Beam recovery without beam correspondence

Abstract

A technique for beam failure recovery in a wireless communication system is disclosed. In one aspect, a user equipment (UE) detects a beam failure of a first downlink beam received at the UE from a base station, sends a random access channel (RACH) request to the base station identifying one or more candidate downlink beams received at the UE from the base station, and receives a response to the RACH request from the base station in response to sending the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Provisional Application No. 62 / 750,225, filed on October 24, 2018, entitled “BEAM RECOVERY WITHOUT BEAMCORRESPONDENCE,” and U.S. Non-Provisional Application No. 16 / 598,946, filed on October 10, 2019, entitled “BEAM RECOVERY WITHOUT BEAM CORRESPONDENCE,” both of which are assigned to the present assignee and are expressly incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates generally to wireless communication systems, and more particularly to beam recovery without beam correspondence in a wireless communication system supporting primary cell (PCell) and secondary cell (SCell) carrier aggregation operations. Background Art

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcasting. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, or even global level. An exemplary telecommunication standard is the fifth generation (5G) telecommunication standard known as "New Radio" (NR). NR is part of a continuous mobile broadband evolution released by the Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with the Internet of Things (IoT)) and other requirements. Some aspects of 5G NR may be based on the fourth generation (4G) telecommunication standard known as the Long Term Evolution (LTE) standard. There is a need for further improvements in NR technology. These improvements may also be applicable to other multiple access technologies and telecommunication standards that employ these technologies. Summary of the invention

[0006] A simplified overview of one or more aspects disclosed herein is given below. Likewise, the following overview should not be considered an exhaustive overview of all contemplated aspects, nor should the following overview be considered to identify important or critical elements related to all contemplated aspects or to define the scope associated with any particular aspect. Therefore, the sole purpose of the following overview is to give some concepts of one or more aspects related to the mechanisms disclosed herein in a simplified form before the detailed embodiments given below.

[0007] On the one hand, a beam failure recovery method in a wireless communication system includes: detecting, by a user equipment (UE), a beam failure of a first downlink beam received at the UE from a base station, sending, by the UE to the base station, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station, and receiving, at the UE from the base station, a response to the RACH request in response to sending the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0008] In one aspect, a beam failure recovery method in a wireless communication system includes: receiving, at a base station, from a UE a RACH request identifying one or more candidate downlink beams received at the UE from the base station, and sending, in response to receiving the RACH request, from the base station to the UE a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace a first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0009] In one aspect, an apparatus for beam failure recovery in a wireless communication system includes: at least one processor of a UE, configured to: detect a beam failure of a first downlink beam received at the UE from a base station, send a RACH request to the base station identifying one or more candidate downlink beams received at the UE from the base station, and receive a response to the RACH request from the base station in response to sending the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0010] In one aspect, an apparatus for beam failure recovery in a wireless communication system includes: at least one processor of a base station serving a UE, configured to: receive a RACH request from the UE to identify one or more candidate downlink beams received at the UE from the base station, and in response to receiving the RACH request, send a response to the RACH request to the UE, the response identifying a second downlink beam from the one or more candidate downlink beams to replace a first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0011] In one aspect, an apparatus for beam failure recovery in a wireless communication system includes: a component for detecting, by a UE, a beam failure of a first downlink beam received at the UE from a base station, a component for sending, by the UE to the base station, a RACH request identifying one or more candidate downlink beams received at the UE from the base station, and a component for receiving, at the UE from the base station, a response to the RACH request in response to sending the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0012] In one aspect, an apparatus for beam failure recovery in a wireless communication system includes: a component for receiving, at a base station, a RACH request from a UE that identifies one or more candidate downlink beams received at the UE from the base station, and a component for sending, in response to receiving the RACH request, a response to the RACH request from the base station to the UE, the response identifying a second downlink beam from the one or more candidate downlink beams to replace a first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0013] In one aspect, a non-transitory computer-readable medium storing computer-executable instructions includes computer-executable instructions including: at least one instruction instructing a UE to detect a beam failure of a first downlink beam received at the UE from a base station, at least one instruction instructing the UE to send a RACH request to the base station identifying one or more candidate downlink beams received at the UE from the base station, and at least one instruction instructing the UE to receive a response to the RACH request from the base station in response to sending the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0014] In one aspect, a non-transitory computer-readable medium storing computer-executable instructions includes computer-executable instructions including: at least one instruction instructing a base station to receive, from a UE, a RACH request identifying one or more candidate downlink beams received at the UE from the base station, and at least one instruction instructing the base station to send, to the UE, in response to receiving the RACH request, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace a first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0015] Other objects and advantages associated with the various aspects disclosed herein will be apparent to those skilled in the art based on the drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are presented to aid in describing various aspects of the disclosure and are provided solely for illustration of these aspects and not limitation thereof.

[0017] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network according to aspects of the present disclosure.

[0018] Figure 2A and Figure 2B Exemplary wireless network structures according to various aspects of the present disclosure are shown.

[0019] Figure 3 is a diagram illustrating an example of a base station and a UE in an access network according to aspects of the present disclosure.

[0020] 4A to 4D is a diagram illustrating an example of a frame structure and channels within the frame structure according to aspects of the present disclosure.

[0021] Figure 5 is a diagram illustrating a base station in communication with a UE according to aspects of the present disclosure.

[0022] Figure 6 is a diagram of an exemplary RACH-based SpCell beam failure recovery process according to various aspects of the present disclosure.

[0023] Figure 7 is a diagram of an exemplary SCell beam recovery process with PCell assistance and without assuming any beam correspondence in accordance with aspects of the present disclosure.

[0024] Fig. 8A and Figure 8B is a diagram illustrating an example of a first solution according to aspects of the present disclosure.

[0025] Fig. 9A and Fig. 9B is a diagram illustrating an example of a second solution according to aspects of the present disclosure.

[0026] Fig. 10A and Fig. 10B is a diagram illustrating an example of a third solution according to aspects of the present disclosure.

[0027] Fig.11 and Fig.12 An exemplary method of beam failure recovery in a wireless communication system according to aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0028] Various aspects of the present disclosure are provided in the following description and related drawings, which relate to various examples provided for illustrative purposes. Alternative aspects may be designed without departing from the scope of the present disclosure. In addition, well-known aspects of the present disclosure may not be described in detail or may be omitted to avoid obscuring more relevant details.

[0029] The disclosure set forth below in conjunction with the accompanying drawings is intended to be a description of various configurations and is not intended to represent a unique configuration in which the concepts described herein can be practiced. In order to provide a thorough understanding of the various concepts, the disclosure includes specific details. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring these concepts.

[0030] Those skilled in the art will appreciate that any of a variety of different technologies and techniques may be used to represent the information and signals described below. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the following specification may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof, depending in part on the specific application, in part on the desired design, in part on the corresponding technology, etc.

[0031] In addition, many aspects are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It should be understood that the various actions described herein may be performed by specific circuits (e.g., application specific integrated circuits (ASICs)), by program instructions executed by one or more processors, or by a combination of both. In addition, for each aspect described herein, the corresponding form of any such aspect may be implemented, for example, as "configured logic" that performs the described actions.

[0032] As used herein, unless otherwise noted, the terms "user equipment" (UE) and "base station" are not intended to be specific or otherwise limited to any specific radio access technology (RAT). Generally speaking, a UE can be any wireless communication device (e.g., a mobile phone, a router, a tablet, a laptop, a tracking device, a wearable device (e.g., a smart watch, glasses, augmented reality (AR) / virtual reality (VR) headsets, etc.), a vehicle (e.g., a car, a motorcycle, a bicycle, etc.), an Internet of Things (IoT) device, etc.) used by a user to communicate over a wireless communication network. A UE can be mobile or can be stationary (e.g., at certain times) and can communicate with a radio access network (RAN). As used herein, the term "UE" can be interchangeably referred to as an "access terminal" or "AT", "client device", "wireless device", "subscriber equipment", "subscriber terminal", "subscriber station", "user terminal" or UT, "mobile terminal", "mobile station" or variants thereof. Typically, a UE can communicate with a core network via a RAN, and through the core network, the UE can connect to external networks such as the Internet and to other UEs. Of course, the UE may also use other mechanisms to connect to the core network and / or the Internet, such as through a wired access network, a wireless local area network (WLAN) network (eg, based on Institute of Electrical and Electronics Engineers (IEEE) 802.11, etc.), and so on.

[0033] A base station may operate according to one of several RATs for communicating with a UE according to the network in which it is deployed, and may be alternatively referred to as an access point (AP), a network node, a NodeB, an evolved NodeB (eNB), a new radio (NR) NodeB (also referred to as a gNB or gNodeB), etc. In addition, in some systems, a base station may provide pure edge node signaling functions, while in other systems, a base station may provide additional control and / or network management functions. The communication link through which a UE may send a signal to a base station is referred to as an uplink (UL) channel (e.g., a reverse traffic channel, a reverse control channel, an access channel, etc.). The communication link through which a base station may send a signal to a UE is referred to as a downlink (DL) or forward link channel (e.g., a paging channel, a control channel, a broadcast channel, a forward traffic channel, etc.). As used herein, the term traffic channel (TCH) may refer to a UL / reverse or DL / forward traffic channel.

[0034] The term "base station" may refer to a single physical transmission point or to multiple physical transmission points that may or may not be co-located. For example, where the term "base station" refers to a single physical transmission point, the physical transmission point may be an antenna of the base station corresponding to a cell of the base station. Where the term "base station" refers to multiple co-located physical transmission points, the physical transmission point may be an array of antennas of the base station (e.g., as in a multiple-input multiple-output (MIMO) system, or where the base station employs beamforming). Where the term "base station" refers to multiple non-co-located physical transmission points, the physical transmission point may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transmission medium) or a remote radio head (RRH) (a remote base station connected to a serving base station). Alternatively, the non-co-located physical transmission point may be a serving base station that receives measurement reports from the UE and a neighboring base station of a reference radio frequency (RF) signal that the UE is measuring.

[0035] According to various aspects, Figure 1 An exemplary wireless communication system 100 is shown. The wireless communication system 100, which may also be referred to as a wireless wide area network (WWAN), may include various base stations 102 and various UEs 104. In an aspect, the base stations 102 may include eNBs where the wireless communication system 100 corresponds to an LTE network, or gNBs where the wireless communication system 100 corresponds to a 5G network, or a combination of both.

[0036] The base stations 102 may collectively form a RAN and interface with a core network 170 (e.g., an evolved packet core (EPC) or a next generation core (NGC)) via a backhaul link 122, and through the core network 170 to one or more location servers 172. The base stations 102 may perform, among other functions, functions related to one or more of: transmission of user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, RAN sharing, multimedia broadcast multicast service (MBMS), user and device tracking, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (e.g., via EPC / NGC) over the backhaul link 122, which may be wired or wireless.

[0037] Base stations 102 may communicate wirelessly with UEs 104. Each of base stations 102 may provide communication coverage for a corresponding geographic coverage area 110. In one aspect, base stations 102 in each geographic coverage area 110 may support one or more cells. A "cell" is a logical communication entity used to communicate with a base station (e.g., on a certain frequency resource, referred to as a carrier frequency, component carrier, carrier, frequency band, etc.), and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) used to distinguish cells operating via the same or different carrier frequencies. In some cases, different cells may be configured according to different protocol types (e.g., machine type communication (MTC), narrowband IoT (NB-IoT), enhanced mobile broadband (eMBB)) or other) that may provide access to different types of UEs. In some cases, the term "cell" may also refer to a geographic coverage area (e.g., a sector) of a base station as long as a carrier frequency can be detected and used for communication within certain portions of the geographic coverage area 110.

[0038] In cellular networks, "macro cell" base stations provide connectivity and coverage for a large number of users within a certain geographic area. Macro network deployments are carefully planned, designed, and implemented to provide good coverage within that geographic area. However, even such careful planning cannot fully accommodate channel characteristics, such as fading, multipath, shadowing, etc., especially in indoor environments. Therefore, in order to improve indoor or other specific geographic coverage, such as for residential homes and office buildings, additional "small cell" base stations have begun to be deployed to supplement the coverage of conventional macro networks. Small cell base stations can also provide incremental capacity growth, a richer user experience, etc. Small cell base stations are typically low-power base stations, which may include or otherwise be referred to as femtocells, picocells, microcells, etc.

[0039] Although the geographic coverage areas 110 of neighboring macrocell base stations 102 may partially overlap (e.g., in a handoff region), some geographic coverage areas 110 may be substantially overlapped by a larger geographic coverage area 110. For example, a small cell base station 102' may have a geographic coverage area 110' that substantially overlaps with the geographic coverage areas 110 of one or more macrocell base stations 102. A network that includes both small cell base stations and macrocell base stations may be referred to as a heterogeneous network. A heterogeneous network may also include a home eNB (HeNB) that may provide services to a restricted group called a closed subscriber group (CSG).

[0040] The communication link 120 between the base station 102 and the UE 104 may include UL (also referred to as reverse link) transmissions from the UE 104 to the base station 102 and / or DL ​​(also referred to as forward link) transmissions from the base station 102 to the UE 104. The communication link 120 may use MIMO antenna techniques including spatial multiplexing, beamforming, and / or transmit diversity. The communication link 120 may be over one or more carrier frequencies. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​compared to UL).

[0041] The wireless communication system 100 may also include a wireless local area network (WLAN) access point (AP) 150 that communicates with a WLAN station (STA) 152 via a communication link 154 in an unlicensed spectrum (e.g., 5 GHz). When communicating in the unlicensed spectrum, the WLAN STA 152 and / or the WLAN AP 150 may perform a clear channel assessment (CCA) to determine whether the channel is available before communicating.

[0042] The small cell base station 102' can operate in licensed and / or unlicensed spectrum. When operating in the unlicensed spectrum, the small cell base station 102' can adopt LTE or 5G technology and use the same 5GHz unlicensed spectrum used by the WLAN AP 150. The small cell base station 102' adopting LTE / 5G in the unlicensed spectrum can increase the coverage of the access network and / or increase its capacity. LTE in the unlicensed spectrum can be referred to as LTE Unlicensed (LTE-U), Licensed Assisted Access (LAA), or MulteFire.

[0043] The wireless communication system 100 may also include a millimeter wave (mmW) base station 180, which can communicate with UE 182 at millimeter wave frequencies and / or near millimeter wave frequencies. Extremely high frequency (EHF) is part of RF in the electromagnetic spectrum. EHF ranges from 30GHz to 300GHz, with wavelengths between 1 mm and 10 mm. Radio waves in this band may be referred to as millimeter waves. Near mmW may extend down to 3GHz frequencies with a wavelength of 100 mm. The super high frequency (SHF) band extends between 3GHz and 30GHz, also known as centimeter waves. Communications using millimeter wave / near millimeter wave radio frequency bands have higher path losses and relatively short ranges. The mmW base station 180 and UE 182 can utilize beamforming (transmitting and / or receiving) on ​​the mmW communication link 184 to compensate for the extremely high path losses and short distances. In addition, it should be understood that in an alternative configuration, one or more base stations 102 may also use mmW or near mmW and beamforming to transmit. Therefore, it should be understood that the foregoing diagrams are merely examples, and should not be construed as limiting the various aspects disclosed herein.

[0044] Transmit beamforming is a technique for focusing an RF signal in a specific direction. Traditionally, when a network node (e.g., a base station) broadcasts an RF signal, it broadcasts the signal in all directions (omnidirectional). With transmit beamforming, the network node determines the location of a given target device (e.g., a UE) (relative to the transmitting network node) and projects a stronger downlink RF signal in that specific direction, thereby providing a faster (in terms of data rate) and stronger RF signal to the receiving (multiple) devices. In order to change the directionality of the RF signal when transmitting, the network node can control the phase and relative amplitude of the RF signal at each of the one or more transmitters that broadcast the RF signal. For example, the network node can use an antenna array (referred to as a "phased array" or "antenna array") that produces a beam of RF waves that can be "steered" to point in different directions without actually moving the antenna. Specifically, the RF current from the transmitter is fed to each antenna in the correct phase relationship, so that the radio waves from the separate antennas are added together in the desired direction to increase the radiation, while canceling in the undesired direction to suppress the radiation.

[0045] In receive beamforming, the receiver uses receive beams to amplify RF signals detected on a given channel. For example, the receiver may increase the gain setting and / or adjust the phase setting of the antenna array in a particular direction to amplify the RF signals received from that direction (e.g., increase its gain level). Therefore, when it is said that the receiver forms a beam in a certain direction, it means that the beam gain in that direction is high relative to the beam gain along other directions, or that the beam gain in that direction is the highest compared to the beam gain in that direction of all other receive beams available to the receiver. This results in the RF signal received from that direction having a stronger received signal strength (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), signal to interference plus noise ratio (SINR), etc.).

[0046] The transmit beams can be quasi-colocated, which means that they appear to the receiver to have the same parameters, regardless of whether the transmit antennas themselves are physically colocated. In NR, there are four types of quasi-colocated (QCL) relationships. Specifically, a given type of QCL relationship means that certain parameters about the second reference RF signal on the second beam can be derived from information about the source reference RF signal on the source beam. Therefore, if the source reference RF signal is QCL type A, the receiver can use the source reference RF signal to estimate the Doppler shift, Doppler spread, average delay, and delay spread of the second reference RF signal sent on the same channel. If the source reference RF signal is QCL type B, the receiver can use the source reference RF signal to estimate the Doppler shift and Doppler spread of the second reference RF signal sent on the same channel. If the source reference RF signal is QCL type C, the receiver can use the source reference RF signal to estimate the Doppler shift and average delay of the second reference RF signal sent on the same channel. If the source reference RF signal is QCL type D, the receiver can use the source reference RF signal to estimate the spatial reception parameters of the second reference RF signal sent on the same channel.

[0047] In NR, the spectrum in which wireless nodes (e.g., base stations 102 / 180, UEs 104 / 182) operate is divided into multiple frequency ranges: FR1 (from 450 to 6000 MHz), FR2 (from 24250 to 52600 MHz), FR3 (above 52600 MHz), and FR4 (between FR1 and FR2). In a multi-carrier system such as 5G, one of the carrier frequencies is called the "primary carrier" or "anchor carrier" or "primary serving cell" or "PCell", and the remaining carrier frequencies are called "secondary carriers" or "secondary serving cells" or "Scells".

[0048] For example, the base station 102 / UE 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz) bandwidth per component carrier allocated in carrier aggregation up to a total of Yx MHz (x component carriers) for transmission in each direction. The component carriers may or may not be spectrally adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​compared to UL).

[0049] In carrier aggregation, the anchor carrier is a carrier operating on the primary frequency (e.g., FR1) used by the UE 104 / 182 and the cell in which the UE 104 / 182 performs an initial radio resource control (RRC) connection establishment procedure or initiates an RRC connection reestablishment procedure. The primary carrier carries all common and UE-specific control channels. The secondary carrier is a carrier operating on a second frequency (e.g., FR2) that can be configured once an RRC connection is established between the UE 104 and the anchor carrier, and can be used to provide additional radio resources. The secondary carrier may contain only necessary signaling information and signals, for example, since both the primary uplink and downlink carriers are typically UE-specific, there may be no UE-specific signaling information and signals in the secondary carrier. This means that different UEs 104 / 182 in a cell may have different downlink primary carriers. The same is true for the uplink primary carrier. The network is able to change the primary carrier of any UE 104 / 182 at any time. This is done, for example, to balance the load on different carriers. Because a "serving cell" (whether PCell or SCell) corresponds to a carrier frequency / component carrier on which some base stations are communicating, the terms "cell", "serving cell", "component carrier", "carrier frequency", etc. may be used interchangeably.

[0050] For example, still refer to Figure 1 , the base station 102 / UE 104 can use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz) bandwidth per carrier allocated in a carrier aggregation up to a total of Yx MHz (x component carriers) for transmission in each direction. The component carriers may be adjacent to each other or not adjacent to each other in the spectrum. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​compared to UL). One of the component carriers utilized by the macrocell base station 102 may be an anchor carrier (or "PCell"), while the other component carriers utilized by the macrocell base station 102 and / or the mmW base station 180 may be, for example, an auxiliary carrier ("Scell"). The simultaneous transmission and / or reception of multiple carriers enables the UE 104 / 182 to significantly increase its data transmission and / or reception rate. For example, two 20 MHz aggregated carriers in a multi-carrier system will theoretically result in a doubling of the data rate (i.e., 40 MHz) compared to the rate achieved by a single 20 MHz carrier.

[0051] In order to operate on multiple carrier frequencies, the base station 102 / UE 104 is equipped with multiple receivers and / or transmitters. For example, the UE 104 may have two receivers, namely receiver 1 and receiver 2, where receiver 1 is a multi-band receiver that can be tuned to either the X band or the Y band (i.e., carrier frequencies), while receiver 2 is a single-band receiver that can only be tuned to the Z band. In this example, if the UE 104 is served in band X, band X will be referred to as the PCell or active carrier frequency, and receiver 1 will need to tune from band X to band Y (SCell) in order to measure band Y (and vice versa). In contrast, regardless of whether the UE 104 is served in band X or band Y, due to the separate receiver 2, the UE 104 can measure band Z without interrupting service on band X or band Y.

[0052] The wireless communication system 100 may also include one or more UEs, such as UE 190, that are indirectly connected to one or more communication networks via one or more device-to-device (D2D) peer-to-peer (P2P) links. Figure 1 In the example of , UE 190 has a D2D P2P link 192, where one of UE 104 is connected to one of base stations 102 (e.g., through which UE 190 can indirectly obtain cellular connectivity), and has a D2D P2P link 194, where WLAN STA 152 is connected to WLAN AP 150 (through which UE 190 can indirectly obtain WLAN-based Internet connectivity). In an aspect, the D2D communication link 192 can use one or more side link channels, such as a physical side link broadcast channel (PSBCH), a physical side link discovery channel (PSDCH), a physical side link shared channel (PSSCH), and a physical side link control channel (PSCCH). D2D communication can be performed through various wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, LTE Direct (LTE-D), WiFi Direct (WiFi-D), Bluetooth, ZigBee, Z-Wave, Wi-Fi based on IEEE 802.11 standards, LTE, or NR.

[0053] The wireless communication system 100 may also include a UE 164 that may communicate with the macrocell base station 102 via a communication link 120 and / or communicate with the mmW base station 180 via a mmW communication link 184. For example, the macrocell base station 102 may support a PCell and one or more SCells for the UE 164, and the mmW base station 180 may support one or more SCells for the UE 164. In one aspect, the UE 164 may include a beam failure recovery (BFR) manager 166 that may enable the UE 164 to perform UE operations described herein, such as, for example, with reference to Figure 6 , Figure 7 , Fig. 8A , Figure 8B , Fig. 9A , Fig. 9B , Fig. 10A , Fig. 10B , Fig.11 and Fig.12 Please note that although Figure 1 Only one UE is shown as having a BFR manager 166, but Figure 1 Any UE in the may be configured to perform the UE operations described herein.

[0054] According to various aspects, Figure 2A An exemplary wireless network structure 200 is shown. For example, NGC 210 (also referred to as "5GC") can be functionally viewed as a control plane function 214 (e.g., UE registration, authentication, network access, gateway selection, etc.) and a user plane function 212 (e.g., UE gateway function, access to data networks, IP routing, etc.), which can operate in conjunction to form a core network. A user plane interface (NG-U) 213 and a control plane interface (NG-C) 215 connect the gNB 222 to the NGC 210, specifically to the control plane function 214 and the user plane function 212. In another configuration, the eNB 224 can also be connected to the NGC 210 via the NG-C 215 to the control plane function 214 and the NG-U 213 to the user plane function 212. In addition, the eNB 224 can communicate directly with the gNB 222 via the backhaul connection 223. In some configurations, the new RAN 220 may have only one or more gNBs 222, while other configurations include one or more of both eNBs 224 and gNBs 222. Either the gNB 222 or the eNB 224 may communicate with the UE 204 (e.g., Figure 1204). Another optional aspect may include a location server 230 (which may correspond to location server 172), which may communicate with NGC 210 to provide location assistance for UE 204. Location server 230 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules distributed across multiple physical servers, etc.), or alternatively, may each correspond to a single server. Location server 230 may be configured to support one or more location services for UE 204, which may be connected to location server 230 via the core network, NGC 210, and / or via the Internet (not shown). In addition, location server 230 may be integrated into a component of the core network, or alternatively may be external to the core network.

[0055] According to various aspects, Figure 2B Another exemplary wireless network structure 250 is shown. For example, the NGC 260 (also referred to as "5GC") can be functionally viewed as a control plane function provided by an access and mobility management function (AMF) / user plane function (UPF) 264 and a user plane function provided by a session management function (SMF) 262, which can operate in conjunction to form a core network (i.e., NGC 260). The user plane interface 263 and the control plane interface 265 connect the eNB 224 to the NGC 260, and specifically to the SMF 262 and the AMF / UPF 264, respectively. In another configuration, the gNB 222 can also be connected to the NGC 260 via a control plane interface 265 to the AMF / UPF 264 and a user plane interface 263 to the SMF 262. In addition, the eNB 224 can communicate directly with the gNB 222 over a backhaul connection 223 with or without gNB direct connectivity to the NGC 260. In some configurations, the new RAN 220 may have only one or more gNBs 222, while other configurations include one or more of both eNBs 224 and gNBs 222. Either the gNB 222 or the eNB 224 may communicate with the UE 204 (e.g., Figure 1 The base station of the new RAN 220 communicates with the AMF side of the AMF / UPF 264 through the N2 interface, and communicates with the UPF side of the AMF / UPF 264 through the N3 interface.

[0056] The functions of AMF include registration management, connection management, reachability management, mobility management, lawful interception, transmission of session management (SM) messages between UE 204 and SMF 262, transparent proxy service for routing SM messages, access authentication and access authorization, transmission of short message service (SMS) messages between UE 204 and short message service function (SMSF) (not shown), and security anchor function (SEAF). AMF also interacts with authentication server function (AUSF) (not shown) and UE 204, and receives intermediate keys established as a result of the UE 204 authentication process. In the case of authentication based on UMTS (Universal Mobile Telecommunications System) User Identity Module (USIM), AMF retrieves security materials from AUSF. The functions of AMF also include security context management (SCM). SCM receives keys from SEAF, which uses the keys to derive access network-specific keys. The functions of AMF also include location service management for regulatory services, transmission of location service messages between UE 204 and location management function (LMF) 270 (which may correspond to location server 172) and between new RAN 220 and LMF 270, allocation of Evolved Packet System (EPS) bearer identifiers for interworking with EPS, and notification of mobility events of UE 204. In addition, AMF also supports functions for non-3rd Generation Partnership Project (3GPP) access networks.

[0057] The functions of the UPF include: acting as an anchor point for intra-RAT / inter-RAT mobility (when applicable), acting as an external protocol data unit (PDU) session point for interconnection with the data network (not shown), providing packet routing and forwarding, packet inspection, user plane policy rule enforcement (e.g., gating, redirection, traffic steering), lawful interception (user plane collection), traffic usage reporting, user plane quality of service (QoS) processing (e.g., UL / DL rate enforcement, reflective QoS marking in DL), UL traffic verification (service data flow (SDF) to QoS flow mapping), transport level packet marking in UL and DL, DL packet buffering and DL data notification triggering, and sending and forwarding of one or more "end markers" to the source RAN node.

[0058] The functions of SMF 262 include session management, UE Internet Protocol (IP) address allocation and management, selection and control of user plane functions, configuring traffic steering at UPF to route traffic to the correct destination, controlling partial policy enforcement and QoS, and downlink data notification. The interface through which SMF 262 communicates with the AMF side of AMF / UPF 264 is called the N11 interface.

[0059] Another optional aspect may include LMF 270, which may communicate with NGC 260 to provide location assistance for UE 204. LMF 270 may be implemented as multiple separate servers (e.g., physically separate servers, different software modules on a single server, different software modules distributed across multiple physical servers, etc.), or alternatively, each may correspond to a single server. LMF 270 may be configured to support one or more location services for UE 204, which may be connected to LMF 270 via a core network, NGC 260, and / or via the Internet (not shown).

[0060] On the one hand, Figure 2A and Figure 2B The illustrated UE 204 may be configured to perform UE operations as described herein. For example, the UE 204 may be configured to detect a beam failure of a first downlink beam received at the UE 204 from a base station (e.g., gNB 222), send a RACH request to the base station identifying one or more candidate downlink beams received at the UE 204 from the base station, and receive a response to the RACH request from the base station. The response may identify a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam, and may also indicate a type of beam recovery associated with the second downlink beam for which the base station has reserved downlink beam resources.

[0061] On the one hand, Figure 2A and Figure 2B The illustrated gNB 222 may be configured to perform base station operations as described herein. For example, the gNB 222 may be configured to receive a RACH request from a UE (e.g., UE 204) identifying one or more candidate downlink beams received at the UE from the gNB 222, and to send a response to the RACH request to the UE. The response may identify a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam, and may also indicate a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0062] According to various aspects, Figure 3 An exemplary base station 302 (e.g., an eNB, a gNB, a small cell AP, a WLAN AP, etc.) is shown communicating with an exemplary UE 304 in a wireless network according to aspects of the present disclosure. The base station 302 may correspond to any base station described herein, such as Figure 1 Base stations 102, 150 and 180 or Figure 2A and Figure 2B UE 304 may correspond to any UE described herein, such as Figure 1 UE 104, 152, 182, 190 or Figure 2A and Figure 2B UE 204 in. In the DL, IP packets from the core network (NGC 210 / EPC 260) may be provided to the controller / processor 375. The controller / processor 375 implements functions for a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides the following functions: RRC layer functions associated with broadcasting of system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-RAT mobility, and measurement configuration for UE measurement reporting; PDCP layer functions related to header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with transmission of upper layer packet data units (PDUs), error correction through automatic repeat request (ARQ), concatenation, segmentation and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with mapping between logical channels and transport channels, scheduling information reporting, error correction, priority handling, and logical channel prioritization.

[0063] The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functions associated with various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection on the transmission channel, forward error correction (FEC) encoding / decoding of the transmission channel, interleaving, rate matching, mapping to physical channels, modulation / demodulation of physical channels, and MIMO antenna processing. The TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols can then be split into parallel streams. Each stream can then be mapped to an orthogonal frequency division multiplexing (OFDM) subcarrier, multiplexed with a reference signal (e.g., pilot) in the time domain and / or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine coding and modulation schemes, as well as for spatial processing. Channel estimates may be derived from channel condition feedback and / or reference signals sent by the UE 304. Each spatial stream may then be provided to one or more different antennas 320 via a separate transmitter 318a. Each transmitter 318a may modulate an RF carrier with a corresponding spatial stream for transmission.

[0064] At the UE 304, each receiver 354a receives a signal through its corresponding antenna 352. Each receiver 354a recovers the information modulated onto the RF carrier and provides the information to the RX processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functions associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial streams sent to the UE 304. If multiple spatial streams are sent to the UE 304, they can be combined into a single OFDM symbol stream by the RX processor 356. The RX processor 356 then converts the OFDM symbol stream from the time domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. By determining the most likely signal constellation point sent by the base station 302, the symbols on each subcarrier and the reference signal are recovered and demodulated. These soft decisions can be based on the channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally sent on the physical channel by the base station 302. The data and control signals are then provided to the controller / processor 359, which implements layer 3 and layer 2 functions.

[0065] The controller / processor 359 may be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport channels and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the core network. The controller / processor 359 is also responsible for error detection.

[0066] Similar to the functions described in conjunction with the DL transmission of the base station 302, the controller / processor 359 provides the following functions: RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with transmission of upper layer PDUs, error correction through ARQ, concatenation, segmentation and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs into transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), priority handling, and logical channel prioritization.

[0067] Channel estimates derived by the channel estimator 358 from a reference signal or feedback sent by the base station 302 may be used by the TX processor 368 to select appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antennas 352 via separate transmitters 354 b. Each transmitter 354 b may modulate an RF carrier with a corresponding spatial stream for transmission. In one aspect, the transmitter 354 b and the receiver 354 a may be one or more transceivers, one or more separate transmitters, one or more separate receivers, or any combination thereof.

[0068] UL transmissions are processed at the base station 302 in a manner similar to that described in conjunction with the receiver functionality at the UE 304. Each receiver 318b receives a signal through its respective antenna 320. Each receiver 318b recovers information modulated onto an RF carrier and provides the information to the RX processor 370. In an aspect, the transmitter 318a and the receiver 318b may be one or more transceivers, one or more separate transmitters, one or more separate receivers, or any combination thereof.

[0069] The controller / processor 375 may be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover IP packets from the UE 304. The IP packets from the controller / processor 375 may be provided to the core network. The controller / processor 375 is also responsible for error detection.

[0070] On the one hand, Figure 3 The UE 304 shown in FIG. 3 may be configured to perform UE operations described herein. For example, the receiver(s) 354a may be configured to detect a beam failure of a first downlink beam received at the UE 304 from a base station (e.g., the base station 302), the transmitter(s) 354b may be configured to send a RACH request to the base station identifying one or more candidate downlink beams received at the UE 304 from the base station, and the receiver(s) 354a may be configured to receive a response to the RACH request from the base station. The response may identify a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam, and may also indicate a type of beam recovery associated with the second downlink beam for which the base station has reserved downlink beam resources.

[0071] On the one hand, Figure 2A and Figure 2B The illustrated base station 302 may be configured to perform base station operations as described herein. For example, the receiver(s) 318b may be configured to receive a RACH request from a UE (e.g., UE 304) identifying one or more candidate downlink beams received at the UE from the base station 302, and the transmitter(s) 318a may be configured to send a response to the RACH request to the UE. The response may identify a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam, and may also indicate a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved.

[0072] Figure 4A is a diagram 400 showing an example of a DL frame structure in accordance with aspects of the present disclosure. Figure 4B is a diagram 430 showing an example of channels within a DL frame structure in accordance with aspects of the present disclosure. Figure 4C is a diagram 450 showing an example of a UL frame structure in accordance with aspects of the present disclosure. Figure 4D480 is a diagram showing an example of channels within a UL frame structure according to aspects of the present disclosure. Other wireless communication technologies may have different frame structures and / or different channels. In the time domain, a frame (10 milliseconds) may be divided into 10 equally sized subframes (1 millisecond each). Each subframe may include two consecutive time slots (0.5 milliseconds each).

[0073] A resource grid can be used to represent two time slots, each of which includes one or more time-concurrent resource blocks (RBs) (also called physical RBs (PRBs)) in the frequency domain. The resource grid is further divided into multiple resource elements (REs). An RE may correspond to one symbol length in the time domain and one subcarrier in the frequency domain. For a normal cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols in the time domain (for DL, OFDM symbols; for UL, SC-FDMA symbols), for a total of 84 REs. For an extended cyclic prefix, an RB may contain 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

[0074] like Figure 4A As shown, some REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. DL-RS can include cell-specific reference signals (CRS) (sometimes also called "common reference signals"), UE-specific reference signals (UE-RS), and channel state information reference signals (CSI-RS). Figure 4A CRS for antenna ports 0, 1, 2 and 3 (denoted as R0, R1, R2 and R3 respectively), UE-RS for antenna port 5 (denoted as R5), and CSI-RS for antenna port 15 (denoted as R) are shown.

[0075] Figure 4B An example of various channels within a DL subframe of a frame is shown. The Physical Control Format Indicator Channel (PCFICH) is within symbol 0 of slot 0 and carries a Control Format Indicator (CFI) indicating whether the Physical Downlink Control Channel (PDCCH) occupies 1, 2, or 3 symbols ( Figure 4B A PDCCH occupying 3 symbols is shown. The PDCCH carries DL control information (DCI) within one or more control channel elements (CCEs), each CCE comprising nine RE groups (REGs), each REG comprising four consecutive REs in an OFDM symbol. A UE may be configured with a UE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs ( Figure 4BTwo RB pairs are shown, with each subset comprising one RB pair). A physical HARQ indicator channel (PHICH) is also within symbol 0 of slot 0 and carries a HARQ indicator (HI) that indicates HARQ acknowledgement (ACK) / negative ACK (NACK) feedback based on a physical uplink shared channel (PUSCH). A primary synchronization channel (PSCH) may be within symbol 6 of slot 0 within subframes 0 and 5 of a frame. The PSCH carries a primary synchronization signal (PSS), which is used by the UE to determine subframe / symbol timing and a physical layer identification. A secondary synchronization channel (SSCH) may be within symbol 5 of slot 0 within subframes 0 and 5 of a frame. The SSCH carries a secondary synchronization signal (SSS), which is used by the UE to determine a physical layer cell identification group number and radio frame timing. Based on the physical layer identification and the physical layer cell identification group number, the UE may determine a physical cell identifier (PCI). Based on the PCI, the UE may determine the location of the DL-RS described above. The physical broadcast channel (PBCH) carrying the master information block (MIB) can be logically grouped with the PSCH and SSCH to form a synchronization signal (SS) block. The MIB provides a number of RBs in the DL system bandwidth, PHICH configuration, and system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not sent over the PBCH (such as the system information block (SIB)), and paging messages.

[0076] like Figure 4C As shown, some REs carry a demodulation reference signal (DMRS) for channel estimation at the base station. The UE may additionally send a sounding reference signal (SRS) in the last symbol of the subframe. The SRS may have a comb structure, and the UE may send the SRS on one of the combs. The base station may use the SRS for channel quality estimation to implement frequency-based scheduling on the UL.

[0077] Figure 4D Examples of various channels within a UL subframe of a frame according to various aspects of the present disclosure are shown. A physical random access channel (PRACH) may be configured within one or more subframes within a frame based on the PRACH. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows a UE to perform initial system access and achieve UL synchronization. The physical uplink control channel (PUCCH) may be located at the edge of the UL system bandwidth. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicators (CQI), precoding matrix indicators (PMI), rank indicators (RI), and HARQ ACK / NACK feedback. The PUSCH carries data and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and / or UCI.

[0078] As described above, some wireless communication networks such as NR may employ beamforming at mmW frequencies or near mmW frequencies to increase network capacity. In addition to microwave frequencies (e.g., in the "sub-6" GHz or FR1 bands), the use of mmW frequencies may also be supported for communications, such as when carrier aggregation is used. Figure 5 5 is a diagram 500 showing a base station 502 in communication with a UE 504 in accordance with aspects of the present disclosure. In one aspect, the base station 502 and the UE 504 may correspond to any of the beamforming-capable base stations and UEs described herein, such as at Figure 1 Base station 180 and UE 182 in.

[0079] refer to Figure 5 , the base station 502 may transmit beamformed signals to the UE 504 on one or more beams 502a, 502b, 502c, 502d, 502e, 502f, 502g, 502h, each beam having a beam identifier that can be used by the base station 504 to identify the corresponding beam. In the case where the base station utilizes a single antenna array to perform beamforming toward the UE 504, the base station 502 may perform "beam scanning" by transmitting first beam 502a, then beam 502b, and so on until finally transmitting beam 502h. Alternatively, the base station 502 may transmit beams 502a-502h in a pattern, such as beam 502a, then beam 502h, then beam 502b, then beam 502g, and so on. In the case where the base station 502 uses multiple antenna arrays to perform beamforming toward the UE 504, each antenna array can perform beam scanning of a subset of the beams 502a-502h. Alternatively, each of the beams 502a-502h can correspond to a single antenna or antenna array.

[0080] UE 504 may receive beamformed signals from base station 502 on one or more receive beams 504a, 504b, 504c, 504d. Note that for simplicity, depending on which of base station 502 and UE 504 is transmitting and which is receiving, Figure 5The beams shown in represent transmit beams or receive beams. Thus, UE 504 may also transmit beamformed signals to base station 502 on one or more of beams 504a-504d, and base station 502 may receive beamformed signals from UE 504 on one or more of beams 502a-502h. Because communications at high mmW frequencies utilize directionality (e.g., communications via directional beams 502a-h and 504a-d) to compensate for higher propagation losses, base station 502 and UE 504 may need to align their transmit (and receive) beams during both initial network access and subsequent data transmission to ensure maximum gain. Base station 502 and UE 504 may determine the best beam for communicating with each other, and subsequent communications between base station 502 and UE 504 may be conducted via the selected beam.

[0081] Therefore, the base station 502 and the UE 504 may perform beam training to align the transmit and receive beams of the base station 502 and the UE 504. For example, depending on environmental conditions and other factors, the base station 502 and the UE 504 may determine that the best transmit and receive beams are 502d and 504b, respectively, or beams 502e and 504c, respectively. The direction of the best transmit beam of the base station 502 may be the same as or different from the direction of the best receive beam, and similarly, the direction of the best receive beam of the UE 504 may be the same as or different from the direction of the best transmit beam.

[0082] However, due to UE mobility / movement, beam reconfiguration at the base station 502, and / or other factors, a DL beam (e.g., including a DL control link) that may have been a preferred active beam may not be detected at the UE 504, or the signal quality may drop below a threshold, causing the UE 504 to consider it as a beam / link failure. A beam recovery process may be employed to recover from such a beam failure. A beam failure may refer to, for example, the failure to detect a strong (e.g., signal power greater than a threshold) active beam, which in some aspects may correspond to a control channel that transmits control information from the network. In some aspects, to facilitate beam failure detection, a UE (e.g., UE 504) may be pre-configured with a beam identifier (ID) of a first set of beams to be monitored (referred to as "set_q0"), a monitoring period, an RSRP threshold, etc. Recovery may be triggered when the RSRP associated with one or more monitored beams (as detected by the UE 504) is below a threshold. The recovery process may include the UE 504 identifying a new beam (corresponding to a beam ID that may be included in the second set of possible beams, referred to as "set_q1"), for example, and performing a RACH process using pre-configured time and frequency resources corresponding to the new preferred beam. The beam IDs corresponding to the beams in the second set of beams (set_q1) may be pre-configured at the UE 504 for beam failure recovery purposes. For example, the UE 504 may monitor the DL beams (based on the beam IDs and resources identified in the second set), perform measurements, and determine (e.g., based on the measurements) which of all received and measured beams may be the beam that is most suitable for reception at the UE 504 from the perspective of the UE 504.

[0083] If beam correspondence is assumed (i.e., the direction of the best receive beam used by UE 504 is also considered to be the best direction of the transmit beam used by UE 504), UE 504 can assume the same beam configuration for both reception and transmission. That is, based on the monitored DL reference signal from base station 502, UE 504 can determine its preferred UL transmit beam weight, which will be the same as the weight of the DL receive beam used to receive the DL reference signal.

[0084] In the absence of an assumed beam correspondence (e.g., deemed inappropriate in a given scenario or for other reasons), the UE 504 may not derive the UL transmit beam from the DL receive beam. Instead, separate signaling is required to select UL transmit and DL receive beam weights and for UL to DL beam pairing. The UE 504 may perform a RACH procedure (e.g., using pre-configured time and frequency resources indicated in the second beam set set_q1) to identify the UL transmit beam. Performing the RACH procedure using the pre-configured time and frequency resources may include, for example, sending a RACH preamble on one or more UL transmit beams (corresponding to the beam IDs in the second beam set set_q1) on the allocated RACH resources corresponding to the one or more beams. Based on the RACH procedure, the UE 504 may be able to determine and confirm with the base station 502 which UL direction may be the best beam direction for a UL channel (e.g., PUCCH). In this way, both the UL transmit beam and the DL receive beam may be reestablished, and beam recovery may be completed.

[0085] In certain aspects, carrier aggregation may be utilized where communications between a base station 502 and a UE 504 are supported by multiple carrier components (e.g., a PCell and one or more SCells). For example, a PCell may correspond to a microwave band and / or other relatively lower frequency band (e.g., a FR1 band or a sub-6 band) compared to a mmW band, while one or more SCells may correspond to a mmW band (e.g., a FR2 band). On the one hand, when PCell and SCell operations are supported in a communication system and there is no correspondence between UL receive and DL transmit beams, assistance from the PCell may be utilized to enhance the SCell recovery process. In other words, if a beam / link failure occurs in the SCell, assistance from the PCell may be utilized to facilitate the SCell beam recovery process. Such an approach may reduce delays and wait times associated with the beam recovery process and allow for faster recovery of failed links in the SCell.

[0086] In the examples shown below, for simplicity, the PCell and SCell are shown as being associated with a single base station (e.g., the hardware / circuitry used to implement the PCell and SCell may be co-located at the same base station). However, in some other configurations, the PCell and SCell may be associated with different base stations that may be synchronized.

[0087] Figure 6 FIG6 is a diagram 600 of an exemplary RACH-based SpCell beam failure recovery process according to aspects of the present disclosure. Figure 6In the example of FIG. 5 , a base station 602 (illustrated as “gNB” and which may correspond to any base station described herein, such as base station 502) supports a PCell or a primary (i.e., in-use) SCell (collectively, “SpCell”). A UE 604 (which may correspond to any UE described herein, such as UE 504) monitors the received signal strength (e.g., RSRP) of a periodic reference signal transmitted by base station 602 on a first set (“set_q0”) of DL transmit beams 606 of the SpCell. The first set of DL transmit beams 606 may correspond to a periodic reference signal transmitted by base station 602 in the mmW frequency range. Figure 5 The first set of DL transmit beams 606 is referred to as a “failure detection resource set” because the base station 602 sends beam IDs of the beams in the first set of DL transmit beams 606 to the UE 604 to enable the UE 604 to monitor these beams to determine whether a DL control link (i.e., a control channel that transmits control information from the network) between the base station 602 and the UE 604 is active. Figure 6 In the example of , the first set of DL transmit beams 606 includes two beams. However, there may be only one beam or more than two beams in the first set of DL transmit beams 606.

[0088] At 610, UE 604 fails to detect a periodic reference signal transmitted on at least one beam in the first set of DL transmit beams 606 and / or detects a signal quality threshold value (at Figure 6 The Qout threshold may be configured by the base station 602. More specifically, the layer 1 ( Figure 6 The “L1”) function in the UE 604 (e.g., implemented in the RX processor 356) detects that the measured quality metric of the periodic reference signal is below the Qout threshold and sends an out-of-sync (OOS) indication to the controller / processor 359 (which implements the layer 2 and layer 3 functions of the UE 604). In response to receiving the OOS indication, the controller / processor 359 of the UE 604 starts a beam failure detection (BFD) timer and initializes a beam failure indicator (BFI) counter to “1”.

[0089] At 615, UE 604 again fails to detect a periodic reference signal transmitted on at least one beam in the first set of DL transmit beams 606, and / or again detects a quality metric associated with the reference signal that has fallen below the Qout threshold. Again, more specifically, the layer 1 function of UE 604 detects that the measured quality metric of the periodic reference signal is below the Qout threshold, and sends another OOS indication to the controller / processor 359. The controller / processor 359 increments the BFI count to "2". Because the BFI count has reached the maximum count ("MaxCnt") threshold while the BFD timer is running, UE 604 determines that there has been a beam failure of at least one beam (e.g., a DL control beam) in the first set of DL transmit beams 606. Because there is a failure of the DL control beam (corresponding to a DL control channel that transmits control information from the network), UE 604 assumes that the corresponding UL control beam (corresponding to a UL control channel for transmitting control information to the network) also has a failure. In this way, UE 604 needs to identify a new DL control beam and re-establish the UL control beam.

[0090] Thus, at 620, in response to the beam failure detection at 615, the UE 604 initiates a beam failure recovery procedure. More specifically, the controller / processor 359 of the UE 604 requests the layer 1 function of the UE 604 (implemented by the RX processor 356) to identify at least one beam in a second set ("set_q1") of DL transmit beams 608 that carries a periodic reference signal having a received signal strength greater than a signal quality threshold (denoted as "Qin"). The second set of DL transmit beams 608 may correspond to a 400 MHz band in the mmW frequency range. Figure 5 The second set of DL transmit beams 608 is referred to as a “candidate beam reference signal list”. The UE 604 may receive both the beam ID and the Qin threshold of the beams in the second set of DL transmit beams 608 from the base station 602. Figure 6 In the example of , the second set of DL transmit beams 608 includes four beams, one of which (shaded) carries a periodic reference signal with a received signal strength greater than the Qin threshold. However, as will be appreciated, there may be more or less than four beams in the second set of DL transmit beams 608, and there may be more than one beam that satisfies the Qin threshold. The RX processor 356 reports the identified candidate beams to the controller / processor 359. The identified candidate beam may then be used as a new DL control beam, although not necessarily immediately.

[0091] At 625, to reestablish the UL control beam, UE 604 transmits one or more candidate DL beams identified at 620 (at Figure 6 More specifically, the controller / processor 359 instructs the RX processor 356 to send a RACH preamble to the base station 602 (which may be pre-stored by the base station 602 or provided to the UE 604). The RX processor 356 sends a RACH preamble (also referred to as message 1 (“Msg1”)) on the pre-configured RACH resources for the one or more candidate UL transmit beams corresponding to the one or more candidate DL transmit beams identified at 620. The pre-configured RACH resources may correspond to a SpCell (e.g., in a mmW band). Although in Figure 6 Not shown, but at 625, UE 604 also starts a beam failure recovery (BFR) timer, which defines a contention-free random access (CFRA) window.

[0092] The one or more candidate DL transmit beams identified at 620 may include a different beam than the DL transmit beam associated with the beam failure. As used herein, a "beam" is defined by beam weights associated with an antenna array of UE 604. Thus, in some aspects, the weights applied to each antenna in the array to construct a transmit or receive beam, whether for UL transmission by UE 604 or DL ​​reception by UE 604, define the beam. Thus, one or more candidate UL transmit beams on which to transmit a RACH preamble may have different weights than the DL transmit beam associated with the beam failure, even though such candidate UL transmit beams are generally in a similar direction as the DL transmit beam for which the failure was indicated.

[0093] At 630, the base station 602 sends a response (referred to as a "Msg1 response") with a cell radio network temporary identifier (C-RNTI) to the UE 604 via a PDCCH associated with the SpCell. For example, the response may include cyclic redundancy check (CRC) bits scrambled by the C-RNTI. After the RX processor 356 of the UE 604 processes the received response with the C-RNTI from the base station 602 via the SpCell PDCCH and determines that the received PDCCH is addressed to the C-RNTI, the controller / processor 359 determines that the beam failure recovery process is complete and stops the BFR timer started at 625. In an aspect, the C-RNTI may be mapped to a beam direction determined by the base station 602 as the best direction for a UL channel (e.g., PUCCH) of the UE 604. Therefore, upon receiving the response with the C-RNTI from the base station 602, the UE 604 is able to determine the optimal UL transmit beam that is most suitable for the UL channel.

[0094] The operations at 630 are part of a first scenario in which the UE 604 successfully recovers from the beam failure detected at 615. However, such recovery may not always occur, or at least not before the expiration of the BFR timer started at 625. If the BFR timer expires before the beam failure recovery procedure is successfully completed, then at 635, the UE 604 determines that a radio link failure (RLF) has occurred.

[0095] exist Figure 6 In the example shown in Figure 1, the SCell beam recovery process is completed without assistance from the PCell. Figure 6 One problem with the described beam failure recovery process is that the base station 602 and the UE 604 may need to repeat operations 620 to 630 an unknown number of times to determine the UL transmit beam that is most suitable for the UL channel. In addition, dedicated RACH resources may be required on the SCell, and additional overhead may also be associated (e.g., due to RACH messages and signaling). Although dedicated RACH resources can be used by the UE 604 in the case of beam failure recovery, at other times, the dedicated resources have no reason to be retained and cannot be used for other purposes, which is an undesirable effect. As such, a more efficient beam failure recovery process would be beneficial.

[0096] As described above, when PCell and SCell operations are supported in a communication system and there is no correspondence between UL and DL beams, assistance from the PCell can be used to enhance the SCell recovery process. For example, beam failure detection can be performed based on a virtual control resource set (CORESET) in the SCell, and the CORESET beam (of type D spatial QCL) can be a PDSCH beam (of type D spatial QCL). More specifically, in some scenarios, the actual control signaling for scheduling PDSCH may occur through the PCell. Therefore, in order to detect control signal failures in the SCell, the reference signal in the SCell is used together with the above-mentioned QCL assumption to serve as a virtual CORESET.

[0097] Figure 7 is a diagram 700 of an exemplary SCell beam recovery process with PCell assistance and without assuming any beam correspondence in accordance with aspects of the present disclosure. Figure 7 The illustrated process may be performed by a base station 702 (shown as a “gNB”) and a UE 704, which may correspond to any of the base stations and UEs described herein.

[0098] exist Figure 7In the example beam recovery process of , the beam recovery CORESET (for beam recovery in SCell) may not be activated unless needed, so the base station 702 is not prevented from using the beam recovery resources for other purposes. Figure 7 The exemplary beam recovery process may facilitate on-demand activation of RACH resources for the SCell via the PCell.

[0099] At 705, as referenced above Figure 6 As described in 610 and 615, UE 704 detects SCell DL transmit beam failure. When SCell DL transmit beam failure is detected, UE 704 may trigger a beam recovery process.

[0100] At 710, UE 704 sends a special scheduling request (SR) to base station 702 via PCell (which may operate in a sub-6 GHz frequency band). The scheduling request may be a specially configured SR for the SCell beam failure recovery procedure, and may provide an indication to base station 702 via PCell that an SCell DL transmit beam failure has occurred.

[0101] At 715, in response to receiving the special SR, the base station 702 requests a beam index report from the UE 704 via the PCell. Specifically, the base station 702 may send a dedicated PDCCH order, for example, a specially configured message sent via the PCell, the message including a request for a first layer RSRP report for the SCell DL transmit beam and / or a request for reporting a beam ID corresponding to a preferred DL transmit beam determined by the UE 704.

[0102] At 720, in response to the request for a beam index report for the SCell DL transmit beam, and based on the information about the beam ID and the corresponding resources, the UE 704 measures a DL reference signal (e.g., a synchronization signal block (SSB) and / or other reference signals) transmitted via the DL transmit beam to identify the best / preferred DL transmit beam direction, as described above with respect to Figure 6 620 of . UE 704 may generate a layer 1 RSRP report for a DL transmit beam based on the measurement. Moreover, based on the measurement, UE 704 may identify a preferred DL transmit beam (or beam set) for a directional DL channel (e.g., PDCCH). UE 704 may send the layer 1 RSRP report and / or the beam ID of the preferred DL transmit beam to base station 702 via the PUCCH in the PCell.

[0103] At 725, based on the report received via the PUCCH in the PCell, the base station 702 triggers an on-demand RACH for SCell recovery. For example, the base station 702 may reserve a set of RACH resources associated with the SCell for performing the RACH. The set of resources associated with the SCell beam recovery may include resources for sending a RACH preamble via a candidate UL transmit beam (e.g., in a frequency band corresponding to the SCell).

[0104] At 730, UE 704 performs a RACH procedure for one or more UL transmit beams corresponding to the one or more candidate DL transmit beams identified at 720. More specifically, UE 704 sends a RACH preamble (which may be pre-stored by base station 702 or provided to UE 704) to base station 702, as described above with reference to FIG. Figure 6 625. UE 704 transmits a RACH preamble (ie, "Msg1") on one or more candidate UL transmit beams on the RACH resources configured at 725. The configured RACH resources may correspond to a SCell (eg, in a mmW frequency band).

[0105] At 735, base station 702 sends a response (referred to as "Msg1 Response" or "Msg2") to UE 704, as described above with reference to Figure 6 As discussed in 630 of . After UE 704 processes the received response, UE 704 is able to determine the optimal UL transmit beam that is most suitable for the uplink channel.

[0106] At 740, the UE 704 reconfigures the transmission configuration indicator (TCI) state for the PUCCH. The reconfiguration of the TCI state confirms that the UL transmit beam identified at 735 will be used for the PUCCH.

[0107] Although the beam failure recovery process in which the UE establishes a new UL control beam has been described above, it should be understood that the techniques described herein are also applicable to selecting a new UL transmit beam and / or DL ​​receive beam in response to a failure of a PCell or SCell. For example, when selecting a new DL receive beam for a PCell or SCell, Figure 7, the Msg1 sent at 730 may identify candidate receive beams for the PCell or SCell, and the response at 735 may identify one of those beams to be used for the PCell or SCell, rather than identifying a UL control beam. In that case, it may be useful for the UE 704 to be able to determine which type of beam recovery the Msg1 response received at 735 is associated with, e.g., PCell beam recovery (for uplink transmit beams and / or downlink receive beams), SCell beam recovery (for uplink transmit beams and / or downlink receive beams), or UL transmission / control beam recovery. More generally, it may be useful for the UE to be able to determine that the message in the beam recovery process is associated with the type of beam, e.g., whether the beam is associated with the PCell or the SCell. Additionally or alternatively, it may be useful for the UE to be able to determine whether the beam is an uplink beam or a downlink beam. In the case where the beam is associated with an SCell, information about the beam type associated with the beam recovery process may include whether it is a downlink-only beam or a downlink and uplink beam. In addition, information about whether the SCell is self-scheduled (with its own control resources) or cross-scheduled (without its own control resources) may also be included in the information about the type of beam. In order to solve this problem, the present disclosure proposes three solutions. The first solution is to configure a separate BFR CORESET for each of the different types of beam recovery (i.e., PCell beam recovery, SCell beam recovery, and / or UL transmission / control beam recovery). The second solution is to configure the same BFR CORESET for each of the different types of beam recovery, but use different RNTIs for the different types of beam recovery to scramble the PDCCH. The third solution is to configure the same BFR CORESET for each of the different types of beam recovery and use the same DCI, but use an additional bit to convey which type of recovery response it is.

[0108] Fig. 8A is a diagram 800A showing an example of a first solution according to aspects of the present disclosure. Fig. 8A The illustrated process may be performed by a base station 802 (illustrated as "gNB") in communication with a UE 804, which may correspond to any of the base stations and UEs described herein. In a first solution, the base station 802 reserves a unique beam recovery resource (e.g., CORESET) for each use case (e.g., PCell recovery, SCell recovery, or UL beam recovery). That is, the base station 802 reserves a different CORESET for each type of beam recovery (e.g., PCell recovery, SCell recovery, UL beam recovery).

[0109] At 805, similar to Figure 7 UE 804 sends a special beam failure recovery request (BFRQ) Msg1 to base station 802 based on the RACH preamble code sent at 730. BFRQ Msg1 can be sent on one or more candidate UL transmission beams, such as Figure 6 620 / 625 or Figure 7 The one or more candidate UL transmit beams corresponding to the one or more candidate DL transmit beams identified at 720. Fig. 8A In the example, one or more candidate UL transmit beams are used for PCell instead of SCell, and are intended to identify a new PCell instead of a new UL transmit / control beam. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is PCell recovery in this case.

[0110] At 810, base station 802 sends a response to Msg1 in a CORESET reserved for PCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 804. The UE 804 may further include a response message 735, except that the recovery is for the PCell DL transmit beam. That is, the type of beam recovery is indicated by the identifier of the reserved CORESET. In one aspect, the response indicates a candidate beam determined by the base station 802 as the best DL transmit beam for the PCell, and the base station 802 has reserved resources for it. Therefore, upon receiving the response from the base station 802, the UE 804 uses the identified candidate DL transmit beam as a new beam for the PCell.

[0111] At 815, similar to Figure 7 At 740, UE 804 reconfigures the TCI state for the PDCCH (because the recovery is for the PCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the PCell.

[0112] Figure 8B is a diagram 800B showing a second example of the first solution according to aspects of the present disclosure. Figure 8B The process shown may be performed by a base station 802 in communication with a UE 804. At 820, the UE 804 sends a special BFRQMsg1 to the base station 802, similar to Figure 7 BFRQ Msg1 may be sent on one or more candidate UL transmit beams, for example, with Figure 6 620 / 625 or Figure 7The one or more candidate UL transmit beams corresponding to the one or more candidate DL transmit beams identified at 720. Figure 8B In the example of , one or more candidate UL transmit beams are used for SCell and are intended to identify a new SCell rather than a new UL transmit beam. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is SCell recovery.

[0113] At 825, the base station 802 sends a response to Msg1 in the CORESET for SCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 735, except that the recovery is for the SCell DL transmit beam. In one aspect, the response indicates a candidate beam determined by the base station 802 as the best DL transmit beam for the SCell, and the base station 802 has reserved resources for it. Therefore, upon receiving the response from the base station 802, the UE 804 uses the identified candidate DL transmit beam as a new beam for the SCell.

[0114] At 830, similar to Figure 7 At 740, UE 804 reconfigures the TCI state for the PDCCH (because the recovery is for the SCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the SCell.

[0115] Fig. 9A is a diagram 900A illustrating an example of a second solution according to aspects of the present disclosure. Fig. 9A The illustrated process may be performed by a base station 902 (illustrated as "gNB") in communication with a UE 904, which may correspond to any of the base stations and UEs described herein. In a second solution, the base station 902 configures the same beam failure recovery CORESET, but scrambles the PDCCH with different RNTIs for different types of recovery (e.g., PCell, SCell, or UL control beams). In this way, the same beam recovery resources (e.g., RACH resources) may be used, but with different scrambling sequences for each use case (e.g., PCell recovery, SCell recovery, or UL beam recovery).

[0116] At 905, UE 904 sends a special BFRQ Msg1 to base station 902, similar to Fig. 8A 805 and Figure 8B BFRQ Msg1 sent at 820 of FIG. BFRQ Msg1 can be sent on one or more candidate UL transmit beams, such as Figure 6620 / 625 or Figure 7 The one or more candidate UL transmit beams corresponding to the one or more candidate beams identified at 720. Fig. 9A In the example, one or more candidate beams are used for PCell instead of SCell, and the purpose is to identify a new PCell instead of a new UL transmit beam for SCell. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is PCell recovery here.

[0117] At 910, base station 902 sends a response to Msg1 in CORESET for PCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 735, except that the recovery is for a PCell DL transmit beam. In one aspect, the response may include a PDCCH scrambled by an RNTI corresponding to the type of recovery (e.g., PCell recovery, SCell recovery, or UL beam recovery). The UE 904 may be notified of a specific RNTI for decoding the response. Since the RNTI for each recovery type is different, any type of beam failure recovery process may reuse the same resources (e.g., RACH resources). In one aspect, the response indicates a candidate beam determined by the base station 902 as the best DL transmit beam for the PCell, and the base station 902 has reserved resources for it. Therefore, upon receiving the response from the base station 902, the UE 904 uses the identified candidate DL transmit beam as a new beam for the PCell.

[0118] At 915, similar to Figure 7 At 740, UE 904 reconfigures the TCI state for the PDCCH (because the recovery is for the PCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the PCell.

[0119] Fig. 9B 900B is a diagram illustrating a second example of the second solution according to aspects of the present disclosure. Fig. 9B The process shown may be performed by a base station 902 in communication with a UE 904. At 920, the UE 904 sends a special BFRQMsg1 to the base station 902, similar to Fig. 9A BFRQ Msg1 sent at 905 of FIG. BFRQ Msg1 can be sent on one or more candidate UL transmit beams, such as Figure 6 620 / 625 or Figure 7 The one or more candidate UL transmit beams corresponding to the one or more candidate beams identified at 720. Fig. 9B In the example of , one or more candidate beams are used for SCell and are intended to identify a new DL transmit beam for SCell rather than a new UL transmit beam for SCell. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is SCell recovery.

[0120] At 925, the base station 902 sends a response to Msg1 in the CORESET for SCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 735, except that the recovery is for the SCell DL transmit beam. In one aspect, the response may include a different RNTI (from Fig. 9A In one aspect, the response indicates a candidate beam determined by the base station 902 as the best DL transmit beam for the SCell, and for which the base station 902 has reserved resources. Therefore, upon receiving the response from the base station 902, the UE 904 uses the identified candidate DL transmit beam as a new beam for the SCell.

[0121] At 930, similar to Figure 7 At 740, the UE 904 reconfigures the TCI state for the PDCCH (because the recovery is for the SCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the SCell.

[0122] Fig. 10A is a diagram 1000A showing an example of a third solution according to aspects of the present disclosure. Fig. 10A The process shown may be performed by a base station 1002 (shown as "gNB") in communication with a UE 1004, which may correspond to any of the base stations and UEs described herein. In a third solution, the base station 1002 configures the same beam failure recovery CORESET for each recovery type and uses the same DCI, but adds additional bits to the DCI to convey the type of recovery. For example, the base station 1002 may reuse the carrier indicator field (CIF) used for carrier scheduling or some other similar mechanism.

[0123] At 1005, UE 1004 sends a special BFRQ Msg1 to base station 1002, similar to Fig. 9A 905 and Fig. 9B BFRQ Msg1 sent at 920 of FIG. BFRQ Msg1 can be sent on one or more candidate UL transmit beams, such as Figure 6 620 / 625 or Figure 7 The one or more candidate UL transmit beams corresponding to the one or more candidate beams identified at 720. Fig. 10A In the example of , one or more candidate beams are used for PCell instead of SCell, and the purpose is to identify a new DL transmit beam for the cell instead of a new UL transmit beam for the SCell. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is PCell recovery in this case.

[0124] At 1010, base station 1002 sends a response to Msg1 in CORESET for PCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 735, except that the recovery is for the PCell DL transmit beam. In one aspect, the response may include a PDCCH scrambled by the RNTI. In one aspect, for each recovery type (e.g., PCell recovery, SCell recovery, or UL beam recovery), the RNTI is the same so that any beam failure recovery process can reuse the same resources (e.g., RACH resources). In addition, for each recovery type, the DCI in the response may be the same. In order to distinguish the recovery type, the base station 1002 will add additional bits to the response that are different depending on the recovery type. The mapping of these additional bits to different types of recovery can be notified to the UE 1004 in order to decode the response. In one aspect, the response indicates a candidate beam determined by the base station 1002 as the best DL transmit beam for the PCell, and the base station 1002 has reserved resources for it. Therefore, upon receiving the response from the base station 1002, the UE 1004 uses the identified candidate DL transmit beam as the new beam for the PCell.

[0125] At 1015, similar to Figure 7 At 740, UE 1004 reconfigures the TCI state for the PDCCH (because the recovery is for the PCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the PCell.

[0126] Fig. 10B is a diagram 1000B showing an example of a third solution according to aspects of the present disclosure. Fig. 10B The process shown may be performed by a base station 1002 in communication with a UE 1004. At 1020, the UE 1004 sends a special BFRQMsg1 to the base station 1002, similar to Fig. 10A BFRQ Msg1 sent at 1005 of FIG. BFRQ Msg1 can be sent on one or more candidate UL transmit beams, such as Figure 6 620 / 625 or Figure 7 The one or more candidate UL transmit beams corresponding to the one or more candidate beams identified at 720. Fig. 10B In the example of , one or more candidate beams are used for SCell and are intended to identify new DL transmissions for SCell rather than new UL transmission beams for SCell. In addition, BFRQ Msg1 is not only sent on (multiple) candidate beams, but also specifies the type of recovery, which is SCell recovery.

[0127] At 1025, the base station 1002 sends a response to Msg1 in the CORESET for SCell beam failure recovery, similar to Figure 6 630 and / or Figure 7 735, except that the recovery is for the SCell transmit beam. In one aspect, the response may include Fig. 10A The UE 1004 receives a PDCCH scrambled with the same RNTI in the UE 1004, which has the same DCI bits, but has additional bits to distinguish SCell recovery from PCell recovery. In one aspect, the response indicates a candidate beam determined by the base station 1002 as the best DL transmit beam for the PCell, and the base station 1002 has reserved resources for it. Therefore, upon receiving the response from the base station 1002, the UE 1004 uses the identified candidate DL transmit beam as a new beam for the SCell.

[0128] At 1030, similar to Figure 7 At 740, UE 1004 reconfigures the TCI state for the PDCCH (because the recovery is for the SCell, not the UL control beam). The reconfiguration of the TCI state confirms that the identified DL transmit beam will be used for the PDCCH of the SCell.

[0129] Fig.11 An exemplary method 1100 of beam failure recovery in a wireless communication system, such as the wireless communication system 100, in accordance with aspects of the present disclosure is shown. The method 1100 may be performed by a UE, such as any of the UEs described herein.

[0130] At 1110, the UE (e.g., the RX processor 356 via the receiver(s) 354) detects a beam failure of a first downlink (transmit) beam received at the UE from a base station (e.g., any base station described herein), such as Figure 6 610 and 615 and Figure 7 As shown in 705. The first downlink beam can be associated with a PCell or SCell supported by the base station.

[0131] At 1120, the UE (e.g., TX processor 368 via transmitter(s) 354) sends a RACH request to the base station identifying one or more candidate downlink beams received at the UE from the base station, such as Figure 7 730 Fig. 8A 805 Figure 8B 820 Fig. 9A 905 Fig. 9B 920 Fig. 10A 1005 and Fig. 10B As shown at 1020 of . A RACH request may be sent using an uplink beam different from the uplink beam associated with the beam failure. Thus, in one example, a beam failure indication may be sent using the same weight for receiving a candidate beam (from one or more candidate beams) having a weight different from the downlink beam indicated as a failure, even if such a candidate beam is generally in a direction similar to the downlink beam indicated as a failure. Additionally or alternatively, a beam failure indication may be sent using a different carrier frequency and / or different resources than the downlink beam associated with the beam failure. In some implementations, one or more candidate downlink beams included in the RACH request may have been pre-indicated by the base station and stored in, for example, a BeamFailureRecoveryConfig parameter in the RRC layer. Such beam failure recovery parameters may be received from the base station in a unicast message using PDCCH or PDSCH or in a broadcast in PDSCH. In various examples, contention-free RACH information may be carried in a broadcast PDSCH.

[0132] At 1130, in response to sending the RACH request, the UE (e.g., the RX processor 356 via the receiver(s) 354) receives a response to the RACH request from the base station, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam restoration associated with the second downlink beam for which the base station has reserved downlink beam resources, such as Figure 7 735 Fig. 8A 810 Figure 8B 825 Fig. 9A 910 Fig. 9B 925 Fig. 10A 1010 and Fig. 10B As shown at 1025.

[0133] Fig.12 An exemplary method 1200 of beam failure recovery in a wireless communication system, such as the wireless communication system 100, in accordance with aspects of the present disclosure is shown. The method 1200 may be performed by a base station, such as any base station described herein.

[0134] At 1210, the base station (e.g., RX processor 370 via receiver(s) 318) optionally receives a message from a UE (e.g., any UE described herein) indicating that a beam failure has occurred at the UE, such as at Figure 7 12. The beam failure may be a failure of a DL transmit beam associated with a PCell supported by the base station or an SCell supported by the base station. Operation 1210 is optional because the UE does not need to send a message indicating that a beam failure has occurred, but may only send a RACH request, as shown at 1220. As described above with reference to 1120, the message indicating that a beam failure has occurred may be sent using a beam different from the beam associated with the beam failure, like the RACH request.

[0135] At 1220, the base station (e.g., RX processor 370 via receiver(s) 318) receives from the UE a RACH request identifying one or more candidate downlink beams received at the UE from the base station, such as Figure 7 730 Fig. 8A 805 Figure 8B 820 Fig. 9A 905 Fig. 9B 920 Fig. 10A 1005 and Fig. 10B As shown at 1020.

[0136] At 1230, in response to receiving the RACH request, the base station (e.g., the TX processor 316 via the transmitter(s) 318) sends a response to the RACH request to the UE, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved, such as Figure 7 735 Fig. 8A 810 Figure 8B 825 Fig. 9A 910 Fig. 9B 925 Fig. 10A 1010 and Fig. 10B As shown at 1025.

[0137] It should be understood that any reference to an element using names such as "first", "second" etc. herein does not generally limit the quantity or order of those elements. On the contrary, these names can be used as a convenient method to distinguish two or more elements or element instances in this article. Therefore, the reference to the first element and the second element does not mean that only two elements can be used there, or the first element must be before the second element in some way. In addition, unless otherwise specified, a group of elements may include one or more elements. In addition, the term "at least one of A, B or C" or "one or more of A, B or C" or "at least one of the group consisting of A, B and C" used in the specification or claim means "A or B or C or any combination of these elements". For example, the term may include A, or B, or C, or A and B, or A and C, or A and B and C, or 2A, or 2B, or 2C, etc.

[0138] In view of the above description and explanation, it will be appreciated by those skilled in the art that the various illustrative logic blocks, modules, circuits and algorithmic steps described in conjunction with the various aspects disclosed herein can be implemented as electronic hardware, computer software or a combination of the two. In order to clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits and steps have been described above generally according to their functions. Whether such functions are implemented as hardware or software depends on specific applications and the design constraints imposed according to the overall system. The technician can implement the functions in different ways for each specific application, but such implementation method decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0139] Thus, it should be understood that, for example, a device or any component of a device may be configured (or made operable or adapted) to provide the functionality taught herein. For example, this may be achieved by producing (e.g., manufacturing) the device or component so that it can provide the functionality; by programming the device or component so that it can provide the functionality; or by using some other suitable specific implementation technology. As an example, an integrated circuit may be manufactured to provide the necessary functionality. As another example, an integrated circuit may be manufactured to support the necessary functionality and then configured (e.g., via programming) to provide the necessary functionality. As yet another example, a processor circuit may execute code to provide the necessary functionality.

[0140] In addition, the methods, sequences and / or algorithms described in conjunction with the various aspects disclosed herein may be directly embodied in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a random access memory (RAM), flash memory, read-only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Alternatively, the storage medium may be integrated with the processor (e.g., a cache memory).

[0141]

[0013] It should also be appreciated, therefore, that certain aspects of the present disclosure can include, for example, a computer-readable medium embodying a method for beam failure recovery in a wireless communication system.

[0142] Although the foregoing disclosure shows various illustrative aspects, it should be noted that various changes and modifications may be made to the examples shown without departing from the scope defined by the appended claims. The present disclosure is not intended to be limited to the specifically shown examples. For example, unless otherwise stated, the functions, steps, and / or actions of the method claims according to the various aspects of the present disclosure described herein do not need to be performed in any particular order. In addition, although certain aspects may be described or claimed in the singular, the plural form is also contemplated unless a limitation to the singular form is explicitly stated.

Claims

1. A method for beam failure recovery in a wireless communication system, comprising: detecting, by a user equipment UE, a beam failure of a first downlink beam received at the UE from a base station; sending, by the UE to the base station, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as receiving, at the UE, from the base station, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam restoration associated with the second downlink beam for which the base station has reserved downlink beam resources; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery. 2 . The method according to claim 1 , wherein the first downlink beam is a downlink transmission beam for an SCell supported by the base station. 3 . The method according to claim 2 , wherein the first downlink beam uses a millimeter wave (mmW) frequency band to transmit a periodic reference signal. 4 . The method according to claim 1 , wherein the first downlink beam is a downlink transmission beam for a PCell supported by the base station. The method according to claim 4 , wherein the first downlink beam uses a mmW frequency band to transmit a periodic reference signal.

6. The method according to claim 1, further comprising: receiving, at the UE, a physical downlink control channel (PDCCH) order from the base station; performing, by the UE, a RACH procedure in response to the PDCCH order, wherein the RACH procedure includes sending the RACH request and receiving a response to the RACH request; as well as An uplink transmission beam is determined by the UE based on the RACH process.

7. The method of claim 6, wherein the uplink transmit beam is associated with an SCell supported by the base station.

8. The method of claim 6, wherein the uplink transmit beam is associated with a PCell supported by the base station.

9. A method for beam failure recovery in a wireless communication system, comprising: receiving, at a base station from a user equipment (UE), a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as transmitting, from the base station to the UE, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam associated with the beam failure and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

10. The method according to claim 9, further comprising: A message is received at the base station from the UE indicating that a beam failure has occurred at the UE.

11. The method of claim 10, wherein the message from the UE indicating that the beam failure has occurred comprises a scheduling request (SR). 12 . The method of claim 9 , wherein the base station reserves a different CORESET for each of the PCell recovery and the SCell recovery. 13 . The method of claim 9 , wherein the base station reserves the same CORESET for each of the PCell recovery and the SCell recovery.

14. The method according to claim 9, wherein the first downlink beam is a downlink transmission beam for an SCell supported by the base station.

15. The method of claim 9, wherein the base station transmits a periodic reference signal on the first downlink beam, and wherein the first downlink beam operates on a millimeter wave (mmW) frequency band. 16 . The method according to claim 9 , wherein the first downlink beam is a downlink transmission beam for a PCell supported by the base station.

17. The method according to claim 9, further comprising: Sending a physical downlink control channel (PDCCH) command to the UE through the base station; as well as A RACH procedure is performed by the base station after sending the PDCCH order, wherein the RACH procedure includes receiving the RACH request and sending a response to the RACH request, and wherein the UE determines an uplink transmission beam based on the RACH procedure.

18. The method according to claim 17, wherein the uplink transmit beam is associated with an SCell supported by the base station, or The uplink transmit beam is associated with a PCell supported by the base station.

19. A device for beam failure recovery in a wireless communication system, comprising: At least one processor of a user equipment UE, configured to: detecting a beam failure of a first downlink beam received at the UE from a base station; sending, to the base station, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as receiving, from the base station in response to sending the RACH request, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam restoration associated with the second downlink beam for which downlink beam resources have been reserved; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

20. A device for beam failure recovery in a wireless communication system, comprising: At least one processor of a base station serving a user equipment UE, and configured to: receiving, from the UE, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as sending, in response to receiving the RACH request, a response to the RACH request to the UE, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam associated with the beam failure and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

21. A device for beam failure recovery in a wireless communication system comprising: means for detecting, by a user equipment (UE), a beam failure of a first downlink beam received at the UE from a base station; means for sending, by the UE to the base station, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as means for receiving, at the UE, from the base station, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam restoration associated with the second downlink beam for which the base station has reserved downlink beam resources; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

22. A device for beam failure recovery in a wireless communication system comprising: means for receiving, at a base station, from a user equipment (UE), a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as means for sending, from the base station to the UE, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam associated with the beam failure and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

23. A non-transitory computer-readable medium storing computer-executable instructions, which, when executed by at least one processor of a user equipment (UE), cause the UE to: detecting, by a user equipment UE, a beam failure of a first downlink beam received at the UE from a base station; sending, by the UE to the base station, a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; as well as receiving, at the UE, from the base station, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam and indicating a type of beam restoration associated with the second downlink beam for which the base station has reserved downlink beam resources; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

24. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by at least one processor of a base station, cause the base station to: receiving, at a base station from a user equipment (UE), a random access channel (RACH) request identifying one or more candidate downlink beams received at the UE from the base station; and transmitting, from the base station to the UE, a response to the RACH request, the response identifying a second downlink beam from the one or more candidate downlink beams to replace the first downlink beam associated with the beam failure and indicating a type of beam recovery associated with the second downlink beam for which downlink beam resources have been reserved; The type of beam recovery is indicated by an identifier of a different control resource set CORESET for each of the primary cell PCell recovery and the secondary cell SCell recovery; or wherein the type of the beam restoration is indicated by an identity of the same CORESET scrambled with a different Radio Network Temporary Identifier RNTI for each of the PCell restoration and the SCell restoration; or The type of beam recovery is indicated by the same CORESET, the same downlink control information DCI, and different additional bits used to distinguish between the PCell recovery and the SCell recovery.

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