Methods and apparatus for bidirectional sidelink beam failure detection

Abstract

Methods, systems, and devices for wireless communication are described. For example, the described techniques provide for configuring sidelink beam failure detection reference signals for determining a beam failure on a sidelink between a first sidelink user equipment (UE) and a second sidelink UE. The first UE can determine a first set of sidelink beam failure detection reference signals to transmit to the second UE and a second set of sidelink beam failure detection reference signals to receive from the second UE. The first UE can transmit the first set to the second UE using a set of sidelink transmit beams. The first UE can further monitor for the determined second set using a set of sidelink receive beams. Based on the first and second sets of sidelink beam failure detection reference signals, the first and second UEs can communicate over the sidelink.

Description

[0001] Cross-referencing

[0002] This patent application claims priority to U.S. Patent Application No. 17349644, filed June 16, 2021, entitled "TECHNIQUES FOR BI-DIRECTIONAL SIDELINK BEAM FAILURE DETECTION", and U.S. Provisional Patent Application No. 63 / 053,083, filed July 17, 2020, entitled "TECHNIQUES FOR BI-DIRECTIONAL SIDELINK BEAM FAILURE DETECTION", each of which is assigned to the assignee of this application and is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to wireless communications, including techniques for bidirectional sidelink beam fault detection. Background Technology

[0004] Wireless communication systems are widely deployed to provide various types of communication content, such as voice, video, packet data, message sending and receiving, broadcasting, and so on. These systems can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of such multiple access systems include fourth-generation (4G) systems (such as Long Term Evolution (LTE) systems, LTE-A Advanced (LTE-A) systems, or LTE-A Pro systems) and fifth-generation (5G) systems, which may be referred to as NR systems. These systems can employ various technologies, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or Discrete Fourier Transform Extended Orthogonal Frequency Division Multiplexing (DFT-S-OFDM). A wireless multiple access communication system may include one or more base stations or one or more network access nodes, each of which simultaneously supports communication from multiple communication devices, which may also be referred to as User Equipment (UE).

[0005] UEs and base stations can communicate via beamforming to improve communication reliability and efficiency. In some cases, beamforming communication may fail due to congestion, movement, or other reasons. When a beam fails, the base station and UE can identify a new beam for communication. Summary of the Invention

[0006] The described techniques relate to improved methods, systems, devices, and apparatuses that support techniques for bi-directional sidelink beam failure detection. For example, the described techniques provide for a sidelink beam failure detection reference signal configured for determining a beam failure on a sidelink between a first sidelink user equipment (UE) and a second sidelink UE. The first UE can determine a first set of sidelink beam failure detection reference signals to transmit to the second UE, and the first UE can determine a second set of sidelink beam failure detection reference signals to receive from the second UE. The first UE can transmit the first set of sidelink beam failure detection reference signals to the second UE using a set of sidelink transmit beams. The first UE can also monitor for the determined second set of sidelink beam failure detection reference signals using a set of sidelink receive beams. Based on the first and second sets of sidelink beam failure detection reference signals, the first and second UEs can communicate over the sidelink.

[0007] A method of wireless communication is described at a first UE. The method can include transmitting a first set of sidelink beam failure detection reference signals to a second UE using a set of sidelink transmit beams, monitoring for a second set of sidelink beam failure detection reference signals using a set of sidelink receive beams, and communicating with the second UE over a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0008] An apparatus for wireless communication at a first UE is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to transmit a first set of sidelink beam failure detection reference signals to a second UE using a set of sidelink transmit beams, monitor for a second set of sidelink beam failure detection reference signals using a set of sidelink receive beams, and communicate with the second UE over a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0009] Another apparatus for wireless communication at a first UE is described. The apparatus can include means for transmitting a first set of sidelink beam failure detection reference signals to a second UE using a set of sidelink transmit beams, monitoring for a second set of sidelink beam failure detection reference signals using a set of sidelink receive beams, and communicating with the second UE over a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0010] A non-transitory computer-readable medium storing code for wireless communications at a first UE is described. The code can include instructions executable by a processor to transmit, to a second UE, a set of first sidelink beam failure detection reference signals using a set of sidelink transmit beams, monitor for a set of second sidelink beam failure detection reference signals using a set of sidelink receive beams, and communicate with the second UE on a sidelink based on the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0011] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving, from the second UE, a control message configuring the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0012] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for transmitting, to the second UE, a first control message configuring the set of second sidelink beam failure detection reference signals that the second UE can transmit to the first UE, the set of first sidelink beam failure detection reference signals that the second UE can receive from the first UE, or both the set of second sidelink beam failure detection reference signals and the set of first sidelink beam failure detection reference signals.

[0013] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving, from a base station, a second control message configuring the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of second sidelink beam failure detection reference signals and the set of first sidelink beam failure detection reference signals, where the first control message can be transmitted to the second UE based on receiving the second control message from the base station.

[0014] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving, from a base station, a control message configuring the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0015] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for receiving, from the second UE, a control message indicating a counter threshold of a beam failure indication counter, an expiration timer value of a beam failure indication timer, or both the counter threshold of the beam failure indication timer and the expiration timer value of the beam failure indication timer.

[0016] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for transmitting, to the second UE, a control message indicating a counter threshold of a beam failure indication counter, an expiration timer value of a beam failure indication timer, or both the counter threshold of the beam failure indication timer and the expiration timer value of the beam failure indication timer.

[0017] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for receiving, from a base station, a control message indicating a counter threshold of a beam failure indication counter, an expiration timer value of a beam failure indication timer, or both the counter threshold of the beam failure indication timer and the expiration timer value of the beam failure indication timer.

[0018] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for detecting a beam failure based on monitoring for reception of the second set of sidelink beam failure detection reference signals; and performing a beam failure recovery procedure with the second UE based on detecting the beam failure.

[0019] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals based on detecting the beam failure, where the beam failure recovery procedure can be performed with the second UE based on refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals.

[0020] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for transmitting, to the second UE, a base station, or both the second UE and the base station, an indication of the beam failure, where the beam failure recovery procedure can be performed based on transmitting the indication.

[0021] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for determining that a reference signal received power of one or more of the second set of sidelink beam failure detection reference signals can be below a received power threshold, initiating a beam failure timer based on the determination that the reference signal received power can be below the received power threshold, and incrementing a beam failure counter each time the second set of sidelink beam failure detection reference signals is received with the reference signal received power below the received power threshold prior to expiration of the beam failure timer, where the beam failure can be detected based on the beam failure counter reaching a counter threshold.

[0022] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for receiving, from the second UE or base station, an indication of a beam failure associated with the second UE, and performing a beam failure recovery procedure with the second UE based on receiving the indication.

[0023] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for incrementing a beam failure counter based on receiving the indication of the beam failure, where the beam failure recovery procedure can be performed based on the beam failure counter reaching a counter threshold.

[0024] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for adjusting one or more sidelink receive beams used to receive the second set of sidelink beam failure detection reference signals.

[0025] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for transmitting, to the second UE, an indication of adjusting the one or more sidelink receive beams.

[0026] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means for, or instructions for receiving, from the second UE, an indication of adjusting one or more sidelink receive beams used by the second UE to receive the first set of sidelink beam failure detection reference signals.

[0027] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include a sidelink synchronization signal block or a sidelink channel state information reference signal.

[0028] In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a first periodicity associated with transmitting the first set of sidelink beam failure detection reference signals can be different than a second periodicity for monitoring for reception of the second set of sidelink beam failure detection reference signals.

[0029] A method of wireless communication is described. The method can include transmitting, to a first UE, a control message indicating a first set of sidelink beam failure detection reference signals to be transmitted to a second UE, a second set of sidelink beam failure detection reference signals to be received from the second UE, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals; and communicating with the first UE or the second UE based on transmitting the control message.

[0030] An apparatus for wireless communication at a base station is described. The apparatus can include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions can be executable by the processor to cause the apparatus to transmit, to a first UE, a control message indicating a first set of sidelink beam failure detection reference signals to be transmitted to a second UE, a second set of sidelink beam failure detection reference signals to be received from the second UE, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals; and communicate with the first UE or the second UE based on transmitting the control message.

[0031] Another apparatus for wireless communication at a base station is described. The apparatus can include means for transmitting, to a first UE, a control message indicating a first set of sidelink beam failure detection reference signals to be transmitted to a second UE, a second set of sidelink beam failure detection reference signals to be received from the second UE, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals; and communicating with the first UE or the second UE based on transmitting the control message.

[0032] A non-transitory computer-readable medium storing code for wireless communications at a base station is described. The code can include instructions executable by a processor to transmit, to a first UE, a control message indicating a set of first sidelink beam failure detection reference signals to be transmitted to a second UE, a set of second sidelink beam failure detection reference signals to be received from the second UE, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals, and communicate with the first UE or the second UE based on transmitting the control message.

[0033] In some examples of the method, device, and non-transitory computer-readable medium described herein, transmitting the control message can include operations, features, means, or instructions for transmitting, to the first UE, an indication that the first UE can communicate the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals to the second UE.

[0034] In some examples of the method, device, and non-transitory computer-readable medium described herein, transmitting the control message can include operations, features, means, or instructions for transmitting, to the first UE, a control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0035] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein can further include operations, features, means, or instructions for receiving, from the first UE, an indication of a beam failure associated with a sidelink between the first UE and the second UE, and transmitting, to the second UE, an indication of the beam failure. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 An example of a wireless communications system that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated.

[0037] Figure 2 An example of a wireless communications system that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated.

[0038] Figure 3A And Figure 3B An example of a communication timeline that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated.

[0039] Figure 4 An example of a process flow diagram that illustrates techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is described.

[0040] Figure 5 And Figure 6 A block diagram of a device that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0041] Figure 7 A block diagram of a communications manager that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0042] Figure 8 A diagram of a system including a device that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0043] Figure 9 And Figure 10 A block diagram of a device that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0044] Figure 11 A block diagram of a communications manager that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0045] Figure 12 A diagram of a system including a device that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown.

[0046] Figure 13 And Figure 14 A flow diagram illustrating a method that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0047] Some wireless communications systems can support beamformed communications to improve signal reliability and efficiency, among other benefits. User equipment (UEs) and base stations can utilize beamforming for communications, and in some cases, a set of beams used for communications between a UE and a base station can fail or become unavailable for communications. These occurrences can be due to blockage by physical objects, movement of the UE or base station, or some other cause. In such cases, one or both devices can detect that a beam failure has occurred and identify a new set of beams for communications.

[0048] Wireless communications systems can also support communications between UEs or other nodes in the network. In this case, a device (e.g., a UE) can establish a sidelink for communications. Further, a device can communicate on the sidelink using beamforming. When a UE 115 utilizes beamforming on a sidelink, a first UE can utilize different transmit and receive beams to communicate with a second UE. More specifically, a first beam used by the first UE to transmit to the second UE can be different from a second beam used by the first UE to receive from the second UE. This scenario can occur due to a maximum permissible emission (MPE) issue (e.g., a transmit beam pointing towards a user’s head can not be used). For example, a receive beam can point towards a user’s head, but the same beam can not be used for transmission. As described above with respect to access links (e.g., base station to UE communications), sidelink beams can fail due to various issues. In the case where the transmit and receive beams are different, monitoring by only one of the devices, as performed in access links, can be unhelpful to identify when a beam fails. Implementations described herein provide techniques for identifying sidelink beam failures.

[0049] For example, a first sidelink UE can be configured with a first set of sidelink beam failure detection reference signals (BFD-RS) that can be transmitted to a second UE over a sidelink. Further, the first sidelink UE can be configured with a second set of sidelink BFD-RS that the first UE is to receive from the second UE. The second UE can be similarly configured with the first set of sidelink BFD-RS (to receive from the first UE) and the second set of BFD-RS (to transmit to the first UE). Each UE can monitor a reference signal received power (RSRP) of the respective reference signals and identify a beam failure condition based on the RSRP. For example, if one or more of the received BFD-RS is below a threshold, one of the UEs can initiate a beam failure recovery procedure to identify a new beam for communications. The UEs can be configured with the respective BFD-RS based on a pre-configuration, a control message received from a base station, or control information received from another sidelink UE. That is, a UE of a sidelink can configure a BFD-RS for another sidelink UE to transmit and / or receive (e.g., monitor).

[0050] Aspects of the subject matter described herein can be implemented to realize one or more advantages. The described techniques can support improved sidelink beamforming frameworks, reduce signaling overhead, and improve reliability, among other advantages. As such, supported techniques can include improved network operations, and in some examples, can promote network efficiency and other benefits.

[0051] Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are further described with respect to wireless communications systems, communication timelines, and process flow diagrams. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts related to techniques for bi-directional sidelink beam failure detection.

[0052] Figure 1 An example of a wireless communications system 100 that supports techniques for bi-directional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated. The wireless communications system 100 can include one or more base stations 105, one or more UEs 115, and a core network 130. In some examples, the wireless communications system 100 can be a Long Term Evolution (LTE) network, an LTE- Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some examples, the wireless communications system 100 can support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, communications with low-cost and low-complexity devices, or any combination thereof.

[0053] The base stations 105 can be dispersed throughout the geographic area 100 and can be

[0054] The UEs 115 can be dispersed throughout the geographic area 100, and each UE 115 can be stationary or mobile or both at different times. The UEs 115 can be devices in different forms Figure 1 Some example UEs 115 are illustrated in FIG. 1. The UEs 115 described herein can be able to communicate with various types of devices, such as other UEs 115, base stations 105, or network equipment (e.g., core network nodes, relay devices, integrated access and backhaul (IAB) nodes, or other network equipment), as shown in FIG. 1. Figure 1

[0055] ​The base stations 105 can communicate with the core network 130, or with one another, or both. For example, the base stations 105 can interface with the core network 130 through one or more backhaul links 120 (e.g., via an SI, N2, N3, or other interface). The base stations 105 can communicate with one another over the backhaul links 120 (e.g., via an X2, Xn, or other interface) either directly (e.g., direct

[0056] One or more of the base stations 105 described herein can include or can be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or giga-NodeB (either of which can be referred to as a gNB), a Home NodeB, a Home eNodeB, or other suitable terminology.

[0057] A UE 115 can include or can be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” can also be referred to as a unit, a station, a terminal, or a client, among other examples. A UE 115 can also include or can 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, a UE 115 can include or 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 communications (MTC) device, among other examples, which can be implemented in various objects such as appliances or vehicles, meters or other equipment, among other examples.

[0058] The UEs 115 described herein can be able to communicate with various types of devices, such as other UEs 115 that can sometimes act as relays or Figure 1 network equipment including base stations 105 and customer premises equipment, as shown in FIG. 1.

[0059] The UEs 115 and the base stations 105 can wirelessly communicate with one another via one or more communication links 125 over one or more carriers. The term “carrier” can refer to a set of radio frequency spectrum resources with a defined physical layer structure configured to carry physical layer signaling or user data. For example, a carrier used for a communication link 125 can include a portion of the radio frequency spectrum band that can be used for transmitting or receiving physical layer signaling or user data according to one or more physical layer structures (e.g., a numerology) for a given radio access technology (e.g., LTE, LTE-A, LTE-A Pro, NR). Each physical layer structure can include one or more physical channels carrying physical layer signaling or user data. A carrier can be associated with a bandwidth (e.g., 20 MHz) and can be positioned at any frequency within the radio frequency spectrum band. In some examples, the carrier can be associated with a transmit power and a receive power used by a base station 105 to transmit or receive data to or from a UE 115. A carrier can be partitioned into sub-carriers (e.g., resource blocks (RBs) or physical resource blocks (PRBs)) that carry physical layer signaling or user data. Each sub-carrier can be a frequency sub-band, and a UE 115 can utilize the sub-carriers to transmit or receive data to or from a base station 105. The sub-carriers can be interlaced across the carrier.

[0060] In some examples (e.g., in a carrier aggregation configuration), a carrier can also have acquisition signaling or control signaling that coordinates operations of other carriers. A carrier can be associated with a frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)) and can be positioned according to a channel raster for discovery by UEs 115. Carriers can be operated in a standalone mode where initial acquisition and connection can be achieved via carriers, or carriers can be operated in a non-standalone mode that uses different carriers (e.g., different carriers for a same or a different radio access technology) for attachment.

[0061] The communication links 125 shown in wireless communication system 100 can include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Carriers can carry downlink or uplink communications (e.g., in an FDD mode), or can be configured to carry downlink and uplink communications (e.g., in a TDD mode).

[0062] A carrier can be associated with a bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth can be referred to as a “system bandwidth” of the carrier or wireless communications system 100. For example, the carrier bandwidth can be one of a number of determined bandwidths for carriers of a radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 megahertz (MHz)). Devices of wireless communications system 100 (e.g., base stations 105, UEs 115, or both) can have hardware configurations that support communications over the carrier bandwidth, or can be configurable to support communications over one of a set of carrier bandwidths. In some examples, wireless communications system 100 can include base stations 105 or UEs 115 that support simultaneous communications via carriers associated with multiple carrier bandwidths. In some examples, each served UE 115 can be configured for operating over portions (e.g., sub-bands, BWPs) or all of a carrier bandwidth.

[0063] Signal waveforms transmitted over a carrier can be composed of multiple subcarriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)). In OFDM systems, a resource element can consist of one symbol period (e.g., the duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element can depend on the modulation scheme (e.g., the order of the modulation scheme, the code rate of the modulation scheme, or both). Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rates for the UE 115. A wireless communications resource can refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers or beams), and the use of multiple spatial layers can further increase the data rate for communications with a UE 115.

[0064] One or more parameter sets, which can include subcarrier spacing (Af) and cyclic prefix, can be supported for a carrier. A carrier can be partitioned into one or more BWPs with the same or different parameter designs. In some examples, a UE 115 can be configured with multiple BWPs. In some examples, a single BWP for a carrier can be active at a given time, and communications for a UE 115 can be limited to one or more active BWPs.

[0065] Time intervals for a base station 105 or UE 115 can be expressed in multiples of a basic time unit, which may, for example, be a sampling period of Ts= 1 / (A s f · Nf) seconds, where Af max · Nf) seconds, where Af maxNfmay represent the largest supported discrete Fourier transform (DFT) size. Time intervals of the communications resources can be organized as radio frames, each radio frame having a particular duration (e.g., 10 milliseconds (ms)). Each radio frame can be identified by a system frame number (SFN) (e.g., ranging from 0 to 1023).

[0066] Each frame can include a number of consecutive numbered subframes or slots, and each subframe or slot can have the same duration. In some examples, a frame can be divided (e.g., in the time domain) into subframes, and each subframe can be further divided into slots. Alternatively, each frame can include a variable number of slots, and the number of slots can depend on the subcarrier spacing. Each slot can include a number of symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). In some wireless communications systems 100, a slot can be further divided into multiple mini-slots containing one or more symbols. Excluding the cyclic prefix, each symbol period can contain one or more (e.g., Nf) sampling periods. The duration of a symbol period can depend on the subcarrier spacing or the operating spectrum band.

[0067] A subframe, a slot, a mini-slot, or a symbol can be the smallest scheduling unit (e.g., in the time domain) of the wireless communications system 100 and can be referred to as a transmission time interval (TTI). In some examples, the TTI duration (e.g., the number of symbol periods in a TTI) can be variable. Additionally or alternatively, the smallest scheduling unit of the wireless communications system 100 can be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs)).

[0068] Physical channels can be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel can be multiplexed on a downlink carrier, for example, using one or more of time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. A control region (e.g., a control resource set (CORESET)) for a physical control channel can be defined in terms of a number of symbol periods and can extend across the system bandwidth or a subset of the system bandwidth of the carrier. One or more control regions (e.g., CORESETs) can be configured for a set of UEs 115. For example, one or more of the UEs 115 can monitor or search the control region according to one or more search space sets for control information, and each search space set can comprise one or multiple control channel candidates in one or multiple aggregation levels arranged in a cascaded manner. An aggregation level for a control channel candidate can refer to a number of control channel resources (e.g., control channel elements (CCEs)) associated with encoded information for a control information format having a given payload size. A search space set can comprise common search space sets configured for sending control information to multiple UEs 115 and UE-specific search space sets configured for sending control information to a specific UE 115.

[0069] Each base station 105 can provide communication coverage for one or more cells (e.g., macro cells, small cells, hot spots, or other types of cells, or any combination thereof) The term “cell” can refer to a logical communication entity used for communication with a base station 105 (e.g., on a carrier) and can be associated with a identifier, such as a physical cell identifier (PCID), a virtual cell identifier (VCID), or otherwise, used to distinguish neighboring cells. In some examples, the cell can also refer to a geographical area 110 or a subset of a geographical area 110 (e.g., a sector) over which a logical communication entity operates. The size of such a cell can depend on various factors such as capabilities of the base station 105 and can range from a small area (e.g., a structure, a subset of a structure) to a large area. For example, a cell can be or include a building, a subset of a building, or an outdoor space between or overlapping with geographical areas 110, among other examples.

[0070] A macro cell can cover a relatively large geographic area (e.g., several kilometers in radius) and can allow unrestricted access to all UEs 115 with service subscriptions with the network provider. A small cell can be associated with a lower- power base station 105 (compared to a macro cell) and can include one or more cells with a radius of less than 1 km (e.g., a micro cell, a pico cell, a femto cell, and / or the like). Small cells can provide service to specific areas, such as a

[0071] In some examples, a carrier can support multiple cells, and different cells of the carrier can be configured according to different protocol types (e.g., MTC, Narrowband IoT (NB-IoT), Enhanced Mobile Broadband (eMBB)) that can provide access to different types of devices.

[0072] In some examples, base stations 105 can be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies can overlap, but the different geographic coverage areas 110 can be supported by the same base station 105. In other examples, the overlapping geographic coverage areas 110 associated with different technologies can be supported by different base stations 105. The wireless communications system 100 can include, for example, a heterogeneous network in which different types of the base stations 105 provide coverage for various geographic coverage areas 110 using the same or different radio access technologies.

[0073] The wireless communications system 100 can support synchronous or asynchronous operation. For synchronous operation, the base stations 105 can have similar frame timings, and transmissions from different base stations 105 can be approximately aligned in time. For asynchronous operation, the base stations 105 can have different frame timings, and transmissions from different base stations 105 can not be aligned in time. The techniques described herein can be used for either synchronous or asynchronous operation.

[0074] Some UEs 115, such as MTC or IoT devices, can be low cost or low complexity devices, and can provide 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 one another or a base station 105 without the need for human intervention. In some examples, M2M communication or MTC can include communications from devices that integrate sensors or meters to measure or capture information and relay such information to a central server or application program that makes use of the information or presents the information to humans in an intuitive manner. 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, wildlife monitoring, weather and geological event monitoring, fleet management, remote security sensing, physical access control, and transaction-based business charging.

[0075] Some UEs 115 can be configured to employ operating modes that reduce power consumption, such as a half-duplex

[0076] The wireless communications system 100 can be configured to support ultra-reliable communications or low-latency communications, or various combinations thereof. For example, the wireless communications system 100 can be configured to support ultra-reliable low-latency communications (URLLC) or mission critical communications. UEs 115 can be designed to support ultra-reliable, low-latency, or mission critical functions (e.g., mission critical function). Ultra-reliable communications can include private communication or group communication and can be supported by one or more mission critical services such as mission critical push-to-talk (MCPTT), mission critical video (MCVideo), or mission critical data (MCData). Support for mission critical functions can include prioritization of services, and mission critical services can be used for public safety or general commercial applications. The terms ultra-reliable, low-latency, mission critical, and ultra-reliable low- latency can be used interchangeably herein.

[0077] In some examples, UEs 115 can also be able to communicate directly with other UEs 115 using a device-to-device (D2D) communication link 135 (e.g., using a peer-to-peer (P2P) or D2D protocol). One or more UEs 115 utilizing D2D communications can be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group can be outside the geographic coverage area 110 of a base station 105, or be otherwise unable to receive transmissions from a base station 105. In some examples, groups of UEs 115 communicating via D2D communications can utilize a one-to-many (1 :M) system in which each UE 115 transmits to every other UE 115 in the group. In some examples, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

[0078] In some systems, the D2D communication link 135 can be an example of a communication channel, such as a sidelink communication channel, between vehicles (e.g., UEs 115). In some examples, vehicles can communicate using vehicle-to-everything (V2X) communications, vehicle-to-vehicle (V2V) communications, or some combination of these. A vehicle can signal information related to traffic conditions, signal scheduling, weather, safety, emergencies, or any other information relevant to a V2X system. In some examples, vehicles in a V2X system can communicate with roadside infrastructure, such as roadside units, via one or more network nodes (e.g., base stations 105) using vehicle-to-network (V2N) communications, or with a network, or with both.

[0079] 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 5G core (5GC), which can include at least one control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and at least one user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW) that actually serves as the 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 for UEs 115 served by base stations 105 associated with the core network 130. User IP packets can be transferred through the user plane entity, which can provide IP address allocation as well as other functions. The user plane entity can be connected to the network’s

[0080] Some of the network devices, such as a base station 105, can include subcomponents such as an access network entity 140, which can be an example of an access node controller (ANC). Each access network entity 140 can communicate with the UEs 115 through one or more other access network transmission entities 145, which can be referred to as radio heads, smart radio heads, or transmission / reception points (TRPs). Each access network transmission entity 145 can include one or more antenna panels. In some configurations, various functions of each access network entity 140 or base station 105 can be distributed across various network devices (e.g., radio heads and ANCs) or consolidated into a single network device (e.g., a base station 105).

[0081] Wireless communications system 100 can operate using one or more spectral bands, for example, in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). For example, the 300-MHz to 3-GHz region is known as the ultra-high frequency (UHF) or decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves can be blocked or redirected by buildings and environmental features, but the waves penetrate structures sufficiently for

[0082] Wireless communications system 100 can also operate in a super high frequency (SHF) region using spectrum bands from 3 GHz to 30 GHz, also known as the centimeter band, or in an extremely high frequency (EHF) region of the spectrum from 30 GHz to 300 GHz, also known as the millimeter band. In some examples, wireless communications system 100 can support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices can be even smaller and more closely spaced than UHF antennas. In some examples, this can facilitate use of antenna arrays within a device. However, the propagation of EHF transmissions can be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. Techniques disclosed herein can be employed across transmissions that use one or more different frequency regions, and designated frequency bands across these regions can vary depending on the particular region.

[0083] Wireless communications system 100 can utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 can employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed frequency band such as the 5 GHz industrial, scientific, and medical (ISM) band. When operating in unlicensed frequency

[0084] Base stations 105 or UEs 115 can be equipped with multiple antennas, which can be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. The antennas of a base station 105 or a UE 115 can be co-located within one or more antenna arrays or antenna panels. In some examples, the antennas of a base station 105 can be located at different geographic locations. A base station 105 can have antenna arrays or antenna panels that have a number of rows and columns of antenna ports that the base station 105 can use for beamforming with a UE 115. Similarly, a UE 115 can have one or more antenna arrays or antenna panels that support various MIMO or beamforming operations. Additionally or alternatively, antenna panels can support radio frequency beamforming for signals transmitted via antenna ports.

[0085] Base stations 105 or UEs 115 can use MIMO communications to exploit multipath signal propagation and increase the spectral efficiency of a frequency channel by transmitting or receiving multiple signals via different spatial layers. Such techniques can be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by a transmitting device via different antennas or different combinations of antennas. Similarly, the multiple signals can be received by a 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 bits 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 used 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 multiple-user MIMO (MU-MIMO), where multiple spatial layers are transmitted to multiple devices.

[0086] Beamforming, which can 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 receiving device (e.g., a base station 105, a UE 115) to shape or steer a beam of energy in the manner of an antenna beam. The beam can be shaped or steered over time, for example, in response to the movement of a receiving device. The beam can be formed using a combination of signals transmitted or received via antenna elements of an array of antenna elements. The shape of the beam can be

[0087] A base station 105 or UE 115 can use beam sweeping techniques as part of a beamforming operation. For example, a base station 105 can use multiple antennas or antenna arrays (e.g., antenna panels) to conduct beamforming operations for directional communications with a UE 115. Some signals (e.g., synchronization signals, reference signals, beam- selection signals, or other control signals) can be transmitted by a base station 105 multiple times in different directions. For example, the base station 105 can transmit a signal according to different beamforming weight sets associated with different directions, and the beamforming weight sets can be applied to the same resources used to transmit the signal. Transmissions in different beam directions can be used to identify (e.g., by the transmitting device such as a base station 105, or by the receiving device such as a UE 115) a beam direction for subsequent transmission or reception by the base station 105.

[0088] Some signals, such as data signals associated with a receiving device, can be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115). In some examples, the beam direction associated with transmissions along a single beam direction can be determined based on a signal that was transmitted in one or more beam directions. For example, a UE 115 can receive one or more of the signals transmitted by the base station 105 in different directions, and can report to the base station 105 an indication of the signal that the UE 115 received with a highest signal quality, or other acceptable signal quality.

[0089] In some examples, transmissions by a device (e.g., by a base station 105 or a UE 115) can be performed using multiple beam directions, and the device can use a combination of digital precoding or radio frequency beamforming to generate a combined beam for transmission (e.g., from a base station 105 to a UE 115). A UE 115 can report feedback that indicates precoding weights for one or more beam directions, and the feedback can correspond to a configured number of beams across a system bandwidth or one or more sub-bands. A base station 105 can transmit reference signals (e.g., a cell-specific reference signal (CRS), a channel state information reference signal (CSI-RS)) that can be precoded or unprecoded. A UE 115 can provide feedback for beam selection, which can be a precoding matrix indicator (PMI) or codebook-based feedback (e.g., a multi-panel type codebook, a linear combination type codebook, a port selection type codebook). Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 can employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115) or for transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

[0090] A receiving device (e.g., a UE 115) can try multiple receive configurations (e.g., directional listening) when receiving various signals from base stations 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device can try multiple receive directions by differentially rotating a polarization plane of an antenna over time, measuring for signals received in different receive directions, or any combination thereof. In some examples, the receiving device can use a single receive configuration to receive signals along a single beam direction (e.g., when receiving a data signal). The single receive configuration can be aligned in a beam direction determined based on listening in different receive directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio (SNR), or otherwise acceptable signal quality based on listening in multiple beam directions).

[0091] The wireless communications system 100 can be a packet-based network that operates according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer can be IP -based. A Radio Link Control (RLC) layer can perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (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 retransmissions by the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer can provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data. At the physical layer, transport channels can be mapped to physical channels.

[0092] The UEs 115 and the base stations 105 can support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique used to increase the likelihood that data is received correctly over a communication link 125. HARQ can include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ can improve throughput rates over a MAC layer, in poor radio conditions or with poor signal-to-noise (SNR) conditions. In some examples, a device can support same-slot HARQ feedback, where the device can provide HARQ feedback in a specific time slot for data received in a previous time slot. In other cases, the device can provide HARQ feedback in a subsequent time slot or according to some other time interval.

[0093] As described, the wireless communications system can support beamformed communications between base stations 105 and UEs 115. The base stations 105 and UEs 115 can communicate using beams on an access link. In some cases, a beam used for communication on the access link can fail due to blockage, movement of the base station 105 and / or UE 115, or some other condition. One or both of the devices can detect the beam failure and identify a new set of beams for communication. For example, a base station 105 can periodically transmit a reference signal using one or more transmit beams. A UE 115 can monitor the RSRP of the reference signal and determine that a beam failure has occurred based on the RSRP. The UE 115 can report the beam failure to the base station 105 and initiate a beam recovery procedure.

[0094] The UEs 115 can also utilize beamforming to communicate with other UEs over the sidelink. In some cases, a transmit beam used by a first UE 115 to transmit over the sidelink to a second UE 115 can be different than a receive beam used by the first UE 115 to receive from the second UE 115 over the sidelink. This can be due to MPE issues, but it should be understood that this can be caused by other conditions. For example, the first UE 115 can use a first beam to receive from the second UE 115, but the first UE 115 can not use the same first beam to transmit to the second UE due to the first beam pointing at the user’s head. In this case, the first UE 115 can utilize a different second beam to transmit to the second UE 115. In cases where the sidelink transmit and sidelink receive beams are different, monitoring for beam failure by one of the UEs 115 of the sidelink can not be sufficient to identify a beam failure. That is, a beam failure can occur on one of the misaligned beams at one of the UEs 115, but the beam failure can not be detected by the UE 115 since the UE 115 is not monitoring the transmit beam.

[0095] Implementations described herein provide techniques for configuring two UEs 115 of a sidelink to transmit and receive BFD-RSs such that a beam failure can be identified by one or both of the UEs 115. For example, a first UE 115 of a sidelink can be configured with a first set of sidelink BFD-RSs to transmit to a second UE 115 of the sidelink, and the first UE 115 can also be configured with a second set of BFD-RSs to monitor or receive from the second UE 115 of the sidelink. The second UE 115 can be similarly configured with the two sets of BFD-RSs. Thus, since both UEs 115 are configured with respective BFD-RSs, each UE 115 is able to identify a beam failure. These and other implementations are further described with reference to the following figures.

[0096] Figure 2 An example of a wireless communications system 200 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated. In some examples, wireless communications system 200 can implement aspects of wireless communications system 100. Wireless communications system 200 includes base station 230, UE 220, UE 225, which can be examples of the corresponding devices Figure 1Examples of corresponding devices. The base stations 230 can communicate with the UEs 115 within a coverage area 235. For example, the base stations 230 communicate with the UEs 220 and 225 through access links. Also, the UEs 220 and 225 can communicate with each other through a sidelink. It should be understood that the implementations described herein can apply to other devices that can communicate through a sidelink, such as integrated access and backhaul (IAB) nodes, which can be referred to as UEs (e.g., UEs 115, UEs 220, and UEs 225).

[0097] In some examples, the base station 230 can transmit a control message 205, a downlink control information message, a radio resource control (RRC) message, a medium access control - control element (MAC-CE), and / or the like that configures the UEs 220 and / or 225 with resources for sidelink communications. In other examples, one or both of the UEs can determine such resources for the sidelink without input from the base station 230. As illustrated, each of the UEs 220 and 225 can communicate on the sidelink with one or more beams 210. In some examples, a UE can transmit and receive on the sidelink using the same beam 210. For example, the UE 220 can transmit and receive communications on the sidelink to and from the UE 225 using the beam 210-a. Similarly, the UE 225 can transmit and receive on the sidelink using the same beam 210. However, in certain cases, the transmit and receive beams for the sidelink can be different. In certain cases, this can be due to MPE conditions. For example, the UE 220 can receive communications from the UE 225 using the beam 210-b. However, a different beam 210-c can be used for transmission because the beam 210-b is pointed at the user’s head.

[0098] According to the techniques described herein, UE 220 and UE 225 can be configured with a first set of BFD-RS and a second set of BFD-RS. For example, UE 220 can be configured with a first set of BFD-RS to periodically or aperiodically transmit to second UE 225, and UE 220 can also be configured with a second set of BFD-RS to monitor reception from second UE 225. UE 220 and UE 225 can be configured with the set of reference signals by base station 230, by other UEs, or can be preconfigured with the set of reference signals. In one example, control message 205-a transmitted to UE 220 can include an indication of one or both of the first set of BFD-RS and the second set of BFD-RS. Base station 230 can also send control message 205-b to UE 225, and control message 205-b can include an indication of one or both of the first set of BFD-RS and the second set of BFD-RS. However, in some examples, UE 220 can relay the indication of one or both of the first set of BFD-RS and the second set of BFD-RS to second UE 225. That is, after receiving the configuration via control message 205-a, first UE 220 can relay the configuration to second UE 225 (e.g., using a sidelink control information (SCI) message, an RRC message, etc.). This can occur, for example, when one of the UEs 115 is outside of the coverage area 110 of the base station. In other examples, UE 220 or UE 225 can identify the configuration of one or both of the first set of BFD-RS and the second set of BFD-RS and transmit the configuration (e.g., using SCI or RRC) to the other UE.

[0099] As such, each of UE 220 and UE 226 can be configured with parameters, such as slTxRadioLinkMonitoringRS and slRxRadioLinkMonitoringRS, which can be used for beam failure detection. For example, slTxRadioLinkMonitoringRS can indicate a list of BFD-RSs to be transmitted and corresponding transmit beams, while slRxRadioLinkMonitoringRS can indicate a list of BFD-RSs to be received and corresponding receive beams. Each of UE 220 and UE 225 can be configured with a beam failure indication (BFI) counter to count the number of times each BFD-RS is received below a threshold. For example, each time UE 220 receives a second set of BFD-RSs from UE 225 with RSRP below an RSRP threshold, UE 220 can increment the counter. If the BFI counter reaches a maximum value or threshold count before expiration of a timer, UE 220 can determine that a beam failure has occurred and trigger a beam failure recovery procedure. As discussed with respect to the set of BFD-RSs, UE 220 and UE 225 can be configured with the counter threshold and timer by base station 230, other UEs of the sidelink, and / or based on pre-configuration.

[0100] The BFD-RSs can be an example of a sidelink synchronization signal block (SSB), a sidelink channel state information reference signal (CSI-RS), or a combination of the two. For example, a sidelink SSB can include a set of synchronization signals (e.g., primary synchronization signal (PSS) and secondary synchronization signal (PSS)) that can be used as BFD-RSs. Further, each UE 220 and UE 225 can be configured with different sets or combinations of different reference signals. For example, UE 220 can be configured to transmit a SL SSB and a CSI-RS as a first set of BFD-RSs, and UE 220 can be configured to transmit a repetition of the SL SSB as a second set of BFD-RSs. Further, UE 220 and UE 225 are configured to monitor for BFD-RSs transmitted by other UEs. For example, UE 225 is configured to monitor for a sidelink SSB and / or a sidelink CSI-RS transmitted by UE 220 for beam failure detection. That is, the parameter slRxRadioLinkMonitoringRS for UE 225 can include an indication of the SL SSB and / or sidelink CSI-RS to be transmitted by UE 220.

[0101] Figure 3A and Figure 3BAn example of a communication timeline 300 that supports techniques for bi-directional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated. In some examples, the communication timeline 300 can implement aspects of wireless communications system 100. The communication timeline 300 includes UE 325 and UE 330, which can be examples of the UEs described with reference to Figure 1 and Figure 2

[0102] Figure 3A A timeline 300-a illustrating a set of occasions 310 in which UE 325 transmits BFD-RSs to UE 330, while Figure 3B A timeline 300-b illustrating a set of occasions 315 in which UE 330 transmits BFD-RSs to UE 325. It should be understood that the set of occasions 310 and the set of occasions 315 can be staggered with respect to each other, positioned in sequence, or positioned in other formats. That is, UE 325 can transmit one or more BFD-RSs during a first occasion 310-a, and then UE 330 can transmit one or more BFD-RSs during a second occasion 315-a that is subsequent to the first occasion 310-a. Other timeline configurations of BFD-RS transmission occasions are contemplated within the scope of the present disclosure.

[0103] According to aspects of the disclosure described herein, UE 325 and UE 330 can be configured with a set of BFD-RSs. For example, a base station (e.g., base station 105 as shown in Figure 1 illustrated) can configure both UE 325 and UE 330 with a first set of BFD-RSs and a second set of BFD-RSs, where the first set corresponds to transmission by UE 325 and reception by UE 330, and the second set corresponds to transmission by UE 330 and reception by UE 325. In another example, UE 325 can receive a control message indicating the first set of BFD-RSs and the second set of BFD-RSs, and transmit the control message to UE 330 with an indication of the first set, the second set, or both, as indicated by the base station. In yet another example, UE 330 can identify the first set of BFD-RSs and the second set of BFD-RSs, and transmit a control message to UE 325 with an indication of the first set, the second set, or both.

[0104] ​As shown, the UE 325 is configured to transmit a set of BFD-RSs including SSBs and CSI-RSs. As such, during each occasion 310, the UE 325 transmits SSBs and CSI-RSs using one or more beams. Further, the UE 330 is configured to monitor for reception of SSBs and CSI-RSs during each occasion 310 using one or more beams. The UE 325 and the UE 330 can also be configured with an RSRP threshold, a beam failure detection counter, a beam failure detection counter threshold, and a beam failure detection timer. According to some implementations, when the UE detects RSRP of a BFD-RS in the set below the threshold, the UE can initiate the timer. If the UE detects RSRP of a BFD-RS in the set below the threshold before the timer expires, the UE can increment the counter. If the counter reaches the counter threshold, the UE 115 can determine that a beam failure has occurred and initiate a beam failure recovery procedure.

[0105] In Figure 3AIn this case, the UE 325 transmits a first set of BFD-RS (e.g., SSB and CSI-RS) on one or more transmit beams during the first occasion 310-a and the UE 330 receives the set of BFD-RS using one or more receive beams and determines that the RSRP is above a threshold. During the occasion 310-b, the UE 330 determines that the first set of BFD-RS is received with RSRP below the threshold. In response, the UE 330 initiates the BFD timer 320-a. Prior to expiration of the timer, the UE 330 receives the first set of BFD-RS during the occasion 310-c. Since these BFD-RS are received with RSRP above the threshold, the UE 330 does not increment the counter. The BFD timer 320-a expires prior to the counter reaching the counter threshold (e.g., counter threshold) (e.g., the timer reaches an expiration timer value). As such, the UE 330 can not determine that a beam failure has occurred and the UE 330 can reset the counter. At occasion 310-d, the UE 330 receives the first set of BFD-RS with RSRP below the threshold. In response, the UE 330 initiates the BFD timer 320-b. Prior to expiration of the BFD timer 320-b, the UE 330 receives the first set of BFD-RS with RSRP below the threshold at occasion 310-d. In response, the UE 330 increments the counter. In this example, the counter reaches the counter threshold prior to expiration of the BFD timer 320-b. Accordingly, the UE 330 can determine that a beam failure has occurred. In response, the UE 330 can initiate a beam failure recovery procedure. During the occasion 315-a, occasion 315-b, and occasion 315-c, the UE 325 receives a second set of BFD-RS above the threshold. As such, the UE 325 can not initiate a beam failure recovery procedure. Accordingly, the UE 330 can determine a beam failure during the same period that the UE 325 receives reference signals with RSRP above the threshold. As described herein, this can be due to misalignment of individual beams as a result of MPE conditions.

[0106] In Figure 3B this case, the UE 330 transmits a second set of BFD-RS during the occasion 310-b and the UE 325 monitors for reception of the second set of BFD-RS. As shown, the second set of BFD-RS can include SSBs. It should be understood that other configurations of BFD-RS are also contemplated within the scope of the present disclosure. The UE 325 receives the second set of BFD-RS with RSRP above the threshold during the occasion 315-a, occasion 315-b, and occasion 315-c. As such, the UE 325 can not determine that a beam failure has occurred.

[0107] In some cases, when beam failure is determined, the UEs can exchange notifications. For example, when UE 330 determines that beam failure occurred after occasion 310-d, UE 330 can transmit an indication of the beam failure to UE 325. The indication can be transmitted via SCI, RRC signaling, or using another type of signaling. In this case, the indication of the beam failure can be counted into a counter maintained by UE 325. More specifically, if UE 325 initiated the counter due to receiving the second set of BFD-RSs below the threshold, and UE 325 receives the indication of the beam failure from UE 330, UE 325 can increment the counter. As such, the UEs 115 can work in coordination to identify beam failure.

[0108] In some examples, when a UE 115 (e.g., UE 330) determines that beam failure occurred due to receiving BFD-RSs below a threshold, the UE 330 can refrain from transmitting a subsequent reference signal, such as another UE 115 that triggers a sidelink to determine that beam failure has occurred. As such, both UEs 115 can initiate a beam failure recovery procedure. For example, when UE 330 determines that beam failure occurred after occasion 310-d, UE 330 can refrain from a subsequent BFD-RS (e.g., the second set of BFD-RSs). Accordingly, since UE 325 can be configured to monitor for the reference signal without receiving the reference signal, UE 325 can also identify that beam failure has occurred.

[0109] Figure 4 An example of a process flow 400 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is illustrated. In some examples, process flow 400 can implement aspects of wireless communication system 100. Process flow 400 can include UE 470, UE 475, and base station 480, which can be examples of the corresponding devices described with reference to FIG. 3. UE 470 and UE 475 can communicate over a sidelink communication channel. Figure 1 As shown by reference number 405, UE 470 can transmit a first set of reference signals to UE 475. The first set of reference signals can include a first set of beam failure detection (BFD) reference signals (BFD-RSs) and a first set of synchronization signal blocks (SSBs). The first set of BFD-RSs can be transmitted by UE 470 to UE 475 to enable UE 475 to determine whether a beam failure has occurred. The first set of SSBs can be transmitted by UE 470 to UE 475 to enable UE 475 to determine whether a beam failure has occurred.

[0110] At 405, UE 475 can receive, from base station 480, a control message that configures a first set of sidelink beam failure detection reference signals, a second set of sidelink beam failure detection reference signals, or both the second set of sidelink beam failure detection reference signals and the first set of sidelink beam failure detection reference signals. At 410, UE 475 can transmit, to UE 470, a sidelink control message that configures the second set of sidelink beam failure detection reference signals that the second UE 470 is to transmit to the first UE 475, the first set of sidelink beam failure detection reference signals that the second UE 470 is to receive from the first UE 475, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0111] At 415, UE 475 can determine a first set of sidelink beam failure detection reference signals to transmit to second UE 470. At 420, UE 475 can determine a second set of sidelink beam failure detection reference signals to receive from second UE 470. As illustrated, UE 475 can determine the first and second sets of beam failure detection reference signals based on a control message received from a base station. However, in some cases, UE 475 can determine the first and second sets of beam failure detection reference signals based on a reconfiguration, network conditions, etc. In some cases, UE 475 can receive a control message from second UE 470, and the control message can configure the first and second sets of beam failure detection reference signals.

[0112] At 425, UE 470 can determine a first set of sidelink beam failure detection reference signals to receive from first UE 475. At 430, UE 470 can determine a second set of sidelink beam failure detection reference signals to transmit to first UE 475. The determinations can be based on a control message received from base station 480.

[0113] At 435, UE 475 can transmit, to second UE 470, the first set of sidelink beam failure detection reference signals using a set of sidelink transmit beams, and at 440, UE 470 can monitor for the determined first set of sidelink beam failure detection reference signals using a set of sidelink receive beams.

[0114] At 445, UE 470 can transmit a second sidelink beam fault detection reference signal set to the first UE 475 using the sidelink transmit beam set, and at 450, UE 475 can monitor the determined second sidelink beam fault detection reference signal set using the sidelink receive beam set. As described herein, the first and second sidelink beam fault detection reference signal sets may include a sidelink SSB, a sidelink CSI-RS, or a combination thereof. In some cases, the first and second sets may include different combinations of sidelink SSB and sidelink CSI-RS. Furthermore, the first and second sets may be transmitted according to different periodicities or transmission modes.

[0115] At 455, UE 475 may communicate with the second UE 470 on a sidelink based at least in part on the first sidelink beam fault detection reference signal set and the second sidelink beam fault detection reference signal set. In some cases, this may include identifying a beam fault and initiating a beam fault recovery procedure.

[0116] Figure 5 A block diagram 500 of an apparatus 505 supporting techniques for bidirectional sidelink beam fault detection according to various aspects of this disclosure is shown. Apparatus 505 may be an example of various aspects of a UE 115 as described herein. Apparatus 505 may include a receiver 510, a communications manager 515, and a transmitter 520. Apparatus 505 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

[0117] Receiver 510 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to techniques used for bidirectional sidelink beam fault detection). This information can be transmitted to other components of device 505. Receiver 510 can be a reference... Figure 8 Examples of various aspects of the transceiver 820 described. The receiver 510 may utilize a single antenna or an array of antennas.

[0118] Communication manager 515 can determine a first set of sidelink beam fault detection reference signals to be transmitted to the second UE; determine a second set of sidelink beam fault detection reference signals to be received from the second UE; transmit the first set of sidelink beam fault detection reference signals to the second UE using a sidelink transmit beam set; monitor the determined second set of sidelink beam fault detection reference signals using a sidelink receive beam set; and communicate with the second UE on a sidelink based on the first set of sidelink beam fault detection reference signals and the second set of sidelink beam fault detection reference signals. Communication manager 515 may be an example of various aspects of communication manager 810 described herein.

[0119] The communications manager 515, or its sub-components, can be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 515, or its sub-components can be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field- programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0120] The communications manager 515, or its sub-components, can be physically located in various places in the apparatus, including but not limited to centralized

[0121] The transmitter 520 can transmit signals generated by other components of the device 505. In some examples, the transmitter 520 can be collocated with a receiver 510 in a transceiver component. For example, the transmitter 520 can be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 520 can utilize a single antenna or a set of antennas. Figure 8

[0122] In some examples, the communications manager 515 can be implemented as an integrated circuit or chipset for a mobile device modem, and the receiver 510 and transmitter 520 can be implemented as analog components (e.g., amplifiers, filters, antennas) coupled with the mobile device modem to enable wireless transmission and reception over one or more frequency bands.

[0123] The communications manager 515 as described herein can be implemented to realize one or more potential advantages. One implementation can allow the device 505 to more efficiently coordinate beam failure detection reference signals with another device 505, and more specifically to determine reference signals for determining a beam failure of a sidelink with a second device. For example, the device 505 can identify a first set of sidelink beam failure detection reference signals to transmit to another device, identify a second set of sidelink beam failure detection reference signals to receive from a second UE, and transmit and receive the reference signals in accordance with the determination.

[0124] ​Based on implementing sidelink beam failure detection techniques as described herein, a processor of a UE 115 (e.g., of a control receiver 510, a transmitter 520, or a transceiver 820 as described with reference to Figure 8 The processor of a UE 115 can improve reliability of communications over a sidelink and reduce signaling overhead as beam failures can be more efficiently identified based on implementing sidelink beam failure detection techniques as described herein.

[0125] Figure 6 A block diagram 600 of a device 605 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The device 605 can be an example of aspects of a device 505 or a UE 115 as described herein. The device 605 can include a receiver 610, a communications manager 615, and a transmitter 645. The device 605 can also include a processor. Each of these components can be in communication with one another (e.g., via one or more buses).

[0126] The receiver 610 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to techniques for bidirectional sidelink beam failure detection, etc.). Information can be passed on to other components of the device 605. The receiver 610 can be an example of aspects of the transceiver 820 described with reference to Figure 8 The receiver 610 can utilize a single antenna or a set of antennas.

[0127] The communications manager 615 can be an example of aspects of the communications manager 515 as described herein. The communications manager 615 can include a transmit BFD-RS component 620, a receive BFD-RS component 625, a BFD-RS transmission interface 630, a BFD-RS reception interface 635, and a communications interface 640. The communications manager 615 can be an example of aspects of the communications manager 810 described herein.

[0128] The transmit BFD-RS component 620 can determine a set of first sidelink beam failure detection reference signals to transmit to a second UE.

[0129] The receive BFD-RS component 625 can determine a set of second sidelink beam failure detection reference signals to receive from a second UE.

[0130] The BFD-RS transmission interface 630 can transmit the set of first sidelink beam failure detection reference signals to the second UE using a set of sidelink transmit beams.

[0131] The BFD-RS reception interface 635 can monitor for the determined set of second sidelink beam failure detection reference signals using a set of sidelink receive beams.

[0132] The communication interface 640 can communicate with the second UE on a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0133] The transmitter 645 can transmit signals generated by other components of the device 605. In some examples, the transmitter 645 can be collocated with a receiver 610 in a transceiver component. For example, the transmitter 645 can be an example of aspects of the transceiver 820 described with reference to FIG. 8. The transmitter 645 can utilize a single antenna or a set of antennas. Figure 8

[0134] Figure 7 A block diagram 700 of a communications manager 705 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The communications manager 705 can be an example of aspects of the communications manager 515, the communications manager 615, or the communications manager 810 described herein. The communications manager 705 can include a transmission BFD-RS component 710, a reception BFD-RS component 715, a BFD-RS transmission interface 720, a BFD-RS reception interface 725, a communication interface 730, a sidelink control message interface 735, a downlink control message interface 740, a beam failure detection component 745, a beam failure recovery component 750, a beam failure indication component 755, and a beam adjustment component 760. Each of these components can communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0135] The transmission BFD-RS component 710 can determine a first set of sidelink beam failure detection reference signals to transmit to a second UE.

[0136] The reception BFD-RS component 715 can determine a second set of sidelink beam failure detection reference signals to receive from a second UE.

[0137] The BFD-RS transmission interface 720 can transmit the first set of sidelink beam failure detection reference signals to the second UE using a set of sidelink transmit beams.

[0138] In some examples, the BFD-RS transmission interface 720 can refrain from transmitting one or more of the first set of sidelink beam failure detection reference signals based on detecting a beam failure, where the beam failure recovery procedure is performed with the second UE based on refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals.

[0139] In some cases, a first periodicity associated with transmitting the first set of sidelink beam failure detection reference signals is different than a second periodicity for monitoring reception of the second set of sidelink beam failure detection reference signals. ​

[0140] The BFD-RS reception interface 725 can monitor the determined set of second sidelink beam failure detection reference signals using a set of sidelink receive beams.

[0141] The communication interface 730 can communicate with the second UE on a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0142] The sidelink control message interface 735 can receive, from the second UE, a control message configuring the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0143] In some examples, the sidelink control message interface 735 can transmit, to the second UE, a first control message configuring the second set of sidelink beam failure detection reference signals that the second UE is to transmit to the first UE, the first set of sidelink beam failure detection reference signals that the second UE is to receive from the first UE, or both the second set of sidelink beam failure detection reference signals and the first set of sidelink beam failure detection reference signals.

[0144] In some examples, the sidelink control message interface 735 can receive, from the second UE, a control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0145] In some examples, the sidelink control message interface 735 can transmit, to the second UE, a control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0146] The downlink control message interface 740 can receive, from a base station, a second control message configuring the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the second set of sidelink beam failure detection reference signals and the first set of sidelink beam failure detection reference signals, where the first control message is transmitted to the second UE based on receiving the second control message from the base station.

[0147] In some examples, the downlink control message interface 740 can receive, from the base station, a control message that configures the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0148] In some examples, the downlink control message interface 740 can receive, from the base station, a control message that indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0149] In some cases, the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include a sidelink synchronization signal block or a sidelink channel state information reference signal.

[0150] The beam failure detection component 745 detects a beam failure based on monitoring reception of the second set of sidelink beam failure detection reference signals.

[0151] In some examples, the beam failure detection component 745 can determine that a reference signal received power of one or more of the second set of sidelink beam failure detection reference signals is below a received power threshold.

[0152] In some examples, the beam failure detection component 745 can initiate a beam failure timer based on determining that the reference signal received power is below the received power threshold.

[0153] In some examples, the beam failure detection component 745 can increment a beam failure counter each time the second set of sidelink beam failure detection reference signals is received with the reference signal received power below the received power threshold prior to expiration of the beam failure timer, where the beam failure is detected based on the beam failure counter reaching a counter threshold. In some examples, the beam failure timer expires based on an expiration time value of a beam failure indication timer. In some examples, the counter threshold is a counter threshold for a beam failure indication counter.

[0154] In some examples, the beam failure detection component 745 can increment a beam failure counter based on receiving an indication of the beam failure, where the beam failure recovery procedure is performed based on the beam failure counter reaching a counter threshold.

[0155] The beam failure recovery component 750 performs a beam failure recovery procedure with the second UE based on detecting the beam failure.

[0156] In some examples, the beam failure recovery component 750 can perform a beam failure recovery procedure with the second UE based on receiving the indication.

[0157] The beam failure indication component 755 transmits, to the second UE, a base station, or both the second UE and the base station, an indication of the beam failure, where the beam failure recovery procedure is performed based on transmitting the indication.

[0158] In some examples, the beam failure indication component 755 can receive, from the second UE or a base station, an indication of a beam failure associated with the second UE.

[0159] The beam adjustment component 760 can adjust one or more sidelink receive beams used to receive the set of second sidelink beam failure detection reference signals.

[0160] In some examples, the beam adjustment component 760 can transmit, to the second UE, an indication of adjusting the one or more sidelink receive beams.

[0161] In some examples, the beam adjustment component 760 can receive, from the second UE, an indication of adjusting one or more sidelink receive beams used by the second UE to receive the set of first sidelink beam failure detection reference signals.

[0162] Figure 8 A diagram illustrating a system 800 including a device 805 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The device 805 can be an example of or include the components of device 505, device 605, or a UE 115 as described herein. The device 805 can include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 810, an I / O controller 815, a transceiver 820, an antenna 825, memory 830, and a processor 840. These components can be in electronic communication via one or more buses (e.g., bus 845).

[0163] The communications manager 810 can determine a first set of sidelink beam failure detection reference signals to transmit to a second UE, determine a second set of sidelink beam failure detection reference signals to receive from the second UE, transmit the first set of sidelink beam failure detection reference signals to the second UE using a set of sidelink transmit beams, monitor for the determined second set of sidelink beam failure detection reference signals using a set of sidelink receive beams, and communicate with the second UE on a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0164] The I / O controller 815 can manage input and output signals for the device 805. The I / O controller 815 can also manage peripherals not integrated into the device 805. In some cases, the I / O controller 815 can represent a physical connection or port to or another known operating system. In other cases, the I / O controller 815 can represent or interact with a modem, a keyboard, a mouse, a touchscreen, or similar devices. In some cases, the I / O controller 815 can be implemented as part of a processor. In some cases, a user can interact with the device 815 via the I / O controller 815 or via hardware components controlled by the I / O controller 815.

[0165] The transceiver 820 can communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 820 can represent a wireless transceiver and can communicate bi-directionally with another wireless transceiver. The transceiver 820 can also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0166] In some cases, the wireless device can include a single antenna 825. However, in some cases the device can have more than one antenna 825, which can be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0167] The memory 830 can include RAM and ROM. The memory 830 can store computer-readable, computer-executable code 835 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 830 can contain, among other computer-readable code 835, a basic input / output system (BIOS) that can control basic hardware or software operation such as the interaction with peripheral components or devices.

[0168] The processor 840 can include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 840 can be configured to operate a memory array using a memory controller. In other cases, a memory controller can be integrated into the processor 840. The processor 840 can be configured to execute computer-readable instructions stored in a memory (e.g., the memory 830) to cause the device 805 to perform various functions (e.g., functions or tasks supporting techniques for bi-directional sidelink beam failure detection).

[0169] The code 835 can include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 835 can be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 835 can not be directly executable by the processor 840 but can cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0170] Figure 9 FIG. 9 shows a block diagram of a device 905 that supports techniques for bi-directional sidelink beam failure detection in accordance with aspects of the present disclosure. The device 905 can be an example of aspects of a base station 105 as described herein. The device 905 can include a receiver 910, a communications manager 915, and a transmitter 920. The device 905 can also include a processor. Each of these components can be in communication with one another (e.g., via one or more buses).

[0171] The receiver 910 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to techniques for bi-directional sidelink beam failure detection, etc.). Information can be passed on to other components of the device 905. The receiver 910 can be an example of aspects of the transceiver 1220 described with reference to FIG. 12. The receiver 910 can utilize a single antenna or a set of antennas. Figure 12

[0172] The communications manager 915 can transmit, to a first UE, a control message indicating a set of first sidelink beam failure detection reference signals to be transmitted to a second UE, a set of second sidelink beam failure detection reference signals to be received from the second UE, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals; and communicate with the first UE or the second UE based on transmitting the control message. The communications manager 915 can be an example of aspects of the communications manager 1210 described herein.

[0173] ​The communications manager 915, or its sub-components, can be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 915, or its sub-components can be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0174] The communications manager 915, or its sub-components, can be physically located in various places in the apparatus including but not limited to centralized in a place, distributed among multiple places, or some combination thereof. In some examples, the communications manager 915 or its sub-components can be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 915 or its sub-components can be combined with one or more other hardware components, including but not limited to an input / output (I / O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0175] The transmitter 920 can transmit signals generated by other components of the device 905. In some examples, the transmitter 920 can be collocated with a receiver 910 in a transceiver component. The transmitter 920 can be an example of aspects of the transceiver 1220 described with reference to Figure 12 The transmitter 920 can utilize a single antenna or a set of antennas.

[0176] Figure 10 A block diagram 1000 of a device 1005 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The device 1005 can be an example of aspects of a device 905 or a base station 105 as described herein. The device 1005 can include a receiver 1010, a communications manager 1015, and a transmitter 1030. The device 1005 can also include a processor. Each of these components can be in communication with one another (e.g., via one or more buses).

[0177] The receiver 1010 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to techniques for bidirectional sidelink beam failure detection, etc.). Information can be passed on to other components of the device 1005. The receiver 1010 can be an example of aspects of the transceiver 1220 described with reference to Figure 12 The receiver 1010 can utilize a single antenna or a set of antennas.

[0178] The communications manager 1015 can be an example of aspects of the communications manager 915 as described herein. The communications manager 1015 can include a downlink control message interface 1020 and a communications interface 1025. The communications manager 1015 can be an example of aspects of the communications manager 1210 described herein.

[0179] The downlink control message interface 1020 can transmit, to a first UE, a control message indicating a set of first sidelink beam failure detection reference signals to be transmitted to a second UE, a set of second sidelink beam failure detection reference signals to be received from the second UE, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0180] The communications interface 1025 can communicate with the first UE or the second UE based on transmitting the control message.

[0181] The transmitter 1030 can transmit signals generated by other components of the device 1005. In some examples, the transmitter 1030 can be collocated with a receiver 1010 in a transceiver component. The transmitter 1030 can be an example of aspects of the transmitter 1220 described with reference to FIG. 12. The transmitter 1030 can utilize a single antenna or a set of antennas. Figure 12

[0182] Figure 11 A block diagram 1100 of a communications manager 1105 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The communications manager 1105 can be an example of aspects of a communications manager 915, a communications manager 1015, or a communications manager 1210 described herein. The communications manager 1105 can include a downlink control message interface 1110, a communications interface 1115, a beam failure detection component 1120, and a beam failure indication component 1125. Each of these components can communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0183] The downlink control message interface 1110 can transmit, to a first UE, a control message indicating a set of first sidelink beam failure detection reference signals to be transmitted to a second UE, a set of second sidelink beam failure detection reference signals to be received from the second UE, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0184] ​In some examples, the downlink control message interface 1110 can transmit, to the first UE, an indication that the first UE is to communicate, to the second UE, the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

[0185] In some examples, the downlink control message interface 1110 can transmit, to the first UE, a control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0186] The communication interface 1115 can communicate, with the first UE or the second UE, based on transmitting the control message.

[0187] The beam failure detection component 1120 receives, from the first UE, an indication of a beam failure associated with a sidelink between the first UE and the second UE.

[0188] The beam failure indication component 1125 transmits, to the second UE, an indication of the beam failure.

[0189] Figure 12 A diagram illustrating a system 1200 including a device 1205 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The device 1205 can be an example of or include the components of device 905, device 1005, or a base station 105 as described herein. The device 1205 can include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communication manager 1210, a network communications manager 1215, a transceiver 1220, an antenna 1225, memory 1230, a processor 1240, and an inter-station communications manager 1245. These components can be in electronic communication via one or more buses (e.g., bus 1250).

[0190] The communication manager 1210 can transmit, to a first UE, a control message indicating a first set of sidelink beam failure detection reference signals to be transmitted to a second UE, a second set of sidelink beam failure detection reference signals to be received from the second UE, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals; and communicate, with the first UE or the second UE, based on transmitting the control message.

[0191] The network communications manager 1215 can manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network communications manager 1215 can manage the transfer of data communications for client devices, such as one or more UEs 115.

[0192] The transceiver 1220 can communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1220 can represent a wireless transceiver and can communicate bi-directionally with another wireless transceiver. The transceiver 1220 can also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0193] In some cases, the wireless device can include a single antenna 1225. However, in some cases the device can have more than one antenna, which can be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0194] The memory 1230 can include RAM, ROM, or a combination thereof. The memory 1230 can store computer-readable code 1235 including instructions that, when executed by a processor (e.g., the processor 1240), cause the device to perform various functions described herein. In some cases, the memory 1230 can include, for example, a BIOS, which can control basic hardware or software operation such as the interaction with peripheral components or devices.

[0195] The processor 1240 can include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 1240 can be configured to operate a memory array. In some cases, a memory controller can be included in the processor 1240. The processor 1240 can be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1230) to cause the device 1205 to perform various functions (e.g., functions or tasks in support of the techniques for bi-directional sidelink beam failure detection).

[0196] The inter-station communications manager 1245 can manage communications with other base station 105, and can include a controller or scheduler for controlling

[0197] The code 1235 can include instructions for implementing aspects of the present disclosure including instructions for supporting wireless communications. The code 1235 can be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1235 can not be directly executable by the processor 1240 but can cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0198] Figure 13 A flow diagram illustrating a method 1300 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The operations of method 1300 can be implemented by a UE 115 or its components as described herein. For example, the operations of method 1300 can be performed by a communications manager as described with reference to Figures 5 to 8 FIGS. 13 through 16 as described herein. Additionally or alternatively, the UE can perform aspects of the functions described below using special- purpose hardware.

[0199] At 1315, the UE can transmit, to a second UE, a first set of sidelink beam failure detection reference signals using a set of sidelink transmit beams. The operations of 1315 can be performed according to the methods described herein. In some examples, aspects of the operations of 1315 can be performed by a BFD-RS transmission interface as described with reference to Figures 5 to 8 FIGS. 13 through 16 as described herein. Additionally or alternatively, the UE can perform aspects of the functions described below using special- purpose hardware.

[0200] At 1310, the UE can monitor for a second set of sidelink beam failure detection reference signals using a set of sidelink receive beams. The operations of 1320 can be performed according to the methods described herein. In some examples, aspects of the operations of 1320 can be performed by a BFD-RS reception interface as described with reference to Figures 5 to 8 FIGS. 13 through 16 as described herein. Additionally or alternatively, the UE can perform aspects of the functions described below using special- purpose hardware.

[0201] At 1325, the UE can communicate with the second UE on a sidelink based on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals. The operations of 1325 can be performed according to the methods described herein. In some examples, aspects of the operations of 1325 can be performed by a communications interface as described with reference to Figures 5 to 8 FIGS. 13 through 16 as described herein. Additionally or alternatively, the UE can perform aspects of the functions described below using special- purpose hardware.

[0202] Figure 14 A flow diagram illustrating a method 1400 that supports techniques for bidirectional sidelink beam failure detection in accordance with aspects of the present disclosure is shown. The operations of method 1400 can be implemented by a base station 105 or its components as described herein. For example, the operations of method 1400 can be performed by a communications manager as described with reference to Figures 9 to 12The described communication manager performs. In some examples, the base station can execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, the base station can perform aspects of the functions described below using special-purpose hardware.

[0203] At 1405, the base station can transmit, to a first UE, a control message indicating a set of first sidelink beam failure detection reference signals to be transmitted to a second UE, a set of second sidelink beam failure detection reference signals to be received from the second UE, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals. The operations of 1405 can be performed according to the methods described herein. In some examples, aspects of the operations of 1405 can be performed by a downlink control message interface as described with reference to Figures 9 to 12 FIGs. 13 through 16, and / or any other suitable component of a wireless

[0204] At 1410, the base station can communicate with the first UE or the second UE based on transmitting the control message. The operations of 1410 can be performed according to the methods described herein. In some examples, aspects of the operations of 1410 can be performed by a communication interface as described with reference to Figures 9 to 12 FIGs. 13 through 16, and / or any other suitable component of a wireless

[0205] An overview of aspects of the present disclosure is provided below:

[0206] Aspect 1 : A method for wireless communication at a first UE, comprising: transmitting, to a second UE, a set of first sidelink beam failure detection reference signals using a set of sidelink transmit beams; monitoring for a set of second sidelink beam failure detection reference signals using a set of sidelink receive beams; and communicating with the second UE on a sidelink based at least in part on the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0207] Aspect 2: The method of aspect 1, further comprising: receiving, from the second UE, a control message configuring the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0208] Aspect 3: The method of aspect 1, further comprising: transmitting, to the second UE, a first control message that configures the set of second sidelink beam failure detection reference signals that the second UE is to transmit to the first UE, the set of first sidelink beam failure detection reference signals that the second UE is to receive from the first UE, or both the set of second sidelink beam failure detection reference signals and the set of first sidelink beam failure detection reference signals.

[0209] Aspect 4: The method of aspect 3, further comprising: receiving, from a base station, a second control message that configures the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of second sidelink beam failure detection reference signals and the set of first sidelink beam failure detection reference signals, wherein the first control message is transmitted to the second UE based at least in part on receiving the second control message from the base station.

[0210] Aspect 5: The method of any one of aspects 2 through 4, further comprising: receiving, from a base station, a control message that configures the set of first sidelink beam failure detection reference signals, the set of second sidelink beam failure detection reference signals, or both the set of first sidelink beam failure detection reference signals and the set of second sidelink beam failure detection reference signals.

[0211] Aspect 6: The method of any one of aspects 1 through 5, further comprising: receiving, from the second UE, a control message that indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0212] Aspect 7: The method of any one of aspects 1 through 5, further comprising: transmitting, to the second UE, a control message that indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0213] Aspect 8: The method of any one of aspects 1 through 5 and 7, further comprising: receiving, from a base station, a control message that indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0214] Aspect 9: The method of any one of aspects 1 through 8, further comprising: detecting a beam failure based at least in part on monitoring reception of the second set of sidelink beam failure detection reference signals; and performing a beam failure recovery procedure with the second UE based at least in part on detecting the beam failure.

[0215] Aspect 10: The method of aspect 9, further comprising: refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals based at least in part on detecting the beam failure, wherein the beam failure recovery procedure is performed with the second UE based at least in part on refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals.

[0216] Aspect 11: The method of any one of aspects 9 through 10, further comprising: transmitting an indication of the beam failure to the second UE, a base station, or both the second UE and the base station, wherein the beam failure recovery procedure is performed based at least in part on transmitting the indication.

[0217] Aspect 12: The method of any one of aspects 9 through 11, further comprising: determining that a reference signal received power of one or more of the second set of sidelink beam failure detection reference signals is below a received power threshold; initiating a beam failure timer based at least in part on determining that the reference signal received power is below the received power threshold; and incrementing a beam failure counter each time the second set of sidelink beam failure detection reference signals is received with the reference signal received power below the received power threshold prior to expiration of the beam failure timer, wherein the beam failure is detected based at least in part on the beam failure counter reaching a counter threshold.

[0218] Aspect 13: The method of any one of aspects 1 through 12, further comprising: receiving an indication of a beam failure associated with the second UE from the second UE or a base station; and performing a beam failure recovery procedure with the second UE based at least in part on receiving the indication.

[0219] Aspect 14: The method of aspect 13, further comprising: incrementing a beam failure counter based at least in part on receiving the indication of the beam failure, wherein the beam failure recovery procedure is performed based at least in part on the beam failure counter reaching a counter threshold.

[0220] Aspect 15: The method of any one of aspects 1 through 14, further comprising: adjusting one or more sidelink receive beams used to receive the second set of sidelink beam failure detection reference signals.

[0221] Aspect 16: The method of aspect 15, further comprising: transmitting, to the second UE, an indication to adjust the one or more sidelink receive beams.

[0222] Aspect 17: The method of any one of aspects 1 through 16, further comprising: receiving, from the second UE, an indication to adjust one or more sidelink receive beams used by the second UE to receive the first set of sidelink beam failure detection reference signals.

[0223] Aspect 18: The method of any one of aspects 1 through 17, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals comprise a sidelink synchronization signal block or a sidelink channel state information reference signal.

[0224] Aspect 19: The method of any one of aspects 1 through 18, wherein a first periodicity associated with transmitting the first set of sidelink beam failure detection reference signals is different than a second periodicity for monitoring reception of the second set of sidelink beam failure detection reference signals.

[0225] Aspect 20: A method for wireless communication at a base station, comprising: transmitting, to a first UE, a control message indicating a first set of sidelink beam failure detection reference signals to be transmitted to a second UE, a second set of sidelink beam failure detection reference signals to be received from the second UE, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals; and communicating with the first UE or the second UE based at least in part on transmitting the control message.

[0226] Aspect 21: The method of aspect 20, wherein transmitting the control message comprises: transmitting, to the first UE, an indication that the first UE is to communicate the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals to the second UE.

[0227] Aspect 22: The method of any one of aspects 20 through 21, wherein transmitting a control message comprises: transmitting, to the first UE, a control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

[0228] Aspect 23: The method of any of aspects 20 through 22, further comprising: receiving, from the first UE, an indication of a beam failure associated with a sidelink between the first UE and the second UE; and transmitting, to the second UE, an indication of the beam failure.

[0229] Aspect 24: An apparatus for wireless communication at a first UE, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any of aspects 1 through 19.

[0230] Aspect 25: An apparatus for wireless communication at a first UE, comprising at least one means for performing the method of any of aspects 1 through 19.

[0231] Aspect 26: A non-transitory computer-readable medium storing code for wireless communication at a first UE, the code comprising instructions executable by a processor to perform the method of any of aspects 1 through 19.

[0232] Aspect 27: An apparatus for wireless communication at a base station, comprising a processor; memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to perform the method of any of aspects 20 through 23.

[0233] Aspect 28: An apparatus for wireless communication at a base station, comprising at least one means for performing the method of any of aspects 20 through 23.

[0234] Aspect 29: A non-transitory computer-readable medium storing code for wireless communication at a base station, the code comprising instructions executable by a processor to perform the method of any of aspects 20 through 23.

[0235] It should be noted that the methods described herein describe possible implementations, and that the operations and the steps can be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods can be combined.

[0236] Although aspects of an LTE, LTE-A, LTE-A Pro, or NR system can be described for purposes of illustration, and it is possible that an LTE, LTE-A, LTE-A Pro, or NR network can be employed in most described aspects, other wireless communication systems can also employ aspects described herein. For example, an 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 can employ aspects described herein.

[0237] Information and signals described herein can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0238] The various illustrative blocks and components described herein can be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, a FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. A processor can 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).

[0239] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations fall within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations thereof. Features implementing functions can also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

[0240] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. 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 random-access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a 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. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0241] As used herein, including in the claims “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of’ or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as “based on condition A” can be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.”

[0242] In the drawings, like reference numerals refer to items of like functionality. In addition, the various features of the figures can be identified, where appropriate, with a letter or number that appears in italics and follows a description of the item in the first paragraph of the respective section that the item appears in. If only the first reference numeral is used in the description, the description can apply to any one, or combination, of the similar components identified with the same first reference numeral, regardless of the second, or subsequent, reference numerals.

[0243] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that can be implemented or that are within the scope of the claims. The term “example” used herein means “serving as an example, instance, or illustration,” and not “preferred” over other examples. The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0244] The description herein is presented to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for wireless communication at a first user equipment (UE), comprising: receiving, from a second UE, a first control message including control information that configures a first set of sidelink beam failure detection reference signals that the first UE is to transmit to the second UE using a set of sidelink transmit beams and that configures a second set of sidelink beam failure detection reference signals that the first UE is to receive from the second UE using a set of sidelink receive beams, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include respective sidelink synchronization signal blocks; transmitting, to the second UE, the first set of sidelink beam failure detection reference signals using the set of sidelink transmit beams; monitoring for the second set of sidelink beam failure detection reference signals using the set of sidelink receive beams, the second set of sidelink beam failure detection reference signals being different than the first set of sidelink beam failure detection reference signals; and communicating with the second UE on a sidelink based at least in part on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

2. The method of claim 1, wherein the first control message indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

3. The method of claim 1, further comprising: transmitting, to the second UE, a second control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

4. The method of claim 1, further comprising: receiving, from a network entity, a second control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

5. The method of claim 1, further comprising: detecting a beam failure based at least in part on monitoring for reception of the second set of sidelink beam failure detection reference signals; and performing, with the second UE, a beam failure recovery procedure based at least in part on detecting the beam failure.

6. The method of claim 5, further comprising: ​ ​ inhibiting transmission of one or more of the first set of sidelink beam failure detection reference signals based at least in part on detecting the beam failure, wherein the beam failure recovery procedure is performed with the second UE based at least in part on inhibiting transmission of one or more of the first set of sidelink beam failure detection reference signals.

7. The method of claim 5, further comprising: transmitting, to the second UE, a network entity, or both the second UE and the network entity, an indication of the beam failure, wherein the beam failure recovery procedure is performed based at least in part on transmitting the indication.

8. The method of claim 5, further comprising: determining that a reference signal received power of one or more of the second set of sidelink beam failure detection reference signals is below a received power threshold; initiating a beam failure timer based at least in part on determining that the reference signal received power is below the received power threshold; and incrementing a beam failure counter each time the second set of sidelink beam failure detection reference signals is received with the reference signal received power below the received power threshold prior to expiration of the beam failure timer, wherein the beam failure is detected based at least in part on the beam failure counter reaching a counter threshold.

9. The method of claim 1, further comprising: receiving, from the second UE or a network entity, an indication of a beam failure associated with the second UE; and performing a beam failure recovery procedure with the second UE based at least in part on receiving the indication.

10. The method of claim 9, further comprising: incrementing a beam failure counter based at least in part on receiving the indication of the beam failure, wherein the beam failure recovery procedure is performed based at least in part on the beam failure counter reaching a counter threshold.

11. The method of claim 1, further comprising: adjusting one or more sidelink receive beams used to receive the second set of sidelink beam failure detection reference signals.

12. The method of claim 11, further comprising: transmitting, to the second UE, an indication of adjusting the one or more sidelink receive beams.

13. The method of claim 1, further comprising: receiving, from the second UE, an indication of adjusting one or more sidelink receive beams used by the second UE to receive the first set of sidelink beam failure detection reference signals.

14. The method of claim 1, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidellink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals additionally comprise a sidelink channel state information reference signal.

15. The method of claim 1, wherein a first periodicity associated with transmitting the first set of sidelink beam failure detection reference signals is different than a second periodicity used for monitoring for reception of the second set of sidelink beam failure detection reference signals.

16. An apparatus for wireless communication at a first user equipment (UE), comprising one or more processors; one or more memories coupled with the one or more processors; and instructions stored in the one or more memories and executable by the one or more processors to cause the apparatus to: receive, from a second UE, a first control message including control information that configures a first set of sidelink beam failure detection reference signals that the first UE is to transmit to the second UE using a set of sidelink transmit beams and configures a second set of sidelink beam failure detection reference signals that the first UE is to receive from the second UE using a set of sidelink receive beams, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include respective sidelink synchronization signal blocks; transmit, to the second UE, the first set of sidelink beam failure detection reference signals using the set of sidelink transmit beams; monitor for the second set of sidelink beam failure detection reference signals using the set of sidelink receive beams, the second set of sidelink beam failure detection reference signals being different than the first set of sidelink beam failure detection reference signals; and communicate with the second UE on a sidelink based at least in part on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

17. The apparatus of claim 16, wherein the first control message indicates a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

18. The apparatus of claim 16, wherein the instructions are further executable by the one or more processors to cause the apparatus to: transmit, to the second UE, a second control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

19. The apparatus of claim 16, wherein the instructions are further executable by the one or more processors to cause the apparatus to: receive, from a network entity, a second control message indicating a counter threshold for a beam failure indication counter, an expiration timer value for a beam failure indication timer, or both the counter threshold for the beam failure indication counter and the expiration timer value for the beam failure indication timer.

20. The apparatus of claim 16, wherein the instructions are executable by the one or more processors to further cause the apparatus to: detect a beam failure based at least in part on monitoring for reception of the second set of sidelink beam failure detection reference signals; and perform a beam failure recovery procedure with the second UE based at least in part on detecting the beam failure.

21. The apparatus of claim 20, wherein the instructions are executable by the one or more processors to further cause the apparatus to: refrain from transmitting one or more of the first set of sidelink beam failure detection reference signals based at least in part on detecting the beam failure, wherein the beam failure recovery procedure is performed with the second UE based at least in part on refraining from transmitting one or more of the first set of sidelink beam failure detection reference signals.

22. The apparatus of claim 20, wherein the instructions are executable by the one or more processors to further cause the apparatus to: transmit, to the second UE, a network entity, or both the second UE and the network entity, an indication of the beam failure, wherein the beam failure recovery procedure is performed based at least in part on transmitting the indication.

23. The apparatus of claim 20, wherein the instructions are executable by the one or more processors to further cause the apparatus to: determine that a reference signal received power of one or more of the second set of sidelink beam failure detection reference signals is below a received power threshold; initiate a beam failure timer based at least in part on determining that the reference signal received power is below the received power threshold; and increment a beam failure counter prior to expiration of the beam failure timer each time the second set of sidelink beam failure detection reference signals is received with the reference signal received power below the received power threshold, wherein the beam failure is detected based at least in part on the beam failure counter reaching a counter threshold.

24. The apparatus of claim 16, wherein the instructions are executable by the one or more processors to further cause the apparatus to: receive, from the second UE or a network entity, an indication of a beam failure associated with the second UE; and perform a beam failure recovery procedure with the second UE based at least in part on receiving the indication.

25. The apparatus of claim 24, wherein the instructions are executable by the one or more processors to further cause the apparatus to: increment a beam failure counter based at least in part on receiving the indication of the beam failure, wherein the beam failure recovery procedure is performed based at least in part on the beam failure counter reaching a counter threshold.

26. The apparatus of claim 16, wherein the instructions are executable by the one or more processors to further cause the apparatus to: adjust one or more sidelink receive beams used to receive the second set of sidelink beam failure detection reference signals.

27. The apparatus of claim 26, wherein the instructions are executable by the one or more processors to further cause the apparatus to: transmit, to the second UE, an indication of the adjustment of the one or more sidelink receive beams.

28. The apparatus of claim 16, wherein the instructions are executable by the one or more processors to further cause the apparatus to: receive, from the second UE, an indication of adjustment of one or more sidelink receive beams used by the second UE to receive the first set of sidelink beam failure detection reference signals.

29. The apparatus of claim 16, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidellink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals additionally include a sidelink channel state information reference signal.

30. The apparatus of claim 16, wherein a first periodicity associated with transmitting the first set of sidelink beam failure detection reference signals is different from a second periodicity used to monitor for reception of the second set of sidelink beam failure detection reference signals.

31. An apparatus for wireless communication at a first user equipment (UE), comprising means for receiving, from a second UE, a first control message including control information that configures a first set of sidelink beam failure detection reference signals that the first UE is to transmit to the second UE using a set of sidelink transmit beams and that configures a second set of sidelink beam failure detection reference signals that the first UE is to receive from the second UE using a set of sidelink receive beams, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include respective sidelink synchronization signal blocks; means for transmitting, to the second UE, the first set of sidelink beam failure detection reference signals using the set of sidelink transmit beams; means for monitoring for the second set of sidelink beam failure detection reference signals using the set of sidelink receive beams, the second set of sidelink beam failure detection reference signals being different from the first set of sidelink beam failure detection reference signals; and means for communicating with the second UE on a sidelink based at least in part on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals.

32. A non-transitory computer-readable medium storing code for wireless communication at a first user equipment (UE), the code comprising instructions executable by a processor to: receive, from a second UE, a first control message comprising control information that configures a first set of sidelink beam failure detection reference signals that the first UE is to transmit to the second UE using a set of sidelink transmit beams and that configures a second set of sidelink beam failure detection reference signals that the first UE is to receive from the second UE using a set of sidelink receive beams, wherein the first set of sidelink beam failure detection reference signals, the second set of sidelink beam failure detection reference signals, or both the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals include respective sidelink synchronization signal blocks; transmit, to the second UE, the first set of sidelink beam failure detection reference signals using the set of sidelink transmit beams; monitor for the second set of sidelink beam failure detection reference signals using the set of sidelink receive beams, the second set of sidelink beam failure detection reference signals being different than the first set of sidelink beam failure detection reference signals; and communicate with the second UE on a sidelink based at least in part on the first set of sidelink beam failure detection reference signals and the second set of sidelink beam failure detection reference signals. ​

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