to one or both of the first base station and the second base station, and monitoring for a third transmission opportunity for the message is based on the selected configuration.

[0164] In some examples, the notification component 750 may send a notification message indicating that the UE did not monitor the second transmission opportunity, and monitoring for the third transmission opportunity is further based on sending this notification message.

[0165] Additionally or alternatively, the communication link component 710 may simultaneously maintain a first communication link with the first base station and a second communication link with the second base station based on the execution of a dual active link handover. The contention transmission opportunity identifier 715 may identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station. The prioritization component 720 may select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a first message from the second base station based on the identified time. In some cases, the second transmission opportunity may correspond to a monitoring opportunity for a control channel message or a downlink grant for a data channel message. The notification component 750 may send a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity.

[0166] In some examples, transmitting the notification message may be related to transmitting a scheduled uplink message to the second base station, the scheduled uplink message including the notification message. In some other examples, transmitting the notification message may be related to transmitting the notification message within a grant-free uplink resource. In some cases, the notification message further indicates one or both of a search space schedule for the first base station and a periodic data transmission schedule for the first base station. In some cases, the notification message indicates a type of channel associated with the second transmission opportunity, a search configuration for the second transmission opportunity, a timing opportunity for the second transmission opportunity, or a combination thereof.

[0167] A message receiving component 755 may receive a first message from one or both of the first base station and the second base station at the third transmission opportunity based on the notification message.

[0168] The configuration component 730 may receive a configuration from the second base station related to performing a dual active link handover, the configuration being received based on the notification message. In some cases, the configuration may include one or both of a retransmission timer for retransmission of a first message missed during the second transmission opportunity when the UE is performing a dual active link handover indicating a time relationship between the second transmission opportunity and the third transmission opportunity, and a slot aggregation configuration including one or both of a number of repetitions of the first message within the set of slots and a periodicity for the repetitions of the first message within the set of slots.

[0169] In some examples, the slot aggregation component 745 may receive a slot aggregation configuration associated with performing a dual active link handover, where the slot aggregation configuration indicates a number of repetitions of the first message within a set of slots, and the notification message includes an indication of which repetitions were missed and how many repetitions one or both were missed.

[0170] In some examples, the competing transmission opportunity identifier 715 may select a first communications beam for communicating with a first base station in a first bandwidth and the UE is configured to communicate using a single communications beam at a time. The competing transmission opportunity identifier 715 may determine that the identified time is less than a threshold time for switching from the first communications beam for communicating with the first base station in the first bandwidth to a second communications beam for communicating with a second base station in the second bandwidth, and selecting to communicate on the first transmission opportunity instead of monitoring the second transmission opportunity may be further based on determining. In some cases, the first transmission opportunity and the first communications beam for communicating with the first base station in the first bandwidth are selected based on the first base station, the second base station, a first channel associated with the first transmission opportunity, a second channel associated with the second transmission opportunity, a first quality of service associated with traffic for the first channel, a second quality of service associated with traffic for the second channel, a first timing resource for the first transmission opportunity, a second timing resource for the second transmission opportunity, or a combination thereof.

[0171] In some cases, a threshold time for switching from a first communications beam for communicating with a first base station in a first bandwidth to a second communications beam for communicating with a second base station in a second bandwidth exceeds a threshold time for switching from the first communications beam for communicating with the first base station to a third communications beam for communicating with the first base station. In some cases, the first transmission opportunity and the second transmission opportunity at least partially overlap in time.

[0172] 8 illustrates a diagram of a system 800 including a device 805 supporting error handling in dual active link handover according to an aspect of the disclosure. The device 805 may be an example of or may include components of a device 505, a device 605, or a UE 115 as described herein. The device 805 may include components for two-way voice and data communication, including components for transmitting and receiving communications, including a communications manager 810, an I / O controller 815, a transceiver 820, an antenna 825, a memory 830, and a processor 840. These components may be in electronic communication over one or more buses (e.g., bus 845).

[0173] In some cases, the communications manager 810 may simultaneously maintain a first communications link with a first base station and a second communications link with a second base station based on the execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station based on the identified time, select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a message from the second base station based on the identified time, and monitor a third transmission opportunity for a message from the second base station based on the execution of the dual active link handover. Additionally or alternatively, the communications manager 810 may simultaneously maintain a first communications link with the first base station and a second communications link with the second base station based on the execution of a dual active link handover, identify a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station, and based on the identified time, select to communicate with the first base station at the first transmission opportunity instead of monitoring the second transmission opportunity for a first message from the second base station, and send a notification message to the second base station indicating that the UE (e.g., device 805) did not monitor the second transmission opportunity.

[0174] The I / O controller 815 may manage input and output signals for the device 805. The I / O controller 815 may also manage peripheral devices that are not built into the device 805. In some cases, the I / O controller 815 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 815 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 815 may represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I / O controller 815 may be implemented as part of a processor. In some cases, a user may interact with the device 805 through the I / O controller 815 or through hardware components controlled by the I / O controller 815.

[0175] The transceiver 820 may communicate bidirectionally via one or more antennas, wired links, or wireless links as described herein. For example, the transceiver 820 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 820 may also include a modem for modulating packets, providing the modulated packets to an antenna for transmission, and demodulating packets received from the antenna.

[0176] In some cases, a wireless device may include a single antenna 825. In some cases, however, a device may have two or more antennas 825 that may be capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0177] The memory 830 may include random access memory (RAM) and read only memory (ROM). The memory 830 may store computer-readable computer-executable code 835 that includes instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 830 may include a basic I / O system (BIOS) that may control basic hardware or software operations, such as interactions with peripheral components or devices, among others.

[0178] The processor 840 may include intelligent hardware devices (e.g., a general purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 840 may be configured to operate a memory array using a memory controller. In other cases, the memory controller may be incorporated within the processor 840. The processor 840 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks supporting message processing in dual active link handover).

[0179] The code 835 may include instructions for implementing aspects of the disclosure, including instructions for supporting wireless communication. The code 835 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 835 may not be directly executable by the processor 840, but may (e.g., when compiled and executed) cause a computer to perform functions described herein.

[0180] 9 illustrates a diagram 900 of a device 905 supporting error handling in dual active link handover according to an embodiment of the disclosure. The device 905 may be an example of an embodiment of a base station 105 as described herein. The device 905 may include a receiver 910, a communications manager 915, and a transmitter 920. 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).

[0181] 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 message processing in dual active link handover, etc.). The information may be passed to other components of the device 905. The receiver 910 may be an example of an aspect of the transceiver 1220 described with respect to FIG. 12. The receiver 910 may utilize a single antenna or a set of antennas.

[0182] The communications manager 915 may support wireless communications at a first base station. In some cases, the communications manager 915 may identify that the UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with a second base station while performing the dual active link handover, transmit a message to the UE at a first transmit opportunity, and transmit a message to the UE at a second transmit opportunity following the first transmit opportunity based on the UE performing the dual active link handover. Additionally or alternatively, the communications manager 915 may identify that the UE is performing a dual active link handover, where the UE simultaneously maintains a first communications link with a first base station and a second communications link with a second base station while performing the dual active link handover; based on the performance of the dual active link handover, receive a notification message from the UE indicating that the UE did not monitor the first transmission opportunity; and based on the notification message, determine whether to retransmit the message to one or both of the UE and the second base station.

[0183] Activities performed by the communications manager 915 as described herein may be implemented to realize one or more potential advantages. For example, transmitting a message to the UE on a second transmission opportunity following a first transmission opportunity based on the UE's execution of a dual active link handover, receiving a notification message from the UE indicating that the UE did not monitor the first transmission opportunity based on the execution of a dual active link handover, or both may reduce packet loss at the UE. In some cases, configuring slot aggregation or a shorter retransmission timer for packet retransmission during a dual active link handover operation may reduce latency associated with transmitting a packet to the UE (e.g., from a non-prioritized base station). Additionally or alternatively, receiving a notification that the UE dropped a monitoring opportunity may reduce latency associated with retransmitting a packet originally transmitted on the dropped monitoring opportunity. Thus, the techniques described herein may improve transmission reliability and latency when a UE is connected to multiple base stations during a dual active link handover.

[0184] Communications manager 915 may be one example of an aspect of communications manager 1210 described herein. Communications manager 915, or subcomponents thereof, 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 915, or subcomponents thereof, may be performed by a general purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in this disclosure.

[0185] The communications manager 915 or its subcomponents may be physically located in various locations, including being distributed such that portions of the functionality are implemented at different physical locations by one or more physical components. In some examples, the communications manager 915 or its subcomponents may be separate and distinct components according to various aspects of the present disclosure. In some examples, the communications manager 915 or its subcomponents may be combined with one or more other hardware components, including, but not limited to, an 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 present disclosure.

[0186] The transmitter 920 may transmit signals generated by other components of the device 905. In some examples, the transmitter 920 may be collocated with the receiver 910 in a transceiver module. For example, the transmitter 920 may be an example of an aspect of the transceiver 1220 described with reference to FIG. 12. The transmitter 920 may utilize a single antenna or a set of antennas.

[0187] 10 illustrates a diagram 1000 of a device 1005 supporting error handling in dual active link handover according to an aspect of the disclosure. The device 1005 may be an example of an aspect of a device 905 or a base station 105 as described herein. The device 1005 may include a receiver 1010, a communications manager 1015, and a transmitter 1040. The device 1005 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0188] The receiver 1010 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 message processing in dual active link handover, etc.). The information may be passed to other components of the device 1005. The receiver 1010 may be an example of an aspect of the transceiver 1220 described with respect to FIG. 12. The receiver 1010 may utilize a single antenna or a set of antennas.

[0189] The communications manager 1015 may be an example of an aspect of the communications manager 915 as described herein. The communications manager 1015 may include a dual active link handover identifier 1020, a message sending component 1025, a notification receiving component 1030, a retransmission determining component 1035, or a combination thereof. The communications manager 1015 may be an example of an aspect of the communications manager 1210 as described herein. The communications manager 1015 may implement wireless communications at the first base station.

[0190] In some cases, the dual active link handover identifier 1020 may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with a first base station and a second communication link with a second base station while performing the dual active link handover. The message transmitting component 1025 may transmit a message to the UE at the first transmission opportunity and may transmit a message to the UE at a second transmission opportunity following the first transmission opportunity based on the UE performing the dual active link handover.

[0191] The dual active link handover identifier 1020 may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with a first base station and a second communication link with a second base station while performing the dual active link handover. The notification receiving component 1030 may receive a notification message from the UE indicating that the UE did not monitor the first transmission opportunity based on the performance of the dual active link handover. The retransmission determination component 1035 may determine whether to retransmit the message to one or both of the UE and the second base station based on the notification message.

[0192] The transmitter 1040 may transmit signals generated by other components of the device 1005. In some examples, the transmitter 1040 may be collocated with the receiver 1010 in a transceiver module. For example, the transmitter 1040 may be an example of an aspect of the transceiver 1220 described with reference to FIG. 12. The transmitter 1040 may utilize a single antenna or a set of antennas.

[0193] FIG. 11 illustrates a diagram 1100 of a communications manager 1105 supporting error handling in dual active link handover according to an aspect of the disclosure. The communications manager 1105 may be an example of an aspect of the communications manager 915, communications manager 1015, or communications manager 1210 described herein. The communications manager 1105 may include a dual active link handover identifier 1110, a message sending component 1115, a configuration component 1120, a dual active link handover command component 1125, a retransmission timer component 1130, a slot aggregation configuration component 1135, a retransmission component 1140, a slot aggregation component 1145, a notification receiving component 1150, a retransmission decision component 1155, a message forwarding component 1160, or a combination thereof. Each of these modules may be in direct or indirect communication with one another (e.g., via one or more buses). The communications manager 1105 may be implemented in a first base station to handle wireless communications.

[0194] In some cases, the dual active link handover identifier 1110 may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with the first base station and a second communication link with the second base station while performing the dual active link handover. In some cases, the first base station includes a source base station of the dual active link handover or a target base station of the dual active link handover. The message transmitting component 1115 may transmit a message to the UE at the first transmission opportunity. In addition, the message transmitting component 1115 may transmit a message to the UE at a second transmission opportunity following the first transmission opportunity based on the UE performing the dual active link handover.

[0195] The configuration component 1120 may configure the UE with a configuration related to the UE performing a dual active link handover, the configuration indicating a time relationship between a first transmission opportunity and a second transmission opportunity. For example, the UE may implement the configuration when the UE is performing a dual active link handover, or may otherwise implement a different configuration. The dual active link handover command component 1125 may send a configuration message, a dual active link handover command, or both, to the UE indicating the configuration.

[0196] In some cases, the time relationship between the first and second transmission opportunities includes a retransmission timer for retransmission of a message missed during the first transmission opportunity when the UE is performing a dual active link handover. The retransmission timer component 1130 may configure a retransmission timer for the retransmission, where the retransmission timer is shorter than a default retransmission timer.

[0197] The slot aggregation component 1135 may configure the UE with a slot aggregation configuration associated with the UE performing a dual active link handover, and transmitting the message at the first transmission opportunity and the second transmission opportunity is based on the slot aggregation configuration. In some examples, the dual active link handover command component 1125 may send a configuration message, a dual active link handover command, or both to the UE indicating a slot aggregation configuration, the slot aggregation configuration including one or both of a number of repetitions of the message within the set of slots and a periodicity of the message within the set of slots.

[0198] The retransmitting component 1140 may determine that the UE did not receive the message at the first transmit opportunity, and transmitting the message at the second transmit opportunity includes retransmitting the message at the second transmit opportunity based on the determining. In some examples, the retransmitting component 1140 may receive a notification message from the UE indicating that the UE did not monitor the first transmit opportunity, and the determining is based on the notification message.

[0199] A slot aggregation component 1145 may perform slot aggregation, and the message is transmitted at the first transmit opportunity and the second transmit opportunity based on the slot aggregation.

[0200] Additionally or alternatively, the dual active link handover identifier 1110 may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with the first base station and a second communication link with the second base station while performing the dual active link handover. In some cases, the first base station includes a source base station of the dual active link handover or a target base station of the dual active link handover. The notification receiving component 1150 may receive a notification message from the UE based on the performance of the dual active link handover, indicating that the UE did not monitor a first transmission opportunity. In some cases, the first transmission opportunity may correspond to a monitoring opportunity for a control channel message or a downlink grant for a data channel message. The retransmission determination component 1155 may determine whether to retransmit the message to one or both of the UE and the second base station based on the notification message.

[0201] In some examples, the notification receiving component 1150 may identify that the first transmission opportunity is unused. In some examples, receiving the notification message may be related to receiving a scheduled uplink message from the UE, the scheduled uplink message including the notification message. In some other examples, receiving the notification message may be related to receiving the notification message within a grant-free uplink resource. In some cases, the notification message indicates a type of channel associated with the first transmission opportunity, a search configuration for the first transmission opportunity, a timing opportunity for the first transmission opportunity, or a combination thereof.

[0202] In some examples, the message transmitting component 1115 may transmit a message to the UE at a first transmit opportunity and, based on the determination, may retransmit the message to the UE at a second transmit opportunity.

[0203] In some examples, the configuration component 1120 may send a configuration to the UE related to the UE performing a dual active link handover based on the notification message, and retransmitting the message at the second transmission opportunity is based on the configuration. In some cases, the configuration includes one or both of a retransmission timer for retransmission of a message missed during the first transmission opportunity when the UE is performing a dual active link handover indicating a time relationship between the first transmission opportunity and the second transmission opportunity, and a slot aggregation configuration including one or both of a number of repetitions of a message within a set of slots and a periodicity for the repetition of a message within a set of slots.

[0204] In some cases, the notification message further indicates one or both of a search space schedule for the second base station and a periodic data transmission schedule for the second base station, and the second transmission opportunity is based on one or both of the search space schedule and the periodic data transmission schedule for the second base station.

[0205] In some cases, the slot aggregation component 1135 may send a slot aggregation configuration to the UE related to the UE performing a dual active link handover, where the slot aggregation configuration indicates the number of repetitions of the message within a set of slots, and the notification message includes an indication of which repetitions were missed and how many repetitions one or both were missed by the UE.

[0206] In some examples, the message transmitting component 1115 may transmit a message to the UE at the first transmission opportunity, and the message forwarding component 1160 may forward the message to the second base station based on the notification message.

[0207] 12 illustrates a diagram of a system 1200 including a device 1205 supporting error handling in dual active link handover according to an aspect of the disclosure. The device 1205 may be an example of or may include components of a device 905, a device 1005, or a base station 105 as described herein. The device 1205 may include components for two-way voice and data communication, including components for transmitting and receiving communications, including a communications manager 1210, a network communications manager 1215, a transceiver 1220, an antenna 1225, a memory 1230, a processor 1240, and an inter-station communications manager 1245. These components may be in electronic communication via one or more buses (e.g., a bus 1250).

[0208] The communications manager 1210 may be implemented in a first base station. In some cases, the communications manager 1210 may identify that the UE is performing a dual active link handover, where the UE simultaneously maintains a first communication link with the first base station and a second communication link with the second base station while performing the dual active link handover, transmit a message to the UE at a first transmission opportunity, and transmit a message to the UE at a second transmission opportunity following the first transmission opportunity based on the UE performing the dual active link handover. Additionally or alternatively, the communications manager 1210 may identify that the UE is performing a dual active link handover, where the UE simultaneously maintains a first communications link with a first base station and a second communications link with a second base station while performing the dual active link handover; based on the performance of the dual active link handover, receive a notification message from the UE indicating that the UE did not monitor the first transmission opportunity; and based on the notification message, determine whether to retransmit the message to one or both of the UE and the second base station.

[0209] The network communications manager 1215 may manage communications with the core network 130 (e.g., via one or more wired backhaul links). For example, the network communications manager 1215 may manage the transfer of data communications for client devices, such as one or more UEs 115.

[0210] The transceiver 1220 may communicate bidirectionally via one or more antennas, wired links, or wireless links as described herein. For example, the transceiver 1220 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 1220 may also include a modem for modulating packets, providing the modulated packets to an antenna for transmission, and demodulating packets received from the antenna.

[0211] In some cases, a wireless device may include a single antenna 1225. However, in some cases, a device may have two or more antennas 1225 that may be capable of simultaneously transmitting or receiving multiple wireless transmissions.

[0212] The memory 1230 may include RAM, ROM, or a combination thereof. The memory 1230 may store computer-readable code 1235 including instructions that, when executed by a processor (e.g., the processor 1240), cause the device to perform various functions described herein. In some cases, the memory 1230 may include a BIOS that may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0213] The processor 1240 may include intelligent hardware devices (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 1240 may be configured to operate a memory array using a memory controller. In some cases, the memory controller may be integrated into the processor 1240. The processor 1240 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 1230) to cause the device 1205 to perform various functions (e.g., functions or tasks supporting message processing in dual active link handover).

[0214] The inter-station communications manager 1245 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 1245 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 1245 may provide an X2 interface in LTE / LTE-A wireless communications network technology to communicate between the base stations 105.

[0215] Code 1235 may include instructions for implementing aspects of the disclosure, including instructions for supporting wireless communications. Code 1235 may be stored in a non-transitory computer-readable medium, such as a system memory or other type of memory. In some cases, code 1235 may not be directly executable by processor 1240, but may (e.g., when compiled and executed) cause a computer to perform functions described herein.

[0216] FIG. 13 illustrates a flow chart illustrating a method 1300 for supporting error handling in a dual active link handover according to an aspect of the disclosure. The operations of the method 1300 may be implemented by the UE 115 or components thereof as described herein. For example, the operations of the method 1300 may be performed by a communications manager as described with reference to FIGS. 5-8. 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 1305, the UE may simultaneously maintain a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover. For example, the UE may have an existing connection with a source base station and may establish a connection with a target base station during the dual active link handover process. The operations of 1305 may be performed according to methods described herein. In some examples, aspects of the operations of 1305 may be performed by communication link components such as those described with reference to FIGS. 5-8.

[0218] At 1310, the UE may identify a time between a first transmission opportunity associated with a first base station and a second transmission opportunity associated with a second base station. The operations of 1310 may be performed in accordance with methods described herein. In some examples, aspects of the operations of 1310 may be performed by a contention transmission opportunity identifier, as described with reference to FIGS. 5-8.

[0219] At 1315, the UE may select to communicate with the first base station in the first transmit opportunity instead of monitoring the second transmit opportunity for a message from the second base station based on the identified time. For example, the identified time may not be long enough for the UE to switch beams, bandwidths, cells, etc., to communicate with both the base stations in the first and second transmit opportunities. For example, the first transmit opportunity may partially or completely overlap with the second transmit opportunity, or the two transmit opportunities may be relatively close in time (e.g., within a threshold time difference range). The operations of 1315 may be performed according to methods described herein. In some examples, aspects of the operations of 1315 may be performed by a prioritization component, such as described with reference to FIGS. 5-8.

[0220] At 1320, the UE may monitor the third transmission opportunity for a message from the second base station based on the execution of the dual active link handover. For example, the base station may retransmit the message or transmit multiple repetitions of the message in a slot aggregation procedure. The UE may monitor the retransmission for one or more repetitions to receive the message (e.g., even if the UE refrained from receiving the message in the second transmission opportunity). The operations of 1320 may be performed according to methods described herein. In some examples, aspects of the operations of 1320 may be performed by a monitoring component as described with reference to FIGS. 5-8.

[0221] FIG. 14 illustrates a flow chart illustrating a method 1400 for supporting error handling in dual active link handover according to aspects of the disclosure. The operations of method 1400 may be implemented by a base station 105 or components thereof as described herein. For example, the operations of method 1400 may be performed by a communications manager as described with reference to FIGS. 9-12. 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.

[0222] At 1405, a base station (e.g., a first base station) may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with the first base station and a second communication link with the second base station while performing the dual active link handover. For example, if the base station is a source base station in the dual active link handover, the base station may identify that the UE is performing a dual active link handover based on sending a handover command to the UE. If the base station is a target base station in the dual active link handover, the base station may receive an indication from the source base station or the UE indicating that the UE is performing a dual active link handover. The operations of 1405 may be performed according to methods described herein. In some examples, aspects of the operations of 1405 may be performed by a dual active link handover identifier, as described with reference to FIGS. 9-12.

[0223] At 1410, the base station may transmit a message to the UE at the first transmission opportunity. The operations of 1410 may be performed in accordance with methods described herein. In some examples, aspects of the operations of 1410 may be performed by a message transmission component as described with reference to FIGS.

[0224] At 1415, the base station may transmit a message to the UE at a second transmission opportunity subsequent to the first transmission opportunity based on the execution of a dual active link handover by the UE. For example, the base station may send a retransmission of the message (e.g., if the UE dropped the transmission of the message at 1410) or may transmit multiple repetitions of the message in a slot aggregation procedure. The operations of 1415 may be performed according to methods described herein. In some examples, aspects of the operations of 1415 may be performed by a message transmitting component as described with reference to FIGS. 9-12.

[0225] FIG. 15 illustrates a flow chart illustrating a method 1500 for supporting error handling in a dual active link handover according to an aspect of the disclosure. The operations of method 1500 may be implemented by the UE 115 or components thereof as described herein. For example, the operations of method 1500 may be performed by a communications manager as described with reference to FIGS. 5-8. 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.

[0226] At 1505, the UE may simultaneously maintain a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover. The operations of 1505 may be performed according to methods described herein. In some examples, aspects of the operations of 1505 may be performed by communication link components such as those described with reference to FIGS. 5-8.

[0227] At 1510, the UE may identify a time between a first transmission opportunity associated with a first base station and a second transmission opportunity associated with a second base station. The operations of 1510 may be performed according to methods described herein. In some examples, aspects of the operations of 1510 may be performed by a contention transmission opportunity identifier, as described with reference to FIGS. 5-8.

[0228] At 1515, the UE may select to communicate with the first base station in the first transmission opportunity instead of monitoring the second transmission opportunity for the first message from the second base station based on the identified time. For example, the first transmission opportunity and the second transmission opportunity may be contention opportunities (e.g., overlapping or non-overlapping contention opportunities). The operations of 1515 may be performed according to methods described herein. In some examples, aspects of the operations of 1515 may be performed by a prioritization component, such as described with reference to FIGS. 5-8.

[0229] At 1520, the UE may send a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity. The operations of 1520 may be performed according to methods described herein. In some examples, aspects of the operations of 1520 may be performed by a notification component, such as those described with reference to FIGS. 5-8.

[0230] FIG. 16 illustrates a flow chart illustrating a method 1600 for supporting error handling in dual active link handover according to an aspect of the disclosure. The operations of the method 1600 may be implemented by a base station 105 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. 9-12. 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.

[0231] At 1605, a base station (e.g., a first base station) may identify that the UE is performing a dual active link handover, and the UE simultaneously maintains a first communication link with the first base station and a second communication link with the second base station while performing the dual active link handover. 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 dual active link handover identifier, as described with reference to FIGS. 9-12.

[0232] At 1610, the base station may receive a notification message from the UE indicating that the UE did not monitor the first transmission opportunity based on the execution of the dual active link handover. The operations of 1610 may be performed according to methods described herein. In some examples, aspects of the operations of 1610 may be performed by a notification receiving component, such as those described with reference to FIGS. 9-12.

[0233] At 1615, the base station may determine whether to retransmit the message to one or both of the UE and the second base station based on the notification message. For example, if the base station did not transmit the message on the first transmission opportunity that was dropped, the base station may not retransmit the message. If the base station transmitted the message on the first transmission opportunity that was dropped, the base station may retransmit the message to the UE or may forward the message to the second base station, which may transmit the message to the UE (e.g., based on the UE prioritizing transmissions from the second 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 retransmission decision component, such as those described with reference to FIGS. 9-12.

[0234] It should be noted that the methods described herein represent possible implementations, that the acts and steps may be rearranged or otherwise modified, and that other implementations are possible. Additionally, aspects from two or more of the methods may be combined.

[0235] Aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described by way of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used throughout much of the description, although the techniques described herein may be applicable to other than LTE, LTE-A, LTE-A Pro, or NR networks. For example, the techniques described may be applicable to various other wireless communications systems, such as Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, as well as other systems and radio technologies not explicitly mentioned herein.

[0236] The information and signals described herein may be represented using any of a wide variety of technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0237] The various example blocks and components described in connection with the disclosure herein may be implemented or performed using a general purpose processor, a DSP, an ASIC, a CPU, 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 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).

[0238] 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 through a computer-readable medium as one or more instructions or codes. Other examples and implementations are within the scope and spirit of the present disclosure and claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. The features implementing the functions may also be physically located in various locations, including being distributed such that parts of the functions are implemented in different physical locations. The term "and / or" as used herein, including in the claims, when used in a list of two or more items means that any one of the listed items may be employed alone, or any combination of two or more of the listed items may be employed. For example, if a composition is described as including components A, B, and / or C, the composition may include only A, only B, only C, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C. Also, as used in this specification, including the claims, "or" used in a list of items (e.g., a list of items ending in a phrase such as "at least one of" or "one or more of") indicates a disjunctive 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).

[0239] Additionally, the phrase "based on" as used herein should not be construed as a reference to a closed set of conditions. For example, an example step described as "based on condition A" may be based on both condition A and condition B without departing from the scope of this disclosure. In other words, the phrase "based on" as used herein should be construed similarly to the phrase "based at least in part on."

[0240] Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that enables 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 RAM, 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 in the definition of computer-readable media. As used herein, disk and disc include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, 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.

[0241] 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.

[0242] The description set forth herein with respect to the accompanying drawings describes exemplary configurations and does not represent every example that may be implemented or that falls within the scope of the claims. As used herein, the term "example" 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, known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0243] 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 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 should be accorded the widest scope consistent with the principles and novel features disclosed herein. [Explanation of symbols]

[0244] 100 Wireless communication manager, wireless communication system 105 base station, source base station, target base station 105-a Base station, source base station 105-b Base station, target base station 105-c Base station, first base station 105-d Base station, second base station 105-e base station 105-f base station 110 Coverage Area, Geographical Coverage Area 110-a Coverage Area 110-b Coverage Area 115 UE 115-a UE 115-b UE 115-c UE 120 backhaul links 125 Communication Links 130 Core Network 135 Peer-to-Peer (P2P) or Device-to-Device (D2D) communication links (using D2D protocols) 140 Access Network Entity 145 Access Network Transmission Entity 150 Network Operator IP Services 200 Wireless Communication Manager 205 Communication Channels 210 Communication Channels 215 receiving beam 220 receiving beam 300 Process Flow 400 Process Flow 505 Devices 510 Receiver 515 Communications Manager 520 Transmitter 600 Figures 605 Devices 610 Receiver 615 Communications Manager 620 Communication Link Components 625 Competing Transmission Opportunity Identifier 630 Prioritization Components 635 Monitoring Components 640 Notification Component 645 Transmitter 700 Figures 705 Communications Manager 710 Communication Link Components 715 Competing Transmission Opportunity Identifier 720 Prioritization Components 725 Monitoring Components 730 Component 735 Dual Active Link Handover Command Component 740 Retransmission Timer Component 745 Slot Aggregation Components 750 Notification Component 755 Message Receiving Component 800 Systems 805 Devices 810 Communications Manager 815 I / O Controller 820 Transceiver 825 Antenna 830 Memory 835 Code 840 Processor 845 Bus 900 Figures 905 Devices 910 Receiver 915 Communications Manager 920 Transmitter 1000 Figures 1005 Devices 1010 Receiver 1015 Communications Manager 1020 Dual Active Link Handover Identifier 1025 Message transmission component 1030 Notification Receiving Component 1035 Retransmission Decision Component 1040 Transmitter 1100 Figure 1105 Communications Manager 1110 Dual Active Link Handover Identifier 1115 Message transmission component 1120 Component 1125 Dual Active Link Handover Command Component 1130 Retransmission Timer Component 1135 Slot Aggregation Configuration Component 1140 Retransmission Component 1145 Slot Aggregation Component 1150 Notification Reception Component 1155 Retransmission Decision Component 1160 Message Transfer Components 1200 System 1205 Devices 1210 Communications Manager 1215 Network Communications Manager 1220 Transceiver 1225 Antenna 1230 Memory 1235 Computer readable code, code 1240 Processor 1245 Inter-Station Communication Manager 1300 methods 1400 methods 1500 ways 1600 methods

Claims

1. 1. A method for wireless communication in a user equipment (UE), comprising: simultaneously maintaining a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover; identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station; selecting, based on the identified time, to communicate with the first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a message from the second base station; monitoring a third transmission opportunity for the message from the second base station based on performing the dual active link handover; A method comprising:

2. identifying a configuration associated with performing the dual active link handover; determining a time relationship between the second transmission opportunity and the third transmission opportunity based on the configuration; The method of claim 1, further comprising:

3. 3. The method of claim 2, wherein the time relationship between the second transmission opportunity and the third transmission opportunity includes a retransmission timer for retransmission of the message missed during the second transmission opportunity when the UE is performing the dual active link handover, the retransmission timer being shorter than a default retransmission timer.

4. transmitting a notification message indicating that the UE did not monitor the second transmission opportunity, wherein the monitoring for the third transmission opportunity is further based on the transmitting the notification message. The method of claim 1, further comprising:

5. 1. A method for wireless communication in a user equipment (UE), comprising: simultaneously maintaining a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover; identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station; selecting, based on the identified time, to communicate with a first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a first message from the second base station; sending a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity; A method comprising:

6. receiving the first message from one or both of the first base station and the second base station at a third transmission opportunity based on the notification message; 6. The method of claim 5, further comprising:

7. The method of claim 5 , wherein the second transmission opportunity corresponds to a monitoring opportunity for a control channel message or a downlink grant for a data channel message.

8. The method of claim 5 , wherein the notification message further indicates one or both of a search space schedule for the first base station and a periodic data transmission schedule for the first base station.

9. selecting a first communications beam for communicating with the first base station at the first transmission opportunity and a first bandwidth, where the UE is configured to communicate using a single communications beam at a time; determining that the identified time is less than a threshold time for switching from the first communications beam for communicating with the first base station in the first bandwidth to a second communications beam for communicating with the second base station in a second bandwidth, wherein the selecting to communicate in the first transmission opportunity instead of monitoring the second transmission opportunity is further based on the determining step; 6. The method of claim 5, further comprising:

10. 10. The method of claim 9, wherein the first transmission opportunity and the second transmission opportunity at least partially overlap in time.

11. An apparatus for wireless communication in a user equipment (UE), comprising: means for simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on performing a dual active link handover; means for identifying a time between a first transmit opportunity associated with the first base station and a second transmit opportunity associated with the second base station; means for selecting, based on the identified time, to communicate with the first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a message from the second base station; means for monitoring a third transmission opportunity for the message from the second base station based on performing the dual active link handover; 13. An apparatus comprising:

12. 12. Apparatus according to claim 11, further comprising means for carrying out the method according to any one of claims 2 to 4.

13. An apparatus for wireless communication in a user equipment (UE), comprising: means for simultaneously maintaining a first communication link with a first base station and a second communication link with a second base station based on performing a dual active link handover; means for identifying a time between a first transmit opportunity associated with the first base station and a second transmit opportunity associated with the second base station; means for selecting, based on the identified time, to communicate with the first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a first message from the second base station; means for transmitting a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity; 13. An apparatus comprising:

14. 1. A non-transitory computer readable medium storing code for wireless communication in a user equipment (UE), the code comprising: concurrently maintaining a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover; identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station; selecting, based on the identified time, to communicate with the first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a message from the second base station; monitoring a third transmission opportunity for the message from the second base station based on performing the dual active link handover; contains instructions executable by a processor to Non-transitory computer-readable medium.

15. 1. A non-transitory computer readable medium storing code for wireless communication in a user equipment (UE), the code comprising: concurrently maintaining a first communication link with the first base station and a second communication link with the second base station based on performing a dual active link handover; identifying a time between a first transmission opportunity associated with the first base station and a second transmission opportunity associated with the second base station; selecting, based on the identified time, to communicate with the first base station during the first transmit opportunity instead of monitoring the second transmit opportunity for a first message from the second base station; sending a notification message to the second base station indicating that the UE did not monitor the second transmission opportunity; contains instructions executable by a processor to Non-transitory computer-readable medium.

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