Cell configuration and management for L1 / L2 mobility

Abstract

A wireless transmit / receive unit (WTRU) may be configured to implement a layer 1 / layer 2 (L1 / L2) based inter-cell mobility procedure with reduced latency during handover or other mobility operations. The WTRU may be configured to receive configuration information associated with a plurality of candidate cells. The configuration information may be associated with physical layer measurements for each candidate cell. The configuration information may include measurement criteria. The WTRU may be configured to determine a subset of the plurality of candidate cells, where each candidate cell in the subset is determined based on the measurement criteria. The WTRU may be configured to send a report indicating the subset, perform physical layer measurements on the subset, and receive an instruction to perform a layer handover to a candidate cell of the subset.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 309,231, filed February 11, 2022, and U.S. Provisional Patent Application No. 63 / 394,778, filed August 3, 2022, which are incorporated by reference in their entireties. [Background technology]

[0002] Users of mobile networks expect fast response times. For example, when a user enters a network, transitions from one network to another, or opens an application, the user may expect the action to occur quickly and / or transparently. Users may be less tolerant of network delays or dropouts. In addition, the amount of data handled by the network continues to increase. Using traditional networks to handle the increased data throughput may result in delays and dropouts. Summary of the Invention

[0003] A wireless transmit / receive unit (WTRU) may be configured to implement a layer 1 / layer 2 (L1 / L2) based inter-cell mobility procedure, e.g., with reduced latency during handover or other mobility operations. For example, a WTRU may be configured to implement an inter-cell mobility procedure that utilizes one or more mobility procedures designed to reduce latency during mobility events.

[0004] For example, the WTRU may be configured to maintain configurations for multiple candidate cells to enable fast application of the configuration for a candidate cell when a mobility procedure is initiated. The WTRU may use dynamic switching mechanisms between candidate serving cells (e.g., a primary cell (PCell, SpCell) and / or a secondary cell (SCell)) based on L1 (e.g., physical layer) and / or L2 (e.g., medium access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and / or radio resource control (RRC)) signaling. The WTRU may implement physical layer-based techniques for inter-cell beam management, including physical layer / layer 1 (PHY / L1) measurement reporting and beam indication signaling. During or after a mobility event, the WTRU may implement a timing advance procedure to reduce latency associated with acquiring timing synchronization. The WTRU and / or the network may utilize centralized unit (CU)-distributed unit (DU) interface signaling (e.g., at a gNodeB (gNB)) to support WTRU mobility.

[0005] The WTRU may receive configuration information associated with one or more candidate cells. The configuration information may be associated with one or more physical layer measurements for the one or more candidate cells. For example, the WTRU may receive a set of RRC configurations for the candidate cells for L1 / L2 mobility. The WTRU may perform beam measurements for a subset of the candidate cells. When the WTRU experiences a mobility event, the WTRU may indicate to the network an identity of the subset of candidate cells for which the WTRU is performing beam measurements.

[0006] To support lower layer (L1 / L2) mobility, the WTRU may receive a set of RRC configurations for a group of candidate neighbor cells for a given (e.g., current) serving cell. Each RRC configuration may apply to one of the neighbor cells or to more than one of the neighbor cells. The WTRU may be configured by the RRC with metrics for one or more (e.g., or each) of the candidate cells. For example, the metrics may include a reference signal received power (RSRP) threshold associated with the candidate cell. The WTRU may be configured with a defined transition time period, which may be configured for the group of neighbor cells or for a particular neighbor cell.

[0007] The WTRU may apply the RRC configuration and activate neighbor beam management for the configured subset of candidate cells. When applying the RRC configuration, the WTRU may perform a neighbor beam management procedure. The neighbor cell beam management procedure may include performing and / or reporting beam measurements associated with the subset of neighbor cells without triggering a beam failure detection procedure.

[0008] The WTRU may determine a subset of candidate serving cells for neighbor cell beam management. In some scenarios, the WTRU may determine the subset of candidate cells (e.g., serving cells) based on configured metric criteria, WTRU capabilities, and / or the number of configured serving cells utilized by the WTRU. For example, the subset of candidate cells (e.g., neighbor cells) may be selected to be all candidate cells determined to have an RSRP above a threshold, e.g., assuming that the number of candidates meeting the metric does not exceed the processing capabilities of the WTRU. In some examples, the metric may include reference signal received power (RSRP). For example, the metric may include RSRP above a threshold. The subset of the multiple candidate cells may include all candidate cells above an RSRP threshold. The metric may include channel state information-reference signal received power (CSI-RSRP). In some examples, determining the subset of the multiple candidate cells may be based at least in part on the number of configured candidate cells. For example, the number of configured candidate cells may be greater than a threshold.

[0009] The WTRU may be configured to report an identity of a subset of candidate cells to the network. For example, when the subset is changed (e.g., due to an RSRP change or a mobility event), the WTRU may report the new subset to the network. In examples, the reporting may be by the MAC CE or by triggering a beam measurement report indicating the subset. In some scenarios, the report may include a bitmap. The bitmap may be in the MAC CE. An instruction to perform a handover may be received in downlink control information (DCI). The report may be sent, for example, to a base station. The WTRU may report to the network upon a change to one or more of the candidate cells in the subset of multiple candidate cells, in some examples.

[0010] The WTRU may be configured to perform one or more physical layer measurements for a subset of the plurality of candidate cells. In some scenarios, the WTRU may be configured to perform one or more measurements for one or more of the candidate cells. In some examples, the physical layer measurements may be one or more of radio link monitoring measurements or beam measurements. The WTRU may be configured to receive an instruction to perform a handover. The handover may be a lower layer handover in some examples. The handover may be performed, for example, to one or more of the candidate cells of the subset of the plurality of candidate cells. In some scenarios, the candidate cell may be maintained as a candidate cell in the plurality of candidate cells for a predetermined period of time. The predetermined period of time may be measured from receipt of the instruction to perform the handover. In some examples, the handover may be initiated after one or more of a beam failure or a failed beam failure recovery.

[0011] The WTRU may be configured to switch beams utilized for transmission and / or reception. Upon receiving and / or implementing a beam switch from a beam in a first cell (e.g., a current serving cell) to a beam of a second cell (e.g., a non-serving cell), the WTRU may change the serving cell to the second cell associated with the new beam. The WTRU may, for example, remove the second cell from the subset of candidate cells. The WTRU may add the first cell (e.g., the old serving cell) to the subset of candidate cells. For example, the WTRU may add the first cell to the subset of candidate cells for at least a configured period of time associated with a configured transition timer. The WTRU may release the configuration of any candidate cell that is not in the subset. For example, the WTRU may release the configuration of any candidate cell that is not in the subset after implementing a beam switch. In some scenarios, the WTRU may be configured to determine a target configuration. The target configuration may be based at least in part on one or more anchor cell identities, for example. The anchor cell identity may be used, for example, to apply a candidate cell configuration.

[0012] An example method for implementing L1 / L2 mobility may include configuring a WTRU with a set of radio resource control (RRC) configurations for each of a group of neighboring cell candidates neighboring a serving cell, each configuration of the set of configurations including a measurement criterion and a transition time period. The WTRU applies the RRC configurations for each of a subset of the group of neighboring cell candidates, activates neighboring beam management for each of the subset of the group of neighboring cell candidates, reports the subset of the group of neighboring cell candidates to a network, receives a beam switch on a cell indicating a beam of a non-serving cell, and upon receiving the beam switch, changes the current serving cell to a new serving cell that is the non-serving cell for which the beam switch was received, removes the new serving cell from the subset of the group of neighboring cell candidates, adds the original current serving cell to the subset of the group of neighboring cell candidates, and releases the RRC configurations for any candidate cells not in the subset of the group of neighboring cell candidates.

[0013] The WTRU may be configured to receive configuration information. The configuration information may be associated with a plurality of candidate cells. The configuration information may include configuration information associated with physical layer measurements. The physical layer measurements may be for each candidate cell. Additionally or alternatively, the configuration information may include one or more measurement criteria.

[0014] The WTRU may be configured to determine a subset of candidate cells. For example, each candidate cell in the subset of candidate cells may be determined based on a metric. The candidate cells may include all candidate cells above a reference signal received power (RSRP) threshold. Additionally or alternatively, the WTRU may be configured to send a report. The report may indicate the subset of candidate cells. The report indicating the subset of candidate cells may include a bitmap. The report may be sent via a medium access control (MAC) control element (CE). The report may be sent to the base station.

[0015] The WTRU may be configured to perform physical layer measurements on a subset of the plurality of candidate cells. The WTRU may be configured to receive an indication. The indication may be to perform a lower layer handover. The lower layer handover may be to a candidate cell. The candidate cell may be of a subset of the plurality of candidate cells. The indication may be received via a MAC CE. Additionally or alternatively, the indication may be received via a downlink control information (DCI).

[0016] The physical layer measurements may include radio link monitoring (RLM) measurements. Additionally or alternatively, the physical layer measurements may include beam measurements. The metrics may include reference signal received power. For example, the metrics may include reference signal received power exceeding a threshold. [Brief description of the drawings]

[0017] [Figure 1A] FIG. 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] FIG. 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A, according to one embodiment. [Figure 1C] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1D] FIG. 1D is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communications system illustrated in FIG. 1A, according to one embodiment. [Diagram 2] FIG. 2 is an illustration of an example relating mobility speed and WTRU complexity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. Communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communications system 100 may enable multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communications system 100 may use 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 multicarrier (FBMC), and the like.

[0019] 1A, communications 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, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of 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 transmit and / or receive wireless signals, and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, paging, mobile phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., for remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain context), consumer electronics devices, devices operating in commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0020] 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 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, etc. Although the base stations 114a, 114b are each illustrated as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0021] 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 transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one 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, using beamforming to transmit and / or receive signals in a desired spatial direction.

[0022] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d via 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).

[0023] More specifically, as noted above, the communications system 100 may be a multiple access system, but may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a and the WTRUs 102a, 102b, 102c in the RAN 104 / 113 may implement a radio technology, such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communications 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 ​​Uplink Packet Access (HSUPA).

[0024] In one 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), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0025] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology, such as New Radio (NR) radio access, which may establish the air interface 116 using NR technology.

[0026] In one 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 implement LTE radio access and NR radio access together, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to and from multiple types of base stations (e.g., eNBs and gNBs).

[0027] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology 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), or the like.

[0028] 1A 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 localized area, such as an office, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. 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 one 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 establish a picocell or a femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106 / 115.

[0029] The RAN 104 / 113 may communicate with the CN 106 / 115, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as, for example, 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 high level security functions such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may communicate directly or indirectly with other RANs that use 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 communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0030] The CN 106 / 115 may also act 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 providing 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), user datagram protocol (UDP), and / or the internet protocol (IP) of the TCP / IP Internet protocol suite. The networks 112 may include wired 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 use the same RAT as the RANs 104 / 113 or a different RAT.

[0031] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications 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 over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may employ a cellular-based wireless technology, and a base station 114b, which may employ an IEEE 802 wireless technology.

[0032] Figure 1B is a system diagram illustrating an example WTRU 102. As shown in Figure 1B, 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 understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0033] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), multiple 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 coding, 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 FIG. 1B illustrates the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0034] The transmit / receive element 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0035] 1B 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.

[0036] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0037] The processor 118 of the WTRU 102 may be coupled to and may receive user-entered data from 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). 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 non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), 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, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0038] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0039] The processor 118 may also be coupled to a 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, 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 being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by way of any suitable location determination method while remaining consistent with an embodiment.

[0040] The processor 118 may further be coupled to other peripherals 138, which may include one or more software 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 videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulated (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, and the like. The peripherals 138 may include one or more sensors, which may be one or more of 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.

[0041] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals associated with a particular subframe (e.g., for both the UL (e.g., for transmission) and the downlink (e.g., for reception) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmission and reception of some or all of the signals (e.g., associated with a particular subframe for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0042] 1C is a system diagram illustrating the RAN 104 and the CN 106, according to one embodiment. As mentioned above, the RAN 104 may employ E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0043] The RAN 104 may include eNodeBs 160a, 160b, 160c, although it will be understood that the RAN 104 may include any number of eNodeBs while remaining consistent with an embodiment. The eNodeBs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the eNodeBs 160a, 160b, 160c may implement MIMO technology. Thus, the eNodeB 160a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0044] Each of the eNodeBs 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 the UL and / or DL, etc. As shown in FIG 1C, the eNodeBs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0045] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing elements is illustrated as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0046] The MME 162 may be connected to each of the eNodeBs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attachment 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.

[0047] The SGW 164 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNodeB handover, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0048] The SGW 164 may be connected to a 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.

[0049] 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 communicate with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves 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 and / or wireless networks owned and / or operated by other service providers.

[0050] Although the WTRU is depicted in FIGS. 1A-1D as a wireless terminal, in certain representative embodiments, it is contemplated that such a terminal may use a wired communications interface (e.g., temporarily or permanently) with the communications network.

[0051] In an exemplary embodiment, the other network 112 may be a WLAN.

[0052] A WLAN in infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access or interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic into and / or out of the BSS. Traffic originating from outside the BSS to the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. Traffic between STAs within the BSS may be sent, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between (e.g., directly between) the source STA and the destination STA using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad-hoc" communication mode.

[0053] When using an 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit a beacon 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 that is dynamically set via signaling. The primary channel may be the operating channel of the BSS, but may be used by STAs to establish a connection with the AP. In certain representative embodiments, for example, in an 802.11 system, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / 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.

[0054] A High Throughput (HT) STA may use a 40 MHz wide channel for communication, which may be formed, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels.

[0055] A Very High Throughput (VHT) STA may support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. A 40 MHz and / or 80 MHz channel may be formed by combining multiple contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed and the combined data may be sent to the Medium Access Control (MAC).

[0056] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter-type control / machine-type communication, such as MTC devices in macro coverage areas. MTC devices may have limited capabilities, including certain capabilities, for example, support for (e.g., support only for) certain and / or limited bandwidths. MTC devices may include batteries with above-threshold battery life (e.g., to maintain very long battery life).

[0057] WLAN systems that may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that may be designated as a primary channel. 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 configured and / or limited by the STAs among all STAs operating in the BSS that support the smallest bandwidth operating mode. In an 802.11ah embodiment, the primary channel may be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration may depend on the status of the primary channel. For example, if the primary channel is active due to a STA (that only supports the 1 MHz mode of operation) transmitting to the AP, the entire available frequency band may be considered active even though most of the frequency band may remain dormant and available.

[0058] In the United States, the available frequency bands that can be used by 802.11ah are 902MHz to 928MHz. In South Korea, the available frequency bands are 917.5MHz to 923.5MHz. In Japan, the available frequency bands are 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz depending on the country code.

[0059] 1D is a system diagram illustrating the RAN 113 and the CN 115, according to one embodiment. As mentioned 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 communicate with the CN 115.

[0060] The RAN 113 may include gNBs 180a, 180b, 180c, although it will be understood 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 an embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may transmit and / or receive wireless signals to and from the WTRU 102a, for example, using multiple antennas. In one 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 one embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or gNB 180c).

[0061] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the 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 different or scalable lengths (e.g., including different numbers of OFDM symbols and / or lasting different lengths of absolute time).

[0062] 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 without accessing another RAN (e.g., eNodeBs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with and connect to a gNB 180a, 180b, 180c while also communicating with and connecting to another RAN, such as an eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeBs 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0063] 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 the UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0064] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. Although each of the foregoing elements is illustrated as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0065] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. The network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 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 massive 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.

[0066] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 115 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 115 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions such as managing and allocating WTRU 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.

[0067] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an 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 UPFs 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.

[0068] The CN 115 may facilitate communication with other networks. For example, the CN 115 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves 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 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 through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0069] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-ab, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0070] The emulation device may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for testing purposes and / or may use terrestrial wireless communication to implement the tests.

[0071] The one or more emulation devices may perform one or more functions, inclusive, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, for example, one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0072] The WTRU may transmit and / or receive physical channels and / or reference signals. The physical channels and / or reference signals may be transmitted and / or received according to at least one spatial domain filter. The term "beam" may be used to refer to a spatial domain filter. In this specification, the terms spatial filter and tx beam may be used interchangeably.

[0073] The WTRU may transmit physical channels and / or signals using a spatial domain filter (e.g., the same spatial domain filter used to receive a reference signal (RS)). For example, the RS may include a channel state information reference signal (CSI-RS) and / or a synchronized signal (SS) block. The WTRU transmission may be referred to as a "target." The received RS or SS block may be referred to as a "reference" or "source." In some scenarios, the WTRU may transmit a target physical channel or signal according to a spatial relationship to such RS or SS block.

[0074] The WTRU may transmit a first physical channel and / or signal according to a spatial domain filter (e.g., the same spatial domain filter used to transmit a second physical channel and / or signal). The first transmission may be referred to as the "target" or "source." The second transmission may be referred to as the "reference." In some examples, the WTRU may be said to transmit a first (e.g., target) physical channel and / or signal according to a spatial relationship to a second (e.g., reference) physical channel and / or signal.

[0075] The spatial relationship may be implicit. The spatial relationship may be configured by RRC and / or signaled by MAC CE and / or DCI. For example, the WTRU may implicitly transmit a physical uplink shared channel (PUSCH) and / or a demodulation reference signal (DM-RS) for the PUSCH. For example, the transmission may be transmitted according to a spatial domain filter (e.g., the same spatial domain filter as a sounding reference signal (SRS)). The SRS may be indicated by an SRS resource indicator (SRI) and / or indicated in the DCI and / or configured by RRC. In another example, the spatial relationship may be set by RRC for the SRI and / or signaled by MAC CE for the PUCCH. Such a spatial relationship may also be referred to as a "beam indication."

[0076] The WTRU may receive a first (e.g., target) downlink channel and / or signal. For example, the WTRU may receive the first downlink channel according to a spatial domain filter (e.g., the same spatial domain filter) and / or spatial reception parameters as the second (e.g., reference) downlink channel and / or signal. For example, an association may exist between a physical channel, such as a PDCCH or PDSCH, and / or the respective DM-RS. The first and second signals may be reference signals. In some scenarios, the WTRU may receive the first (e.g., target) downlink channel and / or signal according to the same spatial domain filter and / or spatial reception parameters as the second (e.g., reference) downlink channel and / or signal when the WTRU is configured with a quasi-colocation (QCL) assumption type D between the corresponding antenna ports. The association may be configured as a transmission configuration indicator (TCI) state. The WTRU may be indicated by an association between the CSI-RS and / or SS block and the DM-RS. The association may be based on an index, for example. The index may be to a set of TCI states configured by the RRC and / or signaled by the MAC CE. Such an indication may also be referred to as a "beam indication."

[0077] In a beamformed system, for example, the WTRU may be configured to maintain one or more beam pairs. In some scenarios, the WTRU may monitor a periodic CSI-RS (e.g., a certain periodic CSI-RS). The WTRU may monitor the periodic CSI-RS to evaluate its quality and / or calculate a corresponding quality metric. For example, the WTRU may monitor the periodic CSI-RS on a serving DL beam. The PHY entity of the WTRU may report a beam failure instance (BFI). The beam failure instance may be reported to the MAC sublayer. For example, if the beam quality in a given RS period for one or more beams (e.g., all beams) in the maintain set falls below a configured threshold, the PHY entity of the WTRU reports a BFI.

[0078] The WTRU may maintain a beam failure detection (BFD) procedure. The BFD procedure may include periodic measurements of maintained beams and / or a beam failure recovery (BFR) request. The BFR request may be reported to the network upon detecting a beam failure. BFR may be configured for beam maintenance on, for example, the PCell and / or the SCell. In some examples, BFD measurements may be performed when BFD and / or discontinuous reception (DRX) are configured. BFD measurements may be performed at the maximum of the DRX period and / or the CSI-RS period. The WTRU may maintain a BFD procedure to re-establish a lost beam pair. Re-establishment of a lost beam pair may be faster than the RLM / RLF procedure.

[0079] The MAC entity may maintain a beam failure instance (BFI) counter. The BFI counter may be used for beam failure detection. In some scenarios, the MAC entity may count the number of beam failure instance indications. The number of beam failure instance indications may be received, for example, from the PHY entity. The BFI counter may exceed a certain maximum number of BFIs. A BFR request may be triggered to inform the serving gNB that a beam failure has been detected. The BFR request may be triggered when the BFI counter exceeds a certain maximum number of BFIs.

[0080] In some scenarios, the MAC entity may reset the BFI counter. The MAC entity may reset the BFI counter after a beam failure detection timer (BFD timer) expires. This may be useful, for example, to provide some hysteresis in the detection function. In some examples, the WTRU may reset the BFD timer every time a BFI is indicated. For example, the MAC entity may reset the BFI counter after not observing a BFI indication from the PHY for a number (e.g., three) consecutive CSI-RS periods, e.g., if the BFD timer is configured for that number (e.g., three) CSI-RS periods.

[0081] In some scenarios, the WTRU may initiate a random access procedure for beam re-establishment. The WTRU may initiate the random access procedure, for example, to report a BFR request for a detected beam failure for the SpCell. The WTRU may select an appropriate PRACH preamble and / or PRACH resource. The selection may be based on a measured best downlink beam (e.g., CSI-RS and / or DL ​​synchronization signal block (SSB)). The WTRU may be configured to re-establish a beam pair. The WTRU may be configured to re-establish a beam pair when a determination is made that there is an association between the DL beam and / or the UL preamble and / or the PRACH occasion. The downlink beam selected by the WTRU may be tested by receiving a random access response (RAR). The re-establishment random access (RA) procedure may be faster if the gNB configures a set of contention-free PRACH preambles / resources. For example, the contention-free PRACH preambles / resources may be prioritized for selection by the WTRU. The prioritization may be done when initiating an RA procedure. In some scenarios, the WTRU may transmit a MAC CE indicating the cell for which a beam failure is detected. The WTRU may transmit a MAC CE to report a BFR request for a beam failure detected for an Scell. In some scenarios, L1 / L2 based inter-cell mobility mechanisms and / or procedures may reduce latency. For example, configuration and / or maintenance for multiple candidate cells may enable fast application of configurations for candidate cells (e.g., RAN2, RAN3). Dynamic switching mechanisms between candidate serving cells (e.g., SpCell and / or SCell) may be applicable based on L1 / L2 signaling (e.g., Ran2, RAN1). In some scenarios, L1 extensions for inter-cell beam management may include one or more of L1 measurements and / or reports and beam direction (e.g., RAN1, RAN2). For example, RAN2 may be used for inter-cell beam management and / or beam direction. In some scenarios, timing advance management (e.g., RAN1, RAN2) may exist. Centralized unit-distributed unit (CU-DU) interface signaling for L1 / L2 mobility support (e.g., RAN3) may exist. In some examples, beam switching techniques may be used for L1 / L2 mobility to change cells using beam mobility techniques as herein.

[0082] The WTRU may be configured to perform Layer 1 / PHY mobility procedures and / or Layer 2 / MAC / RLC / PDCP / RRC mobility procedures. Certain handover commands may include a cell configuration. For example, the cell configuration may include a target cell configuration, which may be indicated, for example, as a delta configuration on the source cell configuration. L1 / L2 mobility as described herein may refer to a WTRU configured to perform mobility (e.g., frequent mobility without significant signaling overhead). The WTRU may be provided with cell configurations of one or more (e.g., multiple) cells available at the WTRU. For example, the configurations may not be fully provided to the WTRU (e.g., a confirmation may refer to a cell as a delta configuration). The WTRU may store a radio resource control (RRC) configuration for each cell. The WTRU may apply the RRC configuration and / or indicate that the cell is in a deactivated state. For example, indicating that a cell is in a deactivated state may enable the WTRU to perform beam measurements on beams associated with non-serving cells, which may be used (e.g., by the network) to trigger L1 / L2 mobility. The WTRU may be configured to switch beams utilized for transmission and / or reception. For example, upon receiving and / or performing a beam switch from a beam in a first cell (e.g., the current serving cell) to a beam of a second cell (e.g., a non-serving cell), the WTRU may change the WTRU's serving cell to the second cell associated with the new beam. The WTRU may remove the second cell from the subset of candidate cells. The WTRU may add the first cell (e.g., the old serving cell) to the subset of candidate cells. For example, the WTRU may add the first cell to the subset of candidate cells for at least a configured period of time associated with a configured transition timer. The WTRU may release the configuration of any candidate cell that is not in the subset. For example, the WTRU may release the configuration of any candidate cell that is not in the subset after performing beam switching. In some embodiments, the WTRU may be configured to determine a target configuration.The target configuration may be based, for example, at least in part, on one or more anchor cell identities, which may be used, for example, to apply the candidate cell configuration.

[0083] FIG. 2 illustrates an example associated with mobility speed and WTRU complexity. The example illustrated in FIG. 2 may consider, for example, different modeling of cell configurations in a WTRU 202 in a New Radio (NR) network. The network may include a base station 214. In some scenarios, there may be multiple WTRUs 102 and / or multiple base stations 214, as described herein. As the complexity of the WTRU 202 and the number of network resources increase, the latency associated with L1 / L2 operations may decrease. For example, a dormant Scell ​​configuration 244 (e.g., dormant behavior) has lower latency than both a deactivated Scell ​​configuration 242 (e.g., carrier aggregation) and a stored cell configuration 240 (e.g., CHO). FIG. 2 also illustrates that a deactivated Scell ​​configuration 242 (e.g., carrier aggregation) has lower latency than a stored cell configuration 240 (e.g., CHO).

[0084] 2 shows that the dormant Scell ​​configuration 244 (e.g., dormant behavior) has higher WTRU complexity and network resource usage than both the deactivated Scell ​​configuration 242 (e.g., carrier aggregation) and the stored cell configuration 240 (e.g., CHO). The deactivated Scell ​​configuration 242 (e.g., carrier aggregation) also has higher WTRU complexity and network resource usage than the stored cell configuration 240 (e.g., CHO).

[0085] A WTRU may be configured to perform conditional handover (CHO) and conditional primary Scell ​​(PSCell) addition / change CPA / CPC in an NR radio network. For example, the L1 / L2 mobility described herein may implement conditional handover and / or conditional PSCell addition / change. For example, in a conditional handover (CHO), the WTRU may be configured (e.g., via an RRC reconfiguration message) with an HO target (e.g., target cell configuration) and associated conditions for cell measurement events (e.g., events A3 / A5 and corresponding cells). The WTRU may start monitoring the associated conditions. For example, the WTRU may start monitoring the associated conditions following configuration by receiving a CHO command. If the conditions are satisfied, the WTRU may trigger a HO (reconfiguration) to the associated cell with the given configuration. In the case of a conditional PSCell change (CPC) and / or a conditional PSCell addition (CPA), the WTRU may trigger a PSCell change or addition associated with the stored PSCell configuration. For example, in the case of a conditional PSCell change (CPC) and / or a conditional PSCell addition (CPA), the WTRU may trigger a PSCell change or addition associated with the stored PSCell configuration upon triggering an associated condition defined by a measurement event.

[0086] A wireless transmit / receive unit (WTRU) may be configured to implement a Layer 1 / Layer 2 (L1 / L2) based inter-cell mobility procedure, e.g., with reduced latency during handover or other mobility operations. For example, a WTRU may be configured to implement an inter-cell mobility procedure that utilizes one or more mobility procedures designed to reduce latency during mobility events.

[0087] For example, the WTRU may be configured to maintain configurations for multiple candidate cells to enable fast application of configurations for candidate cells when a mobility procedure is initiated. The WTRU may use dynamic switching mechanisms between candidate serving cells (e.g., primary cell (PCell, SpCell) and / or secondary cell (SCell)) based on L1 (e.g., physical layer) and / or L2 (e.g., medium access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and / or radio resource control (RRC)) signaling. The WTRU may implement physical layer-based techniques for inter-cell beam management, including physical layer / layer 1 (PHY / L1) measurement reporting and beam indication signaling. During or after a mobility event, the WTRU may implement a timing advance procedure to reduce latency associated with acquiring timing synchronization. The WTRU and / or the network may utilize centralized unit (CU)-distributed unit (DU) interface signaling (eg, at a gNodeB (gNB)) to support WTRU mobility.

[0088] The WTRU may receive configuration information associated with one or more candidate cells. The configuration information may be associated with one or more physical layer measurements for the one or more candidate cells. For example, the WTRU may receive a set of RRC configurations for the candidate cells for L1 / L2 mobility. The WTRU may perform beam measurements for a subset of the candidate cells. When the WTRU experiences a mobility event, the WTRU may indicate to the network an identity of the subset of candidate cells for which the WTRU is performing beam measurements.

[0089] To support lower layer (L1 / L2) mobility, the WTRU may receive a set of RRC configurations for a group of candidate neighbor cells for a given (e.g., current) serving cell. Each RRC configuration may apply to one of the neighbor cells or to more than one of the neighbor cells. The WTRU may be configured by the RRC with metrics for one or more (e.g., or each) of the candidate cells. For example, the metrics may include a Reference Signal Received Power (RSRP) threshold associated with the candidate cell. The WTRU may be configured with a defined transition time period, which may be configured for the group of neighbor cells or for a particular neighbor cell.

[0090] The WTRU may apply the RRC configuration and activate neighbor beam management for the configured subset of candidate cells. When applying the RRC configuration, the WTRU may perform a neighbor beam management procedure. The neighbor cell beam management procedure may include performing and / or reporting beam measurements associated with the subset of neighbor cells without triggering a beam failure detection procedure.

[0091] The WTRU may determine a subset of candidate serving cells for neighbor cell beam management. In some scenarios, the WTRU may determine the subset of candidate cells (e.g., serving cells) based on configured metric criteria, WTRU capabilities, and / or the number of configured serving cells utilized by the WTRU. For example, the subset of candidate cells (e.g., neighbor cells) may be selected to be all candidate cells determined to have an RSRP above a threshold, e.g., assuming that the number of candidates meeting the metric does not exceed the processing capabilities of the WTRU. In some examples, the metric may include Reference Signal Received Power (RSRP). For example, the metric may include RSRP above a threshold. The subset of the multiple candidate cells may include all candidate cells above an RSRP threshold. The metric may include Channel State Information-Reference Signal Received Power (CSI-RSRP). In some examples, determining the subset of the multiple candidate cells may be based at least in part on the number of configured candidate cells. For example, the number of configured candidate cells may be greater than a threshold.

[0092] The WTRU may be configured to report an identity of a subset of candidate cells to the network. For example, when the subset changes (e.g., due to an RSRP change or a mobility event), the WTRU may report the new subset to the network. In examples, the reporting may be by the MAC CE or by triggering a beam measurement report indicating the subset. In some scenarios, the report may include a bitmap. The bitmap may be in the MAC CE. An instruction to perform a handover may be received in downlink control information (DCI). The report may be sent, for example, to a base station. The WTRU may report to the network upon a change to one or more of the candidate cells in the subset of multiple candidate cells, in some examples.

[0093] The WTRU may be configured to perform one or more physical layer measurements for a subset of the plurality of candidate cells. In some scenarios, the WTRU may be configured to perform one or more measurements for one or more of the candidate cells. In some examples, the physical layer measurements may be one or more of radio link monitoring measurements or beam measurements. The WTRU may be configured to receive an instruction to perform a handover. The handover may be a lower layer handover in some examples. The handover may be performed, for example, to one or more of the candidate cells of the subset of the plurality of candidate cells. In some scenarios, the candidate cell may be maintained as a candidate cell in the plurality of candidate cells for a predetermined period of time. The predetermined period of time may be measured from receipt of the instruction to perform the handover. In some examples, the handover may be initiated after one or more of a beam failure or a failed beam failure recovery.

[0094] The WTRU may be configured to switch beams utilized for transmission and / or reception. Upon receiving and / or implementing a beam switch from a beam in a first cell (e.g., a current serving cell) to a beam of a second cell (e.g., a non-serving cell), the WTRU may change the serving cell to the second cell associated with the new beam. The WTRU may, for example, remove the second cell from the subset of candidate cells. The WTRU may add the first cell (e.g., the old serving cell) to the subset of candidate cells. For example, the WTRU may add the first cell to the subset of candidate cells for at least a configured period of time associated with a configured transition timer. The WTRU may release the configuration of any candidate cell that is not in the subset. For example, the WTRU may release the configuration of any candidate cell that is not in the subset after implementing a beam switch. In some scenarios, the WTRU may be configured to determine a target configuration. The target configuration may be based at least in part on one or more anchor cell identities, for example. The anchor cell identity may be used, for example, to apply a candidate cell configuration.

[0095] An example method for implementing L1 / L2 mobility may include configuring a WTRU with a set of radio resource control (RRC) configurations for each of a group of neighboring cell candidates neighboring a serving cell, each configuration of the set of configurations including a measurement criterion and a transition time period. The WTRU applies the RRC configurations for each of a subset of the group of neighboring cell candidates, activates neighboring beam management for each of the subset of the group of neighboring cell candidates, reports the subset of the group of neighboring cell candidates to a network, receives a beam switch on a cell indicating a beam of a non-serving cell, and upon receiving the beam switch, changes the current serving cell to a new serving cell that is the non-serving cell for which the beam switch was received, removes the new serving cell from the subset of the group of neighboring cell candidates, adds the original current serving cell to the subset of the group of neighboring cell candidates, and releases the RRC configurations for any candidate cells not in the subset of the group of neighboring cell candidates.

[0096] The WTRU may be configured to receive configuration information. The configuration information may be associated with a plurality of candidate cells. The configuration information may include configuration information associated with physical layer measurements. The physical layer measurements may be for each candidate cell. Additionally or alternatively, the configuration information may include one or more measurement criteria.

[0097] The WTRU may be configured to determine a subset of the plurality of candidate cells. For example, each candidate cell in the subset of the plurality of candidate cells may be determined based on a metric. The plurality of candidate cells may include all candidate cells above a reference signal received power (RSRP) threshold. Additionally or alternatively, the WTRU may be configured to send a report. The report may indicate the subset of the plurality of candidate cells. The report indicating the subset of the plurality of candidate cells may include a bitmap. The report may be sent via a medium access control (MAC) control element (CE). The report may be sent to the base station.

[0098] The WTRU may be configured to perform physical layer measurements on a subset of the plurality of candidate cells. The WTRU may be configured to receive an indication. The indication may be to perform a lower layer handover. The lower layer handover may be to a candidate cell. The candidate cell may be of a subset of the plurality of candidate cells. The indication may be received via a MAC CE. Additionally or alternatively, the indication may be received via a downlink control information (DCI).

[0099] The physical layer measurements may include radio link monitoring (RLM) measurements. Additionally or alternatively, the physical layer measurements may include beam measurements. The metrics may include reference signal received power. For example, the metrics may include reference signal received power exceeding a threshold.

[0100] The WTRU may be configured to implement MAC and / or RRC layer procedures to support L1 / L2 mobility.

[0101] As described herein, the term SCell may refer to a serving cell, which may include a primary cell (PCell), a primary cell among secondary cells (PSCell), and / or a secondary cell (sCell) (e.g., in carrier aggregation). The architecture for L1 / L2 mobility may include a WTRU configured with a stored configuration associated with one or more cells (e.g., candidate cells). For example, the stored cell configuration may be specific (e.g., or associated) to (e.g., one) PSCell and / or (e.g., one) SCell. In certain scenarios, a common set of candidate cells may be associated with multiple cells (e.g., possibly including SpCellI). A candidate cell may be configured with an association (e.g., reference) to a subset of SCells (e.g., possibly including SpCells). A SCell may also or alternatively be configured with an association (e.g., reference) to a subset of candidate cells. For example, multiple SCells may have an association to the same candidate cell.

[0102] The WTRU may identify or determine a subset of cells in the set of candidate cells as potential L1 / L2 mobility target (PLMT) cells (e.g., a list of PLMT cells). The list of PLMT cells may also be referred to herein as a set of PLMT cells. For example, the list of PLMT cells for a given set of candidate cells may be configured by the network. The WTRU may update (e.g., add and / or remove) cells in the list of PLMT cells. For example, the WTRU may add candidate cells to the list of PLMT cells based on rules defined herein. In some scenarios, a PLMT cell may be removed from the list of PLMT cells. The removed PLMT cell may remain a candidate cell. The WTRU may receive configuration information associated with one or more candidate cells. The configuration information may be associated with one or more physical layer measurements (e.g., RLM, beam measurements, SSB, and / or CSI-RS) for the one or more candidate cells.

[0103] L1 / L2 mobility may be implemented by receiving signaling (e.g., beam change, transmission configuration indicator (TCI) state change, etc.) via L1 / L2 signaling. For example, L1 / L2 mobility signaling may be implemented via downlink control information (DCI) or medium access control (MAC) control element (CE). L1 / L2 mobility signaling may be used, for example, to update the current serving cell to a PLMT cell. For example, the network may signal a beam switch to a beam associated with a non-serving PLMT cell. Upon receiving such signaling, the WTRU may implement a serving cell change from the serving cell to a PLMT cell for which the WTRU has already applied and verified an RRC configuration.

[0104] As described herein, the term SCell may be used to refer to a serving cell, which may be a PCell, a PSCell, or a SCell (eg, a secondary cell in carrier aggregation).

[0105] The WTRU may be configured to implement certain behaviors towards deactivated and dormant SCells, for example, to facilitate improved L1 / L2 mobility.

[0106] A WTRU may be served by a serving cell (e.g., cell A). The WTRU may be provided with an RRC configuration, e.g., via the serving cell. For example, the RRC configuration may be associated with one or more candidate cells B, C, D, etc. The candidate cells and their configurations may be associated with serving cell A. Alternatively or additionally, a candidate cell may be common to several serving cells (e.g., cells C and D may be candidate cells when served by cells A and B).

[0107] The WTRU may receive one or more candidate cell configurations (e.g., via a system information block (SIB) and / or RRC signaling (e.g., dedicated RRC signaling)). The WTRU may receive RRC signaling, for example, from a serving cell. For example, in certain scenarios, the WTRU may store the candidate cell configuration without applying (e.g., applying immediately) the configuration. For example, the WTRU may store the candidate cell configuration and wait a period of time before applying the configuration. The period of time may be based on a threshold. Alternatively or additionally, the WTRU may receive an instruction to apply (e.g., apply immediately) the candidate cell configuration. For example, the instruction to apply the candidate cell configuration may be received from the network.

[0108] A WTRU that applies the stored candidate cell configuration may behave similarly to a WTRU that adds a secondary cell (e.g., in carrier aggregation). In certain examples, the WTRU may treat such a secondary cell as a dormant SCell. For example, the WTRU may treat the secondary cell as a dormant cell after applying the configuration. In some examples, the WTRU may not perform physical downlink control channel (PDCCH) decoding and / or physical uplink control channel (PUCCH) transmission on the secondary cell. The WTRU may alternatively or additionally perform beam management (e.g., on the secondary cell). In certain scenarios, the beam management procedure performed on the candidate cell may differ from the beam management procedure performed on the secondary cell (e.g., in carrier aggregation (CA)). Performing beam management on the candidate cell may enable the WTRU to report beam measurements. The beam measurement report may be transmitted to the network (e.g., in connection with L1 / L2 mobility). The WTRU may initiate beam measurement reporting based on the TCI state configuration. The TCI state configuration may be associated with a cell provided in an RRC configuration from the serving cell. In some examples, the WTRU may initiate beam measurement reporting following application of a stored configuration for a candidate cell and / or addition of a cell as a PLMT cell. The WTRU may remove a cell from being a PLMT cell. The WTRU may stop beam measurement reporting. For example, the WTRU may stop beam measurement reporting for a cell that the WTRU removes from being a PLMT cell. The WTRU may additionally or alternatively release the RRC configuration for the cell (e.g., the cell that was removed from being a PLMT cell). In some examples, the WTRU may store (e.g., continue to store) the RRC configuration for a cell that is removed from being a PLMT cell, e.g., if the cell remains a candidate cell.Additionally or alternatively, the WTRU may perform radio link monitoring / radio link failure (RLM / RLF) separately for cells that are PLMT cells. For example, the WTRU may use different configurations associated with RLM / RLF. Additionally or alternatively, the WTRU may monitor one or more reference symbols (e.g., different reference symbols), use one or more RLF timers (e.g., different RLF timers), use Qin values ​​(e.g., different Qin values), and / or use Qout values ​​(e.g., different Qout values).

[0109] In some examples, the WTRU may treat the cell as a deactivated SCell. For example, the WTRU may treat the cell as a deactivated cell after applying a configuration to deactivate the cell. In some examples, the WTRU may apply an RRC configuration for the candidate cell and / or may not perform beam management and / or RLM / RLF for the cell. The WTRU may initiate beam management and / or RLM / RLF for the cell. For example, the WTRU may initiate beam management and / or RLM / RLF for the cell based on signaling received from the network (e.g., via a MAC CE, such as an activation / deactivation MAC CE). If the WTRU initiates beam management and / or RLM / RLF for the cell based on signaling received from the network (e.g., a MAC CE), the WTRU may treat the cell as a dormant SCell (e.g., also referred to herein as a PLMT cell) as described herein. For example, the WTRU may receive a MAC CE that activates or deactivates beam measurements / reports and / or RLM / RLF for that WTRU (e.g., without starting any PDCCH monitoring) until the WTRU receives an L1 / L2 mobility trigger. Additionally or alternatively, the WTRU may add (e.g., autonomously add) the cell to the PLMT cells based on any of the techniques described herein. In some examples (e.g., when the WTRU autonomously adds a cell to the list of PLMT cells), the WTRU may initiate beam management and measurement reporting to the network.

[0110] The WTRU may be configured to implement beam management procedures for PLMT cells.

[0111] The WTRU may receive an indication associated with a TCI state configuration. For example, the TCI state configuration may be used to control beam management for a set of CSI configurations. One of the following may further apply:

[0112] The WTRU may receive a TCI state configuration. For example, the TCI state configuration may be used by the WTRU to control beam management for a set of CSI configurations. The TCI state configuration may be configured by a serving cell (e.g., via RRC). In a particular scenario, the TCI state configuration received from the serving cell may be applied to a CSI configuration applied to a neighboring cell (e.g., a PLMT cell). Such a configuration may differ from the CSI configuration applied to the neighboring cell after L1 / L2 mobility. For example, the WTRU may switch from a first TCI state configuration to a second TCI state configuration (e.g., in connection with L1 / L2 mobility).

[0113] The WTRU may receive signaling (e.g., MAC CE) to select a subset of TCI states (e.g., configured by RRC) for PLMT cells and / or to control beam measurements. For example, such signaling may be received from a serving cell. The WTRU may receive signaling (e.g., via DCI) to change the beams being measured on a list of PLMT cells for beam reporting, for example.

[0114] The WTRU may deactivate or stop beam measurements for the PLMT cell, for example, based on receiving a deactivation command. For example, the deactivation command received by the WTRU may be similar to or may include a deactivation MAC CE. For example, following activation, the WTRU may resume beam management, for example, using a previous (e.g., last) TCI state selected for that PLMT cell.

[0115] The WTRU may be configured to implement a procedure for managing the candidate cell configuration. One or more of the following may apply:

[0116] The WTRU may be configured with a set of candidate cells, for example, via an RRC configuration (e.g., PHY, MAC, etc.). For example, the RRC configuration may indicate parameters to be used by the WTRU when operating on the set of candidate cells. A candidate cell or candidate cell list may be associated with one or more SCells (e.g., SCells that may be activated in the WTRU). However, in certain scenarios, a candidate cell may not be an activated / deactivated SCell in the WTRU.

[0117] The WTRU may be with a candidate cell. The WTRU may store the candidate cell configuration, for example, without applying the candidate cell configuration. The WTRU may be configured with rules / events for triggering application of the candidate cell configuration. Additionally or alternatively, the WTRU may be configured with rules / events for when to initiate L1 measurements (e.g., beam measurements) for a candidate cell (e.g., a candidate cell for which a configuration has been applied in the WTRU). A similar (e.g., the same) set of rules may be used, for example, to apply a candidate cell RRC configuration in the WTRU and / or to initiate L1 measurements. For example, if a configured rule / event triggers the WTRU to apply an RRC configuration, the WTRU may initiate L1 measurements for the cell (e.g., in accordance with the L1 configuration). Additionally or alternatively, the WTRU may be configured with a first rule / event for applying an RRC configuration and a second rule / event for initiating L1 measurements. The first rule / event and / or the second rule / event may be based on L3 measurements (e.g., L3 measurements performed by the WTRU for a candidate cell). The WTRU may be configured with L3 measurements to perform for the candidate cell. The WTRU may perform L3 measurements. In certain scenarios, the WTRU may perform L3 measurements and not report L3 measurements. The WTRU may use such measurements, for example, as part of the criteria for applying the cell configuration and / or for initiating L1 measurements. For example, the WTRU may be configured with a first L3 measurement-based event to trigger the application of the candidate cell and / or a second L3 measurement event to initiate L1 measurements. Alternatively or additionally, the WTRU may be configured with an L3 measurement-based event to trigger the application of the candidate cell and another trigger to initiate L1 measurements (e.g., network signaling, positioning triggers, etc. as described herein).

[0118] In certain scenarios, some RRC parameters / configurations / information elements (IEs) may not be affected by L1 / L2 mobility. For example, the WTRU may maintain previously configured parameters / IEs. Additionally or alternatively, the WTRU may apply non-maintained RRC parameters. In some examples, the WTRU may maintain previously configured parameters upon L1 / L2 mobility and / or apply non-maintained RRC parameters upon L1 / L2 mobility. The RRC configuration for the target L1 / L2 mobility may be associated with a set of parameters / IEs that are stored (e.g., remain stored). For example, the set of parameters / IEs may be stored as a PLMT cell and / or with L1 / L2 mobility. The parameters / IEs may not be applied in certain scenarios. The parameters / IEs may be stored and / or applied by the WTRU when adding a cell to a list of PLMT cells and / or when applying a configuration. For example, the WTRU may apply the RRC configuration upon, for example, applying a cell configuration or adding a cell as a PLMT cell. The WTRU may additionally or alternatively apply the RRC configuration, except for one or more IEs. One or more IEs that may not be applied may, for example, remain stored but not applied. In some examples, the WTRU may apply the RRC configuration upon applying the cell configuration and / or upon adding the cell as a PLMT cell. The IEs may be applied at a later time, such as, for example, upon L3 reconfiguration (e.g., L3 mobility and / or L3 reconfiguration) and / or cell change (e.g., network controlled anchor cell change). In some examples, one or more of the candidate cell list, events / conditions related to the candidate cell list, a particular cell to be considered (e.g., always) as a PLMT cell for a given anchor or serving cell, and / or any configuration parameters related to maintaining the candidate or PLMT cell may not be applied by the WTRU during adding the cell as a PLMT cell. The WTRU may be provided with RLM / RLF configurations that remain unchanged in certain scenarios.For example, the RLM / RLF configuration may remain unchanged in L1 / L2 mobility. Additionally or alternatively, the RLM / RLF configuration may be changed upon L3 handover (e.g., only upon L3 handover). The WTRU may receive a condition (e.g., a trigger) to perform RLM / RLF on the PLMT cell and / or may apply the RLM / RLF configuration during the L3 handover procedure. As a result, these parameters may not change due to L1 / L2 mobility. In some examples, the stored parameters for a cell may differ from the parameters applied to the target cell. For example, the stored parameters for a cell may differ from the parameters applied to the target cell after L1 / L2 mobility.

[0119] Certain RRC parameters may be applied based on the addition of a cell to the PLMT list in L1 / L2 mobility. The RRC configuration for a candidate cell may be divided into one or more (e.g., two) parts. The parts may include a first part and a second part. For example, the WTRU may apply the first part when the WTRU adds the candidate cell to the PLMT list and / or when it applies the configuration. The second part may be applied, for example, in L1 / L2 mobility. The WTRU may use the candidate cell list. For example, the candidate cell list when the WTRU is served by cell B may be configured by cell A. The WTRU served by cell A may apply the configuration of cell B (e.g., when cell B is added to the PLMT list). In certain scenarios, the WTRU may not apply the candidate cell list until L1 / L2 mobility is triggered, for example. For example, the WTRU may apply the beam measurement and / or reporting configuration of the PLMT cell. The WTRU may apply the beam measurement and / or reporting configuration of the PLMT cell. For example, the WTRU may apply a beam measurement and / or reporting configuration upon PLMT addition. The WTRU may apply one or more of a PDCCH configuration, a PUCCH configuration, a data decoding transmission configuration, etc. For example, the WTRU may apply one or more of a PDCCH configuration, a PUCCH configuration, a data decoding transmission configuration, etc. upon L1 / L2 handover. In some examples, the WTRU may maintain a beam measurement and / or reporting configuration. For example, the WTRU may maintain a beam measurement and / or reporting configuration when a cell is added to the PLMT list. The WTRU may apply certain parameters for a target cell. For example, the WTRU may apply certain parameters for a target cell prior to L1 / L2 mobility (e.g., which may avoid RRC reconfiguration latency). The WTRU may ensure that some configurations (e.g., parameters controlling the addition of candidates to a candidate cell list and / or a list of PLMT cells) are applied (e.g., may be applied) across one or more cells (e.g., the serving cell and / or the candidate cell).

[0120] The WTRU may request an RRC configuration for a cell (e.g., a candidate cell) from the network (e.g., using an RRC message such as dedicatedSIBRequest or the like). For example, the WTRU may request the RRC configuration to avoid storing multiple cell configurations at the WTRU for mobility and / or to reduce the signaling overhead of providing multiple candidate cell configurations at each cell for each WTRU. The RRC configurations for candidate cells used in a cell may be stored in a separate system information block (SIB). For example, if the RRC configurations associated with the candidate cells are stored in separate SIBs, the WTRU may use dedicatedSIBRequest and / or SI Request to obtain system information (SI) (e.g., if the WTRU is unable to receive SI from a broadcast at a given time). Alternatively or additionally, the WTRU may request the RRC configuration for one or more candidate cells. For example, the WTRU may use a modified version of the RRC message and / or dedicatedSIBRequest to request (e.g., individually request) the RRC configuration for one or more candidate cells. In some examples, the WTRU may request a candidate cell configuration for a subset of the candidate cells. The WTRU may request a candidate cell configuration for a subset of the candidate cell requests based on one or more conditions. For example, the WTRU may request a candidate cell configuration for a subset of the candidate cells based on adding the candidate cells as PLMT cells. In some examples, the WTRU may trigger a request to obtain a candidate cell configuration based on one or more of: a measured cell quality is above a threshold, the WTRU's location is within a specified distance of the cell, and / or one or more triggers for adding the candidate cell as a PLMT cell are also triggers for the WTRU to request a configuration for the candidate cell.

[0121] In certain scenarios, a candidate cell configuration failure may occur. For example, a configuration failure may occur when a WTRU applies a candidate cell RRC configuration. The WTRU may report the candidate cell configuration failure to the network, and the configuration failure report may be sent immediately (e.g., upon configuration failure), at a subsequent event trigger, and / or based on a condition. For example, a condition that triggers the WTRU to send a configuration failure report may be after a configuration failure occurs. In some examples, the WTRU may send / report a candidate cell configuration failure at one or more of the following times: When the number of configuration failures is greater than a certain threshold, when an L3 mobility procedure succeeds / fails, when an L1 mobility procedure succeeds / fails, when a beam failure is detected on the SCell and / or on the candidate cell, when the number of candidate cells with active L1 measurements falls below a threshold, when the number of candidate cells with inactive L1 measurements falls below a threshold, when the number of candidate cells with applied RRC configuration falls below a threshold, when the number of candidate cells with applied RRC configuration but without active L1 measurements falls below a threshold, when the total number of candidate cells with no pending reconfiguration failures (e.g., to be reported) falls below a threshold, when a configured number of RRC configuration failures occur, and / or when an alternative candidate cell cannot be found that meets the criteria for adding a candidate cell. In some examples, the alternative candidate cell may not result in a configuration failure. Alternatively or additionally, the WTRU may report a configuration failure when a configured number of RRC configuration failures occur.

[0122] The WTRU may apply the candidate cell configuration. In some examples, the candidate cell application may fail. The WTRU may perform one or more of the following upon a configuration failure of the candidate cell configuration (e.g., when attempting to apply the configuration): the WTRU may report the failure, the WTRU may release the configuration, the WTRU may retain the configuration, the WTRU may retain the configuration until the WTRU receives a subsequent RRC reconfiguration from the network, the WTRU may decide to retain or release the configuration based on any of these conditions, the WTRU may release the candidate cell configuration, the WTRU may release the candidate cell configuration to apply in L3 mobility and / or in L1 / L2 mobility, the WTRU may be configured with rules regarding whether to release the candidate cell RRC configuration in the event of a failure to apply the configuration. Additionally or alternatively, the WTRU may release the configuration upon failure (e.g., unless the candidate cell is an identified anchor cell). The reporting failure may occur immediately and / or upon a subsequent event trigger and / or upon satisfaction of a condition (eg, as described herein).

[0123] The WTRU may attempt to add another candidate cell to the PLMT list and / or apply another cell configuration. For example, the WTRU may attempt to add another cell configuration if the WTRU finds another candidate cell. For example, the other candidate cell may meet the criteria for being added as a PLMT cell. In some examples, the WTRU may avoid and / or delay reporting a failure. For example, the WTRU may avoid and / or delay reporting a failure if the application of the configuration is successful. Alternatively or additionally (e.g., if the WTRU cannot find another configuration that meets the criteria and / or all subsequent selected candidate cells also result in a configuration error), the WTRU may report a failure.

[0124] The WTRU may report a candidate cell RRC reconfiguration failure. For example, the candidate cell RRC reconfiguration failure may be reported via an RRC message (e.g., UE Assistance Information) transmitted by the WTRU. The RRC reconfiguration failure report may include one or more of the following information (e.g., associated with each of the one or more candidate cells for which an RRC reconfiguration failure is reported): a cell identity (e.g., cell ID) for each candidate cell, an index assigned to the candidate cell RRC reconfiguration (e.g., when the index is provided to the WTRU), an identity (e.g., cell ID) of the cell from which the WTRU initially received the configuration for the candidate cell, an identity (e.g., cell ID) of the cell that serves as an anchor cell (e.g., as described herein) for the SCell, and / or RRM measurements for one or more other candidate cells and / or the candidate cell that has the failed reconfiguration.

[0125] The WTRU may maintain an anchor cell identity. For example, the anchor cell identity may be maintained to apply a candidate cell configuration and / or L3 mobility. The WTRU may maintain the anchor cell identity. For example, the WTRU may maintain the anchor cell identity for each SCell. In some examples, the WTRU may maintain the anchor cell identity to apply different stored cell configurations at the WTRU during L1 / L2 mobility. The anchor cell may be configured via a delta RRC configuration. The candidate cell may have a delta configuration. For example, the WTRU may receive one or more candidate cell configurations in the form of a delta configuration. The WTRU may determine a full-cell configuration. The WTRU may determine the full-cell configuration by applying the delta configuration to an existing configuration. Additionally or alternatively, the WTRU may apply the delta configuration to an existing configuration on the anchor cell. For example, the WTRU may determine the full-cell configuration by applying its cell configuration (e.g., obtained using delta signaling) to the anchor cell configuration associated with the SCell. In some examples, the WTRU may apply the RRC configuration for the target cell to the anchor cell upon HO / CHO / conditional PSCell addition or change (CPAC). For example, during HO / CHO / CPAC from a SCell to a target cell, the WTRU may apply the RRC configuration for the target cell to the anchor cell upon HO / CHO / CPAC and / or may not apply to the SCell configuration that is the source of the mobility. The WTRU may change the SCell from the source cell to the target cell (e.g., where the target cell is one of the candidate cells for L1 / L2 mobility). For example, the WTRU may change the SCell from the source cell to the target cell without changing the anchor cell. In some examples, the WTRU may change the SCell from the source cell to the target cell during L1 / L2 mobility.

[0126] The network may control / initiate the anchor cell change. In some examples, the anchor cell change may be implemented by the network via RRC signaling. For example, the WTRU may receive an RRC message on a serving cell. The RRC message may indicate that the WTRU will change the anchor cell for that serving cell. The RRC message may include a cell ID of the cell that will be the new anchor cell. The WTRU may receive a cell index associated with the candidate cell to identify the new anchor cell.

[0127] The WTRU may change the reference cell configuration for one or more (e.g., all) future mobility commands and / or configurations of a new candidate cell. In some examples, based on a network-controlled anchor cell change, the WTRU may change the reference cell configuration for one or more (e.g., all) future mobility commands and / or configurations of a new candidate cell. For example, upon receiving L3 mobility (HO / CHO / CPAC), the WTRU may apply one or more delta configurations. Additionally or alternatively, the WTRU may apply one or more delta configurations upon receiving a new candidate cell with / after a network-controlled anchor cell change. The one or more delta configurations may be applied on top of the configuration of the new anchor cell (which may be indicated in the anchor cell change, for example).

[0128] The WTRU may receive a candidate cell configuration and / or a conditional handover command. For example, the WTRU may receive a candidate cell configuration and / or a conditional handover command along with a network-controlled anchor cell change. In some examples, the WTRU may determine a target cell configuration for the candidate cell and / or the CHO candidate. For example, the WTRU may determine a target cell configuration for the candidate cell and / or the CHO candidate based on a new anchor cell in the anchor cell change.

[0129] In certain scenarios, the WTRU may fail the anchor cell change. For example, the WTRU may fail the anchor cell change due to one or more of the following: the WTRU attempts to apply the configuration of the anchor cell and the configuration fails, the cell ID and / or index indicated in the anchor cell change is not a serving cell or a stored / configured candidate cell, and / or the WTRU is asked to add a candidate cell as a PLMT cell in the anchor cell change and the configuration fails.

[0130] The WTRU may maintain the current anchor cell, maintain operation for the current serving cell change, and / or ignore any CHO candidates and / or candidate cells included in the anchor cell change. For example, if the WTRU fails during the anchor cell change, it may maintain the current anchor cell, maintain operation for the current serving cell change, and / or ignore any CHO candidates and / or candidate cells included in the anchor cell change.

[0131] The WTRU may perform one or more of the following upon a successful anchor cell change: release one or more (e.g., all) candidate cells stored at the moment of receiving the anchor cell change, release one or more (e.g., all) candidate cells stored at the moment of receiving the anchor cell change that are not currently PLMT cells, release one or more (e.g., all) candidate cells stored at the moment of receiving the anchor cell change whose configuration has not been applied (e.g., since the time of last L3 mobility) and / or since the time of last anchor cell change) and / or was not (e.g., never) a PLMT cell, and / or report (e.g., in a confirmatory RRC message) certain information associated with the candidate cells. For example, the information associated with the candidate cells reported by the WTRU may include one or more of the following: candidate cells released by the WTRU, candidate cells maintained by the WTRU, candidate cells that are PLMT cells and / or cells with released and / or maintained applied configurations, or L3 measurements of any of the candidate cells. Alternatively or additionally, the WTRU may release one or more candidate cells. As described herein, information associated with the candidate cells may be reported by the WTRU via a bitmap.

[0132] The WTRU may be configured to perform a conditional anchor cell change. For example, the WTRU may trigger and / or inform the network of the anchor cell change. The WTRU may base the triggering of the anchor cell change on the occurrence of one or more conditions. The WTRU may be configured with one or more measurement events (e.g., similar to CHO for performing a conditional anchor cell change). The one or more measurement events may relate to either the current anchor cell, the current serving cell, and / or a candidate serving cell. The WTRU may be configured with a new / updated set of events for the conditional anchor cell change. For example, the new / updated set of events may be based on any of the events described for adding a PLMT cell.

[0133] The WTRU may be configured to maintain and / or utilize a PLMT list to facilitate L1 / L2 mobility procedures. For example, the WTRU may be configured with one or more events / triggers for adding / removing a candidate cell from the list of PLMT cells. The WTRU may be configured with one or more conditions for applying a stored configuration of a candidate cell and / or for adding a stored / configured candidate cell as a PLMT cell. For example, the one or more conditions for applying a stored configuration of a candidate cell and / or for adding a stored / configured candidate cell as a PLMT cell may be based on one or more measurement events. For example, for each candidate cell, the WTRU may be configured with a condition for applying the configuration of the candidate cell and / or for adding the candidate cell as a PLMT cell. In some scenarios, the condition for applying a stored configuration of a candidate cell and / or for adding a stored / configured candidate cell as a PLMT cell may be associated with L3 measurements of the candidate cell. For example, the condition may be associated with measurements on a serving cell. Alternatively or additionally, the condition for applying the stored configuration of the candidate cell and / or for adding the stored / configured candidate cell as a PLMT cell may be one of the conditions described herein.

[0134] The WTRU may be configured with a condition (e.g., a single condition) for the serving cell and / or a condition (e.g., a single condition) for one or more (e.g., a set or all) candidate cells associated with the serving cell. For example (e.g., when configured with a set of candidate cells), the WTRU may receive a condition for adding one or more of the candidate cells to a list of candidate cells. In some examples, the one or more candidate cell configurations may be applied and / or added as PLMT. The event may be based on one or more legacy L3 measurement events. For example, the one or more L3 events may relate to the serving cell and / or the list of candidate cells. In some examples, the event may include one or more of the serving cell quality falling below a threshold, the candidate cell quality exceeding a serving cell quality threshold, the candidate cell quality exceeding a threshold, or any combination thereof.

[0135] The WTRU may be configured with conditions for removing a candidate cell as a PLMT cell on a per candidate, per serving cell, and / or per set of candidates (eg, all candidates).

[0136] In a particular scenario, the conditions for removing a candidate cell as a PLMT cell, on a candidate-by-candidate, serving-cell-by-serving-cell, and / or set of candidates (e.g., all candidates), may relate to one or more L3 measurements. For example, the conditions may include one or more of: the serving cell exceeds a threshold, the candidate cell quality does not exceed a threshold, the candidate cell quality does not exceed a serving cell quality threshold, or any combination thereof.

[0137] The WTRU may apply an L3 measurement event. For example, the WTRU may apply an L3 measurement event by comparing one or more candidate non-PLMT cells to one or more candidate PLMT cells. In another scenario, the WTRU may apply an L3 measurement event by comparing one or more candidate PLMT cells. In another example, the WTRU may apply an L3 measurement event by comparing one or more candidate non-PLMT cells. In some examples, the event may be a new event type. For example, an event may be defined for RRM measurements between one or more (e.g., multiple) cells.

[0138] An A3-like event may involve multiple cells. An A3-like event may compare a neighboring cell to a serving cell. Alternatively or additionally, an A3-like event may trigger an event when a neighboring cell exceeds a threshold and / or exceeds a value associated with a serving cell. For example, the WTRU may add a candidate cell to a list of PLMT cells. In some examples, the WTRU may add a candidate cell to a list of PLMT cells if the candidate cell is threshold better than all current PLMT cells. In some examples, the WTRU may add a candidate cell as a PLMT cell if the candidate is threshold better than the best current PLMT cell. For example, the WTRU may add a candidate cell as a PLMT cell if the candidate is threshold better than at least X (e.g., a configured number) current PLMT cells. For example, the WTRU may add a candidate cell as a PLMT cell if the candidate cell is threshold better than the average of the current PLMT cells. In some examples, an A3-like event similar to that herein may be defined for removal of a current PLMT cell.

[0139] The A5-like event may involve multiple cells. The A5-like event may compare a neighboring cell to a threshold. Additionally or alternatively, the A5-like event may compare a serving cell to a threshold (e.g., a different threshold). For example, the WTRU may replace a PLMT cell with a candidate non-PLMT cell. In some examples, the WTRU may replace a PLMT cell with a candidate non-PLMT cell, e.g., if the PLMT cell does not exceed a threshold and / or the non-PLMT cell exceeds a threshold. For example, the WTRU may replace a PLMT cell with a candidate non-PLMT cell if at least X (e.g., a configured number) PLMT cells do not exceed a threshold and / or at least Y (e.g., a configured number) non-PLMT candidate cells exceed a threshold. X and Y may be configured with the event and / or predefined in some examples. For removal of a current PLMT cell, an A5-like event similar to that herein may be defined.

[0140] In some scenarios, the WTRU may be configured with events and / or conditions for adding a candidate cell to the list of PLMT cells and / or for removing a candidate cell from the list of PLMT cells.

[0141] The WTRU may consider various conditions to determine the number of PLMT cells for a serving cell. For example, the WTRU may be configured with a maximum / minimum number of PLMT cells. In some scenarios, the WTRU may ensure (e.g., based on other conditions) that the number of PLMT cells does not exceed a maximum value and / or is not less than a minimum value. In some scenarios, the WTRU may determine the number of PLMT cells based on WTRU capabilities. For example, the total number of PLMT cells (e.g., across cell groups, per serving cell, etc.) should not exceed WTRU capabilities. In another example, the total number of configured cells (e.g., potentially across cell groups, frequencies, bands, etc.) should not exceed WTRU capabilities. For example, the total number of serving and PLMT cells (e.g., across cell groups, frequencies, bands, etc.) should not exceed WTRU capabilities. In some scenarios, the WTRU may be configured per serving cell.

[0142] In certain scenarios, the WTRU may determine the number of PLMT cells. For example, the WTRU may determine the number of PLMT cells for a serving cell based on a data rate. In some scenarios, the number of PLMT cells maintained by the WTRU may be a function of the data rate at the WTRU (e.g., calculated across all bearers) and / or a function of buffer occupancy at the WTRU.

[0143] The WTRU may determine the number of PLMT cells, e.g., for a serving cell, based on a mobility criterion. For example, the number of PLMT cells maintained by the WTRU may be a function of the speed of the WTRU. In some scenarios, the number of PLMT cells maintained by the WTRU may be a function of the number of mobility events (e.g., L3 mobility and / or L1 / L2 mobility) performed at the WTRU over a period of time. For example, the period of time may be a recent period of time.

[0144] The WTRU may determine the number of PLMT cells, for example for a serving cell, based on the frequency range / band. In some scenarios, the WTRU may be configured with a number of PLMT cells to maintain for a particular frequency / band. For example, a particular frequency / band may be associated with a serving cell.

[0145] In certain scenarios, the WTRU may determine the number of PLMT cells, for example for a serving cell, based on beam characteristics. For example, the WTRU may be configured with the number of PLMT cells to maintain. The number of PLMT cells to maintain may be related to the beam width, the number of beams. Additionally or alternatively, the number of PLMT cells to maintain may be related to any characteristic of the beam associated with either the serving cell, the PLMT cell, and / or a combination thereof.

[0146] The WTRU may determine the number of PLMT cells, for example for a serving cell, based on the numerology. In some scenarios, the WTRU may be configured with the number of PLMT cells to maintain based on the numerology configured for the serving cell, the PLMT cells, the candidate cells, and / or combinations thereof.

[0147] In some scenarios, the WTRU may determine the number of PLMT cells, for example for a serving cell, based on L1 / L2 and / or L3 measurements. In some examples, the WTRU may be configured with the number of PLMT cells determined based on L3 measurements of the serving cell and / or L3 measurements of candidate cells and / or PLMT cells. In some scenarios, the WTRU may be configured to keep a PLMT cell as long as the cell satisfies some L3 measurement criteria.

[0148] The WTRU may determine, for example, the number of PLMT cells for a serving cell based on the number of candidate cells configured for the serving cell. In some examples, the WTRU may be configured with a set of one or more candidate cells for each serving cell. In certain scenarios, the number of PLMT cells maintained while being served by the serving cell may be a function (e.g., a ratio) of the number of candidate cells configured for the serving cell.

[0149] In certain scenarios, the WTRU may determine the number of PLMT cells, e.g., for a serving cell, based on conditions / triggers for beam failure detection / recovery. For example, the WTRU may isolate / replace a PLMT cell with another candidate cell when the WTRU detects beam failure on a beam. In some scenarios, the beam may be the best beam associated with the cell and / or a configured number of beams. The WTRU may perform the removal / replacement immediately and / or following a configured time period. For example, the WTRU may add a candidate cell as a PLMT cell if the WTRU performs successful beam failure recovery on a beam belonging to the candidate cell.

[0150] The WTRU may be configured to add a candidate cell as a PLMT cell and / or remove a candidate cell as a PLMT cell based on time-related conditions / triggers. For example, the WTRU may add a candidate cell as a PLMT cell and / or quarantine a cell as a PLMT cell if, for example, any of the conditions herein are satisfied for the PLMT cell for at least a configured period of time.

[0151] The WTRU may be configured to add a candidate cell as a PLMT cell and / or remove a candidate cell as a PLMT cell based on location-related conditions / triggers. For example, the WTRU may be configured with a location to associate with each cell (e.g., in a candidate cell configuration). In some scenarios, the WTRU may add a candidate cell as a PLMT cell if the WTRU's location is within X (e.g., a configured number) meters of the configured location for the cell. In some examples, the WTRU may remove a PLMT cell if the WTRU's location is further than Y (e.g., a configured number) meters from the configured location for the cell.

[0152] The WTRU may be configured to add a candidate cell as a PLMT cell and / or remove a candidate cell as a PLMT cell based on conditions / triggers related to changes in cell quality. For example, the WTRU may remove a PLMT cell if the cell quality degrades by more than a certain amount (e.g., a configured number) within a configured period of time.

[0153] The WTRU may be configured to add a candidate cell as a PLMT cell and / or remove a candidate cell as a PLMT cell based on a condition / trigger. For example, the condition / trigger may be based on L1 / L2 mobility and / or L3 mobility / reconfiguration. In some scenarios, the WTRU may determine a new set of lists of PLMT cells due to a reconfiguration of candidate cells. The WTRU may determine a new set of lists of PLMT cells, for example, following L1 mobility. In some examples, if a PLMT cell is removed due to removal of one or more candidate cells in the WTRU's stored candidate cell configuration, the WTRU may select a new PLMT cell to replace the removed cell.

[0154] The WTRU may be configured to add a candidate cell as a PLMT cell and / or remove a candidate cell as a PLMT cell based on conditions / triggers, e.g., based on cell activation / deactivation and / or dormancy. For example, the WTRU may add / remove a PLMT cell associated with a serving cell based on one or more of: serving cell addition / removal, cell activation / deactivation, a cell being moved in / out of dormancy, and / or any combination thereof (e.g., to satisfy WTRU capabilities).

[0155] In some scenarios, the number of cells meeting certain criteria for addition / removal (e.g., a larger number) may be greater than the number allowed based on the triggers / conditions described herein. For example, the number of cells allowed for addition / removal may be based on other criteria (e.g., a maximum number) that may be configured. The WTRU may select one or more cells to add / remove. In scenarios exceeding the maximum number, for example, the WTRU may use other conditions described herein to determine the particular cells to add / remove. For example, the WTRU may select the cell with the best / worst RRM measurements and / or location for addition / removal.

[0156] The WTRU may initiate L1 / L2 mobility upon receiving network signaling (e.g., DCI on the serving cell). In some scenarios, the signaling may consist of an explicit instruction to perform cell mobility (e.g., implicitly / explicitly including cell identity). The WTRU may select the best beam on the target cell to perform communication following receipt of the DCI. Alternatively or additionally, the signaling may be a DCI indicating a change in beam / TCI status. For example, the beam / TCI status may indicate a beam and / or TCI status configuration associated with a neighboring cell. In some scenarios, the WTRU may determine whether the beam indicated in the DCI is associated with one of the serving cell and / or PLMT cells. For example, upon receiving the DCI, the WTRU may determine whether the beam indicated in the DCI is associated with one of the serving cell and / or PLMT cells. In some examples, the WTRU may initiate an action associated with L1 / L2 mobility. For example, the WTRU may initiate any action herein associated with L1 / L2 mobility when associated with a PLMT cell. Alternatively or additionally, the WTRU may receive a MAC CE that triggers L1 / L2 mobility. For example, the WTRU may receive a MAC CE that activates one or more TCI states associated with a different cell. The WTRU may implicitly and / or explicitly determine L1 / L2 mobility from the contents of the MAC CE (e.g., cell identity, or TCI state configuration identity). In some scenarios, the WTRU may trigger L1 / L2 mobility if the MAC CE indicates activation of a TCI state associated with a different cell. Furthermore, the above combinations may also trigger L1 / L2 mobility.

[0157] In certain scenarios, for example, upon triggering L1 / L2 mobility, the WTRU may perform one or more of the following actions in any order: The WTRU may send an acknowledgment to the source cell before or after successful completion of L1 / L2 mobility. For example, the WTRU may send an acknowledgment to the source cell (e.g., in response to a trigger, which may be from a DL assignment). The WTRU may send an acknowledgment following successful reception and / or transmission on the target cell. The WTRU may stop monitoring the PDCCH of the source cell. For example, the WTRU may stop monitoring the PDCCH of the source cell upon triggering L1 / L2 mobility. The WTRU may initiate a RACH to the target cell or a UL transmission to the target cell. For example, the WTRU may initiate a RACH to the target cell or a UL transmission to the target cell upon triggering L1 / L2 mobility. In some scenarios, the WTRU may perform either a two-step RACH procedure or a four-step RACH procedure. For example, the WTRU may perform a two-step or four-step RACH procedure based on whether the target cell is UL synchronized with the source cell, whether L1 / L2 mobility was triggered by DCI or MAC CE from the source cell, and / or whether the WTRU had a pending UL grant when L1 / L2 mobility was triggered, and / or any combination thereof.

[0158] The WTRU may apply any non-applied portion or portions of the target cell RRC configuration (e.g., as described above). For example, the WTRU may apply any non-applied portion or portions upon triggering L1 / L2 mobility. The WTRU may apply the RRC configuration, for example, after the WTRU has successfully transmitted / received to the target cell. In some scenarios, the WTRU may return to the source cell configuration and / or trigger a RACH transmission to the source cell in case of L1 / L2 mobility failure. For example, upon triggering L1 / L2 mobility, the WTRU may return to the source cell configuration and / or trigger a RACH transmission to the source cell in case of L1 / L2 mobility failure. For example, the WTRU may fail L1 / L2 mobility if the WTRU detects beam failure before any successful DL / UL transmission with the target cell and / or if the WTRU fails to receive a DL transmission from the target cell after a period of time and / or several attempts (e.g., of a RACH procedure).

[0159] In some scenarios, the WTRU may add the source cell as a PLMT cell, e.g., for at least a period of time. The WTRU may add the source cell as a PLMT cell upon successful L1 / L2 mobility. In some embodiments, the WTRU may be configured with a period of time during which the source cell should be a PLMT cell and / or may maintain the source cell as a PLMT cell for at least that period of time. For example, the WTRU may perform beam management as described herein for at least that period of time for the source cell (e.g., following mobility). The WTRU may perform one or more of: removing the new serving cell from the set of configured candidate cells, applying stored RRC configurations for the candidate cells (e.g., and L1 / L2 mobility parameters) associated with the new serving cell, determining a new set of list of PLMT cells from the new / updated candidate cells and associated L1 / L2 mobility parameters, and releasing the configuration of any cells that were isolated from the list of PLMT cells, or any combination thereof. For example, upon successful L1 / L2 mobility, the WTRU may perform one or more of: removing the new serving cell from the set of configured candidate cells; applying stored RRC configurations for the candidate cells (e.g., and L1 / L2 mobility parameters) associated with the new serving cell; determining a new set of list of PLMT cells from the new / updated candidate cells and associated L1 / L2 mobility parameters; and releasing the configuration of any cells that were isolated from the list of PLMT cells, or any combination thereof.

[0160] The WTRU may be configured to perform beam management on one or more PLMT cells. In some scenarios, the WTRU may be configured to perform a modified form of beam management on the PLMT cell. For example, the modified beam management may include one or more of performing beam measurements for the PLMT cell, reporting beam measurements for the serving cell, performing / reporting beam measurements with reduced or different periodicity, performing / reporting beam measurements without triggering beam failure detection and / or recovery, performing beam failure detection / reporting without any recovery action, performing a modified beam failure detection procedure as described herein, or any combination thereof.

[0161] The WTRU may perform beam failure detection for a particular PLMT cell (e.g., for RLM / RLF) and / or trigger an indication of beam failure to the network. For example, the WTRU may use the same / similar conditions for performing RLM to perform beam failure detection. In some scenarios, the WTRU may use the same conditions for reporting RLF to report beam failure.

[0162] In some scenarios, the WTRU may implement beam failure and / or trigger indication for one or more cells. For example, the WTRU may be configured with a condition based on whether beam failure is detected / reported for a PLMT cell. For example, the WTRU may report beam failure for cells with RSRP above a threshold. For example, the WTRU may report beam failure for cells whose indicated location has a certain distance from the WTRU's location. For example, the WTRU may report beam failure only for a subset of candidate cells for a given serving cell, as configured by the network. In some scenarios, the WTRU may determine the subset of candidate serving cells based on configured metrics, WTRU capabilities, and / or the number of configured serving cells utilized by the WTRU. For example, the subset of neighbor cells may be selected to be all candidate cells that are determined to have RSRP above a threshold (e.g., assuming that the number of candidates meeting the criteria does not exceed the processing capabilities of the WTRU). In some examples, the criteria may include a Reference Signal Received Power (RSRP) and / or an RSRP threshold. For example, if the criteria includes an RSRP threshold, the subset of the multiple candidate cells may include candidate cells (e.g., all candidate cells) associated with an RSRP measurement above the RSRP threshold. The metric criteria may include Channel State Information-Reference Signal Received Power (CSI-RSRP). Alternatively or additionally, the metric may include Synchronization Signal Block-Reference Signal Received Power (SSB-RSRP). In some scenarios, determining the subset of the multiple candidate cells may be based at least in part on a number of configured candidate cells. For example, the number of configured candidate cells may be greater than a threshold.

[0163] In some scenarios, a beam failure indication (e.g., MAC CE) may be reported to the serving cell. For example, the WTRU may report one or more cells for which beam failure is detected along with a beam failure report. The MAC CE may include one or more cell IDs and / or indices (e.g., associated with PLMT cells) for which beam failure was triggered. In some examples, the report may include a bitmap. The bitmap may be included in the MAC CE. An instruction to perform a handover may be received in downlink control information (DCI). In some examples, the report may be sent to and / or received from the base station. The WTRU may report to the network upon a change to one or more of the candidate cells in a subset of the multiple candidate cells in some scenarios.

[0164] The WTRU may be configured to receive and / or transmit configuration information. For example, the configuration information may be associated with one or more candidate cells. In some examples, the configuration information may include one or more of a physical layer measurement and a metric. The metric may include, for example, an RSRP above a threshold. In some scenarios, the WTRU may be configured to perform one or more physical layer measurements for a subset of the plurality of candidate cells. For example, the one or more physical layer measurements may be associated with the configuration information. In some embodiments, the one or more physical layer measurements may include one or more of radio link monitoring and beam measurements. In some examples, the WTRU may be configured to perform one or more measurements for one or more of the candidate cells. The subset of the one or more plurality of candidate cells may include one or more candidate cells above an RSRP threshold.

[0165] The WTRU may be configured to determine a subset of one or more candidate cells. For example, the WTRU may determine one or more candidate cells in the subset based on a metric. In some examples, the WTRU may be configured to send and / or receive a report indicating the subset of one or more candidate cells. For example, the report may include a bitmap. In some scenarios, the report may be sent and / or received via a MAC CE.

[0166] The WTRU may be configured to receive an indication to perform a handover. The handover may be, for example, a lower layer handover (e.g., L1 / L2 mobility). For example, a lower layer handover may be associated with lower latency (e.g., compared to other handover techniques). The WTRU may be configured with an RRC configuration. The RRC configuration may be synchronized to a target cell (e.g., for a lower layer handover). The lower layer handover may be performed to one or more of a subset of the multiple candidate cells. In some scenarios, a candidate cell may be maintained as a candidate cell in the multiple candidate cells for a predetermined period of time. The predetermined period of time may be measured from receipt of an indication to perform a handover. In some embodiments, the handover may be initiated after one or more of a beam failure or a failed beam failure recovery. In some examples, the indication may be received and / or sent via one or more of a MAC CE and a DCI. The WTRU may be configured to maintain one or more candidate cell configurations after receipt of an indication to perform a handover.

[0167] The WTRU may be configured with conditions for whether and / or when to perform beam failure reporting to the network. For example, the WTRU may use conditions to determine whether and / or when to perform beam failure reporting to the network following beam failure detection. In some scenarios, the conditions for whether and / or when to perform beam failure reporting to the network may be similar to the conditions associated with adding a cell as a PLMT cell. For example, the WTRU may delay reporting of beam failure detected on a PLMT cell until a time after certain conditions described herein are satisfied. For example, the WTRU may delay reporting of beam failure detected on a PLMT cell until the number of PLMT cells with / without beam failure reaches a threshold. Alternatively or additionally, the WTRU may delay beam failure recovery until L1 / L2 mobility is triggered for the cell. For example, the WTRU may keep beam failure pending for a PLMT cell upon detection of beam failure on the PLMT cell. If the WTRU triggers L1 / L2 mobility to that cell and the beam failure is still pending, the WTRU may initiate a beam failure recovery-like procedure (e.g., RACH to a different beam) during L1 / L2 mobility. The WTRU may report pending beam failure during L1 / L2 mobility to a target cell, for example, if the beam failure occurs on a PLMT cell other than the target cell of the mobility.

[0168] In some scenarios, the WTRU may keep a detected beam failure pending for a certain time period. For example, the WTRU may detect a beam failure but not report the beam failure during the time period. When the time period expires and the conditions for reporting the beam failure are not met, the WTRU may, in some scenarios, cancel a pending beam failure report associated with one or more PLMT cells.

[0169] In an example embodiment, the WTRU may trigger L1 / L2 mobility as a result of beam failure on the serving cell. In one example, if the WTRU determines that a beam on a PLMT cell is better than any beam associated with the serving cell, e.g., by a threshold amount, following beam failure detection on the serving cell, the WTRU may trigger L1 / L2 mobility to that cell. In another example, if the WTRU triggers beam failure recovery on the serving cell and the beam failure recovery is unsuccessful, the WTRU may initiate L1 / L2 mobility to the PLMT cell. In some scenarios, the WTRU may initiate L1 / L2 mobility if a PLMT cell is discovered that satisfies any of the conditions herein.

[0170] In some scenarios, a WTRU that triggers L1 / L2 mobility due to a failure to recover from a beam failure may initiate re-establishment (e.g., rather than performing any of the recovery actions described herein for L1 / L2 mobility failure). For example, following a failed L1 / L2 mobility, a WTRU that triggers L1 / L2 mobility due to a failure to recover from a beam failure may initiate re-establishment. A WTRU that triggers L1 / L2 mobility due to a beam failure on a serving cell may, in some scenarios, report the beam failure to a target of the L1 / L2 mobility (e.g., using a MAC CE). For example, the WTRU may trigger L1 / L2 mobility to a PLMT cell that does not have a pending beam failure and / or a PLMT cell whose BFI counter meets certain criteria.

[0171] The WTRU may maintain a beam failure context (e.g., BFI counter, BFR timer) for a PLMT cell. For example, the WTRU may maintain a beam failure context for a PLMT cell when the WTRU performs L1 / L2 mobility for that cell. Alternatively or additionally, the WTRU may retain only some parts of the context (e.g., the WTRU may reset timers but not counters). Alternatively or additionally, the WTRU may reset the entire context for the cell. Alternatively or additionally, the WTRU may modify the context, e.g., subtract a configured value from the counter / timer.

[0172] In some embodiments, the WTRU may maintain a single beam failure context (e.g., BFI, counter, etc.) for configured PLMT cells (e.g., all configured PLMT cells). For example, the WTRU may increment the (e.g., single BFI) counter if the WTRU receives a beam failure indication from a PHY layer associated with any of the PLMT cells in the list of PLMT cells. Alternatively or additionally, the WTRU may increment the BFI counter. For example, the WTRU may increment the BFI counter if the WTRU receives a beam failure indication from at least N (e.g., a configured number) PLMT cells in the list of PLMT cells.

[0173] The processes described herein may be implemented in a computer program, software, and / or firmware embodied in a computer readable medium for execution by a computer and / or a processor. Examples of computer readable media include, but are not limited to, electronic signals (e.g., transmitted over 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, internal hard disks and removable disks, magneto-optical media, and / or optical media such as CD-ROM disks and / or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, a WTRU, a terminal, a base station, an RNC, and / or any host computer.

Claims

1. 1. A method implemented by a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information associated with a plurality of candidate cells, the configuration information comprising: configuration information associated with physical layer measurements for each candidate cell; receiving a metric; determining a subset of the plurality of candidate cells, each candidate cell in the subset of the plurality of candidate cells being determined based on the metric; sending a report indicating the subset of the plurality of candidate cells; performing physical layer measurements on the subset of the plurality of candidate cells; and receiving an indication to perform a lower layer handover to a candidate cell of the subset of the plurality of candidate cells.

2. The method of claim 1 , wherein the physical layer measurements include one or more of radio link monitoring (RLM) measurements or beam measurements.

3. The method of claim 1 , wherein the metric comprises a reference signal received power (RSRP) above a threshold.

4. The method of claim 1 , wherein the report indicating the subset of the plurality of candidate cells comprises a bitmap, the report being sent via a medium access control (MAC) control element (CE).

5. The method of claim 1 , wherein the indication is received via a Medium Access Control (MAC) Control Element (CE) or Downlink Control Information (DCI).

6. The method of claim 1 , further comprising maintaining a candidate cell in the subset of the plurality of candidate cells for a predetermined period of time after receiving the indication to perform the lower layer handover.

7. The method of claim 1 , wherein the report is sent to a base station.

8. The method of claim 1 , wherein the subset of the plurality of candidate cells comprises all candidate cells that are above a reference signal received power (RSRP) threshold.

9. 1. A wireless transmit / receive unit (WTRU) comprising a receiver, the WTRU comprising: receiving configuration information associated with a plurality of candidate cells, the configuration information including physical layer measurement configuration information and measurement criteria for each candidate cell; determining a subset of the plurality of candidate cells, each candidate cell in the subset of the plurality of candidate cells being determined to satisfy the metric; sending a report, the report indicating the subset of the plurality of candidate cells; performing physical layer measurements on the subset of the plurality of candidate cells; and receiving an indication to perform a lower layer handover to one of the subset of the plurality of candidate cells.

10. The WTRU of claim 9 , wherein the physical layer measurements include one or more of radio link monitoring (RLM) measurements or beam measurements.

11. The WTRU of claim 9 , wherein the metric comprises a reference signal received power (RSRP) exceeding a threshold.

12. The WTRU of claim 9 , wherein the report comprises a bitmap in a medium access control (MAC) control element (CE).

13. The WTRU of claim 9 , wherein the indication is received via a Medium Access Control (MAC) Control Element (CE) or Downlink Control Information (DCI).

14. 10. The WTRU of claim 9, further configured to maintain a candidate cell in the subset of the plurality of candidate cells for a predetermined period of time after receiving the indication to perform the lower layer handover.

15. The WTRU of claim 9 , further configured to send the report to a base station.

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