WO2020220372A1

WO2020220372A1 - Beam failure recovery using two-step contention free random access channel procedure

Info

Publication number: WO2020220372A1
Application number: PCT/CN2019/085403
Authority: WO
Inventors: Linhai He; Ruiming Zheng; Jing LEI
Original assignee: Qualcomm Incorporated
Priority date: 2019-05-02
Filing date: 2019-05-02
Publication date: 2020-11-05

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources. The communication may be associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH), and may include information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH). Numerous other aspects are provided.

Description

BEAM FAILURE RECOVERY USING TWO-STEP CONTENTION FREE RANDOM ACCESS CHANNEL PROCEDURE

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for beam failure recovery (BFR) using a two-step contention free random access channel (CFRA) procedure.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs) . A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP) , a radio head, a transmit receive point (TRP) , a New Radio (NR) BS, a 5G Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New Radio (NR) , which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP) . NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL) , using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM) ) on the uplink (UL) , as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method of wireless communication, performed by a user equipment (UE) , may include transmitting a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to transmit a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a PUSCH.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to: transmit a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a PUSCH.

In some aspects, an apparatus for wireless communication may include means for transmitting a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the apparatus, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a PUSCH.

In some aspects, a method of wireless communication, performed by a UE, may include detecting a beam failure associated with an active bandwidth part (BWP) of the UE; measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; determining that a set of beam failure recovery (BFR) resources is configured for the active BWP; and transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a method of wireless communication, performed by a UE, may include detecting a beam failure associated with a serving cell of the UE, wherein the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell, the serving cell being one of the primary cell or the secondary cell; measuring, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell; selecting a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell; and transmitting a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the UE, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a method of wireless communication, performed by a UE, may include detecting a beam failure associated with an active BWP of the UE; measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; switching to an initial BWP, associated with the UE, based at least in part on determining that no BFR resources are configured for the active BWP; and transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to detect a beam failure associated with an active BWP of the UE; measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; determine that a set of BFR resources is configured for the active BWP; and transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to: detect a beam failure associated with an active BWP of the UE; measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; determine that a set of BFR resources is configured for the active BWP; and transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, an apparatus for wireless communication may include means for detecting a beam failure associated with an active BWP of the apparatus; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; means for selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; means for determining that a set of BFR resources is configured for the active BWP; and means for transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to detect a beam failure associated with an active BWP of the UE; measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; switch to an initial BWP, associated with the UE, based at least in part on determining that no BFR resources are configured for the active BWP; and transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to: detect a beam failure associated with an active BWP of the UE; measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; switch to an initial BWP, associated with the UE, based at least in part on determining that no BFR resources are configured for the active BWP; and transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, an apparatus for wireless communication may include means for detecting a beam failure associated with an active BWP of the apparatus; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; means for selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; means for switching to an initial BWP, associated with the apparatus, based at least in part on determining that no BFR resources are configured for the active BWP; and means for transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to detect a beam failure associated with a serving cell of the UE, wherein the UE is configured to communicate based at least in a CA configuration associated with a primary cell and a secondary cell, the serving cell being one of the primary cell or the secondary cell; measure, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell; select a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell; and transmit a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the UE, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to: detect a beam failure associated with a serving cell of the UE, wherein the UE is configured to communicate based at least in part a CA configuration associated with a primary cell and a secondary cell, the serving cell being one of the primary cell or the secondary cell; measure, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell; select a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell; and transmit a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the UE, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, an apparatus for wireless communication may include means for detecting a beam failure associated with a serving cell of the apparatus, wherein the apparatus is configured to communicate based at least in part on a CA configuration associated with a primary cell and a secondary cell, the serving cell being one of the primary cell or the secondary cell; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell; means for selecting a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell; and means for transmitting a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the apparatus, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

In some aspects, a method of wireless communication, performed by a base station, may include receiving a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .

In some aspects, a base station for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to receive a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a base station, may cause the one or more processors to: receive a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .

In some aspects, an apparatus for wireless communication may include means for receiving a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and processing system as substantially described herein with reference to and as illustrated by the accompanying drawings, appendix, and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a base station in communication with a UE in a wireless communication network, in accordance with various aspects of the present disclosure.

Figs. 3-5 are diagrams illustrating examples of beam failure recovery using a two-step contention free random access procedure, in accordance with various aspects of the present disclosure.

Figs. 6-10 are diagrams illustrating example processes performed, for example, by wireless communication devices, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

It should be noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

Fig. 1 is a diagram illustrating a wireless network 100 in which aspects of the present disclosure may be practiced. The wireless network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. The wireless network 100 may include a number of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a 5G node B (NB) , an access point, a transmit receive point (TRP) , and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG) ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in Fig. 1, a BS 110a may be a macro BS for a macro cell 102a, a BS 110b may be a pico BS for a pico cell 102b, and a BS 110c may be a femto BS for a femto cell 102c. A BS may support one or multiple (e.g., three) cells. The terms “eNB” , “base station” , “NR BS” , “gNB” , “TRP” , “AP” , “node B” , “5G NB” , and “cell” may be used interchangeably herein.

In some aspects, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network.

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

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts) .

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120a, 120b, 120c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet) ) , an entertainment device (e.g., a music or video device, or a satellite radio) , a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE) . UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some aspects, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (e.g., without using a base station 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like) , a mesh network, and/or the like. In this case, the UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the base station 110.

As indicated above, Fig. 1 is provided as an example. Other examples may differ from what is described with regard to Fig. 1.

Fig. 2 shows a block diagram of a design 200 of base station 110 and UE 120, which may be one of the base stations and one of the UEs in Fig. 1. Base station 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general T ≥ 1 and R ≥ 1.

At base station 110, a transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS (s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS) ) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to various aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

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

On the uplink, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like) , and transmitted to base station 110. At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. Base station 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

Controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with beam failure recovery (BFR) using a two-step contention free random access channel (CFRA) procedure, as described in more detail elsewhere herein. For example, controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 600 of Fig. 6, process 700 of Fig. 7, process 800 of Fig. 8, process 900 of Fig. 9, process 1000 of Fig. 10, and/or other processes as described herein.

Memories

242 and 282 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, UE 120 may include means for detecting a beam failure associated with an active bandwidth part (BWP) of the apparatus; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; means for selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; means for determining that a set of BFR resources is configured for the active BWP; means for transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, wherein the communication is associated with a two-step CFRA procedure, and wherein the communication includes information that identifies the target beam associated with the active BWP; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

In some aspects, UE 120 may include means for transmitting a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the apparatus, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a PUSCH; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

In some aspects, UE 120 may include means for detecting a beam failure associated with an active BWP of UE 120; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP; means for selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams; means for switching to an initial BWP, associated with UE 120, based at least in part on determining that no BFR resources are configured for the active BWP; means for transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a PUSCH; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

In some aspects, UE 120 may include means for detecting a beam failure associated with a serving cell of UE 120, wherein UE 120 is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell, the serving cell being one of the primary cell or the secondary cell; means for measuring, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell; means for selecting a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell; means for transmitting a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of UE 120, wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a PRACH, and wherein the communication includes information that identifies a target beam associated with performing the BFR, the information that identifies the target beam being transmitted over a PUSCH; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with Fig. 2.

In some aspects, a base station 110 may include means for receiving a communication, associated with a BFR procedure, in one or more BFR resources of a set of BFR resources, wherein the communication is associated with transmission of a preamble sequence uniquely associated with UE 120, the preamble sequence being received over a PRACH, and wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a PUSCH.

As indicated above, Fig. 2 is provided as an example. Other examples may differ from what is described with regard to Fig. 2.

A two-step random access channel (RACH) procedure includes two steps (rather than four steps, as in a traditional four-step contention based RACH (CBRA) procedure) . In the two-step RACH procedure, a UE transmits a first communication (sometimes referred to as msgA) that includes a randomly selected preamble and a payload (e.g., a physical uplink shared channel (PUSCH) payload) . A base station, after receiving the communication and processing the RACH request associated with the first communication, transmits a second communication (aresponsive communication, sometimes referred to as msgB) to the UE to confirm completion of the RACH request.

A contention free RACH (CFRA) procedure also includes two steps (e.g., because the network provides a dedicated preamble for a given UE and, therefore, there is no contention involved) . Generally, there are two kinds of events that can use the CFRA procedure: handover and beam failure recovery (BFR) . Typically, to support BFRs that use a CFRA procedure, a network configures dedicated resources to be used in association with performing BFRs (herein referred to as BFR resources) . Each RACH occasion in this dedicated configuration corresponds to a respective one of a set of candidate beams configured for a UE. Here, the set of candidate beams for the UE can be defined on a per bandwidth part (BWP) basis. Each UE is also configured with a dedicated preamble that represents the UE (which differs from a contention based scenario in which the UE randomly selects a preamble from a predefined set of preambles) . When a beam failure is detected, a UE first determines in which BWP to perform a BFR. If a set of BFR resources is configured for the current active BWP, then the UE remains in the active BWP and performs a BFR. Otherwise, the UE switches to an initial BWP and performs the BFR in the initial BWP. The UE selects a target beam as a new serving beam from the set of candidate beams configured for the BWP in which the UE is to perform the BFR (i.e., the active BWP or the initial BWP) . The UE then transmits its dedicated preamble in a RACH occasion that corresponds to the target beam. The UE then monitors a BFR search space on a physical downlink control channel (PDCCH) for a communication addressed to a cell radio network temporary identifier (C-RNTI) assigned to the UE. The RACH portion of the BFR is complete if the UE receives such a PDCCH communication. Finally, the network (e.g., a base station in the network) reconfigures a transmission configuration indicator (TCI) state of the UE based on the target beam indicated by the UE during the performance of the BFR.

Some aspects described herein provide techniques and apparatuses for BFR using a two-step CFRA procedure. In some aspects, when performing the BFR using the two-step CFRA procedure, a UE can include additional information in a payload of a first communication associated with performing the BFR, which reduces overall latency of the BFR procedure, as described below. Additional details regarding performing a BFR using a two-step CFRA procedure are described below.

Figs. 3-5 are diagrams illustrating examples associated with BFR using a two-step CFRA procedure, in accordance with various aspects of the present disclosure.

In some aspects, as illustrated by the examples associated with Figs. 3-5, a UE (e.g., UE 120) may transmit a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources. Here, the communication may be associated with transmission of a preamble sequence uniquely associated with the UE (i.e., a dedicated preamble) , and the preamble sequence may be transmitted over, for example, a physical random access channel (PRACH) . Further, the communication may include information that identifies a target beam associated with performing the BFR procedure, and the information that identifies the target beam may be transmitted over, for example, a physical uplink shared channel (PUSCH) . Figs. 3-5 describe various scenarios that can transmit such a communication.

Fig. 3 is a diagram illustrating an example 300 associated with BFR using a two-step CFRA procedure when a set of BFR resources is configured for an active BWP associated with a UE.

As shown by reference number 302, a UE (e.g., UE 120) may detect a beam failure associated with an active BWP of the UE, and may measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP (e.g., a set of possible target beams for the UE to recover a link with a base station) . An active BWP is a BWP used for communication of uplink and downlink traffic (as compared to an initial BWP, which is a BWP used for initial connection setup and initial configuration) . Generally, an active BWP has a wider bandwidth than an initial BWP and, therefore, can be used to achieve comparatively higher throughput. In general, a UE uses an initial BWP during initial connection setup and initial configuration, and then switches to an active BWP for use in association with transmitting and receiving traffic after the initial connection and configuration is complete.

As shown by reference 304, the UE may select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams. In some aspects, the target beam is a candidate beam with a characteristic (e.g., a reference signal received power (RSRP) ) that satisfies a threshold for link recovery.

In some aspects, after selecting the target beam, the UE may determine whether a set of BFR resources is configured for the active BWP. In some aspects, the UE may determine whether a set of BFR resources is configured for the active BWP based at least in part on configuration information accessible by the UE (e.g., when the UE has previously received a configuration indicating BFR resources are configured for the active BWP) . As shown by reference 306, in some aspects, the UE may determine that a set of BFR resources is configured for the active BWP. An example in which the UE determines that no BFR resources are configured for the active BWP is described below in association with Fig. 4.

As shown by reference 308, based at least in part on determining that a set of BFR resources is configured for the active BWP, the UE may transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP. In some aspects, the communication includes the dedicated preamble associated with the UE, as well as information that identifies the target beam associated with the active BWP. The information that identifies the target beam may include, for example, an index corresponding to the target beam (e.g., such that the target beam can be identified using the index) . In some aspects, the information that identifies the target beam may be transmitted in a payload of the communication (e.g., in a msgA payload) . In some aspects, the information that identifies the target beam is transmitted in a medium access control (MAC) control element (CE) . In some aspects, the communication may include a dedicate preamble associated with the UE, and the dedicated preamble may be transmitted over a PRACH. In some aspects, Further, the communication may include the information that identifies the target beam, and the information that identifies the target beam may be transmitted over a PUSCH.

Here, since the communication includes the information that identifies the target beam, the UE can transmit the communication using one or more BFR resources, of the set of BFR resources, that do not correspond to the target beam. In other words, since the communication includes the information that identifies the target beam, the UE can select any usable beam in association with performing the BFR. Thus, the UE can transmit the communication without waiting for a RACH occasion including BFR resources that correspond to the target beam, thereby reducing RACH latency and overall latency associated with performing the BFR. Thus, in some aspects, the one or more BFR resources in which the communication is transmitted may precede (e.g., in the time domain) one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

In some aspects, the UE may be configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell (e.g., a cell associated with sub-6 GHz communications) and a secondary cell (e.g., a cell associated with millimeter wave communications) . In some aspects, BFR resources can be configured for both the primary cell and the secondary cell. In such a case, the above-described two-step CFRA BFR technique can be used when the active BWP is associated with the primary cell or when the active BWP is associated with the secondary cell. In other words, either one of the primary and secondary cells can perform BFR separately (in whichever cell the beam failure occurs) .

Notably, the BFR using the two-step CFRA procedure as described in association with Fig. 3 does not require dedicated resources for transmitting the payload including the information that identifies the target beam and, therefore, is not costly in terms of resource usage. For example, performances of BFR occur relatively rarely for a given UE, and it is even more rare that multiple UEs experience beam failures at the same time. This allows multiple UEs to share uplink resources (e.g., PUSCH resources) for transmitting a communication associated with the two-step CFRA BFR. For example, each UE still has a respective dedicated preamble and can identify RACH occasions (e.g., as in regular CFRA BFR) . However, for the two-step CFRA BFR, multiple preambles can be mapped to the same uplink resource (e.g., the same one or more BFR resources) . For example, when more than one UE performs a two-step CFRA BFR at the same time, and each transmits a respective payload using the same uplink resource (e.g., a same PUSCH resource) , the network can still decode each UE’s dedicated preamble, but cannot decode the payloads. In such a case, the network can provide a respective uplink grant to each UE, and each UE can transmit another communication, including the payload, using a set of resources identified by the uplink grant. Accordingly, there is no need for dedicated uplink recourses for transmitting the first communication (i.e., the uplink resources can be shared) .

As indicated above, Fig. 3 is provided as an example. Other examples may differ from what is described with respect to Fig. 3.

Fig. 4 is a diagram illustrating an example 400 associated with BFR using a two-step CFRA procedure when no BFR resources are configured for an active BWP associated with a UE.

As shown by reference number 402, a UE (e.g., UE 120) may detect a beam failure associated with an active BWP of the UE, and may measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP (e.g., in a manner similar to that described above in association with Fig. 3) .

As shown by reference 404, the UE may select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams (e.g., in a manner similar to that described above in association with Fig. 3) .

In some aspects, after selecting the target beam, the UE may determine whether a set of BFR resources is configured for the active BWP. As shown by reference 406, in some aspects, the UE may determine that no BFR resources are configured for the active BWP. For example, the UE may receive a configuration indicating a set of BFR resources configured for an initial BWP only (i.e., a configuration that does not indicate BFR resources for the active BWP) , and may determine that no BFR resources are configured for the active BWP.

As shown by reference 408, based at least in part on determining that no BFR resources are configured for the active BWP, the UE may switch to an initial BWP associated with the UE (from the active BWP) .

As shown by reference 410, after switching to the initial BWP, the UE may transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the initial BWP. As described above, in some aspects, the communication includes the dedicated preamble associated with the UE, as well as information that identifies the target beam associated with the active BWP (e.g., an index corresponding to the target beam) . In some aspects, the information that identifies the target beam may be transmitted in a payload of the communication (e.g., in a msgA payload) . In some aspects, the information that identifies the target beam is transmitted in a MAC-CE. In some aspects, the communication may include a dedicate preamble associated with the UE, and the dedicated preamble may be transmitted over a PRACH. In some aspects, Further, the communication may include the information that identifies the target beam, and the information that identifies the target beam may be transmitted over a PUSCH.

In some aspects, the communication may include information that identifies the active BWP. For example, the payload of the communication may include an index or identifier that identifies the active BWP. Additionally, or alternatively, the information that identifies the target beam may further identify the active BWP. For example, the information that identifies the target beam may also identify the active BWP (e.g., when unique indices are assigned to target beams across different BWPs) .

In this example, the UE transmits the communication using one or more BFR resources that do not correspond to the target beam. In other words, since the BFR resources are configured for the initial BWP, the one or more BFR resources in which the UE transmits the communication need not correspond to the target beam associated with the active BWP. Thus, the UE can select any usable beam, associated with the initial BWP, and use the selected beam for transmitting the communication in association with performing the BFR, thereby reducing RACH latency and overall latency associated with performing the BFR. Here, the one or more BFR resources in which the communication is transmitted need not correspond or be related to the target beam (e.g., since the communication includes the information that identifies the target beam) .

In some aspects, after the BFR on the initial BWP is complete, the network (e.g., a base station 110) can indicate to the UE to switch back to the active BWP, and the UE can switch back the active BWP, accordingly. Here, the network can directly configure a TCI state of the UE based at least in part on the target beam indicated by the UE in the first communication. Notably, there is no need to perform beam management associated with the UE in this case, thereby reducing latency of beam recovery.

In some aspects, the UE may be configured to communicate based at least in a CA configuration associated with a primary cell and a secondary cell. In some aspects, BFR resources can be configured for both the primary cell and the secondary cell. In such a case, the above-described two-step CFRA BFR technique can be used when the active BWP and the initial BWP are associated with the primary cell or when the active BWP and the initial BWP are associated with the secondary cell. In other words, either one of the primary and secondary cells can perform BFR separately (in whichever cell the beam failure occurs) .

Notably, the BFR using the two-step CFRA procedure as described in association with Fig. 4 does not require dedicated resources for transmitting the payload including the information that identifies the target beam and, therefore, is not costly in terms of resource usage (e.g., for similar reasons as described in association with Fig. 3) . Here, in the rare case when multiple UEs transmit their respective payloads using a shared uplink resource, the network can provide a respective uplink grant to each UE, and each UE can transmit another communication, including the payload, using a set of resources identified by the uplink grant. Accordingly, there is no need for dedicated uplink recourses for transmitting the first communication (i.e., the uplink resources can be shared) .

As indicated above, Fig. 4 is provided as an example. Other examples may differ from what is described with respect to Fig. 4.

As described above, in some aspects, the UE may be configured to communicate based at least in a CA configuration associated with a primary cell (e.g., a cell associated with sub-6 GHz communications) and a secondary cell (e.g., a cell associated with millimeter wave communications) . In some aspects, BFR resources can be configured for the primary cell, but cannot be configured for the secondary cell. Fig. 5 is a diagram illustrating an example 500 associated with performing a BFR, associated with a serving cell of a UE, using a two-step CFRA procedure when BFR resources are configured only for a primary cell of the UE.

As shown by reference number 502, a UE (e.g., UE 120) may detect a beam failure associated with the serving cell of the UE (e.g., a beam failure associated with a beam used for communication with the serving cell) , and may measure, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell (e.g., in a manner similar to that described above in association with Fig. 3) . In some aspects, the serving cell may be the secondary cell or may be the primary cell.

As shown by reference 504, the UE may select a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams (e.g., in a manner similar to that described above in association with Fig. 3) .

As shown by reference 506, after selecting the target beam associated with the serving cell, the UE may transmit a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources associated with the primary cell. As described above, in some aspects, the communication includes the dedicate preamble associated with the UE, as well as information that identifies the target beam associated with the secondary cell (e.g., an index corresponding to the target beam) . In some aspects, the information that identifies the target beam may be transmitted in a payload of the communication (e.g., in a msgA payload) . In some aspects, the information that identifies the target beam is transmitted in a MAC-CE. In some aspects, the communication may include a dedicate preamble associated with the UE, and the dedicated preamble may be transmitted over a PRACH. In some aspects, Further, the communication may include the information that identifies the target beam, and the information that identifies the target beam may be transmitted over a PUSCH.

Here, since the communication includes the information that identifies the target beam, the UE can transmit the communication using one or more BFR resources, of the set of BFR resources, that do not correspond to the target beam. In other words, since the communication includes the information that identifies the target beam, the UE can select any usable beam in association with performing the BFR. Thus, the UE can transmit the communication without waiting for a RACH occasion including BFR resources that correspond to the target beam. For example, since BFR resources are configured only for the primary cell, target beams associated with the secondary cell and target beams associated with the primary cell are mapped to the set of BFR resources associated with the primary cell. Here, the UE need not wait for a RACH occasion corresponding to the target beam in order to transmit the communication, thereby reducing RACH latency and overall latency associated with performing the BFR. Thus, in some aspects, the one or more BFR resources in which the communication is transmitted may precede (e.g., in the time domain) one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

Notably, the BFR using the two-step CFRA procedure as described in association with Fig. 5 does not require dedicated resources for transmitting the payload including the information that identifies the target beam and, therefore, is not costly in terms of resource usage (e.g., for similar reasons as described in association with Fig. 3) . Here, in the rare case when multiple UEs transmit their respective payloads using a shared uplink resource, the network can provide a respective uplink grant to each UE, and each UE can transmit another communication, including the payload, using a set of resources identified by the uplink grant. As such, there is no need for dedicated uplink recourses for transmitting the first communication (i.e., the uplink resources can be shared) .

As indicated above, Fig. 5 is provided as an example. Other examples may differ from what is described with respect to Fig. 5.

Fig. 6 is a diagram illustrating an example process 600 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 600 is an example where a UE (e.g., UE 120 and/or the like) performs operations associated with beam failure recovery using a two-step CFRA procedure.

As shown in Fig. 6, in some aspects, process 600 may include transmitting a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources (block 610) . For example, the UE (e.g., using transmit processor 264, controller/processor 280, memory 282, and/or the like) may transmit a communication, associated with performing a BFR procedure, using one or more BFR resources of a set of BFR resources, as described above. In some aspects, the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) . In some aspects, the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .

Process 600 may include additional aspects, such as any single implementation or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect the UE may detect a beam failure associated with the UE, and measure, based at least in part on detecting the beam failure, a set of candidate beams. The UE may then select the target beam based at least in part on measuring the set of candidate beams.

In a second aspect, alone or in combination with the first aspect, the UE may determine that the set of BFR resources is configured for an active bandwidth part (BWP) associated with the UE. Here, when transmitting the communication, the UE may transmit the communication in the one or more BFR resources of the set of BFR resources associated with the active BWP.

In a third aspect, alone or in combination with the first aspect, the UE may determine that no BFR resources are configured for an BWP associated with the UE, and may switch to an initial BWP associated with the UE based at least in part on determining that no BFR resources are configured for the active BWP. Here, when transmitting the communication, the UE may transmit the communication in the one or more BFR resources of the set of BFR resources, the set of resources being configured for the initial BWP.

In a fourth aspect, alone or in combination with any one or more of the first through third aspects, the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell. Here, the BFR may be for a beam failure associated with the secondary cell, and the set of BFR resources is associated with the primary cell.

In a fifth aspect, alone or in combination with any one or more of the first through fourth aspects, the one or more BFR resources in which the communication is transmitted do not correspond to the target beam.

In a sixth aspect, alone or in combination with any one or more of the first through fifth aspects, the one or more BFR resources in which the communication is transmitted precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

In a seventh aspect, alone or in combination with any one or more of the first through sixth aspects, the information that identifies the target beam is transmitted in a medium access control (MAC) control element (CE) .

In an eighth aspect, alone or in combination with any one or more of the first through seventh aspects, the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.

In a ninth aspect, alone or in combination with any one or more of the first through eighth aspects, the UE may receive an uplink grant after transmitting the communication using the one or more BFR resources of the set of BFR resources, and may transmit another communication using a set of resources identified by the uplink grant. Here, the other communication includes the information that identifies the target beam.

Although Fig. 6 shows example blocks of process 600, in some aspects, process 600 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 6. Additionally, or alternatively, two or more of the blocks of process 600 may be performed in parallel.

Fig. 7 is a diagram illustrating an example process 700 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 700 is an example where a UE (e.g., UE 120 and/or the like) performs operations associated with beam failure recovery using a two-step CFRA procedure.

As shown in Fig. 7, in some aspects, process 700 may include detecting a beam failure associated with an active BWP of the UE (block 710) . For example, the UE (e.g., using receive processor 258, controller/processor 280, memory 282, and/or the like) may detect a beam failure associated with an active BWP of the UE, as described above.

As further shown in Fig. 7, in some aspects, process 700 may include measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP (block 720) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP, as described above.

As further shown in Fig. 7, in some aspects, process 700 may include selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams (block 730) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams, as described above.

As further shown in Fig. 7, in some aspects, process 700 may include determining that a set of BFR resources is configured for the active BWP (block 740) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may determine that a set of BFR resources is configured for the active BWP, as described above.

As further shown in Fig. 7, in some aspects, process 700 may include transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP (block 750) . For example, the UE (e.g., using transmit processor 264, controller/processor 280, memory 282, and/or the like) may transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of the set of BFR resources configured for the active BWP, as described above. In some aspects, the communication is associated with a two-step contention CFRA procedure. In some aspects, the communication includes information that identifies the target beam associated with the active BWP.

Process 700 may include additional aspects, such as any single implementation or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, the one or more BFR resources in which the communication is transmitted do not correspond to the target beam.

In a second aspect, alone or in combination with the first aspects, the one or more BFR resources in which the communication is transmitted precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

In a third aspect, alone or in combination with any one or more of the first and second aspects, the information that identifies the target beam is transmitted in a medium access control (MAC) control element (CE) .

In a fourth aspect, alone or in combination with any one or more of the first through third aspects, the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell

In a fifth aspect, alone or in combination with any one or more of the first through fourth aspects, the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.

In a sixth aspect, alone or in combination with any one or more of the first through fifth aspects, the UE may receive an uplink grant after transmitting the communication using the one or more BFR resources of the set of BFR resources configured for the active BWP, and may transmit another communication using a set of resources identified by the uplink grant. Here, the other communication includes the information that identifies the target beam associated with the active BWP.

Although Fig. 7 shows example blocks of process 700, in some aspects, process 700 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 7. Additionally, or alternatively, two or more of the blocks of process 700 may be performed in parallel.

Fig. 8 is a diagram illustrating an example process 800 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 800 is an example where a UE (e.g., UE 120 and/or the like) performs operations associated with beam failure recovery using a two-step CFRA procedure.

As shown in Fig. 8, in some aspects, process 800 may include detecting a beam failure associated with an active BWP of the UE (block 810) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may detect a beam failure associated with an active BWP of the UE, as described above.

As further shown in Fig. 8, in some aspects, process 800 may include measuring, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP (block 820) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may measure, based at least in part on detecting the beam failure, a set of candidate beams configured for the active BWP, as described above.

As further shown in Fig. 8, in some aspects, process 800 may include selecting a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams (block 830) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may select a target beam, associated with the active BWP, based at least in part on measuring the set of candidate beams, as described above.

As further shown in Fig. 8, in some aspects, process 800 may include switching to an initial BWP, associated with the UE, based at least in part on determining that no BFR resources are configured for the active BWP (block 840) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may switch to an initial BWP, associated with the UE, based at least in part on determining that no BFR resources are configured for the active BWP, as described above.

As further shown in Fig. 8, in some aspects, process 800 may include transmitting a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP (block 850) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may transmit a communication, associated with performing a BFR for the active BWP, using one or more BFR resources of a set of BFR resources configured for the initial BWP, as described above. In some aspects, the communication is associated with a two-step CFRA procedure. In some aspects, the communication includes information that identifies the target beam associated with the active BWP.

Process 800 may include additional aspects, such as any single implementation or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, the communication includes information that identifies the active BWP.

In a second aspect, alone or in combination with the first aspect, the information that identifies the target beam further identifies the active BWP.

In a third aspect, alone or in combination with any one or more of the first aspect and second aspects, the UE may switch back to the active BWP based at least in part on an indication received from a base station (e.g., base station 110) .

In a fourth aspect, alone or in combination with any one or more of the first through third aspects, the UE may select a beam associated with the initial BWP, and may transmit the communication using the selected beam.

In a fifth aspect, alone or in combination with any one or more of the first through fourth aspects, a transmission configuration indicator (TCI) state is configured on the UE based at least in part on the target beam.

In a sixth aspect, alone or in combination with any one or more of the first through fifth aspects, the information that identifies the target beam is transmitted in a medium access control (MAC) control element (CE) .

In a seventh aspect, alone or in combination with any one or more of the first through sixth aspects, the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell.

In a eighth aspect, alone or in combination with any one or more of the first through seventh aspects, the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.

In a ninth aspect, alone or in combination with any one or more of the first through eighth aspects, the UE may receive an uplink grant after transmitting the communication using the one or more BFR resources of the set of BFR resources configured for the initial BWP, and may transmit another communication using a set of resources identified by the uplink grant. Here, the other communication includes the information that identifies the target beam associated with the active BWP.

Although Fig. 8 shows example blocks of process 800, in some aspects, process 800 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 8. Additionally, or alternatively, two or more of the blocks of process 800 may be performed in parallel.

Fig. 9 is a diagram illustrating an example process 900 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 900 is an example where a UE (e.g., UE 120 and/or the like) performs operations associated with beam failure recovery using a two-step CFRA procedure.

As shown in Fig. 9, in some aspects, process 900 may include detecting a beam failure associated with a serving cell of the UE (block 910) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may detect a beam failure associated with a serving cell of the UE, as described above. In some aspects, the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell, and the serving cell is one of the primary cell or the secondary cell.

As further shown in Fig. 9, in some aspects, process 900 may include measuring, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell (block 920) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may measure, based at least in part on detecting the beam failure, a set of candidate beams associated with the serving cell, as described above.

As further shown in Fig. 9, in some aspects, process 900 may include selecting a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell (block 930) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may select a target beam, associated with the serving cell, based at least in part on measuring the set of candidate beams associated with the serving cell, as described above.

As further shown in Fig. 9, in some aspects, process 900 may include transmitting a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the UE (block 940) . For example, the UE (e.g., using receive processor 258, transmit processor 264, controller/processor 280, memory 282, and/or the like) may transmit a communication, associated with performing a BFR associated with the serving cell, using one or more BFR resources of a set of BFR resources associated with a primary cell of the UE, as described above. In some aspects, the communication is associated with a two-step CFRA procedure. In some aspects, the communication includes information that identifies the target beam associated with the serving cell.

Process 900 may include additional aspects, such as any single implementation or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a second aspect, alone or in combination with the first aspect, the one or more BFR resources in which the communication is transmitted precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

In a fourth aspect, alone or in combination with any one or more of the first through third aspects, the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.

In a fifth aspect, alone or in combination with any one or more of the first through fourth aspects, the UE may receive an uplink grant after transmitting the communication using the one or more BFR resources associated with the primary cell, and may transmit another communication using a set of resources identified by the uplink grant. Here, the other communication includes the information that identifies the target beam associated with the serving cell.

Although Fig. 9 shows example blocks of process 900, in some aspects, process 900 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 9. Additionally, or alternatively, two or more of the blocks of process 900 may be performed in parallel.

Fig. 10 is a diagram illustrating an example process 1000 performed, for example, by a base station, in accordance with various aspects of the present disclosure. Example process 1000 is an example where a base station (e.g., base station 110 and/or the like) performs operations associated with BFR using a two-step CFRA procedure.

As shown in Fig. 10, in some aspects, process 1000 may include receiving a communication, associated with a BFR procedure, in one or more BFR resources of a set of BFR resources (block 1010) . For example, the base station (e.g., using receive processor 238, controller/processor 240, memory 242, and/or the like) may receive a communication, associated with a BFR procedure, in one or more BFR resources of a set of BFR resources, as described above. In some aspects, the communication is associated with transmission of a preamble sequence uniquely associated with a UE (e.g., UE 120) , the preamble sequence being received over a PRACH. In some aspects, the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a PUSCH.

Process 1000 may include additional aspects, such as any single implementation or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, the one or more BFR resources in which the communication is received do not correspond to the target beam.

In a second aspect, alone or in combination with the first aspect, the one or more BFR resources in which the communication is received precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.

In a third aspect, alone or in combination with the any one or more of the first and second aspects, the information that identifies the target beam is received in a medium access control (MAC) control element (CE) .

In a fourth aspect, alone or in combination with the any one or more of the first through third aspects, The method of claim 1, further comprising configuring a transmission configuration indicator (TCI) state on the UE based at least in part on the target beam. Here, the base station may configure the TCI state on the UE without performing a beam management procedure associated with the UE.

In a fifth aspect, alone or in combination with the any one or more of the first through fourth aspects, the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.

In a fifth aspect, alone or in combination with the any one or more of the first through fourth aspects, the base station may transmit an uplink grant after receiving the communication in the one or more BFR resources of the set of BFR resources, and receive another communication in a set of resources identified by the uplink grant. Here, the other communication includes the information that identifies the target beam.

Although Fig. 10 shows example blocks of process 1000, in some aspects, process 1000 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 10. Additionally, or alternatively, two or more of the blocks of process 1000 may be performed in parallel.

Further disclosure is included in the appendix. The appendix is provided as an example only, and is to be considered part of the specification. A definition, illustration, or other description in the appendix does not supersede or override similar information included in the detailed description or figures. Furthermore, a definition, illustration, or other description in the detailed description or figures does not supersede or override similar information included in the appendix. Furthermore, the appendix is not intended to limit the disclosure of possible aspects.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term “component” is intended to be broadly construed as hardware, firmware, and/or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, and/or a combination of hardware and software.

As used herein, satisfying a threshold may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, firmware, and/or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code-it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) , and may be used interchangeably with “one or more. ” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

Beam Failure Recovery Using Two-Step CFRA procedure

Information

● Rel-16 will support two-step RACH, which consists of only two steps instead of four steps in the traditional contention-based RACH (CBRA) procedure

○ msgA transmission which includes both a preamble and PUSCH payload

○ msgB, i.e. response from network to confirm the completion of the RACH request

● There are debates regarding whether two-step RACH can be used for contention-free RACH procedure (CFRA)

○ Existing CFRA consists of only two steps too, because network provides a dedicated preamble for UE and hence there is no contention involved

○ There are two kinds of events that can use CFRA: handover and beam failure recovery (BFR)

● For handover, UE can include RRC Reconfiguration Complete message and/or other additional information in the payload of msgA to speed up the handover procedure. So there are benefits (ie latency reduction) for using two-step CFRA for handover

● For BFR, we think UE can also include extra information in msgA payload to help reduce the overall latency of a BFR procedure.

○ Key claims are related to for scenario and what information to include

Information -regular CFRA BFR in Rel-15

● Steps in CFRA BFR

○ NW can choose to configure dedicated resources for BFR

○ Each RACH occasion in this dedicated PRACH configuration corresponds to one of the reference beams configured for the UE

● Set of reference beams for UE is defined on a per BWP basis

○ Each US is also configured with a dedicated preamble which represents UE

○ After beam failure is detected, UE first decides in which BWP to perform BFR

● If the current active BWP has BFR resource, it stays in the current BWP and perform BFR

● Otherwise, it switches to initial BWP and perform BFR in the initial BWP

○ UE selects a desired beam as its new serving beam from the set of reference beams configured for the BWP in which it performs BWP

○ UE then transmits its dedicated preamble in the RACH occasion corresponds to the selected beam (the new target beam)

○ UE then monitors BFR search space on PDCCH for any message addresses to its C-RNTI

● RACH part of BFR is complete if UE receives a PDCCH msg that meets the above criteria

○ NW will reconfigure UE’s TCI state based on the new reference beam indicated by UE during BFR procedure

Two-step enhancements-Example Aspect 1

BFR in current active BWP

● If the active BWP has BFR resources configured

○ UE does not need to perform BWP switch to initial BWP to perform BFR

○ RACH occasions in BFR configuration have to be mapped to all the actually transmitted reference beams in that active BWP

● Or mapped to NW’s receiving beams, which typically are comparable to transmitted reference beams in numbers

○ This would mean PRACH configuration period can be long in some cases

● As a result, UE may have to wait a long time before the first RACH occasion associated with its target reference beam comes up

○ If UE can include index of its target reference beam in its msg A payload, then UE can select any usable beam that is available sooner to perform BFR => this reduces RACH latency

● This index can be sent in a MAC CE

● With two-step CBRA BFR available, why do we still need two-step CFRA BFR?

○ CFRA has no contention => shorter RACH latency, which is important for BFR

○ Two-step CFRA BFR does not need to have dedicated PUSCH resource, so it is not expensive in resource to support (see last slide for details)

Two-step enhancements -Example Aspect 2

BFR in initial BWP after a BWP switch

● If Active BWP does not have any BFR resource configured

○ UE has to fall back to initial BWP to perform BFR

○ Active BWP can be a wide BWP located in a different frequency band as the initial BWP

● This means that active BWP and initial BWP may have different set of reference beams

○ For example, active BWP may be configured with CSI-RS while initial BWP has only SSB configured

○ Since initial BWP has narrow bandwidth, only SSBs (which are wide beams) may be configured as reference beams

● In this case, UE has to perform the following:

○ first switch to initial BWP

○ perform measurements on the reference beams configured for the initial BWP

○ Perform BFR using BFR resources in initial BWP, which RACH occasions are tied to reference beams for initial BWP

○ After BFR is complete, network likely will switch UE back to a wider active BWP (for higher throughput)

○ Typically wide BWPs use wide-band CSI-RS (narrow beam) as reference beams

○ Network therefore needs to perform beam management procedure for UE to refine its beams based on CSI-RS

○ Network reconfigures UE’s TCI state to finally completes the RACH procedure

○ So the full recovery procedure consists of both BFR and beam management

○ With two-step CFRA based BFR, beam management is not needed

Two-step enhancements-Example Aspect 2

BFR in initial BWP after a BWP switch

● After beam failure is detected in active BWP

○ UE performs measurement on reference beams in the current active BWP and select a target beam configured for that BWP for recovery

○ It then switches to the initial BWP to perform two-step CFRA BFR

● The PUSCH payload in its msgA includes the index of its target beam in the active BWP

● Again, this index can be sent in a MAC CE

○ UE selects a suitable reference beam configured for initial BWP to send its msgA

● “Suitable” = good enough for UE to send msgA to network

● However, this selected beam does not have to be, or related to, UE’s target beam for recovery

○ Because msgA already includes UE’s preferred target beam. So there is no need to stick to the mapping between RACH occasion and target beam

● This relaxed requirement helps reduce RACH latency because of the same reason explained in Case 1

Two-step enhancements-Example Aspect 2

BFR in initial BWP after a BWP switch

● After BFR on initial BWP is complete

○ NW can switch UE back to the active BWP

○ NW can directly configure UE’s new TCI states based on the target reference beam indicated by UE in its msgA PUSCH payload.

○ No need to perform the beam management procedure required in the baseline case => reduces overall latency of recovery

Two-step enhancements-Example Aspect 3

BFR for SCells in inter-band CA configuration

● In inter-band CA configuration (e.g. FR1+FR2) , Pcell and Scells have different set of transmitted reference beams

○ FR1 cells have up to 8 beams, FR2 cells have up to 64 beams

● There are two ways to configure BFR resources

○ Both PCell and (some) SCells can be configured with BFR resources (not supported in Rel-15)

● FR1 and FR2 cells can perform BFR separately, depending on where cell failure occurs. Then the design in Case 1 and Case 2 applies

○ Only PCell can be configured with BFR resources (Rel-15 spec)

● The same arguments explained for Case 2 apply here too

● More details on this case in the next two slides

Two-step enhancements-Example Aspect 3

BFR for SCells in inter-band CA configuration

● Since only PCell is configured with BFR resources, BFR resources on PCell need to mapped to all the transmitted reference beams on all PCell and Scells

=> BFR resource will have long PRACH configuration period (can have up to 8+64 beams)

=> potentially long RACH latency, for reasons described in Case 1 &2

○ Enhancement with two-step CFRA

● On the serving cell where beam failure has occurred, UE performs measurements on candidate beams and select a new target beam for recovery

● It includes the index of the selected target beam in its msgA payload, which is sent over BFR resources in PCell. Again this index can be sent in a MAC CE.

● Why is this enhancement beneficial for BFR

● It allows NW to configure BFR resources on PCell based on the reference beams transmitted on PCell only, instead of all reference beams across all serving cells

○ In case PCell is in FR1 band, at most 8 beams => PRACH configuration period for BFR on PCell can be very short, which enables low RACH latency

PUSCH resource allocation for two-step CFRA BFR

● Network does not need to allocate dedicated PUSCH resource for two-step CFRA BFR

○ Otherwise it can be quite expensive

● Reasons

○ BFR does not happen often. And it is even rarer that multiple UEs have beam failures at the same time

○ This fact allows multiple UEs to share their msgA PUSCH resources for two-step CFRA BFR

● Each UE still has its dedicated preamble and RACH occasions as in regular CFRA BFR

● But for two-step CFRA BFR, multiple preambles can be mapped to the same PUSCH resource

● How this works

○ If only one UE performs two-step CFRA BFR, UE’s dedicated preamble indicates its identity. So network has no problem identify which UE is the TB sent over the shared PUSCH resource for

○ If more than one UE perform two-step CFRA BFR at the same time and transmit their payloads over the same PUSCH resource, network can still decode each UE’s dedicated preamble but no their payloads

○ To resolve collision in this case, network can provide a UL grant to UE. UE then sends network its msg A payload over this dedicated UL grant to network

Claims

A method of wireless communication, performed by a user equipment (UE) , comprising:

transmitting a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .
The method of claim 1, further comprising:

detecting a beam failure associated with the UE;

measuring, based at least in part on detecting the beam failure, a set of candidate beams; and

selecting the target beam based at least in part on measuring the set of candidate beams.
The method of claim 1, further comprising:

determining that the set of beam failure recovery (BFR) resources is configured for an active bandwidth part (BWP) associated with the UE; and

wherein transmitting the communication further comprises:

transmitting the communication in the one or more BFR resources of the set of BFR resources associated with the active BWP.
The method of claim 1, further comprising:

determining that no BFR resources are configured for an active bandwidth part (BWP) associated with the UE;

switching to an initial BWP associated with the UE based at least in part on determining that no BFR resources are configured for the active BWP; and

wherein transmitting the communication further comprises:

transmitting the communication in the one or more BFR resources of the set of BFR resources, the set of resources being configured for the initial BWP.
The method of claim 1, wherein the UE is configured to communicate based at least in a carrier aggregation (CA) configuration associated with a primary cell and a secondary cell,

wherein the BFR is for a beam failure associated with the secondary cell, and

wherein the set of BFR resources is associated with the primary cell.
The method of claim 1, wherein the one or more BFR resources in which the communication is transmitted do not correspond to the target beam.
The method of claim 1, wherein the one or more BFR resources in which the communication is transmitted precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.
The method of claim 1, wherein the information that identifies the target beam is transmitted in a medium access control (MAC) control element (CE) .
The method of claim 1, wherein a transmission configuration indicator (TCI) state is configured on the UE based at least in part on the target beam.
The method of claim 1, wherein the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.
The method of claim 1, further comprising:

receiving an uplink grant after transmitting the communication using the one or more BFR resources of the set of BFR resources; and

transmitting another communication using a set of resources identified by the uplink grant,

wherein the other communication includes the information that identifies the target beam.
A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

transmit a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a user equipment (UE) , cause the one or more processors to:

transmit a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with the UE, the preamble sequence being transmitted over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .
An apparatus for wireless communication, comprising:

means for transmitting a communication, associated with performing a beam failure recovery (BFR) procedure, using one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with the apparatus, the preamble sequence being transmitted over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with performing the BFR procedure, the information that identifies the target beam being transmitted over a physical uplink shared channel (PUSCH) .
A method of wireless communication, performed by a base station, comprising: receiving a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .
The method of claim 15, wherein the one or more BFR resources in which the communication is received do not correspond to the target beam.
The method of claim 15, wherein the one or more BFR resources in which the communication is received precede one or more other BFR resources, of the set of BFR resources, that correspond to the target beam.
The method of claim 15, wherein the information that identifies the target beam is received in a medium access control (MAC) control element (CE) .
The method of claim 15, further comprising configuring a transmission configuration indicator (TCI) state on the UE based at least in part on the target beam,

wherein configuring the TCI state on the UE being is performed without performing a beam management procedure associated with the UE.
The method of claim 15, wherein the one or more BFR resources include one or more shared physical uplink shared channel (PUSCH) resources.
The method of claim 15, further comprising:

transmitting an uplink grant after receiving the communication in the one or more BFR resources of the set of BFR resources; and

receiving another communication in a set of resources identified by the uplink grant,

wherein the other communication includes the information that identifies the target beam.
A base station for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

receive a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a base station, cause the one or more processors to:

receive a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .
An apparatus for wireless communication, comprising:

means for receiving a communication, associated with a beam failure recovery (BFR) procedure, in one or more BFR resources of a set of BFR resources,

wherein the communication is associated with transmission of a preamble sequence uniquely associated with a user equipment (UE) , the preamble sequence being received over a physical random access channel (PRACH) , and

wherein the communication includes information that identifies a target beam associated with the BFR procedure, the information that identifies the target beam being received over a physical uplink shared channel (PUSCH) .
A method, device, apparatus, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and/or processing system as substantially described herein with candidate to and as illustrated by the accompanying drawings, specification, and appendix.