PDCCH command PRACH transmission in multi-TRP operation

Abstract

The WTRU may receive downlink control information (DCI) from a first transmit / receive (TRP). The DCI may indicate that the WTRU is to transmit a physical random access channel (PRACH) transmission. The DCI may include an indication of a preamble, an indication of a first PRACH mask, and / or an indication associated with a first synchronization signal block (SSB), and / or an indication of a reference signal (RS). The WTRU may be configured to transmit the preamble in a first PRACH resource to a second TRP. The first TRP and / or the second TRP may be associated with a same physical cell identity (PCI). The WTRU may receive a first response to the preamble from the second TRP. The first response may include a first timing advance (TA) command for the second timing alignment for transmission to the second TRP and / or an index indicating the second TRP.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 334,976 filed in the United States on April 26, 2022, the entirety of which is incorporated herein by reference. Background Art Technical Field

[0003] The present disclosure relates generally to wireless communication systems. In particular, the present disclosure relates to methods and apparatus for multiple transmit / receive points (mTRP) with multiple timing advance (TA) operations in wireless communication systems.

[0004] Description of Related Technology

[0005] The growing demand for wireless data traffic following the commercialization of 4G communication systems has been a driving force behind efforts to develop improved 5G communication systems. Therefore, 5G communication systems or pre-5G communication systems are referred to as systems that come after 4G network communication systems (Beyond 4G networks) or after LTE systems (Post LTE).

[0006] In order to achieve high data rates, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands, such as, for example, 60 GHz (60 GHz) bands. In order to reduce the path loss of radio waves and increase the propagation distance of radio waves in ultra-high frequency bands, beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technologies used in 5G communication systems are being discussed.

[0007] For systematic network improvement, evolved small cells, advanced small cells, cloud radio access networks (cloud radio access networks: cloud RAN), ultra-dense networks (ultra-dense networks), device-to-device communication (D2D), wireless backhaul, mobile networks, collaborative communications, coordinated multi-point (CoMP) and interference cancellation technology development are being further developed in 5G communication systems.

[0008] In addition, advanced coding and modulation (ACM) methods such as FQAM (hybrid FSK and QAM modulation) and SWSC (sliding window superposition coding) and advanced access technologies such as filter bank multi-carrier (FBMC), NOMA (non-orthogonal multiple access) and sparse code multiple access (SCMA) are being studied in 5G systems. Summary of the invention

[0009] Systems, methods, and apparatus are described herein with respect to a multiple transmit / receive point (mTRP) with multiple timing advance (TA) operations in a wireless system. A wireless transmit / receive unit (WTRU) may receive a PDCCH command for triggering a physical random access channel (PRACH) transmission when the WTRU is configured in a multi-TRP operation in a multi-TRP deployment and / or transmit one or more first PRACHs in accordance with the received PDCCH command by using one or more of an indicated preamble index, a synchronization signal (SS) index / physical broadcast channel (PBCH), and / or a PRACH mask.

[0010] In an example, the implementation may include determining an uplink TA value for sending an uplink signal, wherein the uplink TA value is determined based on a single TA loop, and / or sending one or more PRACHs for initiating a second TA loop based on receiving an indication to send a second PRACH.

[0011] In an example, the implementation may include operating a timing advance timer (TAT) for one or more TRPs associated with a TRP link, and / or determining one or more expected TRPs for one or more TAs indicated based on a received PDCCH.

[0012] Systems, methods, and apparatus may include receiving one or more timing advance groups (TAGs) for a serving cell, wherein one or more (e.g., each) TAG is associated with a TRP link, and / or applying a TAG associated with the TRP.

[0013] Systems, methods, and apparatus related to PDCCH command PRACH transmission in mTRP operation are described herein. A WTRU may receive downlink control information (DCI) from a first transmit / receive (TRP). The DCI may indicate that the WTRU is to transmit a physical random access channel (PRACH). The DCI may include an indication of a preamble, an indication of a first PRACH mask, and / or an indication associated with a first synchronization signal block (SSB), and / or an indication of a reference signal (RS). The WTRU may be configured to transmit the preamble to a second TRP in a first PRACH resource. The first PRACH resource may be determined based on, for example, the first PRACH mask and / or the first SSB. The preamble may be transmitted using a spatial filter determined based on, for example, an indicated RS. The first TRP and / or the second TRP may be associated with the same physical cell identifier (PCI).

[0014] The WTRU may determine to send the preamble to the second TRP based on, for example, the spatial filter. The WTRU may maintain a first timing alignment for transmission to the first TRP and / or maintain a second timing alignment for transmission to the second TRP. The WTRU may receive a first response to the preamble from the second TRP. The first response may include a first timing advance (TA) command for the second timing alignment for transmission to the second TRP and / or an index indicating the second TRP. The first response may be a random access response (RAR). The WTRU may be configured to use the determined spatial filter and / or utilize timing based on the first TA command to send an uplink (UL) transmission to the second TRP. The WTRU may use the indicated RS to determine the spatial filter used to send the preamble to the second TRP.

[0015] The WTRU may receive the DCI in a PDDCH order that triggers the PRACH transmission. The DCI may include an indication of a second PRACH mask and / or an indication associated with a second SSB. The WTRU may use a second PRACH resource determined based on, for example, the second PRACH mask and / or the second SSB to send the preamble to the first TRP. The WTRU may receive a second response from the first TRP to the preamble sent using the second PRACH resource. The second response may include a timing advance command for the first timing alignment for the transmission to the first TRP. The second response may include an index of the first TRP. The DCI may include a timing advance (TA) medium access control (MAC) control element (CE). The MAC CE may indicate a TRP index. The TRP may indicate that the TA is associated with the first TRP and / or the second TRP. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0017] Figure 1B is an example of an embodiment in which Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within the illustrated communication system;

[0018] Figure 1C is an example of an embodiment in which Figure 1A a system diagram of an example Radio Access Network (RAN) and an example Core Network (CN) used within the illustrated communication system;

[0019] Figure 1D is an example of an embodiment in which Figure 1AA system diagram of another example RAN and another example CN used within the illustrated communication system;

[0020] Figure 2 is a diagram illustrating an example of an absolute timing advance command medium access control (MAC) control element (CE) format;

[0021] Figure 3 is a diagram illustrating an example of a relative timing advance command MAC CE format;

[0022] Figure 4 is a system diagram illustrating example timing alignment for a secondary transmit / receive point (sTRP). DETAILED DESCRIPTION

[0023] Figure 1A 1 is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0024] like Figure 1AAs shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110 and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a “station” and / or “STA”) may be configured to send and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0025] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B, a Home Node B, a Home eNode B, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0026] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSC), radio network controllers (RNC), relay nodes, etc. Base station 114a and / or base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies (which may be referred to as cells (not shown)). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Therefore, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In an embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0027] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0028] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0029] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0030] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using New Radio (NR).

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may together implement LTE radio access and NR radio access, for example using the dual connectivity (DC) principle. Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0032] 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), etc.

[0033] Figure 1AThe base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), 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 an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology (such as IEEE 802.15) to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0034] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Although not described in detail in the text, the CN 106 / 115 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0035] The CN 106 / 115 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired communication networks and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 / 113 or a different RAT.

[0036] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0037] Figure 1B is a system diagram illustrating an example WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0038] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0039] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from the base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In an embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, IR, UV or visible light signals. In another embodiment, the send / receive element 122 may be configured to send and / or receive both RF signals and optical signals. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0040] Although the transmit / receive element 122 Figure 1B 1 as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0041] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0042] The processor 118 of the WTRU 102 may be coupled to and may receive user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0043] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0044] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0045] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripheral device 138 may include one or more sensors, which may be one or more of the following: a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0046] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and / or substantially eliminating self-interference via signal processing performed via hardware (e.g., a choke) or via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for both UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0047] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 in accordance with an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0048] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0049] Each of the evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0050] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements is depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0051] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0052] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handover, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0053] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0054] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or may be in communication with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers.

[0055] Although the WTRU Figures 1A to 1D Although described as wireless terminals, it is contemplated that in certain representative embodiments, such terminals may (eg, temporarily or permanently) use a wired communication interface with a communication network.

[0056] In a representative embodiment, the other network 112 may be a WLAN.

[0057] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a BSS and one or more stations (STA) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be transmitted to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be transmitted by the AP, for example, wherein the source STA may transmit traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be transmitted between the source STA and the destination STA (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (eg, all STAs in the STA) may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0058] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a width dynamically set via signaling. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including the AP) may listen to the primary channel. If the primary channel is listened / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0059] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0060] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be sent by the transmitter STA. At the receiver of the receiver STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be transmitted to the medium access control (MAC).

[0061] 802.11af and 802.11ah support operating modes below 1 GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support instrument type control / machine type communications, such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0062] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is sending to the AP, the entire available band may be considered busy even if most of the band remains idle and may be available.

[0063] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0064] Figure 1D1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0065] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0066] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmit time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0067] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNB 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeB 160a, 160b, 160c may act as a mobility anchor for the WTRUs 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0068] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0069] Figure 1DThe illustrated CN 115 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0070] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of NAS signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services utilized by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0071] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0072] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0073] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local data network (DN) 185a, 185b via an N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the local DN 185a, 185b.

[0074] Given that Figures 1A to 1D as well as Figures 1A to 1D , one or more or all of the functions described herein for one or more of the following may be performed by one or more simulation devices (not shown): WTRU 102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF 182a-182ab, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0075] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0076] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (e.g., which can include one or more antennas) can be used by the simulation device to send and / or receive data.

[0077] The term aTRP is used herein interchangeably with the term secondary transmit / receive point (sTRP).

[0078] In an example, one of the new radio (NR) multiple input multiple output (MIMO) features may be mTRP operation, where the TRPs share the same PCI. As an evolution, in Rel-17, the work may have expanded the scope of mTRP scenarios with one or more different features, including a unified transmit configuration identifier (TCI) concept that enables faster and / or more (e.g., much more) efficient management of one or more TCI states and / or beam management. Reception from one or more TRPs may have been determined within a cyclic prefix. This may have achieved full timing synchronization determined between one or more TRPs (e.g., alignment of one or more transmissions between / among one or more TRPs). For example, synchronization may include the WTRU maintaining timing alignment for transmissions with two or more TRPs. For example, the WTRU may maintain (e.g., use) a first timing alignment for transmissions to a first TRP and maintain (e.g., use) a second timing alignment for transmissions to a second TRP.

[0079] In an example, the MIMO evolution work item may have taken a step forward and / or may be intended to diversify one or more deployments by implementing two timing advance (TA) loops based on, for example, two non-co-located TRPs, two WTRU antenna panels, up to 4 UL MIMO layers, two layers per panel, and / or based on mDCI (e.g., multi-DCI) reception and / or simultaneous / overlapping physical uplink shared channel (PUSCH) PUSCH+PUSCH and / or physical uplink control channel (PUCCH) PUCCH-PUCCH UL transmissions.

[0080] Figure 2 2 is a diagram illustrating an example of an absolute timing advance command MAC CE 200. In an example, the absolute timing advance command MAC CE 200 may be identified by a MAC subheader with an extended logical channel ID (eLCID). The MAC indication may have a fixed size and / or may include, for example, Figure 2 In an example, the timing advance command field may indicate an index value TA. In an example, TA may be used to control the amount of timing adjustment that the MAC entity may have to apply. In an example, the size of the TA command field may be 12 bits. In an example, R202 may be a reserved bit, which may be set to 0, for example. The MAC CE 200 may indicate whether the TA is associated with the first TRP and / or the second TRP. For example, the MAC CE 200 may indicate a TRP index indicating that the TA is associated with the first TRP and / or the second TRP.

[0081] Figure 3 is a diagram illustrating an example of a relative timing advance command MAC CE 300. In an example, the WTRU may receive a relative TA command format when in connected mode. In an example, the TA command MAC CE 300 may be identified by a MAC subheader with an LCID. In an example, the command may have a fixed size and / or may include, for example, Figure 3, a single octet shown in . In an example, the timing advance group (TAG) identifier (TAG ID) field 302 may indicate the TAG identifier of the addressed TAG. In an example, the TAG including the SpCell may have a TAG identifier of 0. In an example, the length of this field may be 2 bits. In an example, the TA command field 304 may indicate an index value TA (e.g., 0, 1, 2, 3, 4, 5...63, etc.). The timing advance command field 304 may be used to control the timing adjustment amount that the MAC entity must apply. In an example, the length of this field may be 6 bits. The MAC CE 300 may indicate whether the TA is associated with the first TRP and / or the second TRP. For example, the MAC CE 300 may indicate a TRP index, which indicates that the TA is associated with the first TRP and / or the second TRP. For example, the TAG ID field 302 may indicate a TRP index.

[0082] In an example, in a transmission system with single TA support, a serving cell may be associated with a single TAG, wherein one or more (e.g., each) TAG may be associated with a single time alignment timer. In an example, if the WTRU does not receive an update within the time window set by the timer, the timer may time out and / or the WTRU may suspend one or more (e.g., all) UL transmissions to the affected cell except for random access preamble transmissions and / or MsgA transmissions. In an example, if the timer times out, the WTRU may clear one or more (e.g., all) HARQ buffers. In an example, if the timer times out, the WTRU may release one or more (e.g., all) configured PUCCHs and / or sounding reference signals (SRS). In an example, if the timer times out, the WTRU may clear one or more (e.g., all) configured downlink assignments. In an example, if the timer times out, the WTRU may clear one or more (e.g., all) configured UL grants. In an example, if the timer expires, the WTRU may clear one or more (e.g., any, all) PUSCH resources for semi-persistent CSI of one or more (e.g., all) serving cells when the timeAlignementTimer associated with the PTAG expires. The PTAG may be, for example, a TAG group to which the SpCell belongs (e.g., otherwise one or more timeout actions may be performed (only) for one or more serving cells associated with the TAG). In an example, if the timer expires, the WTRU may clear one or more PUSCH resources for semi-persistent CSI of all serving cells when the timeAlignementTimer associated with the PTAG expires. The PTAG may be, for example, a TAG group to which the SpCell belongs. In an example, if the timer expires, the WTRU may clear all PUSCH resources for semi-persistent CSI of one or more serving cells when the timeAlignementTimer associated with the PTAG expires. The PTAG may be, for example, a TAG group to which the SpCell belongs. In an example, if the timer expires, the WTRU may clear all PUSCH resources for semi-persistent CSI of all serving cells when the timeAlignementTimer associated with the PTAG expires. The PTAG may be, for example, a TAG group to which the SpCell belongs. In an example, a timeout action may be performed for a serving cell associated with the TAG. In an example, a timeout action may be performed only for a serving cell associated with the TAG.

[0083] In an example, in NR operation, a MAC CE carrying a TA command may be associated with a specific cell. For example, in a multi-transmit / receive point (multi-TRP or mTRP) scenario within a cell where multiple TRPs may be associated with the same cell, a separate TA indication for one or more (e.g., each) transmit / receive points (TRPs) may not be supported. In an example, if separate TA indications for one or more (e.g., each) TRPs are supported, it may be difficult to estimate one or more separate TA values ​​for one or more (e.g., each) TRP links. For example, in an intra-cell mTRP scenario, the PCI may include a serving cell. The serving cell may be referred to as a primary TRP (pTRP). The pTRP may have an SSB configuration. For example, in an intra-cell mTRP scenario, the PCI may include an additional TRP (sTRP) that may not have an SSB configuration. In an example, the sTRP may be measured by the WTRU on a channel state information-reference signal (CSI-RS) and / or one or more tracking RSs. In an example, a MAC CE carrying a TA command may be associated with a MAC entity having a specific cell. For example, the MAC CE TA command may not be associated with a primary TRP. For example, the MAC CE TA command may not be associated with an sTRP, as described herein. In an example, the association of timing advance measurements and / or TA commands may be initiated per individual radio link and / or one or more simultaneous TA commands and / or their (e.g., corresponding) applications. The MAC CE may indicate whether the TA command is associated with a primary TRP and / or a secondary TRP. For example, the MAC CE may indicate a TRP index indicating that the TA command is associated with a primary TRP and / or a secondary TRP.

[0084] Provided herein are systems, methods and / or apparatuses related to procedures for initiating one or more (e.g., multiple) TA measurements and / or updates. Provided herein are systems, methods and / or apparatuses related to procedures for indicating and / or associating one or more (e.g., multiple) TAs to a TRP.

[0085] Provided herein are systems, methods, and / or apparatus related to procedures for initiating and / or maintaining one or more (e.g., multiple) TA measurements. In a multi-DCI multi-TRP transmission with multiple TA support, a WTRU may receive a PDCCH command random access channel (RACH) to update one or more TA values ​​for one or more (e.g., each) TRP links.

[0086] Systems, methods, and / or apparatus may include PDCCH commands for PRACH transmissions in multiple TRPs. The gNB may trigger the transmission of PRACH to reestablish synchronization for uplink transmissions of the WTRU (e.g., including a set of one or more PRACH resources). Such initiation may occur for one or more different reasons. For example, the gNB may trigger the transmission of PRACH when the WTRU has not been scheduled for transmission within a certain duration. In NR, the triggering of random access transmissions for reestablishing synchronization may be achieved through a PDCCH command. Through the PDCCH command, the DCI may provide relevant information for the transmission of PRACH (e.g., such as a preamble index and / or an SSB index). The PRACH may serve as a reference point for determining the associated RACH timing. The WTRU may receive a DCI from a first TRP. The DCI may indicate that the WTRU will send a PRACH transmission. The DCI may include an indication of a preamble, an indication of a first PRACH mask, an indication associated with a first SSB, and / or an indication of an RS. The WTRU may receive the DCI in a PDCCH order that triggers the PRACH transmission.

[0087] The WTRU may determine a spatial filter based on the indicated RS. The WTRU may determine to send the preamble to the second TRP based on the spatial filter. The WTRU may send the preamble to the second TRP in a first PRACH resource that may be determined based on, for example, the first PRACH mask and / or the first SSB. The preamble may be sent using a spatial filter determined based on the indicated RS. The first TRP and the second TRP may be associated with the same physical cell identifier (PCI). The WTRU may receive a response to the preamble (e.g., such as a random access response (RAR)) from the second TRP. The response may include a timing advance (TA) command for timing alignment of the transmission to the second TRP and / or an index indicating the second TRP.

[0088] In an mTRP deployment, the WTRU may maintain its synchronization with one or more (e.g., two or more) different TRPs. For example, in an mTRP deployment, the WTRU may be required to maintain its synchronization with at least two different TRPs. For example, the WTRU may dynamically switch between a single TRP transmission mode and a multi-TRP transmission mode, which may require, for example, maintaining accurate timing synchronization at all times. For example, the WTRU may use a first timing alignment with a first TRP, and may use a second timing alignment with a second TRP. For example, if the WTRU may dynamically switch between a single TYP transmission mode and a multi-TYP transmission mode, the WTRU may be configured to sometimes (e.g., always) maintain accurate timing synchronization (e.g., including a set of one or more PRACH resources). As described herein, a PDCCH command (e.g., from a pTRP intended to transmit PRACH to an sTRP for UL synchronization / timing alignment) may include one or more of the following: a preamble identifier; a TRP indication indicating an sTRP (e.g., a CORESETPOOL index); an SSB index (e.g., associated with a pTRP); a PRACH mask; and / or an RS indicator associated with an sTRP (e.g., a CSI-RS and / or a tracking RS). If timing alignment for a pTRP and an sTRP includes a PDCCH command, the PDCCH command may include a second SSB index (e.g., associated with a pTRP) and / or a second PRACH mask. As described herein, the PDCCH command may include one or more of the following: a TRP index; a pTRP SSB index for determining a PRACH resource; and / or an sTRP RS for determining a filter for transmission (Tx). As described herein, the WTRU may use the determined PRACH resources and / or the determined spatial filter to transmit a preamble based on a preamble identifier. As described herein, the WTRU may send a preamble based on a preamble identifier using a determined PRACH resource and / or a determined spatial filter. If the timing alignment for the pTRP and the sTRP includes a PDCCH command, the WTRU may send the same preamble to the pTRP based on a second SSB index and / or a second PRACH mask. The WTRU may receive a RAR including a TRP indication and / or a TA indication. If the timing alignment for the pTRP and the sTRP includes a PDCCH command, the RAR may include a second TA. The WTRU may send an UL transmission to the sTRP using a determined spatial filter and / or utilizing timing based on a TA indication.

[0089] In a multi-TRP deployment, a WTRU configured in multi-TRP operation may receive a PDCCH command to trigger a PRACH transmission. In an example, for example, once the WTRU receives a PDCCH command for a PRACH transmission with respect to single-DCI multi-TRP operation or multi-DCI multi-TRP operation, the WTRU may be configured to have one or more of the behaviors described herein.

[0090] In single DCI multi-TRP operation, PRACH transmission may occur for the TRP that initiated the PDCCH command PRACH. In an example, the WTRU may transmit a single PRACH based on the received PDCCH command by using the indicated preamble index (e.g., one or more PRACH resources), synchronization signal (SS) / PBCH index (e.g., SSB index), and / or PRACH mask. In an example (e.g., in this case), the WTRU may use the demodulation reference signal (DMRS) of the received PDCCH as an RS source for transmitting spatial information (e.g., a spatial filter based on an RS indicator) for the preamble (e.g., using a determined PRACH resource and / or a determined spatial filter based on a preamble identifier). For example, the WTRU may transmit the preamble using a spatial filter based on an indicated RS (e.g., such as a DMRS). In an example, the WTRU may receive a random access response (RAR) message including a TA and a TRP indication. In an example, the WTRU may apply the indicated TA for one or more (e.g., all) future transmissions to one or more (e.g., two) TRPs until the next TA indication. In an example, the WTRU may receive an implicit and / or explicit indication, e.g., in a RAR message, that the WTRU may apply the indicated TA to the TRP that initiated (e.g., TRP indication) the PDCCH command for one or more (e.g., all) future transmissions until the next TA indication. For example, the WTRU may receive a response message (e.g., RAR message) in response to the preamble. The response message may include a TA command for timing alignment of the transmission to the TRP that initiated the PDCCH command.

[0091] In single DCI multiple TRP operation, a PRACH transmission may occur for a TRP that has not initiated a PDCCH command PRACH. The WTRU may receive a DCI from a first TRP. For example, the DCI may be received in a PDCCH command. The DCI may indicate that the WTRU will send a PRACH transmission. In an example, based on an information element (e.g., a field) that may be carried by the same PDCCH, the WTRU may, for example, based on a received PDCCH command, send a single PRACH to a second TRP (e.g., a TRP that has not initiated a PDCCH command / DCI) by using an indicated preamble index (e.g., one or more PRACH resources), an SS / PBCH index (e.g., an SSB index associated with a pTRP), a TRP index, and / or a PRACH mask. For example, the DCI may include an indication of a preamble, an indication of a first PRACH mask, an indication of a second PRACH mask, an indication associated with a first SSB, an indication associated with a second SSB, and / or an indication of an RS. The first TRP and the second TRP may be associated with the same physical cell identifier (PCI). Additionally or alternatively, the WTRU may detect an RS index indicated in a received PDCCH, which may be an RS source for spatial information (e.g., a spatial filter determined based on an RS source) for sending a preamble. For example, the WTRU may determine spatial information (e.g., a spatial filter) for sending a preamble to the second TRP based on the indicated RS (e.g., such as an RS index or a DMRS). The WTRU may send a preamble using a spatial filter determined based on the indicated RS (e.g., such as a DMRS). For example, the WTRU may determine to send a preamble to the second TRP based on spatial information (e.g., a spatial filter). In an example, the indicated RS may be associated with other TRPs. For example, the DCI may include an indication of a preamble (e.g., such as a preamble index), an indication of a PRACH mask, an indication associated with an SSB (e.g., such as an SS / PBCH index), and / or an indication of a reference signal (RS) (e.g., such as an RS index). The DCI may be received in an information element that may be carried by the same PDCCH. The WTRU may send a preamble to a second TRP in a first PRACH resource determined based on a first PRACH mask and / or a first SSB. The WTRU may receive RAR information including a TA. For example, the WTRU may receive a response message (e.g., a RAR message) in response to the preamble. The response message may include a TA command for timing alignment of transmissions to a second TRP (e.g., a TRP for which a PDCCH command PRACH was not initiated). For example, the WTRU may apply an indicated TA for one or more (e.g., all) future transmissions (e.g., by a TA command) to one or more (e.g., two) TRPs (e.g., TRP indications) until the next TA indication.For example, the WTRU may receive an implicit and / or explicit indication, e.g., in a RAR message, that the WTRU may apply the indicated TA to one or more (e.g., all) future TRPs for which a PDCCH command PRACH is not initiated until a next TA indication (e.g., a TRP indication) for the TRP. For example, the WTRU may receive an implicit or explicit indication, e.g., in a RAR message, that the WTRU may apply the indicated TA (e.g., only) to TRPs for which a PDCCH command PRACH is not initiated until a next TA indication is given for the TRP. For example, the WTRU may use the determined spatial filter and utilize timing based on the TA command to transmit an uplink transmission to a second TRP.

[0092] In single DCI multi-TRP operation, PRACH transmission for two TRPs may be based on the received PDCCH command PRACH. In an example, the WTRU may send one or more PRACHs based on the information carried by the received PDCCH. The WTRU may detect one or more indicated values ​​of one or more of the following: a preamble index (e.g., one or more PRACH resources), an SS / PBCH index (e.g., an SSB index), and / or a PRACH mask. Additionally or alternatively, the WTRU may detect an RS index indicated in a received PDCCH, which may serve as an RS source for sending spatial information for the preamble (e.g., a spatial filter based on an RS indicator). In an example, the WTRU may receive a single PRACH index, one or more (e.g., two) synchronization signal block (SSB) / PBCH indexes, one or more (e.g., two) PRACH mask values, and one (e.g., or more) RS indexes. The WTRU may transmit one or more (e.g., two) PRACHs at two different times using the same preamble index based on the indicated (e.g., two) SSB / PBCH indexes, (e.g., two) PRACH mask values, (e.g., two) DMRSs of the PDCCH, and / or RS indicated in the PDCCH for the first transmission and / or the second transmission. In an example, the WTRU may receive a RAR message including a single TA and / or TRP indication. For example, the WTRU may apply the indicated TA for one or more (e.g., all) future transmissions to one or more (e.g., two) TRPs (e.g., TRP indications) until the next TA indication. For example, the WTRU may receive (e.g., in a RAR message) an implicit and / or explicit indication that the WTRU may apply the indicated TA (e.g., only) to the TRPs of the PDCCH command PRACH initiated and / or not initiated for one or more (e.g., all) future transmissions until the next TA indication. In an example, the WTRU may receive a RAR message including one or more TAs. Based on one or more rules and / or received indications, the WTRU may select one or more of the indicated TA values ​​for one or more (e.g., all) future transmissions and / or apply the one or more TA values ​​to one or more (e.g., all) TRPs until the next TA indication. The WTRU may apply the one or more indicated TA values ​​to one or more corresponding TRPs.

[0093] In an example, in a single DCI multi-TRP operation, the PRACH transmission for two TRPs may be based on the received PDCCH command PRACH. In an example, the WTRU may send more than one PRACH based on the information carried by the received PDCCH. In an example, the WTRU may detect one or more indicated values ​​of at least one of the following: a preamble index, for example, an SS / PBCH index and a PRACH mask. In an example, the WTRU may detect an RS index indicated in a received PDCCH, which may be used as an RS source for spatial information for sending a preamble. In an example, the WTRU may receive a single PRACH index, two SSB / PBCH indexes, two PRACH mask values, and / or an RS index. In an example, the WTRU may send two PRACHs at two different times using the same preamble index based on the indicated two SSB / PBCH indexes, two PRACH mask values, two DMRS using the PDCCH, and / or the RS indicated in the PDCCH for the first transmission and / or the second transmission.

[0094] In an example, the WTRU may receive a RAR message containing a single TA. In an example, the WTRU may apply the indicated TA for one or more (e.g., all) future transmissions to two TRPs until the next TA indication. In an example, the WTRU may receive, for example, an implicit and / or explicit indication in a RAR message, that the WTRU may apply the indicated TA to TRPs for which a PDCCH command PRACH is initiated or not initiated for one or more future transmissions until the next TA indication. In an example, the WTRU may receive, for example, an implicit and / or explicit indication in a RAR message, that the WTRU may apply the indicated TA only to TRPs for which a PDCCH command PRACH is initiated or not initiated for one or more (e.g., all) future transmissions until the next TA indication. In an example, the WTRU may receive a RAR message including more than one TA. In an example, based on a rule and / or a received indication, the WTRU may select one or more TA values ​​from the indicated TA values ​​for one or more future transmissions and / or apply the one or more TA values ​​to two TRPs until the next TA indication. In an example, based on a rule or received indication, the WTRU may select one of the indicated TA values ​​for one or more (e.g., all) future transmissions and / or apply the one TA value to two TRPs until the next TA indication. In an example, the WTRU may apply the indicated TA value to the corresponding TRP. In an example, a single DCI multi-TRP operation may include a PRACH transmission according to the last indicated multi-TRP mode. For example, in a single DCI multi-TRP transmission, the WTRU may be dynamically scheduled to alternate between single TRP transmissions and multi-TRP transmissions. Additionally or alternatively, for example, the WTRU may switch the order of transmissions. In an example, if the last scheduled uplink transmission is intended for two TRPs (e.g., a multi-TRP operation mode indicated by an SRS resource indicator (SRI) (e.g., code point 10 and / or code point 11)), the WTRU may send a PRACH to one or more (e.g., two) TRPs. Additionally or alternatively, if the last scheduled uplink transmission is intended for (e.g., only) one TRP in the TRP (e.g., a single TRP operation mode indicated by an SRI (e.g., code point 00 and / or code point 01)), the WTRU may send PRACH according to the corresponding TRP.

[0095] In multi-DCI multi-TRP operation, the WTRU may transmit a single PRACH per TRP based on a PDCCH command received from one or more (e.g., each) TRPs. For example, for one or more (e.g., each) transmissions, the WTRU may use the indicated preamble index, SS / PBCH index, and / or PRACH mask. In an example, the WTRU may use the DMRS of one or more (e.g., each) received PDCCHs as an RS source for transmitting spatial information (e.g., a spatial filter based on an RS indicator) for one or more (e.g., each) preambles. In an example, the WTRU may receive a single RAR message including a single TA and / or TRP indication. For example, the WTRU may apply the indicated TA for one or more (e.g., all) future transmissions to one or more (e.g., two) TRPs (e.g., TRP indications) until the next TA indication. For example, the WTRU may receive, for example, an implicit and / or explicit indication in a RAR message that the WTRU may apply the indicated TA (e.g., only) to one of the TRPs (e.g., associated with one of the CORSETPoolIndex). In an example, the WTRU may receive a single RAR message including one or more (e.g., two) TA values. In an example, the WTRU may apply the indicated TA value to the corresponding TRP. In an example, the WTRU may receive one or more RAR messages. One or more (e.g., each) RAR messages may correspond to one or more PRACH transmissions. One or more (e.g., each) RAR messages may include one or more TAs. The WTRU may receive one or more (e.g., multiple) TA commands in one or more RAR messages. In an example, based on a rule and / or the received indication, the WTRU may select one or more TA values ​​from the indicated TA values ​​for one or more (e.g., all) future transmissions and / or apply the one or more TA values ​​to one or more (e.g., two) TRPs until the next TA indication. In an example, based on a rule and / or a received indication, the WTRU may select one of the indicated TA values ​​for future transmissions (e.g., all future transmissions) and / or apply the one TA value to both TRPs until the next TA indication. In an example, the WTRU may apply the one or more indicated TA values ​​to one or more corresponding TRPs.

[0096] In an example, in NR, the PDCCH command PRACH may be carried by DCI format 1_0 and / or may be scrambled by the C-RNTI. In an example, if the field corresponding to "frequency domain resource assignment" is 1, the remaining one or more fields may be interpreted as follows. For example, the random access preamble index may be 6 bits. For example, the reserved bits may be 10-12 bits. In an example, if the value of the "random access preamble index" is not (e.g., not all) zero, the UL / SUL indicator may be 1 bit, the SS / PBCH index may be 6 bits, and / or the PRACH mask index may be 4 bits.

[0097] Indications of one or more of the following examples may be used to support implementation of the examples and / or implementations described herein. In an implementation, indications of one or more of the following implementations may support implementation of the above examples and implementations. One implementation may include an RS used as a source of indication of spatial information (e.g., a spatial filter based on an RS indicator), the spatial information being included for sending a preamble associated with a second TRP. Additionally or alternatively, the examples may include additional preambles that may be associated with the second TRP. Additionally or alternatively, the examples may include additional SS / PBCH indexes. Additionally or alternatively, the examples may include additional PRACH mask indexes.

[0098] In an example, the remaining reserved bits may be 10. The indication of one or more examples described herein may be associated with overhead. For example, one or more of the following examples may be used to reduce overhead. The example may include a WTRU that may use an SSB associated with an indicated SS / PBCH index as an RS source for spatial information (e.g., a spatial filter based on an RS indicator) that is included for sending a second preamble. Additionally or alternatively, the example may include a WTRU that may use a (e.g., the same) preamble for PRACH transmissions to a first TRP and a second TRP. Additionally or alternatively, if supported by capabilities reported by the WTRU, the example may include a WTRU that may use the same SS / PBCH and / or PRACH mask index to send one or more (e.g., two) preambles. Additionally or alternatively, the example may include a WTRU that may use the same SS / PBCH index but a different PRACH mask for one or more transmissions of a first PRACH and / or a second PRACH. Additionally or alternatively, examples may include a WTRU that may use the same PRACH mask but different SS / PBCH indices for one or more transmissions of the first PRACH and / or the second PRACH.

[0099] Systems, methods, and apparatus related to subsequent RACH transmissions of a second TA loop are provided herein. In an example, the WTRU may determine (e.g., and / or use) an uplink TA value for transmitting an uplink signal based on a single TA support (e.g., a single TA loop is maintained by a cumulative TA control mechanism). For example, single TA support may be applied based on a first PRACH that the WTRU has sent. For example, single TA support may be applied based on a first PRACH that the WTRU has sent during an initial access procedure. For example, single TA support may be applied based on a first PRACH that the WTRU has sent after receiving a PDCCH command based on single TA (e.g., and / or TAG) support, and / or single TA support may be applied to communicate with a first TRP (e.g., a primary TRP, a single TRP, and / or a cell, etc.).

[0100] In an example, the WTRU may be instructed (e.g., from a gNB) to send a second PRACH (e.g., via a PDCCH command, via a PDCCH command for "second TA initiation", by an indication for initiating a second TA loop, etc.), where the second PRACH transmission may be used to initiate (e.g., create, update, add, newly initiate, and / or maintain, etc.) a second TA loop in addition to the (e.g., ongoing) first TA loop (e.g., a single TA loop). In an example, the WTRU may determine (e.g., based on the PDCCH command) a PRACH for general (e.g., existing) PRACH transmissions based on single TA support (e.g., to date) and / or for a special (e.g., based on the PDCCH command) PRACH for initiating (e.g., and / or updating) the second TA loop. For example, the WTRU target determination may be based on an explicit indicator associated with (e.g., included in) a DCI. The DCI indicates a special (e.g., based on the PDCCH command) PRACH for initiating and / or updating the second TA loop. For example, WTRU target determination may be based on implicit indications including one or more configuration parameters associated with a special (e.g., PDCCH command-based) PRACH (e.g., preamble index, SSB index, SS / PBCH index, PRACH mask, and / or one or more PRACH resources, etc.).

[0101] In response to receiving a special (e.g., based on a PDCCH command) PRACH for initiating (e.g., and / or updating) a second TA loop, the WTRU may send the special PRACH to the second TRP. For example, sending the special PRACH to the second TRP may be based on one or more of the following. Sending the special PRACH to the second TRP may be based on beam / TCI-related parameters that may be associated with the special PRACH. Sending the special PRACH to the second TRP may be based on a unified TCI associated with the second TRP (e.g., a source RS of the unified TCI). Sending the special PRACH to the second TRP may be based on a source quasi-co-sited (e.g., QCL) RS associated with the special PRACH. Sending the special PRACH to the second TRP may be based on additional and / or separate timing reference points (e.g., based on a spatial filter based on an RS indicator) obtained and / or measured from a DL RS associated with the special PRACH (e.g., a TRS associated with the second TRP, an SSB associated with the second TRP, and / or a DL RS associated with the second TRP, etc.).

[0102] In response to sending the special PRACH, the WTRU may receive a RAR. In an example, the RAR may include an indication of a second TA value (e.g., to be applied to a second TA loop). In an example, the RAR may be a second RAR to be sent from a second TRP. In an example, based on a preconfiguration delivered to the WTRU, the RAR may be a first RAR to be sent from a first TRP (e.g., a primary TRP). In an example, a beam / TCI for the first RAR sent from the first TRP may be preconfigured to the WTRU.

[0103] In response to receiving the RAR, the WTRU may (e.g., be configured to) create (e.g., a new) second TA loop for accumulation (e.g., if configured), wherein the second TA loop may include the second TA value as an initial value for the second TA loop. In response to receiving the RAR, for example, if the accumulation TA mode is not configured, the WTRU may apply the second TA value for one or more subsequent uplink transmissions to the second TRP (e.g., associated with the second TRP) until a next RAR associated with the second TRP is received.

[0104] In an example, the WTRU may maintain a first TA loop based on a first timing reference point (e.g., obtained and / or measured from a first DL RS that may be associated with a first TRP) and / or one or more first TA values, which may be accumulated based on receiving one or more TA commands that may be associated with the first TA loop. In an example, the WTRU may maintain a second TA loop based on a second timing reference point (e.g., obtained and / or measured from a second DL RS associated with a second TRP) and / or one or more second TA values, which may be accumulated based on receiving one or more TA commands that may be associated with the second TA loop. Reliability and / or flexibility in managing one or more (e.g., two) separate TA values ​​and / or loops may be improved for the first TRP and / or the second TRP, respectively. The improvement in reliability and / or flexibility may be based on creating a separate second TA loop in response to receiving a DCI including the special (e.g., based on a PDCCH command) PRACH.

[0105] In an example, the WTRU may (e.g., be configured to) apply one or more second TA values ​​(e.g., to be accumulated based on receiving one or more TA commands that may be associated with a second TA loop) based on a first timing reference point (e.g., obtained and / or measured from a first DLRS that may be associated with a first TRP). In an example, applying one or more second TA values ​​based on the first timing reference point (e.g., applied to the second TA loop) may imply that the timing reference (e.g., point) may be shared by the first TRP and / or the second TRP. In an example, the TA accumulation loop may be separated between the first TRP and the second TRP. In an example, applying one or more second TA values ​​based on the first timing reference point (e.g., applied to the second TA loop) may imply that the timing reference (e.g., point) may be shared by the first TRP and the second TRP, but the TA accumulation loop is separated between the first TRP and the second TRP.

[0106] In an example, the WTRU may maintain a first TA loop based on a first timing reference point (e.g., obtained and / or measured from a first DL RS associated with a first TRP) and / or one or more first TA values, which are accumulated based on receiving one or more TA commands associated with the first TA loop. In an example, the WTRU may maintain a second TA loop based on the same first timing reference point (e.g., shared between a first TRP and a second TRP) and / or one or more second TA values, which are accumulated based on receiving one or more TA commands that may be associated with the second TA loop. WTRU implementation complexity may be reduced when managing two separate TA values ​​and / or loops toward the first TRP and / or the second TRP, respectively, which may be based on an obtained shared timing reference point, which may be based on a DL RS.

[0107] In an example, the WTRU may (e.g., be configured to) apply a sequential RACH transmission after a first RACH transmission. In an example, the WTRU may have one or more RACH transmissions after a known and / or pre-configured time interval. The time interval between one or more (e.g., each) PRACH transmissions may be fixed, semi-statically, and / or dynamically indicated and / or configured. In an example, the time interval may be configured and / or indicated based on reported WTRU capabilities. In an example, the WTRU may determine the time interval based on another system parameter and / or operating mode (e.g., cell index, TDD / FDD, BWP index, multiple TA loop configurations, and / or multiple TRP related configurations, etc.).

[0108] In an example, in a sequential RACH transmission, the WTRU may use the same or different RACH resources. For example, the RACH resources used for each transmission may be selected and / or indicated from the same and / or TRP-based configured pool. In an example, once the WTRU receives a DCI from one of the TRPs that includes a PDCCH command RACH to initiate a RACH transmission for one or more (e.g., all) TRP links, the WTRU may follow one or more of the following rules for determining the order of RACH transmissions for one or more (e.g., each) TRPs. In an example, the WTRU may (e.g., always) start sequential RACH transmissions using a TRP that has transmitted a PDCCH command RACH. Additionally or alternatively, the WTRU may (e.g., always) start sequential RACH transmissions using a fixed TRP link (e.g., a link associated with a primary TRP, and / or a link associated with CORESETPoolIndex=0, etc.). In an example, the WTRU may start sequential RACH transmissions using a TRP that may have the closest RACH opportunity.

[0109] In an example, once the WTRU receives a DCI from one of the TRPs that includes a PDCCH commanding a RACH, the WTRU may resolve the conflict with an uplink transmission that has been scheduled for another TRP link based on one or more of the following. In an example, the WTRU may ignore the received grant and / or discard the scheduled uplink transmission. Additionally or alternatively, instead of discarding the scheduled transmission, the WTRU may delay the RACH until the next RACH transmission opportunity. Alternatively or additionally, if the scheduled uplink transmission is intended for a PUCCH and / or for a PUSCH including HARQ feedback, the WTRU may ignore the PDCCH commanding the RACH and / or may continue with the scheduled transmission.

[0110] Multi-TA operations may be performed within a TAG. Examples may include timing alignment timeouts. In an example, configuration and / or operation of a timing advance timer (TAT) may occur per TRP. The WTRU may be configured with a timing advance timer (TAT) per TRP. The TAT may be configured independently per TRP link, for example, as part of a TRP-specific TAG configuration. The TAT configuration may include one or more of the following. The TAT configuration may include a TRP identifier (e.g., the TRP to which the TAT is applied). The TAT configuration may include a TAG identifier. The TAT configuration may include a TAT duration (e.g., a duration in ms). The TAT configuration may include one or more WTRU actions to be performed when the TAT timer expires. The TAT configuration may include one or more TRP links to which one or more timeout actions will be applied. The TAT configuration may include one or more serving cells to which one or more timeout actions will be applied.

[0111] Additionally or alternatively, the TAT configuration for the TRP may include an incremental configuration from a reference TRP and / or TAG, and / or a TAT configuration (e.g., a TAT configuration for a pTRP and / or a common TAT configuration provided in system information). Additionally or alternatively, the incremental TAT configuration may include one or more of the following: a reference TRP and / or TAG and / or a TAT configuration identifier; and / or an incremental configuration and / or TAG configuration from a reference TRP and / or TAT. For example, the incremental configuration and / or TAG configuration from a reference TRP and / or TAT may consist of one or more of the following: an offset time and / or an offset timer duration.

[0112] Each TRP timing alignment timer may include one or more start and / or stop conditions. The WTRU may start and / or restart the TAT timer associated with the TRP link (e.g., upon receiving one or more of the following). Upon receiving a timing advance command MAC CE, the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving an absolute timing advance command (e.g., in response to an MSGA (PRACH) transmission including a C-RNTI MAC CE), the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving a DCI, the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving a TAG configuration and / or reconfiguration, the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving a TAT configuration and / or reconfiguration, the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving a TAT configuration and / or reconfiguration, the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving system information (e.g., SIB1), the WTRU may start and / or restart the TAT timer associated with the TRP link. Upon receiving an RRC message (e.g., RRCSetup), the WTRU may start and / or restart the TAT timer associated with the TRP link.

[0113] For example, under one or more conditions, the WTRU may stop the TAT timer associated with the TRP link. For example, when contention resolution is deemed unsuccessful, the WTRU may stop the TAT timer associated with the TRP link. For example, when contention resolution is deemed successful for a system information (SI) request, for example, after sending HARQ feedback for a MAC protocol data unit (PDU) (which may include a WTRU contention resolution identity MAC CE), the WTRU may stop the TAT timer associated with the TRP link.

[0114] The WTRU may start, restart and / or stop TAT based on which TRP link and / or serving cell receives and / or sends a message (e.g., a timing advance command MAC CE). For example, in response to a message sent / received on a TRP link, the WTRU may perform one or more TAT actions associated with the TRP. For example, in response to one or more messages sent and / or received on a TRP link, the WTRU may (e.g., only) perform one or more TAT actions associated with the TRP. For example, in response to one or more messages sent and / or received on a pTRP link, the WTRU may (e.g., only) perform one or more TAT actions associated with the TRP. For example, in response to one or more messages sent and / or received on one or more TRP links associated with the same serving cell, the WTRU may (e.g., only) perform one or more TAT actions associated with the TRP. For example, in response to one or more messages sent and / or received on one or more TRP links associated with a SpCell, the WTRU may (e.g., only) perform one or more TAT actions associated with the TRP.

[0115] The per-TRP timing alignment timer may include one or more TAT timeout conditions. If the TAT associated with the TRP times out, the WTRU may perform one or more actions. Additionally or alternatively, the WTRU may perform a TAT timeout action at a fixed offset before the timer times out and / or at a fixed time after the TAT times out. The WTRU may perform one or more timeout actions. The WTRU may perform a timeout action to initiate a RACH. The WTRU may perform a timeout action to clear one or more (e.g., all) HARQ buffers. The WTRU may perform a timeout action to notify the network. The WTRU may perform a timeout action to release one or more (e.g., all) configured PUCCHs. The WTRU may perform a timeout action to release one or more (e.g., all) configured SRSs. The WTRU may perform a timeout action to clear one or more configured downlink assignments. The WTRU may perform a timeout action to clear one or more configured uplink grants. The WTRU may perform a timeout action to clear one or more PUSCH resources used for semi-persistent CSI reporting. The WTRU may perform a timeout action to maintain the current N TA timeout action until a subsequent value is updated by the network (e.g., via a TA command).

[0116] The WTRU may configure and / or perform different sets of one or more timeout actions based on one or more of the following conditions: which TRP link the timed-out TAT is associated with (e.g., whether the timed-out TAT is associated with a pTRP and / or sTRP); which serving cell the timed-out TAT is associated with (e.g., whether the timed-out TAT is associated with a TRP belonging to a SpCell, a PsCell, and / or a SCell); and / or the number of TRPs with a timed-out TAT (e.g., if one or more (multiple) TRPs have a timed-out TAT, the WTRU may perform different sets of one or more actions).

[0117] The WTRU may be configured and / or perform one or more timeout actions (e.g., only) for TRP links associated with an expired TAT timer. Additionally or alternatively, the WTRU may be configured and / or perform one or more timeout actions for one or more additional links (e.g., depending on the configuration). For example, the WTRU may perform one or more of the timeout actions described herein for a TRP link associated with a timer that has timed out. For example, the WTRU may perform one or more of the timeout actions described herein for one or more (e.g., all) TRP links associated with a serving cell. For example, the WTRU may perform one or more of the timeout actions described herein for one or more (e.g., all) TRP links associated with a serving cell.

[0118] In an example, upon expiration of the TAT for a TRP, the WTRU may suspend UL transmission to the affected TRP and / or may maintain one or more HARQ buffers. The WTRU may send (e.g., pending) data on the suspended TRP to the still valid TRP. In an example, the WTRU's transmission of (e.g., pending) data on the suspended TRP may depend on data priority, one or more available resources, and / or configuration.

[0119] The WTRU may be configured for notification of a TAT timeout. Upon TAT timeout for one or more TRP links, the WTRU may notify the network of the TAT timeout via one or more of the following methods. The WTRU may notify the network of the TAT timeout by initiating a RACH transmission on the affected TRP link. For example, the WTRU may receive a single PDCCH command RACH to initiate a RACH transmission to obtain an updated TA on the affected link. For example, additionally or alternatively, a single received PDCCH command RACH may initiate a RACH transmission on one or more (e.g., all) TRP links. For example, the WTRU may receive a separate PDCCH command RACH for one or more (e.g., each) TRP links, wherein the first PDCCH may be associated with a TRP link (associated with the affected timer). Additionally or alternatively, the WTRU may notify the network of the TAT timeout by transmitting an implicit and / or explicit notification to the gNB over a link whose timer has not yet expired. For example, the notification may indicate to the gNB that the timer of the other link has expired, so that the gNB may send a PDCCH command RACH for the affected link. For example, if one or more (e.g., each) TAG is associated with a different subset of RACH resources, the WTRU may perform an implicit indication by using one or more PRACH resources of the affected TAG for the TRP associated with the TAG with still valid TA information.

[0120] The WTRU may be configured to exceed a maximum receive time difference and / or a maximum transmit time difference. Deployment of multiple TRP configurations that may support a receive time difference exceeding a cyclic prefix (CP) may present challenges to the WTRU architecture. For example, if the receive time difference exceeds a certain level, one or more (e.g., two) baseband units may be included. Including one or more additional baseband units may result in a more expensive device. The receive difference time limit may be beneficial in maintaining one or more objectives of the feature in terms of throughput and / or robustness of data transmission (e.g., due to the non-co-located nature of the TRPs and / or one or more propagation properties in one or more different frequency ranges).

[0121] The maximum receive time difference (MRTD) and / or the maximum transmit time difference (MTTD) may characterize one or more thresholds expressed in time units, symbol units, and / or one or more portions of a symbol that may be specific to the WTRU hardware architecture. For example, a WTRU that may have this capability may be designed with a single baseband unit. For example, when the MRTD and / or MTTD is below a certain time threshold, communications with one or more (e.g., two) TRPs in the downlink and / or uplink may be processed simultaneously. In an example, one or more (e.g., two) baseband units may be included for this feature.

[0122] In a multi-TRP deployment, one or more TRPs may be at different distances from the WTRU. In an example, the TA value indicated in one or more of the one or more timing advance commands for one or more (e.g., each) TRPs may result in a relative time difference that exceeds the maximum transmit time difference (MTTD) capability of the WTRU.

[0123] The WTRU may be configured as a multi-TRP. The multi-TRP may include one or more additional TRP candidate measurement settings and / or reports. The one or more additional TRPs may be added to the primary TRP by the network before and / or (e.g., only) after the WTRU reports one or more measurement results. In practice, the network may configure the WTRU to measure one or more additional TRP candidates in the area served by the primary TRP. The WTRU may, for example, report one or more capabilities of the WTRU for multi-TRP deployment at registration and / or upon network request. The WTRU may report its supported MRTD and / or MTTD as thresholds. The network may, for example, configure the WTRU for one or more additional TRP candidate measurements and / or reports taking into account the WTRU's multi-TRP operation timing capabilities. In an example, the WTRU may measure one or more additional candidates and / or their relative reception time difference with the primary TRP (pTRP), and / or may report one or more candidates, for example, the RSRP and / or RSRQ levels of the one or more candidates exceed the reporting quality threshold and / or the relative time difference is less than the WTRU reported capability for MRTD. Additionally or alternatively, the WTRU may be configured to report the RSRP and / or RSRQ of one or more additional TRP candidates, and / or their relative reception time difference with a primary TRP (pTRP), e.g., without (e.g., any) limitations regarding supported MRTD capabilities.

[0124] For example, upon receiving a measurement report that may have one or more additional TRP candidates within one or more reporting conditions, the network may configure an additional TRP (e.g., sTRP) for the WTRU. For example, upon receiving a reconfiguration message that may have an sTRP attached, the WTRU may measure (e.g., measure again) the relative receive time difference. For example, at the time of the most recent measurement of the sTRP relative receive time difference, when the receive time difference is within the capabilities reported by the WTRU, the WTRU may confirm the reconfiguration message to the network, and / or may report a reconfiguration failure (e.g., if the last measured relative receive time difference exceeds the supported MRTD). In the example, there may be a reconfiguration failure cause field that may indicate "exceeds MRTD". For example, a reconfiguration failure may be transmitted as a beam failure for the reasons indicated herein. For example, if the last measured relative receive time difference of the configured candidate has one or more WTRU capabilities, the WTRU may initiate an uplink time synchronization procedure with the configured sTRP.

[0125] Additionally or alternatively, the WTRU may be configured with one or more additional sTRPs that comply with (e.g., may follow) MRTD and / or RSRP and / or RSRQ thresholds. The WTRU may be configured with one or more TCI states for one or more (e.g., each) combinations of pTRP-sTRP, and / or may activate one or more TCI combinations (e.g., a selected and / or optimal TCI combination) based on, for example, one or more recent WTRU-reported measurement results. For example, when a TCI combination is activated, the WTRU may initiate one or more UL synchronization procedures with the most recently (e.g., recently) activated sTRP (e.g., based on a determined spatial filter and / or utilizing timing based on a TA indication). For example, if UL synchronization results in exceeding the MTTD supported by the WTRU, a beam failure report with a reason of "exceeding MTTD" may be transmitted to the network. For example, upon receiving a failure message with a cause of "MTTD exceeded", the network may activate a different TCI state combination and / or (e.g., completely) reconfigure the WTRU, e.g., with one or more other sTRP candidates and / or with one or more other TCI state combinations with pTRP. Additionally or alternatively, the network may remove multi-TRP related operations from the WTRU configuration.

[0126] The WTRU may be configured with one or more timing advance operations for multiple TRPs associated with MRTD and / or MTTD. A WTRU that may be mobile in an environment may receive one or more timing advance commands for one or more (e.g., two) TRPs, for example, after adding an sTRP and / or synchronizing with an sTRP successfully (e.g., simultaneously). TRP deployment and / or WTRU mobility may result in one or more situations where MRTD and / or MTTD may be exceeded. Exceeding MRTD and / or MTTD may result in a radio link failure for an active sTRP. In an example, the WTRU may report the problem.

[0127] In an example, if the relative difference between the TA advance values ​​exceeds the MRTD and / or MTTD thresholds, the WTRU may do one or more of the following. In an example, if the relative difference between the TA advance values ​​exceeds the MRTD or MTTD thresholds, the WTRU may transmit an indication of the error and / or problem to the gNB. The indication may be transmitted via a pTRP. The pTRP may remain anchored on an RRC message, MAC CE, and / or UCI on the physical layer. Additionally or alternatively, the indication may be a radio link failure (RLF) indication for the sTRP.

[0128] Upon receiving a notification from the WTRU, the network may perform one or more of the actions herein, and / or (e.g., any) combination of the actions herein. For example, upon receiving a notification from the WTRU, the network may reconfigure the WTRU to have one or more other TCI states containing one or more other combinations of pTRP-sTRP candidates, which may be based on one or more latest measurement reports received from the WTRU, and / or may be followed by TCI activation for different combinations and / or may continue operation in multi-DCI mode. For example, upon receiving a notification from the WTRU, if there are no other combinations with the configured TCI pool containing multiple TRP combinations, the WTRU may fall back to single DCI mode and / or may continue mTRP operation in TDM mode. For example, upon receiving a notification from the WTRU, the WTRU may declare a beam failure on the sTRP while indicating the strongest (e.g., best) TCI combination from the configured TCI pool based on one or more measurements in the (e.g., last) measurement. The indication of the (e.g., best target) TCI combination may be based on the (e.g., minimum) measured MRTD. For example, following a beam failure indication, the WTRU may continue to monitor the CORESET associated with the sTRP (e.g., in CORESETPOOLIndex 1) for beam indications within the DCI from one or more active TCIs.

[0129] The WTRU may be configured with the timing of application of one or more TA commands. In a multi-TRP transmission, a WTRU (e.g., with simultaneous uplink transmission capability) may receive a TA command for one or more of the TRP links. For example, when TA is applied to one or more consecutive time slots, overlap between UL TRP transmissions for the TRPs may occur. One or more TA commands may be applied (e.g., always applied) at the beginning of a time slot, and / or one or more rules may be applied to one or more symbols of a time slot (e.g., applied to the last one or more symbols of a time slot and / or the first symbol or the first multiple symbols), which may be applied to a closed range of a time slot boundary (e.g., a few symbols).

[0130] One or more transmissions may occur based on the relative timeline of ongoing transmissions of a first transmission and / or a second transmission associated with an updated TA, as described herein. When the updated TA may cause the associated UL transmission to be later than the ongoing first transmission, the ongoing transmission may proceed as planned. Additionally or alternatively, for example, when one or more overlapping UL transmissions between TRPs may not be allowed, the transmission associated with the link with the updated TA may be shortened by the number of overlapping samples toward the end. For example, if the updated TA timeslot causes the associated transmission to be earlier than the ongoing first transmission, the ongoing transmission may proceed as planned. Additionally or alternatively, when one or more overlapping UL transmissions between TRPs may not be allowed, the transmission associated with the link with the updated TA may be shortened at the beginning, for example, by the number of overlapping samples. In an example, shortening for transmission alignment may be performed by considering priority rules. In an example, the alignment of one or more transmissions may be shortened by considering priority rules. For example, the WTRU may shorten the PUSCH slot (e.g., instead of the PUCCH) if the PUCCH overlaps with the PUSCH and / or the TA application may imply shortening the PUCCH (e.g., using normal overlap shortening rules where ongoing transmissions may be protected). In an example, the PUSCH with CSI and / or (e.g., any) UCI ​​may be protected on the (e.g., normal) PUSCH and thus, for example, the (e.g., normal) PUSCH may be shortened.

[0131] The WTRU may be configured according to one or more procedures for indicating and / or associating one or more (e.g., multiple) TAs to one or more TRPs. In an example, a (e.g., specific) flag in a MAC CE may indicate whether the indicated TA may be used for a first TRP link and / or a second TRP link. For example, the flag may be indicated in one or more of (e.g., two) fields that may be reserved for a TAG ID. In an example, for example, a CORESETPoolIndex bit may be added to the MAC CE to indicate the intended TRP link. Additionally or alternatively, for example, CORESETPoolIndex may be associated with one or more TAG IDs in the TAG ID to provide a link. In an example, the WTRU may determine the intended TRP for TA indication, for example, based on a scheduled PDCCH. For example, if a PDCCH scheduling a PDSCH including a MAC CE TA command arrives at CORESETPoolIndex=0, the indicated TA may be applied to the TRP link associated with CORESETPoolIndex=0. In an example, the indicated TA may be applied to a TRP link that may be associated with a CORESET (e.g., CORESETPoolIndex=1). For example, if a PDCCH scheduling a PDSCH containing a MAC CE TA command arrives at CORESETPoolIndex=0, the indicated TA may be applied to a TRP link associated with CORESETPoolIndex=0, otherwise it may be applied to a TRP link associated with a CORESET (e.g., CORESETPoolIndex=1). In an example, the MAC CE may include TA information for one or more TRP links. In an example, the WTRU may (e.g., simultaneously) update the TA information for one or more TRP links. In an example, the WTRU may (e.g., simultaneously) update the TA information for one or more (e.g., multiple) TRP links. The association with the first TRP link and / or the second TRP link may be based on the order of the values ​​indicated in the MAC CE and / or CORESETPoolIndex, etc. For example, the indicated TA information may be an absolute TA value for one or more (e.g., each) TRPs, and / or in the form of their relative difference. The WTRU may receive a TA value for a first TRP link (e.g., TA1) and / or a relative difference for a second TRP link (e.g., TA_delta) to determine the TA for the second link (e.g., TA2=TA1+TA_delta). For example, once the WTRU may receive one or more TA indications for one or more TRPs, the WTRU may apply one or more rules as described herein to determine the priority of application for one or more (e.g., each) TRPs.The WTRU may apply the TA to one or more (e.g., each) TRP links, for example, based on the timing of the scheduled transmissions. For example, once the WTRU receives one or more TA indications for more than one TRP, the WTRU may (e.g., first) apply the TA to the TRP links with earlier scheduled transmissions. In the example, once the WTRU receives one or more TA indications for more than one TRP, the WTRU may (e.g., first) apply the TA to the TRP links associated with the primary TRP and / or associated with CORESETPoolIndex=0.

[0132] The WTRU may be configured with one or more (e.g., multiple) TAGs per serving cell. One or more timing advance groups (TAGs) may be provided to the WTRU per serving cell. One or more (e.g., each) TAG configurations may be associated with one or more different (e.g., different) TRP links. For example, if the WTRU supports multi-TRP and / or multi-TA operation, the WTRU may (e.g., only) apply the TAG configuration associated with the secondary sTRP and / or additional sTRP.

[0133] The TAG configuration for a TRP may include one or more of the parameters described herein: TAG ID; TRP identifier (e.g., which TRP the TAG configuration applies to, etc.); whether the TAG applies to a pTRP and / or an sTRP; and / or a timeAlignmentTimer (TAT) value and / or a TimeAlignmentTimerCommon value. The WTRU may receive TAG configuration information related to a primary TRP (pTRP) and / or one or more additional TRPs (e.g., sTRP) via system information (e.g., SIB1 and / or within UplinkConfigCommonSIB) and / or via dedicated signaling (e.g., via RRC signaling, DCI, and / or MAC CE). For example, one or more TimeAlignmentTimerCommon parameters associated with one or more TRPs within the system information (e.g., within SIB1 via UplinkConfigCommonSIB) may be provided to the WTRU. For example, one or more (e.g., multiple) TAG configurations within a MAC-CellGroupConfig may be provided to the WTRU via a TAG-Config (e.g., via RRC), where TAG information may be provided for one or more (e.g., each) TRPs. For example, the TAG-Config may include a tag-ID and / or timeAlignmentTimer configuration for a primary TRP (pTRP) and / or one or more additional TRPs (sTRPs). For example, there may be one or more (e.g., multiple) TAG-Config information elements within a MAC-CellGroupConfig, where one or more (e.g., each) of these information elements may correspond to a TRP of a cell.

[0134] For example, if the WTRU receives a dedicated TAG configuration (e.g., via RRC signaling and / or MAC CE), the WTRU may override the TAG configuration for one or more TRPs provided via broadcast signaling (e.g., via UplinkConfigCommonSIB within SIB1).

[0135] For example, a TAG configuration for a set of X TRPs may be provided to the WTRU via broadcast signaling (e.g., within system information), and / or a TAG configuration for a set of Y TRPs may be provided to the WTRU via dedicated signaling (e.g., RRC configuration and / or MAC CE). For example, if set X and set Y include the same TRP, the WTRU may overwrite one or more (e.g., or all) TAG configurations (and / or one or more associated parameters) provided in set X (e.g., via broadcast signaling) with the same content provided in set Y. For example, if set X and set Y include one or more different TRPs, and if set Y includes a TAG configuration for a pTRP, the WTRU may apply the TAG configuration to one or more (e.g., all) TRPs within set X that are not included in set Y. For example, if set X and set Y include one or more different TRPs, the WTRU may update (e.g., only) the TAG configuration for the TRPs provided in both set X and set Y. For example, the configuration for one or more (e.g., all) TRPs within set X that are not provided in set Y may be maintained or deleted. For example, the one or more actions that the WTRU takes may be explicitly instructed via configuration and / or within system information.

[0136] If the WTRU and / or cell can support multi-TRP multi-TA operation and (e.g., only support) one TAG configuration, one or more of the following may be included. The WTRU may apply the TAG information to one or more (e.g., or all) TRPs (e.g., pTRPs and / or one or more sTRPs) associated with the serving cell. The WTRU may be (e.g., explicitly) indicated whether the TAG configuration applies to the pTRP and / or one or more sTRPs. For example, the indication may be provided within MAC-CellGroupConfig, TAG-Config, SIB1 and / or one or more (e.g., any, some) other broadcasts (e.g., system information), RRC and / or MAC (e.g., MAC CE) signaling. For example, when the RRC state transitions (e.g., via a flag) to RRC_INACTIVE and / or RRC_IDLE, the WTRU may apply one or more previously stored TAG configurations. For example, the flag may be included in the (e.g., TAG) configuration. For example, the default TAG configuration may include one or more parameters included in the TAG configuration (e.g., TAT value). The default TAG configuration may be provided, for example, via system information (e.g., SIB1). In an example, the (e.g., system) information may be provided via a dedicated configuration (e.g., via RRC), for example, upon RRC state transition (e.g., upon receiving an RRC Setup and / or RRC Release containing a suspend config message).

[0137] Figure 4 Depicted is a system diagram illustrating example timing alignment for an sTRP 400. A WTRU 406 may be configured with a primary TRP (pTRP) 402 and / or a secondary TRP (sTRP) 404 and / or a set of one or more PRACH resources.

[0138] At 408, the pTRP 402 may transmit a PDCCH command for the PRACH to the sTRP 404 to the WTRU 406. The PDDCH command may include a preamble identifier, a TRP indication associated with the sTRP 404 (e.g., such as a CORESETPOOL index), a first SSB index (e.g., associated with the pTRP 402), a second SSB index, a first PRACH mask, a second PRACH mask, a TRP index, and / or an RS indicator associated with the sTRP 404 (e.g., CSI-RS and / or tracking RS). The WTRU 406 may use the RS indicator to determine a spatial filter for transmission (Tx). If the timing alignment for the pTRP 402 and the sTRP 404 includes (e.g., only) one PDCCH command, the PDDCH command may include a second SSB index (e.g., associated with the pTRP 402) and / or a second PRACH mask.

[0139] At 410, the WTRU 406 may transmit a PRACH (e.g., preamble) transmission to the sTRP 404. The preamble may use a determined PRACH resource and / or a (e.g., determined) spatial filter based on a preamble identifier (e.g., at 408). For example, the WTRU 406 may determine a spatial filter based on an RS indicator (e.g., the RS indicator indicated at 408). The WTRU 406 may determine to transmit a preamble to the sTRP 404 based on the spatial filter at 410. The WTRU 406 may use the determined spatial filter to transmit the PRACH to the sTRP 404. The WTRU 406 may determine a PRACH resource for the transmission to the sTRP 404 based on an SSB index (e.g., associated with a pTRP), one or more PRACH resources, and / or a PRACH mask. If the timing alignment for the pTRP 402 and the sTRP 404 includes (e.g., only) one PDCCH command, the WTRU 406 may send the same preamble to the pTRP 402 based on a second SSB index and / or a second PRACH mask.

[0140] At 412, the sTRP 404 may transmit a (e.g., a first) response message to the WTRU 406. The (e.g., first) response may be a RAR message. The RAR message may include a TRP index, a TA (e.g., a TA indication), and / or an sTRP UL grant. The WTRU 406 may receive the first response to the preamble. The first response may include a first timing advance (TA) command for the second timing alignment for the transmission to the sTRP 404 and / or an index indicating the sTRP 404. If the timing alignment for the pTRP 402 and the sTRP 404 includes (e.g., only) one PDCCH command, the RAR message may include the second TA.

[0141] At 414, the WTRU 406 may transmit UL Tx (e.g., Msg3) to the sTRP 404. The WTRU 406 may transmit UL Tx to the sTRP 404 at 414 using the determined spatial filter and / or timing based on the (e.g., first) TA indication / command.

Claims

1. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising a processor, the processor configured to: receiving configuration information indicating a first timing advance group (TAG) for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier (ID) and the second TAG is associated with a second TAG ID, the configuration information indicating a first duration of a first timing alignment timer (TAT) associated with the first TAG for the serving cell, and the configuration information indicating a second duration of a second TAT associated with the second TAG for the serving cell; Starting the first TAT; Starting the second TAT; determining that the first TAT associated with the first TAG for the serving cell has timed out; based on determining that the first TAT associated with the first TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the first TAG for the serving cell; maintaining a hybrid automatic repeat request (HARQ) buffer associated with the serving cell when the first TAT associated with the first TAG for the serving cell times out; determining that the second TAT associated with the second TAG for the serving cell has timed out; based on determining that the second TAT associated with the second TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell; flushing the HARQ buffer associated with the serving cell based on that the second TAT associated with the second TAG for the serving cell has timed out; as well as At least one of the first TAT or the second TAT is started or restarted based on receiving a timing advance command medium access control (MAC) control element (CE).

2. A WTRU according to claim 1, wherein the first TAG for the service cell is associated with a first transmit / receive point (TRP) for the service cell, and the second TAG for the service cell is associated with a second TRP for the service cell.

3. A WTRU according to claim 2, wherein a first transmission configuration information (TCI) state is associated with a transmission corresponding to the first TRP, the first TRP is associated with the first TAG used for the serving cell, and a second TCI state is associated with a transmission corresponding to the second TRP, the second TRP is associated with the second TAG used for the serving cell.

4. The WTRU of claim 1 , wherein the processor is configured to: After the first TAT associated with the first TAG for the serving cell expires, uplink transmission associated with the second TAG for the serving cell continues to be performed.

5. The WTRU of claim 1 , wherein the processor is configured to: suspending at least one uplink transmission associated with the first TAG for the serving cell based at least on determining that the first TAT associated with the first TAG for the serving cell has timed out; and At least one uplink transmission associated with the second TAG for the serving cell is suspended based at least on a determination that the second TAT associated with the second TAG for the serving cell has timed out.

6. The WTRU of claim 5, wherein the processor being configured to suspend the at least one uplink transmission comprises the processor being configured to suspend transmissions other than a random access preamble transmission or a MsgA transmission.

7. The WTRU of claim 1 , wherein the serving cell is a first serving cell, and wherein the processor is configured to flush the HARQ buffer comprises the processor being configured to flush all HARQ buffers for the first serving cell and a second serving cell.

8. The WTRU of claim 1, wherein the processor is configured to receive the MAC CE, the MAC CE activating a first transmit configuration indicator (TCI) state group for controlling a resource set (coreset), and wherein the TCI state group includes at least one TCI state, the at least one TCI state including the first TCI state.

9. A WTRU according to claim 8, wherein the processor is configured to determine that a demodulation reference signal (DMRS) antenna port associated with reception of one or more physical downlink control channels in the coreset is quasi-co-located with one or more downlink reference signals configured by the at least one TCI state, wherein the processor is configured to receive downlink control information (DCI) via the coreset, wherein the DCI indicates a second TCI state, wherein the TCI state group includes the second TCI state, and wherein reception of a transport block (TB) based on the TCI state group includes at least one DMRS of the TB being quasi-co-located with a second reference signal indicated by the second TCI state.

10. The WTRU of claim 1 , wherein the processor is configured to: Based on the second TAT associated with the second TAG for the serving cell having timed out, one or more configured physical uplink control channel (PUCCH) resources and one or more configured sounding reference signal (SRS) resources are released.

11. A method performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information indicating a first timing advance group (TAG) for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier (ID) and the second TAG is associated with a second TAG ID, the configuration information indicating a first duration of a first timing alignment timer (TAT) associated with the first TAG for the serving cell, and the configuration information indicating a second duration of a second TAT associated with the second TAG for the serving cell; Starting the first TAT; Starting the second TAT; determining that the first TAT associated with the first TAG for the serving cell has timed out; based on determining that the first TAT associated with the first TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the first TAG for the serving cell; maintaining a hybrid automatic repeat request (HARQ) buffer associated with the serving cell when the first TAT associated with the first TAG for the serving cell times out; determining that the second TAT associated with the second TAG for the serving cell has timed out; based on determining that the second TAT associated with the second TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell; flushing the HARQ buffer associated with the serving cell based on that the second TAT associated with the second TAG for the serving cell has timed out; as well as At least one of the first TAT or the second TAT is started or restarted based on receiving a timing advance command medium access control (MAC) control element (CE).

12. The method of claim 11, wherein the first TAG for the serving cell is associated with a first transmit / receive point (TRP) for the serving cell, and the second TAG for the serving cell is associated with a second TRP for the serving cell.

13. A method according to claim 12, wherein a first transmission configuration information (TCI) state is associated with a transmission corresponding to the first TRP, the first TRP is associated with the first TAG used for the service cell, and a second TCI state is associated with a transmission corresponding to the second TRP, the second TRP is associated with the second TAG used for the service cell.

14. The method according to claim 11, wherein the method further comprises: After the first TAT associated with the first TAG for the serving cell expires, uplink transmission associated with the second TAG for the serving cell continues to be performed.

15. The method according to claim 11, wherein the method further comprises: suspending at least one uplink transmission associated with the first TAG for the serving cell based at least on determining that the first TAT associated with the first TAG for the serving cell has timed out; as well as At least one uplink transmission associated with the second TAG for the serving cell is suspended based at least on a determination that the second TAT associated with the second TAG for the serving cell has timed out.

16. The method of claim 15, wherein suspending the at least one uplink transmission comprises suspending transmissions other than random access preamble transmissions or MsgA transmissions.

17. The method of claim 11, wherein the serving cell is a first serving cell, and wherein flushing the HARQ buffer comprises flushing all HARQ buffers for the first serving cell and a second serving cell.

18. The method according to claim 11, wherein the method further comprises: receiving the MAC CE, the MAC CE activating a first transmission configuration indicator (TCI) state group for controlling a resource set (coreset), and wherein the TCI state group includes at least one TCI state, the at least one TCI state including the first TCI state; determining that a demodulation reference signal (DMRS) antenna port associated with reception of one or more physical downlink control channels in the coreset is quasi-co-located with one or more downlink reference signals configured by the at least one TCI state; as well as Downlink control information (DCI) is received via the coreset, wherein the DCI indicates a second TCI state, wherein the TCI state group includes the second TCI state, and wherein reception of a transport block (TB) based on the TCI state group includes at least one DMRS of the TB being quasi-co-located with a second reference signal indicated by the second TCI state.

19. The method according to claim 11, wherein the method further comprises: Based on the second TAT associated with the second TAG for the serving cell having timed out, one or more configured physical uplink control channel (PUCCH) resources and one or more configured sounding reference signal (SRS) resources are released.

20. A wireless transmit / receive unit (WTRU), the wireless transmit / receive unit (WTRU) comprising: A processor, the processor being configured to: receiving configuration information indicating a first timing advance group (TAG) for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier (ID) and the second TAG is associated with a second TAG ID, the configuration information indicating a first duration of a first timing alignment timer (TAT) associated with the first TAG for the serving cell, and the configuration information indicating a second duration of a second TAT associated with the second TAG for the serving cell; Starting the first TAT; Starting the second TAT; determining that the first TAT associated with the first TAG for the serving cell has timed out; based at least on determining that the first TAT associated with the first TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the first TAG for the serving cell; When the first TAT associated with the first TAG for the serving cell times out, determining not to flush a hybrid automatic repeat request (HARQ) buffer associated with the serving cell; determining that the second TAT associated with the second TAG for the serving cell has timed out; based on determining that the second TAT associated with the second TAG for the serving cell has timed out, clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell; flushing the HARQ buffer associated with the serving cell based on that the second TAT associated with the second TAG for the serving cell has timed out; as well as At least one of the first TAT or the second TAT is started or restarted based on receiving a timing advance command medium access control (MAC) control element (CE).

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