Techniques for reliable mobility

Abstract

The WTRU may receive configuration information for transitioning from a source cell to a target cell, the configuration information including at least one parameter. The WTRU may send an indication of one or more measurements associated with the source cell and the target cell, and may receive signaling associated with the transition, the signaling including at least one value of the at least one parameter associated with the transition. The WTRU may transition to the target cell using the at least one value of the at least one parameter associated with the transition. Configuration information may be received via RRC signaling. The indication of one or more measurements may be sent via L1 and / or L2 signaling and may be via CSI reporting. The at least one parameter may include a RACH preamble, a timing advance, a C-RNTI, an initial grant for the target cell, and / or a beam indication. The signaling may be received via MAC CE and / or DCI signaling.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 395,066, filed on August 4, 2022, which is hereby incorporated by reference in its entirety. Background Art

[0003] A source next generation Node B (gNB) may configure a wireless transmit / receive unit (WTRU) with certain measurement procedures, and the WTRU may transmit reports according to the measurement configuration. The source gNB may determine to hand over the WTRU based on the received measurements. The source gNB may send a Handover Request message to a target gNB, passing a transparent radio resource control (RRC) container including information for preparing the handover on the target side. Admission control may be performed by the target gNB. If the WTRU is able to be admitted, the target gNB may prepare for the handover (e.g., using physical layer 1 (L1) / data link layer 2 (L2)) and send a Handover Request Confirm message to the source gNB, which may, for example, include a transparent RRC container (e.g., to be transmitted as an RRC message to the WTRU to perform the handover). The source gNB may trigger a user-to-user (Uu) handover, for example, by sending an RRCReconfiguration message to the WTRU. For example, the RRCReconfiguration message may include specific information for accessing the target cell, such as: a target cell identifier (ID), a new cell radio network temporary identifier (C-RNTI), and / or a target gNB security algorithm identifier for the selected security algorithm. In addition, or alternatively, the RRCReconfiguration message may include: a set of dedicated random access channel (RACH) resources, an association between RACH resources and synchronization signal blocks (SSBs), an association between RACH resources and WTRU-specific channel state information reference signal (CSI-RS) configurations, common RACH resources, system information (SI) of the target cell, etc. Summary of the invention

[0004] A wireless transmit receive unit (WTRU) may receive configuration information including a conditional handover (CHO) configuration from a network node. The terms "user equipment (UE)" and "WTRU" may be used interchangeably herein. For example, a CHO configuration may be associated with a trigger and a target cell. The CHO may include an indication of one or more of: an identifier of the target cell; an identifier of a source configuration; and / or an identifier of an additional configuration. The trigger may include a handover (HO) command and / or a measurement event. The WTRU may determine that the trigger associated with the CHO configuration is satisfied. For example, if the trigger is a HO command, when the WTRU (e.g., from the target cell) receives the HO command, the WTRU may determine that the trigger is satisfied. In response to determining that the trigger is satisfied, the WTRU may initiate a CHO with the target cell. For example, the CHO may be initiated via a random access channel (RACH) process. In addition, or alternatively, the CHO may be initiated via a RACH-free process.

[0005] An example method for reliable mobility may be performed by a WTRU. The method may include receiving configuration information for transitioning from a source cell to at least one target cell. The configuration information may include at least one parameter associated with the transition. The WTRU may send an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell. The WTRU may receive signaling including information associated with the transition to the first target cell. The signaling may include at least one value of the at least one parameter associated with the transition. The WTRU may use the at least one value of the at least one parameter associated with the transition to transition to the first target cell. The configuration information may be received via radio resource control (RRC) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be sent via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof. The at least one parameter may include at least one of the following: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof. The signaling including information associated with the transition to the first target cell may be received via a medium access control (MAC) control element (CE). The signaling including information associated with the transition to the first target cell may be received via downlink control information (DCI) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be sent via a channel state information (CSI) report.

[0006] An example WTRU configured for reliable mobility may include a transceiver and a processor. The processor may be configured to receive, via the transceiver, configuration information for transitioning from a source cell to at least one target cell. The configuration information may include at least one parameter associated with the transition. The processor may be configured to send, via the transceiver, an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell. The processor may be configured to receive, via the transceiver, signaling including information associated with the transition to the first target cell. The signaling may include at least one value of the at least one parameter associated with the transition. The processor may be configured to transition to the first target cell using the at least one value of the at least one parameter associated with the transition. The configuration information may be received via radio resource control (RRC) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be sent via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof. The at least one parameter may include at least one of the following: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof. The signaling including information associated with the transition to the first target cell may be received via a medium access control (MAC) control element (CE). The signaling including information associated with the transition to the first target cell may be received via downlink control information (DCI) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be sent via a channel state information (CSI) report.

[0007] An example network node for implementing reliable mobility may include a transceiver and a processor. The processor may be configured to transmit configuration information for transitioning from a source cell to at least one target cell via the transceiver. The configuration information may include at least one parameter associated with the transition. The processor may be configured to receive an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell via the transceiver. The processor may be configured to transmit signaling including information associated with the transition to the first target cell via the transceiver. The signaling may include at least one value of the at least one parameter associated with the transition. The configuration information may be transmitted via radio resource control (RRC) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be received via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof. The at least one parameter may include at least one of the following: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof. The signaling including information associated with the transition to the first target cell may be transmitted via a medium access control (MAC) control element (CE). The signaling including information associated with the transition to the first target cell may be transmitted via downlink control information (DCI) signaling. The indication of the one or more measurements associated with the source cell and the first target cell may be received via a channel state information (CSI) report. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0009] Figure 1B is an example of an embodiment in which Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within an illustrated communication system;

[0010] Figure 1C is an example of an embodiment in which Figure 1A A system diagram of an example Radio Access Network (RAN) and an example Core Network (CN) used within the illustrated communication system;

[0011] Figure 1D is an example of an embodiment in which Figure 1A A system diagram of another example RAN and another example CN used within the illustrated communication system;

[0012] Figure 2 A sample handover is illustrated;

[0013] Figure 3 An example conditional handover (CHO) is illustrated;

[0014] Figure 4 Example layer 1 / layer 2 (L1 / L2) inter-cell mobility is illustrated;

[0015] Figure 5 illustrates an example transition configuration; and / or

[0016] Figure 6 An example of updating / changing the primary cell (PCell) of a WTRU is illustrated. DETAILED DESCRIPTION

[0017] 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.

[0018] 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 a user equipment (WTRU), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a WTRU.

[0019] 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.

[0020] 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.

[0021] 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).

[0022] 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, among others. 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).

[0023] 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), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0024] 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).

[0025] 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).

[0026] 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).

[0027] 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 local areas such as commercial venues, homes, vehicles, campuses, industrial facilities, sky corridors (e.g., for use by drones), and roads. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0028] 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 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0037] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to the 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.

[0038] 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.

[0039] 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, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device and activity tracker, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geolocation sensor; altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor and / or humidity sensor.

[0040] 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 signal processing performed by hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via the processor 118). In an embodiment, the WTRU 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0050] In a representative embodiment, the other network 112 may be a WLAN.

[0051] 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 out of the BSS. Traffic originating from outside the BSS to a STA may be reached by the AP and may be delivered to the STA. Traffic originating from a STA to a destination outside the BSS may be transmitted to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Direct link establishment (DLS) may be utilized to transmit point-to-point traffic between a source STA and a destination STA (e.g., directly between them). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0052] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0053] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0054] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be sent by the transmitter STA. At the receiver of the receiver STA, the operations for the 80+80 configuration described above can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0055] 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).

[0056] 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) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is sending to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0057] 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.

[0058] 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.

[0059] 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, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or the gNB 180c).

[0060] 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 transmit time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0061] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility 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 eNode-B 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 eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may serve as a mobility anchor point 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.

[0062] 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.

[0063] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0064] 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 and mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, 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.

[0065] 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, and providing downlink data notifications. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0066] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring, etc.

[0067] 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.

[0068] 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 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 may be used to test other devices and / or simulate network and / or WTRU functions.

[0069] 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.

[0070] 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 can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0071] As used herein, a network node may include any suitable network entity, such as, for example, a base station, a base transceiver station (BTS), a Node B, an evolved Node B, a Home Node B, a Home evolved Node B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, a relay node, an access control and mobility management function (AMF), a source node or a target node, the like, or any suitable combination thereof.

[0072] Figure 2 An example handover process in a network (e.g., NR) is illustrated. One or more of the following may apply. The WTRU (e.g., WTRU 102) context within the source gNB (e.g., gNB 202) may contain information about roaming and access restrictions, which may be provided at connection establishment or at RA (Registration Area) update in step 206. The source gNB 202 may configure the WTRU 102 (in Figure 2104), and at step 208, the WTRU 102 may transmit a report according to the measurement configuration. At step 210, the source gNB 202 may determine to hand over the WTRU 102 based on the received measurements. At step 212, the source gNB 202 may send a handover request message to the target gNB 204, conveying, for example, a transparent RRC container that may include information for preparing the handover on the target side. For example, the information may include one or more of the following: target cell ID, generated 5G NR key (KgNB), C-RNTI of the WTRU in the source gNB, radio resource management (RRM) configuration including WTRU inactivity time, basic access stratum (AS) configuration including antenna information and downlink (DL) carrier frequency, current quality of service (QoS) flow to data radio bearer (DRB) mapping rules applied to the WTRU, system information B1 (SIB1) from the source gNB, WTRU capabilities for different radio access technologies (RATs), protocol data unit (PDU) session related information and / or measurement information reported by the WTRU (e.g., including beam related information if available). Admission control may be performed by the target gNB 204 at step 214. If the WTRU 012 can be admitted, the target gNB 204 may prepare for handover (e.g., using L1 / L2) and send a handover request confirm message to the source gNB 202 at step 216. The handover request confirmation message may include, for example, a transparent RRC container (e.g., to be transmitted to the WTRU 102 as an RRC message to perform the handover). At step 218, the source gNB 202 may trigger the Uu handover, for example, by sending an RRCReconfiguration message to the WTRU 102. For example, the RRCReconfiguration message may include specific information for accessing the target cell, such as: a target cell ID, a new C-RNTI and / or a target gNB security algorithm identifier for a selected security algorithm. In addition, or alternatively, the RRCReconfiguration message may 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, system information (SI) of the target cell, etc.

[0073] like Figure 2As shown, a source network node (such as source gNB 202) may send a secondary node (SN) state transfer message to a target network node (such as target gNB 204). For example, the SN state transfer message may include an indication of an uplink packet data convergence protocol (PDCP) SN receiver state and / or a downlink PDCP SN transmitter state for a DRB for which the PDCP state reservation is applicable (e.g., for radio link control (RLC) acknowledged mode (AM)). At step 220, the source gNB may deliver buffered data and new data from the UPF to the WTRU. At step 224, the WTRU 102 may synchronize with the target cell and complete the RRC handover process at step 228, for example, by transmitting an RRCReconfigurationComplete message to the target gNB 204. At step 226, the target gNB may buffer user data received from the source gNB. At step 230, the target gNB 204 may send a path switch request message to a network node, such as an access control and mobility management function (AMF) 205, for example, to trigger the network (e.g., 5G core network (5GC)) to switch the DL data path towards the target gNB 204 and / or establish a new generation core (NG-C) interface instance towards the target gNB 204. The 5GC may switch the DL data path towards the target gNB 204. At step 232, a user plane function (UPF) may send one or more end marker packets on the old path to the source gNB 202 (e.g., on a per protocol data unit (PDU) session / tunnel basis). The UPF may release any user plane / TNL (transport network layer) resources towards the source gNB 202. At step 234, the AMF 205 may acknowledge the path switch request message with a path switch request acknowledgement message. At step 236, upon receiving the Path Switch Request Ack message from the AMF 205, the target gNB 204 may transmit a Context Release to the WTRU to notify the source gNB 202 of the handover success. The source gNB 202 may then release the radio and control plane related resources associated with the WTRU context. Any ongoing data forwarding may continue.

[0074] Some networks (e.g., NR) may perform conditional handover (CHO) and conditional primary and secondary serving cell (PSCell) change (CPC). One or more of the following may apply. Some networks may have implemented CHO and / or CPC / conditional PSCell addition (CPA) that may be used to reduce the likelihood of radio link failure (RLF) and / or handover failure (HOF). CHO and CPA / CPAC may be collectively referred to as CPAC.

[0075] In some networks (e.g., legacy LTE / NR), handover may be triggered by a measurement report. However, the network may not be prevented from transmitting a HO command to the WTRU (e.g., even in the absence of a measurement report). For example, the WTRU may be configured with an A3 event that triggers a measurement report to be transmitted when the radio signal level / quality (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), etc.) of a neighboring cell becomes better than the radio signal level / quality of a primary serving cell (PCell) or a primary secondary serving cell (PSCell) (e.g., in the case of dual connectivity (DC)). The WTRU may monitor the serving cell and the neighboring cells and may transmit a measurement report when conditions are met (e.g., when the radio signal level / quality of a neighboring cell becomes better than the radio signal level / quality of a PCell and / or a PSCell). Upon receiving such a report, the network (e.g., the current serving node / cell) may prepare and send a HO command (e.g., an RRC ReConfiguration message including reconfigurationWithSync) to the WTRU. In response to receiving the HO command, the WTRU may (eg, immediately) perform the HO and connect to the target cell.

[0076] However, CHO may be different from the scenarios described above. One or more of the following may apply. In a network implementing CHO, multiple handover targets may be prepared (e.g., compared to only one target in other implementations). In a network implementing CHO, the WTRU may not perform (e.g., immediately) CHO. Instead, the WTRU may be configured with a trigger condition (e.g., a set of radio conditions), and when / if the trigger condition is met, the WTRU may perform a handover towards one of the targets.

[0077] The CHO command may be transmitted when, for example, the radio conditions towards the current serving cell are still good, which may reduce (e.g., two) major failure points. For example, the major failure points may include a failure to transmit a measurement report (e.g., if the link quality to the current serving cell drops below an acceptable level when the measurement report is triggered in a normal handover), and / or a failure to receive a handover command (e.g., if the link quality to the current serving cell drops below an acceptable level after the WTRU has transmitted a measurement report but before it has received a HO command).

[0078] The trigger conditions for CHO may also or alternatively be based on the radio quality of the serving cell and the neighboring cells (e.g., similar to the conditions used in traditional NR / LTE for triggering measurement reports). For example, the WTRU may be configured with CHO and an associated HO command associated with an A3-like trigger condition. The WTRU may monitor the current cell and the serving cell, and when the A3 trigger condition is met, the WTRU may execute the associated HO command and switch its connection towards the target cell (e.g., instead of transmitting a measurement report).

[0079] Figure 3 An example CHO configuration and execution is illustrated. At step 304, a source node (e.g., a gNB) may transmit a CHO request (e.g., a handover request message) to one or more target nodes (e.g., gNBs). At step 306, the target node may transmit a CHO request ACK (e.g., in the handover request ACK, including a transparent container that includes an RRCReconfiguration). At step 302, the source gNB may send a CHO configuration to the WTRU (e.g., sending an RRCReconfiguration to the WTRU, thereby providing the target gNB configuration to be applied when performing CHO, and the conditions to be met, such as measurement events A3 / A5). At step 308, the WTRU may monitor the CHO conditions for the target cell (e.g., performing radio quality measurements and evaluating configured events). At step 310, if the conditions are met, the WTRU may perform a HO (e.g., applying the target gNB configuration once the event criteria are met). At step 312, the WTRU may send a CHO configuration to the target node (e.g., RRCReconfigurationComplete). At step 314, the target node may detect that the handover is complete (e.g., based on receipt of an RRCReconfigurationComplete message), perform the NGAP path switching process, and trigger the release of the WTRU context in the source gNB.

[0080] CHO may be used to prevent unnecessary reestablishment (e.g., in the event of a radio link failure). As described herein, a WTRU may be configured with one or more CHO targets. If the WTRU experiences RLF before a trigger condition for any of the targets is met, the WTRU may, for example, directly execute a HO command associated with a target cell (e.g., a target cell for which it is prepared) instead of continuing with a full reestablishment procedure. However, in other networks (e.g., legacy LTE / NR), an RRC reestablishment procedure may be initiated, which may result in an interruption time for the WTRU's bearers.

[0081] In dual connectivity (DC) scenarios, CPC and CPA may be considered as extensions of CHO.The WTRU may be configured with trigger conditions for PSCell change or addition, and when the trigger conditions are met, the WTRU may execute the associated PSCell change command or PSCell add command.

[0082] Inter-cell beam management and / or inter-cell L1 / L2 mobility may be performed. One or more of the following may apply. In some networks (e.g., NR R17), inter-cell L1 / L2 mobility may be used for beam management (e.g., in carrier aggregation (CA)). However, cell changes / additions may not be supported.

[0083] In certain networks (e.g., NR R18), it may be useful to specify mechanisms and procedures for L1 / L2-based inter-cell mobility for mobility latency reduction. One or more of the following may apply. Configuration and maintenance for multiple candidate cells may be specified to allow configuration for candidate cells (e.g., RAN2, RAN3) to be quickly applied. A dynamic switching mechanism (e.g., between candidate serving cells including SpCells and SCells) may be specified and / or may be applicable to certain scenarios based on L1 / L2 signaling (e.g., RAN2, RAN1). L1 enhancements for inter-cell beam management may be specified, including L1 measurements and reporting and beam indications (e.g., RAN1, RAN2). For example, RAN2 may be involved, for example, to further clarify the interaction between L1 enhancements for inter-cell beam management and dynamic switching mechanisms between candidate serving cells. Timing advance management may be specified (e.g., RAN1, RAN2). Centralized unit-data unit (CU-DU) interface signaling may be specified to support L1 / L2 mobility (e.g., RAN3, where necessary). For example, frequency range 2 (FR2) specific enhancements may not be excluded. In addition, or alternatively, procedures for L1 / L2-based inter-cell mobility may be defined for one or more of the following scenarios: standalone scenarios; CA and NR-DC scenarios (e.g., there is a serving cell change within a cell group (CG)); intra-DU scenarios and intra-distributed unit (DU) scenarios within a centralized unit (CU) (e.g., which may apply to standalone and CA); intra-frequency scenarios and inter-frequency scenarios; frequency range 1 (FR1) scenarios and FR2 scenarios; and / or scenarios where the source cell and the target cell are synchronized or asynchronous. Inter-CU scenarios may not be included.

[0084] L1 / L2-based mobility may be supported in certain networks (e.g., 5G R17). For example, (e.g., in R17) inter-cell beam management may handle intra-DU scenarios and intra-frequency scenarios. In this case, the serving cell may remain unchanged (e.g., if it is not possible to change the serving cell using L1 / L2-based mobility). In FR2 deployments, CA may be used to utilize available bandwidth, for example, to aggregate one or more (e.g., multiple) component carriers (CCs) in (e.g., one) frequency band. These CCs may be transmitted using analog beam pairs (e.g., the same analog beam pair, such as a gNB beam and a WTRU beam). The WTRU may be configured with one or more (e.g., 64) transmission configuration indicator (TCI) states for receiving a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH). Each TCI state may include / associated with a reference signal (RS) or synchronization signal and a physical broadcast control channel block (SSB) that the WTRU may reference, for example, for setting its beam. The SSB may be associated with a non-serving physical cell ID (PCI). Medium access control (MAC) signaling (e.g., TCI state indication for WTRU-specific PDCCH MAC control element (CE)) may be used to activate the TCI state for a given coreset / PDCCH. Receipt of PDCCH transmissions from non-serving cells may be supported by indicating a MAC CE for the TCI state associated with the non-serving PCI. MAC signaling (e.g., "TCI state activation / deactivation for WTRU-specific PDSCH") may be used to activate a subset of TCI states (e.g., up to 8 TCI states) in the TCI state for PDSCH reception. Downlink control information (DCI) may be used to indicate a subset of TCI states for PDSCH reception. "Unified TCI state" associated with different update mechanisms (e.g., DCI-based update mechanisms) may be supported. Multi-TRP technology (e.g., unified TCI state with multiple TRPs) may be supported in certain networks (e.g., 5G R18).

[0085] L1 / L2 inter-cell mobility may be used to improve handover latency (e.g., compared to conventional L3 handover or CHO). One or more of the following may apply. The WTRU may transmit (e.g., may transmit first) a measurement report (e.g., using RRC signaling). In response to the measurement report, the network may provide additional measurement configurations and / or CHO configurations. However, in other scenarios, the network may provide a configuration indicating a target cell (e.g., after the WTRU reports using RRC signaling that the cell meets configured radio quality criteria). In such scenarios, the WTRU may delay transmitting the measurement report (e.g., in order to reduce the handover failure rate) until the WTRU receives an RRC reconfiguration from the network indicating the target cell configuration and / or measurement criteria, which may be used to determine when the WTRU should trigger the CHO configuration. However, in any of the above scenarios, there may be a certain amount of delay (e.g., due to the transmission of the measurement report and the reception of the target configuration, e.g., in the case of a conventional (non-conditional) handover).

[0086] L1 / L2-based inter-cell mobility can be used to allow configurations for candidate cells to be quickly applied, including, for example, dynamic switching between a secondary cell (SCell) and a primary cell (PCell) (e.g., switching roles between SCell and PCell) without performing RRC signaling. In some networks (e.g., 5G R18), inter-CU scenarios may not be supported, for example, because the PDCP anchor point may (e.g., may need to) be relocated. RRC-based methods that support inter-CU handovers may be provided. In addition, or alternatively, L1 / L2 can be used to allow CA operations to be enabled (e.g., immediately enabled when the serving cell changes).

[0087] Figure 4 Example L1 / L2 inter-cell mobility operations using CA are illustrated. Figure 4 As shown, the candidate cell group can be configured through RRC, and the dynamic switching between PCell and SCell can be achieved using L1 / L2 signaling.

[0088] A RACH-less handover may be performed. One or more of the following may apply. A RACH-less handover may be used (e.g., as used by E-UTRA systems in R14) to reduce mobility interruption time. The target eNB may indicate the uplink timing to be used for the target cell in the handover command. The target eNB may also or alternatively provide a pre-allocated uplink grant for sending a handover complete message.

[0089] Radio link monitoring may be performed. One or more of the following may be applied. For example, the WTRU may perform radio link monitoring (RLM) at the SpCell to maintain the radio link. Certain techniques may be used to indicate desynchronization errors (e.g., physical layer problems) and / or synchronization errors associated with the radio link. Certain techniques may be used to declare a radio link failure (RLF) and / or recover physical layer problems. The WTRU may monitor the downlink radio link quality, for example based on a reference signal configured as an RLM-RS resource, to determine the downlink radio link quality of the PCell and PSCell. The configured RLM-RS resources may include one or more SSBs, one or more CSI-RSs, and / or a mixture of SSBs and CSI-RSs. For example, the WTRU may not need to perform RLM outside of an active DL BWP.

[0090] The WTRU may evaluate whether the downlink radio link quality on the configured RLM-RS resources is less than a threshold value (e.g., Qout_SSB), the configured RLM-RS resources being estimated during an evaluation time (e.g., TEvaluate_out_SSB ms). The WTRU may also or alternatively evaluate whether the downlink radio link quality on the configured RLM-RS resources is greater than another threshold value (e.g., Qin_SSB), the configured RLM-RS resources being estimated during another evaluation time (e.g., within TEvaluate_in_SSB[ms]).

[0091] The WTRU may detect an out-of-sync error associated with a radio link. One or more of the following may apply. Upon receiving a certain number (e.g., N310) of consecutive "out-of-sync" indications for a SpCell (e.g., from a lower layer when the T300, T301, T304, T311, and T319 timers are not running), the WTRU may start a timer (e.g., T310) for the corresponding SpCell.

[0092] The WTRU may recover from certain physical layer problems. One or more of the following may apply. Upon receiving a certain number (e.g., N310) of consecutive "out of sync" indications for a SpCell (e.g., from a lower layer while a T310 timer is running), the WTRU may stop the timer (e.g., T310) for the corresponding SpCell. The WTRU may maintain the RRC connection, for example, without requiring explicit signaling (e.g., the WTRU maintains the entire radio resource configuration). For example, a period of time during which L1 reports neither "in sync" nor "out of sync" may not affect the evaluation of the certain number of consecutive "in sync" or "out of sync" indications.

[0093] The WTRU may declare RLF upon expiration of a timer (eg, T310).

[0094] If the WTRU changes its PCell while the WTRU is in connected mode, the WTRU may determine (e.g., may need to determine) a timing advance for uplink transmissions in the updated PCell (e.g., the target PCell) and receive PDCCH transmissions (e.g., with increased reliability). However, such a procedure is not yet provided when performing a PCell change as part of L1 / L2 mobility.

[0095] Techniques associated with changing PCell as part of L1 / L2 mobility are described herein. One or more of the following may apply. The WTRU may determine the best quality cell, for example, based on neighbor cell measurements and / or serving cell measurements. The WTRU may report the best quality cell, for example, via uplink signaling (e.g., uplink MAC CE), which may be used to indicate information of candidate target cells (e.g., PCI, CGI, and / or frequency of the cell).

[0096] The WTRU may synchronize to / with the target cell and may start monitoring the PDCCH of the reported candidate target cell. The WTRU may wait for a PDCCH instruction associated with a HO command (e.g., or a MAC CE indicating a HO command) from the gNB.

[0097] The WTRU may receive a PDCCH instruction associated with a HO command from a candidate target cell. The PDCCH instruction associated with the HO command may be used to command the WTRU to perform a HO from a current serving cell (e.g., SpCell) to another cell. For example, the WTRU may receive a PDCCH instruction associated with the HO command. In addition, or alternatively, the WTRU may receive a MAC CE associated with the HO command from the current serving cell. The MAC CE associated with the HO command may indicate target cell information, wherein the WTRU may perform a HO from the current serving cell to a given target cell.

[0098] The WTRU may receive configuration information including a conditional handover (CHO) configuration. For example, the CHO configuration may be associated with a trigger and a target cell. The CHO may include an indication of one or more of: an identifier of the target cell; an identifier of the source configuration; and / or an identifier of an additional configuration. The trigger may include a handover (HO) command and / or a measurement event. The WTRU may determine that the trigger associated with the CHO configuration is satisfied. For example, if the trigger is a HO command, when the WTRU (e.g., from the target cell) receives the HO command, the WTRU may determine that the trigger is satisfied. In response to determining that the trigger is satisfied, the WTRU may initiate a CHO with the target cell. For example, the CHO may be initiated via a random access channel (RACH) procedure. In addition, or alternatively, the CHO may be initiated via a RACH-free procedure.

[0099] A framework associated with L1 / L2 mobility may be provided. For example, the WTRU may be configured with CHO and / or mobility triggers. One or more of the following may apply. The WTRU may receive and optionally store a set of one or more conditional configurations, for example, via RRC signaling. At any given time, at least one of the conditional configurations may be active (e.g., or "serving"), and the remaining configurations may be stored but inactive (e.g., "non-serving"). In certain scenarios, there may be (e.g., at most one) conditional configuration that is in an "active" state, and such conditional configuration may be referred to as an "active configuration" (e.g., or "serving configuration").

[0100] The conditional configuration may include a subset of RRC parameters (e.g., all RRC parameters) that the WTRU uses to operate in connected mode. If, for example, a specific condition or mobility trigger is met, the WTRU may change the state of (e.g., at least one) conditional configuration from "inactive" to "active" (e.g., or vice versa). For example, the condition or mobility trigger may include one or more of the following. If the WTRU receives an indication from a MAC control element (e.g., or DCI) that a first "active" configuration is to be changed to "inactive" and a second "inactive" configuration is to be changed to "active", the WTRU may change the state of the conditional configuration from "inactive" to "active". If the WTRU determines that a measurement event is triggered in an active configuration, the WTRU may change the state of the conditional configuration from "inactive" to "active". For example, the measurement event may be associated with changing the first "active" configuration to "inactive" and changing the second "inactive" configuration to "active". In addition, or alternatively, if the first configuration and the second configuration have different PCells, the WTRU may change / update its PCell accordingly.

[0101] As described herein, when the WTRU performs such a state change for (e.g., at least one) conditional configuration, the currently active conditional configuration may be referred to as the "source" configuration before the change, and the conditional configuration active after the change may be referred to as the "target" configuration. Similarly, the source PCell and the target PCell may refer to the PCell in the corresponding source configuration and target configuration. As described herein, the process for changing / updating the PCell may be referred to as a change of active configuration and / or a handover (HO) command.

[0102] The WTRU may receive an additional configuration (e.g., a transition configuration). The transition configuration may, for example, be specific to a change of an active configuration from a first configuration to a second configuration. For example, the transition configuration may be defined using one or more of: an identification of a source configuration; an identification of a target configuration; and / or an identification of an additional configuration (e.g., for at least one additional configuration, the additional configuration may be applicable when the WTRU changes the active configuration from the source to the target).

[0103] As described herein, the additional configuration may include one or more of: a measurement event, a measurement object, and / or a measurement configuration; a process type for the transition (e.g., a random access process or a RACH-free process); one or more parameters or resources for performing the process (e.g., one or more dedicated preambles, preconfigured grants, scheduling request resources, etc.); and / or (e.g., at least one) security parameter (e.g., KgNB).

[0104] The transition configuration may be implemented by associated identification of the source configuration, the target configuration, and / or the additional configuration. Additionally or alternatively, if, for example, the conditional configuration is the target configuration, each conditional configuration may include (e.g., one) transition configuration for each possible source configuration. Additionally or alternatively, if, for example, the conditional configuration is the source configuration, each conditional configuration may include (e.g., one) transition configuration for each possible target configuration.

[0105] The WTRU may be configured to synchronize to / with a new / updated PCell. One or more of the following may apply. For example, if a change in the active configuration results in a change in the PCell, the WTRU may be configured to synchronize to / with a new / updated PCell. It should be noted that the techniques described herein may also or alternatively be used for changes / updates of the WTRU's PSCell.

[0106] The WTRU may use a RACH-free procedure to update / change its PCell. One or more of the following may apply. For example, if the WTRU is initiating a change to an active configuration, the WTRU may determine that a RACH-free procedure is applicable. The RACH-free procedure may be initiated in response to receiving signaling (e.g., a HO command) in the source PCell.

[0107] The WTRU may initiate the procedure after receiving signaling (e.g., such as a MAC CE or DCI indicating a change in the active configuration, such as a HO command). After receiving the MAC CE, the WTRU may initiate receiving the PDCCH in the target PCell (e.g., using the configuration provided for performing the RACH-less procedure). For example, the WTRU may monitor the PDCCH in the target PCell in the search space and using the C-RNTI (e.g., the C-RNTI configured for the RACH-less procedure).

[0108] The WTRU may initiate the transmission of a MAC CE, for example, to indicate that the WTRU has performed a handover in the target configuration. The MAC CE may, for example, include: a WTRU identity (e.g., in the source cell and / or the target cell); and / or a reference to a MAC CE that has triggered the HO command. Such a reference may consist of an identifier included in the HO command. For the transmission of the MAC CE, the WTRU may utilize a configured grant (CG) resource that may be provided for a RACH-free procedure, or a dynamic grant received from the PDCCH. The WTRU may also initiate a scheduling request procedure using a scheduling request (SR) resource provided for a RACH-free procedure. The WTRU may also receive a MAC CE or DCI confirming the completion of the handover. In some cases (e.g., if the WTRU is provided with a configured grant for sending a MAC CE indicating the execution of the handover), the WTRU may also or alternatively expect a MAC CE or DCI. The WTRU may start a timer at the initial transmission of the PUSCH containing the MAC CE, and stop the timer upon receipt of the MAC CE or DCI. If the timer expires (eg, or if a scheduling request failure occurs), the WTRU may determine that the handover has failed and perform actions accordingly.

[0109] The PDCCH resources, CG resources and / or SR resources provided for the RACH-free process may be valid for a period of time (e.g., a limited duration after initiating the process). For example, the time period may also or alternatively be configured as part of the RACH-free configuration.

[0110] A RACH-free process for updating / changing the PCell of the WTRU may be initiated by a measurement event. One or more of the following may apply. When a measurement event is triggered, the WTRU may initiate a RACH-free process. The WTRU may transmit a measurement report in the source PCell (e.g., via RRC or using a MAC CE). The WTRU may then monitor (e.g., receive) the PDCCH in the target PCell as described herein. The WTRU may continue to receive the PDCCH in the source PCell. The WTRU may initiate reception of the PDCCH in the target PCell, for example, upon expiration of a timer. For example, the timer may be started when a PUSCH including a MAC CE is sent (e.g., or resent). The value of the timer may be predefined or configured, for example, by RRC. For example, the timer may be used to provide the network with an opportunity to request a HARQ retransmission of a PUSCH including a MAC CE (e.g., if the initial transmission is not successfully detected).

[0111] The RACH-free process for updating / changing the PCell of the WTRU may be initiated by a HO command and / or a confirmation by the target cell. One or more of the following may apply. The WTRU may receive signaling including a HO command and / or a confirmation of the HO, such as a DCI or MAC CE in the target cell. The WTRU may stop receiving / monitoring the PDCCH in the source cell. The WTRU may also or alternatively initiate the sending of a MAC CE, which may be used to confirm the completion of the process. For example, when initiating the reception of the PDCCH in the target PCell, the WTRU may start a timer (e.g., a supervision timer). The WTRU may stop the timer, for example, in response to receiving a DCI or MAC CE. If the timer expires, the WTRU may determine that the handover has failed and perform actions accordingly.

[0112] In certain scenarios, a HO failure may occur. One or more of the following may apply. If the WTRU determines that the HO procedure has failed, the WTRU may interrupt reception of PDCCH in the target cell and resume reception of PDCCH in the source cell (e.g., if PDCCH monitoring in the source cell has been stopped). The WTRU may initiate transmission of a MAC CE, which may be used to indicate a HO failure.

[0113] The WTRU may determine the type of transition procedure. One or more of the following may apply. As part of a change in active configuration, the WTRU may determine (e.g., may first determine) the type of transition procedure to be performed. The type of transition procedure may include one or more of the following: a random access procedure (e.g., 4 steps or 2 steps); and / or a RACH-less procedure (e.g., with or without make-before-break).

[0114] The WTRU may obtain resources for a transition procedure. One or more of the following may apply. The WTRU may (e.g., after determining the type of transition procedure to be performed) obtain resources and / or parameters associated with the type of transition procedure (e.g., random access resources or RACH-free resources). For example, these resources may include: a common RACH configuration (e.g., RACH-ConfigCommon or RACH-ConfigCommonTwoStepRA); a dedicated RACH configuration (e.g., RACH-ConfigDedicated); a PDCCH configuration of the target PCell (e.g., including a search space); a PUCCH and / or PUSCH configuration of the target PCell; an initial bandwidth part (BWP) of the target PCell; a configured grant configuration (e.g., for an initial transmission in the target PCell); a scheduling request (SR) resource for an initial transmission in the target PCell; an indication of a timing advance adjustment; an indication of whether to apply zero timing advance; and / or (e.g., at least one) RNTI (e.g., C-RNTI).

[0115] When changing the active configuration from a source configuration to a target configuration, the WTRU may determine the type of transition procedure and / or associated resources based on parameters included in the corresponding configuration. One or more of the following may apply. For example, each configuration may include a "timing advance group" identifier. If, for example, the timing advance group identifiers associated with the source configuration and the target configuration are different, the WTRU may perform a random access procedure. For example, if the timing advance group identifiers of the source and target are the same (e.g., or equal), the WTRU may perform a RACH-free procedure. If the timing advance group identifiers of the source and target are the same (e.g., or equal), the WTRU may not adjust the timing advance.

[0116] The WTRU may determine the type of transition procedure and / or associated resources based on the target configuration. One or more of the following may apply. For example, if, for example, the type of transition procedure is a random access procedure, such target configuration may indicate an applicable common RACH configuration. For example, such target configuration may indicate that the type of transition procedure is a random access procedure for any change to an active configuration using a given target configuration.

[0117] The WTRU may determine the type of transition procedure and / or associated resources based on the received transition configuration for the applicable combination of the source configuration and the target configuration. For example, applicable timing adjustments, (e.g., at least one configured grant, and / or SR resources (e.g., in the case of a RACH-less procedure)) may be configured as part of the transition configuration for a given combination of the source configuration and the target configuration.

[0118] The WTRU may determine to perform a random access transition procedure based on signaling (e.g., DCI or MAC CE). One or more of the following may apply. Such signaling may, for example, be signaling that triggers a change in an active configuration (e.g., included in the signaling). For example, the WTRU may receive a MAC CE indicating a change in the active configuration. The MAC CE may include a field indicating whether random access is to be performed. In addition, or alternatively, the WTRU may determine whether to perform a random access transition procedure based on the presence of a specific field in the MAC CE. For example, if (e.g., only if) there is a field in the MAC CE indicating a preamble (e.g., or whether a dedicated preamble is used), the WTRU may determine to perform a random access transition procedure.

[0119] The WTRU may determine the resources for the transition process based on signaling (e.g., MAC CE). The WTRU may receive an indication of a set of resources (e.g., configured via RRC) for an applicable target configuration or transition configuration. For example, RRC may be used to configure a set of one or more (e.g., 4) dedicated preambles (e.g., or configured grants, or SR resources) as part of the target configuration. If a change in the active configuration occurs, the WTRU may receive an indication of the applicable dedicated preamble (e.g., or configured grants, or SR resources) via a MAC CE, which may allow for facilitation of resource management for the network (e.g., because it brings flexibility to dynamically assign resources to each WTRU participating in L1 / L2 mobility).

[0120] Figure 5 Example transition configurations are illustrated. In this example, the WTRU has been provided with 4 configurations (e.g., corresponding to 4 cells) and a transition (e.g., temporary or intermediate) configuration to be applied when configuration 3 is to be applied after configuration 4 (e.g., when performing a handover from cell 4 to cell 3).

[0121] Figure 6 An example of updating / changing a WTRU's PCell (eg, or PSCell) is illustrated. At step 602, the WTRU may receive (eg, via RRC) a request for at least one potential target cell (in Figure 6The first signaling may include a first signaling (depicted as cell 1, cell 2 and cell 3 in FIG). The first signaling may be provided by a network node associated with the source cell. The first signaling may include a set of values ​​of at least one resource and / or parameter applicable to the transition to the target cell, such as, for example, a preamble for RACH (regardless of whether the process is a RACH-based process or a RACH-free process), an initial grant in the target cell, a C-RNTI, a timing advance or a beam indication, etc., or any suitable combination thereof. The first signaling may include a set of values ​​associated with at least one resource and / or parameter applicable to the WTRU transitioning from the current cell to the target cell. The set of values ​​may include a single value or multiple values. The parameters may include a preamble for RACH, an initial grant in the target cell, an RNTI, a parameter (or multiple parameters) associated with a RACH-based process, a parameter (or multiple parameters) associated with a RACH-free process and a timing advance, etc., or any suitable combination thereof. Although Figure 6 Three configurations are depicted: Configuration 1, Configuration 2, and Configuration 3 (each including RACH preamble parameters), but the first signaling should not be limited to this. Each configuration may include RACH-based parameters or RACH-free parameters. At step 604, the WTRU may provide an indication of one or more measurements associated with the source cell and the target cell. The WTRU may indicate (e.g., via a MAC CE) that the target cell has become better than the current (source) cell. The indication may be transmitted to a network node associated with the source cell. As shown in FIG. Figure 6 As depicted, the WTRU indicates that cell 2 is better than the current (source) cell. At step 606, the WTRU may receive second signaling (e.g., via a MAC CE). The second signaling may be received from a network node associated with the source cell. The second signaling may include an indication of a handover to the indicated target cell. The second signaling may include an indication of a value (or values) to be used associated with the handover. The value (or values) may be used for a parameter (or parameters) from at least one parameter provided in the first signaling. For example, Figure 6 As depicted, the second signaling includes an indication to switch cell 2 and provides an indication to use specific parameters of configuration 2 provided in the first signaling. Figure 6In the example depiction of , the second signaling indicates the second parameter of configuration 2 (i.e., preamble 5) as provided in the first signaling. Specifically, as depicted, the second signaling includes an indication of 01:5. "01" is a binary value (e.g., from values ​​00, 01, 10, 11) indicating which of the parameters is to be used. Thus, "01" indicates the second parameter value, i.e., preamble 5. At step 608, the WTRU may use the value (or values) indicated for the associated parameter (or parameters) to switch to the target cell. The WTRU may provide an indication to the target cell that a handover is occurring or has occurred. The indication may be provided to a network node associated with the target cell.

[0122] A HO command may be received from the PDCCH of the target cell (e.g., make before break). One or more of the following may apply. To support L1 / L2 inter-cell mobility, the synchronization process towards / with the target cell may be improved. One or more of the following may apply. The WTRU may, for example, perform synchronization towards / with a candidate target cell prior to the HO procedure.

[0123] The WTRU may perform one or more of the following to support make-before-break HO. The WTRU may determine the best quality cell (e.g., based on measurements of neighboring cells and / or measurements of a serving cell). The WTRU may report the best quality cell, for example, via uplink signaling (e.g., uplink MAC CE), which may be used to indicate information of a candidate target cell (e.g., PCI, CGI, and / or frequency of the cell). The WTRU may monitor the PDCCH of the reported candidate target cell. The WTRU may wait for a PDCCH instruction associated with a HO command from the gNB (e.g., or a MAC CE indicating a HO command). The WTRU may receive a PDCCH instruction associated with the HO command from the candidate target cell. The PDCCH instruction associated with the HO command may be used to command / instruct the WTRU to perform a HO from a current serving cell (e.g., SpCell) to a candidate target cell (e.g., where the WTRU may receive a PDCCH instruction associated with the HO command). In addition, or alternatively, the WTRU may receive a MAC CE associated with the HO command, for example, from the current serving cell. The MAC CE associated with the HO command may be used to indicate the target cell information (eg, where the WTRU performs a HO from a current serving cell to a given target cell).

[0124] RLM may be performed at the candidate target cell, for example, using PDCCH monitoring. One or more of the following may apply. When the WTRU monitors the PDCCH of the reported candidate target cell and waits for a PDCCH instruction associated with a HO command from the gNB, the WTRU may perform RLM at the candidate target cell (e.g., as described herein) while the WTRU monitors the PDCCH from the candidate target cell. If the WTRU declares RLF at the candidate target cell, the WTRU may stop monitoring the PDCCH from the candidate target cell.

[0125] A PDCCH monitoring timer may be implemented, for example, to avoid the WTRU permanently monitoring the PDCCH of a candidate target cell. A protection timer may be introduced. When the WTRU starts monitoring the PDCCH of a reported candidate target cell, the WTRU may start the protection timer. The WTRU may continue to monitor the PDCCH until the protection timer expires. The duration of the protection timer may be predefined and / or configured (e.g., by a configurable parameter given via RRC signaling). If the protection timer expires, the WTRU may abort the HO towards the candidate target cell and may stop monitoring the PDCCH at that cell. The HO failure event may be reported to the gNB via uplink signaling (e.g., uplink MAC CE), which may indicate the HO failure event and / or may include candidate target cell information.

[0126] Configurable PDCCH monitoring. One or more of the following may apply. When the WTRU starts monitoring the PDCCH of the reported candidate target cell, the gNB may configure (e.g., explicitly configure) the WTRU with a search space (SS) for the PDCCH instructions associated with the HO command reception. The SS may be similar (e.g., the same as the SS of the candidate target cell in CORESET#0) and / or may be configured separately (e.g., so that the WTRU can monitor a limited / target search space). The PDCCH monitoring configuration for the PDCCH instructions associated with the HO command may also indicate whether the WTRU is to monitor (e.g., only monitor) the PDCCH of the candidate target cell or whether the WTRU is to monitor the PDCCH from the current serving cell and / or the PDCCH from the candidate target cell. The WTRU may indicate whether the WTRU is able to monitor both the PDCCH of the serving cell and the PDCCH of the candidate target cell simultaneously and / or whether the WTRU is able to monitor the PDCCH of the serving cell or the PDCCH of the candidate target cell.

[0127] Link management may be performed. For example, radio link monitoring (RLM) may be performed at the candidate target cell. One or more of the following may apply. The WTRU may determine whether the WTRU has suitable radio conditions at the candidate target cell before the HO process (e.g., to reduce the probability of HO failure). For example, when the WTRU monitors the PDCCH from the candidate target cell, the WTRU may perform RLM at the candidate target cell before the HO process. The gNB may provide the WTRU with an RLM configuration (e.g., IE "RadioLinkMonitoringRS") for each candidate target cell, for example, enabling the WTRU to perform RLM at one or more candidate target cells. For example, the RLM configuration may be provided as part of the measurement configuration.

[0128] If, for example, the WTRU continuously performs RLM at a candidate target cell, the WTRU may drain its battery.Candidate cell RLM may be performed for a limited duration of time (eg, to save the WTRU's battery).

[0129] The battery of the WTRU may be saved. One or more of the following may apply. The WTRU may initiate RLM at a candidate target cell if (e.g., only if) certain conditions are met. For example, the conditions for performing RLM may include: the radio conditions of the current serving cell (e.g., SpCell) are below a certain threshold (e.g., RSRP and / or RSRQ are below a threshold); the radio conditions of the candidate target cell are above a threshold (e.g., RSRP and / or RSRQ of the candidate target cell are above a threshold); and / or the radio conditions of the candidate target cell are determined to be better than the radio conditions of the current serving cell (e.g., SpCell). The WTRU may consider these conditions to be met if (e.g., only if) these conditions are met for a certain amount of time. For example, the amount of time may be predefined and / or configured. If one or more of the conditions are met, the WTRU may initiate / indicate RLF. The WTRU may report the candidate target cells that meet the conditions, for example, through uplink signaling.

[0130] For example, RLM candidate cell reporting may be used to save the WTRU's battery. One or more of the following may apply. If certain conditions (e.g., as described herein) are met, the WTRU may report candidate target cells, e.g., via uplink signaling (e.g., uplink MAC CE).

[0131] The battery of the WTRU may be saved, for example, via an RLM command. One or more of the following may apply. The gNB may transmit a command to the WTRU indicating that the WTRU is to perform RLM at a particular candidate target cell. For example, the command may be delivered via a downlink MAC CE and may include an RLM command indication and a candidate target cell for which the RLM is to be performed. The gNB may determine the content of the RLM command, for example, based on a generated generation report (e.g., as described herein).

[0132] A radio link failure (RLF) may be declared at a candidate target cell (e.g., by the WTRU). One or more of the following may apply. For example, when the WTRU performs RLM at a candidate target cell, the WTRU may declare synchronization and / or out-of-sync. If the WTRU detects a certain number of consecutive out-of-sync indications, the WTRU may declare a radio link failure (RLF) at the candidate target cell and may determine that the candidate target cell is no longer a candidate as the next SpCell. The RLF declaration may be delayed, for example, by a timer (e.g., after detecting a certain number of consecutive out-of-sync indications). If the WTRU detects a certain number of consecutive in-sync indications while the timer is running, the WTRU may determine that the physical layer problem has been handled and stop the timer (e.g., the WTRU no longer declares that an RLF has occurred). The number of consecutive out-of-sync indications, the number of consecutive in-sync indications, and / or the timer may be predefined and / or configured, for example, by RRC signaling (e.g., as part of the RLM configuration for the candidate target cell).

[0133] If the WTRU declares RLF at a candidate target cell, the WTRU may no longer perform RLM at the candidate target cell. The WTRU may report the RLF event to the gNB, for example, via uplink signaling (e.g., uplink MAC CE). For example, the uplink signaling may include information associated with the candidate target cell for which RLF was declared. Similarly, the WTRU may perform beam management at the candidate target cell and / or may determine (e.g., based on the beam management state) whether to continue the HO attempt towards the candidate target cell.

Claims

1. A method performed by a wireless transmit receive unit (WTRU), the method comprising: receiving configuration information for transitioning from a source cell to at least one target cell, the configuration information comprising at least one parameter associated with the transition; sending an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell; receiving signaling comprising information associated with the transition to the first target cell, wherein the signaling comprises at least one value of the at least one parameter associated with the transition; and The at least one value of the at least one parameter associated with the transition is used to transition to the first target cell.

2. The method of claim 1, wherein the configuration information is received via radio resource control (RRC) signaling.

3. The method of claim 1, wherein the indication of the one or more measurements associated with the source cell and the first target cell is sent via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof.

4. The method of claim 1, wherein the at least one parameter comprises at least one of: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof.

5. The method of claim 1, wherein the signaling including information associated with the transition to the first target cell is received via a medium access control (MAC) control element (CE).

6. The method of claim 1, wherein the signaling including information associated with the transition to the first target cell is received via downlink control information (DCI) signaling.

7. The method of claim 1, wherein the indication of the one or more measurements associated with the source cell and the first target cell is sent via a channel state information (CSI) report.

8. A wireless transmit receive unit (WTRU), comprising: Transceiver; and A processor, the processor being configured to: receiving, via the transceiver, configuration information for transitioning from a source cell to at least one target cell, the configuration information comprising at least one parameter associated with the transition; sending, via the transceiver, an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell; receiving, via the transceiver, signaling comprising information associated with the transition to the first target cell, wherein the signaling comprises at least one value of the at least one parameter associated with the transition; and The at least one value of the at least one parameter associated with the transition is used to transition to the first target cell.

9. The WTRU of claim 8, wherein the configuration information is received via radio resource control (RRC) signaling.

10. The WTRU of claim 8, wherein the indication of the one or more measurements associated with the source cell and the first target cell is sent via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof.

11. The WTRU of claim 8, wherein the at least one parameter comprises at least one of: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof.

12. The WTRU of claim 8, wherein the signaling including information associated with the transition to the first target cell is received via a medium access control (MAC) control element (CE).

13. The WTRU of claim 8, wherein the signaling including information associated with the transition to the first target cell is received via downlink control information (DCI) signaling.

14. The WTRU of claim 8, wherein the indication of the one or more measurements associated with the source cell and the first target cell is sent via a channel state information (CSI) report.

15. A network node, comprising: Transceiver; and A processor, the processor being configured to: transmitting, via the transceiver, configuration information for transitioning from a source cell to at least one target cell, the configuration information comprising at least one parameter associated with the transition; receiving, via the transceiver, an indication of one or more measurements associated with the source cell and a first target cell of the at least one target cell; and Signaling including information associated with the transition to the first target cell is transmitted via the transceiver, wherein the signaling includes at least one value of the at least one parameter associated with the transition.

16. The network node of claim 15, wherein the configuration information is transmitted via Radio Resource Control (RRC) signaling.

17. The network node of claim 15, wherein the indication of the one or more measurements associated with the source cell and the first target cell is received via layer 1 (L1) signaling, layer 2 (L2) signaling, or a combination thereof.

18. The network node of claim 15, wherein the at least one parameter comprises at least one of: a random access channel (RACH) preamble, a timing advance, a cell radio network temporary identifier (C-RNTI), an initial grant for the first target cell, a beam indication, or a combination thereof.

19. The network node of claim 15, wherein the signaling including information associated with the transition to the first target cell is transmitted via at least one of: a medium access control (MAC) control element (CE), downlink control information (DCI) signaling, or a combination thereof.

20. The network node of claim 15, wherein the indication of the one or more measurements associated with the source cell and the first target cell is sent via a channel state information (CSI) report.

Images