PDCCH command PRACH transmission in multi-TRP operation

Abstract

A WTRU may receive downlink control information (DCI) from a first transmit / receive point (TRP). The DCI may indicate that the WTRU transmits 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 a preamble within a first PRACH resource to a second TRP. The first TRP and / or the second TRP may be associated with the same physical cell identification information (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 a second timing alignment for transmission to the second TRP, and / or an index indicating the second TRP.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 334,976, filed in the United States on April 26, 2022, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates generally to wireless communication systems, and more particularly to a method and apparatus for multi-transmission / reception point (mTRP) with multiple timing advance (TA) operations in a wireless communication system. [Background technology]

[0003] After the commercialization of 4G communication systems, efforts are underway to develop improved 5G communication systems due to the increasing demand for wireless data traffic. Therefore, 5G communication systems or pre-5G communication systems are also called communication systems that are beyond 4G networks or post-LTE systems (Post LTE).

[0004] To achieve high data rates, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands (e.g., the 60 GHz band). To mitigate the path loss of radio waves in the ultra-high frequency bands and increase the propagation distance of radio waves, 5G communication systems are considering beamforming, massive MIMO, full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antenna technologies.

[0005] To improve the system's network, the development of evolved small cells, advanced small cells, cloud radio access networks (Cloud RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, mobile networks, cooperative communication, coordinated multi-point (CoMP), and interference cancellation technologies are being further advanced in the 5G communication system.

[0006] In addition, advanced coding modulation (ACM) schemes such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), as well as advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non-orthogonal multiple access), and sparse code multiple access (SCMA) are being researched for 5G systems. Summary of the Invention

[0007] SUMMARY OF THE INVENTION

[0003] A wireless transmit / receive unit (WTRU) may receive a PDCCH command for triggering a Physical Random Access Channel (PRACH) transmission and / or transmit one or more first PRACHs according to 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 when the WTRU is configured for multi-TRP operation in a multi-TRP deployment.

[0008] In an example, an implementation may include determining an uplink TA value for transmission of an uplink signal, the uplink TA value being determined based on a single TA loop, and / or transmitting one or more PRACHs to initiate a second TA loop based on receiving an instruction to transmit a second PRACH.

[0009] In an example, an 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 intended TRPs for the indicated one or more TAs based on the received PDCCH.

[0010] The systems, methods, and apparatus may include receiving one or more timing advance groups (TAGs) for a serving cell, where one or more (e.g., each) TAG is associated with a TRP link, and / or applying a TAG associated with a TRP.

[0011] Systems, methods, and apparatuses are described herein for PDCCH command PRACH transmission in mTRP operation. A WTRU may receive downlink control information (DCI) from a first transmit / receive (TRP). The DCI may indicate that the WTRU will 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 to a second TRP in the first PRACH resource. The first PRACH resource may be determined, for example, based on the first PRACH mask and / or the first SSB. The preamble may be transmitted using a spatial filter determined, for example, based on the indicated RS. The first TRP and / or the second TRP may be associated with the same physical cell identity (PCI).

[0012] The WTRU may determine to transmit a preamble to a second TRP based on, for example, a spatial filter. The WTRU may maintain a first timing alignment for transmissions to the first TRP and / or maintain a second timing alignment for transmissions 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 a second timing alignment for transmissions 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 transmit an uplink (UL) transmission to the second TRP using the determined spatial filter and / or with timing based on the first TA command. The WTRU may determine a spatial filter to use to transmit the preamble to the second TRP using the indicated RS.

[0013] The WTRU may receive a DCI in the PDDCH command that triggers a 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 transmit a preamble to a first TRP, for example, using a second PRACH resource determined based on the second PRACH mask and / or the second SSB. The WTRU may receive a second response to the preamble transmitted using the second PRACH resource from the first TRP. The second response may include a timing advance command for first timing alignment for 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 explanation of the drawings]

[0014] [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an exemplary wireless transmit / receive unit (WTRU) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1C] 1A is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1D] 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 2] A diagram illustrating an example of an absolute timing advance command medium access control (MAC) control element (CE) format. [Figure 3] A diagram illustrating an example of a relative timing advance command MAC CE format. [Figure 4] FIG. 1 is a system diagram illustrating an exemplary timing alignment for a secondary transmit / receive point (sTRP). DETAILED DESCRIPTION OF THE INVENTION

[0015] 1A is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. 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 use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0016] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RANs 104 / 113, CNs 106 / 115, public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of 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 transmit 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 mobile phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., for remote surgery), an industrial device and application (e.g., a robot and / or other wireless device operating in an industrial and / or automated processing chain context), a consumer electronics device, a device operating on a commercial wireless network and / or an industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be referred to interchangeably as a UE.

[0017] The communications 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 configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications 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 eNodeB, a Home Node B, a Home eNodeB, a gNB, an NR Node B, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each depicted as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

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

[0019] 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).

[0020] More specifically, as noted above, the communications system 100 may be a multiple-access system, but may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 / 113 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communications 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 ​​Uplink Packet Access (HSUPA).

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

[0022] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as New Radio (NR) radio access, which may establish the air interface 116 using NR.

[0023] In one 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 jointly implement LTE radio access and NR radio access, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0024] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology 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), or the like.

[0025] 1A 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, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or femtocell. 1A, the base station 114b may have a direct connection to the Internet 110. Therefore, the base station 114b may not need to access the Internet 110 through the CN 106 / 115.

[0026] The RAN 104 / 113 may communicate with the CN 106 / 115, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as different throughput, latency, error tolerance, reliability, data throughput, and mobility requirements. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it will be understood that the RAN 104 / 113 and / or the CN 106 / 115 may communicate directly or indirectly with other RANs that use 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 communicate with another RAN (not shown) using GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0027] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing 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) of the TCP / IP Internet protocol suite. The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may use the same RAT as the RAN 104 / 113 or a different RAT.

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

[0029] 1B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1B, 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 understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0030] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

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

[0032] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may use 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.

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

[0034] The processor 118 of the WTRU 102 may be coupled to and may receive user-entered 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. Additionally, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0035] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components within 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 batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0036] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or instead of, information from the GPS chipset 136, the WTRU 102 may receive location information from base stations (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 obtain location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0037] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripheral device 138 may include one or more sensors, which may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, a direction 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.

[0038] The WTRU 102 may include a full-duplex radio where transmission and reception of some or all of the signals (e.g., associated with a particular subframe for both the UL (e.g., for transmission) and downlink (e.g., for reception)) may be parallel and / or simultaneous. The full-duplex radio may include an interference management unit 139 for reducing and or substantially eliminating self-interference through either hardware (e.g., chokes) or processor-mediated signal processing (e.g., via a separate processor (not shown) or processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmitting and receiving some or all of the signals (e.g., associated with a particular subframe for either the UL (e.g., for transmission) or downlink (e.g., for reception)).

[0039] 1C is a system diagram illustrating the RAN 104 and the CN 106, according to one embodiment. As mentioned above, the RAN 104 may use E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also communicate with the CN 106.

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

[0041] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. As shown in FIG. 1C, the eNodeBs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0042] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing elements is depicted as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0043] The MME 162 may be connected to each of the eNodeBs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during 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.

[0044] The SGW 164 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNodeB handover, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

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

[0046] 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 landline communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

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

[0048] In a representative embodiment, the other network 112 may be a WLAN.

[0049] A WLAN in infrastructure Basic Service Set (BSS) mode may have an access point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access or interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic into and / or out of the BSS. Traffic originating outside the BSS and destined for a STA may arrive through the AP and be sent to the STA. Traffic originating at a STA and destined for a destination outside the BSS may be sent to the AP to be sent to the respective destination. Traffic between STAs within a BSS may be sent through the AP, for example, where the source STA may send traffic to the AP, and the AP may send traffic to the destination STA. Traffic between STAs within a BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between (e.g., directly between) a source STA and a destination STA using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs within or using the IBSS (e.g., all of the STAs) may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad hoc" communication mode.

[0050] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit 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 that is dynamically configured via signaling. The primary channel may be the operating channel of the BSS and may be used by STAs to establish a connection with the AP. In certain representative embodiments, for example, in an 802.11 system, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA may back off. One STA (e.g., only one station) may transmit in a given BSS at any given time.

[0051] High Throughput (HT) STAs may use 40 MHz wide channels for communication, which may be formed, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels.

[0052] A Very High Throughput (VHT) STA may support channels with widths of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz. A 40 MHz and / or 80 MHz channel may be formed by combining adjacent 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-adjacent 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may separate the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time-domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed, and the combined data may be sent to Medium Access Control (MAC).

[0053] Sub-1 GHz operating modes are supported by 802.11af and 802.11ah. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah may support meter-type control / machine-type communications, such as MTC devices within macro coverage areas. MTC devices may have limited capabilities, including support for (e.g., only) certain and / or limited bandwidths. MTC devices may include batteries with above-threshold battery life (e.g., to maintain very long battery life).

[0054] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that can be designated as a primary channel. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be configured and / or limited by a STA from among all STAs operating in the BSS that support the minimum bandwidth operating mode. In an 802.11ah embodiment, the primary channel can be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration can depend on the status of the primary channel. For example, if the primary channel is active due to a STA (that only supports 1 MHz mode of operation) transmitting to the AP, the entire available frequency band may be considered active, even though most of the frequency band may remain inactive and available.

[0055] In the United States, the available frequency band that can be used by 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.

[0056] 1D is a system diagram illustrating the RAN 113 and the CN 115, according to one embodiment. As noted above, the RAN 113 may use NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also communicate with the CN 115.

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

[0058] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol 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 transmission time intervals (TTIs) of different or scalable lengths (e.g., including different numbers of OFDM symbols and / or lasting different lengths of absolute time).

[0059] 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 without accessing another RAN (e.g., eNodeBs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with and connect to gNBs 180a, 180b, 180c while also communicating with and connecting to another RAN, such as eNodeBs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles 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 eNodeBs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0060] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D , the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0061] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements is depicted as part of the CN 115, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0062] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating NAS signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, 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.

[0063] The SMFs 183a and 183b may be connected to the AMFs 182a and 182b in the CN 115 via an N11 interface. The SMFs 183a and 183b may also be connected to the UPFs 184a and 184b in the CN 115 via an N4 interface. The SMFs 183a and 183b may select and control the UPFs 184a and 184b and configure the routing of traffic through the UPFs 184a and 184b. The SMFs 183a and 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.

[0064] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks such as the Internet 110 to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions such as routing and forwarding packets, enforcing user plane policy, supporting multi-homed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, etc.

[0065] The CN 115 may facilitate communication with other networks. For example, the CN 115 may include or 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 and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local data networks (DNs) 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0066] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-d, base stations 114a-b, eNodeBs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-ab, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0067] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation devices may be directly coupled to another device for testing purposes and / or may perform testing using terrestrial wireless communication.

[0068] One or more emulation devices may perform one or more functions, inclusive, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, e.g., one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0069] The term aTRP may be used interchangeably herein with the term secondary transmission / reception point (sTRP).

[0070] In an example, one of the New Radio (NR) multiple-input multiple-output (MIMO) features could have been mTRP operation, where TRPs share the same PCI. As an evolution, in Rel-17, this work could have expanded the scope of mTRP scenarios with one or more different features, including a unified Transmit Configuration Identification (TCI) concept, which allows for faster and / or more efficient (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 could have enabled complete timing synchronization (e.g., alignment of one or more transmissions between one or more TRPs) determined between one or more TRPs. For example, synchronization could include a WTRU maintaining timing alignment for transmissions with two or more TRPs. For example, a WTRU could maintain (e.g., use) a first timing alignment for transmissions to a first TRP and a second timing alignment for transmissions to a second TRP.

[0071] In examples, the MIMO evolution work item may go a step further and / or may be intended to diversify one or more deployments, for example, by enabling two Timing Advance (TA) loops based on two non-co-located TRPs, two WTRU antenna panels, up to four 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.

[0072] FIG. 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 two (e.g., two or more) octets defined as shown in FIG. 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, R 202 may be a reserved bit that may be set to 0, for example. The MAC CE 200 may indicate whether the TA is associated with a first TRP and / or a second TRP. For example, the MAC CE 200 may indicate a TRP index indicating that the TA is associated with a first TRP and / or a second TRP.

[0073] FIG. 3 is a diagram illustrating an example of a relative timing advance command MAC CE 300. In an example, a WTRU may receive a relative TA command format while 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 a single octet as shown in FIG. 3. In an example, a timing advance group (TAG) identity (TAG ID) field 302 may indicate the TAG identity of the addressed TAG. In an example, a TAG containing an SpCell may have a TAG identity of 0. In an example, the length of the 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 amount of timing adjustment the MAC entity must apply. In an example, the length of the 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 indicating that the TA is associated with the first TRP and / or the second TRP. For example, the TAG ID field 302 may indicate the TRP index.

[0074] In an example, in a transmission system with single TA support, a serving cell may be associated with a single TAG, in which case 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 a time window set by the timer, the timer may expire, and / or the WTRU may suspend one or more (e.g., all) UL transmissions to the affected cell apart from random access preamble and / or MsgA transmissions. In an example, if the timer expires, the WTRU may flush one or more (e.g., all) HARQ buffers. In an example, if the timer expires, the WTRU may release one or more (e.g., all) configured PUCCHs and / or sounding reference signals (SRSs). In an example, if the timer expires, the WTRU may clear one or more (e.g., all) configured downlink allocations. In an example, if the timer expires, the WTRU may clear one or more (e.g., all) configured UL grants. In an example, if a timer expires, the WTRU may clear one or more (e.g., any, all) PUSCH resources for semi-persistent CSI for one or more (e.g., all) serving cells upon expiration of a timeAlignmentTimer associated with a PTAG, where the PTAG may be, for example, a TAG group to which the SpCell belongs (e.g., otherwise, one or more expiry actions may be performed (only) for one or more serving cells associated with the TAG). In an example, if a timer expires, the WTRU may clear one or more PUSCH resources for semi-persistent CSI for all serving cells upon expiration of a timeAlignmentTimer associated with a PTAG, where the PTAG may be, for example, a TAG group to which the SpCell belongs. In an example, if a timer expires, the WTRU may clear all PUSCH resources for semi-persistent CSI for one or more serving cells upon expiration of a timeAlignmentTimer associated with a PTAG, where 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 for all serving cells upon expiration of the timeAlignmentTimer associated with the PTAG, where the PTAG may be, for example, the TAG group to which the SpCell belongs. In an example, the expiration action may be performed on the serving cells associated with the TAG. In an example, the expiration action may be performed only on the serving cells associated with the TAG.

[0075] In an example, in NR operation, a MAC CE carrying a TA command may be associated with a specific cell. For example, in an intra-cell multi-transmission / reception point (multi-TRP, or mTRP) scenario in which multiple TRPs may be associated with the same cell, individual TA indications for one or more (e.g., each) transmission / reception points (TRPs) may not be supported. In an example, if individual TA indications for one or more (e.g., each) TRPs are supported, it may be difficult to estimate one or more individual 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 with a Channel State Information-Reference Signal (CSI-RS) and / or one or more tracking RSs. In an example, the MAC CE carrying the TA command may be associated with a MAC entity having a particular 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, timing advance measurements and / or TA command associations may be initiated for each individual radio link and / or for one or more simultaneous TA commands and / or their (e.g., respective) 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.

[0076] Provided herein are systems, methods, and / or devices relating to procedures for initiating one or more (e.g., multiple) TA measurements and / or updates. Provided herein are systems, methods, and / or devices relating to procedures for indicating and / or associating one or more (e.g., multiple) TAs to a TRP.

[0077] Provided herein are systems, methods, and / or apparatuses relating 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 instruction Random Access Channel (RACH) to update one or more TA values ​​for one or more (e.g., each) TRP links.

[0078] The system, method, and / or apparatus may include a PDCCH command PRACH transmission in multi-TRP. The gNB may trigger a PRACH transmission (e.g., including one or more sets of PRACH resources) to re-establish synchronization for uplink transmissions by the WTRU. Such initiation may occur for one or more different reasons. For example, the gNB may trigger a PRACH transmission when the WTRU has not been scheduled for transmission for a certain duration. In NR, the triggering of a random access transmission to re-establish synchronization may be implemented through a PDCCH command, whereby the DCI may provide relevant information for the transmission of the PRACH (e.g., preamble index and / or SSB index, etc.) that may be used as a reference point for determining an associated RACH occasion. The WTRU may receive a DCI from a first TRP. The DCI may indicate that the WTRU will transmit a PRACH transmission. The DCI may include an indication of a preamble, an indication of a first PRACH mask, an indication associated with the first SSB, and / or an indication of an RS. The WTRU may receive the DCI in a PDCCH command that triggers a PRACH transmission.

[0079] The WTRU may determine a spatial filter based on the indicated RS. The WTRU may determine to transmit a preamble to the second TRP based on the spatial filter. The WTRU may transmit the preamble to the second TRP on a first PRACH resource, which may be determined based on, for example, the first PRACH mask and / or the first SSB. The preamble may be transmitted using the spatial filter determined based on the indicated RS. The first TRP and the second TRP may be associated with the same physical cell identity (PCI). The WTRU may receive a response to the preamble (e.g., a random access response (RAR) or the like) from the second TRP. The response may include a timing advance (TA) command for timing alignment for transmission to the second TRP and / or an index indicating the second TRP.

[0080] In an mTRP deployment, a WTRU may maintain its synchronization with one or more (e.g., two or more) different TRPs. For example, in an mTRP deployment, a WTRU may be required to maintain its synchronization with at least two different TRPs. By way of example, a WTRU may be dynamically switched between a single-TRP transmission mode and a multi-TRP transmission mode, which may require maintaining precise timing synchronization, for example, at all times. For example, a WTRU may use a first timing alignment with a first TRP and a second timing alignment with a second TRP. A WTRU may be configured to maintain precise timing synchronization (e.g., including one or more sets of PRACH resources) at all times, for example, when the WTRU may be dynamically switched between a single-TYP transmission mode and a multi-TYP transmission mode. As described herein, a PDCCH command (e.g., sending a PRACH from a pTRP to an sTRP for UL synchronization / timing alignment) may include one or more of the following: a preamble identifier, a TRP indication indicating the sTRP (e.g., a CORESETPOOL index), an SSB index (e.g., associated with the pTRP), a PRACH mask, and / or an RS indicator (e.g., a CSI-RS and / or tracking RS) associated with the sTRP. If timing alignment for a pTRP and an sTRP includes one PDCCH command, the PDCCH command may include a second SSB index and / or a second PRACH mask (e.g., associated with the pTRP). As described herein, the PDCCH command may include one or more of the following: a TRP index, a pTRP SSB index for determining PRACH resources, and / or an sTRP RS for determining a filter for transmission (Tx). As described herein, the WTRU may transmit a preamble based on the preamble identifier using the determined PRACH resource and / or the determined spatial filter.As described herein, the WTRU may transmit a preamble based on a preamble identifier using the determined PRACH resource and / or the determined spatial filter. If the timing alignment for the pTRP and sTRP includes one PDCCH command, the WTRU may transmit the same preamble to the pTRP based on a second SSB index and / or a second PRACH mask. The WTRU may receive an RAR including a TRP indication and / or a TA indication. If the timing alignment for the pTRP and sTRP includes one PDCCH command, the RAR may include a second TA. The WTRU may transmit an UL transmission to the sTRP using the determined spatial filter and / or with timing based on the TA indication.

[0081] In a multi-TRP deployment, a WTRU configured for multi-TRP operation may receive a PDCCH command to trigger a PRACH transmission. In an example, the WTRU may be configured with one or more of the behaviors described herein, e.g., when the WTRU receives a PDCCH command for a PRACH transmission for single DCI multi-TRP operation or multiple DCI multi-TRP operation.

[0082] In single DCI multi-TRP operation, the PRACH transmission may be made to the TRP that originates the PDCCH command PRACH. In an example, the WTRU may transmit a single PRACH according to 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 a demodulation reference signal (DMRS) of the received PDCCH as an RS source for spatial information (e.g., a spatial filter based on an RS indicator) for the transmission of the preamble (e.g., based on the determined PRACH resource and / or preamble identifier using the determined spatial filter). For example, the WTRU may transmit the preamble using a spatial filter based on the indicated RS (e.g., DMRS, etc.). 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., both) TRPs until the next TA instruction. In an example, the WTRU may receive an implicit and / or explicit indication, e.g., in an RAR message, that the WTRU may apply the indicated TA to the TRP (e.g., TRP instruction) issuing the PDCCH command for one or more (e.g., all) future transmissions until the next TA instruction. For example, the WTRU may receive a response message (e.g., an RAR message) in response to the preamble. The response message may include a TA command for timing alignment for transmissions to the TRP issuing the PDCCH command.

[0083] In single-DCI multi-TRP operation, a PRACH transmission may be made to a TRP that does not issue 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 transmit a PRACH transmission. In an example, based on information elements that may be carried by the same PDCCH (e.g., fields), the WTRU may transmit a single PRACH to a second TRP (e.g., a TRP that does not issue a PDCCH command / DCI) according to the received PDCCH command, for example, by using an indicated preamble index (e.g., one or more PRACH resources), SS / PBCH index (e.g., SSB index associated with the pTRP), TRP index, and / or 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 identity (PCI). Additionally or alternatively, the WTRU may detect an RS index indicated in the received PDCCH, and the RS index may be used as an RS source for spatial information (e.g., a spatial filter determined based on the RS source) for transmitting the preamble. For example, the WTRU may determine spatial information (e.g., a spatial filter) to use for transmitting the preamble to the second TRP based on the indicated RS (e.g., an RS index or a DMRS, etc.). The WTRU may transmit the preamble using a spatial filter determined based on the indicated RS (e.g., a DMRS, etc.). For example, the WTRU may determine to transmit the preamble to the second TRP based on the spatial information (e.g., a spatial filter). In an example, the indicated RS may be associated with another TRP. For example, the DCI may include an indication of a preamble (e.g., a preamble index, etc.), an indication of a PRACH mask, an indication associated with an SSB (e.g., an SS / PBCH index, etc.), and / or an indication of a reference signal (RS) (e.g., an RS index, etc.).The DCI may be received in an information element that may be carried by the same PDCCH. The WTRU may transmit a preamble to a second TRP in a first PRACH resource determined based on the first PRACH mask and / or the first SSB. The WTRU may receive an RAR message including a TA. For example, the WTRU may receive a response message (e.g., an RAR message) in response to the preamble. The response message may include a TA command for timing alignment for transmissions to the second TRP (e.g., a TRP that is not transmitting a PDCCH command PRACH). For example, the WTRU may apply the TA indicated (e.g., by the TA command) for one or more (e.g., all) future transmissions to one or more (e.g., both) 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 an RAR message, that the WTRU may apply the indicated TA to a TRP that is not issuing a PDCCH command PRACH for one or more (e.g., all) future transmissions until the next TA indication for this TRP (e.g., a TRP indication). For example, the WTRU may receive an implicit or explicit indication, e.g., in an RAR message, that the WTRU may apply the indicated TA to a TRP (e.g., only that TRP) that is not issuing a PDCCH command PRACH for future (e.g., all) transmissions until the next TA indication. For example, the WTRU may transmit an uplink transmission to the second TRP using the determined spatial filter with timing based on the TA command.

[0084] In single-DCI multi-TRP operation, PRACH transmission for both TRPs may be based on the received PDCCH command PRACH. In an example, the WTRU may transmit one or more PRACHs according to information carried by the received PDCCH. The WTRU may detect one or more indicated values ​​for one or more of 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 indicated RS index in the received PDCCH, which may be used as an RS source for spatial information (e.g., a spatial filter based on the RS indicator) for the preamble transmission. In an example, the WTRU may receive a single PRACH index, one or more (e.g., two) synchronization signal block (SSB) / PBCH indices, one or more (e.g., two) PRACH mask values, and one (e.g., one or more) RS indexes. The WTRU may transmit one or more (e.g., two) PRACHs using the same preamble index on two different occasions according to the indicated (e.g., two) SSB / PBCH indices, (e.g., two) PRACH mask values, (e.g., two) DMRSs of the PDCCH, and / or the indicated RSs in the PDCCH for the first and / or second transmissions. In an example, the WTRU may receive an 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., both) 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 an RAR message) that the WTRU may apply the indicated TA to (e.g., only) TRPs that originate and / or do not originate PDCCH orders PRACH for one or more (e.g., all) future transmissions until the next TA indication. In an example, the WTRU may receive an RAR message that includes one or more TAs.According to one or more rules and / or received instructions, the WTRU may select and / or apply one or more of the indicated TA values ​​for one or more (e.g., all) future transmissions to one or more (e.g., all) TRPs until the next TA instruction. The WTRU may apply the one or more indicated TA values ​​to one or more corresponding TRPs.

[0085] In an example, in single-DCI multi-TRP operation, PRACH transmission for both TRPs may be based on a received PDCCH command PRACH. In an example, a WTRU may transmit two or more PRACHs according to information carried by a received PDCCH. In an example, a WTRU may detect one or more indicated values ​​for at least one of a preamble index, e.g., an SS / PBCH index, and a PRACH mask. In an example, a WTRU may detect an indicated RS index in a received PDCCH, and the RS index may be used as an RS source for spatial information for transmission of the preamble. In an example, a WTRU may receive a single PRACH index, two SSB / PBCH indices, two PRACH mask values, and / or one RS index. In an example, the WTRU may transmit two PRACHs using the same preamble index on two different occasions according to the two indicated SSB / PBCH indices, two PRACH mask values, and using two DMRSs of the PDCCH and / or the indicated RSs in the PDCCH for the first and / or second transmissions.

[0086] In an example, a WTRU may receive an RAR message including a single TA. In an example, the WTRU may apply the indicated TA for one or more (e.g., all) future transmissions to both TRPs until the next TA instruction. In an example, the WTRU may receive an implicit and / or explicit indication in the RAR message that the WTRU may apply the indicated TA to TRPs that may and / or may not be transmitting PDCCH orders PRACH for one or more future transmissions until the next TA instruction. In an example, the WTRU may receive an implicit and / or explicit indication in the RAR message that the WTRU may apply the indicated TA only to TRPs that may and / or may not be transmitting PDCCH orders PRACH for one or more (e.g., all) future transmissions until the next TA instruction. In an example, the WTRU may receive an RAR message including two or more TAs. In an example, according to rules and / or received instructions, the WTRU may select and / or apply one or more of the indicated TA values ​​for one or more future transmissions to both TRPs until the next TA instruction. In an example, according to a rule or a received instruction, the WTRU may select and / or apply one of the indicated TA values ​​for one or more (e.g., all) future transmissions to both TRPs until the next TA instruction. In an example, the WTRU may apply the indicated TA values ​​to the corresponding TRPs. In an example, single DCI multi-TRP operation may include PRACH transmission according to the last indicated multi-TRP mode. In single DCI multi-TRP transmission, for example, the WTRU may be dynamically scheduled to alternate between single-TRP 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 was for both TRPs (e.g., multi-TRP operation mode indicated by the SRS Resource Indicator (SRI), e.g., code points 10 and / or 11), the WTRU may transmit PRACH for one or more (e.g., both) TRPs.Additionally or alternatively, if the last scheduled uplink transmission was intended for one of the TRPs (e.g., only that TRP) (e.g., single-TRP operation mode indicated by SRI, e.g., code points 00 and / or 01), the WTRU may transmit the PRACH according to the corresponding TRP.

[0087] In multi-DCI multi-TRP operation, the WTRU may transmit a single PRACH per TRP according to received PDCCH instructions received from one or more (e.g., each) TRP. 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 PDCCH as the RS source for spatial information (e.g., spatial filter based on the RS indicator) for the transmission of one or more (e.g., each) preamble. 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., both) TRPs (e.g., TRP indications) until the next TA instruction. For example, the WTRU may receive an implicit and / or explicit indication, e.g., in an RAR message, that the WTRU may apply an indicated TA to one (e.g., only) of the TRPs associated with, e.g., one of the CORSETPoolIndexes. 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 transmit one or more RAR messages. One or more (e.g., each) RAR message may correspond to one or more PRACH transmissions. One or more (e.g., each) RAR message may include one or more TAs. The WTRU may receive one or more (e.g., multiple) TA commands in the one or more RAR messages. In an example, according to rules and / or received instructions, the WTRU may select and / or apply one or more of the indicated TA values ​​to one or more (e.g., both) TRPs for one or more (e.g., all) future transmissions until the next TA indication. In an example, according to a rule or received instruction, the WTRU may select and / or apply one of the indicated TA values ​​for future transmissions (e.g., all future transmissions) for both TRPs until the next TA instruction.In an example, the WTRU may apply one or more indicated TA values ​​to one or more corresponding TRPs.

[0088] In an example, in NR, the PDCCH command PRACH may be carried by DCI format 1_0 and / or may be scrambled by C-RNTI. In an example, if the field corresponding to "Frequency Domain Resource Allocation" 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 "Random Access Preamble Index" is not (e.g., 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.

[0089] One or more of the following example indications may be used to support implementation of the examples and / or embodiments described herein. In one embodiment, one or more of the following example indications may support implementation of the above-described examples and embodiments. One may include an RS to be used as a source for indicating spatial information (e.g., a spatial filter based on an RS indicator) to be included for transmission of a preamble associated with the second TRP. Additionally or alternatively, examples may include additional preambles that may be associated with the second TRP. Additionally or alternatively, examples may include additional SS / PBCH indices. Additionally or alternatively, examples may include additional PRACH mask indices.

[0090] In an example, the remaining reserved bits may be 10. One or more example indications described herein may be associated with overhead. The overhead may be reduced, for example, using one or more of the following examples. An 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) included for transmission of the second preamble. Additionally or alternatively, an example may include a WTRU that may use (e.g., the same) preamble for PRACH transmissions to the first and second TRP. Additionally or alternatively, an example may include a WTRU that may use the same SS / PBCH and / or PRACH mask index for transmission of one or more (e.g., both) preambles, if supported by the WTRU's reported capabilities. Additionally or alternatively, an example may include a WTRU that may use the same SS / PBCH index but different PRACH masks for one or more transmissions of the first and / or 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 and / or second PRACH.

[0091] Systems, methods, and apparatuses related to subsequent RACH transmissions for a second TA loop are provided herein. In an example, a 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 maintained by a cumulative TA control mechanism). For example, the single TA support may be applied based on a first PRACH transmitted by the WTRU. For example, the single TA support may be applied based on a first PRACH transmitted by the WTRU during an initial access procedure. For example, the single TA support may be applied based on a first PRACH transmitted by the WTRU after receiving a PDCCH command based on the single TA (e.g., and / or TAG) support and / or for communication with a first TRP (e.g., a primary TRP, one single TRP, cell, etc.).

[0092] In an example, the WTRU may be indicated (e.g., from the gNB) to transmit a second PRACH (e.g., via a PDCCH command, via a "Start Second TA" PDCCH command, by an instruction to start a second TA loop, etc.), where the second PRACH transmission may be for starting (e.g., creating, updating, adding, newly starting, maintaining, etc.) a second TA loop in addition to (e.g., an ongoing) first TA loop (e.g., a single TA loop). In an example, the WTRU may determine that the PRACH (e.g., based on the PDCCH command) is for a general (e.g., existing) PRACH transmission based on (e.g., previous) single TA support and / or is for a special (e.g., PDCCH-commanded) PRACH for starting (e.g., and / or updating) a second TA loop. For example, the WTRU target determination may be based on an explicit indicator associated with (e.g., included in) a DCI indicating a special (e.g., PDCCH-commanded) PRACH for initiating and / or updating the second TA loop. For example, the WTRU target determination may be based on an implicit indication including one or more configuration parameters (e.g., preamble index, SSB index, SS / PBCH index, PRACH mask, one or more PRACH resources, etc.) associated with the special (e.g., PDCCH-commanded) PRACH.

[0093] In response to receiving a special (e.g., PDCCH-commanded) PRACH to initiate (e.g., and / or update) the second TA loop, the WTRU may transmit the special PRACH toward the second TRP. For example, transmitting the special PRACH toward the second TRP may be based on one or more of the following: The transmitting the special PRACH toward the second TRP may be based on beam / TCI-related parameters that may be associated with the special PRACH. The transmitting the special PRACH toward the second TRP may be based on a unified TCI associated with the second TRP (e.g., its source RS). The transmitting the special PRACH toward the second TRP may be based on a source quasi-co-location (e.g., quasi-co-location, QCL) RS associated with the special PRACH. Transmitting the special PRACH for the second TRP may be based on an additional and / or separate timing reference (e.g., an RS indicator, a point-based spatial filter) 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, a DL RS associated with the second TRP, etc.).

[0094] The WTRU may receive an RAR in response to transmitting the special PRACH. In an example, the RAR may include an indication of a second TA value (e.g., to be applied for a second TA loop). In an example, the RAR may be a second RAR transmitted from a second TRP. In an example, the RAR may be a first RAR transmitted from a first TRP (e.g., a primary TRP) based on pre-configuration delivered to the WTRU. In an example, the beam / TCI for the first RAR being transmitted from the first TRP may be pre-configured in the WTRU.

[0095] In response to receiving the RAR, the WTRU may create (e.g., be configured to create) a (e.g., new) second TA loop for accumulation (e.g., if configured), where 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, the WTRU may apply the second TA value for one or more subsequent uplink transmissions toward (e.g., associated with) the second TRP until a next RAR associated with the second TRP is received, e.g., if cumulative TA mode is not configured.

[0096] 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 ​​that 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 that may be associated with a second TRP) and / or one or more second TA values ​​that may be accumulated based on receiving one or more TA commands that may be associated with the second TA loop. Increased reliability and / or flexibility in managing one or more (e.g., two) separate TA values ​​and / or loops may result, each toward the first TRP and / or the second TRP. The increased reliability and / or flexibility may be based on creating a separate second TA loop in response to receiving DCI that includes a special (e.g., PDCCH-commanded) PRACH.

[0097] In an example, the WTRU may apply (e.g., be configured to apply) one or more second TA values ​​(e.g., 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 DL RS that may be associated with a first TRP). In an example, applying one or more second TA values ​​(e.g., to a second TA loop) based on a first timing reference point may imply that a timing reference (e.g., point) may be shared for 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 ​​(e.g., to a second TA loop) based on a first timing reference point may imply that a timing reference (e.g., point) may be shared for the first TRP and / or the second TRP, but that the TA accumulation loop is separated between the first TRP and the second TRP.

[0098] 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 ​​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 the first TRP and a second TRP) and / or one or more second TA values ​​accumulated based on receiving one or more TA commands that may be associated with the second TA loop. WTRU implementation complexity may be reduced in managing two separate TA values ​​and / or loops, each directed toward the first TRP and / or the second TRP, which may be based on a obtained shared timing reference point, which may be based on a DL RS.

[0099] In an example, the WTRU may apply (e.g., be configured to apply) sequential RACH transmissions after the first RACH transmission. In an example, the WTRU may have one or more RACH transmissions after a known and / or preconfigured 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, multiple TRP-related configurations, etc.).

[0100] In an example, in sequential RACH transmissions, the WTRU may use the same or different RACH resources. For example, the RACH resources for each transmission may be selected and / or indicated from the same pool and / or a TRP-based configured pool. In an example, when the WTRU receives a DCI from one of the TRPs including a PDCCH command RACH to initiate RACH transmissions for one or more (e.g., all) TRP links, the WTRU may follow one or more of the following rules to determine the order of RACH transmissions for one or more (e.g., each) TRP. In an example, the WTRU may (e.g., always) initiate sequential RACH transmissions using the TRP that sent the PDCCH command RACH. Additionally or alternatively, the WTRU may (e.g., always) initiate sequential RACH transmissions using a fixed TRP link (e.g., a link associated with the primary TRP, a link associated with CORESETPoolIndex=0, etc.). In an example, the WTRU may initiate sequential RACH transmissions using the TRP that may have the closest RACH occasion.

[0101] In an example, when a WTRU receives a DCI including a PDCCH command RACH from one of the TRPs, the WTRU may resolve the collision with an already scheduled uplink transmission for the other TRP link based on one or more of the following: In an example, the WTRU may ignore the received grant and / or drop the scheduled uplink transmission. Additionally or alternatively, instead of dropping the scheduled transmission, the WTRU may delay the RACH until the next RACH transmission occasion. Alternatively or additionally, if the scheduled uplink transmission is for a PUCCH and / or a PUSCH including HARQ feedback, the WTRU may ignore the PDCCH command RACH and / or proceed with the scheduled transmission.

[0102] Multi-TA operation may be performed within a TAG. An example may include timing alignment expiration. In an example, configuration and / or operation of a timing advance timer (TAT) may be performed per TRP. A 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. A TAT configuration may include one or more of the following: A TAT configuration may include a TRP identifier (e.g., the TRP to which the TAT applies). A TAT configuration may include a TAG identifier. A TAT configuration may include a TAT duration (e.g., the duration in ms). A TAT configuration may include one or more WTRU actions to perform upon TAT timer expiration. A TAT configuration may include one or more TRP links to which one or more expiry actions should apply. A TAT configuration may include one or more serving cells to which one or more expiry actions should apply.

[0103] Additionally or alternatively, the TAT configuration for a TRP may include a delta configuration from a reference TRP and / or TAG and / or TAT configuration (e.g., a TAT configuration for a pTRP and / or a common TAT configuration provided in the system information). Additionally or alternatively, the delta TAT configuration may include one or more of a reference TRP and / or TAG and / or TAT configuration identifier and / or a delta configuration from the reference TRP and / or TAT and / or TAG configuration. For example, the delta configuration from the reference TRP and / or TAT and / or TAG configuration may consist of one or more of an offset time and / or an offset timer duration.

[0104] The timing alignment timer for each TRP 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, for example, upon receiving one or more of the following: The WTRU may start and / or restart the TAT timer associated with the TRP link 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 a MSGA (PRACH) transmission containing 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 a TAT timer associated with a TRP link upon receiving system information (e.g., SIB1). The WTRU may start and / or restart a TAT timer associated with a TRP link upon receiving an RRC message (e.g., RRCSetup).

[0105] The WTRU may, for example, stop a TAT timer associated with a TRP link under one or more conditions. The WTRU may, for example, stop a TAT timer associated with a TRP link when contention resolution is deemed unsuccessful. The WTRU may, for example, stop a TAT timer associated with a TRP link when contention resolution is deemed successful for a system information (SI) request, for example, after transmitting HARQ feedback for a MAC Protocol Data Unit (PDU), which may include a WTRU contention resolution identity MAC CE.

[0106] The WTRU may start, resume, and / or stop the TAT based on which TRP link and / or serving cell receives and / or transmits a message (e.g., a timing advance command MAC CE). For example, the WTRU may perform one or more TAT actions associated with a TRP in response to a message transmitted / received on a TRP link. For example, the WTRU may perform one or more TAT actions associated with a TRP (e.g., only that action) in response to one or more messages transmitted and / or received on a TRP link. For example, the WTRU may perform one or more TAT actions associated with a TRP (e.g., only that action) in response to one or more messages transmitted and / or received on a pTRP link. For example, the WTRU may perform one or more TAT actions associated with a TRP (e.g., only that action) in response to one or more messages transmitted and / or received on one or more TRP links associated with the same serving cell. For example, the WTRU may perform one or more TAT actions associated with a TRP (e.g., only that action) in response to one or more messages transmitted and / or received on one or more TRP links associated with the SpCell.

[0107] The timing alignment timer for each TRP may include one or more TAT expiration conditions. The WTRU may perform one or more actions if the TAT associated with the TRP expires. Additionally or alternatively, the WTRU may perform a TAT expiration action at a fixed offset before timer expiration and / or at a fixed time after TAT expiration. The WTRU may perform one or more expiration actions. The WTRU may perform an expiration action to initiate a RACH. The WTRU may perform an expiration action to flush one or more (e.g., all) HARQ buffers. The WTRU may perform an expiration action to notify the network. The WTRU may perform an expiration action to release one or more (e.g., all) configured PUCCHs. The WTRU may perform an expiration action to release one or more (e.g., all) configured SRSs. The WTRU may perform an expiration action to clear one or more configured downlink allocations. The WTRU may perform an expiration action to clear one or more configured uplink grants. The WTRU may perform an expiration action to clear one or more PUSCH resources for semi-persistent CSI reporting. The WTRU may use the current N PUSCH resource count until a subsequent value is updated by the network (e.g., via a TA command). TA , and may take expiration actions that maintain the

[0108] The WTRU may be configured with and / or may perform a different set of one or more expiry actions depending on one or more of the following conditions: which TRP link is associated with the expired TAT (e.g., whether the expired TAT is associated with a pTRP and / or an sTRP, which serving cell the expired TAT is associated with (e.g., whether the expired TAT is associated with a TRP belonging to an SpCell, PsCell, and / or SCell), and / or the number of TRPs with expired TATs (e.g., the WTRU may perform a different set of one or more actions if one or more TRP(s) have expired TATs).

[0109] The WTRU may be configured with and / or perform one or more expiration actions for (e.g., only for) the TRP link associated with the expired TAT timer. Additionally or alternatively, the WTRU may be configured with and / or perform one or more expiration actions for one or more additional links (e.g., depending on the configuration). For example, the WTRU may perform one or more of the expiration actions as described herein for the TRP link associated with the expired timer. For example, the WTRU may perform one or more of the expiration actions as described herein for one or more (e.g., all) TRP links associated with the serving cell. For example, the WTRU may perform one or more of the expiration actions as described herein for one or more TRP links associated with one or more (e.g., all) serving cells.

[0110] In an example, upon expiration of the TAT for one TRP, the WTRU may suspend UL transmission to the affected TRP and / or maintain one or more HARQ buffers. The WTRU may transmit (e.g., pending) data on the suspended TRP to a still-active TRP. In an example, the WTRU transmission of (e.g., pending) data on the suspended TRP may depend on data priority, one or more available resources, and / or configuration.

[0111] The WTRU may be configured for notification of TAT expiration. Upon expiration of the TAT for one or more TRP links, the WTRU may notify the network of the TAT expiration via one or more of the following methods: The WTRU may notify the network of the TAT expiration via initiating a RACH transmission on the affected TRP links. For example, the WTRU may receive a single PDCCH command RACH to initiate a RACH transmission to obtain an updated TA on the affected links. Additionally or alternatively, for example, 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, where the first PDCCH may be associated with the TRP link associated with the affecting timer. Additionally or alternatively, the WTRU may notify the network of the TAT expiration by sending an implicit and / or explicit notification to the gNB through that link whose timer has not expired. For example, the notification may indicate to the gNB the expiration of a timer for the other link so that the gNB can send a PDCCH command RACH for the affected link. For example, if one or more (e.g., each) TAGs are associated with a different subset of RACH resources, the WTRU may implement the implicit indication by using one or more PRACH resources of the affecting TAG for the TRP associated with the TAG that still has valid TA information.

[0112] The WTRU may be configured with respect to exceeding a maximum reception time difference and / or a maximum transmission time difference. Deployment of a multi-TRP configuration that can support more than a cyclic prefix (CP) reception time difference may pose challenges to the WTRU architecture. If the reception time difference exceeds a certain level, for example, 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. A reception difference time limit may be beneficial in terms of data transmission throughput and / or robustness (e.g., due to the non-co-located nature of the TRPs and / or one or more propagation characteristics in one or more different frequency ranges) to maintain one or more targets for this feature.

[0113] The maximum receive time difference (MRTD) and / or maximum transmit time difference (MTTD) may represent one or more thresholds expressed in units of time, units of symbols, and / or one or more fractions of a symbol, which 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, communications with one or more (e.g., both) TRPs in the downlink and / or uplink may be processed simultaneously while the MRTD and / or MTTD are below a certain time threshold. In an example, one or more (e.g., two) baseband units may be included for this feature.

[0114] In a multi-TRP deployment, one or more TRPs may not have similar distances from the WTRU. In an example, one or more TA values ​​indicated in one or more timing advance commands for one or more (e.g., each) TRP may result in a relative time difference that may exceed the maximum transmission time difference (MTTD) capability of the WTRU.

[0115] A WTRU may be configured for multi-TRP. Multi-TRP may include one or more additional TRP candidate measurement setup and / or reporting. The one or more additional TRPs may be added by the network to the primary TRP before and / or after (e.g., only after) one or more measurements are reported by the WTRU. Procedurally, 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 report one or more capabilities of the WTRU for multi-TRP deployment, for example, at registration and / or upon network request. The WTRU may report the WTRU's supported MRTD and / or MTTD as thresholds. The network may configure the WTRU for one or more additional TRP candidate measurement and / or reporting, for example, taking into account the WTRU's multi-TRP operation timing capabilities. In an example, the WTRU may measure their relative reception time differences for one or more additional candidates and / or primary TRPs (pTRPs) and / or report relative time differences for one or more candidates and / or MRTDs that have RSRP and / or RSRQ levels above a reporting quality threshold, for example, that are less than the WTRU's reported capabilities. Additionally or alternatively, the WTRU may be configured to report their relative reception time differences for one or more additional TRP candidates RSRP and / or RSRQ and / or primary TRPs (pTRPs), for example, without restrictions (e.g., without any restrictions) on supported MRTD capabilities.

[0116] Upon receiving a measurement report that may have one or more additional TRP candidates within one or more reporting conditions, for example, the network may configure the WTRU with the additional TRP (e.g., sTRP). For example, upon receiving a reconfiguration message that may have an sTRP added, the WTRU may measure (e.g., measure again) the relative reception time difference. For example, at the most recent measurement of the sTRP relative reception time difference, the WTRU may acknowledge the reconfiguration message to the network when the reception time difference is within its reported capabilities and / or may report a reconfiguration failure, for example, if the last measured relative reception time difference exceeds the supported MRTD. In an example, there may be a reconfiguration failure reason field that may indicate "MRTD exceeded." The reconfiguration failure may be transmitted, for example, as a beam failure, with a reason as indicated herein. If the last measured relative reception time difference of the configured candidates is within one or more WTRU capabilities, for example, the WTRU may initiate an uplink time synchronization procedure using the configured sTRP.

[0117] Additionally or alternatively, the WTRU may be configured with one or more additional sTRPs that adhere to (e.g., may comply with) 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) pTRP-sTRP combinations and / or may activate one or more TCI combinations (e.g., selected and / or best TCI combinations), for example, based on one or more most recent measurements reported by the WTRU. Upon activation of a TCI combination, for example, the WTRU may initiate one or more UL synchronization procedures using the most recently (e.g., newly) activated sTRP (e.g., based on a determined spatial filter and / or with timing based on a TA indication). If UL synchronization leads to exceeding the MTTD supported by the WTRU, for example, a beam failure report with cause "exceeding MTTD" may be sent 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 reconfigure the WTRU (e.g., completely) with, for example, one or more other TCI state combinations with one or more other sTRP candidates and / or pTRPs. Additionally or alternatively, the network may remove multi-TRP related operations from the WTRU configuration.

[0118] A WTRU may be configured for one or more timing advance operations for multiple TRPs in relation to MRTD and / or MTTD. A WTRU that may be mobile in the environment may receive one or more timing advance commands for one or more (e.g., both) TRPs (e.g., simultaneously), for example, after adding an sTRP and / or after successfully synchronizing with an sTRP. TRP deployment and / or WTRU mobility may lead to one or more situations in which MRTD and / or MTTD may be exceeded. Exceeding MRTD and / or MTTD may lead to radio link failure of an active sTRP. In an example, the WTRU may report the problem.

[0119] In an example, if the relative difference between the TA advance values ​​exceeds an MRTD and / or MTTD threshold, the WTRU may do one or more of the following: In an example, if the relative difference between the TA advance values ​​exceeds an MRTD or MTTD threshold, the WTRU may send an error and / or problem indication to the gNB. This indication may be sent via the pTRP. The pTRP may remain anchored via an RRC message on the physical layer, MAC CE, and / or UCI. Additionally or alternatively, this indication may be a Radio Link Failure (RLF) indication for the sTRP.

[0120] Upon receiving a notification from the WTRU, the network may perform one or more of the actions herein and / or a (e.g., any) combination of the actions herein. For example, upon receiving a notification from the WTRU, the network may reconfigure the WTRU in one or more other TCI states with one or more other combined 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 a different combination, and / or may continue operating in multi-DCI mode. For example, upon receiving a notification from the WTRU, if there is no other combination with a configured TCI pool with a multi-TRP combination, the WTRU may fall back to single-DCI mode and / or 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 indicating the strongest (e.g., best) TCI combination from the configured TCI pool based on one or more of the (e.g., last) measurements. The indication of the (e.g., best target) TCI combination may be based on the (e.g., smallest) measured MRTD. Following a beam failure indication, for example, the WTRU may continue to monitor the CORESET associated with the sTRP (e.g., in CORESETPOOLIndex1) for beam indications in DCIs from one or more active TCIs.

[0121] A WTRU may be configured with respect to the application timing of one or more TA commands. In a multi-TRP transmission, a WTRU (e.g., with simultaneous uplink transmission capability) may receive TA commands for one or more of the TRP links. Overlap between UL TRP transmissions for a TRP may occur, for example, when a TA is applied for one or more consecutive slots. One or more TA commands may be applied at the beginning of a slot (e.g., may always be applied), and / or one or more rules may be applicable to one or more symbols of a slot (e.g., the last symbol and / or the first symbol of a slot), which may be applied within a closed range of slot boundaries (e.g., several symbols).

[0122] Depending on the relative timeline of the first transmission, the ongoing transmission, and / or the second transmission associated with the updated TA, one or more of the following may occur, as described herein: When the updated TA allows an associated UL transmission to occur later than the first ongoing transmission, the ongoing transmission may proceed as scheduled. Additionally or alternatively, a transmission associated with a link with an updated TA may be shortened toward the end by the number of overlapping samples, e.g., when one or more overlapping UL transmissions between TRPs may not be permitted. For example, an ongoing transmission may proceed as scheduled when the updated TA slot allows an associated transmission to occur earlier than the first ongoing transmission. Additionally or alternatively, a transmission associated with a link with an updated TA may be shortened at the beginning by the number of overlapping samples, e.g., when one or more overlapping UL transmissions between TRPs may not be permitted. In an example, shortening for the alignment of transmissions may be done by considering priority rules. In an example, shortened alignment of one or more transmissions may be done by considering priority rules. For example, the WTRU may shorten a PUSCH slot (e.g., instead of a PUCCH) if the PUCCH overlaps with a 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, a PUSCH with CSI and / or (e.g., any) UCI ​​may be protected over the (e.g., normal) PUSCH, and thus, for example, the (e.g., normal) PUSCH may be shortened.

[0123] The WTRU may be configured with 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 the MAC CE may indicate whether the indicated TA may be targeted to the first and / or second TRP links. For example, this flag may be indicated in one or more of the (e.g., two) fields that may be reserved for TAG IDs. In an example, a CORESETPoolIndex bit may be added to the MAC CE to indicate, for example, the targeted TRP link. Additionally or alternatively, the CORESETPoolIndex may be associated with one or more of the TAG IDs, for example, to provide linkage. In an example, the WTRU may determine the TRP targeted by the TA indication based on, for example, a scheduling PDCCH. For example, if a PDCCH scheduling a PDSCH containing a MAC CE TA command comes in with CORESETPoolIndex=0, the indicated TA may apply to the TRP link associated with CORESETPoolIndex=0. In an example, the indicated TA may apply to a TRP link that may be associated with a CORESET (e.g., CORESETPoolIndex=1). For example, if a PDCCH scheduling a PDSCH including a MAC CE TA command comes in with CORESETPoolIndex=0, the indicated TA may apply to the TRP link associated with CORESETPoolIndex=0; otherwise, it may apply to the TRP link associated with a CORESET, e.g., CORESETPoolIndex=1. In an example, a MAC CE may include TA information for one or more TRP links. In an example, a WTRU may update (e.g., simultaneously) TA information for one or more TRP links. In an example, a WTRU may update (e.g., simultaneously) TA information for one or more (e.g., multiple) TRP links. Association to the first and / or second TRP links 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 in the form of absolute TA values ​​for one or more (e.g., each) TRP and / or their relative difference.A WTRU may receive a TA value (e.g., TA1) for a first TRP link and / or a relative difference (e.g., TA_delta) for a second TRP link to determine a TA for the second link (e.g., as TA2=TA1+TA_delta). For example, if a WTRU may receive one or more TA indications for one or more TRPs, the WTRU may apply one or more rules to determine the priority of an application for one or more (e.g., each) TRP, as described herein. The WTRU may apply the TA for one or more (e.g., each) TRP links, for example, according to the timing of scheduled transmissions. For example, if a WTRU receives one or more TA indications for two or more TRPs, the WTRU may apply the TA for the TRP link having an earlier scheduled transmission (e.g., first). In an example, if a WTRU receives one or more TA indications for two or more TRPs, the WTRU may apply the TA for the TRP link associated with the primary TRP and / or associated with CORESETPoolIndex=0 (e.g., first).

[0124] A WTRU may be configured with one or more (e.g., multiple) TAGs per serving cell. The WTRU may be provided with one or more Timing Advance Groups (TAGs) per serving cell. One or more (e.g., each) TAG configurations may be associated with one or more different (e.g., a different) TRP links. The WTRU may apply (e.g., only) TAG configurations associated with secondary and / or additional sTRPs, for example, if the WTRU supports multi-TRP and / or multi-TA operation.

[0125] The TAG configuration for a TRP may include one or more of the following parameters, as described herein: a TAG ID, a 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. A WTRU may receive TAG configuration information for a primary TRP (pTRP) and / or one or more additional TRPs (e.g., sTRPs) via system information (e.g., in SIB1 and / or UplinkConfigCommonSIB) and / or via dedicated signaling (e.g., via RRC signaling, DCI, and / or MAC CE). For example, the WTRU may be provided with one or more TimeAlignmentTimerCommon parameters associated with one or more TRPs in the system information (e.g., in SIB1 via UplinkConfigCommonSIB). The WTRU may be provided (e.g., via RRC) with one or more (e.g., multiple) TAG configurations within the MAC-CellGroupConfig, e.g., via a TAG-Config, where TAG information may be provided for one or more (e.g., each) TRP. For example, the TAG-Config may include a tag-ID and / or timeAlignmentTimer configuration for the 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 the MAC-CellGroupConfig, where one or more (e.g., each) may correspond to a TRP of the cell.

[0126] The WTRU may, for example, override a TAG configuration for one or more TRPs provided via broadcast signaling (e.g., in SIB1 via UplinkConfigCommonSIB) if the WTRU receives a dedicated TAG configuration (e.g., via RRC signaling and / or MAC CE).

[0127] The WTRU may be provided with a TAG configuration for set X of TRPs, e.g., via broadcast signaling (e.g., in system information), and / or a TAG configuration for set Y of TRPs, e.g., via dedicated signaling (e.g., RRC configuration and / or MAC CE). For example, if set X and set Y include the same TRPs, 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 those provided in set Y. For example, if set X and set Y include one or more different TRPs, and set Y includes a TAG configuration for pTRPs, the WTRU may apply this TAG configuration to one or more (e.g., all) TRPs in 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 the TAG configuration for (e.g., only) the TRPs provided in both set X and set Y. For example, configurations for one or more (e.g., or all) TRPs in set X that are not provided in set Y may be, for example, kept or removed. The one or more actions the WTRU takes may be indicated explicitly, for example, via configuration and / or in system information.

[0128] If the WTRU and / or cell may support multi-TRP multi-TA operation and (e.g., only) one TAG configuration, one or more of the following may be included: The WTRU may apply 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 (e.g., explicitly) indicate whether the TAG configuration applies to the pTRPs and / or one or more sTRPs. For example, this indication may be provided in the MAC-CellGroupConfig, TAG-Config, SIB1, and / or one or more (e.g., any, some) other broadcast (e.g., system information), RRC, and / or MAC (e.g., MAC CE) signaling. The WTRU may apply one or more previously stored TAG configurations (e.g., via a flag), for example, upon an RRC state transition to RRC_INACTIVE and / or RRC_IDLE. This flag may, for example, be included in the (e.g., TAG) configuration. For example, the default TAG configuration may include one or more parameters (e.g., TAT values) included in the TAG configuration. The default TAG configuration may be provided, for example, via system information (e.g., SIB1). In an example, this (e.g., system) information may be provided via a dedicated configuration (e.g., via RRC) upon an RRC state transition (e.g., upon receipt of an RRC Setup and / or RRC Release with suspend config message).

[0129] 4 depicts a system diagram illustrating an 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.

[0130] At 408, the pTRP 402 may send a PDCCH command for the PRACH to the sTRP 404 to the WTRU 406. The PDCCH command may include a preamble identifier, a TRP indication (e.g., a CORESETPOOL index, etc.) associated with the sTRP 404, 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 (e.g., a CSI-RS and / or a tracking RS) associated with the sTRP 404. 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 PDCCH command may include a second SSB index (e.g., associated with the pTRP 402) and / or a second PRACH mask.

[0131] At 410, the WTRU 406 may send a PRACH (e.g., preamble) transmission to the sTRP 404. The preamble may be based on a preamble identifier (e.g., at 408) using a determined PRACH resource and / or a (e.g., determined) spatial filter. For example, the WTRU 406 may determine a spatial filter based on an RS indicator (e.g., the RS indicator shown at 408). The WTRU 406 may determine to send a preamble to the sTRP 404 based on the spatial filter. The WTRU 406 may use the determined spatial filter to send the PRACH to the sTRP 404. The WTRU 406 may determine a PRACH resource for transmission to the sTRP 404 based on an SSB index (e.g., associated with the pTRP), one or more PRACH resources, and / or a PRACH mask. If the timing alignment for pTRP 402 and sTRP 404 includes (eg, only) one PDCCH command, the WTRU 406 may transmit the same preamble to pTRP 402 based on a second SSB index and / or a second PRACH mask.

[0132] At 412, the sTRP 404 may send a (e.g., first) response message to the WTRU 406. The (e.g., first) response may be an 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 a second timing alignment for 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.

[0133] At 414, the WTRU 406 may send a UL Tx (e.g., Msg3) to the sTRP 404. The WTRU 406 may use a spatial filter and / or timing determined based on the (e.g., first) TA indication / command to send the UL Tx to the sTRP 404 at 414.

Claims

1. 1. A wireless transmit / receive unit (WTRU), comprising: a processor, the processor comprising: receiving configuration information indicating a first Timing Advance Group (TAG) for a serving cell associated with a first TAG ID and a second TAG for the serving cell 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 indicating a second duration of a second TAT associated with the second TAG for the serving cell; Initiating the first TAT; initiating the second TAT; determining that the first TAT associated with the first TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants associated with the first TAG for the serving cell based on determining that the first TAT associated with the first TAG for the serving cell has expired; 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 expires; determining that the second TAT associated with the second TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell based on determining that the second TAT associated with the second TAG for the serving cell has expired; Flushing the HARQ buffer associated with the serving cell based on expiration of the second TAT associated with the second TAG for the serving cell; and starting or restarting at least one of the first TAT or the second TAT based on receiving a timing advance command medium access control (MAC) control element (CE).

2. 2. The WTRU of claim 1, wherein the first TAG for the serving cell is associated with a first transmission / reception point (TRP) for the serving cell, and the second TAG for the serving cell is associated with a second TRP for the serving cell.

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

4. the processor:

2. The WTRU of claim 1, configured to continue performing uplink transmissions associated with the second TAG for the serving cell after the first TAT associated with the first TAG for the serving cell expires.

5. the processor: suspending at least one uplink transmission associated with the first TAG to the serving cell based at least on determining that the first TAT associated with the first TAG for the serving cell has expired; and suspending at least one uplink transmission associated with the second TAG to the serving cell based at least on determining that the second TAT associated with the second TAG for the serving cell has expired.

6. 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 a transmission other than a random access preamble transmission or an MsgA transmission.

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

8. 2. The WTRU of claim 1, wherein the processor is configured to receive the MAC CE that activates a first transmission configuration indicator (TCI) state group for a control resource set (core set), the TCI state group including at least one TCI state including a first TCI state.

9. 10. The WTRU of claim 8, wherein the processor is configured to determine that demodulation reference signal (DMRS) antenna ports associated with one or more physical downlink control channel reception in the core set are quasi-colocated with one or more downlink reference signals configured by the at least one TCI state, and wherein the processor is configured to receive downlink control information (DCI) via the core set, the DCI indicating a second TCI state, the TCI state group including 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 that is quasi-colocated with a second reference signal indicated by the second TCI state.

10. the processor:

2. The WTRU of claim 1, configured to release one or more configured physical uplink control channel (PUCCH) resources and one or more configured sounding reference signal (SRS) resources based on expiration of the second TAT associated with the second TAG for the serving cell.

11. 1. A method, implemented by a wireless transmit / receive unit (WTRU), comprising: receiving configuration information indicating a first Timing Advance Group (TAG) for a serving cell, the first TAG being associated with a first TAG ID, and a second TAG for the serving cell being 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 a second duration of a second TAT associated with the second TAG for the serving cell; Initiating the first TAT; initiating the second TAT; determining that the first TAT associated with the first TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants associated with the first TAG for the serving cell based on determining that the first TAT associated with the first TAG for the serving cell has expired; 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 expires; determining that the second TAT associated with the second TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell based on determining that the second TAT associated with the second TAG for the serving cell has expired; Flushing the HARQ buffer associated with the serving cell based on expiration of the second TAT associated with the second TAG for the serving cell; and starting or restarting at least one of the first TAT or the second TAT based on receiving a timing advance command medium access control (MAC) control element (CE).

12. 12. The method of claim 11, wherein the first TAG for the serving cell is associated with a first transmission / reception 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. 13. The method of claim 12, wherein a first transmission configuration information (TCI) state is associated with a transmission corresponding to the first TRP associated with the first TAG for the serving cell, and a second TCI state is associated with a transmission corresponding to the second TRP associated with the second TAG for the serving cell.

14. 12. The method of claim 11, further comprising: continuing to perform uplink transmissions associated with the second TAG for the serving cell after the first TAT associated with the first TAG for the serving cell expires.

15. The method comprises: suspending at least one uplink transmission associated with the first TAG to the serving cell based at least on determining that the first TAT associated with the first TAG for the serving cell has expired; suspending at least one uplink transmission associated with the second TAG to the serving cell based at least on determining that the second TAT associated with the second TAG for the serving cell has expired.

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

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

18. The method comprises: receiving the MAC CE activating a first Transmission Configuration Indicator (TCI) state group for a control resource set (core set), the TCI state group including at least one TCI state including a first TCI state; determining that demodulation reference signal (DMRS) antenna ports associated with one or more physical downlink control channel receptions in the core set are quasi-colocated with one or more downlink reference signals configured according to the at least one TCI state; receiving downlink control information (DCI) via the core set, the DCI indicating a second TCI state, the TCI state group including the second TCI state, and receiving a transport block (TB) based on the TCI state group including at least one DMRS of the TB being quasi-colocated with a second reference signal indicated by the second TCI state.

19. 12. The method of claim 11 , further comprising: releasing one or more configured physical uplink control channel (PUCCH) resources and one or more configured sounding reference signal (SRS) resources based on expiration of the second TAT associated with the second TAG for the serving cell.

20. 1. A wireless transmit / receive unit (WTRU), comprising: a processor, the processor comprising: receiving configuration information indicating a first Timing Advance Group (TAG) for a serving cell associated with a first TAG ID and a second TAG for the serving cell 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 indicating a second duration of a second TAT associated with the second TAG for the serving cell; Initiating the first TAT; initiating the second TAT; determining that the first TAT associated with the first TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants 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 expired; determining not to flush 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 expires; determining that the second TAT associated with the second TAG for the serving cell has expired; clearing one or more configured downlink assignments and one or more configured uplink grants associated with the second TAG for the serving cell based on determining that the second TAT associated with the second TAG for the serving cell has expired; Flushing the HARQ buffer associated with the serving cell based on expiration of the second TAT associated with the second TAG for the serving cell; and starting or restarting at least one of the first TAT or the second TAT based on receiving a timing advance command medium access control (MAC) control element (CE).

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