Timing Advance in Multi-Panel TX Scenarios

Abstract

A method and apparatus for timing advance in a multi-panel TX scenario is disclosed. A user equipment (UE) includes a processor and a transceiver coupled to the processor, the processor is configured to receive, via the transceiver, information related to a plurality of timing advances (TAs) for uplink transmissions to a network, each TA being associated with a link associated with a cell of the network, and to determine, from the information received via the transceiver, each TA for performing uplink transmissions to one or more cells of the network.

Description

[Technical Field]

[0001] The subject matter disclosed herein relates generally to wireless communications, and more particularly to methods and apparatus for timing advance in multi-panel TX scenarios. [Background technology]

[0002] The following abbreviations are defined by this specification, at least some of which will be mentioned in the description that follows: New Radio (NR), Very Large Scale Integration (VLSI), Random Access Memory (RAM), Read Only Memory (ROM), Erasable Programmable Read Only Memory (EPROM or Flash Memory), Compact Disc Read Only Memory (CD-ROM), Local Area Network (LAN), Wide Area Network (WAN), User Equipment (UE), Evolved Node B (eNB), Next Generation Node B (gNB), Uplink (UL), Downlink (DL), Central Processing Unit (CPU), Graphics Processing Unit (GPU), Field Programmable Gate Array (FPGA), Orthogonal Frequency Division Multiplexing (OFDM), Radio Resource Control (RRC), User Entity / Equipment (Mobile Terminal), Transmitter (TX), Receiver (RX), Time Alignment or Timing Advance or Timing Adjustment (TA), Timing Advance Group (TAG), Primary TAG (PTAG), Secondary TAG (STAG), Timing Advance Command (TAC), Timing Advance Timer (TAT), Random Access Channel (RACH), Random Access Response (RAR), Transmit / Receive Point (TRP), Time Division Multiplexing (TDM), Control Resource Set (CORESET), Reference Signal (RS), Medium Access Control (MAC), MAC Control Element (MAC CE), Logical Channel Index (LCID), Downlink Shared Channel (DL-SCH), Protocol Data Unit (PDU), Hybrid Automatic Repeat Request (HARQ), Physical Uplink Control Channel (PUCCH), Physical Uplink Shared Channel (PUSCH), Channel State Information (CSI), Sounding Reference Signal (SRS), Physical Downlink Control Channel (PDCCH).

[0003] TA, which may stand for time alignment or timing advance or timing adjustment, is used to adjust the uplink frame timing relative to the downlink frame timing. The TA value, which may be the amount of timing adjustment, depends on the propaganda delay of the signal from the gNB to the UE. Therefore, different UEs have different TAs to the gNB. The MAC entity of the UE manages the TA of the UE.

[0004] Conventionally, a UE can be served by multiple serving cells. Among the multiple serving cells, a group of cells that use the same timing reference cell and the same TA value when configured for UL transmission belong to one Timing Advance Group (TAG). The TAG that contains the SpCell is called the Primary TAG (PTAG), while each of the other TAGs is called a Secondary TAG (STAG).

[0005] Figure 1 shows an example of legacy PTAG and STAG. From Figure 1, it can be seen that SpCell#1 and SCell#2 belong to the PTAG, and SCell#3 belongs to the STAG. The UE manages one TA (e.g., one TA value) per TAG. This means that, from the UE's perspective, SpCell#1 and SCell#2 have the same TA (e.g., TA1), while SCell#3 has a different TA (e.g., TA2). From the UE's perspective, each cell (e.g., each of SpCell#1, SCell#2, and SCell#3) has one TA, regardless of whether the TA value of one cell (e.g., TA1 of SpCell#1) is the same as the TA value of another cell (e.g., TA1 of SCell#2) or different from the TA value of yet another cell (e.g., TA2 of SCell#3).

[0006] A cell may have multiple (e.g., two) TRPs. A UE may transmit UL signals (e.g., PUSCH and / or PUCCH transmissions) to multiple TRPs. In NR Release 17, multiple TRPs are limited to two TRPs. In addition, a UE can only transmit UL signals to two TRPs in a TDM manner (i.e., asynchronously, not simultaneously), for example, using two panels of the UE. When multiple (e.g., two) TRPs are sufficiently close, the TA between the UE and one TRP and the TA between the UE and the other TRP can be considered the same. Therefore, even though a cell may have multiple (e.g., two) TRPs, the UE still assumes one TA value for that cell.

[0007] To increase cell coverage, multiple TRPs may be placed at different locations within a cell. Under this condition, the TA from the UE to one of the multiple TRPs will be significantly different from the TA from the UE to another of the multiple TRPs (e.g., two TRPs). This means that the UE must transmit an UL signal to one TRP of a cell using one TA, and transmit the same or another UL signal to another TRP of the cell using a different TA.

[0008] Therefore, the UE must manage at least two TAs for a cell that has multiple (e.g., two) TRPs located separately. When the UE transmits UL signals to multiple (e.g., two) TRPs of a cell, the UE typically has multiple (e.g., two) panels, each of which is used to transmit UL signals to a different TRP. This can be called a multi-panel, multi-TRP scenario. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to enhance TA in multi-panel multi-TRP scenarios. [Means for solving the problem]

[0010] A method and apparatus for timing advance in a multi-panel TX scenario is disclosed.

[0011] In one embodiment, a UE comprises a processor and a transceiver coupled to the processor, the processor being configured to: receive, via the transceiver, information related to multiple Timing Advances (TAs) for uplink transmissions to a network, where each TA is associated with a link associated with a cell of the network, and determine, from the information received via the transceiver, each TA for performing uplink transmissions to one or more cells of the network. The processor may be further configured to receive, via the transceiver, one or more timers, where each timer is associated with one or more links and maintains validity of TAs associated with the one or more links. Specifically, the timers relate to Timing Advance Groups (TAGs) per link or to links per TAG.

[0012] In one embodiment, the processor is further configured to transmit, via the transceiver, a UE capability that supports multiple TA maintenance.

[0013] In another embodiment, the timer is associated with a Timing Advance Group (TAG) per link or link per TAG.

[0014] In some embodiments, the link used to perform initial access is a primary link. The primary link may be associated with one cell. One or more other links are secondary links. Each secondary link may be associated with one or more cells.

[0015] In one embodiment, each TA may be indicated by a timing advance command (TAC). A TAC received from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set may be applied to the uplink (UL) panel associated with that DL TRP or the UL beam associated with that DL beam. Alternatively, each TAC is contained within a TAC medium access control (MAC) control element (CE) that identifies the link associated with that TAC. The TAC MAC CE may be of fixed or variable size, identified by a MAC subheader with a logical channel identity (LCID). Alternatively, a TAC contained within a TAC MAC CE that does not identify a link is determined to be the TAC of the primary link. Alternatively, each TAC is contained within a MAC random access response (RAR), which identifies the link associated with that TAC. The MAC RAR may be of fixed or variable size, identified by a MAC subheader with a logical channel identity (LCID).

[0016] In some embodiments, if a timer associated with a configured uplink grant or link related to a UL resource expires, transmission on that UL resource may be paused or the resource associated with that link may be cleared.

[0017] In another embodiment, a network device comprises a processor and a transceiver coupled to the processor, the processor configured to generate information related to a plurality of timing advances (TAs) for uplink transmissions from a user equipment (UE) to the network device, each TA being associated with a link between the network device and the UE, and to transmit, via the transceiver, the information related to the plurality of TAs to the UE.

[0018] In yet another embodiment, a method performed by a UE includes receiving information related to a plurality of timing advances (TAs) for uplink transmissions to a network, each TA being associated with a link associated with a cell of the network, and determining, from the information received from the transceiver, each TA for performing uplink transmissions to one or more cells of the network.

[0019] In a further embodiment, a method implemented in a network device includes generating information related to a plurality of timing advances (TAs) for uplink transmissions from a user equipment (UE) to the network device, each TA being associated with a link between the network device and the UE, and transmitting the information related to the plurality of TAs to the UE.

[0020] A more particular description of the above-briefly described embodiments will be provided by reference to specific embodiments illustrated in the accompanying drawings, in which the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings, with the understanding that these drawings illustrate only some embodiments and, therefore, should not be considered limiting in scope. [Brief explanation of the drawings]

[0021] [Figure 1] A diagram showing an example of a legacy PTAG and STAG. [Figure 2] FIG. 2 illustrates an example of a second sub-embodiment of the first embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of a fourth subembodiment of the first embodiment. [Figure 4(a)] A figure showing an example of a new TAC MAC CE format. [Figure 4(b)] A figure showing an example of a new TAC MAC CE format. [Figure 4(c)]A figure showing an example of a new TAC MAC CE format. [Figure 4(d)] A figure showing an example of a new TAC MAC CE format. [Figure 4(e)] A figure showing an example of a new TAC MAC CE format. [Figure 5] FIG. 1 is a schematic flow chart diagram illustrating one embodiment of a method. [Figure 6] FIG. 10 is a schematic flow chart diagram illustrating a further embodiment of a method. [Figure 7] 1 is a schematic block diagram illustrating an apparatus according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] As will be appreciated by those skilled in the art, some aspects of the embodiments may be embodied as a system, apparatus, method, or program product. Accordingly, the embodiments may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be referred to generally herein as a "circuit," "module," or "system." Furthermore, the embodiments may take the form of a program product embodied in one or more computer-readable storage devices that store machine-readable code, computer-readable code, and / or program code, hereinafter referred to as "code." The storage devices may be tangible, non-transitory, and / or non-transmittable. The storage devices may not embody signals. In certain embodiments, the storage devices use signals only to access the code.

[0023] Some functional units described herein may be referred to as "modules" to more specifically emphasize their independent implementation. For example, a module may be implemented as a hardware circuit comprising custom very large scale integrated (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented as a programmable hardware device such as a field programmable gate array, programmable array logic, programmable logic device, or the like.

[0024] Modules may be implemented as code and / or software for execution by various types of processors. A particular module of code may, by way of example, comprise one or more physical or logical blocks of executable code, which may, by way of example, be organized as objects, procedures, or functions. Nevertheless, the executable files of a particular module need not be physically located together, but may comprise distinct instructions stored in different locations that, when logically combined together, comprise the module and accomplish the stated purpose of the module.

[0025] Indeed, a module of code may contain a single instruction, many instructions, and may even be distributed across several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein in modules, and the operational data may be embodied in any suitable form and organized within any suitable type of data structure. This operational data may be collected as a single data set or distributed across different locations, including across different computer-readable storage devices. When a module or portions of a module are implemented as software, the software portions are stored on one or more computer-readable storage devices.

[0026] Any combination of one or more computer-readable mediums may be utilized. The computer-readable medium may be a computer-readable storage medium. The computer-readable storage medium may be a storage device that stores code. The storage device may be, for example, but is not necessarily, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micro-mechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

[0027] A non-exhaustive list of more specific examples of storage devices includes the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0028] The code for carrying out the operations of the embodiments may include any number of lines and may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Python, Ruby, Java, Smalltalk, C++, and the like, and conventional procedural programming languages ​​such as the "C" programming language, and / or machine code such as assembly language. The code may run entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the last scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or a connection may be made to an external computer (e.g., through the Internet using an Internet Service Provider).

[0029] Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Thus, throughout this specification, the appearances of the phrases "in one embodiment," "in an embodiment," and similar language may, but do not necessarily, all refer to the same embodiment, but may mean "one or more, but not all, embodiments" unless expressly specified otherwise. The words "including," "comprising," and "having," and variations thereof, mean "including but not limited to," unless expressly specified otherwise. An enumerated list of items does not imply that any or all of the items are mutually exclusive unless expressly specified otherwise. The words "a," "an," and "the" also refer to "one or more" unless expressly specified otherwise.

[0030] Furthermore, the described features, structures, or characteristics of various embodiments may be combined in any suitable manner. In the description that follows, numerous specific details are provided, such as examples of programming, software modules, user selections, network transactions, database queries, database structures, hardware modules, hardware circuits, hardware chips, etc., to provide a thorough understanding of the embodiments. However, one skilled in the art will recognize that the embodiments can be practiced without one or more of the specific details, or can be practiced with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid any obscurity of aspects of the embodiments.

[0031] Aspects of different embodiments are described below with reference to schematic flowchart illustrations and / or schematic block diagrams of methods, apparatus, systems, and program products according to the embodiments. It will be understood that each block of the schematic flowchart illustrations and / or schematic block diagrams, and combinations of blocks in the schematic flowchart illustrations and / or schematic block diagrams, can be implemented by code. This code can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce machine-readable instructions that, when executed by the processor of the computer or other programmable data processing apparatus, produce means for implementing the functions of one or more blocks specified in the schematic flowchart illustrations and / or schematic block diagrams.

[0032] The code may also be stored in a storage device that can direct a computer, other programmable data processing apparatus, or other device to function in a particular manner, such that the instructions stored in the storage device produce an article of manufacture that includes instructions that implement the functions specified in one or more blocks of the schematic flowchart diagrams and / or schematic block diagrams.

[0033] The code may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause the computer, other programmable apparatus, or other device to perform a series of operational steps, thereby producing a computer-implemented process; thus, the code running on the computer or other programmable apparatus results in a process for implementing the functions specified in one or more blocks of the flowcharts and / or block diagrams.

[0034] The schematic flowchart diagrams and / or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatus, systems, methods, and program products according to various embodiments. In this regard, each block in the schematic flowchart diagrams and / or schematic block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions of code for implementing the specified logical function(s).

[0035] It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. Other steps and methods may be conceived that are equivalent to the illustrated figures in terms of function, logic, or effect on one or more blocks or portions thereof.

[0036] While various arrow and line types may be used in the flowcharts and / or block diagrams, it is understood that they do not limit the scope of the corresponding embodiments. Indeed, some arrows or other connectors may be used merely to indicate the logical flow of the illustrated embodiments. By way of example, arrows may indicate waiting or monitoring periods of unspecified duration between enumerated steps of the illustrated embodiments. It will also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, can be implemented by a dedicated hardware-based system that performs the specified functions or acts, or by a combination of dedicated hardware and code.

[0037] The description of an element in each figure may refer to the element in the succeeding figure. Like numbers refer to like elements in all figures, including alternative embodiments of like elements.

[0038] Reference is now made in detail to several embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided based on specific network architectures and new service scenarios, such as 3GPP® 5G, 3GPP® LTE, 3GPP® NR-U, and NR radio access operating with shared spectrum channel access. All embodiments in the present application are intended to be applicable to similar technical challenges as well as evolution of network architectures and new service scenarios. Furthermore, the terminology described in the present application may change, but this should not affect the principles of the present application. The embodiments of the present disclosure may also be applied to unlicensed spectrum scenarios.

[0039] In a multi-panel multi-TRP scenario, the UE is required to manage multiple TAs (e.g., from the same TAG) simultaneously. As mentioned in the background section, TA as referred to in this application refers to time alignment or timing advance or timing adjustment, while TA value as referred to in this application refers to the amount of timing adjustment.

[0040] The first embodiment relates to modeling multiple TAs in a multi-panel, multi-TRP scenario. "Multi-TRP" means that a serving cell can have multiple (e.g., two) TRPs. "Multi-panel" means that a UE can have multiple (e.g., two) panels. Under the condition that a UE with two panels (e.g., Panel #1 and Panel #2) transmits an UL signal (PUCCH and / or PUSCH transmission) to a serving cell with two TRPs (e.g., TRP #1 and TRP #2), the UE may use one panel (e.g., Panel #1) to transmit an UL signal to one TRP (e.g., TRP #1) of the serving cell and use the other panel (e.g., Panel #2) to transmit an UL signal to another TRP (e.g., TRP #2) of the serving cell.

[0041] The TRP#1 and TRP#2 of a serving cell may be located separately, resulting in a different TA (e.g., TA1) being used when transmitting an UL signal from panel#1 to TRP#1 and a different TA (e.g., TA2) being used when transmitting an UL signal from panel#2 to TRP#2. A UE is required to manage multiple different TAs (e.g., TA1 and TA2) per serving cell. TA1 may be denoted as the TA associated with the link (e.g., link#1) from panel#1 to TRP#1, and TA2 may be denoted as the TA associated with the link (e.g., link#2) from panel#2 to TRP#2.

[0042] In this application, links are defined such that different links are associated with different TAs. Links may be denoted as from a panel to a TRP. Because a specific panel (e.g., panel #1) is used to transmit an UL signal to a specific TRP (e.g., TRP #1), a link may be denoted as either a panel or a TRP. For example, if link #1 from panel #1 to TRP #1 is associated with TA #1 and link #2 from panel #2 to TRP #1 is associated with TA #2, then TA #1 associated with link #1 may be denoted as TA #1 associated with panel #1, while TA #2 associated with link #2 may be denoted as TA #2 associated with panel #2. As another example, if link #1 from panel #1 to TRP #1 is associated with TA #1 and link #2 from panel #1 to TRP #2 is associated with TA #2, then TA #1 associated with link #1 may be denoted as TA #1 associated with TRP #1, while TA #2 associated with link #2 may be denoted as TA #2 associated with TRP #2. Obviously, a link may alternatively be denoted as a panel set (or panel group) or a TRP set (or TRP group), assuming that the same TA is associated with a panel set (consisting of multiple panels) or a TRP group (consisting of multiple TRPs). Multiple beams are transmitted from one panel. In addition, multiple beams used for reception belong to one TRP. Therefore, alternatively, a link may be denoted by one beam or a beam set (or beam group) consisting of multiple beams. A panel corresponds to a set of Reference Signals (RSs) (which may be called RS set). A TRP corresponds to a pool of CORESETs with the same CORESETPoolIndex. Therefore, alternatively, an RS set or a CORESET pool may denote a link. Alternatively, a cell (serving or non-serving) may denote a link.Each of the above items (e.g., panel, panel set, TRP, TRP set, beam, beam set, RS set, CORESET pool, cell) for indicating a link may have an index (ID), which means that the ID of each of the above items may alternatively indicate a link. In addition, a beam failure detection ID may alternatively indicate a link. Incidentally, in a multi-TRP (i.e., multiple TRPs (e.g., two TRPs)) scenario, multiple TRPs (e.g., two TRPs) may belong to different cells (e.g., two cells). Under this condition, a link may be associated with multiple (e.g., two) cells.

[0043] According to a first subembodiment of the first embodiment, a TA is identified per link (e.g., per link per cell). That is, each link has a separate TA. This means that one TA (i.e., one TA) is configured to be associated with each link. The UE manages or maintains one TA per link. A TA timer (TAT) (e.g., timeAlignmentTimer) is configured per TA (i.e., per link) or per TA (i.e., per cell) by RRC signaling (which means that all links of a cell, each with a different TA, have the same TAT). In other words, each TAT is associated with one or more links. The TAT associated with a link maintains the validity of the TA associated with that link. The validity of a TA means how long a TA is valid or how long the MAC entity of the UE considers the TA to be valid.

[0044] Optionally, the UE may indicate to the base station (e.g., gNB) its UE capability to support multiple TA maintenance (e.g., support "TA is identified per link") so that the TA can be identified per link.

[0045] Optionally, the link used, configured, or indicated to perform initial access may be defined or configured by RRC signaling as a "primary link." The primary link may be associated with one cell. The remaining links (i.e., links that are not the primary link) may be defined as "secondary links" or "other links." Each secondary link may be associated with one or more (e.g., two) cells.

[0046] According to a first subembodiment of the first embodiment, when multiple TAs are configured, each of which is identified for each link, a TAG (either a PTAG or a STAG) is not allowed to be configured by the base station, or the TAG is considered to be disabled by the UE even if it is configured by the base station.

[0047] According to a second subembodiment of the first embodiment, a TA is identified per TAG per link (i.e., for each link within each TAG). That is, each link within each TAG has a separate TA. This means that a TA is associated with each link of each TAG. FIG. 2 shows an example of the second subembodiment of the first embodiment. In FIG. 2, links are represented by panels (e.g., Panel #1, Panel #2). FIG. 2 shows four links, namely, Panel #1 of PTAG, Panel #2 of PTAG, Panel #1 of STAG, and Panel #2 of STAG. Therefore, the UE is required to manage or maintain one TA for each of the four links. A TA timer (e.g., timeAlignmentTimer) is configured per TA (i.e., per link per TAG) or per TAG by RRC signaling (which means that all links of one TAG, each with a different TA, have the same TAT). For example, timeAlignmentTimer_TAG 1-1 is configured to be associated with panel #1 of the PTAG, timeAlignmentTimer_TAG 1-2 is configured to be associated with panel #2 of the PTAG, timeAlignmentTimer_TAG 2-1 is configured to be associated with panel #1 of the STAG, and timeAlignmentTimer_TAG 2-2 is configured to be associated with panel #2 of the STAG.

[0048] Optionally, the UE may indicate to the base station (e.g., gNB) its UE capability to support multiple TA maintenance (e.g., support "TA is identified per link per TAG") so that a TA can be identified per link per TAG.

[0049] Optionally, the link of a PTAG used, configured, or indicated to perform initial access may be defined as the "primary link." Alternatively, one link may be configured by the network as the "primary link." The remaining links (i.e., links that are not the primary link) may be defined as "secondary links" or "other links." Optionally, the link of each TAG (e.g., each STAG) used, configured, or indicated to perform initial access may be defined or configured as the "primary link" (e.g., "the primary link for that STAG") by RRC signaling. Alternatively, one link within a TAG (e.g., a STAG) may be indicated, defined, or configured by the network as the "primary link" (e.g., "the primary link for that STAG"). The remaining links within that TAG (i.e., links that are not the primary link) may be defined as the "secondary links" or "other links" for that TAG.

[0050] The TAG configuration follows the legacy TAG configuration.

[0051] According to a third subembodiment of the first embodiment, a legacy TAG is reused, and the TA indicated in the legacy TAG and the TAT associated with the legacy TAG are considered to be the TA and TAT associated with the primary link. In this case, the link used, configured, or indicated to perform initial access can be defined or configured as the “primary link” by RRC signaling. The remaining links (i.e., links that are not the primary link) can be defined as “secondary links” or “other links.” Alternatively, the link of each TAG (e.g., each STAG) used, configured, or indicated to perform initial access can be defined or configured as the “primary link” (e.g., “the primary link of that STAG”) by RRC signaling. Alternatively, one link in a TAG (e.g., a STAG) can be indicated, defined, or configured by the network as the “primary link” (e.g., “the primary link of that STAG”). The remaining links in the TAG (i.e., links that are not the primary link) can be defined as the "secondary links" or "other links" of the TAG. TAs for the remaining links are identified for each link. A new TAT (e.g., timeAlignmentTimer_additionalpanel) is configured to be associated with each "secondary link" or "other link."

[0052] Optionally, the UE may indicate to the base station (e.g., gNB) a UE capability supporting multiple TA maintenance (e.g., "the legacy TAG is reused to identify the primary link, and the remaining TAs associated with the other links are identified on a link-by-link basis"). According to a third subembodiment of the first embodiment, the TA of the primary link may be identified by the legacy TAG, and the TAs of the other links may be identified on a link-by-link basis.

[0053] According to a fourth subembodiment of the first embodiment, a TA is identified per link per TAG (i.e., per TAG within each link). That is, each TAG within each link has a separate TA. This means that a TAG is configured to be associated with a link. FIG. 3 shows an example of the fourth subembodiment of the first embodiment. In FIG. 3, links are represented by panels (e.g., Panel #1, Panel #2). FIG. 3 shows four links: a PTAG in Panel #1, a PTAG in Panel #2, a STAG in Panel #1, and a STAG in Panel #2. Therefore, the UE needs to manage or maintain one TA for each of the four links. A TA timer (e.g., timeAlignmentTimer) is configured per TA (i.e., per TAG per link) or per TAG by RRC signaling (which means that all links associated with one TAG, each with a different TA, have the same TAT).

[0054] Optionally, the UE may indicate to the base station (e.g., gNB) its UE capability to support multiple TA maintenance (e.g., support "TA is identified per TAG per link") so that a TA can be identified per TAG per link.

[0055] Optionally, the link used, configured, or indicated to perform the initial access, or the link configured by the network, is called the primary link. The remaining links (i.e., links that are not the primary link) can be defined as "secondary links" or "other links."

[0056] The TAG configuration follows the legacy TAG configuration.

[0057] Generally, according to the first embodiment, a plurality of TAs are identified. At least some of the plurality of TAs are identified as being associated with at least one link proposed in the present application. A TAT is proposed that is associated with one link (i.e., associated with the TA associated with the link) or that is associated with multiple links (i.e., associated with each TA associated with each of the multiple links).

[0058] A second embodiment relates to indicating multiple TA values.

[0059] According to the prior art, the MAC entity of the UE maintains only one TA per TAG. The TA of each TAG is indicated by the TAC MAC CE or the TAC in the RAR. Ambiguity may occur if the legacy TAC MAC CE and / or the legacy TAC in the RAR is used to indicate the TA when multiple TAs are introduced. In view of the above, some new solutions are proposed to indicate multiple TA values.

[0060] According to a first subembodiment of the second embodiment, DL TRP (or DL ​​beam set) reception is associated with UL panel (or UL beam set) transmission. The association between DL TRP and UL panel (or between DL beam set and UL beam set) can be configured, indicated, predefined, or obtained by a beam management procedure. Thus, the TAC received from the DL TRP (or DL ​​beam set) (i.e., the TAC contained in the TAC MAC CE or the TAC contained in the RAR) is applied to the UL panel (or UL beam set associated with the DL TRP) associated with the DL TRP. Optionally, if TAGs are not allowed (e.g., according to the first subembodiment of the first embodiment), the field "TAG ID" may be ignored.

[0061] According to a second subembodiment of the second embodiment, a new TAC MAC CE is proposed to indicate multiple TAs. The new TAC MAC CE should identify the link, for example, by including a link ID. The new TAC MAC CE should also identify the TAG, for example, by including a TAG ID, if a TAG is used in identifying the TA (for example, according to the second, third, or fourth subembodiment of the first embodiment). If a cell (e.g., a serving cell or a neighboring cell) is used to indicate the link, a field called "cell ID" can be included.

[0062] A new TAC MAC CE may have a fixed size or a variable size. For example, a new TAC MAC CE with a fixed size may indicate a fixed number of TAC fields. A new TAC MAC CE with a variable size may include one or more TAC fields, each indicating the TA value of one link. Whether a new TAC MAC CE has a fixed size or a variable size can be identified by a different LCID. For example, a reserved value of LCID for DL-SCH can be used to identify a new TAC MAC CE. For example, a TAC MAC CE with a fixed size may be identified by a MAC subheader with an LCID of "35," and a TAC MAC CE with a variable size may be identified by a MAC subheader with an LCID of "36." Needless to say, any other value of unoccupied LCID can be used to identify a new TAC MAC CE. When a legacy TAC MAC CE is received under conditions in which a TAG is reused according to the third subembodiment of the first embodiment, the TAC contained within the legacy TAC MAC CE is determined to indicate the TA associated with the primary link.

[0063] Some examples of the new TAC MAC CE formats are shown in Figures 4(a) to 4(e).

[0064] Figure 4(a) shows a first example of a TAC MAC CE, which has a fixed size (e.g., 1 octet) and contains a Timing Advance Command (TAC) (indicating a TA) associated with one link identified by a LINK ID. The LINK ID field in Figure 4(a) has 2 bits. The TAC field in Figure 4(a) has 6 bits.

[0065] Figure 4(b) shows a second example of a TAC MAC CE that has a variable size (e.g., m octets, where m is an integer) and indicates one or more TACs, each associated with one of m links identified by m LINK IDs. Because each LINK ID field has 2 bits, m can only be 1, 2, 3, or 4. Each TAC field in Figure 4(b) has 6 bits.

[0066] Figure 4(c) shows a third example of a TAC MAC CE having a variable size (e.g., 2 to m+1 octets, where m is an integer from 1 to 8) and indicating one or more TACs, each associated with one of LINK0 to LINK7, representing a given link. i (i=0 to 7) is set to 1, LINK i contains the TAC associated with the LINK i (i=0 to 7) is set to 0, LINK i In other words, m is set to 1. i (i=0 to 7). Each of the LINK0 to LINK7 fields in Figure 4(c) has 1 bit. Each TAC field in Figure 4(c) has 8 bits.

[0067] FIG. 4(d) shows a fourth example of a TAC MAC CE having a variable size (e.g., 2 to 2m octets, where m is an integer) and indicating one or more TACs each associated with a link identified by a LINK ID in the TAG ID (e.g., for the second subembodiment of the first embodiment) or a link identified by a TAG ID in the LINK ID (e.g., for the fourth subembodiment of the first embodiment). Each TAG ID field in FIG. 4(d) has 2 bits. Each LINK ID field in FIG. 4(d) has 3 bits. Each TAC field in FIG. 4(d) has 8 bits. Each R (reserved) field in FIG. 4(d) has 1 bit. It is clear that the "TAG ID" field, the "LINK ID" field, and the three "R" fields within an octet can be arranged arbitrarily within that one octet.

[0068] FIG. 4(e) shows a fifth example of a TAC MAC CE having a variable size (e.g., 3 to m+2 octets, where m is an integer from 1 to 8) and indicating (e.g., for a second subembodiment of the first embodiment) one or more TACs each associated with a link identified by a link (indicated by one of LINK0 to LINK7 representing a given link) of a TAG (indicated by a TAG ID). i If (i=0 to 7) is set to 1, the LINK of the TAG indicated by the TAG ID i contains the TAC associated with the LINK i If (i=0 to 7) is set to 0, the LINK of the TAG indicated by the TAG ID i In other words, m is set to 1. i(i=0 to 7). The TAG ID field in Figure 4(e) has 2 bits. Each LINK ID field in Figure 4(e) has 1 bit. Each TA command field in Figure 4(e) has 8 bits. Each R (reserved) field in Figure 4(e) has 1 bit. Oct1 to Oct m+2 can be repeated to indicate the TACs of multiple TAGs with different TAG IDs.

[0069] The number of bits of each field (e.g., the number of bits of the LINK ID field, the number of bits of the TAG ID field, etc.) is not limited to the number of bits shown in each example of TAC MAC CE shown in Figures 4(a) to 4(e), and can be adjusted according to actual use, because the TAC MAC CE can have a variable size.

[0070] According to a third subembodiment of the second embodiment, when a DL TRP (or DL ​​beam set) reception is not associated with a UL panel (or UL beam set) transmission, the MAC RAR used to indicate the TAC is enhanced.

[0071] The legacy MAC RAR can indicate one TA to the UE within the RACH procedure, where that one TA is for one TAG (i.e., for one cell). When multiple TAs, each associated with a link, must be indicated to the UE by the MAC RAR, the legacy MAC RAR needs to be enhanced.

[0072] Specifically, the new MAC RAR should identify the link associated with the TAC, for example, by including the link's Link ID. In addition, the MAC RAR may include one or more TAC fields, each of which indicates a TA associated with a link identified, for example, by a Link ID field. The new MAC RAR should also identify the TAG, if the TAG is used in identifying the TA (for example, according to the second and fourth subembodiments of the first embodiment), for example, by including a TAG ID.

[0073] Similar to the new TAC MAC CE proposed in the second sub-embodiment of the second embodiment, the new MAC RAR can have a fixed size or a variable size. In addition, whether the new TAC MAC CE has a fixed size or a variable size can be identified by a different LCID.

[0074] Existing fields contained within the legacy MAC RAR (e.g., the "Temporary C-RNTI" field and / or the "R" field) can be configured to have new purposes. For example, they can be used to indicate the length of the RAR payload, or the number of TAC fields, or the number of links for which TAC is indicated, or whether one or more TAC fields are included.

[0075] Incidentally, when a legacy MAC RAR is received (e.g., under conditions where a TAG is reused according to the third subembodiment of the first embodiment), the TAC contained in the legacy MAC RAR is determined to indicate the TA associated with the primary link.

[0076] Optionally, the RACH procedure initiated by the PDCCH indication can be enhanced to indicate that the UE can acquire one or more TAs, each of which is associated with a link. This can be achieved by introducing a new DCI format or by reusing DCI format 1_0 by adding some new fields. Alternatively, this can also be achieved by designing RRC or MAC signaling to initiate the RACH procedure or by introducing a new procedure.

[0077] In the second embodiment described above, the TA is indicated by the TAC. Alternatively, the TA is indicated directly by the TAC only for the primary link, the indicated link, or the configured link. Meanwhile, the delta value compared to the primary link, the indicated link, or the configured link can be used to indicate the TA of other links. For example, the TA of other links = delta value + TA of the primary link.

[0078] The third embodiment relates to enhancing the TAT.

[0079] A TAT (e.g., timeAlignmentTimer) is a timer configured by RRC signaling and associated with a link (i.e., associated with the TA of that link) or multiple links (i.e., associated with the TA of each of the multiple links). While a TAT is running and before the TAT expires, the TA of the link associated with the TAT is valid.

[0080] (1) Starting and stopping TAT

[0081] When a TAT associated with one or more links is running, if a (new) TAC indicating a (new) TA for that link is received in an RAR, the received TAC should be ignored.

[0082] When the UE decides to apply a TA for a link, the TAT associated with one or more links is started, e.g., when a TAC for a link is received, the TAT associated with the link (i.e., related to the TA indicated by that TAC) is started.

[0083] When contention resolution is deemed unsuccessful, the TAT associated with the link is stopped.

[0084] In addition, when the contention resolution is deemed successful for the SI request, the TAT associated with the link is stopped after transmitting HARQ feedback for the MAC PDU containing the UE Contention Resolution Identity MAC CE.

[0085] (2) Behavior when TAT is not running

[0086] When the TAT (timeAlignmentTimer) associated with a link is not running, the MAC entity (of the UE) shall not perform any uplink transmissions on that link except for random access preamble and MSGA transmissions.

[0087] Additionally, when the TAT (timeAlignmentTimer) associated with the primary link (if configured) is not running, the MAC entity (of the UE) shall not perform any uplink transmissions on any serving cell or on any other link, except for random access preamble and msgA (message A) transmissions on the SpCell or primary link.

[0088] (3) Behavior when TAT (timeAlignmentTimer) expires

[0089] (3-1) When the TAT associated with a link expires, if there is any TAT associated with the TAG in progress, no uplink transmission should be performed on the link associated with the expired TAT.

[0090] If all TATs associated with the links of a PTAG expire, the following steps are performed: flush all HARQ buffers for all serving cells; if configured, notify RRC to release PUCCH for all serving cells; if configured, notify RRC to release SRS for all serving cells; clear any configured downlink assignments and configured uplink grants; clear any PUSCH resources for semi-persistent CSI reporting; consider all running timeAlignmentTimers as expired; and clear the N allocations specified in TS 38.211 [8] for all TAGs. TA Maintain.

[0091] When all TATs associated with the links of a STAG (i.e., not a PTAG) expire, the following steps are performed for all serving cells belonging to that STAG: flush all HARQ buffers; notify RRC to release PUCCH, if configured; notify RRC to release SRS, if configured; clear any configured downlink assignments and configured uplink grants; clear any PUSCH resources for semi-persistent CSI reporting, if any; and clear the N resources for that STAG as specified in TS 38.211 [8]. TA Maintain.

[0092] If an expired TAT is associated with a configured uplink grant or link associated with an UL resource, transmission on that UL resource is paused or the resource associated with that link is cleared.

[0093] Additionally, if an expired TAT is associated with a link related to a configured uplink grant or UL resource, and there are any TATs associated with other links that are running, transmission on that UL resource is paused or the resources associated with that link are cleared.

[0094] When all TATs associated with the links of a TAG expire, all pre-configured resources associated with that TAG are cleared.

[0095] 5 is a schematic flow chart diagram illustrating one embodiment of a method 500 according to the present application. In some embodiments, the method 500 is performed by a device such as a remote unit (UE). In some embodiments, the method 500 may be performed by a processor executing program code, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, etc.

[0096] The method 500 may be performed by a UE and may include receiving information related to multiple timing advances (TAs) for uplink transmissions to a network 502, where each TA is associated with a link associated with a cell of the network, and determining each TA for performing uplink transmissions to one or more cells of the network from the information received from the transceiver 504. The method may further include receiving one or more timers, where each timer is associated with one or more links and maintains validity of TAs associated with the one or more links. Specifically, the timers relate to a timing advance group (TAG) per link or to a link per TAG.

[0097] In some embodiments, the method may further include transmitting a UE capability that supports multiple TA maintenance.

[0098] In some embodiments, the timers are associated with a Timing Advance Group (TAG) per link or link per TAG.

[0099] The link used to perform initial access is the primary link. The primary link may be associated with one cell. One or more other links are secondary links. Each secondary link may be associated with one or more cells.

[0100] Each TA may be indicated by a timing advance command (TAC). A TAC received from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set may be applied to the uplink (UL) panel associated with that DL TRP or the UL beam associated with that DL beam. Alternatively, each TAC is contained within a TAC medium access control (MAC) control element (CE) that identifies the link associated with that TAC. The TAC MAC CE may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID). Alternatively, a TAC contained within a TAC MAC CE that does not identify a link is determined as the TAC of the primary link. Alternatively, each TAC is contained within a MAC random access response (RAR), which identifies the link associated with that TAC. The MAC RAR may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID).

[0101] If a timer associated with a configured uplink grant or a link related to a UL resource expires, transmission on that UL resource may be paused or the resource associated with that link may be cleared.

[0102] 6 is a schematic flow chart diagram illustrating a further embodiment of a method 600 according to the present application. In some embodiments, the method 600 is performed by an apparatus such as a base unit or a network device. In some embodiments, the method 600 may be performed by a processor executing program code, such as a microcontroller, microprocessor, CPU, GPU, auxiliary processing unit, FPGA, etc.

[0103] The method 600 may be performed by a network device and may include generating 602 information related to multiple timing advances (TAs) for uplink transmissions from a user equipment (UE) to the network device, where each TA is associated with a link between the network device and the UE, and transmitting the information related to the multiple TAs to the UE. The method may further include generating one or more timers, where each timer is associated with one or more links and maintains validity of TAs associated with the one or more links, and transmitting the one or more timers to the UE. Specifically, the timers are related to a timing advance group (TAG) per link or a link per TAG.

[0104] In some embodiments, the method may further include receiving a UE capability that supports multiple TA maintenance.

[0105] In some embodiments, the timers are associated with a Timing Advance Group (TAG) per link or link per TAG.

[0106] The link used to perform initial access is the primary link. The primary link may be associated with one cell. One or more other links are secondary links. Each secondary link may be associated with one or more cells.

[0107] Each TA may be indicated by a timing advance command (TAC). A TAC transmitted from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set may apply to the uplink (UL) panel associated with that DL TRP or the UL beam associated with that DL beam. Alternatively, each TAC is contained within a TAC medium access control (MAC) control element (CE) that identifies the link associated with that TAC. The TAC MAC CE may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID). Alternatively, a TAC contained within a TAC MAC CE that does not identify a link is determined as the TAC of the primary link. Alternatively, each TAC is contained within a MAC random access response (RAR), which identifies the link associated with that TAC. The MAC RAR may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID).

[0108] FIG. 7 is a schematic block diagram illustrating an apparatus according to one embodiment.

[0109] 7, a UE (i.e., a remote unit or terminal device) includes a processor, a memory, and a transceiver, which implements the functions, processes, and / or methods proposed in FIG.

[0110] The UE may comprise a processor and a transceiver coupled to the processor, the processor being configured to: receive, via the transceiver, information related to multiple timing advances (TAs) for uplink transmissions to a network, where each TA is associated with a link associated with a cell of the network; and determine, from the information received via the transceiver, each TA for performing uplink transmissions to one or more cells of the network. The processor may further be configured to receive, via the transceiver, one or more timers, where each timer is associated with one or more links and maintains validity of TAs associated with the one or more links. Specifically, the timers relate to a timing advance group (TAG) per link or to a link per TAG.

[0111] In some embodiments, the processor is further configured to transmit, via the transceiver, a UE capability that supports multiple TA maintenance.

[0112] In some embodiments, the timers are associated with a Timing Advance Group (TAG) per link or link per TAG.

[0113] The link used to perform initial access is the primary link. The primary link may be associated with one cell. One or more other links are secondary links. Each secondary link may be associated with one or more cells.

[0114] Each TA may be indicated by a timing advance command (TAC). A TAC received from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set may be applied to the uplink (UL) panel associated with that DL TRP or the UL beam associated with that DL beam. Alternatively, each TAC is contained within a TAC medium access control (MAC) control element (CE) that identifies the link associated with that TAC. The TAC MAC CE may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID). Alternatively, a TAC contained within a TAC MAC CE that does not identify a link is determined as the TAC of the primary link. Alternatively, each TAC is contained within a MAC random access response (RAR), which identifies the link associated with that TAC. The MAC RAR may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID).

[0115] If a timer associated with a configured uplink grant or a link related to a UL resource expires, transmission on that UL resource may be paused or the resource associated with that link may be cleared.

[0116] 7, a gNB (i.e., a base unit or network device) includes a processor, a memory, and a transceiver. The processor implements the functions, processes, and / or methods proposed in FIG.

[0117] The network device comprises a processor and a transceiver coupled to the processor, the processor being configured to generate information related to multiple timing advances (TAs) for uplink transmissions from a user equipment (UE) to the network device, each TA being associated with a link between the network device and the UE, and to transmit, via the transceiver, the information related to the multiple TAs to the UE. The processor is further configured to generate one or more timers, each timer being associated with one or more links and maintaining validity of TAs associated with the one or more links, and to transmit the one or more timers to the UE. Specifically, the timers are related to a timing advance group (TAG) per link or a link per TAG.

[0118] In some embodiments, the processor is further configured to receive a UE capability that supports multiple TA maintenance.

[0119] In some embodiments, the timers are associated with a Timing Advance Group (TAG) per link or link per TAG.

[0120] The link used to perform initial access is the primary link. The primary link may be associated with one cell. One or more other links are secondary links. Each secondary link may be associated with one or more cells.

[0121] Each TA may be indicated by a timing advance command (TAC). A TAC transmitted from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set may apply to the uplink (UL) panel associated with that DL TRP or the UL beam associated with that DL beam. Alternatively, each TAC is contained within a TAC medium access control (MAC) control element (CE) that identifies the link associated with that TAC. The TAC MAC CE may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID). Alternatively, a TAC contained within a TAC MAC CE that does not identify a link is determined as the TAC of the primary link. Alternatively, each TAC is contained within a MAC random access response (RAR), which identifies the link associated with that TAC. The MAC RAR may be of fixed or variable size, identified by a MAC subheader with a logical channel identifier (LCID).

[0122] The layers of the wireless interface protocol may be implemented by a processor. A memory is connected to the processor for storing various information for driving the processor. A transceiver is connected to the processor for transmitting and / or receiving wireless signals. Needless to say, the transceiver may be implemented as a transmitter for transmitting wireless signals and a receiver for receiving wireless signals.

[0123] The memory may be located internal or external to the processor and may be connected to the processor by a variety of well known means.

[0124] In the above-described embodiments, the elements and features of the embodiments are combined in a predetermined manner. Each element or feature should be considered optional unless otherwise explicitly specified. Each element or feature may be implemented without being associated with other elements or features. Furthermore, an embodiment may be configured by associating several elements and / or features. The order of operations described in an embodiment may be changed. Some elements or features of any embodiment may be included in another embodiment or may be replaced with corresponding elements and features of another embodiment. It is clear that claims not explicitly recited in the claims may be combined with each other to form one embodiment or included in a new claim.

[0125] Embodiments may be implemented by hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, according to a hardware implementation, the example embodiments described herein may be implemented using one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0126] The embodiments may be embodied in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. [Explanation of symbols]

[0127] #1 SpCell #2, #3 SCell

Claims

1. A user equipment (UE) for wireless communications, comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor may be configured to: receiving information related to a plurality of timing advances (TAs) for uplink transmission to a network, each TA associated with a link associated with a cell of the network; receiving one or more time alignment timers, each of the one or more time alignment timers being associated with a corresponding link and relating to a Timing Advance Group (TAG) of the link and maintaining validity of the TA associated with the link; determining, from the received information, respective TAs for performing uplink transmissions to one or more cells of the network; A user equipment (UE) configured to perform the following:

2. A UE as described in claim 1, wherein the at least one processor is configured to cause the UE to start the time alignment timer of the corresponding link when a timing advance command (TAC) for the link is received.

3. The at least one processor in the UE: The UE of claim 1 , further configured to: transmit a UE capability that supports multiple TA maintenance.

4. The UE of claim 1 , wherein each TA is indicated by a timing advance command (TAC).

5. the at least one processor is configured such that the TAC received from a downlink (DL) transmission / reception point (TRP) or DL ​​beam set is applied to an uplink (UL) panel associated with the DL TRP or a UL beam associated with a DL beam. The UE of claim 4.

6. 5. The UE of claim 4, wherein each TAC is contained within a TAC Medium Access Control (MAC) Control Element (CE) that identifies a link associated with the TAC.

7. 7. The UE of claim 6, wherein the TAC MAC CE is of fixed size or variable size identified by a MAC subheader having a logical channel identifier (LCID).

8. The UE of claim 4 , wherein the TAC contained in a TAC MAC CE that does not identify the link is determined as the TAC of a primary link.

9. 5. The UE of claim 4, wherein each TAC is contained within a MAC Random Access Response (RAR) that identifies a link associated with the TAC.

10. 10. The UE of claim 9, wherein the MAC RAR is of a fixed size or a variable size identified by a MAC subheader having a logical channel identifier (LCID).

11. 2. The UE of claim 1, wherein the at least one processor is configured to pause transmission on an uplink resource or clear resources associated with a link when a time alignment timer associated with a configured uplink grant or UL resource expires.

12. 1. A method implemented by a user equipment (UE), comprising: receiving information relating to a plurality of Timing Advances (TAs) for uplink transmission to a network, each TA being associated with a link associated with a cell of the network; receiving one or more time alignment timers, each of the one or more time alignment timers being associated with a corresponding link and relating to a Timing Advance Group (TAG) of the link and maintaining the validity of the TA associated with the link; determining, from the received information, respective TAs for performing uplink transmissions to one or more cells of the network; A method comprising:

13. The method of claim 12, further comprising starting the time alignment timer of the corresponding link when a timing advance command (TAC) of the link is received.

14. A base station for wireless communications, comprising: At least one memory; at least one processor coupled to said at least one memory; Equipped with The at least one processor may be configured to: generating information related to a plurality of timing advances (TAs) for uplink transmissions from a user equipment (UE) to the base station, each TA being associated with a link between the base station and the UE; generating one or more time alignment timers, each of the one or more time alignment timers being associated with a corresponding link and relating to a Timing Advance Group (TAG) of the link and maintaining the validity of the TA associated with the link; transmitting the information relating to a plurality of TAs and the one or more time alignment timers to the UE; A base station configured to perform the above.

15. A processor for wireless communications, comprising: receiving information related to a plurality of timing advances (TAs) for uplink transmission to a network, each TA associated with a link associated with a cell of the network; receiving one or more time alignment timers, each of the one or more time alignment timers being associated with a corresponding link and relating to a Timing Advance Group (TAG) of the link and maintaining validity of the TA associated with the link; determining, from the received information, respective TAs for performing uplink transmissions to one or more cells of the network; a processor configured to:

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