Multiple timing advance methods for uplink transmission in a single cell

Abstract

This disclosure generally relates to wireless communication networks, and more particularly to time advance (TA) management for multipoint transmission / reception in a single cell. Examples of various implementations are described for a serving cell to configure and signal associations between serving cell TRPs with multiple TAs managed by a wireless terminal, and for the wireless terminal to obtain initial and updated TAs for these TRPs. Various additional embodiments are further disclosed, providing examples of procedures for handling uplink time alignment timer (TAT) expiration when multiple TRPs are involved, particularly when TATs for some TRPs have expired, but TATs for some other TRPs are still available.

Description

Technical Field

[0001] Technical Field This disclosure generally relates to wireless communication networks, and more particularly, to time advance (TA) management for multipoint transmission / reception in one cell.

Background Art

[0002] Background In cellular wireless networks, for transmission time synchronization purposes, the network side may require the wireless terminal to account for the transmission time delay for uplink transmission by starting the transmission by a time advance (TA) before the scheduled reception time by the network node. The amount of TA can be determined by the signal propagation delay between the wireless terminal and the wireless network node. The TA may change as the wireless terminal moves within the serving cell or from one serving cell to another serving cell. Therefore, TA management of the wireless terminal is an important aspect in wireless networks.

Summary of the Invention

Means for Solving the Problems

[0003] Summary This disclosure relates in general to wireless communication networks, and more particularly to time advance (TA) management for multipoint transmission / reception in a single cell. Specifically, when multiple transmission / reception points (mTRPs) are provided in a serving cell for an mTRP-enabled wireless terminal, each mTRP may be associated with a TA for uplink transmissions from the wireless terminal. The TAs of these multiple TRPs may be different. For the wireless terminal to correctly determine which TA to apply to a scheduled uplink transmission, an association between a TA identifier and a TRP must be provided to the wireless terminal. The following disclosure describes examples of various implementations for a serving cell to configure and signal such associations to a wireless terminal, allowing the wireless terminal to obtain initial and updated TAs for these TRPs. Various additional embodiments are further described that provide examples of procedures for handling uplink time alignment timer (TAT) expiration when multiple TRPs are involved, particularly when TATs for some TRPs have expired, but TATs for some other TRPs are still available.

[0004] In one embodiment, a method is disclosed that is performed by a wireless terminal communicating with a serving cell. The method is to determine whether a first active time alignment timer (TAT) and a second active TAT have expired, wherein the first active TAT and the second active TAT are associated with a first time advance group (TAG) and a second TAG, respectively, and the first TAG and the second TAG are associated with a first transmission-receive point (TRP) and a second TRP, respectively; and to perform a first step when it is determined that the first TAT has expired while the second TAT is still available; and to perform a second step when it is determined that both the first TAT and the second TAT have expired, wherein the second step is different from the first step.

[0005] In the above example of implementation, the first step includes automatically assigning resources associated with the first TRP to the second TRP.

[0006] In any one of the above implementation examples, the first step includes suspending the resources associated with the first TRP. The first step also includes releasing the resources associated with the first TRP. The resources comprise at least one of a PUCCH resource and a Sounding Reference Signal (SRS) resource.

[0007] In any of the above examples of implementations, the second step includes one or more of the following: flushing all Hybrid Automatic Repeating Request (HARQ) buffers for the serving cell; notifying the Radio Research Control (RRC) entity to release configured PUCCH for the serving cell; notifying the RRC entity to release configured SRS resources for the serving cell; clearing configured downlink assignments and uplink permissions for the serving cell and clearing PUSCH resources for semi-persistent Channel Status Information (CSI) reporting; or maintaining the current time advance values ​​of the first and second TAGs.

[0008] In any one of the above implementation examples, the serving cell has a special cell (spCell), which is either a primary cell or a primary-secondary cell, and the second step further includes setting all running TATs to expire.

[0009] In any one of the above implementation examples, the first TAG maps to a first control resource set (CORESET) pool consisting of serving cells for wireless terminals, and the second TAG maps to a second CORESET pool consisting of serving cells for wireless terminals.

[0010] In any of the above implementation examples, 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, and the first activated TCI state and the second activated TCI state are associated with the first TRP and the second TRP, and are in a list of serving cell TCL states corresponding to multiple TRPs.

[0011] In any of the above implementation examples, one of the first TAG and the second TAG maps to one of a pool of control resource sets (CORESETs) comprised of serving cells for wireless terminals, and the other of the first TAG and the second TAG corresponds to an activated TCI state in a list of TCI states associated with multiple TRPs.

[0012] In any of the above implementation examples, the first activated TCI state, the second activated TCI state, or the activated TCI state in the list of TCI states is dynamically indicated via MAC CE.

[0013] In some other implementations, a method is disclosed that is performed by a wireless terminal communicating with a serving cell. The method may include determining whether a first time alignment timer (TAT) and a second TAT have expired, wherein the first TAT and the second TAT are associated with a first time advance group (TAG) and a second TAG, respectively, and the first TAG and the second TAG are associated with a primary transmission-receive point (TRP) and a secondary TRP, respectively, and performing a first step when it is determined that the second TAT has expired while the first TAT is still available, and performing a second step when it is determined that the first TAT has expired, regardless of whether the second TAT has expired, wherein the second step is different from the first step.

[0014] In the example implementation described above, the first step includes automatically assigning the resources associated with the secondary TRP to the primary TRP, the first step includes suspending the resources associated with the secondary TRP, and the first step includes releasing the resources associated with the secondary TRP. The resources include at least one of a PUCCH resource and a Sounding Reference Signal (SRS) resource.

[0015] In any of the above implementation examples, the second step includes one or more of the following: flushing all HARQ buffers for the serving cell; notifying the RRC entity to release configured PUCCH for the serving cell; notifying the RRC entity to release configured SRS resources for the serving cell; clearing configured downlink assignments and uplink permissions for the serving cell; clearing PUSCH resources for semi-persistent CSI reporting; or maintaining the current time advance values ​​for the first and second TAGs.

[0016] In any one of the above implementation examples, the serving cell comprises a special cell (spCell), the special cell being either a primary cell or a primary-secondary cell, and the second step includes one or more of the following: flushing all HARQ buffers for the serving cell; notifying the RRC entity to release configured PUCCH for the serving cell; notifying the RRC entity to release configured SRS resources for the serving cell; clearing configured downlink assignments and uplink permissions for the serving cell; clearing PUSCH resources for semi-persistent CSI reporting; considering all running TATs expired; or maintaining the current time advance values ​​for the first and second TAGs.

[0017] In any one of the above implementation examples, the first TAG maps to a first control resource set (CORESET) pool consisting of serving cells for wireless terminals, and the second TAG maps to a second CORESET pool consisting of serving cells for wireless terminals.

[0018] In any of the above implementation examples, 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, and the first activated TCI state and the second activated TCI state are associated with the primary TRP and secondary TRP, and are in a list of TCL states of the serving cell that correspond to multiple TRPs.

[0019] In any of the above implementation examples, one of the first TAG and the second TAG maps to one of a plurality of CORESET pools consisting of serving cells for wireless terminals, and the other of the first TAG and the second TAG corresponds to an activated TCI state in a list of TCI states associated with a plurality of TRPs.

[0020] In any of the above implementation examples, the first activated TCI state, the second activated TCI state, or the activated TCI state in the list of TCI states is dynamically indicated via MAC CE.

[0021] In some other embodiments, the electronic device comprises a memory for storing instructions and a processor for executing instructions in order to carry out any of the methods described above.

[0022] In some further embodiments, a computer program product is disclosed that includes a non-transitory computer-readable program medium having computer code stored thereon. The computer code, when executed by a processor, can cause the processor to implement any one of the above methods.

[0023] The above embodiments and other aspects and alternatives of their implementations are described in more detail in the following drawings, description, and claims.

Brief Description of the Drawings

[0024] Brief Description of the Drawings [Figure 1] FIG. 1 illustrates an example of a wireless communication network including a wireless access network, a core network, and a data network.

[0025] [Figure 2] FIG. 2 illustrates an example of a wireless access network including a plurality of mobile stations / terminals or user equipment (UE) and wireless access network nodes that communicate with each other via an over-the-air wireless communication interface.

[0026] [Figure 3] FIG. 3 shows an example of a radio access network (RAN) architecture.

[0027] [Figure 4] FIG. 4 shows an example of a communication protocol stack in a wireless access network node or a wireless terminal device including various network layers.

[0028] [Figure 5] FIG. 5 illustrates an example of a procedure for PDCCH-ordered RACH to obtain a TRP-specific TA.

Modes for Carrying Out the Invention

[0029] Detailed explanation The technologies and examples of the implementations and / or embodiments described herein may be used to configure and manage time advance in multipoint transmission-reception environments in wireless communication networks. The term “over-the-air radio interface” is used interchangeably with “air interface” or “radio interface” in this disclosure. The term “exemplary” is used to mean “an example of” and does not mean an ideal or preferred example, implementation, or embodiment unless otherwise specified. Section headers are used in this disclosure to facilitate understanding of the implementations disclosed and are not intended to limit the technologies disclosed within a section to the corresponding section only. The implementations disclosed may be further embodied in various different forms, and therefore the scope of this disclosure or claimed subject matter is intended to be construed as not being limited to any of the embodiments described below. Various implementations may be embodied as methods, devices, components, systems, or non-temporary computer-readable media. Thus, embodiments of this disclosure may take the form of, for example, hardware, software, firmware, or any combination thereof.

[0030] This disclosure relates in general to wireless communication networks, and more particularly to time advance (TA) management for multipoint transmission / reception in a single cell. Specifically, when multiple transmission / reception points (mTRPs) are provided in a serving cell for an mTRP-enabled wireless terminal, each mTRP may be associated with a TA for uplink transmissions from the wireless terminal. The TAs of these multiple TRPs may be different. For the wireless terminal to correctly determine which TA to apply to a scheduled uplink transmission, an association between a TA identifier and a TRP must be provided to the wireless terminal. The following disclosure describes examples of various implementations for a serving cell to configure and signal such associations to a wireless terminal, allowing the wireless terminal to obtain initial and updated TAs for these TRPs. Various additional embodiments are further described that provide examples of procedures for handling uplink time alignment timer (TAT) expiration when multiple TRPs are involved, particularly when TATs for some TRPs have expired, but TATs for some other TRPs are still available.

[0031] Wireless Network Overview An example of a wireless communication network shown as 100 in Figure 1 may include wireless terminal devices or user equipment (UEs) 110, 111, and 112, a carrier network 102, various service applications 140, and other data networks 150. Wireless terminal devices or UEs may alternatively be referred to as wireless terminals. The carrier network 102 may include, for example, access network nodes 120 and 121, and a core network 130. The carrier network 110 may be configured within the UEs 110, 111, and 112 to transmit voice, data, and other information (collectively referred to as data traffic) between the UEs and service applications 140, or between the UEs and other data networks 150. The access network nodes 120 and 121 may be configured as various wireless access network nodes (alternatively referred to as wireless base stations, WANN) for interacting with the UEs on one side of a communication session and the core network 130 on the other side. The term “access network” may be more broadly used to refer to the combination of wireless terminal devices 110, 111, 112 and access network nodes 120, 121. The wireless access network may 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 traffic routing. Service applications 140 may be hosted by various application servers located outside the core network 130 but connected to the core network 130. Similarly, other data networks 150 may also be connected to the core network 130.

[0032] In the example of wireless communication network 100 in Figure 1, UEs can communicate with each other via a wireless access network. For example, UEs 110 and 112 can be connected to the same access network node 120 and communicate with each other via the same access network node 120. UEs can communicate with each other via both the access network and the core network. For example, UE 110 may be connected to access network node 120, while UE 111 may be connected to access network node 121, and therefore UEs 110 and UE 111 can communicate with each other via access network nodes 120 and 121, as well as the core network 130. UEs can further communicate with service applications 140 and data networks 150 via the core network 130. Furthermore, UEs can communicate directly with each other via sidelink communication, as shown by 113.

[0033] Figure 2 further illustrates an example system diagram of a wireless access network 120, including a WANN 202 serving UEs 110 and 112 via an over-the-air interface 204. Wireless transmission resources for the over-the-air interface 204 include a combination of frequency, time, and spatial resources. Each of UEs 110 and 112 can be a mobile or fixed terminal device with a mobile access unit, such as a SIM / USIM module, installed for accessing the wireless communication network 100. Each of UEs 110 and 112 may be implemented as a terminal device including, but is not limited to, a mobile phone, smartphone, tablet, laptop computer, vehicle-mounted communication equipment, roadside communication equipment, sensor devices, smart appliances (such as televisions, refrigerators, ovens), or other devices that can communicate wirelessly over the network. As shown in Figure 2, each of the UEs, such as UE 112, may include a transceiver circuit 206 coupled to one or more antennas 208 to perform wireless communication with another UE, such as WANN 120 or UE 110. The transceiver circuit 206 may be coupled to the processor 210, and the processor 210 may be coupled to memory 212 or other storage devices. Memory 212 may be temporary or non-temporary, and may internally store computer instructions or code, which, when read and executed by the processor 210, cause the processor 210 to implement various methods of the methods described herein.

[0034] Similarly, WANN120 may include a wireless base station or other wireless network access point that can communicate wirelessly with one or more UEs via the over-the-air interface 204 and also communicate with the core network 130. For example, WANN120 may be implemented in the form of a 2G base station, a 3G nodeB, an LTE eNB, a 4G LTE base station, a 5G NR base station of a 5G gNB, a 5G central-unit base station, or a 5G distributed-unit base station, without limitation. Each of these types of WANNs may be configured to perform a corresponding set of wireless network functions. WANN202 may include a transceiver circuit 214 coupled to one or more antennas 216, which may include various forms of antenna towers 218, to perform wireless communication with UEs 110 and 112. The transceiver circuit 214 may be coupled to one or more processors 220, which may be further coupled to memory 222 or other storage devices. Memory 222 may be temporary or non-temporary, and may store instructions or code within it, which, when read and executed by one or more processors 220, cause one or more processors 220 to implement various functions of the WANN120 described herein.

[0035] In a wireless access network, such as the example shown in Figure 2, data packets can be transmitted as protocol data units (PDUs). The data contained in a data packet can be packaged as PDUs at various network layers, wrapped in nested and / or hierarchical protocol headers. PDUs can be communicated between a transmitting device or transmission end (these two terms are used interchangeably) and a receiving device or reception end (these two terms are also used interchangeably) once a connection (e.g., a radio link control (RRC) connection) is established between the transmitting and receiving ends. Either the transmitting or receiving device may be a wireless terminal device, such as devices 110 and 120 in Figure 2, or a wireless access network node, such as node 202 in Figure 2. Each device may be both a transmitting and receiving device for bidirectional communication.

[0036] The core network 130 in Figure 1 may include various geographically distributed and interconnected network nodes to provide network coverage of the service area of ​​the carrier network 102. These network nodes may be implemented as dedicated hardware network nodes, or they may be virtualized and implemented as virtual machines or software entities. Each of these network nodes may consist of one or more types of network functions that collectively provide the provisioning and routing capabilities of the core network 130.

[0037] Returning to the Wireless Radio Access Network (RAN), Figure 3 illustrates an example of a RAN 340 communicating with the core network 310 and wireless terminals UE1-UE7. The RAN 340 may include one or more different types of wireless base stations or WANN 320 and 321, including but not limited to gNBs, eNodeBs, NodeBs, or other types of base stations. The RAN 340 can be backhauled to the core network 310. The WANN 320 may further include, for example, a central unit (CU) 322 and a number of separate access network nodes in the form of one or more distributed units (DUs) 324 and 326. The CU 322 is connected to DU1 324 and DU2 326 via various interfaces, for example, an F1 interface. The F1 interface may further include an F1-C interface and an F1-U interface, for example, which can be used to carry control plane information and user plane data, respectively. In some embodiments, the CU may be a gNB central unit (gNB-CU), and the DU may be a gNB distributed unit (gNB-DU). The various implementations described below are provided in the context of 5G cellular wireless networks, but the basic principles described herein are applicable to other generations of cellular networks, as well as other types of wireless access networks, including Wi-Fi, Bluetooth®, ZigBee®, and WiMax networks, but are not limited to these.

[0038] A UE may be connected to the network via an air interface by a WANN320. A UE may be served by at least one cell. Each cell is associated with a coverage area. These cells may alternatively be referred to as serving cells. Coverage areas between cells may partially overlap. Each UE may be actively communicating with at least one cell, but may be potentially connected to or connectable to more than one cell. In the example in Figure 1, UE1, UE2, and UE3 may be served by cell 1 330 of DU1, while UE4 and UE5 may be served by cell 2 332 of DU1, and UE6 and UE7 may be served by cell 3 associated with DU2. In some implementations, a UE may be served by two or more cells simultaneously. Each UE is mobile, and the signal strength and signal quality from various cells in a UE may depend on the location and mobility of the UE.

[0039] In some implementation examples, the cells shown in Figure 3 may be alternatively referred to as serving cells. Serving cells may be grouped into serving cell groups (CGs). A serving cell group may be either a master CG (MCG) or a secondary CG (SCG). Within each type of cell group, there may be one primary cell and one or more secondary cells. For example, a primary cell in an MSG may be called a PCell, while a primary cell in an SCG may be called a PScell. All secondary cells in either an MCG or an SCG may be called SCells. A primary cell containing both a PCell and a PScell ​​may be collectively called a spCell (special cell). All of these cells may be referred to as serving cells or simply cells. The terms “cell” and “serving cell” may be used interchangeably in a general manner unless otherwise specified. The term “serving cell” may refer to a cell that is, will, or can serve a UE. In other words, a “serving cell” does not necessarily have to be currently serving a UE. The various embodiments described below may often refer to one of the serving cell types described above, but the basic principles apply to all types of serving cells in both types of serving cell groups.

[0040] Figure 4 further illustrates a simplified diagram of the various network layers involved in the transmission of a user-plane PDU from a transmitting device 402 to a receiving device 404 in the wireless access network example of Figures 1-3. Figure 4 is not intended to include all essential device components or network layers for handling PDU transmission. Figure 4 illustrates that data packaged by the upper network layer 420 in the transmitting device 402 may be transmitted to the corresponding upper layer 430 (such as the radio resource control or RRC layer) in the receiving device 304, via the physical (PHY) layer and radio interface of the transmitting and receiving devices, such as the packet data convergence protocol layer (PDCP layer, not shown in Figure 4) and radio link control (RLC) layers 422, 406 of the transmitting device, as well as the medium access control (MAC) layer 434 and RLC layer 432 of the receiving device. Various network entities in each of these layers may be configured to handle PDU transmission and retransmission.

[0041] In Figure 4, the upper layer 420 may be referred to as layer 3 or L3, while the intermediate layers such as the RLC layer and / or MAC layer and / or PDCP layer (not shown in Figure 4) may be collectively referred to as layer 2 or L2, and the term layer 1 is used to refer to layers such as the physical layer and radio interface-related layers. In some cases, the term “low layer” may be used to refer to the collection of L1 and L2, and the term “high layer” may be used to refer to layer 3. In some situations, the term “lower layer” may be used to refer to layers within L1, L2, and L3 that are lower than the current base layer. Control signaling may be initiated and triggered within each of L1-L3 and various network layers within them. These signaling messages may be encapsulated, cascaded into lower layer packages, and transmitted over assigned control or data over the air radio resources and interfaces. The term “layer” generally includes its various corresponding entities. For example, the MAC layer includes the corresponding MAC entities that may be created. Layer 1 includes, for example, the PHY entities. Layer 2, in another example, includes the MAC layer / entity, RLC layer / entity, Service Data Adaptive Protocol (SDAP) layer, and / or PDCP layer / entity.

[0042] Time Advance (TA) In the case of communication on an air interface from each UE to a base station, the timing of uplink transmissions can be controlled according to a time advance (TA). The time advance of each UE relative to the base station helps to ensure that uplink transmissions from all UEs are synchronized when received by the base station. The TA of a particular UE communicating with a base station via a serving cell essentially depends on the transmission propagation delay (DU) which is directly related to the path length from the UE to the base station. UEs generally need to acquire and maintain their TA with respect to the base station they communicate with in order to effectively control the timing of their uplink signal transmissions using their allocated uplink transmission resources.

[0043] In a wireless connection based on a random access procedure, the TA may first communicate with the UE from the base station during the random access process in the random access response (RAR) following a random access request by the UE. Time advance may also be communicated to the UE via a MAC control element (MAC CE) that includes a timing advance command (TAC), for example, for TA updates.

[0044] Time advance in multiple transmission-receiving point (mTRP) transmission Multiple Transmission-Receive Point (mTRP) transmission technology allows wireless access network nodes and UEs to use different antenna panels and / or RF chains for transmission-reception (RX-TX). In other words, mTRP technology allows wireless networks and / or UEs to transmit / receive multiple radio / data streams simultaneously.

[0045] For example, a serving cell for a UE may be provided with one or more antenna panels from the network side. Each antenna panel may consist of multiple beams. The beams may be used as TRPs. Thus, mTRP services may be provided to the UE by the serving cell simultaneously via two or more beams from the same or different antenna panels. Using mTRPs provided by the same serving cell may be referred to as intra-cell mTRP. In some implementations, particularly when the UE is at a cell boundary or cell crossover, a serving cell without handover may rely on the TRPs of neighboring cells to provide mTRP services to the UE. For example, an intra-serving cell's TRP and another TRP from a neighboring cell may be used together to provide mTRP services to the UE. Such a situation may be referred to as inter-cell mTRP. Such neighboring cells may be managed, for example, by the same DU or by DUs managed by the same CU. While it may be permissible for a serving cell to have all the TRPs it uses to provide mTRP services to a UE provided by neighboring cells, even if it has none of its own, such a situation can still be preferably avoided by initiating a handover of service to one of the neighboring cells.

[0046] 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. Of all configurable TRPs, a subset of TRPs, for example, two or more TRPs, can be actively used to provide mTRP services to the UE for uplink transmission simultaneously. The UE can be configured, for example, to manage uplink TAs using TAGroups (TAGs). Each TAG can be associated with a TA value for application to uplink transmission. The UE can be configured to manage multiple TAGs simultaneously, identified by TAG IDs, in order to maintain multiple TAs. In a single TRP (sTRP) situation, a cell can be associated with one TAG, but each TAG can be associated with multiple cells having similar TAs. In order for the UE to apply the correct TA value for uplink transmission, the UE can obtain the TAG ID from a scheduling message from the serving cell for uplink transmission and use the corresponding TA, which is maintained either through initial acquisition or subsequent updates from the network.

[0047] However, in the case of an mTRP situation, a serving cell may use multiple TRPs to serve a UE. Multiple TRPs may be characterized by separate TAs, and therefore a TRP may need to be associated with multiple TAGs. Thus, compared to an sTRP situation, a cell may need to be associated with multiple TAGs in order for the UE to correctly apply the TA when an mTRP service is provided.

[0048] The following further disclosures describe examples of various implementations for a serving cell to configure such associations and signal to a wireless terminal, and for the wireless terminal to obtain the initial and updated TAs of these TRPs. Various additional embodiments are further described that provide examples of procedures for handling uplink time alignment timer (TAT) expiration when multiple TRPs are involved, particularly when the TATs for some TRPs have expired, but the TATs for some other TRPs are still available.

[0049] TRP and TAG association for mTRP As mentioned earlier, each TRP can be associated with its own TA, so a serving cell providing multiple TRPs to a UE can be associated with multiple TAs that need to be applied by the UE for uplink transmission. These TAs may be sufficiently distinct and therefore may not fall within the range that can be represented by a single TAG. In other words, a serving cell may need to be associated with multiple TAGs. The appropriate TAG may need to be identified by the UE in order to transmit to the corresponding TRP.

[0050] In some implementation examples, a serving cell may be directly configured with two TAGs. For example, the two TAGs for a serving cell may be called tag-Id and additionalTag-Id. These two TAG IDs may be configured directly in the serving cell configuration (e.g., servingCellConfig) and provided to the UE as that serving cell via a corresponding configuration message. Each of these TAG IDs may be associated with or mapped to one TRP of the serving cell, and therefore mapped to a corresponding TA. The mapping relationship may be known to the UE by, for example, a given specification. When scheduling an uplink transmission for the UE, the scheduling message from the serving cell may include information that allows the UE to determine which TRP should be used for the uplink transmission, and the UE may then determine the TAG IDs that map to the TRP notified by the serving cell for the uplink transmission, thereby using the correct TA to perform the uplink transmission.

[0051] In some further examples of implementations, the mapping between the TAG ID configured for a serving cell and the TRP of the serving cell may be strictly specified as a correspondence between TAG IDs to a set of control resources (CORESET) used to schedule the UE's uplink transmissions. For example, a CORESET may include a set of PDCCH resources configured to schedule the UE's uplink transmissions. A CORESET may consist of multiple pools, identified, for example, as CORESETPoolid=0 and CORESETPoolid=1. Each CORESET pool may contain multiple CORESETs. The correspondence between the TAG ID configured for a serving cell and the CORESET pool may also be strictly specified. For example, a tag-Id may correspond to CORESETPoolid=0, while an additionalTag-Id may correspond to CORESETPoolid=1, and vice versa. Such implementations require that the PDCCH resources within each of these CORESET pools can be used to schedule uplink transmission resources used by a corresponding TRP. A TRP associated with a CORESETPoolid is referred to as being represented by a CORESETPoolid.

[0052] Therefore, in this way, uplink transmissions scheduled using control resources in CORESETPoolid=0 are configured to be received by one TRP associated with the tag-Id, while uplink transmissions scheduled using control resources in CORESETPoolid=1 are configured to be received by another TRP associated with the additionaltag-Id. When a UE receives a scheduling message (for example, via a Downlink Control Information (DCI) message), it can identify the TAG ID (either the tag-Id or additionaltag-Id) based on the CORESETPoolid to which the control resource in the monitored scheduling message belongs, and based on a strictly specified (predetermined) relationship between the CORESETPoolid and the TAG ID.

[0053] In some other examples of implementations, a serving cell may have a list of Transmission Configuration Indicator (TCI) states used for UL transmission. Each of these TCI states (rather than the CORESET pool in the examples of implementations above) may be associated with a TAG. For example, the tag-Id and / or additionalTag-Id are composed of a TCI-State. Thus, in examples of such implementations, the TAG to which a TRP belongs is determined by the TCI state currently activated / used by the TRP. A TCI state can represent a beam or beamset in a general sense.

[0054] In an example of such an implementation, the association may be configured from TAG to TRP via the TCI state. Such an association may be configured dynamically. For example, the relationship between TCI-state and TAG may be dynamically adjusted by a DL media access control (MAC) control element (CE). In an example of this implementation, the DL MAC CE may include at least one of the following information items: 1) Serving cell Id to represent the serving cell to which the DL MAC CE applies; 2) BWP Id to represent the BWP to which the DL MAC CE applies; 3) TCI state ID to represent the TCI state Id to which the DL MAC CE applies; and 4) tag-Id to associate the TAG indicated by the tag-Id with the TCI state indicated by the TCI state ID field.

[0055] In some other examples, a serving cell may consist of 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 use in UL transmission, each of which may be associated with a TAG or consist of a TAG.

[0056] As an example of associating a TAG with a TRP, a TAG indicated by a tag-Id configured in a serving cell configuration (e.g., servingCellConfig) may be fixedly associated with the TRP of the serving cell represented by CORESETPoolId=0. However, a TAG associated with a TRP represented by CORESETPoolId=1 may be determined by the currently activated and / or used TCI state for this TRP. Or, conversely, a TAG indicated by a tag-Id configured in a serving cell configuration (e.g., servingCellConfig) may be fixedly associated with the TRP of the serving cell represented by CORESETPoolId=1, whereas a TAG associated with a TRP represented by CORESETPoolId=0 may be determined by the currently activated and / or used TCI state for this TRP.

[0057] TAG / TA management In sTRP, each cell is associated with one TAG. In mTRP, a cell can be associated with multiple TAGs. The TAG list can be constructed using the following implementation examples.

[0058] In some implementation examples, tags for different TRPs of a single serving cell may come from a common pool (e.g., tag-ToAddModList). For example, with respect to the tag to which a SpCell belongs, the TAG-Id associated with the TRP indicated by CORESETPoolIndex=0 in the SpCell may be 0, and the TAG-Id associated with the TRP indicated by CORESETPoolIndex=1 in the SpCell may also be 0. In another example, the tag-Id configured in a serving cell (e.g., servingCellConfig) is equal to 0.

[0059] In some other implementation examples, tags for different TRPs may come from two separate pools (e.g., tag-ToAddModList, additionalTag-ToAddModList). For example, tags configured in tag-ToAddModlist may apply to TRPs associated with the TRP indicated by CORESETPoolId=0 in each serving cell, while tags configured in additionalTag-ToAddModList(additionTAG-Id) may apply to TRPs associated with CORESETPoolId=1 in each serving cell, and vice versa.

[0060] In other implementation examples, with respect to the TAG to which SpCell belongs, the TAG ID associated with the TRP indicated by CORESETPoolId=0 may be 0, but the additionalTAG ID associated with the TRP indicated by CORESETPoolId=1 may be 0, and vice versa.

[0061] Regarding DL MAC CE-based TA acquisition, in one implementation, in order to reuse an existing DL TA command MAC CE to indicate the TA of a TAG, if a Time Advance Command (TAC) is received within MAC CE, the Timing Advance Command may be applied to the TAG associated with the TRP from which the TAC was received.

[0062] In some implementations, a new additional TAC may be introduced within the MAC CE. The payload of the new additional TAC MAC CE may be the same as that of a legacy TAC MAC CE, but with a different logical channel ID (LCID).

[0063] Time Alignment Timer (TAT) Expiration Handling for mTRP To maintain synchronization for receiving uplink transmissions from the UE at the base station, a Time Alignment Timer (TAT) may be maintained by the UE for each TAG. Such TAT values ​​may be configured in various ways and signaled from the base station. The configured TAT value for a TAG may be used to indicate the time for which a previously given TA value associated with the TAG is considered valid. Expiration of the TAT may indicate that the TA is no longer valid and should be updated before it is used to control the timing of the corresponding uplink transmission. The TAT can be started or restarted in various circumstances. For example, the TAT may be started or restarted at the UE when the UE receives a Timing Advance Command (TAC) with an updated TA for the TAG. The TAC may be carried, for example, in a MAC Random Access Response (RAR) or MAC CE.

[0064] In an sTRP situation, a serving cell is associated with only one TAG, and therefore only one TAT. When the TAT associated with a serving cell expires, it indicates that the TA associated with the corresponding TAG is no longer valid and that the uplink should not be transmitted using such an expired TA to control its transmission timing. In response, the UE then performs a set of flushing, notification, clearing, and other procedures upon TAT expiration to prevent accidental uplink transmission using the wrong TA.

[0065] However, in an mTRP situation, a serving cell may be associated with multiple TAGs, each of which may be managed according to a TAT. Thus, multiple TATs may be started, restarted, and terminated in the UE with respect to the serving cell. TATs associated with a serving cell may not expire simultaneously. One TAT may expire earlier than another TAT associated with a serving cell. In a situation where some TATs associated with a serving cell have expired, but others have not (meaning their corresponding TAs are still available), the serving cell can still receive uplink transmissions using the TRPs corresponding to the non-expired TAs. Therefore, the various procedures that the UE may take after the expiration of several TATs may differ from those in an sTRP situation. Further examples of various implementations are provided below.

[0066] In some implementation examples, all TRPs of a serving cell may be processed on the same basis, and therefore, the expiration of TAT associated with one TRP of a serving cell in the UE does not have to be processed as the difference from the expiration of TAT associated with another TRP of the serving cell. However, the expiration procedure in the UE may depend on whether the TATs of all TAGs associated with the serving cell have expired. In a situation where a serving cell is associated with two TAGs, and therefore two TATs, an example of a common step may include the following: Step 1: The UE determines whether the TAT of the TAG for the serving cell's TRP has expired. If so, proceed to Step 2. Otherwise, proceed to Terminate. Step 2: The UE determines whether the TAT of the TAG for both TRPs in the serving cell has expired. If so, proceed to Step 3. Otherwise, proceed to Step 6. Step 3: The UE determines whether the serving cell is a SpCell. If so, proceed to Step 4. Otherwise, proceed to Step 5. Step 4: The UE performs the following actions: - Flushes all HARQ buffers in all serving cells; - If configured, notify the RRC entity to release PUCCH for all serving cells; - If configured, notify the RRC entity to release a Sounding Reference Signal (SRS) for all serving cells; - Clear any configured downlink assignments and configured uplink permissions; - Clear any PUSCH resources for semi-persistent Channel Status Information (CSI) reporting; - All running TATs within the MAC entity are considered expired; - The current TA values ​​of all TAGs (N so that future updates can be performed incrementally). TA (referring to) maintain. Step 5: The UE performs the following actions: - Flushes all HARQ buffers in the serving cell; - If configured, notify the RRC entity to release the PUCCH of the serving cell; - If configured, notify the RRC entity to release the SRS of the serving cell; - Clear any configured downlink assignments and configured uplink permissions for serving cells. - Clear any PUSCH resources for semi-permanent CSI reporting to serving cells; -TA values ​​for both TAGs (N so that future updates can be done differentially) TA (referring to) maintain. Step 6: The UE operates according to an example of a partial expiration procedure, as described below, and then terminates.

[0067] In the example of a partial expiration procedure, if two TAGs exist associated with a serving cell, it may not be appropriate to flush the HARQ buffer, release the serving cell's PUCCH / SRS / , and clear the serving cell's CG and / or SPS when only the TA of one of the two TRPs associated with the serving cell has expired (with an expired TAT), while the TA of the other TRP is still available.

[0068] Thus, with respect to a serving cell, if the TAT for both TAGs expires, or if the TAT for both TRPs expires, the UE may consider the UL transmission to the serving cell to be out of sync, and therefore the HARQ buffer should be flushed, PUCCH / SRS / should be released, CG / SPS should be cleared, etc. The procedure described above in step 4 or step 5 may be performed when the TAT for both TAGs expires, or when the TAT for both TRPs expires, depending on whether the serving cell is a SpCell or not. However, if the TAT for one of the TRPs has expired, but the other TAT is still active (meaning, for example, that a TA value for that TRP is available), the serving cell is still available for the UE to perform UL transmission with the other TRP, and a partial expiration procedure may be performed instead. A partial expiration procedure may be one of the following examples. If the TAT of one of the serving cells' TRPs has expired, but the TATs of the other TRPs have not, the UE may automatically switch the TCI state (or beam) of the TRP with the expired associated TAT to the current TCI state of the TRP with the non-expired associated TAT (for example, the mode changes from mTRP (m=2) to sTRP). In other words, UL resources associated with the TRP with the expired associated TAT (e.g., associated PUCCH resources (sets) / SRS resources (sets) / CG / PUSCH resources for a semi-persistent CSI-RS, etc.) may be reassociated with the remaining TRPs with non-expired TATs; ·If the TAT of one of the serving cells' TRPs has expired, the UE may suspend the associated UL resources (e.g., associated PUCCH resources(set), SRS resources(set), CG, or SPS, etc.) associated with the TRP whose associated TAT has expired; or If the TAT of one of the serving cells' TRPs has expired, but the TATs of the other TRPs have not expired, the UE may release the UL resources associated with the TRP whose associated TAT has expired (e.g., associated PUCCH resources(set), SRS resources(set), CG, or SPS, etc.).

[0069] In some other implementation examples, the TRPs of a serving cell may be handled differently, and therefore, the expiration of a TAT associated with one TRP of a serving cell in the UE may be handled differently from the expiration of a TAT associated with another TRP of the serving cell. For example, suppose two TRPs are associated with a serving cell, one of which is treated as the primary TRP and the other as the secondary TRP. For example, the TRP associated with CORESETPoolId=0 may be considered the primary TRP, and the other TRP may be considered the secondary TRP, or vice versa. In another example, with respect to a serving cell, a TRP is considered the primary TRP of the serving cell if the TAG to which it belongs is identified by a tag-Id present in the serving cell configuration (e.g., servingCellConfig). A TRP is considered the secondary TRP of the serving cell if the TAG to which it belongs is identified by a tag-Id present in the TCI state configuration. In another example, with respect to a serving cell, if the TAG to which the TRP belongs is identified by its tag-Id from a list named tag-ToAddModlList, then the TRP is considered the primary TRP of the serving cell. If the TAG to which the TRP belongs is identified by its additionalTag-Id from a list named additionalTag-ToAddModList, then the TRP is considered the secondary TRP of the serving cell. A typical expiration procedure may be performed as an example of the following steps. Step 1. The UE determines whether the TAG's TAT ​​for the TRP has expired. If so, proceed to Step 2. Otherwise, proceed to Exit. Step 2: The UE determines whether the TRP associated with the expired TAT is a primary TRP (for example, whether it is associated with CORESETPoolId=0). If so, proceed to Step 3. Otherwise, proceed to Step 6. Step 3: The UE determines whether the serving cell to which the primary TRP belongs is a SpCell. If so, proceed to Step 4. Otherwise, proceed to Step 5. Step 4: The UE performs the following actions: - Flushes all HARQ buffers for all serving cells; - If configured, notify RRC to release PUCCH for all serving cells; - If configured, notify the RRC to release SRS for all serving cells; - Clear any configured downlink assignments and configured uplink permissions; - Clear any PUSCH resources for semi-permanent CSI reports; - All running TATs are considered expired; -TA values ​​for all TAGs (N so that future updates can be performed incrementally) TA (referring to) maintain Step 5: The UE performs the following actions: - Flushes all HARQ buffers for serving cells; - If configured, notify the RRC entity to release the PUCCH for the serving cell; - If configured, notify the RRC entity to release the SRS for the serving cell; - Clear any configured downlink assignments and configured uplink permissions for serving cells. - Clear any PUSCH resources for semi-permanent CSI reporting to serving cells; - The TA value of this TAG (N so that future updates can be performed incrementally) TA (referring to) maintain. Step 6: The UE operates according to the implementation described below, and then terminates.

[0070] Therefore, in the example of the steps above, with respect to the serving cell, the TAT of the primary TAG has expired (e.g., the TAG of the TRP associated with CORESETPoolID=0), and the UE then considers the TA for the serving cell to be expired (e.g., the serving cell is considered to be in a UL out-of-sync state), regardless of the state of the TAT for the secondary TRP (e.g., the TAG of the TRP associated with CORESETPoolId=1, or associated with the TCI state). In an example of such an implementation, if the TA of a TRP has expired and the TRP is a secondary TRP, the serving cell may still be available for the UE to perform UL transmission on the primary TRP.

[0071] An example of the procedure referenced in Step 6, where the TA for the primary TRP has not expired, may be as follows: The UE may automatically switch the TCI state (or beam) of a secondary TRP to the current TCI state of the primary TRP if the TAT for the secondary TRP has expired and the TAT for the primary TRP has not expired. In other words, UL resources assigned to or associated with a secondary TRP (e.g., associated PUCCH resources(set) / SRS resources(set) / CG / SPS, etc.) may be reassigned to or reassociated with the primary TRP; ·UE may suspend associated UL resources (e.g., associated PUCCH resources(set), SRS resources(set), CG, or SPS, etc.) of a serving cell if the TAT of the secondary TRP has expired but the TAT of the primary TRP has not expired; or If the TAT of the secondary TRP has expired but the TAT of the primary TRP has not expired, the UE may release the UL resources associated with the secondary TRP of the serving cell (e.g., associated PUCCH resources(set), SRS resources(set), CG, or SPS, etc.).

[0072] In some other implementation examples, the two tags of a serving cell may be handled differently, and therefore, the expiration of the TAT of a serving cell's tag in the UE may be handled differently from the expiration of the TAT of the other tag of the serving cell. For example, suppose two tags are configured within a serving cell, one of which is treated as the primary tag for the serving cell and the other as the secondary tag for the serving cell. For example, the tag indicated by the tag-Id present in servingCellConfig may be considered the primary tag, while the tag-Id present in TCI state configuration may be considered the secondary tag, or vice versa. In another example, the primary and secondary tags are configurable. In yet another example, the primary tag is the tag indicated by the tag-Id from tag-ToAddModList, and the secondary tag is the tag indicated by additionalTag-Id from additionalTag-ToAddModList. A general expiration procedure may be performed as an example of the following steps. Step 1. The UE determines whether the TAG's TAT ​​for the serving cell has expired. If so, proceed to Step 2. Otherwise, proceed to Terminate. Step 2: The UE determines whether the TAG is the primary TAG for the serving cell. If so, proceed to Step 3. Otherwise, proceed to Step 6. Step 3: The UE determines whether the serving cell is a SpCell. If so, proceed to Step 4. Otherwise, proceed to Step 5. Step 4: The UE performs the following actions: - Flushes all HARQ buffers for all serving cells; - If configured, notify RRC to release PUCCH for all serving cells; - If configured, notify the RRC to release SRS for all serving cells; - Clear any configured downlink assignments and configured uplink permissions; - Clear any PUSCH resources for semi-permanent CSI reports; - All running TATs are considered expired; -TA values ​​for all TAGs (N so that future updates can be performed incrementally) TA (referring to) maintain Step 5: The UE performs the following actions: - Flushes all HARQ buffers for serving cells; - If configured, notify the RRC entity to release the PUCCH for the serving cell; - If configured, notify the RRC entity to release the SRS for the serving cell; - Clear any configured downlink assignments and configured uplink permissions for serving cells; - Clear any PUSCH resources for semi-permanent CSI reporting to serving cells; - The TA value of this TAG (N so that future updates can be performed incrementally) TA (referring to) maintain. Step 6: The UE operates according to the implementation described below, and then terminates.

[0073] Therefore, in the example of the steps above, with respect to the serving cell, the TAT of the primary TAG expires, and thereafter the UE considers the serving cell's TA to be expired, regardless of the state of the secondary TAG's TAT ​​(for example, considering the serving cell to be in a UL out-of-sync state). In an example of such an implementation, with respect to the serving cell, if the TAG's TAT ​​has expired and the TAG is a secondary TAG, the serving cell may still be available for the UE to perform UL transmission with the TRP associated with the primary TAG.

[0074] An example of the procedure referenced in step 6, where the TA of the serving cell's primary TAG has not expired, may be as follows: If the UE determines that the TAT for the secondary TAG has expired and the TAT for the primary TAG is available, it may automatically switch the TCI state (or beam) of the TRP associated with the secondary TAG to the currently used TCI state of the TRP associated with the primary TAG. In other words, UL resources assigned to / associated with TRPs belonging to the secondary TAG (e.g., associated PUCCH resources(set) / SRS resources(set) / CG / SPS, etc.) may be switched to the currently used TCI state of the TRP belonging to the primary TAG. ·UE may suspend associated UL resources (e.g., associated PUCCH resources(sets), SRS resources(sets), CGs, or SPSs, etc.) belonging to the secondary TAG of a serving cell if the TAT of the secondary TAG has expired but the TAT of the primary TAG has not expired; or If the TAT of the secondary TRP has expired and the TA of the primary TRP is available, the UE may release the UL resources associated with the failed secondary TRP (e.g., associated PUCCH resources(set) / SRS resources(set) / CG / SPS, etc.) belonging to the secondary TAG of the serving cell.

[0075] RACH-based TA acquisition for TRP-specific TAs from inter-cell mTRPs Generally, the TA for a TAG can be obtained from the network via a RACH response. The RACH process can be initiated by the UE after the RACH configuration has been provided by the network. Alternatively, the RACH process may be ordered by the network via a PDCCH sequence, for example, referred to as a PDCCH-ordered RACH. The TA value for uplink transmission resulting from the RACH process can be provided to the UE as part of a Random Access Response (RAR).

[0076] In the case of obtaining intra-cell TAs for multiple TRPs, the UE may, after receiving the RACH configuration as usual, request random access to the serving cell and obtain a TA for one of the serving cell's TRPs to establish uplink / downlink communication with the serving cell. Subsequently, TAs for the other TRPs can be obtained in various ways, such as MAC CE or SRS.

[0077] In inter-cell mTRP situations, one or more TRPs from neighboring cells other than the serving cell may be involved. In such situations, it may be undesirable for the UE to initiate a normal RACH procedure with neighboring cells in order to obtain TRP-specific TAs, similar to a handover procedure. Therefore, a PDCCH ordering RACH procedure may be performed for the limited purpose of obtaining TRP-specific TAs. An example of a TRP-specific TA acquisition procedure based on the PDCCH ordering RACH process is illustrated in Figure 5, and includes an example of the following steps. Step 0: The network (NW) sends the RACH Configuration to the PDCCH ordering RACH for TRP-specific TA acquisition to the UE. Step 1: The network sends a PDCCH sequence to the UE to trigger RACH in order to obtain TA. Step 2: The UE, in conjunction with the RACH Configuration, selects the RACH resource (RACH occasion) for the preamble according to the received PDCCH order. Step 3: The UE sends the preamble shown on the indicated RACH occasion to the NW (e.g., via MSG1). Step 4: The UE starts a random access response monitoring window, the ra-ResponseWindow, and monitors the search space for the PDCCH for RAR reception. Step 5: The UE receives the RAR from the NW (e.g., via MSG2) and extracts the TAC with the RAT for the indicated TAG / TRP.

[0078] More specifically, in step 0, the RACH configuration for PDCCH-ordered RACH may be obtained in the following implementation form. RACH configuration transmission / reception may be performed in a manner distinct from normal RACH configuration so that the UE can identify RACH resources for TA acquisition without being assigned specific RACH resources. In the example of step 0, the UE may, in order to obtain the RACH configuration of a neighboring cell for PDCCH-ordered RACH, look up the broadcasted neighboring cell's main information block (MIB) according to an additional PCT index, additionalPCIIndex, and then look up the neighboring cell's system information block 1 (SIB1) according to the received MIB. In other words, no specific RACH resource is assigned to the UE by the neighboring cell; instead, the UE identifies the RACH resource for TA acquisition of TRP-specific TAs in the neighboring cell by monitoring the broadcast MIB information to identify the SIB1 information.

[0079] In some other implementation examples of Step 0, the RACH configuration for PDCCH ordering RACH for serving cells and neighboring cells is explicitly configured in the UL BWP of the serving cell. For example, the RACH configuration may be configured for TRP-specific TA acquisition associated with a secondary TRP (e.g., a TRP associated with CORESETPoolId=1). In another example, the RACH configuration may be configured for TRP-specific TA acquisition associated with a TAG. In several other examples, the RACH configuration may be configured for TRP-specific TA acquisition associated with an additional PCI index.

[0080] More specifically regarding step 1 above, the PDCCH sequence for the RACH procedure may include at least one of the following pieces of information, corresponding to the specific RACH configuration described above. • TRP indication, e.g., CORESETPoolID; • TAG indication, e.g.: Tag-Id; or • Additional cell indications, e.g., AdditionalPCIIndex

[0081] For further details on step 2 above, the following example substeps may be applied by the UE. Substep 2-1: Determine whether RACH is initiated by the PDCCH sequence and whether the serving cell from which RACH is initiated consists of more than one TAG. If so, proceed to substep 2-2. Otherwise, proceed to substep 3. Substep 2-2: Select the RACH resource associated with the TRP / TAG / AdditionalPCI, as indicated by the PDCCH sequence or determined by the UE according to the PDCCH sequence. Substep 2-3: Select RACH resources that are not associated with TRP / TAG / AdditionalPCI.

[0082] In response to this, the RACH configuration may be designed to include both cell-specific RACH configurations, and then a list of RACH configurations according to the TRP / TAG / AdditionalPCTIndex described above.

[0083] PDU Set In some embodiments, multiple PDUs constitute a PDU set. All PDUs within a single PDU set are required by the receiver for decoding. If it is known that one of the PDUs in a PDU set exceeds the delay budget or is lost, all other PDUs in the PDU set should be discarded by the transmitter.

[0084] Given that only the PDCP entity (e.g., located within the gNB-CU) knows which PDUs belong to the same PDU set, and that the lower layer (e.g., the RLC entity located within the gNB-DU) knows which PDU(s) failed to transmit, the lower layer should notify the PDCP entity when it detects a PDU that it failed to transmit. If the PDCP entity receives notification that the first PDU(s) failed to transmit successfully and that a second PDU(s) belonging to the same PDU set as the first PDU(s) has been delivered to the lower layer, the PDCP entity can deliver information about the second PDU(s) to the lower layer so that the lower layer can stop transmitting the second PDU(s).

[0085] In summary, a lower-layer entity transmits information about a first PDU(or PDU) that failed to transmit to a higher-layer entity. The higher-layer entity transmits information about a second PDU(or PDU) to the lower layer to prevent further transmission of the second PDU(or PDU) (for example, the lower layer stops transmitting the second PDU(or PDU)). If the first and second PDU(or PDU) belong to the same PDU set, the lower-layer entity is an eRLC entity or gNB-DU, and the higher layer is an ePDCP entity or gNB-CU.

[0086] The above description and accompanying drawings provide examples of specific embodiments and implementations. However, the described subject matter may be embodied in a variety of different forms, and it is intended that the subject matter covered or claimed is not limited to any example of the embodiments described herein. A reasonably broad range of the subject matter claimed or covered is intended. In particular, for example, the subject matter may be embodied as a method, device, component, system, or non-temporary computer-readable medium for storing computer code. Accordingly, embodiments may take the form of, for example, hardware, software, firmware, storage medium, or any combination thereof. For example, an embodiment of the method described above may be implemented by a component, device, or system including memory and a processor by executing computer code stored in memory.

[0087] Throughout this specification and the claims, terms may have nuances implied or suggested in context beyond their expressly 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 a different embodiment. For example, the subject matter described in the claims is intended to include combinations of examples of embodiments, either in whole or in part.

[0088] In general, terms can be understood at least partially from their use in context. For example, terms such as “and,” “or,” or “and / or” as used herein may have various meanings that may at least partially depend on the context in which such terms are used. Typically, when “or” is used to relate a list such as A, B, or C, it is intended to mean A, B, and C, used here in an inclusive sense, as well as A, B, or C, used here in an exclusive sense. In addition, the term “one or more” as used herein may be used at least partially, depending on the context, to describe any function, structure, or characteristic in a singular sense, or to describe a combination of functions, structures, or characteristics in a plural sense. Similarly, terms such as “a,” “an,” or “the” may be understood, at least partially, depending on the context, to convey either a singular or plural usage. Furthermore, the term “based on” may be understood not necessarily to convey an exclusive set of factors, but instead, at least partially, depending on the context, to allow for the presence of additional factors that are not necessarily explicitly described.

[0089] Throughout this specification, references to features, advantages, or similar terms do not imply that all features and advantages that may be realized by the present solution should or will be included in any single implementation thereof. Rather, terms referring to features and advantages should be understood to mean that certain features, advantages, or characteristics described in relation to the embodiments are included in at least one embodiment of the present solution. Accordingly, descriptions of features and advantages, as well as similar terms throughout this specification, may, but not necessarily, refer to the same embodiment.

[0090] Furthermore, the described features, advantages, and characteristics of this solution may be combined in any suitable manner in one or more embodiments. As those skilled in the art will see, in light of the description herein, this solution can be implemented without one or more of the specific features or advantages of a particular embodiment. In other examples, additional features and advantages may be recognized in certain embodiments where they are not present in all embodiments of this solution.

Claims

1. A method performed by a wireless terminal communicating with a serving cell, wherein the method is Determining whether a first active time alignment timer (TAT) and a second active TAT have expired, wherein the first active TAT and the second active TAT are associated with a first time advance group (TAG) and a second TAG, respectively, and the first TAG and the second TAG are associated with a first transmit-receive point (TRP) and a second TRP, respectively. The first procedure is performed when it is determined that the first TAT has expired while the second TAT is still available, The second procedure is performed when it is determined that both the first TAT and the second TAT have expired, and the second procedure is different from the first procedure. Methods that include...

2. The method according to claim 1, wherein the first step includes automatically assigning the resources associated with the first TRP to the second TRP.

3. The method according to claim 1, wherein the first step includes suspending the resources associated with the first TRP.

4. The method according to claim 1, wherein the first step includes releasing the resources associated with the first TRP.

5. The method according to any one of claims 2 to 4, wherein the resource comprises at least one of a PUCCH resource and a Sounding Reference Signal (SRS) resource.

6. The second procedure described above is, Flushing all Hybrid Automatic Repeating Request (HARQ) buffers for the serving cell, Notifying the Radio Research Control (RRC) entity to release the configured PUCCH for the serving cell, Notifying the RRC entity to release the configured SRS resources for the serving cell, Clear the configured downlink assignments and uplink permissions for the serving cell. Clearing the PUSCH resource for semi-persistent channel status information (CSI) reporting, or Maintain the current time advance values ​​of the first TAG and the second TAG. The method according to any one of claims 1 to 4, comprising one or more of the above.

7. The serving cell includes a special cell (spCell), which is either a primary cell or a primary-secondary cell. The method according to claim 6, wherein the second step further comprises setting all running TATs to expired.

8. The first TAG is mapped to a first control resource set (CORESET) pool composed of the serving cells for the wireless terminal, The method according to claim 1, wherein the second TAG is mapped to a second CORESET pool composed of the serving cells for the wireless terminal.

9. The method according to claim 1, wherein the first TAG and the second TAG correspond to a first activated transmission configuration indicator (TCI) state and a second activated TCI state of the serving cell, respectively, and the first activated TCI state and the second activated TCI state are associated with the first TRP and the second TRP, and are in a list of TCL states of the serving cell corresponding to a plurality of TRPs.

10. One of the first TAG and the second TAG is mapped to one of a plurality of control resource set (CORESET) pools composed of the serving cells for the wireless terminal. The method according to claim 1, wherein the other of the first TAG and the second TAG corresponds to an activated TCI state in a list of TCI states associated with a plurality of TRPs.

11. The method according to any one of claims 9 and 10, wherein the first activated TCI state, the second activated TCI state, or the activated TCI state in the list of TCI states is dynamically indicated via MAC CE.

12. A method performed by a wireless terminal communicating with a serving cell, wherein the method is Determining whether a first time alignment timer (TAT) and a second TAT have expired, wherein the first TAT and the second TAT are associated with a first time advance group (TAG) and a second TAG, respectively, and the first TAG and the second TAG are associated with a primary transmission-receive point (TRP) and a secondary TRP, respectively. The first procedure is performed when it is determined that the second TAT has expired while the first TAT is still available, The second procedure is performed when it is determined that the first TAT has expired, regardless of whether the second TAT has expired, and the second procedure is different from the first procedure. Methods that include...

13. The method according to claim 12, wherein the first step includes automatically assigning the resources associated with the secondary TRP to the primary TRP.

14. The method according to claim 12, wherein the first step includes suspending the resources associated with the secondary TRP.

15. The method according to claim 12, wherein the first step includes releasing the resources associated with the secondary TRP.

16. The method according to any one of claims 13 to 15, wherein the resource comprises at least one of a PUCCH resource and a Sounding Reference Signal (SRS) resource.

17. The second procedure described above is, Flushing all HARQ buffers for the aforementioned serving cell, Notifying the RRC entity to release the configured PUCCH for the serving cell, Notifying the RRC entity to release the configured SRS resources for the serving cell, Clear the configured downlink assignments and uplink permissions for the serving cell. Clearing PUCH resources for semi-permanent CSI reporting, or Maintain the current time advance values ​​of the first TAG and the second TAG. The method according to any one of claims 12 to 15, comprising one or more of the above.

18. The serving cell comprises a special cell (spCell), which is either a primary cell or a primary secondary cell. The second procedure described above is, Flushing all HARQ buffers for the aforementioned serving cell, Notifying the RRC entity to release the configured PUCCH for the serving cell, Notifying the RRC entity to release the configured SRS resources for the serving cell, Clear the configured downlink assignments and uplink permissions for the serving cell. Clearing PUCH resources for semi-permanent CSI reporting, To consider all running TATs as expired, or, Maintain the current time advance values ​​of the first TAG and the second TAG. The method according to claim 17, further comprising one or more of the above.

19. The first TAG is mapped to a first control resource set (CORESET) pool composed of the serving cells for the wireless terminal, The method according to claim 12, wherein the second TAG is mapped to a second CORESET pool composed of the serving cells for the wireless terminal.

20. The method according to claim 12, wherein the first TAG and the second TAG correspond to a first activated transmission configuration indicator (TCI) state and a second activated TCI state of the serving cell, respectively, and the first activated TCI state and the second activated TCI state are associated with the primary TRP and the secondary TRP, and are in a list of TCL states of the serving cell corresponding to a plurality of TRPs.

21. One of the first TAG and the second TAG is mapped to one of a plurality of CORESET pools composed of the serving cells for the wireless terminal. The method according to claim 12, wherein the other of the first TAG and the second TAG corresponds to an activated TCI state in a list of TCI states associated with a plurality of TRPs.

22. The method according to any one of claims 20 and 21, wherein the first activated TCI state, the second activated TCI state, or the activated TCI state in the list of TCI states is dynamically indicated via MAC CE.

23. The wireless terminal according to any one of claims 1 to 22, wherein the wireless terminal comprises a processor and memory, and the processor is configured to read computer code from the memory and cause the wireless terminal to perform the method according to any one of claims 1 to 22.

24. A computer program product comprising a non-temporary computer-readable program medium storing computer code, wherein the computer code, when executed by a processor of a wireless terminal according to any one of claims 1 to 22, causes the processor to perform the method according to any one of claims 1 to 22.

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