Method for activating preconfigured cell configuration using medium access control (MAC) control element (CE)

Abstract

A wireless transmit / receive unit (WTRU) is capable of receiving a radio resource control (RRC) message including configuration information. The configuration information can include one or more pre-configured candidate cell configurations. Each of the pre-configured candidate cell configurations can include a special cell (SpCell) configuration, a secondary cell (SCell) configuration, and / or a candidate cell index. The WTRU can receive a medium access control (MAC) control element (CE). The MAC CE can indicate application of a first pre-configured candidate cell configuration of the one or more pre-configured candidate cell configurations and an activation state for each SCell in the first pre-configured candidate cell configuration. The WTRU can initiate a handover to the SpCell in the first pre-configured candidate cell configuration based on the indication in the MAC CE. The WTRU is capable of transmitting data to the SCell activated by the MAC CE.

Description

[0001] This application is a divisional application of patent application number 202380063021.5, filed on August 2, 2023, having the title “Method for activating preconfigured cell configuration using medium access control (MAC) control element (CE)”, the benefit of priority of which is hereby claimed.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 395,072, filed on August 4, 2022, and U.S. Provisional Patent Application No. 63 / 410,404, filed on September 27, 2022, which are hereby incorporated by reference in their entirety. BACKGROUND

[0004] L1 / L2-based mobility can include inter-cell beam management in intra-distributed unit (DU) and intra-frequency scenarios. In this case, the serving cell remains unchanged (e.g., it is not possible to change the serving cell using L1 / 2-based mobility). In frequency range 2 (FR2) deployments, carrier aggregation (CA) can be used to aggregate multiple control channels (CCs) in one frequency band using available bandwidth, for example. The CCs can be transmitted using the same analog beam pair (e.g., gNB beam and / or WTRU beam). A WTRU can be configured with transmission configuration indicator (TCI) states (for receiving physical downlink control channel (PDCCH) and / or physical downlink shared channel (PDSCH). The number of TCI states can be quite large (e.g., 64). Each TCI state can include a reference signal (RS) and / or synchronization signal block (SSB). The WTRU can refer to the TCI to set the beam of the WTRU. The SSB can be associated with a non-serving physical cell identity (PCI). Medium access control (MAC) signaling (e.g., TCI state indication for WTRU-specific PDCCH medium access control (MAC) control element (CE)) can activate the TCI state for Coreset / PDCCH. Receiving PDCCH from a non-serving cell can be supported by a MAC CE indicating a TCI state associated with a non-serving PCI. MAC signaling (e.g., TCI state activation / deactivation for WTRU-specific PDSCH) can activate a subset of (e.g., up to) 8 TCI states for PDSCH reception. DCI can indicate which of the 8 TCI states are activated. In the case of multiple transmission / reception points (TRPs), unified TCI states can be provided with different update mechanisms (e.g., based on DCI). SUMMARY

[0005] Methods and / or apparatuses are provided for activating preconfigured cell configurations using medium access control (MAC) control elements (CEs). The methods and / or apparatuses can provide for L1 / L2 based inter-cell mobility. The methods and apparatuses can provide for a downlink MAC CE for controlling simultaneous special cell (SpCell) and / or secondary cell (Scell) change. The methods and / or apparatuses can provide for a two-stage activation of a serving cell, where an initial command activates target cell measurements and / or a second command activates a handover and / or handoff. The methods and / or apparatuses can provide for network confirmation of a WTRU determined cell set.

[0006] A WTRU can receive a radio resource control (RRC) message including a list of candidate cells. The WTRU can perform one or more handover preparation procedures associated with one or more SCells and / or candidate cells on the list of candidate cells. The one or more handover preparation procedures can include one or more of performing measurements associated with one or more target SpCells, obtaining timing advance information for the one or more target SpCells, and / or starting tracking beams on the one or more target SpCells. The WTRU can receive a MAC CE. The MAC CE can indicate a first SpCell (e.g., a current SpCell) and one or more second SpCells. The first SpCell can be a current SpCell. The one or more second SpCells can be target SpCells. The MAC CE can include one or more target SpCell indexes indicating the one or more second SpCells associated with a handover. The WTRU can monitor one or more handover conditions for the one or more second SpCells. The one or more handover conditions can include one or more of a timer, a measurement threshold, and / or a beam failure detection. The measurement threshold can be associated with radio link monitoring (RLM) measurements. Upon satisfaction of the one or more handover conditions, the WTRU can transmit a reconfiguration complete message to a target SpCell (e.g., of the one or more target SpCells).

[0007] The WTRU can receive Radio Resource Control (RRC) messages that include configuration information. The configuration information may include one or more pre-configured candidate cell configurations. Each pre-configured candidate cell configuration may include one or more of a Special Cell (SpCell) configuration, a Secondary Cell (SCell) configuration, and / or a candidate cell index. The WTRU can receive a Media Access Control (MAC) control element (CE). The MAC CE may indicate the application of a first pre-configured candidate cell configuration among one or more pre-configured candidate cell configurations and the activation status for each SCell in the first pre-configured candidate cell configuration. The WTRU may initiate a handover to an SpCell in the first pre-configured candidate cell configuration based on the reception of the MAC CE. The WTRU may send data to the SCell activated by the MAC CE.

[0008] The WTRU can determine whether to activate the SCell in the first pre-configured candidate cell configuration based on the activation status indicated in the MAC CE.

[0009] The MAC CE may indicate the Transmit Configuration Indicator (TCI) status for one or more cells in a first pre-configured candidate cell configuration. The MAC CE may include flags indicating whether the first pre-configured candidate cell configuration is applied to the Primary Cell Group (MCG) and / or Secondary Cell Group (SCG). The MAC CE may also include flags indicating whether the first pre-configured candidate cell configuration corresponding to a previously reported index is applied.

[0010] The MAC CE can be a first MAC CE. The WTRU can be further configured to receive a second MAC CE that activates a first pre-configured candidate cell configuration indicated in the first MAC CE. The MAC CE can be the first MAC CE. The WTRU can be further configured to receive a second MAC CE, wherein the second MAC CE initiates a target SpCell measurement. The WTRU can be further configured to receive a second MAC CE that indicates which SpCells in the first pre-configured candidate cell configuration will initiate SpCell handover.

[0011] The handover can be a conditional handover to multiple SpCells. A conditional handover can be based on one or more radio quality measurements of multiple SpCells and a first pre-configured candidate cell configuration. Attached Figure Description

[0012] FIG. 1A This is a system diagram illustrating an example communication system that can be implemented in one or more of the disclosed embodiments.

[0013] FIG. 1BThis is an example of what can be achieved according to the implementation plan. FIG. 1A A system diagram of an example wireless transceiver unit (WTRU) used in the illustrated communication system.

[0014] FIG. 1C This is an example of what can be achieved according to the implementation plan. FIG. 1A System diagrams of example radio access networks (RAN) and example core networks (CN) used in the illustrated communication system.

[0015] FIG. 1D This is an example of what can be achieved according to the implementation plan. FIG. 1A A system diagram of another example RAN and another example CN used in the illustrated communication system.

[0016] FIG. 2 An example handover scenario is described.

[0017] FIG. 3 An example of a conditional handover configuration and / or execution process is described.

[0018] FIG. 4 Example L1 / L2 inter-cell mobility operations are described.

[0019] FIG. 5 Example Media Access Control (MAC) Control Element (CE) decoding is depicted.

[0020] FIG. 6 Example operations for handover using MAC CE special cell (SpCell) and secondary cell (SCell) are described.

[0021] FIG. 7 An example MAC CE decoder with additional bits is described.

[0022] FIG. 8 An example MAC CE decoder with an additional octet is described.

[0023] FIG. 9 An example MAC CE decoder with a single octet is depicted.

[0024] FIG. 10 Another example of MAC CE decoding is described.

[0025] FIG. 11 Another example of MAC CE decoding is described. Detailed Implementation

[0026] FIG. 1AThis is a diagram illustrating an example communication system 100 that may implement one or more of the disclosed embodiments. Communication system 100 may be a multiple access system providing content such as voice, data, video, messaging, and broadcasting to multiple wireless users. Communication system 100 enables multiple wireless users to access such content through the sharing of system resources (including wireless bandwidth). For example, 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 Extended OFDM (ZT UW DTS-s OFDM), Unique Word OFDM (UW-OFDM), Resource Block Filtered OFDM, and Filter Bank Multicarrier (FBMC), etc.

[0027] like FIG. 1A As shown, the communication system 100 may include wireless transceiver units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, Public Switched Telephone Network (PSTN) 108, Internet 110, and other networks 112. However, 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, and 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, WTRUs 102a, 102b, 102c, and 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronics devices, and devices operating on commercial and / or industrial wireless networks, etc. Any of WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0028] The communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a and 114b can be any type of device configured to wirelessly interface with one or more of WTRUs 102a, 102b, 102c, and 102d to facilitate access to one or more communication networks (such as CN 106 / 115, Internet 110, and / or other networks 112). By way of example, base stations 114a and 114b can be transceiver base stations (BTS), Node B, evolved Node B, home Node B, home evolved Node B, gNB, NR Node B, site controller, access point (AP), wireless router, etc. Although base stations 114a and 114b are each depicted as a single element, it should be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0029] 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 (BSCs), radio network controllers (RNCs), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive radio signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of radio services to a specific geographic area, which may be relatively fixed or changeable 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. Thus, in one embodiment, base station 114a may include three transceivers, for example, one transceiver per sector of the cell. In embodiments, 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 transmit and / or receive signals in desired spatial directions.

[0030] Base stations 114a and 114b can communicate with one or more of WTRUs 102a, 102b, 102c, and 102d via air interface 116, which can be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). Any suitable radio access technology (RAT) can be used to establish air interface 116.

[0031] More specifically, as noted above, communication system 100 can be a multiple access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, base stations 114a and WTRUs 102a, 102b, and 102c in RAN 104 / 113 can implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which can use Wideband CDMA (WCDMA) to establish air interfaces 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).

[0032] In the implementation scheme, base station 114a and WTRUs 102a, 102b, 102c can implement radio technologies such as evolved UMTS terrestrial radio access (E-UTRA), which can use Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-APro) to establish air interface 116.

[0033] In the implementation scheme, base station 114a and WTRUs 102a, 102b, 102c can implement radio technologies such as NR radio access, which can use New Radio (NR) to establish air interface 116.

[0034] In the implementation scheme, base station 114a and WTRUs 102a, 102b, and 102c can implement various radio access technologies. For example, base station 114a and WTRUs 102a, 102b, and 102c can, for example, use the dual connectivity (DC) principle to implement both LTE and NR radio access. Therefore, the air interface utilized by WTRUs 102a, 102b, and 102c can be characterized by various types of radio access technologies and / or transmissions to / from various types of base stations (e.g., eNBs and gNBs).

[0035] In other implementations, base station 114a and WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (e.g., Wi-Fi), IEEE 802.16 (e.g., WiMAX), CDMA2000, CDMA2000 1X, CDMA2000EV-DO, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rate GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0036] FIG. 1A Base station 114b can be, for example, a wireless router, a home node B, a home evolution node B, or an access point, and can utilize any suitable RAT to facilitate wireless connectivity in local areas such as commercial locations, homes, vehicles, campuses, industrial facilities, air corridors (e.g., for use by drones), and roads. In one embodiment, base station 114b and WTRUs 102c, 102d can implement radio technologies such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, base station 114b and WTRUs 102c, 102d can implement radio technologies such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base station 114b and WTRUs 102c, 102d can utilize cellular-based RATs (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish picocells or femtocells. FIG. 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.

[0037] RAN 104 / 113 can communicate with CN 106 / 115, which can be any type of network configured to provide voice, data, application, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRU 102a, 102b, 102c, and 102d. Data can have different Quality of Service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. CN 106 / 115 can provide call control, billing services, location-based services, prepaid calling, internet connectivity, video distribution, and / or perform advanced security functions such as user authentication. Although not explicitly stated... FIG. 1AAs shown, but it should be understood that RAN 104 / 113 and / or CN106 / 115 can communicate directly or indirectly with other RANs that use the same RAT as RAN 104 / 113 or a different RAT. For example, in addition to being connected to RAN 104 / 113 which can utilize NR radio technology, CN 106 / 115 can also communicate with another RAN (not shown) that uses GSM, UMTS, CDMA2000, WiMAX, E-UTRA or WiFi radio technology.

[0038] CN 106 / 115 may also act as a gateway for WTRU 102a, 102b, 102c, 102d to access PSTN 108, the Internet 110, and / or other networks 112. PSTN 108 may include a circuit-switched telephone network providing Common Old-Style Telephone Service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices using common communication protocols such as Transmit Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) from the TCP / IP Internet Protocol suite. Network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs, which may use the same RAT as RAN 104 / 113 or a different RAT.

[0039] Some or all of the WTRUs 102a, 102b, 102c, and 102d in the communication system 100 may include multi-mode capabilities (e.g., WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). For example, FIG. 1A The WTRU 102c shown can be configured to communicate with a base station 114a that can employ cellular-based radio technology and with a base station 114b that can employ IEEE 802 radio technology.

[0040] FIG. 1B This is a system diagram illustrating the example WTRU 102. For example... FIG. 1B As shown, WTRU 102 may include a processor 118, a transceiver 120, a transmitting / receiving element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138, etc. It should be understood that, while remaining consistent with the implementation, WTRU 102 may include any sub-combination of the foregoing elements.

[0041] Processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. Processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functions that enable WTRU 102 to operate in a wireless environment. Processor 118 may be coupled to transceiver 120, which may be coupled to transmitting / receiving element 122. Although FIG. 1B The processor 118 and transceiver 120 are depicted as separate components, but it should be understood that the processor 118 and transceiver 120 may be integrated together in an electronic package or chip.

[0042] Transmitting / receiving element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via air interface 116. For example, in one embodiment, transmitting / receiving element 122 may be an antenna configured to transmit and / or receive RF signals. In another embodiment, transmitting / receiving element 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, transmitting / receiving element 122 may be configured to transmit and / or receive both RF signals and optical signals. It should be understood that transmitting / receiving element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0043] Although the transmitting / receiving element 122 is in FIG. 1B While depicted as a single element, WTRU 102 may include any number of transmitting / receiving elements 122. More specifically, WTRU 102 may employ MIMO technology. Thus, in one embodiment, WTRU 102 may include two or more transmitting / receiving elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals via air interface 116.

[0044] Transceiver 120 can be configured to modulate signals to be transmitted by transmitting / receiving element 122 and demodulate signals to be received by transmitting / receiving element 122. As noted above, WTRU 102 may have multi-mode capability. For example, transceiver 120 may therefore include multiple transceivers to enable WTRU 102 to communicate via multiple RATs (such as NR and IEEE 802.11).

[0045] The processor 118 of WTRU 102 can be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) unit or an organic light-emitting diode (OLED) display unit) and can receive user input data therefrom. The processor 118 can also output user data to the speaker / microphone 124, keypad 126, and / or display / touchpad 128. Additionally, the processor 118 can access information from any type of suitable memory (such as non-removable memory 130 and / or removable memory 132) and store data in such suitable memory. Non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. Removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, and a secure digital storage (SD) card, etc. In other embodiments, processor 118 may access information from memory that is not physically located on WTRU 102 (such as on a server or home computer (not shown)) and store the data in that memory.

[0046] The processor 118 may receive power from the power supply 134 and may be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry cell battery packs (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, and fuel cells, etc.

[0047] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) about the current location of the WTRU 102. In addition to or instead of the information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) via air interface 116, and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be understood that, while remaining consistent with the implementation, the WTRU 102 may acquire location information using any suitable location determination method.

[0048] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software and / or hardware modules providing additional features, functions, and / or wired or wireless connectivity. For example, peripheral device 138 may include an accelerometer, electronic compass, satellite transceiver, digital camera (for photos and / or video), Universal Serial Bus (USB) port, vibration device, television transceiver, hands-free headset, etc. Modules, FM radio units, digital music players, media players, video game player modules, internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. Peripheral devices 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors; geolocation sensors; altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and / or humidity sensors.

[0049] WTRU 102 may include a full-duplex radio, for which the transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and / or substantially eliminating self-interference through signal processing via hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, WTRU 102 may include a half-duplex radio, for which the transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception) may be concurrent and / or simultaneous.

[0050] FIG. 1C This is a system diagram illustrating RAN 104 and CN 106 according to the implementation scheme. As noted above, RAN 104 can communicate with WTRUs 102a, 102b, and 102c via air interface 116 using E-UTRA radio technology. RAN 104 can also communicate with CN 106.

[0051] RAN 104 may include evolved Node Bs 160a, 160b, and 160c; however, it should be understood that RAN 104 may include any number of evolved Node Bs while remaining consistent with the implementation scheme. Each evolved Node B 160a, 160b, and 160c may include one or more transceivers for communicating with WTRUs 102a, 102b, and 102c via air interface 116. In one implementation, evolved Node Bs 160a, 160b, and 160c may implement MIMO technology. Therefore, evolved Node B 160a may, for example, use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU 102a.

[0052] Each of the evolved nodes B 160a, 160b, and 160c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, and user scheduling in the UL and / or DL, etc. FIG. 1C As shown, evolution nodes B 160a, 160b, and 160c can communicate with each other via the X2 interface.

[0053] FIG. 1C The CN 106 shown 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 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.

[0054] MME 162 can connect to each of the evolved nodes B 162a, 162b, and 162c in RAN 104 via the S1 interface and can act as a control node. For example, MME 162 can be responsible for authenticating users of WTRUs 102a, 102b, and 102c, activating / deactivating bearers, and selecting a specific serving gateway during the initial attachment of WTRUs 102a, 102b, and 102c. MME 162 can provide control plane functions for handover between RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0055] The SGW 164 can connect to each of the evolved Nodes B 160a, 160b, and 160c in RAN 104 via the S1 interface. The SGW 164 typically routes and forwards user data packets to and from WTRUs 102a, 102b, and 102c. The SGW 164 can perform other functions such as anchoring the user plane during handover between evolved Nodes B, triggering paging when DL data is available for WTRUs 102a, 102b, and 102c, and managing and storing the context of WTRUs 102a, 102b, and 102c.

[0056] SGW 164 can be connected to PGW 166, which provides WTRU 102a, 102b, 102c with access to packet-switched networks (such as Internet 110) to facilitate communication between WTRU 102a, 102b, 102c and IP-enabled devices.

[0057] CN 106 can facilitate communication with other networks. For example, CN 106 can provide WTRUs 102a, 102b, and 102c with access to a circuit-switched network (such as PSTN 108) to facilitate communication between WTRUs 102a, 102b, and 102c and traditional landline communication equipment. For example, CN 106 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 106 and PSTN 108, or be able to communicate with such an IP gateway. Furthermore, CN 106 can provide WTRUs 102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0058] Despite WTRU in FIGS. 1A-1D While described as a wireless terminal, it is conceivable that in some representative implementations, such a terminal may (e.g., temporarily or permanently) use a wired communication interface with a communication network.

[0059] In a representative implementation, the other network 112 may be a WLAN.

[0060] A WLAN in Infrastructure Basic Services Set (BSS) mode may have an access point (AP) for the BSS and one or more sites (STAs) associated with that AP. The AP may have an access or 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 outside the BSS destined for a STA can be delivered to the STA via the AP. Traffic originating from a STA destined for an external BSS destination can be transmitted to the AP for delivery to the appropriate destination. Traffic between STAs within the BSS can be transmitted via the AP, for example, where a source STA can transmit traffic to the AP, and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic can be transmitted between a source STA and a destination STA (e.g., directly between them) using Direct Link Establishment (DLS). In some representative implementations, the DLS may use 802.11e DLS or 802.11z Tunneled DLS (TDLS). WLANs using the Standalone BSS (IBSS) mode may not have an access point (AP), and STAs within the IBSS or using the IBSS (e.g., all STAs) can communicate directly with each other. The IBSS communication mode may sometimes be referred to as a "self-organizing" communication mode in this document.

[0061] When operating in 802.11ac infrastructure mode or a similar mode, the AP can transmit beacons on a fixed channel, such as the primary channel. The primary channel can be of fixed width (e.g., a 20 MHz bandwidth) or dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by the STA to establish a connection with the AP. In some representative implementations, such as in an 802.11 system, Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) can be implemented. For CSMA / CA, each STA (including the AP) can listen on the primary channel. If the primary channel is listened to / detected and / or determined to be busy by a particular STA, that particular STA can back off. A single STA (e.g., only one station) can transmit at any given time within a given BSS.

[0062] High-throughput (HT) STAs can communicate using a 40MHz wide channel, for example, by combining a primary 20MHz channel with adjacent or non-adjacent 20MHz channels to form a 40MHz wide channel.

[0063] Very High Throughput (VHT) STAs support channels with widths of 20MHz, 40MHz, 80MHz, and / or 160MHz. 40MHz and / or 80MHz channels can be formed by combining consecutive 20MHz channels. A 160MHz channel can be formed by combining eight consecutive 20MHz channels, or by combining two non-consecutive 80MHz channels (this can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, data can be processed by a segment parser that can split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing can be performed separately on each stream. These streams can be mapped to two 80MHz channels, and data can be transmitted through the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration can be reversed, and the combined data can be transmitted to the Media Access Control (MAC).

[0064] 802.11af and 802.11ah support operating modes below 1 GHz. Compared to those used in 802.11n and 802.11ac, 802.11af and 802.11ah reduce channel operating bandwidth and carrier. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV white space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative implementations, 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 (e.g., only support) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain a very long battery life).

[0065] WLAN systems supporting multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as the primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by STAs operating in the BSS (each supporting a minimum bandwidth operating mode). In the 802.11ah example, for STAs supporting (e.g., only supporting) a 1MHz mode (e.g., MTC type devices), the primary channel can 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 Sense and / or Network Allocation Vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy, for example, because an STA (supporting only the 1MHz operating mode) is transmitting to the AP, the entire available band can be considered busy even if most of the band remains idle and potentially available.

[0066] 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 available bandwidth for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0067] FIG. 1D This is a system diagram illustrating RAN 113 and CN 115 according to the implementation scheme. As noted above, RAN 113 may employ NR radio technology to communicate with WTRUs 102a, 102b, and 102c via air interface 116. RAN 113 may also communicate with CN 115.

[0068] RAN 113 may include gNBs 180a, 180b, and 180c, but it should be understood that RAN 113 may include any number of gNBs while maintaining consistency with the implementation. Each of gNBs 180a, 180b, and 180c may include one or more transceivers for communicating with WTRUs 102a, 102b, and 102c via air interface 116. In one implementation, gNBs 180a, 180b, and 180c may implement MIMO technology. For example, gNBs 180a and 180b may utilize beamforming to transmit and / or receive signals from gNBs 180a, 180b, and 180c. Therefore, gNB 180a may, for example, use multiple antennas to transmit radio signals to and / or receive radio signals from WTRU 102a. In another implementation, gNBs 180a, 180b, and 180c may implement carrier aggregation technology. For example, gNB 180a can transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In implementations, gNBs 180a, 180b, and 180c may implement Cooperative Multipoint (CoMP) technology. For example, WTRU 102a may receive cooperative transmissions from gNBs 180a and 180b (and / or gNB 180c).

[0069] WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using transmissions associated with an expandable set of parameters. For example, OFDM symbol spacing and / or OFDM subcarrier spacing can vary depending on different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using subframes or transmission time intervals (TTIs) of various or expandable lengths (e.g., containing different numbers of OFDM symbols and / or continuously varying absolute time lengths).

[0070] gNBs 180a, 180b, and 180c can be configured to communicate with WTRUs 102a, 102b, and 102c in standalone and / or non-standalone configurations. In standalone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c without accessing other RANs (e.g., evolved Node Bs 160a, 160b, and 160c). In standalone configuration, WTRUs 102a, 102b, and 102c can use one or more of gNBs 180a, 180b, and 180c as mobility anchors. In standalone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using signals in unlicensed frequency bands. In a non-standalone configuration, WTRUs 102a, 102b, and 102c can communicate / connect with gNBs 180a, 180b, and 180c, and also with another RAN (such as evolved Node B 160a, 160b, and 160c). For example, WTRUs 102a, 102b, and 102c can implement DC principles to communicate substantially simultaneously with one or more gNBs 180a, 180b, and 180c and one or more evolved Node B 160a, 160b, and 160c. In a non-standalone configuration, evolved Node B 160a, 160b, and 160c can act as mobility anchors for WTRUs 102a, 102b, and 102c, and gNBs 180a, 180b, and 180c can provide additional coverage and / or throughput for serving WTRUs 102a, 102b, and 102c.

[0071] Each of gNBs 180a, 180b, and 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, network slicing support, dual connectivity, interoperability between NR and E-UTRA, routing of user plane data to User Plane Functions (UPF) 184a and 184b, and routing of control plane information to Access and Mobility Management Functions (AMF) 182a and 182b, etc. FIG. 1D As shown, gNB 180a, 180b, and 180c can communicate with each other via the Xn interface.

[0072] FIG. 1DThe CN 115 shown may include one or more of AMF 182a, 182b, one or more of UPF 184a, 184b, one or more Session Management Functions (SMF) 183a, 183b, and possible Data Networks (DN) 185a, 185b. Although each of the foregoing elements is depicted as part of CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0073] AMF 182a and 182b can connect to one or more of the gNBs 180a, 180b, and 180c in RAN 113 via the N2 interface and can act as control nodes. For example, AMF 182a and 182b can be responsible for authenticating users of WTRU 102a, 102b, and 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting specific SMF 183a and 183b, managing registration areas, terminating NAS signaling, and managing mobility, etc. AMF 182a and 182b can use network slicing to customize CN support for WTRU 102a, 102b, and 102c based on the type of service utilized by WTRU 102a, 102b, and 102c. For example, different network slices can be established for different use cases, such as services that rely on Ultra Reliable Low Latency (URLLC) access, services that rely on Enhanced Mobile Broadband (eMBB) access, and / or services that rely on Machine Type Communication (MTC) access. AMF 162 can provide control plane functions for handover between 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).

[0074] SMFs 183a and 183b can connect to AMFs 182a and 182b in CN 115 via the N11 interface. SMFs 183a and 183b can also connect to UPFs 184a and 184b in CN 115 via the N4 interface. SMFs 183a and 183b can select and control UPFs 184a and 184b, and configure service routing through UPFs 184a and 184b. SMFs 183a and 183b can perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. PDU session types can be IP-based, non-IP-based, and Ethernet-based, etc.

[0075] UPF 184a and 184b can be connected via the N3 interface to one or more of the gNBs 180a, 180b, and 180c in RAN 113. These gNBs can provide WTRU 102a, 102b, and 102c with access to a packet-switched network (such as the Internet 110) to facilitate communication between WTRU 102a, 102b, and 102c and IP-enabled devices. UPF 184 and 184b can perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multihomed PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring.

[0076] CN 115 can facilitate communication with other networks. For example, CN 115 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 115 and PSTN 108, or be able to communicate with such an IP gateway. Furthermore, CN 115 can provide WTRUs 102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, WTRUs 102a, 102b, and 102c can be connected to DN 185a and 185b via UPF 184a and 184b through the N3 interface to UPF 184a and 184b and the N6 interface between UPF 184a and 184b and local data networks (DNs) 185a and 185b.

[0077] Given FIGS. 1A-1D as well as FIGS. 1A-1D The corresponding descriptions herein refer to one or more of the functions described herein, or all of the functions described in one or more of the following: 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 emulation device can be one or more devices configured to mimic one or more of the functions described herein. For example, the emulation device can be used to test other devices and / or simulate network and / or WTRU functions.

[0078] Simulation devices can be designed to perform one or more tests on other devices in a laboratory environment and / or a carrier 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 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. Simulation devices may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communication to perform tests.

[0079] One or more emulation devices may perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, emulation devices may be used in test scenarios within a test laboratory and / or non-deployed (e.g., testing) wired and / or wireless communication networks to perform testing of one or more components. One or more emulation devices may be test rigs. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0080] FIG. 2 An example handover scenario 200 is depicted. At 204, the WTRU context within the source gNB 203 may include user data and / or information regarding roaming and / or access restrictions, which are provided, for example, at connection establishment and / or at the last advance timing (TA) update. At 208, the source gNB 203 and / or the target gNB 205 may be configured with mobility information provided by the Access and Mobility Management Function (AMF) 207. At 212, the source gNB 203 may configure WTRU measurement control, processes, and / or WTRU reporting, for example, based on measurement configuration. At 216, the source gNB 203 may determine the handover WTRU 201 based on, for example, received measurements. At 220, the source gNB 203 may transmit a handover request message to the target gNB 205. The handover request message may include a transparent RRC container with the necessary information to prepare for the handover at the target side. The information may include one or more of the following: target cell ID, KgNB*, cell radio network temporary identifier (C-RNTI) of WTRU 201 in source gNB 203, RRM configuration including WTRU inactive time, basic AS configuration including antenna information and DL carrier frequency, current QoS flow to DRB mapping rules applied to WTRU 201, SIB1 from source gNB 203, WTRU capabilities for different random access technologies (RAT), protocol data unit (PDU) session-related information and / or measurement information of WTRU reports including beam-related information (if available).

[0081] At 224, admission control can be performed by the target gNB 205. If WTRU 201 is admitted, the target gNB 205 can prepare for handover using L1 / L2. At 228, the target gNB 205 can send a handover acknowledgment (ACK) (e.g., a handover request acknowledgment) to the source gNB 203. The handover ACK may include a transparent container to be sent to WTRU 201 as an RRC message to perform the handover. At 232, the source gNB 205 can trigger Uu handover by sending an RRCReconfiguration message to WTRU 201. The RRCReconfiguration message may include information required for access to the target cell: at least the target cell ID, the new C-RNTI, and / or the target gNB 205 security algorithm identifier for the selected security algorithm. The RRCReconfiguration message transmitted at position 232 may also include a set of Dedicated Random Access Channel (RACH) resources, the association between RACH resources and SSBs, the association between RACH resources and WTRU-specific Channel State Information Reference Signal (CSI-RS) configurations, public RACH resources, and / or system information of the target cell.

[0082] At 244, the source gNB 203 may transmit an SN state transition message to the target gNB 205 to transfer the UL packet PDCP SN receiver state and / or downlink PDCP SN transmitter state of the data radio barrier (DRB) to which, for example, Packet Data Convergence Protocol (PDCP) state retention (e.g., for Radio Link Control (RLC) Acknowledgment Mode (AM)) applies. The SN state transition process may transfer the uplink PDCP SN and / or HFN receiver state and / or downlink PDCP SN and / or HFN transmitter state. This transition may occur during Xn handover from the source to the target NG-RAN node, between NG-RAN nodes involved in dual connectivity, and / or after retrieving the WTRU context for RRC reconstruction. This transition may occur for each corresponding DRB of the source DRB configuration to which the PDCP SN and HFN state retention applies. At 248, WTRU 201 can synchronize with the target cell and / or complete the RRC handover process by transmitting an RRCReconfigurationComplete message to the target gNB 205. At 252, UPF 209 can transmit user data to the source gNB 203 and / or the target gNB 205 (e.g., via the source gNB 203). At 256, the target gNB 203 can buffer user data received from the source gNB. At 260, WTRU 201, source gNB 203, and / or target gNB 205 can complete the RAN handover. At 264, the target gNB 205 can indicate successful handover to the source gNB 203. At 268, the source gNB 203 can indicate SN state transition to the target gNB 205. At 272, UPF 209 may transmit user data to source gNB 203 and / or target gNB 205 (e.g., via source gNB 203). At 276, target gNB 205 may communicate user data with WTRU 201 and / or UPF 209.

[0083] At 280, the target gNB 205 may send a path switching request message to the AMF 207, for example, to trigger the core network (e.g., 5GC) to switch the DL data path toward the target gNB 205 and / or establish a Next Generation Control Plane (NG-C) interface instance toward the target gNB 205. At 284, the core network may switch the DL data path toward the target gNB 205. At 288, the UPF 209 may send one or more "end marker" packets toward the source gNB 203 on the old path according to the PDU session and / or tunnel. The UPF 209 may then release any U-plane and / or Transport Network Layer (TNL) resources toward the source gNB 203 at 288. At 292, the target 205 processes user data. At 296, the AMF 207 may acknowledge the path switching request message using a path switching request acknowledgment message. At point 298, upon receiving a path handover request confirmation message from AMF 207, the target gNB 205 may transmit a UE context release message to the source gNB 203. The target gNB 205 may transmit the UE context release message to, for example, notify the source gNB 203 of a successful handover. The source gNB 203 may then (e.g., based on the reception of the UE context release message) release radio and / or C-plane related resources associated with the WTRU context. FIG. 2 (Not shown in the image). Any ongoing data forwarding can continue.

[0084] Conditional handover (CHO) and conditional primary / secondary serving cell (PSCell) addition / change (CPA / CPC, or collectively CPAC) can be provided. CHO and / or CPAC can reduce the likelihood of radio link failure (RLF) and / or handover failure (HOF).

[0085] Traditional handover is typically triggered by a measurement report, but even without a measurement report, nothing prevents the network from transmitting a handover (HO) command to the WTRU. For example, in dual connectivity (DC) scenarios, when the radio signal level / quality (RSRP, RSRQ, etc.) of a neighboring cell becomes better than the primary serving cell (PCell) or PSCell, the WTRU is configured with an A3 event to trigger the transmission of a measurement report. The WTRU can monitor the serving cell and / or neighboring cells and can transmit a measurement report when one or more conditions are met. Upon receiving such a report, the network (e.g., the current serving node / cell) can prepare an HO command (e.g., an RRC reconfiguration message with `reconfigurationWithSync`). The network can then transmit the HO command to the WTRU. The WTRU can execute (e.g., immediately) the HO, thereby enabling the WTRU to connect to the target cell.

[0086] Conditional handover (CHO) may involve preparing multiple handover targets (e.g., compared to a single target in a conventional handover). The WTRU may not execute a CHO immediately as in the case of a conventional handover. For example, the WTRU may be configured with one or more trigger conditions (e.g., a set of radio conditions). When one or more trigger conditions are met, the WTRU may perform a handover toward one of the targets.

[0087] A CHO command may be transmitted when radio conditions toward the current serving cell remain favorable. Transmitting a CHO command under favorable conditions mitigates two major points of failure in conventional handover: failure to transmit measurement reports (e.g., if the link quality to the current serving cell is below acceptable levels when a measurement report is triggered during normal handover) and failure to receive a handover command (e.g., if the link quality to the current serving cell is below acceptable levels after the WTRU has transmitted a measurement report but before that WTRU has received the HO command).

[0088] The triggering condition for a CHO can be based on the radio quality of the serving cell and / or neighboring cells (e.g., conditions similar to those used in conventional NR / LTE for triggering measurement reports). For example, a WTRU can be configured with a CHO having a triggering condition similar to A3 and an associated HO command. The WTRU can monitor the current serving cell. When the A3 triggering condition is met, the WTRU can execute the associated HO command and / or switch the WTRU's connection toward the target cell (e.g., instead of transmitting measurement reports).

[0089] FIG. 3 An example conditional handover configuration and / or execution process 300 is depicted. At 304, the example CHO configuration and execution process may include a source node 303 transmitting a CHO request to one or more target nodes 305. At 308, one or more target nodes 305 may respond with a CHO request ACK. At 312, the source node 303 may transmit a CHO configuration message to WTRU 301. At 316, WTRU 301 may monitor one or more CHO conditions on the target nodes 305. At 320, when the conditions are met, WTRU 301 may execute the HO. At 324, WTRU 301 may transmit a CHO acknowledgment message to the target nodes 305. At 328, the target node 305 may perform a path switch and / or WTRU 301 context release.

[0090] In the case of an RLF (Responsive Low-Level Fault), a Chokepoint (CHO) can prevent unnecessary rebuilding. For example, a WTRU (WTRU) may be configured with multiple CHO targets. In this case, the WTRU may experience an RLF before the triggering conditions are met for any of the targets. Traditional HO operations may trigger an RRC (Responsive Low-Level Call) rebuilding process, which can result in a considerable interruption of the WTRU's bearer. With a CHO, if the WTRU terminates its HO for a cell with an associated CHO after detecting an RLF (e.g., the target cell is already CHO-ready), the WTRU can directly execute the HO command associated with that target cell (e.g., instead of continuing the full rebuilding process).

[0091] CPC and / or CPA can be extensions of CHO in a dual connectivity (DC) scenario. WTRU can be configured with trigger conditions for PSCell changes and / or additions. If the trigger conditions are met, the WTRU can execute the associated PSCell change and / or PSCell add commands.

[0092] Inter-cell L1 / L2 mobility can be used to manage beams in CA. L1 / L2-based inter-cell mobility can support reduced mobility latency. L1 / L2-based inter-cell mobility can include configuration and / or maintenance for multiple candidate cells, for example, to allow for rapid application of candidate cell configurations. L1 / L2-based inter-cell mobility can include dynamic handover mechanisms between candidate serving cells (e.g., including SpCell and / or SCell), for example, for potential application scenarios based on L1 / L2 signaling. L1 / L2-based inter-cell mobility can include one or more L1 enhancements for inter-cell beam management (e.g., L1 measurement and / or reporting, and / or beam indication). L1 / L2-based inter-cell mobility can include advance timing management. If needed, L1 / L2-based inter-cell mobility can include centralized cell-distributed cell (CU-DU) interface signaling to support L1 / L2 mobility.

[0093] L1 / L2-based inter-cell mobility is applicable to stand-alone, CA, and NR-DC scenarios with serving cell changes within a cell group (CG). L1 / L2-based inter-cell mobility is applicable to intra-DU and intra-CU / inter-DU scenarios (e.g., applicable to stand-alone and / or CA). L1 / L2-based inter-cell mobility is applicable to both intra-frequency and inter-frequency scenarios. L1 / L2-based inter-cell mobility is applicable to both frequency range 1 (FR1) and frequency range 2 (FR2). L1 / L2-based inter-cell mobility may be applicable when the source and target cells are synchronized or asynchronous. L1 / L2-based inter-cell mobility may be applicable when inter-CU scenarios are not included.

[0094] L1 / L2-based mobility can include inter-cell beam management in intra-DU and intra-frequency scenarios. In this case, the serving cell remains unchanged (e.g., it is not possible to change the serving cell using L1 / L2-based mobility). In FR2 deployments, carrier aggregation (CA) can be used to aggregate multiple control channels (CCs) in a frequency band using available bandwidth (e.g.,). These CCs can be transmitted using the same analog beam pair (e.g., gNB beam and / or WTRU beam). The WTRU can be configured with transmit configuration indicator (TCI) states for receiving physical downlink control channels (PDCCH) and / or physical downlink shared channels (PDSCH). Each TCI state can include a WTRU reference to set the reference signal (RS) and / or synchronization signal block (SSB) for the WTRU's beam. The SSB can be associated with a non-serving physical cell identifier (PCI). Medium access control (MAC) signaling (e.g., TCI state indication for a WTRU-specific PDCCH medium access control (MAC) control element (CE)) can activate the TCI state for the Coreset / PDCCH. PDCCH reception from a non-serving cell can be supported via MAC CE indicating the TCI state associated with the non-serving PCI. MAC signaling (e.g., TCI state activation / deactivation for a WTRU-specific PDSCH) can activate a subset of (e.g., up to) eight TCI states for PDSCH reception. DCI can indicate which of the eight TCI states are activated. In the case of multiple transmit / receive points (TRP), a unified TCI state with different update mechanisms (e.g., DCI-based) can be provided.

[0095] When using regular L3 handover or conditional handover, the WTRU can use RRC signaling to transmit measurement reports. In response to the measurement reports, the network can provide additional measurement configurations and / or CHO configurations. With regular HO, the network can provide a configuration for the target cell after the WTRU reports that the cell meets the configured radio quality criteria using RRC signaling. With CHO, the network can provide the target cell configuration in advance and / or determine when the WTRU should trigger the measurement criteria for CHO configuration (e.g., to reduce HO failure rates due to delays in transmitting measurement reports and then receiving RRC reconfiguration). Both CHO and conditional HO can suffer some delay, for example, due to transmitting measurement reports and / or receiving target configurations, especially in the case of regular (unconditional) HO.

[0096] Compared to conventional L3 HO or conditional handover, L1 / L2 inter-cell mobility can improve HO latency. L1 / L2-based inter-cell mobility enables rapid application of configurations for candidate cells, including, for example, dynamic handover between SCells and / or handover of PCells (e.g., role switching between SCells and PCells) without executing RRC signaling. For example, L1 / L2-based inter-cell mobility may not support inter-CU scenarios because this requires relocation of the PDCP anchor. RRC-based methods can support inter-CU handover.

[0097] In the example, a traditional L3 handover mechanism may include releasing the active SCell before the WTRU completes the handover of the target cell to the coverage area of ​​the new site. The active SCell may (e.g., only) be added back after a successful HO. This can lead to a decrease in throughput during the handover. L1 / L2-based inter-cell mobility allows CA operation to be enabled immediately when the serving cell changes.

[0098] FIG. 4 An example of L1 / L2 inter-cell mobility operation 400 is depicted. At 404, in the example L1 / L2 inter-cell mobility operation 400, candidate cell groups can be configured via dynamic handover of RRC and / or PCell and / or SCell. At 408, dynamic handover of PCell and / or SCell can be implemented using L1 / L2 signaling.

[0099] At 412, to perform fast handover between cells (specifically SpCells (e.g., PCells and / or PSCells)), pre-configuration of candidate cells can be performed at the RRC layer. In the example, this configuration can be applied upon receiving an indication from L1 / L2. Candidate cells may have one or more of SpCell and / or SCell configurations. The SpCell and / or SCell configurations can be applied dynamically based on indications at lower layers.

[0100] Additional configurations associated with pre-configured SCells and / or SpCells can be provided. For example, measurement configurations and / or assignment to candidate cells can be configured to perform at least one of the following processes before and / or during reconfiguration: synchronization, TA management, inter-cell beam management, RLM, and / or BFD.

[0101] It may be necessary to reference the pre-configured settings in the RRC in an efficient manner to minimize the signaling required to perform the handover.

[0102] The WTRU can be configured to receive RRC messages including a list of candidate cells. The WTRU can perform one or more HO preparation procedures associated with one or more SCells or candidate cells on the candidate cell list. The one or more HO preparation procedures may include one or more of the following: performing measurements associated with one or more target SpCells, obtaining timing advance information for one or more target SpCells, and / or initiating beam tracking on one or more target SpCells. The WTRU can receive a Medium Access Control (MAC) control element (CE). The MAC CE may indicate a first SpCell and one or more second SpCells. The first SpCell may be the current SpCell. The one or more second SpCells may be target SpCells (e.g., one or more target SpCells). The MAC CE may include a target SpCell index indicating one or more second SpCells associated with the HO. The WTRU can monitor one or more HO conditions for one or more second SpCells. The one or more HO conditions may include one or more of a timer, a measurement threshold, and / or beam fault detection (BFD). The measurement threshold may be associated with Radio Link Monitoring (RLM) measurements. When one or more HO conditions are met, the WTRU may send a reconfiguration complete message to the target SpCell (e.g., in one or more target SpCells).

[0103] MAC CE can be used to signal cell handover (e.g., to improve the reliability of cell handover commands). HARQ can be used to send MAC CE compared to L1 signaling such as DCI. Using HARQ for transmission improves transmission reliability by reducing the likelihood of losing downlink control commands in the air.

[0104] The MAC CE may include information referencing an index of the RRC configurations of cells that have been configured (e.g., activated) and / or reconfigured (e.g., changed roles from SCell to SpCell) for the currently serving cell and / or cells involved in a specific part of the L1 / L2 mobility procedure. The MAC CE may refer to the cell index to provide indications of the current roles of those cells and / or the activation status of the cells. The cell index and / or indications of the current roles of those cells may identify which configurations to apply and / or which configuration(s) to release.

[0105] FIG. 5Example MAC CE decoding 500 is depicted. The network may transmit MAC CE 500 to the WTRU. Before receiving MAC CE 500, the WTRU may receive configuration information from the network. In example MAC CE decoding 500, the network may first pre-configure (e.g., up to 32) a list of cells using RRC signaling with SCell configuration and / or SpCell configuration and index. For example, the WTRU may receive an RRC message including configuration information. The configuration information may include one or more pre-configured candidate cell configurations. Each pre-configured candidate cell configuration may include SpCell configuration, SCell configuration, and / or candidate cell index.

[0106] MAC CE 500 can indicate which of the pre-configured candidate cell configurations should be applied. For example, MAC CE 500 can indicate which pre-configured candidate cell configurations among the pre-configured candidate cell configurations to apply. MAC CE 500 can indicate the activation status (e.g., activated or deactivated) for each SCell in the indicated pre-configured candidate cell configuration. Each of the 32 cells in the pre-configured candidate cell configuration can be identified using one bit from octet 2 504b to octet 5 504e, and this bitmap (e.g., candidate cell index) can be used to configure, activate, and / or deactivate each cell as an SCell. An integer "1" indicates that a cell is activated as a serving cell. An integer "0" indicates that a candidate is deactivated as a serving cell. A specific cell can be identified using the SpCell index (e.g., a value between 0 and 31) in octet 1 504a. Although the remaining 3 bits are shown as reserved, these bits can be defined for specific purposes (e.g., to enable enhancements in future versions, such as conditional L1 / 2 cell handover, inter-CU reconfiguration, or to indicate specific scenarios, such as NR-DC and / or DAP handover).

[0107] The combination of an integer value for the SpCell index and a bitmap identifying the SCell can be an efficient decoding method for performing both SCell activation / deactivation and SpCell modification using a single MAC CE. For example, a WTRU can initiate a handover to an SpCell based on MAC CE 500 in an indicated pre-configured candidate cell configuration (e.g., in the SPCell index). The WTRU can be configured to send data to the SCell activated by MAC CE 500. For example, the WTRU can determine whether to activate an SCell in the indicated pre-configured candidate cell configuration based on the activation status indicated in MAC CE 500. As described herein, MAC CE 500 can indicate the TCI status for one or more cells in the indicated pre-configured candidate cell configuration.

[0108] FIG. 6 Example operation 600 of SpCell and / or SCell handover using MAC CE is depicted. Network 610 may have RRC layer 612 and MAC layer 614. WTRU 620 may have MAC layer 622 and RRC layer 624. SpCell handover may also be referred to as handover. If the SpCell is a PSCell, the SpCell handover may be referred to as SCG change. RRC signaling can be used to change the SpCell. RRC may perform one or more procedures, such as releasing the current SpCell configuration, exporting a new security key, applying a new SpCell configuration, resetting counters, instructing lower layers to clear buffers (e.g., performing a MAC reset), etc. After applying the new SpCell configuration, WTRU 620 can complete the handover by sending a reconfiguration complete message to the new SpCell. The RRC procedures used to perform and / or complete the reconfiguration may remain unchanged. Additional enhancements can be made to further optimize the reconfiguration process (e.g., using MACCE to indicate handover completion, and / or implicit handover completion based on decoding of the first uplink and / or downlink transmissions and / or receptions).

[0109] At 604, initiating an RRC reconfiguration may include changes to both SpCell and SCell configurations that are pre-provided using RRC signaling and activated using MACCE. RRC reconfiguration may work with existing RRC reconfiguration procedures and / or with enhanced RRC procedures (e.g., MAC and / or RLC, etc.). For example, network 610 may transmit an RRC reconfiguration from its RRC layer 612 to the RRC layer 624 of WTRU 620. In addition to dynamically initiating handover (SpCell changes) and performing SCell changes (e.g., activation / deactivation), a relatively large number (e.g., up to 32) of cells may be configured with pre-configured SpCell and / or SCell configurations, and / or a limited number of cells may be activated as serving cells (e.g., up to 8). At 608, many truncated versions of existing MAC CEs are available for routine operation. For example, SCell activation and / or deactivation, Power Clearance Report (PHR), and / or Beam Fault Recovery (BFR) have truncated versions that can advantageously replace the full versions for resource reduction. For instance, the SCell portion of the MAC CE may not activate and / or deactivate the SCell. The SCell portion of the MAC CE can inform the WTRU620 which candidate cells can be considered SCells and which cannot. For example, network 610 can transmit a cell activation command from its MAC layer 614 to the MAC layer 622 of network 620 at 608. Those candidate cells configured as SCells can then undergo individual activation and / or deactivation.

[0110] FIG. 7 An example MAC CE decoder 700 with additional bits is depicted. The MAC CE decoder 700 can be further optimized, for example, by reinterpreting the 32 bits used to reference the SCell. The MAC CE decoder 700 may include first considering that cells indicated in the SpCell index field (e.g., or configurations) are not included in the SCell list.

[0111] Example MAC CE decoder 700 may include using an additional bit for another purpose (e.g., when used with...). FIG. 5 (Compared to MAC CE decoding 500 shown). Since one cell in the cell is indicated as a PCell, that cell cannot simultaneously be an SCell. Therefore, the PCell index can be removed from the bitmap and / or the remaining (e.g., only the remaining) 31 cells can be referenced. A PCell can have (e.g., always has) index 0, and an SCell can have (e.g., always has) indices 1-31. In example MAC CE decoding 700, for example, the indices can be renumbered from PCell index +1 to 32, and from PCell index to 31, to correctly interpret the MAC CE and / or identify the correct RRC configuration to be applied.

[0112] FIG. 8 Another example MAC CE decoder 800 with additional octets is depicted. The MAC CE 800 may include one or more additional octets 804a-f (e.g., when used with...). FIG. 5 (Compared to the MAC CE 800 shown). In the example, one or more octets 804a-f may indicate one or more target SpCell indices. The target SpCell may be indicated before cell change activation to perform, for example, some handover preparation steps. Handover preparation steps may include initiating measurements (such as RLM and / or BFD), synchronizing to the target cell before handover, obtaining timing advance information for the target before cell handover, and / or initiating beam tracking on the target cell. One or more handover preparation steps may be activated before handover of the SpCell to improve, for example, the latency and / or reliability of the cell handover itself. The MAC CE 800 may provide indication of the status of one or more Transmit Configuration Indicators (TCIs) associated with the target cell to perform measurements (e.g., inter-cell beam management, uplink synchronization, and / or other processes). For example, the MAC CE 800 may indicate the TCI status for one or more cells in a pre-configured candidate cell configuration.

[0113] In the example, both the current SpCell and / or the target SpCell can be indicated when switching to a new SpCell while simultaneously activating radio link monitoring and / or other handover preparation steps on the new SpCell.

[0114] In the example, the SpCell index may not be required. The MAC CE may provide (e.g., only) the target SpCell index and may provide one or more target or current SCells. In this case, the WTRU may not immediately activate any SpCell switchover. Instead, the WTRU may initiate handover preparation steps, such as one or more procedures described above.

[0115] In the example, a bit (e.g., one bit out of R bits) may indicate whether the MAC CE command corresponds to the primary cell group (MCG) (e.g., PCell and / or SCell) and / or the secondary cell group (SGC) (e.g., PSCell, SCell).

[0116] In the example, the indexes of the SpCell of the MCG and / or the SpCell of the SCG can be included in the same command.

[0117] Indication for a target SpCell may require one or more conditions to activate SpCell change (e.g., conditional handover). These conditions may include, for example, process conditions, timer conditions, and / or measurement conditions (e.g., conditional handover can be configured). The WTRU may begin evaluating triggering conditions upon receiving the relevant target SpCell indication in the MAC CE. When the conditions are met, handover can be initiated. For example, the WTRU may initiate handover based on one or more radio quality measurements of the SpCell in a pre-configured candidate cell configuration.

[0118] One or more conditions may include a second MAC CE that indicates an "activation" command, such as "activate the configuration indicated in the previous MAC CE". For example, upon receiving a target PCell indication, the WTRU may begin executing and / or reporting measurements. When the reported measurements are determined by the network to be suitable for performing a cell change, the network may activate the cell change.

[0119] FIG. 9 Another example MAC CE decoder 900 with a single octet is depicted. Activating the MAC CE can be a single octet 904, which may include, for example... FIG. 9 The single active bit shown. Activating MAC CE may include multiple bits indicating one of several previously activated configurations.

[0120] Activation at the MAC address can be performed in two phases. The first activation phase may include receiving an activation MAC CE at the WTRU indicating the target configuration (e.g., a target SpCell). The second activation phase may include activating the cell change using the activation MAC CE. For example, the network may first use the first MAC CE to activate N target SpCells. Then, the network may determine which of those N target SpCells will perform SpCell changes to use the N bits in the second MAC CE.

[0121] In the example, activating the MAC CE confirms the WTRU selection for the target configuration. For example, the WTRU may be configured with measurements. For example, the WTRU may (e.g., using RRC measurement reports, some L1 measurement reports, and / or in the uplink MAC CE) report a list of one or more best cells. This activation references the reported list of cells, and the WTRU can use the stored RRC configuration to initiate a SpCell change to the previously reported best cell.

[0122] FIG. 10 Another example MAC CE decoder 1000 is depicted. MAC CE decoder 1000 may include a SpCell index, a target SpCell index, and / or 32 bits, as described herein. MAC CE decoder 1000 may include one or more octets 1004a-g to indicate an additional configuration.

[0123] In the example, one or more additional octets 1004a-g can notify the WTRU which SCells should be activated and / or deactivated. (For example, in...) FIG. 10 The 32 bits marked "C" indicate which candidate cells are considered SCells. In this example, the maximum number of serving cells can be 8 out of the possible 32 candidates (e.g., 1 SpCell and 7 SCells). One or more additional octets 1004a-g can indicate which SCells among the 7 SCells are activated / deactivated. One or more additional octets 1004a-g can inform the WTRU of any other candidate cell roles. For example, one or more additional octets can inform the WTRU which cells are used for L1 inter-cell beam management procedures (e.g., the possibility of performing beam management procedures on cells other than the current SpCell), which cells perform RLM, etc.

[0124] In the example, one or more candidate cell configurations may include (e.g., using IE CellGroupConfig) one or more cell group configurations. Candidate cell configurations may include (e.g., using RRC reconfiguration messages) one or more RRC reconfigurations. For example, when a candidate cell belongs to a different DU (e.g., in this case, a new cell group configuration might be needed because the new cell group configuration could include DU-specific information such as RLC and / or MAC configuration) and / or CU (e.g., in this case, RRC reconfiguration can be used), the candidate cell configuration may include one or more cell group configurations and / or RRC reconfigurations. For example, RRC reconfiguration may include CU-specific information, such as PDCP and / or SDAP configuration and / or measurement configuration.

[0125] In the example, the MAC CE that triggers the cell change could point to the cell group configuration and / or the full RRC reconfiguration. In this case, an explicit index could be provided (e.g., similar to...). FIG. 7 The octet in the array is 1, but for example, where the index points to the cell group index or the full configuration index instead of the SpCell index. The pre-configured candidate configuration may include necessary information, such as the serving cell (e.g., the SpCell and SCell to be configured when activating the cell group).

[0126] In the examples, MAC CE may indicate the cell group index and / or the full configuration index. In some examples, MAC CE may additionally or alternatively specify which cells to include. For example, a cell group (e.g., corresponding to a specific DU) may be pre-configured and / or associated with multiple potential target cells (e.g., belonging to that DU). For example, MAC CE may indicate the cell group and cells to be configured as SpCells and the cells to be configured as SCells. FIG. 11 Example encoding is provided.

[0127] FIG. 11 Another example MAC CE decoder 1100 is depicted. MAC CE decoder 1100 may include a cell group index provided in octet 11104a, a SpCell index provided in octet 2 1104b, and / or octets 3 1104c-6 1104f may be used to indicate which SCells should be configured as part of the cell group.

[0128] In some examples, if the CU changes, the network can provide a MAC CE including the RRC reconfiguration index; if the DU changes, the network can provide a MAC CE including the cell group index; and / or if the cell changes but, for example, the CU and / or DU do not change, the network can provide a MAC CE including the candidate cell index (e.g., only the candidate cell index). The type and / or content of the MAC CE sent to the WTRU can be used to determine whether to perform intra-DU (e.g., no cell group change) procedures (e.g., no MAC reset), inter-DU (e.g., cell group changeable) procedures (e.g., MAC reset and / or RLC reconstruction), and / or inter-CU (e.g., full RRC reconfiguration or RB configuration changeable) procedures (e.g., PDCP reconstruction, security refresh).

[0129] The MAC CE decoder 1100 can combine, in a single command, the activation and / or deactivation of the current SpCell (e.g., PCell, PSCell), the target SpCell (e.g., PCell, PSCell), one or more SCells, and / or indications of which cells belong to a group of cells to which additional requirements apply. Alternatively or additionally, the MAC CE decoder 1100 can combine target cell group configuration, target RRC reconfiguration, target DU, and / or target CU.

Claims

1. A wireless transceiver unit (WTRU), the wireless transceiver unit (WTRU) comprising a processor and a memory, the processor being configured to: Receive a Radio Resource Control (RRC) message including configuration information, the configuration information including one or more pre-configured candidate cell configurations, wherein each pre-configured candidate cell configuration includes a special cell (SpCell) configuration, one or more secondary cell (SCell) configurations, and a candidate cell index; Receive Medium Access Control (MAC) Control Element (CE), wherein the MACCE includes a Target Configuration Identifier (ID) and an indication of one or more Transmit Configuration Indicator (TCI) states, wherein the Target Configuration Identifier indicates a target SpCell associated with both the one or more pre-configured candidate cell configurations and candidate cell indices, and the indication of the one or more TCI states is associated with the target SpCell; Initiate a handover to the target SpCell based on the target configuration ID; as well as Activate one or more TCI states associated with the target SpCell.

2. The WTRU of claim 1, wherein each of the one or more pre-configured candidate cell configurations further comprises: The activation status of each SCell associated with each of the one or more SCell configurations.

3. The WTRU of claim 2, wherein the processor is further configured to: Based on the activation status indicated in the one or more pre-configured candidate cell configurations included in the RRC message, activate the one or more SCells associated with the one or more SCell configurations.

4. The WTRU of claim 1, wherein the processor is further configured to: After receiving the MAC CE, an RRC reconfiguration complete message is sent to the target SpCell.

5. The WTRU of claim 1, wherein the MAC CE further includes a downlink TCI state ID associated with each of the one or more TCI states, wherein the downlink TCI state ID indicates the activation of one or more downlink TCI states associated with the target SpCell.

6. The WTRU of claim 1, wherein the MAC CE further includes an uplink TCI state ID associated with each of the one or more TCI states, wherein the uplink TCI state ID indicates the activation of one or more uplink TCI states associated with the target SpCell.

7. The WTRU of claim 1, wherein the indication of the one or more TCI states associated with the target SpCell includes a beam associated with each TCI state.

8. The WTRU of claim 1, wherein the processor is further configured to: After selecting the target SpCell during the timer's operation, a handover to the target SpCell is initiated.

9. The WTRU of claim 1, wherein the MAC CE is a first MAC CE that does not activate at least one SCell in the first pre-configured candidate cell configuration of the one or more pre-configured candidate cell configurations, and the WTRU is further configured to receive a second MAC CE that activates at least one SCell in the first pre-configured candidate cell configuration of the one or more pre-configured candidate cell configurations indicated in the first MAC CE.

10. The WTRU of claim 1, wherein the MAC CE is a first MAC CE, and the WTRU is further configured to receive a second MAC CE, wherein the second MAC CE initiates a measurement of at least one SCell.

11. A method implemented by a wireless transmit / receive unit (WTRU), the method comprising: Receive a Radio Resource Control (RRC) message including configuration information, the configuration information including one or more pre-configured candidate cell configurations, wherein each pre-configured candidate cell configuration includes a special cell (SpCell) configuration, one or more secondary cell (SCell) configurations, and a candidate cell index; Receive Medium Access Control (MAC) Control Element (CE), wherein the MACCE includes a Target Configuration Identifier (ID) and an indication of one or more Transmit Configuration Indicator (TCI) states, wherein the Target Configuration Identifier indicates a target SpCell associated with both the one or more pre-configured candidate cell configurations and candidate cell indices, and the indication of the one or more TCI states is associated with the target SpCell; Initiate a handover to the target SpCell based on the target configuration ID; as well as Activate one or more TCI states associated with the target SpCell.

12. The method of claim 11, wherein each of the one or more pre-configured candidate cell configurations further comprises: The activation status of each SCell associated with each of the one or more SCell configurations.

13. The method according to claim 12, further comprising: Based on the activation status indicated in the one or more pre-configured candidate cell configurations included in the RRC message, activate the one or more SCells associated with the one or more SCell configurations.

14. The method according to claim 11, further comprising: After receiving the MAC CE, an RRC reconfiguration complete message is sent to the target SpCell.

15. The method of claim 11, wherein the MAC CE further includes a downlink TCI state ID associated with each of the one or more TCI states, wherein the downlink TCI state ID indicates the activation of the one or more downlink TCI states associated with the target SpCell.

16. The method of claim 11, wherein the MAC CE further includes an uplink TCI state ID associated with each of the one or more TCI states, wherein the uplink TCI state ID indicates activation of the one or more uplink TCI states associated with the target SpCell.

17. The method of claim 11, wherein the indication of the one or more TCI states associated with the target SpCell includes a beam associated with each TCI state.

18. The method according to claim 11, further comprising: After selecting the target SpCell during the timer's operation, a handover to the target SpCell is initiated.

19. The method of claim 11, wherein the MAC CE is a first MAC CE that does not activate at least one SCell in a first pre-configured candidate cell configuration of the one or more pre-configured candidate cell configurations, and the WTRU is further configured to receive a second MAC CE that activates at least one SCell in the first pre-configured candidate cell configuration of the one or more pre-configured candidate cell configurations indicated in the first MAC CE.

20. The method of claim 11, wherein the MAC CE is a first MAC CE, and the WTRU is further configured to receive a second MAC CE, wherein the second MAC CE initiates a measurement of at least one SCell.

21. A wireless transceiver unit (WTRU), the wireless transceiver unit (WTRU) comprising a processor and a memory, the processor being configured to: Receive Conditional Handover (CHO) configuration messages from network entities; Monitor one or more CHO conditions of the target entity; Based on the CHO configuration message, determine whether the one or more CHO conditions are met; A transfer to the target entity is initiated when one or more CHO conditions are met; as well as Send a CHO confirmation message to the target entity.

22. The WTRU of claim 21, wherein after receiving a CHO request ACK from the target entity, the network entity is triggered to transmit the CHO configuration message to the WTRU.

23. The WTRU of claim 21, wherein the target entity performs path switching and WTRU context release after the handover is completed.

24. A method implemented by a wireless transmit / receive unit (WTRU), the method comprising: Receive Conditional Handover (CHO) configuration messages from network entities; Monitor one or more CHO conditions of the target entity; Based on the CHO configuration message, determine whether the one or more CHO conditions are met; A transfer to the target entity is initiated when one or more CHO conditions are met; as well as Send a CHO confirmation message to the target entity.

25. The method of claim 24, wherein after receiving a CHO request ACK from the target entity, the network entity is triggered to transmit the CHO configuration message to the WTRU.

26. The method of claim 24, wherein the target entity performs path switching and WTRU context release after the handover is completed.

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