ENHANCED UE BEHAVIOR IN PREDICTION AND MANAGEMENT OF BEAM FAILURES

Aspects of the present disclosure address beam management enhancement with the assistance of a cooperative relay UE over a sidelink (SL) channel. A UE may include a memory and a processor. The processor may use machine learning and channel condition measurements to predict an upcoming Uu link beam failure (BF). Based on the prediction, the processor may request SL data resources from a base station, wherein the processor may receive an allocated SL channel and a relay UE. When the Uu link fails, the processor can transmit a beam failure recovery (BFR) signal to the base station using the relay UE over the SL channel. The present disclosure overcomes the deficiencies of conventional BFR processes in which the BF forces the UE to perform a contentious RACH procedure, causing time delays and power consumption.

BACKGROUND

Technical Field

The present disclosure generally relates to communication systems, and more particularly, to handling beam failures in network operation.

INTRODUCTION

SUMMARY

UEs are increasingly capable of using multi-path communication using two or more spatial beams positioned to facilitate such capability. Some new UE configurations, including in 5G NR may also use a cooperative UE, also known as a relay UE, to enable the UE to exchange configurations with the base station using a sidelink (SL) channel and the relay messages between the UE and the base station. In conventional processes when beam failure (BF) is detected, the UE is relegated to performing a contentious random access channel (RACH). RACHs can be time consuming and stand to quickly drain a UE of power.

Accordingly, to overcome these conventional shortcomings, aspects of the present disclosure use a memory and at least one processor to address beam management enhancement over a sidelink (SL) channel. The processor may use machine learning, channel condition measurements and other techniques to predict an upcoming Uu link beam failure (BF). Based on the prediction, the processor may request SL data resources from a base station, wherein the processor may receive an allocated SL channel and a relay UE. When the Uu link fails, the processor can transmit a beam failure recovery (BFR) signal to the base station using the relay UE over the SL channel. Among other benefits, the present disclosure can use the SL and relay UE to quickly reestablish one or more connections, and thus overcomes the deficiencies of conventional beam failure recovery (BFR) processes in which the BF effectively necessitates that the UE perform a contentious RACH procedure along with the attendant time delays and power consumption before connection can be reestablished.

In one aspect of the disclosure, a method and an apparatus are provided. The apparatus for wireless communication at a user equipment (UE) may include a memory and at least one processor coupled to the memory. The at least one processor may be configured to predict a future Uu link beam failure (BF). The at least one processor may request, based on the prediction, sidelink (SL) data resources from a base station. The at least one processor may receive an allocated SL channel and a relay UE. The at least one processor may transmit, when the Uu link beam fails, a beam failure recovery (BFR) signal to a base station via the relay UE over the SL channel.

In another aspect of the disclosure, a method and an apparatus are provided. The apparatus for wireless communication at a user equipment (UE) may include a memory, and at least one processor coupled to the memory. The at least one processor may be configured to predict an upcoming Uu link beam failure (BF). The at least one processor may further sense a sidelink (SL) channel quality in preparation for transmitting a beam failure recovery (BFR) medium access control/control element (MAC CE) over the SL channel via a relay UE. In response, the at least one processor may transmit the BFR MAC CE over the SL channel via the relay UE.

DETAILED DESCRIPTION

The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs)152via communication links154, e.g., in a 5 gigahertz (GHz) unlicensed frequency spectrum or the like. When communicating in an unlicensed frequency spectrum, the STAs152/AP150may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

Although the present disclosure may focus on 5G NR, the concepts and various aspects described herein may be applicable to other similar areas, such as LTE, LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), Global System for Mobile communications (GSM), or other wireless/radio access technologies.

Referring again toFIG.1, in certain aspects, the base station180may be configured to allocate one or more sidelink (SL) resources, including a SL channel (198) to a requesting UE. Further, in certain aspects, the UE104, which includes beams182″ and is coupled to Beam Failure Recovery (BFR) Component198, may be configured to predict a future beam failure (BF), via a sensing procedure or an algorithm provided by the UE or configured by base station180. Based on an allocation by the base station180to the UE104of the requested resources, the UE may thereupon prepare the SL for a Beam Failure Recovery Medium Access Control/Control Element (BFR MAC CE) such that when the BF in fact occurs, the UE can rapidly transmit the BFR MAC CE over the relay link using the relay UE to the base station (e.g., gNB-DU180).

The present disclosure concerns addressing BFs in environments such as enhanced multi-path communication with UE cooperation, enhanced layer two single hop UE to relay UE to network operations, and other network configurations involving UE multi-beams in which a beam failure (BF) scenario becomes relevant, and ultimately requires re-acquisition of the network connection. Thus, the present disclosure in concerned with beam management enhancement in a variety of context. One such context may include the assistance of a cooperative UE—known herein as a relay UE—that may be used as a sidelink (SL). Thus, for example, in an example network cell having a base station and a UE, the UE may exchange information directly with the base station over a standard Universal Mobile Telecommunications Service (UNITS) or “Uu” link, which may define a unique connection between a UE and a network via a base station.

In conventional beam failure recovery (BFR) processes, the UE ordinarily performs a RACH procedure as discussed above. A RACH procedure may be defined by a sequence of processes between the UE and base station that ultimately enables the UE to obtain uplink synchronization with the network. RACH procedures may be contention-based, meaning that the RACH may have a plurality of UEs attempting to access it. This in turn may require multiple attempts before a UE can successfully access the network. In general, a window of time exists for a UE to receive a responsive. In case of failure, the UE generally engages in a waiting period before transmitting another RACH request. After the UE successfully receives a response containing information like an RA-preamble identifier that matches the transmitted identifier, then the process can move onto uplink scheduling. In short, every time BFR is necessary, the RACH process consumes potentially significant time and power before network synchronization with the UE is obtained again.

In one aspect of the disclosure, the RACH process is avoided in BFR. Instead, the UE may be connected to a relay UE via an SL channel. In some configurations, the relay UE may be exchanging data with the UE prior to the BF. In other embodiments, the network may configure the relay UE in response to a request as described herein. The utilization of the relay UE may result in enhanced beam management and thereby obviate the need for the use of the RACH. BFR and the relay UE can be used for fast BFR report information, which can be transmitted over the SL channel via the relay UE to the base station. The techniques described herein can improve quality of service (QoS) of serving traffic, can increase network reliability, can reduce overall latency and importantly, can save UE power. This savings of UE power can be especially beneficial in light of the power consumption required for the use of multiple beams.

FIG.4is a diagram400showing a method for a UE to determine whether a beam failure (BF) is present on the channel.FIG.4represents an example conventional method of determining a beam failure at a UE. The technique described inFIG.4may be conducted at the Media Access Control (MAC) layer423or the physical (PHY) layer429, or some combination thereof. In the technique, a UE using spatial beams on a network may constantly monitor a periodic Beam failure detection reference signal (BFD-RS) at the PHY layer. The BFD-RS may be, for example, a channel state information reference signal (CSI-RS), a synchronization signal block (SSB), or the like.

At the PHY layer, the UE may identify beam failure instance (BFI) indicators. The horizontal axis of the diagram inFIG.4may be time. The UE may identify a BFI indicator at every occasion of the BFD-RS 431. Meanwhile, procedures at the PHY layer may estimate a block error rate (BLER). If the BLER meets a threshold, the PHY layer may then issue a BFI indicator (e.g., B=1, B=2, etc.); otherwise if the threshold is not met, no BFI indicator is issued.

At the first indication of a BFI (here, B=1), a BFD timer is started for a given UE. In general, the PHY indicates the BFI to the MAC layer, and the MAC controls the BFD timer and the BFI counting procedure described herein. With the issuance of each BFI indicator, the MAC layer423increases the BFI count by 1. If the total BFI counts reaches a MaxCount threshold (e.g., 4 in the example ofFIG.4) prior to expiration of the UE BFD timer, UE declares BF and may proceed to initiate the BFR procedure. Otherwise, if the BFD timer set by the UE expires (427) prior to the total BFI counts reach the MaxCount threshold (e.g., MaxCount=6), the UE does not declare BF, the total BFI count may be reset to 0, and the BFD timer may be reset by the UE at the next identification of a BFI indicator.

Once BFD has occurred, the UE may attempt to recover the beam in the PCell (e.g., gNB) using RACH. In addition to the above-noted shortcomings of this approach, another problem with the procedure outlined inFIG.4is that the UE has no prior knowledge as to the status of BFD. That is to say, the UE may determine BF only at the time that the triggering BFI indicator is detected using the BFD-RS 431 prior to expiration of the timer, only then does the UE determine that BF has occurred. Thus only then can the UE begin corrective action. This delay due to the indeterminacy of whether or not the BFI count will meet the MaxCount threshold prior to the timer expiration may add further delay to those that are already imposed by the RACH access procedure. Thus the timing of BFR is further delayed, exacerbating the problem.

Accordingly, in various aspects of the disclosure, an alternative network configuration is proposed which may eliminate or ameliorate the above-described problems. An exemplary system model through which these aspects can be realized is shown in FIG.FIG.5is a diagram500illustrating an example of a UE504.acommunicating with a base station502over a Uu link518including radio unit (RU)532and with a relay UE504.bover a PC 5 link on a sidelink (SL) channel520. In various configurations, the UE504.amay exchange data (transmit and receive) with base station502using relay504.bover sidelink520and Uu link521including RU530. In some configurations, as described further below, the UE504.amay not yet be actively connected with relay UE504.b.

Referring still toFIG.5, UE504.amay include beams531,533and535. UE504.amay be configured to monitor multiple beams (including the three beams illustrated) for beam condition maintenance and BFR. The UE504.aand502may choose the beam having the best signal quality for communication. As noted, the UE504.amay also be connected to relay UE504.bover sidelink520through the PC5 interface. In the configuration shown, UE504.bis coupled to the same gNB502as UE504.a, albeit over a different Uu link521. As indicated, data communication between the UE504.aand gNB502can be transmitted directly over Uu link518and/or relayed via relay504.b. Thus, in a case where relay UE504.bhas already been configured by gNB502to connect in this fashion to UE504.a, the gNB502or the UE504.acan offload data to Uu link521and sidelink520if, for example, the relay504.bis otherwise idle or the Uu link518is nearing full capacity. Mode 1 or mode 2 may be used inFIG.5. That is, the UE configuration may be established by the gNB502(mode 1), or by the UE504.a(mode 2).

Referring back to the various aspects identified above,FIG.6is a diagram600illustrating an example of a UE604.acommunicating with a base station (e.g., gNB-DU602) over a Uu link618(including RU630) and communicating a BFR MAC CE642with the same base station using a relay UE504.bover sidelink620and Uu link610/RU632. In an initial configuration, UE604.amay engage in a prediction of a beam failure (BF). The prediction may be based on an algorithm provided by the base station602and configured at UE604.a, or the prediction may be provided directly by UE604.a. In some arrangements, one or more types of machine learning may be employed to facilitate predicting BFs. Alternatively or in addition, various channel condition measurements may be made during discontinuous reception (DRX ON), including, for example signal-to-interference & noise ratio (SINR), Reference Signal Received Powder (RSRP), path loss, and other indicators of channel quality. BF prediction may also be based on one or more predefined triggering events. Example triggering events may be configured by the gNB, and/or may include conventional BFI counts including a threshold MaxCount. Other predefined triggering events include a consecutive number of recorded BFIs (whether in this interval or in one or more previous intervals), or some more general channel quality-related event (e.g., SINR drops by a predefined number of decibels).

Prediction algorithms and predefined triggering events may be established in a radio resource control (RRC) communications. Multiple values of the above parameters, and other channel-quality based parameters may be simultaneously configured. In some case, the gNB may use a MAC control element (MAC CE) or downlink control information (DCI) to dynamically switch the parameter values, add criteria, etc. that may be used in connection with BF prediction.

With further reference toFIG.6, it is assumed in this configuration that the sidelink-based relay UE604.boperates under mode 1 scheduling. In mode 1, the base station (e.g., gNB or eNB) assigns and manages the sidelink radio resources for UE to UE communications using the Uu interface. When the UE604.apredicts the occurrence of Uu link BF that may occur in the near future as shown in615, the prediction may involve one or more of the above-identified algorithms and predefined triggering events. A key aspect of this example is that based on this prediction, the UE604.aadvantageously may prepare the SL channel620to initiate a BFR MAC CE transmission, such as transmission642originating from UE604.a, over SL channel620and via relay UE604.bover Uu link610to gNB602.

Thus, in various embodiments, the UE may request the gNB for SL data transmission resources using a MAC CE, the BFR MAC CE or uplink control information (UCI). Content in the request may include, for example, (i) one or more reasons for the request, (ii) an expected response deadline for the resources (e.g., if the UE has predicted a time that the BF may occur), (iii) a preferred SL relay UE (e.g., relay UE604.bif that device is nearby), and/or (iv) one more SL channel measurements (such as channel quality measurements between UE604.aand the requested relay UE604.b). In one configuration, if the UE604.adoes not receive a response to the request for resources after some predetermined time period T, then the UE may resend the request. In some arrangements, the UE may be configured to resend up to a certain number N of resource requests.

The response from the gNB602may enable UE604.ato switch beams immediately, for example, to enable subsequent communications to proceed, with a very small lag time, if any, between the initial prediction and the actions that follow.

In another aspect of the disclosure, the enhanced UE behavior for beam prediction can be employed in other modes. As an example of one such mode,FIG.7is a diagram700illustrating an example of a UE704.apredicting a beam failure (BF) and requesting SL resources to transmit a beam failure recovery (BFR) signal over the allocated SL channel. Unlike inFIG.6, the scenario ofFIG.7is in the context of mode 2. In mode 2, the UEs, rather than the base stations, select the SL resources for transmitting and receiving of data. Like inFIG.6,FIG.7includes a UE704.acommunicating with a gNB-DU702over Uu link728(including RUL730).FIG.7also shows a relay UE704.bthat can exchange data over its own network Uu link721(including RU732) with gNB-DU702. Relay UE704.bmay be connected to UE704.avia SL channel720. In some deployments, relay UE704.bhas not yet connected to UE704.a.

Initially, the UE704.amay be communicating in the normal course with gNB702over Uu link728using an appropriate beam of a set of beams (see, e.g.FIG.5). Meanwhile, at the PHY layer, the UE may be monitoring one or more parameters in a concerted effort to detect the likelihood of any beam failure. In determining whether to make a prediction, the UE704.amay use all the resources at its disposal as discussed with respect to other embodiments. These include without limitation prediction algorithms, predefined triggering events, the individual prior experience of the UE704.a, and others.

Referring still toFIG.7, a time may come when UE704.apredicts that a Uu link beam failure is likely to occur in the foreseeable future. At this point, the integrity of the Uu link728relative to the UE beam(s) remains stable. Thus while communications over the link728may proceed, the UE may initiate SL sensing757. The nature of the sensing may depend at least in part on whether the UE704.ais preconfigured with the SL relay UE704.bover SL channel720. In this case, the UE704.acan measure the SL channel quality on the SL channel720(e.g., SINR, RSRP, etc.) relative to the preconfigured relay UE704.band assuming the quality remains acceptable, the UE may prepare to initiate a BFR MAC CE transmission742via the SL channel720and Uu link721to the gNB-DU702. The content of the BFR MAC CE742may include content described above relative toFIG.6, or variations thereof. If, by contrast, the UE705.ais not preconfigured with a SL relay UE, in this case the sensing757of the UE704.amay involve UE704.aproceeding to measure the SL channel quality and interference characteristics with one or more neighboring UEs. The UE704.amay thereupon select the best candidate UE based on the measurements. In some configurations, the UE may select a list of the best candidate UEs on the sidelink720and prepare a for BFR MC CE transmission742via the selected UE to gNB702. Here again, the BFR MC CE742may include the content described above relative toFIG.6, etc.

Depending on the QoS requirement of the serving traffic on Uu link between the UE and gNB, in some configurations where SL transmission opportunities are deemed important, the UE704.amay preoccupy the SL channel720by transmitting dummy data, such as when UE transmission opportunities are present on the SL720. When the UE704.ais free, the UE may proceed to transmit. It will be appreciated by practitioners in the art that this transmission of dummy data, especially if prolonged, may waste SL resources. Accordingly, this function may ideally be configured and overseen by the gNB, in which case the UE may preoccupy the UE704.amay preoccupy the SL with dummy data to accommodate transmission opportunities as they are available. Such an urgent request by involve URLLC (Ultra Reliable Low Latency Communications traffic), for instance.

FIG.8is a timing diagram800illustrating a UE802predicting a future Uu link beam failure (BF) at Uu link806and requesting SL data resources808for use in transmitting a beam failure recovery (BFR) signal808to a base station via a relay UE and the SL link. Referring to UE802, as before, the UE802at box810may use one or more machine learning techniques along with channel condition measurements of the SL, whether the measurements are made from the UE802or the gNB804, to predict possible or likely Uu beam failures. In an affirmative case, where a beam failure is likely in the near future, the UE802may send its prediction806over Uu link810to base station804.

Thereafter, may request SL data resources based on the prediction. The request may be made via link810, via MAC CE or UCI. Content in the request may include reasons for the request, an expected response deadline for the resources (e.g., if the UE has predicted a time that the BF may occur), a preferred SL relay UE (e.g., relay UE802.rif that device is nearby), and/or one or more SL channel measurements (such as channel quality measurements between UE604.aand the requested relay UE604.b).

At812, and prior to the beam failure, the gNB804may transmit the requested information such as an allocated SL channel (820) and the requested relay UE (802.r). Having received the SL resources, the UE at816may transmit, upon failure of the Uu link, a BFR signal to the base station802via the relay UE802—such as a BFR MAC UE from the UE802to relay UE802.r(818a). This BFR MAC UE or other uplink control information is transmitted from relay UE to base station804(818b). The base station804can thereafter configure the UE802with proper beam positioning or switching and can send this response back through the relay UE802.r. Once the UE corrects the problem and repositions the beam or switches to the proper beam, communications directly to and from UE802and base station804can resume.

FIG.9is a flowchart900of a method of wireless communication of a UE. The UE that may perform the steps inFIG.9may include, for example, any of the UEs104inFIG.1, including the UE coupled to component198(i.e., the UE with multiple spatial beams182″), UE350(FIG.3), UE504.a(FIG.5), UE604.a(FIG.6), UE704.a(FIG.7), UE802(FIG.8), and UE1002(FIG.10). Referring initially to block902, the UE may predict an upcoming Uu link beam failure coming up. In so doing the UE may use any of the algorithms or triggering events described in this disclosure.

Thereupon, at block904, the UE may sense a sidelink (SL) channel quality in preparation for transmitting a beam failure recovery (BFR) medium access control/control element (BFR MAC CE) over the SL channel via a relay UE. At block906, the UE may transmit the BFR MAC CE over the SL channel via the relay UE. The contents of the BFR MAC CE may be as previously described, or it may include additional or fewer pieces of information that is specific to the configuration.

The dashed lines inFIG.9represent optional steps. For example, at block910, the sensing of the SL channel quality in block904may include that the UE measures, when the UE is preconfigured to exchange data with the base station via the relay UE, a channel strength between the UE and the relay UE such that if the strength meets a threshold, the UE prepares to transmit the BFR MAC CE over the SL channel via the relay UE. Optionally, the sensing step of block904may include that the UE measures, if the UE is not preconfigured to exchange data with the base station via the relay UE, a channel strength relative to a plurality of neighboring UEs to select a best one or more candidate relay UEs on the SL channel, and the UE thus prepares the best one or more candidate relay UEs for the BFR MAC CE transmission.

Further, after transmit step of906is complete, the UE may transmit the BFR MAC CE using one of the candidate relay UEs over the SL channel, as in block908.

FIG.10is a diagram illustrating an example of a hardware implementation for an example apparatus.

FIG.10is a diagram1000illustrating an example of a hardware implementation for an apparatus1002. The apparatus1002is a UE and includes a cellular baseband processor1004(also referred to as a modem) coupled to a cellular RF transceiver1022and one or more subscriber identity modules (SIM) cards1020, an application processor1006coupled to a secure digital (SD) card1008and a screen1010, a Bluetooth module1012, a wireless local area network (WLAN) module1014, a Global Positioning System (GPS) module1016, and a power supply1018. The cellular baseband processor1004communicates through the cellular RF transceiver1022with the UE104and/or BS102/180. The cellular baseband processor1004may include a computer-readable medium/memory. The computer-readable medium/memory may be non-transitory. The cellular baseband processor1004is responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor1004, causes the cellular baseband processor1004to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor1004when executing software. The cellular baseband processor1004further includes a reception component1030, a communication manager1032, and a transmission component1034. The communication manager1032includes the one or more illustrated components. The components within the communication manager1032may be stored in the computer-readable medium/memory and/or configured as hardware within the cellular baseband processor1004. The cellular baseband processor1004may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359. In one configuration, the apparatus1002may be a modem chip and include just the baseband processor1004, and in another configuration, the apparatus1002may be the entire UE (e.g., see350ofFIG.3) and include the aforediscussed additional modules of the apparatus1002.

The communication manager1032includes a component1040that is configured to predict a likely occurrence of a beam failure in the near future, e.g., as described in connection with reference numeral615ofFIG.6and reference numeral806inFIG.8

The communication manager1032further includes a component1042that receives input in the form of data from Component1050SL data from Component1044and responsive information to SL requesting component1046is configured to transmit BFR MAC CE or UCI elements from the UE1002to the relay UE and then the base station e.g., as described in connection with steps642inFIG.6,742inFIG.7,818ainFIG.8, and906inFIG.9. The communication manager1032further includes a component1044that receives input in the form of SL information from Component1050, relay data from Component1042, the SL identification from Component1046and is configured to manage the sidelink between UEs e.g., as described in connection with620inFIG.6,720inFIG.7,818ainFIG.8, and906inFIG.9.

The communication manager1032further includes a component1046that receives input in the form of SL data from Component1044and responsive information to SL requesting component1046is configured to transmit BFR MAC CE or UCI elements from the UE1002to the relay UE and then the base station e.g., as described in connection with steps642inFIG.6,742inFIG.7,818ainFIG.8, and906inFIG.9.

The communication manager1032further includes a component1048that receives input in the form of SL data from Component1044and responsive information to SL requesting component1046is configured to receive data in the form of predicted beam failures in Component1040, beam failure recovery data in Component948, e.g., a described in connection with steps902and906ofFIG.9. The communication manager1032further includes a component1050that receives input in the form of BF prediction data from Component1040, and BF algorithms and predefined triggering events from BFR Component1048, e.g., a described in connection with steps902,904,910and912ofFIG.9.

In one configuration, the apparatus1002, and in particular the cellular baseband processor1004, includes means for predicting, means for requesting, means for receiving, means for transmitting, The aforementioned means may be one or more of the aforementioned components of the apparatus1002configured to perform the functions recited by the aforementioned means. As described supra, the apparatus1002may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the aforementioned means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the aforementioned means.

The following examples are illustrative only and may be combined with aspects of other embodiments or teachings described herein, without limitation.Example 1 is an apparatus for wireless communication at a user equipment (UE), comprising: a memory; and at least one processor coupled to the memory and configured to: predict a future Uu link beam failure (BF); request, based on the prediction, sidelink (SL) data resources from a base station; receive an allocated SL channel and a relay UE; and transmit, when the Uu link beam fails, a beam failure recovery (BFR) signal to a base station via the relay UE over the SL channel.Example 2 is the apparatus of example 1, wherein the relay UE comprises a relay UE used prior to the BF at least in part by the UE for transmitting data to the base station via the SL.Example 3 is the apparatus of any of Examples 1 and 2, wherein the relay UE is operating under mode 1 scheduling.Example 4 is the apparatus of any of Examples 1 to 3, wherein the at least one processor is further configured to predict the future Uu BF using a prediction algorithm provided by the UE, or by the base station via radio resource control (RRC) communications.Example 5 is the apparatus of any of Examples 1 to 4, wherein during the prediction, the at least one processor is further configured to identify a predefined triggering event provided by the UE or the base station.Example 6 is the apparatus of any of Examples 1 to 5, wherein the predefined triggering event comprises a beam failure instance (BFI) count meeting a threshold prior to expiration of a timer.Example 7 is the apparatus of any of Examples 1 to 6, wherein in response to the request for SL data resources, the UE receives an allocation of BFR medium access control/control element (BFE MAC CE) or uplink control information (UCI) for responding to the predicted Uu link beam failure.Example 8 is the apparatus of any of Examples 1 to 7, wherein the at least one processor is further configured to transmit a BFR signal over the SL channel using the BFR MAC CE or the uplink control information (UFI).Example 9 is the apparatus of any of Examples 1 to 8, wherein the request for SL data resources includes a reason for the request, an anticipated response deadline of a UE using the SL data resources, a preferred relay node, or an SL measurementExample 10 is the apparatus of any of Examples 1 to 9, wherein the beam failure prediction is configured by the base station, is based on UE autonomy, uses machine learning, or is based on a channel condition measurement.Example 11 is an apparatus for wireless communication at a user equipment (UE), comprising: a memory; at least one processor coupled to the memory and configured to: predict an upcoming Uu link beam failure (BF); sense a sidelink (SL) channel quality in preparation for transmitting a beam failure recovery (BFR) medium access control/control element (MAC CE) over the SL channel via a relay UE; and transmit the BFR MAC CE over the SL channel via the relay UE.Example 12 is an apparatus of Example 11, wherein the relay UE is configured to operate under mode 2 scheduling.Example 13 is an apparatus of any of Examples 11 and 12, wherein the at least one processor is further configured to sense an SL channel quality such that, when the UE is preconfigured to exchange data with the base station via the relay UE over the SL channel, the at least one processor is configured to measure a channel quality between the UE and the relay UE and if the quality meets a threshold, the at least one processor is configured to prepare to transmit the BFR MAC CE over the SL channel via the relay UE.Example 14 is an apparatus of any of any of Examples 11 to 13, wherein the at least one processor is further configured to measure, when the UE is not preconfigured with the relay UE, a channel quality relative to a plurality of neighboring UEs, to select a best one or more candidate relay UEs on the SL channel, and to prepare the best one or more candidate relay UEs for the BFR MAC CE transmission.Example 15 is an apparatus of any of Examples 11 to 14, wherein the at least one processor is further configured to transmit the BFR MAC CE using one of the candidate relay UEs over the SL channel.Example 16 is an apparatus of any of Examples 11 to 15, wherein the at least one processor is configured to transmit dummy data over the SL channel to enable the UE to transmit the BFR MAC CE quickly when necessary.Example 17 is an apparatus for wireless communication at a user equipment (UE), comprising: predicting means configured to predict a future Uu link beam failure (BF); requesting means configured to request sidelink (SL) data resources from a base station; receiving means configured to receive an allocated SL channel and a relay UE; and transmit means configured to transmit, when the Uu link beam fails, a beam failure recovery (BFR) signal to a base station via the relay UE over the SL channel.Example 18 is an apparatus of Example 17, wherein the relay UE is used prior to the BF at least in part by the UE for exchanging data with the base station via the SL.Example 19 is an apparatus of any of Examples 17 and 18, wherein the relay UE is operating under mode 1 scheduling.Example 20 is an apparatus of any of Examples 17 to 19, wherein the predicting means is further configured to predict the future Uu BF using a prediction algorithm provided by the UE, or by the base station via radio resource control (RRC) communicationsExample 21 is an apparatus of any of Examples 17 to 20, wherein the predefined triggering event comprises a beam failure instance (BFI) count meeting a threshold prior to expiration of a timer.Example 22 is an apparatus of any of Examples 17 to 21, wherein in response to the request for SL data resources, the requesting means receives an allocation of BFR medium access control/control element (BFE MAC CE) or uplink control information (UCI) for responding to the predicted Uu link beam failure.Example 23 is an apparatus of any of Examples 17 to 22, wherein the transmit means is further configured to transmit a BFR signal over the SL channel using the BFR MAC CE or the uplink control information (UFI).Example 24 is an apparatus of any of Examples 17 to 23, wherein the request for SL data resources includes a reason for the request, an anticipated response deadline of a UE using the SL data resources, a preferred relay node, or an SL measurement.Example 25 is a method for wireless communication at a user equipment (UE), comprising: predicting an upcoming Uu link beam failure (BF); sensing a sidelink (SL) channel quality in preparation for transmitting a beam failure recovery (BFR) medium access control/control element (MAC CE) over the SL channel via a relay UE; and transmitting the BFR MAC CE over the SL channel via the relay UE.Example 26 is the method of Example 25, wherein the relay UE is configured to operate under mode 2 scheduling.Example 27 is the method of any of Examples 25 and 26, wherein sensing an SL channel quality comprises measuring, when the UE is preconfigured to exchange data with the base station via the relay UE, a channel strength between the UE and the relay UE such that if the strength meets a threshold, preparing to transmit the BFR MAC CE over the SL channel via the relay UE.Example 28 is the method of any of Examples 25 to 27, wherein sensing an SL channel quality comprises measuring, if the UE is not preconfigured to exchange data with the base station via the relay UE, a channel strength relative to a plurality of neighboring UEs to select a best one or more candidate relay UEs on the SL channel, and preparing the best one or more candidate relay UEs for the BFR MAC CE transmission.Example 29 is the method of any of Examples 25 to 28, further comprising transmitting the BFR MAC CE using one of the candidate relay UEs over the SL channel.Example 30 is the method of any of Examples 25 to 29, wherein upon receiving base station authorization, the at least one processor is configured to transmit dummy data over the SL channel to enable the UE to transmit the BFR MAC CE quickly when necessary.