Timing control for multi-panel WTRU transmissions

Abstract

A wireless transmit / receive unit (WTRU) may determine that a cell is associated with a first transmit and receive point (TRP) and a second TRP based on the received configuration information. The first TRP may be associated with a first timing advance group (TAG). The second TRP may be associated with a second TAG. The first TAG may be a primary TAG. The WTRU may determine that a first time alignment timer (TAT) associated with the first TAG has expired. The WTRU may determine, based on the determination that the first TAT has expired, that a timing advance (TA) associated with the second TAG will be used for transmission to the cell. The WTRU may send a transmission to the cell according to the TA associated with the second TAG.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 421,867, filed on November 2, 2022, and U.S. Provisional Patent Application No. 63 / 540,707, filed on September 27, 2023, the disclosures of which are incorporated herein by reference in their entireties. Background of the Invention

[0003] Mobile communication using wireless communication continues to evolve. The fifth generation can be referred to as 5G. The previous generation (conventional) mobile communication can be, for example, the fourth generation (4G) Long - Term Evolution (LTE). Summary of the Invention

[0004] Systems, methods, and means for transmitting transmissions to a cell associated with multiple transmission and reception points (TRPs) are described herein. In an example, a wireless transmit / receive unit (WTRU) may determine that a cell is associated with a first transmission and reception point (TRP) and a second TRP based on received configuration information. The first TRP may be associated with a first timing advance group (TAG). The second TRP may be associated with a second TAG. The first TAG may be the primary TAG. The WTRU may determine that a first duration (e.g., a first time alignment timer (TAT)) associated with the first TAG has expired. Based on the determination that the first duration has expired, the WTRU may determine that a timing advance (TA) associated with the second TAG will be used for transmissions to the cell. The WTRU may transmit to the cell based on the TA associated with the second TAG.

[0005] In an example, a cell may be associated with two primary TAGs: a first TAG may be a first primary TAG associated with the cell; and a second TAG associated with a second TRP may be a second primary TAG associated with the cell. The first primary TAG may be associated with a first duration, and the second primary TAG may be associated with a second duration (e.g., a second TAT). A WTRU may determine data and / or control information to be sent to the cell. The WTRU may determine that the first duration associated with the first primary TAG has expired and that the second duration associated with the second primary TAG has not expired, and based on that determination, send data and / or control information to the cell based on the TA associated with the second TAG. Based on the determination that the first duration associated with the first primary TAG has expired and the second duration associated with the second primary TAG has not expired, the WTRU may inhibit sending data and / or control information based on the TA associated with the first TAG. In some examples, the WTRU may determine to retransmit data and / or control information transmitted via a first TRP (e.g., after the WTRU determines that transmitting data and / or control information via the first TRP has failed). Based on the determination that the first duration associated with the first primary TAG has expired, the WTRU may transmit data and / or control information via a second TRP, and when transmitting data and / or control information via the second TRP, the hybrid automatic repeat request (HARQ) buffer associated with the first TRP may still include the data and / or control information or a copy of the data and / or control information.

[0006] In some examples, based on the determination that the first duration associated with the first primary TAG has expired, the WTRU performs one or more of the following: maintain the HARQ buffer associated with the first TRP; release resources associated with physical uplink control channel (PUCCH) transmissions scheduled to be sent to the cell or the first TRP; release resources associated with sounding reference signals (SRSs) to be sent to the cell or the first TRP; release resources scheduled via a downlink allocation configured for downlink transmissions associated with the cell or the first TRP; release resources scheduled via an uplink grant configured for uplink transmissions associated with the cell or the first TRP; or release resources scheduled for physical uplink shared channel (PUSCH) transmissions for semi-persistent channel state information (CSI) reporting associated with the cell or the first TRP.

[0007] In an example, the cell may be associated with a primary TAG, which may be a first TAG. The WTRU may determine that a time (e.g., an offset time before the expiration of the TAT associated with the primary TAG) has arrived. Based on the determination that the time has arrived, the WTRU may send a request to change the primary TAG from a first TAG associated with a first TRP to a second TAG associated with a second TRP. The request may be sent before the expiration of a first duration associated with the first TAG. For example, the WTRU may use a TA associated with the second TAG to send a first transmission including the request. The first transmission may include an indication that an offset time before the expiration of the first duration has arrived. In some examples, the WTRU may determine that the first duration will expire at a first time. The WTRU may determine that a difference between the current time and the first time is less than or equal to a value. The WTRU may send a request to change the primary TAG from the first TAG associated with the first TRP to the second TAG associated with the second TRP based on the determination that the difference between the current time and the first time is less than or equal to a value, and the request may be sent before the expiration of the first duration. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0009] Figure 1B is a system diagram of an example wireless transmit / receive unit (WTRU) that may be used within the communication system shown in Figure 1A in accordance with one embodiment;

[0010] Figure 1C is a system diagram of an example radio access network (RAN) and an example core network (CN) that may be used within the communication system shown in Figure 1A in accordance with one embodiment;

[0011] Figure 1D is a system diagram of additional example RANs and additional example CNs that may be used within the communication system shown in Figure 1A in accordance with one embodiment;

[0012] Figure 2 illustrates an example of multi-TRP (MTRP) operation and transition with multiple timing advance group (TAG) associations.

[0013] Figure 3 illustrates examples of PTAG transition or PTAG maintenance on different TRPs.

[0014] Figure 4 illustrates an example 400 of TAG transition for transmission. Detailed implementation manners

[0015] Figure 1A FIG. is a diagram illustrating an exemplary communication system 100 in which one or more of the disclosed embodiments may be implemented. The communication system 100 may be a multi-access system that provides content such as voice, data, video, messages, broadcasts, etc. to a plurality of wireless users. The communication system 100 may enable the plurality of wireless users to access such content by sharing system resources including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero-tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), and the like.

[0016] As Figure 1A shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a CN 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, but 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 one of which may be referred to as a "station" and / or "STA" - may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular telephones, personal digital assistants (PDAs), smartphones, laptop computers, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated processing chain environment), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, and the like. Any one of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0017] The communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks such as CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, base stations 114a, 114b may be base transceiver stations (BTSs), Node-Bs, eNode Bs, home Node Bs, home eNode Bs, gNBs, NR NodeBs, site controllers, access points (APs), wireless routers, and the like. Although base stations 114a, 114b are each depicted as a single element, it will be appreciated that base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0018] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown) such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for wireless services to a particular geographic area, which may be relatively fixed or may change over time. The cell may also be divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0019] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). Any suitable radio access technology (RAT) may be used to establish air interface 116.

[0020] More specifically, as described above, the communication system 100 can be a multi-access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base stations 114a and the WTRUs 102a, 102b, 102c in the RAN 104 / 113 can implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which can use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0021] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can use Long-Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro) to establish the air interface 116.

[0022] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement radio technologies such as NR radio access, which can use New Radio (NR) to establish the air interface 116.

[0023] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement multiple radio access technologies. For example, the base stations 114a and the WTRUs 102a, 102b, 102c can implement LTE radio access and NR radio access together, for example, using the Dual Connectivity (DC) principle. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c can be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNB and gNB).

[0024] 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.

[0025] Figure 1A The base station 114b in [description] may be, for example, a wireless router, a Home Node B, a Home eNode B, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area such as a commercial venue, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for drones), a road, 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 one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a Wireless Personal Area Network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a pico cell or a femto cell. As Figure 1A shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106 / 115.

[0026] The RAN 104 / 113 may communicate with the CN 106 / 115, and the CN 106 / 115 may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different Quality of Service (QoS) requirements such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 may provide call control, billing services, location-based services for mobile devices, prepaid calls, Internet connectivity, video distribution, etc., and / or perform advanced security functions such as user authentication. Although inFigure 1A is not shown, but it will be appreciated that RAN 104 / 113 and / or CN 106 / 115 may communicate directly or indirectly with other RANs that employ the same RAT as RAN 104 / 113 or a different RAT. For example, in addition to being connected to RAN 104 / 113 that may utilize NR radio technology, CN106 / 115 may also communicate with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0027] CN 106 / 115 may also be used as a gateway for WTRU 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices (which use common communication protocols such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite). The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN that is connected to one or more RANs, which may employ the same RAT as RAN 104 / 113 or a different RAT.

[0028] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, Figure 1A the WTRU 102c shown in may be configured to communicate with a base station 114a that may employ a cellular-based radio technology and with a base station 114b that may employ IEEE 802 radio technology.

[0029] Figure 1B is a system diagram of an illustrative example WTRU 102. As Figure 1B shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138, etc. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with the embodiments.

[0030] The processor 118 can be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 can perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 can be coupled to the transceiver 120, and the transceiver 120 can be coupled to the transmit / receive element 122. Although Figure 1B the processor 118 and the transceiver 120 are depicted as separate components, it will be appreciated that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0031] The transmit / receive element 122 can be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 can be a transmitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and / or receive both RF and optical signals. It will be appreciated that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0032] Although in Figure 1B the transmit / receive element 122 is described as a single element, the WTRU 102 can include any number of transmit / receive elements 122. More specifically, the WTRU 102 can employ MIMO technology. Thus, in one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals via the air interface 116.

[0033] The transceiver 120 can be configured to modulate the signals to be transmitted by the transmit / receive element 122 and demodulate the signals received by the transmit / receive element 122. As described above, the WTRU 102 can have multi-mode capabilities. Thus, the transceiver 120 can include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs (such as NR and IEEE 802.11), for example.

[0034] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from: the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keyboard 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: a memory that is not physically located on the WTRU 102 (such as a server or a home computer (not shown)).

[0035] The processor 118 may receive power from the power supply 134 and may be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry cells (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), a solar cell, a fuel cell, and the like.

[0036] 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 instead of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116, and / or may determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by any suitable location determination means while remaining consistent with the embodiments.

[0037] The processor 118 may be further coupled to other peripheral devices 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 peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, an electronic game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, and the like. The peripheral devices 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geographical location sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, an attitude sensor, a biosensor, and / or a humidity sensor.

[0038] The WTRU 102 may include a full-duplex radio for which the transmission and reception of some or all signals (e.g., associated with a particular subframe for both UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and / or substantially eliminate self-interference via hardware (e.g., a choke) or via signal processing by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which the transmission and reception of some or all signals (e.g., associated with a particular subframe for UL (e.g., for transmission) or downlink (e.g., for reception)).

[0039] Figure 1C is a system diagram of an illustrated RAN 104 and CN 106 according to one embodiment. As described above, the RAN 104 may communicate with the WTRU 102a, 102b, 102c via the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0040] The RAN 104 may include eNode-Bs 160a, 160b, 160c, although it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with the embodiments. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c via the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0041] 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, user scheduling in the UL and / or DL, and the like. As Figure 1C shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via the X2 interface.

[0042] Figure 1C The CN 106 shown may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (or PGW) 166. Although each of the foregoing elements is 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.

[0043] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via the S1 interface and may act 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 the initial attachment of the WTRUs 102a, 102b, 102c, and the like. The MME 162 may provide control plane functions for interworking between the RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0044] The SGW 164 can be connected via the S1 interface to each of the eNode-Bs 160a, 160b, 160c in the RAN 104. The SGW 164 can generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 can perform other functions such as anchoring the user plane during handovers between eNode Bs, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0045] The SGW 164 can be connected to the PGW 166, which can provide the WTRUs 102a, 102b, 102c with access to a packet switched network (such as the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0046] The CN 106 can facilitate communication with other networks. For example, the CN 106 can provide the WTRUs 102a, 102b, 102c with access to a circuit switched network such as the PSTN 108 to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, the CN 106 can include or communicate with the following: 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 can provide the WTRUs 102a, 102b, 102c with access to other networks 112, which can include other wired and / or wireless networks owned and / or operated by other service providers.

[0047] Although the WTRU is described as a wireless terminal in Figure 1A - Figure 1D it is contemplated that in some representative embodiments, such a terminal can (e.g., temporarily or permanently) use a wired communication interface with the communication network.

[0048] In a representative embodiment, another network 112 can be a WLAN.

[0049] In a wireless local area network (WLAN) in infrastructure basic service set (BSS) mode, there can be an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP can have access to or be connected to a distributed system (DS) or another type of wired / wireless network that carries traffic into and / or out of the BSS. Traffic destined for an STA from outside the BSS can reach the STA through the AP and can be delivered to the STA. Traffic originating from an STA to a destination outside the BSS can be sent to the AP to be delivered to the corresponding destination. For example, traffic between STAs within the BSS can be sent through the AP, where the source STA can send the traffic to the AP and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS can be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic can be sent between the source STA and the destination STA using direct link setup (DLS) (e.g., directly between the source STA and the destination STA). In some representative embodiments, DLS can use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using independent BSS (IBSS) mode may not have an AP, and STAs within the IBSS or using the IBSS (e.g., all STAs) can communicate directly with each other. The IBSS communication mode is sometimes referred to as the "ad hoc" communication mode in this document.

[0050] When using 802.11ac infrastructure operation mode or a similar operation mode, the AP can transmit beacons on a fixed channel (such as the primary channel). The primary channel can be of a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by the STAs to establish a connection with the AP. In some representative embodiments, for example, in 802.11 systems, carrier sense multiple access with collision avoidance (CSMA / CA) can be implemented. For CSMA / CA, STAs including the AP (e.g., each STA) can sense the primary channel. If the primary channel is sensed / detected by a particular STA and / or determined to be busy, that particular STA can back off. One STA (e.g., only one station) can transmit at any given time in a given BSS.

[0051] High throughput (HT) STAs can communicate using a 40 MHz wide channel, for example, by combining the primary 20 MHz channel with an adjacent or non-adjacent 20 MHz channel to form a 40 MHz wide channel.

[0052] A very high throughput (VHT) STA can support channels that are 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide. 40 MHz and / or 80 MHz channels can be formed by combining adjacent 20 MHz channels. A 160 MHz channel can be formed by combining eight adjacent 20 MHz channels, or by combining two non - adjacent 80 MHz channels - this can be referred to as an 80 + 80 configuration. For the 80 + 80 configuration, after channel coding, the data can pass through a segment parser that can split the data into two streams. The inverse fast Fourier transform (IFFT) processing and time - domain processing can be performed separately on each stream. These streams can be mapped to two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the above operations for the 80 + 80 configuration can be reversed, and the combined data can be sent to the media access control (MAC).

[0053] 802.11af and 802.11ah support operation modes below 1 GHz. Relative to the operation modes used in 802.11n and 802.11ac, the channel operation bandwidth and carrier are reduced in 802.11af and 802.11ah. 802.11af 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, 802.11ah can support metering - type control / machine - type communication, such as MTC devices in a macro - coverage area. MTC devices can have certain capabilities (e.g., limited capabilities), which include supporting (e.g., only supporting) certain and / or limited bandwidths. MTC devices can include a battery with a battery life higher than a threshold (e.g., to maintain a very long battery life).

[0054] A WLAN system that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) includes a channel that can be designated as the primary channel. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or restricted by the STA that supports the minimum bandwidth operation mode among all STAs operating in the BSS. In the example of 802.11ah, for an STA that supports (e.g., only supports) the 1MHz mode (e.g., an MTC type device), the primary channel can be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operation modes. Carrier sensing and / or network allocation vector (NAV) settings can depend on the state of the primary channel. If the primary channel is busy, for example, due to an STA (which only supports the 1MHz operation mode) transmitting to the AP, the entire available frequency band can be considered busy, even if most of the frequency band remains idle and can be available.

[0055] In the United States, the available frequency band that can be used by 802.11ah is from 902MHz to 928MHz. In Korea, the available frequency band is from 917.5MHz to 923.5MHz. In Japan, the available frequency band is from 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0056] Figure 1D FIG. is a system diagram illustrating RAN 113 and CN 115 according to one embodiment. As described above, RAN 113 can communicate with WTRUs 102a, 102b, 102c via air interface 116 using NR radio technology. RAN 113 can also communicate with CN 115.

[0057] The RAN 113 may include gNBs 180a, 180b, 180c, although it should be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with the embodiments. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c via the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to the WTRU 102a and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or gNB 180c).

[0058] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol interval and / or the OFDM subcarrier interval may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may use subframes or transmission time intervals (TTIs) of various or scalable lengths (e.g., which contain different numbers of OFDM symbols and / or last for different lengths of absolute time) to communicate with the gNBs 180a, 180b, 180c.

[0059] gNBs 180a, 180b, 180c can be configured to communicate with WTRUs 102a, 102b, 102c in a stand-alone configuration and / or in a non-stand-alone configuration. In a stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c without also accessing another RAN (e.g., such as eNode-Bs 160a, 160b, 160c). In a stand-alone configuration, WTRUs 102a, 102b, 102c can utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor. In a stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-stand-alone configuration, WTRUs 102a, 102b, 102c can communicate / connect with gNBs 180a, 180b, 180c while also communicating / connecting with another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c can implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-stand-alone configuration, eNode-Bs 160a, 160b, 160c can act as a mobility anchor for WTRUs 102a, 102b, 102c, and gNBs 180a, 180b, 180c can provide additional coverage and / or throughput for serving WTRUs 102a, 102b, 102c.

[0060] Each of gNBs 180a, 180b, 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, network slice support, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPFs) 184a, 184b, routing of control plane information to access and mobility management functions (AMFs) 182a, 182b, and the like. As Figure 1D shown, gNBs 180a, 180b, 180c can communicate with each other via the Xn interface.

[0061] Figure 1DThe CN 115 shown in [Figure 0] 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 Data Networks (DN) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by entities other than the CN operator.

[0062] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, managing the registration area, terminating NAS signaling, mobility management, and the like. The AMF 182a, 182b may use network slicing in order to customize the CN support for the WTRUs 102a, 102b, 102c based on the type of service the WTRUs 102a, 102b, 102c are utilizing. 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 182 may provide control plane functions for interworking between the RAN 113 and other RANs (not shown) employing other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0063] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. The PDU session type may be IP-based, non-IP-based, Ethernet-based, and the like.

[0064] UPF 184a and 184b can be connected to one or more of gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which can provide access to a packet switched network (such as the Internet 110) for the WTRUs 102a, 102b, 102c to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPF 184a, 184b can 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.

[0065] The CN 115 can facilitate communication with other networks. For example, the CN 115 can include or communicate with the following: an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. Additionally, the CN 115 can provide access to other networks 112 for the WTRUs 102a, 102b, 102c, and the other networks 112 can include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c can be connected to local DNs 185a, 185b via the N3 interface to the UPF 184a, 184b and the N6 interface between the UPF 184a, 184b and the data networks (DNs) 185a, 185b through the UPF 184a, 184b.

[0066] In view of Figure 1A - Figure 1D and Figure 1A - Figure 1D the corresponding descriptions of, one or more or all of the functions of one or more of the WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DNs 185a-b, and / or any other device(s) described herein can be performed by one or more emulation devices (not shown). The emulation device(s) can be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation device(s) can be used to test other devices and / or simulate network and / or WTRU functions.

[0067] A simulation device can be designed to perform one or more tests on other devices in a laboratory environment and / or an operator network environment. For example, one or more simulation devices can perform 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 to test other devices within the communication network. One or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. A simulation device can be directly coupled to another device for testing purposes and / or can perform tests using over-the-air wireless communication.

[0068] One or more simulation devices can perform one or more functions (including all functions) without being implemented / deployed as part of a wired and / or wireless communication network. For example, a simulation device can be used in test scenarios in a test laboratory and / or a non-deployed (e.g., test) wired and / or wireless communication network to enable testing of one or more components. One or more simulation devices can be test devices. A simulation device can use direct RF coupling and / or wireless communication via an RF circuit (e.g., which can include one or more antennas) to transmit and / or receive data.

[0069] Systems, methods, and means for timing control of multi-panel WTRU transmissions are described herein. For example, a WTRU can determine a transmission / reception point identity (TRP-id) based on physical downlink control channel (PDCCH) related information for monitoring the downlink control information (DCI) format of PDCCH commands, e.g., based on a control resource set (CORESET) pool identity (CORESETPoolID), CORESET-id, PDCCH search space id, and / or PDCCH candidate resources.

[0070] A WTRU can determine one or more parameters for physical random access channel (PRACH) transmission of a physical downlink control channel (PDCCH) command, e.g., based on a transmission / reception point identity (TRP-id). The one or more parameters can include, for example, at least one of the following: a random access preamble index (ra-PreambleIndex); an uplink (UL) / supplementary uplink (SUL) indicator; a synchronization signal (SS) / physical broadcast channel (PBCH) index, which can determine a random access channel (RACH) occasion; a PRACH mask index, which can determine a subset of the RACH occasions determined according to the SS / PBCH index; and so on.

[0071] A WTRU may transmit a Physical Random Access Channel (PRACH) for a Physical Downlink Control Channel (PDCCH) command based on at least one determined parameter. In response to the PRACH transmission for the PDCCH command, the WTRU may receive a Random Access Response (RAR). The RAR associated with the PRACH transmission for the PDCCH command may include one or more of the following: associated PRACH preamble related information, associated TRP-id, associated TAG, or associated SRS resource set information.

[0072] A WTRU may elevate a Timing Advance Group (TAG) (e.g., a (P)STAG configured in a Special Cell (SpCell)) to a Primary TAG (PTAG), e.g., based on one or more of the following conditions: whether the Primary Cell (pCell) includes multiple TRPs; network (NW) configuration (e.g., RRC configuration enabling / disabling the elevation to the PTAG); NW indication (e.g., via an (explicit) indication received in system information, Media Access Control (MAC) Control Element (CE), and / or Downlink Control Information (DCI)); whether the Time Alignment Timer (TAT) associated with the PTAG has expired or is about to expire; whether the TAT associated with the PSTAG is still running; whether the TAT associated with the PSTAG has a configured remaining amount of time; and / or whether the Reference Signal Received Power (RSRP) on one or more TRP links is higher than a threshold.

[0073] A WTRU may transition from a first TAG to a second TAG. For example, the WTRU may determine that a first TAT associated with the first TAG is about to expire. The WTRU may transmit (e.g., to a second TRP associated with the second TAG or to a second cell associated with the second TAG) a message indicating that the first TAT is about to expire (e.g., the remaining time until the first TAT expires / before the first TAT expires may be less than a threshold, where the threshold may be configured or indicated from the gNB to the WTRU).

[0074] In an example, a WTRU may receive configuration information indicating cells associated with a first transmission and reception point (TRP) and a second TRP. The first TRP may be associated with a first timing advance group (TAG) and a first timing alignment timer (TAT), and the second TRP may be associated with a second TAG and a second TAT. The first TAG may be the primary TAG. The WTRU may determine that an offset time from the expiration of the first TAT has arrived. Based on the determination that the offset time from the expiration of the first TAT has arrived, the WTRU may use a first timing advance (TA) associated with the second TAG to send a first transmission. The first transmission may include a request to convert the second TAG to the primary TAG. The WTRU may receive approval of the request. The WTRU may use a second TA associated with the second TAG to send a second transmission (e.g., the second transmission may be sent after the expiration of the first TAT). The second transmission may be sent to the second TRP or second cell associated with the second TAG. Before the expiration of the first TAT, the first transmission may be sent to the second TRP or second cell. The first transmission may include an indication that the offset time from the expiration of the first TAT has arrived. When the TAT associated with the primary TAG has not expired, the WTRU may be allowed to transmit to the cell (and the second cell).

[0075] PTAG conversion behavior may be applicable based on different scenarios (e.g., a 1-PTAG model or a 2-PTAG model). The 2-PTAG model may include more than one PTAG (e.g., both TAGs of a cell may be PTAGs), where the WTRU may transmit information indicating that the second TAG will be used to determine whether to perform recovery (e.g., one or more recovery actions herein) across cells.

[0076] Examples of PTAG conversion in a multi-TRP and CA scenario may be provided. For example, a WTRU may receive configuration information indicating that a first cell is associated with a first and a second TRP, where the first TRP is associated with a first TAG (e.g., a PTAG) and a first TAT, and the second TRP may be associated with a second TAG and a second TAT. The WTRU may determine that the first TAT is about to expire (e.g., an offset from expiration). The WTRU may transmit a message indicating that the first TAT is about to expire and a request to convert the PTAG from the first TAG to the second TAG to the second TRP or the second cell associated with the second TAG. The WTRU may receive confirmation of the conversion request. After the expiration of the first TAT, the WTRU may transmit an UL signal to the first cell or the second cell (e.g., using the TA associated with the second TAG).

[0077] Example TAG associations between a TRP / cell and a WTRU panel can be provided. For example, the WTRU may receive configuration information indicating first and second SRS resource sets for simultaneous Tx from multiple WTRU panels (STxMP). The WTRU may receive a scheduling grant (e.g., for UL channels or signals from the STxMP) that indicates that first and second sets of layers for the UL are associated with respective first and second TAGs / PCIs (e.g., physical cell IDs, e.g., inter-cell MTRP). Based on more than one SRS resource indicator (SRI) associated with the scheduling grant, the WTRU may determine that the first and second sets of layers are mapped to the first and second SRS resource sets (WTRU panels), respectively. The WTRU may transmit the first set of layers from the first WTRU panel using a first TA based on the first TAG (and first PCI), and (e.g., simultaneously) transmit the second set of layers from the second WTRU panel using a second TA based on the second TAG (and second PCI).

[0078] Systems, methods, and means for transmitting to a cell associated with multiple transmission and reception points (TRPs) are described herein. In an example, a wireless transmit / receive unit (WTRU) may determine that a cell is associated with a first transmission and reception point (TRP) and a second TRP based on received configuration information. The first TRP may be associated with a first timing advance group (TAG). The second TRP may be associated with a second TAG. The first TAG may be a primary TAG. The WTRU may determine that a first duration (e.g., a first time alignment timer (TAT)) associated with the first TAG has expired. Based on the determination that the first duration has expired, the WTRU may determine that a timing advance (TA) associated with the second TAG will be used for transmission to the cell. The WTRU may transmit to the cell based on the TA associated with the second TAG.

[0079] In an example, a cell may be associated with two primary TAGs: a first TAG may be a first primary TAG associated with the cell; and a second TAG associated with a second TRP may be a second primary TAG associated with the cell. The first primary TAG may be associated with a first duration, and the second primary TAG may be associated with a second duration (e.g., a second TAT). A WTRU may determine data and / or control information to be sent to the cell. The WTRU may determine that the first duration associated with the first primary TAG has expired and that the second duration associated with the second primary TAG has not expired, and based on that determination, send data and / or control information to the cell based on the TA associated with the second TAG. Based on the determination that the first duration associated with the first primary TAG has expired and the second duration associated with the second primary TAG has not expired, the WTRU may suppress sending data and / or control information based on the TA associated with the first TAG. In some examples, the WTRU may determine to retransmit data and / or control information transmitted via a first TRP (e.g., after the WTRU determines that transmitting data and / or control information via the first TRP has failed). Based on the determination that the first duration associated with the first primary TAG has expired, the WTRU may transmit data and / or control information via a second TRP, and when transmitting data and / or control information via the second TRP, the hybrid automatic repeat request (HARQ) buffer associated with the first TRP may still include data and / or control information or a copy of the data and / or control information.

[0080] In some examples, based on the determination that the first duration associated with the first primary TAG has expired, the WTRU performs one or more of the following: maintaining the HARQ buffer associated with the first TRP; releasing resources associated with physical uplink control channel (PUCCH) transmissions scheduled to be sent to the cell or the first TRP; releasing resources associated with sounding reference signals (SRSs) to be sent to the cell or the first TRP; releasing resources scheduled via a downlink allocation configured for downlink transmissions associated with the cell or the first TRP; releasing resources scheduled via an uplink grant configured for uplink transmissions associated with the cell or the first TRP; or releasing resources scheduled for physical uplink shared channel (PUSCH) transmissions for semi-persistent channel state information (CSI) reporting associated with the cell or the first TRP.

[0081] In an example, the cell may be associated with a primary TAG, which may be a first TAG. The WTRU may determine that a time (e.g., an offset time before the expiration of the TAT associated with the primary TAG) has arrived. Based on the determination that the time has arrived, the WTRU may send a request to change the primary TAG from a first TAG associated with a first TRP to a second TAG associated with a second TRP. The request may be sent before the expiration of a first duration associated with the first TAG. For example, the WTRU may use a TA associated with the second TAG to send a first transmission including the request. The first transmission may include an indication that an offset time before the expiration of the first duration has arrived. In some examples, the WTRU may determine that the first duration will expire at a first time. The WTRU may determine that a difference between the current time and the first time is less than or equal to a value. The WTRU may send a request to change the primary TAG from a first TAG associated with a first TRP to a second TAG associated with a second TRP based on the determination that the difference between the current time and the first time is less than or equal to a value, and the request may be sent before the expiration of the first duration.

[0082] A unified Transmission Configuration Indicator (TCI) framework may support (e.g., one) unified TCI (e.g., joint or a pair of separate DL / UL). For example, a unified TCI may be indicated / maintained at the WTRU to (e.g., simultaneously) apply to control / data channels, which may be different from per-channel separate beam control.

[0083] Multi-Transmission and Reception Point (MTRP) may support: multi-DCI-based MTRP (MDCI-MTRP), e.g., based on CORESETPoolIndex = 0 or 1, to support eMBB; and / or single-DCI-based MTRP (SDCI-MTRP), e.g., based on multiple (e.g., up to two) TCI states associated with the code points in the TCI field in the DCI, for repeated transmission across TRPs, and / or for reliability enhancement. MTRP may be used interchangeably with MTRP, mTRP, M-TRP, and multiple transmission and reception points.

[0084] It can support multiple-input multiple-output (MIMO). For example, for higher UL throughput / reliability, simultaneous multi-panel UL transmission can be facilitated. For example, for customer premises equipment (CPE) / fixed wireless access (FWA) / vehicles / industrial equipment (if applicable), frequency range two (FR2) and / or multi-TRP can be supported with, for example, one or more (e.g., up to two (2)) TRPs and / or one or more (e.g., up to two (2)) panels. UL precoding indication can be provided for PUSCH, e.g., without introducing a new codebook for multi-panel simultaneous transmission. For example, the total number of layers across all panels can be up to four. For example, considering single-DCI- and multi-DCI-based multi-TRP operations, one or more codewords (e.g., up to two in total) can exist across one or more (e.g., all) panels.

[0085] For multi-TRP operations, one or more (e.g., two) timing advances (TAs) can exist for UL multi-DCI. For example, power control for UL single-DCI for multi-TRP operations can be extended using the unified TCI framework.

[0086] Latency and / or flexibility can be improved for or based on the association between WTRU multi-panels, TRPs, multiple TAGs, inter-cell MTRP scenarios, etc. For example, if / when the TA procedure (e.g., the link between the WTRU panel and the TRP) is determined to fail, e.g., if / when the corresponding duration / period (e.g., timer) expires, the UL performance of simultaneous transmission from multiple panels (STxMP) can be improved.

[0087] In this document, terms such as "a", "an", and similar terms / phrases are interpreted as "one or more" and "at least one", and can be used interchangeably with "one or more" and "at least one". Terms ending with the suffix "(s)" are interpreted as "one or more" and "at least one". The term "can" is interpreted as "can, for example" and is used interchangeably with "can, for example". For example, the symbol, sign, or notation of the forward slash " / " is interpreted as "and / or" unless otherwise explicitly stated. For example, "A / B" can be interpreted as "A and / or B".

[0088] The WTRU can transmit and / or receive physical channel transmissions or reference signals according to at least one spatial domain filter. The spatial domain filter can be referred to as a beam.

[0089] A WTRU may transmit a physical channel and / or signal using the same spatial domain filter as that used for receiving a reference signal (RS), such as a channel state information (CSI) RS (CSI-RS) or a synchronization signal (SS) block. The WTRU transmission may be referred to as the target. The received RS or SS block may be referred to as the reference or source. It may be said that the WTRU (e.g., in this case) transmits the target physical channel or signal based on the spatial relationship with the reference RS or SS block.

[0090] A WTRU may transmit a first physical channel or signal using the same spatial domain filter as that used for transmitting a second physical channel or signal. The first and second transmissions may be referred to as "target" and "reference" (or "source"), respectively. It may be said that the WTRU (e.g., in this case) transmits the first (target) physical channel or signal based on the spatial relationship with respect to the second (reference) physical channel or signal.

[0091] The spatial relationship may be implicit, configured by RRC, and / or signaled by a MAC CE or DCI. For example, a WTRU may transmit a PUSCH and the DM-RS of the PUSCH based on the same spatial domain filter (e.g., implicitly) as that of a sounding reference signal (SRS) indicated by a sounding reference signal resource indicator (SRI) (e.g., indicated in a DCI or configured by RRC). In some examples, the spatial relationship may be configured by RRC for an SRI or signaled by a MAC CE for a PUCCH. This spatial relationship may be referred to as beam indication.

[0092] A WTRU may receive a first (target) downlink channel or signal based on the same spatial domain filter or spatial reception parameter as that of a second (reference) downlink channel or signal. For example, such an association may exist between a physical channel such as a PDCCH or a PDSCH and the corresponding DM-RS of that physical channel. For example, an association may exist if / when the first and second signals are reference signals and the WTRU is configured with a quasi-co-location (QCL) assumption type D between the corresponding antenna ports. The association may be configured as a transmission configuration indicator (TCI) state. A WTRU may indicate, for example, the association between a CSI-RS or an SS block and a DM-RS by indexing a set of TCI states (e.g., receiving an indication of the association between a CSI-RS or an SS block and a DM-RS), and this index may be configured by RRC and / or signaled by a MAC CE. The indication may be referred to as beam indication.

[0093] A unified TCI (e.g., a common TCI, a common beam, a common RS, etc.) can be referred to as a beam / RS that can be used (e.g., simultaneously used) for multiple physical channels / signals. The term TCI can include a TCI state that includes at least one source RS to provide a reference for determining quasi-co-location (QCL) and / or a spatial filter (e.g., a WTRU assumption).

[0094] In some examples, a WTRU may receive (e.g., from a gNB) an indication of a first unified TCI that will be used / applied to a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH) (e.g., and a downlink RS). The (one or more) source reference signals in the first unified TCI may provide common QCL information, e.g., for WTRU-specific (e.g., UE-specific) reception on the PDSCH and / or all or a subset of a CORESET in a component carrier (CC). In some examples, a WTRU may receive (e.g., from a gNB) an indication of a second unified TCI that can be used / applied to an uplink control channel (e.g., a PUCCH) and / or an uplink shared channel (e.g., a PUSCH) and, e.g., an uplink RS. The one or more source reference signals in the second unified TCI may provide a reference for determining (one or more) common UL TX spatial filters, e.g., for all or a subset of a PUSCH based on a dynamic grant / configured grant and dedicated PUCCH resources in a CC.

[0095] A WTRU may be configured with a first mode for the unified TCI (e.g., a separate UL TCI mode). The indicated unified TCI (e.g., the first unified TCI or the second unified TCI) may be applicable to the downlink (e.g., based on the first unified TCI) and / or the uplink (e.g., based on the second unified TCI).

[0096] In some examples, a WTRU may receive (e.g., from a gNB) an indication of a second unified TCI that can be (e.g., generally) used / applied to a PDCCH, a PDSCH, a PUCCH, and / or a PUSCH (e.g., and a DL RS and / or an UL RS).

[0097] A WTRU may be configured with a second mode for the unified TCI (e.g., a Joint TCI mode). The indicated unified TCI (e.g., a third unified TCI) may be applicable to the downlink and the uplink (e.g., based on the third unified TCI).

[0098] A WTRU may determine a TCI state applicable for transmission and / or reception, e.g., by (e.g., first) determining a unified TCI state instance applicable for transmission and / or reception. The WTRU may determine the TCI state corresponding to the unified TCI state instance. Transmission may include at least PUCCH, PUSCH, or SRS. Reception may include at least PDCCH, PDSCH, or CSI-RS. The unified TCI state instance may be referred to as a TCI state group, a TCI state process, a unified TCI pool, a TCI state group, a set of time domain instances / timestamps / time slots / symbols, and / or a set of frequency domain instances / radio bearer (RB) sub-bands, etc. The unified TCI state instance may be equivalent to and / or identified by the following: CORESET pool identity (e.g., CORESETPoolIndex, TRP indicator, and / or the like).

[0099] As used in one or more examples herein, the term "unified TCI" may refer to (one or more) unified TCI states, unified TCI instances, TCI, and / or TCI states. As used in one or more examples herein, the term "TRP" may refer to a transmission point (TP), a reception point (RP), a radio remote head (RRH), a distributed antenna (DA), a base station (BS), a sector (e.g., a sector of a BS), and / or a cell (e.g., a geographical cell area served by a BS).

[0100] The TRP, SRI, and / or path loss (PL) reference RS may be configured. The WTRU may utilize one or more TRP configurations (e.g., may receive a configuration associated with one or more TRPs). The WTRU may transmit to and / or from one or more (e.g., configured) TRPs. The WTRU may utilize one or more TRP configurations for one or more cells. The cell may be a serving cell and / or a secondary cell.

[0101] The WTRU may utilize at least one RS configuration, e.g., for the purpose of channel measurement. The at least one RS may be represented as a channel measurement resource (CMR). The at least one RS may include CSI-RS, a synchronization signal block (SSB), or other downlink RS transmitted from a TRP to the WTRU. The CMR may utilize a TCI state configuration and / or otherwise be associated with the TCI state. The WTRU may utilize a CMR group configuration, e.g., where the CMRs transmitted from the same TRP may be configured. Each group may be identified by a CMR group index (e.g., group 1). The WTRU may utilize (e.g., one) CMR group configuration for each TRP. The WTRU may receive a link between (e.g., one) CMR group index and another CMR group index, and / or a link between (e.g., one) RS index from (e.g., one) CMR group and another RS index from another group.

[0102] The WTRU may utilize the following configurations (e.g., receive the following configurations): one or more path loss (PL) reference groups (e.g., sets) and / or one or more SRS groups, SRI, and / or SRS resource sets.

[0103] The PL reference group may correspond to and / or be associated with the TRP. The PL reference group may include, identify, correspond to, and / or be associated with one or more TCI states, SRI, reference signal sets (e.g., CSI-RS sets, SRI sets), CORESET indices, and / or reference signals (e.g., CSI-RS, SSB).

[0104] The WTRU may receive a configuration (e.g., any configuration described herein). For example, the configuration may be received from the gNB or the TRP. For example, the WTRU may receive a configuration of one or more TRPs, one or more PL reference groups, and / or one or more SRI sets. The WTRU may (e.g., implicitly) determine the association between the RS set / group and the TRP. For example, the WTRU may utilize multiple (e.g., two) SRS resource set configurations. The WTRU may (e.g., determine) transmit to the TRP1 with SRS in the first resource set and transmit to the TRP2 with SRS in the second resource set. For example, the configuration may be received via RRC signaling.

[0105] The examples described herein may apply to the TRP, PL reference group, SRI group, and SRI set. For example, although some examples may be described in terms of one of the following: TRP; PL reference group; SRI group; and SRI set, the example may also apply to other terms listed herein. The terms "set" and "group" may be used interchangeably in one or more examples herein.

[0106] The WTRU may report a subset of channel state information (CSI) components. The CSI components may correspond to, for example, one or more of the following: CSI-RS resource indicator (CRI); SSB resource indicator (SSBRI); indication of the panel received at the WTRU (e.g., panel identity or group identity); measurements such as L1-RSRP, L1-SINR (e.g., cri-RSRP, cri-SINR, ssb-index-RSRP, ssb-index-SINR) obtained from the SSB or CSI-RS; and / or other channel state information such as rank indicator (RI), channel quality indicator (CQI), precoding matrix indicator (PMI), layer index (LI), and / or the like.

[0107] The grant or allocation may include one or more attributes or be associated with one or more attributes. Attributes of the grant or allocation may include, for example, at least one of the following: frequency assignment; an aspect of time assignment, such as duration; priority; modulation and coding scheme; transport block size; multiple spatial layers; multiple transport blocks; TCI state, CRI, or SRI; number of repetitions; an indication of whether the repetition scheme is type A or type B; an indication of whether the grant is a configured grant type 1, type 2, or dynamic grant; an indication of whether the allocation is a dynamic allocation or a semi-persistent scheduling (e.g., configured) allocation; a configured grant index or semi-persistent allocation index; the periodicity of the configured grant or allocation; channel access priority class (CAPC); (e.g., any) parameter for scheduling the grant or allocation (e.g., in DCI, provided by MAC, or provided by RRC).

[0108] An indication in DCI (e.g., an indication received using DCI) may include, for example, at least one of the following: an (e.g., explicit) indication of a DCI field or radio network identifier (RNTI) for masking the cyclic redundancy check (CRC) of the PDCCH; or an (e.g., implicit) indication of an attribute, such as DCI format, DCI size, CORESET or search space, aggregation level, the first resource element of the received DCI (e.g., the index of the first control channel element), for example where the mapping between the attribute and the value may be signaled by RRC or MAC.

[0109] As used in one or more examples herein, the term "signal" may refer to one or more of the following: sounding reference signal (SRS); channel state information-reference signal (CSI-RS); demodulation reference signal (DM-RS); phase tracking reference signal (PT-RS); and / or synchronization signal block (SSB).

[0110] As used in one or more examples herein, the term "channel" may refer to one or more of the following: physical downlink control channel (PDCCH); physical downlink shared channel (PDSCH); physical uplink control channel (PUCCH); physical uplink shared channel (PUSCH); physical random access channel (PRACH); and so on.

[0111] As used in one or more examples herein, the term "downlink reception" may refer to one or more of the following: Rx opportunity, PDCCH, PDSCH, and / or SSB reception. As used in one or more examples herein, the term "uplink transmission" may refer to one or more of the following: transmission (Tx) opportunity, PUCCH, PUSCH, PRACH, and / or SRS transmission.

[0112] As used in one or more examples herein, the term "reference signal (RS)" may refer to one or more of the following: RS resource, RS resource set, RS port, and / or RS port group. As used in one or more examples herein, the term "RS" may refer to one or more of the following: SSB, CSI-RS, SRS, and / or DM-RS. As used in one or more examples herein, the term "time instance" may refer to a time slot, a symbol, and / or a subframe.

[0113] TA procedures can be implemented for UL Tx modes, such as including MTRP / MPUE (e.g., a WTRU / UE with multiple panels). For MTRP / MPUE, there can be one or more UL Tx modes. The WTRU can be configured (e.g., from the gNB) with one or more UL transmission modes (e.g., schemes, scenarios, behaviors, methods, procedures, programs). The UL Tx mode (in one or more of the UL Tx modes, for example) can be based on at least one of, for example, the following: case A (sPanel, sTRP); case B (sPanel, selective-TRP); case C (selective-panel, sTRP); case D (selective-panel, selective-TRP); case E (STxMP, sTRP); case F (STxMP, selective-TRP); case G (STxMP, multi-TRP); and / or case X. Case A (e.g., sPanel, sTRP) can be indicated by UL Tx based on a single WTRU panel (e.g., a set of antennas, a Tx entity that controls Tx beam / power / timing, etc.) and / or orientation (e.g., going to, associated with, pointing to, linked to) a TRP / cell. Case A can be associated with a TA procedure based on a TAG, for example. Case B (e.g., sPanel, selective-TRP) can be indicated by UL Tx based on a single WTRU panel orientation to a selected / indicated TRP / cell among more than one TRP / cell. Case B can be associated with one or more TA procedures (e.g., two TA procedures based on two PTAGs) based on one or more TAGs. For example, the WTRU can be based on the selected / indicated TRP / cell (e.g., as Figure 4to determine the TA process in one or more TA processes as shown by 408 in []. Case C (e.g., selective-panel, sTRP) can be indicated by the UL Tx based on the WTRU panel selected / indicated in more than one WTRU panel, towards the TRP / cell. Case C can be associated with one or more TA processes based on one or more TAGs (e.g., two TA processes based on two PTAGs). For example, the WTRU can determine the TA process in one or more TA processes based on the selected / indicated WTRU panel. Case D (e.g., selective-panel, selective-TRP) can be indicated by the UL Tx based on the WTRU panel selected / indicated in more than one WTRU panel, towards the TRP / cell selected / indicated in more than one TRP / cell. Case D can be associated with one or more TA processes based on one or more TAGs (e.g., two TA processes based on two PTAGs). For example, the WTRU can determine the TA process in one or more TA processes based on the selected / indicated WTRU panel and / or the selected / indicated TRP / cell. Case E (e.g., STxMP, sTRP) can be indicated by the UL Tx (e.g., simultaneously) based on more than one WTRU panel (e.g., STxMP) towards a (single) TRP / cell. Case E can be associated with one or more TA processes based on one or more TAGs (e.g., two TA processes based on two PTAGs). The WTRU can determine the first TA process (e.g., in one or more TA processes) corresponding to the first WTRU panel among the multiple WTRU panels. The WTRU can determine the second TA process (e.g., in one or more TA processes) corresponding to the second WTRU panel among the multiple WTRU panels. The second TA process can be associated with the first TA process (e.g., based on an offset parameter). Case F (e.g., STxMP, selective-TRP) can be the UL Tx (e.g., simultaneously) based on more than one WTRU panel (e.g., STxMP) towards the selected / indicated TRP / cell in more than one TRP / cell. Case F can be associated with one or more TA processes based on one or more TAGs (e.g., two TA processes based on two PTAGs). For example, the WTRU can determine the first TA process in one or more TA processes based on the selected / indicated TRP / cell. The first TA process can correspond to the first WTRU panel among the multiple WTRU panels. The WTRU can determine the second TA process (e.g., in one or more TA processes) corresponding to the second WTRU panel among the multiple WTRU panels. The second TA process can be associated with the first TA process (e.g., based on an offset parameter).Scenario G (e.g., STxMP, multi-TRP) can be indicated by UL Tx (e.g., simultaneously) towards more than one TRP / cell based on more than one WTRU panel (e.g., STxMP), e.g., based on one or more associations / links between the WTRU panel (e.g., in more than one WTRU panel) and the TRP / cell (e.g., in more than one TRP / cell). Scenario G can be associated with one or more TA procedures based on one or more TAGs (e.g., two TA procedures based on two PTAGs). The WTRU can determine a first TA procedure among the one or more TA procedures. The first TA procedure can be determined based on a first combination between the first TRP / cell and the first WTRU panel among the multiple WTRU panels. The WTRU can determine a second TA procedure among the one or more TA procedures. For example, the second TA procedure can be determined based on a second combination between the second TRP / cell and the second WTRU panel among the multiple WTRU panels. Scenario X can be indicated by UL Tx based on a predefined / preconfigured type of WTRU Tx behavior, which can be based on one or more Tx-related parameters (e.g., including (one or more) target TRP / cells). The WTRU can (e.g., explicitly) determine the TRP / cell based on an indication / configuration from the gNB and / or (e.g., implicitly) based on a received DCI field / value or a higher layer parameter / value. For example, the TRP / cell can be associated based on at least one of a CORESET pool index, a TRP / cell identifier, and / or a parameter for representing the TRP / cell. In some examples, UL Tx can be at least one of PUSCH, PUCCH, SRS, PRACH, DMRS, and / or a (pre)defined / (pre)configured type of UL signal. One or more examples / embodiments described herein can be applicable to at least one scenario (e.g., Tx mode, scheme, behavior, method, procedure, program) indicated as Scenario A, Scenario B, Scenario C, Scenario D, Scenario E, Scenario F, Scenario G, and Scenario X. For example, in at least one scenario indicated as Scenario A, Scenario B, Scenario C, Scenario D, Scenario E, Scenario F, Scenario G, and Scenario X, the second TA procedure among the one or more TA procedures can be determined as shown in. Figure 4 as shown in 406 of.

[0114] There may be a TAG association between the TRP / cell and the WTRU panel (e.g., UE panel). The WTRU may report its ability to dynamically transition between single-panel UL and MTRP / multi-panel mode (e.g., STxMP). The WTRU may receive an authorization. The authorization may indicate (e.g., dynamically indicate) the WTRU to be scheduled between sTRP / mTRP and / or between single-panel / STxMP. The authorization / indication may apply to PUSCH / PUCCH or transmissions associated with PUSCH / PUCCH. In some examples of mTRP, the authorization may indicate one or more (e.g., two) sets of SRI / transmission precoding matrix indicator (TPMI) and power control parameters, where (e.g., each) set is associated with a TRP. In some examples, the authorization may include an SRS resource set indicator, which may include one or more (e.g., two) bits that (e.g., dynamically) indicate to the WTRU the scheduling between single-panel on resource set 1, resource set 2 or mTRP with multiple (e.g., two) resource sets. The bit indication (e.g., additional bit indication) may transition between the foregoing behavior and STxMP. The WTRU may adjust its precoder / spatial filter / transmission power for each TRP.

[0115] The link between the WTRU panel and the TRP (e.g., each link) may have different propagation times. The TRPs may be time-aligned or may not be time-aligned. When multiple (e.g., two) panels are used in STxMP, a single TAG may not be sufficient to achieve proper time alignment.

[0116] Timing control can be provided for MTRP / multi-panel mode (e.g., STxMP). In some examples, the WTRU can be scheduled / configured to transmit MTRP / multi-panel based UL (e.g., STxMP UL) of PUSCH or PUCCH on a subset of component carriers (CCs), and transmit single panel on a second subset of CCs. The first component carrier (CC1) can be associated with multiple (e.g., two) configured TAGs. One or more other CCs can be (e.g., each) configured with a single TAG. For example, if / when CC1 with MTRP / multi-panel operation mode (e.g., STxMP mode) is activated, the WTRU can (e.g., determine) use multiple (e.g., two) TAGs. (E.g., each) TAG can be configured with its corresponding duration / period (e.g., a timer such as a timing alignment timer). Although one or more examples herein may describe using a timing alignment timer, it will be appreciated that the (one or more) examples contemplate a duration / period used in association with timing alignment and / or timing advance. For example, the WTRU can determine the transmission time for PUSCH or PUCCH on (e.g., each) panel based on the TAG associated with (e.g., each) physical channel.

[0117] For example, the WTRU can be scheduled to transmit using a subset of layers on a first panel, and transmit using a second subset of layers on a second panel. The WTRU can, for example, use the first TAG as a reference to determine the time instance T1 for transmission on the first panel. The WTRU can, for example, use the second TAG as a reference (e.g., simultaneously) to determine the time instance T2 for transmission on the second panel.

[0118] For example, the WTRU can (e.g., similarly) use the first TAG as a reference to determine the time instance T1 for PUCCH on the first panel, and can use the second TAG as a reference to determine the time instance T2 for PUCCH on the second panel.

[0119] Table 1 shows an example configuration of CCs and TAGs. The WTRU can receive such a configuration where CC1 can be used for MTRP / multi-panel mode (e.g., STxMP operation mode), and CC2 / CC3 can be used for single panel operation mode. For example, if the WTRU is scheduled in CC1, the WTRU can (e.g., determine) use TAG1 and TAG2 to calculate the transmission time for the corresponding UL panel transmission. TAG1 and / or TAG2 can be (one or more) PTAGs.

[0120] Table 1 – Example TAG Allocation to CCs for STxMP

[0121] Component Carrier TAG Identity CC1 {TAG1, TAG2} CC2 TAG1 CC3 TAG2

[0122] A WTRU may receive (e.g., a single) MAC-CE to update multiple (e.g., two) timing advance values. In some examples, the timing advance command MAC-CE may include an octet (e.g., a single octet) containing the TAG identity, and / or a timing advance command for the indicated TAG. In some examples, the timing advance command MAC-CE may be used for MTRP / multi-panel mode (e.g., STxMP), which includes (e.g., one) octet for each configured TAG identity for the MTRP / multi-panel mode (e.g., STxMP), and / or a timing advance command for each octet. The WTRU may receive the MAC-CE. For example, based on the indicated TAG, the WTRU may (e.g., simultaneously) adjust the timing advance values of multiple panels.

[0123] TAG association may be provided for MTRP / multi-panel based PUSCH (e.g., STxMP PUSCH). The WTRU may determine multiple TAGs to use. The WTRU may obtain information about the TAGs used for each panel use (e.g., obtain additional information). For example, the WTRU may determine such information after determining the multiple TAGs to use. In some examples, the WTRU may determine the association between a TAG (e.g., TAG#X) and a panel based on the association between an RS group (e.g., SRS resource set, CSI-RS resource set, SSB) and the TAG.

[0124] The WTRU may determine that the TRPs (e.g., all TRPs) configured with TAG#X may include groups (e.g., one group) that may share the same timing. The WTRU may receive a configuration of an SRS resource set. The Xth TAG may be associated with the Yth SRS resource set. In some examples, multiple resource sets (e.g., two resource sets) may be utilized. For example, SRS resource set 1 may include SRS resources that the WTRU may transmit from panel 1, and SRS resource set 2 may include SRS resources that the WTRU may transmit from panel 2. SRS resource set 1 is associated with TAG#1, and SRS resource set 2 may be associated with TAG#2. The configuration may include an association with a physical cell ID (PCI) number (e.g., Z) and / or an indication that (e.g., each) PCI may represent a TRP. For example (e.g., in the case of inter-cell), a CC (e.g., one CC) may be configured with multiple PCIs, and / or the TAG may be based on the target PCI of PUCCH transmission and / or PUSCH transmission. The association between X, Y, and Z may be configured with an RS group. For example, the SRS resource set configuration may include the X, Z values configured for each SRS resource. The WTRU may receive authorization for scheduling an STxMP PUSCH. The authorization may include, for example, the scheduled CC, the operation mode, multiple (e.g., two) SRIs for determining the spatial filters for each panel, and multiple (e.g., two) TPMIs for determining the precoding layer / port association for each panel. The WTRU may determine (e.g., based on the configuration of the TAG for the SRI) that the first SRI from the authorization is in SRS resource set Y of cell Z. The WTRU may apply TAG X. The WTRU may determine (e.g., similarly) the TAG of the second SRI in the authorization. The WTRU may transmit the PUSCH using the STxMP operation mode. The WTRU may apply the TA together with the respective TAG for each panel.

[0125] In some examples, (e.g., similarly) TAG associations may be used for mTRP PUSCH that is not in the STxMP operation mode. For example (e.g., using mTRP PUSCH repetition), the WTRU may transmit a repetition of the PUSCH in the TDM operation mode (e.g., the PUSCH repetitions may not overlap in time). For example, the WTRU may determine the timing of each PUSCH repetition (e.g., each) based on an authorization indicating the SRI and / or the mTRP operation mode of each PUSCH. The WTRU may determine the TAG for each PUSCH transmission (e.g., based on the TAG association with the SRI), for example, similar to the STxMP case. The TAG determined for PUSCH transmission may be a PTAG associated with an unexpired TAT.

[0126] TRP selection for WTRU panel (e.g., UE panel) association can be dynamic. For example, in the context of intra-cell or inter-cell MTRP, a multi-panel WTRU can be configured with an anchor TRP (e.g., where the RRC signaling entity is based and secondary TRPs). In some examples, the anchor / primary TRP (pTRP) can be fixed. For example, triggered by radio resource management (RRM) measurements, reception beyond the supported MRTD or MTTD, or radio link monitoring (RLM) / radio link failure (RLF) issues, additional TRPs or secondary TRPs can be (e.g., eventually) changed.

[0127] A WTRU can (e.g., initially, before being configured for MTRP operation) (e.g., by the network) be configured with RRM measurements for MTRP operation. In one example, a specific intra-cell TRP (e.g., based on CSI-RS based RSRP measurements) or an inter-cell specific PCI can be used as a candidate for MTRP operation.

[0128] TAG group candidates can be beam groups belonging to a cell (e.g., PCI) or co-located or quasi-co-located TRPs (e.g., PCI or associated beams).

[0129] The same TAG-based measurement configuration and activation can be applied to, for example, MTRP. The RRM measurement configuration for MTRP can be grouped (e.g., by the gNB) into co-located or quasi-co-located TRP groups. The co-located or quasi-co-located TRP groups can be part of the same TAG. A WTRU can support multiple TAGs (e.g., two TAGs, such as two PTAGs) operating simultaneously. In some examples, for a TRP group (e.g., a TRP with a third TAG), there can be (e.g., additional) measurement gaps. In an example, the measurements related to TAG1 and TAG2 can be without gaps, while the third TAG3 TRP group can use gaps. For example, a WTRU can support "n" measurement groups without gaps. The "n + 1" measurement group can use a network-configured gap.

[0130] A WTRU that supports multiple TAGs (e.g., two TAGs) when operating in MTRP mode can have multiple resource sets (e.g., two resource sets). For example, when the pTRP maintains its configuration, the secondary TRP can be (e.g., more dynamically) switched out or configured to maintain coverage and quality of service.

[0131] Candidates for secondary TRP configuration may have the same TAG2. The WTRU may measure (e.g., continuously measure) and evaluate the quality of such candidates for secondary TRP configuration and report it to the network. For example, if / when a secondary TRP candidate becomes better than the currently configured TRP by a margin (e.g., RSRP) for a (e.g., selected / threshold) amount of time, the WTRU may report the quality periodically or based on an event. For example, if / when the maximum received timing difference (MRTD) or maximum transmission timing difference (MTTD) supported by the WTRU is exceeded when the network receives periodic measurements of TRP candidates from the WTRU, the WTRU may (e.g., alternatively) trigger a report. The measurement of the TRP candidate may be included (e.g., piggybacked) in the triggered report. The network may activate RRC preconfigured candidates within the TAG2 group, e.g., via a MAC-CE or DCI command. For example, the association of the resource set with the newly activated candidate may be resolved by the RRC preconfiguration set for each candidate or by inheriting the old aTRP resource set (e.g., to reduce overhead configuration).

[0132] For example, different TAG-based measurement configurations and activations may be applied if / when the TAG3 of the secondary TRP candidate group is configured. For example, if / when the TAG3 of the secondary TRP candidate group is configured, the network may configure a measurement gap. The WTRU may report RRM-based measurements of the TAG3 group candidates. The report may include, for example, auxiliary information according to the received time difference. For example, the conditions for TAG2 replacement may be fulfilled based on an event (e.g., event-based fulfillment), RLM / RLF, and / or quality of service below a threshold.

[0133] The network may send a MAC CE command for TAG3-based secondary TRP activation. The MAC CE command may include (e.g., together with the activation command) a PRACH command and / or an SRS transmission command, for example, for the new secondary TRP. A rough TA command may be included (e.g., alternatively) for the newly activated secondary TRP, which may be applied, for example, at the first valid UL grant of the secondary TRP.

[0134] The network may activate a new secondary TRP using a DCI command. The WTRU may (e.g., in such a case) switch to single DCI (sDCI) mode and / or perform PRACH and / or SRS transmission for the SRS resource set associated with the new secondary TRP. For example, after establishing UL synchronization with the new secondary TRP, the network may resume multi DCI (mDCI) operation.

[0135] Multi-TAG hopping operations can be performed. The WTRU can be configured with multiple TAGs (e.g., two PTAGs). When cycling through the active TAGs, the WTRU can receive and transmit using sDCI. In some examples, the number of active TAGs can be more than two, while the maximum simultaneous TAG support operation can be two. The WTRU can (e.g., alternatively) be configured with more than one active TRP within a TAG. For example, if / when different TAG TRPs are configured, the WTRU can operate using mDCI within the same TAG combined with sDCI. The network can configure the TAG hopping pattern for transmission and reception on time slots at the frame level.

[0136] TRP activation delay can be implemented. The TRP activation delay with MTRP context may depend on the type of TRP candidate. For example, the activation delay within the same TAG group can be defined by the time for the WTRU to confirm the activation command (Ack), and then the network can start scheduling the WTRU. Activation completion can (e.g., alternatively) be considered completed, for example, (e.g., only) after the valid CSI report of the newly activated TRP.

[0137] The activation delay (e.g., if / when different TAG TRPs are activated) can include the completion of the UL synchronization process. For example, if PRACH is utilized, the reception of the TA command in the RAR message can be considered activation completion, or the Ack of the MAC CE command. For example, if PRACH is replaced by SRS transmission, the activation delay can include the fulfillment of the first valid UL grant (e.g., correct reception by the network) by the WTRU.

[0138] Dynamic TRP selection can be implemented. In some examples, the WTRU configured for inter-cell MTRP operation can utilize additional PCI configuration. The WTRU can receive more than one TAG configuration. (For example, each) TAG can be associated with at least one PCI. For example, the WTRU can receive two (2) TAG information corresponding to the serving cell and an additional cell (e.g., information associated with two PTAGs). TAG1 can be associated with the first PCI, and TAG2 can be associated with the second PCI, or for example, TAG1 can be associated with the first PCI, TAG2 can be associated with the second PCI, and dTAG3 can be associated with the third and fourth PCIs.

[0139] Figure 2 An example of MTRP operation and transition with multiple TAG associations is illustrated. As Figure 2As shown, the WTRU may receive three (3) TAG configurations. The third TAG configuration may be associated with multiple (e.g., two) different PCIs (e.g., two different secondary or additional cells). In some examples (e.g., where the TAG is associated with two different PCIs), the WTRU may be indicated (e.g., also) semi-statically and / or via L1 / L2 signaling representing an incremental value of a potential time offset. For example, if / when applying the TAG information to the timing of transmissions to at least one cell associated with the TAG, the WTRU may apply an additional correction (e.g., accordingly).

[0140] The WTRU may receive a configuration (e.g., for inter-cell MTRP) indicating the association of the TAG with a PCI (e.g., each TAG is associated with a corresponding PCI of the STxMP). The first PCI may be (e.g., always) the serving cell PCI, which may operate as an anchor TRP, for example, such that it is not affected by the dynamic TRP selection (e.g., STxMP) of the MTRP scheme, but may be fixed to map to SRS resource set 1, for example, unless reconfigured by RRC. For example, the WTRU may receive a (semi-)dynamic indication for selecting a PCI (e.g., via MAC-CE), where the selected PCI may have a pre-association with an SRS resource set (e.g., for STxMP). For example, if a second PCI is selected / indicated via MAC-CE (e.g., assuming the previous third PCI was selected and has been used), the associated SRS resource set 2 (e.g., additional to the fixed SRS resource set 1 (with TAG1)) may be used for the MTRP scheme (e.g., STxMP PUSCH).

[0141] For example, for a single-panel WTRU, an SRS resource set (e.g., each SRS resource set) may be associated with different spatial information or antenna groups. For example, for a multi-panel WTRU, an SRS resource (e.g., each) may be associated with a different antenna panel. A WTRU configured for inter-cell MTRP operation, for example, may utilize more than one SRS resource set configuration. An SRS resource set (e.g., each SRS resource set) may be associated with a PCI. The WTRU may determine the TAG associated with its SRS and / or other uplink transmissions from the PCI associated with the SRS resource set.

[0142] In some examples, a WTRU may be configured with more than one additional PCI (e.g., additional cell). The WTRU may utilize a CSI-RS configuration for CSI measurement and reporting (e.g., further configuration). The WTRU may use the SSB of the configured additional cell as a QCL source. The new PCI may be signaled from a semi-statically configured list of PCI. The new PCI may be indicated as the source of the TCI for downlink and / or uplink transmission, such as for PDSCH, PDCCH, SRS, PUSCH, etc. The new PCI may be indicated to the WTRU via L1 / L2 signaling. In some examples, the indication of the new PCI may be used to indicate (e.g., implicitly indicate) the application of different TAG information for uplink transmission.

[0143] In some examples, a WTRU configured for in-cell MTRP operation may receive more than one TAG configuration. (e.g., each) TAG may be associated with at least one TCI. The TAG information may be used to determine the uplink transmission configuration. The uplink transmission configuration may be interpreted as different spatial information, different antenna groups, and / or different panels. In some examples, the WTRU may receive multiple sets of TAG information corresponding to first and second spatial information. For example, TAG1 may be associated with the first spatial information of the same panel, and TAG2 may be associated with the second spatial information of the same panel, or for example, TAG1 may be associated with the first WTRU panel, and TAG2 may be associated with the second WTRU panel, or for example, TAG1 may be associated with the first antenna group, and TAG2 may be associated with the second antenna group. TAG1 and / or TAG2 may be (one or more) PTAGs.

[0144] In some examples, the uplink transmission configuration may be associated with and derived from the indicated downlink TCI information. In some examples, a new TCI may be indicated to the WTRU from a configured list of TCI information. The new TCI may be indicated as the QCL source for uplink transmission, such as for SRS, PUSCH, etc. The WTRU may be indicated of the new TCI by MAC-CE or DCI. In some examples, the indication of the new TCI may be used to (e.g., implicitly) indicate the application of different TAG information for uplink transmission.

[0145] A WTRU configured for in-cell MTRP operation may utilize more than one SRS resource set configuration. (e.g., each) SRS resource set may be associated with a different TCI or CORESETPoolIndex. The WTRU may determine the TAG associated with its SRS and / or other uplink transmissions, for example, based on the TCI or CORESETPoolIndex associated with the SRS resource set.

[0146] TRP-specific PDCCH commands may have associated MTRP / MPUE behavior or MTRP / MPWTRU behavior. The WTRU may perform PRACH transmissions of TRP-specific PDCCH commands. In some examples, the WTRU may perform a PRACH transmission of a PDCCH command to a TRP. The TRP may be one of multiple TRPs associated with multi-TRP (mTRP) operation of a WTRU (e.g., a WTRU with multiple panels, a multi-panel user equipment (MPUE)). For example, the WTRU may utilize multiple TRP configurations for transmission and reception. The WTRU may (e.g., be instructed) transmit a PRACH (e.g., a PRACH of a PDCCH command) to a TRP (e.g., one of the TRPs) configured for mTRP operation. The WTRU may determine one or more parameters, time / frequency resources, and / or preambles based on the determined TRP. One or more of the following may apply. A TRP identity (e.g., TRP-id) may be assigned or designated to (e.g., each) TRP of the multiple TRPs configured or determined for mTRP operation. The lowest TRP-id may be assigned to the serving TRP. The serving TRP may be the serving cell where the WTRU may perform initial access, RRC connection establishment, receive broadcast information, etc. In one or more examples herein, the serving TRP may be used interchangeably with the primary TRP, the master TRP, and the anchor TRP. The TRP-id may be associated with a physical cell ID (PCID). In some examples, the TRP-id may be used interchangeably with the cell id and / or the physical cell ID. (e.g., a single) PCID may be associated with multiple TRP-ids, or vice versa. For example, the PRACH preamble for a PRACH transmission of a PDCCH command may be determined based on the TRP-id to which the PRACH preamble is transmitted. A PRACH preamble may be configured for each TRP-id. For example, the WTRU may determine the PRACH preamble based on the TRP-id determined for the PRACH transmission of the PDCCH command. For example, the RACH occasion may be determined based on the SS / PBCH index associated with the TRP-id. For example, for a PDCCH command, the SS / PBCH index may be indicated in the DCI. The SS / PBCH index may determine the associated RACH occasion for the PRACH transmission. Based on the TRP-id, a different interpretation of the SS / PBCH index may be made. In some examples, if / when a first TRP-id (e.g., TRP-id = y1) is used or determined, the SS / PBCH index = x may determine a first set of RACH occasions. If / when a second TRP-id (e.g., TRP-id = y2) is used or determined, the SS / PBCH index = x may determine a second set of PRACH occasions. In some examples, the SS / PBCH index may be associated with the TRP-id.For example, a first subset of the SS / PBCH index may be associated with a first TRP-id, and a second subset of the SS / PBCH index may be associated with a second TRP-id, and so on. The PRACH mask index may be used to determine a subset of RACH occasions for PRACH transmission. For example, a subset of RACH occasions may be determined based on the TRP-id of a given PRACH mask index.

[0147] A PRACH transmission for which a PDCCH command may be referred to as the PDCCH command. A TRP-id may be determined for the PRACH transmission of the PDCCH command. For example, one or more parameters for the PRACH transmission of the PDCCH command may be determined based on the determined, selected, indicated, or used TRP-id. The one or more parameters may include at least one of the following: a random access preamble index (ra-PreambleIndex); a UL / SUL indicator, which may indicate which uplink carrier is used for PRACH transmission when supplementary uplink is configured in the serving cell configuration; an SS / PBCH index, which may determine a RACH occasion; a PRACH mask index, which may determine a subset of RACH occasions (e.g., determined according to the SS / PBCH index); and so on.

[0148] In some examples, the TRP-id can be determined based on PDCCH-related information for the DCI format used to monitor PDCCH commands. One or more of the following may apply: CORESETPoolID; CORESET-id; PDCCH search space id; and / or PDCCH candidate resources. In one example, the WTRU can receive the DCI of the PDCCH command in a PDCCH search space. The PDCCH search space can be associated with a CORESET having a CORESETPoolID. The WTRU can determine the TRP-id, for example, based on the CORESETPoolID that can be associated with the search space in which the WTRU receives the PDCCH command. The CORESETPoolID can be associated with the TRP-id and / or the PCID. In one example, the WTRU can receive the DCI of the PDCCH command in a PDCCH search space. The PDCCH search space can be associated with the CORESET-id. For example, the WTRU can determine the TRP-id based on the CORESET-id associated with the PDCCH search space. The CORESET-id can be associated with the TRP id and / or the PCID. In one example, the WTRU can receive the DCI of the PDCCH command in a PDCCH search space, which can be associated with the PDCCH search space identity. For example, the WTRU can determine the TRP-id or the PCID based on the PDCCH search space identity. The search space id can be associated with the TRPid and / or the PCID. In one example, one or more PDCCH candidate resources can be used, configured, or available in the PDCCH search space. For example, the WTRU can determine the TRP-id and / or the PCID based on which PDCCH candidate resource is used for the DCI to trigger the PDCCH command. For example, a first subset of the PDCCH candidate resources can be associated with a first TRP-id, and a second subset of the PDCCH candidate resources can be associated with a second TRP-id.

[0149] In some examples, the TRP-id can be indicated (e.g., explicitly indicated) in the DCI that triggers the PDCCH command. For example, the TRP-id or the PCID can be indicated (e.g., explicitly indicated) in the DCI format used to trigger the PDCCH command. One or more bits (e.g., reserved bits) can be used to indicate the TRP-id.

[0150] In some examples, one or more (e.g., existing) fields may be used to indicate the TRP-id (e.g., implicitly) in the DCI. One or more of the following may apply. For example, if the frequency domain resource allocation field has a first value (e.g., all ones), the first TRP-id (e.g., the serving TRP) may be used or determined. For example, if the frequency domain resource allocation field has a second value (e.g., all zeros), the second TRP-id (e.g., the secondary TRP) may be used or determined. The UL / SUL indicator may be used to indicate the TRP-id. For example, UL or SUL may be determined based on one or more of the following: semi-static configuration (e.g., RRC or MAC-CE); and / or (predetermined) as a UL carrier. The MSB or LSB of the PRACH mask index may be used to indicate the TRP-id. A subset of the PRACH mask index may apply to a subset of RACH occasion determination.

[0151] In some examples, one or more C-RNTIs may be used for DCI-triggered PDCCH commands. A first C-RNTI may be associated with a first TRP-id, and a second C-RNTI may be associated with a second TRP-id. In some examples (e.g., for a given C-RNTI), a mask may be used. For example, a first mask may be all zeros, a second mask may be all zeros except for the last bit, and so on. In some examples, one or more C-RNTIs may be configured (e.g., via higher layer signaling). (E.g., each) C-RNTI may be associated with a TRP-id.

[0152] In some examples, the slot index may be associated with the TRP-id. For example, if the WTRU receives a PDCCH command in a slot having a first slot index, the first TRP-id may be used or determined. For example, if the WTRU receives a PDCCH command in a slot having a second slot index, the second TRP-id may be used or determined. One or more of the following may apply. For example, the first slot index and the second slot index may be determined based on one or more of the following: whether the slot index is even or odd; whether the slot index satisfies a condition (e.g., modulo x becomes 0); and / or whether the slot includes flexible symbols. For example, the first slot index and the second slot index may be configured via higher layer signaling.

[0153] After the PRACH transmission of a PDCCH command, the WTRU behavior can be configured. The WTRU can receive a RAR associated with the PRACH transmission of the PDCCH command. The RAR can include at least one of the following information: information related to the associated PRACH preamble; the associated TRP-id; the associated TAG; and / or information on the associated SRS resource set. The WTRU can determine the TA of the uplink transmission associated with the TRP-id based on the received RAR.

[0154] Time synchronization maintenance can be implemented for each TAG. A cell (e.g., a primary cell (PCell)) can be an MTRP cell. A cell (e.g., an MTRP cell) can include multiple (e.g., two or more) timing advance groups (TAGs), e.g., as shown in 302 of Figure 3 or as shown in 402 of Figure 4 . (For example, each) TAG can be associated with one or more TRPs (e.g., one or more TRPs associated with the TAG can be associated with the same WTRU-TRP timing alignment).

[0155] In an example, one or more TAGs (e.g., two TAGs) can be defined as (one or more) PTAGs, e.g., if the MTRP cell is a PCell.

[0156] In some examples, the PTAG can be associated with a pTRP, and one or more TAGs (e.g., additional TAGs other than the PTAG) belonging to the PCell can be described herein as PSTAGs, as indicated in Table 2 below.

[0157] Table 2

[0158] CC1(SpCell): TAG1, TAG2 → PTAG, PSTAG

[0159] For example, if the MTRP cell is a serving cell (such as a secondary cell (SCell)), then (e.g., any) TAG (e.g., other than the PTAG or PSTAG) can be described herein as an STAG. The SCell may have at least one of the following: a PTAG, a PSTAG, or an STAG. One or more additional TAGs belonging to the SCell can be described herein as aSTAGs, as indicated in Table 3 below.

[0160] Table 3

[0161]

[0162] The DL timing reference can be determined. In one example, as described herein, the WTRU may be configured in CC1 (e.g., SpCell) with at least one MTRP mode / situation (e.g., at least one of situation B, situation C, situation D, situation E, situation F, situation G, situation X). For example, the WTRU may (e.g., be configured / indicated to) transmit a first UL Tx portion (e.g., a first set of (one or more) layers, PUCCH1, and / or from a first WTRU panel (e.g., UE panel)) based on a first DL timing reference, which may be determined based on the same cell (SpCell) associated with the PTAG.

[0163] In some examples, the WTRU may (e.g., be configured / indicated to) transmit a second UL Tx portion (e.g., a second set of (one or more) layers, PUCCH2, and / or from a second WTRU panel) based on, for example, a second DL timing reference, which may be determined based on one or more (e.g., any one) of the activated SCell(s) associated with (e.g., the secondary TAG (STAG) and / or aSTAG) and / or the same cell (SpCell) associated with the PSTAG and / or PTAG. The WTRU may receive configuration / indication on how to determine the second DL timing reference.

[0164] One or more durations / periods associated with time alignment (e.g., time alignment timer (TAT)) may be used to perform or maintain time synchronization. The WTRU (e.g., a WTRU connected to an MTRP cell) may be associated with (e.g., configured with or configured to maintain) one or more time alignment timers (TAT). The TAT may be associated with a TAG (e.g., each TAT may be associated with a corresponding TAG). The TAT may start, expire, and / or be reset. For example, the TAT may be reset based on receiving a timing advance command addressed to the TAG associated with the TAT.

[0165] The WTRU may perform one or more of the following actions (referred to herein as "recovery actions" in one or more examples) based on the expiration of the TAT (e.g., as determined at 404 in Figure 4 ): release the PUCCH of one or more serving cells and / or TRPs; release the SRS of one or more serving cells and / or TRPs; clear the configured downlink allocation and / or configured uplink grant; clear the PUSCH resources for semi-persistent CSI reporting; maintain the N of one or more TAGs TA; Refresh the HARQ buffer(s) (e.g., all HARQ buffers) for one or more serving cells and / or TRPs; Consider one or more running timers (e.g., time alignment timer) as expired.

[0166] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may release the resources associated with a physical uplink control channel (PUCCH) transmission scheduled to be sent to the TRP (and / or cell). In one or more examples herein, the TAT associated with the TRP may be the TAT associated with a TAG associated with the TRP (e.g., PTAG). The resource may have been scheduled for PUCCH transmission. The resource may not be used for PUCCH transmission when released.

[0167] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may release the resources associated with a sounding reference signal (SRS) to be sent to the TRP (and / or cell). The resource may have been scheduled for SRS transmission. The resource may not be used for SRS transmission when released.

[0168] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may release the resources scheduled via a downlink allocation configured for a downlink transmission associated with the TRP (and / or cell). The resource may have been scheduled for downlink transmission. The resource may not be used for downlink transmission when released.

[0169] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may release the resources scheduled via an uplink grant configured for an uplink transmission associated with the TRP (and / or cell). The resource may have been scheduled for uplink transmission. The resource may not be used for uplink transmission when released.

[0170] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may release the resources scheduled for a physical uplink shared channel (PUSCH) transmission for a channel state information (CSI) report (e.g., semi-persistent CSI report) associated with the TRP (and / or cell). The resource may have been scheduled for PUSCH transmission for channel state information (CSI) reporting. The resource may not be used for PUSCH transmission when released.

[0171] For example, based on the determination that the TAT associated with the TRP (and / or cell) has expired, the WTRU may maintain the current N TA, and may not release the N associated with the TRP (and / or cell) TA . For example, when the WTRU later receives a new timing advance command, the WTRU may determine to use the maintained N TA as the starting reference value for determining the timing advance value.

[0172] For example, based on a determination that a TAT associated with a TRP (and / or cell) has expired, the WTRU may or may not reset (e.g., flush) a hybrid automatic repeat request (HARQ) buffer associated with the TRP (and / or cell). In an example, the WTRU may maintain one or more HARQ buffers (e.g., all HARQ buffers for one or more serving cells and / or TRPs). For example, the WTRU may maintain a HARQ buffer associated with a first TRP (e.g., the TRP associated with the expired TAT). The WTRU may determine that information transmitted via the first TRP (e.g., data or control information) will be retransmitted (e.g., after the WTRU determines that the information transmission via the first TRP has failed). The WTRU may transmit information via a second TRP based on a determination that the TAT associated with the first TRP has expired, and when transmitting information via the second TRP, the HARQ buffer associated with the first TRP may still include the information or a copy of the information. In an example, the WTRU may determine that information (e.g., data or control information sent from and / or received via the first TRP) will be received via a retransmission from a second TRP (e.g., after the WTRU determines that the information reception via the first TRP has failed and the WTRU has transmitted a NACK). Based on a determination that the TAT associated with the first TRP has expired, the WTRU may receive the information as a retransmission via the second TRP, and when receiving the information as a retransmission via the second TRP, may still use the HARQ buffer associated with the first TRP (e.g., based on the included information or a copy of the information). In some examples, the WTRU may not maintain a HARQ buffer associated with the first TRP. For example, the WTRU may receive a transmission (e.g., a retransmission of data and / or control information that the WTRU failed to receive) via a TRP (e.g., a second TRP) whose associated TAT was not expired at the time of transmission. A transmission (e.g., which includes data and / or control information) may be sent to the first TRP. The WTRU may attempt to decode the transmission. If the WTRU fails to decode the transmission, the WTRU may transmit a NACK, for example, via the first TRP. Information (e.g., data and / or control information) that has been sent to the WTRU may be saved in a HARQ buffer associated with the first TRP. The first TRP may be associated with a first TAT, and the second TRP may be associated with a second TAT. The WTRU may determine that the first TAT has expired. The WTRU may reset the HARQ buffer associated with the first TRP based on a determination that the first TAT has expired. The WTRU may determine that the second TAT has not expired. For example, using the second TRP and / or according to a TA associated with a TAG associated with the second TRP, the WTRU may receive a retransmission of information that the WTRU failed to decode.

[0173] For example, depending on whether the expiration of the TAT is associated with a PTAG, PSTAG, STAG, and / or aSTAG, the WTRU may perform one or more (e.g., a subset of) the recovery actions described herein. In an example, if a first PTAG associated with a SpCell (e.g., a pCell or another special cell) expires, the WTRU may perform one or more of the recovery actions described herein. The SpCell may be associated with a second PTAG. One or more of the recovery actions described herein may be performed in association with a first TRP associated with a first TAG (e.g., the first PTAG). If the TAT associated with a second TAG (e.g., the second PTAG) has not expired, one or more of the recovery actions described herein may not be performed in association with a second TRP associated with the second TAG. In some examples, if a STAG associated with a serving cell (e.g., a SCell) expires, the WTRU may perform one or more of the recovery actions described herein. The SCell may be associated with another TAG (e.g., an aSTAG) whose TAT has not expired. One or more of the recovery actions described herein may be performed in association with a first TRP associated with the STAG. One or more of the recovery actions described herein may not be performed in association with a second TRP associated with (one or more) other TAGs.

[0174] The WTRU may perform one or more of the actions described herein to different scales (e.g., reset zero, some, or all HARQ buffers). For example, the WTRU may perform one or more of the recovery actions described herein depending on the associated TAG classification (e.g., whether the expiration of the TAT is associated with a PTAG, PSTAG, STAG, and / or aSTAG): for all TRPs in a serving cell (e.g., in all serving cells); for one or more TRPs in a serving cell (e.g., all TRPs except some (e.g., pTRP)) in a serving cell (e.g., in all serving cells); for all TRPs in one or more (e.g., all) serving cells associated with the TAG associated with the expired TAG (e.g., in all (one or more) serving cells belonging to that TAG); for one or more TRPs in one or more (e.g., all) serving cells associated with the expired TAG (e.g., in all (one or more) serving cells belonging to that TAG) (e.g., all TRPs except some (e.g., pTRP)); for all TRPs in a serving cell; and / or for one or more TRPs in a serving cell.

[0175] In an example, if the TAT associated with a PTAG expires, the WTRU may perform one or more recovery actions on some or all of the TRPs in a serving cell (e.g., all serving cells). For example, the WTRU may release resources associated with a physical uplink control channel (PUCCH) transmission scheduled to be sent to a cell or a first TRP, release resources associated with a sounding reference signal (SRS) to be sent to a cell or a first TRP, release resources scheduled via a downlink allocation configured for a downlink transmission associated with a cell or a first TRP, release resources scheduled via an uplink grant configured for an uplink transmission associated with a cell or a first TRP, release resources scheduled for a physical uplink shared channel (PUSCH) transmission for a semi-persistent channel state information (CSI) report associated with a cell or a first TRP, but the WTRU may not flush the HARQ buffers associated with some or all of the TRPs in a serving cell (e.g., all serving cells). In some examples, if the PSTAG expires, the WTRU may perform one or more recovery actions on some or all of the TRPs in a serving cell (e.g., all serving cells, e.g., except for the (one or more) TRPs associated with the PTAG). In some examples, if the TAT associated with an STAG expires, the WTRU may perform one or more recovery actions on some or all of the TRPs in a serving cell associated with the STAG (e.g., all serving cells belonging to the STAG). In some examples, if the TAT associated with an aSTAG expires, the WTRU may perform one or more recovery actions on some or all of the TRPs associated with the aSTAG (e.g., all TRPs belonging to the aSTAG).

[0176] The duration (e.g., TAT) associated with a PTAG may expire. For example, if the WTRU avoids the expiration of the TAT associated with the PTAG (and / or the (one or more) impacts due to expiration), the WTRU may avoid additional data loss and / or service interruption, which in some examples may result in recovery actions on one or more serving cells (e.g., all serving cells, not just the (one or more) serving cells associated with the PTAG). Another PTAG may be configured and / or promoted.

[0177] For example, based on configuration, a cell (e.g., a PCell) may be associated with more than one PTAG. For example, if the TAT associated with a first PTAG expires and the TATs associated with one or more TAGs (e.g., one or more PSTAGs) are still valid, the WTRU may promote the TAG (e.g., PSTAG) to a second PTAG (e.g., in the case where the PCell is an MTRP cell).

[0178] A TAG (e.g., PSTAG) can be promoted to a PTAG (e.g., by PTAG addition or PTAG swapping). In an example, in addition to the first PTAG, a second PTAG can also be configured. In some examples, the WTRU can promote a PSTAG to a PTAG. The WTRU can promote a TAG (e.g., PSTAG) to a PTAG, for example, subject to one or more of the following conditions: whether the PCell includes multiple TRPs; based on the NW configuration (e.g., RRC configuration enabling / disabling the promotion to PTAG), which can be per TAG or can have a configuration for the TAG (e.g., one configuration for all TAGs); based on the NW indication (e.g., via an explicit indication received in system information, MAC CE, or DCI); whether the TAT associated with the PTAG has expired or is about to expire; whether the TAT associated with another TAG (e.g., PSTAG) is still running; whether the TAT associated with another TAG (e.g., PSTAG) has a configured remaining amount of time; or whether the RSRP on one or more TRP links is higher than a threshold; and / or based on at least one procedure / behavior related to L1 / L2 mobility management / disposition, e.g., for fast handover (e.g., to switch to a new serving cell / TRP / PCI) versus layer 3 (L3)-based handover (e.g., a handover involving longer time and / or RRM procedures). The WTRU can use the TA associated with the additional configuration and / or the promoted PTAG to send UL transmissions to a cell (e.g., the PCell).

[0179] If the cell includes multiple TRPs, the WTRU can determine to use the TA associated with the additional configuration and / or the promoted PTAG to send UL transmissions to the cell (e.g., the PCell). In an example, the WTRU can (or not) promote a TAG (e.g., PSTAG) to a PTAG based on the determination of whether the PCell includes multiple TRPs. For example, if the PCell does not include multiple TRPs, the WTRU may not promote the TAG to a PTAG. If the PCell includes multiple TRPs and / or meets one or more other conditions, the WTRU can promote the TAG to a PTAG.

[0180] The WTRU may determine to send a UL transmission to a cell (e.g., the PCell) using a TA associated with an additional configuration and / or a promoted PTAG based on the NW configuration. The cell may be configured with a first PTAG and a second PTAG and may send an NW configuration indicating this, which may be a per-TAG configuration or may have a configuration for one or more TAGs (e.g., one configuration for all TAGs). For example, the NW configuration may include an RRC configuration (e.g., an RRC configuration enabling / disabling promotion of the PTAG). The WTRU may receive the NW configuration and / or determine based on the NW configuration that the cell is configured with a first PTAG and a second PTAG. The WTRU may receive the NW configuration and / or determine based on the NW configuration that the second PTAG will be promoted. In an example, the WTRU may promote a TAG (e.g., the PSTAG) to a PTAG based on the NW configuration, which may be a per-TAG configuration or may have a configuration for one or more TAGs (e.g., one configuration for all TAGs).

[0181] The WTRU may determine to send a UL transmission to a cell (e.g., the PCell) using a TA associated with an additional configuration and / or a promoted PTAG based on the NW indication. The cell (e.g., the PCell) may be configured with a first PTAG and a second PTAG and may send an NW indication indicating this. The WTRU may receive the NW indication (e.g., via an explicit indication received in system information, a MAC CE, or DCI). The WTRU may determine based on the NW indication that the cell is configured with a first PTAG and a second PTAG. The WTRU may receive the NW indication and / or determine based on the NW indication that the second PTAG will be promoted. In an example, the WTRU may promote a TAG (e.g., the PSTAG) to a PTAG based on the NW indication (e.g., via an explicit indication received in system information, a MAC CE, or DCI).

[0182] If the TAT associated with the first PTAG has expired, the WTRU may determine to use the TA associated with an additional configuration and / or an enhanced PTAG to send an UL transmission to a cell (e.g., the PCell). If the TAT associated with the first PTAG is about to expire, the WTRU may use the TA associated with an additional configuration and / or an enhanced PTAG to send an UL transmission to a cell (e.g., the PCell). In an example, the WTRU may (or may not) elevate a TAG (e.g., the PSTAG) to a PTAG based on a determination of whether the TAT associated with the PTAG has expired (or a determination of whether the TAT is about to expire). For example, the WTRU may elevate a TAG (e.g., the PSTAG) to a PTAG based on a determination that the TAT associated with the PTAG has expired or is about to expire, and the WTRU may not elevate the TAG to a PTAG based on a determination that the TAT associated with the PTAG has not expired and is not about to expire.

[0183] If the TAT associated with the first PTAG has expired and the TAT associated with an additional configuration and / or an enhanced PTAG (e.g., the PSTAG) is still running, the WTRU may determine to use the TA associated with an additional configuration and / or an enhanced PTAG to send an UL transmission to a cell (e.g., the PCell). In an example, the WTRU may (or may not) elevate a TAG (e.g., the PSTAG) to a PTAG based on a determination of whether the TAT associated with the TAG is still running. For example, the WTRU may elevate a TAG (e.g., the PSTAG) to a PTAG based on a determination that the TAT associated with the PTAG has expired or is about to expire and the TAT associated with the TAG (e.g., the PSTAG) is still running. Based on a determination that the TAT associated with the TAG has expired or is about to expire, the WTRU may not elevate the TAG to a PTAG.

[0184] If the TAT associated with the first PTAG has expired and the TAT associated with an additional configuration and / or an elevated PTAG (e.g., PSTAG) has a configured remaining amount of time, the WTRU may determine to use the TA associated with the additional configuration and / or the elevated PTAG to send an UL transmission to a cell (e.g., PCell). In an example, the WTRU may promote (or not promote) a TAG (e.g., PSTAG) to a PTAG based on a determination of whether the TAT associated with the TAG (e.g., PSTAG) has a configured remaining amount of time. For example, the WTRU may promote a TAG (e.g., PSTAG) to a PTAG based on a determination that the TAT associated with the PTAG has expired or is about to expire and a determination that the TAT associated with the TAG has a configured remaining amount of time. Based on a determination that the TAT associated with the TAG does not have a configured remaining amount of time, the WTRU may not promote the TAG to a PTAG.

[0185] If the RSRP on one or more TRP links associated with an additional configuration and / or an elevated PTAG is higher than a threshold, the WTRU may determine to use the TA associated with the additional configuration and / or the elevated PTAG to send an UL transmission to a cell (e.g., PCell). In an example, the WTRU may promote (or not promote) a TAG (e.g., PSTAG) to a PTAG based on a determination of whether the RSRP on one or more TRP links associated with the TAG is higher than a threshold. For example, the WTRU may promote a TAG (e.g., PSTAG) to a PTAG based on a determination that the TAT associated with the PTAG has expired or is about to expire and a determination that the RSRP on one or more TRP links associated with the TAG is higher than a threshold. Based on a determination that the RSRP on one or more TRP links associated with the TAG is not higher than the threshold, the WTRU may not promote the TAG to a PTAG.

[0186] If, for example, at Figure 3If the additional PTAG shown at 308 is configured to be available and / or made available by promotion, the WTRU may use the TA associated with the additional configuration and / or promoted PTAG to send UL transmissions to a cell (e.g., the PCell). In an example, for instance, if one or more of the conditions described herein are met, the WTRU may promote a TAG (e.g., the PSTAG) to a PTAG. For example, the WTRU may send UL transmissions (e.g., the WTRU may promote a TAG to a PTAG to send UL transmissions) according to the TA associated with the TAG when one or more of the following occur: when the TAT associated with the PTAG expires; when the offset time from the expiration of the TAT associated with the PTAG has arrived; when an NW indication / command is received; and / or when the offset time from the reception time of the NW indication / command has arrived.

[0187] In an example, if the TAT associated with the first PTAG expires, the WTRU may send UL transmissions according to the TA associated with the second PTAG. The WTRU may determine that the TAT associated with the first TAG has expired, and based on the determination that the first TAT has expired, the WTRU may determine that the TA associated with the second TAG will be used for transmissions to the cell. The WTRU may send a transmission to the cell according to the TA associated with the second TAG. In some examples, the WTRU may determine the data or control information to be sent to the cell. The WTRU may determine that the TAT associated with the second TAG has not expired. Based on the determination that the TAT associated with the first TAG has expired and the determination that the TAT associated with the second TAG has not expired, the WTRU may send data or control information to the cell according to the TA associated with the second TAG. Based on the determination that the TAT associated with the first TAG has expired and the determination that the TAT associated with the second TAG has not expired, the WTRU may refrain from using the TA associated with the first TAG to send data or control information. For example, based on the determination that the TAT associated with the first TAG has expired and the determination that the TAT associated with the second TAG has not expired, the WTRU may refrain from using the TA associated with the first TAG to send (e.g., any) UL transmissions other than random access preambles and MSGA transmissions.

[0188] The WTRU may activate a stored configuration (e.g., perform an RRC reconfiguration and / or activate a conditional handover (CHO) configuration) to determine that a second TAG will be used for transmission (e.g., to elevate a PSTAG associated with a TRP to a PTAG). Activation of the configuration may be based on, for example, the expiration of the TAT associated with the first TAG and / or receipt of an NW indication / confirmation. In an example, the first TAG and / or the second TAG may be one or more PTAGs. In some examples, the WTRU may, for example, delay performing one or more recovery actions while waiting for confirmation from the NW regarding the elevation of the PSTAG.

[0189] The expiration and / or impending expiration (e.g., near expiration) of a TAT (e.g., a PTAG TAT) may be indicated, for example, as shown in Figure 3 304. In an example, the WTRU may indicate to the network that the TAT associated with a TAG (e.g., the TAT associated with a first PTAG) has expired. In some examples, the WTRU may indicate that the TAT associated with a TAG (e.g., the TAT associated with a first PTAG) is impending expiration (e.g., the WTRU may send the indication at a fixed offset time from or before the expiration of the TAT). For example, the WTRU may send an indication to one or more of the following: a TRP associated with a PTAG (e.g., a first PTAG or a second PTAG); a TRP associated with a PSTAG; a TRP link associated with the highest RSRP; a (e.g., any) TRP link associated with an RSRP above a threshold; a (e.g., any) TRP link associated with a valid TAT (e.g., the TAT is still running); or a (e.g., any) TRP link associated with a TAT having a certain amount of remaining time before the expiration of the TAG (e.g., a fixed amount of time remaining before the expiration of the TAT).

[0190] Various methods may be used to indicate the expiration and / or impending expiration of a TAT (e.g., a PTAG TAT). In an example, the WTRU may send an indication, for example, via one or more of the following methods: a MAC CE; an RRC (e.g., a (one or more) WTRU information response message); during a RACH (e.g., Msg3, Msg5, MsgA); a UCI; a PUSCH resource; or a PUCCH resource.

[0191] The expiration and / or indication of the impending expiration of a TAT (e.g., a PTAG TAT) may include other information or be sent together with other information. In an example, the WTRU may include within the indication or may send together with the indication one or more of, for example, the following information pieces: an indication of the impending expiration of the TAT (e.g., a flag indicating the impending expiration of the TAT associated with a PTAG); a request to elevate one or more TAGs (e.g., one or more PSTAGs) to a (one or more) PTAG; the remaining time before the expiration of the TAT (e.g., the TAT associated with a (one or more) PTAG); the TRP to be elevated (e.g., the preferred TRP to be elevated) and / or the TAG to be elevated (e.g., the PSTAG to be elevated to a PTAG); the remaining time before the expiration of a (one or more) specific TAT (e.g., before the expiration of the TAT for some or all PSTAGs); or the (one or more) RSRP of one or more TRP links.

[0192] Which information is included in the indication (or sent together with the indication) may be based on one or more of the following (e.g., the information that the WTRU may include within the indication may depend on one or more of the following): the signaling method for sending the information (e.g., RRC vs. MAC CE vs. RACH signaling); NW configuration and / or request; whether the TAG (e.g., PTAG) has expired or is about to expire; whether a valid alternative link is available (e.g., whether a valid alternative link is available for elevation); how many valid alternative links are available; or whether a stored configuration (e.g., the stored configuration in one or more examples herein) is available (e.g., whether the stored configuration is available for elevating a PSTAG to a PTAG).

[0193] For example, the WTRU may send the indication based on a configuration. The configuration may indicate, for example, one or more of the following: an offset from the expiration for transmitting the indication; the signaling method; and / or the type of information to be sent within the indication.

[0194] The WTRU may receive an acknowledgment of a request to use a second TAG for UL transmission, e.g., as in Figure 3As shown in 306. The confirmation of the request can be indicated via the network. The network can send a confirmation (e.g., a confirmation response) based on (e.g., according to) the receipt of an indication (e.g., a PTAG expiration indication) in one or more examples herein and / or a request (e.g., a PSTAG promotion request) in one or more examples herein. In some examples, the network can indicate the confirmation of a PTAG exchange (e.g., a virtual PTAG exchange). The confirmation (e.g., the confirmation response) can include, for example, one or more of the following pieces of information: a HARQ ACK feedback for the request (e.g., a PTAG exchange request); an explicit confirmation (e.g., a flag) indicating that the request is accepted; a configuration indicating that the second TAG will be used for UL transmission (e.g., a configuration that promotes the PSTAG to the PTAG); the activation time for using the second TAG for UL transmission (e.g., the activation time for promoting the PSTAG to the PTAG); or an indication of which TAG will be used for UL transmission (e.g., an indication of which PSTAG to promote among multiple candidates).

[0195] For example, the WTRU can receive a confirmation (e.g., an NW confirmation) via one or more of the following methods: MAC CE; RRC; during the RACH (e.g., Msg2, Msg4, MsgB); DCI; PDSCH resources; and / or PDCCH resources.

[0196] The WTRU can receive approval for a request to use the second TAG for UL transmission (e.g., an NW response indicating that the PTAG exchange request is accepted). In an example, the WTRU can use the TA associated with the second TAG to send a UL transmission based on the approval of the request, e.g., according to (e.g., any) conditions within the NW confirmation. In some examples, the WTRU can promote the PSTAG to the PTAG (e.g., based on the receipt of the NW response), e.g., according to (e.g., any) conditions (e.g., the activation time indicated in the NW confirmation (message) and / or the configuration indication within the NW confirmation) within the NW confirmation.

[0197] The NW can reject the request (e.g., a request for PTAG promotion). For example, if the WTRU does not receive a response from the NW, the WTRU can assume that the request (e.g., a request to promote the PSTAG to the PTAG) is rejected. For example, if the WTRU does not receive a response after one or more of the following: the expiration of a duration / period (e.g., a PTAG timer, such as the TAT associated with the PTAG) before receiving an NW response (e.g., a confirmation); the WTRU does not receive an NW response within X time and / or Y resource units; and / or the candidate TAG for UL transmission (e.g., the candidate TAG for promotion) becomes invalid before the NW response.

[0198] If the request (eg, PSTAG promotion request) is rejected and / or the WTRU does not receive a response to the request in a timely manner, the WTRU may perform actions associated with TAG expiration (eg, PTAG expiration).

[0199] The WTRU may indicate that the WTRU will send an UL transmission using a second PTAG or has already sent an UL transmission using a second PTAG. In some examples, the WTRU may confirm the PTAG promotion. If the TAG is successfully promoted to a PTAG, the WTRU may indicate the successful promotion of the TAG (e.g., PSTAG) to a PTAG to the network. For example, the WTRU may perform a RACH on a TRP associated with the second PTAG (e.g., the promoted PTAG). In some examples, the WTRU may send this indication (e.g., explicitly, such as via an acknowledgment MAC CE).

[0200] One or more examples herein may be applicable to SCells. In an example (e.g., as described herein), PTAG may replace STAG, and PSTAG may be replaced with aSTAG. In an example, a TAG associated with an SCell may be promoted. One or more examples (e.g., as described herein) may (e.g., additionally and / or alternatively) be applicable to promoting aSTAG to STAG for a TRP belonging to an SCell.

[0201] Figure 3 Examples of PTAG conversion or maintenance at different TRPs are shown.

[0202] In the example (e.g., as in the example based on Figure 3 In the example shown), at 302, the WTRU may receive configuration information indicating that a first cell is associated with a first and a second TRP (e.g., where the first and second TRPs are each associated with a corresponding first and second timing advance group (TAG), the first and second TAGs are each associated with a corresponding first and second time alignment timer (TAT), and the first TAG is a primary TAG). At 304, the WTRU may determine that the first TAT is about to expire (e.g., the current time may be an offset time before the first TAT expires (e.g., the offset time has been reached), or the remaining time until the first TAT expires (e.g., before the first TAT expires) may be less than a threshold, where the threshold may be configured or indicated to the WTRU (e.g., from the gNB). In the example, the WTRU may report its capability information related to the threshold. In one or more examples herein, the terms "expire" and "expire" may be used interchangeably.

[0203] At 304, the WTRU may, for example, based on that determination, transmit a message indicating that the first TAT is about to expire to a second TRP associated with the second TAG or to a second cell associated with the second TAG (e.g., the current time may be an offset time before the expiration of the first TAT (e.g., the offset time has been reached), or the remaining time until the expiration of the first TAT (e.g., before the first TAT expires) may be less than a threshold, where the threshold may be configured or indicated to the WTRU (e.g., from the gNB)) and / or may transmit a request to switch the primary TAG from the first TAG to the second TAG. At 306, the WTRU may receive an acknowledgement (e.g., approval) of the switch request. At 308, after the expiration of the first TAT (e.g., when the second TAT has not expired), the WTRU may transmit one or more UL signals to the first cell or the second cell (e.g., using the TA associated with the second TAG). For example, when the TAT associated with the primary TAG has not expired, the WTRU may be allowed to transmit to the first cell (and the second cell). By switching the primary TAG to a different TAG (e.g., a different PTAG) before the expiration and / or inactivation of the TAT associated with the primary TAG, the WTRU may maintain the ability to transmit UL signals or channels (e.g., the WTRU may improve its performance by being able to transmit after the expiration of the timer of the initial primary TAG). In an example (e.g., alternatively), the (one or more) PTAG switching (e.g., swapping) behavior may be applicable based on a 1-PTAG model or a 2-PTAG model.

[0204] For the 1-PTAG model, the TAG may be a PTAG (e.g., only one TAG of the SpCell is a PTAG and the other TAG of the SpCell is an STAG). For example, the SpCell may include a pCell or other special cell (e.g., in a different cell group, such as in a dual-connectivity scenario, etc.). In an example, the TAG associated with a certain TAG ID (e.g., the TAGID with the lowest index in the SpCell) may be the PTAG.

[0205] For the 2-PTAG model, more than one TAG may be a PTAG (e.g., both TAGs of the SpCell are PTAGs). For example, the SpCell may include a PCell or other special cell (e.g., in a different cell group, such as in a dual-connectivity scenario, etc.).

[0206] In an example, the 2-PTAG model may be applied. For example, Figure 3 the example of may be applicable to the 2PTAG model. In Figure 3In an example, a WTRU may be associated with one or more cells (e.g., SpCel and SCell). A WTRU may avoid performing expiration actions on one or more cells if a TRP of one of the one or more cells has a valid TAT (e.g., as long as a TRP of a first cell (e.g., SpCell, PCell) still has a valid TAT, the WTRU may continue to operate (e.g., communicate, DL reception and / or UL transmission) on the first cell and may avoid performing expiration actions on all cells (e.g., including SCell)). In an example, a WTRU may receive configuration information indicating that a first cell is associated with a first and a second TRP (e.g., wherein the first and second TRPs are each associated with a corresponding first and second TAG, the first and second TAGs are each associated with a corresponding first and second TAT, and both the first TAG and the second TAG may be a primary TAG, as in Figure 4 The WTRU may determine that the first TAT is about to expire (e.g., the current time may be an offset time before the first TAT expires (e.g., the offset time has been reached), or the remaining time until the first TAT expires (e.g., before the first TAT expires) may be less than a threshold, where the threshold may be configured or indicated to the WTRU (e.g., from the gNB). In an example, the WTRU may report its capability information related to the threshold.

[0207] The WTRU may, for example, based on the determination, transmit a message to a second TRP associated with the second TAG or to a second cell associated with the second TAG indicating that the first TAT is about to expire and / or a message indicating that the second TAG will be used (e.g., the WTRU may transmit an indication, information, or request indicating that the second TAG rather than the first TAG will be used (e.g., applied to) determine whether to perform a "recovery action" across cells). For example, when the 2-PTAG model of the present invention is used, the WTRU may perform a virtual PTAG conversion or exchange (e.g., a "virtual" PTAG conversion or exchange (from the first TAG to the second TAG), although both the first and second TAGs are PTAGs in the 2-PTAG model). The WTRU may receive an acknowledgment (e.g., an approval) of the indication (or information / request). After the first TAT expires (e.g., when the second TAT has not expired), the WTRU may transmit one or more UL signals to the first cell or the second cell (e.g., using the TA associated with the second TAG, for example, as in Figure 4 408).

[0208] Figure 4Illustrated is an example 400 of TAG conversion for transmission. At 402, the WTRU may determine that a cell is associated with a first TRP and a second TRP based on received configuration information. The first TRP may be associated with a first TAG. The second TRP may be associated with a second TAG. The first TAG may be the primary TAG. At 404, the WTRU may determine that a first duration (e.g., a first TAT) associated with the first TAG has expired. At 406, based on the determination that the first duration has expired, the WTRU may determine that the TA associated with the second TAG will be used for transmission to the cell. At 408, the WTRU may send a transmission to the cell based on the TA associated with the second TAG.

[0209] The expiration of the TAT may be associated with the PSTAG or the aSTAG. For a TRP that is not the primary TRP of the cell, the TAT may expire. For example, if the TAT associated with the TAG of the TRP expires, the WTRU may suspend or delay a resume action, or (e.g., only) perform a resume action on a limited subset of (e.g., one or more) TRPs.

[0210] For example, if / when the TAT associated with a non-primary TAG (e.g., the PSTAG or the aSTAG) has expired or is about to expire, the WTRU may notify the network (e.g., similar to the example described for PSTAG elevation). The network may respond, for example, by instructing to perform one or more of the following actions: trigger a cell search to find another candidate cell / PCI from another candidate PCI list; revert to the sTRP; and / or perform one or more resume actions (e.g., as described herein).

[0211] The WTRU may perform one or more actions (e.g., as described herein) based on configuration and / or conditionally (such as based on whether the expired TAT is associated with the PSTAG or the aSTAG).

[0212] One or more examples described herein may be applicable to other scenarios (or applied in combination with or based on other scenarios), such as L1 / L2 mobility management / disposition, which may provide fast handovers (e.g., to switch to a new serving cell / TRP / PCI), as opposed to layer 3 (L3)-based handovers, which may involve longer times and / or RRM procedures.

[0213] Although the above features and elements are described in a particular combination, each feature or element may be used alone, without the other features and elements of the preferred embodiment, or in various combinations with or without other features and elements.

[0214] Although the implementations described herein may consider 3GPP specific protocols, it should be understood that the implementations described herein are not limited to this scenario and can be applied to other wireless systems. For example, although the solutions described herein consider LTE, LTE-A, New Radio (NR) or 5G specific protocols, it should be understood that the solutions described herein are not limited to this scenario and are also applicable to other wireless systems.

[0215] The above process can be implemented in a computer program, software, and / or firmware, which is incorporated in a computer-readable medium for execution by a computer and / or a processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted via wired and / or wireless connections) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and / or optical media such as compact disc (CD)-ROM discs and / or digital versatile disc (DVD). A processor associated with the software can be used to implement a radio frequency transceiver for use in a WTRU, a terminal, a base station, an RNC, and / or any host computer.

Claims

1. A wireless transmit / receive unit (WTRU) comprising: a processor configured to: determine, based on received configuration information, that a cell is associated with a first transmission and reception point (TRP) and a second TRP, wherein the first TRP is associated with a first timing advance group (TAG) and the second TRP is associated with a second TAG, and wherein the first TAG is the primary TAG; determine that a first timing alignment timer (TAT) associated with the first TAG has expired; based on the determination that the first TAT has expired, determine that a timing advance (TA) associated with the second TAG will be used for transmission to the cell; and transmit a transmission to the cell based on the TA associated with the second TAG.

2. The WTRU according to claim 1, wherein the cell is associated with two primary TAGs, the first TAG is the first primary TAG associated with the cell, and the second TAG associated with the second TRP is the second primary TAG associated with the cell.

3. The WTRU according to claim 1, wherein the second TAG is associated with a second TAT, and the processor is further configured to: determine data or control information to be transmitted to the cell; determine that the second TAT has not expired; and transmit the data or control information to the cell based on the TA associated with the second TAG, based on the determination that the first TAT has expired and the determination that the second TAT has not expired.

4. The WTRU according to claim 3, wherein the processor is further configured to inhibit transmission of data or control information based on the TA associated with the first TAG, based on the determination that the first TAT has expired and the determination that the second TAT has not expired.

5. The WTRU according to claim 1, wherein the processor is further configured to: determine that data or control information transmitted via the first TRP will be retransmitted; and Based on the determination that the first TAT has expired, transmit the data or control information via the second TRP, wherein, when transmitting the data or control information via the second TRP, a hybrid automatic repeat request (HARQ) buffer associated with the first TRP includes the data or control information.

6. The WTRU according to claim 1 or 5, wherein the processor is further configured, based on the determination that the first TAT has expired, to perform one or more of the following: release resources associated with a physical uplink control channel (PUCCH) transmission scheduled to be transmitted to the cell or the first TRP; release resources associated with a sounding reference signal (SRS) to be transmitted to the cell or the first TRP; release resources scheduled via a downlink allocation configured for a downlink transmission associated with the cell or the first TRP; release resources scheduled via an uplink grant configured for an uplink transmission associated with the cell or the first TRP; or release resources scheduled for a physical uplink shared channel (PUSCH) transmission for a semi-persistent channel state information (CSI) report associated with the cell or the first TRP.

7. The WTRU according to claim 1, wherein the processor is further configured to: Determine that an offset time before the expiration of a first TAT has arrived; and Based on the determination that an offset time before the expiration of a first TAT has arrived, send a request to change a primary TAG from a first TAG associated with a first TRP to a second TAG associated with a second TRP, and wherein the request is sent before the expiration of the first TAT.

8. The WTRU according to claim 7, wherein the processor is further configured to send a first transmission based on the TA associated with the second TAG, wherein the first transmission includes the request, and wherein the first transmission further includes an indication that an offset time before the expiration of the first TAT has arrived.

9. The WTRU according to claim 1, wherein the processor is further configured to: Determine that the first TAT expires at a first time; and Determine that a difference between a current time and the first time is less than or equal to a value; and Based on the determination that the difference between the current time and the first time is less than or equal to a value, send a request to change a primary TAG from a first TAG associated with a first TRP to a second TAG associated with a second TRP, and wherein the request is sent before the expiration of the first TAT.

10. A method performed by a wireless transmit / receive unit (WTRU), comprising: Determine, based on received configuration information, that a cell is associated with a first transmit and receive point (TRP) and a second TRP, wherein the first TRP is associated with a first timing advance group (TAG) and the second TRP is associated with a second TAG, and wherein the first TAG is the primary TAG; Determine that a first time alignment timer (TAT) associated with the first TAG has expired; Based on the determination that the first TAT has expired, determine that a timing advance (TA) associated with the second TAG will be used for transmissions to the cell; and Based on the TA associated with the second TAG, send a transmission to the cell.

11. The method according to claim 10, wherein the cell is associated with two primary TAGs, the first TAG is a first primary TAG associated with the cell, and the second TAG associated with the second TRP is a second primary TAG associated with the cell.

12. The method according to claim 10, wherein the second TAG is associated with a second TAT, and the method further comprises: Determine data or control information to be sent to the cell; Determine that the second TAT has not expired; and Based on the determination that the first TAT has expired and the determination that the second TAT has not expired, send the data or control information to the cell based on the TA associated with the second TAG.

13. The method according to claim 12, further comprising suppressing the transmission of the data or control information based on the TA associated with the first TAG, based on the determination that the first TAT has expired and the determination that the second TAT has not expired.

14. The method according to claim 10, further comprising: Determine that data or control information transmitted via the first TRP will be retransmitted; and Based on the determination that the first TAT has expired, transmit the data or control information via the second TRP, wherein when transmitting the data or control information via the second TRP, a hybrid automatic repeat request (HARQ) buffer associated with the first TRP includes the data or control information.

15. The method according to claim 10 or claim 14, further comprising, based on the determination that the first TAT has expired, performing one or more of the following: releasing resources associated with a physical uplink control channel (PUCCH) transmission scheduled to be sent to a cell or the first TRP; releasing resources associated with a sounding reference signal (SRS) to be sent to a cell or the first TRP; releasing resources scheduled via a downlink allocation configured for a downlink transmission associated with a cell or the first TRP; releasing resources scheduled via an uplink grant configured for an uplink transmission associated with a cell or the first TRP; or releasing resources scheduled for a physical uplink shared channel (PUSCH) transmission for a semi-persistent channel state information (CSI) report associated with a cell or the first TRP.

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