Method and apparatus for beam failure detection

Abstract

Certain aspects of the present disclosure provide techniques for beam failure detection in a second frequency band based on measurements in a first frequency band. A method executable by a user equipment (UE) includes: receiving one or more reference signals (RSs) on a first radio frequency band; and initiating beam failure recovery on a second radio frequency band at least in part based on the one or more RSs on the first radio frequency band. The UE may measure the one or more RSs on the first radio frequency band; and perform beam failure detection (BFD) for the second radio frequency band at least in part based on one or more measurements of the one or more RSs on the first radio frequency band.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Application No. 17 / 158,656, filed on January 26, 2021, which claims the benefit and priority of U.S. Provisional Patent Application No. 62 / 968,668, filed on January 31, 2020. The entire contents of these two applications are hereby incorporated by reference.

[0003] Introduction

[0004] Aspects of the present disclosure relate to wireless communication, and more particularly, to techniques for beam failure detection.

[0005] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasting, etc. These wireless communication systems may employ multiple access technologies that are capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access systems include Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, 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, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, to name just a few.

[0006] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at the city, national, regional, and even global levels. New Radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is an enhanced set of the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by using OFDMA with cyclic prefix (CP) on the downlink (DL) and uplink (UL) to improve spectral efficiency, reduce costs, improve services, utilize new spectrum, and better integrate with other open standards. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0007] However, as the demand for mobile broadband access continues to grow, there is a need for further improvements to NR and LTE technologies. Preferably, these improvements should be applicable to other multiple access technologies and telecommunication standards that employ these technologies.

[0008] Summary

[0009] The systems, methods, and devices of the present disclosure each have several aspects, and no single aspect alone is responsible for their desirable attributes. Without limiting the scope of the present disclosure as set forth in the appended claims, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled "Detailed Description," it will be understood how the features of the present disclosure provide advantages including improved beam failure detection (BFD).

[0010] Certain aspects of the subject matter described in the present disclosure may be implemented in a method for wireless communication by a user equipment (UE). The method generally includes: receiving one or more reference signals (RS) on a first radio frequency band; and initiating a beam failure recovery procedure on a second radio frequency band at least in part based on the one or more RS received on the first radio frequency band.

[0011] Certain aspects of the subject matter described in the present disclosure may be implemented in a device for wireless communication by a UE. The device generally includes: means for receiving one or more RS on a first radio frequency band; and means for initiating a beam failure recovery procedure on a second radio frequency band at least in part based on the one or more RS received on the first radio frequency band.

[0012] Certain aspects of the subject matter described in the present disclosure may be implemented in a device for wireless communication. The device generally includes a memory and at least one processor coupled to the memory. The memory and the at least one processor are generally configured to: receive one or more RS on a first radio frequency band; and initiate a beam failure recovery procedure on a second radio frequency band at least in part based on the one or more RS received on the first radio frequency band.

[0013] Certain aspects of the subject matter described in the present disclosure may be implemented in a computer-readable medium having stored thereon computer-executable code for wireless communication. The computer-readable medium generally includes: code for receiving one or more RS on a first radio frequency band; and code for initiating a beam failure recovery procedure on a second radio frequency band at least in part based on the one or more RS received on the first radio frequency band.

[0014] Certain aspects of the subject matter described in the present disclosure may be implemented in a method for wireless communication by a UE. The method generally includes: measuring one or more RS on a first radio frequency band. The method generally includes: determining beam failure detection (BFD) of a second radio frequency band at least in part based on the measurement of the one or more RS on the first radio frequency band.

[0015] Certain aspects of the subject matter described in this disclosure may be implemented in a method for wireless communication by a base station (BS). The method generally includes: transmitting first one or more RSs to a UE on a first radio frequency band. The method generally includes: receiving, in response to the first one or more RSs on the first radio frequency band, a request from the UE to transmit second one or more RSs on a second radio frequency band. The method generally includes: transmitting the second one or more RSs to the UE on the second radio frequency band.

[0016] Certain aspects of the subject matter described in this disclosure may be implemented in an apparatus for wireless communication. The apparatus generally includes a memory and at least one processor coupled to the memory. The memory and the at least one processor are generally configured to: measure one or more RSs on a first radio frequency band; and determine a BFD of a second radio frequency band based at least in part on the measurement of the one or more RSs on the first radio frequency band.

[0017] Certain aspects of the subject matter described in this disclosure may be implemented in an apparatus for wireless communication. The apparatus generally includes a memory and at least one processor coupled to the memory. The memory and the at least one processor are generally configured to: transmit first one or more RSs to a UE on a first radio frequency band; receive, in response to the first one or more RSs on the first radio frequency band, a request from the UE to transmit second one or more RSs on a second radio frequency band; and transmit the second one or more RSs to the UE on the second radio frequency band.

[0018] Certain aspects of the subject matter described in this disclosure may be implemented in a device for wireless communication. The device generally includes: means for measuring one or more RSs on a first radio frequency band; and means for determining a BFD of a second radio frequency band based at least in part on the measurement of the one or more RSs on the first radio frequency band.

[0019] Certain aspects of the subject matter described in this disclosure may be implemented in a device for wireless communication. The device generally includes: means for transmitting first one or more RSs to a UE on a first radio frequency band; means for receiving, in response to the first one or more RSs on the first radio frequency band, a request from the UE to transmit second one or more RSs on a second radio frequency band; and means for transmitting the second one or more RSs to the UE on the second radio frequency band.

[0020] Certain aspects of the subject matter described in this disclosure can be implemented in a computer-readable medium having stored thereon computer-executable code for wireless communication. The computer-readable medium generally includes: code for measuring one or more RSs on a first radio frequency band; and code for determining a BFD of a second radio frequency band based at least in part on the measurement of the one or more RSs on the first radio frequency band.

[0021] Certain aspects of the subject matter described in this disclosure can be implemented in a computer-readable medium having stored thereon computer-executable code for wireless communication. The computer-readable medium generally includes: code for transmitting a first one or more RSs to a UE on a first radio frequency band; code for receiving, in response to the first one or more RSs on the first radio frequency band, a request from the UE to transmit a second one or more RSs on a second radio frequency band; and code for transmitting the second one or more RSs to the UE on the second radio frequency band.

[0022] To achieve the foregoing and related ends, one or more of these aspects include the features hereinafter fully described and particularly pointed out in the claims. The following description and the drawings set forth in detail certain illustrative features of one or more of these aspects. However, these features are merely indicative of the many ways in which the principles of various aspects may be employed. Brief Description of the Drawings

[0024] To understand the manner in which the above-recited features of the present disclosure can be obtained, a more particular description, in which some aspects are illustrated in the drawings, may be had by reference to the aspects. It should be noted, however, that the drawings illustrate only certain typical aspects of the present disclosure and are not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

[0025] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0026] Figure 2 is a block diagram conceptually illustrating the design of an example base station (BS) and user equipment (UE) in accordance with certain aspects of the present disclosure.

[0027] Figure 3 is an example frame format for New Radio (NR) in accordance with certain aspects of the present disclosure.

[0028] Figure 4 is a diagram illustrating an example frequency range in accordance with certain aspects of the present disclosure.

[0029] Figure 5 illustrates an example networking environment in which a prediction model is used for channel estimation in accordance with certain aspects of the present disclosure.

[0030] Figure 6 An example node in a networking environment is described that uses a prediction model for channel estimation for beam failure detection in accordance with certain aspects of the present disclosure.

[0031] Figure 7 A flowchart illustrates example operations for wireless communication by a UE in accordance with certain aspects of the present disclosure.

[0032] Figure 8 A flowchart illustrates example operations for wireless communication by a UE in accordance with certain aspects of the present disclosure.

[0033] Figure 9 A flowchart illustrates example operations for wireless communication by a BS in accordance with certain aspects of the present disclosure.

[0034] Figure 10A A decision tree diagram illustrates example operations for wireless communication by a UE in accordance with certain aspects of the present disclosure.

[0035] Figure 10B Another decision tree diagram illustrates example operations for wireless communication by a UE in accordance with certain aspects of the present disclosure.

[0036] Figure 11A A call flow diagram illustrates example signaling in accordance with certain aspects of the present disclosure.

[0037] Figure 11B A call flow diagram illustrates example signaling in accordance with certain aspects of the present disclosure.

[0038] Figure 12 A communication device is described that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

[0039] Figure 13 A communication device is described that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

[0040] For ease of understanding, where possible, the same reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized in other aspects without specific recitation.

[0041] Detailed Description

[0042] Aspects of the present disclosure provide an apparatus, method, processing system, and computer-readable medium for performing beam failure detection (BFD) for a second radio frequency band based on measurements in a first radio frequency band. As used herein, a radio frequency band may also be referred to as a frequency band or frequency range.

[0043] In some systems, machine learning (ML) techniques may be used to predict channel characteristics in a second radio frequency band based on measurements in a first radio frequency band. For example, measurements in a first radio frequency band (e.g., the sub-6 GHz band, sometimes also referred to as FR1) may be simpler and more power-efficient than performing measurements in a different band (e.g., the millimeter wave (mmW) band, sometimes also referred to as FR2, which may be in a frequency range from 24.25 GHz to 52.6 GHz). In one example, measurements in the first band may be more efficient than measurements in the second band. For example, measurements in the first band may be more efficient than measurements in the second band due to the hardware characteristics of the UE. Additionally, by using measurements from the first band, the measurement overhead in the second band may be lower.

[0044] In some examples, BFD in the FR2 band may be detected / reported based on reference signal (RS) measurements in the FR1 band (or other bands, such as measurements on FR2 to estimate the channel and perform BFD for FR4). In some examples, the UE may detect a beam failure in the second band based on an estimate from RS measurements in the first band (e.g., without performing any RS measurements in the second band). For example, the UE may estimate (e.g., predict) the reference signal received power (RSRP) of the serving beam in the second band based on RS measurements in the first band. If the estimated RSRP of the second band is equal to or higher than the BFD threshold of the second band, or outside the margin of the BFD threshold of the second band, the UE may determine that there is no beam failure for the second band without further RS measurements in the second band. If the RSRP estimate of the serving beam in the second band is within the margin (e.g., close to the BFD threshold of the second band), or within the margin for a threshold number of measurement instances, the UE may request the base station to transmit a BFD RS on the second band (e.g., "BFD RS on demand"). The UE may then measure and determine the BFD RS on the second band to determine whether the second band is in a beam failure. In some examples, the request for the RS is sent on a physical uplink control channel (PUCCH). If the RSRP is outside the margin below the BFD threshold of the second band, the UE may determine that the serving beam in the second band is not in or not close to a beam failure.

[0045] The following description provides examples of performing BFD in a second frequency band based on measurements in a first frequency band in a communication system, and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made to the functions and arrangements of the elements discussed without departing from the scope of the disclosure. Various examples may appropriately omit, substitute, or add various procedures or components. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, the features described with reference to some examples may be combined in some other examples. For example, any number of aspects set forth herein may be used to implement an apparatus or practice a method. Additionally, the scope of the disclosure is intended to cover such apparatus or methods practiced using other structures, functionality, or a combination of structures and functionality that supplement or are in addition to the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be implemented by one or more elements of the claims. The term "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any aspect described herein as "exemplary" need not be construed as superior or better than other aspects.

[0046] In general, any number of wireless networks may be deployed in a given geographical area. Each wireless network may support a specific radio access technology (RAT) and may operate on one or more frequencies. The RAT may also be referred to as a radio technology, air interface, etc. The frequency may also be referred to as a carrier, subcarrier, frequency channel, tone, sub-band, etc. Each frequency may support a single RAT in a given geographical area to avoid interference between wireless networks of different RATs.

[0047] The techniques described herein may be used in various wireless networks and radio technologies. Although aspects may be described herein using terms typically associated with 3G, 4G, and / or new radio (e.g., 5G NR) wireless technologies, aspects of the disclosure may be applied in communication systems based on other generations.

[0048] New radio (e.g., 5G NR) access may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeted at wide bandwidth, millimeter wave (mmW) targeted at high carrier frequencies, massive machine type communication MTC (mMTC) targeted at non-backward compatible MTC technologies, and / or mission critical targeted at ultra-reliable low latency communication (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTIs) to meet the corresponding quality of service (QoS) requirements. Additionally, these services may coexist in the same subframe.

[0049] NR supports beamforming and the beam direction can be dynamically configured. MIMO transmission with precoding is also supported. The MIMO configuration in DL can support up to 8 transmit antennas (multi-layer DL transmission with up to 8 streams) and up to 2 streams per UE. Multi-layer transmission with up to 2 streams per UE is supported. Up to 8 serving cells can be used to support the aggregation of multiple cells.

[0050] The electromagnetic spectrum is typically subdivided into various categories, bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating bands have been identified as frequency range designations FR1 (410 MHz – 7.125 GHz) and FR2 (24.25 GHz – 52.6 GHz). It should be understood that although a part of FR1 is greater than 6 GHz, in various documents and articles, FR1 is typically (interchangeably) referred to as the "sub-6 GHz band". A similar naming issue sometimes occurs with respect to FR2. Although different from the extremely high frequency (EHF) band (30 GHz – 300 GHz) identified by the International Telecommunication Union (ITU) as the "millimeter wave" band, FR2 is typically (interchangeably) referred to as the "millimeter wave" band in various documents and articles.

[0051] The frequencies between FR1 and FR2 are generally referred to as mid-band frequencies. Recent 5G NR research has identified the operating bands of these mid-band frequencies as frequency range designations FR3 (7.125 GHz – 24.25 GHz). The bands falling within FR3 can inherit FR1 characteristics and / or FR2 characteristics, and thus can effectively extend the features of FR1 and / or FR2 into the mid-band frequencies. Additionally, higher frequency bands are currently being explored to extend 5G NR operation above 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR4a or FR4-1 (52.6 GHz – 71 GHz), FR4 (52.6 GHz – 114.25 GHz), and FR5 (114.25 GHz – 300 GHz). Each of these higher frequency bands falls within the EHF band.

[0052] Taking the above aspects into account, unless otherwise specifically stated, it should be understood that if used in this article, terms such as "sub-6 GHz" can generally represent frequencies that can be less than 6 GHz, can be within FR1, or can include mid-band frequencies. Additionally, unless otherwise specifically stated, it should be understood that if used in this article, terms such as "millimeter wave" can generally represent frequencies that can include mid-band frequencies, can be within FR2, FR4, FR4-a or FR4-1, and / or FR5, or can be within the EHF band.

[0053] Figure 1An example wireless communication network 100 in which aspects of the present disclosure may be implemented is described. For example, the wireless communication network 100 may be a NR system (e.g., a 5G NR network). As Figure 1 shown, the wireless communication network 100 may be in communication with a core network 132. The core network 132 may be in communication with one or more base stations (BSs) 110a-z (also each individually referred to herein as a BS 110 or collectively as BS 110), user equipment (UEs) 120a-y (also each individually referred to herein as a UE 120 or collectively as UEs 120), and other network entities in the wireless communication network 100 via one or more interfaces. The core network 132 may include one or more core network nodes 134.

[0054] The BS 110 may provide communication coverage for a particular geographic area (sometimes referred to as a “cell”), which may be stationary or may move according to the location of the mobile BS 110. In some examples, the BSs 110 may be interconnected with each other and / or with one or more other BSs or network nodes (not shown) in the wireless communication network 100 using any suitable transport network via various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.). In Figure 1 the example shown, BSs 110a, 110b, and 110c may be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x may be a pico BS for pico cell 102x. BSs 110y and 110z may be femto BSs for femto cells 102y and 102z, respectively. A BS may support one or more cells.

[0055] The BS 110 communicates with UEs 120 in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc.) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. The wireless communication network 100 may also include relay stations (e.g., relay station 110r) (also referred to as relays, etc.) that receive transmissions of data and / or other information from an upstream station (e.g., BS 110a or UE 120r) and send the transmissions of the data and / or other information to a downstream station (e.g., UE 120 or BS 110), or that relay transmissions between UEs 120 to facilitate communication between the devices. The BS 110 and the UE 120 may communicate with each other using beams. As Figure 1 shown, BS 110a may use a serving beam 101 (e.g., from a set of beams) to communicate with UE 120a.

[0056] The network controller 130 can communicate with a set of BSs 110 and provide coordination and control for these BSs 110 (e.g., via the backhaul). In various aspects, the network controller 130 can communicate with a core network 132 (e.g., a 5G core network (5GC)), which provides various network functions such as access and mobility management, session management, user plane function, policy control function, authentication server function, unified data management, application function, network exposure function, network repository function, network slice selection function, etc.

[0057] According to certain aspects, the BSs 110 and the UEs 120 can be configured for BFD. As Figure 1 shown, the BS 110a includes a BFD manager 112. As Figure 1 shown, the UE 120a includes a BFD manager 122. According to aspects of the present disclosure, the BFD manager 112 and / or the BFD manager 122 can be configured to perform BFD in a second frequency band based on measurements in a first frequency band.

[0058] Figure 2 illustrates example components of the BS 110a and the UE 120a (e.g., in the Figure 1 wireless communication network 100) that can be used to implement aspects of the present disclosure.

[0059] At the BS 110a, the transmit processor 220 can receive data from the data source 212 and control information from the controller / processor 240. The control information can be used for the physical broadcast channel (PBCH), the physical control format indicator channel (PCFICH), the physical hybrid ARQ indicator channel (PHICH), the physical downlink control channel (PDCCH), the group common PDCCH (GC PDCCH), etc. The data can be used for the physical downlink shared channel (PDSCH), etc. The media access control (MAC)-control element (MAC-CE) is a MAC layer communication structure that can be used for the exchange of control commands between wireless nodes. The MAC-CE can be carried in a shared channel (such as the physical downlink shared channel (PDSCH), the physical uplink shared channel (PUSCH), or the physical sidelink shared channel (PSSCH)).

[0060] The processor 220 may process (e.g., encode and symbol map) data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols (such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and channel state information reference signal (CSI-RS)). The transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, control symbols, and / or reference symbols, if applicable, and may provide the output symbol streams to the modulators (MOD) in the transceivers 232a - 232t. Each modulator may process the corresponding output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The downlink signals from the modulators in the transceivers 232a - 232t may be transmitted via the antennas 234a - 234t, respectively.

[0061] At the UE 120a, the antennas 252a - 252r may receive the downlink signals from the BS 110a and may provide the received signals to the demodulators (DEMOD) in the transceivers 254a - 254r, respectively. Each demodulator may condition (e.g., filter, amplify, down-convert, and digitize) the respective received signals to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. The MIMO detector 256 may obtain the received symbols from all the demodulators in the transceivers 254a - 254r, perform MIMO detection on these received symbols, if applicable, and provide detected symbols. The receive processor 258 may process (e.g., demodulate, de-interleave, and decode) these detected symbols, provide the decoded data for the UE 120a to the data sink 260, and provide the decoded control information to the controller / processor 280.

[0062] On the uplink, at UE 120a, the transmit processor 264 may receive and process data from the data source 262 (e.g., for the physical uplink shared channel (PUSCH)) and control information from the controller / processor 280 (e.g., for the physical uplink control channel (PUCCH)). The transmit processor 264 may also generate reference symbols for reference signals (e.g., sounding reference signals (SRS)). The symbols from the transmit processor 264 may be precoded by the TX MIMO processor 266 when applicable, further processed by the modulator in the transceiver 254a - 254r (e.g., for SC - FDM, etc.), and transmitted to BS110a. At BS110a, the uplink signal from UE 120a may be received by the antenna 234, processed by the demodulator in the transceiver 232, detected by the MIMO detector 236 when applicable, and further processed by the receive processor 238 to obtain the decoded data and control information transmitted by UE 120a. The receive processor 238 may provide the decoded data to the data sink 239 and the decoded control information to the controller / processor 240.

[0063] The memories 242 and 282 may store data and program codes for BS110a and UE 120a, respectively. The scheduler 244 may schedule the UE for data transmission on the downlink and / or uplink.

[0064] The antenna 252, processors 266, 258, 264, and / or the controller / processor 280 of UE 120a, and / or the antenna 234, processors 220, 230, 238, and / or the controller / processor 240 of BS110a may be used to perform the various techniques and methods described herein. For example, as Figure 2 shown, the controller / processor 240 of BS110a has a BFD manager 241 and the controller / processor 280 of UE 120a has a BFD manager 281. In accordance with the aspects described herein, the BFD manager 241 and / or the BFD manager 281 may be configured to perform BFD on a second frequency band based on measurements in a first frequency band. Although shown at the controller / processor, other components of UE 120a and BS110a may also be used to perform the operations described herein.

[0065] NR can utilize Orthogonal Frequency Division Multiplexing (OFDM) with a Cyclic Prefix (CP) on both the uplink and downlink. NR can support half-duplex operation using Time Division Duplex (TDD). OFDM and Single Carrier Frequency Division Multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are also often referred to as frequency tones, frequency bins, etc. Each subcarrier can be modulated with data. The modulated symbols can be transmitted using OFDM in the frequency domain and using SC-FDM in the time domain. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The minimum resource allocation (so-called Resource Block (RB)) can be 12 consecutive subcarriers. The system bandwidth can also be divided into subbands. For example, one subband can cover multiple RBs. NR can support a base Subcarrier Spacing (SCS) of 15KHz, and other SCSs (e.g., 30kHz, 60kHz, 120kHz, 240kHz, etc.) can be defined relative to the base SCS.

[0066] Figure 3 is a diagram showing an example of Frame Format 300 for NR. The transmission timeline for each of the downlink and uplink can be divided into radio frames. Each radio frame can have a predetermined duration (e.g., 10 ms), and can be divided into 10 subframes with indices 0 to 9, each subframe being 1 ms. Each subframe can contain a variable number of time slots (e.g., 1, 2, 4, 8, 16,... time slots), depending on the SCS. Each time slot can include a variable number of symbol periods (e.g., 7 or 14 symbols), depending on the SCS. An index can be assigned to the symbol periods in each time slot. The sub-slot structure refers to a transmission time interval with a duration less than a time slot (e.g., 2, 3, or 4 symbols). Each symbol in a time slot can indicate the link direction for data transmission (e.g., DL, UL, or flexible), and the link direction for each subframe can be switched dynamically. The link direction can be based on the time slot format. Each time slot can include DL / UL data as well as DL / UL control information.

[0067] In some systems, a UE may be configured for beam failure detection (BFD). For example, when a channel estimate fails to meet a BFD threshold, the UE may detect a beam failure. The UE may be configured with a beam failure recovery procedure via radio resource control (RRC) signaling. The beam failure recovery procedure may include sending a beam recovery request message to a serving BS (e.g., a gNB). For example, when a beam failure is detected on a serving beam (e.g., a (the) serving synchronization signal block (SSB) / CSI-RS), the UE may send a random access channel (RACH) message indicating a new beam (such as by indicating a new SSB or CSI-RS) to the serving BS. The UE may detect a beam failure by counting (the) beam failure instances indicated to the UE by a lower layer. If the beam failure recovery is reconfigured by an upper layer during an ongoing random access procedure for beam failure recovery, the UE stops the ongoing random access procedure and initiates a new random access procedure with the new configuration.

[0068] The beam failure detection and beam failure recovery parameters configured by RRC may include: beamFailureInstanceMaxCount (maximum beam failure instance count) for beam failure detection; beamFailureDetectionTimer (beam failure detection timer) for beam failure detection; beamFailureRecoveryTimer (beam failure recovery timer) for beam failure recovery procedures; rsrp-ThresholdSSB (rsrp - threshold SSB): RSRP threshold for beam failure recovery; powerRampingStep: powerRampingStep (power ramping step) for beam failure recovery; powerRampingStepHighPriority: powerRampingStepHighPriority (high - priority power ramping step) for beam failure recovery; preambleReceivedTargetPower: preambleReceivedTarget Power (preamble received target power) for beam failure recovery; preambleTransMax: preambleTransMax for beam failure recovery; scalingFactorBI: scalingFactorBI (scaling factor BI) for beam failure recovery; ssb - perRACH - Occasion: ssb - perRACH - Occasion (ssb - per RACH - occasion) for beam failure recovery; ra - ResponseWindow (ra - response window): time window for monitoring responses for beam failure recovery using contention - free random access preambles; prach - ConfigurationIndex: prach - ConfigurationIndex (prach - configuration index) for beam failure recovery; ra - ssb - OccasionMaskIndex: ra - ssb - OccasionMaskIndex (ra - ssb - occasion mask index) for beam failure recovery; and / or ra - OccasionList: ra - Occasion List (ra - occasion list) for beam failure recovery. The UE may also be configured with the parameter BFI_COUNTER: a counter indicated for a beam failure instance, which is initially set to 0.

[0069] In some examples, the UE and the BS operate in the same environment; however, the UE may operate at different frequencies with different channel attributes. There may be some cross-frequency correlation between the channel characteristics in different frequency bands. Machine learning (ML) techniques can be used to predict the channel characteristics in a second frequency band based on measurements in a first frequency band.

[0070] In some examples, the ML techniques involve training a model, such as a prediction model. The model can be used to predict (e.g., estimate) the channel characteristics in a second frequency band based on measurements in a first frequency band. The model can be trained based on training data (e.g., training information), which may include feedback, such as feedback associated with the measurements in the first frequency band compared to the measurements in the second frequency band. For example, as Figure 4 shown, measurements on the first frequency band 403 in FR1 402 can be used to predict the channel characteristics in the second frequency band 405 in FR2 404. Alternatively, measurements in any of FR1 402, FR2 404, FR3 406, or FR4 408 (or another frequency range) can be used to predict the channel characteristics in another of these frequency ranges.

[0071] Figure 5 Illustrates an example networking environment 500 in which a prediction model 524 is used for channel estimation in accordance with certain aspects of the present disclosure. As Figure 5 shown, the networking environment 500 includes nodes 520, a training system 530, and a training repository 515 communicatively coupled via a network 505. The nodes 520 can be UEs (e.g., such as UE120a in the wireless communication network 100). The network 505 can be a wireless network, such as the wireless communication network 100, which can be a 5G NR network. Although the training system 530, the nodes 520, and the training repository 515 are Figure 5 illustrated as separate components, those skilled in the art will recognize that the training system 530, the nodes 520, and the training repository 515 can be implemented on any number of computing systems, implemented as one or more self-standing systems, or implemented in a distributed environment.

[0072] The training system 530 generally includes a prediction model training manager 532 that uses the training data to generate a prediction model 524 for channel estimation on a second frequency band based on measurements on a first frequency band. The prediction model 524 can be determined based on the information in the training repository 515.

[0073] The training repository 515 may include training data acquired before and / or after the deployment of the node 520. The node 520 may be trained in a simulated communication environment (e.g., in a field test, a drive test) before the deployment of the node 520. For example, various channel estimations may be tested to obtain training information related to measurements and / or estimations. This information may be stored in the training repository 515. After deployment, the training repository 515 may be updated to include feedback associated with the channel estimation performed by the node 520. The training repository may also be updated with information from other BSs and / or UEs, for example, based on the experience learned from these BSs and / or UEs (which may be associated with the procedures performed by these BSs and / or UEs).

[0074] The prediction model training manager 532 may use the information in the training repository 515 to determine a prediction model 524 (e.g., an algorithm) for estimating channel characteristics in a second frequency band based on measurements in a first frequency band. The prediction model training manager 532 may use various different types of machine learning algorithms to form the prediction model 524. The training system 530 may be located on the node 520, a BS in the network 505, or a different entity that determines the prediction model 524. If located on a different entity, the prediction model 524 is provided to the node 520. The training repository 515 may be a storage device, such as a memory. The training repository 515 may be located on the node 520, the training system 530, or another entity in the network 505. The training repository 515 may be in cloud storage. The training repository 515 may receive training information from the node 520, an entity in the network 505 (e.g., a BS or a UE in the network 505), the cloud, or other sources.

[0075] Machine learning may use any suitable machine learning algorithm. In some non-limiting examples, the machine learning algorithm is a supervised learning algorithm, a deep learning algorithm, an artificial neural network algorithm, or other types of machine learning algorithms.

[0076] In some examples, machine learning (e.g., used by the training system 430) is performed using a deep convolutional network (DCN). A DCN is a network in a convolutional network configured with additional pooling and normalization layers. DCNs have achieved state-of-the-art performance on many tasks. A DCN can be trained using supervised learning, where both the input and the output targets are known for many exemplars and are used to modify the weights of the network by using the gradient descent method. A DCN can be a feed-forward network. Additionally, as described above, the connections from the neurons in the first layer of the DCN to the groups of neurons in the next higher layer are shared across the neurons in the first layer. The feed-forward and shared connections of the DCN can be used for fast processing. The computational burden of the DCN can be much smaller than that of, for example, a neural network of a similar size that includes recurrent or feedback connections.

[0077] In some examples, machine learning (e.g., used by training system 430) is performed using a neural network. The neural network can be designed to have various connectivity patterns. In a feedforward network, information is passed from lower layers to higher layers, where each neuron in a given layer communicates to neurons in a higher layer. Hierarchical representations can be built in successive layers of the feedforward network. The neural network can also have recurrent or feedback (also referred to as top-down) connections. In a recurrent connection, the output from a neuron in a given layer can be communicated to another neuron in the same layer. Recurrent architectures can help identify patterns that span more than one chunk of input data presented sequentially to the neural network. Connections from neurons in a given layer to neurons in lower layers are referred to as feedback (or top-down) connections. Networks with many feedback connections can be beneficial when the identification of high-level concepts can assist in discerning specific low-level features of the input.

[0078] An artificial neural network, which can include a group of interconnected artificial neurons (e.g., neuron models), is a computing device or represents a method performed by a computing device. These neural networks can be used in a variety of applications and / or devices, such as Internet Protocol (IP) cameras, Internet of Things (IoT) devices, autonomous vehicles, and / or service robots. Individual nodes in an artificial neural network can mimic biological neurons by taking in input data and performing simple operations on the data. The result of the simple operations performed on the input data is selectively passed to other neurons. Weight values are associated with each vector and node in the network, and these values constrain how the input data relates to the output data. For example, the input data for each node can be multiplied by the corresponding weight value, and the products can be summed. The sum of these products can be adjusted by an optional bias, and an activation function can be applied to the result to produce the output signal or "output activation" of the node. The weight values can initially be determined by the iterative flow of training data through the network (e.g., the weight values are established during a training phase in which the network learns how to identify specific categories based on the characteristic features of typical input data for various categories).

[0079] Different types of artificial neural networks, such as recurrent neural networks (RNNs), multi-layer perceptron (MLP) neural networks, convolutional neural networks (CNNs), etc., can be used to implement machine learning (e.g., used by training system 530). The RNN works by saving the output of one layer and feeding that output back to the input to help predict the result of that layer. In an MLP neural network, data can be fed into the input layer, and one or more hidden layers provide several levels of abstraction of the data. Subsequently, a prediction can be made for the output layer based on the abstracted data. The MLP can be particularly suitable for classification prediction problems where the input is assigned a class or label. A convolutional neural network (CNN) is a feed-forward artificial neural network. A convolutional neural network can include a collection of artificial neurons, each having a receptive field (e.g., a spatially local region of the input space) and together spelling out an input space. Convolutional neural networks have numerous applications. Specifically, CNNs have been widely used in the fields of pattern recognition and classification. In a hierarchical neural network architecture, the output of the first layer of artificial neurons becomes the input of the second layer of artificial neurons, the output of the second layer of artificial neurons becomes the input of the third layer of artificial neurons, and so on. A convolutional neural network can be trained to recognize a hierarchy of features. The computations in a convolutional neural network architecture can be distributed over a population of processing nodes, which can be configured in one or more computational chains. These multi-layer architectures can be trained one layer at a time and can use backpropagation for fine-tuning.

[0080] In some examples, when using a machine learning algorithm, training system 530 generates vectors from the information in training repository 515. In some examples, training repository 515 stores vectors. In some examples, a vector maps one or more features to a label. For example, a feature can correspond to a measurement on a first frequency band. A label can correspond to the predicted channel characteristics of a second frequency band (e.g., as will be discussed in more detail below, according to certain aspects, the label can be the estimated RSRP of a serving beam in the second frequency band). Prediction model training manager 532 can use the vectors to train prediction model 524 for node 520. As discussed above, vectors can be associated with weights in a machine learning algorithm.

[0081] Using machine learning to estimate channel characteristics on a second frequency band based on measurements in a first frequency band can provide advantages. For example, measurements in a first frequency band (e.g., the sub-6 GHz frequency band, also known as FR1) can be simpler and more power-efficient than performing measurements in a different frequency band (e.g., the millimeter wave frequency band, also known as FR2). This can be due to the hardware characteristics of the UE. Additionally, by using measurements from the first frequency band, measurements in the second frequency band can be reduced or eliminated, thereby reducing the measurement overhead in the second frequency band.

[0082] Example BFD in the second frequency band based on measurements in the first frequency band

[0083] According to some aspects, beam failure detection (BFD) in a second frequency band can be based on measurements in a first frequency band. For example, a user equipment (UE) can estimate the channel characteristics of the second frequency band based on measurements in the first frequency band. For example, the UE can estimate the reference signal received power (RSRP) of the serving beam in the second frequency band based on reference signal (RS) measurements in the first frequency band. In some examples, the UE uses a machine learning (ML) algorithm to predict the channel characteristics of the second frequency band based on measurements in the first frequency band. In some examples, the UE can detect a beam failure in the second frequency band based on RS measurements in the first frequency band.

[0084] In some examples, the UE can detect a beam failure in the second frequency band without performing any RS measurements in the second frequency band. For example, if the (an) RSRP estimate of the serving beam in the second frequency band determined based on RS measurements in the first frequency band is equal to or higher than the BFD threshold of the second frequency band, the UE can determine that there is no beam failure for the second frequency band. However, if the channel estimate of the second frequency band is below the BFD threshold of the second frequency band, the UE can determine a beam failure event for the second frequency band (e.g., when the RSRP estimate of the second frequency band is below the BFD threshold for a number of threshold measurement instances of the second frequency band).

[0085] In some examples, when the estimated RSRP of the second frequency band is within a margin of the BFD threshold of the second frequency band (e.g., close to the BFD threshold of the second frequency band), the UE can detect a beam failure in the second frequency band by further performing RS measurements in the second frequency band. In this scenario, when the estimated RSRP of the second frequency band is higher than the BFD threshold but within the margin of the BFD threshold, the UE can request the BFD RS of the second frequency band (e.g., "BFD RS on demand") in order to subsequently measure and determine a beam failure detection event in the second frequency band. The UE can send a request for the BFD RS on the PUCCH. If the measured RSRP on the second frequency band is higher than the BFD threshold of the second frequency band, the UE can determine that the serving beam of the second frequency band is not in a beam failure. If the measured RSRP on the second frequency band is lower than the BFD threshold of the second frequency band, the UE can determine a beam failure event for the second frequency band (e.g., when the measured RSRP of the second frequency band is below the BFD threshold for a number of threshold measurement instances of the second frequency band).

[0086] According to some aspects, the UE can perform beam failure detection in a higher frequency band (e.g., FR2) based on RS measurements in a lower frequency band (e.g., FR1). The frequency bands can be any frequency bands and can be in any frequency range (e.g., FR1, FR2, FR4, etc.).

[0087] As Figure 6As shown, a node (such as Figure 5 node 520 in the environment 500 described in Figure 5 ) may include a measurement manager 602. The measurement manager 602 may be configured to measure one or more RSs on a first frequency band at 604.

[0088] Measurements from the measurement manager 602 may be provided to a prediction model 524 at a channel estimation manager 522. The channel estimation manager 522 may input the measurements into a machine learning algorithm. These inputs may include any measurements in the first frequency band. The inputs to the machine learning algorithm may include RS measurements in the first frequency band. As Figure 6 shown, in some examples, the measurement manager 602 measures the RS on the first frequency band at 604 to provide a measurement result 606, which may include a reference signal received power (RSRP) measurement in the first frequency band, location information of the UE (e.g., which may be used to learn the beam direction), raw channel measurements, channel impulse response (CIR) measurements, angle of departure (AoD) measurements (e.g., AoD of the strongest multipath component (MPC)), delay distribution of the strongest MPC, and / or other measurements in the first frequency band and / or other inputs that may be used by the machine learning algorithm to estimate the channel characteristics of a second frequency band and / or predict the RSRP of a beam (e.g., a serving beam) at the second frequency band.

[0089] In some examples, the output of the machine learning algorithm is the predicted RSRP value of a beam in the second frequency band. As Figure 6 shown, the prediction model 524 may be configured to estimate the RSRP of the second frequency band and provide these estimates to a BFD manager 610. In some examples, the prediction model may be located at the BS. For example, the UE may report measurements on the first frequency band to the BS and the BS may use these measurements to estimate the channel characteristics of the second frequency band. The BS may then provide these estimates to the UE, and / or the BS may use these estimates to detect a beam failure of a serving beam in the second frequency band.

[0090] In some examples, the machine learning algorithm is trained using historical training data, which includes measurements in the first frequency band (including one or more previous measurements of the inputs discussed above), previous measurements of the channel characteristics of the second frequency band, and / or previous measurements in the second frequency band compared to the measurements and / or estimates from the first frequency band, in order to train the machine learning algorithm. In some examples, the machine learning algorithm is further based on information related to the environment. In some examples, machine learning may be trained for various different environments, and the prediction model used may be based on the current environment.

[0091] According to certain aspects, the BFD manager 610 uses the channel characteristics of the second band (e.g., the RSRP of the serving beam), estimated from the RS measurements on the first band using a machine learning algorithm, to determine the beams on the second band that are in or approaching a fault. For example, the BFD manager 610 may be configured to compare, at 612, the RSRP estimate of the second band with the BFD threshold of the second band. The BFD manager 610 may also keep track of the number of measurement instances where the RSRP estimate of the second band is below the RSRP threshold of the second band. The BFD manager 610 may compare the number of measurement instances where the RSRP estimate of the second band is below the RSRP threshold of the second band with the threshold number of instances of the second band. When the number of measurement instances where the RSRP estimate of the second band is below the RSRP threshold of the second band reaches or exceeds the threshold number of instances of the second band, the BFD manager 610 may determine a beam fault on the second band.

[0092] In some examples, if the BFD manager 610 determines that a beam is in a fault (when the estimated RSRP value of the second band is below the BFD threshold of the second band by a number of instances that reaches or exceeds the threshold number of measurements), the BFD manager 610 may initiate a BFR at 616, for example, by sending a beam fault recovery (BFR) message to the BS. In such a case, the node 620 may not perform any BFD RS measurements on the second band. The BFR message may be a random access channel (RACH) message indicating a new beam for the second band. In some examples, if the estimated RSRP is above the BFD threshold of the second band, the BFD manager 628 may determine that the beam is not in a fault.

[0093] In some examples, the BFD manager 610 may request the network (e.g., the BS) to send an RS on a second frequency band based on measurements on a first frequency band. This may be referred to as "on-demand" BFD RS. The BFD manager 610 may send this request on the PUCCH. For example, when the estimated RSRP is close to or near the BFD threshold of the second frequency band (e.g., above the BFD threshold and within a margin of the BFD threshold), the BFD manager 610 may send a request for the BFD RS on the second frequency band at 614. Subsequently, the node 620 may measure the RS on the second frequency band to determine the actual RSRP value of the second frequency band and determine whether the beam of the second frequency band is in a fault based on the actual RSRP measured on the RS of the second frequency band. When the BFD manager 610 determines that the beam is in a fault based on the actual RSRP, the BFD manager 610 may initiate a BFR at 616. In some examples, if the actual RSRP is equal to or higher than the BFD threshold of the second frequency band, the BFD manager 628 may determine that the beam is not in a fault and does not initiate a BFR. In some examples, if the estimated RSRP is not close to the BFD threshold of the second frequency band (e.g., outside the margin of the BFD threshold), the BFD manager 628 may determine that the beam is not close to a fault and may not request the RS on the second frequency band and does not initiate a BFR.

[0094] Thus, the node 620 may measure on the first frequency band, which may be more power efficient than measuring on the second frequency band. Additionally, by replacing the reference signal with data, the signaling overhead associated with the reference signal in the second frequency band may be lower, as the node 620 may rely on measuring the "on-demand" reference signal on the second frequency band, thus having an efficient signaling overhead and saving power.

[0095] Figure 7 is a flowchart illustrating an example operation 700 for wireless communication in accordance with certain aspects of the present disclosure. The operation 700 may be performed, for example, by a UE (e.g., the UE 120a in the wireless communication network 100 such as). The operation 700 may be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Additionally, the signal transmission and reception performed by the UE in operation 600 may be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In certain aspects, the signal transmission and / or reception performed by the UE may be implemented by obtaining and / or outputting signals via a bus interface of one or more processors (e.g., the controller / processor 280).

[0096] Operation 700 may begin at 705 with measuring one or more RSs on a first radio frequency band. In some examples, the first radio frequency band is in a lower frequency range than a second radio frequency band. In some examples, the first radio frequency band is in a sub-6 GHz frequency range, while the second radio frequency band is in a mmW frequency range. In some examples, the measurements on the first radio frequency band include one or more RSRP measurements, one or more positioning measurements, one or more raw channel measurements, one or more CIR measurements, one or more AoD measurements, one or more latency measurements, or a combination thereof.

[0097] At 710, the UE determines a BFD for the second radio frequency band based at least in part on the measurements of the one or more RSs on the first radio frequency band. In some examples, determining the BFD for the second radio frequency band includes: using a machine learning (ML) algorithm with the measurements of the one or more RSs on the first radio frequency band as inputs to estimate one or more channel parameters for the second radio frequency band. In some examples, the one or more estimated channel parameters include one or more estimated RSRP values.

[0098] In some examples, determining the BFD for the second radio frequency band includes: reporting a BFD (e.g., initiating beam failure recovery) when the estimated RSRP of the serving beam for the second radio frequency band is below the beam failure threshold for the second radio frequency band by a threshold measurement instance number for the second band or more. In some examples, determining the BFD for the second radio frequency band includes: when the estimated RSRP of the serving beam for the second radio frequency band is within a margin of the BFD threshold for the second radio frequency band, requesting one or more RSs on the second radio frequency band; measuring the one or more RSs on the second radio frequency band; and reporting the BFD for the second radio frequency band (e.g., and / or initiating a beam failure recovery procedure) based on the measurements of the one or more RSs on the second radio frequency band reaching or exceeding the threshold measurement instance number for the second band.

[0099] Figure 8 is a flow chart illustrating an example operation 800 for wireless communication in accordance with certain aspects of the present disclosure. Operation 800 may be performed, for example, by a UE (e.g., such as UE 120a in wireless communication network 100). Operation 800 may be implemented as a software component executed and run on one or more processors (e.g., Figure 2 the controller / processor 280). Further, signal transmission and reception by the UE in operation 800 may be implemented, for example, by one or more antennas (e.g., Figure 2 the antenna 252). In certain aspects, signal transmission and / or reception by the UE may be implemented by obtaining and / or outputting signals via a bus interface of one or more processors (e.g., the controller / processor 280).

[0100] Operation 800 may start at 805 with receiving one or more RSs on a first radio frequency band.

[0101] At 810, the UE may measure the one or more RSs on the first radio frequency band. For example, the UE may perform RSRP measurement, positioning measurement, raw channel measurement, CIR measurement, AoD measurement, and / or latency measurement.

[0102] At 815, the UE may perform BFD for a second radio frequency band at least partially based on one or more measurements of the one or more RSs on the first radio frequency band. The first radio frequency band may be in a lower frequency range (e.g., in the sub-6 GHz radio frequency range) than the second radio frequency band (e.g., in the mmW radio frequency range). At 820, the UE may use an ML algorithm with the one or more measurements of the one or more RSs on the first radio frequency band as inputs to estimate one or more channel parameters (e.g., RSRP) of the second radio frequency band. At 825, the UE compares the estimated one or more channel parameters of the second radio frequency band with a BFD threshold of the second radio frequency band. For example, the UE may compare the estimated one or more channel parameters of the second radio frequency band with a channel parameter threshold of the second radio frequency band. The UE may track the number of measurement instances where the estimated one or more channel parameters of the second radio frequency band are below the channel parameter threshold of the second radio frequency band. The UE may compare the number of measurement instances where the estimated one or more channel parameters of the second radio frequency band are below the channel parameter threshold of the second radio frequency band with a threshold number of measurement instances of the second radio frequency band.

[0103] When the number of measurement instances where the estimated one or more channel parameters of the second radio frequency band are below the channel parameter threshold of the second radio frequency band reaches or exceeds the threshold number of measurement instances of the second radio frequency band, the UE may detect a beam failure of the second radio frequency band. At 830, when the estimated one or more channel parameters of the second radio frequency band are within a predefined margin of the BFD threshold of the second radio frequency band, the UE may request one or more RSs on the second radio frequency band. The UE may measure the one or more RSs on the second radio frequency band (e.g., on-demand BFD RS), compare the one or more measurements of the one or more RSs on the second radio frequency band with the channel parameter threshold of the second radio frequency band, and track the number of measurement instances where the measurements of the one or more RSs on the second radio frequency band are below the channel parameter threshold of the second radio frequency band.

[0104] At 835, the UE initiates a beam failure recovery procedure for the second radio frequency band at least partially based on one or more RSs received on the first radio frequency band.

[0105] Figure 9is a flow chart illustrating an example operation 900 for wireless communication in accordance with certain aspects of the present disclosure. Operation 900 may be performed, for example, by a BS (such as BS110a in wireless communication network 100, for example). Operation 900 may be an operation performed by the BS that is complementary to operation 900 performed by a UE. Operation 900 may be implemented as a software component executed and run on one or more processors (such as the controller / processor 240 of, for example, Figure 2 ). In addition, signal transmission and reception by the BS in operation 900 may be implemented, for example, by one or more antennas (such as the antenna 234 of, for example, Figure 2 ). In certain aspects, signal transmission and / or reception by the BS may be implemented by obtaining and / or outputting signals via a bus interface of one or more processors (such as the controller / processor 240).

[0106] Operation 900 may begin at 905 with the transmission of a first one or more RSs to a UE on a first radio frequency band.

[0107] At 910, the BS receives, in response to the first one or more RSs on the first radio frequency band, a request from the UE to transmit a second one or more RSs on a second radio frequency band.

[0108] At 915, the BS transmits the second one or more RSs to the UE on the second radio frequency band.

[0109] In some examples, at 920, the BS receives a beam failure recovery request message from the UE for the second radio frequency band. For example, the beam failure recovery request message may be at least partially based on the second one or more RSs transmitted on the second radio frequency band.

[0110] In some examples, the first radio frequency band is in a sub-6 GHz frequency range, and the second radio frequency band is in a millimeter wave frequency range.

[0111] Figure 10AIt is a decision tree diagram illustrating an example operation 1000a for wireless communication by a UE in accordance with certain aspects of the present disclosure. As shown in FIG. 10, the UE measures one or more RSs on a first frequency band at 1002. At 1004, the UE estimates the RSRP of a serving beam on a second frequency band based on measurements in the first frequency band (e.g., the measurements performed at 1002). At 1006, the UE compares the estimated RSRP of the second frequency band with the BFD threshold of the second frequency band. If the estimated RSRP of the second frequency band is equal to or higher than the BFD threshold of the second frequency band, at 1022, the UE may determine that there is no beam failure (and may return to block 1002 to measure the RS on the first frequency band). If the estimated RSRP of the second frequency band is lower than the BFD threshold of the second frequency band, the UE may initiate a BFR for the second frequency band at 1012. For example, the UE may count measurement instances in which the estimated RSRP of the second frequency band is lower than the BFD threshold of the second frequency band. When the number of measurement instances in which the estimated RSRP of the second frequency band is lower than the BFD threshold of the second frequency band is less than the threshold number of measurement instances, the UE may return to block 1002 to measure the RS on the first frequency band. When the number of measurement instances in which the estimated RSRP of the second frequency band is equal to or higher than the BFD threshold of the second frequency band is equal to or higher than the threshold number of measurement instances, the UE initiates a BFR at 1012.

[0112] Figure 10B It is another decision tree diagram illustrating an example operation 1000b for wireless communication by a UE in accordance with certain aspects of the present disclosure. As Figure 10BAs shown, the UE may further check at 1006 whether the estimated RSRP is within the margin of the BFD threshold of the second band. If the UE determines at 1006b that the estimated RSRP of the second band is higher than the BFD threshold of the second band and higher than the margin of the BFD threshold, the UE may determine at 1024b that there is no beam failure (e.g., and may return to block 1002 to measure the RS on the first band). On the other hand, if the UE determines at 1006b that the estimated RSRP is higher than the BFD threshold of the second band and within the margin of the BFD threshold, the UE may request one or more BFD RSs of the second band (e.g., on-demand BFD RS) at 1014. At 1016, the UE measures the one or more BFD RSs on the second band. The UE may determine the actual RSRP of the second band based on the measurement of the BFD RS on the second band. At 1018, the UE determines whether the actual measured RSRP of the second band is lower than the BFD threshold of the second band. If not, the UE determines at 1022 that there is no beam failure for the second band (e.g., for the serving cell of the second band). If so, the UE may initiate beam failure recovery for the second band at 1020. For example, the UE may count the measurement instances where the actual measured RSRP of the second band is lower than the BFD threshold of the second band. When the number of measurement instances where the actual measured RSRP of the second band is lower than the BFD threshold of the second band is less than the threshold number of measurement instances, the UE may return to block 1016 to measure the RS on the second band. When the number of measurement instances where the actual measured RSRP of the second band is equal to or higher than the BFD threshold of the second band is equal to or higher than the threshold number of measurement instances, the UE initiates BFR at 1020.

[0113] Figure 11A is a call flow diagram illustrating example signaling 1100a in accordance with certain aspects of the present disclosure. At 1102, the BS transmits one or more RSs to the UE on the first band. At 1104, the UE measures the one or more RSs on the first band. In some examples, a beam failure event has not occurred. In this case, at 1106a, the UE estimates one or more channel characteristics on the second band and the estimated channel characteristics are equal to or higher than the BFD threshold, and at 1108a, the UE may determine that there is no beam failure on the second band. In some examples, a beam failure event has occurred. In this case, at 1106b, the UE estimates one or more channel characteristics on the second band and the estimated channel characteristics are lower than the BFD threshold, and at 1108b, when the number of measurement instances where the estimated channel characteristics are lower than the BFD threshold is equal to or higher than the threshold number of measurement instances, the UE may initiate beam failure recovery on the second band.

[0114] Figure 11BCall flow diagram 1100b illustrating example signaling in accordance with certain aspects of the present disclosure. At 1102, the BS transmits one or more RSs to the UE on a first frequency band. At 1104, the UE measures the one or more RSs on the first frequency band. In some examples, a beam may be approaching failure. At 1106c, the UE estimates one or more channel characteristics on a second frequency band and the estimated channel characteristics are within the BFD threshold. At 1108c, the UE requests one or more RSs on the second frequency band. At 1110, the BS transmits the requested one or more RSs to the UE on the second frequency band. At 1112, the UE measures the one or more RSs on the second frequency band. In some examples, a beam failure event has not occurred. At 1114a, the measured channel characteristics are equal to or higher than the BFD threshold, and at 1116a, the UE may determine that there is no beam failure on the second frequency band. In some examples, a beam failure event has occurred. At 1114b, the measured channel characteristics are lower than the BFD threshold, and at 1116b, when the number of measurement instances where the estimated channel characteristics are lower than the BFD threshold is equal to or higher than the threshold number of measurement instances, the UE may initiate beam failure recovery on the second frequency band.

[0115] Figure 12 Illustrates a communication device 1200 that may include various components (e.g., corresponding to apparatus plus function components) configured to perform operations (such as, Figure 7 and / or Figure 8 the operations illustrated in

[0116] The processing system 1202 includes a processor 1204 coupled to a computer-readable medium / memory 1212 via a bus 1206. In certain aspects, the computer-readable medium / memory 1212 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 1204, cause the processor 1204 to perform Figure 7 and / or Figure 8The operations described in, or other operations for performing the various techniques discussed herein for performing BFD on a second frequency band based on measurements on a first frequency band. In some aspects, in accordance with aspects of the present disclosure, the computer-readable medium / memory 1212 stores code 1214 for receiving; code 1216 for measuring; code 1218 for executing; code 1220 for estimating; code 1222 for comparing; code 1224 for requesting; and / or code 1226 for initiating. In some aspects, the processor 1204 has circuitry configured to implement the code stored in the computer-readable medium / memory 1212. In accordance with aspects of the present disclosure, the processor 1204 includes circuitry 1228 for receiving; circuitry 1230 for measuring; circuitry 1232 for executing; circuitry 1234 for estimating; circuitry 1236 for comparing; circuitry 1238 for requesting; and / or circuitry 1240 for initiating.

[0117] Figure 13 illustrates a communication device 1300 that may include various components (e.g., corresponding to apparatus-plus-function components) configured to perform operations for the techniques disclosed herein, such as Figure 9 the operations illustrated in. The communication device 1300 includes a processing system 1302 coupled to a transceiver 1308 (e.g., a transmitter and / or a receiver). The transceiver 1308 is configured to transmit and receive signals for the communication device 1300 (such as the various signals described herein) via an antenna 1310. The processing system 1302 may be configured to perform processing functions for the communication device 1300, including processing signals received and / or to be transmitted by the communication device 1300.

[0118] The processing system 1302 includes a processor 1304 coupled to a computer-readable medium / memory 1312 via a bus 1306. In some aspects, the computer-readable medium / memory 1312 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 1304, cause the processor 1304 to perform Figure 9The operations described herein, or other operations for performing the various techniques discussed herein for performing BFD on a second radio frequency band based on measurements on a first radio frequency band. In some aspects, in accordance with aspects of the present disclosure, the computer-readable medium / memory 1312 stores code 1314 for transmitting a first one or more reference signals (RSs) to a UE on a first radio frequency band; code 1316 for receiving, from the UE, a request for a second one or more RSs on a second radio frequency band in response to the first one or more RSs on the first radio frequency band; code 1318 for transmitting the second one or more RSs to the UE on the second radio frequency band; and / or code 1320 for receiving, from the UE, a beam failure recovery request message for the second radio frequency band. In some aspects, the processor 1304 has circuitry configured to implement the code stored in the computer-readable medium / memory 1312. In accordance with aspects of the present disclosure, the processor 1304 includes circuitry 1322 for transmitting a first one or more RSs to a UE on a first radio frequency band; circuitry 1324 for receiving, from the UE, a request to transmit a second one or more RSs on a second radio frequency band in response to the first one or more RSs on the first radio frequency band; circuitry 1326 for transmitting the second one or more RSs to the UE on the second radio frequency band; and / or circuitry 1328 for receiving, from the UE, a beam failure recovery request message for the second radio frequency band.

[0119] Exemplary Aspects

[0120] Implementing examples are described in the following numbered clauses:

[0121] Aspect 1. A method for wireless communication by a user equipment (UE), comprising: receiving one or more reference signals (RSs) on a first radio frequency band; and initiating a beam failure recovery procedure for a second radio frequency band based at least in part on the one or more RSs received on the first radio frequency band.

[0122] Aspect 2. The method of aspect 1, further comprising: measuring the one or more RSs on the first radio frequency band; and performing beam failure detection (BFD) for the second radio frequency band based at least in part on one or more measurements of the one or more RSs on the first radio frequency band.

[0123] Aspect 3. The method of aspect 2, wherein performing BFD for the second radio frequency band comprises: using a machine learning (ML) algorithm to estimate one or more channel parameters of the second radio frequency band with one or more measurements of the one or more RSs on the first radio frequency band as inputs; and comparing the estimated one or more channel parameters of the second radio frequency band with a BFD threshold for the second radio frequency band.

[0124] Aspect 4. The method as described in Aspect 3, wherein performing BFD for the second radio frequency band includes: when one or more estimated channel parameters of the second radio frequency band are below the BFD threshold of the second radio frequency band and reach or exceed a threshold measurement instance number, detecting a beam failure for the second radio frequency band.

[0125] Aspect 5. The method as described in any one of Aspects 3 to 4, wherein performing BFD for the second radio frequency band includes: when one or more estimated channel parameters of the second radio frequency band are within a predefined margin of the BFD threshold of the second radio frequency band, requesting one or more reference signals (RSs) on the second radio frequency band; measuring the one or more RSs on the second radio frequency band; and comparing one or more measurements of the one or more RSs on the second radio frequency band with the BFD threshold of the second radio frequency band.

[0126] Aspect 6. The method as described in Aspect 5, wherein requesting the one or more RSs on the second radio frequency band includes: requesting a base station (BS) to transmit one or more on-demand beam failure detection (BFD) RSs on the second radio frequency band.

[0127] Aspect 7. The method as described in any one of Aspects 2 to 6, wherein the one or more measurements on the first radio frequency band include one or more reference signal received power (RSRP) measurements, one or more positioning measurements, one or more raw channel measurements, one or more channel impulse response (CIR) measurements, one or more angle of departure (AoD) measurements, one or more delay measurements, or a combination thereof.

[0128] Aspect 8. The method as described in any one of Aspects 2 to 7, wherein the one or more estimated channel parameters include one or more estimated reference signal received power (RSRP) values.

[0129] Aspect 9. The method as described in any one of Aspects 1 to 8, wherein the first radio frequency band is in the sub-6 GHz radio frequency range, and the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

[0130] Aspect 10. A method for wireless communication by a base station (BS), including: transmitting first one or more reference signals (RSs) to a user equipment (UE) on a first radio frequency band; in response to the first one or more RSs on the first radio frequency band, receiving from the UE a request to transmit second one or more RSs on a second radio frequency band; and transmitting the second one or more RSs to the UE on the second radio frequency band.

[0131] Aspect 11. The method as described in aspect 10 further includes: receiving, from the UE, a beam failure recovery request message for the second radio frequency band.

[0132] Aspect 12. The method as described in any one of aspects 10 to 11, wherein the first radio frequency band is in the sub-6 GHz radio frequency range, and the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

[0133] Aspect 13. The method as described in any one of aspects 10 to 12, wherein receiving, from the UE, a request to transmit the second one or more RSs on the second radio frequency band includes: receiving the request on a physical uplink control channel (PUCCH).

[0134] Aspect 14. The method as described in any one of aspects 1 to 13, wherein receiving, from the UE, a request to transmit the second one or more RSs on the second radio frequency band includes: receiving, from the UE, a request to transmit one or more beam failure detection (BFD) RSs on demand on the second radio frequency band.

[0135] Aspect 15. An apparatus comprising means for performing the method as described in any one of aspects 1 to 14.

[0136] Aspect 16. An apparatus comprising: at least one processor and a memory coupled to the at least one processor, the memory including code that can be executed by the at least one processor to cause the apparatus to perform the method as described in any one of aspects 1 to 14.

[0137] Aspect 17. A computer-readable medium having stored thereon computer-executable code for wireless communication, the computer-executable code, when executed by at least one processor, causing an apparatus to perform the method as described in any one of aspects 1 to 14.

[0138] Additional Considerations

[0139] The techniques described herein can be used in a variety of wireless communication technologies such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms “network” and “system” are often used interchangeably. CDMA networks may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers the IS-2000, IS-95, and IS-856 standards. TDMA networks may implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are UMTS versions that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR is an emerging wireless communication technology that is under development.

[0140] In 3GPP, the term "cell" can refer to the coverage area of a Node B (NB) and / or the NB subsystem serving that coverage area, depending on the context in which the term is used. In the NR system, the terms "cell" and BS, next-generation Node B (gNB or g B node), access point (AP), distributed unit (DU), carrier, or transmit receive point (TRP) may be used interchangeably. A BS may provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell may cover a relatively large geographical area (e.g., with a radius of several kilometers) and may allow unconstrained access by UEs with a service subscription. A pico cell may cover a relatively small geographical area and may allow unconstrained access by UEs with a service subscription. A femto cell may cover a relatively small geographical area (e.g., a residence) and may allow constrained access by UEs associated with that femto cell (e.g., UEs in a closed subscriber group (CSG), UEs of users in a residence, etc.). The BS for a macro cell may be referred to as a macro BS. The BS for a pico cell may be referred to as a pico BS. The BS for a femto cell may be referred to as a femto BS or a home BS.

[0141] A UE may also be referred to as a mobile station, terminal, access terminal, subscriber unit, station, customer premise equipment (CPE), cellular phone, smart phone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, appliance, medical device or equipment, biometric sensor / device, wearable device (such as a smartwatch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet, etc.)), entertainment device (e.g., music device, video device, satellite radio, etc.), vehicle component or sensor, smart meter / sensor, industrial manufacturing equipment, global positioning system device, or any other suitable device configured to communicate via wireless or wired media. Some UEs may be considered machine type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which may communicate with a BS, another device (e.g., a remote device), or some other entity. A wireless node may provide connectivity to a network (e.g., a wide area network such as the Internet or a cellular network) or provide connectivity to the network, for example, via a wired or wireless communication link. Some UEs may be considered Internet of Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

[0142] In some examples, access to an air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all of the devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for the scheduled communication, the subordinate entities utilize the resources allocated by the scheduling entity. A base station is not the only entity that can be used as a scheduling entity. In some examples, a UE may act as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may act as a scheduling entity in a peer-to-peer (P2P) network and / or in a mesh network. In a mesh network example, UEs may communicate directly with each other in addition to communicating with a scheduling entity.

[0143] The various methods disclosed herein include one or more steps or acts for implementing the method. These method steps and / or acts may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of the steps or acts is specified, the order and / or use of the specific steps and / or acts may be altered without departing from the scope of the claims.

[0144] As used herein, a phrase that recites “at least one” of a list of items refers to any combination of those items, including a single member. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, a - b, a - c, b - c, and a - b - c, as well as any combination with multiple of the same element (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 ordering of a, b, and c).

[0145] As used herein, the term “determine” covers a variety of actions. For example, “determine” may include computing, calculating, processing, deriving, researching, looking up (e.g., looking up in a table, a database, or another data structure), ascertaining, and the like. Also, “determine” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Also, “determine” may include parsing, selecting, choosing, establishing, and the like.

[0146] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein the recitation of a singular element is not intended to mean "one and only one" (unless specifically so stated) but "one or more." The term "some," unless specifically stated otherwise, means one or more. Elements of the various aspects described throughout this disclosure that are presently known or later come to be known to those of ordinary skill in the art as structural and functional equivalents are expressly incorporated herein by reference and are intended to be covered by the claims. In addition, nothing disclosed herein is intended to be dedicated to the public, whether or not such disclosure is explicitly recited in the claims. No element of a claim should be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

[0147] The various operations of the methods described above can be performed by any suitable means capable of performing the corresponding functions. These means may include various hardware and / or software components and / or modules, including but not limited to circuits, application specific integrated circuits (ASICs), or processors. In general, where there are operations illustrated in the figures, these operations may have corresponding paired means-plus-function components with similar numbers.

[0148] The various illustrative logical blocks, modules, and circuits described in connection with the present disclosure can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0149] If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system can be implemented with a bus architecture. Depending on the specific application of the processing system and overall design constraints, the bus may include any number of interconnected buses and bridges. The bus can link together various circuits including a processor, a machine-readable medium, and a bus interface. The bus interface can be used to connect, via the bus, a network adapter, etc. to the processing system. The network adapter can be used to implement the signal processing functions of the PHY layer. In the case of a user terminal (see Figure 1 ), a user interface (such as, for example, a keypad, a display, a mouse, a joystick, etc.) can also be connected to the bus. The bus can also link various other circuits such as a timing source, peripherals, voltage regulators, power management circuits, and similar circuits, which are well known in the art and will not be described further herein. The processor can be implemented with one or more general-purpose and / or special-purpose processors. Examples include a microprocessor, a microcontroller, a DSP processor, and other circuitry capable of executing software. Depending on the specific application and overall design constraints imposed on the overall system, those of ordinary skill in the art will recognize how best to implement the functionality described with respect to the processing system.

[0150] If implemented in software, the functions can be stored on or transmitted via a computer-readable medium as one or more instructions or code. Software should be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The computer-readable medium includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including executing software modules stored on the machine-readable storage medium. The computer-readable storage medium may be coupled to the processor such that the processor can read from and write to the storage medium. In an alternative, the storage medium may be integrated into the processor. As an example, the machine-readable medium may include a transmission line, a carrier modulated by data, and / or a computer-readable storage medium separate from the wireless node having instructions stored thereon, all of which can be accessed by the processor via the bus interface. Alternatively or additionally, the machine-readable medium or any part thereof may be integrated into the processor, such as may be the case with a cache and / or a general register file. As an example, examples of the machine-readable medium may include RAM (Random Access Memory), flash memory, ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable medium may be embodied in a computer program product.

[0151] A software module can include a single instruction or many instructions and can be distributed over several different code segments, distributed among different programs, and across multiple storage media. A computer-readable medium can include several software modules. These software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. These software modules can include a transmission module and a reception module. Each software module can reside in a single storage device or be distributed across multiple storage devices. As an example, when a triggering event occurs, the software module can be loaded from a hard drive into RAM. During execution of the software module, the processor can load some of the instructions into a cache to increase access speed. One or more cache lines can then be loaded into the general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when the processor executes instructions from the software module.

[0152] Likewise, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a web site, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology such as infrared, radio, and microwave is included in the definition of the medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and disc, where disk often magnetically reproduces data, while disc optically reproduces data with a laser. Thus, in some aspects, a computer-readable medium can include a non-transitory computer-readable medium (e.g., a tangible medium). Additionally, for other aspects, a computer-readable medium can include a transitory computer-readable medium (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media.

[0153] Accordingly, some aspects can include a computer program product for performing the operations given herein. For example, such a computer program product can include a computer-readable medium having (and / or encoded thereon) instructions that can be executed by one or more processors to perform the operations described herein, such as instructions for performing the operations described and illustrated in Figures 4 - 13 herein.

[0154] In addition, it should be appreciated that modules and / or other suitable means for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by a user terminal and / or a base station where applicable. For example, such devices can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage device (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or a floppy disk, etc.) such that once the storage device is coupled to or provided to the user terminal and / or the base station, the device can obtain the various methods. In addition, any other suitable technique can be utilized that is adapted to provide the methods and techniques described herein to the device.

[0155] It will be understood that the claims are not limited to the exact configurations and components set forth above. Various changes, substitutions, and modifications can be made in the layout, operation, and details of the methods and apparatuses described above without departing from the scope of the claims.

Claims

1. A method for wireless communication by a user equipment (UE), comprising: Receiving one or more first reference signals (RS) on a first radio frequency band; Measuring the one or more first RS on the first radio frequency band; Using a machine learning (ML) algorithm to estimate one or more channel parameters of a second radio frequency band with the one or more measurements of the one or more first RS on the first radio frequency band as inputs; Based on the estimated one or more channel parameters of the second radio frequency band, sending a request for one or more second RS on the second radio frequency band; And Initiating a beam failure recovery procedure for the second radio frequency band at least partially based on the one or more second RS received on the second radio frequency band.

2. The method according to claim 1, further comprising: Performing beam failure detection (BFD) for the second radio frequency band at least partially based on the one or more measurements of the one or more first RS on the first radio frequency band.

3. The method according to claim 2, wherein, Performing BFD for the second radio frequency band includes: And Comparing the estimated one or more channel parameters of the second radio frequency band with a BFD threshold of the second radio frequency band.

4. The method according to claim 3, wherein, Performing BFD for the second radio frequency band includes: When the estimated one or more channel parameters of the second radio frequency band are below the BFD threshold of the second radio frequency band by a threshold measurement instance number or more, detecting a beam failure for the second radio frequency band.

5. The method according to claim 3, wherein, Requesting the one or more second RS on the second radio frequency band includes: when the estimated one or more channel parameters of the second radio frequency band are within a predefined margin of the BFD threshold of the second radio frequency band, requesting the one or more second RS on the second radio frequency band; and Performing BFD for the second radio frequency band includes: Measuring the one or more second RS on the second radio frequency band; and Comparing the one or more measurements of the one or more second RS on the second radio frequency band with the BFD threshold of the second radio frequency band.

6. The method according to claim 5, wherein, Requesting the one or more second RS on the second radio frequency band includes: requesting a scheduling entity to transmit one or more on-demand beam failure detection (BFD) RS on the second radio frequency band.

7. The method according to claim 2, wherein, The one or more measurements on the first radio frequency band include one or more reference signal received power (RSRP) measurements, one or more positioning measurements, one or more raw channel measurements, one or more channel impulse response (CIR) measurements, one or more angle of departure (AoD) measurements, one or more delay measurements, or a combination thereof.

8. The method according to claim 3, wherein The estimated one or more channel parameters include estimated one or more reference signal received power (RSRP) values.

9. The method according to claim 1, wherein The first radio frequency band is in the sub-6 GHz radio frequency range, while the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

10. A method for wireless communication by a scheduling entity, comprising: Transmit a first one or more reference signals (RS) to a user equipment (UE) on a first radio frequency band; Receive, in response to the first one or more RS on the first radio frequency band, a request from the UE to transmit a second one or more RS on a second radio frequency band, wherein the request is transmitted by the UE based on measurements of the first one or more RS on the first radio frequency band; Transmit the second one or more RS to the UE on the second radio frequency band; and Receive, in response to the second one or more RS, a beam failure recovery request message from the UE.

11. The method according to claim 10, wherein, The first radio frequency band is in the sub-6 GHz radio frequency range, and the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

12. The method according to claim 10, wherein, Receiving a request from the UE to transmit the second one or more RS on the second radio frequency band includes: receiving the request on a physical uplink control channel (PUCCH).

13. The method according to claim 10, wherein Receiving a request from the UE to transmit the second one or more RS on the second radio frequency band includes: receiving from the UE a request to transmit one or more on-demand beam failure detection (BFD) RS on the second radio frequency band.

14. An apparatus for wireless communication, comprising: A memory; And At least one processor coupled to the memory, the memory and the processor being configured to: Receive a first one or more reference signals (RS) on a first radio frequency band; Measure the first one or more RS on the first radio frequency band; Use a machine learning (ML) algorithm with the one or more measurements of the first one or more RS on the first radio frequency band as inputs to estimate one or more channel parameters of a second radio frequency band; Based on the estimated one or more channel parameters of the second radio frequency band, send a request for a second one or more RS on the second radio frequency band; And Initiate a beam failure recovery procedure for the second radio frequency band at least in part based on the second one or more RS received on the second radio frequency band.

15. The device according to claim 14, wherein, The memory and the processor are further configured to: Perform beam failure detection (BFD) for the second radio frequency band at least in part based on the one or more measurements of the first one or more RS on the first radio frequency band.

16. The device according to claim 15, wherein, The memory and the processor are further configured to: Compare the estimated one or more channel parameters of the second radio frequency band with a BFD threshold of the second radio frequency band.

17. The device according to claim 16, wherein, The memory and the processor are configured to: Detect a beam failure for the second radio frequency band when the estimated one or more channel parameters of the second radio frequency band are below the BFD threshold of the second radio frequency band by a threshold measurement instance number or more.

18. The apparatus according to claim 16, wherein, The memory and the processor are configured to: Request the second one or more RS on the second radio frequency band when the estimated one or more channel parameters of the second radio frequency band are within a predefined margin of the BFD threshold of the second radio frequency band. Measure the second one or more RSs on the second radio frequency band; And Compare one or more measurements of the second one or more RSs on the second radio frequency band with the BFD threshold of the second radio frequency band.

19. The apparatus according to claim 18, wherein, The memory and the processor are configured to: request a scheduling entity to transmit one or more on-demand beam failure detection (BFD) RSs on the second radio frequency band.

20. The apparatus according to claim 15, wherein, The one or more measurements on the first radio frequency band include one or more reference signal received power (RSRP) measurements, one or more positioning measurements, one or more raw channel measurements, one or more channel impulse response (CIR) measurements, one or more angle of departure (AoD) measurements, one or more delay measurements, or a combination thereof.

21. The device according to claim 16, wherein, The one or more estimated channel parameters include one or more estimated reference signal received power (RSRP) values.

22. The apparatus according to claim 14, wherein, The first radio frequency band is in the sub-6 GHz radio frequency range, while the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

23. An apparatus for wireless communication, comprising: A memory; And At least one processor coupled to the memory, the memory and the processor being configured to: Transmit a first one or more reference signals (RSs) to a user equipment (UE) on a first radio frequency band; In response to the first one or more RSs on the first radio frequency band, receive from the UE a request to transmit a second one or more RSs on a second radio frequency band, wherein the request is transmitted by the UE based on measurements of the first one or more RSs on the first radio frequency band; Transmit the second one or more RSs to the UE on the second radio frequency band; and In response to the second one or more RSs, receive a beam failure recovery request message from the UE.

24. The device according to claim 23, wherein, The first radio frequency band is in the sub-6 GHz radio frequency range, while the second radio frequency band is in the millimeter wave (mmW) radio frequency range.

25. The device according to claim 23, wherein, The memory and the processor are configured to: receive the request on a physical uplink control channel (PUCCH).

26. The device according to claim 23, wherein, The memory and the processor are configured to: receive from the UE a request to transmit one or more on-demand beam failure detection (BFD) RSs on the second radio frequency band.

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