Techniques for primary sidelink carrier update in sidelink carrier aggregation

Abstract

Methods, systems, and devices for wireless communication are described. A user equipment (UE) may transmit a first set of reference signals via a primary sidelink carrier of a sidelink carrier aggregation configuration and a second set of reference signals via one or more secondary sidelink carriers of the sidelink carrier aggregation configuration. The UE may receive, based on the reference signal, a measurement message indicating measurements of a set of beams corresponding to a secondary sidelink carrier of the sidelink carrier aggregation configuration based on a beam failure instance of the primary sidelink carrier. The UE may send a control message via Layer 1 signaling or Layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating that the primary sidelink carrier is switched to the set of beams.

Description

[0001] Cross - reference

[0002] This patent application claims the benefit of U.S. Patent Application No. 18 / 057,608, filed on November 21, 2022, by HANIF et al., entitled "TECHNIQUES FOR PRIMARY SIDELINK CARRIER UPDATING IN SIDELINK CARRIER AGGREGATION", which is assigned to the assignee of the present application and is hereby incorporated by reference in its entirety. Technical Field

[0003] The following relates to wireless communication, including techniques for primary sidelink carrier updating in sidelink carrier aggregation. Background Art

[0004] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, messaging, broadcasting, etc. 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 multi - access systems include fourth - generation (4G) systems (such as Long - Term Evolution (LTE) systems, LTE - Advanced (LTE - A) systems, or LTE - A Pro systems) and fifth - generation (5G) systems (which may be referred to as New Radio (NR) systems). These systems may employ techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA), or Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT - S - OFDM). A wireless multi - access communication system may include one or more base stations, each of which supports wireless communication for communication devices, which may be referred to as user equipment (UE). Summary of the Invention

[0005] The described techniques relate to improved methods, systems, devices, and apparatuses that support techniques for primary sidelink carrier updating in sidelink carrier aggregation. For example, the described techniques allow a user equipment (UE) to perform independent beam management procedures for each sidelink component carrier in a sidelink carrier aggregation configuration. If the primary sidelink carrier experiences a beam failure, but one of the secondary sidelink carriers is available, the UE may switch the primary sidelink carrier to one of the available secondary carriers. For example, in the case where another secondary sidelink carrier is available, the transmitting UE may perform a primary sidelink carrier beam change, switch, or reselection by conveying auxiliary information to the receiving UE via the secondary sidelink carrier.

[0006] The UE may perform a primary sidelink carrier switch at different times regarding beam failure detection (BFD) and beam failure recovery (BFR) procedures. In some cases, the transmitting UE may initiate BFR and may attempt a random access procedure to recover the primary sidelink carrier. In cases where the random access procedure is unsuccessful but one of the secondary sidelink carriers is available, the UE may attempt to change the primary sidelink carrier to one of the available secondary sidelink carriers. In some examples, the transmitting UE may change the primary sidelink carrier before detecting a beam failure and performing the BFD procedure. For example, if the UE determines that a secondary sidelink carrier has a higher quality than the primary sidelink carrier before detecting a beam failure and performing BFR, the UE may change the primary sidelink carrier to the secondary sidelink carrier. In some other examples, the transmitting UE may change the primary sidelink carrier before performing a random access procedure during BFR. In some examples described herein, the transmitting UE and the receiving UE may initiate timers for BFR, where the transmitting UE and the receiving UE switch between phases of BFR and BFD based on these timers. For example, the transmitting UE or the receiving UE or both may initiate a first timer during BFR when performing beam reselection for the primary sidelink carrier. If the first timer expires, the UE may move to the next phase of the BFR procedure and initiate a second timer for performing a random access procedure for the primary sidelink carrier before declaring RLF.

[0007] A method for wireless communication at a first UE is described. The method may include: transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating switching the primary sidelink carrier to the set of beams.

[0008] A device for wireless communication at a first UE is described. The device may include a processor and a memory coupled to the processor. The memory may include instructions executable by the processor to cause the device to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; receive a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and transmit a control message via layer 1 signaling or layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0009] Another device for wireless communication at a first UE is described. The device may include: means for transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; means for receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and means for transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0010] A non-transitory computer-readable medium storing code for wireless communication at a first UE is described. The code may include instructions executable by a processor to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; receive a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and transmit a control message via layer 1 signaling or layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0011] Some examples of the methods, devices, and non-transitory computer-readable media described herein may further include operations, features, means, or instructions for the following actions: transmitting sidelink control information via the set of beams based on a handover of the primary sidelink carrier to the set of beams.

[0012] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: maintaining a radio resource control link of a primary side link carrier based on a set of beams corresponding to the secondary side link carrier and switching the primary side link carrier to the set of beams corresponding to the secondary side link carrier.

[0013] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: determining that measurements of a set of beams corresponding to the secondary side link carrier meet a threshold associated with maintaining a radio resource control link of the primary side link carrier, wherein transmitting the control message may be based on the measurements of the set of beams meeting the threshold.

[0014] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the control message may be transmitted based on measurements of a set of beams corresponding to the secondary side link carrier being higher than measurements of a second set of beams corresponding to the primary side link carrier.

[0015] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the control message may be transmitted prior to a BFD procedure based on the beam failure instance.

[0016] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: initiating a BFD procedure based on the beam failure instance, wherein the control message may be transmitted during the BFD procedure.

[0017] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: initiating a BFR procedure based on the number of beam failure instances meeting a threshold, wherein the control message may be transmitted during the BFR procedure.

[0018] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the measurement message may be received based on the number of beam failure instances meeting a threshold.

[0019] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: receiving a second control message indicating BFD and initiating a first BFR timer based on the BFD.

[0020] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: detecting the expiration of the first BFR timer, wherein transmitting the control message may be based on the expiration of the first BFR timer.

[0021] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the first BFR timer may be associated with beam reselection.

[0022] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: detecting the expiration of the first BFR timer and initiating a second BFR timer associated with performing a random access procedure for the primary sidelink carrier.

[0023] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the primary sidelink carrier corresponds to a first frequency range, and the secondary sidelink carrier corresponds to a second frequency range.

[0024] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the primary sidelink carrier corresponds to a first radio frequency spectrum band in the radio frequency range, and the secondary sidelink carrier corresponds to a second radio frequency spectrum band in the radio frequency range.

[0025] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the primary sidelink carrier and the secondary sidelink carrier correspond to the same radio frequency spectrum band.

[0026] A method for wireless communication at a first UE is described. The method may include: transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiating a first timer associated with BFR based on a BFD of the primary sidelink carrier; and transmitting a set of BFR reference signals via one or more beams of the primary sidelink carrier when the first timer associated with BFR is active.

[0027] Describes an apparatus for wireless communication at a first UE. The apparatus may include a processor and a memory coupled to the processor. The memory may include instructions that can be executed by the processor to cause the apparatus to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with a BFR based on the BFD of the primary sidelink carrier; and when the first timer associated with the BFR is active, transmit a set of BFR reference signals via one or more beams of the primary sidelink carrier.

[0028] Describes another apparatus for wireless communication at a first UE. The apparatus may include: means for transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; means for initiating a first timer associated with a BFR based on the BFD of the primary sidelink carrier; and means for transmitting a set of BFR reference signals via one or more beams of the primary sidelink carrier when the first timer associated with the BFR is active.

[0029] Describes a non-transitory computer-readable medium storing code for wireless communication at a first UE. The code may include instructions that can be executed by a processor to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with a BFR based on the BFD of the primary sidelink carrier; and when the first timer associated with the BFR is active, transmit a set of BFR reference signals via one or more beams of the primary sidelink carrier.

[0030] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for the following actions: initiate a second timer associated with a BFR based on the expiration of the first timer, and perform a random access procedure for the primary sidelink carrier when the second timer is active.

[0031] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for the following actions: receive a control message indicating the BFD of the primary sidelink carrier based on the number of beam failure instances meeting a threshold, wherein initiating the first timer may be based on the control message indicating BFD.

[0032] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: detecting a beam failure of the primary sidelink carrier based on a beam failure timer at a first UE exceeding a threshold.

[0033] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, transmitting the set of BFR reference signals may include operations, features, components, or instructions for the following actions: transmitting the set of BFR reference signals via a subset of BFR reference signal resources from a set of BFR reference signal resources.

[0034] A method for wireless communication at a second UE is described. The method may include: receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; transmitting a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and receiving, based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, a control message via layer 1 signaling or layer 2 signaling, the control message indicating switching the primary sidelink carrier to the set of beams.

[0035] An apparatus for wireless communication at a second UE is described. The apparatus may include a processor and a memory coupled to the processor. The memory may include instructions executable by the processor to cause the apparatus: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; transmit a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and receive, based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, a control message via layer 1 signaling or layer 2 signaling, the control message indicating switching the primary sidelink carrier to the set of beams.

[0036] Describes another apparatus for wireless communication at a second UE. The apparatus may include: means for receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; means for transmitting a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and means for receiving a control message via layer 1 signaling or layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating switching the primary sidelink carrier to the set of beams.

[0037] Describes a non-transitory computer-readable medium storing code for wireless communication at a second UE. The code may include instructions executable by a processor to: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; transmit a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier; and receive a control message via layer 1 signaling or layer 2 signaling based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating switching the primary sidelink carrier to the set of beams.

[0038] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for the following actions: receiving sidelink control information via the set of beams based on switching the primary sidelink carrier to the set of beams.

[0039] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, the control message may be received prior to a BFD procedure based on the beam failure instance.

[0040] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for the following actions: initiating a BFD procedure based on the beam failure instance, wherein the control message may be received during the BFD procedure.

[0041] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may further include operations, features, components, or instructions for the following actions: initiating a BFR procedure based on the number of beam failure instances meeting a threshold, wherein the control message may be received during the BFR procedure.

[0042] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: determining that the number of beam failure instances meets a threshold, wherein transmitting the measurement message may be based on the number of beam failure instances meeting the threshold.

[0043] A method for wireless communication at a second UE is described. The method may include: receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiating a first timer associated with a BFR based on a BFD of the primary sidelink carrier; and when the first timer associated with the BFR is active, monitoring a set of BFR reference signals via one or more beams of the primary sidelink carrier.

[0044] An apparatus for wireless communication at a second UE is described. The apparatus may include a processor and a memory coupled to the processor. The memory may include instructions executable by the processor to cause the apparatus to: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with a BFR based on a BFD of the primary sidelink carrier; and when the first timer associated with the BFR is active, monitor a set of BFR reference signals via one or more beams of the primary sidelink carrier.

[0045] Another apparatus for wireless communication at a second UE is described. The apparatus may include: means for receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; means for initiating a first timer associated with a BFR based on a BFD of the primary sidelink carrier; and means for monitoring a set of BFR reference signals via one or more beams of the primary sidelink carrier when the first timer associated with the BFR is active.

[0046] A non-transitory computer-readable medium storing code for wireless communication at a second UE is described. The code may include instructions executable by a processor to: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with a BFR based on a BFD of the primary sidelink carrier; and when the first timer associated with the BFR is active, monitor a set of BFR reference signals via one or more beams of the primary sidelink carrier.

[0047] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: initiating a second timer associated with a BFR based on the expiration of the first timer, and performing a random access procedure for the primary sidelink carrier while the second timer is active.

[0048] Some examples of the methods, apparatuses, and non-transitory computer-readable media described herein may also include operations, features, components, or instructions for the following actions: sending a control message indicating a BFD of the primary sidelink carrier based on the number of beam failure instances meeting a threshold, wherein initiating the first timer may be based on the control message indicating a BFD.

[0049] In some examples of the methods, apparatuses, and non-transitory computer-readable media described herein, sending the set of BFR reference signals may include operations, features, components, or instructions for the following actions: monitoring the set of BFR reference signals via a subset of BFR reference signal resources from a set of BFR reference signal resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Examples of wireless communication systems that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0051] Figure 2 Examples of wireless communication systems that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0052] Figure 3 Examples of flowcharts that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0053] Figure 4 Examples of process flows that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0054] Figure 5 Examples of flowcharts that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0055] Figure 6 Examples of process flows that illustrate techniques supporting primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure are shown.

[0056] Figure 7An example of a flowchart illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown.

[0057] Figure 8 An example of a process flow illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown.

[0058] Figure 9 and Figure 10 A block diagram of an apparatus illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown.

[0059] Figure 11 A block diagram of a communication manager illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown.

[0060] Figure 12 A diagram of a system including an apparatus illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown.

[0061] Figures 13 to 16 A flowchart of a method illustrating techniques supporting primary side - link carrier updates in side - link carrier aggregation in accordance with one or more aspects of the present disclosure is shown. Detailed Description

[0062] In some wireless communication systems, a first user equipment (UE) may communicate with a second UE using side - link carrier aggregation, where the first UE and the second UE may communicate via a primary side - link carrier and one or more secondary side - link carriers. The primary side - link carrier may be used for control signaling, and the secondary side - link carriers may be used for data and control signaling. In some cases, a secondary side - link carrier may be removed, activated, or deactivated based on throughput. During communication between the first UE and the second UE, radio link monitoring (RLM) and radio link failure (RLF) may be managed and announced via the primary side - link carrier rather than the secondary side - link carriers. In some cases, if the primary side - link carrier experiences a beam failure or performs beam failure recovery (BFR), the UE may perform a random access procedure to re - establish the primary side - link carrier. If the random access procedure is unsuccessful, the UE may announce an RLF. However, announcing an RLF for the primary side - link carrier may suspend signaling for other secondary side - link carriers and may cause an increase in communication latency between the first UE and the second UE.

[0063] In some examples, the UE may perform independent beam management procedures for each component carrier. In some cases, the transmitting UE may independently configure and transmit beam failure detection (BFD) reference signals (BFD-RS) on the primary sidelink carrier and the secondary sidelink carriers. In some examples, if the primary sidelink carrier experiences a beam failure but one of the secondary sidelink carriers is available, the UE may switch the primary sidelink carrier to one of the available secondary carriers. For example, in the case where another secondary sidelink carrier is available, the transmitting UE may perform a primary sidelink carrier beam change, handover, or reselection by conveying auxiliary information to the receiving UE via the secondary sidelink carrier.

[0064] The techniques, systems, and methods of the present disclosure may support performing primary sidelink carrier handovers at different times with respect to the BFD and BFR procedures. In some cases, the transmitting UE may initiate a BFR and may attempt a random access procedure to recover the primary sidelink carrier. In the case where the random access procedure is unsuccessful but one of the secondary sidelink carriers is available, the UE may attempt to change the primary sidelink carrier to one of the available secondary sidelink carriers. In some examples related to the techniques described elsewhere herein, the transmitting UE may change the primary sidelink carrier before detecting a beam failure and performing the BFD procedure. For example, if the UE determines that a secondary sidelink carrier has a higher quality than the primary sidelink carrier before detecting a beam failure and performing a BFR, the UE may change the primary sidelink carrier to the secondary sidelink carrier. In some other examples, the transmitting UE may change the primary sidelink carrier before performing a random access procedure during a BFR. In some examples described herein, the transmitting UE and the receiving UE may initiate timers for the BFR, where the transmitting UE and the receiving UE switch between phases of the BFR and BFD based on these timers. For example, the transmitting UE or the receiving UE or both may start a first timer during a BFR when performing beam reselection for the primary sidelink carrier. If the first timer expires, the UE may move to the next phase of the BFR procedure and start a second timer for performing a random access procedure for the primary sidelink carrier before declaring an RLF.

[0065] Aspects of the present disclosure are first described in the context of a wireless communication system. Aspects of the present disclosure are further illustrated and described by means of apparatus diagrams, system diagrams, and flowcharts related to techniques for primary sidelink carrier updates in sidelink carrier aggregation.

[0066] Figure 1An example of a wireless communication system 100 that illustrates techniques supporting primary side-link carrier updates in side-link carrier aggregation in accordance with one or more aspects of the present disclosure is provided. The wireless communication system 100 may include one or more network entities 105, one or more UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, a New Radio (NR) network, or a network operating in accordance with other systems and radio technologies including future systems and radio technologies not explicitly mentioned herein.

[0067] The network entities 105 may be dispersed throughout a geographic area to form the wireless communication system 100 and may include devices in different forms or having different capabilities. In various examples, the network entities 105 may be referred to as network elements, mobility elements, radio access network (RAN) nodes, or network equipment, among other designations. In some examples, the network entities 105 and the UEs 115 may communicate wirelessly via one or more communication links 125 (e.g., radio frequency (RF) access links). For example, the network entity 105 may support a coverage area 110 (e.g., a geographic coverage area) within which the UEs 115 and the network entity 105 may establish one or more communication links 125. The coverage area 110 may be an example of a geographic area within which the network entity 105 and the UEs 115 may support the conveyance of signals in accordance with one or more radio access technologies (RATs).

[0068] The UEs 115 may be dispersed throughout the coverage area 110 of the wireless communication system 100, and each UE 115 may be stationary or mobile or stationary and mobile at different times. The UEs 115 may be devices in different forms or having different capabilities. Figure 1 Some example UEs 115 are illustrated. The UEs 115 described herein may be capable of supporting communication with various types of devices (such as other UEs 115 or network entities 105 as Figure 1 illustrated).

[0069] As described herein, a node of the wireless communication system 100 (which may be referred to as a network node or a wireless node) can be a network entity 105 (e.g., any network entity described herein), a UE 115 (e.g., any UE described herein), a network controller, a device, an equipment, a computing system, one or more components, or another suitable processing entity configured to perform any of the techniques described herein. For example, the node can be a UE 115. As another example, the node can be a network entity 105. As yet another example, a first node can be configured to communicate with a second node or a third node. In one aspect of this example, the first node can be a UE 115, the second node can be a network entity 105, and the third node can be a UE 115. In another aspect of this example, the first node can be a UE 115, the second node can be a network entity 105, and the third node can be a network entity 105. In other aspects of this example, the first node, the second node, and the third node can be different from these examples. Similarly, references to UE 115, network entity 105, device, equipment, computing system, etc. can include the disclosure of UE 115, network entity 105, device, equipment, computing system, etc. as nodes. For example, the disclosure that UE 115 is configured to receive information from network entity 105 also discloses that a first node is configured to receive information from a second node.

[0070] In some examples, network entity 105 can communicate with core network 130 or with each other or both. For example, network entity 105 can communicate with core network 130 via one or more backhaul communication links 120 (e.g., according to S1, N2, N3, or other interface protocols). In some examples, network entity 105 can communicate with each other directly (e.g., directly between network entities 105) or indirectly (e.g., via core network 130) via backhaul communication link 120 (e.g., according to X2, Xn, or other interface protocols). In some examples, network entity 105 can communicate with each other via midhaul communication link 162 (e.g., according to midhaul interface protocol) or fronthaul communication link 168 (e.g., according to fronthaul interface protocol) or any combination thereof. Backhaul communication link 120, midhaul communication link 162, or fronthaul communication link 168 can be or include one or more wired links (e.g., electrical link, optical fiber link), one or more wireless links (e.g., radio link, wireless optical link), etc. or various combinations thereof. UE 115 can communicate with core network 130 via communication link 155.

[0071] One or more of the network entities 105 described herein may include or may be referred to as a base station 140 (e.g., transceiver base station, radio base station, NR base station, access point, radio transceiver, Node B, evolved Node B (eNB), next-generation Node B or giga Node B (any of which may be referred to as gNB), 5G NB, next-generation eNB (ng-eNB), home Node B, home evolved Node B, or other suitable terms). In some examples, the network entity 105 (e.g., base station 140) may be implemented in an integrated (e.g., monolithic, stand-alone) base station architecture that may be configured to utilize a protocol stack physically or logically integrated within a single network entity 105 (e.g., a single RAN node, such as base station 140).

[0072] In some examples, the network entity 105 may be implemented in a disaggregated architecture (e.g., disaggregated base station architecture, disaggregated RAN architecture) that may be configured to utilize a protocol stack physically or logically distributed between two or more network entities 105 (such as an integrated access backhaul (IAB) network, open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance), or virtualized RAN (vRAN) (e.g., cloud RAN (C-RAN))). For example, the network entity 105 may include one or more of the following: a central unit (CU) 160, a distributed unit (DU) 165, a radio unit (RU) 170, a RAN intelligent controller (RIC) 175 (e.g., near real-time RIC (near RT RIC), non-real-time RIC (non RT RIC)), a service management and orchestration (SMO) 180 system, or any combination thereof. The RU 170 may also be referred to as a radio head, intelligent radio head, remote radio head (RRH), remote radio unit (RRU), or transmit receive point (TRP). One or more components of the network entity 105 in the disaggregated RAN architecture may be co-located, or one or more components of the network entity 105 may be located in distributed locations (e.g., separate physical locations). In some examples, one or more network entities 105 of the disaggregated RAN architecture may be implemented as virtual units (e.g., virtual CU (VCU), virtual DU (VDU), virtual RU (VRU)).

[0073] The functional split between the CU 160, DU 165, and RU 170 is flexible and can support different functions, depending on which functions are performed at the CU 160, DU 165, or RU 170 (e.g., network layer functions, protocol layer functions, baseband functions, RF functions, and any combination thereof). For example, a functional split of the protocol stack can be employed between the CU 160 and the DU 165 such that the CU 160 can support one or more layers of the protocol stack and the DU 165 can support one or more different layers of the protocol stack. In some examples, the CU 160 can host higher protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functions and signaling (e.g., radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP)). The CU 160 can be connected to one or more DU 165s or RU 170s, and one or more DU 165s or RU 170s can host lower protocol layers, such as layer 1 (L1) (e.g., physical (PHY) layer) or L2 (e.g., radio link control (RLC) layer, media access control (MAC) layer) functionality and signaling, and can each be at least partially controlled by the CU 160. Additionally or alternatively, a functional split of the protocol stack can be employed between the DU 165 and the RU 170 such that the DU 165 can support one or more layers of the protocol stack and the RU 170 can support one or more different layers of the protocol stack. The DU 165 can support one or more different cells (e.g., via one or more RU 170s). In some cases, the functional split between the CU 160 and the DU 165 or between the DU 165 and the RU 170 can be within a protocol layer (e.g., some functions of a protocol layer can be performed by one of the CU 160, DU 165, or RU 170, while other functions of that protocol layer are performed by a different one of the CU 160, DU 165, or RU 170). The CU 160 can be further functionally split into a CU control plane (CU-CP) and a CU user plane (CU-UP) function. The CU 160 can be connected to one or more DU 165s via an intermediate transport communication link 162 (e.g., F1, F1-c, F1-u), and the DU 165 can be connected to one or more RU 170s via a fronthaul communication link 168 (e.g., open fronthaul (FH) interface). In some examples, the intermediate transport communication link 162 or the fronthaul communication link 168 can be implemented according to the interfaces (e.g., channels) between the layers of the protocol stack, the layers of which are supported by the respective network entities 105 communicating via these communication links).

[0074] In some wireless communication systems (e.g., wireless communication system 100), the infrastructure and spectrum resources for radio access may support wireless backhaul link capabilities to supplement a wired backhaul connection and thereby provide an IAB network architecture (e.g., to a core network 130). In some cases, in an IAB network, one or more network entities 105 (e.g., IAB nodes 104) may be controlled in part by each other. One or more IAB nodes 104 may be referred to as donor entities or IAB donors. One or more DUs 165 or one or more RUs 170 may be controlled in part by one or more CUs 160 associated with a donor network entity 105 (e.g., donor base station 140). One or more donor network entities 105 (e.g., IAB donors) may communicate with one or more additional network entities 105 (e.g., IAB nodes 104) via the supported access and backhaul links (e.g., backhaul communication link 120). An IAB node 104 may include an IAB mobile terminal (IAB-MT) controlled (e.g., scheduled) by a DU 165 of a coupled IAB donor. The IAB-MT may include a separate antenna set for relaying communication with a UE 115 or may share the same antenna (e.g., of an RU 170 of the IAB node 104) for access via the DU 165 of the IAB node 104 (e.g., referred to as a virtual IAB-MT (vIAB-MT)). In some examples, the IAB node 104 may include a DU 165 that supports communication links with additional entities (e.g., IAB nodes 104, UEs 115) within a relay chain or configuration (e.g., downstream) of the access network. In such cases, one or more components of a split RAN architecture (e.g., one or more IAB nodes 104 or components of an IAB node 104) may be configured to operate in accordance with the techniques described herein.

[0075] For example, the access network (AN) or RAN may include communication between an access node (e.g., an IAB donor), an IAB node 104, and one or more UEs 115. The IAB donor may facilitate the connection between the core network 130 and the AN (e.g., via a wired or wireless connection to the core network 130). That is, the IAB donor may refer to a RAN node having a wired or wireless connection to the core network 130. The IAB donor may include a CU 160 and at least one DU 165 (e.g., and an RU 170), in which case the CU 160 may communicate with the core network 130 via an interface (e.g., a backhaul link). The IAB donor and the IAB node 104 may communicate via an F1 interface according to a protocol that defines signaling messages (e.g., the F1 AP protocol). Additionally or alternatively, the CU 160 may communicate with the core network via an interface (which may be an example of a part of the backhaul link) and may communicate with other CUs 160 (e.g., CUs 160 associated with alternative IAB donors) via an Xn-C interface (which may be an example of a part of the backhaul link).

[0076] The IAB node 104 may refer to a RAN node that provides IAB functionality (e.g., access for UEs 115, wireless self-backhaul capabilities, etc.). The DU 165 may act as a distributed scheduling node towards the child nodes associated with the IAB node 104, and the IAB-MT may act as a scheduled node towards the parent node associated with the IAB node 104. That is, the IAB donor may be referred to as a parent node that communicates with one or more child nodes (e.g., the IAB donor may relay the transmission of a UE through one or more other IAB nodes 104). Additionally or alternatively, depending on the relay chain or configuration of the AN, the IAB node 104 may also be referred to as a parent node or a child node of other IAB nodes 104. Thus, the IAB-MT entity of the IAB node 104 may provide a Uu interface for the child IAB node 104 to receive signaling from the parent IAB node 104, and the DU interface (e.g., the DU 165) may provide a Uu interface for the parent IAB node 104 to signal to the child IAB node 104 or the UE 115.

[0077] For example, the IAB node 104 may be referred to as a parent node that supports communication for a child IAB node or as a child IAB node associated with an IAB donor or both. The IAB donor may include a CU 160 having a wired or wireless connection (e.g., a fronthaul communication link 120) to the core network 130 and may act as the parent node of the IAB node 104. For example, the DU 165 of the IAB donor may relay transmissions to the UE 115 via the IAB node 104, or may signal transmissions directly to the UE 115, or both. The CU 160 of the IAB donor may signal the communication link establishment to the IAB node 104 via the F1 interface, and the IAB node 104 may schedule transmissions (e.g., transmissions relayed from the IAB donor to the UE 115) via the DU 165. That is, data may be relayed to and from the IAB node 104 via signaling over the NR Uu interface to the MT of the IAB node 104. Communication with the IAB node 104 may be scheduled by the DU 165 of the IAB donor, and communication with the IAB node 104 may be scheduled by the DU 165 of the IAB node 104.

[0078] In the case where the techniques described herein are applied in the context of a split RAN architecture, one or more components of the split RAN architecture may be configured to support the techniques described herein for primary side link carrier update in side link carrier aggregation. For example, some operations described as being performed by the UE 115 or the network entity 105 (e.g., the base station 140) may additionally or alternatively be performed by one or more components of the split RAN architecture (e.g., the IAB node 104, the DU 165, the CU 160, the RU 170, the RIC 175, the SMO 180).

[0079] The UE 115 may include or may be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device or some other suitable term, where "device" may also be referred to as a unit, a station, a terminal, or a client, etc. The UE 115 may also include or may 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 may be referred to as a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communication (MTC) device, etc., which may be implemented in various objects such as appliances or vehicles, meters, etc.

[0080] The UE 115 described herein may be capable of communicating with various types of devices, such as other UEs 115 that may sometimes act as relays, and network entities 105 and network equipment including macro eNBs or gNBs, small cell eNBs or gNBs, or relay base stations, etc., as Figure 1 shown.

[0081] The UE 115 and the network entity 105 may communicate wirelessly with each other via one or more communication links 125 (e.g., access links) using resources associated with one or more carriers. The term "carrier" may refer to a set of RF spectral resources having a defined physical layer structure for supporting the communication link 125. For example, a carrier for the communication link 125 may include a portion (e.g., bandwidth part (BWP)) of an RF spectral band operating 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 acquisition signaling (e.g., synchronization signals, system information), control signaling for coordinating carrier operation, user data, or other signaling. The wireless communication system 100 may support communication with the UE 115 using carrier aggregation or multi-carrier operation. According to a carrier aggregation configuration, the UE 115 may be configured to have multiple downlink component carriers and one or more uplink component carriers. Carrier aggregation may be used for both frequency division duplex (FDD) and time division duplex (TDD) component carriers. Communication between the network entity 105 and other devices may refer to communication between these devices and any part (e.g., entity, sub-entity) of the network entity 105. For example, the terms "transmit", "receive", or "communicate" when referring to the network entity 105 may refer to any part of the network entity 105 of the RAN (e.g., base station 140, CU 160, DU 165, RU 170) communicating with another device (e.g., directly or via one or more other network entities 105).

[0082] In some examples, such as in a carrier aggregation configuration, a carrier may also have acquisition signaling or control signaling for coordinating the operation of other carriers. A carrier may be associated with a frequency channel (e.g., evolved universal mobile telecommunications system terrestrial radio access (E-UTRA) absolute RF channel number (EARFCN)) and may be identified according to a channel raster for discovery by the UE 115. A carrier may operate in independent mode, in which case initial acquisition and connection may be performed by the UE 115 via the carrier, or a carrier may operate in non-independent mode, in which case a different carrier (e.g., of the same or different radio access technology) is used to anchor the connection.

[0083] The communication link 125 shown in the wireless communication system 100 may include a downlink transmission (e.g., forward link transmission) from the network entity 105 to the UE 115, an uplink transmission (e.g., reverse link transmission) from the UE 115 to the network entity 105, or both, as well as other transmission configurations. A carrier may carry downlink communication or uplink communication (e.g., in FDD mode), or may be configured to carry both downlink communication and uplink communication (e.g., in TDD mode).

[0084] A carrier may be associated with a particular bandwidth of the RF spectrum, and in some examples, the carrier bandwidth may be referred to as the "system bandwidth" of the carrier or the wireless communication system 100. For example, the carrier bandwidth may be one of a set of bandwidths for carriers of a particular radio access technology (e.g., 1.4 megahertz (MHz), 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, 40 MHz, or 80 MHz). Devices of the wireless communication system 100 (e.g., the network entity 105, the UE 115, or both) may have a hardware configuration that supports communication using a particular carrier bandwidth, or may be capable of being configured to support communication using one of a set of carrier bandwidths. In some examples, the wireless communication system 100 may include a network entity 105 or a UE 115 that supports concurrent communication using carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 may be configured to operate using a portion (e.g., subband, BWP) or all of the carrier bandwidth.

[0085] The signal waveform transmitted via a carrier may include 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 employing an MCM technique, a resource element may refer to the resource of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, in which case the symbol period and the subcarrier spacing may be inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme, the decoding rate of the modulation scheme, or both), such that a relatively high number of resource elements (e.g., during the transmission duration) and a relatively high order of the modulation scheme may correspond to a relatively high communication rate. Wireless communication resources may refer to a combination of RF spectrum resources, time resources, and spatial resources (e.g., spatial layers or beams), and the use of multiple spatial resources may increase the data rate or data integrity for communication with the UE 115.

[0086] One or more parameter sets for a carrier may be supported, and the parameter sets may include subcarrier spacing (Δf) and cyclic prefixes. A carrier may be divided into one or more BWPs with the same or different parameter sets. 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 communications of a UE 115 may be constrained to one or more active BWPs.

[0087] The time interval for the network entity 105 or the UE 115 may be expressed in multiples of a basic time unit, which may be, for example, a sampling period T s =1 / (Δf max ·N f ) seconds, where Δf max It can represent the supported subcarrier spacing, and N f The supported discrete Fourier transform (DFT) size may be indicated. The time intervals of the communication resources 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., in the range of 0 to 1023).

[0088] Each frame may include multiple consecutively numbered subframes or time slots, and each subframe or time slot may have the same duration. In some examples, the frame may be divided into subframes (e.g., in the time domain), and each subframe may be further divided into a certain number of time slots. Alternatively, each frame may include a variable number of time slots, and the number of time slots may depend on the subcarrier spacing. Each time slot may include a certain number of symbol periods (e.g., depending on the length of the cyclic prefix appended in front of each symbol period). In some wireless communication systems 100, the time slot may be further divided into a plurality of micro time slots associated with one or more symbols. Excluding the cyclic prefix, each symbol period may be associated with one or more (e.g., N f The duration of a symbol period may depend on the subcarrier spacing or the operating frequency band.

[0089] A subframe, slot, mini-slot, or symbol may be the smallest scheduling unit (e.g., in the time domain) of the wireless communication system 100 and may be referred to as a transmit 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 communication system 100 may be dynamically selected (e.g., in a burst of a shortened TTI (sTTI)).

[0090] Physical channels can be reused according to various techniques for communication using a carrier. For example, one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques can be used to multiplex physical control channels and physical data channels to signal via a downlink carrier. The control region of a physical control channel (e.g., control resource set (CORESET)) can be defined by a set of symbol periods and can extend across the system bandwidth of a carrier or a subset of the system bandwidth. One or more control regions (e.g., CORESET) can be configured for a set of UEs 115. For example, one or more of the UEs 115 can monitor or search a control region for control information according to one or more search space sets, and each search space set can include one or more control channel candidates in one or more aggregation levels arranged in a cascaded manner. The aggregation level of a control channel candidate can refer to the amount of control channel resources (e.g., control channel elements (CCE)) associated with the coded information for a control information format with a given payload size. The search space sets can include: a common search space set configured to transmit control information to multiple UEs 115, and a UE-specific search space set for transmitting control information to a specific UE 115.

[0091] Network entity 105 can provide communication coverage via one or more cells (e.g., macro cells, small cells, hotspots, or other types of cells or any combination thereof). The term "cell" can refer to a logical communication entity for communicating with network entity 105 (e.g., using a carrier) and can be associated with an identifier (e.g., physical cell identifier (PCID), virtual cell identifier (VCID), or other identifier) for distinguishing adjacent cells. In some examples, a cell can also refer to a coverage area 110 or a portion of the coverage area 110 (e.g., a sector) within which the logical communication entity operates. Depending on various factors (such as the capabilities of network entity 105), the scope of such cells can range from a smaller area (e.g., a structure, a subset of a structure) to a larger area. For example, a cell can be or can include a building, a subset of a building, or an external space between or overlapping with coverage areas 110, etc.

[0092] Macro cells typically cover a relatively large geographical area (e.g., with a radius of several kilometers) and may allow unrestricted access by UEs 115 having a service subscription with the network provider supporting the macro cell. Compared to macro cells, small cells may be associated with lower power network entities 105 (e.g., lower power base stations 140), and small cells may operate using the same or different (e.g., licensed, unlicensed) frequency bands as macro cells. Small cells may provide unrestricted access to UEs 115 having a service subscription with the network provider, or may provide restricted access to UEs 115 associated with the small cell (e.g., UEs 115 in a closed subscriber group (CSG), UEs 115 associated with users in a home or office). Network entity 105 may support one or more cells and may also support communication via one or more cells using one or more component carriers.

[0093] In some examples, a carrier may support multiple cells and may be configured with different cells according to different protocol types that may provide access for different types of devices (e.g., MTC, narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)).

[0094] In some examples, network entity 105 (e.g., base station 140, RU 170) may be movable and thus provide communication coverage for a mobile coverage area 110. In some examples, different coverage areas 110 associated with different technologies may overlap, but different coverage areas 110 may be supported by the same network entity 105. In some other examples, overlapping coverage areas 110 associated with different technologies may be supported by different network entities 105. Wireless communication system 100 may include, for example, a heterogeneous network in which different types of network entities 105 use the same or different radio access technologies to provide coverage for various coverage areas 110.

[0095] Wireless communication system 100 may support synchronous or asynchronous operation. For synchronous operation, network entity 105 (e.g., base station 140) may have similar frame timing, and transmissions from different network entities 105 may be approximately aligned in time. For asynchronous operation, network entity 105 may have different frame timing, and in some examples, transmissions from different network entities 105 may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operation.

[0096] Some UEs 115 (such as MTC or IoT devices) can be low-cost or low-complexity devices and can allow for automated communication between machines (e.g., via machine-to-machine (M2M) communication). M2M communication or MTC can refer to data communication technologies that allow devices to communicate with each other or a device to communicate with a network entity 105 (e.g., base station 140) without human intervention. In some examples, M2M communication or MTC can include communication from devices with integrated sensors or meters to measure or capture information and relay such information to a central server or application that uses the information or presents the information to a person interacting with the application. Some UEs 115 can be designed to collect information or enable automated behavior of machines or other devices. Examples of applications for MTC devices include: smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wilderness survival monitoring, weather and geographical event monitoring, formation management and tracking, remote security sensing, physical access control, and transaction-based commercial charging.

[0097] Some UEs 115 can be configured to operate in power-saving modes, such as half-duplex communication (e.g., a mode that supports one-way communication via transmission or reception but not concurrent transmission and reception). In some examples, half-duplex communication can be performed at a reduced peak rate. Other energy-saving techniques for UEs 115 include: entering a power-saving deep sleep mode when not participating in active communication, operating using limited bandwidth (e.g., according to narrowband communication), or a combination of these techniques. For example, some UEs 115 can be configured to operate using a narrowband protocol type associated with a defined portion or range within a carrier, within a guard band of the carrier, or outside the carrier (e.g., a set of subcarriers or resource blocks (RBs)).

[0098] The wireless communication system 100 can be configured to support ultra-reliable communication or low-latency communication or various combinations thereof. For example, the wireless communication system 100 can be configured to support ultra-reliable low-latency communication (URLLC). The UEs 115 can be designed to support ultra-reliable or low-latency or critical functions. Ultra-reliable communication can include private communication or group communication and can be supported by one or more services (such as push-to-talk, video, or data). Support for ultra-reliable, low-latency functions can include prioritization of services, and such services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, and ultra-reliable low-latency can be used interchangeably herein.

[0099] In some examples, UE 115 may be configured to support communicating directly with other UEs 115 via a device-to-device (D2D) communication link 135 (e.g., according to a peer-to-peer (P2P), D2D, or sidelink protocol). In some examples, one or more UEs 115 performing D2D communication in a group may be within the coverage area 110 of a network entity 105 (e.g., base station 140, RU 170), and the network entity may support aspects of such D2D communication configured (e.g., scheduled) by the network entity 105. In some examples, one or more UEs 115 in such a group may be outside the coverage area 110 of the network entity 105, or may otherwise be unable or not configured to receive transmissions from the network entity 105. In some examples, a group of UEs 115 communicating via D2D communication may support a one-to-many (1:M) system, where each UE 115 transmits to each of the other UEs 115 in the group. In some examples, the network entity 105 may facilitate the scheduling of resources for D2D communication. In some other examples, D2D communication may be performed between UEs 115 without involving the network entity 105.

[0100] In some systems, the D2D communication link 135 may be an example of a communication channel (such as a sidelink communication channel) between vehicles (e.g., UE 115). In some examples, vehicles may communicate using vehicle-to-everything (V2X) communication, vehicle-to-vehicle (V2V) communication, or some combination of these. Vehicles may signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information related to the V2X system. In some examples, vehicles in a V2X system may communicate with roadside infrastructure (such as roadside units), or communicate with the network via vehicle-to-network (V2N) communication through one or more network nodes (e.g., network entity 105, base station 140, RU 170), or both.

[0101] The core network 130 can provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 can be an evolved packet core (EPC) or a 5G core (5GC), which can include at least one control plane entity for managing access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity for routing packets or interconnecting to external networks (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). The control plane entity can manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management of the UE 115 served by a network entity 105 (e.g., a base station 140) associated with the core network 130. User IP packets can be transferred through the user plane entity, which can provide IP address allocation and other functions. The user plane entity can be connected to the IP services 150 of one or more network operators. The IP services 150 can include access to the Internet, an intranet, an IP multimedia subsystem (IMS), or packet-switched streaming services.

[0102] The wireless communication system 100 can operate using one or more frequency bands that can be in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or the decimeter band, because the wavelength ranges from approximately one decimeter to one meter in length. UHF waves can be blocked or redirected by buildings and environmental features (which can be referred to as clutter), but these waves can be sufficient to penetrate structures so that a macro cell can serve a UE 115 located indoors. Compared to communication using smaller frequencies and longer wavelengths in the high frequency (HF) or very high frequency (VHF) portions of the spectrum below 300 MHz, communication using UHF waves can be associated with smaller antennas and shorter ranges (e.g., less than 100 kilometers).

[0103] The wireless communication system 100 may also operate in the Super High Frequency (SHF) region (also known as the centimeter band) that can be in the range of 3 GHz to 30 GHz or in the Extremely High Frequency (EHF) region of the spectrum (e.g., 30 GHz to 300 GHz) (also known as the millimeter band). In some examples, the wireless communication system 100 may support millimeter wave (mmW) communication between the UE 115 and the network entity 105 (e.g., the base station 140, the RU 170), and the EHF antennas of the corresponding devices may be smaller and closer spaced than UHF antennas. In some examples, such techniques may facilitate the use of antenna arrays within a device. However, the propagation of EHF transmissions may have even greater attenuation and shorter range compared to SHF or UHF transmissions. The techniques disclosed herein may be employed across transmissions using one or more different frequency regions, and the use of frequency bands designated across these frequency regions may vary by country or regulatory body.

[0104] The wireless communication system 100 may utilize licensed and unlicensed RF spectrum bands. For example, the wireless communication system 100 may use an unlicensed band (such as the 5 GHz Industrial, Scientific, and Medical (ISM) band) to employ Licensed-Assisted Access (LAA), Long-Term Evolution Unlicensed (LTE-U) radio access technology, or NR technology. When operating using an unlicensed RF spectrum band, devices such as the network entity 105 and the UE 115 may employ carrier sensing for collision detection and avoidance. In some examples, operations using an unlicensed band may be based on a carrier aggregation configuration (e.g., LAA) in combination with a component carrier operating using a licensed band. Operations using unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer (P2P) transmissions, device-to-device (D2D) transmissions, and so on.

[0105] The network entity 105 (e.g., the base station 140, the RU 170) or the UE 115 may be equipped with multiple antennas that can be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communication, or beamforming. The antennas of the network entity 105 or the UE 115 may be located within one or more antenna arrays or antenna panels, which can support MIMO operations or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some examples, the antennas or antenna arrays associated with the network entity 105 may be located at different geographical locations. The network entity 105 may include an antenna array having a set of antenna ports in multiple rows and columns that the network entity 105 can use to support beamforming for communication with the UE 115. Similarly, the UE 115 may include one or more antenna arrays that can support various MIMO or beamforming operations. Additionally or alternatively, an antenna panel may support RF beamforming for signals transmitted via the antenna ports.

[0106] The network entity 105 or the UE 115 can use MIMO communication to utilize multipath signal propagation and improve spectral efficiency by transmitting or receiving multiple signals via different spatial layers. Such techniques may be referred to as spatial multiplexing. The multiple signals can be transmitted, for example, by the transmitting device via different antennas or different combinations of antennas. Similarly, the multiple signals can be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals can be referred to as a separate spatial stream and can carry information associated with the same data stream (e.g., the same codeword) or different data streams (e.g., different codewords). Different spatial layers can be associated with different antenna ports for channel measurement and reporting. MIMO techniques include: single-user MIMO (SU-MIMO), where multiple spatial layers are transmitted to the same receiving device; and multi-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

[0107] Beamforming (which may also be referred to as spatial filtering, directional transmission, or directional reception) is a signal processing technique that can be used at a transmitting device or a receiving device (e.g., network entity 105, UE 115) to shape or direct an antenna beam (e.g., a transmit beam, a receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming can be achieved by combining the signals conveyed via the antenna elements of an antenna array such that some signals propagating in a particular orientation relative to the antenna array experience constructive interference while other signals experience destructive interference. The adjustment of the signals conveyed via the antenna elements can include the transmitting device or the receiving device applying an amplitude offset, a phase offset, or both to the signals carried via the antenna elements associated with the device. The adjustment associated with each of these antenna elements can be defined by a set of beamforming weights associated with a particular orientation (e.g., relative to the antenna array of the transmitting device or the receiving device or relative to some other orientation).

[0108] The network entity 105 or the UE 115 may use beam scanning techniques as part of the beamforming operation. For example, the network entity 105 (e.g., the base station 140, the RU 170) may use multiple antennas or antenna arrays (e.g., antenna panels) to perform beamforming operations for directional communication with the UE 115. Some signals (e.g., synchronization signals, reference signals, beam selection signals, or other control signals) may be sent by the network entity 105 multiple times along different directions. For example, the network entity 105 may send signals according to different beamforming weight sets associated with different transmission directions. The transmissions along different beam directions may be used to identify (e.g., by the transmitting device, such as the network entity 105, or by the receiving device, such as the UE 115) the beam directions for later transmission or reception by the network entity 105.

[0109] Some signals (such as data signals associated with a specific receiving device) may be sent by the transmitting device (e.g., the transmitting network entity 105, the transmitting UE 115) along a single beam direction (e.g., the direction associated with the receiving device (such as the receiving network entity 105 or the receiving UE 115)). In some examples, the beam direction associated with the transmission along a single beam direction may be determined based on the signals transmitted along one or more beam directions. For example, the UE 115 may receive one or more of the signals sent by the network entity 105 along different directions and may report to the network entity 105 an indication of the signal that the UE 115 receives with the highest signal quality or other acceptable signal quality.

[0110] In some examples, transmissions performed by a device (e.g., by network entity 105 or UE 115) may be carried out using multiple beam directions, and the device may use a combination of digital precoding or beamforming to generate a combined beam for transmission (e.g., from network entity 105 to UE 115). UE 115 may report feedback indicating precoding weights for one or more beam directions, and the feedback may correspond to a configured beam set across the system bandwidth or one or more sub-bands. Network entity 105 may transmit reference signals (e.g., cell-specific reference signal (CRS), channel state information reference signal (CSI-RS)), which may or may not be precoded. UE 115 may provide feedback for beam selection, which may be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., multi-panel type codebook, linear combination type codebook, port selection type codebook). Although these techniques are described with reference to signals transmitted by network entity 105 (e.g., base station 140, RU 170) along one or more directions, UE 115 may use similar techniques for transmitting signals multiple times along different directions (e.g., for identifying beam directions used by UE 115 for subsequent transmissions or receptions), or for transmitting signals along a single direction (e.g., for transmitting data to a receiving device).

[0111] A receiving device (e.g., UE 115) may perform reception operations according to multiple reception configurations (e.g., directional listening) when receiving various signals (such as synchronization signals, reference signals, beam selection signals, or other control signals) from a receiving device (e.g., network entity 105). For example, the receiving device may perform reception according to multiple reception directions by: receiving via different antenna sub-arrays, processing the received signals according to different antenna sub-arrays, receiving according to different sets of receive beamforming weights (e.g., different directional listening weight sets) applied to signals received at multiple antenna elements of an antenna array, or processing the received signals according to different sets of receive beamforming weights applied to signals received at multiple antenna elements of an antenna array. Any of these operations may be referred to as "listening" according to different reception configurations or reception directions. In some examples, the receiving device may use a single reception configuration to receive along a single beam direction (e.g., when receiving a data signal). The single reception configuration may be aligned along a beam direction determined based on listening according to different reception configuration directions (e.g., a beam direction determined to have the highest signal strength, highest signal-to-noise ratio (SNR), or other acceptable signal quality based on listening according to multiple beam directions).

[0112] The wireless communication system 100 can be a packet-based network that operates according to a hierarchical protocol stack. In the user plane, the communication at the bearer or PDCP layer can be IP-based. The RLC layer can perform packet segmentation and reassembly for conveyance via logical channels. The MAC layer can perform priority handling and multiplexing of logical channels into transport channels. The MAC layer can also use error detection techniques, error correction techniques, or both to support retransmission to improve link efficiency. In the control plane, the RRC layer can provide the establishment, configuration, and maintenance of the RRC connection that supports the radio bearers for user plane data between the UE 115 and the network entity 105 or the core network 130. The PHY layer can map the transport channels to physical channels.

[0113] The UE 115 and the network entity 105 can support the retransmission of data to increase the likelihood that the data is successfully received. Hybrid automatic repeat request (HARQ) feedback is a technique for increasing the likelihood of correctly receiving data via a communication link (e.g., communication link 125, D2D communication link 135). HARQ can include a combination of error detection (e.g., using cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve the throughput at the MAC layer under poor radio conditions (e.g., low signal-to-noise ratio conditions). In some examples, the device can support same-slot HARQ feedback, in which case the device can provide HARQ feedback for the data received via the previous symbols in a particular slot in that slot. In some other examples, the device can provide HARQ feedback in a subsequent slot or according to some other time interval.

[0114] In some cases, the wireless communication system 100 can support mmW signaling for sidelink communication. For example, the wireless communication system 200 can support mmW sidelink communication for network, communication, and information systems (NCIS) and extended reality (XR), which can have high throughput and low latency. Additionally or alternatively, the wireless communication system 200 can offload Uu traffic from the Uu link to the sidelink, which can increase spectrum utilization efficiency and reduce latency. Using mmW communication via the sidelink (e.g., in frequency range 2, frequency range 2x, frequency range 4, etc.) can support high throughput and low latency communication.

[0115] In some examples, the wireless communication system can support beam management for the sidelink, such as beam management for mmW sidelink communication. The beam management procedure can compensate for the large path loss in mmW communication. Beam management can include initial beam pairing, beam maintenance, indication and update, and BFR, and other procedures. Such procedures can benefit mmW sidelink communication relative to the Uu link communication between the UE 115 and the network entity 105, because the communication can be offloaded from the Uu link, thereby freeing up space for other communications.

[0116] In some examples, mmW sidelink communication may support carrier aggregation. Carrier aggregation can be a technique for increasing throughput (e.g., increasing the data transmission rate over a given time period) by supporting a larger bandwidth than other techniques. In some cases, mmW communication for carrier aggregation can be used for signaling such as component carrier activation / deactivation, cross-carrier grant and beam indication, and multi-bit HARQ-ACK feedback. In some cases, mmW sidelink communication may support in-band or inter-band sidelink carrier aggregation, where the same or different component carriers are used for both Uu communication and sidelink communication. Thus, beam management, carrier aggregation, and other procedures that are conventionally performed on the Uu link can be performed using sidelink communication (including mmW sidelink communication) to increase efficiency and throughput and reduce the load on the Uu link.

[0117] In some examples, Uu link carrier aggregation may perform procedures on different cells. For example, Uu link carrier aggregation may include a primary cell (PCell) and one or more secondary cells (SCells). SCells can be added and removed or activated and deactivated from the Uu link without any additional procedures, whereas changing the PCell may constitute a cell handover procedure. UE 115 may measure the SCells of the Uu carrier aggregation scheme, but the PCell may announce or perform RLM and radio link failure (RLF). In some examples, the PCell and PUCCH-SCell may carry PUCCH messages, while other SCells may not be used for transmitting uplink control signaling. In some examples, random access channel (RACH) resources are available on the PCell but not on the SCells. In some examples, for the master cell group (MCG), the SCells may become dormant, but the PCell may remain active to maintain the connection between wireless devices.

[0118] In some cases, the Uu link may execute procedures such as the BFD procedure between the UE 115 and the network entity 105. In some cases, the network entity 105 may configure the UE 115 for BFD via each serving cell MAC entity when communicating with the UE 115. The UE 115 may be configured with a beam failure instance (BFI) counter (e.g., BFI_COUNTER) and a BFD timer (e.g., beamFailureDetectionTimer), and the BFI counter may be initially set to zero. When a beam failure is detected, the BFD timer may be reset, and the beam failure instance counter may be incremented by one. If the beam failure instance counter meets a threshold or reaches the beam failure instance maximum value (e.g., beamFialureInstanceMaxCount) and the serving cell associated with the beam failure instance counter is an SCell, the device (e.g., the network entity 105 or the UE 115) may initiate a BFR procedure. If the serving cell is not an SCell (e.g., the serving cell is a PCell), the device may initiate a RACH procedure on a secondary cell group (e.g., a group of SCells) to select a new serving cell from the secondary cell group (e.g., an SCell replacing the PCell).

[0119] In some examples, the BFD timer may expire, and the device may reset the beam failure instance counter to zero. In some examples, the BFD timer, the beam failure maximum count, or the reference signal for BFD may be reconfigured by the upper layer associated with the serving cell, and the device may reset the beam failure instance counter to zero. If the serving cell is the primary cell and the random access procedure initiated for BFR of the primary cell is successful, the device may reset the beam failure instance counter to zero, stop the BFR timer, and consider the BFR procedure successful. In some examples, the serving cell is an SCell, and the device receives a PDCCH that addresses an uplink grant for a new transmission (e.g., a transmission of a HARQ process for the transmission of a BFR MAC control element (MAC CE) or a truncated BFR MAC-CE, which may contain BFR information of the serving cell), or the device receives an indication that the SCell has been deactivated. Accordingly, the device may reset the beam failure instance counter to zero, consider the BFR procedure successful and completed, and cancel all triggered BFR procedures for the serving cell. Using such techniques, the UE 115 may execute the BFD and BFR procedures with the network entity 105, however such procedures may be time-consuming and may result in an increase in overhead on the Uu link.

[0120] The wireless communication system described herein, such as wireless communication system 100, may support a UE 115 to perform BFD and BFR procedures on a sidelink channel with another UE 115 to reduce the overhead on the Uu link. The sidelink channel may be an example of a PC5-RRC connection established between UE 115-a and UE 115-b in a given direction.

[0121] In some wireless communication systems, a first UE 115 may communicate with a second UE 115 using sidelink carrier aggregation, where the first UE 115 and the second UE 115 may communicate via a primary sidelink carrier and one or more secondary sidelink carriers. The primary sidelink carrier may be used for control signaling, and the secondary sidelink carriers may be used for data and control signaling. In some cases, a secondary sidelink carrier may be removed, activated, or deactivated based on throughput. During the communication between the first UE 115 and the second UE 115, RLM and RL may be managed and announced via the primary sidelink carrier instead of the secondary sidelink carriers. In some cases, if the primary sidelink carrier experiences beam failure or performs BFR, the UE 115 may perform a random access procedure to re-establish the primary sidelink carrier. If the random access procedure is unsuccessful, the UE 115 may announce RLF. However, announcing RLF for the primary sidelink carrier may suspend the signaling for other secondary sidelink carriers and may cause an increase in the communication delay between the first UE 115 and the second UE 115.

[0122] In some examples, the UE 115 may perform an independent beam management procedure for each component carrier. In some cases, the transmitting UE 115 may independently configure and transmit BFD-RS on the primary sidelink carrier and the secondary sidelink carriers. In some examples, if the primary sidelink carrier experiences beam failure, but one of the secondary sidelink carriers is available, the UE 115 may switch the primary sidelink carrier to one of the available secondary carriers. For example, in the case where another secondary sidelink carrier is available, the transmitting UE 115 may perform a primary sidelink carrier beam change, handover, or reselection by conveying auxiliary information to the receiving UE 115 via the secondary sidelink carrier.

[0123] The techniques, systems, and methods of the present disclosure may support performing a primary sidelink carrier switch at different times with respect to BFD and BFR procedures. In some cases, the transmitting UE 115 may initiate a BFR and may attempt a random access procedure to resume the primary sidelink carrier. In the case where the random access procedure is unsuccessful but one of the secondary sidelink carriers is available, the UE 115 may attempt to change the primary sidelink carrier to one of the available secondary sidelink carriers. In some examples related to the techniques described elsewhere herein, the transmitting UE 115 may change the primary sidelink carrier before detecting a beam failure and performing a BFD procedure. For example, if the UE 115 determines that a secondary sidelink carrier has higher quality than the primary sidelink carrier before detecting a beam failure and performing a BFR, the UE 115 may change the primary sidelink carrier to the secondary sidelink carrier. In some other examples, the transmitting UE 115 may change the primary sidelink carrier before performing a random access procedure during a BFR. In such examples, the transmitting UE 115 and the receiving UE 115 may initiate timers for the BFR, where the transmitting UE 115 and the receiving UE 115 switch between phases of the BFR and BFD based on these timers. Such procedures where the UE 115 initiates a BFR timer during BFD and BFR procedures and performs a change of the primary sidelink carrier before or during BFD or BFR may be described elsewhere herein, including with reference to Figure 3 – Figure 8 。

[0124] Figure 2 FIG. illustrates an example of a wireless communication system 200 supporting techniques for primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure. In some examples, the wireless communication system 200 may implement or be implemented by the wireless communication system 100. For example, the wireless communication system 200 may include UE 115-a and UE 115-b, which may represent examples of the corresponding devices described herein (e.g., with reference to Figure 1 ). In some examples, UE 115-a and UE 115-b may communicate via a communication link, which may be an example of the sidelink or communication link 125 described with reference to Figure 1 .

[0125] In some examples of the wireless communication system 200, mmW sidelink communication may enable carrier aggregation. In some cases, carrier aggregation may include sidelink carrier aggregation of sidelink channels. The sidelink channels may include a primary component carrier (PCC) (e.g., such as PCC 205) and one or more secondary component carriers (SCCs) (e.g., such as the first SCC 215-a to the nth SCC 215-n). The PCC 205 may be an example of the primary sidelink carrier, the primary sidelink cell, or the primary sidelink component carrier described herein. The SCC 215 may be an example of the secondary sidelink carrier, the secondary sidelink cell, or the secondary sidelink component carrier described herein.

[0126] In some examples, the PCC 205 and the SCC 215 may be configured in different radio frequency spectrum bands or radio frequency ranges. For example, the PCC 205 may be configured in a first frequency range (e.g., frequency range 1 (FR1)), and the SCC 215 may be configured in a second frequency range (e.g., frequency range 2 (FR2)). In some cases, the PCC 205 may correspond to a first radio frequency spectrum band in a radio frequency range (e.g., FR2), and the SCC 215 may correspond to a second radio frequency spectrum band in the same radio frequency range, or the PCC 205 and the SCC 215 may correspond to the same radio frequency spectrum band in the same radio frequency range.

[0127] The PCC 205 may be defined according to the transmitting UE 115 (e.g., such as UE 115-a) of each sidelink channel. The sidelink channel from UE 115-a to UE 115-b may be configured with the PCC 205, and the sidelink channel from UE 115-b to UE 115-a may be configured with a separate PCC. For example, a second PC5-RCC connection may be established between UE 115-a and UE 115-b in the direction from UE 115-b to UE 115-a. In some cases, UE 115-a may perform a RACH procedure on the PCC 205 but not on the SCC 215. Performing RACH on the PCC 205 may enable the BFR procedure. In some examples, UE 115-a may perform RLM or announce RLF on the PCC 205. In some examples, UE 115-a may transmit an SSB on the PCC 205. For example, UE 115-a may transmit an SSB periodically, semi-periodically, or aperiodically based on the power limit and interference mitigation metrics configured at UE 115-a.

[0128] The SCC 215 can also be defined according to the transmitting UE 115 of each sidelink channel. In some cases, the BFR procedure on the SCC 215 can include measurement-based beam changes, which can be performed on the BFR reference signal (BFR-RS) or the BFD BFD-RS 210. In some examples, the UE 115-a can periodically, semi-periodically, or aperiodically transmit SSBs via the SCC 215 based on the power limit and interference mitigation metrics configured at the UE 115-a.

[0129] UE 115 communication via sidelink carrier aggregation can perform independent beam management procedures. For example, the beam management procedures for sidelink carrier aggregation can be performed per direction and per component carrier. Each transmitting UE 115 can independently configure and transmit a set of BFD-RSs on the PCC and a set of SCCs. For example, the UE 115-a can configure and transmit a set of BFD-RSs on the PCC 205 and the SCC 215. For example, the set of BFD-RSs for the PCC 205 can include the BFD-RS 210-a and the BFD-RS 210-b, the set of BFD-RSs for the first SCC 215-a can include the BFD-RS 210-c and the BFD-RS 210-d, and the set of BFD-RSs for the nth SCC 215-n can include the BFD-RS 210-e and the BFD-RS 210-f. In some cases, the BFD-RS 210 can be an example of an SSB or a CSI-RS for BFD. The UE 115-b can perform measurements on the set of beams of the BFD-RS 210 configured for the PCC 205 and the SCC 215. If the UE 115-b detects that the measurement of the BFD-RS 210 in the set of BFD-RSs of a component carrier is below a threshold, the UE 115-b can increment the beam failure instance counter associated with that component carrier. For example, if all the beams in the configured set of BFD-RSs of a component carrier have measurements below the configured threshold, the beam failure instance counter associated with that component carrier can be incremented.

[0130] UE 115-b can be configured with BFD-RS210 measurement thresholds, beam failure instance counters, and beam failure instance counter maximum values to detect beam failures. In some examples, the beam failure instance counter maximum value can be equal to one less than the number of BFD-RS210s in the set associated with the component carrier. A beam failure can be detected when the beam failure instance counter is higher than the beam failure instance counter maximum value, and UE 115-b can report a BFD indication (e.g., via MAC-CE) to UE 115-a. For example, UE 115-b can be configured with a beam failure instance counter maximum value X, and UE 115-b can detect that the RSRP of X+1 BFD-RSs is below the measurement threshold. When UE 115-b increments the beam failure instance counter, the beam failure instance counter can exceed the beam failure instance counter maximum value, indicating a beam failure on the corresponding component carrier.

[0131] The techniques of the present disclosure support a transition procedure from PCC 205 to one of the SCCs in SCC 215 in combination with BFD and BFR procedures. When BFD is indicated at UE 115-b, UE 115-a can determine to perform a PCC beam change, handover, or reselection based on the availability of SCC 215. In some examples, UE 115-a can perform a PCC beam change by sending or delivering assistance information to UE 115-b via lower layer signaling (e.g., via MAC-CE) on SCC 215. In some cases, the PCC beam reselection may not be successful, and UE 115-b can perform a RACH procedure to resume PCC 205. In some examples, for a more efficient and faster RACH procedure, UE 115-a can send BFD-RS210 to UE 115-b. UE 115-b can perform a RACH procedure, and UE 115-a can send a RACH response to UE 115-b on PCC 205 so that UE 115 can perform a beam refinement procedure.

[0132] In some examples, to save power and avoid interference to other adjacent UEs 115, UE 115-a may enter a power saving mode. In the power saving mode, UE 115-a may transmit only a limited set of BFD-RS beams (e.g., SSB for BFD or control state information reference signal (CSI-RS)), and transmit the SSB (e.g., for initial discovery of a beam or rediscovery of a beam) based on a trigger (e.g., such as a beam failure instance) rather than periodically. However, if UE 115-b indicates a beam failure (e.g., BFD) to UE 115-a, then UE 115-a may transmit a complete set of BFD-RS beams on PCC 205 for UE 115-b to perform a RACH procedure. In some other examples, UE 115-a may detect the absence of an adjacent UE 115 and may enter a performance mode. In the performance mode, UE 115-a may periodically transmit the SSB along with a complete BFD-RS set. In some cases, the performance mode may defend against symmetric failures because the SSB may already be available for the RACH procedure and there may be no additional trigger or transmission for UE 115-b to perform the RACH procedure, thus reducing the latency and delay when performing the BFR procedure.

[0133] The wireless communication systems described herein, such as wireless communication system 200, may support techniques for sidelink BFD and BFR. For example, UE 115-a may perform a PCC cell change, where UE 115-a switches PCC 205 to a component carrier with reliable performance (e.g., SCC 215). The wireless communication system 200 may support multiple options or timings for performing a PCC cell change. In a first example, UE 115-a may switch to a component carrier with reliable performance to prevent RLF, such as a component carrier in FR2. For example, if there is strong interference to PCC 205 (e.g., in FR1), UE 115-a may switch PCC 205 to an available and reliable SCC (e.g., in FR2). In a second example, UE 115-a may use layer 1 (L1) or layer 2 (L2) signaling and switch to a component carrier with reliable performance before performing BFR. In a third example, UE 115-a may use L1 or L2 signaling to switch to a component carrier with reliable performance after performing BFR but before performing a random access procedure. For example, a PCC change may be triggered before BFD or BFR when the SCC 215 performance is better than that of PCC 205, during BFD or BFR (e.g., based on L1 or L2 mobility), or after BFR but before performing a random access procedure or declaring RLF. The PCC change may be an inter-band change between frequency range 1 and 2, an inter-band change from frequency range 2 to 2, or an intra-band change from frequency range 2 to 2. - Further descriptions of the BFD / BFR procedures and PCC 205 changes can be found in Figure 3 – Figure 8 description.

[0134] When PCC 205 is defined according to the transmitting UE 115 of each sidelink channel for mode 2 sidelink operation, some of the techniques described herein may be implemented for BFD and BFR. In some cases, UEs 115, such as UE 115-a or UE 115-b, may use separate timers for different procedures during BFR, such as a first timer for beam reselection and a second timer for the RACH procedure for PCC 205. In some examples, UE 115- may send BFR-RS, CSI-RS, or SSB aperiodically to reduce energy consumption (e.g., when operating in a power saving mode) or send BFR-RS, CSI-RS, or SSB periodically to reduce the latency in the beam refinement procedure (e.g., performance mode).

[0135] Figure 3 An example of a flowchart 300 is illustrated that supports techniques for primary sidelink carrier update in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure.

[0136] In some examples, flow chart 300 may be implemented by or in wireless communication system 100 and wireless communication system 200. Flow chart 300 may depict switching a primary sidelink carrier such as PCC to a secondary sidelink component carrier such as secondary sidelink carrier or SCC with reliable performance to prevent RLF. In such cases, the first UE or transmitting UE 115 may detect strong interference to the PCC (e.g., in a mode 2 mobility scenario), and the first UE 115 may switch to an available SCC to be used as the PCC. The PCC and SCC may be examples of the PCC 205 and SCC 215 described Figure 2 herein. In some cases, the UE115 may be configured with a set of SCCs including one or more SCCs.

[0137] At 305, two UEs 115 in sidelink communication may perform normal operations, exchanging control signaling and data messages bidirectionally. The first UE 115 may transmit reference signals such as BFD-RS, CSI-RS, SSB, or any combination thereof, which may be received by the second UE 115, and the second UE 115 may detect that the measurement of the reference signals is below a measurement threshold. In some examples, the first UE 115 or the second UE 115 or both may trigger a beam reselection process based on the measurement being below the measurement threshold. In some examples, the UE 115 may initiate a BFD procedure. For example, the first UE 115 may transmit BFD-RS (e.g., SSB, CSI-RS) to be measured by the second UE115.

[0138] At 310, the UE 115 may perform beam measurements on the BFD-RS. For example, the first UE 115 may transmit a set of BFD-RS to the second UE 115 via the beam of the PCC, and the second UE 115 may measure the set of BFD-RS. In some examples, the RSRP of one of the BFD-RS on the PCC may be below the measurement threshold, which may indicate a beam failure instance, and the second UE 115 may increment a beam failure instance counter at 315. In some examples, the second UE 115 may send a measurement report for the PCC beam measurement, indicating the beam failure instance or the measurement of the PCC beam or both.

[0139] In some cases, at 320, the UE 115 may detect that the beam failure instance counter value is higher than zero but lower than the maximum beam failure instance value. At 325, the first UE 115 may transmit a BFD-RS on the beam of the SCC configured for the first UE 115. The second UE 115 may receive the BFD-RS and perform SCC beam measurements. In some examples, the second UE 115 may send a measurement report to the first UE 115, and the measurement report may indicate the SCC beam measurements.

[0140] At 330, the first UE 115 or the second UE 115 or both may compare the beam measurements of the SCCs in the SCC group with the measurements of the PCC beam. If the UE 115 determines that no available SCC has sufficient conditions to replace the PCC, the UE 115 may perform additional beam measurements on the subsequent SCCs in the group (e.g., the UE 115 may repeat 325). In some examples, if the UE 115 determines that no SCC is in good condition or can support the PC5-RRC sidelink, the UE may return to performing PCC beam measurements on the next PCC beam. In some examples, the first UE 115 or the second UE 115 or both may determine that the measured SCC can be used to replace the current PCC. If the UE 115 determines that the available SCC is in good condition (e.g., the SCC can maintain the PC5-RRC sidelink channel), the UE 115 may initiate an SCC-to-PCC cell change procedure at 335. The UE 115 may initiate the SCC-to-PCC cell change procedure and return to normal operation without performing the entire BFD or BFR procedure.

[0141] Therefore, the SCC-to-PCC cell change procedure can reduce the overhead and latency on the PC5-RRC sidelink channel. If the cell change procedure is unsuccessful, the first UE 115 may declare RLF at 340. If the first UE 115 reports RLF, the UE 115 may discard the PC5-RRC sidelink connection and may attempt to re-establish the connection. However, the techniques described herein may enable the UE 115 to report RLF earlier than in the case where the UE 115 has performed the full BFD and BFR procedures, thus reducing the total latency in sidelink communication.

[0142] If the SCC-to-PCC cell change procedure is successful at 335, the UE 115 may return to normal operation at 305. The first UE 115 may change from transmitting on the previous PCC beam to transmitting on the beam of the selected SCC. In some cases, the first UE 115 may switch to using the beam of the SCC as the new PCC because the performance of the SCC may be better than the previous PCC, and the SCC can maintain the PC5-RRC sidelink connection.

[0143] In some examples, at 345, the first UE 115 or the second UE 115 or both may increment a beam failure instance counter, and the beam failure instance counter may exceed a maximum beam failure instance counter value. If the beam failure instance counter exceeds or meets the maximum beam failure instance counter value, the first UE 115 or the second UE 115 or both may initiate a BFR procedure at 350. If the beam failure instance counter does not exceed the maximum beam failure instance counter value, the UE 115 may return to performing PCC beam measurements at 310.

[0144] At 355, the UE 115 may initiate a PCC beam reselection procedure. If the PCC beam reselection procedure is successful, the first UE 115 may select a different beam for the PCC for communication, end the BFR procedure at 560, and return to normal operation at 305. If the PCC beam reselection procedure is not successful, the UE 115 may initiate a RACH recovery procedure at 360. If the RACH recovery procedure is successful, the UE 115 may end the BFR procedure at 365 and return to normal operation at 305. If the RACH recovery procedure is not successful, the UE 115 may initiate an SCC to PCC cell change procedure.

[0145] In some cases, these procedures may be timer-based. For example, two UEs 115 in a sidelink connection may run timers associated with BFD and BFR procedures. In some examples, the timers may be used to determine when to advance to the next phase in BFD or BFR, such as in the case where a message sent by one of the UEs 115 is missed or not received. In some examples, these timers may reduce latency and delay in BFD and BFR procedures because if a UE 115 reports that a timer has expired, the UE 115 may transition to the next phase of BFD or BFR. For example, if one of the UEs 115 reports that a timer associated with the BFD procedure has expired, the UE 115 may transition to the BFR procedure. Additionally or alternatively, if a UE 115 reports that a timer associated with the BFR procedure has expired, the UE 115 may report an RLF at 340, which may prevent further delay and enable the UE 115 to re-establish a sidelink connection at a faster rate. Timers associated with BFD and BFR procedures at the UE 115 are further described. Figure 4 Further description.

[0146] Figure 4An example of process flow 400 is shown that supports techniques for primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure. In some examples, process flow 400 may implement aspects of wireless communication system 100, wireless communication system 200, or flowchart 300, or may be implemented by aspects of wireless communication system 100, wireless communication system 200, or flowchart 300. For example, process flow 400 may include UE 115-c and UE 115-d, which may represent examples of corresponding devices described herein. In some cases, the process flow may use a set of timers (such as the timers referenced Figure 3 and described) to describe the processes of the BFD and BFR procedures.

[0147] In the following description of process flow 400, the operations between UE 115-c and UE 115-d may be performed in a different order or at different times. Some operations may also be excluded from process flow 400, or other operations may be added. Although UE 115-c and UE 115-d are shown performing the operations of process flow 400, some aspects of some operations may also be performed by one or more other wireless devices.

[0148] UE 115-c may transmit a first set of reference signals via the PCC configured for sidelink carrier aggregation and a second set of reference signals via one or more SCCs configured for sidelink carrier aggregation. At 405, UE 115-d may detect a beam failure on a set of beams of UE 115-c associated with the first set of reference signals via the PCC. In some cases, UE 115-d may determine that the measurement of the reference signals associated with the set of beams of UE 115-c is below a threshold, which indicates a beam failure. For example, the CSI measurement of the beam may be below a specific threshold. Thus, beam reselection may be triggered and the BFD procedure may be initiated.

[0149] At 410, UE 115-d may initiate a BFR phase one reception timer for the beam reselection procedure. UE 115-d may use the BFR phase one reception timer to determine whether UE 115-d has missed a message from UE 115-c for the BFR procedure. In some cases, UE 115-d may reset the BFR phase one reception timer each time it receives a message from UE 115-c and may start the BFR phase one reception timer each time UE 115-d sends a message to UE 115-c.

[0150] At 415, in some examples, UE 115-c may receive a control message from UE 115-d, which indicates BFD of the PCC based on the number of beam failure instances meeting a threshold. UE 115-c may initiate a first timer (e.g., phase one transmission timer) based on the control message indicating BFD. In some cases, the number of beam failure instances may be greater than zero but less than the maximum value of beam failure instances. In some other examples, if UE 115-d indicates that the number of beam failure instances meets the threshold (e.g., higher than the maximum value of beam failure instances), UE 115 may initiate the BFR procedure described herein. In some examples, the control message indicating BFD may be referred to as a BFD report.

[0151] At 420, UE 115-c may initiate a first timer associated with BFD based on the BFD of the PCC. In some cases, this first timer may be referred to as the BFR phase one transmission timer. In some examples, UE 115-c may initiate BFR phase one transmission in response to the control message indicating the BFD report at 415. UE 115-c may use the BFR phase one transmission timer to determine whether UE 115-c has missed a message from UE 115-d. In some cases, UE 115-d may reset the BFR phase one transmission timer each time a message is received from UE115-d, and may start the BFR phase one transmission timer each time UE 115-c sends a message to UE 115-d.

[0152] At 425, UE 115-c may send a set of BFR-RSs via one or more beams of the PCC while the first timer associated with BFD (e.g., BFR phase one transmission timer) is active. In some cases, the BFR-RS may be an SSB or a CSI-RS. In some examples, UE 115-c may send the set of BFR-RSs via a subset of BFR-RSs from a BFR-RS resource set.

[0153] At 430, UE 115-d may perform measurements on the BFR-RS and send the measurements to UE 115-c. In some cases, UE 115-d may also indicate whether the measurements meet the BFR-RS threshold. In some examples, UE 115-d may indicate a preferred beam or beam set using the BFR-RS measurements. In some examples, based on the indication of the preferred beam or beam set, UE 115 may perform a PCC beam switching or changing procedure to one or more preferred beams indicated by UE 115-d. At 435, UE 115-c may send sidelink control information on one or more preferred beams.

[0154] In some cases, at 440, UE 115-d may miss or not receive the SCI on one or more preferred beams. At 445, the BFR phase one reception timer may expire based on UE 115-d missing the SCI from UE 115-c. In some cases, in response to the BFR phase one reception timer expiring, UE 115 may initiate the BFR procedure. In some other cases, the RSRP of all beams in the configured BFD-RS set may be lower than a specific threshold of a threshold measurement quantity, and UE115-c and UE 115-d may initiate the BFR procedure described herein.

[0155] At 450, UE 115-d may initiate the BFR phase two reception timer for the RACH procedure. At 455, UE115-c may initiate a second timer associated with BFR (e.g., the BFR phase two transmission timer). In some examples, the second timer (e.g., a HARQ-based timer or counter for BFR) may be part of the maximum HARQ timer. In some examples, the second timer may be initiated based on the expiration of the first timer. For example, if the beam failure is resolved in the first phase (e.g., when the first timer is active), then UE 115-d may not initiate the second phase of beam recovery (e.g., initiate the second timer and procedure when the second timer is active). The BFR phase two reception timer and the BFR phase two transmission timer may operate similarly to the BFR phase one reception timer and the BFR phase one transmission timer. However, when one of the phase two timers expires, UE 115-c or UE 115-d or both may declare RLF.

[0156] At 460, UE 115-c may send an SSB to UE 115-d. At 470, UE 115 may perform the RACH procedure for PCC while the second timer is active. The RACH procedure may be performed using the SSB sent from UE 115-c to UE 115-d. For example, at 465, UE 115-d may attempt to perform the RACH procedure using the SSB sent at 460. In some cases, the RACH procedure may not be successful, and UE 115-c or UE 115-d or both may declare RLF. After declaring RLF, UE 115 may discard the PC5-RRC connection and may attempt to re-establish the sidelink connection before resuming communication.

[0157] At 470, in some embodiments, control messages or BFD reports sent from UE 115-d to UE 115-c may be missed by UE 115-c. Accordingly, a failure timer or counter at UE 115-c may expire at 475. When the failure timer or counter expires at UE 115-c, UE 115-c may initiate a first timer and perform a BFR operation. For example, UE 115-c may send a beam set of BFR-RS to UE 115-d.

[0158] In some examples, at 480, UE 115-c may miss BFR-RS measurements sent from UE 115-d. If UE 115-c does not receive BFR-RS measurements, a BFR phase one transmission timer may expire at 445, and UE 115 may perform a BFR procedure to prevent RLF.

[0159] In some examples, UE 115-c and UE 115-d may symmetrically detect BFD. For example, at 485, UE 115-c may also detect BFD (e.g., in addition to UE 115-d detecting BFD). Since UE 115-c may expect to receive control messages or BFD reports from UE 115-d, UE 115-c may initiate a BFR phase zero transmission timer at 490. If UE 115-c does not receive a BFD report from UE 115-d when the BFR phase zero transmission timer expires, UE 115-c may perform a BFR procedure. For example, UE 115-c may miss a BFD report at 470, and the BFR phase zero transmission timer may expire. After the BFR phase zero transmission timer expires, UE 115-c may initiate a BFR phase one transmission timer and perform a BFR procedure.

[0160] Figure 5 An example of a flowchart 500 is illustrated that supports techniques for primary side link carrier updates in side link carrier aggregation in accordance with one or more aspects of the present disclosure. In some examples, flowchart 500 may be implemented in or by wireless communication system 100 and wireless communication system 200. Flowchart 500 may depict switching to a component carrier with reliable performance in frequency range 2 (e.g., based on L1 / L2 mobility with a preconfigured RRC configuration with a MAC-CE activation command) to prevent RLF. In such cases, UE 115 may detect strong interference in frequency range 1 (e.g., in a mode 2 mobility scenario) using L1 / L2 mobility. The PCC and SCC may be examples of the PCC 205 and SCC 215 described. In some cases, UE 115 may be configured with a set of SCCs that includes one or more SCCs. Figure 2 In some cases, UE 115 may be configured with a set of SCCs that includes one or more SCCs.

[0161] At 505, two UEs 115 in sidelink communication may perform normal operations on the PCC, exchanging control signaling and data messages bidirectionally. The first UE 115 may send a reference signal to the second UE 115, and the second UE 115 may detect that the reference signal sent from the first UE 115 is below a measurement threshold. Accordingly, the first UE 115 or the second UE 115 or both may trigger a beam reselection process and may initiate a BFD procedure. In some cases, as part of the BFD procedure, the first UE 115 may send a BFD-RS (e.g., SSB, CSI-RS) to be measured by the second UE 115.

[0162] At 510, the UE 115 may perform beam measurements on the BFD-RS, which is described in more detail (e.g., at 310 of Figure 3 ). In some examples, the beam measurement of one of the BFD-RSs in the BFD-RS may be below the indicated measurement threshold, and the UE 115 may increment a beam failure instance counter at 515. In some cases, at 520, the UE 115 may detect that the beam failure instance is greater than zero but less than the maximum beam failure instance value. At 525, the UE 115 may perform beam measurements on the SCC. The UE 115 may perform SCC beam measurements before the UE 115 initiates a BFD procedure to determine whether the SCC can replace the PCC. Figure 3 For example, at 525, the UE 115 may detect that the SCC in the SCC group has a higher quality than the PCC. In some examples, the UE 115 may determine at 530 whether the SCC is capable of maintaining the PC5-RRC sidelink channel between the UEs 115. If the UE 115 determines that the SCC has a high quality and can maintain the sidelink channel, the UE 115 may initiate a PCC update at 535 and start the SCC-to-PCC cell change procedure. This process may provide improved efficiency because the UE 115 may not complete the BFD procedure or perform a BFR procedure. In some examples, the procedure for determining whether the SCC can replace the PCC may occur during or before the BFD procedure (as illustrated).

[0163] However, if the UE 115 determines that the SCC is not in good condition or cannot maintain the sidelink channel, the UE 115 may perform the BFD procedure. For example, the UE 115 may perform additional PCC beam measurements and track additional beam failure instances. In some examples, the UE 115 may continue to check whether the SCC is available to replace the PCC with a high enough quality.

[0164]

[0165]

[0165] At 540, the UE 115 may continue to monitor the PCC until the beam failure instance count exceeds the beam failure instance maximum. For example, when the RSRP measurements of all the beams in the configured BFD-RS set are below the configured measurement threshold for a threshold number of times, the UE 115 may trigger the BFR procedure at 545.

[0166] At 550, the UE 115 may initiate a PCC beam reselection procedure. If successful, the UE 115 may select a different beam for the PCC for communication, end the BFR procedure at 560, and begin normal operation. In some cases, the UE 115 may determine that the PCC beam reselection procedure is unsuccessful, and the UE 115 may initiate a RACH recovery procedure at 555. If the UE 115 determines that the RACH recovery procedure is unsuccessful, the first UE 115 may declare RLF at 565. Additionally or alternatively, the UE 115 may determine that the RACH recovery procedure is successful, and the UE 115 may end the BFR procedure at 560, select a different PCC beam for communication, and return to normal operation.

[0167] In some examples, as referenced Figure 3 described, the UE 115 may have timers associated with the BFD and BFR procedures. Further description and use of the timers for such procedures where the SCC-to-PCC cell change procedure may occur before or during the BFD procedure may be referenced elsewhere herein Figure 6 described.

[0168] Figure 6 Illustrates an example of a process flow 600 that supports techniques for primary side link carrier update in side link carrier aggregation in accordance with one or more aspects of the present disclosure.

[0169] In some examples, the process flow 600 may implement aspects of the wireless communication system 100, the wireless communication system 200, or the flow chart 500, or the process flow 600 may be implemented by aspects of the wireless communication system 100 or the wireless communication system 200. For example, the process flow 600 may include UE 115-e and UE 115-f, which may represent examples of the corresponding devices described herein. In some cases, the process flow may use a set of timers (e.g., such as the timers referenced Figure 3 – Figure 5 described) to describe the processes of the BFD and BFR procedures and perform the SCC-to-PCC cell change procedure before or during the BFD procedure.

[0170] In the following description of procedure flow 600, operations between UE 115-e and UE 115-f may be performed in a different order or at different times. Some operations may also be excluded from procedure flow 600, or additional operations may be added. Although UE 115-e and UE 115-f are shown as performing the operations of procedure flow 600, some aspects of some operations may also be performed by one or more other wireless devices.

[0171] UE 115-e may send a first set of reference signals via the PCC of side-link carrier aggregation and a second set of reference signals via one or more SCCs configured for side-link carrier aggregation. At 605, UE 115-e may receive a measurement message that indicates measurements for a set of beams corresponding to an SCC configured for side-link carrier aggregation based on detecting a beam failure instance of the PCC. For example, UE 115-f may detect a beam failure instance of one or more beams of the PCC and send a measurement report indicating measurements for the beams of one or more SCCs. In some cases, UE 115-f may determine that the measurements for the set of beams corresponding to the SCC meet a threshold associated with maintaining the RRC control link of the PCC (e.g., such as a PC5-RRC control link). In some examples, the measurement message may be received based on the number of beam failure instances meeting a threshold.

[0172] At 610, UE 115-e may send a control message via L1 signaling or L2 signaling based on the measurements for the set of beams and a beam failure instance of the primary side-link carrier, the control message indicating a handover of the primary side-link carrier to the set of beams. In some examples, an SCI or a MAC message may be an example of L1 signaling or L2 signaling. In some examples, the handover of the PCC to the set of beams corresponding to the SCC may be based on the set of beams corresponding to the SCC maintaining the RRC control link of the PCC. For example, based on the measurements, the SCC may support maintaining the RRC link of the PCC. Thus, in some cases, UE 115-e may send a control message based on the set of beams meeting a threshold for maintaining the RRC control link of the PCC. In some other examples, the control message may be sent based on the measurements for the set of beams corresponding to the SCC being higher than the measurements for a second set of beams corresponding to the PCC. In such cases, the control message may be sent prior to a BFD procedure based on the beam failure instance.

[0173] At 615, the UE 115-f may send an indication of a preferred beam in the set of beams corresponding to the SCC. In some cases, the UE 115-f may send an indication of a set of preferred beams, which may be a subset of the set of beams corresponding to the SCC. In some cases, the UE 115-e may send an SCI via the preferred beam at 620 based on switching the PCC to the set of beams. After 615, the PCC may be switched to the previous SCC, or the beam of the PCC may be changed to a beam of the previous SCC that can support maintaining the RRC link or has a higher quality than the previous PCC.

[0174] In some examples, the UE 115-f may detect a beam failure of a set of beams of the UE 115-e associated with a first set of reference signals via the PCC at 625. For example, if the PCC beam change is unsuccessful, or the quality of the new PCC degrades, the UE 115-f may detect the beam failure. In some cases, the UE 115-f may determine that the measurement of the reference signal associated with the set of beams of the UE 115-e may be below a threshold, which indicates a beam failure. Therefore, the UE 115-f may initiate a BFR phase one reception timer at 630, which is described in more detail with reference to Figure 4 (e.g., Figure 4 410).

[0175] At 635, the UE 115-e may receive a second control message (e.g., a BFD report) from the UE 115-f indicating BFD. In some cases, at 640, the UE 115-e may initiate a first BFR timer (e.g., a BFR phase one transmission timer) based on the BFD report. In some cases, the first BFR timer may be associated with beam reselection.

[0176] In some examples, the UE 115-e and the UE 115-f may initiate a BFD procedure based on a beam failure instance. For example, at 645, the UE 115-e may send BFR-RS for the UE 115-f to measure. At 655, the UE 115-f may send BFR-RS measurements indicating one or more preferred beams. At 660, the UE 115-e may send an SCI message to the UE 115-f on the indicated one or more preferred beams.

[0177] Additionally or alternatively, if the beam reselection in the BFD procedure is unsuccessful, the UE 115-e and the UE 115-f may perform a BFR procedure. If the BFR procedure is unsuccessful, the UE 115-e may declare RLF. The BFR procedure may be described with reference to Figure 4 for description.

[0178] Figure 7An example of a flow chart 700 is illustrated that supports techniques for primary sidelink carrier update in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure. In some examples, the flow chart 700 may be implemented by or in a wireless communication system 100 and a wireless communication system 200. The flow chart 700 may depict switching to a component carrier (e.g., based on L1 / L2 mobility with a preconfigured RRC configuration with a MAC-CE activation command) having reliable performance (e.g., in frequency range 1) before performing a RACH procedure after a BFR is unsuccessful. The PCC and SCC may be examples of the PCC 205 and SCC 215 described Figure 2 herein.

[0179] At 705, two UEs 115 in sidelink communication may perform normal operations on the PCC, exchanging control signaling and data messages bidirectionally. However, in some cases, a beam reselection procedure may be triggered, and the UE 115 may initiate a BFD procedure.

[0180] At 710, the UE 115 may perform PCC beam measurements on the BFD-RS. In some examples, the RSRP of the beam measurement of one of the BFD-RSs in the BFR-RS may be below a measurement threshold, and the UE 115 may increment a beam failure instance counter at 715. At 720, the UE 115 may increment the beam failure instance counter and check at 720 whether the beam failure instance counter has exceeded a maximum beam failure instance counter value. If the beam failure instance counter has not exceeded the maximum beam failure instance counter value, the UE 115 may return to performing PCC beam measurements. If the number of beam failure instances meets or exceeds the maximum beam failure instance counter value, the UE 115 may initiate a BFR procedure at 725.

[0181] At 730, the number of beam failure instances is higher than zero but lower than the maximum beam failure instance value, and the UE 115 may perform SCC beam measurements at 735. At 740, the UE 115 may compare the measurements of the SCCs in the SCC set to determine whether an SCC is capable of supporting replacement of the current PCC. If the UE 115 determines that no SCC has a high enough quality to replace the PCC, the UE 115 may initiate the BFR procedure at 725. If the UE 115 determines that the SCC is in good condition (e.g., the SCC can maintain the PC5-RRC sidelink channel), the UE 115 may initiate a PCC update based on L1 / L2 mobility at 745 and start the SCC-to-PCC cell change procedure. The UE 115 may perform a PCC update procedure to update the PCC to an SCC that can support the sidelink channel without performing the entire BFR procedure. If the PCC update procedure is successful, the UE 115 may switch to communicating using the selected SCC, end the BFR procedure at 750, and start normal operation again.

[0182] However, if the PCC update procedure is not successful, the UE 115 may perform a RACH recovery procedure at 755. In some cases, the RACH procedure may not be successful, and the UE 115 may report RLF at 760.

[0183] If no SCC is capable of supporting the sidelink or is in good condition and the BFR procedure is initiated, the UE 115 may start PCC beam reselection at 765. If the PCC beam reselection is successful, the UE 115 may end the BFR procedure at 750 and resume normal operation. If the PCC beam reselection procedure is not successful, the UE 115 may initiate a PCC update procedure before performing the RACH procedure.

[0184] In some examples, as described with reference to Figure 3 the UE 115 may have timers associated with the BFD and BFR procedures. Further description and use of the timers for such procedures where the SCC-to-PCC cell change procedure may occur before or during the BFR procedure may be referred to Figure 8 for description.

[0185] Figure 8 Illustrates an example of a process flow 800 that supports techniques for primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure.

[0186] In some examples, process flow 800 may implement aspects of wireless communication system 100, wireless communication system 200, or flow chart 700, or process flow 800 may be implemented by aspects of wireless communication system 100, wireless communication system 200, or flow chart 700. For example, process flow 800 may include UE 115-g and UE 115-h, which may represent examples of corresponding devices described herein. In some cases, the process flow may use a set of timers (e.g., the timers referenced Figure 3 – Figure 7 to describe the procedures for BFD and BFR, and perform the SCC to PCC cell change procedure before or during the BFR procedure.

[0187] In the following description of process flow 800, the operations between UE 115-g and UE 115-h may be performed in a different order or at different times. Some operations may also be excluded from process flow 800, or other operations may be added. Although UE 115-g and UE 115-h are shown as performing the operations of process flow 800, some aspects of some operations may also be performed by one or more other wireless devices.

[0188] UE 115-g may transmit a first set of reference signals via the PCC of side-link carrier aggregation and a second set of reference signals via one or more SCCs configured for side-link carrier aggregation. At 802, UE 115-h may detect a beam failure on a set of beams associated with the first set of reference signals of UE 115-g via the PCC. In some cases, UE 115-h may determine that the measurement of the reference signals associated with this set of beams of UE 115-g is below a threshold, which indicates a beam failure. UE 115-h may initiate a BFR phase one receive timer at 804, which may be referenced Figure 4 (e.g., at 410 in Figure 4 described in more detail).

[0189] At 806, UE 115-g may receive a BFD report from UE 115-h indicating a beam failure. In some cases, UE 115-g may initiate a first BFR timer (e.g., BFR phase one transmit timer) at 808 based on the reported beam failure instance. In some cases, the first BFR timing may be associated with beam reselection.

[0190] In some examples, UE 115-g and UE 115-h may initiate a BFD procedure based on a beam failure instance. For example, at 810, UE 115-g may send a set of BFR-RSs for UE 115-h to measure. UE 115-h may measure the BFR-RSs sent by UE 115-g, and at 812, UE 115-h may send a measurement report indicating the measurement of the BFR-RSs and one or more preferred beams based on the measurement. At 814, UE 115-g may send an SCI message to UE 115-h on one or more preferred beams.

[0191] In some examples, UE 115-h may receive a measurement message that indicates a measurement of a set of beams corresponding to an SCC configured with side-link carrier aggregation based on a beam failure instance of the PCC. In some cases, at 818, UE 115-h may miss or not receive an SCI from UE 115-g. At 820, the BFR phase 1 reception timer may expire, and UE 115-g and UE 115-h may initiate a BFR procedure based on the expiration of the BFR phase 1 timer. Before the BFR procedure, in some implementations, UE 115-g and UE 115-h may attempt a PCC update before completing the BFR procedure because the RACH procedure may be latency-intensive.

[0192] In some cases, UE 115-h may determine that the measurement of a set of beams corresponding to the SCC meets a threshold associated with maintaining the RRC control link of the PCC (e.g., such as the PC5-RRC control link). In some examples, the measurement message at 816 may be received based on the number of beam failure instances meeting the threshold. At 822, UE 115-g may send a control message via L1 signaling or L2 signaling based on the measurement of the one or more beams and a beam failure instance of the primary side-link carrier, the control message indicating a handover of the primary side-link carrier to the one or more beams indicated by the measurement message (e.g., PCC update). In some examples, the handover of the PCC to the set of beams corresponding to the SCC may be based on the set of beams corresponding to the SCC maintaining the RRC control link of the PCC. Thus, in some cases, UE 115-g may send a control message at 822 based on the set of beams meeting the threshold for maintaining the RRC control link of the PCC.

[0193] In some other examples, UE 115-g may send a control message based on the measurement of the set of beams corresponding to the SCC being higher than the measurement of a second set of beams corresponding to the PCC. For example, UE 115-g may send a control message before the BFR procedure based on detecting a beam failure instance. In some other cases, the control message may be sent based on the expiration of a first BFR timer at 820.

[0194] At 824, UE 115-h may indicate to UE 115-g a preferred beam among the set of beams corresponding to the SCC. In some cases, UE 115-h may send a set of preferred beams, which may be a subset of the set of beams corresponding to the SCC. At 826, UE 115-g may send an SCI to UE 115-h based on switching the PCC to the set of beams via the indicated preferred beam. In some cases, this PCC beam switching procedure may be performed before or during the BFR procedure, such as before the RACH procedure.

[0195] However, in some cases, the PCC update procedure (e.g., at 822 to 826) may not be successful, there may be no reliable SCC, or the beam failure instance counter may exceed the maximum value, and UE 115-g may trigger the BFR procedure (e.g., steps 830 to 832). Additionally or alternatively, at 828, UE 115-g may miss a measurement message, or UE 115-g may not receive an indication of the preferred beam at 838. If UE 115-g misses the measurement message, the first BFR timer may expire at 820, and UE 115-g may initiate a second BFR timer (e.g., BFR phase two transmission timer) associated with performing the RACH procedure for the PCC at 830. In some examples, at 832, UE 115-h may also initiate a second BFR timer (e.g., BFR phase two reception timer) associated with performing the RACH procedure. In some cases, the control message sent by UE 115-g at 822 may be sent after UE 115-g and UE 115-h initiate the second BFR timer during the BFR procedure.

[0196] At 834, UE 115-g may send an SSB to UE 115-h. At 836, when the second BFR time is active, UE 115-g and UE 115-h may perform the RACH procedure for the PCC. At 836, the performed RACH procedure may target or use the SSB sent from UE 115-g to UE 115-h. In some cases, the RACH procedure may not be successful, and UE 115-g may declare RLF. After declaring RLF, UE 115 may discard the PC5-RRC connection and may attempt to re-establish the sidelink connection before resuming communication. In some examples, instead of performing the PCC update, the BFR procedure may be initiated.

[0197] At 840, in some specific implementations, control messages or BFD reports sent by UE 115-h to UE 115-g may be missed by UE 115-g. UE 115-g may detect at 842 that a failure timer has expired or a failure counter has met a threshold. The failure timer or counter may be a HARQ-based timer or counter and may be part of a maximum HARQ timer. Additionally or alternatively, at 844, UE 115-c may miss BFR-RS measurements from UE 115-h. If UE 115-g misses BFR-RS measurements, the first-phase transmission timer may expire at 820 and UE 115 may perform a BFR procedure to prevent RLF. If the BFR procedure fails, including the PCC update procedure and the RACH procedure, UE 115-g may declare RLF, discard the sidelink channel, and may attempt to re-establish the connection.

[0198] Figure 9 Block diagram 900 illustrates a device 905 that supports techniques for primary sidelink carrier update in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure. Device 905 may be an example of aspects of UE 115 as described herein. Device 905 may include a receiver 910, a transmitter 915, and a communication manager 920. Device 905 may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0199] Receiver 910 may provide components for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to techniques for primary sidelink carrier update in sidelink carrier aggregation). The information may be passed to other components of device 905. Receiver 910 may utilize a single antenna or a set of multiple antennas.

[0200] Transmitter 915 may provide components for transmitting signals generated by other components of device 905. For example, transmitter 915 may transmit information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to techniques for primary sidelink carrier update in sidelink carrier aggregation). In some examples, transmitter 915 may be co-located with receiver 910 in a transceiver module. Transmitter 915 may utilize a single antenna or a set of multiple antennas.

[0201] The communication manager 920, the receiver 910, the transmitter 915, or various combinations thereof or their various components can be examples of components for performing various aspects of the techniques for primary sidelink carrier updates in sidelink carrier aggregation as described herein. For example, the communication manager 920, the receiver 910, the transmitter 915, or various combinations or components thereof can support methods for performing one or more of the functions described herein.

[0202] In some examples, the communication manager 920, the receiver 910, the transmitter 915, or various combinations or components thereof can be implemented in hardware (e.g., in a communication management circuit). The hardware can include a processor, a digital signal processor (DSP), a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, a microcontroller, discrete gate or transistor logic, discrete hardware components, or any combination thereof configured to or otherwise supporting components for performing the functions described in this disclosure. In some examples, the processor and the memory coupled to the processor can be configured to perform one or more of the functions described herein (e.g., by the processor executing instructions stored in the memory).

[0203] Additionally or alternatively, in some examples, the communication manager 920, the receiver 910, the transmitter 915, or various combinations or components thereof can be implemented in code executed by a processor (e.g., implemented as communication management software or firmware). If implemented in code executed by a processor, the functions of the communication manager 920, the receiver 910, the transmitter 915, or various combinations or components thereof can be performed by a general purpose processor, a DSP, a CPU, an ASIC, an FPGA, a microcontroller, or any combination of these or other programmable logic devices configured to or otherwise supporting components for performing the functions described in this disclosure.

[0204] In some examples, the communication manager 920 can be configured to use or otherwise cooperate with the receiver 910, the transmitter 915, or both to perform various operations (e.g., receive, obtain, monitor, output, transmit). For example, the communication manager 920 can receive information from the receiver 910, convey information to the transmitter 915, or integrate with the receiver 910, the transmitter 915, or both to obtain information, output information, or perform various other operations as described herein.

[0205] According to examples disclosed herein, communication manager 920 may support wireless communication at a first UE. For example, communication manager 920 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 920 may be configured to or otherwise support components for receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. Communication manager 920 may be configured to or otherwise support components for transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0206] Additionally or alternatively, according to examples disclosed herein, communication manager 920 may support wireless communication at a first UE. For example, communication manager 920 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 920 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. Communication manager 920 may be configured to or otherwise support components for transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

[0207] Additionally or alternatively, according to examples disclosed herein, communication manager 920 may support wireless communication at a second UE. For example, communication manager 920 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 920 may be configured to or otherwise support components for transmitting a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. Communication manager 920 may be configured to or otherwise support components for receiving a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0208] Additionally or alternatively, in accordance with examples as disclosed herein, communication manager 920 may support wireless communication at a second UE. For example, communication manager 920 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 920 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. Communication manager 920 may be configured to or otherwise support components for monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while a first timer associated with beam failure recovery is active.

[0209] By including or configuring communication manager 920 in accordance with examples as described herein, device 905 (e.g., a processor that controls or otherwise couples receiver 910, transmitter 915, communication manager 920, or combinations thereof) may support techniques for reducing processing and power consumption by preventing power-intensive procedures such as random access procedures or beam failure recovery.

[0210] Figure 10 Block diagram 1000 illustrates a device 1005 that supports techniques for primary sidelink carrier updates in sidelink carrier aggregation, in accordance with one or more aspects of the present disclosure. Device 1005 may be an example of aspects of device 905 or UE 115 as described herein. Device 1005 may include a receiver 1010, a transmitter 1015, and a communication manager 1020. Device 1005 may also include a processor. Each of these components may communicate with one another (e.g., via one or more buses).

[0211] Receiver 1010 may provide components for receiving information (such as packets, user data, control information, or any combination thereof) associated with various information channels (e.g., control channels, data channels, information channels related to techniques for primary sidelink carrier updates in sidelink carrier aggregation). The information may be passed to other components of device 1005. Receiver 1010 may utilize a single antenna or a set of multiple antennas.

[0212] Transmitter 1015 may provide components for transmitting signals generated by other components of device 1005. For example, transmitter 1015 may transmit information associated with various information channels (e.g., control channels, data channels, information channels related to techniques for primary sidelink carrier update in sidelink carrier aggregation), such as packets, user data, control information, or any combination thereof. In some examples, transmitter 1015 may be co-located with receiver 1010 in a transceiver module. Transmitter 1015 may utilize a single antenna or a group of multiple antennas.

[0213] Device 1005 or its various components may be examples of components for performing various aspects of the techniques for primary sidelink carrier update in sidelink carrier aggregation as described herein. For example, communication manager 1020 may include reference signal transmission component 1025, beam failure indication component 1030, primary carrier change indication component 1035, timer component 1040, beam failure recovery component 1045, reference signal reception component 1050, or any combination thereof. Communication manager 1020 may be an example of aspects of communication manager 920 as described herein. In some examples, communication manager 1020 or its various components may be configured to use or otherwise cooperate with receiver 1010, transmitter 1015, or both to perform various operations (e.g., receive, obtain, monitor, output, transmit). For example, communication manager 1020 may receive information from receiver 1010, convey information to transmitter 1015, or integrate with receiver 1010, transmitter 1015, or both to obtain information, output information, or perform various other operations as described herein.

[0214] According to examples disclosed herein, communication manager 1020 may support wireless communication at a first UE. Reference signal transmission component 1025 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Beam failure indication component 1030 may be configured to or otherwise support components for receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. Primary carrier change indication component 1035 may be configured to or otherwise support components for transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0215] Additionally or alternatively, according to the examples disclosed herein, communication manager 1020 may support wireless communication at a first UE. The reference signal transmission component 1025 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The timer component 1040 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. The beam failure recovery component 1045 may be configured to or otherwise support components for transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier when the first timer associated with beam failure recovery is active.

[0216] Additionally or alternatively, according to the examples disclosed herein, communication manager 1020 may support wireless communication at a second UE. The reference signal reception component 1050 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The beam failure indication component 1030 may be configured to or otherwise support components for transmitting a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. The primary carrier change indication component 1035 may be configured to or otherwise support components for receiving a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and a beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0217] Additionally or alternatively, according to the examples disclosed herein, communication manager 1020 may support wireless communication at a second UE. The reference signal reception component 1050 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The timer component 1040 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. The beam failure recovery component 1045 may be configured to or otherwise support components for monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier when the first timer associated with beam failure recovery is active.

[0218] Figure 11FIG. 1100 is a block diagram of a communication manager 1120 that illustrates techniques in support of primary sidelink carrier updates in sidelink carrier aggregation in accordance with one or more aspects of the present disclosure. The communication manager 1120 may be an example of aspects of the communication manager 920, the communication manager 1020, or both as described herein. The communication manager 1120 or its various components may be examples of components for performing various aspects of the techniques for primary sidelink carrier updates in sidelink carrier aggregation as described herein. For example, the communication manager 1120 may include a reference signal transmission component 1125, a beam failure indication component 1130, a primary carrier change indication component 1135, a timer component 1140, a beam failure recovery component 1145, a reference signal reception component 1150, a sidelink communication component 1155, a sidelink carrier switching component 1160, a cell change condition component 1165, or any combination thereof. Each of these components may communicate directly or indirectly with each other (e.g., via one or more buses).

[0219] In accordance with an example as disclosed herein, the communication manager 1120 may support wireless communication at a first UE. The reference signal transmission component 1125 may be configured to or otherwise support a component for transmitting a first set of reference signals via a primary sidelink carrier configured via sidelink carrier aggregation and a second set of reference signals via one or more secondary sidelink carriers configured via sidelink carrier aggregation. The beam failure indication component 1130 may be configured to or otherwise support a component for receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to a secondary sidelink carrier configured with the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. The primary carrier change indication component 1135 may be configured to or otherwise support a component for transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a switch of the primary sidelink carrier to the set of beams.

[0220] In some examples, the sidelink communication component 1155 may be configured to or otherwise support a component for transmitting sidelink control information via the set of beams based on a switch of the primary sidelink carrier to the set of beams.

[0221] In some examples, the sidelink carrier switching component 1160 may be configured to or otherwise support a component for switching the primary sidelink carrier to a set of beams corresponding to the secondary sidelink carrier based on maintaining a radio resource control link of the primary sidelink carrier with the set of beams corresponding to the secondary sidelink carrier.

[0222] In some examples, the cell change condition component 1165 may be configured to or otherwise support components for determining that measurements of the set of beams corresponding to the secondary sidelink carrier meet a threshold associated with maintaining a radio resource control link for the primary sidelink carrier, wherein the control message is sent based on the measurements of the set of beams meeting the threshold.

[0223] In some examples, the control message is sent based on measurements of the set of beams corresponding to the secondary sidelink carrier being higher than measurements of a second set of beams corresponding to the primary sidelink carrier.

[0224] In some examples, the control message is sent prior to a beam failure detection procedure based on a beam failure instance.

[0225] In some examples, the primary carrier change indication component 1135 may be configured to or otherwise support components for initiating a beam failure detection procedure based on a beam failure instance, wherein the control message is sent during the beam failure detection procedure.

[0226] In some examples, the primary carrier change indication component 1135 may be configured to or otherwise support components for initiating a beam failure recovery procedure based on the number of beam failure instances meeting a threshold, wherein the control message is sent during the beam failure recovery procedure.

[0227] In some examples, a measurement message is received based on the number of beam failure instances meeting a threshold.

[0228] In some examples, the timer component 1140 may be configured to or otherwise support components for receiving a second control message indicating beam failure detection. In some examples, the timer component 1140 may be configured to or otherwise support components for initiating a first beam failure recovery timer based on the beam failure detection.

[0229] In some examples, the timer component 1140 may be configured to or otherwise support components for detecting expiration of the first beam failure recovery timer, wherein the control message is sent based on the expiration of the first beam failure recovery timer.

[0230] In some examples, the first beam failure recovery timer is associated with beam reselection.

[0231] In some examples, the timer component 1140 may be configured to or otherwise support components for detecting expiration of the first beam failure recovery timer. In some examples, the timer component 1140 may be configured to or otherwise support components for initiating a second beam failure recovery timer associated with performing a random access procedure for the primary sidelink carrier.

[0232] In some examples, the primary sidelink carrier corresponds to a first frequency range and the secondary sidelink carrier corresponds to a second frequency range.

[0233] In some examples, the primary sidelink carrier corresponds to a first radio frequency spectrum band in the radio frequency range and the secondary sidelink carrier corresponds to a second radio frequency spectrum band in the radio frequency range.

[0234] In some examples, the primary sidelink carrier and the secondary sidelink carrier correspond to the same radio frequency spectrum band.

[0235] Additionally or alternatively, according to examples disclosed herein, the communication manager 1120 may support wireless communication at a first UE. In some examples, the reference signal transmission component 1125 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The timer component 1140 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. The beam failure recovery component 1145 may be configured to or otherwise support components for transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier when the first timer associated with beam failure recovery is active.

[0236] In some examples, the timer component 1140 may be configured to or otherwise support components for initiating a second timer associated with beam failure recovery based on the expiration of the first timer. In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for performing a random access procedure for the primary sidelink carrier when the second timer is active.

[0237] In some examples, the beam failure indication component 1130 may be configured to or otherwise support components for receiving a control message indicating beam failure detection of the primary sidelink carrier based on the number of beam failure instances meeting a threshold, wherein the initiation of the first timer is based on the control message indicating beam failure detection.

[0238] In some examples, the timer component 1140 may be configured to or otherwise support components for detecting beam failure of the primary sidelink carrier based on a beam failure timer at the first UE exceeding a threshold.

[0239] In some examples, to support transmitting the set of beam failure recovery reference signals, the beam failure recovery component 1145 may be configured to or otherwise support components for transmitting the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

[0240] Additionally or alternatively, according to examples disclosed herein, the communication manager 1120 may support wireless communication at a second UE. The reference signal receiving component 1150 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. In some examples, the beam failure indication component 1130 may be configured to or otherwise support components for transmitting a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. In some examples, the primary carrier change indication component 1135 may be configured to or otherwise support components for receiving a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating switching the primary sidelink carrier to the set of beams.

[0241] In some examples, the sidelink communication component 1155 may be configured to or otherwise support components for receiving sidelink control information via the set of beams based on switching the primary sidelink carrier to the set of beams.

[0242] In some examples, the control message is received prior to a beam failure detection procedure based on a beam failure instance.

[0243] In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for initiating a beam failure detection procedure based on a beam failure instance, wherein the control message is received during the beam failure detection procedure.

[0244] In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for initiating a beam failure recovery procedure based on the number of beam failure instances meeting a threshold, wherein the control message is received during the beam failure recovery procedure.

[0245] In some examples, the beam failure indication component 1130 may be configured to or otherwise support components for determining that the number of beam failure instances meets a threshold, wherein transmitting the measurement message is based on the number of beam failure instances meeting a threshold.

[0246] Additionally or alternatively, according to examples disclosed herein, the communication manager 1120 may support wireless communication at a second UE. In some examples, the reference signal receiving component 1150 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. In some examples, the timer component 1140 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

[0247] In some examples, the timer component 1140 may be configured to or otherwise support components for initiating a second timer associated with beam failure recovery based on expiration of the first timer. In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for performing a random access procedure for the primary sidelink carrier while the second timer is active.

[0248] In some examples, the beam failure recovery component 1145 may be configured to or otherwise support components for sending a control message indicating beam failure detection of the primary sidelink carrier based on the number of beam failure instances meeting a threshold, wherein initiation of the first timer is based on the control message indicating beam failure detection.

[0249] In some examples, to support sending the set of beam failure recovery reference signals, the beam failure recovery component 1145 may be configured to or otherwise support components for monitoring the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

[0250] Figure 12FIG. illustrates a system 1200 including a device 1205 that supports techniques for primary side - link carrier update in side - link carrier aggregation in accordance with one or more aspects of the present disclosure. The device 1205 may be an example of, or include components of, the device 905, the device 1005, or the UE 115 as described herein. The device 1205 may communicate (e.g., wirelessly) with one or more network entities 105, one or more UEs 115, or any combination thereof. The device 1205 may include components for two - way voice and data communication, including components for sending and receiving communications, such as a communication manager 1220, an input / output (I / O) controller 1210, a transceiver 1215, an antenna 1225, a memory 1230, code 1235, and a processor 1240. These components may communicate electronically or otherwise be coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., bus 1245).

[0251] The I / O controller 1210 may manage the input signals and output signals of the device 1205. The I / O controller 1210 may also manage peripheral devices not integrated into the device 1205. In some cases, the I / O controller 1210 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 1210 may utilize an operating system, such as or another known operating system. Additionally or alternatively, the I / O controller 1210 may represent, or interact with, a modem, a keyboard, a mouse, a touch screen, or similar device. In some cases, the I / O controller 1210 may be implemented as part of a processor (such as the processor 1240). In some cases, a user may interact with the device 1205 via the I / O controller 1210 or via hardware components controlled by the I / O controller 1210.

[0252] In some cases, device 1205 may include a single antenna 1225. However, in some other cases, device 1205 may have more than one antenna 1225, and the more than one antenna may be capable of concurrently transmitting or receiving multiple wireless transmissions. Transceiver 1215 may communicate bidirectionally via one or more antennas 1225, wired or wireless links, as described herein. For example, transceiver 1215 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. Transceiver 1215 may also include a modem that is configured to: modulate a packet; provide the modulated packet to one or more antennas 1225 for transmission; and demodulate a packet received from one or more antennas 1225. Transceiver 1215 or transceiver 1215 and one or more antennas 1225 may be examples of transmitter 915, transmitter 1015, receiver 910, receiver 1010, or any combination thereof or their components, as described herein.

[0253] Memory 1230 may include random access memory (RAM) and read only memory (ROM). Memory 1230 may store computer-readable, computer-executable code 1235 that includes instructions that, when executed by processor 1240, cause device 1205 to perform the various functions described herein. Code 1235 may be stored in a non-transitory computer-readable medium (such as system memory) or another 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 the functions described herein. In some cases, memory 1230 may contain a basic input / output system (BIOS) or the like that may control basic hardware or software operations, such as interactions with peripheral components or devices.

[0254] 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, processor 1240 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated into processor 1240. Processor 1240 may be configured to execute computer-readable instructions stored in a memory (e.g., memory 1230) to cause device 1205 to perform various functions (e.g., support functions or tasks for techniques for primary side link carrier update in side link carrier aggregation). For example, device 1205 or components of device 1205 may include processor 1240 and memory 1230 coupled or coupled to processor 1240, and processor 1240 and memory 1230 are configured to perform the various functions described herein.

[0255] According to an example as disclosed herein, the communication manager 1220 may support wireless communication at a first UE. For example, the communication manager 1220 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The communication manager 1220 may be configured to or otherwise support components for receiving a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. The communication manager 1220 may be configured to or otherwise support components for transmitting a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0256] Additionally or alternatively, according to an example as disclosed herein, the communication manager 1220 may support wireless communication at a first UE. For example, the communication manager 1220 may be configured to or otherwise support components for transmitting a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. The communication manager 1220 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on a beam failure detection for the primary sidelink carrier. The communication manager 1220 may be configured to or otherwise support components for transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

[0257] Additionally or alternatively, according to examples disclosed herein, communication manager 1220 may support wireless communication at a second UE. For example, communication manager 1220 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 1220 may be configured to or otherwise support components for sending a measurement message based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured for the sidelink carrier aggregation based on a beam failure instance of the primary sidelink carrier. Communication manager 1220 may be configured to or otherwise support components for receiving a control message via layer 1 signaling or layer 2 signaling based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating to switch the primary sidelink carrier to the set of beams.

[0258] Additionally or alternatively, according to examples disclosed herein, communication manager 1220 may support wireless communication at a second UE. For example, communication manager 1220 may be configured to or otherwise support components for receiving a first set of reference signals via a primary sidelink carrier configured for sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured for sidelink carrier aggregation. Communication manager 1220 may be configured to or otherwise support components for initiating a first timer associated with beam failure recovery based on beam failure detection for the primary sidelink carrier. Communication manager 1220 may be configured to or otherwise support components for monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

[0259] By including or configuring communication manager 1220 according to examples described herein, device 1205 may support techniques for improving communication reliability and reducing latency by preventing RLF of a primary sidelink carrier configured for sidelink carrier aggregation.

[0260] In some examples, the communication manager 1220 may be configured to perform various operations (e.g., receive, monitor, transmit) using or otherwise cooperating with the transceiver 1215, one or more antennas 1225, or any combination thereof. Although the communication manager 1220 is illustrated as a separate component, in some examples, one or more functions described with reference to the communication manager 1220 may be supported or performed by the processor 1240, the memory 1230, the code 1235, or any combination thereof. For example, the code 1235 may include instructions that are executable by the processor 1240 to cause the device 1205 to perform various aspects of the techniques for primary sidelink carrier update in a sidelink carrier aggregation configuration as described herein, or the processor 1240 and the memory 1230 may be otherwise configured to perform or support such operations.

[0261] Figure 13 A flow chart illustrating a method 1300 of supporting techniques for primary sidelink carrier update in a sidelink carrier aggregation configuration according to one or more aspects of the present disclosure is illustrated. The operations of the method 1300 may be implemented by a UE or components thereof as described herein. For example, the operations of the method 1300 may be implemented by a UE or components thereof as described in reference to Figures 1 to 12 The described UE 115 may be performed. In some examples, the UE may execute an instruction set to control the functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform various aspects of the described functions.

[0262] At 1305, the method may include sending a first set of reference signals via a primary sidelink carrier of a sidelink carrier aggregation configuration and sending a second set of reference signals via one or more secondary sidelink carriers of the sidelink carrier aggregation configuration. The operations of 1305 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1305 may be performed as described in reference Figure 11 The described reference signal sending component 1125 performs.

[0263] At 1310, the method may include receiving a measurement message based at least in part on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to a secondary sidelink carrier of the sidelink carrier aggregation configuration based at least in part on a beam failure instance of the primary sidelink carrier. The operations of 1310 may be performed according to examples as disclosed herein. In some examples, aspects of the operations of 1310 may be performed by reference to Figure 11 The beam failure indication component 1130 is described to perform.

[0264] At 1315, the method may include transmitting, via layer 1 signaling or layer 2 signaling, a control message that indicates a switch of the primary sidelink carrier to the set of beams, based at least in part on measurements of the set of beams and beam failure instances of the primary sidelink carrier. The operations at 1315 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operations at 1315 may be performed by a primary carrier change indication component 1135 as described with reference to Figure 11 The primary carrier change indication component 1135 described.

[0265] Figure 14 FIG. illustrates a flowchart of a method 1400 that illustrates techniques for supporting an update of a primary sidelink carrier in a sidelink carrier aggregation configuration, in accordance with one or more aspects of the present disclosure. The operations of method 1400 may be implemented by a UE or components thereof as described herein. For example, the operations of method 1400 may be performed by a UE 115 as described with reference to Figures 1 to 12 The UE 115 described. In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0266] At 1405, the method may include transmitting a first set of reference signals via a primary sidelink carrier of a sidelink carrier aggregation configuration and transmitting a second set of reference signals via one or more secondary sidelink carriers of the sidelink carrier aggregation configuration. The operations at 1405 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operations at 1405 may be performed by a reference signal transmission component 1125 as described with reference to Figure 11 The reference signal transmission component 1125 described.

[0267] At 1410, the method may include initiating a first timer associated with beam failure recovery, based at least in part on beam failure detection of the primary sidelink carrier. The operations at 1410 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operations at 1410 may be performed by a timer component 1140 as described with reference to Figure 11 The timer component 1140 described.

[0268] At 1415, the method may include transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while a first timer associated with beam failure recovery is active. The operations at 1415 may be performed in accordance with the examples disclosed herein. In some examples, aspects of the operations at 1415 may be performed by a beam failure recovery component 1145 as described with reference to Figure 11 The beam failure recovery component 1145 described.

[0269] Figure 15FIG. 1500 is a flow diagram illustrating a method 1500 that exemplifies techniques supporting primary sidelink carrier updates in a sidelink carrier aggregation configuration. Operations of method 1500 may be implemented by a UE or components thereof as described herein. For example, operations of method 1500 may be performed by a UE 115 as described with reference to Figures 1 to 12 In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0270] At 1505, the method may include receiving a first set of reference signals via a primary sidelink carrier of a sidelink carrier aggregation configuration and receiving a second set of reference signals via one or more secondary sidelink carriers of the sidelink carrier aggregation configuration. The operation of 1505 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1505 may be performed by a reference signal receiving component 1150 as described with reference to Figure 11 In some examples, aspects of the operation of 1505 may be performed by a reference signal receiving component 1150 as described with reference to

[0271] At 1510, the method may include transmitting a measurement message at least partially based on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to a secondary sidelink carrier of the sidelink carrier aggregation configuration at least partially based on a beam failure instance of the primary sidelink carrier. The operation of 1510 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1510 may be performed by a beam failure indication component 1130 as described with reference to Figure 11 In some examples, aspects of the operation of 1510 may be performed by a beam failure indication component 1130 as described with reference to

[0272] At 1515, the method may include receiving a control message via layer 1 signaling or layer 2 signaling at least partially based on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams. The operation of 1515 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1515 may be performed by a primary carrier change indication component 1135 as described with reference to Figure 11 In some examples, aspects of the operation of 1515 may be performed by a primary carrier change indication component 1135 as described with reference to

[0273] Figure 16 FIG. 1600 is a flow diagram illustrating a method 1600 that exemplifies techniques supporting primary sidelink carrier updates in a sidelink carrier aggregation configuration. Operations of method 1600 may be implemented by a UE or components thereof as described herein. For example, operations of method 1600 may be performed by a UE 115 as described with reference to Figures 1 to 12performed by the described UE 115. In some examples, the UE may execute an instruction set to control functional elements of the UE to perform the described functions. Additionally or alternatively, the UE may use dedicated hardware to perform aspects of the described functions.

[0274] At 1605, the method may include receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by sidelink carrier aggregation. The operation of 1605 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1605 may be performed by a reference signal receiving component 1150 as described in reference to Figure 11 the described reference signal receiving component 1150.

[0275] At 1610, the method may include initiating a first timer associated with beam failure recovery based at least in part on beam failure detection of the primary sidelink carrier. The operation of 1610 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1610 may be performed by a timer component 1140 as described in reference to Figure 11 the described timer component 1140.

[0276] At 1615, the method may include monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while a first timer associated with beam failure recovery is active. The operation of 1615 may be performed in accordance with examples disclosed herein. In some examples, aspects of the operation of 1615 may be performed by a beam failure recovery component 1145 as described in reference to Figure 11 the described beam failure recovery component 1145.

[0277] An overview of aspects of the present disclosure is provided below:

[0278] Aspect 1: A method for wireless communication at a first UE, the method comprising: transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by sidelink carrier aggregation; receiving a measurement message based at least in part on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based at least in part on a beam failure instance of the primary sidelink carrier; and transmitting a control message via layer 1 signaling or layer 2 signaling based at least in part on the measurements of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

[0279] Aspect 2: The method according to aspect 1, the method further comprising: transmitting sidelink control information via the set of beams, at least partially based on switching the primary sidelink carrier to the set of beams.

[0280] Aspect 3: The method according to any one of aspects 1 to 2, the method further comprising: switching the primary sidelink carrier to the set of beams corresponding to the secondary sidelink carrier, at least partially based on maintaining a radio resource control link of the primary sidelink carrier corresponding to the set of beams of the secondary sidelink carrier.

[0281] Aspect 4: The method according to any one of aspects 1 to 3, the method further comprising: determining that a measurement of the set of beams corresponding to the secondary sidelink carrier satisfies a threshold associated with maintaining a radio resource control link of the primary sidelink carrier, wherein transmitting the control message is at least partially based on the measurement of the set of beams satisfying the threshold.

[0282] Aspect 5: The method according to any one of aspects 1 to 4, wherein the control message is transmitted at least partially based on a measurement of the set of beams corresponding to the secondary sidelink carrier being higher than a measurement of a second set of beams corresponding to the primary sidelink carrier.

[0283] Aspect 6: The method according to any one of aspects 1 to 5, wherein the control message is transmitted prior to a beam failure detection procedure that is at least partially based on the beam failure instance.

[0284] Aspect 7: The method according to any one of aspects 1 to 5, the method further comprising: initiating a beam failure detection procedure at least partially based on the beam failure instance, wherein the control message is transmitted during the beam failure detection procedure.

[0285] Aspect 8: The method according to any one of aspects 1 to 5, the method further comprising: initiating a beam failure recovery procedure at least partially based on a number of beam failure instances satisfying a threshold, wherein the control message is transmitted during the beam failure recovery procedure.

[0286] Aspect 9: The method according to any one of aspects 1 to 8, wherein the measurement message is received at least partially based on a number of beam failure instances satisfying a threshold.

[0287] Aspect 10: The method according to any one of aspects 1 to 9, the method further comprising: receiving a second control message indicating beam failure detection; and initiating a first beam failure recovery timer at least partially based on the beam failure detection.

[0288] Aspect 11: The method according to aspect 10, the method further comprising: detecting an expiration of the first beam failure recovery timer, wherein transmitting the control message is at least partially based on the expiration of the first beam failure recovery timer.

[0289] Aspect 12: The method according to any one of aspects 10 to 11, wherein the first beam failure recovery timer is associated with beam reselection.

[0290] Aspect 13: The method according to any one of aspects 10 to 12, the method further comprising: detecting an expiration of the first beam failure recovery timer; and initiating a second beam failure recovery timer associated with performing a random access procedure for the primary sidelink carrier.

[0291] Aspect 14: The method according to any one of aspects 1 to 13, wherein the primary sidelink carrier corresponds to a first frequency range, and the secondary sidelink carrier corresponds to a second frequency range.

[0292] Aspect 15: The method according to any one of aspects 1 to 14, wherein the primary sidelink carrier corresponds to a first radio frequency spectrum band in a radio frequency range, and the secondary sidelink carrier corresponds to a second radio frequency spectrum band in the radio frequency range.

[0293] Aspect 16: The method according to any one of aspects 1 to 15, wherein the primary sidelink carrier and the secondary sidelink carrier correspond to the same radio frequency spectrum band.

[0294] Aspect 17: A method for wireless communication at a first UE, the method comprising: transmitting a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmitting a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiating a first timer associated with beam failure recovery at least partially based on beam failure detection of the primary sidelink carrier; and transmitting a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier when the first timer associated with beam failure recovery is active.

[0295] Aspect 18: The method according to aspect 17, the method further comprising: initiating a second timer associated with beam failure recovery at least partially based on expiration of the first timer; and performing a random access procedure for the primary sidelink carrier when the second timer is active.

[0296] Aspect 19: The method according to any one of aspects 17 to 18, the method further comprising: receiving a control message indicating the beam failure detection of the primary sidelink carrier based at least in part on the number of beam failure instances meeting a threshold, wherein initiating the first timer is based at least in part on the control message indicating the beam failure detection.

[0297] Aspect 20: The method according to any one of aspects 17 to 19, the method further comprising: detecting a beam failure of the primary sidelink carrier based at least in part on the beam failure timer at the first UE exceeding a threshold.

[0298] Aspect 21: The method according to any one of aspects 17 to 20, wherein transmitting the set of beam failure recovery reference signals comprises: transmitting the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

[0299] Aspect 22: A method for wireless communication at a second UE, the method comprising: receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; transmitting a measurement message based at least in part on the first set of reference signals and the second set of reference signals, the measurement message indicating measurements of a set of beams corresponding to the secondary sidelink carriers configured by the sidelink carrier aggregation based at least in part on beam failure instances of the primary sidelink carrier; and receiving a control message via layer 1 signaling or layer 2 signaling based at least in part on the measurements of the set of beams and the beam failure instances of the primary sidelink carrier, the control message indicating switching the primary sidelink carrier to the set of beams.

[0300] Aspect 23: The method according to aspect 22, the method further comprising: receiving sidelink control information via the set of beams based at least in part on switching the primary sidelink carrier to the set of beams.

[0301] Aspect 24: The method according to any one of aspects 22 to 23, wherein the control message is received prior to a beam failure detection procedure based at least in part on the beam failure instances.

[0302] Aspect 25: The method according to any one of aspects 22 to 24, the method further comprising: initiating a beam failure detection procedure based at least in part on the beam failure instances, wherein the control message is received during the beam failure detection procedure.

[0303] Aspect 26: The method according to any one of aspects 22 to 27, the method further comprising: initiating a beam failure recovery procedure at least in part based on the number of beam failure instances meeting a threshold, wherein the control message is received during the beam failure recovery procedure.

[0304] Aspect 28: The method according to any one of aspects 22 to 26, the method further comprising: determining that the number of beam failure instances meets a threshold, wherein transmitting the measurement message is at least in part based on the number of beam failure instances meeting the threshold.

[0305] Aspect 29: A method for wireless communication at a second UE, the method comprising: receiving a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receiving a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiating a first timer associated with beam failure recovery at least in part based on beam failure detection of the primary sidelink carrier; and monitoring a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

[0306] Aspect 30: The method according to aspect 29, the method further comprising: initiating a second timer associated with beam failure recovery at least in part based on expiration of the first timer; and performing a random access procedure for the primary sidelink carrier while the second timer is active.

[0307] Aspect 31: The method according to any one of aspects 29 to 30, the method further comprising: transmitting a control message indicating the beam failure detection of the primary sidelink carrier at least in part based on the number of beam failure instances meeting a threshold, wherein initiating the first timer is at least in part based on the control message indicating the beam failure detection.

[0308] Aspect 32: The method according to any one of aspects 29 to 31, wherein transmitting the set of beam failure recovery reference signals comprises: monitoring the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

[0309] Aspect 33: An apparatus for wireless communication at a first UE, the apparatus comprising: a processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the apparatus to perform the method according to any one of aspects 1 to 16.

[0310] Aspect 34: An apparatus for wireless communication at a first UE, the apparatus including at least one component for performing the method according to any one of Aspects 1 to 16.

[0311] Aspect 35: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code including instructions executable by a processor to perform the method according to any one of Aspects 1 to 16.

[0312] Aspect 36: An apparatus for wireless communication at a first UE, the apparatus including: a processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the apparatus to perform the method according to any one of Aspects 17 to 21.

[0313] Aspect 37: An apparatus for wireless communication at a first UE, the apparatus including at least one component for performing the method according to any one of Aspects 17 to 21.

[0314] Aspect 38: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code including instructions executable by a processor to perform the method according to any one of Aspects 17 to 21.

[0315] Aspect 39: An apparatus for wireless communication at a second UE, the apparatus including: a processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the apparatus to perform the method according to any one of Aspects 22 to 28.

[0316] Aspect 40: An apparatus for wireless communication at a second UE, the apparatus including at least one component for performing the method according to any one of Aspects 22 to 28.

[0317] Aspect 41: A non-transitory computer-readable medium storing code for wireless communication at a second UE, the code including instructions executable by a processor to perform the method according to any one of Aspects 22 to 28.

[0318] Aspect 42: An apparatus for wireless communication at a second UE, the apparatus including: a processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the apparatus to perform the method according to any one of Aspects 29 to 32.

[0319] Aspect 43: An apparatus for wireless communication at a second UE, the apparatus including at least one component for performing the method according to any one of Aspects 29 to 32.

[0320] Aspect 44: A non-transitory computer-readable medium storing code for wireless communication at a second UE, the code including instructions executable by a processor to perform the method according to any one of Aspects 29 to 32.

[0321] It should be noted that the methods described herein describe possible specific implementations, and the operations and steps may be rearranged or otherwise modified and other specific implementations are also possible. In addition, aspects from two or more methods may be combined.

[0322] Although aspects of LTE, LTE-A, LTE-A Pro, or NR systems may be described for example purposes and the LTE, LTE-A, LTE-A Pro, or NR terms may be used in most of the description, the techniques described herein are also applicable to networks other than LTE, LTE-A, LTE-A Pro, or NR networks. For example, the described techniques may be applicable to various other wireless communication 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, and other systems and radio technologies not explicitly mentioned herein.

[0323] The information and signals described herein may be represented using any of a variety of different technologies and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the specification may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0324] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or performed using a general-purpose processor, DSP, ASIC, CPU, 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. The general-purpose processor may be a microprocessor, but in the alternative, the processor may be any processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0325] The functions described herein can be implemented using hardware, software executed by a processor, firmware, or any combination thereof. If implemented using software executed by a processor, the functions can be stored as one or more instructions or code on a computer-readable medium or transmitted using one or more instructions or code on a computer-readable medium. Other examples and specific implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination of these items. The features implementing the functions can also be physically located at different positions, including being distributed such that various portions of the functions are implemented at different physical locations.

[0326] Computer-readable media includes both non-transitory computer storage media and communication media, which includes any medium that facilitates transfer of a computer program from one location to another. A non-transitory storage medium can 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 can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disc (CD) ROM or other optical disc 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 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 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, then 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 medium. As used herein, disk and disc include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc. Disk can magnetically reproduce data, and disc can optically reproduce data using lasers. Combinations of the above are also included within the scope of computer-readable media.

[0327] As used herein (including in the claims), the "or" used in a list of items (e.g., a list of items accompanied by a phrase such as "at least one of" or "one or more of") indicates an inclusive listing such that, for example, the listing 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). Additionally, as used herein, the phrase "based on" 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 the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on".

[0328] The term "determine" encompasses a variety of actions, and thus, "determine" can include operations such as calculating, computing, processing, deriving, researching, looking up (such as looking up in a table, database, or other data structure), ascertaining, and similar actions. Additionally, "determine" can include receiving (e.g., receiving information), accessing (e.g., accessing data stored in a memory), etc. Further, "determine" can include parsing, obtaining, selecting, choosing, establishing, and other such similar actions.

[0329] In the figures, similar components or features may have the same reference numeral. Additionally, various components of the same type can be distinguished by adding a dash and a second numeral used to differentiate between similar components after the reference numeral. If only the first reference numeral is used in the specification, the description can apply to any of the similar components having the same first reference numeral, regardless of the second reference numeral or other subsequent reference numerals.

[0330] The description set forth herein in conjunction with the figures describes example configurations and does not represent all examples that can be implemented or are within the scope of the claims. The term "example" as used herein means "serving as an example, instance, or illustration" and not "preferred" or "advantageous over other examples". The detailed description includes specific details for providing an understanding of the described techniques. However, the techniques can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0331] The description provided herein is to enable a person of ordinary skill in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to a person of ordinary skill in the art, and the general principles defined herein can 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 broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for wireless communication at a first user equipment (UE), the apparatus comprising: Processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the device to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; receive a measurement message at least partially based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to a secondary sidelink carrier configured by the sidelink carrier aggregation at least partially based on a beam failure instance of the primary sidelink carrier; and send a control message via layer 1 signaling or layer 2 signaling at least partially based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

2. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Transmit sidelink control information via the set of beams, at least in part based on switching the primary sidelink carrier to the set of beams.

3. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Switch the primary sidelink carrier to the set of beams corresponding to the secondary sidelink carrier, at least in part based on maintaining a radio resource control link of the primary sidelink carrier with respect to the set of beams corresponding to the secondary sidelink carrier.

4. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Determine that a measurement of the set of beams corresponding to the secondary sidelink carrier meets a threshold associated with maintaining a radio resource control link of the primary sidelink carrier, wherein transmitting the control message is at least in part based on the measurement of the set of beams meeting the threshold.

5. The apparatus according to claim 1, wherein the control message is transmitted at least in part based on a measurement of the set of beams corresponding to the secondary sidelink carrier being higher than a measurement of a second set of beams corresponding to the primary sidelink carrier.

6. The apparatus according to claim 1, wherein the control message is transmitted prior to a beam failure detection procedure based at least in part on the beam failure instance.

7. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a beam failure detection procedure at least in part based on the beam failure instance, wherein the control message is transmitted during the beam failure detection procedure.

8. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a beam failure recovery procedure at least in part based on a number of beam failure instances meeting a threshold, wherein the control message is transmitted during the beam failure recovery procedure.

9. The apparatus according to claim 1, wherein the measurement message is received at least in part based on the number of beam failure instances meeting a threshold.

10. The apparatus according to claim 1, wherein the instructions are further executable by the processor to cause the apparatus to: receive a second control message indicating beam failure detection; and initiate a first beam failure recovery timer at least in part based on the beam failure detection.

11. The apparatus according to claim 10, wherein the instructions are further executable by the processor to cause the apparatus to: detect expiration of the first beam failure recovery timer, wherein transmitting the control message is at least in part based on the expiration of the first beam failure recovery timer.

12. The apparatus according to claim 10, wherein: The first beam failure recovery timer is associated with beam reselection.

13. The apparatus according to claim 10, wherein the instructions are further executable by the processor to cause the apparatus to: detect expiration of the first beam failure recovery timer; and initiate a second beam failure recovery timer associated with performing a random access procedure for the primary side link carrier.

14. The apparatus according to claim 1, wherein the primary side link carrier corresponds to a first frequency range, and the secondary side link carrier corresponds to a second frequency range.

15. The apparatus according to claim 1, wherein the primary side link carrier corresponds to a first radio frequency spectrum band in the radio frequency range, and the secondary side link carrier corresponds to a second radio frequency spectrum band in the radio frequency range.

16. The apparatus according to claim 1, wherein the primary side link carrier and the secondary side link carrier correspond to the same radio frequency spectrum band.

17. An apparatus for wireless communication at a first user equipment (UE), the apparatus comprising: Processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the device to: transmit a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and transmit a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with beam failure recovery at least partially based on a beam failure detection of the primary sidelink carrier; and transmit a set of beam failure recovery reference signals via one or more beams of the primary sidelink carrier while the first timer associated with beam failure recovery is active.

18. The apparatus according to claim 17, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a second timer associated with beam failure recovery at least in part based on the expiration of the first timer; and Perform a random access procedure for the primary side link carrier while the second timer is active.

19. The apparatus according to claim 17, wherein the instructions are further executable by the processor to cause the apparatus to: Receive a control message indicating the beam failure detection of the primary side link carrier at least in part based on the number of beam failure instances meeting a threshold, wherein initiating the first timer is at least in part based on the control message indicating the beam failure detection.

20. The apparatus according to claim 17, wherein the instructions are further executable by the processor to cause the apparatus to: Detect a beam failure of the primary side link carrier at least in part based on a beam failure timer at the first UE exceeding a threshold.

21. The apparatus according to claim 17, wherein the instructions for transmitting the set of beam failure recovery reference signals are executable by the processor to cause the apparatus to: Transmit the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

22. An apparatus for wireless communication at a second user equipment (UE), the apparatus comprising: Processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the device to: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; send a measurement message at least partially based on the first set of reference signals and the second set of reference signals, the measurement message indicating a measurement of a set of beams corresponding to a secondary sidelink carrier configured by the sidelink carrier aggregation at least partially based on a beam failure instance of the primary sidelink carrier; and receive a control message via layer 1 signaling or layer 2 signaling at least partially based on the measurement of the set of beams and the beam failure instance of the primary sidelink carrier, the control message indicating a handover of the primary sidelink carrier to the set of beams.

23. The apparatus according to claim 22, wherein the instructions are further executable by the processor to cause the apparatus to: Receive side link control information via the set of beams at least in part based on switching the primary side link carrier to the set of beams.

24. The apparatus according to claim 22, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a beam failure detection procedure at least in part based on the beam failure instance, wherein the control message is received during the beam failure detection procedure.

25. The apparatus according to claim 22, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a beam failure recovery procedure at least in part based on the number of beam failure instances meeting a threshold, wherein the control message is received during the beam failure recovery procedure.

26. The apparatus according to claim 22, wherein the instructions are further executable by the processor to cause the apparatus to: Determine that the number of beam failure instances meets a threshold, wherein transmitting the measurement message is at least in part based on the number of beam failure instances meeting the threshold.

27. An apparatus for wireless communication at a second user equipment (UE), the apparatus comprising: Processor; and a memory coupled to the processor, the memory storing instructions executable by the processor to cause the device to: receive a first set of reference signals via a primary sidelink carrier configured by sidelink carrier aggregation and receive a second set of reference signals via one or more secondary sidelink carriers configured by the sidelink carrier aggregation; initiate a first timer associated with beam failure recovery at least partially based on a beam failure detection of the primary sidelink carrier; and When the first timer associated with beam failure recovery is active, monitor a set of beam failure recovery reference signals via one or more beams of the primary side link carrier.

28. The apparatus according to claim 27, wherein the instructions are further executable by the processor to cause the apparatus to: Initiate a second timer associated with beam failure recovery at least in part based on the expiration of the first timer; and Perform a random access procedure for the primary side link carrier while the second timer is active.

29. The apparatus according to claim 27, wherein the instructions are further executable by the processor to cause the apparatus to: Transmit a control message indicating the beam failure detection of the primary side link carrier at least in part based on the number of beam failure instances meeting a threshold, wherein initiating the first timer is at least in part based on the control message indicating the beam failure detection.

30. The apparatus according to claim 27, wherein the instructions for transmitting the set of beam failure recovery reference signals are executable by the processor to cause the apparatus to: Monitor the set of beam failure recovery reference signals via a subset of beam failure recovery reference signal resources from a set of beam failure recovery reference signal resources.

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