Method executed by wireless terminal, wireless terminal and computer program product

Abstract

The present disclosure is generally directed to a wireless communication network, and specifically discloses a method performed by a wireless terminal, a wireless terminal, and a computer program product. Various example embodiments are described in which a serving cell configures associations between TRPs of the serving cell and a plurality of TAs managed by a wireless terminal and signals the associations, as well as for the wireless terminal to obtain initial and updated TAs for the TRPs. Various additional embodiments are also disclosed, providing an example process for handling uplink time alignment timer (TAT) timeout when multiple TRPs are involved, particularly where TATs of certain TRPs have timeout while TATs of certain other TRPs are still available.

Description

[0001] This application is a divisional of the Chinese Patent Application No. 202380095937.9, filed on April 7, 2023, with the title of “A method of multiple timing advance for uplink transmission in a cell”. TECHNICAL FIELD

[0002] The present disclosure is generally directed to wireless communication networks, and in particular to timing advance (TA) management for multi-point transmission / reception in a cell. BACKGROUND

[0003] In a cellular wireless network, for the purpose of transmission time synchronization, the network side can require a wireless terminal to initiate a transmission by advancing a timing advance (TA) before a reception time scheduled by a network node to account for the transmission time delay for uplink transmission. The amount of TA can be determined by the signal propagation delay between the wireless terminal and the wireless network node. When the wireless terminal moves within a serving cell or moves from one serving cell to another, the TA can change. Therefore, TA management for a wireless terminal is a key aspect in a wireless network. SUMMARY

[0004] The present disclosure is generally directed to wireless communication networks, and in particular to timing advance (TA) management for multi-point transmission / reception in a cell. Specifically, when multiple transmission / reception points (mTRP) are provided for a wireless terminal with mTRP capability in a serving cell, each mTRP can be associated with a TA from the wireless terminal for uplink transmission. These TAs for multiple TRPs can be different. In order for the wireless terminal to correctly determine the TA to apply for a scheduled uplink transmission, the wireless terminal must be provided with the association between the TA identifier and the TRP. The following disclosure describes various example implementations of a serving cell configuring and signaling such an association to a wireless terminal, and the wireless terminal obtaining the initial and updated TAs for these TRPs. Various additional embodiments are also described, providing example procedures for handling uplink time alignment timer (TAT) expiration when multiple TRPs are involved, in particular when the TAs for some TRPs have expired while the TAs for some other TRPs are still available.

[0005] In one example embodiment, a method performed by a wireless terminal communicating with a serving cell is disclosed. The method may include: determining whether a first active timing alignment timer (TAT) and a second active TAT have timed out, the first active TAT and the second active TAT being associated with a first timing advance group (TAG) and a second TAG, respectively, and the first TAG and the second TAG being associated with a first transmit reception point (TRP) and a second TRP, respectively; performing a first procedure when it is determined that the first TAT has timed out while the second TAT is still available; and performing a second procedure, different from the first procedure, when it is determined that both the first TAT and the second TAT have timed out.

[0006] In the above example implementation, the first process includes automatically assigning resources associated with the first TRP to the second TRP.

[0007] In any of the above example implementations, the first process includes suspending resources associated with the first TRP. The first process also includes releasing resources associated with the first TRP. These resources include at least one of PUCCH resources and sounding reference signal (SRS) resources.

[0008] In any of the above example implementations, the second process includes one or more of the following steps: refreshing all Hybrid Automatic Repeat Request (HARQ) buffers for the serving cell; notifying the Radio Resource Control (RRC) entity to release the PUCCH configured for the serving cell; notifying the RRC entity to release the SRS resources configured for the serving cell; clearing the configured downlink allocation and uplink grant for the serving cell; clearing the PUSCH resources used for semi-persistent Channel State Information (CSI) reporting; or maintaining the current timing advance values ​​of the first TAG and the second TAG.

[0009] In any of the above example implementations, the serving cell includes a specific cell (spCell), which is a primary cell or a primary-secondary cell; and the second process also includes setting all running TATs to timeout.

[0010] In any of the above example implementations, the first TAG is mapped to a first control resource set (CORESET) pool configured by the serving cell for the wireless terminal; and the second TAG is mapped to a second CORESET pool configured by the serving cell for the wireless terminal.

[0011] In any of the above example implementations, the first TAG and the second TAG correspond to the first activated Transport Configuration Indicator (TCI) state and the second activated TCI state of the serving cell, respectively. The first activated TCI state and the second activated TCI state are associated with the first TRP and the second TRP, and are in the TCI state list of the serving cell corresponding to multiple TRPs.

[0012] In any of the above example implementations, one of the first TAG and the second TAG is mapped to one of a plurality of control resource set (CORESET) pools configured by the serving cell for the radio terminal; and the other of the first TAG and the second TAG corresponds to an activated TCI state in a TCI state list associated with a plurality of TRPs.

[0013] In any of the above example implementations, the first activated TCI state, the second activated TCI state, or the activated TCI state in the TCI state list is dynamically indicated via MAC CE.

[0014] In some other embodiments, a method performed by a wireless terminal communicating with a serving cell is disclosed. The method may include: determining whether a first time alignment timer (TAT) and a second TAT have timed out, the first TAT and the second TAT being associated with a first time advance group (TAG) and a second TAG, respectively, the first TAG and the second TAG being associated with a primary transmit receiver point (TRP) and a secondary TRP, respectively; performing a first procedure when it is determined that the second TAT has timed out while the first TAT is still available; and performing a second procedure, distinct from the first procedure, regardless of whether the second TAT has timed out, when it is determined that the first TAT has timed out.

[0015] In the above example implementation, the first process includes automatically assigning resources associated with the secondary TRP to the primary TRP. The first process includes suspending resources associated with the secondary TRP. The first process includes releasing resources associated with the secondary TRP. These resources include at least one of PUCCH resources and Sound Reference Signal (SRS) resources.

[0016] In any of the above example implementations, the second process includes one or more of the following steps: refreshing all HARQ caches for the serving cell; notifying the RRC entity to release the PUCCH configured for the serving cell; notifying the RRC entity to release the SRS resources configured for the serving cell; clearing the downlink allocation and uplink grant configured for the serving cell; clearing the PUSCH resources used for semi-persistent CSI reporting; or maintaining the current time advance values ​​of the first TAG and the second TAG.

[0017] In any of the above example implementations, the serving cell includes a specific cell (spCell), which is a primary cell or a primary-secondary cell; and the second process further includes one or more of the following steps: refreshing all HARQ caches for the serving cell; notifying the RRC entity to release the PUCCH configured for the serving cell; notifying the RRC entity to release the SRS resources configured for the serving cell; clearing the downlink allocation and uplink grant configured for the serving cell; clearing the PUSCH resources used for semi-persistent CSI reporting; treating all running TATs as timed out; or maintaining the current time advance values ​​of the first TAG and the second TAG.

[0018] In any of the above example implementations, the first TAG is mapped to a first control resource set (CORESET) pool configured by the serving cell for the wireless terminal; the second TAG is mapped to a second CORESET pool configured by the serving cell for the wireless terminal.

[0019] In any of the above example implementations, the first TAG and the second TAG correspond to the first activated Transport Configuration Indicator (TCI) state and the second activated TCI state of the serving cell, respectively. The first activated TCI state and the second activated TCI state are associated with the primary TRP and the secondary TRP, and are in the TCI state list of the serving cell corresponding to multiple TRPs.

[0020] In any of the above example implementations, one of the first TAG and the second TAG is mapped to one of a plurality of CORESET pools configured by the serving cell for the radio terminal; and the other of the first TAG and the second TAG corresponds to an activated TCI state in a TCI state list associated with a plurality of TRPs.

[0021] In any of the above example implementations, the first activated TCI state, the second activated TCI state, or the activated TCI state in the TCI state list is dynamically indicated via MAC CE.

[0022] In some other embodiments, an electronic device includes a memory for storing instructions and a processor for executing the instructions to implement any of the methods described above.

[0023] In some other embodiments, a computer program product is disclosed, comprising a non-transitory computer-readable program medium having computer code stored thereon. When executed by a processor, the computer code can cause the processor to perform any of the methods described above.

[0024] Other aspects and alternatives to the above embodiments and their implementation are described in more detail in the following drawings, description and claims. Attached Figure Description

[0025] FIG. 1 An example wireless communication network including a wireless access network, a core network, and a data network is shown.

[0026] FIG. 2 An example radio access network is shown, comprising multiple mobile stations / terminals or user equipment (UEs) and radio access network nodes communicating with each other via an over-the-air radio communication interface.

[0027] FIG. 3 An example radio access network (RAN) architecture is shown.

[0028] FIG. 4 An example communication protocol stack is shown in a wireless access network node or wireless terminal device that includes various network layers.

[0029] FIG. 5 An example procedure is shown for the RACH instruction of the PDCCH used to obtain the TRP-specific TA. Detailed Implementation

[0030] The techniques and implementation methods and / or examples of embodiments described in this disclosure can be used to configure and manage inter-point transmission and reception environments in wireless communication networks. In this disclosure, the term "over-the-air interface" is used interchangeably with "air interface" or "radio interface." The term "exemplary" is used to mean "an example of..." and, unless otherwise stated, does not imply an ideal or preferred example, implementation method, or embodiment. Section headings are used in this disclosure to facilitate understanding of the disclosed implementation methods and are not intended to limit the techniques disclosed in a section to the corresponding section. The disclosed implementation methods can also be embodied in various different forms, and therefore, the scope of this disclosure or the claimed subject matter is intended to be construed as not being limited to any of the embodiments presented below. Various implementation methods can be embodied as methods, apparatuses, components, systems, or non-transient computer-readable media. Therefore, embodiments of this disclosure can take the form of, for example, hardware, software, firmware, or any combination thereof.

[0031] This disclosure is generally directed to wireless communication networks, and more particularly to multipoint transmission / reception timing advance (TA) management within a single cell. Specifically, when multiple transmission / reception points (mTRPs) are provided in a serving cell for a wireless terminal with mTRP capability, each mTRP can be associated with a TA from the wireless terminal for uplink transmission. These TAs for the multiple TRPs may be different. In order for the wireless terminal to correctly determine the TA applied to the scheduled uplink transmission, the association between the TA identifier and the TRP must be provided to the wireless terminal. The following disclosure describes various example implementations of the serving cell configuring such an association and signaling such association to the wireless terminal, as well as various additional embodiments of the wireless terminal obtaining the initial and updated TAs for these TRPs. Various additional embodiments are also described, providing example procedures for handling uplink time alignment timer (TAT) timeouts when multiple TRPs are involved, particularly when the TATs of some TRPs have expired while the TATs of some other TRPs are still available.

[0032] Wireless network overview

[0033] like FIG. 1As shown in 100, the example wireless communication network may include wireless terminal devices or user equipment (UEs) 110, 111, and 112, an operator network 102, various service applications 140, and other data networks 150. The wireless terminal devices or UEs may alternatively be referred to as wireless terminals. For example, the operator network 102 may include access network nodes 120 and 121 and a core network 130. The operator network 102 may be configured to transmit voice, data, and other information (collectively referred to as data services) between UEs 110, UEs 111, and UEs 112, between UEs and service applications 140, or between UEs and other data networks 150. Access network nodes 120 and 121 may be configured as various radio access network nodes (WANNs, alternatively referred to as radio base stations) to interact with the UE on one side of the communication session and the core network 130 on the other side. The term "access network" can be used more broadly to refer to a combination of wireless terminal equipment 110, UE 111, and UE 112, as well as access network nodes 120 and 121. The radio access network can alternatively be referred to as a radio access network (RAN). The core network 130 may include various network nodes configured to control communication sessions and perform network access management and service routing. Service applications 140 may be hosted by various application servers deployed outside the core network 130 but connected to it. Similarly, other data networks 150 may also be connected to the core network 130.

[0034] exist FIG. 1 In the example wireless communication network 100, UEs can communicate with each other via a radio access network. For example, UE 110 and UE 112 can be connected to the same access network node 120 and communicate through that node. UEs can communicate with each other via both the access network and the core network. For example, UE 110 can be connected to access network node 120, and UE 111 can be connected to access network node 121; therefore, UE 110 and UE 111 can communicate with each other via access network nodes 120 and 121 and the core network 130. UEs can also communicate with the serving application 140 and the data network 150 via the core network 130. Furthermore, as shown in 113, UEs can communicate directly with each other via sidelink communication.

[0035] FIG. 2An example system diagram of a radio access network 120 is also shown, which includes a WANN 202 providing services to UE 110 and UE 112 via an air interface 204. The radio transmission resources used for the air interface 204 include a combination of frequency, time, and / or spatial resources. Each of UE 110 and UE 112 can be a mobile or fixed terminal device equipped with a mobile access unit (such as a SIM / USIM module) for accessing the wireless communication network 100. Both UE 110 and UE 112 can be implemented as terminal devices, including but not limited to mobile phones, smartphones, tablets, laptops, in-vehicle communication devices, roadside communication devices, sensor devices, smart appliances (such as televisions, refrigerators, and ovens), or other devices capable of wireless communication over a network. FIG. 2 As shown, each of the UEs, such as UE 112, may include transceiver circuitry 206 coupled to one or more antennas 208 to enable wireless communication with WANN 120 or another UE, such as UE 110. Transceiver circuitry 206 may also be coupled to processor 210, which may also be coupled to memory 212 or other storage devices. Memory 212 may be transient or non-transient and may store computer instructions or code therein that, when read and executed by processor 210, cause processor 210 to implement the various methods described herein.

[0036] Similarly, WANN 120 may include a wireless base station or other wireless network access point capable of wirelessly communicating with one or more UEs and the core network 130 via air interface 204. For example, WANN 120 may be implemented without limitation as a 2G base station, 3G nodeB, LTE eNB, 4G LTE base station, 5G NR base station of 5G gNB, 5G centralized unit base station, or 5G distributed unit base station. Each type of WANN can be configured to perform a corresponding set of wireless network functions. WANN 202 may include transceiver circuitry 214 coupled to one or more antennas 216, which may include various forms of antenna towers 218 to enable wireless communication with UE 110 and UE 112. Transceiver circuitry 214 may be coupled to one or more processors 220, which may also be coupled to memory 222 or other storage devices. The memory 222 may be transient or non-transient and may store instructions or code therein that, when read and executed by one or more processors 220, enable one or more processors 220 to perform various functions of the WANN 120 as described herein.

[0037] Such as FIG. 2In the example radio access network described, data packets can be transmitted as Protocol Data Units (PDUs). The data contained therein can be encapsulated into PDUs at various network layers, wrapped with nested and / or layered protocol headers. Once a connection is established between the transmitting and receiving ends (e.g., a Radio Link Control (RRC) connection), PDUs can be transmitted between the transmitting device or transmitting end (these two terms can be used interchangeably) and the receiving device or receiving end (these two terms can also be used interchangeably). Either the transmitting device or the receiving device can be, for example, a... FIG. 2 Wireless terminal devices such as devices 110 and 120, or such as... FIG. 2 Wireless access network nodes, such as node 202. Each device can be both a transmitting device and a receiving device for bidirectional communication.

[0038] FIG. 1 The core network 130 may include various geographically distributed and interconnected network nodes to provide network coverage for the service area of ​​the carrier network 102. These network nodes may be implemented as dedicated hardware network nodes. Alternatively, these network nodes may be virtualized and implemented as virtual machines or software entities. Each of these network nodes may be configured with one or more types of network functions, which together provide configuration and routing capabilities for the core network 130.

[0039] Returning to the Radio Access Network (RAN). FIG. 3 An example RAN 340 communicating with core network 310 and radio terminals UE1 through UE7 is shown. RAN 340 may include one or more radio base stations of various types or WANNs 320 and 321, which may include, but are not limited to, gNBs, eNodeBs, NodeBs, or other types of base stations. RAN 340 may be backhauled to core network 310. For example, WANN 320 may also include multiple individual access network nodes in the form of a centralized unit (CU) 322 and one or more distributed units (DUs) 324 and 326. CU 322 is connected to DU1 324 and DU2 326 via various interfaces (e.g., F1 interfaces). The F1 interface may also include, for example, an F1-C interface and an F1-U interface, which may be used to carry control plane information and user plane data, respectively. In some embodiments, the CU may be a gNB centralized unit (gNB-CU), and the DU may be a gNB distributed unit (gNB-DU). While the various implementations described below are provided in the context of 5G cellular wireless networks, the basic principles described herein are applicable to other types of radio access networks, including but not limited to other generations of cellular networks, as well as Wi-Fi, Bluetooth, ZigBee, and WiMax networks.

[0040] The UE can connect to the network via the WANN 320 through the air interface. The UE can be served by at least one cell. Each cell is associated with a coverage area. These cells can be alternatively referred to as the serving cell. The coverage areas between cells may partially overlap. Each UE can actively communicate with at least one cell and can potentially connect to or be able to connect to more than one cell. FIG. 1 In the example, UE1, UE2, and UE3 can be served by cell 1 330 of DU1, while UE4 and UE5 can be served by cell 2 332 of DU1, and UE6 and UE7 can be served by cell 3 associated with DU2. In some implementations, a UE can be served by two or more cells simultaneously. Each UE can be mobile, and the signal strength and quality from the individual cells at the UE's location may depend on the UE's location and mobility.

[0041] In some example implementations, FIG. 3 The cells shown can alternatively be referred to as serving cells. Serving cells can be grouped into serving cell groups (CGs). A serving cell group can be a primary CG (MCG) or a secondary CG (SCG). In each type of cell group, there may be one primary cell and one or more secondary cells. For example, the primary cell in an MSG can be referred to as PCell, while the primary cell in an SCG can be referred to as PScell. Secondary cells in either an MCG or an SCG can be referred to as SCell. The primary cells, including both PCell and PScell, can be collectively referred to as spCell (specific cell). All of these cells can be referred to as serving cells or cells. Unless specifically distinguished, the terms "cell" and "serving cell" can be used interchangeably in a general manner. The term "serving cell" can refer to a cell that is currently serving the UE, will serve the UE, or may serve the UE. In other words, a "serving cell" may not currently be providing service to the UE. Although the various embodiments described below may sometimes involve one of the above-described serving cell types, the basic principles apply to all types of serving cells in both types of serving cell groups.

[0042] FIG. 4 Further demonstrated in FIGS. 1-3 A simplified view of the various network layers involved in transmitting a user plane PDU from transmitting device 402 to receiving device 404 in an example wireless access network. FIG. 4 It is not intended to include all the basic device components or network layers used to process PDU transmissions. FIG. 4 This illustrates that data packaged by the upper network layer 420 at transmission device 402 can be transmitted via the packet data convergence protocol layer (PDCP layer) of the transmission device. FIG. 4The PHY layer of the transmitting and receiving devices (as shown in 406) and the Media Access Control (MAC) layer 434 and RLC layer 432 of the receiving device are transmitted to the corresponding upper layer 430 (such as the Radio Resource Control layer or RRC layer) at the receiving device 304. Various network entities in each of these layers can be configured to handle the transmission and retransmission of PDUs.

[0043] exist FIG. 4 In the middle, the upper layer 420 can be referred to as layer 3 or L3, while layers such as RLC layer and / or MAC layer and / or PDCP layer ( FIG. 4 Intermediate layers (not shown in the diagram) can be collectively referred to as Layer 2 or L2, while the term Layer 1 is used to refer to layers such as the physical layer and layers associated with radio interfaces. In some cases, the term "lower layer" can be used to refer to the set of L1 and L2, while the term "higher layer" can be used to refer to Layer 3. In some cases, the term "lower layer" can be used to refer to layers among L1, L2, and L3 that are below the current reference layer. Control signaling can be initiated and triggered within each of L1 to L3 and within each of the network layers therein. These signaling messages can be encapsulated and concatenated into packets of the lower layer and transmitted via allocated control or data air radio resources and interfaces. The term "layer" typically includes its various corresponding entities. For example, the MAC layer includes corresponding MAC entities that can be created. For example, Layer 1 includes PHY entities. As another example, Layer 2 includes MAC layer / entities, RLC layer / entities, Serving Data Adaptation Protocol (SDAP) layer, and / or PDCP layer / entities.

[0044] Time advance (TA)

[0045] For communication in the air interface from each UE to the base station, the timing of uplink transmissions can be controlled based on time advance (TA). The time advance of each UE relative to the base station helps ensure that uplink transmissions from all UEs are synchronized when received by the base station. The TA of a particular UE communicating with the base station via the serving cell is essentially dependent on the transmission propagation delay, which is directly related to the path length from the UE to the base station (e.g., DU as described above). UEs typically need to acquire and maintain the TA associated with the base station they are communicating with in order to effectively control the timing of their uplink signal transmissions using any allocated uplink transmission resources.

[0046] In a radio connection based on a random access procedure, the TA can initially be transmitted from the base station to the UE during the random access procedure in the random access response (RAR) after the UE's random access request. The time advance can also be transmitted to the UE via a MAC control unit (MAC CE) that includes a timing advance command (TAC), for example, for TA updates.

[0047] Time advance in multi-transmission reception point (mTRP) transmissions

[0048] Multiple Transmitter-Receiver Point (mTRP) transmission technology allows radio access network nodes and UEs to perform transmit-receive (RX-TX) operations using different antenna panels and / or RF chains. In other words, mTRP technology allows the wireless network and / or UE to transmit / receive multiple radio / data streams simultaneously.

[0049] For example, one or more antenna panels can be provided to the serving cell of the UE from the network side. Each antenna panel can be configured with multiple beams. The beams can be used as TRPs. In this way, mTRP service can be provided to the UE simultaneously by the serving cell via two or more beams from the same or different antenna panels. Using mTRPs provided by the same serving cell can be referred to as intra-cell mTRP. In some implementations, particularly when the UE is located at cell boundaries and cell crossover areas, the serving cell can provide mTRP service to the UE by relying on the TRPs of neighboring cells without handover. For example, a TRP in the serving cell and another TRP from its neighboring cell can be used together to provide mTRP service to the UE. This situation can be referred to as inter-cell mTRP. For example, these neighboring cells can be managed by the same DU or by a DU managed by the same CU. Although it is permissible for all TRPs used by the serving cell to provide mTRP service to the UE to be provided from its neighboring cells, and none of the TRPs to be provided from its own cell, this situation can still be preferably avoided by initiating a service handover to one of the neighboring cells.

[0050] Each TRP can be associated with its own uplink TA, depending on the signal path of the corresponding beam from the UE to the TRP. Among all configurable TRPs, a subset of TRPs (e.g., two or more) can be effectively used to simultaneously provide mTRP services to the UE for uplink transmissions. For example, the UE can be configured with TA groups (TAGs) to manage uplink TAs. Each TAG can be associated with a TA value to be applied to uplink transmissions. The UE can be configured to manage multiple TAGs identified by TAG IDs simultaneously to maintain multiple TAs. In the case of a single TRP (sTRP), one cell can be associated with one TAG, and each TAG can be associated with multiple cells with similar TAs. To ensure the UE applies the correct TA value for uplink transmissions, the UE obtains the TAG ID from the scheduling message from the serving cell for uplink transmissions and uses the corresponding TA maintained via initial acquisition or subsequent updates from the network.

[0051] However, in the mTRP scenario, the serving cell may potentially use multiple TRPs to provide service to the UE. These multiple TRPs can be characterized by different TAs, and therefore a TRP may need to be associated with multiple TAGs. Thus, compared to the sTRP scenario, when providing mTRP service, a cell may need to be associated with multiple TAGs in order for the UE to correctly apply the TA.

[0052] The following further disclosure describes various example implementations for configuring such associations in the serving cell and signaling such associations to the radio terminal, as well as for the radio terminal obtaining the initial and updated TAs of these TRPs. Various additional embodiments are also described, providing example procedures for handling uplink time alignment timer (TAT) timeouts when multiple TRPs are involved, particularly when the TATs of some TRPs have expired while the TATs of some other TRPs are still available.

[0053] Association of TRPs to TAGs for mTRP

[0054] As described above, because each TRP can be associated with its own TA, a serving cell providing multiple TRPs to the UE can be associated with multiple TAs that the UE needs to use for uplink transmissions. These TAs may be different enough that they may not fall into the category that can be represented by a single TAG. In other words, a serving cell may need to be associated with multiple TAGs. The UE may need to identify the appropriate TAG in order to transmit to the corresponding TRP.

[0055] In some example implementations, the serving cell can be directly configured with two tags. For example, the two tags of the serving cell can be referred to as tag-Id and additionalTag-Id. These two tag IDs can be configured directly in the serving cell configuration (e.g., servingCellConfig) and provided to the UE as its serving cell via the corresponding configuration message. Each of these tag IDs can be associated with or mapped to a TRP of the serving cell, and thus mapped to the corresponding TA. This mapping relationship can be made known to the UE through, for example, a predefined specification. When scheduling uplink transmissions for the UE, the scheduling message from the serving cell can contain information that allows the UE to determine the TRP to be used in the uplink transmission, and then the UE can determine the tag ID mapped to the TRP for uplink transmission notified by the serving cell, thereby using the correct TA to perform the uplink transmission.

[0056] In some other example implementations, the mapping between the TAG ID configured for the serving cell and the TRP of the serving cell may be hard-specified as a correspondence between the TAG ID and the control resource set (CORESET) used to schedule uplink transmissions for the UE. For example, a CORESET may include a set of PDCCH resources configured to schedule uplink transmissions for the UE. CORESETs may come from multiple pools, for example, identified as CORESETPoolid=0 and CORESETPoolid=1. Each CORESET pool may include multiple CORESETs. The correspondence between the TAG ID configured for the serving cell and the CORESET pool may be hard-specified. For example, tag-Id may correspond to CORESETPoolid=0, while additionalTag-Id may correspond to CORESETPoolid=1, and vice versa. Such an implementation would require that the PDCCH resources within each CORESET in these CORESET pools can be used to schedule uplink transmission resources used by a corresponding TRP. The TRP associated with a CORESETPoolid is referred to as being represented by the CORESETPoolid.

[0057] Therefore, in this way, uplink transmissions scheduled using control resources within CORESETPoolid=0 will be configured to be received by a TRP associated with tag-Id, while uplink transmissions scheduled using control resources within CORESETPoolid=1 will be configured to be received by another TRP associated with additional tag-Id. Upon receiving a scheduling message (e.g., via a downlink control information (DCI) message), the UE will be able to identify the TAG ID (either tag-Id or additional tag-id) based on the CORESETPoolid to which the control resources of the monitored scheduling message belong and based on the hard-assigned (predefined) relationship between CORESETPoolId and TAG ID.

[0058] In some other example implementations, the serving cell may have a list of Transport Configuration Indicator (TCI) states for UL transmissions. Each of these TCI states (rather than the CORESET pool in the example implementations above) may be associated with a TAG. For example, tag-Id and / or additionalTag-Id are configured under TCI-State. In such example implementations, the TAG to which the TRP belongs is therefore determined by the TRP's currently active / used TCI state. In general, a TCI state may represent a beam or a set of beams.

[0059] In such an example implementation, the association from TAG to TRP can be configured via TCI status. This association can be configured dynamically. For example, the relationship between TCI status and TAG can be dynamically adjusted by the DL Media Access Control (MAC) control unit (CE). In such an example implementation, the DL MAC CE may include at least one of the following information items: 1) Serving Cell Id: indicating the serving cell to which the DL MAC CE applies; 2) BWP Id: indicating the BWP to which the DL MAC CE applies; 3) TCI Status ID: indicating the TCI status ID to which the DL MAC CE applies; 4) tag-Id: associating the TAG indicated by the tag-Id with the TCI status indicated by the TCI status Id field.

[0060] In some other examples, the serving cell may be configured with a TAG indicated by a TAG-Id, and the serving cell may also have a list of TCI states that are activated or indicated for UL transmission, and each of these TCI states may be associated with a TAG or configured with a TAG.

[0061] As an example of associating a TAG with a TRP, a TAG indicated by a tag-Id configured in the serving cell configuration (e.g., servingCellConfig) can be permanently associated with the TRP of the serving cell represented by CORESETPoolId=0. However, a TAG associated with a TRP represented by CORESETPoolId=1 can be determined by the current activation and / or TCI state of that TRP. Conversely, a TAG indicated by a tag-Id configured in the serving cell configuration (e.g., servingCellConfig) can be permanently associated with the TRP of the serving cell represented by CORESETPoolId=1, while a TAG associated with a TRP represented by CORESETPoolId=0 can be determined by the current activation and / or TCI state of that TRP.

[0062] TAG / TA management

[0063] In sTRP, each cell is associated with one TAG. In mTRP, a cell may be associated with multiple TAGs. The TAG list can be configured using the following example implementation.

[0064] In some example implementations, the tags for different TRPs of a serving cell can come from a common pool (e.g., tag-ToAddModList). For example, for a tag belonging to SpCell, the TAG-Id associated with the TRP indicated by CORESETPoolIndex=0 in SpCell can be 0, or the TAG-Id associated with the TRP indicated by CORESETPoolIndex=1 in SpCell can be 0. As another example, the tag-Id configured in the serving cell (e.g., servingCellConfig) is equal to 0.

[0065] In some other example implementations, the tags for different TRPs can come from two separate pools (e.g., tag-ToAddModList, additionalTag-ToAddModList). For example, a tag configured in tag-ToAddModList can be applied to the TRP associated with the TRP indicated by CORESETPoolId=0 in each serving cell, while a tag configured in additionalTag-ToAddModList (additionTAG-Id) can be applied to the TRP associated with CORESETPoolId=1 in each serving cell, and vice versa.

[0066] In such other example implementations, for the TAG to which SpCell belongs, the TAG Id associated with the TRP indicated by CORESETPoolId=0 can be 0, while the additional TAG Id associated with the TRP indicated by CORESETPoolId=1 can be 0, and vice versa.

[0067] For TA acquisition based on DL MAC CE, in one implementation, in order to reuse the existing DL TA command MACCE to indicate the TA of a TAG, if a timing advance command (TAC) is received in the MAC CE, the timing advance command can be applied to the TAG associated with the TRP that receives the TAC.

[0068] In some implementations, a new additional TAC can be introduced into the MAC CE. The payload of this new additional TAC MAC CE can be the same as that of a conventional TAC MAC EC with a different Logical Channel ID (LCID).

[0069] Time alignment timer (TAT) timeout handling for mTRP

[0070] To maintain synchronization of uplink transmissions received from the UE at the base station, the UE can maintain a Time Alignment Timer (TAT) for each TAG. This TAT ​​value can be configured and signaled from the base station in various ways. The configured TAT value for a TAG can be used to indicate how long a previously given TA value associated with the TAG is considered valid. A TAT timeout can indicate that the TA is no longer valid and should be updated before the timing used to control the corresponding uplink transmission. TAT can be started or restarted under various circumstances. For example, TAT can be started or restarted at the UE when it receives a Timing Advance Command (TAC) with an updated TA for the TAG. For example, the TAC can be carried in a MAC Random Access Response (RAR) or a MAC CE.

[0071] In the sTRP scenario, a serving cell is associated with only one TAG and therefore with one TAT. When the TAT associated with the serving cell times out, it indicates that the TA associated with the corresponding TAG is no longer valid and should not be used to control its transmission timing for uplink transmission. Accordingly, the UE will then perform a set of refresh, notification, clearing, and other procedures upon TAT timeout to prevent unintentional uplink transmission using an incorrect TA.

[0072] However, in the mTRP scenario, a serving cell may be associated with multiple TAGs, and each of these TAGs can be managed according to a TAT. Thus, multiple TATs can be initiated, restarted, and timed out at the UE associated with the serving cell. TATs associated with the serving cell may not time out simultaneously. One TAT may time out earlier than another TAT associated with the serving cell. Even if some TATs associated with the serving cell have timed out while others associated with the serving cell have not (meaning those corresponding TATs are still available), the serving cell can still use the TRP corresponding to the untimed TATs to receive uplink transmissions. Therefore, the various procedures that a UE can perform after some TATs time out may differ from the sTRP scenario. Various example implementations are further provided below.

[0073] In some example implementations, all TRPs of the serving cell can be processed on the same basis, and thus, the timeout of a TAT associated with one TRP of the serving cell at the UE may not be treated differently from the timeout of a TAT associated with another TRP of the serving cell. However, the timeout process at the UE may depend on whether the TATs of all TAGs associated with the serving cell have timed out. For the case where the serving cell is associated with two TAGs and therefore with two TATs, exemplary general steps may include:

[0074] • Step 1: The UE determines whether the TAT of the TAG used for the TRP of the serving cell has timed out. If yes, proceed to step 2. If not, end the process.

[0075] • Step 2: The UE determines whether the TAT of the TAG for the two TRPs of the serving cell has timed out. If yes, proceed to step 3. If not, proceed to step 6.

[0076] • Step 3: The UE determines whether the serving cell is a SpCell. If yes, proceed to step 4. If not, proceed to step 5.

[0077] • Step 4: The UE performs the following operations:

[0078] - Refresh all HARQ caches used for all serving cells;

[0079] - Notify the RRC entity to release the PUCCH used for all serving cells (if configured);

[0080] - Notify the RRC entity to release the Sound Reference Signal (SRS) for all serving cells (if configured);

[0081] - Clear any configured downlink allocations and configured uplink grants;

[0082] - Clear any PUSCH resources used for semi-persistent channel state information (CSI) reporting;

[0083] - Treat all running TATs in the MAC entity as timed out;

[0084] - Keep the current TA value of all TAGs (referred to as N) TA So that differential updates can be performed in the future.

[0085] • Step 5: The UE performs the following operations:

[0086] - Refresh all HARQ caches used to serve the cell;

[0087] - Notify the RRC entity to release the PUCCH used for serving the cell (if it has been configured);

[0088] - Notify the RRC entity to release the SRS used for serving the cell (if it has been configured);

[0089] - Clear any configured downlink allocations and configured uplink grants for the serving cell;

[0090] - Clear any PUSCH resources for semi-persistent CSI reporting for the serving cell;

[0091] - Maintain the TA values ​​(called N) of both tags. TA So that differential updates can be performed in the future.

[0092] • Step 6: The UE performs an operation according to the example partial timeout procedure described below, and then ends.

[0093] During the example timeout process, and when two TAGs are associated with and exist for the serving cell, it may be unreasonable to refresh the HARQ cache, release the serving cell's PUCCH / SRS, clear the serving cell's CG and / or SPS when only one of the two TRPs associated with the serving cell has expired (TAT timeout) and the other TRP's TA is still available.

[0094] Therefore, for the serving cell, if the TAT for both TAGs or both TRPs time out, the UE can consider the UL transmission for the serving cell to be out of sync and should therefore refresh the HARQ buffer, release the PUCCH / SRS, clear the CG / SPS, etc. Depending on whether the serving cell is a SpCell, when the TAT for both TAGs or both TRPs time out, the procedure shown in step 4 or 5 above can be performed. However, if the TAT for any one TRP has timed out, and the TAT for the other TRP is still active (e.g., this means that the TA value for that TRP is available), the serving cell can still be used by the UE to perform UL transmissions using the other TRP, and a partial timeout procedure can be performed instead. This partial timeout procedure can be one of the following examples:

[0095] • If the TAT of any TRP in the serving cell has expired, and the TAT of another TRP has not expired, the UE can automatically switch the TCI state (or beam) of its associated TRP with expired TAT to the current TCI state of its associated TRP with non-expired TAT (e.g., the mode changes from mTRP (m=2) to sTRP). In other words, the UL resources associated with its associated TRP with expired TAT (e.g., the associated PUCCH resource(set) / SRS resource(set) / CG / PUSCH resources, etc. for semi-persistent CSI-RS) can be reassociated with the remaining TRPs with non-expired TA;

[0096] • If the TAT of any TRP in the serving cell times out, and the TAT of another TRP does not time out, the UE may suspend the associated UL resources of the TRP whose TAT has timed out (e.g., the associated PUCCH resource(s), SRS resource(s), CG, or SPS, etc.); or

[0097] • If the TAT of any TRP in the serving cell times out, and the TAT of another TRP does not time out, the UE may release the UL resources associated with the TRP whose TAT has timed out (e.g., the associated PUCCH resource(set), SRS resource(set), CG or SPS, etc.).

[0098] In some other example implementations, the TRPs of the serving cell can be treated differently, such that the timeout of the TAT associated with one TRP of the serving cell at the UE can be treated differently from the timeout of the TAT associated with another TRP of the serving cell. For example, suppose two TRPs are associated with a serving cell, one TRP is considered the primary TRP and the other is considered the secondary TRP. For example, the TRP associated with CORESETPoolId=0 can be considered the primary TRP, and the other TRP can be considered the secondary TRP, and vice versa. For another example, for the serving cell, if the TRP's tag is identified by a tag-Id present in the serving cell configuration (e.g., servingCellConfig), then the TRP is considered the primary TRP of the serving cell. If the TRP's tag is identified by a tag-Id present in the TCI state configuration, then the TRP is considered the secondary TRP of the serving cell. For yet another example, for the serving cell, if the TRP's tag is identified by a tag-Id in a list named tag-ToAddModlList, then the TRP is considered the primary TRP of the serving cell. If a TRP's tag is identified by its additionalTag-Id in a list named additionalTag-ToAddModList, then that TRP is considered a secondary TRP of the serving cell. The typical timeout procedure can be implemented using the following example steps:

[0099] • Step 1: The UE determines whether the TAT for the TAG used in the TRP has timed out. If yes, proceed to step 2. If not, end the process.

[0100] • Step 2: The UE determines whether the TRP associated with the timeout TAT is the primary TRP (e.g., whether it is associated with CORESETPoolId=0). If yes, proceed to step 3. Otherwise, proceed to step 6.

[0101] • Step 3: The UE determines whether the serving cell to which the primary TRP belongs is SpCell. If yes, proceed to step 4. Otherwise, proceed to step 5.

[0102] • Step 4: The UE performs the following operations:

[0103] - Refresh all HARQ caches used for all serving cells;

[0104] - Notify RRC to release PUCCHs used for all serving cells (if configured);

[0105] - Notify RRC to release SRS for all serving cells (if configured);

[0106] - Clear any configured downlink allocations and configured uplink grants;

[0107] - Clear any PUSCH resources used for semi-persistent CSI reporting;

[0108] - Treat all running TATs as timed out;

[0109] - Maintain the TA value (called N) for all tags. TA (so that differential updates can be performed in the future)

[0110] • Step 5: The UE performs the following operations:

[0111] - Refresh all HARQ caches used to serve the cell;

[0112] - Notify the RRC entity to release the PUCCH used for serving the cell (if it has been configured);

[0113] - Notify the RRC entity to release the SRS used for serving the cell (if it has been configured);

[0114] - Clear any configured downlink allocations and configured uplink grants for the serving cell;

[0115] - Clear any PUSCH resources for semi-persistent CSI reporting for the serving cell;

[0116] - Maintain the TA value (called N) of this TAG. TA So that differential updates can be performed in the future.

[0117] • Step 6: The UE performs the operation according to the implementation method described below, and then ends.

[0118] Therefore, in the example steps described above, if the TAT of the primary TAG for the serving cell has timed out (e.g., the TAG of the TRP associated with CORESETPoolID=0), the UE then assumes that the TA of the serving cell has timed out (e.g., the serving cell is in a UL out-of-sync state), regardless of the state of the TAT used for the secondary TRP (e.g., the TAG of the TRP associated with CORESETPoolId=1, or the TAG of the TRP associated with the TCI state). In such an example implementation, if the TA of a TRP has timed out and the TRP is a secondary TRP, the serving cell can still be used by the UE to perform UL transmissions using the primary TRP.

[0119] The following could be an example of the process mentioned in step 6, in which the TA of the main TRP has not yet timed out:

[0120] • If the TAT of the secondary TRP times out, but the TAT of the primary TRP does not time out, the UE can automatically switch the TCI state (or beam) of the secondary TRP to the current TCI state of the primary TRP. In other words, UL resources allocated to or associated with the secondary TRP (e.g., related PUCCH resource(set) / SRS resource(set) / CG / SPS, etc.) can be reassigned to or reassociated with the primary TRP.

[0121] • If the TAT of the secondary TRP times out, but the TAT of the primary TRP does not time out, the UE can suspend the associated UL resources (e.g., associated PUCCH resources(set), SRS resources(set), CG, or SPS, etc.) associated with the secondary TRP of the serving cell; or

[0122] • If the TAT of the secondary TRP times out, but the TAT of the primary TRP does not time out, the UE can release the UL resources associated with the secondary TRP of the serving cell (e.g., the associated PUCCH resource(set), SRS resource(set), CG or SPS, etc.).

[0123] In some other example implementations, the two tags of the serving cell can be handled differently, and thus, the TAT timeout of the serving cell's tag at the UE can be handled differently from the TAT timeout of the other tag of the serving cell. For example, suppose two tags are configured within the serving cell, one of which is considered the primary tag of the serving cell, and the other is considered the secondary tag of the serving cell. For example, the tag indicated by the tag-Id existing in servingCellConfig can be considered the primary tag, while the tag indicated by the tag-Id existing in TCI state configuration can be considered the secondary tag, and vice versa. Furthermore, the primary and secondary tags are configurable. For example, the primary tag is indicated by the tag-Id in tag-ToAddModList, and the secondary tag is indicated by the additonaTag-Id in additionalTag-ToAddModList. A typical timeout procedure can be implemented as follows:

[0124] • Step 1: The UE determines whether the TAT used for the serving cell's TAG has timed out. If yes, proceed to Step 2. If not, end the process.

[0125] • Step 2: The UE determines whether the TAG is the primary TAG of the serving cell. If yes, proceed to step 3. Otherwise, proceed to step 6.

[0126] • Step 3: The UE determines whether the serving cell is a SpCell. If yes, proceed to step 4. Otherwise, proceed to step 5.

[0127] • Step 4: The UE performs the following operations:

[0128] - Refresh all HARQ caches used for all serving cells;

[0129] - Notify RRC to release PUCCHs used for all serving cells (if configured);

[0130] - Notify RRC to release SRS for all serving cells (if configured);

[0131] - Clear any configured downlink allocations and configured uplink grants;

[0132] - Clear any PUSCH resources used for semi-persistent CSI reporting;

[0133] - Treat all running TATs as timed out;

[0134] - Maintain the TA value (called N) for all tags. TA (so that differential updates can be performed in the future)

[0135] • Step 5: The UE performs the following operations:

[0136] - Refresh all HARQ caches used to serve the cell;

[0137] - Notify the RRC entity to release the PUCCH used for serving the cell (if it has been configured);

[0138] - Notify the RRC entity to release the SRS used for serving the cell (if it has been configured);

[0139] - Clear any configured downlink allocations and configured uplink grants for the serving cell;

[0140] - Clear any PUSCH resources for semi-persistent CSI reporting for the serving cell;

[0141] - Maintain the TA value (called N) of this TAG. TA So that differential updates can be performed in the future.

[0142] • Step 6: The UE performs the operation according to the implementation method described below, and then ends.

[0143] Therefore, in the example steps described above, if the TAT of the primary TAG has expired for the serving cell, the UE considers the TA of the serving cell to have expired (e.g., considers the serving cell to be in a state of UL asynchrony), regardless of the state of the TAT of the secondary TAG. In such an example implementation, if the TAT of a TAG has expired for the serving cell, and that TAG is a secondary TAG, the serving cell can still be used by the UE to perform UL transmissions using the TRP associated with the primary TAG.

[0144] The following could be an example of the process mentioned in step 6, in which the TA of the primary TAG of the serving cell has not yet timed out:

[0145] • If it is determined that the TAT of the secondary TAG has expired and the TAT of the primary TAG is available, the UE can automatically switch the TCI state (or beam) of the TRP associated with the secondary TAG to the TCI state currently used by the TRP associated with the primary TAG. In other words, the TRP assigned to the secondary TAG / the UL resources associated with the TRP of the secondary TAG (e.g., the relevant PUCCH resource(set) / SRS resource(set) / CG / SPS, etc.) can be switched to the TCI state currently used by the TRP of the primary TAG;

[0146] • If the TAT of the secondary TAG times out, but the TAT of the primary TAG does not time out, the UE can suspend the associated UL resources related to the TRP of the secondary TAG belonging to the serving cell (e.g., associated PUCCH resources(set), SRS resources(set), CG or SPS, etc.); or

[0147] • If the TAT of the secondary TRP times out and the TA of the primary TRP is available, the UE can release the UL resources associated with the failed secondary TRP belonging to the serving cell (e.g., the associated PUCCH resource(set) / SRS resource(set) / CG / SPS, etc.).

[0148] RACH-based TA acquisition for TRP-specific TA from inter-cell mTRP

[0149] Typically, the TA of a TAG can be obtained from the network via a RACH response. After the network provides RACH configuration, the RACH procedure can be initiated by the UE. Alternatively, the RACH procedure can be instructed by the network via, for example, a PDCCH instruction (referred to as a PDCCH-instructed RACH). As a result of the RACH procedure, the TA value transmitted on the uplink can be provided to the UE as part of the Random Access Response (RAR).

[0150] For intra-cell TA acquisition across multiple TRPs, the UE can request random access to the serving cell after receiving the RACH configuration normally, and obtain a TA for one TRP within that serving cell to establish uplink / downlink communication with that serving cell. Subsequently, TAs for other TRPs can be obtained through various means (such as via MAC CE or via SRS).

[0151] In the case of inter-cell mTRP, one or more TRPs from neighboring cells outside the serving cell may be involved. In this situation, the UE may not want to initiate a normal RACH procedure with neighboring cells to obtain the TA specific to those TRPs, which would be similar to a handover procedure. Therefore, obtaining the TRP... Specific The limited purpose of the TA is to implement the RACH procedure instructed by the PDCCH. FIG. 5 The document illustrates an exemplary TRP-specific TA acquisition process based on the RACH procedure instructed by the PDCCH, including the following exemplary steps:

[0152] • Step 0: The network (NW) sends RACH configuration to the UE for use with the RACH instructed by the PDCCH obtained for the TRP-specific TA.

[0153] • Step 1: NW sends a PDCCH command to UE to trigger RACH for TA acquisition.

[0154] • Step 2: The UE selects the RACH resource (RACH timing) for the preamble based on the received PDCCH instruction and the RACH configuration.

[0155] • Step 3: The UE sends the indicated preamble to the NW at the indicated RACH timing (e.g., via MSG 1).

[0156] • Step 4: The UE starts the random access response monitoring window ra-ResponseWindow and monitors the search space of the PDCCH used for RAR reception.

[0157] • Step 5: The UE receives the RAR from the NW (e.g., via MSG 2) and extracts the TAC for the indicated TAG / TRP from the RAT.

[0158] More specifically, in step 0, the RACH configuration for the RACH instructed by the PDCCH can be obtained in the following implementation. RACH configuration transmission / reception can be performed in a manner different from the normal RACH configuration, enabling the UE to identify the RACH resources used for TA acquisition without allocating specific RACH resources. In the example of step 0, the UE can search the broadcast master information block (MIB) of the neighboring cell based on the additional PCT index, and then search the system information block 1 (SIB1) of the neighboring cell based on the received MIB, in order to obtain the RACH configuration for the RACH instructed by the PDCCH in the neighboring cell. In other words, the neighboring cell does not specify specific RACH resources for the UE; instead, the UE identifies the RACH resources for TA acquisition for the TRP-specific TA in the neighboring cell by monitoring the broadcast MIB information and identifying the SIB1 information.

[0159] In some other example implementations of step 0, the RACH configuration for the RACH instructed by the PDCCH for the serving cell and neighboring cells is explicitly configured in the UL BWP of the serving cell. For example, this RACH configuration can be configured for TRP-specific TA acquisition associated with a secondary TRP (e.g., a TRP associated with CORESETPoolId=1). Alternatively, the RACH configuration can be configured for TRP-specific TA acquisition associated with a TAG. In still other examples, the RACH configuration can be configured for TRP-specific TA acquisition associated with an additional PCI index.

[0160] More specifically, for step 1 above, corresponding to the specific RACH configuration described above, the PDCCH instruction used for this RACH procedure may include at least one of the following:

[0161] • TRP indicator, such as CORESETPoolID;

[0162] • TAG instructions, such as: Tag-Id; or

[0163] • Additional cell indications, such as: AdditionalPCIIndex

[0164] More specifically, for step 2 above, the UE can apply the following exemplary sub-steps:

[0165] • Sub-step 2-1: Determine whether the RACH was initiated by a PDCCH command, and whether the serving cell initiating the RACH is configured with more than one TAG. If yes, proceed to sub-step 2-2. If not, proceed to sub-step 3.

[0166] • Sub-step 2-2: Select the RACH resource associated with the TRP / TAG / AdditionalPCI indicated by the PDCCH command or determined by the UE according to the PDCCH command.

[0167] • Sub-steps 2-3: Select RACH resources that are not associated with any TRP / TAG / AdditionalPCI.

[0168] Accordingly, the RACH configuration can be designed to include cell-specific RACH configurations, and then include a list of RACH configurations according to the TRP / TAG / AdditionalPCTIndex mentioned above.

[0169] PDU set

[0170] In some embodiments, multiple PDUs constitute a PDU set. The receiving side requires all PDUs in a PDU set to decode. If one PDU in the PDU set exceeds the delay budget or is known to be lost, the transmitting side should discard all other PDUs in the PDU set.

[0171] Considering that only the PDCP entity (e.g., located in the gNB-CU) knows which PDUs belong to the same PDU set, and the lower layer (e.g., the RLC entity located in the gNB-DU) knows which PDU transmissions failed, the lower layer should notify the PDCP entity of the PDU transmission failure once a PDU transmission failure is detected. If the PDCP entity receives a notification of a first PDU transmission failure, and a second PDU belonging to the same PDU set as the first PDU has been passed to the lower layer, the PDCP entity can pass the information of the second PDU to the lower layer, thereby allowing the lower layer to stop transmitting the second PDU.

[0172] In summary, the lower-layer entity sends the first PDU information (which failed to be transmitted) to the upper-layer entity; and the upper-layer entity sends the second PDU information to the lower layer, thereby preventing the second PDU from being transmitted (e.g., causing the lower layer to stop transmitting the second PDU). When the first and second PDUs belong to the same PDU set, the lower-layer entity is an e RLC entity or gNB-DU, and the upper-layer entity is an e PDCP entity or gNB-CU.

[0173] The above description and accompanying drawings provide specific example embodiments and implementations. However, the described subject matter can be embodied in a variety of different forms, and therefore, the covered or claimed subject matter is intended to be construed as not being limited to any of the example embodiments set forth herein. A reasonably broad scope is intended for the claimed or covered subject matter. Among other things, the subject matter can be embodied as a method, apparatus, component, system, or non-transitory computer-readable medium for storing computer code. Therefore, embodiments can take the form, for example, hardware, software, firmware, storage medium, or any combination thereof. For example, the above-described method embodiments can be implemented by a component, apparatus, or system including a memory and a processor by executing computer code stored in the memory.

[0174] Throughout the specification and claims, terms may have nuanced meanings suggested or implied in the context, rather than just their explicitly stated meanings. Similarly, the phrase "in one embodiment / implementation" as used herein does not necessarily refer to the same embodiment, and the phrase "in another embodiment / implementation" as used herein does not necessarily refer to different embodiments. For example, the subject matter intended to be claimed includes a whole or partial combination of exemplary embodiments.

[0175] Generally, terms can be understood, at least in part, based on their usage in the context. For example, terms such as “and,” “or,” or “and / or” as used herein can include a variety of meanings, which can be understood, at least in part, based on the context in which these terms are used. Typically, “or,” when used in an associative list such as A, B, or C, means A, B, and C (in an inclusive sense) and A, B, or C (in an exclusive sense). Furthermore, the term “one or more” as used herein can be used, at least in part, to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Similarly, terms such as “a,” “an,” or “the” can be understood to indicate either a singular or plural usage, at least in part, based on the context. Moreover, the term “based on” can be understood to not necessarily be intended to convey an exclusive set of factors; rather, it can allow for the presence of other factors that are not necessarily explicitly described, at least in part, based on the context.

[0176] References to features, advantages, or similar language in this specification do not imply that all features and advantages achievable through this solution should be or are included in any single implementation thereof. Rather, references to features and advantages are to be understood as meaning that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of this solution. Therefore, the discussion of features and advantages, as well as similar language, throughout this specification may, but not necessarily, refer to the same embodiments.

[0177] Furthermore, the features, advantages, and characteristics described in this solution can be combined in any suitable manner in one or more embodiments. Based on the description herein, those skilled in the art will recognize that this solution can be practiced without one or more specific features or advantages of a particular embodiment. In other instances, additional features and advantages that may not be present in all embodiments of this solution may be recognized in certain embodiments.

Claims

1. A method performed by a wireless terminal communicating with a serving cell, the method comprising: Determine whether the first activation time alignment timer TAT and the second activation timer TAT have timed out. The first activation timer TAT and the second activation timer TAT are respectively associated with the first time advance group TAG and the second TAG. When it is determined that the first TAT has timed out while the second TAT is still running, execute the first process; as well as When it is determined that both the first TAT and the second TAT have timed out, the second process is executed.

2. The method according to claim 1, wherein, The first process includes suspending the resources associated with the first TAG.

3. The method according to claim 1, wherein, The first process includes releasing the resources associated with the first TAG.

4. The method according to claim 2, wherein, The resources include at least one of the Physical Uplink Control Channel (PUCCH) resources and the Sounding Reference Signal (SRS) resources.

5. The method according to claim 1, wherein, The second process includes one or more of the following steps: Clear all HARQ caches for Hybrid Automatic Repeat Requests (HARQ) used for the serving cell; The Radio Resource Control (RRC) entity is notified to release the PUCCH configured for the serving cell; The RRC entity is notified to release the SRS resources configured for the serving cell; Clear the downlink allocation and uplink grant configured for the serving cell; Clear the Physical Uplink Shared Channel (PUSCH) resources used for semi-persistent Channel State Information (CSI) reporting; or Maintain the current time advance values ​​for the first TAG and the second TAG.

6. The method according to claim 5, wherein: The serving cell includes a specific cell (spCell), which is a primary cell or a primary-secondary cell; and The second process also includes setting all running TATs to timeout.

7. The method according to claim 1, wherein, The first TAG and the second TAG correspond to the first activated Transmission Configuration Indicator (TCI) state and the second activated TCI state of the serving cell, respectively.

8. The method according to claim 1, wherein: One of the first TAG and the second TAG is mapped to one of the multiple control resource set (CORESET) pools configured by the serving cell for the radio terminal; and The first TAG and the second TAG correspond to an activated TCI state in a list of TCI states associated with multiple Transmission Receiver Points (TRPs).

9. The method according to claim 1, wherein, The first process includes not clearing the HARQ cache, or not releasing the PUCCH or SRS of the serving cell.

10. The method according to claim 1, wherein, The list of TCI states used for UL transmission of the wireless terminal is configured in the serving cell, and each TCI state is associated with a TAG.

11. The method according to claim 1, wherein, The RACH configuration for the random access channel RACH directed by the physical downlink control channel PDCCH is configured in the uplink bandwidth portion (UL BWP) of the serving cell, and the RACH configuration is configured for TRP-specific time advance TA acquisition associated with the additional physical cell identifier (PCI) index.

12. A method performed by a wireless terminal communicating with a serving cell, the method comprising: Determine whether the first time alignment timer TAT and the second timer TAT have timed out, the first timer TAT and the second timer TAT are respectively associated with the first time advance group TAG and the second TAG; When it is determined that the second TAT has timed out while the first TAT is still running, execute the first process; as well as When it is determined that the first TAT has expired, the second process is executed regardless of whether the second TAT has expired.

13. The method according to claim 12, wherein, The first process includes suspending the resources associated with the second TAG.

14. The method according to claim 12, wherein, The first process includes releasing the resources associated with the second TAG.

15. The method according to claim 13, wherein, The resources include at least one of the Physical Uplink Control Channel (PUCCH) resources and the Sounding Reference Signal (SRS) resources.

16. The method according to claim 12, wherein, The second process includes one or more of the following steps: Clear all HARQ caches for Hybrid Automatic Repeat Requests (HARQ) used for the serving cell; The Radio Resource Control (RRC) entity is notified to release the PUCCH configured for the serving cell; The RRC entity is notified to release the SRS resources configured for the serving cell; Clear the downlink allocation and uplink authorization configured for the serving cell; Clear the Physical Uplink Shared Channel (PUSCH) resources used for semi-persistent Channel State Information (CSI) reporting; or Maintain the current time advance values ​​for the first TAG and the second TAG.

17. The method according to claim 12, wherein, The first TAG and the second TAG correspond to the first activated Transmission Configuration Indicator (TCI) state and the second activated TCI state of the serving cell, respectively.

18. The method according to claim 12, wherein: One of the first TAG and the second TAG is mapped to one of the multiple control resource set (CORESET) pools configured by the serving cell for the radio terminal; and The first TAG and the second TAG correspond to an activated TCI state in a list of TCI states associated with multiple Transmission Receiver Points (TRPs).

19. A wireless terminal, comprising a processor and a memory, wherein, The processor is configured to read computer code from the memory to cause the wireless terminal to perform the method according to any one of claims 1-18.

20. A computer program product comprising a non-transient computer-readable program medium having computer code stored thereon, the computer code, when executed by a processor, implementing the method of any one of claims 1 to 18.

Images