Beam failure recovery associated with high frequency communications

Abstract

Systems, methods, and instrumentalities are described herein for beam failure recovery associated with high frequency communications. A wireless transmit receive unit (WTRU) may receive configuration information for candidate beam reference signals (RS) of a first type or a second type. Upon detecting a beam failure, the WTRU may determine a beam failure recovery type (e.g., one-step beam failure recovery or two-step beam failure recovery) and select and transmit a first type of candidate beam RS to the network. The WTRU may measure a subset of candidate beam RSs of a second type (e.g., associated with the candidate beam RSs of the first type). Based on the measurement, the WTRU may select a second type of candidate beam RS from a subset of the second type of candidate beam RS and transmit it to the network.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 334,968, filed on April 26, 2022, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Mobile communications using wireless communications continue to evolve. The fifth generation may be referred to as 5G. Previous (legacy) mobile communications may be, for example, fourth generation (4G) Long Term Evolution (LTE). Summary of the invention

[0004] Systems, methods, and means for beam failure recovery associated with high frequency communications are described herein. A wireless transmit receive unit (WTRU) may be configured to receive configuration information indicating a first type of candidate beam reference signal (RS) and a second type of candidate beam RS. The WTRU may detect a beam failure and determine a beam failure recovery (BFR) type. If the determined BFR type is a two-step BFR type, the WTRU may select a candidate beam RS from the first type of candidate beam RS and send an indication of the selected candidate beam RS to the network. The WTRU may also determine a subset of second type candidate beam RSs associated with the selected candidate beam RS and perform measurements on the subset of second type candidate beam RSs during a first monitoring window. Based on the measurements, the WTRU may select a second type candidate beam RS from the subset and send an indication of the selected second type candidate beam RS to the network.

[0005] The first type of candidate beam reference signal may be associated with a wide beam and the second type of candidate beam reference signal may be associated with a narrow beam. The WTRU may determine the BFR type as one of a one-step BFR type or a two-step BFR type. The subset of the second type of candidate beam RS may be further determined based on an association between the first type of candidate RS and the second type of candidate beam RS.

[0006] The BFR type may be determined based on one or more of: a frequency range (FR); a subcarrier spacing (SCS); a measurement; or a configuration. Detecting a beam failure may be based on a measurement of a beam failure detection reference signal (BFD RS) corresponding to the beam failure. The WTRU may determine a BFD parameter set based on the type of the BFD RS, and the BFD parameter set may include one or more timers, event counters, or thresholds. The WTRU may determine a beam failure based on the parameters.

[0007] The WTRU may send an indication of the selected candidate beam RS using either a physical random access channel (PRACH) preamble or a resource. The WTRU may determine a subset of the second type candidate beam RSs based on a configured association with the selected candidate beam RSs of the wide beam pattern or through an indication received in a PDCCH transmission.

[0008] The WTRU may monitor the PDCCH transmission in the second monitoring window using the selected candidate beam RS. The WTRU may receive the PDCCH transmission in the second monitoring window using the selected candidate beam RS, and the PDCCH transmission may include an indication of an acknowledgment. The WTRU may send an indication of the selected second type candidate beam RS using a PRACH transmission.

[0009] The WTRU may receive configuration information for beam failure recovery reference signal (BFR-RS) sets, and each BFR-RS set may include resources and configuration associated with beam failure recovery. The WTRU may select one or more BFR-RS sets for beam failure recovery based on either a priority or a beam quality measurement, and may determine a second type candidate beam RS using a highest priority BFR-RS from the selected one or more BFR-RS sets or by sequentially using each selected BFR-RS set based on priority to attempt to determine a new candidate beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0011] Figure 1B is an example of an embodiment in which Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within the illustrated communication system;

[0012] Figure 1C is an example of an embodiment in which Figure 1A a system diagram of an example Radio Access Network (RAN) and an example Core Network (CN) used within the illustrated communication system;

[0013] Figure 1D is an example of an embodiment in which Figure 1A A system diagram of another example RAN and another example CN used within the illustrated communication system;

[0014] Figure 2 An example of hierarchical beamforming by gNB is illustrated.

[0015] Figure 3An example of hierarchical beamforming by IRS is illustrated.

[0016] Figure 4 An example of a two-step beam determination process (eg, a beam determination process for determining a new beam) is illustrated.

[0017] Figure 5 An example configuration of multiple BFR RS sets for new beam determination is illustrated.

[0018] Figure 6 Examples involving single-step and two-step beam failure recovery are illustrated. DETAILED DESCRIPTION

[0019] Figure 1A 1 is a diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0020] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0021] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0022] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0023] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0024] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0025] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0026] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0027] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0028] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0029] Figure 1AThe base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology (such as IEEE 802.11) to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology (such as IEEE 802.15) to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0030] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Although not described in detail in the text, the CN 106 / 115 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0031] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0032] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0033] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0034] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0035] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from the base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, IR, UV or visible light signals. In another embodiment, the send / receive element 122 may be configured to send and / or receive both RF signals and optical signals. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0036] Although the transmit / receive element 122 Figure 1B 1 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0037] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0038] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0039] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0040] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0041] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0042] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via signal processing performed via hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via the processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0043] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0044] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0045] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0046] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0047] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0048] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0049] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0050] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0051] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0052] In a representative embodiment, the other network 112 may be a WLAN.

[0053] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STA) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be transmitted to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the destination STA (e.g., directly between them) using a direct link establishment (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0054] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may send beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may listen to the primary channel. If the primary channel is listened / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0055] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0056] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be sent by the transmitter STA. At the receiver of the receiver STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0057] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0058] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) a 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only a 1MHz operating mode) is sending to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0059] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0060] Figure 1D 1 is a system diagram illustrating the RAN 113 and the CN 115 according to one embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0061] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 108b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or the gNB 180c).

[0062] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0063] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRU 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the evolved Node-B 160a, 160b, 160c. For example, the WTRU 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more evolved Node-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the evolved Node-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRU 102a, 102b, 102c.

[0064] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0065] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0066] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0067] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure the traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0068] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0069] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0070] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF 182a-182b, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0071] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0072] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) can be used by the simulation device to send and / or receive data.

[0073] In higher frequency communications, beam failure recovery may be achieved through hierarchical beamforming. Higher frequency communications may be subject to path loss. For example, antenna gain may be increased to compensate for path loss (e.g., high path loss). Antenna gain (e.g., increasing antenna gain) may result in (e.g., highly) directional narrow beams and / or may position network nodes (e.g., gNBs, access points, relays, IRSs, etc.) close to the user. For example, beam failure recovery (e.g., in such networks) may be challenging if small movements / rotations of the WTRU or objects that block radio wave propagation may make multiple candidate beams unsuitable for beam failure recovery. Candidate beams may be monitored to find a suitable beam pair in the event of a beam failure, for example, to avoid frequent radio link failures (RLFs). For example, if beam monitoring is performed in a time division multiplexing (TDM) manner, monitoring a large number of candidate beams may degrade throughput, which may result in excessive overhead of time / frequency resources. Monitoring (e.g., many) candidate beams may increase the power consumption of the WTRU.

[0074] The WTRU may support beam failure recovery in high frequency communications with (e.g., limited) overhead and / or with power efficiency, for example, based on one or more of: a beam failure indication by the WTRU; a multi-step (e.g., two-step) candidate beam determination; a determination by the WTRU of whether to use a single-step beam failure recovery procedure or a multi-step (e.g., two-step) beam failure recovery procedure; and / or determination of one or more (e.g., monitored) BFR-RS sets to perform beam failure recovery.

[0075] The WTRU may support beam failure recovery through beam failure indication. The WTRU may send an UL signal (e.g., one or more of SRS, PRACH, PUCCH and / or PUSCH (MAC-CE)) that may indicate a beam failure and a determined best candidate beam. In an example, the WTRU may perform a preamble transmission with maximum power on one or more UL resources associated with the determined candidate beam. In an example, the WTRU may perform a preamble transmission with power ramp-up operation on one or more UL resources associated with the determined (e.g., best) candidate beam. In an example, the WTRU may perform a preamble repetition on one or more UL resources associated with the determined (e.g., best) candidate beam for better coverage. The WTRU may (e.g., simultaneously or concurrently) indicate a first type of candidate beam and a second type of candidate beam. In an example, if the WTRU reports one or more beams of the first type, the WTRU may recover the beam based on a first type of BFR operation. In an example, if the WTRU reports one or more beams of the second type, the WTRU may recover the beam based on the second type of BFR operation. The candidate beams of the first type for beam failure recovery may be updated (e.g., dynamically), for example, based on one or more of: beam failure detection resources configured for the WTRU (e.g., the beam of the first type corresponds to the beam of the second type in failureDetectionResources); configured TCI states for PDSCH or PDCCH reception (e.g., the beam of the first type corresponds to RS quasi co-location (QCL) type-D with PDSCH DM-RS or PDCCH DM-RS); and / or activated TCI states for PDSCH reception (e.g., the beam of the first type corresponds to RS QCL type-D with PDSCH DM-RS or PDCCH DM-RS).

[0076] Beam failure recovery may be supported via multi-step (e.g., two-step) candidate beam determination. The WTRU may receive one or more RSs for a second type of candidate beam based on one or more reported (e.g., best) beams of the first type. In an example, the WTRU may receive a confirmation PDCCH (e.g., a compact PDCCH indicating RS resources / resource sets for beam scanning of a second type of candidate beam, for example, using a configured CORESET. For example, the WTRU-specific confirmation may include a WTRU-specific PDCCH configuration and / or format, cyclic redundancy check (CRC) scrambling using a WTRU-specific radio network identifier (RNTI) (e.g., a cell RNTI (C-RNTI)), etc. The WTRU may receive a second type of candidate beam associated with a reported (e.g., best) first type of candidate beam. The WTRU may monitor the second type of candidate beam, for example, based on a monitoring window and / or a counter. For example, the second type of candidate beam detection based on reference signal received power (RSRP) and / or based on energy detection may be used to detect the second type of candidate beam. In an example of a second type of candidate beam detection based on RSRP, the WTRU may (e.g., expect) to receive a second type of beam having a higher RSRP than a first type of candidate beam for beam failure indication. In an example of a second type of candidate beam detection based on energy detection, the WTRU may determine whether the WTRU has received a second type of candidate beam. The WTRU may determine the second type of candidate beam, for example, based on beam measurements. The WTRU may, for example, report one or more (e.g., best) second type of candidate beam indices. The WTRU may receive a PDCCH transmission confirming the candidate beam selection, for example, via the BFR CORESET. For example, if no PDCCH transmission is received, for example, via the BFR CORESET, the transmit (e.g., Tx) power may, for example, be ramped up to resend the preamble.

[0077] The WTRU may determine whether to use a single-step (first type BFR or type 1 BFR) beam failure recovery procedure or a multi-step (e.g., two-step, second type BFR or type 2 BFR) beam failure recovery procedure. In an example, the WTRU may receive an explicit or implicit indication (e.g., from the gNB) regarding the beam failure recovery procedure. For example, the implicit indication may be based on one or more of the following: aggregation level, CORESET pool index, CORESET duration, CCE to REG mapping type, REG bundling size, interlace size of BFRCORESET, etc. The WTRU may determine whether to use a single-step beam failure recovery procedure or a two-step beam failure recovery procedure, for example, based on one or more of: the number of BFRs during the time interval; the number of beam failure instances during the time interval; the expiration of a counter / timer (e.g., if the BFR fails to provide a new candidate beam (e.g., a beam identified from the WTRU's candidate beams via the BFR) during a predetermined time duration, the WTRU may switch to a two-step beam failure recovery procedure); the subcarrier spacing / frequency range; the remaining power of the WTRU (e.g., if the remaining power is indicated to the gNB, the BFR may, for example, be executed using a single-step BFR and monitor a large number of beams if the WTRU has remaining battery power); the beam widths for data and control channels supported by the IRS / relay / access point / gNB; or the mobility of the WTRU (e.g., a fast-moving WTRU may determine to use a two-step new beam determination procedure).

[0078] In an example, a WTRU may be configured with more than one BFR-RS set. A BFR-RS set may be associated with (e.g., one) network node (e.g., IRS, relay, access point, gNB). A BFR-RS set may include resources and configurations that may be used to independently handle beam failure recovery for a WTRU. A BFR-RS set may include, for example, one or more of: a set of beam failure detection resources; a set of candidate beam resources of a first type; a set of candidate beam resources of a second type; UL resources (e.g., a set of preambles, etc.); a CORESET for compact PDCCH transmission; and / or a BFR CORESET.

[0079] The WTRU may select a subset of the BFR-RS set to be actively monitored (e.g., the WTRU may monitor resources available for beam failure recovery of an activated BFR-RS set). In an example, the WTRU may select one or more BFR-RS sets as an activated set, for example based on beam measurements. The WTRU may monitor a set of RS resources that may include beam resources of a first type that are configured as candidate beams of a first type of a set of configured BFR-RS sets. The WTRU may select a subset of the configured BFR-RS set to be actively monitored, for example based on the quality of the (e.g., best) candidate beams of the first type of the BFR-RS set (e.g., subject to a preconfigured threshold). The WTRU may activate monitoring of a subset of the BFR-RS set, for example based on a DCI and / or MAC-CE indication.

[0080] The activated BFR-RS set for the WTRU may be assigned a priority. The WTRU may determine the priority of the BFR-RS set, for example, based on a beam quality measurement of a candidate beam of a first type associated with the active BFR-RS set and / or based on a MAC-CE indication and / or a DCI indication. In an example, the WTRU may perform a beam quality measurement of a candidate beam of a first type for the BFR-RS set. The WTRU may determine the beam quality of a (e.g., best) candidate beam of a first type for the BFR-RS set. The WTRU may assign a priority, for example, based on the (e.g., best) candidate beam of the first type. The WTRU may assign a priority to the activated BFR-RS set, for example, based on the number of candidate beams of the first type exceeding a preconfigured threshold. The WTRU may determine the priority of the BFR-RS set, for example, based on a MAC-CE indication and / or a DCI indication.

[0081] The WTRU may determine one or more BFR-RS sets to perform beam failure recovery. In an example, the WTRU may perform beam failure recovery via a highest priority active BFR-RS set. The WTRU may perform the beam failure recovery procedure in a sequential manner, for example based on the priority of the activated BFR-RS sets. In an example, the WTRU may determine a new beam of the second type via the highest priority BFR-RS set. For example, if a first attempt to determine a new beam of the second type fails, the WTRU may use the next BFR-RS set in the priority order.

[0082] A PCell beam failure recovery procedure may be implemented. In an example of a beam failure recovery (BFR) procedure, a WTRU may (e.g., continuously) monitor a set of WTRU-specific periodic reference signals (RS) (e.g., synchronization signal blocks (SSBs) and / or channel state information-reference signals (CSI-RS)) associated with a beam used for physical downlink control channel (PDCCH) transmissions. A set of periodic CSI-RS resource configuration indices and / or synchronization signal (SS) / PBCH block indices (e.g., set FailureDetectionResources) may be provided to the WTRU (e.g., for a bandwidth part (BWP) of a serving cell). ). For example, if no RS is provided for beam failure detection purposes, the WTRU may perform beam monitoring based on the set of RSs indicated by the activated TCI-state for PDCCH reception. For example, if multiple (e.g., two) RSs are present in the TCI state, the set The RS index with the QCL-Type D configuration for the corresponding TCI state may be included. For example, if the WTRU-specific periodic RS set If the measured beam quality becomes below a threshold for a configured number of times (e.g., beamFailureInstanceMaxCount) within a predetermined time interval (e.g., beamFailureDetectionTimer), the WTRU may declare a beam failure and initiate a beam failure recovery procedure to identify a candidate beam (e.g., subject to a timer such as beamFailureRecoveryTimer).

[0083] The candidate beam can be selected from a set of WTRU-specific periodic RS (e.g., SSB and / or CSI-RS) configured by candidateBeamRSList in the RRC configuration The WTRU may (e.g., after discovering a new beam) send a beam recovery request and a beam failure indication (e.g., to the gNB), for example, via a dedicated physical random access response channel (PRACH). The gNB may determine the candidate beams, for example, based on an association between a PRACH resource and a (e.g., periodic) CSI-RS configuration index and / or SS / PBCH block index. The WTRU may receive a recovery response from the gNB (e.g., after receiving the PRACH). In an example, a dedicated CORESET may be provided to the WTRU via a link to a search space set (e.g., provided by a recoverySearchSpaceId configuration in RRC) for monitoring the PDCCH in the CORESET. For example, the UE may receive a PDCCH from the gNB via the CORESET to confirm the new beam selection. For example, if the response (e.g., from the gNB) is successfully received by the WTRU, the beam recovery process may be successful (e.g., and a new beam pair link may be established). For example, if the WTRU does not successfully receive a response from the gNB, the WTRU may perform an additional beam recovery request, for example, by ramping up the transmit power sent by the PRACH. For example, if the additional beam recovery request fails to elicit a successfully received response from the gNB, the WTRU may initiate a contention-based RACH procedure, which may include cell reselection.

[0084] The beam failure recovery process may be efficient and applicable to higher frequency communications. The beam determination process may be multiple (e.g., two) steps. In an example, a wide (e.g., wider) candidate beam may be determined (e.g., in a first step). A narrow (e.g., narrower) candidate beam may be determined for the WTRU (e.g., in a second step), for example, by using a configured hierarchical relationship between the wider and narrower candidate beams.

[0085] Higher carrier frequencies (such as FR2-2) may have higher path loss, which may be compensated by having higher antenna gain (e.g., using narrow beams). Beam failure recovery using narrow beams may be challenging, given that small movements of the WTRU may make several candidate beams unsuitable for beam failure recovery. The beam failure recovery problem may be complicated by using network equipment located near the WTRU and / or at a lower altitude. The network equipment may include, for example, access points, indoor base stations, relays, intelligent reflecting surfaces (IRS), etc. In an example of a BFR process, a large number of candidate beams may be monitored by the WTRU, for example, to avoid (e.g., frequent) radio link failures due to beam failures. Monitoring a large number of candidate beams may degrade throughput and increase power consumption of the WTRU. A reduction in the number of candidate beams to be monitored may maintain or increase throughput and / or reduce power consumption. Network densification may result in network equipment approaching the WTRU (e.g., being positioned close to it). The WTRU may use network equipment of neighboring WTRUs to recover from beam failures. A beam failure recovery process designed for higher carrier frequencies may work with one or more network devices (eg, equipment).

[0086] One or more processes may be used to implement beam failure recovery for higher frequency communications.

[0087] In an example procedure for beam failure recovery for higher frequency communications, the WTRU may be configured with a first type of candidate beams for beam failure recovery and a second type of candidate beams for beam failure recovery. The WTRU may use the first type and / or the second type of candidate beams to monitor and detect beam failures.

[0088] In an example procedure for beam failure recovery for higher frequency communications, the WTRU may perform beam failure indication via a first type of beam failure indication resource and a second type of beam failure indication resource.

[0089] In an example procedure for beam failure recovery for higher frequency communications, the WTRU may determine a beam failure recovery procedure. The WTRU may adapt (e.g., based on the determination), e.g., by (e.g., dynamically) switching between a first type of beam failure recovery procedure and a second type of beam failure recovery procedure.

[0090] In an example procedure of beam failure recovery for higher frequency communications, the WTRU may perform beam failure recovery using multiple (eg, two) types of candidate beams based on a second type of beam failure recovery procedure.

[0091] In an example procedure of beam failure recovery for higher frequency communications, the WTRU may perform a second type of beam failure recovery procedure with multiple sets of beam failure recovery resources.

[0092] The WTRU may send or receive a physical channel or a reference signal according to at least one spatial domain filter.The term "beam" may (eg, be used to) refer to a spatial domain filter.

[0093] The WTRU may transmit a physical channel or signal using the same spatial domain filters as used to receive the RS (e.g., CSI-RS) or SS block. The WTRU transmission may be referred to as the "target". The received RS or SS block may be referred to as the "reference" or "source". The WTRU (e.g., in this case) may transmit the target physical channel or signal based on the spatial relationship of the reference RS or SS block.

[0094] The WTRU may transmit a first physical channel or signal according to the same spatial domain filter as used to transmit a second physical channel or signal. The first transmission and the second transmission may be referred to as a target and / or a reference (e.g., source), respectively. The WTRU may be said to transmit a first (e.g., target) physical channel or signal according to a spatial relationship with reference to a second (e.g., reference) physical channel or signal.

[0095] For example, the spatial relationship may be implicit, configured by RRC, or signaled by MAC CE or DCI. In an example, the WTRU may (e.g., implicitly) send PUSCH and demodulation reference signal (DM-RS) for PUSCH according to the same spatial domain filter as the SRS indicated by the SRS resource indicator (SRI), which is indicated in the DCI or configured by RRC. The spatial relationship may be configured by RRC for SRI or signaled by MAC CE for PUCCH. The spatial relationship may (e.g., also) be referred to as "beam indication".

[0096] The WTRU may receive a first (e.g., target) downlink channel or signal based on the same spatial domain filter or spatial reception parameters as a second (e.g., reference) downlink channel or signal. In an example, an association may exist between a physical channel (e.g., a PDCCH or PDSCH) and a corresponding DM-RS of the physical channel. For example, if the WTRU is configured with a quasi co-location (QCL) assumption type D between corresponding antenna ports, an association may exist (e.g., at least if the first signal and the second signal are reference signals). The association may be configured as a transmission configuration indicator (TCI) state. The association between a CSI-RS or SS block and a DM-RS may be indicated to the WTRU, for example, by an index to a TCI state set (configured by the RRC and / or signaled by the MAC CE). The indication may (e.g., also) be referred to as a "beam indication."

[0097] Beam failures can be monitored and detected.

[0098] Figure 2An example of hierarchical beamforming by gNB is illustrated.

[0099] Figure 3 An example of hierarchical beamforming by IRS is illustrated.

[0100] As described herein, beams may be used interchangeably with one or more of the following: reference signal; sounding reference signal (SRS); channel state information-reference signal (CSI-RS); demodulation reference signal (DM-RS); phase tracking reference signal (PT-RS); synchronization signal block (SSB); and the like.

[0101] As described herein, channel may be used interchangeably with one or more of: PDCCH; PDSCH; physical uplink control channel (PUCCH); physical uplink shared channel (PUSCH); physical random access channel (PRACH); and the like.

[0102] As described herein, CSI reporting may be used interchangeably with one or more of the following: CSI measurement, beam reporting, and beam measurement, among others.

[0103] As described herein, quality may be used interchangeably with one or more of the following: reference signal received power (RSRP), reference signal received quality (RSRQ), signal to interference and noise ratio (SINR), channel quality indicator (CQI), modulation and coding scheme (MCS), assumed PDCCH block error rate (BLER), etc.

[0104] Configurations for beam failure recovery (BFR) are available.

[0105] In an example of a BFR configuration, the WTRU may be configured with one or more sets of beam failure detection (BFD) RSs (e.g., or For example, if the WTRU is configured with two or more sets of BFD RSs. It can be a set of beam failure detection RSs associated with the i-th link.

[0106] In an example, multiple links may be configured for an operational mode. A first set of BFD-RS (e.g., ) may be associated with a first link (eg, a direct link), and a second set of BFD-RSs (eg, ) may be associated with a second link (e.g., a reconfigurable intelligent surface (RIS) link).

[0107] The configuration of one or more sets of BFD-RS may be based on an implicit configuration. For example, if the WTRU does not receive an explicit configuration of one or more sets of BFD-RS, the WTRU may determine one or more sets of BFD-RS based on one or more RSs (e.g., RSs with QCL Type-D in a configured TCI state for PDCCH reception).

[0108] In an example, the WTRU may determine one or more BFD-RS sets based on an explicit / implicit CORESET / search space group configuration / indication. The CORESET / search space group configuration / indication may be based on one or more of: a link ID / type of the CORESET; a CORESET / search space type; and / or an ID configuration (e.g., a CORESET / search space ID and / or a TCI state ID).

[0109] In the example of CORESET / search space group configuration / indication based on link ID / type of CORESET, the WTRU may be configured with one or more CORESETs with link ID and / or link type. The WTRU may determine the CORESET group for one or more CORESETs based on the link ID and / or link type, for example. For example, the WTRU may receive the link ID in a TCI state configuration (e.g., instead of a CORESET configuration). For example, the WTRU may determine that the RS associated with a first link ID and / or link type (e.g., a first link or a first RS type) is a first BFD-RS set, and the RS associated with a second link ID and / or link type (e.g., a second link or a second RS type) is a second BFD-RS set.

[0110] In the example of CORESET / search space group configuration / indication based on an ID configuration (e.g., CORESET / search space ID and / or TCI state ID), the WTRU may determine the CORESET group based on the ID. The WTRU may determine the RS associated with the first CORESET as the first BFD-RS set, for example, based on a comparison of the associated ID of the first CORESET with the threshold, such as if the associated ID of the first CORESET is less than (e.g., or equal to) a threshold. The WTRU may determine the RS associated with the first CORESET as the second BFD-RS set, for example, based on a comparison of the associated ID of the first CORESET with the threshold, such as if the associated ID of the first CORESET is greater than a threshold.

[0111] In an example of a BFR configuration, the WTRU may be configured with one or more sets of candidate beam (CB) RSs (e.g., or in may be a set of CB-RS associated with the i-th link). In an example, multiple links may be configured for an operation mode. A first set of CB-RS (e.g., ) may be associated with a first link (eg, a direct link), and a second set of CB-RSs (eg, ) may be associated with a second link (eg, an RIS link). The CB-RS in the set may be associated with one or more uplink resources (eg, PRACH, PUCCH, PUSCH, and / or SRS).

[0112] In an example of a BFR configuration, the WTRU may be configured with one or more sets of uplink resources (e.g., S or S i , where S i The uplink resource may be an uplink resource associated with the i-th link) for new candidate beam indication. In an example, multiple links may be configured for an operation mode. A first uplink resource (e.g., S1) may be associated with a first link (e.g., a direct link), and a second uplink resource (e.g., S2) may be associated with a second link (e.g., a RIS link). The uplink resource may be one or more of the following: a PRACH resource, a PUCCH resource (e.g., for a scheduling request), an RS resource (e.g., an SRS resource), etc.

[0113] In the example of a BFR configuration, the WTRU may be configured with one or more sets of search spaces (e.g., C or C i , where C i The search space (e.g., C1) may be associated with a first link (e.g., a direct link), and the second search space (e.g., C2) may be associated with a second link (e.g., a RIS link).

[0114] Hierarchical beamforming can support beam failure recovery.

[0115] Beam failure recovery for the WTRU may be supported, for example, by using associations between different types of beam resources. Beam resources may include, for example, CSI-RS, SSB, TCI state, etc. A beam resource (BR) may be identified, for example, by an ID (e.g., CSI-RS resource ID, SSB index, TCI state ID).

[0116] In an example, a WTRU may be configured with one or more sets of beam resources of a first type and sets of beam resources of a second type. Figure 2 and Figure 3 An example configuration is shown. Figure 2 and Figure 3 As shown in the example in , BR set #1 and BR set #2 may represent a first type of beam resource set and a second type of beam resource set, respectively. The beam resource of BR set #2 may be associated with at least one beam resource of BR set #1. One or more beam resources of BR set #2 may be associated with the same beam resource of BR set #1. The beam resources of BR set #1 and BR set #2 may be characterized by different beam widths. For example, Figure 2 and Figure 3 As illustrated, each beam of BS set #1 having a large beamwidth may be associated with one or more beam resources of BS set #2 having a narrow beamwidth. The beam resources of BR set #1 may be in the same frequency range or in a different frequency range (e.g., a lower frequency range) than the associated beam resources of BR set #2.

[0117] A beam resource of a first type (eg, a wide beam pattern) may be used interchangeably with a beam of a first type and / or a first beam. A beam resource of a second type (eg, a narrow beam pattern) may be used interchangeably with a beam of a second type and / or a second beam.

[0118] An association may be created (eg, established) between the first beam and the second beam.

[0119] The WTRU may be configured with one or more beams of a first type (e.g., a first beam) and one or more beams of a second type (e.g., a second beam). The WTRU may determine the beam type based on, for example, one or more of: gNB indication / configuration; TCI state ID / CSI-RS ID / SSB ID grouping / partitioning; frequency range; configured network nodes; subcarrier spacing (SCS); etc.

[0120] In an example where the WTRU determines the beam type based on a gNB indication / configuration, the WTRU may receive an indication and / or configuration indicating the beam type (e.g., based on one or more of RRC, MAC-CE, and DCI).

[0121] In an example where the WTRU determines the beam type based on TCI state ID / CSI-RS ID / SSB ID grouping / partitioning, the TCI state and / or CSI-RS may be grouped or partitioned. For example, the type of beam may be indicated as an attribute of a group or partition. In an example, the WTRU may receive an indication and / or configuration indicating that a non-zero power (NZP)-CSI-RS-ResourceSet has an attribute of a first type or a second type. In an example, the WTRU may be configured with a number N of TCI states. The WTRU may receive an indication and / or configuration that the number N of TCI states is divided into M partitions (e.g., a partition may be indicated by N bits, where a bit may correspond to a TCI state with which the WTRU is configured, and where a bit set to "1" may indicate a specific TCI state belonging to a partition). The WTRU may receive an indication and / or configuration indicating the beam type as an attribute of a partition.

[0122] In an example where the WTRU determines the beam type based on a frequency range, the WTRU may determine the beam type based on the frequency range that the beam is associated with. In an example, a beam having a carrier frequency FR2-1 may be a beam of the first type and a beam having a carrier frequency FR2-2 may be a beam of the second type.

[0123] In an example where the WTRU determines the beam type based on a configured network node, the WTRU may determine the beam type based on the network node to which the beam and / or beam set is associated. In an example, the first beam may be a beam received (e.g., directly) from the gNB and the second beam may be a beam received via a reconfigurable intelligent surface (RIS).

[0124] In an example where the WTRU determines the beam type based on the SCS, a beam / beam set received through a (eg, specific) SCS / configured to be received through the SCS may be determined as a first beam or a second beam.

[0125] A first beam may be associated with one or more second beams.

[0126] In an example where a first beam is associated with one or more second beams, the first beam may be associated with a set of second beams based on one or more of: a configuration of a first beam ID; a configuration of the first beam ID for a set of second beams; etc. In an example where a first beam is associated with a set of second beams based on a configuration of the first beam ID, the WTRU may receive an indication and / or configuration of the first beam ID for the second beam.

[0127] In an example where a first beam is associated with one or more second beams, the WTRU may receive an indication and / or configuration of a first beam ID for a set of second beams identified by the ID. In an example, the WTRU may receive an indication and / or configuration indicating that a NZP-CSI-RS-ResourceSet for a second type of beam is associated with a specific first beam. In an example, the WTRU may receive an indication and / or configuration indicating that a group / partition of TCI states with which the WTRU is configured is a second type of beam and that the group / partition is associated with a specific first beam.

[0128] The WTRU may perform beam failure detection, where one or more of the following may be applied.

[0129] The WTRU may be configured with one or more BFD-RSs. The WTRU may be configured with one or more of the following beam failure detection (BFD) parameters for one type of beam (eg, a first beam and a second beam): beamFailureDetectionTimer, beamFailureInstanceMaxCount, threshold, etc.

[0130] The beam failure detection time (e.g., beamFailureDetectionTimer) may indicate, for example, the maximum (e.g., highest) duration that the WTRU may spend for beam failure detection before the beam failure instance (BFI) counter is reset.

[0131] The beam failure instance threshold (eg, beamFailureInstanceMaxCount) may indicate, for example, the number of BFIs that the WTRU may count to detect a beam failure before the beamFailureDetectionTimer expires.

[0132] The threshold may indicate when to increment the number of beam failure instances. In an example, the WTRU may detect the number of beam failure instances and increment the number of beam failure instances if / when the measurement quality of all or part of the BFD-RS is less than a threshold.

[0133] The WTRU may be configured with the same or different values ​​for BFD parameters associated with different beam types. In an example, the WTRU may be configured with one or more first values ​​(e.g., relatively small values) of beamFailureInstanceMaxCount and beamFailureDetectionTimer for the BFD-RS associated with a beam of the second type. In an example, the WTRU may be configured with a (e.g., high) threshold for the BFD-RS associated with a beam of the first type.

[0134] The WTRU may be configured with quantized values ​​of BFD parameters for one or more types of beams and / or parameter offsets for BFD parameters associated with other types of beams. In an example, the WTRU may be configured with a beam quality threshold for a second type of beam and / or a value of an offset beam quality (e.g., Threshold_Offset) for a first type of beam. The WTRU may calculate the threshold for a first type of beam, for example, based on (e.g., according to) the configured quality threshold and offset (e.g., Threshold_Offset) for a second type of beam.

[0135] The WTRU may measure the quality of the BFD-RS.

[0136] The WTRU may determine (eg, declare) a BFI, for example, based on (eg, compared to) the measured quality of the BFD-RS and a configured threshold.

[0137] The WTRU may associate a BFI to a specific BFD-RS. In an example, the WTRU may associate a BFI to a beam of a first type, a beam of a second type, and / or beams of the first and second types, for example, based on the BFD-RS on which the WTRU may detect the BFI (e.g., after measuring beam quality).

[0138] The WTRU may use a variable (e.g., BFI_COUNTER) to count the number of beam failure instances, which may be initially set to zero. The variable (e.g., BFI_COUNTER) may be BFD-RS specific. In an example, the WTRU may initialize and / or monitor (e.g., track) one or more BFI_COUNTERs (e.g., BFI_COUNTER_RS1, BFI_COUNTER_RS2, etc.).

[0139] For example, if / when the associated BFI_COUNTER reaches the corresponding beam failure instance threshold (e.g., beamFailureInstanceMaxCount), for example, assuming that the configured beam failure detection timer (e.g., beamFailureDetectionTimer) for the BFD-RS has not expired, the WTRU may detect a beam failure on a specific BFD-RS.

[0140] For example, depending on the BFD-RS, the WTRU may declare a beam failure specific to a beam type.The WTRU may declare a beam failure on a beam of a first type, a beam of a second type, or beams of both types, for example, based on the BFD-RS for which the WTRU detected a beam failure.

[0141] In an example, the WTRU may determine a BFD parameter set from a plurality of BFD parameter sets (e.g., one or more of beamFailureDetectionTimer (e.g., timer), beamFailureInstanceMaxCount (e.g., event counter), and / or threshold). The WTRU may determine the BFD parameter set based on the type of the BFD RS, and the BFD parameter set may include the timer, event counter, and / or threshold. The WTRU may determine a beam failure based on the parameter.

[0142] The determination may be based, for example, on the type of BFD-RS. For example, if the WTRU detects a beam failure by measuring one or more first beams, the WTRU may apply a first set of BFD parameters for beam failure detection. For example, if the WTRU detects a beam failure by measuring one or more second beams, the WTRU may apply a second set of BFD parameters for beam failure detection.

[0143] In an example, the WTRU may apply a differential BFD parameter set based on the configured BFD parameter set. For example, if the WTRU detects a beam failure by measuring one or more of the first beams (or the second beam), the WTRU may apply a differential value. Examples of differential values ​​may include, for example, one or more of the following: the WTRU may add / subtract A from the beamFailureDetectionTimer; the WTRU may add / subtract B from the beamFailureInstanceMaxCount; the WTRU may add / subtract C from the threshold; etc. One or more of A, B, and / or C may be configured / indicated, for example, by one or more of RRC, MAC-CE, and / or DCI.

[0144] In an example, for example, if / when the WTRU detects a beam failure, e.g., by measuring one or more first beams, the WTRU may add / subtract additional quality values ​​(e.g., SINR, RSRP, RSRQ, PDCCH assumed BLER, etc.) from the measurements. For example, if the WTRU determines a PDCCH assumed BLER of X%, e.g., by measuring a first beam, the WTRU may use X+Y percentage (%) as the determined PDCCH assumed BLER for beam failure detection.

[0145] Candidate beams may be monitored for beam failure recovery.

[0146] The WTRU may be configured with one or more types of beams (e.g., CB-RS) for candidate beam measurement and / or for new candidate beam determination. The term "beam" may be used interchangeably with beam reference signal, beam reference measurement signal, CSI-RS, SSB, and / or reference signal.

[0147] A beam of a first type (e.g., a first beam) may be associated with one or more beams of a second type (e.g., a second beam). In an example, one or more first beams may be used, configured, or determined. A first beam may be associated with a set of second beams. In an example, a first beam may be referred to as a wide beam, and a second beam may be referred to as a narrow beam. A wide beam may correspond to one or more narrow beams. In an example, a first beam may be a beam received (e.g., directly) from a gNB, and a second beam may be a beam received through a RIS.

[0148] In an example, the WTRU may be triggered and / or may determine to measure one or more candidate beams, for example based on one or more conditions that may be configured and / or predefined. The WTRU may determine to measure a subset of candidate beams within a set of candidate beams that may be determined and / or configured, for example based on one or more of the following conditions: the type of beam used for the BFD RS and / or the beam quality of the first beam and / or the second beam.

[0149] In an example where a candidate beam set is determined and / or configured based on a type of beam for a BFD RS, one or more second beams may be configured as a BFD RS set for the WTRU. The WTRU may detect a beam failure for the BFD RS set. In an example, the WTRU may perform candidate beam measurements for (e.g., all) beams within the one or more candidate beams. In an example, the WTRU may perform candidate beam measurements for (e.g., only) one or more first beams within the one or more candidate beams. In an example, the WTRU may perform candidate beam measurements for (e.g., only) one or more first beams within the one or more candidate beams. In an example, the WTRU may perform candidate beam measurements for (e.g., only) one or more second beams that may be associated with (e.g., previously determined, indicated, or reported) the same first beam within the one or more candidate beams.

[0150] In an example where a set of candidate beams is determined and / or configured based on beam qualities of a first beam and / or a second beam, the WTRU may perform measurements on a first beam among the candidate beams. For example, if at least one of the first beams satisfies one or more (e.g., (pre)defined or (pre)configured) criteria (e.g., thresholds or other requirements), the WTRU may skip measurements on a second beam among the candidate beams. For example, if the first beam does not satisfy one or more (e.g., (pre)defined or (pre)configured) criteria (e.g., thresholds or other requirements), the WTRU may perform measurements on a second beam among the candidate beams.

[0151] In an example, the WTRU may perform measurements for a subset of candidate beams. For example, the subset may be determined based on an operating mode. For example, if the WTRU is in a first operating mode, a first subset may be used or determined. For example, if the WTRU is in a second operating mode, a second subset may be used or determined. The operating mode may include, for example, at least one of: a RIS assisted mode, a RIS non-assisted mode, a hierarchical beam mode, and / or a non-hierarchical beam mode. The operating mode may be determined, for example, based on one or more of: an (e.g., explicit) indication from the network / gNB (e.g., broadcast via SIB, semi-static configuration via RRC and / or MAC-CE, dynamic indication via DCI); a set of beams determined / configured for beam failure detection RS (e.g., q0); channel conditions (e.g., delay spread, beam quality, etc.); and / or the number of beams configured or used.

[0152] In an example, the WTRU may determine a parameter set for new beam candidate selection from among a plurality of parameter sets for new beam candidate selection. The determination may be based on the type of CB-RS. For example, if the WTRU selects the new beam by measuring one or more first beams, the WTRU may apply a first CB parameter set for the new beam selection. For example, if the WTRU selects the new beam by measuring one or more second beams, the WTRU may apply a second CB parameter set for the new beam selection.

[0153] In an example, the WTRU may add / subtract an additional value from the quality measurement, for example, if the WTRU measures one or more first beams. For example, if the WTRU measures XdB by measuring the first beam, the WTRU may use X+YdB as the measured RSRP value for new beam selection. For example, if the WTRU does not measure XdB by measuring the first beam, the WTRU may use the measured value XdB for new beam selection.

[0154] A beam failure indication may be determined, indicated, triggered, etc. by the WTRU.

[0155] Figure 4An example of a two-step beam determination process (e.g., a beam determination process for determining a new beam) is illustrated. The WTRU may determine, indicate, or trigger a beam failure indication and / or recovery process, for example, based on beam failure detection. The WTRU may indicate, determine, or be configured with, for example, one or more of the following parameters: BFR_Timer (e.g., a timer may be started at the beam failure recovery process); RSRP_Threshold (e.g., a threshold of RSRP that may be used in beam failure recovery); candidateBeamRSList (e.g., a list of candidate beam reference signal indices that may be monitored, measured, and / or selected during beam failure recovery); power ramp (e.g., parameters may include power ramp step size, received preamble target power, etc.); and / or random access (e.g., PRACH parameters may include preamble index, SSB per RACH opportunity, random access response window, PRACH configuration index, random access opportunity, SSB association mask index, etc.). The above parameters are non-limiting examples of parameters that may be included in beam failure indication and / or recovery. In various implementations, one or more parameters may be included.

[0156] The WTRU may use, receive and / or be configured with one or more sets of reference signals for each BWP for monitoring, measurement and / or selection as resources for beam failure recovery. In an example, the term q1 may be used for a beam failure recovery set. In an example, the term q1,0 or q1,1 may be used as a beam failure recovery set. A beam failure recovery set (e.g., set q1, q1,0 or q1,1) may include one or more reference signals. The reference signal may be, for example, a CSI-RS resource configuration index and / or an SS / PBCH block (SSB) index. In an example, the reference signals included in the beam failure recovery RS set may be based on a candidateBeamRSList, which may be configured as part of the BFR process.

[0157] For example, the WTRU may initiate beam failure recovery based on a random access procedure. In one example, the WTRU may configure random access parameters, start a BFR_Timer, and / or apply a power ramp parameter.

[0158] The WTRU may monitor and / or measure one or more reference signals from the candidateBeamRSList. The WTRU may determine whether at least one of the SSBs has an SS-RSRP higher than a corresponding RSRP_Threshold in the SSBs in the candidateBeamRSList and / or whether at least one of the CSI-RSs has a CSI-RSRP higher than a corresponding SRP_Threshold in the CSI-RS in the candidateBeamRSList.

[0159] The WTRU may select the corresponding reference signal as a candidate new beam / random access resource for the BFR process. In the example, the term q_new may be used to represent the newly selected beam / random access resource. The WTRU may perform a PRACH transmission in the corresponding random access resource. The transmission may be performed based on the spatial relationship with the periodic CSI-RS resource configuration and / or with the SS / PBCH block associated with the index q_new / QCL.

[0160] For example, if uplink channel resources (eg, uplink shared channel resources (UL-SCH)) are available, the WTRU may initiate a MAC-CE beam failure recovery procedure. The WTRU may generate and / or send a BFR MAC-CE on the corresponding uplink channel resources.

[0161] The WTRU may monitor, measure, select and / or report from a larger number of candidate beams at a higher frequency and / or due to a narrower beamwidth, for example, to avoid frequent radio link failures due to beam failures.

[0162] In an example, the WTRU may use hierarchical beamforming for beam failure indication and / or recovery. The WTRU may receive, identify and / or determine that a beam failure recovery procedure is triggered and / or initiated. The WTRU may measure, estimate and / or determine a candidate beam, for example, from a (e.g., configured) list of candidate beam reference signals (e.g., candidateBeamRSList).

[0163] In an example, the WTRU may indicate, recommend and / or report the determined best candidate beam. In an example, the WTRU may indicate the candidate beam, for example, by sending an uplink signal on one or more of SRS, PRACH, PUCCH and / or PUSCH (MAC-CE). In an example, one or more of the following may apply: the WTRU may send UL signals with maximum power on one or more UL resources associated with the determined (e.g., best) candidate beam; the WTRU may send UL signals with power ramp-up operation on one or more UL resources associated with the determined candidate beam; and / or the WTRU may send UL signals with configured and / or determined repetitions (e.g., for coverage enhancement) in one or more UL resources associated with the determined candidate beam.

[0164] The parent candidate BFR RS may be configured. In an example, the WTRU may receive, identify and / or determine one or more candidate beam failure recovery RS lists. The beam reference signals in the first candidate BFR RS list may be associated with the beam reference signals in the second candidate BFR RS list. In an example, at least one of the beam reference signals in the first candidate BFR RS list may be referred to as a parent beam or a fallback beam. One or more beam reference signals in the second candidate BFR RS list may be associated with the same beam reference signal in the first candidate BFR RS list, which may physically correspond to a larger beam width for the beam reference signal in the first BFR RS list and / or may physically correspond to a narrower beam width for the beam reference signal in the second BFR RS list. The WTRU may receive or transmit (e.g., simultaneously) using the beam reference signals from the second BFR RS list and the corresponding parent beam RS from the first BFR RS list.

[0165] In an example, the WTRU may initiate a beam failure recovery procedure by indicating one or more of the determined candidate beam reference signals from the second BFR RS list while simultaneously (e.g., at the same time) indicating the associated parent candidate beam reference signals from the first BFR RS list.

[0166] For example, if the WTRU reports an indication of the candidate beam RS based on one or more parent beam reference signals in the first candidate BFR RS list, the WTRU may initiate a multi-step (e.g., two-step) beam failure recovery procedure (e.g., as described herein). For example, if the WTRU reports an indication of the best candidate beam RS based on one or more parent beam reference signals in the first candidate BFR RS list and / or one or more associated beam reference signals in the second candidate BFR RS list, the WTRU may initiate a single-step beam failure recovery procedure (e.g., as described herein).

[0167] The candidate BFR RS may be updated (e.g., dynamically). In an example, the WTRU may report, recommend, improve and / or update one or more candidate BFR RS lists. In an example, the WTRU may report and / or update a parent candidate BFR RS list. The BFR RS list may be updated, for example, based on one or more of: a beam failure detection reference signal (BFD-RS) and / or a TCI state for PDSCH / PDCCH reception.

[0168] In an example of updating a BFR RS list based on a beam failure detection reference signal (BFD-RS), the WTRU may determine and / or update a list of parent candidate BFR RSs based on a configured BFD reference signal. In an example, the WTRU may measure, monitor and / or identify a list of (e.g., preferred) BFD reference signals. The WTRU may determine and / or update one or more parent candidate BFR RSs that may be associated with an identified (e.g., preferred) parent candidate BFR RS.

[0169] In an example of updating the BFR RS list based on the TCI state for PDSCH / PDCCH reception, the WTRU may determine and / or update the parent candidate BFR RS list based on the configured TCI state for PDSCH / PDCCH reception. In an example, the WTRU may measure, evaluate and / or update one or more of the parent candidate BFR RSs based on antenna port quasi-co-location parameters associated with a reference signal (e.g., SSB and / or CSI-RS) that may be associated with a configured downlink reception (e.g., PDSCH / PDCCH DM-RS).

[0170] The WTRU may determine a beam failure recovery procedure. The WTRU may switch between types of beam failure recovery procedures. In an example, the WTRU may determine the type of beam failure recovery procedure. In an example, the WTRU may determine a first type of beam failure recovery (BFR) procedure (e.g., a one-step beam failure recovery procedure) or a second type of BFR procedure (e.g., a two-step beam failure recovery procedure). The WTRU may determine the type of beam failure recovery procedure, for example, based on one or more of: an explicit / implicit indication from the gNB and / or a type of selected resources for the new candidate beam.

[0171] In an example of determining the type of beam failure recovery procedure based on an explicit / implicit indication from the gNB, the WTRU may receive an explicit or implicit indication, for example, from RRC, MAC, or DCI signaling. In an example, the RRC configuration for beam failure recovery may include an indication of whether to perform a second type of BFR procedure (e.g., a two-step procedure). In an example, the MAC-CE may indicate which recovery procedure to follow, for example together with at least one index to an associated configuration. In an example, the WTRU may receive (e.g., implicit) indication based on one or more of the following: aggregation level, CORESET pool index, CORESET duration, CCE to REG mapping type, REG bundling size, interleaving size of one or more BFR CORESETs, etc.

[0172] In one example, the WTRU may determine the type of beam failure recovery procedure based on the aggregation level / CORESET duration / REG bundling size / interleaving size of one or more BFR CORESETs. For example, if the aggregation level / CORESET duration / REG bundling size / interleaving size exceeds (e.g., falls below) a preconfigured value, the WTRU may select the type of beam failure recovery procedure (e.g., the first type or the second type). In an example, the WTRU may select the type of beam failure recovery procedure (e.g., the first type or the second type) based on whether the WTRU is configured with a BFR CORESET with a pool index of 0 or 1. In an example, the WTRU may select the type of beam failure recovery procedure (e.g., the first type or the second type) based on whether the CCE to REG mapping type of one or more BFR CORESETs is interleaved or non-interleaved.

[0173] In an example of determining the type of beam failure recovery procedure based on the type of selected resources for the new candidate beam, the WTRU may determine the type of procedure based on the selected resources in the set of resources configured as candidate beams (e.g., q1). In an example, the WTRU may select one or more of the resource sets for which the quality (e.g., RSRP, RSRQ, SINR, CQI, and / or assumed PDCCH BLER) is above a (e.g., configured) threshold. For example, if the WTRU selects one or more first beams as new candidate beams, the WTRU may perform a second type of BFR procedure (e.g., a two-step procedure). For example, if the WTRU selects one or more second beams as new candidate beams, the WTRU may perform a first type of BFR procedure (e.g., a one-step procedure).

[0174] The WTRU may be configured with a first threshold and a second threshold corresponding to resources of a first beam and a second beam, respectively. For example, if at least one resource corresponding to the first beam and / or at least one resource corresponding to the second beam meets the criteria, the WTRU may select (e.g., prioritize) the resources corresponding to the second beam. Alternatively, the WTRU may select (e.g., prioritize) the resources corresponding to the first beam. A higher layer may configure an indication of whether to prioritize resources corresponding to the first beam or the second beam.

[0175] In an example, the WTRU may initiate a second type of BFR procedure (e.g., a two-step beam failure recovery procedure) depending on at least one of the following conditions (e.g., being satisfied): whether a first type or second type of beam failure recovery procedure has been initiated or completed more than N times within a time interval T; whether a "procedure selection timer" is running; measurements and / or metrics related to mobility aspects; frequency range (FR) for the serving cell; subcarrier spacing (SCS) for the bandwidth portion; the number of configured TCI states and / or the number of SSBs for the serving cell detected by the WTRU; beam widths for data and / or control channels supported by the IRS / relay / access point / gNB; and / or remaining battery power.

[0176] In an example where a second type of BFR procedure is initiated depending on whether a first type or second type of beam failure recovery procedure is initiated or completed more than N times within a time interval T, N and T may be predefined or configured by higher layers. For example, the WTRU may initiate a second type of beam failure recovery procedure if / when, for example, a beam failure is detected and conditions are met.

[0177] In an example where initiation of the second type of BFR procedure depends on whether a "procedure selection timer" is running, the timer may be started, for example, upon initiation or completion of a beam failure recovery procedure of the first type or the second type. For example, the WTRU may initiate a beam failure recovery procedure of the second type if / when, for example, a beam failure is detected and the procedure selection timer is running. The duration of the procedure selection timer may be predefined or configured by higher layers.

[0178] In an example where the second type of BFR procedure is initiated depending on measurements and / or metrics related to mobility aspects, the WTRU may perform a second type of beam failure recovery procedure if the measurements and / or metrics are above a predefined or configured threshold. The metrics or measurements may include, for example, one or more of: a velocity estimate based on positioning measurements or channel measurements; a Doppler measurement; a number N of changes in TCI states for PDCCH or PDSCH within a time interval T, where N and T may be predefined or configured by higher layers; and / or a number N of changes in CRI (e.g., CSI-RS resource indicator) or SSBRI (e.g., SSB resource indicator) within a time interval T.

[0179] In an example where the second type of BFR procedure is initiated depending on the frequency range (FR) of the serving cell, the WTRU may perform the second type of procedure for FR2 or FR3.

[0180] In an example where the second type of BFR process is initiated depending on the subcarrier spacing (SCS) used for the bandwidth portion, the WTRU may perform the second type of process for the SCS based on (e.g., greater than) a predefined threshold.

[0181] In an example where a second type of BFR process is initiated depending on the number of configured TCI states or the number of SSBs for a serving cell detected by the WTRU, the WTRU may perform the second type of process if / when the number of configured TCI states exceeds a predefined or configured threshold.

[0182] In an example where the second type of BFR procedure is initiated depending on the remaining battery level, the WTRU may perform the second type of procedure based on the remaining battery level compared to a threshold (eg, if the remaining battery level is below the threshold).

[0183] The beam failure recovery procedure may be a one-step beam failure recovery procedure. In an example, the WTRU may determine / select a first type of BFR procedure (e.g., a one-step beam failure recovery procedure). The WTRU may support one or more of the following procedures, for example, for the first type of BFR procedure.

[0184] The WTRU (eg, having determined / selected the first type of BFR process) may select one or more beams (eg, the second beam) as new candidate beams.

[0185] The WTRU (e.g., having determined / selected a first type of BFR process) may transmit one or more UL signals on UL resources that may be associated with one or more selected new candidate beams (e.g., the selected second beam) or may be configured for beam failure recovery. The one or more UL signals may be one or more of the following: PRACH, PUCCH (e.g., including a scheduling request (SR)), MAC-CE, and / or PUSCH.

[0186] A WTRU (e.g., having determined / selected a first type of BFR process) may receive a confirmation PDCCH (e.g., in a CORESET / search space configured for BFR). The PDCCH may be a WTRU-specific DCI or a group DCI. The PDCCH may be a DCI format for scheduling one or more shared channels. A monitoring window and / or counters and thresholds may be used.

[0187] In an example using a monitoring window, the WTRU may detect an acknowledgment PDCCH within the monitoring window. The WTRU may (e.g., if the WTRU does not detect an acknowledgment PDCCH sent by the gNB within the monitoring window) support one or more of the following: a contention-based RACH procedure; and / or a retransmission of one or more UL signals (e.g., by increasing Tx power).

[0188] In an example using a counter and a threshold, the WTRU may detect the confirmation PDCCH based on the counter and the threshold. For example, if the WTRU fails to select a new candidate beam, the WTRU may increase the counter. For example, if the counter is less than (or equal to) the threshold, the WTRU may continue to detect the confirmation PDCCH. The WTRU may (for example, if the WTRU does not select a new candidate beam and / or the WTRU does not detect a set of second beams sent by the gNB before the counter exceeds the threshold) support one or more of the following: a contention-based RACH process; and / or retransmission of one or more UL signals (for example, by increasing Tx power).

[0189] Figure 6 A method involving two-step beam failure recovery is illustrated.

[0190] The WTRU may receive configuration information indicating candidate beam reference signals (RS) of a first type (wide beam mode or type 1) and candidate beam RSs of a second type (narrow beam mode or type 2). The WTRU may detect a beam failure and determine a beam failure recovery (BFR) type. The WTRU may determine the BFR type as one of a one-step BFR type (type 1 BFR) or a two-step BFR type (type 2 BFR). Based on the determined BFR type being a two-step BFR type, the WTRU may do the following. The WTRU may select a candidate beam RS from the candidate beam RSs of the first type and send an indication thereof. The WTRU may determine a subset of candidate beam RSs of the second type based on the selected candidate beam RSs. The WTRU may perform measurements on the subset of candidate beam RSs of the second type during a first monitoring window. The WTRU may select a candidate beam RS of the second type from the subset based on the measurements and send an indication thereof.

[0191] At 1a, the gNB may send a BFD RS, a first type candidate beam RS, and a subset of a second type candidate beam RS (e.g., which may not be a subset linked to the first type beam RS).

[0192] In an example, the WTRU may determine / select a second type of BFR procedure (e.g., a two-step beam failure recovery procedure). The BFR type may be determined based on a frequency range (FR), a subcarrier spacing (SCS), measurements, and / or configuration.

[0193] The WTRU may determine a subset of second type candidate beam RSs based on a configured association with a selected first type candidate beam RS or by receiving an indication in a PDCCH transmission.

[0194] The WTRU may support one or more of the following procedures, for example, for the second type of BFR procedures.

[0195] At 2, the WTRU may measure the BFD RS. If the WTRU detects a beam failure, the WTRU may determine the BFR type (e.g., Type 1: one-step, or Type 2: two-step) and select a candidate beam RS. The WTRU may determine the BFR type as one of a one-step BFR type or a two-step BFR type. Detecting the beam failure may be based on measurement of a beam failure detection reference signal (BFD RS) corresponding to the beam failure. The WTRU may determine a BFD parameter set based on the type of the BFD RS, wherein the BFD parameter set includes one or more timers, event counters, or thresholds. The WTRU may determine the beam failure based on the parameters.

[0196] For Type 2 BFR, the candidate beam RS may be selected from a Type 1 (e.g., wide) set. For Type 1 BFR, the candidate beam may be selected from a Type 2 (e.g., narrow) set. The first type of candidate beam reference signal may be associated with a wide beam and the second type of candidate beam reference signal may be associated with a narrow beam. The WTRU may send an indication of the selected candidate beam RS using either a physical random access channel (PRACH) preamble or a resource.

[0197] The WTRU may select a BFR type based on: FR, SCS; measurements; and / or configuration. The WTRU (e.g., having determined / selected a second type of BFR process) may select one or more first beams as new candidate beams. The WTRU (e.g., having determined / selected a second type of BFR process) may send one or more UL signals on UL resources that may be associated with one or more selected new candidate beams (e.g., the selected first beams) or may be configured for beam failure recovery. The one or more UL signals may be one or more of: PRACH, PUCCH (e.g., including a scheduling request (SR)), MAC-CE, and / or PUSCH. For example, at 3, the WTRU may send an indication of the selected candidate beam RS to the gNB (e.g., a PRACH preamble / resource).

[0198] The WTRU (e.g., having determined / selected the second type of BFR process) may receive a confirmation PDCCH (e.g., in a CORESET / search space configured for BFR). At 4, the WTRU and the gNB may determine to use a subset of type 2 candidate beam RSs associated with the selected / indicated candidate beam RSs. Alternatively, at 4a, the WTRU may receive an indication of a subset of type 2 candidate beam RSs via the PDCCH. At 4a, the gNB may send a PDCCH to confirm the beam indication using the indicated candidate beams.

[0199] The PDCCH may be a WTRU-specific DCI or a group DCI. The DCI may indicate one or more RS resources / resource sets that the WTRU may measure, such as for beam failure recovery using a second beam associated with a selected first beam. The PDCCH may be a specific DCI format for confirmation and / or indication of one or more RS resources / resource sets. One or more of the following may be used for WTRU-specific confirmation: a WTRU-specific PDCCH configuration; a DCI format; and / or CRC scrambling using a WTRU-specific RNTI (e.g., C-RNTI). A monitoring window and / or a counter and threshold may be used.

[0200] At 5, the WTRU may monitor / receive an acknowledgment PDCCH in a monitoring window (e.g., a second monitoring window) using the selected candidate beam. The WTRU may receive a PDCCH transmission in the second monitoring window using the selected candidate beam RS, and the PDCCH transmission may include an indication of the acknowledgment. The WTRU may receive a subset of type 2 candidate beam RS indications, and the monitoring window may be used for the acknowledgment PDCCH. In the example of using a monitoring window, the WTRU may detect an acknowledgment PDCCH within the monitoring window. The WTRU may (e.g., if the WTRU does not detect an acknowledgment PDCCH sent by the gNB within the monitoring window) support one or more of the following: a contention-based RACH process; and / or retransmission of one or more UL signals (e.g., by increasing Tx power).

[0201] In an example using a counter and a threshold, the WTRU may detect the confirmation PDCCH based on the counter and the threshold. For example, if the WTRU fails to select a new candidate beam, the WTRU may increase the counter. For example, if the counter is less than (or equal to) the threshold, the WTRU may continue to detect the confirmation PDCCH. The WTRU may (for example, if the WTRU does not select a new candidate beam and / or the WTRU does not detect a set of second beams sent by the gNB before the counter exceeds the threshold) support one or more of the following: a contention-based RACH process; and / or retransmission of one or more UL signals (for example, by increasing Tx power).

[0202] At 6, the gNB may send the determined (or indicated) subset of type 2 candidate beam RSs. The WTRU may perform measurements of the determined subset of second type candidate beam RSs during the monitoring window. The WTRU may select a second type candidate beam RS (e.g., a beam with the highest L1-RSRP) from the subset of second type candidate beam RSs based on the measurements. The WTRU may send an indication of the selected second type candidate beam RS using a PRACH transmission.

[0203] In step 4a, the WTRU (e.g., having determined / selected a second type of BFR process) may receive a set of second beams associated with the reported first beam (e.g., based on one or more of the following) or a set of second beams indicated by the gNB.

[0204] The WTRU may receive a set of second beams in the RS resources / resource sets associated with the reported first beam. The association may be predefined or configured / indicated by the gNB.

[0205] The WTRU may confirm the RS resources / resource sets indicated by the PDCCH to receive the second beam set.

[0206] The WTRU may measure / monitor the set of second beams based on one or more of: a monitoring window; and / or a counter and threshold.

[0207] At 7, the WTRU may measure a subset of the determined (or indicated) type 2 candidate beam RSs during the monitoring window and select a type 2 candidate beam RS in the subset based on the measurements (e.g., the beam with the highest L1-RSRP). The monitoring window may be used for beam RS selection. In an example where a set of second beams is measured / monitored based on the monitoring window, the WTRU may measure and / or monitor the set of second beams within the monitoring window (e.g., for beam RS selection). The WTRU may (e.g., if the WTRU does not select a new candidate beam and / or the WTRU does not detect a set of second beams transmitted by the gNB within the monitoring window) support one or more of the following: a contention-based RACH process; and / or retransmission of one or more UL signals (e.g., by increasing Tx power).

[0208] In an example of measuring / monitoring a set of second beams based on a counter and a threshold, the WTRU may measure and monitor the set of second beams based on a counter and a threshold. For example, if the WTRU fails to select a new candidate beam, the WTRU may increment the counter. For example, if the counter is less than (e.g., or equal to) the threshold, the WTRU may continue to measure and monitor. The WTRU may (e.g., if the WTRU does not select a new candidate beam and / or the WTRU does not detect a set of second beams transmitted by the gNB before the counter exceeds the threshold) support one or more of: a contention-based RACH process; and / or retransmission of one or more UL signals (e.g., by increasing Tx power).

[0209] The WTRU may select one or more second beams in the set of second beams as new candidate beams, for example based on the quality of the set of second beams. At 8, the WTRU may send an indication of the selected type 2 candidate beam RS to the gNB (e.g., via PRACH).

[0210] In an example, the WTRU may select K (eg, best) beams based on quality (eg, L1-RSRP). K may be preconfigured by RRC and / or MAC-CE and / or DCI.

[0211] The WTRU may send one or more UL signals associated with the one or more second beams. The one or more UL signals may be one or more of: PRACH, PUCCH (e.g., including a scheduling request (SR)), MAC-CE, and / or PUSCH. The UL signal may be sent in UL resources associated with the one or more second beams. The UL signal may include a beam index for the one or more second beams.

[0212] At 9, the gNB may send a PDCCH to confirm the beam indication using the indicated type 2 candidate beam. The WTRU may receive a PDCCH confirming reception of one or more UL signals indicating the new candidate beam, for example, via configuring a CORESET / search space (e.g., for a BFR process). A monitoring window and / or counter and threshold may be used.

[0213] At 10, the WTRU may monitor / receive an ACK PDCCH in a monitoring window using the selected beam. In an example using a monitoring window, the WTRU may detect an ACK PDCCH within the monitoring window. The WTRU may (e.g., if the WTRU does not detect an ACK PDCCH sent by the gNB within the monitoring window) support one or more of the following: a contention-based RACH procedure; and / or a retransmission of one or more UL signals (e.g., by increasing Tx power).

[0214] In an example using a counter and a threshold, the WTRU may detect the confirmation PDCCH based on the counter and the threshold. For example, if the WTRU fails to select a new candidate beam, the WTRU may increase the counter. For example, if the counter is less than (e.g., or equal to) the threshold, the WTRU may continue to detect the confirmation PDCCH. The WTRU may (e.g., if the WTRU does not select a new candidate beam and / or the WTRU does not detect a set of second beams sent by the gNB before the counter exceeds the threshold) support one or more of the following: a contention-based RACH process; and / or retransmission of one or more UL signals (e.g., by increasing Tx power).

[0215] Beam failure recovery can be achieved through multiple beam failure recovery reference signal sets.

[0216] Figure 5 An example configuration of multiple BFR RS sets for determining a new beam through BFR is illustrated. A WTRU may receive configuration information for multiple beam failure recovery reference signal (BFR-RS) sets, and the BFR-RS sets may include resources and configurations associated with beam failure recovery. The WTRU may select one or more BFR-RS sets for beam failure recovery based on either a priority or a beam quality measurement. The WTRU may determine a second type candidate beam using a highest priority BFR-RS from the selected one or more BFR-RS sets or by using each selected BFR-RS set in order based on priority to try to find a new candidate beam.

[0217] A WTRU may be configured with multiple beam failure recovery reference signal (BFR-RS) sets. A BFR-RS set may include (e.g., all) resources and configurations that may be used to (e.g., independently) handle beam failure recovery for the WTRU. In an example, a BFR-RS set may include one or more of: resources for beam failure detection, a set of candidate beams of a first type (e.g., a first candidate beam set), one or more sets of candidate beams of a second type (e.g., a second candidate beam set), one or more sets of UL resources for beam failure indication, a CORESET for compact PDCCH transmission (e.g., to configure beam scanning using the second candidate beam set), and / or a BFR CORESET (e.g., for confirming PDCCH transmission once a new candidate beam has been selected from the second candidate beam set). A subset of UL resources for beam failure indication may be associated with the first candidate beam set, and / or another subset of beam failure resources may be associated with the second candidate beam set.

[0218] For example, Figure 5 As shown, a BFR-RS set may be associated with one or more network nodes (e.g., IRS, relay, access point, gNB, etc.) (e.g., a combination thereof). The BFR-RS set may be identified by an index. For example, the index may be a dedicated index for each BFR-RS set, or an index of the network node to which the BFR-RS set is associated, for example, if the BFR-RS set corresponds to one network node.

[0219] BFR-RS set monitoring may be activated. The WTRU may select a subset of the BFR-RS set with which the WTRU is configured as active. The WTRU may monitor resources available for beam failure recovery of the active BFR-RS set. One or more of the following may apply / perform.

[0220] The WTRU may be configured (eg, via RRC signaling) to monitor one or more active BFR-RS sets.

[0221] The WTRU may be configured (e.g., via RRC signaling) with one or more BFR-RS sets. The WTRU may determine a subset of the BFR-RS set to monitor, e.g., based on downlink (DL) signaling of the gNB. The WTRU may activate monitoring of the subset of the BFR-RS set, e.g., based on a DCI or MAC-CE indication. The WTRU may receive a DCI or MAC-CE carrying a bit set with a bit indicating "1" or "0", e.g., where "1" indicates a BFR-RS set to be activated and "0" indicates a BFR-RS set to be deactivated.

[0222] The WTRU may activate monitoring of one or more BFR-RS sets to be monitored based on beam quality measurements of one or more first and / or second beams. The beam quality measurements may include, for example, one or more of the following: L1-RSRP, L1-SINR, CQI, radio link quality (e.g., assumed BLER of DL / UL physical channels). In an example, a WTRU or a set of WTRUs may monitor a set of RS resources that may include all or part of a first beam resource of a first type of candidate beam configured as a BFR-RS set with which the WTRU may be configured. The WTRU may perform one or more beam quality measurements of the configured set of RS resources. The WTRU may provide (e.g., feedback) the beam measurements to the gNB. The WTRU may (e.g., subsequently) activate monitoring of a selected set of BFR-RS sets based on one or more of the following.

[0223] The WTRU may activate monitoring of a BFR-RS set in a configured set of BFR-RS sets by a (eg, best) candidate beam of the first type that compares to (eg, exceeds) a (eg, configured) threshold.

[0224] The WTRU may activate monitoring based on the order of the BFR-RS sets according to the beam quality of the (e.g., best) candidate beam of the first type of the BFR-RS sets. A (e.g., preconfigured) number of BFR-RS sets to be monitored may be selected from the ordered set of BFR-RS sets.

[0225] The WTRU may activate monitoring of a (e.g., preconfigured) number of BFR-RS sets based on the number of candidate beams of the first type for the BFR-RS sets compared to (e.g., exceeding) a (e.g., preconfigured) threshold. In an example scenario, the WTRU may be configured with three (3) BFR-RS sets (e.g., #1, #2, and #3). The number of BFR-RS sets to monitor may be two (2). The WTRU may determine (e.g., through beam monitoring) that BFR-RS set #1, BFR-RS set #2, and BFR-RS set #3 have three (3), two (2), and one (1) candidate beams of the first type, respectively, that exceed a (e.g., predefined) threshold. The WTRU may (e.g., in this example scenario) activate monitoring BFR-RS set #1 and BFR-RS set #2.

[0226] The activated BFR-RS sets for the WTRU may be assigned a priority. The WTRU may determine the priority of the BFR-RS set, for example, by one or more of: RRC signaling; MAC-CE indication; DCI indication; beam quality measurement of a first type of candidate beam associated with the active BFR-RS set; a BFR-RS set associated with a network node currently serving the WTRU; the number of first type of candidate beam resources configured for the BFR RS set; a BFR RS set index; or applicability of a maximum permitted exposure (MPE) or spectrum absorption rate (SAR) activity issue for the WTRU panel corresponding to the BFR-RS set.

[0227] In an example where the priority of a BFR-RS set is determined based on a beam quality measurement of a first type of candidate beam associated with an active BFR-RS set, the WTRU may perform a beam quality measurement of the first type of candidate beam of the BFR-RS set. For example, the BFR-RS set may be assigned a priority based on the measurement.

[0228] In an example, the WTRU may assign a priority to each BFR-RS set based on a determination of the beam quality of the candidate beams of the first type of the BFR-RS set. In an example, the WTRU may assign a priority based on the best candidate beams of the first type in the BFR-RS set, for example, the BFR-RS set with the highest quality candidate beams of the best first type may be assigned the highest priority. The BFR-RS set with the second highest quality candidate beams of the best first type may be assigned the next priority level, and so on, until (e.g., all) active BFR-RS sets are assigned priorities. In an example, the WTRU may assign a priority based on the worst candidate beams of the first type of the BFR-RS set, for example, the BFR set with the highest quality candidate beams of the worst first type may be assigned the highest priority. The BFR-RS set with the second highest quality candidate beams of the worst first type may be assigned the next priority level, and so on, until (e.g., all) active BFR-RS sets are assigned priorities.

[0229] In an example, the WTRU may assign priorities to the activated BFR-RS sets based on the number of candidate beams of the first type compared to (eg, exceeding) a (eg, preconfigured) threshold.

[0230] In an example where the priorities of the BFR-RS sets are determined based on the BFR-RS set associated with the network node currently serving the WTRU, the WTRU may assign the highest priority to the BFR-RS set associated with the network node currently serving the WTRU. The remaining BFR-RS sets may be assigned priorities based on one or more (e.g., a combination) of the other examples described herein.

[0231] In an example where the priority of a BFR-RS set is determined based on the number of candidate beam resources of the first type configured for the BFR RS set, the WTRU may assign a higher priority to the BFR-RS set with the highest number of configured candidate beams of the first type. The WTRU may assign the second highest priority to the BFR-RS set with the second largest number of candidate beam resources of the first type. In an example where two BFR-RS sets are configured with a similar number of candidate beams of the first type, a higher priority may be assigned to the BFR-RS set with a lower / higher index. The process of assigning priorities may continue until (e.g., all) active BFR-RS sets are assigned priorities.

[0232] In an example where the priorities of BFR-RS sets are determined based on the BFR RS set index, the WTRU may assign the highest priority to the BFR-RS set with the lowest or highest index. The WTRU may assign the next highest priority to the active BFR-RS set with the second lowest or highest index, and so on, until (e.g., all) active BFR-RS sets are assigned priorities.

[0233] In an example where the priority of a BFR-RS set is determined based on the applicability of an MPE or SAR activity issue to a WTRU panel corresponding to the BFR-RS set, a WTRU configured with two BFR-RS sets may assign a different (e.g., lower) priority to the BFR-RS set affected by the MPE or SAR issue than to the other BFR-RS set not affected by MPE or SAR.

[0234] Beam failure recovery may be implemented using one or more active BFR RS sets. For example, if the WTRU activates monitoring of more than one BFR-RS set, the WTRU may select one or more BFR-RS sets to perform beam failure recovery. The WTRU may select one or more BFR-RS sets to perform beam failure recovery based on one or more (e.g., a combination) of the following: a priority of the BFR-RS set; a beam quality measurement of a (e.g., best) first type of candidate beam; an index of the BFR-RS set / an index of a network node associated with the BFR-RS set.

[0235] In an example where one or more BFR-RS sets are selected based on the priorities of the BFR-RS sets to perform beam failure recovery, the WTRU may select a BFR-RS set with the highest priority to perform beam failure recovery. In an example, the WTRU may sort the BFR-RS sets based on the priorities of the BFR-RS sets and / or select a (e.g., configured) number of high priority BFR-RS sets to perform beam failure recovery.

[0236] In an example of selecting one or more BFR-RS sets to perform beam failure recovery based on beam quality measurements of (e.g., best) candidate beams of a first type, the WTRU may (e.g., be configured to) monitor a set of RS resources that may include a plurality of beam resources of a first type configured as candidate beams of a first type for more than one BFR-RS set. In an example, a BFR-RS set with the highest quality candidate beam of the first type may be selected to find a new beam through a beam failure recovery procedure. In an example, the WTRU may select (e.g., all) BFR-RS sets with the highest quality candidate beam resources of the first type that meet (e.g., satisfy) a (e.g., preconfigured) threshold beam quality.

[0237] In an example where one or more BFR-RS sets are selected to perform beam failure recovery based on an index of the BFR-RS set / an index of a network node associated with the BFR-RS set, the WTRU may (e.g., be configured to) select an activated BFR-RS set with the lowest index for new beam identification through beam failure recovery.

[0238] For example, if the WTRU (e.g., only) activates monitoring of (e.g., one) BFR-RS set or selects (e.g., one) BFR-RS set to perform beam failure recovery, the WTRU may select one or more new candidate beams (e.g., one or more second beams) using the activated / selected BFR-RS set. The WTRU may select one or more new candidate beams (e.g., one or more second beams) using the activated / selected BFR-RS set, e.g., as described herein.

[0239] The WTRU may (e.g., determine) to use a first type of BFR process or a second type of BFR process, for example based on one or more of: an explicit / implicit indication from the gNB; the type of selected resources for the new candidate beam; the number N of beam failure recovery processes initiated or completed within a preconfigured time interval T; a process selection timer; measurements or metrics related to mobility aspects; frequency range; SCS; the number of configured TCI states or the number of SSBs detected by the WTRU for the serving cell; the beamwidths for data and control channels supported by the IRS / relay / access point / gNB; and / or the remaining battery power.

[0240] For example, if a second type of beam failure recovery procedure is selected, the WTRU may determine a new candidate beam. The WTRU may determine the new candidate beam, for example, based on one or more of the following: the WTRU may select one or more first beams as new candidate beams; the WTRU may send one or more UL signals on UL resources associated with the selected one or more new candidate beams; the WTRU may, for example, receive an acknowledgment PDCCH in response to the transmitted UL signal indicating the selected new candidate beam (for example, if the WTRU fails to detect the acknowledgment PDCCH in response to the UL signal associated with the one or more new candidate beams, the WTRU may declare that beam failure recovery through the selected BFR-RS set has failed); the WTRU may receive a set of second beams associated with the reported first beam; the WTRU may select a set of second beams as new candidate beams; the WTRU may send one or more UL signals associated with the selected one or more second beams; the WTRU may receive a PDCCH confirming the reception of the one or more UL signals associated with the one or more second beams; and / or for example, if the WTRU does not receive a PDCCH confirmation (for example, if the WTRU fails to detect a confirmation PDCCH in response to the UL signals associated with the one or more second beams, the WTRU may declare that beam failure recovery through the selected BFR-RS set has failed), the WTRU may retransmit the UL signals associated with the selected one or more second beams (for example, by increasing Tx power) and monitor the PDCCH confirmation.

[0241] For example, if a first type of beam failure recovery procedure is selected, the WTRU may determine a new beam (e.g., as described herein). The WTRU may perform one or more of the following to determine the new beam (e.g., if a first type of beam failure recovery procedure is selected): the WTRU may select one or more second beams as new candidate beams; the WTRU may send one or more UL signals on UL resources associated with the one or more second beams; the WTRU may receive a PDCCH confirming reception of the one or more UL signals associated with the one or more second beams; and / or, for example, if the WTRU does not receive a PDCCH confirmation (e.g., if the WTRU fails to detect a confirmation PDCCH in response to the UL signals associated with the one or more second beams, the WTRU may declare that beam failure recovery through the selected BFR-RS set has failed), the WTRU may retransmit the UL signals associated with the selected one or more second beams (e.g., by increasing Tx power) and monitor the PDCCH confirmation.

[0242] For example, if the WTRU selects more than one BFR-RS set, the WTRU may first perform BFR using the highest priority BFR-RS set. If, for example, the WTRU determines that the attempt failed, the WTRU may perform BFR using the next BFR-RS set in the priority order. The process may continue until a new beam is successfully identified using the BFR-RS set, or until (e.g., all) BFR-RS sets are tried. The WTRU may determine an unsuccessful BFR attempt with a BFR-RS set (e.g., based on the type of BFR), for example, by using one or more of the examples described herein with reference to the WTRU attempting BFR using (e.g., one) BFR-RS set. For example, if the WTRU determines that all BFR-RS sets have been tried without successfully finding a new candidate beam, the WTRU may declare RLF.

[0243] Although the above features and elements are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments, or in various combinations with or without the other features and elements.

[0244] Although the implementations described herein may consider 3GPP specific protocols, it should be understood that the implementations described herein are not limited to such scenarios and may be applicable to other wireless systems. For example, although the solutions described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it should be understood that the solutions described herein are not limited to such scenarios and may be applicable to other wireless systems.

[0245] The processes described above may be implemented in a computer program, software, and / or firmware incorporated in a computer-readable medium for execution by a computer and / or processor. Examples of computer-readable media include, but are not limited to, electronic signals (sent via wired and / or wireless connections) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as, but not limited to, built-in hard disks and removable disks), magneto-optical media, and / or optical media (such as compact disk (CD)-ROM disks and / or digital versatile disks (DVDs)). A processor associated with the software may be used to implement a radio frequency transceiver for a WTRU, terminal, base station, RNC, and / or any host computer.

Claims

1. A wireless transmit receive unit (WTRU), the wireless transmit receive unit comprising: A processor, the processor being configured to: receiving configuration information indicating a first type of candidate beam reference signals (RSs) and a second type of candidate beam RSs; Detecting beam failure and determining beam failure recovery (BFR) type; as well as Based on the determined BFR type is a two-step BFR type: selecting a candidate beam RS from the candidate beam RSs of the first type and sending an indication thereof; determining a subset of second type candidate beam RSs based on the selected candidate beam RSs; performing measurements on the subset of the second type candidate beams RS during a first monitoring window; as well as A second type candidate beam RS is selected from the subset based on the measurement and an indication thereof is sent.

2. The WTRU of claim 1 , wherein the candidate beam reference signals of the first type are associated with wide beams and the candidate beam reference signals of the second type are associated with narrow beams.

3. The WTRU of claim 1 , wherein the processor is further configured to determine the BFR type as one of the one-step BFR type or the two-step BFR type.

4. The WTRU of claim 1, wherein the subset of the second type candidate beam RSs is further determined based on an association between the first type candidate RSs and the second type candidate beam RSs.

5. The WTRU of claim 1 , wherein the BFR type is determined based on one or more of: a frequency range (FR); a subcarrier spacing (SCS); a measurement; or configuration.

6. The WTRU of claim 1, wherein detecting a beam failure is based on measurement of a beam failure detection reference signal (BFD RS) corresponding to the beam failure.

7. The WTRU of claim 6, wherein the processor is further configured to: determining a BFD parameter set based on the type of the BFD RS, wherein the BFD parameter set includes one or more timers, event counters, or thresholds; and Beam failure is determined based on the parameters.

8. The WTRU of claim 1, wherein the processor is further configured to send an indication of the selected candidate beam RS using either a physical random access channel (PRACH) preamble or a resource.

9. A WTRU according to claim 1, wherein the processor is further configured to determine the subset of the second type candidate beam RS based on a configured association with the selected first type candidate beam RS or through an indication received in a PDCCH transmission.

10. The WTRU of claim 1 , wherein the processor is further configured to: Monitoring PDCCH transmission in a second monitoring window using the selected candidate beam RS; and The PDCCH transmission is received in the second monitoring window using the selected candidate beam RS, wherein the PDCCH transmission includes an indication of an acknowledgement.

11. The WTRU of claim 1 , wherein the processor is further configured to send an indication of the selected second type candidate beam RS using a PRACH transmission.

12. The WTRU of claim 1 , wherein the processor is further configured to: receiving configuration information for a plurality of beam failure recovery reference signal (BFR-RS) sets, each BFR-RS set including resources and configuration associated with beam failure recovery; and One or more BFR-RS sets are selected for beam failure recovery based on either priority or beam quality measurement, wherein a highest priority BFR-RS from the selected one or more BFR-RS sets is used or a second type of candidate beam RS is determined by attempting to determine a new candidate beam using each selected BFR-RS set in sequence based on priority.

13. A method for a wireless transmit receive unit (WTRU), the method comprising: receiving configuration information indicating a first type of candidate beam reference signals (RSs) and a second type of candidate beam RSs; Detecting beam failure and determining beam failure recovery (BFR) type; as well as Based on the determined BFR type is a two-step BFR type: selecting a candidate beam RS from the candidate beam RSs of the first type and sending an indication thereof; Determining a subset of the second type candidate beam RSs based on the selected candidate beam RSs; performing measurements on the subset of the second type candidate beams RS during a first monitoring window; as well as A second type candidate beam RS is selected from the subset based on the measurement and an indication thereof is sent.

14. The WTRU of claim 13, wherein the candidate beam reference signals of the first type are associated with wide beams and the candidate beam reference signals of the second type are associated with narrow beams.

15. The WTRU of claim 13, wherein the method further comprises determining the BFR type as one of a one-step BFR type or the two-step BFR type.

16. The WTRU of claim 13, wherein the subset of the second type candidate beam RSs is further determined based on an association between the first type candidate RSs and the second type candidate beam RSs.

17. The WTRU of claim 13, wherein the BFR type is determined based on one or more of: frequency range (FR); subcarrier spacing (SCS); measurement; or configuration.

18. The WTRU of claim 13, wherein detecting a beam failure is based on measurement of a beam failure detection reference signal (BFD RS) corresponding to the beam failure.

19. The WTRU of claim 18, wherein the processor is further configured to: determining a BFD parameter set based on the type of the BFD RS, wherein the BFD parameter set includes one or more timers, event counters, or thresholds; and Beam failure is determined based on the parameters.

20. The WTRU of claim 13, wherein the processor is further configured to send an indication of the selected candidate beam RS using any of a physical random access channel (PRACH) preamble or resources.

21. The WTRU of claim 13, wherein the processor is further configured to determine the subset of the second type candidate beam RSs based on a configured association with the selected first type candidate beam RSs or by an indication received in a PDCCH transmission.

22. The WTRU of claim 13, wherein the processor is further configured to: Monitoring PDCCH transmission in a second monitoring window using the selected candidate beam RS; and The PDCCH transmission is received in the second monitoring window using the selected candidate beam RS, wherein the PDCCH transmission includes an indication of an acknowledgement.

23. The WTRU of claim 13, wherein the processor is further configured to send an indication of the selected second type candidate beam RS using a PRACH transmission.

24. The WTRU of claim 13 wherein the processor is further configured to: receiving configuration information for a plurality of beam failure recovery reference signal (BFR-RS) sets, each BFR-RS set including resources and configuration associated with beam failure recovery; and One or more BFR-RS sets are selected for beam failure recovery based on either priority or beam quality measurement, wherein a highest priority BFR-RS from the selected one or more BFR-RS sets is used or a second type of candidate beam RS is determined by attempting to determine a new candidate beam using each selected BFR-RS set in sequence based on priority.

25. A wireless transmit receive unit (WTRU), the wireless transmit receive unit comprising: A processor, the processor being configured to: receiving configuration information indicating candidate beam reference signals (RSs) of a wide beam mode and candidate beam RSs of a narrow beam mode; Detecting beam failure and determining beam failure recovery (BFR) type; as well as Based on the determined BFR type is a two-step BFR type: selecting a candidate beam RS from the candidate beam RSs in the wide beam pattern and sending an indication thereof; Determining a subset of the narrow beam pattern candidate beam RSs based on the selected candidate beam RSs; performing measurements on said subset of narrow beam mode candidate beams RS during a first monitoring window; as well as A narrow beam pattern candidate beam RS is selected from the subset based on the measurements and an indication thereof is sent.

26. The WTRU of claim 25, wherein the processor is further configured to determine the BFR type as one of the one-step BFR type or the two-step BFR type.

27. The WTRU of claim 25, wherein the subset of the narrow beam mode candidate beam RSs is further determined based on an association between the wide beam mode candidate RSs and the narrow beam mode candidate beam RSs.

28. The WTRU of claim 25, wherein the BFR type is determined based on one or more of: frequency range (FR); subcarrier spacing (SCS); measurement; or configuration.

29. The WTRU of claim 25, wherein detecting a beam failure is based on measurement of a beam failure detection reference signal (BFD RS) corresponding to the beam failure.

30. The WTRU of claim 29 wherein the processor is further configured to: determining a BFD parameter set based on the type of the BFD RS, wherein the BFD parameter set includes one or more timers, event counters, or thresholds; and Beam failure is determined based on the parameters.

31. The WTRU of claim 25, wherein the processor is further configured to send an indication of the selected candidate beam RS using either a physical random access channel (PRACH) preamble or a resource.

32. The WTRU of claim 25, wherein the processor is further configured to determine the subset of the narrow beam mode candidate beam RSs based on a configured association with the selected wide beam mode candidate beam RSs or through an indication received in a PDCCH transmission.

33. The WTRU of claim 25 wherein the processor is further configured to: Monitoring PDCCH transmission in a second monitoring window using the selected candidate beam RS; and The PDCCH transmission is received in the second monitoring window using the selected candidate beam RS, wherein the PDCCH transmission includes an indication of an acknowledgement.

34. The WTRU of claim 25, wherein the processor is further configured to transmit an indication of the selected narrow beam pattern candidate beam RS using a PRACH transmission.

35. The WTRU of claim 25 wherein the processor is further configured to: receiving configuration information for a plurality of beam failure recovery reference signal (BFR-RS) sets, each BFR-RS set including resources and configuration associated with beam failure recovery; and selecting one or more BFR-RS sets for beam failure recovery based on either a priority or a beam quality measurement, wherein a narrow beam mode candidate beam RS is determined using a highest priority BFR-RS from the selected one or more BFR-RS sets or by attempting to determine a new candidate beam using each selected BFR-RS set sequentially based on a priority.

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