Pdcch order prach transmission in multi-trp operation

Abstract

A WTRU can receive a downlink control information (DCI) from a first transmission / reception point (TRP). The DCI can indicate that the WTRU is to transmit a physical random access channel (PRACH) transmission. The DCI can 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 can be configured to transmit the preamble to a second TRP in a first PRACH resource. The first TRP and / or the second TRP can be associated with a same physical cell identity (PCI). The WTRU can receive a first response to the preamble from the second TRP. The first response can include a first timing advance (TA) command for the second timing alignment for transmissions to the second TRP and / or an index indicating the second TRP.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 334,976, filed on April 26, 2022, the entire contents of which are incorporated herein by reference. Background Technology Technical Field

[0004] This disclosure generally relates to wireless communication systems. In particular, this disclosure relates to methods and apparatus for multiple transmit / receive points (mTRPs) having multiple timing advance (TA) operations in a wireless communication system.

[0005] Description of the Related Art

[0006] The increasing demand for wireless data traffic following the commercialization of 4G communication systems has become a driving force for efforts to develop and improve 5G communication systems. Therefore, 5G communication systems, or pre-5G communication systems, are referred to as systems following 4G network communication systems (Beyond 4G networks) or systems following LTE systems (Post-LTE).

[0007] To achieve high data rates, 5G communication systems are considered for implementation in very high frequency (mmWave) bands (e.g., 60 gigabyte (60 GHz) bands). To mitigate path loss of radio waves and increase propagation distance in the ultra-high frequency band, beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive MIMO technologies are being discussed for use in 5G communication systems.

[0008] To improve the network system, 5G communication systems are further developing and evolving technologies such as 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, cooperative multipoint (CoMP), and interference cancellation.

[0009] In addition, advanced decoding and modulation (ACM) methods such as FQAM (hybrid FSK and QAM modulation) and SWSC (sliding window superposition decoding) are being researched in 5G systems, as well as advanced access technologies such as filter bank multicarrier (FBMC), NOMA (non-orthogonal multiple access) and sparse code multiple access (SCMA). Summary of the Invention

[0010] Systems, methods, and apparatuses are described herein with respect to multi-transmission / reception point (mTRP) with multiple timing advance (TA) operations in a wireless system. A wireless transmit / receive unit (WTRU) can receive a PDCCH order to trigger a physical random access channel (PRACH) transmission in a multi-TRP operation in a multi-TRP deployment and / or transmit one or more first PRACHs in accordance with the received PDCCH order by using one or more of an indicated preamble index, a synchronization signal (SS) index / physical broadcast channel (PBCH), and / or a PRACH mask.

[0011] In an example, the implementation can include determining an uplink TA value for transmission of an uplink signal, where the uplink TA value is determined based on a single TA loop and / or transmitting one or more PRACHs to initiate a second TA loop based on receiving an indication to transmit a second PRACH.

[0012] In an example, the implementation can 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 based on one or more TAs indicated by a received PDCCH.

[0013] Systems, methods, and apparatuses can 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.

[0014] Systems, methods, and apparatuses are described herein with respect to PDCCH ordered PRACH transmission in mTRP operation. A WTRU can receive downlink control information (DCI) from a first transmission / reception point (TRP). The DCI can indicate that the WTRU is to transmit a physical random access channel (PRACH) transmission. The DCI can 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 can be configured to transmit the preamble to a second TRP in a first PRACH resource. The first PRACH resource can be determined based on, for example, the first PRACH mask and / or the first SSB. The preamble can be transmitted using a spatial filter determined based on, for example, the indicated RS. The first TRP and / or the second TRP can be associated with a same physical cell identity (PCI).

[0015] The WTRU can determine to transmit the preamble to the second TRP based on, for example, the spatial filter. The WTRU can 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 can receive a first response to the preamble from the second TRP. The first response can include a first timing advance (TA) command for the second timing alignment for transmissions to the second TRP and / or an index indicating the second TRP. The first response can be a random access response (RAR). The WTRU can be configured to transmit an uplink (UL) transmission to the second TRP using the determined spatial filter and / or with a timing based on the first TA command. The WTRU can use the indicated RS to determine the spatial filter for transmitting the preamble to the second TRP.

[0016] The WTRU can receive the DCI in a PDDCH order triggering the PRACH transmission. The DCI can include an indication of a second PRACH mask and / or an indication associated with a second SSB. The WTRU can transmit the preamble to the first TRP using a second PRACH resource determined based on, for example, the second PRACH mask and / or the second SSB. The WTRU can receive a second response to the preamble transmitted using the second PRACH resource from the first TRP. The second response can include a timing advance command for the first timing alignment for transmissions to the first TRP. The second response can include an index of the first TRP. The DCI can include a timing advance (TA) medium access control (MAC) control element (CE). The MAC CE can indicate a TRP index. The TRP can indicate a TA associated with the first TRP and / or the second TRP. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments can be implemented;

[0018] Figure 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that can be used within the communications system Figure 1A illustrated in accordance with an embodiment;

[0019] Figure 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that can be used within the communications system Figure 1A illustrated in accordance with an embodiment;

[0020] Figure 1D is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that can be used within the communications system Figure 1ASystem diagram of another example RAN and another example CN used within the illustrated communication system;

[0021] Figure 2 is a diagram illustrating an example of an absolute timing advance command medium access control (MAC) control element (CE) format;

[0022] Figure 3 is a diagram illustrating an example of a relative timing advance command MAC CE format;

[0023] Figure 4 is a system diagram illustrating an example timing alignment for secondary transmission / reception points (sTRPs). DETAILED DESCRIPTION

[0024] Figure 1A is a diagram illustrating an example communication system 100 in which one or more disclosed embodiments can be implemented. The communication system 100 can be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communication system 100 can enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communication system 100 can employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0025] As Figure 1AAs shown, the communication system 100 can include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a CN 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d can 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 can be referred to as a "station" and / or a "STA") can be configured to transmit and / or receive wireless signals, and can include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain environment), a consumer electronics device, a device operating on a commercial and / or industrial wireless network, and the like. Any of the WTRUs 102a, 102b, 102c, and 102d can be interchangeably referred to as a UE.

[0026] The communication system 100 can also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b can be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b can be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b can include any number of interconnected base stations and / or network elements.

[0027] The base stations 114a can be part of the RAN 104 / 113, which can also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base stations 114a and / or the base stations 114b can be configured to transmit and / or receive wireless signals on one or more carrier frequencies (which can be referred to as a cell (not shown)). These frequencies can be in the licensed spectrum, the unlicensed spectrum, or a combination of the licensed and unlicensed spectrums. A cell can provide wireless service to a particular geographic area that can be relatively fixed or can change over time. The cell can further be divided into cell sectors. For example, a cell associated with a base station 114a can be divided into three sectors. Thus, in one embodiment, the base station 114a can include three transceivers, one for each sector of the cell. In an embodiment, the base station 114a can employ Multiple Input Multiple Output (MIMO) techniques and can utilize multiple transceivers for each sector of the cell. For example, beamforming can be used to transmit and / or receive signals in desired spatial directions.

[0028] The base stations 114a, 114b can communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over the air interface 116, which can be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 can be established using any suitable radio access technology (RAT).

[0029] More specifically, as indicated above, the communication system 100 can be a multiple access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 / 113 can implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which can establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0030] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-A Pro.

[0031] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement a radio technology such as NR Radio Access, which can establish the air interface 116 using New Radio (NR).

[0032] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement multiple radio access technologies. For example, the base station 114a and WTRUs 102a, 102b, 102c can implement LTE wireless access and NR wireless access together, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c can be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., an eNB and a gNB).

[0033] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c can implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 IX, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0034] Figure 1AThe base station 114b in the embodiment can be, for example, a wireless router, Home Node B, Home eNode B, or access point, and can utilize any suitable RAT for facilitating wireless connectivity access by the WTRUs 102c, 102d within a local area. In one embodiment, the base station 114b and the WTRUs 102c, 102d can implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d can 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 can utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or femtocell. As shown, the base station 114b can have a direct connection to the Internet 110. Thus, the base station 114b can not be required to access the Internet 110 via the CN 106 / 115. Figure 1A

[0035] The RAN 104 / 113 can be in communication with the CN 106 / 115, which can be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data can have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 can provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not shown in Figure 1A Although not shown in FIG. 10, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 can be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which can employ a NR radio technology, the CN 106 / 115 can also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0036] ​The CN 106 / 115 can also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 can include circuit-switched telephone networks that provide infrastructure for the provision of voice telephony, facsimile, and / or other

[0037] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 can include multi-mode capabilities, e.g., the WTRUs 102a, 102b, 102c, 102d can include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102a, 102b, 102c, 102d can include a transceiver Figure 1A The WTRU 102c shown in Figure 1A can be configured to communicate as a wireless device with the base stations 114a, and 114b using a variety of

[0038] Figure 1B is a system diagram illustrating an example WTRU 102. As shown in Figure 1B The WTRU 102 can include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138, among others. It will be appreciated that the WTRU 102 can include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0039] The processor 118 can be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 can 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 can be coupled to the transceiver 120, which can be coupled to the transmit / receive element 122. While Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it will be understood that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0040] The transmit / receive element 122 can be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 can be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0041] Although the transmit / receive element 122 is depicted in the WTRU 102 Figure 1B In one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (e.g., multiple antennas) to enable MIMO technology. Thus, the WTRU 102 can

[0042] The transceiver 120 can be configured to modulate information to be transmitted by the transmit / receive element 122 and to demodulate information received by the transmit / receive element 122. As indicated above, the WTRU 102 can be a multi-mode device. Thus, the transceiver 120 can include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.

[0043] The processor 118 of the WTRU 102 can be coupled to, and can receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 can also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 can access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 can include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 can include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 can access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0044] The processor 118 can receive power from the power source 134 and can be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 can be any suitable device for powering the WTRU 102. For example, the power source 134 can include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0045] The processor 118 can also be coupled to the GPS chipset 136, which can be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 can receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 can acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment.

[0046] The processor 118 can further couple to other peripherals 138, which can 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 can include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player, an Internet browser, and the like. The peripheral device 138 can include one or more sensors, which can be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, a compass 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.

[0047] The WTRU 102 can include a full duplex radio for which transmission and reception of some or all signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and the downlink (e.g., for reception) can be concurrent and / or simultaneous. The full duplex radio can include an interference management unit 139 to reduce and / or substantially eliminate self-interference and / or to extend a dynamic range in which communications can be successfully conducted. In embodiments, the WRTU 102 can include a half duplex radio for which transmission and reception of some or all signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)) are concurrent but not simultaneous.

[0048] Figure 1C is a system diagram illustrating a RAN 104 and a CN 106 according to an embodiment. As

[0049] The RAN 104 can include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 can include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c can each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c can implement MIMO technology. Accordingly, the eNode-B 160a, for example, can use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0050] Each of the eNode-Bs 160a, 160b, 160c can be associated with a particular cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown, the eNode-Bs 160a, 160b, 160c can communicate with one another over an X2 interface. Figure 1C

[0051] Figure 1C The CN 106 can include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements can be owned and / or operated by an entity other than the CN operator.

[0052] The MME 162 can be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an SI interface and can serve as a control node. For example, the MME 162 can be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activations / deactivations, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 162 can 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.

[0053] The SGW 164 can be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 can generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 can perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0054] The SGW 164 can be connected to the PGW 166, which can 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.

[0055] ​The CN 106 can facilitate communications with other networks. For example, the CN 106 can 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 can include, or can 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 can provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which can include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0056] Although WTRUs are described in Figures 1A-1D representative embodiments as wireless terminals, it is contemplated that in certain representative embodiments such terminals can (e.g., temporarily or permanently) use a wired communication interface to the communication network.

[0057] In representative embodiments, the other network 112 can be a WLAN.

[0058] A WLAN in Infrastructure Basic Service Set (BSS) mode can have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP can have an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out of the BSS. Traffic to STAs that is carried by the DS can be transmitted from the AP. Traffic from STAs that is carried by the DS can be transmitted to the AP. The AP can transmit traffic to the DS and can receive traffic from the DS. The AP can also transmit and receive traffic directly to and from STAs. The AP can coordinate scheduling of wireless distribution of traffic. The AP can also function as a base station of the WLAN.

[0059] When using an 802.11 ac infrastructure mode of operation or similar mode of operation, an AP can transmit beacons on a fixed channel, such as a primary channel. The primary channel can be a fixed width (e.g., 20 MHz wide bandwidth) or a width that is dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by STAs to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) can be implemented, for example, in 802.11 systems. For CSMA / CA, a STA (e.g., each STA), including the AP, can listen to the primary channel. If the primary channel is sensed / detected as busy by a particular STA, the particular STA can back off. Only one STA can transmit in a given BSS at any given time.

[0060] High Throughput (HT) STAs can use 40 MHz wide channels for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0061] Very High Throughput (VHT) STAs can support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. 40 MHz and / or 80 MHz channels can be formed by combining contiguous 20 MHz channels. A 160 MHz channel can be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which can be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data can be parsed by a segment parser that can divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time domain processing can be done on each stream separately. The streams can be mapped to the two 80 MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration can be reversed, and the combined data can be passed to the Medium Access Control (MAC).

[0062] 802.11af and 802.11ah support sub-1 GHz operating modes. The channel operating bandwidth and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11η and 802.1 lac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the television white space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to representative embodiments, 802.11ah can support meter type control / machine type communications, such as MTC devices in a macro coverage area. MTC devices can have certain capabilities, e.g., limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidth. MTC devices can include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0063] WLAN systems that can support multiple channels and channel bandwidths, such as 802.11η, 802.1 lac, 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 largest common operating bandwidth supported by all STAs in a BSS. The bandwidth of the primary channel can be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from among all STAs operating in the BSS. In the example of 802.11ah, for a STA (e.g., a MTC type device) that supports (e.g., only supports) a 1 MHz mode, the primary channel can be 1 MHz wide, even if other STAs in the AP and BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy, e.g., due to a STA (supporting only a 1 MHz operating mode) transmitting to the AP, the entire available frequency band can be considered busy, even if most of the frequency band remains idle and can be available.

[0064] In the United States, the available frequency band for 802.11ah use is 902 MHz to 928 MHz. In Korea, the available frequency band is 917.5 MHz to 923.5 MHz. In Japan, the available frequency band is 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah use is 6 MHz to 26 MHz, depending on the country code.

[0065] Figure 1Dis a system diagram illustrating RAN 113 and CN 115 according to an embodiment. As

[0066] RAN 113 can include gNBs 180a, 180b, 180c, although it will be appreciated that the RAN 113 can include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c can each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c can implement MIMO technology. For example, gNBs 180a, 108b can utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, can use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c can implement carrier aggregation technology. For example, the gNB 180a can transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers can be on unlicensed spectrum while the remaining component carriers can be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c can implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a can receive coordinated transmissions from gNBs 180a and 180b (and / or gNB 180c).

[0067] WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c using transmissions associated with extended numerology. For example, OFDM symbol spacing and / or OFDM subcarrier spacing can vary from different transmissions, different cells, and / or different portions of the wireless transmission spectrum. WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of various or extended lengths (e.g., containing different amounts of OFDM symbols and / or lasting varying lengths of absolute time).

[0068] The gNBs 180a, 180b, 180c can be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In the standalone configuration, the WTRUs 102a, 102b, 102c can communicate with the gNBs 180a, 180b, 180c without also accessing other RANs, such as eNode-Bs 160a, 160b, 160c. In the standalone configuration, the WTRUs 102a, 102b, 102c can utilize WTRU 102a, 102b, 102c components that are common to both ETU-RANs and NR-RANs, such as the transceivers 110 and one or more processors 112. In the standalone configuration, the gNBs 180a, 180b, 180c can act as the mobile core network's point of interconnect for all traffic to and from WTRUs 102a, 102b, 102c accessing only gNBs 180a, 180b, 180c. In the standalone configuration, WTRUs 102a, 102b, 102c can not access other RANs, such as eNode-Bs 160a, 160b, 160c.

[0069] Each of the gNBs 180a, 180b, 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown, the gNBs 180a, 180b, 180c can communicate with one another over an Xn interface. Figure 1D As shown, the gNBs 180a, 180b, 180c can be in communication with the AMF 182a, 182b over an N2 interface; can be in communication with a Session Management Function (SMF) 184a, 184b over an N1 interface; and can be in communication with a User Plane Function (UPF) 184a, 184b over an N3 interface.

[0070] Figure 1DThe illustrated CN 115 can include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements can be owned and / or operated by an entity other than the CN operator.

[0071] The AMF 182a, 182b can be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and can serve as a control node. For example, the AMF 182a, 182b can be responsible for authenticating the WTRUs 102a, 102b, 102c, supporting for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. The AMF 162 can utilize network slicing to customize CN support for the WTRUs 102a, 102b, 102c based on the type of services utilized by the WTRUs 102a, 102b, 102c. For example, different network slices can be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. The AMF 162 can provide control plane functionality 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.

[0072] The SMF 183a, 183b can be connected to AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b can also be connected to the UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b can select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b can perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing downlink data notifications, and the like. A PDU session type can be IP-based, non-IP based, Ethernet-based, and the like.

[0073] The UPF 184a, 184b can be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b can perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering of downlink packets, providing mobility anchoring, and the like.

[0074] The CN 115 can facilitate communications with other networks. For example, the CN 115 can include, or can communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 can provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which can include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c can be connected to a local DN 185a, 185b through the UPF 184a, 184b via an N3 interface between the UPF 184a, 184b and the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the local data network (DN) 185a, 185b.

[0075] In view of Figures 1A-1D And Figures 1A-1D corresponding description, one or more or all of the functions described herein for one or more of the following can be performed by one or more emulation devices (not shown): WTRUs 102a-102d, base stations 114a-114b, eNode-Bs 160a-160c, MME 162, SGW 164, PGW 166, gNBs 180a-180c, AMFs 182a-182b, UPFs 184a-184b, SMFs 183a-183b, DNs 185a-185b, and / or any other device mentioned herein. The emulation devices can be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices can be used to test other devices and / or to simulate a network and / or WTRU functionality.

[0076] The one or more emulation devices can perform the one or more, including all, functions while not implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices can be utilized in testing a laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices can be test equipment. Direct RF coupling and / or wireless communications, via RF circuitry (e.g., which can include one or more antennas) can be used by the emulation devices to transmit and / or receive data.

[0077] The one or more emulation devices can perform the one or more, including all, functions while not implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices can be utilized in testing a laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices can be test equipment. Direct RF coupling and / or wireless communications, via RF circuitry (e.g., which can include one or more antennas) can be used by the emulation devices to transmit and / or receive data.

[0078] The term aTRP can be used interchangeably herein with the term auxiliary transmission / reception point (sTRP).

[0079] In an example, one of the features in New Radio (NR) Multiple Input Multiple Output (MIMO) features can be mTRP operation, where the TRPs share the same PCI. As an evolution, in Rel-17, this work can have extended the range of mTRP scenarios with one or more different features, including a unified transmission configuration identification (TCI) concept that enables faster and / or more (e.g., much more) efficient management of one or more TCI states and / or beam management. Reception from one or more TRPs can have been determined within a cyclic prefix. This can have enabled full timing synchronization determined between one or more TRPs (e.g., alignment of one or more transmissions between / among the one or more TRPs). For example, the synchronization can include a WTRU maintaining timing alignment for transmissions with two or more TRPs. For example, the WTRU can maintain (e.g., use) a first timing alignment for transmissions to a first TRP and maintain (e.g., use) a second timing alignment for transmissions to a second TRP.

[0080] In an example, the MIMO evolution work item can have moved forward and / or can intend to diversify one or more deployments by implementing two timing advance (TA) loops based on, for example, two non-collocated TRPs, two WTRU antenna panels, up to 4 UL MIMO layers, two layers per panel, and / or based on mDCI (e.g., multi-DCI) reception and / or simultaneous / overlapping physical uplink shared channel (PUSCH) PUSCH+PUSCH and / or physical uplink control channel (PUCCH) PUCCH-PUCCH UL transmissions.

[0081] Figure 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 can be identified by a MAC subheader with an extended logical channel ID (eLCID). The MAC indication can have a fixed size and / or can include two (e.g., or more) octets defined as shown in Figure 2 In an example, the timing advance command field can indicate an index value TA. In an example, TA can be used to control the amount of timing adjustment that the MAC entity can have to apply. In an example, the size of the TA command field can be 12 bits. In an example, R202 can be a reserved bit, which can be set to 0, for example. The MAC CE 200 can indicate whether the TA is associated with a first TRP and / or a second TRP. For example, the MAC CE 200 can indicate a TRP index that indicates that the TA is associated with the first TRP and / or the second TRP.

[0082] Figure 3 is a diagram illustrating an example of a relative timing advance command MAC CE 300. In an example, the WTRU can receive a relative TA command format while in a connected mode. In an example, the TA command MAC CE 300 can be identified by a MAC subheader with an LCID. In an example, the command can have a fixed size and / or can include two octets defined as shown in Figure 3In an example, a timing advance group (TAG) identification (TAG ID) field 302 can indicate a TAG identification of a TAG addressed. In an example, a TAG including a SpCell can have a TAG identification of 0. In an example, a length of this field can be 2 bits. In an example, a TA command field 304 can indicate an index value TA (e.g., 0, 1, 2, 3, 4, 5,... 63, etc.). The timing advance command field 304 can be used to control the amount of timing adjustment that the MAC entity has to apply. In an example, a length of this field can be 6 bits. The MAC CE 300 can indicate whether the TA is associated with the first TRP and / or the second TRP. For example, the MAC CE 300 can indicate a TRP index that indicates the TA is associated with the first TRP and / or the second TRP. For example, the TAG ID field 302 can indicate the TRP index.

[0083] In an example, in a transmission system with single TA support, a serving cell can be associated with a single TAG, where one or more (e.g., each) TAG can be associated with a single time alignment timer. In an example, if the WTRU does not receive an update within the time window set by the timer, the timer can time out and / or the WTRU can suspend one or more (e.g., all) UL transmissions to the affected cell except for random access preamble transmission and / or MsgA transmission. In an example, if the timer times out, the WTRU can flush one or more (e.g., all) HARQ buffers. In an example, if the timer times out, the WTRU can release one or more (e.g., all) configured PUCCH and / or Sounding Reference Signal (SRS). In an example, if the timer times out, the WTRU can clear one or more (e.g., all) configured downlink assignments. In an example, if the timer times out, the WTRU can clear one or more (e.g., all) configured UL grants. In an example, if the timer times out for a timeAlignmentTimer associated with a PTAG, the WTRU can clear one or more (e.g., any, all) PUSCH resources for semi-persistent CSI for one or more (e.g., all) serving cells. The PTAG can be, for example, a TAG group to which the SpCell belongs (e.g., the one or more timeout actions can be performed (only) for the one or more serving cells associated with the TAG). In an example, if the timer times out for a timeAlignmentTimer associated with a PTAG, the WTRU can clear one or more PUSCH resources for semi-persistent CSI for all serving cells. The PTAG can be, for example, a TAG group to which the SpCell belongs. In an example, if the timer times out for a timeAlignmentTimer associated with a PTAG, the WTRU can clear all PUSCH resources for semi-persistent CSI for one or more serving cells. The PTAG can be, for example, a TAG group to which the SpCell belongs. In an example, if the timer times out for a timeAlignmentTimer associated with a PTAG, the WTRU can clear all PUSCH resources for semi-persistent CSI for all serving cells. The PTAG can be, for example, a TAG group to which the SpCell belongs. In an example, the timeout actions can be performed for the serving cells associated with the TAG. In an example, the timeout actions can be performed only for the serving cells associated with the TAG.

[0084] In an example, in NR operation, a MAC CE carrying a TA command can be associated with a specific cell. For example, in a cell-internal multi-transmission / reception point (multi-TRP or mTRP) scenario, separate TA indication for one or more (e.g., each) transmission / reception point (TRP) can not be supported. In an example, if separate TA indication for one or more (e.g., each) TRP is supported, it can be difficult to estimate one or more separate TA values for one or more (e.g., each) TRP link. For example, in a cell-internal mTRP scenario, a PCI can include a serving cell. The serving cell can be referred to as a primary TRP (pTRP). The pTRP can have an SSB configuration. For example, in a cell-internal mTRP scenario, a PCI can include an additional TRP (sTRP) that can not have an SSB configuration. In an example, the sTRP can be measured by a WTRU on a channel state information-reference signal (CSI-RS) and / or one or more tracking RSs. In an example, a MAC CE carrying a TA command can be associated with a MAC entity of a specific cell. For example, a MAC CE TA command can not be associated with a primary TRP. For example, a MAC CE TA command can not be associated with a sTRP, as described herein. In an example, a timing advance measurement and / or association of a TA command can be initiated per each separate radio link and / or one or more simultaneous TA commands and / or their (e.g., respective) application. A MAC CE can indicate whether a TA command is associated with a primary TRP and / or a secondary TRP. For example, a MAC CE can indicate a TRP index that indicates a TA command is associated with a primary TRP and / or a secondary TRP.

[0085] Systems, methods, and / or apparatuses related to procedures to initiate one or more (e.g., multiple) TA measurements and / or updates are provided herein. Systems, methods, and / or apparatuses related to procedures to indicate one or more (e.g., multiple) TA and / or association to a TRP are provided herein.

[0086] Systems, methods, and / or apparatuses related to procedures to initiate and / or maintain one or more (e.g., multiple) TA measurements are provided herein. In multi-DCI multi-TRP transmission with multiple TA support, a WTRU can receive a PDCCH order random access channel (RACH) to update one or more TA values for one or more (e.g., each) TRP link.

[0087] Systems, methods, and / or apparatuses can include PDCCH ordered PRACH transmission in multi-TRP. A gNB can trigger transmission of a PRACH to reestablish synchronization for uplink transmissions by a WTRU (e.g., a set of one or more PRACH resources). Such initiation can occur for one or more different reasons. For example, a gNB can trigger transmission of a PRACH when a WTRU has not been scheduled for transmission for a certain duration. In NR, the triggering of a random access transmission for reestablishing synchronization can be implemented through a PDCCH order. Through the PDCCH order, a DCI can provide relevant information for the transmission of a PRACH (e.g., such as a preamble index and / or a SSB index). The PRACH can serve as a reference point for determining an associated RACH occasion. A WTRU can receive a DCI from a first TRP. The DCI can indicate that the WTRU is to transmit a PRACH transmission. The DCI can include an indication of a preamble, an indication of a first PRACH mask, an indication associated with a first SSB, and / or an indication of an RS. The WTRU can receive the DCI in a PDCCH order that triggers the PRACH transmission.

[0088] The WTRU can determine a spatial filter based on the indicated RS. The WTRU can determine to transmit the preamble to the second TRP based on the spatial filter. The WTRU can transmit the preamble to the second TRP in a first PRACH resource that can be determined based on, for example, the first PRACH mask and / or the first SSB. The preamble can be transmitted using a spatial filter determined based on the indicated RS. The first TRP and the second TRP can be associated with a same physical cell identity (PCI). The WTRU can receive a response to the preamble (e.g., such as a random access response (RAR)) from the second TRP. The response can include a timing advance (TA) command for timing alignment for transmissions to the second TRP and / or an index indicating the second TRP.

[0089] In an mTRP deployment, a WTRU can maintain its synchronization with one or more (e.g., two or more) different TRPs. For example, in an mTRP deployment, a WTRU can be required to maintain its synchronization with at least two different TRPs. For example, a WTRU can dynamically switch between single-TRP transmission mode and multi-TRP transmission mode, which can require, for example, accurate timing synchronization at all times. For example, a WTRU can use a first timing alignment with a first TRP and can use a second timing alignment with a second TRP. For example, if a WTRU can dynamically switch between single-TRP transmission mode and multi-TRP transmission mode, the WTRU can be configured to maintain accurate timing synchronization at times (e.g., at all times) (e.g., a set of one or more PRACH resources). As described herein, a PDCCH order (e.g., from a pTRP intended to convey a PRACH to an sTRP for UL synchronization / timing alignment) can include one or more of the following: a preamble identifier; a TRP indication (e.g., a CORESETPOOL index) indicating the sTRP; an SSB index (e.g., associated with the pTRP); a PRACH mask; and / or an RS indicator (e.g., a CSI-RS and / or a tracking RS) associated with the sTRP. If timing alignment for the pTRP and the sTRP includes one PDCCH order, the PDCCH order can include a second SSB index (e.g., associated with the pTRP) and / or a second PRACH mask. As described herein, the PDCCH order can include one or more of the following: a TRP index; a pTRP SSB index for determining a PRACH resource; and / or an sTRP RS for determining a filter for transmission (Tx). As described herein, a WTRU can transmit a preamble based on the preamble identifier using the determined PRACH resource and / or the determined spatial filter. As described herein, a WTRU can transmit a preamble based on the preamble identifier using the determined PRACH resource and / or the determined spatial filter. If timing alignment for the pTRP and the sTRP includes one PDCCH order, the WTRU can transmit the same preamble to the pTRP based on the second SSB index and / or the second PRACH mask. The WTRU can receive a RAR including a TRP indication and / or a TA indication. If timing alignment for the pTRP and the sTRP includes one PDCCH order, the RAR can include a second TA. The WTRU can transmit an UL transmission to the sTRP using the determined spatial filter and / or with a timing based on the TA indication.

[0090] In multi-TRP deployments, a WTRU configured in multi-TRP operation can receive a PDCCH order to trigger a PRACH transmission. In an example, upon receiving a PDCCH order for a PRACH transmission for single-DCI multi-TRP operation or multi-DCI multi-TRP operation, the WTRU can be configured with one or more of the behaviors described herein.

[0091] In single-DCI multi-TRP operation, a PRACH transmission can occur for the TRP that initiated the PDCCH order PRACH. In an example, a WTRU can transmit a single PRACH using an indicated preamble index (e.g., one or more PRACH resources), a synchronization signal (SS) / PBCH index (e.g., SSB index), and / or a PRACH mask according to the received PDCCH order. In an example (e.g., in this case), the WTRU can use a demodulation reference signal (DMRS) of the received PDCCH as a source of RS for spatial information (e.g., spatial filter based on RS indicator) used to transmit the preamble (e.g., determined PRACH resource and / or determined spatial filter based on preamble identifier). For example, the WTRU can transmit the preamble using a spatial filter based on the indicated RS (e.g., such as DMRS). In an example, the WTRU can receive a random access response (RAR) message including a TA and a TRP indication. In an example, the WTRU can apply the indicated TA for one or more (e.g., two) TRPs until the next TA indication for one or more (e.g., all) future transmissions. In an example, the WTRU can receive an implicit and / or explicit indication, e.g., in the RAR message, that the WTRU can apply the indicated TA for the TRP that initiated (e.g., TRP indication) the PDCCH order for one or more (e.g., all) future transmissions until the next TA indication. For example, the WTRU can receive a response message (e.g., RAR message) in response to the preamble. The response message can include a TA command for timing alignment for transmissions to the TRP that initiated the PDCCH order.

[0092] In a single DCI multi-TRP operation, a PRACH transmission can occur for a TRP that does not initiate a PDCCH ordered PRACH. A WTRU can receive a DCI from a first TRP. For example, the DCI can be received in a PDCCH order. The DCI can indicate that the WTRU is to transmit a PRACH transmission. In an example, based on information elements (e.g., fields) that can be carried by the same PDCCH, the WTRU can transmit a single PRACH to a second TRP (e.g., a TRP that does not initiate a PDCCH ordered PRACH), for example, in accordance with the received PDCCH order, using an indicated preamble index (e.g., one or more PRACH resources), an SS / PBCH index (e.g., an SSB index associated with a pTRP), a TRP index, and / or a PRACH mask. For example, the DCI can 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 can be associated with a same physical cell identity (PCI). Additionally or alternatively, the WTRU can detect an RS index indicated in a received PDCCH, which can be a source of RS (e.g., a spatial filter determined based on the source of RS) for transmitting a preamble. For example, the WTRU can determine spatial information (e.g., a spatial filter) for transmitting a preamble to a second TRP based on an indicated RS (e.g., such as an RS index or a DMRS). The WTRU can transmit a preamble using a spatial filter determined based on an indicated RS (e.g., such as a DMRS). For example, the WTRU can determine to transmit a preamble to a second TRP based on spatial information (e.g., a spatial filter). In an example, the indicated RS can be associated with another TRP. For example, a DCI can include an indication of a preamble (e.g., such as a preamble index), an indication of a PRACH mask, an indication associated with an SSB (e.g., such as an SS / PBCH index), and / or an indication of a reference signal (RS) (e.g., such as an RS index). The DCI can be received in information elements that can be carried by the same PDCCH. The WTRU can transmit a preamble to a second TRP in a first PRACH resource determined based on a first PRACH mask and / or a first SSB. The WTRU can receive RAR information including a TA. For example, the WTRU can receive a response message (e.g., a RAR message) in response to a preamble. The response message can include a TA command for timing alignment for transmissions to a second TRP (e.g., a TRP that does not initiate a PDCCH ordered PRACH). For example, the WTRU can apply an indicated TA (e.g., by a TA command) for one or more (e.g., two) TRPs (e.g., a TRP indication) for one or more (e.g., all) future transmissions until a next TA indication.For example, the WTRU can receive an implicit and / or explicit indication, e.g., in the RAR message, that the indicated TA can be applied by the WTRU for one or more (e.g., all) future transmissions to the TRP that did not initiate the PDCCH ordered PRACH until the next TA indication (e.g., TRP indication) for that TRP. For example, the WTRU can receive an implicit or explicit indication, e.g., in the RAR message, that the indicated TA (e.g., only) can be applied by the WTRU for future (e.g., all future) transmissions to the TRP that did not initiate the PDCCH ordered PRACH until the next TA indication. For example, the WTRU can transmit an uplink transmission to the second TRP using the determined spatial filter and with the timing based on the TA command.

[0093] In single-DCI multi-TRP operation, PRACH transmission for two TRPs can be based on a received PDCCH ordering PRACH. In an example, a WTRU can transmit one or more PRACHs according to information carried by a received PDCCH. The WTRU can detect one or more indicated values of one or more of the following: a preamble index (e.g., one or more PRACH resources), an SS / PBCH index (e.g., SSB index), and / or a PRACH mask. Additionally or alternatively, the WTRU can detect an RS index indicated in the received PDCCH, which can be a source of RS for spatial information (e.g., spatial filter based on RS indicator) for transmitting a preamble. In an example, the WTRU can receive a single PRACH index, one or more (e.g., two) synchronization signal blocks (SSBs) / PBCH indices, one or more (e.g., two) PRACH mask values, and one (e.g., or more) RS index. The WTRU can transmit one or more (e.g., two) PRACHs using the same preamble index at two different occasions according to the indicated (e.g., two) SSB / PBCH indices, (e.g., two) PRACH mask values, (e.g., two) DMRS of the PDCCH, and / or RS indicated in the PDCCH for the first transmission and / or the second transmission. In an example, the WTRU can receive a RAR message including a single TA and / or TRP indication. For example, the WTRU can apply the indicated TA for one or more (e.g., all) future transmissions to one or more (e.g., two) TRPs (e.g., TRP indication) until a next TA indication. For example, the WTRU can receive (e.g., in a RAR message) an implicit and / or explicit indication that the WTRU can apply the indicated TA (e.g., only) to a TRP that initiated and / or did not initiate a PDCCH ordering PRACH for one or more (e.g., all) future transmissions until a next TA indication. In an example, the WTRU can receive a RAR message including one or more TAs. According to one or more rules and / or received indications, the WTRU can select one or more of the indicated TA values for one or more (e.g., all) future transmissions and / or apply the one or more TA values to one or more (e.g., all) TRPs until a next TA indication. The WTRU can apply the one or more indicated TA values to one or more corresponding TRPs.

[0094] In an example, in a single DCI multi-TRP operation, PRACH transmission for two TRPs can be based on a received PDCCH ordering PRACH. In an example, a WTRU can transmit more than one PRACH according to information carried by a received PDCCH. In an example, a WTRU can detect one or more indicated values of at least one of the following: a preamble index, e.g., SS / PBCH index, and a PRACH mask. In an example, a WTRU can detect an RS index indicated in a received PDCCH, which can be a source of RS for spatial information for transmitting a preamble. In an example, a WTRU can receive a single PRACH index, two SSB / PBCH indexes, two PRACH mask values, and / or one RS index. In an example, a WTRU can transmit two PRACHs using the same preamble index at two different occasions according to the indicated two SSB / PBCH indexes, two PRACH mask values, two DMRS of the PDCCH, and / or RS indicated in the PDCCH for the first transmission and / or the second transmission.

[0095] In an example, a WTRU can receive a RAR message including a single TA. In an example, the WTRU can apply the indicated TA for one or more (e.g., all) future transmissions to both TRPs until the next TA indication. In an example, the WTRU can receive an implicit and / or explicit indication, e.g., in the RAR message, that the WTRU can apply the indicated TA for one or more future transmissions to initiate or not initiate a PDCCH ordered PRACH to the TRP(s) until the next TA indication. In an example, the WTRU can receive an implicit and / or explicit indication, e.g., in the RAR message, that the WTRU can apply the indicated TA only for one or more (e.g., all) future transmissions to initiate or not initiate a PDCCH ordered PRACH to the TRP(s) until the next TA indication. In an example, the WTRU can receive a RAR message including more than one TA. In an example, the WTRU can select one or more of the indicated TA values for one or more future transmissions and / or apply the one or more TA values to both TRPs until the next TA indication according to a rule and / or received indication. In an example, the WTRU can select one of the indicated TA values for one or more (e.g., all) future transmissions and / or apply the one TA value to both TRPs until the next TA indication according to a rule or received indication. In an example, the WTRU can apply the indicated TA value to the corresponding TRP. In an example, a single-DCI multi-TRP operation can include a PRACH transmission according to a last indicated multi-TRP mode. For example, in a single-DCI multi-TRP transmission, the WTRU can be dynamically scheduled to alternate between single-TRP transmission and multi-TRP transmission. Additionally or alternatively, for example, the WTRU can switch the order of transmission. In an example, if the last scheduled uplink transmission is intended for both TRPs (e.g., a multi-TRP operation mode indicated by a SRS resource indicator (SRI) (e.g., codepoint 10 and / or codepoint 11)), the WTRU can transmit a PRACH to one or more (e.g., both) TRPs. Additionally or alternatively, if the last scheduled uplink transmission is intended (e.g., only) for one of the TRPs (e.g., a single-TRP operation mode indicated by an SRI (e.g., codepoint 00 and / or codepoint 01)), the WTRU can transmit a PRACH according to the corresponding TRP.

[0096] In multi-DCI multi-TRP operation, a WTRU can transmit a single PRACH per TRP according to PDCCH commands received from one or more (e.g., each) TRP. For example, the WTRU can use an indicated preamble index, SS / PBCH index, and / or PRACH mask for one or more (e.g., each) transmission. In an example, the WTRU can use DMRS of one or more (e.g., each) received PDCCH as a RS source for spatial information (e.g., RS indicator based spatial filter) used to transmit one or more (e.g., each) preambles. In an example, the WTRU can receive a single RAR message including a single TA and / or TRP indication. For example, the WTRU can apply an indicated TA for one or more (e.g., all) future transmissions to one or more (e.g., two) TRPs (e.g., TRP indication) until a next TA indication. For example, the WTRU can receive an implicit and / or explicit indication, e.g., in a RAR message, that the WTRU can apply an indicated TA (e.g., only) to one of the TRPs (e.g., associated with one of the CORSETPoolIndices). In an example, the WTRU can receive a single RAR message including one or more (e.g., two) TA values. In an example, the WTRU can apply an indicated TA value to a corresponding TRP. In an example, the WTRU can receive one or more RAR messages. One or more (e.g., each) RAR message can correspond to one or more PRACH transmissions. One or more (e.g., each) RAR message can include one or more TAs. The WTRU can receive one or more (e.g., multiple) TA commands in one or more RAR messages. In an example, according to a rule and / or a received indication, the WTRU can select one or more of the indicated TA values for one or more (e.g., all) future transmissions and / or apply the one or more TA values to one or more (e.g., two) TRPs until a next TA indication. In an example, according to a rule and / or a received indication, the WTRU can select one of the indicated TA values for future transmissions (e.g., all future transmissions) and / or apply the one TA value to two TRPs until a next TA indication. In an example, the WTRU can apply the one or more indicated TA values to one or more corresponding TRPs.

[0097] In an example, in NR, a PDCCH order PRACH can be carried by a DCI format 1 0 and / or can be scrambled by a C-RNTI. In an example, if a field corresponding to a "frequency domain resource assignment" is 1, the remaining one or more fields can be interpreted as follows. For example, a random access preamble index can be 6 bits. For example, a reserved bit can be 10-12 bits. In an example, if a value of the "random access preamble index" is not (e.g., not all) zero, a UL / SUL indicator can be 1 bit, a SS / PBCH index can be 6 bits, and / or a PRACH mask index can be 4 bits.

[0098] Indications of one or more of the following examples can be used to support implementation of examples and / or implementations described herein. In implementations, indications of one or more of the following implementations can support implementation of the above-described examples and implementations. One implementation can include a RS that serves as a source of an indication of spatial information (e.g., RS- indicator based spatial filter) that is included for transmitting a preamble associated with a second TRP. Additionally or alternatively, examples can include an additional preamble that can be associated with the second TRP. Additionally or alternatively, examples can include an additional SS / PBCH index. Additionally or alternatively, examples can include an additional PRACH mask index.

[0099] In an example, the remaining reserved bits can be 10. Indications of one or more of the examples described herein can be associated with overhead. For example, one or more of the following examples can be used to reduce overhead. Examples can include a WTRU that can use an SSB associated with an indicated SS / PBCH index as a source of RS for spatial information (e.g., RS- indicator based spatial filter) that is included for transmitting a second preamble. Additionally or alternatively, examples can include a WTRU that can use a (e.g., same) preamble for PRACH transmissions to a first TRP and a second TRP. Additionally or alternatively, examples can include a WTRU that can use a same SS / PBCH and / or PRACH mask index for transmitting one or more (e.g., two) preambles, if supported by a capability reported by the WTRU. Additionally or alternatively, examples can include a WTRU that can use a same SS / PBCH index but different PRACH masks for one or more transmissions of a first PRACH and / or a second PRACH. Additionally or alternatively, examples can include a WTRU that can use a same PRACH mask but different SS / PBCH indices for one or more transmissions of a first PRACH and / or a second PRACH.

[0100] Systems, methods, and apparatus, related to subsequent RACH transmissions of a second TA loop are provided herein. In an example, a WTRU can determine (e.g., and / or use) an uplink TA value for transmitting an uplink signal based on single TA support (e.g., maintaining a single TA loop by a cumulative TA control mechanism). For example, the single TA support can be applied based on a first PRACH that the WTRU has transmitted. For example, the single TA support can be applied based on a first PRACH that the WTRU has transmitted during an initial access procedure. For example, the single TA support can be applied based on a first PRACH that the WTRU has transmitted after receiving a PDCCH order based on single TA (e.g., and / or TAG) support, and / or the single TA support can be applied to communicate with a first TRP (e.g., a primary TRP, a single TRP, and / or a cell, etc.).

[0101] In an example, a WTRU can be indicated (e.g., from a gNB) to transmit a second PRACH (e.g., via a PDCCH order, via a PDCCH order of a “second TA initiation,” by an indication to initiate a second TA loop, etc.), where the second PRACH transmission can be used to initiate (e.g., create, update, add, newly initiate, and / or maintain, etc.) a second TA loop in addition to (e.g., an ongoing) a first TA loop (e.g., a single TA loop). In an example, a WTRU can determine a PRACH (e.g., based on a PDCCH order) is for a general (e.g., existing) PRACH transmission based on single TA support (e.g., so far), and / or for a special (e.g., PDCCH order based) PRACH for initiating (e.g., and / or updating) a second TA loop. For example, WTRU target determination can be based on an explicit indicator associated with (e.g., included in) a DCI. The DCI indicates a special (e.g., PDCCH order based) PRACH for initiating and / or updating a second TA loop. For example, WTRU target determination can be based on an implicit indication including one or more configuration parameters (e.g., a preamble index, an SSB index, an SS / PBCH index, a PRACH mask, and / or one or more PRACH resources, etc.) associated with a special (e.g., PDCCH order based) PRACH.

[0102] In response to receiving the special (e.g., PDCCH order based) PRACH for initiating (e.g., and / or updating) the second TA loop, the WTRU can transmit the special PRACH to the second TRP. For example, transmitting the special PRACH to the second TRP can be based on one or more of the following. Transmitting the special PRACH to the second TRP can be based on a beam / TCI related parameter that can be associated with the special PRACH. Transmitting the special PRACH to the second TRP can be based on a unified TCI (e.g., source RS of the unified TCI) associated with the second TRP. Transmitting the special PRACH to the second TRP can be based on a source quasi co-location (e.g., QCL) RS associated with the special PRACH. Transmitting the special PRACH to the second TRP can be based on an additional and / or separate timing reference point (e.g., spatial filter based on RS indicator) obtained and / or measured from a DL RS (e.g., TRS associated with the second TRP, SSB associated with the second TRP, and / or DL RS associated with the second TRP, etc.) associated with the special PRACH.

[0103] In response to transmitting the special PRACH, the WTRU can receive a RAR. In an example, the RAR can include an indication of a second TA value (e.g., to be applied for the second TA loop). In an example, the RAR can be a second RAR to be transmitted from the second TRP. In an example, the RAR can be a first RAR to be transmitted from the first TRP (e.g., primary TRP) based on a pre-configuration delivered to the WTRU. In an example, a beam / TCI for the first RAR transmitted from the first TRP can be pre-configured to the WTRU.

[0104] In response to receiving the RAR, the WTRU can (e.g., be configured to) create (e.g., a new) second TA loop for accumulation (e.g., if configured), where the second TA loop can include the second TA value as an initial value for the second TA loop. In response to receiving the RAR, the WTRU can apply the second TA value for one or more subsequent uplink transmissions to the second TRP (e.g., associated with the second TRP) until a next RAR associated with the second TRP is received, e.g., if accumulation TA mode is not configured.

[0105] In an example, a WTRU can maintain a first TA loop based on a first timing reference point (e.g., obtained and / or measured from a first DL RS which can be associated with a first TRP) and / or one or more first TA values which can be accumulated based on receiving one or more TA commands which can be associated with the first TA loop. In an example, a WTRU can maintain a second TA loop based on a second timing reference point (e.g., obtained and / or measured from a second DL RS which can be associated with a second TRP) and / or one or more second TA values which can be accumulated based on receiving one or more TA commands which can be associated with the second TA loop. Reliability and / or flexibility in managing one or more (e.g., two) separate TA values and / or loops can be improved for the first TRP and / or the second TRP, respectively. The improvement in reliability and / or flexibility can be based on creating a separate second TA loop in response to receiving a DCI including a special (e.g., PDCCH order based) PRACH.

[0106] In an example, a WTRU can (e.g., be configured to) apply one or more second TA values (e.g., to be accumulated based on receiving one or more TA commands which can 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 which can 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 can imply that the timing reference (e.g., point) can be shared by the first TRP and / or the second TRP. In an example, the TA accumulation loop can be separate 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 can imply that the timing reference (e.g., point) can be shared by the first TRP and the second TRP, but the TA accumulation loop is separate between the first TRP and the second TRP.

[0107] In an example, a WTRU can 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, a WTRU can maintain a second TA loop based on a same first timing reference point (e.g., shared between the first TRP and a second TRP) and / or one or more second TA values that can be accumulated based on receiving one or more TA commands that can be associated with the second TA loop. Implementing complexity of a WTRU can be reduced in managing two separate TA values and / or loops towards the first TRP and / or the second TRP, which can be based on a shared timing reference point obtained, which can be based on a DL RS.

[0108] In an example, a WTRU can (e.g., be configured to) apply sequential RACH transmissions after a first RACH transmission. In an example, a WTRU can 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 can be fixed, semi-statically and / or dynamically indicated and / or configured. In an example, the time interval can be configured and / or indicated based on a reported WTRU capability. In an example, a WTRU can determine the time interval based on another system parameter and / or mode of operation (e.g., cell index, TDD / FDD, BWP index, multiple TA loop configuration, and / or multiple TRP related configuration, etc.).

[0109] In an example, in a sequential based RACH transmission, a WTRU can use the same or different RACH resources. For example, RACH resources for each transmission can be selected and / or indicated from the same and / or TRP based configured pool. In an example, once a WTRU receives a DCI from one of the TRPs including a PDCCH order RACH to initiate a RACH transmission for one or more (e.g., all) TRP links, the WTRU can follow one or more of the following rules for determining an order of RACH transmission for one or more (e.g., each) TRP. In an example, a WTRU can (e.g., always) start a sequential RACH transmission with the TRP that has transmitted the PDCCH order RACH. Additionally or alternatively, a WTRU can (e.g., always) start a sequential RACH transmission with a fixed TRP link (e.g., a link associated with a primary TRP, and / or a link associated with a CORESETPoolIndex = 0, etc.). In an example, a WTRU can start a sequential RACH transmission with a TRP that can have a closest RACH occasion.

[0110] In an example, once the WTRU receives the DCI from one of the TRPs including the PDCCH ordered RACH, the WTRU can resolve the collision with the already scheduled uplink transmission for another TRP link based on one or more of the following. In an example, the WTRU can ignore the received grant and / or drop the scheduled uplink transmission. Additionally or alternatively, instead of dropping the scheduled transmission, the WTRU can delay the RACH to the next RACH transmission occasion. Alternatively or additionally, if the scheduled uplink transmission is intended for PUCCH and / or for PUSCH including HARQ feedback, the WTRU can ignore the PDCCH ordered RACH and / or can continue the scheduled transmission.

[0111] Multi-TA operation can be performed within a TAG. Examples can include timing alignment timeout. In an example, configuration and / or operation of a timing advance timer (TAT) can occur per TRP. A WTRU can be configured with a timing advance timer (TAT) per TRP. A TAT can be configured independently per TRP link, e.g., as part of a TRP-specific TAG configuration. A TAT configuration can include one or more of the following. A TAT configuration can include a TRP identifier (e.g., the TRP to which the TAT applies). A TAT configuration can include a TAG identifier. A TAT configuration can include a TAT duration (e.g., a duration in ms). A TAT configuration can include one or more WTRU actions to be performed upon TAT timer expiry. A TAT configuration can include one or more TRP links to which one or more timeout actions are to be applied. A TAT configuration can include one or more serving cells to which one or more timeout actions are to be applied.

[0112] Additionally or alternatively, a TAT configuration for a TRP can include a delta configuration from a reference TRP and / or TAG, and / or a TAT configuration (e.g., a TAT configuration for a pTRP and / or a common TAT configuration provided in system information). Additionally or alternatively, a delta TAT configuration can include one or more of the following: a reference TRP and / or TAG and / or TAT configuration identifier; and / or a delta configuration from a reference TRP and / or TAT and / or TAG configuration. For example, a delta configuration from a reference TRP and / or TAT and / or TAG configuration can consist of one or more of the following: an offset time and / or an offset timer duration.

[0113] A per-TRP timing alignment timer can include one or more start and / or stop conditions. A WTRU can start and / or restart a TAT timer associated with a TRP link, for example, upon receiving one or more of the following. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving a timing advance command MAC CE. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving an absolute timing advance command, for example, in response to a MSGA (PRACH) transmission including a C-RNTI MAC CE. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving a DCI. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving a TAG configuration and / or reconfiguration. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving a TAT configuration and / or reconfiguration. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving system information, for example, SIB1. A WTRU can start and / or restart a TAT timer associated with a TRP link upon receiving an RRC message, for example, RRCSetup.

[0114] For example, a WTRU can stop a TAT timer associated with a TRP link under one or more conditions. For example, a WTRU can stop a TAT timer associated with a TRP link when contention resolution is deemed unsuccessful. For example, a WTRU can 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) that can include a WTRU contention resolution identification MAC CE.

[0115] The WTRU can initiate, restart, and / or stop a TAT based on which TRP link and / or serving cell a message (e.g., a timing advance command MAC CE) is received and / or transmitted. For example, the WTRU can 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 can (e.g., only) perform one or more TAT actions associated with a TRP in response to one or more messages transmitted and / or received on a TRP link. For example, the WTRU can (e.g., only) perform one or more TAT actions associated with a TRP in response to one or more messages transmitted and / or received on a pTRP link. For example, the WTRU can (e.g., only) perform one or more TAT actions associated with a TRP 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 can (e.g., only) perform one or more TAT actions associated with a TRP in response to one or more messages transmitted and / or received on one or more TRP links associated with a SpCell.

[0116] Each-TRP timing alignment timer can include one or more TAT expiry conditions. The WTRU can perform one or more actions if a TAT associated with a TRP expires. Additionally or alternatively, the WTRU can perform a TAT expiry action at a fixed offset before the timer expires and / or at a fixed time after the TAT expires. The WTRU can perform one or more expiry actions. The WTRU can perform an expiry action of initiating a RACH. The WTRU can perform an expiry action of flushing one or more (e.g., all) HARQ buffers. The WTRU can perform an expiry action of notifying the network. The WTRU can perform an expiry action of releasing one or more (e.g., all) configured PUCCHs. The WTRU can perform an expiry action of releasing one or more (e.g., all) configured SRSs. The WTRU can perform an expiry action of flushing one or more configured downlink assignments. The WTRU can perform an expiry action of flushing one or more configured uplink grants. The WTRU can perform an expiry action of flushing one or more PUSCH resources for semi-persistent CSI reporting. The WTRU can perform an expiry action of maintaining the current N TA of values until a subsequent value is updated by the network (e.g., via a TA command).

[0117] A WTRU can configure and / or perform a different set of one or more timeout actions depending on one or more of the following conditions: which TRP link the timed-out TAT is associated with (e.g., whether the timed-out TAT is associated with a pTRP and / or sTRP); which serving cell the timed-out TAT is associated with (e.g., whether the timed-out TAT is associated with a TRP belonging to a SpCell, PsCell, and / or SCell); and / or the number of TRPs with timed-out TAT (e.g., if one or more TRP(s) have a timed-out TAT, the WTRU can perform a different set of one or more actions).

[0118] A WTRU can be configured and / or perform (e.g., only) one or more timeout actions for a TRP link associated with a timed-out TAT timer. Additionally or alternatively, a WTRU can be configured and / or perform one or more timeout actions for one or more additional links (e.g., depending on the configuration). For example, a WTRU can perform one or more of the timeout actions described herein for a TRP link associated with a timer that has timed out. For example, a WTRU can perform one or more of the timeout actions described herein for one or more (e.g., all) TRP links associated with a serving cell. For example, a WTRU can perform one or more of the timeout actions described herein for one or more (e.g., all) TRP links associated with one or more (e.g., all) serving cells.

[0119] In an example, upon TAT timeout for one TRP, a WTRU can suspend UL transmissions to the affected TRP and / or can keep one or more HARQ buffers. A WTRU can transmit (e.g., pending) data on the suspended TRP to a TRP that is still valid. In an example, the WTRU’s transmission of (e.g., pending) data on the suspended TRP can depend on data priority, one or more available resources, and / or configuration.

[0120] A WTRU can be configured with a TAT expiration notification. Upon TAT expiration for one or more TRP links, the WTRU can notify the network of the TAT expiration via one or more of the following methods. The WTRU can notify the network of the TAT expiration via initiating a RACH transmission on the affected TRP link(s). For example, the WTRU can receive a single PDCCH order RACH to initiate a RACH transmission to obtain an updated TA on the affected link(s). For example, additionally or alternatively, a single received PDCCH order RACH can initiate a RACH transmission on one or more (e.g., all) TRP links. For example, the WTRU can receive a separate PDCCH order RACH for one or more (e.g., each) TRP link, where a first PDCCH can be associated with a TRP link (associated with the affected timer). Additionally or alternatively, the WTRU can notify the network of the TAT expiration via transmitting an implicit and / or explicit notification to the gNB through a link whose timer has not expired. For example, the notification can indicate to the gNB that the timer of the other link(s) has expired, such that the gNB can send a PDCCH order RACH for the affected link(s). For example, if one or more (e.g., each) TAG is associated with a different subset of RACH resources, the WTRU can perform implicit indication by using one or more PRACH resources of the affected TAG for a TRP associated with a TAG that has still valid TA information.

[0121] A WTRU can be configured with an exceed maximum receive time difference and / or maximum transmit time difference. Deployment of multi-TRP configurations that can support exceed cyclic prefix (CP) receive time difference can pose challenges to the WTRU architecture. For example, one or more (e.g., two) baseband units can be included if the receive time difference exceeds a certain level. Including one or more additional baseband units can result in a more expensive device. Receive difference time limits can be beneficial to maintain one or more goals of the feature in terms of throughput and / or robustness of data transmission (e.g., due to the non-collocated nature of the TRPs and / or one or more propagation properties in one or more different frequency ranges).

[0122] A maximum receive time difference (MRTD) and / or a maximum transmit time difference (MTTD) can characterize one or more thresholds expressed in time units, symbol units, and / or one or more portions of a symbol that can be specific to a WTRU hardware architecture. For example, a WTRU that can have this capability can be designed with a single baseband unit. For example, when the MRTD and / or MTTD is below a certain time threshold, communication with one or more (e.g., two) TRPs in the downlink and / or uplink can be handled simultaneously. In an example, one or more (e.g., two) baseband units can be included for this feature.

[0123] In a multi-TRP deployment, the distance of one or more TRPs to a WTRU can be different. In an example, the TA value indicated in one or more of the one or more timing advance commands for one or more (e.g., each) TRP can result in a relative time difference that can cause the maximum transmission time difference (MTTD) capability of the WTRU to be exceeded.

[0124] A WTRU can be configured for multi-TRP. The multi-TRP can include one or more additional TRP candidate measurement and / or reporting. The one or more additional TRPs can be added to the primary TRP by the network before and / or (e.g., only) after the WTRU reports one or more measurement results. On procedure, the network can configure the WTRU to measure one or more additional TRP candidates in the area served by the primary TRP. The WTRU can report one or more capabilities of the WTRU for multi-TRP deployment, e.g., at registration and / or upon network request. The WTRU can report the MRTD and / or MTTD it supports as a threshold. The network can configure the WTRU for one or more additional TRP candidate measurement and / or reporting, e.g., considering the WTRU’s multi-TRP operation timing capability. In an example, the WTRU can measure one or more additional candidates and / or their relative reception time difference from the primary TRP (pTRP), and / or can report one or more candidates, e.g., whose RSRP and / or RSRQ levels exceed a reporting quality threshold and / or whose relative time difference is less than the WTRU’s reported capability for MRTD. Additionally or alternatively, the WTRU can be configured to report the RSRP and / or RSRQ of one or more additional TRP candidates and / or their relative reception time difference from the primary TRP (pTRP), e.g., without (e.g., any) restriction on the supported MRTD capability.

[0125] For example, upon receiving a measurement report that can have one or more additional TRP candidates within one or more reporting conditions, the network can configure the WTRU with an additional TRP (e.g., sTRP). For example, upon receiving a reconfiguration message that can have an sTRP addition, the WTRU can measure (e.g., re-measure) the relative reception time difference. For example, upon the last measurement of the sTRP relative reception time difference, the WTRU can confirm the reconfiguration message to the network when the reception time difference is within the WTRU’s reported capability, and / or can report a reconfiguration failure (e.g., if the last measured relative reception time difference of the configured candidate exceeds the supported MRTD). In an example, there can be a reconfiguration failure cause field that can indicate “MRTD exceeded.” For example, the reconfiguration failure can be communicated as a beam failure for the reasons indicated herein. For example, if the last measured relative reception time difference of the configured candidate has one or more WTRU capabilities, the WTRU can initiate an uplink time synchronization procedure with the configured sTRP.

[0126] Additionally or alternatively, the WTRU can be configured with one or more additional sTRPs that comply (e.g., can follow) MRTD and / or RSRP and / or RSRQ thresholds. The WTRU can be configured with one or more TCI states for one or more (e.g., each) combination of pTRP-sTRP, and / or one or more TCI combinations (e.g., selected and / or best TCI combinations) can be activated based on, for example, one or more recent WTRU reported measurements. For example, upon TCI combination activation, the WTRU can initiate one or more UL synchronization procedures with the recently (e.g., newly) activated sTRP (e.g., based on determined spatial filters and / or with TA indication based timing). For example, if the UL synchronization results in exceeding the MTTD supported by the WTRU, a beam failure report with an “exceeded MTTD” cause can be transmitted to the network. For example, upon receiving a failure message with an “exceeded MTTD” cause, the network can activate a different TCI state combination and / or (e.g., completely) reconfigure the WTRU, for example, with one or more other sTRP candidates and / or with one or more other TCI state combinations with the pTRP. Additionally or alternatively, the network can remove the multi-TRP related operation from the WTRU configuration.

[0127] The WTRU can be configured with one or more timing advance operations for multi-TRP related to MRTD and / or MTTD. A WTRU that can move in an environment can receive one or more timing advance commands for one or more (e.g., two) TRPs, for example, after (e.g., simultaneously with) adding an sTRP and / or successfully synchronizing with the sTRP. TRP deployment and / or WTRU mobility can result in one or more situations that can exceed MRTD and / or MTTD. Exceeding MRTD and / or MTTD can result in a radio link failure of an active sTRP. In an example, the WTRU can report the issue.

[0128] In an example, if the relative difference between TA advance values exceeds the MRTD and / or MTTD threshold, the WTRU can do one or more of the following. In an example, if the relative difference between TA advance values exceeds the MRTD or MTTD threshold, the WTRU can transmit an indication of the error and / or issue to the gNB. The indication can be transmitted via the pTRP. The pTRP can remain anchored on RRC messages, MAC CEs, and / or UCI on the physical layer. Additionally or alternatively, the indication can be a radio link failure (RLF) indication for the sTRP.

[0129] Upon receiving the notification from the WTRU, the network can perform one or more of the actions herein, and / or a (e.g., any) combination of the actions herein. For example, upon receiving the notification from the WTRU, the network can reconfigure the WTRU with one or more other TCI states containing one or more other combinations of pTRP-sTRP candidates, which can be based on one or more latest measurement reports received from the WTRU, and / or can be followed by TCI activation for the different combinations and / or can continue operation in the multi-DCI mode. For example, upon receiving the notification from the WTRU, the WTRU can fall back into the single-DCI mode and / or can continue mTRP operation in the TDM mode if there are no other combinations with the configured TCI pool containing the multi-TRP combination. For example, upon receiving the notification from the WTRU, the WTRU can declare beam failure on the sTRP while 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 can be based on the (e.g., smallest) measurement’s MRTD. For example, following the beam failure indication, the WTRU can continue to monitor the CORESET associated with the sTRP (e.g., in CORESETPOOLIndex 1) for beam indication within the DCI from one or more active TCIs.

[0130] A WTRU can be configured with the timing of application of one or more TA commands. In multi-TRP transmission, a WTRU (e.g., with simultaneous uplink transmission capability) can receive TA commands for one or more of the TRP links in the TRP link. For example, when TA is applied for one or more consecutive slots, an overlap between UL TRP transmissions for the TRPs can occur. One or more TA commands can be applied (e.g., always applied) at the beginning of a slot, and / or one or more rules can apply to one or more symbols of a slot (e.g., to the last one or more symbols and / or the first symbol or a number of symbols in front of the slot), which can be applied in a closed range (e.g., a few symbols) of the slot boundary.

[0131] One or more transmissions can occur as described herein according to the relative timeline of the ongoing transmission of the first and / or second transmission associated with the updated TA. The ongoing transmission can proceed as scheduled when the updated TA can cause the associated UL transmission to be later than the ongoing first transmission. Additionally or alternatively, for example, when one or more overlapping UL transmissions between TRPs can not be allowed, the transmission associated with the link with the updated TA can be shortened at the end by a number of overlapping samples. For example, if the updated TA slot causes the associated transmission to be earlier than the ongoing first transmission, the ongoing transmission can proceed as scheduled. Additionally or alternatively, when one or more overlapping UL transmissions between TRPs can not be allowed, the transmission associated with the link with the updated TA can be shortened at the start by a number of overlapping samples, for example. In an example, the shortening for transmission alignment can be made by considering priority rules. In an example, the alignment of one or more transmissions can be shortened by considering priority rules. For example, if PUCCH overlaps with PUSCH and / or the TA application can imply shortening the PUCCH (e.g., using normal overlapping shortening rules where the ongoing transmission can be protected), the WTRU can shorten the PUSCH slot (e.g., instead of the PUCCH). In an example, a PUSCH with CSI and / or (e.g., any) UCI can be protected on (e.g., normal) PUSCH, and thus, for example, (e.g., normal) PUSCH can be shortened.

[0132] A WTRU can be configured with one or more procedures for associating one or more (e.g., multiple) TA indications to one or more TRPs. In an example, a (e.g., specific) flag in a MAC CE can indicate whether the indicated TA is applicable for a first TRP link and / or a second TRP link. For example, the flag can be indicated in one or more of the (e.g., two) fields that can be reserved for TAG IDs. In an example, for example, a CORESETPoolIndex bit can be added in a MAC CE to indicate the intended TRP link. Additionally or alternatively, for example, a CORESETPoolIndex can be associated with one or more of the TAG IDs to provide the linkage. In an example, a WTRU can determine the intended TRP for a TA indication, for example, based on a scheduling PDCCH. For example, if a PDCCH that schedules a PDSCH containing a MAC CE TA command comes in CORESETPoolIndex = 0, the indicated TA can be applied to the TRP link associated with CORESETPoolIndex = 0. In an example, the indicated TA can be applied to the TRP link that can be associated with a CORESET (e.g., CORESETPoolIndex = 1). For example, if a PDCCH that schedules a PDSCH containing a MAC CE TA command comes in CORESETPoolIndex = 0, the indicated TA can be applied to the TRP link associated with CORESETPoolIndex = 0, otherwise it can be applied to the TRP link associated with a CORESET (e.g., CORESETPoolIndex = 1). In an example, a MAC CE can include TA information for one or more TRP links. In an example, a WTRU can update (e.g., simultaneously) TA information for one or more TRP links. In an example, a WTRU can update (e.g., simultaneously) TA information for one or more (e.g., multiple) TRP links. The association with a first TRP link and / or a second TRP link can be based on the order of the values indicated in a MAC CE and / or a CORESETPoolIndex, etc. For example, the indicated TA information can be absolute TA values for one or more (e.g., each) TRP, and / or in the form of their relative difference. A WTRU can 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., TA2 = TA1 + TA_delta). For example, once a WTRU can receive one or more TA indications for one or more TRPs, the WTRU can apply one or more rules as described herein to determine the priority of application for one or more (e.g., each) TRP.A WTRU can apply a TA to one or more (e.g., each) TRP link, for example, according to the timing of the scheduled transmissions. For example, once a WTRU receives one or more TA indications for more than one TRP, the WTRU can apply the TA to the TRP link with the earlier scheduled transmission (e.g., first). In an example, once a WTRU receives one or more TA indications for more than one TRP, the WTRU can apply the TA to the TRP link associated with the primary TRP and / or associated with CORESETPoolIndex = 0 (e.g., first).

[0133] A WTRU can be configured with one or more (e.g., multiple) TAGs per serving cell. A WTRU can be provided with one or more timing advance groups (TAGs) per serving cell. One or more (e.g., each) TAG configuration can be associated with one or more different (e.g., different) TRP links. For example, if a WTRU supports multi-TRP and / or multi-TA operation, the WTRU can apply (e.g., only) the TAG configuration associated with a secondary sTRP and / or additional sTRP.

[0134] TAG configuration for a TRP can include one or more of the parameters 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 sTRP; and / or a timeAlignmentTimer (TAT) value and / or a TimeAlignmentTimerCommon value. A WTRU can receive TAG configuration information related to a primary TRP (pTRP) and / or one or more additional TRPs (e.g., sTRPs) via system information (e.g., SIB1 and / or within UplinkConfigCommonSIB) and / or via dedicated signaling (e.g., via RRC signaling, DCI, and / or MAC CE). For example, a WTRU can be provided one or more TimeAlignmentTimerCommon parameters associated with one or more TRPs within system information (e.g., within SIB1 via UplinkConfigCommonSIB). For example, a WTRU can be provided one or more (e.g., multiple) TAG configurations within MAC-CellGroupConfig (e.g., via RRC) via TAG-Config, where TAG information can be provided for one or more (e.g., each) TRP. For example, a TAG-Config can include a tag-ID and / or a timeAlignmentTimer configuration for a primary TRP (pTRP) and / or one or more additional TRPs (sTRPs). For example, there can be one or more (e.g., multiple) TAG-Config information elements within MAC-CellGroupConfig, where one or more (e.g., each) of the information elements can correspond to a TRP of a cell.

[0135] For example, if a WTRU receives a dedicated TAG configuration (e.g., via RRC signaling and / or MAC CE), the WTRU can override the TAG configuration for one or more TRPs provided via broadcast signaling (e.g., within SIB1 via UplinkConfigCommonSIB).

[0136] For example, a WTRU can be provided with TAG configuration for a set of X TRPs via broadcast signaling (e.g., within system information), and / or provided with TAG configuration for a set of Y TRPs via dedicated signaling (e.g., RRC configuration and / or MAC CE). For example, if set X and set Y include the same TRPs, a WTRU can override one or more (e.g., or all) TAG configurations (and / or one or more associated parameters) provided in set X (e.g., via broadcast signaling) with the same content provided in set Y. For example, if set X and set Y include one or more different TRPs, and if set Y includes a TAG configuration for a pTRP, a WTRU can apply that 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, a WTRU can update (e.g., only) the TAG configuration for TRPs provided in both set X and set Y. For example, the configuration for one or more (e.g., all) TRPs in set X that are not provided in set Y can be maintained or deleted. For example, one or more actions a WTRU can take can be explicitly indicated via configuration and / or within system information.

[0137] If a WTRU and / or cell can support multi-TRP multi-TA operation and (e.g., only) one TAG configuration, one or more of the following can be included. A WTRU can apply TAG information to one or more (e.g., or all) TRPs (e.g., a pTRP and / or one or more sTRPs) associated with a serving cell. A WTRU can be (e.g., explicitly) indicated whether a TAG configuration applies to a pTRP and / or one or more sTRPs. For example, the indication can be provided within 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. For example, upon RRC state (e.g., via a flag) transitioning to RRC_INACTIVE and / or RRC_IDLE, a WTRU can apply one or more previously stored TAG configurations. For example, the flag can be included in (e.g., TAG) configuration. For example, a default TAG configuration can include one or more parameters included within a TAG configuration (e.g., TAT value). A default TAG configuration can be provided, for example, via system information (e.g., SIB1). In an example, the (e.g., system) information can be provided via dedicated configuration (e.g., via RRC) upon RRC state transition (e.g., upon receiving a RRC Setup and / or RRC Release containing a suspend config message).

[0138] Figure 4 A system diagram illustrating an example timing alignment for sTRP 400 is depicted. WTRU 406 can 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.

[0139] At 408, pTRP 402 can transmit a PDCCH order for a PRACH to sTRP 404 to WTRU 406. The PDDCH order can include a preamble identifier, a TRP indication (e.g., such as a CORESET POOL index) associated with sTRP 404, a first SSB index (e.g., associated with pTRP 402), a second SSB index, a first PRACH mask, a second PRACH mask, a TRP index, and / or a RS indicator (e.g., CSI-RS and / or tracking RS) associated with sTRP 404. WTRU 406 can use the RS indicator to determine a spatial filter for transmission (Tx). If the timing alignment for pTRP 402 and sTRP 404 includes (e.g., only) one PDCCH order, the PDDCH order can include the second SSB index (e.g., associated with pTRP 402) and / or the second PRACH mask.

[0140] At 410, WTRU 406 can transmit a PRACH (e.g., a preamble) to sTRP 404. The preamble can be based on the preamble identifier (e.g., at 408) using the determined PRACH resource and / or the (e.g., determined) spatial filter. For example, WTRU 406 can determine a spatial filter based on the RS indicator (e.g., indicated at 408). WTRU 406 can determine to transmit the preamble to sTRP 404 at 410 based on the spatial filter. WTRU 406 can transmit the PRACH to sTRP 404 using the determined spatial filter. WTRU 406 can determine a PRACH resource for transmission to sTRP 404 based on the SSB index (e.g., associated with pTRP), the one or more PRACH resources, and / or the PRACH mask. If the timing alignment for pTRP 402 and sTRP 404 includes (e.g., only) one PDCCH order, WTRU 406 can transmit the same preamble to pTRP 402 based on the second SSB index and / or the second PRACH mask.

[0141] At 412, sTRP 404 can transmit (e.g., a first) response message to WTRU 406. The (e.g., first) response can be a RAR message. The RAR message can include a TRP index, a TA (e.g., TA indication), and / or a sTRP UL grant. WTRU 406 can receive the first response to the preamble. The first response can include a first timing advance (TA) command for the second timing alignment for transmissions to sTRP 404 and / or an index indicating sTRP 404. If the timing alignment for pTRP 402 and sTRP 404 includes (e.g., only) one PDCCH command, the RAR message can include a second TA.

[0142] At 414, WTRU 406 can transmit a UL Tx (e.g., Msg3) to sTRP 404. WTRU 406 can transmit the UL Tx to sTRP 404 at 414 using the determined spatial filter and / or timing based on the (e.g., first) TA indication / command.

Claims

1. A wireless transmit / receive unit (WTRU) comprising a processor configured to: receive configuration information indicating a first timing advance group (TAG) for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier (ID), the second TAG is associated with a second TAG ID, the configuration information indicates a first duration of a first timing alignment timer (TAT) associated with the first TAG for the serving cell, and the configuration information indicates a second duration of a second TAT associated with the second TAG for the serving cell; start the first TAT; start the second TAT; determine that the first TAT associated with the first TAG for the serving cell has timed out; clear the 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 timed out; maintain a hybrid automatic repeat request (HARQ) buffer associated with the serving cell when the first TAT associated with the first TAG for the serving cell times out; determine that the second TAT associated with the second TAG for the serving cell has timed out; clear the one or more configured downlink assignments and the 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 timed out; flush the HARQ buffer associated with the serving cell based on the second TAT associated with the second TAG for the serving cell having timed out; and start or restart 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. The WTRU of claim 1, wherein the first TAG for the serving cell is associated with a first transmit / receive point (TRP) for the serving cell and the second TAG for the serving cell is associated with a second TRP for the serving cell.

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

4. The WTRU of claim 1, wherein the processor is configured to: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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.

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

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

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

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

9. 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 receptions in the control resource set are quasi co-located with one or more downlink reference signals configured by the at least one TCI state, wherein the processor is configured to receive a downlink control information, DCI, via the control resource set, wherein the DCI indicates a second TCI state, wherein the TCI state group comprises the second TCI state, and wherein reception of a transport block, TB, based on the TCI state group comprises at least one DMRS of the TB being quasi co-located with a second reference signal indicated by the second TCI state.

10. The WTRU of claim 1, wherein the processor is configured to: release one or more configured physical uplink control channel, PUCCH, resources and one or more configured sounding reference signal, SRS, resources based on the second TAT associated with the second TAG for the serving cell having expired.

11. A method of a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information, the configuration information indicating a first timing advance group, TAG, for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier, ID, the second TAG is associated with a second TAG ID, the configuration information indicates a first duration of a first timing alignment timer, TAT, associated with the first TAG for the serving cell, and the configuration information indicates a second duration of a second TAT associated with the second TAG for the serving cell; starting the first TAT; starting the second TAT; determining that the first TAT associated with the first TAG for the serving cell has timed out; 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 timed out; maintaining a hybrid automatic repeat request, HARQ, buffer associated with the serving cell when the first TAT associated with the first TAG for the serving cell times out; determining that the second TAT associated with the second TAG for the serving cell has timed out; 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 timed out; flushing the HARQ buffer associated with the serving cell based on the second TAT associated with the second TAG for the serving cell having timed out; and 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. 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. The method of claim 12, wherein a first transmission configuration information, TCI, state is associated with transmissions corresponding to the first TRP, the first TRP being associated with the first TAG for the serving cell, and a second TCI state is associated with transmissions corresponding to the second TRP, the second TRP being associated with the second TAG for the serving cell.

14. The method of claim 11, wherein the method further comprises: 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 times out.

15. The method of claim 11, wherein the method further comprises: suspending at least one uplink transmission to the serving cell associated with the first TAG based at least on a determination that the first timing alignment timer (TAT) associated with the first TAG for the serving cell has expired; and suspending at least one uplink transmission to the serving cell associated with the second TAG based at least on a determination that the second TAT associated with the second TAG for the serving cell has expired.

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

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

18. The method of claim 11, wherein the method further comprises: receiving the MAC CE activating a first transmission configuration indicator (TCI) state group for a control resource set, and wherein the TCI state group comprises at least one TCI state, the at least one TCI state comprising a first TCI state; determining that demodulation reference signal (DMRS) antenna ports associated with one or more physical downlink control channel receptions in the control resource set are quasi co-located with one or more downlink reference signals configured by the at least one TCI state; and receiving a downlink control information (DCI) via the control resource set, wherein the DCI indicates a second TCI state, wherein the TCI state group comprises the second TCI state, and wherein reception of a transport block (TB) based on the TCI state group comprises at least one DMRS of the TB being quasi co-located with a second reference signal indicated by the second TCI state.

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

20. A wireless transmit / receive unit (WTRU) comprising: a processor configured to: receive configuration information indicating a first timing advance group (TAG) for a serving cell and a second TAG for the serving cell, wherein the first TAG is associated with a first TAG identifier (ID), the second TAG is associated with a second TAG ID, the configuration information indicates a first duration of a first timing alignment timer (TAT) associated with the first TAG for the serving cell, and the configuration information indicates a second duration of a second TAT associated with the second TAG for the serving cell; start the first TAT; start the second TAT; determine 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 the second TAT associated with the second TAG for the serving cell having expired; 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). ​

Images