Sidelink beam failure detection

Abstract

To address the issue in which there exists a need for further improvements in LTE and NR technologies.SOLUTION: Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a first node may transmit, to a second node on a beamformed link from the first node to the second node, a first signal, wherein the first node and the second node are associated with common timing; determine whether a second signal, based at least in part on the first signal, is received on a beamformed link from the second node to the first node; and transmit a third signal based at least in part on receiving the second signal or perform a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received. Numerous other aspects are provided.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Cross - Reference to Related Applications This patent application claims priority to U.S. Provisional Patent Application No. 62 / 969,544, filed on February 3, 2020, and U.S. Non - Provisional Patent Application No. 17 / 248,162, filed on January 12, 2021, both entitled "SIDELINK BEAM FAILURE DETECTION", which are hereby incorporated by reference in their entirety.

[0002] Aspects of the present disclosure generally relate to wireless communication and, more particularly, to techniques and apparatus for sidelink beam failure detection.

Background Art

[0003] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcast. A typical wireless communication system may utilize a multiple - access technology that is capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple - access technologies include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single - Carrier Frequency Division Multiple Access (SC - FDMA) systems, Time Division - Synchronous Code Division Multiple Access (TD - SCDMA) systems, and Long Term Evolution (LTE). LTE / LTE - Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standards published by the Third Generation Partnership Project (3GPP®).

[0004] A wireless communication network may include several base stations (BSs) that can support communication for several user equipments (UEs). The UE can communicate with the BS via the downlink and the uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As described in more detail herein, the BS may be referred to as a Node B, gNB, access point (AP), radio head, transmission and reception point (TRP), new radio (NR) BS, 5G Node B, etc.

[0005] The above multi-connection technology has been adopted in various telecommunication standards to provide a common protocol that enables various user equipments to communicate at the urban, national, regional, and even world levels. NR, which may also be called 5G, is a set of extensions to the LTE mobile standard published by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, improving services, utilizing new spectra, using cyclic prefix (CP)-orthogonal frequency division multiplexing (OFDM) (CP-OFDM) on the downlink (DL), and using CP-OFDM and / or single carrier frequency division multiplexing (SC-FDM) (also called discrete Fourier transform spread OFDM (DFT-s-OFDM) for example) on the uplink (UL) to better integrate with other open standards, as well as by supporting beamforming, multiple input multiple output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, further improvements to LTE technology and NR technology are needed. Preferably, these improvements should be applicable to other multi-connection technologies and the telecommunication standards that utilize these technologies.

SUMMARY OF THE INVENTION

MEANS FOR SOLVING THE PROBLEM

[0006] In some aspects, the method of wireless communication performed by the first node comprises transmitting a first signal to a second node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; determining whether a second signal is received on a beamformed link from the second node to the first node, at least partially based on the first signal; and transmitting a third signal on a beamformed link from the first node to the second node, at least partially based on receiving the second signal, or performing sidelink beam failure recovery procedures, at least partially based on determining that the second signal is not received.

[0007] In some aspects, the method of wireless communication performed by the second node comprises determining whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; determining whether to transmit a second signal on a beamformed link from the second node to the first node, at least partially based on whether the first signal is received; and receiving a third signal, at least partially based on the second signal, or performing sidelink beam failure recovery procedures, at least partially based on failing to receive the first signal or the third signal.

[0008] In some aspects, a first node for wireless communication may include a memory and one or more processors operably coupled to the memory. The memory or the one or more processors are to transmit a first signal to a second node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing, and to determine, at least in part based on the first signal, whether a second signal is received on the beamformed link from the second node to the first node, and to transmit a third signal at least in part based on receiving the second signal, or to perform sidelink beam failure recovery procedures at least in part based on determining that the second signal is not received.

[0009] In some aspects, a second node for wireless communication may include a memory and one or more processors operably coupled to the memory. The memory or the one or more processors are to determine whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing, and to determine, at least in part based on whether the first signal is received, whether to transmit a second signal on the beamformed link from the second node to the first node, and to receive a third signal at least in part based on the second signal, or to perform sidelink beam failure recovery procedures at least in part based on failing to receive the first signal or the third signal.

[0010] In some aspects, the non-transitory computer-readable medium may store one or more instructions for wireless communication. When the one or more instructions are executed by one or more processors of a first node, the one or more processors are caused to transmit a first signal to a second node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing, and based at least in part on the first signal, determine whether a second signal is received on the beamformed link from the second node to the first node, and based at least in part on receiving the second signal, transmit a third signal, or based at least in part on determining that the second signal is not received, perform sidelink beam failure recovery procedures.

[0011] In some aspects, the non-transitory computer-readable medium may store one or more instructions for wireless communication. When the one or more instructions are executed by one or more processors of a second node, the one or more processors are caused to determine whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing, and based at least in part on whether the first signal is received, determine whether to transmit a second signal on the beamformed link from the second node to the first node, and based at least in part on the second signal, receive a third signal, or based at least in part on failing to receive the first signal or the third signal, perform sidelink beam failure recovery procedures.

[0012] In some aspects, an apparatus for wireless communication comprises means for transmitting a first signal from the apparatus to a second node on a beamformed link from the apparatus to the second node, wherein the apparatus and the second node are associated with a common timing; means for determining whether a second signal is received on the beamformed link from the second node to the apparatus, at least partially based on the first signal; and means for transmitting a third signal on the beamformed link from the first node to the second node, at least partially based on receiving the second signal, or for performing a sidelink beam failure recovery procedure, at least partially based on determining that the second signal is not received.

[0013] In some aspects, an apparatus for wireless communication comprises means for determining whether a first signal is received from a first node on a beamformed link from the first node to the apparatus, wherein the first node and the apparatus are associated with a common timing; means for determining whether to transmit a second signal on the beamformed link from the apparatus to the first node, at least partially based on whether the first signal is received; means for receiving a third signal, at least partially based on the second signal, or means for performing a sidelink beam failure recovery procedure, at least partially based on failing to receive the first signal or the third signal.

[0014] Aspects are described fully herein with reference to the drawings, and include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and / or processing system as shown by the accompanying drawings and the specification.

[0015] The foregoing has outlined rather broadly the features and technical advantages of examples according to the present disclosure so that the manner in which the following inventions are implemented may be better understood. Additional features and advantages will be described below. The disclosed concepts and specific examples may be readily used as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent structures do not depart from the scope of the appended claims. The characteristics of the concepts disclosed herein, both their organization and manner of operation, will be better understood from the following description when considered in connection with the accompanying drawings, along with the related advantages. Each of the drawings is provided for purposes of illustration and description, and not as a definition of the limits of the claims.

[0016] To better understand the foregoing features of the present disclosure in detail, a more specific description may be made of the content briefly summarized above by referring to the manner in which a part thereof is shown in the accompanying drawings. However, it should be noted that since this description may admit other equally effective manners, the accompanying drawings show only some typical manners of the present disclosure and should not be regarded as limiting its scope. The same reference numerals in different drawings may identify the same or similar elements.

Brief Description of the Drawings

[0017]

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[0018] Various aspects of the present disclosure will be described in more detail below with reference to the accompanying drawings. However, the present disclosure may be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout the present disclosure. Rather, these aspects are configured such that the present disclosure is comprehensive and complete and conveys the scope of the present disclosure to those skilled in the art. Based on the teachings herein, it should be understood by those skilled in the art that the scope of the present disclosure includes any aspect of the present disclosure disclosed herein, whether implemented independently of any other aspect of the present disclosure or in combination with any other aspect of the present disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects described herein. In addition, the scope of the present disclosure includes apparatuses or methods practiced using other structures, functionality, or structures and functionality in addition to or other than the various aspects of the present disclosure described herein. It should be understood that any aspect of the present disclosure disclosed herein may be embodied by one or more elements of the claims.

[0019] Next, some aspects of a telecommunications system are presented with reference to various apparatuses and techniques. These apparatuses and techniques are described in the following detailed description and are illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using hardware, software, or a combination thereof. Whether such elements are implemented as hardware or as software depends on the specific application example and the design constraints imposed on the overall system.

[0020] Regarding aspects, terms generally associated with 5G or NR radio access technology (RAT) may be used in this specification to describe them, but it should be noted that the aspects of the present disclosure can be applied to other RATs such as 3G RAT, 4G RAT, and / or RATs following 5G (e.g., 6G).

[0021] FIG. 1 is a diagram showing a wireless network 100 in which aspects of the present disclosure can be practiced. The wireless network 100 can be any other wireless network such as an LTE network, or a 5G or NR network. The wireless network 100 can include several BSs 110 (shown as BS110a, BS110b, BS110c, and BS110d) and other network entities. A BS is an entity that communicates with user equipment (UE) and may be referred to as a base station, NR BS, Node B, gNB, 5G Node B (NB), access point, transmit-receive point (TRP), etc. Each BS can provide communication coverage for a specific geographical area. In 3GPP, the term "cell" can refer to the coverage area of a BS and / or the BS subsystem serving this coverage area depending on the context in which the term is used.

[0022] The BS may provide communication coverage for macrocells, picocells, femtocells, and / or another type of cell. A macrocell may cover a relatively large geographical area (e.g., several kilometers in radius) and may enable unrestricted access by UEs subscribed to the service. A picocell may cover a relatively small geographical area and may enable unrestricted access by UEs subscribed to the service. A femtocell may cover a relatively small geographical area (e.g., a home) and may enable restricted access by UEs associated with the femtocell (e.g., UEs within a Closed Subscriber Group (CSG)). The BS for a macrocell may sometimes be called a macro BS. The BS for a picocell may sometimes be called a pico BS. The BS for a femtocell may sometimes be called a femto BS or a home BS. In the example shown in FIG. 1, BS110a may be a macro BS for macrocell 102a, BS110b may be a pico BS for picocell 102b, and BS110c may be a femto BS for femtocell 102c. The BS may support one or more (e.g., three) cells. The terms "eNB", "base station", "NR BS", "gNB", "TRP", "AP", "Node B", "5G NB", and "cell" may be used interchangeably herein.

[0023] In some aspects, the cell may not necessarily be stationary, and the geographical area of the cell may move according to the location of the mobile BS. In some aspects, the BSs may be interconnected with each other and / or with one or more other BSs or network nodes (not shown) in the wireless network 100 through various types of backhaul interfaces such as direct physical connections, virtual networks, using any suitable transport network.

[0024] Wireless network 100 may also include relay stations. A relay station is an entity that can receive data transmissions from an upstream station (e.g., a BS or a UE) and send the data transmissions to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in FIG. 1, relay BS 110d can communicate with BS 110a and UE 120d to facilitate communication between macro BS 110a and UE 120d. Relay BS may sometimes be referred to as a relay station, relay base station, relay, etc.

[0025] Wireless network 100 may be a heterogeneous network that includes different types of BSs, such as macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmission power levels, different coverage areas, and different impacts on interference in wireless network 100. For example, a macro BS may have a high transmission power level (e.g., 5 to 40 watts), while pico BSs, femto BSs, and relay BSs may have a lower transmission power level (e.g., 0.1 to 2 watts).

[0026] Network controller 130 may be coupled to a set of BSs and may perform coordination and control for these BSs. Network controller 130 can communicate with the BSs via a backhaul. The BSs can also communicate with each other directly or indirectly, for example, via a wireless or wireline backhaul.

[0027] UEs 120 (e.g., 120a, 120b, 120c) may be distributed throughout the wireless network 100, and each UE may be fixed or mobile. UEs may also be referred to as access terminals, terminals, mobile stations, subscriber units, stations, etc. A UE may be a cellular phone (e.g., a smartphone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or instrument, a biosensor / device, a wearable device (smartwatch, smart clothing, smart glasses, smart list band, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicle component or sensor, a smart meter / sensor, an industrial manufacturing device, a global positioning system device, or any other suitable device configured to communicate via a wireless or wired medium.

[0028] Some UEs may be regarded as machine type communication (MTC) UEs, or enhanced or extended machine type communication (eMTC) UEs. MTC UEs and eMTC UEs can communicate with, for example, a base station, another device (such as a remote device), or some other entities, including robots, drones, remote devices, sensors, meters, monitors, location tags, etc. A wireless node can provide connectivity for a network (such as a wide area network like the Internet or a cellular network) or connectivity to the network via, for example, a wired or wireless communication link. Some UEs may be regarded as Internet of Things (IoT) devices and / or may be implemented as narrowband Internet of Things (NB-IoT) devices. Some UEs may be regarded as customer premise equipment (CPE). UE120 may be included within a housing that stores components of UE120, such as a processor component, a memory component, etc.

[0029] Generally, any number of wireless networks can be deployed within a given geographical area. Each wireless network may support a particular radio access technology (RAT) and may operate at one or more frequencies. RATs may also be referred to as wireless technologies, air interfaces, etc. Frequencies may also be referred to as carriers, frequency channels, etc. Each frequency may support a single RAT within a given geographical area to avoid interference between wireless networks of different RATs. In some cases, an NR or 5G RAT network may be deployed.

[0030] In some aspects, two or more UEs 120 (e.g., shown as UE120a and UE120e) may communicate directly using one or more sidelink channels (e.g., without using base station 110 as an intermediary for communicating with each other). For example, UE120 may communicate using peer-to-peer (P2P) communication, device-to-device (D2D) communication, vehicle-to-everything (V2X) protocols (which may include, for example, vehicle-to-vehicle (V2V) protocols, vehicle-to-infrastructure (V2I) protocols, etc.), mesh networks, and the like. In this case, UE120 may perform scheduling operations, resource selection operations, and / or other operations described elsewhere in this specification as being performed by base station 110.

[0031] The devices of the wireless network 100 may communicate using the electromagnetic spectrum, which can be subdivided into various classes, bands, channels, etc. based on frequency or wavelength. For example, the devices of the wireless network 100 may communicate using an operating band having a first frequency range (FR1) that can span from 410 MHz to 7.125 GHz, and / or using an operating band having a second frequency range (FR2) that can span from 24.25 GHz to 52.6 GHz. The frequencies between FR1 and FR2 may sometimes be referred to as intermediate band frequencies. A portion of FR1 is higher than 6 GHz, but FR1 is often referred to as the "sub-6 GHz" band. Similarly, although FR2 is different from the extremely high frequency (EHF) band (30 GHz to 300 GHz) identified by the International Telecommunication Union (ITU) as the "millimeter wave" band, it is often referred to as the "millimeter wave" band. Thus, unless otherwise specified, terms such as "sub-6 GHz" as used in this specification may be understood to broadly represent frequencies below 6 GHz, frequencies within FR1, and / or intermediate band frequencies (e.g., greater than 7.125 GHz). Similarly, unless otherwise specified, terms such as "millimeter wave" as used in this specification may be understood to broadly represent frequencies within the EHF band, frequencies within FR2, and / or intermediate band frequencies (e.g., less than 24.25 GHz). It is contemplated that the frequencies included in FR1 and FR2 may be modified, and the techniques described herein are applicable to those modified frequency ranges.

[0032] As shown above, FIG. 1 is given as an example. Other examples may be different from the example described with respect to FIG. 1.

[0033] FIG. 2 shows a block diagram of a design 200 of a base station 110 and a UE 120, which may be one of the base stations and one of the UEs in FIG. 1. The base station 110 may be equipped with T antennas 234a to 234t, and the UE 120 may be equipped with R antennas 252a to 252r, where generally T≥1 and R≥1.

[0034] At base station 110, transmission processor 220 receives data for one or more UEs from data source 212, selects one or more modulation and coding schemes (MCSs) for each UE based at least in part on channel quality indicators (CQIs) received from the UEs, processes (e.g., encodes and modulates) the data for each UE based at least in part on the MCS selected for the UE, and may provide data symbols to all UEs. Transmission processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI)) and control information (e.g., CQI requests, grants, higher layer signaling, etc.) and may provide overhead symbols and control symbols. Transmission processor 220 may also generate reference symbols for reference signals (e.g., cell-specific reference signals (CRSs)) and synchronization signals (e.g., primary synchronization signals (PSSs) and secondary synchronization signals (SSSs)). Transmission (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, control symbols, overhead symbols, and / or reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a-232t. Each modulator 232 may process its respective output symbol stream (e.g., for OFDM) to obtain an output sample stream. Each modulator 232 may further process the output sample stream (e.g., convert to analog, amplify, filter, and up-convert) to obtain a downlink signal. The T downlink signals from modulators 232a-232t may be transmitted via T antennas 234a-234t, respectively. According to various aspects described in more detail below, the synchronization signals may be generated using position encoding to convey additional information.

[0035] At the UE 120, the antennas 252a-252r may receive downlink signals from the base station 110 and / or other base stations, and may each provide the received signals to the demodulators (DEMOD) 254a-254r. Each demodulator 254 may condition (e.g., filter, amplify, down-convert, and digitize) the received signals to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. The MIMO detector 256 may obtain received symbols from all R demodulators 254a-254r, and may perform MIMO detection on the received symbols, if applicable, and provide the detected symbols. The receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide the decoded data for the UE 120 to the data sink 260, and may provide the decoded control information and system information to the controller / processor 280. The channel processor may determine the reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc. In some aspects, one or more components of the UE 120 may be included in a housing.

[0036] On the uplink, at UE 120, transmission processor 264 may receive and process data from data source 262 and control information (such as for reporting including RSRP, RSSI, RSRQ, CQI, etc.) from controller / processor 280. Transmission processor 264 may also generate reference symbols for one or more reference signals. Symbols from transmission processor 264 may be precoded by TX MIMO processor 266 when applicable, and further processed by modulators 254a - 254r (such as for DFT - s - OFDM, CP - OFDM, etc.) and transmitted to base station 110. At base station 110, uplink signals from UE 120 and other UEs are received by antenna 234, processed by demodulator 232, detected by MIMO detector 236 when applicable, and further processed by receive processor 238 to obtain the decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to data sink 239 and the decoded control information to controller / processor 240. Base station 110 includes communication unit 244 and may communicate with network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller / processor 290, and memory 292.

[0037] The controller / processor 240 of the base station 110, the controller / processor 280 of the UE 120, and / or any other component of FIG. 2 may implement one or more techniques associated with sidelink beam obstruction detection, as described in more detail elsewhere in this specification. For example, the controller / processor 240 of the base station 110, the controller / processor 280 of the UE 120, and / or any other component of FIG. 2 may perform or direct the operations of, for example, process 900 of FIG. 9, process 1000 of FIG. 10, and / or other processes as described herein. The memories 242 and 282 may store data and program code for the base station 110 and the UE 120, respectively. In some aspects, the memory 242 and / or the memory 282 may include a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed by one or more processors of the base station 110 and / or the UE 120, may perform or direct the operations of, for example, process 900 of FIG. 9, process 1000 of FIG. 10, and / or other processes as described herein. The scheduler 246 may schedule the UE for data transmission on the downlink and / or uplink.

[0038] In some aspects, a node (e.g., UE120 or BS110) includes means for transmitting a first signal to a second node on a beamformed link from the first node to the second node, means for determining whether a second signal is received on a beamformed link from the second node to the first node based at least in part on the first signal, means for transmitting a third signal on a beamformed link from the first node to the second node based at least in part on receiving the second signal, means for performing a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received, means for determining whether the first signal is received from the first node on a beamformed link from the first node to the second node, means for determining whether to transmit the second signal on a beamformed link from the second node to the first node based at least in part on whether the first signal is received, means for receiving the third signal based at least in part on the second signal, means for performing a sidelink beam failure recovery procedure based at least in part on failing to receive the first signal or the third signal, means for performing a sidelink beam failure recovery procedure based at least in part on failing a threshold number of times to receive one or more of the first signal or the third signal, and the like. In some aspects, such means may include one or more components of UE120 or BS110 described with respect to FIG. 2, such as controller / processor 280, transmit processor 264, TX MIMO processor 266, MOD254, antenna 252, DEMOD254, MIMO detector 256, receive processor 258, antenna 234, DEMOD232, MIMO detector 236, receive processor 238, controller / processor 240, transmit processor 220, TX MIMO processor 230, MOD232, antenna 234, etc.

[0039] As shown above, FIG. 2 is provided as an example. Other examples may be different from those described with respect to FIG. 2.

[0040] FIG. 3 is a diagram showing an example 300 of sidelink communication according to various aspects of the present disclosure.

[0041] As shown in FIG. 3, a first UE 305-1 can communicate with a second UE 305-2 (and one or more other UEs 305) via one or more sidelink channels 310. The UEs 305-1 and 305-2 may communicate using one or more sidelink channels 310 for P2P communication, D2D communication, V2X communication (which may include, for example, V2V communication, V2I communication, V2P communication, etc.), mesh networking, etc. In some aspects, the UE 305 (e.g., UE 305-1 and / or UE 305-2) may correspond to one or more other UEs described elsewhere in this specification, such as UE 120. In some aspects, one or more sidelink channels 310 may use a ProSe sidelink (PC5) interface and / or may operate in a high frequency band (e.g., 5.9 GHz band). Additionally or alternatively, the UE 305 may use global navigation satellite system (GNSS) timing to synchronize the timing of a transmission time interval (TTI) (e.g., frame, subframe, slot, symbol, etc.) or the timing of a base station 110 associated with one or more of the UEs 305.

[0042] As further shown in FIG. 3, one or more sidelink channels 310 may include a physical sidelink control channel (PSCCH) 315, a physical sidelink shared channel (PSSCH) 320, and / or a physical sidelink feedback channel (PSFCH) 325. The PSCCH 315 may be used to communicate control information, similar to the physical downlink control channel (PDCCH) and / or the physical uplink control channel (PUCCH) used for cellular communication with the base station 110 via an access link or an access channel. The PSSCH 320 may be used to communicate data, similar to the physical downlink shared channel (PDSCH) and / or the physical uplink shared channel (PUSCH) used for cellular communication with the base station 110 via an access link or an access channel. For example, the PSCCH 315 may carry sidelink control information (SCI) 330, and the SCI 330 may indicate various control information used for sidelink communication, such as one or more resources (e.g., time resources, frequency resources, spatial resources, etc.). In that case, a transport block (TB) 335 may be carried on the PSSCH 320. The TB 335 may include data. The PSFCH 325 may be used to communicate sidelink feedback 340 such as hybrid automatic repeat request (HARQ) feedback (e.g., acknowledgement or negative acknowledgement (ACK / NACK) information), transmit power control (TPC), scheduling request (SR), etc.

[0043] In some aspects, one or more sidelink channels 310 may use a resource pool. For example, a scheduling assignment (e.g., included in SCI 330) may be transmitted in a subchannel using specific resource blocks (RBs) over time. In some aspects, data transmissions associated with a scheduling assignment (e.g., on PSSCH 320) may occupy adjacent RBs in the same subframe as the scheduling assignment (e.g., using frequency division multiplexing). In some aspects, the scheduling assignment and associated data transmissions are not transmitted on adjacent RBs.

[0044] In some aspects, UE 305 may operate using a transmission mode, in which case resource selection and / or scheduling is performed by UE 305 (e.g., rather than base station 110). In some aspects, UE 305 may perform resource selection and / or scheduling by detecting channel availability for transmission. For example, UE 305 may measure received signal strength indicator (RSSI) parameters (e.g., sidelink RSSI (S-RSSI) parameters) associated with various sidelink channels, may measure reference signal received power (RSRP) parameters (e.g., PSSCH-RSRP parameters) associated with various sidelink channels, may measure reference signal received quality (RSRQ) parameters (e.g., PSSCH-RSRQ parameters) associated with various sidelink channels, etc., and may select a channel for transmission of sidelink communication based at least in part on the measurements.

[0045] Additionally or alternatively, the UE 305 may perform resource selection and / or scheduling using the SCI 330 received on the PSCCH 315, which may indicate occupied resources, channel parameters, etc. Additionally or alternatively, the UE 305 may perform resource selection and / or scheduling by determining the channel busy rate (CBR) associated with various sidelink channels that may be used for rate control (e.g., by indicating the maximum number of resource blocks that the UE 305 can use for a set of specific subframes).

[0046] In the transmission mode in which resource selection and / or scheduling is performed by the UE 305, the UE 305 may generate a sidelink grant and may transmit the grant in the SCI 330. The sidelink grant may indicate one or more parameters (e.g., transmission parameters) to be used for the next sidelink transmission, such as one or more resource blocks to be used for the next sidelink transmission (e.g., for the TB 335) on the PSSCH 320, one or more subframes to be used for the next sidelink transmission, the modulation and coding scheme (MCS) to be used for the next sidelink transmission, etc. In some aspects, the UE 305 may generate a sidelink grant indicating one or more parameters for semi-persistent scheduling (SPS), such as the periodicity of sidelink transmissions. Additionally or alternatively, the UE 305 may generate a sidelink grant for event-driven scheduling, such as for on-demand sidelink messages.

[0047] As shown above, FIG. 3 is given as an example. Other examples may be different from the example described with respect to FIG. 3.

[0048] FIG. 4 is a diagram illustrating an example 400 of sidelink communication and access link communication according to various aspects of the present disclosure.

[0049] As shown in FIG. 4, the transmitter (Tx) UE 405 and the receiver (Rx) UE 410 may communicate with each other via a sidelink, as described above in connection with FIG. 3. Further, as shown, in some sidelink modes, the base station 110 may communicate with the Tx UE 405 via a first access link. Additionally or alternatively, in some sidelink modes, the base station 110 may communicate with the Rx UE 410 via a second access link. The Tx UE 405 and / or the Rx UE 410 may correspond to one or more UEs described elsewhere in this specification, such as the UE 120 of FIG. 1. Thus, the sidelink may refer to a direct link between UEs 120, and the access link may refer to a direct link between the base station 110 and the UE 120. Sidelink communications may be transmitted via the sidelink, and access link communications may be transmitted via the access link. Access link communications may be either downlink communications (from the base station 110 to the UE 120) or uplink communications (from the UE 120 to the base station 110). In some aspects, the UEs 405 and 410 may not be associated with an access link.

[0050] As shown above, FIG. 4 is given as an example. Other examples may be different from the example described with respect to FIG. 4.

[0051] Two nodes may communicate with each other using sidelink communication. The nodes may be any UE, such as an integrated access and backhaul (IAB) node, a UE associated with vehicle communication, a UE associated with a sidelink network, a reduced-capability UE, etc. Sidelink communication involves the transmission or reception of data between UEs without a relay base station or a scheduling entity and without communication of data via an access link. Sidelink communication may be useful in various applications such as low-latency scenarios, poor coverage scenarios, relay from UE to network or from network to UE, vehicle-to-anything communication, vehicle-to-vehicle communication, etc. The nodes may use beamforming to communicate with each other over the sidelink, thereby improving the wireless performance of the nodes while using less power than omnidirectional or quasi-omnidirectional transmissions with an equivalent range.

[0052] In some cases, the beams on the beamformed sidelink may fail, which means that the beam no longer provides a link to another node. For example, an obstacle may enter the propagation path of the beam, or the node transmitting or receiving the beam may move, thereby causing an outage of the sidelink. In this case, the beamformed sidelink may experience performance degradation or may fail. This can lead to communication interruptions, waste of resources, throughput degradation, etc. Furthermore, it may be difficult to quickly detect a faulty beam on the sidelink if there is no central scheduler associated with the sidelink to arrange for signal transmission or beam outage recovery on the sidelink.

[0053] With some of the techniques and apparatuses described herein, a pair of nodes can perform beam obstruction detection and recovery on a sidelink between the pair of nodes. For example, a pair of nodes associated with a common timing may transmit signals to each other regarding a resource allocation known to the pair of nodes. The pair of nodes may identify a healthy link or an obstructed beam or link at least partially based on whether a signal is received on the allocated resources, and may perform beam failure recovery (BFR) at least partially based on detecting an obstructed beam or link. In this way, a pair of nodes can identify beam obstructions and perform BFR on the sidelink without the involvement of a central scheduler such as a gNB. By identifying beam obstructions and performing BFR on the sidelink without the involvement of a central scheduler, the impact of blocked beams can be reduced, thereby improving wireless link quality, throughput, and resource utilization, and reducing the latency and overhead associated with identifying beam or sidelink failures.

[0054] Figures 5-8 are diagrams illustrating examples 500, 600, 700, and 800 of sidelink beam obstruction detection and recovery according to various aspects of the present disclosure. Examples 500, 600, 700, and 800 include a first UE 120 and a second UE 120 (e.g., UE 305-1, UE 305-2, UE 405, UE 410, etc.), which are referred to as the first UE and the second UE. In some aspects, the first UE may be a first node and the second UE may be a second node. In some aspects, the first UE and / or the second UE may be associated with an access link to BS 110. In some aspects, the first UE and the second UE may not be associated with an access link to BS 110. The operations described in Figures 5-8 are described as being performed by the first UE and the second UE, but these operations may be performed by other types of wireless nodes (e.g., IAB nodes, etc.).

[0055] Figure 5 shows an example 500 of sidelink beam monitoring on an intact sidelink. As shown, the first UE may be associated with a transmit (Tx) beam 505 and a receive (Rx) beam 510. The second UE may be associated with an Rx beam 515 corresponding to the Tx beam 505 and a Tx beam 520 corresponding to the Rx beam 510. The Tx beam 505 and the Rx beam 515 may form a beamformed sidelink 525 from the first UE to the second UE, and the Tx beam 520 and the Rx beam 510 may form a beamformed sidelink 530 from the second UE to the first UE. For example, the beamformed sidelinks 525 and 530 may carry a sidelink channel 310 (shown in FIG. 3) between the first UE and the second UE. In some aspects, the first UE and the second UE may be associated with a single beamformed sidelink that can be used for communication in both directions, which is shown in FIG. 8.

[0056] As indicated by reference number 535, the first UE may transmit a first signal at time T1. For example, the first UE may transmit the first signal on a resource allocation (e.g., a time and / or frequency resource allocation) that is known to both the first UE and the second UE, and the resource allocation is associated with time T1. The first UE and the second UE may be associated with a common timing, which means that the second UE can determine the time T1 at which the first UE transmits the first signal. For example, in some aspects, the first UE and the second UE may have a common timing that is at least partially based on being configured by the base station (e.g., via an access link) to have a common timing. In some aspects, the first UE and the second UE may have a common timing that is at least partially based on their respective positioning systems (e.g., a Global Positioning System (GPS), a Global Navigation Satellite System (GNSS), etc.). By establishing a common timing, the second UE can determine when the first signal is expected (and the first UE can determine when the second signal is expected), and doing so enables sidelink beam monitoring using the first signal, the second signal, and the third signal.

[0057] In some aspects, the first UE and the second UE may determine T1, T2, and / or T3. For example, the first UE and the second UE may communicate with each other to identify (e.g., determine) resource allocations for transmitting / receiving the first signal, the second signal, and the third signal, thereby eliminating the need for a scheduling entity to be involved and saving the computing resources of the scheduling entity. In some aspects, the first UE and the second UE may be configured to have information indicating T1, T2, and / or T3. For example, this information may be defined in a wireless telecommunications standard, thereby saving signaling resources of the UE and BS110 associated with the UE. In some aspects, the first UE and the second UE may receive information indicating T1, T2, and / or T3 (e.g., from a scheduling entity such as BS110), thereby saving the resources of the first UE and the second UE that would otherwise be used to determine T1, T2, and / or T3.

[0058] As indicated by reference numeral 540, the second UE may transmit a second signal on the beamformed sidelink 530. For example, the second UE may transmit the second signal at time T2, at least partially based on receiving a first signal on a resource allocation associated with time T1 (e.g., using a resource allocation associated with time T2 and known to both the first UE and the second UE). In some aspects, T2 may be offset from T1 by a fixed time duration (e.g., approximately 10 ms), and the offset may be configurable, predefined, negotiated by the first UE and the second UE, etc. As indicated by reference numeral 545, the first UE may transmit a third signal on the beamformed sidelink 525. For example, the first UE may transmit the third signal at time T3, at least partially based on receiving the second signal on a resource allocation associated with time T2 (e.g., using a resource allocation known to both the first UE and the second UE and associated with time T3). In some aspects, T3 may be offset from T2 by a fixed time duration (e.g., approximately 10 ms), and the offset may be configurable, predefined, negotiated by the first UE and the second UE, etc.

[0059] By transmitting a second signal based at least in part on receiving a first signal and a third signal based at least in part on receiving the second signal, the first UE and the second UE may determine whether the beamformed sidelink 525 and the beamformed sidelink 530 have ceased to function. For examples of impairments to the beamformed sidelink 525 and / or the beamformed sidelink 530, see FIGS. 6-8. The first signal, the second signal, and / or the third signal may include any form of signaling, such as a reference signal (RS) (e.g., a channel state information (CSI) RS (CSI-RS), a sounding reference signal, etc.), a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), a physical sidelink feedback channel (PSFCH), etc. The first signal, the second signal, and the third signal may all be of the same type of signal or may include two or more different types of signals.

[0060] Performing sidelink beam obstruction detection using the first signal, the second signal, and the third signal may incur lower overhead than some other sidelink beam obstruction detection procedures. For example, in some cases, a first UE may transmit a beacon (e.g., a signal such as a synchronization signal block) on a beamformed sidelink, and a second UE may report to the base station 110 regarding whether the beacon is received. The base station 110 may adjust beam obstruction recovery when the beacon is not received by the second UE. However, base station coordination for monitoring and beam obstruction recovery may incur significant overhead and latency, and may be difficult or impossible in poor access network coverage scenarios. As another example, in some cases, a first UE may transmit a beacon on a beamformed sidelink, and when the beacon is not received, a second UE may initiate random access channel (RACH) procedures on the beamformed sidelink. However, RACH-based sidelink beam obstruction detection procedures may require the first UE and the second UE to continuously maintain RACH resources, which may be more resource-intensive than maintaining resources for the first signal, the second signal, and the third signal.

[0061] Figure 6 shows example 600 where the beamformed sidelink from the first UE to the second UE, as indicated by "X" on the beamformed sidelink, has stopped functioning. As indicated by reference numeral 610, the first UE may transmit a first signal at time T1. As indicated by reference numeral 620, the second UE may determine that the first signal is not received within the threshold time of T1. Thus, as indicated by reference numeral 630, the second UE may not need to transmit a second signal. As indicated by reference numeral 640, the first UE may determine that the second signal is not received at time T2. This can indicate to the first UE that the transmission of the first signal and / or the second signal has failed, meaning that one or more of the beamformed sidelinks between the first UE and the second UE have stopped functioning. Thus, as indicated by reference numeral 650, the first UE may not need to transmit a third signal at time T3.

[0062] As indicated by reference numerals 660 and 670, the first UE and the second UE may perform sidelink BFR procedures, at least in part, based on determining that the first signal, the second signal, and / or the third signal is not received. In some aspects, the first UE and the second UE may perform sidelink BFR procedures, at least in part, based on determining that the first signal and the second signal are not received, thereby reducing the latency associated with performing the sidelink BFR procedures compared to when the sidelink BFR procedures are performed after determining that the third signal is not received.

[0063] In the sidelink BFR procedure, the first UE may transmit beam failure recovery synchronization signals on multiple Tx beams at a predetermined time / frequency location (e.g., resource allocation) known to both the first UE and the second UE. The second UE may receive the beam failure recovery synchronization signals on multiple Rx beams. Based at least in part on receiving the beam failure recovery synchronization signals across multiple Tx-Rx beam combinations, the second UE may determine the best Tx beam to be used by the first UE and the best Rx beam to be used by the second UE for beamformed sidelink from the first UE to the second UE. The second UE may use this information to transmit a RACH signal to the first UE. For example, the RACH signal may use resources configured as part of the sidelink BFR procedure. The first UE may receive a potential beam failure recovery RACH signal from the second UE at a predetermined time / frequency location (e.g., RACH resource) known to both UEs. The second UE may transmit the RACH signal when the first UE is using the Rx beam corresponding to the best Tx beam used by the first UE to transmit the synchronization signal. Upon receiving the RACH signal, the first UE may determine the best Tx beam for beamformed sidelink from the first UE to the second UE. This sidelink BFR procedure may be initiated based at least in part on failing to detect the first, second, and / or third signals (e.g., without base station intervention). It should also be noted that the roles of the first UE and the second UE in the sidelink BFR procedure may be reversed to establish a beamformed link from the second UE to the first UE (e.g., the first UE may perform the RACH procedure and the second UE may transmit the synchronization signal).

[0064] In some aspects, the first UE and / or the second UE may determine a beam obstruction based at least in part on failing to receive a threshold number of signals. For example, the first UE and / or the second UE may declare a beam obstruction when failing to receive N first / second / third signals, or when determining that the procedure of receiving and transmitting the first / second / third signals has failed N times, where N is an integer. By doing so, it is possible to save the computational and communication resources that would otherwise be used to prematurely trigger the sidelink BFR procedure due to a single failed signal transmission.

[0065] FIG. 7 shows an example 700 in which the beamformed sidelink from the second UE to the first UE, as indicated by "X" on the beamformed sidelink from the second UE to the first UE, has stopped functioning. As indicated by reference numeral 710, the first UE may transmit a first signal at time T1. As indicated by reference numeral 720, the second UE may transmit a second signal at time T2 based at least in part on successfully receiving the first signal at time T1. However, the first UE fails to receive the second signal, as indicated by reference numeral 730. Accordingly, the first UE determines that the third signal should not be transmitted to the second UE, as indicated by reference numeral 740. The second UE may determine that the third signal is not received at time T3. Accordingly, the first UE and the second UE may determine that one or more beamformed sidelinks between the second UE and the first UE have stopped functioning because the second UE successfully received the first signal and did not successfully receive the third signal, and because the first UE did not receive the second signal. Accordingly, the first UE and the second UE may perform sidelink BFR procedures, such as the sidelink BFR procedure described in connection with FIG. 6, as indicated by reference numerals 760 and 770.

[0066] The case where both beamformed side links malfunction may be the same as in Examples 600 and 700, because the first UE and the second UE may each determine that the third and second signals should not be transmitted, at least partially based on having failed to receive the second and first signals, respectively.

[0067] Figure 8 shows Example 800 in which a single beamformed side link between a second UE and a first UE is used. For example, the single beamformed side link may be a full-duplex side link using some form of multiplexing, or it can be used to communicate in both directions. In Example 800, as indicated by "X" on the beamformed side link between the second UE and the first UE, the beamformed side link has malfunctioned. Thus, the first signal indicated by reference number 810 is not received by the second UE, as indicated by reference number 820. Thus, the second UE determines not to transmit the second signal, as indicated by reference number 830. The first UE may determine that the second signal is not received at time T2, as indicated by reference number 840, and may determine that the third signal should not be transmitted, as indicated by reference number 850. As indicated by reference numbers 860 and 870, the first UE and the second UE may perform a side link BFR procedure, such as the side link BFR procedure described in connection with FIG. 6, at least partially based on having determined that the beamformed side link has malfunctioned.

[0068] As shown above, FIGS. 5-8 are provided as one or more examples. Other examples may differ from what has been described with respect to FIGS. 5-8.

[0069] FIG. 9 is a diagram illustrating an exemplary process 900, such as may be performed by a first node, according to various aspects of the present disclosure. Exemplary process 900 is an example in which a first node (e.g., UE120, BS110, UE305, UE405, UE410, first UE120 of FIGS. 5 - 8, etc.) performs operations associated with sidelink beam obstruction detection.

[0070] As shown in FIG. 9, in some aspects, process 900 may include transmitting a first signal to a second node on a beamformed link from the first node to the second node, where the first node and the second node are associated with a common timing (block 910). For example, a first node (e.g., using controller / processor 280, transmitting processor 264, TX MIMO processor 266, MOD254, antenna 252, controller / processor 240, transmitting processor 220, TX MIMO processor 230, MOD232, antenna 234, etc.) may transmit the first signal to the second node on a beamformed link from the first node to the second node as described above. In some aspects, the first node and the second node are associated with a common timing.

[0071] As further shown in FIG. 9, in some aspects, process 900 may include determining (block 920) whether a second signal is received on a beamformed link from the second node to the first node, at least partially based on the first signal. For example, a first node (e.g., using antenna 234, DEMOD232, MIMO detector 236, receiving processor 238, controller / processor 240, antenna 252, DEMOD254, MIMO detector 256, receiving processor 258, controller / processor 280, etc.) may determine whether the second signal is received on a beamformed link from the second node to the first node, at least partially based on the first signal as described above.

[0072] As further shown in FIG. 9, in some aspects, process 900 may include transmitting a third signal (block 930) on a beamformed link from a first node to a second node based at least in part on receiving a second signal. For example, a first node (using, e.g., controller / processor 280, transmission processor 264, TX MIMO processor 266, MOD 254, antenna 252, controller / processor 240, transmission processor 220, TX MIMO processor 230, MOD 232, antenna 234, etc.) may transmit a third signal based at least in part on receiving a second signal as described above.

[0073] As further shown in FIG. 9, in some aspects, process 900 may include performing sidelink beam failure recovery procedures (block 940) based at least in part on determining that a second signal has not been received. For example, a first node (using, e.g., controller / processor 240, transmission processor 220, TX MIMO processor 230, MOD 232, antenna 234, controller / processor 280, transmission processor 264, TX MIMO processor 266, MOD 254, antenna 252, etc.) may perform sidelink beam failure recovery procedures based at least in part on determining that a second signal has not been received as described above.

[0074] Process 900 may include additional aspects such as any single aspect or any combination of aspects described with respect to one or more other processes described below and / or elsewhere in this specification.

[0075] In a first aspect, at least one of the first signal, the second signal, or the third signal includes a channel state information reference signal.

[0076] In a second aspect, alone or in combination with the first aspect, the first signal, the second signal, and the third signal are associated with respective resource allocations that are known to the first node and the second node prior to transmission of the first signal.

[0077] In a third aspect, alone or in combination with one or more of the first and second aspects, each resource allocation is determined by one or more of the first node or the second node.

[0078] In a fourth aspect, alone or in combination with one or more of the first to third aspects, each resource allocation is determined by a base station associated with the first node or the second node.

[0079] In a fifth aspect, alone or in combination with one or more of the first to fourth aspects, the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

[0080] In a sixth aspect, alone or in combination with one or more of the first to fifth aspects, a common timing is determined based at least in part on a base station associated with the first node and the second node.

[0081] In a seventh aspect, alone or in combination with one or more of the first to sixth aspects, a common timing is determined based at least in part on a positioning system of the first node and the second node.

[0082] In an eighth aspect, alone or in combination with one or more of the first to seventh aspects, the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe side link interface.

[0083] In a ninth aspect, alone or in combination with one or more of the first to eighth aspects, the first node and the second node include user equipment.

[0084] In a tenth aspect, alone or in combination with one or more of the first to ninth aspects, the first node and the second node include integrated access and backhaul nodes.

[0085] In an eleventh aspect, alone or in combination with one or more of the first to tenth aspects, performing the sidelink beam failure recovery procedure further includes performing the sidelink beam failure recovery procedure based at least in part on having failed a threshold number of times to receive the second signal.

[0086] FIG. 9 shows exemplary blocks of process 900, but in some aspects, process 900 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks compared to the blocks illustrated in FIG. 9. Additionally or alternatively, two or more of the blocks of process 900 may be performed in parallel.

[0087] FIG. 10 is a diagram illustrating an exemplary process 1000 performed, for example, by a second node according to various aspects of the present disclosure. Exemplary process 1000 is an example in which a second node (e.g., UE120, BS110, UE305, UE405, UE410, second UE120, etc. of FIGS. 5 - 8) performs operations associated with sidelink beam failure detection.

[0088] As shown in FIG. 10, in some aspects, process 1000 may include determining whether a first signal is received from a first node on a beamformed link from the first node to a second node, where the first node and the second node are associated with a common timing (block 1010). For example, the second node (using, e.g., antenna 234, DEMOD 232, MIMO detector 236, receive processor 238, controller / processor 240, antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, controller / processor 280, etc.) may determine whether the first signal is received from the first node on a beamformed link from the first node to the second node as described above. In some aspects, the first node and the second node are associated with a common timing.

[0089] As further shown in FIG. 10, in some aspects, process 1000 may include determining whether to transmit a second signal on a beamformed link from the second node to the first node, at least partially based on whether the first signal is received (block 1020). For example, the second node (using, e.g., antenna 234, DEMOD 232, MIMO detector 236, receive processor 238, controller / processor 240, antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, controller / processor 280, etc.) may determine whether to transmit the second signal on a beamformed link from the second node to the first node, at least partially based on whether the first signal is received as described above.

[0090] As further shown in FIG. 10, in some aspects, process 1000 may include receiving (block 1030) a third signal on a beamformed link from a first node to a second node, at least partially based on the second signal. For example, the second node (e.g., using antenna 234, DEMOD 232, MIMO detector 236, receive processor 238, controller / processor 240, antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, controller / processor 280, etc.) may receive the third signal at least partially based on the second signal as described above. In some aspects, the second node may receive the third signal after transmitting the second signal.

[0091] As further shown in FIG. 10, in some aspects, process 1000 may include performing (block 1040) sidelink beam failure recovery procedures, at least partially based on having failed to receive the first signal or the third signal. For example, the second node (e.g., using antenna 234, DEMOD 232, MIMO detector 236, receive processor 238, controller / processor 240, antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, controller / processor 280, etc.) may perform sidelink beam failure recovery procedures at least partially based on having failed to receive the first signal or the third signal as described above. In some aspects, the second node may perform sidelink beam failure recovery procedures after determining that the second signal should not be transmitted.

[0092] Process 1000 may include additional aspects, such as any single aspect or any combination of aspects described below and / or with respect to one or more other processes described elsewhere in this specification.

[0093] In a first aspect, process 1000 includes transmitting a second signal at least partially based on receiving the first signal.

[0094] In a second aspect, at least one of the first signal, the second signal, or the third signal, alone or in combination with the first aspect, includes a channel state information reference signal.

[0095] In a third aspect, alone or in combination with one or more of the first and second aspects, the first signal, the second signal, and the third signal are associated with respective resource allocations that are known to the first node and the second node prior to transmission of the first signal.

[0096] In a fourth aspect, alone or in combination with one or more of the first to third aspects, each resource allocation is determined by one or more of the first node or the second node.

[0097] In a fifth aspect, alone or in combination with one or more of the first to fourth aspects, each resource allocation is determined by a base station associated with the first node or the second node.

[0098] In a sixth aspect, alone or in combination with one or more of the first to fifth aspects, the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

[0099] In a seventh aspect, alone or in combination with one or more of the first to sixth aspects, the common timing is at least partially based on a base station associated with the first node and the second node.

[0100] In an eighth aspect, alone or in combination with one or more of the first to seventh aspects, the common timing is at least partially based on a positioning system of the first node and the second node.

[0101] In a ninth aspect, alone or in combination with one or more of the first to eighth aspects, the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with the ProSe sidelink interface.

[0102] In a tenth aspect, alone or in combination with one or more of the first to ninth aspects, the first node and the second node include user equipment.

[0103] In an eleventh aspect, alone or in combination with one or more of the first to tenth aspects, the first node and the second node include integrated access and backhaul nodes.

[0104] In a twelfth aspect, alone or in combination with one or more of the first to eleventh aspects, performing the sidelink beam failure recovery procedure further includes performing the sidelink beam failure recovery procedure based at least in part on having failed a threshold number of times to receive one or more of the first signal or the third signal.

[0105] FIG. 10 shows exemplary blocks of process 1000, but in some aspects, process 1000 may include additional blocks, fewer blocks, different blocks, or blocks arranged differently compared to the blocks illustrated in FIG. 10. Additionally or alternatively, two or more of the blocks of process 1000 may be performed in parallel.

[0106] The following provides an overview of some aspects of the present disclosure.

[0107] Aspect 1: A method of wireless communication performed by a first node, the method comprising: transmitting a first signal to a second node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; determining whether a second signal is received on a beamformed link from the second node to the first node, based at least in part on the first signal; and transmitting a third signal on a beamformed link from the first node to the second node based at least in part on receiving the second signal, or performing a sidelink beam failure recovery procedure based at least in part on determining that the second signal is not received.

[0108] Aspect 2: The method of Aspect 1, wherein at least one of the first signal, the second signal, or the third signal comprises a channel state information reference signal.

[0109] Aspect 3: The method according to any one of Aspects 1 to 2, wherein the first signal, the second signal, and the third signal are each associated with a respective resource allocation that is known to the first node and the second node before transmission of the first signal.

[0110] Aspect 4: The method of Aspect 3, wherein each resource allocation is determined by one or more of the first node or the second node.

[0111] Aspect 5: The method of Aspect 3, wherein each resource allocation is determined by a base station associated with the first node or the second node.

[0112] Aspect 6: The method according to any one of Aspects 1 to 5, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

[0113] Aspect 7: The method according to any one of Aspects 1 to 6, wherein the common timing is determined at least partially based on a base station associated with the first node and the second node.

[0114] Aspect 8: The method according to any one of Aspects 1 to 7, wherein the common timing is determined at least partially based on a positioning system of the first node and the second node.

[0115] Aspect 9: The method according to any one of Aspects 1 to 8, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface.

[0116] Aspect 10: The method according to any one of Aspects 1 to 9, wherein the first node and the second node include user equipment.

[0117] Aspect 11: The method according to any one of Aspects 1 to 9, wherein the first node and the second node include integrated access and backhaul nodes.

[0118] Aspect 12: The method according to any one of Aspects 1 to 11, wherein the step of performing the sidelink beam failure recovery procedure further includes the step of performing the sidelink beam failure recovery procedure at least partially based on having failed a threshold number of times in receiving the second signal.

[0119] Aspect 13: A method of wireless communication performed by a second node, the method comprising: determining whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; determining whether to transmit a second signal on a beamformed link from the second node to the first node, at least partially based on whether the first signal is received; receiving a third signal at least partially based on the second signal, or performing sidelink beam failure recovery procedures at least partially based on failing to receive the first signal or the third signal.

[0120] Aspect 14: The method of Aspect 13, further comprising transmitting a second signal at least partially based on receiving the first signal.

[0121] Aspect 15: The method according to any one of Aspects 13 to 14, wherein at least one of the first signal, the second signal, or the third signal comprises a channel state information reference signal.

[0122] Aspect 16: The method according to any one of Aspects 13 to 15, wherein the first signal, the second signal, and the third signal are each associated with a respective resource allocation that is known to the first node and the second node before transmission of the first signal.

[0123] Aspect 17: The method of Aspect 16, wherein each resource allocation is determined by one or more of the first node or the second node.

[0124] Aspect 18: The method of Aspect 16, wherein each resource allocation is determined by a base station associated with the first node or the second node.

[0125] Aspect 19: A method according to any of aspects 13 to 18, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

[0126] Aspect 20: A method according to any of aspects 13 to 19, wherein the common timing is at least partially based on a base station associated with the first node and the second node.

[0127] Aspect 21: A method according to any of aspects 13 to 20, wherein the common timing is at least partially based on a positioning system of the first node and the second node.

[0128] Aspect 22: A method according to any of aspects 13 to 21, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe side link interface.

[0129] Aspect 23: A method according to any of aspects 13 to 22, wherein the first node and the second node include user equipment.

[0130] Aspect 24: A method according to any of aspects 13 to 22, wherein the first node and the second node include integrated access and backhaul nodes.

[0131] Aspect 25: A method according to any of aspects 13 to 24, wherein the step of performing a side link beam failure recovery procedure further includes the step of performing a side link beam failure recovery procedure based at least in part on having failed a threshold number of times to receive one or more of the first signal or the third signal.

[0132] An apparatus for wireless communication in a device, the apparatus comprising a processor, a memory coupled to the processor, and instructions stored in the memory and executable by the processor to cause the apparatus to perform a method according to one or more of aspects 1 to 25.

[0133] Aspect 27: A device for wireless communication comprising a memory and one or more processors coupled to the memory, wherein the memory or the one or more processors are configured to implement the method of one or more of Aspects 1 - 25.

[0134] Aspect 28: An apparatus for wireless communication comprising at least one means for implementing the method of one or more of Aspects 1 - 25.

[0135] Aspect 29: A non - transitory computer - readable medium storing code for wireless communication, the code comprising instructions executable by a processor to implement the method of one or more of Aspects 1 - 25.

[0136] Aspect 30: A non - transitory computer - readable medium storing a set of instructions for wireless communication, the set of instructions including one or more instructions that, when executed by one or more processors of a device, cause the device to implement the method of one or more of Aspects 1 - 25.

[0137] The above disclosure provides illustration and description, and is neither comprehensive nor limiting of the aspects in a strict form. Modifications and variations may be made in light of the above disclosure or obtained from practice of the aspects.

[0138] As used herein, the term "component" is to be broadly construed as hardware, firmware, and / or a combination of hardware and software. When used herein, a processor is implemented in hardware, firmware, and / or a combination of hardware and software.

[0139] As used herein, "meeting a threshold" may, depending on the context, refer to a value being greater than, greater than or equal to, less than, less than or equal to, equal to, or not equal to a threshold, etc.

[0140] It will be apparent that the systems and / or methods described herein may be implemented in various forms of hardware, firmware, and / or combinations of hardware and software. It is understood that the actual specific control hardware or software code used to implement these systems and / or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and / or methods have been described herein without reference to specific software code. It should be understood that software and hardware may be designed to implement the systems and / or methods based at least in part on the description herein.

[0141] Even if a particular combination of features is recited in the claims and / or disclosed herein, these combinations do not limit the disclosure in various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and / or not disclosed herein. Each of the dependent claims listed below may be directly dependent on only one claim, but the disclosure in various aspects includes each dependent claim combined with any other claim in the claim set. The phrase referring to an enumeration of items "at least one of" refers to any combination of those items including a single member. By way of example, "at least one of a, b, or c" includes a, b, c, a-b, a-c, b-c, and a-b-c, as well as combinations having multiple of the same elements (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c, or any other order of a, b, and c).

[0142] None of the elements, acts, or instructions used in this specification should be construed as important or essential unless explicitly described as such. Also, as used in this specification, the articles "a" and "an" include one or more items and may be used interchangeably with "one or more." Further, as used in this specification, the terms "set" and "group" include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.) and may be used interchangeably with "one or more." When only one item is intended, the phrase "only one" or similar words are used. Also, as used in this specification, terms such as "has," "having," etc. shall be considered open-ended terms. Further, the phrase "based on" shall mean "at least partially based on" unless explicitly stated otherwise.

Explanation of Signs

[0143] 100 Wireless Network 110 BS, Base Station 110a BS, Macro BS 110b BS 110c BS 110d BS, Relay BS 120 UE 120b UE 120c UE 120d UE 120e UE 130 Network Controller 212 Data Source 220 Transmission Processor 230 Transmission (TX) Multiple-Input Multiple-Output (MIMO) Processor 232 Modulator (MOD), Demodulator 234 Antenna 236 MIMO Detector 238 Reception Processor 239 Data Sink 240 Controller / Processor 242 Memory 244 Communication Unit 246 Scheduler 252 Antenna 254 Demodulator (DEMOD), Modulator 256 MIMO Detector 258 Receiver Processor 260 Data Sink 262 Data Source 264 Transmitter Processor 266 TX MIMO Processor 280 Controller / Processor 282 Memory 290 Controller / Processor 292 Memory 294 Communication Unit 305 UE 310 Sidelink Channel 315 Physical Sidelink Control Channel (PSCCH) 320 Physical Sidelink Shared Channel (PSSCH) 325 Physical Sidelink Feedback Channel (PSFCH) 405 Transmitter (Tx) UE, UE 410 Receiver (Rx) UE, UE 525 Sidelink 530 Sidelink

Claims

1. A first node for wireless communication, comprising: a memory; and one or more processors operably coupled to the memory, wherein the memory and the one or more processors are configured to: transmit a first signal to a second node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; determine whether a second signal is received on the beamformed link from the second node to the first node, at least partially based on the first signal; transmit a third signal on the beamformed link from the first node to the second node, at least partially based on receiving the second signal; or perform a sidelink beam failure recovery procedure, at least partially based on determining that the second signal is not received.

2. The first node according to claim 1, wherein at least one of the first signal, the second signal, or the third signal comprises a channel state information reference signal.

3. The first node according to claim 1, wherein the first signal, the second signal, and the third signal are associated with respective resource allocations that are known to the first node and the second node prior to transmission of the first signal.

4. The first node according to claim 3, wherein the respective resource allocations are determined by one or more of the first node or the second node.

5. The first node according to claim 3, wherein the respective resource allocations are determined by a base station associated with the first node or the second node.

6. The first node according to claim 1, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

7. The first node according to claim 1, wherein the common timing is determined at least partially based on a base station associated with the first node and the second node.

8. The first node according to claim 1, wherein the common timing is determined based at least in part on a positioning system of the first node and the second node.

9. The first node according to claim 1, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface.

10. The first node according to claim 1, wherein the first node and the second node include user equipment.

11. The first node according to claim 1, wherein the first node and the second node include integrated access and backhaul nodes.

12. The first node according to claim 1, wherein the one or more processors are configured to perform the sidelink beam failure recovery procedure based at least in part on having failed a threshold number of times to receive the second signal when performing the sidelink beam failure recovery procedure.

13. A second node for wireless communication, a memory, one or more processors operably coupled to the memory, wherein the memory and the one or more processors are configured to determine whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing, configured to determine whether to transmit a second signal on a beamformed link from the second node to the first node based at least in part on whether the first signal is received, receive a third signal based at least in part on the second signal, or perform a sidelink beam failure recovery procedure based at least in part on having failed to receive the first signal or the third signal.

14. The second node according to claim 13, wherein the one or more processors are further configured to transmit the second signal based at least in part on having received the first signal.

15. The beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link, the second node according to claim 13.

16. The beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface, the second node according to claim 13.

17. When the one or more processors perform the sidelink beam failure recovery procedure, Based at least in part on having failed a threshold number of times to receive one or more of the first signal or the third signal, configured to perform the sidelink beam failure recovery procedure, the second node according to claim 13.

18. A method of wireless communication performed by a first node, Transmitting a first signal to the second node on a beamformed link from the first node to the second node, wherein The first node and the second node are associated with a common timing, the step of Determining whether a second signal is received on a beamformed link from the second node to the first node based at least in part on the first signal, and Based at least in part on receiving the second signal, transmitting a third signal on the beamformed link from the first node to the second node, or Based at least in part on determining that the second signal is not received, performing a sidelink beam failure recovery procedure.

19. At least one of the first signal, the second signal, or the third signal includes a channel state information reference signal, the method according to claim 18.

20. The first signal, the second signal, and the third signal are associated with respective resource allocations known to the first node and the second node prior to transmission of the first signal, the method according to claim 18.

21. The method according to claim 18, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

22. The method according to claim 18, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe sidelink interface.

23. The method according to claim 18, wherein the step of performing the sidelink beam failure recovery procedure further includes the step of performing the sidelink beam failure recovery procedure based at least in part on the reception of the second signal having failed a threshold number of times.

24. A method of wireless communication performed by a second node, comprising the step of determining whether a first signal is received from a first node on a beamformed link from the first node to the second node, wherein the first node and the second node are associated with a common timing; the step of determining whether to transmit a second signal on a beamformed link from the second node to the first node based at least in part on whether the first signal is received; the step of receiving a third signal based at least in part on the second signal, or the step of performing a sidelink beam failure recovery procedure based at least in part on a failure to receive the first signal or the third signal.

25. The method according to claim 24, further comprising the step of transmitting the second signal based at least in part on receiving the first signal.

26. The method according to claim 24, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are the same link.

27. The method according to claim 24, wherein the beamformed link from the first node to the second node and the beamformed link from the second node to the first node are associated with a ProSe side link interface.

28. The method according to claim 24, wherein the first node and the second node include user equipment.

29. The method according to claim 24, wherein the first node and the second node include integrated access and backhaul nodes.

30. The step of performing the side link beam failure recovery procedure The method according to claim 24, further comprising the step of performing the side link beam failure recovery procedure at least partially based on having failed a threshold number of times to receive one or more of the first signal or the third signal.

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