WO2024173491A1

WO2024173491A1 - Prach transmission associated with mac ce and pdcch order

Info

Publication number: WO2024173491A1
Application number: PCT/US2024/015719
Authority: WO
Inventors: Erdem Bala; Paul Marinier; Brian Martin; Janet A. Stern-Berkowitz; Oumer Teyeb; Martino M. Freda; Dylan WATTS
Original assignee: InterDigital Patent Holdings Inc
Current assignee: InterDigital Patent Holdings Inc
Priority date: 2023-02-14
Filing date: 2024-02-14
Publication date: 2024-08-22
Anticipated expiration: 2025-08-14
Also published as: CN120814328A; KR20250150013A; AU2024223574A1

Abstract

Systems, methods, and instrumentalities are described herein related to physical random access channel (PRACH) transmission by medium access control (MAC) channel element (CE) and physical downlink control channel (PDCCH) order. A device (e.g., a wireless transmit/receive unit (WTRU)) may (e.g., be configured to) perform one or more actions. The device may receive configuration information that indicates two sets of cells and random-access information associated with each set of cells. The device may receive an indication selecting one of the received sets of cells. The device may determine one or more random access preambles, resources, and/or parameters associated with a cell (e.g., each cell) in the selected set of cells based on the configuration information and the indication. The device may (e.g., then) receive an indication to transmit a PRACH transmission to a cell in the selected set of cells. The device may send the PRACH transmission to the indicated cell.

Description

PRACH TRANSMISSION ASSOCIATED WITH MAC CE AND PDCCH ORDER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/445,364, filed February 14, 2023 the contents of which are incorporated by reference herein.

BACKGROUND

[0001] Mobile communications using wireless communication continue to evolve. A fifth generation may be referred to as 5G. A previous (legacy) generation of mobile communication may be, for example, fourth generation (4G) long term evolution (LTE).

SUMMARY

[0002] Systems, methods, and instrumentalities are described herein related to physical random access channel (PRACH) transmission by medium access control (MAC) channel element (CE) and physical downlink control channel (PDCCH) order.

[0003] A device (e.g., a wireless transmit/receive unit (WTRU)) may (e.g., be configured to) perform one or more actions. The device may receive configuration information that indicates two sets of cells and random-access information associated with each set of cells. The device may receive an indication (e.g., via MAC CE) selecting one of the received sets of cells. The device may determine one or more random access preambles, resources, and/or parameters associated with a cell (e.g., each cell) in the selected set of cells based on the configuration information and the indication. The device may (e.g., then) receive an indication (e.g., via a PDCCH transmission) to transmit a PRACH transmission, for example, to a cell in the selected set of cells. The device may send the PRACH transmission to the indicated cell. The device may use the determined one or more random access preambles resources, and/or parameters associated with the cell when sending the PRACH transmission.

[0004] The device may receive a timing advance value, for example in response to sending the PRACH transmission to the indicated cell. The device may associate the timing advance value with the indicated cell and/or the selected set of cells. The device may send another PRACH transmission (e.g., future PRACH transmission(s)) to the cell based on the timing advance value. [0005] In examples, the WTRU may determine, for example, based on the received indication (e.g., received in the MAC CE), the physical cell identity (PCI) and/or SSB (e.g., beam or spatial filter) to use for transmission to each cell in the set of cells.

[0006] An example device may include a processor configured to perform one or more actions. For example, a device (e.g., WTRU) may receive configuration information that indicates one or more sets of cells and random-access information associated with the one or more sets of cells. The device may receive an indication of a set of cells, wherein the set of cells is a set of the one or more sets of cells. The device may receive an indication to transmit one or more physical random access channel (PRACH) transmissions to the set of cells, wherein the indication to transmit one or more PRACH transmissions to the set of cells is received via a physical downlink control channel (PDCCH) transmission. The device may send a PRACH transmission to the set of cells.

[0007] The configuration information may be received via radio resource control (RRC) signaling. The indication of the set of cells may be received via a medium access control (MAC) control element (CE). The indication of the set of cells may be one of: an index to the set of cells or a set of cell/synchronization signal/PBCH block (SSB) combinations; or individual cells or cell/SSB combinations. The indication that is received via the PDCCH transmission to transmit one or more PRACH transmissions to the set of cells may be received in a PDCCH order. The PDCCH order may be received via downlink control information (DCI) included in the PDCCH transmission. The PRACH transmission may be sent using a configuration associated with the random-access information. The processor may be (e.g., further) configured to receive timing advance information for at least one cell of the set of cells.

BRIEF DESCRIPTION OF THE DRAWINGS

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

[0009] FIG. 1 B is a system diagram illustrating an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0010] FIG. 1 C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG. 1 A according to an embodiment;

[0011] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0012] FIG. 2 illustrates an example of a measurement model.

[0013] FIG. 3 illustrates an example of L1/2 inter-cell mobility using carrier aggregation. [0014] FIG. 4 illustrates an example of selecting a subset of cells by MAC CE.

[0015] FIG. 5 illustrates an example of dynamically updating a set of target cells.

[0016] FIG. 6 illustrates an example of configured ROs.

[0017] FIG. 7 illustrates an example of allowed ROs.

[0018] FIG. 8 illustrates an example of allocating allowed ROs to different PCIs and re-indexing.

DETAILED DESCRIPTION

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

[0020] As shown in FIG. 1A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104/113, a ON 106/115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated 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 a “ST A”, may be configured to transmit and/or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE. [0021] The communications systems 100 may also include a base station 114a and/or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106/115, the Internet 110, and/or the 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, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

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

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

[0024] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. 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 establish the air interface 115/116/117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access (HSUPA). [0025] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/or LTE-Advanced Pro (LTE-A Pro).

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

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

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

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

[0030] The RAN 104/113 may be in communication with the CN 106/115, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106/115 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or the CN 106/115 may 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 be utilizing a NR radio technology, the CN 106/115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

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

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

[0033] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include 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, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0034] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

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

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

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

[0038] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or 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 the non-removable memory 130 and/or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, 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).

[0039] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the 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, and the like.

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

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

[0042] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the 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 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

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

[0044] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-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 eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a.

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

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

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

[0048] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the 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 user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like. [0049] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

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

[0051] Although the WTRU is described in FIGS. 1 A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

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

[0053] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and/or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11 z tunneled DLS (TDLS). A WLAN using an Independent BSS (I BSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad- hoc” mode of communication.

[0054] When using the 802.11 ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may be implemented, for example in in 802.11 systems. For CSMA/CA, the STAs (e.g., every 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.

[0055] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0056] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0057] Sub 1 GHz modes of operation are supported by 802.11af and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative to those used in 802.11 n, and 802.11 ac. 802.11 af supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non- TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control/Machine-Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and/or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0058] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11 n, 802.11 ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest 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, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes. Carrier sensing and/or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0059] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

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

[0061] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit 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 unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180c).

[0062] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and/or OFDM subcarrier spacing may vary for different transmissions, different cells, and/or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and/or lasting varying lengths of absolute time). [0063] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and/or a non-standalone configuration. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with/connect to gNBs 180a, 180b, 180c while also communicating with/connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and/or throughput for servicing WTRUs 102a, 102b, 102c.

[0064] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and/or DL, support of network slicing, dual connectivity, interworking between NR and E- UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0065] The CN 115 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

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

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

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

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

[0070] In view of Figures 1A-1 D, and the corresponding description of Figures 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and/or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and/or to simulate network and/or WTRU functions.

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

[0072] The one or more emulation devices may perform the one or more, including all, functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and/or a non-deployed (e.g., testing) wired and/or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and/or wireless communications 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.

[0073] In RRC_CONNECTED, a WTRU may measure multiple beams (e.g., at least one beam) of a cell (e.g., each cell). The measurement(s) results (e.g., power values) may be averaged to derive the cell quality. In doing so, the WTRU may be configured to consider a subset of the detected beams. Filtering may take place at different levels (e.g., two different levels). For example, filtering may occur at the physical layer (e.g., to derive beam quality) and/or at the RRC level (e.g., to derive cell quality from multiple beams). Cell quality from beam measurements may be derived similarly for serving cell (s) and/or for non-serving cell(s).

[0074] FIG. 2 shows an example of a measurement model (e.g., high-level measurement model). As shown in FIG. 2, the WTRU may be configured to report measurements (e.g., provide measurement reports), for example by the gNB. Measurement reports may include the measurement results of beams (e.g., a beam). The WTRU may be configured (e.g., by the gNB) to provide measurement reports that include the measurement results of a number of beams, for example the X best beams.

[0075] Channel state information (CSI) may be reported (e.g., from the WTRU to the network, for example a gNB). CSI may be used (e.g., by the network) as an indicator of how good or bad a channel is at a point in time (e.g., any point in time). CSI may be used by the gNB to make scheduling decisions, such as selection of Modulation and Coding Scheme (MCS) and/or to assist with beamforming.

[0076] Time and frequency resources that may be used by the WTRU to report CSI may be controlled by the gNB. CSI may include one or more of, for example: a channel quality indicator (CQI); a precoding matrix indicator (PMI); a CSI-RS resource indicator (CRI); a synchronization signal (SS)/ physical broadcasting channel (PBCH) block resource indicator (SSBRI); a layer indicator (LI); a rank indicator (Rl); an L1-RSRP; an LI signal to interference and noise ratio (L1-SINR); or a Capability[Set] Index.

[0077] For CQI, PMI, CRI, SSBRI, LI, Rl, L1-RSRP, L1-SINR, and/or Capability[Set] Index, a WTRU may be configured (e.g., by higher layers), for example, with N>1 CSI-ReportConfig reporting settings, M>1 CSI-ResourceConfig resource settings, and/or one or two list(s) of trigger states (e.g., given by the higher layer parameters CSI-AperiodicTriggerStateList and CSI-SemiPersistentOnPUSCH-TriggerStateList). A trigger state (e.g., each trigger state) in CSI-AperiodicTriggerStateList may include a list of associated CSI- ReportConfigs. The list of associated CSI-ReportConfigs may indicate the resource set I D(s) for channel and/or for interference. A trigger state (e.g., each trigger state) in CSI-SemiPersistentOnPUSCH- TriggerStateList may include one associated CSI-ReportConfig.

[0078] A reporting setting CSI-ReportConfig (e.g., each report setting CSI-ReportConfig) may be associated with a single downlink BWP (e.g., indicated by higher layer parameter BWP-ld) given in the associated CSI-ResourceConfig for channel measurement. A reporting setting CSI-ReportConfig (e.g., each report setting CSI-ReportConfig) may include the parameter(s) for a CSI reporting band, for example, one or more of: codebook configuration including codebook subset restriction; time-domain behavior; frequency granularity for CQI and PMI; measurement restriction configurations; or the CSI-related quantities to be reported by the WTRU, such as the layer indicator (LI), L1-RSRP, L1 -SI NR, CRI, SSBRI, and/or Capability[Set]lndex.

[0079] The time domain behavior of the CSI-ReportConfig may be indicated by the higher layer parameter reportConfigType and/or may be set to aperiodic, semiPersistentOnPUCCH, semiPersistentOnPUSCH, or periodic. For periodic, semiPersistentOnPUCCH, an/or semiPersistentOnPUSCH CSI reporting, the configured periodicity and slot offset may apply in the numerology of the uplink (UL) bandwidth part (BWP) in which the CSI report may be configured to be transmitted on. The higher layer parameter reportQuantity may indicate the CSI-related, L1 -RSRP-related, L1 -SINR-related and/or Capability[Set]l ndex-related quantities to report. The reportFreqConfiguration may indicate the reporting granularity in the frequency domain, for example, including the CSI reporting band and/or if PMI/CQI reporting is wideband or sub-band. The timeRestrictionForChannelMeasurements parameter in CSI-ReportConfig may be configured to enable time domain restriction for channel measurements. The timeRestrtctionFortnterterenceMeasurements parameter may be configured to enable time domain restriction for interference measurements. The CSI-ReportConfig may (e.g., also) include CodebookConfig, which may include configuration parameters for Type-I, Type II, Enhanced Type II CSI, and/or Further Enhanced Type II Port Selection (e.g., including codebook subset restriction when applicable, and/or configurations of group-based reporting). [0080] A CSI resource setting CSI-ResourceConfig (e.g., each CSI resource setting CSI- ResourceConfig) may include a configuration of a list of S>1 CSI Resource Sets (e.g., given by higher layer parameter csi-RS-ResourceSetList). The list may include references to non-zero power (NZP) CSI- RS resource set(s) and/or SS/PBCH block set(s) or the list may include references to CSI-IM resource set(s). A CSI resource setting (e.g., each CSI resource setting) may be located in the DL BWP (e.g., identified by the higher layer parameter BWP-id). The CSI resource settings linked to a CSI report setting may have the same DL BWP.

[0081] The time domain behavior of the CSI-RS resources within a CSI resource setting may be indicated by the higher layer parameter resourceType. The time domain behavior of CSI-RS resources may be set to aperiodic, periodic, or semi-persistent. For periodic and semi-persistent CSI resource settings (e.g., when the WTRU is configured with groupBasedBeamReporting), the number of CSI resource sets configured may be S=2. Otherwise, the number of CSI-RS resource sets configured may be limited to S=1 . For periodic and semi-persistent CSI resource settings, the configured periodicity and/or slot offset may be given in the numerology of an associated DL BWP, e.g., as given by BWP-id. When a WTRU is configured with multiple CSI-ResourceConfigs comprising the same NZP CSI-RS resource ID, the same time domain behavior may be configured for the CSI-ResourceConfigs. When a WTRU is configured with multiple CSI- ResourceConfigs, for example including the same CSI-IM resource ID, the same time-domain behavior may be configured for the CSI-ResourceConfigs. Some CSI resource settings (e.g., all CSI resource settings) linked to a CSI report setting may have the same time domain behavior.

[0082] One or more of the following may be configured via higher layer signaling for one or more CSI resource settings for channel and interference measurement: a CSI-IM resource for interference measurement; an NZP CSI-RS resource for interference measurement; or an NZP CSI-RS resource for channel measurement.

[0083] A WTRU may be configured with a list of up transmission configuration indicator (TCI)-state configurations. A TCI-state (e.g., each TCI-state) may include parameters for configuring a quasi-co- location relationship between one or more (e.g., two) downlink reference signals and the demodulation reference signal (DM-RS) ports of the PDSCH, the DM-RS port of PDCCH, and/or the CSI-RS port(s) of a CSI-RS resource. The quasi-co-location relationship may be configured by the higher layer parameter qcl- Typel for the first DL RS and/or qcl-Type2 for the second DL RS (e.g., if configured). The quasi-co-location types corresponding to each DL RS may be given by the higher layer parameter qcl-Type in quasi colocation (QCL)-lnfo. The quasi-co-location types corresponding to each DL RS may take one or more of the following values: typeA: {Doppler shift, Doppler spread, average delay, delay spread}; typeB: {Doppler shift, Doppler spread}; typeC: {Doppler shift, average delay}; or typeD: {Spatial Rx parameter}. [0084] Inter-cell L1/L2 mobility may be implemented. Inter-cell L1/L2 mobility may manage the beams in a carrier aggregation (CA) case, and cell change/add may or may not be supported. A mechanism and/or procedures of L1/L2 based inter-cell mobility may be indicated/implemented for mobility latency reduction.

[0085] L1/L2 based mobility and/or inter-cell beam management may address intra-DU and/or intrafrequency scenarios. In this case, the serving cell may remain unchanged (e.g., there may be no possibility to change the serving cell using L1/L2 based mobility). In FR2 deployments, carrier aggregation (CA) may be used to exploit the available bandwidth (e.g., to aggregate multiple CCs in one band). The CCs may be transmitted with the same analog beam pair (e.g., gNB beam and WTRU beam). The WTRU may be configured with TCI states (e.g., 64 TCI states) for reception of PDCCH and PDSCH. A TCI state (e.g., each TCI state) may include an RS or SSB that the WTRU may refer to for setting a beam. The SSB may be associated with a non-serving PCI. MAC signaling (e.g., “TCI state indication for WTRU-specific PDCCH MAC CE”) may activate the TCI state for a CORESET/PDCCH. Reception of PDCCH from a non-serving cell may be supported by MAC CE indicating a TCI state associated with a non-serving PCI. MAC signaling (e.g., “TCI States Activation/Deactivation for WTRU-specific PDSCH”) may activate a subset of TCI states (e.g., up to 8 TCI states) for PDSCH reception. DCI may indicate a particular TCI state of the subset of TCI states (e.g., the 8 TCI states). A “unified TCI state” may be supported with a different updating mechanism (e.g., DCI-based), for example, with or without multi-TRP.

[0086] L1/L2 inter-cell mobility may (e.g., be used to) improve handover latency, for example, compared to a conventional L3 handover and/or conditional handover where the WTRU may first send a measurement report (e.g., using RRC signaling). In response to this, the network may provide a further measurement configuration and/or a conditional handover configuration. With a conventional handover, the network may provide a configuration for a target cell, for example, after the WTRU reports using RRC signaling that the cell meets a configured radio quality criteria.

[0087] L1/L2 based inter-cell mobility may allow a fast application of configurations for candidate cells, for example, including dynamically switching between secondary cells (SCells) and switching of the primary cell (PCell) (e.g., switch the roles between SCell and PCell) without performing RRC signaling. The inter- CU case may be associated with relocation of the packet data convergence protocol (PDCP) anchor. An RRC based approach may support inter-CU handover.

[0088] With the legacy L3 handover mechanisms, currently active SCell (s) (e.g., any currently active SCell(s)) may be released before the WTRU moves (e.g., completes a handover) to a target cell in the coverage area of a new site (e.g., and can only be added back after successful handover), which may lead to throughput degradation during handover. L1/L2 may enable CA operation (e.g., instantaneously upon serving cell change). [0089] FIG. 3 shows an example of L1/L2 inter-cell mobility operation. The candidate cell group may be configured by RRC (e.g., where RRC used herein may refer to RRC signaling). A dynamic switch of PCell and SCell may be achieved using L1/L2 signaling.

[0090] FIG. 3 illustrates an example of L1/L2 inter-cell mobility using carrier aggregation (CA). The baseline procedure for L1/L2 triggered mobility (LTM) may include one or more of the following actions. The WTRU may send a measurement report (e.g., MeasurementReport message) to the gNB. The gNB may decide to use LTM. The gNB may initiate LTM candidate preparation. The gNB may transmit an RRCReconfiguration message to the WTRU, which may include the configuration of one or multiple LTM candidate target cells. The WTRU may store the configuration of LTM candidate cell(s). The WTRU may transmit an RRCReconfigurationComplete message to the gNB. The WTRU may perform DL synchronization and TA acquisition with candidate cell(s), for example, before receiving the LTM cell switch command. The WTRU may perform L1 measurements on the configured LTM candidate cell(s). The WTRU may transmit lower-layer measurement reports to the gNB. The lower-layer measurement reports may be carried on L1 or MAC. The gNB may determine to execute LTM cell switch to a target cell. The gNB may transmit a MAC CE triggering LTM cell switch, for example, by including the candidate configuration index of the target cell. The WTRU may switch to the configuration of the LTM candidate target cell. The WTRU may perform a random access procedure towards the target cell, for example, if TA is not available. The WTRU may indicate successful completion of the LTM cell switch towards the target cell.

[0091] A physical random-access procedure may be triggered upon request of a PRACH transmission by higher layers or by a PDCCH order. A configuration by higher layers for a PRACH transmission may include one or more of the following: a configuration for PRACH transmission, a preamble index, a preamble SCS, a corresponding RA-RNTI, or a PRACH resource. A PRACH may be transmitted using the selected PRACH format.

[0092] For a Type-1 random access procedure, a WTRU may be provided a number N of SS/PBCH block indexes associated with one PRACH occasion and/or a number R of contention based preambles per SS/PBCH block index per valid PRACH occasion (e.g., by ssb-perRACH-OccasionAndCB- PreamblesPerSSB).

[0093] The PRACH occasions may be mapped (e.g., consecutively mapped) per corresponding SS/PBCH block index. The indexing of the PRACH occasion indicated by the mask index value may be reset per mapping cycle of consecutive PRACH occasions per SS/PBCH block index. The WTRU may select, for a PRACH transmission (e.g., each PRACH transmission), the PRACH occasion indicated by PRACH mask index value for the indicated SS/PBCH block index in the first available mapping cycle. [0094] For the indicated preamble index, the ordering of the PRACH occasions may be, for example, first, in increasing order of frequency resource indexes for frequency multiplexed PRACH occasions, second, in increasing order of time resource indexes for time multiplexed PRACH occasions within a PRACH slot, and third, in increasing order of indexes for PRACH slots. The random-access procedure may be initiated by a PDCCH order, by the MAC entity itself, or by RRC (e.g., for certain events).

[0095] A WTRU may need to establish and maintain timing alignment with the cell, for example so that the gNB may successfully receive the WTRU transmission. The WTRU may establish and maintain timing alignment by sending a random-access preamble in PRACH, which may be used by the cell to estimate the timing advance the WTRU may use. The cell may send the estimated timing advance value to the WTRU.

[0096] The WTRU may (e.g., in L1 mobility) establish the timing alignment with candidate cells before cell switch happens, for example, to reduce connection latency. Establishing timing alignment with multiple cells may incur high overhead and/or delay. The most likely target cell(s) may be determined without increasing latency. PRACH may be transmitted to the determined cell(s) without increasing latency.

[0097] Candidate cell sets may include one or more candidate cells. Candidate cell sets may be groups of RRC configuration(s) (e.g., more than one RRC configurations) corresponding to a handover configuration for one or more candidate SpCells and/or SCells. Candidate cell sets may be modelled and/or received as one or more complete RRC Reconfiguration messages, one or more cell group configurations, or one or more cell configurations. A candidate cell configuration (e.g., each candidate cell configuration) may include a candidate configuration identifier. A candidate cell group (e.g., each candidate cell group) may include a candidate cell group identifier. Grouping may be performed at RRC. Switching between different sets of candidate cells may include updating the serving cell indexes and/or candidate configuration indexes, which may be used in L1 and MAC signalling to refer to specific indexes. For example, a MAC CE triggering a reconfiguration may include a candidate configuration index informing the WTRU which cell to perform the reconfiguration to.

[0098] An L1 measurement (e.g., as used herein) may include a measurement of RSRP, RSRP, RSSI, etc., which may be performed by a WTRU of a cell, beam, set of cells, and/or set of beams. An L1 measurement may be performed on CSI-RS resources and/or on SSBs. CSI-RS and CSI-RS resource may be used interchangeably herein.

[0099] As described herein, a WTRU may determine PRACH occasions (RO) to transmit PRACH to one or more candidate cells. A PRACH transmission may be performed (e.g., in response to a condition) so that a candidate cell may estimate the timing advance a WTRU may use to communicate to the cell, for example, after a cell switch.

[0100] SSB and/or CSI-RS indexes may be mapped to valid PRACH occasion(s). [0101] A WTRU may apply independent mapping, for example, if/when determining a random-access occasion for an SSB and/or a CSI-RS. As an example of independent mapping, SSB indexes and CSI-RS indexes may be mapped to the same valid ROs independently. For example, the WTRU may (e.g., first) map the SSB indexes to the valid ROs and (e.g., then) map the CSI-RS indexes to the valid ROs (e.g., or vice versa, where the mapping order may be changed).

[0102] SSB indexes and/or CSI-RS resource indexes may be mapped to valid PRACH occasion(s). For example, SSB indexes and/or CSI-RS resource indexes may be mapped to valid PRACH occasion(s) (e.g., in increasing order) based on one of the following: preamble indexes within a single PRACH occasion (e.g., which may be skipped if/when the preamble index is provided, for example, by configuration or in a PDCCH order); frequency resource indexes for frequency multiplexed PRACH occasions; time resource indexes for time multiplexed PRACH occasions within a PRACH slot; and/or indexes for PRACH slot.

[0103] Valid ROs may be (e.g., partially) non-overlapping for SSB and CSI-RS, for example, if separate PRACH masks are used. For example, SSB indexes may be mapped to a first set of allowed ROs and CSI - RSs indexes may be mapped to a second set of ROs.

[0104] SSB indexes may be mapped to the valid ROs, for example, using a mapping rule as described herein. CSI-RS indexes may be mapped to the ROs to which the SSB that is QCL’ed with the CSI-RS is mapped to. For example, if SSB # 5 and CSI-RS resource # 3 are QCL’ed, then both may be mapped to the same RO.

[0105] SSB indexes and CSI-RS indexes may be combined in a common list. Indexes from the list may be mapped to the valid ROs sequentially. For example, from the list [SSB0 SSB1 ... SSBK CSI-RS0 CSI- RS1 ... CSI-RSN] , SSB0 may be mapped to the first valid PO, SSB1 may be mapped to the second valid PO, etc.

[0106] The ROs may be divided into multiple (e.g., two) groups of valid ROs, for example, by applying multiple (e.g., two) PRACH masks. For example, SSB indexes may be mapped to the valid ROs in a first group and CSI-RS indexes may be mapped to the valid ROs in a second group.

[0107] The mapping techniques (e.g., as described herein) may be applicable to two or more types of signals (e.g., SSB, CSI-RS, and/or other types of signals).

[0108] PRACH transmission may occur to multiple cells.

[0109] In some examples, a WTRU may receive a random-access configuration (e.g., via RRC signaling). A WTRU may receive (e.g., from a serving cell) configuration(s) of one or more sets of candidate cells (e.g., the WTRU may receive the configuration(s) via RRC signaling). The configuration may include (e.g., respective) measurement and/or reporting configurations associated with the one or more sets of cells. A WTRU may receive (e.g., for each set of cells) configuration of one or more SSBs and/or CSI-RS resources associated with a cell. The WTRU may (e.g., for a set of cells) receive configuration of random-access parameters, which may include one or more of the following: a prach- Configurationlndex parameter; msg1 -Frequencystart (e.g., an offset of lowest PRACH transmission occasion in frequency domain with respective to physical resource block (PRB) 0) and/or msg1-FDM (e.g., the number of PRACH transmission occasions frequency division multiplexed in one time instance); the number of SSBs per RACH occasion; a list of CSI-RS and the set of ROs a CSI-RS is associated with; a root sequence index; or a number of preambles.

[0110] A WTRU may be configured with a prach-Configurationlndex parameter. The WTRU may determine (e.g., from the configuration index) one or more of: the preamble format, the frame number, the number of PRACH slots within the frame, the number of time domain PRACH occasions within a PRACH slot, or the duration of a time domain PRACH occasion.

[0111] A WTRU may be configured with msg1 -Frequencystart (e.g., an offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0) and/or msg1-FDM (e.g., the number of PRACH transmission occasions frequency division multiplexed in one time instance). The time/frequency resources over which a preamble is mapped to may be referred to as a PRACH occasion.

[0112] A WTRU may be configured with a list of CSI-RS and/or the set of ROs a CSI-RS is associated with. The configuration may be used, for example, if/when random-access is triggered from higher layers.

[0113] A random-access configuration may be associated with one or more PCIs, e.g., the configuration may provide the random-access parameters to transmit PRACH to one or more cells with the corresponding PCIs. Random-access configurations associated with multiple PCIs (e.g., a first PCI and a second PCI) may include at least one configuration parameter that is different (e.g., between one or more of the associated PCIs). For example, a first PCI may be associated with a first PRACH configuration index and a second PCI may be associated with a second PRACH configuration index. In some examples, different time and/or frequency resources may be configured for different PCIs. In some examples, different root sequences may be configured for different PCIs.

[0114] A random-access configuration may be associated with more than one PCI. An LTM ID may be part of a random-access configuration. Cells (e.g., all cells) within the LTM ID may be associated with the same random-access configuration.

[0115] In some examples, a random-access configuration may be associated with a TCI state. A TCI state may include as a QCL source an SSB index and/or a CSI-RS resource index. The SSB/CSI-RS may be associated (e.g., by configuration) with a PCI. A WTRU may determine (e.g., from the TCI state) the PCI and/or the SSB/CSI-RS index the random-access configuration may be associated with.

[0116] A WTRU may determine a PRACH occasion. [0117] In some examples, a WTRU may receive an indication (e.g., via a MAC CE), which may include an indication to one or more of the sets of cells configured by the RRC. A WTRU may (e.g., using the MAC CE indication and from the configured parameters) determine the random-access parameters associated with the indicated cell(s).

[0118] FIG. 4 illustrates an example of selecting a subset of cells by MAC CE. As shown in FIG. 4, a WTRU may be configured with random-access parameters for cells (e.g., cells 1 to 6). A MAC CE may indicate cells 1 , 3, and 4 to the WTRU. The WTRU may determine the random-access parameters for cells 1 , 3, and 4 from the received configuration information. As an example, the WTRU may determine that the random-access configuration for cells 1 , 3, and 4 is common (e.g., applies to all three cells) and/or that the random-access configuration for cell 2, 5, 6 is common (e.g., applies to all three cells). The WTRU may (e.g., further) determine that the frequency resources of the ROs configured for the two sets of cells are different.

[0119] In some examples, the MAC CE may include an indication to at least one combination of PCI and SSB index or CSI-RS. The combination may correspond to a TCI state. The WTRU may determine (e.g., from the indicated TCI states) the associated PCI and/or SSB/CSI-RS. The WTRU may (e.g., further) determine the corresponding random-access configuration.

[0120] A WTRU may receive an indication (e.g., in a PDCCH order, such as an enhanced PDCCH order used as an example) for PRACH transmission to at least one of the cells, for example one of the cells indicated by the MAC CE (eg., one or more cells in the indicated set of cells). An enhanced PDCCH order may be applicable to the cells (e.g., each cell) received (e.g., successfully) in the latest MAC CE. For example, referring again to the example depicted in FIG. 4, the WTRU may receive an enhanced PDCCH order applicable to cells 1, 3, and 4 (e.g., as received in the MAC CE). An enhanced PDCCH order may include one or more of the following fields: a PCI or an indication to a PCI; an SSB and/or a CSI/RS index associated with the PCI; a preamble index; or a PRACH mask.

[0121] An enhanced PDCCH order may include a PCI or an indication to a PCI. The PCI(s) (e.g., each PCI) indicated in the MAC CE may be assigned an index. For example, a PDCCH order may have a bit field that indicates the index assigned to a PCI (e.g., using the previous example of FIG. 4, bits 00, 10, 11 may indicate PCIs 1, 3, and 4 respectively).

[0122] An enhanced PDCCH order may include an SSB and/or a CSI/RS index associated with the PCI. A WTRU may use an SSB and/or a CSI-RS index to determine the RO among the valid ROs. The WTRU may determine the RO with one or more of the following: a configuration or an application of a mapping rule (e.g., as described herein). For example, an RO or list of ROs that may be associated with an SSB and/or a CSI/RS may be configured (e.g., as part of the random-access configuration). [0123] An enhanced PDCCH order may include a preamble index. A WTRU may determine the preamble to transmit in PRACH from a preamble index.

[0124] An enhanced PDCCH order may include a PRACH mask. A WTRU may determine the allowed PRACH occasions from a PRACH mask.

[0125] In some examples, a PDCCH order may include a TCI state. A TCI state may be associated with a combination (e.g., of PCI, SSB or PCI, CSI-RS). For example, a WTRU may be configured with one or more TCI states (e.g., 8 TCI states). A TCI state may include an SSB index (e.g., as a QCL source). The SSB may be associated with a PCI. A TCI state may include a CSI-RS resource index (e.g., as a QCL source). The CSI-RS may be associated with a PCI. A PDCCH order may not include the PCI index and the SSB/CSI-RS index fields, for example, if/when a TCI state is used.

[0126] In some examples, a WTRU may (e.g., be indicated to) transmit PRACH (e.g., send a PRACH transmission) to more than one cell (e.g., two or more cells) that may be indicated in the MAC CE. Assuming k (e.g., k = 2) ROs for PRACH transmission to k target cells, the PDCCH order may include k PCI indexes and k SSB/CSI-RS indexes, for example, or (e.g., alternatively) k TCI state indications. In some examples, the same preamble may be used for PRACH transmission to k cells or the PDCCH order may include multiple (e.g., k) preamble indexes corresponding to each cell.

[0127] A WTRU may determine the RO for each cell on which the corresponding PRACH may be transmitted, for example, if/when the WTRU is indicated to transmit PRACH to more than one target cell. For example, a WTRU may determine the RO for a first SSB associated with a first PCI and then determine the RO for a second SSB associated with a second PCI.

[0128] In some examples, a PDCCH order may indicate a target cell among the cells configured by RRC (e.g., the PDCCH order may not indicate a cell indicated in a MAC CE). For example, the PDCCH order may indicate one of the TCI states configured by RRC. The PDCCH order may (e.g., alternatively) indicate a (PCI and SSB/CSI-RS) combination configured by RRC. The WTRU may (e.g., from the indication) determine the corresponding random-access configuration.

[0129] The WTRU may perform measurements, for example L1 RSRP measurements on the SSB and/or CSI-RS resources configured by the RRC. One or more (e.g., a set) of SSB and CSI-RS resources may be associated with a candidate cell. A WTRU may report the measurements to the serving cell, for example, in a MAC CE and/or in uplink control information in PUSCH and PUCCH.

[0130] In some examples, a WTRU may (e.g., upon reception of a MAC CE from the serving cell) report one or more measurements to the serving cell, for example in a MAC CE. The measurements may correspond to the PCI/SSB/CSI-RS received in the downlink MAC CE. The measurements reported may be filtered measurements (e.g., filtered L1 RSRP measurements). Reception (e.g., successful reception) of the MAC CE by the serving cell (e.g., indicated by an acknowledgment for the serving cell or not receiving a retransmission grant) may (e.g., implicitly) trigger the WTRU to get and/or update the timing alignment with one or more target cells.

[0131] The WTRU may determine the SSB/CSI-RS associated with the target cell from the measurements. The SSB/CSI-RS (e.g., for a target cell) may be the RS that was reported to the serving cell. For example, the RS may be the RS with the largest RSRP among (e.g., all) RSs associated with the target cell. The WTRU may determine the cell for PRACH transmission from the target cells, for example, based on some criteria. In some examples, the cell selected for PRACH transmission may be the best-k target cells, where k may be configured (e.g., k = 1).

[0132] A WTRU may use the SSB and/or the CSI-RS index to determine the RO among the valid ROs. The WTRU may determine the RO, for example, with one or more of the following methods: a configuration or application of a mapping rule (e.g., as described herein). For example, the RO or list of ROs that may be associated with an SSB and/or a CSI/RS may be configured (e.g., as part of the random-access configuration).

[0133] A WTRU may transmit PRACH (e.g., may send a PRACH transmission to cell(s) in an indicated set of cells). A WTRU may transmit the PRACH, for example, after the valid RO(s) and other PRACH parameters are determined. In some examples, a WTRU may transmit the PRACH once. The WTRU may retransmit the PRACH after receiving another PDCCH order. One time transmission and/or retransmission may occur, for example, if/when a timing alignment with a target cell has been established. In some examples, an enhanced PDCCH order may indicate (e.g., using a 1 -bit field) whether the WTRU transmits the PRACH once or follows other operation, such as applying the parameter preambleTransMax. In some examples, the same indication (e.g., the 1 -bit field) may (e.g., also) indicate to the WTRU not to monitor a random-access response for the PRACH (e.g., because the timing advance information may be sent to the WTRU by the serving cell). The field (e.g., 1 -bit field) may indicate to the WTRU whether the PDCCH order is to trigger RACH for timing alignment or whether the PDCCH order is for another purpose. For example, bit 1 may indicate no repetition, no RAR monitoring, etc. and/or bit 0 may indicate another type of RACH (e.g., legacy RACH).

[0134] In some examples, an enhanced PDCCH order may include a transmit power control field for RACH, for example, if the WTRU does not perform a full RACH procedure with retransmissions (e.g., to enable the network to send another PDCCH order that asks for PRACH with higher power if the network did not receive the first PRACH).

[0135] A device (e.g., a wireless transmit/receive unit (WTRU)) may (e.g., be configured to) perform one or more of the following actions: receive configuration information (e.g., via radio resource control (RRC) signaling) indicating one or more sets of cells (e.g., candidate cells) and/or (e.g., respective) randomaccess information (e.g., preambles, resources, parameters) for use with the one or more sets of cells (e.g., for each of the cells or for each set of cells); receive an indication (e.g., via a MAC CE) selecting a set of the configured sets of cells (e.g., an index to a set of cells or a set of cell/synchronization signal block (SSB) combinations, or an indication of individual cells or cell/SSB combinations); receive an indication such as a PDCCH order (e.g., a PDCCH carrying downlink control information (D )) indicating to transmit one or more PRACH transmissions to a set of cells, where the set of cells may be the selected set of cells (e.g., indicated by the MAC CE); determine a random access preamble, resource, or parameter based on the received random-access configuration information for the selected cell(s) (e.g., for each cell of the selected set of cells and/or for the selected set of cells); send a PRACH transmission (e.g., a PRACH preamble as an example) to the selected cell (s) (e.g., to each of the cells in the selected set of cells) using the determined random access configuration information; or receive timing advance information for at least one (e.g., all) of the cells in the selected set (e.g., from a cell, such as the WTRU’s serving cell). In examples, the WTRU may determine, e.g., based on the received indication (e.g., received in the MAC CE), the physical cell identity (PCI) and/or SSB (e.g., beam or spatial filter) to use for transmission to each cell in the set of cells.

[0136] A WTRU may receive configuration information, for example via RRC. The configuration may indicate sets of cells (e.g., sets of candidate cells). The WTRU may receive random-access information, for example via RRC (e.g., in conjunction with the configuration information). The random-access information may be associated with each of the sets of cells. For example, the random-access information may include preamble(s), resource(s), and/or parameter(s) for use with one or more of the sets of cells (e.g., for each cell or for each set of cells).

[0137] The WTRU may receive an indication of a set of cells (e.g., of the received sets of cells), an index to a set of cells, an index to a set of cell/SBB combinations, an individual cell, or individual cell/SSB combinations. The indication may be received via a MAC CE.

[0138] The WTRU may determine random-access configuration information for the selected cell(s) (e.g., for each cell of the selected set of cells or for the selected set of cells). Random-access configuration information may include one or more of: a random access preamble, resource, or parameter associated with cells in the first set of cells. The random-access configuration information may be determined based on the configuration information and the indication (e.g., the received MAC CE indication).

[0139] The WTRU may receive a PDCCH order indicating to transmit one or more PRACH transmissions (e.g., to a cell or a set of cells). In examples, the PDCCH order may not explicitly indicate the cell or set of cells. In examples, The WTRU may determine to transmit PRACH transmission(s) to the set of cells indicated by the MAC CE based on the PDCCH order. The PDCCH order may be a PDCCH order carrying a DCI. The PDCCH order may be received via a PDCCH transmission.

[0140] The WTRU may send a PRACH transmission to a cell, for example using the random access preamble, resource, or parameter.

[0141] The WTRU may receive a timing advance value based on the PRACH transmission (e.g., in response to the sent PRACH transmission).The WTRU may associate the timing advance value with the cell and/or the set of cells. The WTRU may send another PRACH transmission to the cell based on the timing advance value.

[0142] PRACH transmission may be triggered by a WTRU measurement report ACK.

[0143] A WTRU may receive an RRC configuration. A WTRU may receive (e.g., from a serving cell) a configuration of one or more sets of candidate cells in RRC. A configuration may include measurement and reporting configurations associated with one or more sets of cells. A WTRU may receive (e.g., for each set of cells) a configuration of one or more SSBs and/or CSI-RS resources associated with a cell. A WTRU may receive (e.g., for a set of cells) a configuration of random-access parameters, which may include, for example, one or more of the following: a prach-Configurationlndex parameter; an msg1 -Frequencystart parameter (e.g., an offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0) and/or an msg1-FDM parameter (e.g., the number of PRACH transmission occasions frequency division multiplexed in one time instance); the number of SSBs per RACH occasion; a list of CSI-RS and the set of ROs a CSI-RS is associated with; a root sequence index; and/or a number of preambles.

[0144] A WTRU may be configured with a prach-Configurationlndex parameter. A WTRU may determine (e.g., from the configuration index) one or more of the following: the preamble format, the frame number, the number of PRACH slots within the frame, the number of time domain PRACH occasions within a PRACH slot, or the duration of a time domain PRACH occasion.

[0145] A WTRU may be configured with msg1 -Frequencystart (e.g., an offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0) and/or msg1-FDM (e.g., the number of PRACH transmission occasions frequency division multiplexed in one time instance). The time/frequency resources over which a preamble is mapped to may be referred to as a PRACH occasion.

[0146] A WTRU may be configured with a list of CSI-RS and/or the set of ROs a CSI-RS is associated with. This configuration may be used, for example, if/when random-access is triggered from higher layers.

[0147] A random-access configuration may be associated with one or more PCIs, for example, the configuration may provide the random-access parameters to transmit PRACH to one or more cells with the corresponding PCIs. Random-access configurations associated with a first PCI and a second PCI may include at least one configuration parameter that is different. For example, a first PCI may be associated with a first PRACH configuration index and a second PCI may be associated with a second PRACH configuration index. In some examples, different time and/or frequency resources may be configured for different PCIs. In some examples, different root sequences may be configured for different PCIs.

[0148] A random-access configuration may be associated with more than one PCI. An LTM ID may be part of a random-access configuration. Cells (e.g., all cells) within the LTM ID may be associated with the same random-access configuration.

[0149] In some examples, a random-access configuration may be associated with a TCI state. A TCI state may include as a QCL source, for example, an SSB index and/or a CSI-RS resource index. The SSB/CSI-RS may be associated (e.g., by configuration) to a PCI. The WTRU may determine (e.g., from the TCI state) the PCI and/or the SSB/CSI-RS index the random-access configuration may be associated with. [0150] A WTRU may perform measurement and recommendation. A WTRU may perform measurements (e.g., L1 RSRP measurements on the SSB and/or CSI-RS resources configured by the RRC). One or more (e.g., a set) of SSB and/or CSI-RS resources may be associated with a candidate cell. A WTRU may report the measurements to the serving cell, for example, in a MAC CE or in uplink control information in PUSCH and PUCCH.

[0151] In some examples, a subset of the cells may be determined by the WTRU (e.g., from the reported measurements) or indicated by the serving cell. The subset may be referred to as “target cells.” FIG. 5 illustrates an example of dynamically updating a set of target cells. For example, as shown in FIG. 5, the WTRU may be configured with measurement objects for cells 1 to 6. The subset of the target cells may be dynamically updated, for example, depending on the measurements. The target cells may be considered a set of cells the WTRU may be handed over to if certain conditions hold, e.g., the RSRP of an RS associated with the target cell becomes an offset better than the RSRP of the serving cell. In the example shown in FIG. 5, cell 3 is a serving cell for WTRU A, cell 4 is a serving cell for WTRU B, and cell 6 is a serving cell for WTRU C. Cell 1 and cell 4 are target cells for WTRU A, cell 1 , cell 2 and cell 5 are target cells for WTRU B, and cell 2 and cell 5 are target cells for WTRU C. The measurements reported may be filtered measurements (e.g., filtered L1 RSRP measurements).

[0152] In some examples, a WTRU may report measurements to the serving cell in a MAC CE. The successful reception of the MAC CE (e.g., indicated by an acknowledgment for the serving cell or not receiving a retransmission grant) may (e.g., implicitly) trigger the WTRU to get and/or to update the timing alignment with one or more target cells. A WTRU may determine the SSB/CSI-RS associated with the target cell from the measurements. An SSB/CSI-RS (e.g., for a target cell) may be the RS that was reported to the serving cell. For example, the RS may be the RS with the largest RSRP among (e.g., all) RSs associated with the target cell. The WTRU may determine the cell for PRACH transmission from the target cells, for example, based on one or more conditions and/or criteria. In some examples, the cell selected for PRACH transmission may be the best-k target cells, where k may be configured (e.g., k = 1). [0153] A WTRU may use the SSB and/or the CSI-RS index to determine the RO among the valid ROs. A WTRU may determine the RO with one of the following: a configuration (e.g., the RO or list of ROs that may be associated to a SSB and/or a CSI/RS may be configured, for example, as part of the randomaccess configuration); and/or by applying a mapping rule (e.g., as disclosed herein).

[0154] In some examples, a WTRU may use a random-access configuration associated with a target cell to transmit PRACH. In some examples, a random-access configuration may not be associated with a specific cell. A WTRU may (e.g., be able to) use the random-access resources to transmit PRACH within an LTM area. For example, as a WTRU moves around a set of target cells may be dynamically determined (e.g., based on the WTRU measurements and/or signaling from the serving cell). The WTRU may (e.g., be able to) transmit PRACH to one or more of the target cells, for example, using a common random-access configuration.

[0155] A WTRU may trigger PRACH transmission to a target cell, for example, if the timing advance information of the cell is not up to date. For example, a difference between the current time and the last time a timing advance for the cell was received and/or applied may be above a threshold. In some examples, a time (e.g., timer) that started when the last time a timing advance for the cell was received and/or applied may be expired.

[0156] A WTRU may trigger PRACH transmission to one of the target cells. For example, the target cell may be the cell with the highest RSRP.

[0157] An example procedure may include one or more of the following: a WTRU may perform measurements of candidate cells; the WTRU may send a measurement report (e.g., measurement report may include filtered measurements); the WTRU may update the set of target cells, for example, based on the reported measurements (e.g., after the report is acknowledged); the WTRU may select one or more of the target cells, for example, if certain conditions hold (e.g., the RSRP of a target cell is above a threshold and/or the timing alignment of the target cell is not up to date); the WTRU may determine the RO(s) for the selected target cell (s) and associated SSB/CSI-RS; and/or the WTRU may transmit PRACH on the determined RO(s).

[0158] In some examples, the WTRU may send a WTRU assistance message to the serving cell (e.g., in a MAC CE). The message may include an index of a target cell. Acknowledgment of the message may trigger the WTRU to start PRACH to the target cell. [0159] In some examples, the WTRU may send a timing alignment request MAC CE or a RACH request MAC CE to a cell (e.g., the serving cell). The cell (e.g., serving cell) that receives the MAC CE may send a PDCCH order to the WTRU for RACH transmission.

[0160] In some examples, a WTRU may maintain a set of active TCI states. A TCI state may be associated with a PCI and one or more signals as the QCL source (e.g., an SSB and/or a CSI-RS). A WTRU may report measurements for the TCI states to the serving cell, for example, RSRP of the SSB and/or CSI-RS associated with the TCI states. The WTRU may estimate the QCL properties of the SSBs and/or CSI-RS associated with the active TCI states. In some examples, a WTRU may (e.g., determine to) perform random-access to a cell (e.g., transmit PRACH on a valid RO). The cell may be one of the cells that an active TCI state is associated with. One or more of the following may apply.

[0161] The WTRU may determine and/or be indicated (e.g., by the serving cell) to update the QCL properties of a TCI state. The WTRU may (e.g., determine to) initiate random-access to the cell associated with the TCI state (e.g., select valid ROs and transmit PRACH). An update QCL message from the serving cell may trigger the WTRU to initiate timing alignment procedures towards the cell associated with the TCI state, for example, to prepare and send RACH. The timing alignment procedure may be performed, for example, (e.g., only) if the timing advance information for the cell is not up to date (e.g., as described herein).

[0162] The WTRU may trigger timing alignment procedures towards the cells indicated in the MAC CE, for example, if/when the WTRU receives a MAC CE to activate one or more TCI states. The timing alignment procedure may be performed, for example, (e.g., only) if the timing advance information for the cell is not up to date (e.g., as described herein).

[0163] A timing alignment request (e.g., as by a PDCCH order) may trigger the WTRU to update and/or estimate the QCL properties for the same cell. The WTRU may (e.g., expect to) receive RS(s) (e.g., an aperiodic RS) that the WTRU may use for QCL estimation, for example, if/when the WTRU receives a PDCCH order for RACH transmission. The RS may be associated with the cell towards which the WTRU may initiate RACH transmission. The RS may be the RS (e.g., SSB and/or CSI-RS) indicated in the PDCCH order.

[0164] A PDCCH order to trigger RACH transmission may include a field for a TCI state update request. For example, the field may be a 1 -bit field. The field may indicate if the WTRU should estimate the QCL properties for the PCI and SSB/CSI-RS combination indicated in the PDCCH order. The 1 -bit field may trigger an aperiodic RS transmission that the WTRU may use to estimate the QCL properties.

[0165] A PDCCH order may include bit fields to trigger one or more of RACH transmission and/or QCL property estimation and/or DL synchronization. In an example, bit fields may be given as follows. A WTRU may trigger RACH transmission towards the indicated cell(s) and SSB/CSI-RS index(es), for example, based on bit field value 00. A WTRU may trigger RACH transmission and (e.g., expect to) receive a reference signal (e.g., aperiodic reference signal) that the WTRU may use for QCL purposes, for example, based on bit field value 01 . The RS may be the RS associated with the target cell. A WTRU may trigger RACH, expect an RS for QCL, and expect another RS (e.g., a tracking reference signal) from the target cell for DL synchronization, for example, based on a bit field value 10.

[0166] For example, a device (e.g., a WTRU) may (e.g., be configure to) perform one or more of the following actions: receive configuration information (e.g., via RRC) indicating one or more sets of cells (e.g., candidate cells) and/or random-access information (e.g., preambles, resources, parameters) for use with the one or more sets of cells (e.g., for each of the cells or for each set of cells); perform measurements (e.g., layer one (L1) measurements, reference signal received power (RSRP) measurements) for one or more candidate cells, e.g., where each cell may be associated with a PCI and/or each measurement may be associated with an SSB; select a set of cells from the one or more sets of cells based on the measurements (e.g., a set with RSRP measurements above a threshold); transmit a first indication (e.g., via a MAC CE) indicating at least one of: the selected set of cells, one or more SSBs associated with each cell in the selected set, and/or one or more measurements associated with the cells and/or SSBs; receive a trigger indicating to transmit one or more PRACH transmissions to the set of cells the WTRU selected and indicated (e.g., by the MAC CE) (e.g., the trigger may be an ACK received in response to the transmission of the first indication indicating that the first indication (e.g., the PDSCH carrying the first indication) was received successfully or the trigger may be a DCI or MAC-CE that indicates implicitly or explicitly to transmit PRACH to the set of cells the WTRU indicated by the first indication ); determine the randomaccess configuration information for the selected cell (s) (e.g., for each cell of the selected set of cells or for the selected set of cells); transmit (e.g., based on receiving the trigger) a PRACH (e.g., a PRACH preamble) to the selected cell (s) (e.g., to each of the cells in the selected set of cells) using the determined random access configuration information; and/or receive timing advance information for at least one (e.g., all) of the cells in the selected set (e.g., from a cell such as the WTRU’s serving cell). In examples, the WTRU may determine, e.g., based on the received indication (e.g., received in the MAC CE), the PCI and/or SSB (e.g., beam or spatial filter) to use for transmission to each cell in the set of cells.

[0167] PRACH transmission may occur based on RACH Occasions (ROs).

[0168] There may be multiple PRACH mask index values.

[0169] In some examples, a WTRU may determine and/or be indicated to transmit a signal to more than one cell. A signal may be a random-access preamble. The following methods may be applicable, for example, if the signal is a random-access preamble or a different type of signal/sequence (e.g., the signal may be a sequence, such as a Zadoff-Chu sequence or another type of sequence).

[0170] A WTRU may (e.g., be indicated to) transmit the signal with a PDCCH order. In some examples, the PDCCH order may include an index to a set of configured preambles. The WTRU may (e.g., be expected to) transmit the indicated preamble (e.g., in PRACH). In some examples, the PDCCH order may include multiple indexes for preambles. The first index may indicate a first preamble from a first set of configured preambles, the second index may indicate a second preamble from a second set of configured preambles, etc. The WTRU may (e.g., be expected to) transmit the preambles, for example in PRACH.

[0171] The PDCCH order may include a PRACH mask index. The mask index may indicate the PRACH occasions on which the WTRU is allowed to transmit a random-access preamble. The mask index may point to an entry in a (pre)configured or specified table. An entry in the table may include a list of allowed PRACH occasions. In some examples, a PDCCH order may include two or more PRACH mask indexes. A WTRU may determine the allowed ROs to transmit PRACH to more than one cell from the more than one mask index. The PRACH mask indexes may point to the same table or different tables.

[0172] Tables 1 and 2 are examples of PRACH mask index values. As an example, a WTRU may determine the allowed PRACH occasions from Table 1 using a first PRACH mask and from Table 2 using a second PRACH mask.

[0173] In a first example (e.g., example 1), a WTRU may receive mask indexes 1 and 3. The WTRU may (e.g., using Table 1) determine that the allowed ROs are RO#1 and even numbered ROs. The ROs may be used to send a preamble to a first cell.

[0174] In a second example (e.g., example 2), a WTRU may receive mask indexes 1 and 3. The WTRU may (e.g., using index 1 in Table 1 and index 3 in Table 2) determine that the allowed ROs are RO#1 and odd numbered ROs. The ROs may be used to send a preamble to a second cell.

Table 1 - Example of PRACH mask index values

Table 2 - Example of PRACH mask index values

[0175] In some examples, a (e.g., one) PRACH mask index may indicate two or more values, e.g., by pointing to an entry in a table where the entry may include two or more sets of PRACH occasions. Table 3 is an example of such PRACH mask index values. A WTRU may determine that the first set of ROs indicated by a table entry may be associated a first cell (e.g., the WTRU may use an RO from the set to transmit PRACH to a first cell) and the second set of ROs indicated by a table entry may be associated a second cell (e.g., the WTRU may use an RO from the set to transmit PRACH to a second cell), etc.

Table 3 - Example of PRACH mask index values

[0176] A WTRU may be indicated two or more SSB/CSI-RS indexes. An SSB/CSI-RS index may be used by a WTRU to determine the RO on which a preamble may be transmitted. The SSB/CSI-RS may be associated with different cells. A WTRU may use a rule that specifies how SSBs/CSI-RSs are mapped to ROs, for example, if/when determining the RO occasion from a SSB/CSI-RS index.

[0177] A WTRU may (e.g., determine to) transmit the preamble on an RO selected from one of the allowed ROs, for example, if one preamble index is indicated. A WTRU may (e.g., determine to) transmit the preamble in a first RO selected from the first set of allowed ROs, in a second RO selected from the second set of allowed ROs, etc., for example, if/when the WTRU is indicated two or more sets of allowed ROs. A WTRU may (e.g., determine to) transmit a first preamble in a first RO selected from the first set of allowed ROs, a second preamble in a second RO selected from the second set of allowed ROs, etc., for example, if/when two or more preambles are indicated.

[0178] In some examples, a WTRU procedure may implement one or more of the following, for example, if/when two separate sets of ROs are provided: a WTRU may receive a PDCCH order; the WTRU may determine a preamble index from the PDCCH order; the WTRU may determine a first and a second PRACH mask index value from the PDCCH order (e.g., the WTRU may determine a first set of ROs from the first PRACH mask index value and/or the WTRU may determine a second set of ROs from the second PRACH mask index value); the WTRU may determine a first RO within the first set of ROs from the first SSB/CSI-RS index (e.g., after mapping the SSB/CSU-RS index to the first set of ROs); the WTRU may determine a second RO within the second set of ROs from the second SSB/CSI-RS index (e.g., after mapping the SSB/CSI-RS to the second set of ROs); or the WTRU may transmit the preamble on the first RO and the second RO.

[0179] ROs may be shared between cells. In some examples, a WTRU may be indicated a single PRACH mask index value. The WTRU may determine a set of allowed RO occasions from a combination of SSB/CSI-RS index and PCI index, which may be achieved, for example, using one or more of the following. A WTRU may (e.g., first) allocate subgroups of ROs to different cells. A WTRU may determine (e.g., within a subgroup allocated to a cell) the RO for PRACH transmission from the SSB/CSI-RS associated to the cell. An example is shown in FIGS. 6-8. FIG. 6 illustrates an example of configured ROs. FIG. 7 illustrates an example of allowed ROs, for example, after applying a PRACH mask (e.g., as indicated by the dashed outline applied to RO#2, RO#6, RO#4, RO#8, RO#10, and RO#12). FIG. 8 illustrates an example of allocating allowed ROs to different PCIs and re-indexing.

[0180] A WTRU may (e.g., first) determine the ROs from the configuration parameters (e.g., as shown in FIG. 6). A WTRU may determine the allowed ROs, for example, by applying a PRACH mask (e.g., as shown in FIG. 7). The allowed ROs may be allocated to the PCIs and possibly re-indexed (e.g., as shown in FIG. 8). Corresponding SSB/CSI-RS may be mapped (e.g., for each PCI) to an RO from the ROs allocated to the PCI. A WTRU may assign an index to each (PCI)/(SSB/CSI-RS) combination. The WTRU may (e.g., then) map the combinations to the allowed ROs, e.g., first in frequency, then time, and then PRACH slots. [0181] A WTRU may generate a beam if/when transmitting PRACH, for example, if/when the WTRU is equipped with multiple transmit antennas. The WTRU may (e.g., also) generate multiple beams, for example, if/when the WTRU is equipped with multiple transmit/receive units.

[0182] A WTRU may use k (e.g., k = 2) TXRUs to create multiple (e.g., two) beams in multiple (e.g., two) directions associated with multiple (e.g., two) SSB/CSI-RS, for example, if the WTRU is indicated to send a preamble using beamforming. A WTRU (e.g., with this capability) may (e.g., be able to) transmit the preamble in multiple (e.g., two) different directions on the same time resources. A WTRU (e.g., equipped with a single TXRU) may transmit the preamble in multiple (e.g., two) non-overlapping time occasions. Whether the WTRU can transmit on same time resources may be based on WTRU capability and/or configuration. For example, a WTRU may (e.g., be allowed to) transmit the preambles on the same overlapping time resources if the WTRU has multiple (e.g., two) RF chains and can implement MU-MIMO. [0183] A WTRU may not be allowed ROs to different PCIs on the same time resources, for example, if the WTRU transmits the PRACH associated with different cells on different beams but is equipped with a single transmit chain.

[0184] Although features and elements described above are described in particular combinations, each feature or element may be used alone without the other features and elements of the preferred embodiments, or in various combinations with or without other features and elements.

[0185] Although the implementations described herein may consider 3GPP specific protocols, it is understood that the implementations described herein are not restricted to this scenario and may be applicable to other wireless systems. For example, although the solutions described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it is understood that the solutions described herein are not restricted to this scenario and are applicable to other wireless systems as well.

[0186] The processes described above may be implemented in a computer program, software, and/or firmware incorporated in a computer-readable medium for execution by a computer and/or processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted over wired and/or wireless connections) and/or computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as, but not limited to, internal hard disks and removable disks, magneto-optical media, and/or optical media such as compact disc (CD)-ROM disks, and/or digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, terminal, base station, RNC, and/or any host computer.

Claims

1. A wireless transmit/receive unit (WTRU) comprising: a processor configured to: receive configuration information that indicates a first set of cells, a second set of cells, random-access information associated with the first set of cells, and random-access information associated with the second set of cells; receive a first indication, wherein the first indication indicates the first set of cells; determine a random access preamble, resource, or parameter associated with cells in the first set of cells, wherein the random access preamble, resource, or parameter is determined based on the configuration information and the first indication; receive a second indication, wherein the second indication indicates to transmit a physical random access channel (PRACH) transmission to a cell, and wherein the cell is in the first set of cells; and send the PRACH transmission to at least the cell, wherein the PRACH transmission uses the random access preamble, resource, or parameter.

2. The WTRU of claim 1, wherein the first indication is received via a medium access control (MAC) control element (CE).

3. The WTRU of claim 1, wherein the second indication is received via a physical downlink control channel (PDCCH) transmission.

4. The WTRU of claim 1, wherein the processor is further configured to receive, based on the PRACH transmission, a timing advance value.

5. The WTRU of claim 4, wherein the processor is further configured to send, based on the timing advance value, another PRACH transmission to the cell.

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

7. The WTRU of claim 1, wherein the second indication comprises at least one of an index associated with the first set of cells or a set of cell/SSB combinations.

8. The WTRU of claim 1, wherein the first indication is included in a first transmission and the second indication is included in a second transmission, and wherein the first transmission is received prior to the second transmission.

9. The WTRU of claim 1, wherein the processor being configured to send the PRACH transmission to at least the cell comprises the processor being configured to send the PRACH transmission to a subset of cells in the first set of cells, and wherein the first set of cells includes the cell.

10. A method to be implemented by a wireless transmit/receive unit (WTRU) comprising: receiving configuration information that indicates a first set of cells, a second set of cells, randomaccess information associated with the first set of cells, and random-access information associated with the second set of cells; receiving a first indication, wherein the first indication indicates the first set of cells; receiving a second indication, wherein the second indication indicates to transmit a physical random access channel (PRACH) transmission; and sending the PRACH transmission to a subset of cells in the first set of cells based on the second indication.

11 . The method of claim 10, wherein the first indication is received via a medium access control (MAC) control element (CE).

12. The method of claim 10, wherein the second indication is received via a physical downlink control channel (PDCCH) transmission.

13. The method of claim 10, further comprising receiving, based on the PRACH transmission, a timing advance value.

14. The method of claim 10, wherein the second indication indicates the first set of cells.

15. The method of claim 10, wherein the second indication does not indicate the first set of cells.

16. The method of claim 10, further comprising determining a random access preamble, resource, or parameter associated with cells in the first set of cells, wherein the random access preamble, resource, or parameter is determined based on the configuration information and the first indication, and wherein the PRACH transmission uses the random access preamble, resource, or parameter.