Methods for directional sidelink (SL) beam failure detection

Abstract

A method of wireless communication by a first sidelink user equipment (UE) includes periodically receiving a set of sidelink beam failure detection reference signals (RSs) from a second sidelink UE. The method includes incrementing a beam failure detection (BFD) counter in response to one or more reference signals of the set of sidelink beam failure detection RSs having a received signal strength below a threshold. The first sidelink UE starts a beam failure detection timer in response to a reference signal of the set of sidelink beam failure detection reference signals having a received signal strength below a threshold. Another method performed by a sidelink UE can periodically transmit a set of sidelink BFD RSs to another sidelink UE. The set of sidelink BFD RSs includes one or more sidelink reception RSs. The sidelink UE configures another sidelink UE with a sidelink reception BFD RS.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application No. 17 / 336,118, filed June 1, 2021, entitled "DIRECTIONAL SIDELINK (SL) BEAM FAILURE DETECTION", which claims the benefit of U.S. Provisional Patent Application No. 63 / 047,816, filed July 2, 2020, entitled "DIRECTIONAL SIDELINK (SL) BEAM FAILURE DETECTION", the disclosure of which is expressly incorporated herein by reference in its entirety. Technical Field

[0003] Various aspects of this disclosure generally relate to wireless communication, and more particularly to techniques and apparatus for detecting beam faults in directional sidelinks (SL) of vehicle-to-everything (V2X) networks. Background Technology

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunications services such as telephone, video, data, messaging, and broadcasting. Typical wireless communication systems employ multiple access technologies that enable communication with multiple users by sharing available system resources. Examples of such multiple access technologies include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol enabling different wireless devices to communicate at the city, country, region, and even global levels. An example telecommunications standard is the fifth-generation (5G) New Radio (NR). 5G NR is part of the continuous evolution of mobile broadband, promulgated by the Third Generation Partnership Project (3GPP) to meet new requirements related to latency, reliability, security, scalability (e.g., with the Internet of Things (IoT)), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR can be based on the fourth-generation (4G) Long Term Evolution (LTE) standard. There is a need for further improvements to 5G NR technology. These improvements can also be applied to other multiple access technologies and telecommunications standards that employ them.

[0006] Wireless communication systems may include or provide support for various types of communication systems, such as vehicle-to-everything (V2X) communication systems. V2X systems can be used by vehicles to increase safety and help prevent collisions. Information about severe weather, nearby accidents, road conditions, and / or other information can be conveyed to the driver via V2X systems. In some cases, sidelink user equipment (UEs) (such as vehicles) can communicate directly with each other using D2D communication over a device-to-device (D2D) wireless link. These communications may be referred to as sidelink communications.

[0007] With the increasing demand for sidelink communication, different V2X communication systems compete for the same wireless communication resources. Furthermore, some sidelink UEs may be power-limited. Accordingly, there is a need to improve the efficiency of sidelink wireless communication. Summary of the Invention

[0008] According to various aspects of this disclosure, a method for wireless communication by a first sidelink user equipment (UE) includes: periodically receiving a set of sidelink beam fault detection reference signals (RSS) from a second sidelink UE. The method includes: incrementing a beam fault detection (BFD) counter in response to one or more reference signals in the sidelink beam fault detection RSS set having a received signal strength below a threshold. The first sidelink UE initiates a beam fault detection timer in response to a reference signal in the sidelink beam fault detection RSS set having a received signal strength below the threshold.

[0009] According to other aspects, a method performed by a sidelink UE can periodically transmit a set of sidelink beam fault detection reference signals (RS) to another sidelink UE. This set of sidelink beam fault detection reference signals includes one or more sidelink receive reference signals. The sidelink UE configures the other sidelink UE to have sidelink receive beam fault detection reference signals.

[0010] According to a further aspect, a method for wireless communication by a base station includes: configuring a beam fault detection (BFD) timer expiration value for a sidelink user equipment (UE). The method further includes: configuring the sidelink UE to have a maximum BFD counter value; and / or configuring the sidelink UE to have a sidelink BFD reference signal set.

[0011] In another aspect, a method for wireless communication by a base station receives an indication of a sidelink beam failure from a first sidelink user equipment (UE). The method also reports the indication to a second sidelink UE.

[0012] According to various aspects of this disclosure, a sidelink UE for wireless communication includes: means for periodically receiving a set of sidelink beam fault detection reference signals (RS) from a second sidelink UE. The UE includes: means for incrementing a beam fault detection (BFD) counter in response to one or more reference signals in the sidelink beam fault detection RS set having a received signal strength below a threshold. The sidelink UE includes: means for starting a beam fault detection timer in response to a reference signal in the sidelink beam fault detection RS set having a received signal strength below a threshold.

[0013] According to other aspects, a sidelink UE includes: means for periodically transmitting a set of sidelink beam fault detection reference signals (RS) to another sidelink UE. The set of sidelink beam fault detection reference signals includes one or more sidelink receive reference signals. The sidelink UE also includes means for configuring the other sidelink UE to have the sidelink receive beam fault detection reference signals.

[0014] According to a further aspect, a base station includes: means for configuring a beam fault detection (BFD) timer expiration value for a sidelink user equipment (UE). The base station also includes: means for configuring the sidelink UE to have a maximum BFD counter value; and / or means for configuring the sidelink UE to have a set of sidelink BFD reference signals.

[0015] In other aspects, a base station includes means for receiving an indication of a sidelink beam failure from a first sidelink user equipment (UE). The base station also includes means for reporting the indication to a second sidelink UE.

[0016] According to various aspects of this disclosure, an apparatus for wireless communication in a first sidelink UE includes a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are operable, when executed by the processor, to cause the apparatus to: periodically receive a set of sidelink beam fault detection reference signals (RSS) from a second sidelink UE. The instructions are also operable, when executed by the processor, to cause the apparatus to: increment a beam fault detection (BFD) counter in response to one or more reference signals in the sidelink beam fault detection RSS having a received signal strength below a threshold. The instructions further cause the processor to: start a beam fault detection timer in response to a reference signal in the sidelink beam fault detection RSS having a received signal strength below a threshold.

[0017] According to various aspects of this disclosure, an apparatus for wireless communication in a first sidelink UE includes a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are operable to, when executed by the processor, cause the apparatus to: periodically transmit a set of sidelink beam fault detection reference signals (RS) to the other sidelink UE. The set of sidelink beam fault detection reference signals includes one or more sidelink receive reference signals. The instructions also cause the processor to: configure the other sidelink UE to have sidelink receive beam fault detection reference signals.

[0018] According to various aspects of this disclosure, an apparatus for wireless communication in a base station includes a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions are operable to, when executed by the processor, cause the apparatus to: configure a beam fault detection (BFD) timer expiration value for a sidelink user equipment (UE). The instructions also cause the base station to: configure the sidelink UE to have a maximum BFD counter value; and / or configure the sidelink UE to have a sidelink BFD reference signal set.

[0019] In another aspect of this disclosure, an apparatus for wireless communication in a base station includes a processor, a memory coupled to the processor, and instructions stored in the memory. The instructions, when executed by the processor, cause the apparatus to: receive an indication of a cross-link beam failure from a first sidelink user equipment (UE). The instructions also cause the base station to: report the indication to a second sidelink UE.

[0020] According to one aspect of this disclosure, a non-transient computer-readable medium has program code recorded thereon. The program code is executed by a sidelink user equipment (UE) and includes program code for periodically receiving a set of sidelink beam fault detection reference signals (RSS) from a second sidelink UE. The program code further includes instructions for incrementing a beam fault detection (BFD) counter in response to one or more reference signals in the sidelink beam fault detection RSS having a received signal strength below a threshold. The program code also includes instructions for starting a beam fault detection timer in response to a reference signal in the sidelink beam fault detection RSS having a received signal strength below a threshold.

[0021] According to other aspects, a non-transient computer-readable medium has program code recorded thereon. The program code is executed by a sidelink user equipment (UE) and includes program code for periodically transmitting a set of sidelink beam fault detection reference signals (RS) to another sidelink UE. The set of sidelink beam fault detection reference signals includes one or more sidelink receive reference signals. The program code also includes instructions for configuring the other sidelink UE to have the sidelink receive beam fault detection reference signals.

[0022] According to a further aspect, a non-transient computer-readable medium has program code recorded thereon. This program code is executed by a base station and includes program code for configuring a beam fault detection (BFD) timer expiration value for a sidelink user equipment (UE). The program code also includes instructions for configuring the sidelink UE to have a maximum BFD counter value and / or configuring the sidelink UE to have a set of sidelink BFD reference signals.

[0023] According to other aspects, a non-transient computer-readable medium has program code recorded thereon. The program code is executed by a base station and includes program code for receiving an indication of a sidelink beam failure from a first sidelink user equipment (UE). The program code also includes instructions for reporting the indication to a second sidelink UE.

[0024] The aspects generally include, as described substantially with reference to the accompanying drawings and description and explained as such, methods, apparatus, systems, computer program products, non-transient computer-readable media, user equipment, base stations, wireless communication devices, and processing systems.

[0025] The foregoing has broadly outlined the features and technical advantages of the examples according to this disclosure in an effort to facilitate a better understanding of the following detailed description. Additional features and advantages will be described. The disclosed concepts and specific examples can be readily used as the basis for modifications or the design of other structures for implementing the same purposes as this disclosure. Such equivalent constructions do not depart from the scope of the appended claims. The characteristics of the disclosed concepts, in both their organization and manner of operation, and their associated advantages, will be better understood by considering the following description in conjunction with the accompanying drawings. Each drawing is provided for illustrative and descriptive purposes and not for defining limitations on the claims. Attached Figure Description

[0026] To gain a more detailed understanding of the features described above in this disclosure, reference can be made to various aspects of the above brief overview, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only certain typical aspects of this disclosure and should not be considered as limiting its scope, as other equivalent aspects are permissible in this description. Identical reference numerals in different drawings may identify the same or similar elements.

[0027] Figure 1 This is a diagram illustrating an example of a wireless communication system and access network.

[0028] Figure 2A , Figure 2B , Figure 2C and Figure 2DThese are illustrations illustrating examples of the first 5G New Radio (NR) frame, the downlink (DL) channel within a 5G NR subframe, the second 5G NR frame, and the uplink (UL) channel within a 5G NR subframe.

[0029] Figure 3 This is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

[0030] Figure 4 This is a diagram illustrating examples of vehicle-to-everything (V2X) systems according to various aspects of this disclosure.

[0031] Figure 5 This is a block diagram illustrating an example of a vehicle-to-everything (V2X) system with a roadside unit (RSU) according to various aspects of this disclosure.

[0032] Figure 6 The side-link (SL) communication scheme according to various aspects of this disclosure is explained.

[0033] Figure 7 This is a block diagram illustrating sidelink channels for a first user equipment (UE) and a second UE according to various aspects of this disclosure.

[0034] Figure 8 This is a block diagram illustrating a beam fault detection (BFD) reference signal transmitted from a first user equipment (UE) to a second UE according to various aspects of this disclosure.

[0035] Figure 9 This is a block diagram illustrating various aspects of beam fault detection (BFD) according to this disclosure.

[0036] Figure 10 This is a diagram illustrating an exemplary timeline for monitoring periodically transmitted beam fault detection (BFD) reference signals (RS) according to various aspects of this disclosure.

[0037] Figure 11 This is a block diagram illustrating the configuration for a user equipment (UE) to transmit and receive beam fault detection (BFD) reference signals (RS) according to various aspects of this disclosure.

[0038] Figure 12 This is a block diagram illustrating the configuration of a user equipment (UE) for transmitting and receiving beam fault detection (BFD) reference signals (RS) in a relay environment, according to various aspects of this disclosure.

[0039] Figure 13 This is a flowchart illustrating, for example, an example process performed by a sidelink user equipment according to various aspects of this disclosure.

[0040] Figure 14This is a flowchart illustrating, for example, an example process performed by a sidelink user equipment according to various aspects of this disclosure.

[0041] Figure 15 This is a flowchart illustrating, for example, an example process performed by a base station according to various aspects of this disclosure.

[0042] Figure 16 This is a flowchart illustrating, for example, an example process performed by a base station according to various aspects of this disclosure. Detailed Implementation

[0043] The various aspects of this disclosure are described more fully below with reference to the accompanying drawings. However, this disclosure may be implemented in many different forms and should not be construed as being limited to any specific structure or function given throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art. Based on these teachings, those skilled in the art will appreciate that the scope of this disclosure is intended to cover any aspect of the disclosed disclosure, whether implemented independently of or in combination with any other aspect of this disclosure. For example, any number of the aspects described may be used to implement an apparatus or method of practice. Furthermore, the scope of this disclosure is intended to cover such apparatus or methods practiced using additional structures, functionalities, or structures and functionalities that complement or supplement the various aspects of the described disclosure. It should be understood that any aspect of the disclosed disclosure may be implemented by one or more elements of the claims.

[0044] Several aspects of a telecommunications system will now be described with reference to various devices and techniques. These devices and techniques will be described in the following detailed description and explained in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively, "elements"). These elements can be implemented using hardware, software, or a combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0045] It should be noted that while the aspects may be described using terms commonly associated with 5G and next-generation wireless technologies, the aspects of this disclosure may be applied in communication systems based on other generations, such as and including 3G and / or 4G technologies.

[0046] In cellular communication networks, wireless devices can typically communicate with each other via one or more network entities, such as base stations or scheduling entities. Some networks support device-to-device (D2D) communication, which enables the discovery of nearby devices and communication with them using direct links between devices (e.g., without going through a base station, relay, or another node). D2D communication enables mesh networking and device-to-network relay functionality. Some examples of D2D technologies include Bluetooth pairing, Wi-Fi Direct, Miracast, and LTE-D. D2D communication can also be referred to as point-to-point (P2P) or sidelink communication.

[0047] D2D communication can be implemented using licensed or unlicensed frequency bands. Additionally, D2D communication avoids the overhead of routing to and from the base station. Therefore, D2D communication can improve throughput, reduce latency, and / or increase energy efficiency.

[0048] Types of D2D communication can include vehicle-to-everything (V2X) communication. V2X communication enables autonomous vehicles to communicate with each other. For example, an autonomous vehicle may include multiple sensors (e.g., LiDAR, radar, cameras, etc.). In most cases, the sensors of an autonomous vehicle are line-of-sight sensors. In contrast, V2X communication allows autonomous vehicles to communicate with each other in non-line-of-sight situations.

[0049] Sidelink (SL) communication refers to communication between User Equipment (UE) without tunneling through a Base Station (BS) and / or the core network. Sidelink communication can be transmitted on the Physical Sidelink Control Channel (PSCCH) and the Physical Sidelink Shared Channel (PSSCH). The PSCCH and PSSCH are similar to the Physical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH) in downlink (DL) communication between the BS and the UE. For example, the PSCCH may carry Sidelink Control Information (SCI) and the PSSCH may carry sidelink data (e.g., user data). Each PSCCH is associated with a corresponding PSSCH, where the SCI in the PSCCH may carry reservation and / or scheduling information for sidelink data transmission in the associated PSSCH. Use cases for sidelink communication can include Vehicle-to-Everything (V2X), Industrial Internet of Things (IIoT), and / or NR-Lightweight, etc.

[0050] Sidelink communication can occur in millimeter-wave (mmWave) frequencies. Therefore, beamforming is employed. With beamforming, the beams of the transmitting UE and the receiving UE must be aligned to create a sidelink channel for communication. When the beams between communicating sidelink UEs become misaligned, the signal-to-noise ratio (SNR) decreases, adversely affecting communication between the UEs. Beam misalignment can occur due to UE movement or other changes in the environment (such as when a bus moves between two communicating UEs). It is desirable for the UEs to detect the misalignment so that they can initiate a beam failure recovery process.

[0051] Figure 1 This is a diagram illustrating an example of a wireless communication system and access network 100. The wireless communication system (also known as a wireless wide area network (WWAN)) includes a base station 102, a user interface unit (UE) 104, an evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core (5GC)). Base station 102 may include macrocells (high-power cellular base stations) and / or small cells 102' (low-power cellular base stations). Macrocells include base stations. Small cells 102' include femtocells, picocells, and microcells.

[0052] Base station 102 configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with EPC 160 via backhaul link 132 (e.g., S1 interface). Base station 102 configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN)) can interface with core network 190 via backhaul link 184. Among other functions, base station 102 can also perform one or more of the following functions: user data delivery, radio channel cryptography and cryptography decoding, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of Non-Access Stratum (NAS) messages, NAS node selection, synchronization, Radio Access Network (RAN) sharing, Multimedia Broadcast Multicast Service (MBMS), subscriber and equipment tracking, RAN Information Management (RIM), paging, location, and delivery of alarm messages. Base stations 102 can communicate with each other directly or indirectly (e.g., via EPC 160 or core network 190) via backhaul link 134 (e.g., X2 interface). Backhaul link 134 can be wired or wireless.

[0053] Base station 102 can wirelessly communicate with UE 104. Each base station 102 can provide communication coverage for a corresponding geographic coverage area 110. Overlapping geographic coverage areas 110 may exist. For example, small cell 102' may have a coverage area 110' that overlaps with the coverage areas 110 of one or more macro base stations 102. A network that includes both small cells and macro cells may be referred to as a heterogeneous network. The heterogeneous network may also include a Home Evolved B Node (eNB) (HeNB) that can provide services to a restricted group called a Closed Subscriber Group (CSG). The communication link 120 between base station 102 and UE 104 may include uplink (UL) (also known as reverse link) transmission from UE 104 to base station 102 and / or downlink (DL) (also known as forward link) transmission from base station 102 to UE 104. The communication link 120 may use multiple-input multiple-output (MIMO) antenna technologies, including spatial multiplexing, beamforming, and / or transmit diversity. These communication links may use one or more carriers. For each carrier allocated in a carrier aggregation totaling up to Yx MHz (x component carriers) for transmission in each direction, base station 102 / UE 104 may use a spectrum with a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400 MHz, etc.). These carriers may or may not be adjacent to each other. Carrier allocation may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated to DL compared to UL). Component carriers may include primary component carriers and one or more secondary component carriers. The primary component carrier may be referred to as the primary cell (PCell), and the secondary component carriers may be referred to as secondary cells (SCells).

[0054] Some UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. D2D communication link 158 may use DL / UL WWAN spectrum. D2D communication link 158 may use one or more sidelink channels, such as the Physical Sidelink Broadcast Channel (PSBCH), Physical Sidelink Discovery Channel (PSDCH), Physical Sidelink Shared Channel (PSSCH), and Physical Sidelink Control Channel (PSCCH). D2D communication can be achieved through a wide variety of wireless D2D communication systems, such as FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0055] The wireless communication system may further include a Wi-Fi access point (AP) 150 communicating with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) before communication to determine whether the channel is available.

[0056] Small cell 102' can operate in licensed and / or unlicensed spectrum. When operating in unlicensed spectrum, small cell 102' can employ NR and use the same 5 GHz unlicensed spectrum as that used by Wi-Fi AP 150. Small cell 102' employing NR in unlicensed spectrum can enhance access network coverage and / or increase access network capacity.

[0057] Whether it's a small cell 102' or a large cell (e.g., a macro base station), base station 102 may include an eNB, a gB node (gNB), or another type of base station. Some base stations (such as gNB 180) may operate in conventional sub-6 GHz spectrum, millimeter wave (mmWave) frequencies, and / or near-mmWave frequencies to communicate with UE 104. When gNB 180 operates in mmWave or near-mmWave frequencies, gNB 180 may be referred to as an mmWave base station. Extremely high frequency (EHF) is a portion of the radio frequency (RF) in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and wavelengths between 1 mm and 10 mm. Radio waves in this band may be referred to as millimeter waves. Near-mmWave extends down to 3 GHz frequencies with a wavelength of 100 mm. Ultra-high frequency (SHF) bands extend between 3 GHz and 30 GHz, and are also referred to as centimeter waves. Communication using mmWave / near mmWave radio frequency bands (e.g., 3 GHz–300 GHz) has extremely high path loss and short range. mmWave base station 180 can utilize beamforming 182 with UE 104 to compensate for the extremely high path loss and short range.

[0058] Base station 180 may transmit beamformed signals to UE 104 in one or more transmission directions 182'. UE 104 may receive beamformed signals from base station 180 in one or more reception directions 182'. UE 104 may also transmit beamformed signals to base station 180 in one or more transmission directions. Base station 180 may receive beamformed signals from UE 104 in one or more reception directions. Base station 180 / UE 104 may perform beam training to determine the optimal reception and transmission directions for each of base station 180 / UE 104. The transmission and reception directions of base station 180 may be the same or different. The transmission and reception directions of UE 104 may be the same or different.

[0059] EPC 160 may include Mobility Management Entity (MME) 162, other MMEs 164, Serving Gateway 166, Multimedia Broadcast Multicast Service (MBMS) Gateway 168, Broadcast Multicast Service Center (BM-SC) 170, and Packet Data Network (PDN) Gateway 172. MME 162 may communicate with Home Subscriber Server (HSS) 174. MME 162 is the control node that handles signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are delivered through Serving Gateway 166, which is itself connected to PDN Gateway 172. PDN Gateway 172 provides UE IP address allocation and other functions. PDN Gateway 172 and BM-SC 170 are connected to IP Service 176. IP Service 176 may include the Internet, intranet, IP Multimedia Subsystem (IMS), PS streaming service, and / or other IP services. The BM-SC 170 provides functionality for MBMS user service provisioning and delivery. The BM-SC 170 can serve as an entry point for content provider MBMS transmissions, authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and schedule MBMS transmissions. The MBMS gateway 168 can be used to distribute MBMS traffic to base station 102 belonging to a Broadcast-Specific Service Single Frequency Network (MBSFN) area, and can be responsible for session management (start / stop) and collecting billing information related to Evolved MBMS (eMBMS).

[0060] The core network 190 may include Access and Mobility Management Functions (AMF) 192, other AMFs 193, Session Management Functions (SMF) 194, and User Plane Functions (UPF) 195. AMF 192 may communicate with Unified Data Management (UDM) 196. AMF 192 is the control node that handles signaling between UE 104 and the core network 190. Generally, AMF 192 provides Quality of Service (QoS) streaming and session management. All user Internet Protocol (IP) packets are delivered through UPF 195. UPF 195 provides UE IP address allocation and other functions. UPF 195 connects to IP services 197. IP services 197 may include the Internet, intranet, IP Multimedia Subsystem (IMS), PS streaming service, and / or other IP services.

[0061] Base station 102 may also be referred to as gNB, B-node, evolved B-node (eNB), access point, base transceiver station, radio base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), transmit / receive point (TRP), or any other suitable term. Base station 102 provides UE 104 with access to EPC 160 or core network 190. Examples of UE 104 include cellular phones, smartphones, Session Initiation Protocol (SIP) phones, laptop devices, personal digital assistants (PDAs), satellite radios, GPS devices, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablet devices, smart devices, wearable devices, vehicles, electricity meters, gas pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other similar functional devices. Some UE 104 may be referred to as IoT devices (e.g., parking timers, oil pumps, ovens, vehicles, heart monitors, etc.). UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, radio unit, remote unit, mobile device, radio device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, radio terminal, remote terminal, handheld device, user agent, mobile client, client, or some other suitable term.

[0062] Refer again Figure 1 In some respects, a sidelink UE (such as UE 104) can detect sidelink beam faults. UE 104 may include a beam fault detection component 199 configured to track the strength of a beam fault detection reference signal and initiate a beam fault recovery procedure based on the signal strength. A base station (such as base station 102) may operate using sidelink beam fault characteristics. Base station 102 may include a beam fault detection component 198 configured to communicate with the sidelink UE 104 regarding beam fault functionality.

[0063] While the following description focuses on 5G NR, it can be applied to other similar areas such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0064] Figure 2A This is a diagram 200 illustrating an example of the first subframe within the 5G NR frame structure. Figure 2B Figure 230 is an example illustrating the DL channel within a 5G NR subframe. Figure 2C This is a diagram 250 illustrating an example of the second subframe within the 5G NR frame structure. Figure 2D Figure 280 illustrates an example of the UL channel within a 5G NR subframe. The 5G NR frame structure can be Frequency Division Duplex (FDD), where subframes within a specific set of subcarriers (carrier system bandwidth) are dedicated to either DL or UL; or it can be Time Division Duplex (TDD), where subframes within a specific set of subcarriers (carrier system bandwidth) are dedicated to both DL and UL. Figure 2A , Figure 2C In the provided example, the 5G NR frame structure is assumed to be TDD, where subframe 4 is configured with slot format 28 (mostly DL) and subframe 3 is configured with slot format 34 (mostly UL), where D is DL, U is UL, and X is available for flexible use between DL and UL. Although subframes 3 and 4 are shown as having slot formats 34 and 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are all DL and all UL, respectively. Other slot formats 2-61 include a mixture of DL, UL, and flexible symbols. The UE is configured to have a slot format via the received Slot Format Indicator (SFI) (dynamically configured via DL Control Information (DCI) or semi-statically / statically configured via Radio Resource Control (RRC) signaling). Note that the following description also applies to 5G NR frame structures for TDD.

[0065] Other wireless communication technologies may have different frame structures and / or different channels. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-time slots, which may include 7, 4, or 2 symbols. Each time slot may include 7 or 14 symbols, depending on the time slot configuration. For time slot configuration 0, each time slot may include 14 symbols, while for time slot configuration 1, each time slot may include 7 symbols. Symbols on the DL can be Cyclic Prefix (CP) OFDM (CP-OFDM) symbols. Symbols on the UL can be CP-OFDM symbols (for high-throughput scenarios) or Discrete Fourier Transform (DFT) Extended OFDM (DFT-S-OFDM) symbols (also known as Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols) (for power-constrained scenarios; limited to single-stream transmission). The number of time slots within a subframe is based on the time slot configuration and parameter design. For slot configuration 0, different parameter designs μ from 0 to 5 allow 1, 2, 4, 8, 16, and 32 slots per subframe, respectively. For slot configuration 1, different parameter designs 0 to 2 allow 2, 4, and 8 slots per subframe, respectively. Correspondingly, for slot configuration 0 and parameter design μ, there are 14 symbols per slot and 2 symbols per subframe. μ Each time slot. The subcarrier spacing and symbol length / duration vary depending on the design parameters. The subcarrier spacing can be equal to 2. μ *15kHz, where μ is the parameter design from 0 to 5. Thus, parameter design μ=0 has a subcarrier spacing of 15kHz, while parameter design μ=5 has a subcarrier spacing of 480kHz. Symbol length / duration is inversely correlated with subcarrier spacing. Figures 2A to 2D Examples are provided for a slot configuration of 0 with 14 symbols per slot and a parameter design of μ=0 with 1 slot per subframe. The subcarrier spacing is 15kHz and the symbol duration is approximately 66.7μs.

[0066] The resource grid represents the frame structure. Each time slot includes a resource block (RB) extending 12 consecutive subcarriers (also known as a physical RB (PRB)). The resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0067] like Figure 2A As explained, some REs carry reference (pilot) signals (RS) for the UE. RS may include demodulated RS (DM-RS) for channel estimation at the UE (indicated as R for a particular configuration). x (where 100x is the port number, but other DM-RS configurations are possible) and Channel State Information Reference Signal (CSI-RS). RS may also include Beam Measurement RS (BRS), Beam Refinement RS (BRRS), and Phase Tracking RS (PT-RS).

[0068] Figure 2B Examples of various DL channels within a subframe of a frame are explained. The Physical Downlink Control Channel (PDCCH) carries the DCI within one or more Control Channel Elements (CCEs), each CCE comprising 9 RE Groups (REGs), each REG comprising 4 consecutive REs in OFDM symbols. The Primary Synchronization Signal (PSS) is located within symbol 2 of a specific subframe of the frame. The PSS is used by the UE 104 to determine subframe / symbol timing and physical layer identity. The Secondary Synchronization Signal (SSS) is located within symbol 4 of a specific subframe of the frame. The SSS is used by the UE to determine the physical layer cell identity group number and radio frame timing. Based on the physical layer identity and physical layer cell identity group number, the UE can determine the Physical Cell Identifier (PCI). Based on the PCI, the UE can determine the location of the aforementioned DM-RS. The Physical Broadcast Channel (PBCH) carrying the Primary Information Block (MIB) can logically group together with the PSS and SSS to form a Synchronization Signal (SS) / PBCH block. The MIB provides the number of RBs in the system bandwidth and the System Frame Number (SFN). The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information (such as System Information Blocks (SIBs)) that are not transmitted through the PBCH, and paging messages.

[0069] like Figure 2C As explained, some REs carry DM-RS for channel estimation at the base station (indicated as R for a particular configuration, but other DM-RS configurations are possible). The UE can transmit DM-RS for the Physical Uplink Control Channel (PUCCH) and DM-RS for the Physical Uplink Shared Channel (PUSCH). The PUSCH DM-RS can be transmitted in the first or second symbol of the PUSCH. The PUCCH DM-RS can be transmitted in different configurations depending on whether a short or long PUCCH is transmitted and on the specific PUCCH format used. Although not shown, the UE can transmit a Probe Reference Signal (SRS). The SRS can be used by the base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0070] Figure 2D Examples of various UL channels within a subframe of a frame are explained. The PUCCH can be located as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicators (CQI), precoding matrix indicators (PMI), rank indicators (RI), and hybrid automatic repeat request (HARQ) acknowledgement / negative acknowledgement (ACK / NACK) feedback. The PUCCH carries data and may additionally be used to carry buffer status reports (BSR), power clearance reports (PHR), and / or UCI.

[0071] Figure 3 This is a block diagram showing the communication between base station 310 and UE 350 in the access network. In the DL, IP packets from EPC 160 can be provided to controller / processor 375. Controller / processor 375 implements Layer 3 and Layer 2 functionality. Layer 3 includes the Radio Resource Control (RRC) layer, and Layer 2 includes the Serving Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, and Media Access Control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting system information (e.g., MIB, SIB), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter-Radio Access Technology (RAT) mobility, and measurement configuration of UE measurement reports; PDCP layer functionality associated with header compression / decompression, security (cryptography, cryptographic decoding, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with upper-layer packet data unit (PDU) delivery, error correction via Automatic Repeat Request (ARQ), concatenation, segmentation and reassembly of RLC service data units (SDUs), resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing MAC SDUs onto transport blocks (TBs), demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel priority differentiation.

[0072] Transmit (TX) processor 316 and receive (RX) processor 370 implement Layer 1 functionality associated with various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) decoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. TX processor 316 processes the mapping to the signal constellation based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The encoded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., a pilot) in the time and / or frequency domains, and subsequently combined using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time-domain OFDM symbol stream. The OFDM stream is spatially precoded to generate multiple spatial streams. Channel estimates from channel estimator 374 can be used to determine coding and modulation schemes and for spatial processing. The channel estimates can be derived from reference signals and / or channel condition feedback transmitted by UE 350. Each spatial stream can then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX can use the corresponding spatial stream to modulate a radio frequency (RF) carrier for transmission.

[0073] At UE 350, each receiver 354RX receives signals via its corresponding antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides this information to the receive (RX) processor 356. The TX processor 368 and RX processor 356 implement Layer 1 functionality associated with various signal processing functions. The RX processor 356 can perform spatial processing on the information to recover any spatial stream destined for UE 350. If there are multiple spatial streams destined for UE 350, they can be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then uses a Fast Fourier Transform (FFT) to transform the OFDM symbol stream from the time domain to the frequency domain. The frequency domain signal consists of a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, along with the reference signal, are recovered and demodulated by determining the signal constellation points most likely to be transmitted by base station 310. These soft decisions can be based on a channel estimate calculated by channel estimator 358. These soft decisions are then decoded and deinterleaved to recover the original data and control signals transmitted by base station 310 over the physical channel. This data and control signals are then provided to controller / processor 359, which implements layer 3 and layer 2 functionality.

[0074] The controller / processor 359 may be associated with a memory 360 that stores program code and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, cipher decoding, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller / processor 359 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operation.

[0075] Similar to the functionality described in conjunction with DL transmissions performed by base station 310, controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIB) capture, RRC connection, and measurement reporting; PDCP layer functionality associated with header compression / decompression and security (cryptography, cryptographic decoding, integrity protection, integrity verification); RLC layer functionality associated with upper-layer PDU delivery, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing MAC SDUs onto TBs, demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel priority differentiation.

[0076] The channel estimate derived by the channel estimator 358 from the reference signal or feedback transmitted by the base station 310 can be used by the TX processor 368 to select an appropriate coding and modulation scheme and to facilitate spatial processing. The spatial stream generated by the TX processor 368 can be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX can use the corresponding spatial stream to modulate an RF carrier for transmission.

[0077] UL transmissions are processed at base station 310 in a manner similar to that described in conjunction with the receiver function at UE 350. Each receiver 318RX receives signals via its corresponding antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides that information to the RX processor 370.

[0078] The controller / processor 375 may be associated with a memory 376 that stores program code and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, cipher decoding, header decompression, and control signal processing to recover IP packets from the UE 350. IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operation.

[0079] At least one of the TX processor 368, RX processor 356, and controller / processor 359 can be configured to perform and Figure 1 The beam fault detection component 199 integrates various aspects. Additionally, at least one of the TX processor 316, RX processor 370, and controller / processor 375 can be configured to perform actions related to... Figure 1 The beam fault detection component 198 integrates various aspects.

[0080] In some aspects, UE 104, 350 and / or base station 102, 310 may include means for receiving, means for incrementing, means for initiating, means for resetting, means for declaring, means for adjusting, means for indicating, means for handover, means for configuring, means for notifying, means for transmitting, and / or means for reporting. Such means may include combinations of... Figure 1 and Figure 3 The described UE 104, 350 and / or base station 102, 310 or one or more components.

[0081] Figure 4 This is a diagram of a device-to-device (D2D) communication system 400 (including V2X communication) according to various aspects of this disclosure. For example, the D2D communication system 400 may include V2X communication (e.g., a first UE 450 communicating with a second UE 451). In some aspects, the first UE 450 and / or the second UE 451 may be configured to communicate in licensed radio frequency spectrum and / or shared radio frequency spectrum. The shared radio frequency spectrum may be unlicensed, and therefore a variety of different technologies can be used to communicate using the shared radio frequency spectrum, including New Radio (NR), LTE, Advanced LTE, Licensed Assisted Access (LAA), Dedicated Short Range Communication (DSRC), MuLTEFire, 4G, and so on. The foregoing list of technologies should be considered illustrative and not exhaustive.

[0082] The D2D communication system 400 may use NR radio access technology. Of course, other radio access technologies, such as LTE radio access technology, may be used. In D2D communication (e.g., V2X communication or vehicle-to-vehicle (V2V) communication), UEs 450 and 451 may be on the networks of different mobile network operators (MNOs). Each network may operate in its own radio frequency spectrum. For example, the air interface to the first UE 450 (e.g., the Uu interface) may be on one or more frequency bands different from the air interface to the second UE 451. The first UE 450 and the second UE 451 may communicate via sidelink component carriers (e.g., via the PC5 interface). In some examples, the MNO may schedule sidelink communication between or among UEs 450 and 451 in licensed radio frequency spectrum and / or shared radio frequency spectrum (e.g., the 5 GHz radio spectrum band).

[0083] The shared radio frequency spectrum can be unlicensed, and therefore different technologies can use the shared radio frequency spectrum to communicate. In some respects, the MNO does not schedule D2D communication (e.g., sidelink communication) between or among UEs 450 and 451. The D2D communication system 400 may further include a third UE 452.

[0084] For example, the third UE 452 may operate on a first network 410 (e.g., of the first MNO) or another network. The third UE 452 may be in D2D communication with the first UE 450 and / or the second UE 451. The first base station 420 (e.g., gNB) may communicate with the third UE 452 via downlink (DL) carrier 432 and / or uplink (UL) carrier 442. DL communication may utilize various DL resources (e.g., DL subframes). Figure 2A ) and / or DL ​​channel ( Figure 2B UL communication can utilize various UL resources (e.g., UL subframes). Figure 2C ) and UL channel ( Figure 2D This is performed via UL carrier 442.

[0085] The first network 410 operates in the first spectrum and includes a first base station 420 (e.g., gNB) that communicates with at least the first UE 450, such as... Figures 1 to 3 As described in [the document]. The first base station 420 (e.g., gNB) can communicate with the first UE 450 via DL carrier 430 and / or UL carrier 440. DL communication can utilize various DL resources (e.g., DL subframes). Figure 2A ) and / or DL ​​channel ( Figure 2B UL communication can utilize various UL resources (e.g., UL subframes). Figure 2C ) and UL channel ( Figure 2D This is performed via UL carrier 440.

[0086] In some aspects, the second UE 451 may be on a different network than the first UE 450. In some aspects, the second UE 451 may be on a second network 411 (e.g., of a second MNO). The second network 411 may operate in a second spectrum (e.g., a second spectrum different from the first spectrum) and may include a second base station 421 (e.g., a gNB) communicating with the second UE 451, for example, as Figures 1 to 3 As described in [the text].

[0087] The second base station 421 can communicate with the second UE 451 via DL carrier 431 and UL carrier 441. DL communication uses various DL resources (e.g., DL subframes). Figure 2A ) and / or DL ​​channel ( Figure 2B UL communication is performed via DL carrier 431. UL communication utilizes various UL resources (e.g., UL subframes). Figure 2C ) and / or UL channel ( Figure 2D This is performed via UL carrier 441.

[0088] In a conventional system, the first base station 420 and / or the second base station 421 assign resources to the UE for device-to-device (D2D) communication (e.g., V2X and / or V2V communication). For example, the resources may be a pool of UL resources, which include both orthogonal resources (e.g., one or more Frequency Division Multiplexing (FDM) channels) and non-orthogonal resources (e.g., Code Division Multiplexing (CDM) / Resource Extended Multiple Access (RSMA) in each channel). The first base station 420 and / or the second base station 421 may configure the resources via PDCCH (e.g., faster method) or RRC (e.g., slower method).

[0089] In some systems, each UE 450, 451 autonomously selects resources for D2D communication. For example, each UE 450, 451 can sense and analyze channel occupancy during a sensing window. UE 450, 451 can use the sensed information to select resources from the sensing window. As discussed, one UE 451 can assist another UE 450 in performing resource selection. The assisting UE 451 may be referred to as the receiving UE or partner UE, which can potentially notify the transmitting UE 450. The transmitting UE 450 can transmit information to the receiving UE 451 via sidelink communication.

[0090] D2D communication (e.g., V2X communication and / or V2V communication) may be performed via one or more sidelink carriers 470, 480. The one or more sidelink carriers 470, 480 may include one or more channels, such as, for example, the Physical Sidelink Broadcast Channel (PSBCH), the Physical Sidelink Discovery Channel (PSDCH), the Physical Sidelink Shared Channel (PSSCH), and the Physical Sidelink Control Channel (PSCCH).

[0091] In some examples, sidelink carriers 470 and 480 can operate using the PC5 interface. The first UE 450 can transmit to one or more (e.g., multiple) devices (including to the second UE 451) via the first sidelink carrier 470. The second UE 451 can transmit to one or more (e.g., multiple) devices (including to the first UE 450) via the second sidelink carrier 480.

[0092] In some respects, UL carrier 440 and first sidelink carrier 470 may be aggregated to increase bandwidth. In some respects, first sidelink carrier 470 and / or second sidelink carrier 480 may share a first spectrum (with first network 410) and / or share a second spectrum (with second network 411). In some respects, sidelink carriers 470, 480 may operate in unlicensed / shared radio frequency spectrum.

[0093] In some aspects, sidelink communication on a sidelink carrier can occur between a first UE 450 and a second UE 451. In one aspect, the first UE 450 can perform sidelink communication with one or more (e.g., multiple) devices (including the second UE 451) via a first sidelink carrier 470. For example, the first UE 450 can transmit broadcast transmissions to multiple devices (e.g., the second UE 451 and the third UE 452) via the first sidelink carrier 470. The second UE 451 (e.g., among other UEs) can receive such broadcast transmissions. Additionally or alternatively, the first UE 450 can transmit multicast transmissions to multiple devices (e.g., the second UE 451 and the third UE 452) via the first sidelink carrier 470. The second UE 451 and / or the third UE 452 (e.g., among other UEs) can receive the multicast transmissions. Multicast transmissions can be connectionless or connection-oriented. Multicast transmissions can also be referred to as groupcast transmissions.

[0094] Furthermore, the first UE 450 may transmit unicast transmissions to devices (such as the second UE 451) via a first sidelink carrier 470. The second UE 451 (e.g., among other UEs) may receive the unicast transmissions. Additionally or alternatively, the second UE 451 may perform sidelink communication with one or more (e.g., multiple) devices (including the first UE 450) via a second sidelink carrier 480. For example, the second UE 451 may transmit broadcast transmissions to multiple devices via the second sidelink carrier 480. The first UE 450 (e.g., among other UEs) may receive the broadcast transmissions.

[0095] In another example, the second UE 451 may transmit multicast transmissions to multiple devices (e.g., the first UE 450 and the third UE 452) via a second sidelink carrier 480. The first UE 450 and / or the third UE 452 (e.g., among other UEs) may receive the multicast transmissions. Furthermore, the second UE 451 may transmit unicast transmissions to devices (such as the first UE 450) via the second sidelink carrier 480. The first UE 450 (e.g., among other UEs) may receive the unicast transmissions. The third UE 452 may communicate in a similar manner.

[0096] In some respects, for example, such sidelink communication on a sidelink carrier between the first UE 450 and the second UE 451 can occur without the MNO allocating resources (e.g., one or more portions of resource blocks (RBs), time slots, frequency bands, and / or channels associated with sidelink carriers 470, 480) and / or scheduling such communication. Sidelink communication may include traffic communication (e.g., data communication, control communication, paging communication, and / or system information communication). Furthermore, sidelink communication may include sidelink feedback communication associated with traffic communication (e.g., feedback information transmission for previously received traffic communication). Sidelink communication may employ at least one sidelink communication structure having at least one feedback symbol. The feedback symbol of the sidelink communication structure may be assigned to any sidelink feedback information that can be transmitted between the devices (e.g., the first UE 450, the second UE 451, and / or the third UE 452) in the device-to-device (D2D) communication system 400. As discussed, the UE can be a vehicle (e.g., UE 450, 451), a mobile device (e.g., 452), or another type of device. In some cases, the UE can be a special type of UE, such as a roadside unit (RSU).

[0097] Figure 5 Examples of a V2X system 500 with an RSU 510 according to various aspects of this disclosure are explained. For example... Figure 5As shown, the transmitting UE 504 transmits data to the RSU 510 and the receiving UE 502 via sidelink transmission 512. Additionally or alternatively, the RSU 510 may transmit data to the transmitting UE 504 via sidelink transmission 512. The RSU 510 may forward data received from the transmitting UE 504 to the cellular network (e.g., gNB) 508 via UL transmission 514. The gNB 508 may transmit data received from the RSU 510 to other UEs 506 via DL transmission 516. The RSU 510 may be integrated into traffic infrastructure (e.g., traffic lights, light poles, etc.). For example, as... Figure 5 As shown, RSU 510 is a traffic light located on one side of road 520. RSU 510 may be a self-contained unit, either as an additional or alternative location.

[0098] Figure 6 A sidelink communication scheme 600 according to some aspects of this disclosure is explained. Scheme 600 can be adopted by a UE (such as UE 104) in a network (such as network 100). Figure 6 In the diagram, the x-axis represents time, and the y-axis represents frequency.

[0099] In scheme 600, a shared radio frequency band 601 is divided into multiple sub-channels or frequency sub-bands 602 (shown as 602S0, 602S1, 602S2) in frequency and multiple sidelink frames 604 (shown as 604a, 604b, 604c, 604d) in time for sidelink communication. Band 601 can be at any suitable frequency. Band 601 can have any suitable bandwidth (BW) and can be divided into any suitable number of frequency sub-bands 602. The number of frequency sub-bands 602 can depend on the sidelink communication BW requirements.

[0100] Each sidelink frame 604 includes a sidelink resource 606 in each frequency subband 602. Figure 605 indicates the type of sidelink channel within the sidelink resource 606. In some instances, frequency gaps or guard bands may be specified between adjacent frequency subbands 602, for example, to mitigate adjacent band interference. The sidelink resource 606 may have a structure substantially similar to that of NR sidelink resources. For example, the sidelink resource 606 may include several subcarriers or RBs in frequency and several symbols in time. In some instances, the sidelink resource 606 may have a duration between approximately one millisecond (ms) and approximately 20 ms. Each sidelink resource 606 may include PSCCH 610 and PSSCH 620. PSCCH 610 and PSSCH 620 may be multiplexed in time and / or frequency. Figure 6In the example, for each sidelink resource 606, PSCCH 610 is located during the start symbol period(s) of sidelink resource 606 and occupies a portion of the corresponding frequency subband 602, while PSSCH 620 occupies the remaining time-frequency resources in sidelink resource 606. In some instances, sidelink resource 606 may also include a physical sidelink feedback channel (PSFCH), which, for example, is located during the end symbol period(s) of sidelink resource 606. Generally, PSCCH 610, PSSCH 620, and / or PSFCH may be multiplexed within sidelink resource 606.

[0101] PSCCH 610 can carry SCI 660 and / or sidelink data. Depending on the sidelink application, the sidelink data can be in various forms and types. For example, when the sidelink application is a V2X application, the sidelink data can carry V2X data (e.g., vehicle location information, speed and / or direction, vehicle sensing measurements, etc.). Alternatively, when the sidelink application is an IIoT application, the sidelink data can carry IIoT data (e.g., sensor measurements, device measurements, temperature readings, etc.). PSFCH can be used to carry feedback information, such as HARQACK / NACK for sidelink data received in earlier sidelink resource 606.

[0102] In the NR sidelink frame structure, sidelink frames 604 in resource pool 608 can be temporally consecutive. A sidelink UE (e.g., UE 104) can include a reservation for sidelink resource 606 in a subsequent sidelink frame 604 in SCI 660. Thus, another sidelink UE (e.g., a UE in the same NR-U sidelink system) can perform SCI sensing in resource pool 608 to determine whether sidelink resource 606 is available or occupied. For example, if a sidelink UE detects an SCI indicating a reservation for sidelink resource 606, the sidelink UE can suppress transmission in the reserved sidelink resource 606. If the sidelink UE determines that no reservation for sidelink resource 606 is detected, the sidelink UE can transmit in sidelink resource 606. In this way, SCI sensing can help the UE identify a target frequency subband 602 to reserve for sidelink communication and avoid intra-system conflicts with another sidelink UE in the NR sidelink system. In some respects, the UE can be configured with a sensing window for SCI sensing or monitoring to reduce intra-system conflicts.

[0103] In some aspects, the sidelink UE can be configured with a frequency hopping mode. In this respect, the sidelink UE can hop from one frequency subband 602 in one sidelink frame 604 to another frequency subband 602 in another sidelink frame 604. Figure 6In the example described, during sidelink frame 604a, the sidelink UE is located in frequency subband 602. S2 SCI 660 is transmitted in side link resource 606 to reserve space in frequency subband 602. S1 The next sidelink frame 604b contains sidelink resources 606. Similarly, during sidelink frame 604b, the sidelink UE operates in frequency subband 602. S1 SCI 662 is transmitted in side link resource 606 to reserve the frequency subband 602. S1 The next sidelink frame 604c contains sidelink resources 606. During sidelink frame 604c, the sidelink UE is located in frequency subband 602. S1 SCI 664 is transmitted in side link resource 606 to reserve the frequency subband 602. S0 The next sidelink frame 604d contains sidelink resources 606. During sidelink frame 604d, the sidelink UE is located in frequency subband 602. S0 SCI 668 is transmitted in sidelink resource 606. SCI 668 can reserve sidelink resource 606 in subsequent sidelink frames 604.

[0104] The SCI can also indicate scheduling information and / or destination identifier (ID) that identifies the target receiving sidelink UE of the next sidelink resource 606. Thus, the sidelink UE can monitor SCIs transmitted by other sidelink UEs. After detecting an SCI in sidelink resource 606, the sidelink UE can determine whether it is the target receiving UE based on the destination ID. If the sidelink UE is the target receiving UE, it can proceed to receive and decode the sidelink data indicated by the SCI. In some aspects, multiple sidelink UEs can simultaneously transmit sidelink data in different frequency subbands (e.g., via frequency division multiplexing (FDM)) in sidelink frame 604. For example, in sidelink frame 604b, one pair of sidelink UEs can transmit sidelink data using sidelink resource 606 in frequency subband 602S2, while another pair of sidelink UEs can transmit sidelink data using sidelink resource 606 in frequency subband 602S1.

[0105] In some aspects, scheme 600 is used to synchronize sidelink communication. That is, the sidelink UE can be synchronized in time and aligned in terms of symbol boundaries and sidelink resource boundaries (e.g., the start time of sidelink frame 604). The sidelink UE can perform synchronization in various forms, such as based on a sidelink synchronization signal block (SSB) received from the sidelink UE and / or an NR-U SSB received from the BS (e.g., BS105 and / or 205) when within the coverage of the serving BS. In some aspects, the sidelink UE can be pre-configured with a resource pool 608 in frequency band 601, for example, when within the coverage of the serving BS. Resource pool 608 may include multiple sidelink resources 606. The BS can configure the sidelink UE with a resource pool configuration that indicates resources in frequency band 601 and / or subband 602 and / or timing information associated with sidelink frame 604. In some aspects, scheme 600 includes mode-2 radio resource allocation (RRA) (e.g., supporting autonomous RRA that can be used for sidelink UEs outside coverage or sidelink UEs in partial coverage).

[0106] Sidelink communication can occur in millimeter-wave (mmWave) frequencies. Therefore, beamforming is employed. With beamforming, the beams of the transmitting UE and the receiving UE must be aligned to create a sidelink channel for communication. When the beams between communicating sidelink UEs become misaligned, the signal-to-noise ratio (SNR) decreases, adversely affecting communication between the UEs. Beams may become misaligned due to UE movement or other changes in the environment (such as when a bus moves between two communicating UEs). It is desirable for the UEs to detect the misalignment so that they can initiate a beam failure recovery process. The detection of misalignment is called beam failure detection (BFD).

[0107] Figure 7 This is a block diagram illustrating a sidelink (SL) channel for a first UE (UE1) and a second UE (UE2) according to various aspects of this disclosure. The sidelink channel includes a beam 710 for communication between UE1 and UE2. The channel also includes a beam 720 for communication between UE2 and UE1. In many cases, the transmit (Tx) beam used by UE2 to transmit to UE1 is the same as the receive (Rx) beam used by UE2 to receive from UE1. Figure 7 This scenario is illustrated. However, there are some exceptions when separate and different beams are used for transmission and reception (e.g., due to maximum permissible exposure (MPE) limits).

[0108] When the sidelink channel between UE1 and UE2 changes, or if one or both of UE1 and UE2 move, the sidelink beams 710 and 720 will become misaligned, causing the UEs to be unable to communicate. Aspects of this disclosure include techniques for detecting when the sidelink beams are misaligned (e.g., beam fault detection (BFD)) so that the UEs can begin a process of discovering another beam set to re-establish their connection. This process is referred to as beam fault recovery (BFR).

[0109] Figure 8 This is a block diagram illustrating a beam fault detection (BFD) reference signal (or pilot) transmitted from a first UE (UE1) to a second UE (UE2). According to aspects of this disclosure, the second UE (UE2) has a beam fault detection (BFD) counter configured to count the number of times a BFD reference signal is received from UE1 below a threshold level before the BFD timer expires. In one example, this threshold level could be a Layer 1 Reference Signal Received Power (L1-RSRP) threshold. If the BFD counter equals the maximum BFD counter value before the BFD timer expires, the UE declares a beam fault (BF) and triggers beam fault recovery. The UE declares the beam fault by sending a message indicating the fault.

[0110] According to various aspects of this disclosure, UE1 has a set of BFD transmit reference signals (e.g., slTxRadioLinkMonitoringRS) and UE2 has a set of BFD receive reference signals (e.g., slRxRadioLinkMonitoringRS) for beam fault detection. In some examples, the BFD transmit and receive reference signals may be Side Link Synchronization Block (SL SSB) reference signals and SL Channel State Information Reference Signals (SL CSI-RS).

[0111] The BFD transmit reference signal set (e.g., slTxRadioLinkMonitoringRS) may include a list of beam fault detection (BFD) reference signals to be transmitted. The BFD receive reference signal set (e.g., slRxRadioLinkMonitoringRS) may include a list of beam fault detection (BFD) reference signals to be received.

[0112] The BFD maximum counter value, BFD timer expiration time, BFD transmit reference signal (e.g., slTxRadioLinkMonitoringRs), and BFD receive reference signal (e.g., slRxRadioLinkMonitoringRs) can be configured according to different options. In the first option, for UE1, the transmitter of the BFD reference signal can configure UE2's BFD receive reference signal (e.g., slRxRadioLinkMonitoringRs), BFD maximum counter value, and BFD timer expiration time. In this option, UE1 configures its own BFD transmit reference signal (e.g., slTxRadioLinkMonitoringRs). In the second option, for UE2, the receiver of the BFD reference signal can configure UE1's BFD transmit reference signal (e.g., slTxRadioLinkMonitoringRs), while UE2 configures its own BFD receive reference signal (e.g., slRxRadioLinkMonitoringRs), BFD maximum counter value, and BFD timer expiration time. In the third option, the base station (e.g., gNB) configures all four items: the maximum BFD counter value, the BFD timer expiration time, the BFD transmit reference signal, and the BFD receive reference signal. Additionally, for the first and second options, these configurations can be relayed by the base station to another UE.

[0113] According to various aspects of this disclosure, if a beam fault indication (BFI) is present, certain steps are taken. First, if the BFD timer is not running, the BFD timer is started or restarted. Second, the BFD counter is incremented when the received signal strength (e.g., L1-RSRP) of all received reference signals is less than a threshold (e.g., Qout). In another option, the received signal strength of some of the received reference signals is less than a threshold. A beam fault indication occurs when all signal strengths are less than the threshold (or some signal strengths are less than the threshold). Before the BFD timer expires, if the BFD counter is greater than or equal to the maximum BFD counter value, beam fault recovery (BFR) is triggered and the BFR timer is started. If the BFD timer expires, the BFD counter is reset to 0. In other words, no further beam fault indications occur before the BFD timer expires, indicating that the current beam is still aligned.

[0114] Figure 9 This is a block diagram illustrating various aspects of beam fault detection according to this disclosure. For example... Figure 9As shown, the second UE (UE2) is configured to monitor the first side-link (SL) synchronization block reference signal (SL SSB1) and the first SL channel state information reference signal (SL CSI-RS1) transmitted by the first UE (UE1) for beam fault detection (BFD) between UE1 and UE2. The BFD receive reference signal set of UE2 (e.g., slRxRadioLinkMonitoringRS) includes the first SL SSB (SLSSB1) and the first SL CSI-RS (SL-CSI-RS1). Based on locally stored information, UE2 knows which receive beams 902, 904 to use for receiving this BFD receive reference signal set (e.g., slRxRadioLinkMonitoringRS). UE1 is configured to transmit SL SSB1 and SL CSI-RS1 for UE2 to receive and monitor beam fault detection. The BFD transmit reference signal set of UE1 (e.g., slTxRadioLinkMonitoringRS) includes a first SL SSB (SL SSB1) and a first SL CSI-RS (SLCSI-RS1). Based on locally stored information, UE1 knows which transmit beams 906, 908 to use for transmitting the BFD transmit reference signal set (e.g., slTxRadioLinkMonitoringRS).

[0115] Figure 10 This is a diagram illustrating an exemplary timeline for monitoring periodically transmitted beam fault detection reference signals according to various aspects of this disclosure. At time t1, UE1 transmits BFD reference signals (SSB1 and CSI-RS1 in this case) to UE2. Both received signals are stronger than a threshold. At time t2, UE1 again transmits BFD reference signals (SSB1 and CSI-RS1) to UE2. Both received signals are weaker than the threshold. Consequently, UE2 starts a BFD timer and increments the BFD counter to one. At time t3, UE1 transmits BFD reference signals (SSB1 and CSI-RS1) to UE2. Both signals are stronger than the threshold. Consequently, the BFD counter remains unchanged. At time t4, the BFD timer expires. Because the maximum BFD counter value (e.g., 2 in this example) has not been reached before the BFD timer expires, the BFD counter is reset.

[0116] At time t5, UE1 transmits BFD reference signals (SSB1 and CSI-RS1) to UE2. Both received signals are weaker than the threshold. Therefore, UE2 starts the BFD timer and increments the BFD counter to one. At time t6, UE1 transmits BFD reference signals (SSB1 and CSI-RS1) to UE2. Both signals are weaker than the threshold. Therefore, UE2 increments the BFD counter to 2, which is the maximum value in this example. Because the maximum value is reached before the BFD timer expires, UE2 declares a beam fault.

[0117] although Figure 10 The sequence of events that trigger a beam fault is illustrated, but this disclosure is not limited thereto. For example, a set of strong BFD reference signals may be received between times t5 and t6. In response to the strong reference signal at that time, the counter will not reset. Thus, a weak BFD reference signal at time t6 will still trigger a beam fault declaration.

[0118] According to a further aspect of this disclosure, when UE2 receives a BFD reference signal (e.g., slRxRadioLinkMonitoringRS) from UE1, UE2 can change and / or adjust its receive beam. For example, instead of using receive beam 1 to receive SL-SSB1, UE2 can use an adjacent beam (e.g., receive beam 2) to receive SL-SSB1. This change may occur due to a slight rotation of UE2, and the adjusted beam compensates for this slight rotation. Based on the change in the receive beam used to receive the BFD reference signal (e.g., slRxRadioLinkMonitoringRS), UE2 can send a message to UE1 instructing UE2 to change its receive beam used to receive the BFD reference signal (e.g., slRxRadioLinkMonitoringRS). In response to receiving this message, UE1 can change and / or improve its transmit beam for its BFD reference signal (e.g., slTxRadioLinkMonitoringRS).

[0119] Three options are described for determining which UE transmits the Beam Failure Detection (BFD) reference signal and which UE receives the reference signal. In the first option, a UE is randomly selected as the transmitter. In the first option, the transmitter and receiver roles can change or remain unchanged. If roles change, role switching can occur periodically or based on conditions such as the number of sidelink connections of the UE. When the transmitter and receiver roles change, the receiver UE can trigger beam failure recovery (before the handover) if the BFD counter is not zero or is above a certain threshold (but not the maximum counter value).

[0120] In the second option, if the first UE has many sidelink connections to one or more other sidelink UEs, the first UE can be the transmitter, while the other UEs can be the receivers. Figure 11 An example of the second option is shown. Figure 11 This is a block diagram illustrating the configuration for a user equipment (UE) to transmit and receive beam fault detection (BFD) reference signals (RS) according to various aspects of this disclosure. Figure 11 In this scenario, UE1 has three sidelink connections: to UE2, UE3, and UE4. Each of the other UEs has only a single sidelink connection. Therefore, UE1 is designated as the transmitter because it has more sidelink connections than the other UEs. If UE1 is the receiver, it will receive BFD reference signals from all other UEs. In this case, UE1 tracks multiple sidelinks (e.g., unlike UE2 which tracks the UE1-UE2 sidelink, UE3 which tracks the UE1-UE3 sidelink, and UE4 which tracks the UE1-UE4 sidelink). Furthermore, UE1 may have to send and receive control signals with other UEs to ensure that BFD reference signal resources do not conflict. If UE1 is the transmitter, it will be able to prevent conflicts on its own.

[0121] Figure 12 The scenario for the third option is shown. Figure 12 This is a block diagram illustrating the configuration for a user equipment (UE) to transmit and receive beam fault detection (BFD) reference signals (RS) in a relay environment, according to various aspects of this disclosure. In a third option, the relayed UE transmits the BFD reference signal, and the relay UE receives the BFD reference signal. The relay UE relays uplink traffic from the relayed UE to the base station and relays downlink traffic from the base station to the relayed UE. Figure 12 In the example shown, UE1 is a relay node communicating with a base station (e.g., gNB) via an access link (uU connection). UE1 also communicates with UE2 via a side link. In this example, UE1 is the relay UE, and UE2 is the relayed UE. According to the third option, UE2 transmits a BFD reference signal, and UE1 receives the BFD reference signal. If a beam fault exists, the relay UE can directly notify the gNB. In other aspects, the base station receives an indication of a side link beam fault from UE2. The base station reports this indication to UE1 and can also stop downlink and uplink traffic to and from UE2.

[0122] According to a further aspect of this disclosure, BFD reference signals (e.g., slTxRadioLinkMonitoringRS and slRxRadioLinkMonitoringRS) can be configured based on the Physical Side Link Shared Channel (PSCCH) transmit and receive beams. For example, UE1's BFD transmit reference signal (e.g., slTxRadioLinkMonitoringRS) can be configured based on the PSCCH transmit beam (e.g., for UE1 to transmit control information to UE2) and the PSCCH receive beam (e.g., for UE1 to receive control information from UE2). UE2's BFD receive reference signal (e.g., slRxRadioLinkMonitoringRS) can be configured based on the PSCCH transmit beam (e.g., for UE2 to transmit control information to UE1) and the PSCCH receive beam (e.g., for UE2 to receive control information from UE1).

[0123] As indicated above, Figure 7-12 This is provided as an example. Other examples may differ from the one provided. Figure 7-12 The example described.

[0124] Figure 13 This is a flowchart illustrating an example process 1300 performed, for example, by a sidelink user equipment, according to various aspects of this disclosure. Example process 1300 is an example of directional sidelink beam fault detection. In some aspects, process 1300 may include periodically receiving a set of sidelink beam fault detection (BFD) reference signals (RS) from a second sidelink UE (block 1302). For example, the UE (e.g., using antenna 352, RX / TX 354, RX processor 356, controller / processor 359, and / or memory 360) may periodically receive BFD RS. In some aspects, the UE may periodically switch to a transmitter role to transmit the second sidelink beam fault detection reference signal (RS) set.

[0125] Process 1300 may include incrementing a beam fault detection (BFD) counter (block 1304) in response to at least one reference signal in the sidelink beam fault detection RS set having a received signal strength below a threshold. For example, the UE (e.g., using controller / processor 359 and / or memory 360) may increment the counter. The UE may reset the beam fault detection counter by setting it to zero in response to the beam fault detection timer expiring and no beam fault being declared.

[0126] In some aspects, process 1300 may include starting a beam fault detection timer (block 1306) in response to at least one reference signal in the sidelink beam fault detection reference signal set having a received signal strength below a threshold. For example, the UE (e.g., using controller / processor 359 and / or memory 360) may start the timer. In some aspects, the beam fault detection timer has not been started before the signal strength falls below the threshold. The UE may declare a beam fault in response to the beam fault detection counter reaching its maximum value before the beam fault detection timer expires. The UE may also initiate a beam fault recovery procedure in response to the declaration of a beam fault. In other aspects, the UE may reset the beam fault detection timer by stopping the timer and setting it to zero in response to the beam fault detection timer expiring without a declared beam fault.

[0127] Figure 14 This is a flowchart illustrating, for example, an example process 1400 performed by a sidelink user equipment according to various aspects of this disclosure. Example process 1400 is an example of directional sidelink beam fault detection.

[0128] In some aspects, process 1400 may include periodically transmitting a set of sidelink beam fault detection reference signals (RS) to the second sidelink UE, the set of sidelink beam fault detection reference signals including at least one sidelink receive reference signal (block 1402). For example, the UE (e.g., using antenna 352, RX / TX 354, TX processor 368, controller / processor 359, and / or memory 360) may transmit BFR RS. The set of beam fault detection reference signals may include a sidelink synchronization signal block (SL SSB) reference signal and / or a sidelink channel state information reference signal (SL CSI-RS).

[0129] In some aspects, process 1400 may include configuring a second sidelink UE to have at least one sidelink receive beam fault detection reference signal (block 1404). For example, the UE (e.g., using antenna 352, RX / TX 354, TX processor 368, controller / processor 359, and / or memory 360) may be configured to have a beam fault detection timer expiration value and / or a maximum beam fault detection counter value.

[0130] Figure 15This is a flowchart illustrating an example process 1500 performed by a base station according to various aspects of this disclosure. Example process 1500 is an example of directional sidelink beam fault detection. In some aspects, process 1500 may include configuring a beam fault detection (BFD) timer expiration value for a sidelink user equipment (UE) (block 1502). For example, a base station (e.g., using antenna 320, RX / TX 318, TX processor 316, controller / processor 375, and / or memory 376) may configure the BFD timer expiration value. In some aspects, process 1500 may include configuring the sidelink UE to have a maximum BFD counter value (block 1504). For example, a base station (e.g., using antenna 320, RX / TX 318, TX processor 316, controller / processor 375, and / or memory 376) may configure a maximum BFD counter value. In some aspects, process 1500 may include configuring the sidelink UE to have a sidelink BFD reference signal set (block 1506). For example, a base station (e.g., using antenna 320, RX / TX 318, TX processor 316, controller / processor 375, and / or memory 376) can configure the BFD reference signal set.

[0131] Figure 16 This is a flowchart illustrating an example process 1600 performed by a base station, for example, according to various aspects of this disclosure. Example process 1600 is an example of directional sidelink beam fault detection. In some aspects, process 1600 may include receiving an indication of a sidelink beam fault from a first sidelink user equipment (UE) (block 1602). For example, the base station (e.g., using antenna 320, RX / TX 318, RX processor 370, controller / processor 375, and / or memory 376) receives this indication. Process 1600 may also include reporting the indication to a second sidelink UE (block 1604). For example, the base station (e.g., using antenna 320, RX / TX 318, TX processor 316, controller / processor 375, and / or memory 376) reports the indication.

[0132] Examples of implementations are described in the following numbered clauses.

[0133] 1. A method for wireless communication by a first sidelink user equipment (UE), comprising:

[0134] Periodically receive a set of side link beam fault detection (BFD) reference signals (RS) from the second side link UE;

[0135] In response to at least one reference signal in the sidelink beam fault detection reference signal set having a received signal strength below a threshold, the beam fault detection counter is incremented; and

[0136] A beam fault detection timer is started in response to at least one reference signal in the side link beam fault detection reference signal set having a received signal strength lower than the threshold.

[0137] 2. The method of Clause 1, further comprising: in response to at least one reference signal in the sidelink beam fault detection reference signal set having a received signal strength lower than the threshold, activating the beam fault detection timer, wherein the beam fault detection timer had not been activated before the signal strength was lower than the threshold.

[0138] 3. The methods described in Clause 1 or 2, further including:

[0139] In response to the expiration of the beam fault detection timer and no beam fault being declared, the beam fault detection counter is reset by setting it to zero; and

[0140] In response to the beam fault detection timer expiring without a declared beam fault, the timer is reset by stopping the beam fault detection timer and setting the timer to zero.

[0141] 4. The methods described in any of the above clauses further include:

[0142] A beam fault is declared in response to the beam fault detection counter reaching its maximum value before the beam fault detection timer expires; and

[0143] The beam fault recovery process is initiated in response to a declared beam fault.

[0144] 5. The method of any of the preceding clauses, wherein the set of side link beam fault detection reference signals includes the side link synchronization signal block (SL SSB) reference signal.

[0145] 6. The method of any of the preceding clauses, wherein the set of sidelink beam fault detection reference signals includes a sidelink channel state information reference signal (SL CSI-RS).

[0146] 7. The method of any of the above clauses further includes: receiving information from the second side link UE or base station that transmits the beam fault detection timer expiration value.

[0147] 8. The method of any of the above clauses further includes: receiving information from the second side link UE or base station that conveys the value of the maximum beam fault detection counter.

[0148] 9. The method of any of the above clauses further includes: receiving configuration of the set of sidelink beam fault detection reference signals from the second sidelink UE or base station.

[0149] 10. The method of any of the preceding clauses further includes: adjusting at least one receiving beam by selecting different beams for receiving the set of side link beam fault detection reference signals.

[0150] 11. The method as described in any of the preceding clauses further includes: instructing the adjustment to the second sidelink UE.

[0151] 12. The method of any of the preceding clauses further includes: periodically switching to the transmitter role to transmit a set of second-side link beam fault detection reference signals (RS).

[0152] 13. The method of any of the preceding clauses further includes: declaring a beam fault before the beam fault detection counter reaches its maximum value, prior to transmitting the second sidelink beam fault detection reference signal set.

[0153] 14. The method as described in any of the preceding clauses, wherein the first side link UE is a relay UE.

[0154] 15. The method described in any of the above clauses further includes: notifying the base station of a beam failure.

[0155] 16. The method of any of the preceding clauses further includes: configuring a receive beam for the set of sidelink beam fault detection reference signals based on the physical sidelink control channel (PSCCH) transmit beam and the PSCCH receive beam.

[0156] 17. A method for wireless communication by a first sidelink user equipment (UE), comprising:

[0157] A set of sidelink beam fault detection reference signals (RS) is periodically transmitted to the second sidelink UE, the set of sidelink beam fault detection reference signals including at least one sidelink receive reference signal; and

[0158] The second sidelink UE is configured to have at least one sidelink receive beam fault detection reference signal.

[0159] 18. The method of Clause 17 further includes: configuring the second sidelink UE to have a beam fault detection timer expiration value.

[0160] 19. The method of Clause 17 or 18 further includes: configuring the second sidelink UE to have a maximum beam fault detection counter value.

[0161] 20. The method of any one of clauses 17-19, wherein the beam fault detection reference signal set includes a side link synchronization signal block (SL SSB) reference signal.

[0162] 21. The method of any one of clauses 17-20, wherein the beam fault detection reference signal set includes a side link channel state information reference signal (SL CSI-RS).

[0163] 22. The method as described in any of Clauses 17-21 further includes:

[0164] Receive from the second sidelink UE an indication of a modified receive beam for the at least one sidelink receive beam fault detection reference signal; and

[0165] Update the transmit beam used for the fault detection reference signal of the at least one side link transmit beam.

[0166] 23. The method of any of Clauses 17-22, wherein the first sidelink UE is a relayed UE.

[0167] 24. The method of any one of clauses 17-23 further comprises: configuring the at least one sidelink transmit beam fault detection reference signal based on at least one physical sidelink control channel (PSCCH) transmit beam and at least one PSCCH receive beam.

[0168] 25. The method of any of Clauses 17-24 further includes: periodically switching to the receiver role to monitor the set of second beam fault detection reference signals (RS).

[0169] The foregoing disclosure provides explanations and descriptions, but is not intended to be exhaustive or to limit the aspects to the precise forms disclosed. Modifications and variations may be made in light of the foregoing disclosure or may be obtained through practice.

[0170] As used, the term "component" is intended to be interpreted broadly as hardware, firmware, and / or a combination of hardware and software. As used, a processor is implemented using hardware, firmware, and / or a combination of hardware and software.

[0171] Some aspects are described in conjunction with thresholds. As used, satisfying a threshold can refer to a value 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, etc., depending on the context.

[0172] It will be apparent that the described systems and / or methods can be implemented in various forms, including hardware, firmware, and / or combinations of hardware and software. The actual dedicated control hardware or software code used to implement these systems and / or methods is not limited in any aspect. Thus, the operation and behavior of these systems and / or methods are described without reference to any specific software code—it is understood that software and hardware can be designed to implement these systems and / or methods, at least in part, based on this description.

[0173] Although specific combinations of features are described in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of aspects. In fact, many of these features can be combined in ways not specifically described in the claims and / or disclosed in the specification. Although each dependent claim listed below may be directly subordinated to only one claim, the disclosure of aspects includes each dependent claim being combined with each other claim in this set of claims. The phrase “at least one of” refers to any combination of these items, including single members. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc, as well as any combination having multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c).

[0174] The elements, actions, or instructions used should not be interpreted as critical or necessary unless explicitly stated otherwise. Furthermore, as used, the articles “a” and “a certain” are intended to include one or more items and may be used interchangeably with “one or more.” Additionally, as used, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.) and may be used interchangeably with “one or more.” In cases where only one item is intended, the phrase “only one” or similar language is used. Moreover, as used, the terms “have,” “contain,” “include,” etc., are intended to be open-ended terms. Furthermore, the phrase “based on” is intended to mean “at least partially based on” unless otherwise explicitly stated.

Claims

1. A method of wireless communication by a first sidelink user equipment (UE), comprising: periodically receiving a first set of sidelink beam failure detection (BFD) reference signals (RSs) from a second sidelink UE, the first set of sidelink beam failure detection reference signals comprising a plurality of reference signals; incrementing a beam failure detection counter in response to all of the first set of sidelink beam failure detection reference signals having a received signal strength below a threshold value; starting a beam failure detection timer in response to the first set of sidelink beam failure detection reference signals having a received signal strength below the threshold value; and in response to transitioning to a transmitter role, transmitting a second set of sidelink beam failure detection reference signals, declaring a beam failure prior to transmitting the second set of sidelink beam failure detection reference signals before the beam failure detection counter reaches a maximum value.

2. The method of claim 1, further comprising: starting the beam failure detection timer in response to the first set of sidelink beam failure detection reference signals having a received signal strength below the threshold value, wherein the beam failure detection timer has not been started before the signal strength is below the threshold value.

3. The method of claim 1, further comprising: resetting the beam failure detection counter by setting the beam failure detection counter to zero in response to the beam failure detection timer expiring and a beam failure not being declared; and resetting the beam failure detection timer by stopping the beam failure detection timer and setting the timer to zero in response to the beam failure detection timer expiring and a beam failure not being declared.

4. The method of claim 1, further comprising: starting a beam failure recovery procedure in response to declaring a beam failure.

5. The method of claim 1, wherein the first set of sidelink beam failure detection reference signals comprises a sidelink synchronization signal block (SL SSB) reference signal.

6. The method of claim 1, wherein the first set of sidelink beam failure detection reference signals comprises a sidelink channel state information reference signal (SL CSI-RS).

7. The method of claim 1, further comprising: receiving information conveying a beam failure detection timer expiration value from the second sidelink UE or a network entity.

8. The method of claim 1, further comprising: receiving information conveying a maximum beam failure detection counter value from the second sidelink UE or a network entity.

9. The method of claim 1, further comprising: receiving a configuration of the first set of sidelink beam failure detection reference signals from the second sidelink UE or a network entity.

10. The method of claim 1, further comprising: adjusting at least one receive beam for receiving the first set of sidelink beam failure detection reference signals by selecting a different beam.

11. The method of claim 10, further comprising: indicating the adjustment to the second sidelink UE.

12. The method of claim 1, wherein the first sidelink UE is a relay UE.

13. The method of claim 12, further comprising: informing a network entity of a beam failure.

14. The method of claim 1, further comprising: configuring a receive beam for the first set of sidelink beam failure detection reference signals based on a physical sidelink control channel (PSCCH) transmit beam and a PSCCH receive beam.

15. A method of wireless communication by a first sidelink user equipment (UE), comprising: periodically transmitting a first set of sidelink beam failure detection reference signals (RSs) to a second sidelink UE, the first set of sidelink beam failure detection reference signals including a first reference signal type for a first beam and a second reference signal type for a second beam, wherein the first reference signal type includes a sidelink synchronization signal block (SL SSB) reference signal and the second reference signal type includes a sidelink channel state information reference signal (SL CSI-RS); receiving a beam failure indication from the second sidelink UE prior to expiration of a beam failure detection timer before a beam failure detection counter at the second sidelink UE reaches a maximum beam failure detection counter value; and periodically transitioning to a receiver role to monitor a second set of sidelink beam failure detection reference signals (RSs).

16. The method of claim 15, further comprising: configuring the second sidelink UE with a beam failure detection timer expiration value.

17. The method of claim 15, further comprising: configuring the second sidelink UE with a maximum beam failure detection counter value.

18. The method of claim 15, further comprising: receiving an indication from the second sidelink UE of a changed receive beam for at least one sidelink receive beam failure detection reference signal; and updating a transmit beam for the at least one sidelink transmit beam failure detection reference signal.

19. The method of claim 15, wherein the first sidelink UE is a relay UE.

20. The method of claim 15, further comprising: configuring at least one sidelink transmit beam failure detection reference signal based on at least one physical sidelink control channel (PSCCH) transmit beam and at least one PSCCH receive beam.

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