Apparatus, method and system for RLM and BFD for L1 / L2 mobility

Abstract

A wireless transmit / receive unit (WTRU) may determine to perform RLM on a subset of a set of candidate cells for at least a period of time after receiving a message, may determine to terminate the RLM on the subset of the set of candidate cells once the period of time after receiving the message has passed, may determine to report measurements associated with the RLM performed on the subset of the set of candidate cells at L1 / L2, may receive a handover command for a first candidate cell from the subset of the set of candidate cells, and may determine, based on receiving the handover command, to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 395,242, filed on August 4, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Using L1 beam measurements to make mobility decisions may allow the network to move the WTRU to the best cell faster than L3 measurements (e.g., RSRP), and may help ensure that the WTRU is always served by the best cell / beam. However, fast handover decisions may require the WTRU to determine whether a candidate cell is an acceptable target to avoid handover failures due to temporary fading that may occur just before the handover. In addition, if the serving cell quality has begun to deteriorate, the WTRU may not be able to reliably transmit L1 / L2 measurements to the serving cell. To help reduce the latency of the mobility process, the L1 / L2 mobility commands may come from the target cell itself.

[0004] What is needed is for the WTRU to perform a candidate cell RLM / RLF procedure for a period of time after network instruction based on serving cell measurements. The present disclosure relates to apparatus, methods and systems for performing Radio Link Monitoring (RLM) and Beam Failure Detection (BFD) procedures for L1 / L2 mobility. Summary of the invention

[0005] A wireless transmit / receive unit (WTRU) may include a processor. The processor may be configured to receive a radio resource control (RRC) message including configuration information for radio link monitoring (RLM) for a serving cell and a set of candidate cells, the configuration information including an indication of a time period for the RLM for the set of candidate cells and a reference signal received power (RSRP) threshold for the serving cell. The processor may also be configured to receive a message indicating that RLM will be initiated for at least a subset of the candidate cells using the configuration information for the RLM for the set of candidate cells indicated in the RRC configuration information. The processor may also be configured to determine to perform RLM for the subset of the set of candidate cells within at least the time period after receiving the message. The processor may also be configured to determine to terminate the RLM for the subset of the set of candidate cells once the time period after receiving the message has passed. The processor may also be configured to determine to report measurement results associated with the RLM performed on the subset of the set of candidate cells at L1 / L2. The processor may be further configured to: receive an L1 / L2 handover command for a first candidate cell from the subset of the set of candidate cells. The processor may be further configured to: determine to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell based on receiving the L1 / L2 handover command. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented.

[0007] Figure 1B is an example of a method that can be used according to an embodiment of the present invention. Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within an illustrated communication system.

[0008] Figure 1C is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of an example Radio Access Network (RAN) and an example Core Network (CN) for use within the illustrated communication system.

[0009] Figure 1D is an example of a method that can be used according to an embodiment of the present invention. Figure 1A System diagram of another example RAN and another example CN for use within the illustrated communication system.

[0010] Figure 2 is a process diagram illustrating an example New Radio (NR) handover scenario.

[0011] Figure 3Example L1 / L2 inter-cell mobility operations using carrier aggregation (CA) are illustrated.

[0012] Figure 4 Example RLM and RLF detection mechanisms are illustrated.

[0013] Figure 5 is a diagram illustrating an example call flow of an L1 / L2 inter-cell mobility operation based on L1 / L2 measurement results. DETAILED DESCRIPTION

[0014] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multi-carrier (FBMC), etc.

[0015] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), consumer electronic devices, and devices operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as a WTRU.

[0016] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0017] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of a licensed spectrum and an unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0018] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0019] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0020] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-APro).

[0021] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0022] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0023] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0024] Figure 1AThe base station 114b in may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), or a road. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology (such as IEEE 802.11) to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology (such as IEEE 802.15) to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a microcell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0025] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the text and video, the CN 106 / 115 may be configured to provide voice, data, applications and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0026] 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 that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0027] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0028] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0029] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC) and state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0030] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from a base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, an IR, UV or visible light signal. In another embodiment, the send / receive element 122 may be configured to send and / or receive both an RF signal and an optical signal. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0031] Although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, 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.

[0032] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0033] The processor 118 of the WTRU 102 may be coupled to and may receive user input 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 a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, and a secure digital (SD) memory card, among others. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0034] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0035] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0036] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, and an activity tracker, etc. The peripheral device 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0037] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and / or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0038] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0039] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0040] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, and scheduling of users in the UL and / or DL, among other things. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0041] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0042] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. 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.

[0043] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during an inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0044] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0045] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0046] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0047] In a representative embodiment, the other network 112 may be a WLAN.

[0048] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and may be delivered to the STA. Traffic originating from the STA and destined for a target outside the BSS may be transmitted to the AP to be delivered to the corresponding target. Traffic between STAs within the BSS may be transmitted through the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the target STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source and destination STAs (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. This IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0049] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may send beacons on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may listen to the primary channel. If the primary channel is listened / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0050] High throughput (HT) STAs may communicate using a 40 MHz wide channel (eg, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels) to form a 40 MHz wide channel.

[0051] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and the data can be sent by sending STA. At the receiver of the receiving STA, the above-mentioned operation for 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0052] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0053] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) a 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (which only supports a 1MHz operating mode) is transmitting to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0054] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0055] Figure 1D 1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0056] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0057] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or Transmission Time Intervals (TTIs) of varying or scalable lengths (e.g., including varying numbers of OFDM symbols and / or varying absolute time lengths).

[0058] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while also not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle 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 eNodeB 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0059] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b and routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0060] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0061] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, etc. The AMF 182a, 182b may use network slicing in order to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, and / or 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.

[0062] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 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 notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0063] The UPF 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 UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring, etc.

[0064] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0065] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein for one or more of the following items may be performed by one or more simulation devices (not shown): WTRU102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF 182a-182ab, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device can be used to test other devices and / or simulate network and / or WTRU functions.

[0066] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0067] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) can be used by the simulation device to send and / or receive data.

[0068] Figure 2 is a process diagram illustrating an example New Radio (NR) handover scenario. At 202, an access and mobility function (AMF) may provide mobility control information. For a WTRU within a source gNB, the provided mobility control information may include information about roaming and / or access restrictions. The information about roaming and / or access restrictions may be provided to the WTRU at connection establishment and / or timing advance (TA) update.

[0069] At 204, the source gNB may configure the WTRU measurement control and reporting process and / or the WTRU may report the measurement results according to the measurement configuration.

[0070] At 206, the source gNB may decide to hand over the WTRU based on the reported measurement results.

[0071] At 208, the source gNB may transmit a HANDOVER REQUEST message to the target gNB. For example, the source gNB may issue a HANDOVER REQUEST message by passing a transparent RRC container with necessary information to prepare for the handover on the target side. The necessary information may include at least: target cell ID, KgNB*, C-RNTI of the WTRU in the source gNB, RRM configuration including WTRU inactive time, basic AS configuration including antenna information and DL carrier frequency, current QoS flow to DRB mapping rules applied to the WTRU, SIB1 from the source gNB, WTRU capabilities for different RATs, PDU session related information, and / or measurement information reported by the WTRU including beam related information (e.g., if available).

[0072] The target gNB may perform admission control at 210. If the WTRU is to be admitted, the target gNB may prepare to utilize L1 / L2 handover.

[0073] At 212, the target gNB may transmit a HANDOVER REQUEST ACKNOWLEDGE message to the source gNB. The HANDOVER REQUEST ACKNOWLEDGE message may include a transparent container that will be transmitted to the WTRU as an RRC message to perform the handover.

[0074] At 214, the source gNB may trigger a Uu handover at the WTRU. For example, the source gNB may transmit an RRCReconfiguration message to the WTRU to initiate the Uu handover. The RRCReconfiguration message may contain information required to access the target cell. For example, the RRCReconfiguration message may include at least a target cell ID, a new C-RNTI, and / or a target gNB security algorithm identifier for a selected security algorithm. The RRCReconfiguration message may also include a set of dedicated RACH resources, an association between RACH resources and SSBs, an association between RACH resources and WTRU-specific CSI-RS configurations, common RACH resources, and / or system information of the target cell.

[0075] At 216, the source gNB may transmit an SN STATUS TRANSFER message to the target gNB. The SN STATUS TRANSFER message to the target gNB may convey an uplink PDCP SN receiver status and / or a downlink PDCP SN transmitter status for a DRB to which PDCP status preservation (e.g., for RLC AM) is applied.

[0076] At 218, the WTRU may detach from the old cell (e.g., source gNB) and synchronize to the target cell (e.g., target gNB).

[0077] At 220, the WTRU may complete the RRC handover by transmitting an RRCReconfigurationComplete message to the target gNB.

[0078] At 222, the target gNB may transmit a PATH SWITCH REQUEST message to the AMF to trigger the 5GC. The PATH SWITCH REQUEST message may be transmitted to trigger the 5GC to switch the DL data path towards the target gNB and / or establish an NG-C interface instance towards the target gNB.

[0079] At 224, the 5GC may switch the DL data path toward the target gNB.

[0080] At 226, the UPF may transmit one or more "end marker" packets to the source gNB on the old path for each PDU session / tunnel and / or may release any U-Plane / TNL resources towards the source gNB.

[0081] At 228, the AMF may acknowledge the PATH SWITCH REQUEST message with a PATH SWITCH REQUEST ACKNOWLEDGE message.

[0082] At 230, upon receiving the PATH SWITCH REQUEST ACKNOWLEDGE message from the AMF, the target gNB may transmit a UE CONTEXT RELEASE message to notify the source gNB of the handover success. The source gNB may release the radio and C-plane related resources associated with the WTRU context. Any ongoing data forwarding may continue.

[0083] 3GPP's NR Release 16 (R16) introduces the concepts of conditional handover (CHO) and conditional PSCell addition / change (CPA / CPC, collectively referred to as CPAC). Specifically, in CHO, the WTRU may be configured (via an RRC reconfiguration message) with a HO target (e.g., a target cell configuration) and associated conditions with respect to cell measurement events (e.g., events A3 / A5 and corresponding cells). After being configured by receiving a CHO command, the WTRU may initiate monitoring of the associated status. When the condition is met, the WTRU may trigger a HO (e.g., reconfiguration) to an associated cell with a given configuration. Similarly, for CPC and CPA, the WTRU may trigger a PSCell change or PSCell addition associated with a stored PSCell configuration when the associated condition defined by the measurement event is triggered.

[0084] In one embodiment, the WTRU may be configured for inter-cell L1 / L2 mobility. In 3GPP's NR Release 18 (R18), the purpose of the WI "Further NR Mobility Enhancements" in RP-213565 is to specify mechanisms and procedures for L1 / L2-based inter-cell mobility to reduce mobility delays. For example, multiple candidate cells may be configured and maintained to allow rapid application of configurations for candidate cells [RAN2, RAN3]. In addition, candidate serving cells (including SpCells and SCells) may include dynamic switching mechanisms for potential applicable scenarios based on L1 / L2 signaling [RAN2, RAN1]. In addition, L1 enhancements for inter-cell beam management are provided, including L1 measurements and reporting and beam indications [RAN1, RAN2]. Early RAN2 intervention may be necessary, including further clarification of the interaction between L1 enhancements for inter-cell beam management and dynamic switching mechanisms between candidate serving cells. In addition, timing advance management may be provided [RAN1, RAN2]. In addition, CU-DU interface signaling to support L1 / L2 mobility may be provided.

[0085] In one embodiment, FR2 specific enhancements may not be excluded. In one embodiment, the L1 / L2 based inter-cell mobility process may be applicable in multiple scenarios, including: standalone networking with serving cell change within one CG, CA and NR-DC cases; intra-DU cases and intra-CU inter-DU cases (e.g., applicable to standalone networking and CA (e.g., no new RAN interface is expected)), both intra-frequency and inter-frequency, both FR1 and FR2, and source and target cells that may be synchronized or non-synchronized. The L1 / L2 based inter-cell mobility process may include inter-CU.

[0086] 3GPP's NR Release 17 (R17) includes L1 / L2-based mobility. In R17, inter-cell beam management covers intra-DU scenarios and intra-frequency scenarios. In these scenarios, the serving cell remains unchanged (for example, it is not possible to change the serving cell using L1 / L2-based mobility). In FR2 deployments, CA is typically used to utilize the available bandwidth (for example, in order to aggregate multiple CCs in one band). These CCs are typically transmitted with the same analog beam pair (for example, a gNB beam and a UE beam). The WTRU may be configured with TCI states for receiving PDCCH and PDSCH. For example, the WTRU may be configured with a considerable number (for example, 64) of TCI states. Each TCI state may include an RS or SSB that the WTRU can utilize to set its beam. In R17, the SSB may be associated with a non-serving PCI. MAC signaling (for example, "TCI state indication for WTRU-specific PDCCH MAC CE") may activate the TCI state for Coreset / PDCCH. Receipt of PDCCH from non-serving cells may be supported by a MAC CE message indicating the TCI state associated with the non-serving PCI. MAC signaling (e.g., "TCI state activation / deactivation for WTRU-specific PDSCH") may activate a subset of (e.g., up to) 8 TCI states for PDSCH reception. The DCI may indicate which of the 8 TCI states is activated. R17 also supports "unified TCI states" with different update mechanisms (e.g., DCI-based) without multiple TRPs. R18 supports unified TCI states with multiple TRPs.

[0087] The purpose of L1 / L2 inter-cell mobility may be to improve handover latency. In a conventional or conditional L3 handover, the WTRU typically first transmits a measurement report using RRC signaling. In response to the measurement report, the network may provide additional measurement configurations and potential conditional handover configurations.

[0088] In a conventional L3 handover, the network may provide the configuration for the target cell after the WTRU reports using RRC signaling to indicate that the cell meets the configured radio quality criteria. In a conditional L3 handover, the network may provide the target cell configuration and the measurement criteria that determine when the WTRU should trigger the CHO configuration. These criteria may be provided in advance to help reduce the handover failure rate due to delays in transmitting measurement reports and / or receiving RRC reconfiguration. However, a conventional or conditional L3 handover may be subject to some delays due to the transmission of measurement reports and the reception of the target configuration, especially in the case of a conventional (non-conditional) handover.

[0089] A specific purpose of L1 / L2 based inter-cell mobility configuration may be to allow fast application of configuration for candidate cells, including dynamic switching between SCells and switching of PCells (e.g., switching roles between SCells and PCells) without performing RRC signaling. However, such mobility configuration may not be applicable to inter-CU handovers, as these handovers may require relocation of the PDCP anchor point. Therefore, an RRC-based approach may still be needed to support inter-CU handovers. In addition, one of the purposes of L1 / L2 may be to allow CA operation to be enabled immediately when the serving cell changes.

[0090] Figure 3 is a functional model 300 illustrating an example L1 / L2 inter-cell mobility operation using CA. In the example operation, the candidate cell group may be configured through RRC, and dynamic switching of PCell and SCell may be achieved using L1 / L2 signaling.

[0091] As shown in the functional model 300, the WTRU 302 may dynamically switch between candidate cells as it physically traverses cell 1 (e.g., 3.5 GHz) 304, cell 2 (e.g., 2.1 GHz) 306, cell 3 (e.g., 26 GHz) 308, and cell 4 (e.g., 26 GHz) 310. At a first position 312, the WTRU 302 may be initially configured with cell 1 304 as a primary cell (e.g., PCell 1) and cell 2 308 as a secondary cell (e.g., SCell 2) using CA.

[0092] Cells 1 to 4 304, 306, 308, 310 may be initially configured as candidate cells through an RRC message. In addition, the RRC message may activate a primary cell and a secondary cell. For example, the RRC message may activate cell 1 304 as a primary cell and activate cell 2 as a secondary cell.

[0093] At a second position 314, the WTRU 302 may dynamically switch its secondary cell to cell 3 308 (e.g., SCell 3). At a third position 316, the WTRU 302 may dynamically switch its secondary cell to cell 2 306 (e.g., SCell 2). At a fourth position 318, the WTRU 302 may dynamically switch its primary cell to cell 2 306 (e.g., SCell 2) and its secondary cell to cell 4 310 (e.g., SCell 4). The candidate cell group within the functional model 300 may be configured through RRC messages, and dynamic switching of PCells and SCells may be implemented using L1 / L2 signaling.

[0094] The WTRU may transmit and / or receive physical channels and / or reference signals according to at least one spatial domain filter. The term "beam" may refer to a spatial domain filter. In this document, spatial filter and beam may be used interchangeably.

[0095] The WTRU may transmit a physical channel or signal using the same spatial domain filters as used to receive RS (e.g., such as CSI-RS) or SS blocks. The WTRU transmitting may be referred to as the "target". The received RS or SS block may be referred to as the "reference" or "source". In such cases, the WTRU may be said to transmit the target physical channel or signal based on the spatial relationship of the reference to such RS or SS block.

[0096] The WTRU may transmit a first physical channel or signal according to the same spatial domain filter as used to transmit a second physical channel or signal. The first transmission and the second transmission may be referred to as a "target" and a "reference" (or "source"), respectively. In such a case, the WTRU may be said to transmit the first (e.g., target) physical channel or signal according to a spatial relationship with reference to a second (e.g., reference) physical channel or signal.

[0097] The spatial relationship may be implicit, configured by RRC, or signaled by MAC CE or DCI. For example, the WTRU may implicitly send the DM-RS for PUSCH and PUSCH according to the same spatial domain filter. For example, the WTRU may implicitly send the DM-RS for PUSCH and PUSCH according to the same spatial domain filter as the SRS indicated by the SRI indicated in the DCI or configured by RRC. For example, the spatial relationship may be configured by RRC for SRS Resource Indicator (SRI) or signaled by MAC CE for PUCCH. Such spatial relationship may also be referred to as "beam indication".

[0098] The WTRU may receive a first (i.e., target) downlink channel or signal based on the same spatial domain filters or spatial reception parameters as a second (i.e., reference) downlink channel or signal. For example, such an association may exist between a physical channel (such as a PDCCH or PDSCH) and its corresponding DM-RS. Such an association may exist at least when the first signal and the second signal are reference signals and when the WTRU is configured with a quasi co-location (QCL) assumption type D between corresponding antenna ports. Such an association may be configured as a TCI (transmit configuration indicator) state. In one or more cases, the WTRU may be indicated as an association between a CSI-RS or SS block and a DM-RS by an index to a TCI state set (configured by the RRC and / or signaled by the MAC CE). Such an indication may also be referred to as a "beam indication."

[0099] The WTRU may be configured to maintain one or more beam pairs in a beamformed NR system. The WTRU may monitor a specific periodic CSI-RS on the serving DL beam to assess its quality and may calculate a corresponding quality metric. If the beam quality in a given RS period for all beams in the maintenance set is below a configured threshold, the WTRU's physical (PHY) layer entity may report a beam failure instance (BFI) to the MAC sublayer.

[0100] In order to reestablish the lost beam pair faster than the RLM / RLF process, the WTRU may maintain a BFD process in which the maintained beams are periodically measured. Upon detecting a beam failure, the WTRU may report a beam failure recovery request to the network. Beam failure recovery (BFR) may be configured for PCell and / or SCell beam maintenance. When BFD and / or DRX are configured in a legacy system, BFD measurements may be made at the maximum period of the larger of the DRX cycle and / or the CSI-RS cycle.

[0101] The MAC entity may maintain a beam failure instance counter (BFI counter) for beam failure detection. The MAC entity may count the number of beam failure instance indications received from the PHY layer entity. If the BFI counter exceeds a certain maximum number of BFIs, a BFR request may be triggered to notify the serving gNB that a beam failure has been detected.

[0102] The MAC entity may reset the BFI counter after the beam failure detection timer (BFD timer) has expired. The BFI counter may provide some hysteresis in the detection function. In such cases, the WTRU may reset the BFD timer each time a BFI is indicated. For example, for a BFD timer configured for 3 CSI-RS periods, the MAC entity may reset the BFI counter after no BFI indication is observed from the PHY layer for three consecutive CSI-RS periods.

[0103] To report a BFR request for a beam failure detected for the PCell and PSCell (collectively referred to as SpCell), the WTRU may initiate a random access (RA) procedure for beam reestablishment. In the random access procedure for beam reestablishment, the WTRU may select an appropriate PRACH preamble and / or PRACH resource based on the best measured downlink beam (e.g., CSI-RS or DL ​​SSB). In one embodiment, when the WTRU determines the association between the DL beam and / or UL preamble and / or PRACH opportunity, the WTRU may have a method to reestablish the beam pair. The downlink beam selected by the WTRU may be tested by receiving a random access response (RAR) on the downlink beam. Such a reestablishment RA procedure may be made faster if the gNB configures a specific set of non-contention PRACH preambles / resources that may be preferentially selected by the WTRU when initiating the reestablishment RA procedure. The WTRU may report a BFR request for a beam failure detected for the Scell ​​by sending a MAC CE indicating the cell in which the beam failure was detected.

[0104] A WTRU in the RRC_CONNECTED state may continuously monitor its radio link to ensure it is in good condition and / or sufficiently reliable for communication in a process known as radio link monitoring (RLM).The WTRU may monitor the downlink (DL) quality based on a reference signal broadcast from a serving cell.

[0105] The WTRU may perform RLM on the primary cell (PCell) in single connected operation. The WTRU may perform RLM on the PCell and the primary cell (PSCell) (eg, SpCell) of the secondary cell group in DC operation.

[0106] The WTRU may be configured with an RLM Reference Signal (RLM-RS) to monitor and determine the radio quality of the PCell (and the PSCell in the DC case). For example, the WTRU may be configured with an RLM Reference Signal (RLM-RS) to monitor and / or determine the radio quality of the PCell in a single link operation. Similarly, the WTRU may be configured with an RLM Reference Signal (RLM-RS) to monitor and / or determine the radio quality of the PSCell in DC operation. In one embodiment, the network may configure the WTRU to perform RLM based on SSB (Synchronization Signal Block), CSI-RS (Channel State Information - Reference Signal) and / or a combination of these signal types.

[0107] The WTRU may be configured with thresholds to determine whether the monitored radio link is good and / or sufficiently reliable. outmay correspond to a level at which the DL cannot be reliably received and / or may correspond to an out-of-sync block error rate (BLERout). For example, BLERout may be a 10% block error rate assumed for PDCCH transmissions. For example, Q in can correspond to comparable in Q out The level at which the DL is received significantly more reliably and / or corresponds to a synchronization block error rate (BLERin). For example, BLERin may be an assumed 2% block error rate for PDCCH transmissions.

[0108] The WTRU may be configured with a timer and / or a counter. The WTRU may use a timer and / or a counter to determine the reliability of the link being monitored. For example, N310 may be the number of consecutive times that an out-of-sync indication is received from a lower layer (e.g., PHY) at the RRC before the RRC begins to believe that the monitored link is experiencing reliability issues. For example, N311 may be the number of consecutive times that a synchronization indication is received from a lower layer (e.g., PHY) at the RRC before the RRC believes that the monitored link has become reliable again. For example, T310 may be the duration of a timer that may start when N310 consecutive out-of-sync indications are received from the lower layer and stop when N311 consecutive synchronization indications are received. In one embodiment, if the T310 timer times out before N311 consecutive synchronization indications are received from the lower layer, the RRC may consider the link to be faulty and / or declare an RLF (radio link failure).

[0109] Figure 4 is a process diagram 400 illustrating an example RLM and RLF detection mechanism. The process diagram 400 includes overlapping RLM 402 and radio resource management (RRM) 404 timelines.

[0110] The RML timeline 402 may sequentially include a normal operation portion 402A, a radio problem portion 402B, an RLJ timer T310 portion 402C, and a reestablishment / MCG failure recovery portion 402D. For example, when the signal to interference plus noise ratio (SINR) drops to a defined Q out When the SINR has remained below the defined Q level 402E, a transition from the normal operation portion 402A to the radio problem detected portion 402B may be triggered. out The transition from the detected radio problem portion 402B to the RLF timer T310 portion 402C may be triggered when the SINR fails to remain above the defined Qin level for at least the number of consecutive times configured for N310. The transition from the RLF timer T310 portion 402C to the reestablishment / MCG failure recovery portion 402D may be triggered when the SINR fails to remain above the defined Qin level for the number of consecutive times configured for N311 402G during the configured duration of the T310 timer.

[0111] The RRM timeline 404 may sequentially include a measurement portion, a time to trigger (TTT) portion 404B, a short RLF timer T312 portion 404C, and a reestablishment / MCG failure recovery portion 404D. For example, once the measurement report condition 404E is met, the transition from the measurement portion 404A to the TTT portion 404B may be triggered. When the measurement report is triggered during the duration of the T310 timer 404F, the transition from the TTT portion 404B to the short RLF timer T312 portion 404C may be triggered. The transition from the RLF timer T312 portion 404C to the reestablishment / MCG failure recovery portion 404D may be triggered in the following circumstances: if at the end of the configured duration of the T312 timer, the SINR fails to remain above the defined Qin level for a number of consecutive times configured for N311 404G.

[0112] like Figure 4 As shown, the WTRU may use the T312 timer to detect RLF associated with the measurement report. The measurement report configuration may be associated with the T312 timer. When the reporting condition is met and / or the measurement report configuration associated with the T312 timer is to be transmitted, the WTRU may determine whether the T310 timer is already running. When the RLM has identified a problem and is waiting for recovery, the WTRU may determine that T310 is running. If the WTRU determines that the T310 timer is already running, the WTRU may start the T312 timer, whose duration is set to the configured duration of the T312 timer. If the problem is not resolved before the T312 timer expires, the WTRU may declare RLF. In this way, the WTRU may use the T312 timer to detect a delayed HO. That is, if the measurement report is transmitted earlier than the radio link problem begins, the WTRU may have been handed over to the target cell in a timely manner.

[0113] In L1 / L2 mobility, the WTRU may be prepared by a source cell with an RRC configuration of a set of candidate cells that may be mobility targets (e.g., may become PCells or PSCells). Based on beam measurements of the candidate cells, the NW may use L1 / L2 signaling (e.g., DCI or MAC CE) to trigger mobility (e.g., to facilitate one of the candidate cells to become a PCell or PSCell), which has a smaller processing latency than L3 signaling.

[0114] Using beam measurements to make mobility decisions may allow the network to move the WTRU to the best cell faster than long-term L3 measurements (e.g., RSRP). In addition, using beam measurements to make mobility decisions may help ensure that the WTRU is always served by the best cell / beam. However, faster handover decisions may require the WTRU to determine that a candidate cell is not an acceptable target to avoid HO failures due to temporary fades that may have occurred just before mobility. To reduce the latency of the mobility process itself, the L1 / L2 mobility commands may come from the target cell itself.

[0115] Beam monitoring / RLM / RLF procedures may be performed on some candidate cells before handover. However, if the WTRU performs link monitoring on many cells in addition to the serving cell, the processing overhead on the WTRU may be a problem. In one embodiment, the WTRU may be configured to perform RLM / BFD on candidate cells for L1 / L2 mobility while limiting the processing / measurement overhead at the WTRU.

[0116] Solutions related to RLM / RLF may be applicable to beam failure monitoring / detection. For example, embodiments may relate to procedures at a WTRU for performing RLM and / or detecting or recovering from RLF on a candidate cell in the context of L1 / L2 mobility. Unless otherwise indicated, the same procedures may be applied to beam failure monitoring and detection.

[0117] Detection / recovery of RLM and RLF on candidate cells is provided for L1 / L2 mobility. Candidate cells may correspond to cells to which the WTRU is ready to hand over (e.g., due to having been pre-configured with the RRC configuration for those candidate cells) due to receiving L1 / L2 signaling from the network (e.g., beam switching, or receiving a MAC CE indicating a cell handover). Such candidate cells may include one or more candidate serving cells in the candidate serving cells (e.g., SCells), or even all candidate serving cells or a subset of candidate serving cells. In one embodiment, a subset of candidate serving cells may be serving cells that meet specific criteria.

[0118] In one embodiment, if the WTRU performs RLM and RLF detection / recovery and / or beam failure detection / recovery on a candidate target cell, the WTRU / network may prepare for HO on the candidate target cell. If necessary, the HO command may be reliably transmitted on the target cell. However, the WTRU may be configured with multiple candidate cells (e.g., RRC configuration for potential L1 / L2 mobility targets), and therefore, monitoring RLM / RLF on all of these candidate cells may consume a lot of power at the WTRU.

[0119] L1 / L2 mobility and / or handover may refer to making one of the candidate cells a SpCell. In one embodiment, the WTRU may be configured with L1 / L2 mobility to perform RLM and / or RLF detection / recovery on a candidate target cell.

[0120] The WTRU may be configured to perform RLM and RLF detection / recovery on a candidate target cell. The WTRU may receive one or more configurations of RLM and RLF detection / recovery associated with one or more candidate target cells. For example, the WTRU may receive configuration information for RLM for a serving cell and a set of candidate cells. As described below, the configuration information may include an indication of a time period for RLM for the set of candidate cells. As described above, the WTRU may receive the configuration information via RRC.

[0121] The WTRU may initiate RLM for a candidate cell and / or stop performing RLM for a candidate cell based on one or more of the trigger conditions or any combination thereof. The trigger condition may correspond to an explicit or implicit trigger from the network. For example, the WTRU may initiate RLM for a target cell based on explicit signaling, such as a MAC CE providing an index / identifier of a serving cell. The index may be a pre-configured index identifying the target cell. The WTRU may report measurements associated with the candidate cell.

[0122] The WTRU may sort the reported measurement results (e.g., based on RSRP or some other criteria), and the index of the MAC CE to initiate RLM or stop RLM may correspond to the index in the list reported by the WTRU in the last measurement. For example, the WTRU may receive a MAC CE containing a bitmap, where each bit in the bitmap corresponds to a candidate cell, and a value of "1" indicates that RLM is to be performed on the serving cell, while a value of "0" indicates that RLM is not to be performed on the serving cell. For example, the WTRU may receive an L1 / L2 HO command to switch to one of the candidate cells. Receiving the L1 / L2 HO command may implicitly initiate RLM for the received candidate cell. Receiving the L1 / L2 HO command may also implicitly initiate RLM for another candidate cell and / or implicitly stop performing RLM for another candidate cell.

[0123] The WTRU receives a message indicating that RLM is to be initiated for a subset of the candidate cell set using the configuration information for the RLM for the candidate cell set indicated in the RRC message.

[0124] The trigger may correspond to a condition associated with the measured quality of the SpCell and / or another candidate cell. For example, when the RSRP of the SpCell is below a threshold, the WTRU may initiate RLM on the candidate cell. When the RSRP of the SpCell is below a threshold for a period of time, the WTRU may initiate RLM on the candidate cell. For example, when the RSRP of the serving cell is above a threshold, the WTRU may stop performing RLM on the candidate cell, where RLM is in progress. When the RSRP of the serving cell is above a threshold for a period of time, the WTRU may stop performing RLM on the candidate cell, where RLM is in progress.

[0125] The WTRU may determine to perform RLM on the subset of the candidate cell set for at least a period of time defined in the configuration information after receiving the message.

[0126] The WTRU may report the best N candidate cells to the network. When providing such a report, the WTRU may stop performing RLM on any candidate cells that are not part of the N reported candidate cells. The WTRU may determine to report at L2 / L2 the measurement results associated with the RLM performed on the subset of candidate cells.

[0127] The trigger may correspond to a condition associated with the measured quality of the candidate cell. For example, when the RSRP of the candidate cell itself is above a threshold, the WTRU may initiate RLM for the candidate cell. For example, when the RSRP of the candidate cell itself is above a threshold for a period of time, the WTRU may initiate RLM for the candidate cell.

[0128] When the RSRP of a candidate cell is below a threshold, the WTRU may stop performing RLM on the candidate cell. When the RSRP of a candidate cell is below a threshold for a period of time, the WTRU may stop performing RLM on the candidate cell. Once a time period defined in the configuration has elapsed after receiving the message, the WTRU may determine to terminate performing RLM on the subset of the set of candidate cells.

[0129] When the RSRP of a candidate cell is between a first threshold and a second threshold, the WTRU may perform relaxed RLM on the candidate cell.

[0130] The WTRU may initiate RLM for the top N best candidate cells, where N is configurable.

[0131] The trigger may correspond to a condition associated with the current RLM state of the SpCell or another candidate cell. For example, when a condition related to the RLM state of the SpCell is met, the WTRU may initiate RLM for the candidate cell.

[0132] When the T310 timer has started and / or is running on the SpCell, the WTRU may initiate an RLM on the candidate cell.

[0133] When the T310 timer is stopped on the SpCell (e.g., due to the SpCell coming back into sync) and / or after a period of time that the T310 timer is stopped, the WTRU may stop the RLM of the candidate cell initiated by the start of the T310 timer on the SpCell. Similarly, when the T310 timer is stopped on the SpCell (e.g., due to the SpCell coming back into sync), the WTRU may stop the RLM of the candidate cell initiated by the start of the T310 timer on the SpCell. After a period of time that T310 is stopped, the WTRU may stop the RLM of the candidate cell initiated by the start of the T310 timer on the SpCell.

[0134] A trigger may correspond to a condition associated with the detection of a beam failure on a SpCell. For example, the WTRU may initiate RLM on a candidate cell after detecting a beam failure on a SpCell. The WTRU may initiate RLM on a candidate cell after detecting a certain number of beam failures within a given time period. A trigger may correspond to a condition associated with the amount of time since another trigger occurred.

[0135] The WTRU may report RLF of a candidate target cell. The WTRU may report RLF of one or more candidate cells. For example, the WTRU may use a MAC CE to report the occurrence of RLF on one or more candidate cells. The WTRU may use a bitmap (e.g., a bitmap in which one bit represents each of the configured candidate cells) to report RLF on multiple candidate cells.

[0136] The WTRU may transmit an RLF report when a triggered RLF occurs on any candidate cell. The WTRU may be configured with conditions that determine when to report RLF on one or more candidate cells. The condition may correspond to the number of candidate cells and / or the ratio of candidate cells that have experienced RLF. For example, the WTRU may transmit an RLF report when RLF has been detected on at least X candidate cells, where X may be a configured number. For example, the WTRU may transmit an RLF report when RLF is detected on a certain percentage of candidate cells with activated RLM. The condition may correspond to similar events related to the monitoring of RLM. For example, when the RSRP of the SpCell is below a threshold, the WTRU may monitor RLM on the candidate cells and / or report RLF associated with the candidate cells.

[0137] The WTRU may determine to perform RLM on the subset of the set of candidate cells for at least a time period defined in the configuration information after detecting the RLF on the serving cell. The WTRU may determine to terminate performing RLM on the subset of the set of candidate cells once the time period after detecting the RLF on the serving cell has elapsed. The WTRU may determine to perform RLM on a target candidate cell from the subset of the set of candidate cells based on the detected RLF of the serving cell according to the configuration information for the RLM of the serving cell. No RLF may be detected on the target candidate cell.

[0138] The WTRU may be configured to perform relaxed RLM on a candidate target cell. For example, the relaxed RLM on the candidate cell may include reporting in-specification / out-of-specification (IS / OOS) results less frequently than regular RLM. The relaxed RLM may include monitoring the RS for RLM less frequently than RLM of the SpCell.

[0139] The WTRU may be configured with conditions regarding when to perform normal RLM or relaxed RLM on a candidate cell. Such conditions may be similar to the conditions for initiating RLM on a candidate cell. For example, the WTRU may be configured with an RSRP threshold on the current SpCell. For example, if the SpCell quality is above a threshold, the WTRU may perform relaxed RLM on multiple candidate cells. If the SpCell quality is below a threshold, the WTRU may perform normal RLM on the candidate cell.

[0140] The WTRU may be configured to perform relaxed RLF detection on a candidate cell compared to conventional RLF detection on the SpCell. For example, the WTRU may be configured with N310, N311, and T310 associated with the SpCell. The WTRU may be configured to amplify the values ​​of N310 and T310 and / or to reduce the value of N311 to determine the counter value and / or timer value for RLF detection of the candidate cell. For example, the WTRU may be configured to perform less frequent RLM monitoring on the candidate cell.

[0141] The L1 / L2 handover process / behavior may depend on whether the WTRU is performing RLM on the candidate cell during the L1 / L2 handover. For example, the WTRU may be instructed to perform an L1 / L2 handover to the cell. The WTRU may or may not initiate an RLM process to perform an L1 / L2 handover to the cell. The WTRU may perform different operations for L1 / L2 handover based on whether the WTRU performed RLM on the candidate cell concerned before the handover command.

[0142] Whether RLM is performed on a candidate cell prior to handover may impact the handling of the RLF timers / counters. The determination of whether to reset the RLF counters and / or stop the RLF timers and / or maintain the current counter value and maintain the RLF timers running (e.g., for the case where the RLF timers are running) at the HO may depend on whether RLM is being performed on the selected candidate cell prior to handover. For example, if RLM is performed on the candidate cell, the WTRU may not reset the RLF timers / counters on the cell at the HO. If RLM is not performed on the candidate cell, any RLF timers / counters may be stopped / reset at the HO for that cell. Additionally, if RLM is performed at other candidate cells, the WTRU may be configured to not reset the RLF counters and / or not reset the RLF timers for those candidate cells.

[0143] If RLM is not performed before the HO, the WTRU may transmit an acknowledgement (eg, a MAC CE acknowledgement message) for the HO command. If RLM is performed at the HO, the WTRU may be configured not to transmit an acknowledgement.

[0144] For example, if the WTRU is performing RLM on a candidate cell when HOing to the candidate cell, the WTRU may report RLF results about other candidate target cells (e.g., report RLF results of other candidate cells) at the time of HO (e.g., in the HO Complete message).

[0145] The WTRU may be configured to report cell quality (e.g., CQI) upon receiving a HO. For example, if the WTRU is not performing RLM on the candidate cell, the WTRU may be configured to report cell quality (e.g., CQI) upon receiving a HO. If the WTRU is performing RLM on the candidate cell, the WTRU may be configured not to report cell quality.

[0146] The WTRU may be configured to perform more robust (eg, more frequent) reporting of the UL quality at HO based on whether RLM is being performed on the cell at the time of HO.

[0147] The WTRU may autonomously trigger an L1 / L2 handover when the triggering condition is related to RLM / RLF and / or BFD. The WTRU may perform an L1 / L2 handover to a candidate target cell based on a triggering condition related to RLF and / or BFD. For example, if RLF is triggered on the current SpCell, the WTRU may perform an L1 / L2 handover to the candidate cell. If the L1 / L2 HO triggered by RLF on the SpCell fails, the WTRU may perform an L3 recovery procedure (e.g., reconstruction). For example, if a beam failure is detected on the SpCell, the WTRU may perform an L1 / L2 handover to the candidate cell. If the L1 / L2 HO triggered by beam failure detection on the SpCell fails, the WTRU may be configured to perform a beam failure recovery procedure. For example, if a condition related to RLF (such as T310) starts on the SpCell, the WTRU may perform an L1 / L2 handover to the candidate cell. If the L1 / L2 HO triggered by starting T310 fails, the WTRU may be configured to continue running T310 and / or trigger L3 recovery (eg, re-establishment) if T310 times out.

[0148] The WTRU may receive a handover command for a first candidate cell in a subset of a set of candidate cells (eg, L1 / L2).

[0149] The WTRU may also trigger an L1 / L2 handover upon any of the above trigger conditions based on certain conditions associated with the candidate cell. For example, if the conditions associated with the candidate cell (e.g., the cell to which the WTRU selects to perform an L1 / L2 handover) are met, the WTRU may be configured to perform an L1 / L2 HO. If the conditions associated with the candidate cell are not met, the WTRU may perform an L3 recovery procedure (e.g., reestablishment) or a conventional recovery procedure (e.g., beam failure recovery).

[0150] These conditions may include any combination of the following conditions. For example, the condition may correspond to a scenario where the WTRU is monitoring RLM on at least one candidate cell. In this case, the WTRU may select a candidate cell on which to perform L1 / L2 mobility when triggered. For example, the condition may correspond to at least one candidate cell having a cell quality (e.g., RSRP) above a threshold. In this case, the WTRU may select a candidate cell on which to perform L1 / L2 mobility when triggered. For example, the condition may correspond to the WTRU monitoring RLM on at least one candidate cell where RLF has not been triggered or T310 has not started. For example, the condition may correspond to the WTRU performing beam measurement on at least one candidate cell, and the WTRU may determine that the beam measurement result is better than a threshold.

[0151] The WTRU may be configured to perform re-establishment on one of the candidate cells for which the WTRU has performed RLM (e.g., when the WTRU triggered L1 / L2 mobility has failed). The WTRU may be configured to indicate information to the network regarding the decision to perform the WTRU triggered L1 / L2 mobility. The information may also include measurement results of the previous SpCell, the current SpCell, other candidate cells, and / or other similar types of measurement results.

[0152] One or more WTRU behaviors described herein may be combined to define RLM / RLF related WTRU behaviors before and / or after receiving a L1 / L2 HO command.

[0153] The WTRU may be configured to receive an RRC configuration for a set of candidate cells. The WTRU may be configured to perform beam measurements on all candidate cells. Alternatively or in addition, the WTRU may be configured to perform beam measurements on a subset of candidate cells.

[0154] The WTRU may receive a MAC CE initiating RLM and / or beam measurement on a subset of candidate cells. The WTRU may be configured to rank the candidate cells based on the last measured / reported RSRP.

[0155] The WTRU may be configured to receive a MAC CE organized as a bitmap of the reported best X candidate cells. The bitmap may indicate whether to initiate and / or stop RLM on each of the best candidate cells.

[0156] When initiating RLM, the WTRU may initiate and / or perform RLM on the indicated candidate cells using a relaxed RLM configuration (eg, less frequent RS measurements) upon receiving the MAC CE.

[0157] The WTRU may reset the RLF counter and / or stop the RLF timer associated with the candidate cell indicated to be monitored. The WTRU may be configured to continue performing RLM for a configured period of time after receiving the MAC CE. The WTRU may continue to perform RLM on the candidate cell as long as the serving cell RSRP is below the threshold when the timer expires.

[0158] During RLM execution on a candidate cell, the WTRU may report to the network using MAC CE any cell in which RLF is triggered. The WTRU may be configured to stop performing RLM on the candidate cell until the cell is reconfigured. The WTRU may remove the cell from the list of cells reported by the WTRU for measurement.

[0159] If L1 HO is performed on a candidate cell, the WTRU may stop performing relaxed RLM on the candidate cell (e.g., performing relaxed RLM on the candidate cell). For example, the WTRU may be configured to start normal (i.e., non-relaxed) RLM because the cell is a new SpCell. For example, the WTRU may immediately stop performing RLM on all candidate cells previously indicated by the NW MAC CE.

[0160] The WTRU may be configured with a set of candidate cells via RRC. The WTRU may be configured to receive a MAC CE indicating a subset of candidate cells that may serve as early RLM targets. When T310 is started on the SpCell, the WTRU may initiate RLM on the candidate cells identified by the MAC CE. Other examples as described herein may be used for identification of candidate cells.

[0161] If RLF is triggered on the SpCell, the WTRU may perform an L1 / L2 HO to a candidate cell, as long as the candidate cell has RLM running and RLF has not been triggered. If no such candidate cell is found, the WTRU may be configured to trigger an L3 recovery procedure (e.g., reestablishment) after RLF on the serving cell.

[0162] The WTRU may be configured to perform RLM on a candidate cell even after RLF is detected. For example, the WTRU may be configured to keep a count of the number of RLF instances detected on the candidate cell. The number of RLF instances detected on the candidate cell may be reported to the network later. For example, at the next L1 / L2 HO, the number of RLF instances detected on the candidate cell may be reported to the network later. For example, when a certain number of RLFs have been detected within a given time period, the number of RLF instances detected on the candidate cell may be reported to the network later. If more than a certain number of RLFs are detected within a given time period, the WTRU may be configured to stop performing RLM on the candidate cell.

[0163] Based on receiving the handover command, the WTRU may determine to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell.

[0164] Figure 5 5 is a diagram illustrating an example call flow 500 of L1 / L2 inter-cell mobility operations based on L1 / L2 measurement results. The call flow 500 is an example of the above-described processes and procedures. The call flow 500 involves WTRU behavior related to RLM / RLF before and / or after receiving a L1 / L2 HO command.

[0165] At 502, the serving cell may be configured to determine a potential need for an L1 / L2 handover by the WTRU. At 504, the WTRU may receive a message (e.g., an RRC message) from the serving cell including configuration information for an RLM of the serving cell and a set of candidate cells. The configuration information may include an indication of a time period for the RLM of the set of candidate cells. In some examples, the configuration information may include a reference signal received power (RSRP) threshold for the serving cell.

[0166] At 506, the WTRU receives a message from the serving cell indicating that RLM is to be initiated for a subset of candidate cells using the configuration information for RLM for the set of candidate cells indicated in the RRC message. The message may be a L2 control message such as a MAC CE.

[0167] At 508, the WTRU may determine to perform RLM on the subset of the set of candidate cells for at least a time period after receiving the message. For example, in some examples, the WTRU may determine to terminate performing RLM on the subset of the set of candidate cells once the time period after receiving the message has elapsed. Additionally, in some examples, the WTRU may determine to perform RLM on the subset of the set of candidate cells beyond the time period after receiving the message based on the measured serving cell RSRP being below an RSRP threshold for the serving cell (e.g., where the RSRP threshold is provided via the configuration information). At 510, the WTRU may determine to report measurement results associated with the RLM performed on the subset of the set of candidate cells at L1 / L2.

[0168] At 512, the serving cell may determine that a handover is required. The determination of the handover may be made based on the L1 / L2 measurement results of the subset of candidate cells received from the WTRU. The handover may be an L1 / L2 handover. Figure 5 As shown, the serving cell may select a first candidate cell from the subset of the candidate cell set as the target of the handover.

[0169] At 514, the WTRU may receive a handover command from the serving cell for a target candidate cell in the subset of the set of candidate cells. Figure 5 As shown, the handover command may identify the first candidate cell as the target candidate cell. The handover command may be used for an L1 / L2 handover command.

[0170] At 516, based on receiving the handover command, the WTRU may determine to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell.

[0171] The WTRU may determine L1 / L2 inter-cell mobility operations based on the detected RLF of the candidate cell. For example, when RLM is performed on the subset of the candidate cell set at least within a time period after receiving the message, the WTRYU may detect and report the RLF of the first candidate cell associated with the RLM of the subset of the candidate cell set. The WTRU may receive a handover command for a target candidate cell in the subset of the candidate cell set from the serving cell. The handover command may identify the second candidate cell as the target candidate cell. Based on receiving the handover command, the WTRU may determine to perform RLM on the second candidate cell according to the configuration information of the RLM for the serving cell.

[0172] The WTRY may determine L1 / L2 inter-cell mobility operations based on the detected RLF of the serving cell. For example, the WTRU may detect the RLF on the serving cell when RLM is performed on the subset of the candidate cell set at least within a time period after receiving the message. At least within a time period after detecting the RLF on the serving cell, the WTRU may determine to perform RLM on the subset of the candidate cell set using the configuration information for RLM. Once the time period after detecting the RLF on the serving cell has passed, the WTRU determines to terminate the performance of RLM on the subset of the candidate cell set. The WTRU may determine to perform RLM on the target candidate cell (new serving cell) using the RLM configuration for the serving cell. The determination to perform RLM may be based on the detected RLF of the serving cell. The RLF of the target candidate cell may not have been detected yet.

Claims

1. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising: A processor, the processor being configured to: receiving a radio resource control (RRC) message, the radio resource control (RRC) message including configuration information for radio link monitoring (RLM) for a serving cell and a set of candidate cells, the configuration information including an indication of a time period for the RLM of the set of candidate cells; receiving, using the configuration information for the RLM for the set of candidate cells indicated in the RRC message, a message indicating that RLM is to be initiated for a subset of the set of candidate cells; determining to perform RLM on the subset of the set of candidate cells at least within the time period after receiving the message; determining to terminate performing RLM on the subset of the set of candidate cells once the time period after receiving the message has elapsed; determining to report at L1 / L2 measurements associated with the RML performed on the subset of the set of candidate cells; receiving a handover command for a first candidate cell from the subset of the set of candidate cells; as well as Based on receiving the handover command, it is determined to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell.

2. The WTRU of claim 1 , wherein the handover command is an L1 / L2 handover.

3. The WTRU of claim 1 or 2, wherein the configuration information further comprises a reference signal received power (RSRP) threshold of the serving cell; and The processor is further configured to determine to perform RLM for the subset of the candidate cell set outside the time period after receiving the message based on the measured serving cell RSRP being lower than the RSRP threshold of the serving cell.

4. The WTRU of any one of claims 1 to 3, wherein the message is an L2 control message.

5. The WTRU of claim 4, wherein the message is a MAC Control Element (MAC CE).

6. The WTRU of any one of claims 1 to 5, wherein the processor is further configured to: detecting a radio link failure (RLF) on the first candidate cell; and Based on receiving the L1 / L2 handover command, it is determined to perform RLM on a second candidate cell according to the configuration information of the RLM for the serving cell.

7. The WTRU of claim 6, wherein the processor is further configured to determine to report the RLF of the first candidate cell.

8. The WTRU of any one of claims 1 to 7, wherein the processor is further configured to: detecting a radio link failure (RLF) on the serving cell; determining to perform RLM on the subset of the set of candidate cells at least within the time period after detecting the RLF on the serving cell; determining to terminate performing RLM on the subset of the set of candidate cells once the time period after detecting the RLF on the serving cell has elapsed; as well as Determining, according to the configuration information for the RLM of the serving cell, to perform RLM on a target candidate cell within the subset from the set of candidate cells based on the detected RLF of the serving cell, wherein the RLF of the target candidate cell has not been detected.

9. The WTRU of any one of claims 1 to 8, wherein the RLM for the subset of the set of candidate cells is a relaxed RLM.

10. A method performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving a radio resource control (RRC) message, the radio resource control (RRC) message including configuration information for radio link monitoring (RLM) for a serving cell and a set of candidate cells, the configuration information including an indication of a time period for the RLM of the set of candidate cells; receiving, using the configuration information for the RLM for the set of candidate cells indicated in the RRC message, a message indicating that RLM is to be initiated for a subset of the set of candidate cells; determining to perform RLM on the subset of the set of candidate cells at least within the time period after receiving the message; determining to terminate performing RLM on the subset of the set of candidate cells once the time period after receiving the message has elapsed; determining to report at L1 / L2 measurements associated with the RML performed on the subset of the set of candidate cells; receiving a handover command for a first candidate cell from the subset of the set of candidate cells; as well as Based on receiving the L1 / L2 handover command, it is determined to perform RLM on the first candidate cell according to the configuration information of the RLM for the serving cell. The method of claim 10 , wherein the handover command is an L1 / L2 handover.

12. The method according to claim 10 or 12, wherein the configuration information further includes a reference signal received power (RSRP) threshold of the serving cell; and The processor is further configured to determine to perform RLM for the subset of the candidate cell set outside the time period after receiving the message based on the measured serving cell RSRP being lower than the RSRP threshold of the serving cell.

13. The method according to any one of claims 10 to 12, wherein the message is a L2 control message.

14. The method of claim 13, wherein the message is a MAC Control Element (MAC CE).

15. The method according to any one of claims 10 to 14, further comprising: detecting a radio link failure (RLF) on the first candidate cell; as well as A determination is made based on the RLF detected on the first candidate cell to perform a handover procedure to a second candidate cell within the subset of the set of candidate cells.

16. The method according to claim 15, further comprising: Report the RLF of the first candidate cell.

17. The method according to any one of claims 10 to 16, further comprising: detecting a radio link failure (RLF) on the serving cell; determining to perform RLM on the subset of the set of candidate cells at least within the time period after detecting the RLF on the serving cell; determining to terminate performing RLM on the subset of the set of candidate cells once the time period after detecting the RLF on the serving cell has elapsed; as well as Determining, according to the configuration information for the RLM of the serving cell, to perform RLM on a target candidate cell within the subset from the set of candidate cells based on the detected RLF of the serving cell, wherein the RLF of the target candidate cell has not been detected.

18. The method according to any one of claims 10 to 17, wherein the RLM for the subset of the set of candidate cells is a relaxed RLM.

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