Multiple time alignment timers

Abstract

A method is disclosed that includes determining whether to flush one or more hybrid automatic repeat request (HARQ) buffers based on expiration of at least one of at least two time alignment timers.

Description

Technical Field

[0001] The following exemplary embodiments relate to wireless communication.

Background Art

[0002] In a wireless communication system, a user equipment can apply a timing advance to adjust the timing of an uplink frame in order to align with a downlink frame in the time domain. However, for example, when the user equipment transmits to at least two transmission and reception points simultaneously, there is an issue of how to apply the timing advance.

Summary of the Invention

[0003] The scope of protection required by various exemplary embodiments is defined by the independent claims. Exemplary embodiments and features in this specification that do not fall within the scope of the independent claims are construed as useful examples for understanding the various embodiments.

[0004] According to one aspect, there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least perform determining whether to flush one or more hybrid automatic repeat request (HARQ) buffers based on expiration of at least one of at least two time alignment timers.

[0005] According to another aspect, there is provided an apparatus comprising means for determining whether to flush one or more hybrid automatic repeat request (HARQ) buffers based on expiration of at least one of at least two time alignment timers.

[0006] According to another aspect, there is provided a method including determining whether to flush one or more Hybrid Automatic Repeat reQuest (HARQ) buffers based on expiration of at least one of at least two timing alignment timers.

[0007] According to another aspect, there is provided a computer program including instructions that, when executed by a device, cause the device to at least determine whether to flush one or more Hybrid Automatic Repeat reQuest (HARQ) buffers based on expiration of at least one of at least two timing alignment timers.

[0008] According to another aspect, there is provided a computer-readable medium including program instructions that, when executed by a device, cause the device to at least determine whether to flush one or more Hybrid Automatic Repeat reQuest (HARQ) buffers based on expiration of at least one of at least two timing alignment timers.

[0009] According to another aspect, there is provided a non-transitory computer-readable medium including program instructions that, when executed by a device, cause the device to at least determine whether to flush one or more Hybrid Automatic Repeat reQuest (HARQ) buffers based on expiration of at least one of at least two timing alignment timers.

Brief Description of the Drawings

[0010] Hereinafter, various exemplary embodiments will be described in more detail with reference to the accompanying drawings.

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[0011] The following embodiments are illustrative. In this specification, the term "a," "one," or "some" embodiments may be referred to in several places in the text, but this does not necessarily mean that each reference is to the same embodiment(s), or that a particular feature applies only to a single embodiment. It is also possible to combine the individual features of different embodiments to provide other embodiments.

[0012] In the following, without limiting the exemplary embodiments to such an architecture, as an example of an access architecture to which the exemplary embodiments may be applied, various exemplary embodiments will be described using a radio access architecture based on Long Term Evolution Advanced (LTE Advanced, LTE-A), New Radio (NR, 5G), Beyond 5G, or 6th Generation (6G). It will be apparent to those skilled in the art that the exemplary embodiments can also be applied to other types of communication networks having appropriate means by appropriately adjusting the parameters and procedures. Examples of other options for a suitable system include Universal Mobile Telecommunications System (UMTS) radio access network (UTRAN, or E-UTRAN), Long Term Evolution (LTE, substantially the same as E-UTRA), Wireless Local Area Network (WLAN, or Wi-Fi (registered trademark)), Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth (registered trademark), Personal Communication Service (PCS), ZigBee (registered trademark), Wideband Code Division Multiple Access (WCDMA (registered trademark)), systems using Ultra Wideband (UWB) technology, sensor networks, Mobile Ad Hoc Networks (MANETs), Internet Protocol Multimedia Subsystem (IMS), or combinations thereof.

[0013] FIG. 1 shows an example of a simplified system architecture showing some elements and functional entities, all of which are logical units and whose implementation may be different from that shown. The connections shown in FIG. 1 are logical connections and may be different from actual physical connections. It will be apparent to those skilled in the art that the system may include functions and structures other than those shown in FIG. 1.

[0014] However, the exemplary embodiments are not limited to the systems exemplified, and those skilled in the art can apply this solution to other communication systems having the necessary characteristics.

[0015] The example of FIG. 1 shows a part of an exemplary wireless access network.

[0016] FIG. 1 shows an access node 104, such as an evolved Node B (eNB, or abbreviated as eNodeB) or a next-generation Node B (gNB, or abbreviated as gNodeB), that provides a wireless cell, and user equipment 100 and 102 configured to be wirelessly connected via one or more communication channels within the wireless cell. The physical link from the user equipment to the access node may be referred to as an uplink (UL) or reverse link, and the physical link from the access node to the user equipment may be referred to as a downlink (DL) or forward link. The user equipment can also communicate directly with other user equipment via sidelink (SL) communication. It should be understood that the access node or its functions can be implemented using any entity such as a node, host, server, access point, etc. suitable for such applications.

[0017] A communication system may include one or more access nodes, in which case the access nodes may be configured to communicate with each other via wired or wireless links designed for that purpose. These links can be used for signaling purposes. The access node may be a computing device configured to control the radio resources of the communication system to which it is connected. The access node may also be referred to as a base station, a base transceiver station (BTS), an access point, or any other type of interface device operable in a wireless environment. The access node may include a transceiver or be connected to a transceiver. A connection may be provided from the transceiver of the access node to an antenna unit for establishing a bi-directional radio link to a user equipment. The antenna unit may comprise a plurality of antennas or antenna elements. Further, the access node may be connected to a core network 110 (CN, or next generation core NGC). Depending on the system, the CN-side counterpart may be a serving gateway (S-GW, for routing and forwarding user data packets), a packet data network gateway (P-GW) for providing a connection of the user equipment to an external packet data network, a user plane function (UPF), a mobility management entity (MME), an access and mobility management function (AMF), or a location management function (LMF), etc.

[0018] A user equipment is one type of device for which resources on the air interface are allocated or may be allocated, and thus any function described herein in connection with the user equipment may be implemented in connection with a corresponding device such as a relay node.

[0019] As an example of such a relay node, a Layer 3 relay (self-backhauling relay) towards an access node can be cited. A self-backhauling relay node may also be referred to as an integrated access and backhaul (IAB) node. The IAB node may include two logical parts, namely, a mobile terminal (MT) part responsible for a backhaul link (i.e., a link between the IAB node and a donor node (also known as a parent node)), and a distributed unit (DU) part responsible for an access link (i.e., a child link between the IAB node and a user equipment), and / or an access link between the IAB node and another IAB node (multi-hop scenario).

[0020] Another example of such a relay node is a Layer 1 relay called a repeater. The repeater can amplify a signal received from an access node and transfer it to a user equipment, and / or amplify a signal received from the user equipment and transfer it to the access node.

[0021] The user equipment may also be referred to as a subscriber unit, mobile station, remote terminal, access terminal, user terminal, terminal device, or user equipment (UE). The user equipment may refer to a portable computing device including a wireless mobile communication device that operates regardless of the presence or absence of a subscriber identification module (SIM), which includes a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm device, or measurement device, etc.), laptop and / or touch screen computer, tablet, game machine, notebook, multimedia device, reduced-capability (RedCap) device, wireless sensor device, or any device incorporated in a vehicle, but is not limited thereto.

[0022] The user equipment may be almost a dedicated uplink-only device, examples of which include cameras and video cameras that load images and video clips onto the network. Also, the user equipment may be a device having the ability to operate in the Internet of Things (IoT) network, where the IoT network is a scenario in which the ability to transfer data between things via the network is provided without the need for human-to-human or human-to-computer interaction. The user equipment can also utilize the cloud. In some applications, the user equipment may include a small portable or wearable device (such as a wristwatch, earphone, glasses, etc.) equipped with wireless components, and the computation may be executed in the cloud or by another user equipment. The user equipment (or the layer 3 relay node in the exemplary embodiment) may be configured to execute one or more of the functions of the user equipment.

[0023] The various technologies described herein can also be applied to cyber-physical systems (CPS), which are systems of collaborating computing elements that control physical entities. CPS can enable the implementation and utilization of a large number of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in physical objects in various locations. A mobile cyber-physical system is a subcategory of cyber-physical systems where the physical system may have its own mobility. Examples of mobile physical systems include mobile robots and electronic devices carried by humans or animals.

[0024] Furthermore, although the device has been described as a single entity, it can also be implemented with various units, processors, and / or memory units (not all shown in FIG. 1).

[0025] 5G uses multiple-input multiple-output (MIMO) antennas, enables a larger number of base stations or nodes (so-called small cell concept) than LTE, includes macro sites that operate in cooperation with small-scale base stations, and adopts various radio technologies according to service needs, use cases, and / or available frequencies. 5G mobile communications can support a wide range of use cases and related applications such as video streaming, augmented reality, various data sharing methods, various forms of machine-type applications (including vehicle safety, various sensors, (large-scale) machine-type communication (mMTC) including real-time control, etc.). 5G has multiple radio interfaces such as below 6 GHz, centimeter waves, and millimeter waves, and can also be integrated with existing legacy radio access technologies such as LTE. The integration with LTE can be implemented, at least in the initial stage, as a system where macro coverage is provided by LTE and 5G radio interface access is provided from small cells by aggregation to LTE. In other words, 5G can support both inter-RAT operation (such as LTE-5G) and inter-RI operation (operation between radio interfaces, below 6 GHz, centimeter waves, millimeter waves, etc.). One of the concepts considered to be used in 5G networks is network slicing, where multiple independent dedicated virtual sub-networks (network instances) are created within substantially the same infrastructure, and services with different requirements regarding latency, reliability, throughput, and mobility can be executed.

[0026] The current architecture of the LTE network may be fully distributed wirelessly and fully centralized in the core network. 5G low-latency applications and services need to bring content closer to the wireless that connects to local breakout or multi-access edge computing (MEC). In 5G, it becomes possible to perform analysis and knowledge generation at the data source. In this approach, it may be necessary to utilize resources that are not always connected to the network, such as laptops, smartphones, tablets, sensors, etc. MEC can provide a distributed computing environment for hosting applications and services. It also has the function of storing and processing content near mobile phone subscribers to shorten the response time. Edge computing can cover a wide range of technologies such as wireless sensor networks, mobile data collection, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking, local cloud / fog computing and grid / mesh computing, duet computing, mobile edge computing, cloudlets, distributed data storage and search, self-organizing self-healing networks, remote cloud services, augmented reality and virtual reality, data caching, Internet of Things (where large-scale connectivity and / or latency are important), critical communications (autonomous vehicles, traffic safety, real-time analysis, time-critical control, healthcare applications), etc.

[0027] The communication system can also communicate with other networks such as the public switched telephone network and the Internet 112 and utilize the services provided by them. The communication network can also support the use of cloud services. For example, at least a part of the core network operation can be implemented as a cloud service (illustrated by the "cloud" 114 in this embodiment). The communication system may also include a central control entity, etc., and networks of various operators can also provide facilities for cooperation, for example, in spectrum sharing.

[0028] Edge cloud can be introduced into the radio access network (RAN) by leveraging network function virtualization (NFV) and software-defined networking (SDN). Using edge cloud means that the operation of the access node is at least partially executed by a remote radio head (RRH) or radio unit (RU), or a server, host, or node operably connected to the access node that includes the radio unit. Also, the operation of the node may be distributed across multiple servers, nodes, or hosts. Executing the RAN real-time functions on the RAN side (in the distributed unit (DU) 104) and centrally executing the non-real-time functions (in the central unit (CU) 108) is made possible, for example, by the application of a cloud RAN architecture.

[0029] Also, it should be understood that the division of roles between the operation of the core network and the operation of the access node may be different from that of LTE or may not exist at all. In addition, technological advancements such as big data and all-IP that change the network construction and management methods can also be considered. The 5G (or new radio (NR)) network may be designed to support multiple layers, and the MEC server may be placed between the core and the access node. It should be understood that MEC can also be applied to the 4G network.

[0030] In addition, 5G can also enhance or complement the coverage of 5G services by using non-terrestrial communications such as satellite communications, for example, by providing backhauling. The envisioned use cases include providing service continuity to machine-to-machine (M2M) or Internet of Things (IoT) devices, or passengers in vehicles, or ensuring the service availability of critical communications and future railway / maritime / aviation communications. Satellite communications can utilize a geostationary Earth orbit (GEO) satellite system, but can also utilize a low Earth orbit (LEO) satellite system, especially a mega-satellite system (a system equipped with hundreds of (nano) satellites). At least one satellite 106 of the mega-satellites can cover a plurality of satellite-corresponding network entities forming a terrestrial cell. The terrestrial cell is formed via a terrestrial relay node 104 or by a gNB arranged on the ground or on a satellite.

[0031] The 6G network is expected to adopt a flexible decentralized and / or distributed computing system and architecture, ubiquitous computing, and employ local spectrum licensing, spectrum sharing, infrastructure sharing, and intelligent automated management supported by mobile edge computing, artificial intelligence, short packet communication, and blockchain technology. The main features of 6G include intelligent connection management control function, programmability, integrated sensing and communication, low energy consumption, reliable infrastructure, scalability, and affordability. In addition to these, 6G also targets new use cases, from the integration of localization and sensing functions into the system design to the unification of the user experience across the physical and digital worlds.

[0032] The system to be described is only an example of part of a radio access system. In fact, it is obvious to those skilled in the art that the system may well include multiple access nodes, the user equipment may access multiple radio cells, and the system may also include other devices such as physical layer relay nodes or other network elements. At least one of the access nodes may be a home eNodeB or a home gNodeB.

[0033] Furthermore, the access node can also be divided into a radio transceiver (TRX), i.e., a radio unit (RU) including a transmitter (Tx) and a receiver (Rx), one or more distributed units (DUs) that can be used for so-called layer 1 (L1) processing and real-time layer 2 (L2) processing, and a central unit (CU) (also called a centralized unit) that can be used for non-real-time L2 and layer 3 (L3) processing. For example, the CU can be connected to one or more DUs by using the F1 interface. Such a division enables the centralization of the CU with respect to the cell site and the DUs, while the DUs can be more distributed and may even remain at the cell site. Together, the CU and the DU are sometimes referred to as a baseband or baseband unit (BBU). Also, the CU and the DU may be included in a radio access point (RAP).

[0034] The CU may be defined as a logical node that hosts upper layer protocols such as the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and / or Packet Data Convergence Protocol (PDCP) of the access node. The DU may be defined as a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and / or Physical (PHY) layer of the access node. The operation of the DU may be at least partially controlled by the CU. The CU may include a control plane (CU-CP), which may be defined as a logical node that hosts the control plane part of the RRC of the access node and the PDCP protocol of the CU. The CU may further include a user plane (CU-UP), and the user plane may be defined as a logical node that hosts the user plane part of the PDCP protocol and the SDAP protocol of the CU for the access node.

[0035] A cloud computing platform can also be used for the execution of the CU and / or the DU. The CU may be executed on a cloud computing platform called a virtualized CU (vCU). In addition to the vCU, there may also be a virtualized DU (vDU) executed on the cloud computing platform. Furthermore, there may also be a combination where the DU uses a so-called bare metal solution, such as an application-specific integrated circuit (ASIC) or a customer-specific standard product (CSSP) system-on-chip (SoC) solution. It should also be understood that the distribution of work may be different between the above-mentioned access node units, or between different core network operations and access node operations.

[0036] Furthermore, in the geographical area of a wireless communication system, similar to a plurality of wireless cells, a plurality of different types of wireless cells may be provided. The wireless cell may be a macro cell (or umbrella cell) which is a large cell having a diameter of up to several tens of kilometers, or may be a small cell such as a micro cell, a femto cell, or a pico cell. The access node(s) in FIG. 1 may be of any of these cell types. The cellular wireless system can be implemented as a multi-layer network including a plurality of types of wireless cells. In a multi-layer network, since one access node may provide one type of wireless cell or wireless cells, a plurality of access nodes may be required to provide such a network structure.

[0037] To meet the need to improve the deployment and performance of the communication system, the concept of a "plug and play" access node may be introduced. A network that can use a "plug and play" access node may include a home eNodeB, or in addition to a home gNodeB, a home node B gateway, or an HNB-GW (not shown in FIG. 1). The HNB-GW may be installed within the operator's network and can aggregate traffic from a number of home eNodeBs, or home gNodeBs, and return it to the core network.

[0038] A UE that is far from a transmission and reception point (TRP) may encounter a larger propagation delay than other UEs closer to the TRP. Due to the larger propagation delay, the uplink transmission of a more distant UE may need to be transmitted earlier compared to the uplink transmission of a closer UE so that the uplink transmissions arrive at the TRP simultaneously. The TRP in this embodiment may refer to any entity that can transmit and / or receive a wireless signal, for example, a network node or a remote radio head (RRH).

[0039] Figure 2 is a diagram showing the concept of timing advance. The timing advance (TA) 200 is a negative offset at the UE between the start point of the received downlink (DL) frame 201 and the start point of the transmitted uplink (UL) frame 202. The timing advance can be used to account for the propagation delay between the UE and the TRP. This offset can be used to ensure that the DL frame and the UL frame are synchronized at the TRP (in the time domain). Thus, the UE can adjust its uplink transmission by transmitting uplink symbols in advance according to the amount of time defined by the timing advance.

[0040] TA adjustment can be composed of two parts: 1) a part based on network signaling of TA adjustment for the UE (e.g., timing advance command), and 2) autonomous UL transmission timing adjustment by the UE. In other words, when the UE is assigned a TA value by the network (e.g., via a timing advance command), the UE can track its DL timing and adjust its UL transmission timing to be within the set threshold.

[0041] The timing of UL transmission can be controlled by the network through a timing advance command (TAC) provided periodically in a closed-loop manner. When receiving a TAC from the network for a given timing advance group (TAG), the UE can adjust the uplink timing of the physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH), and / or sounding reference signal (SRS) transmission on the serving cell within the TAG based on the received TAC and the fixed offset value N TA,offset and.

[0042] Downlink, uplink, and sidelink transmissions may be organized into radio frames having a period of 10 ms, and a given radio frame includes 10 subframes of 1 ms. The uplink frame number i for transmissions from the UE starts before the start point of the corresponding downlink frame at the UE according to the timing advance, and this timing advance is, for example, T TA =(N TA +N TA,offset )T c and may be calculated as such.

[0043] T TA is the calculated timing advance between the uplink and downlink applied by the UE. N TA is the timing advance value provided by the network (e.g., broadcast or provided by TAC). N TA,offset is a fixed offset value, but may vary according to different frequency bands and subcarrier spacings. T c is the basic time unit of NR and is, for example, 0.509 ns.

[0044] Currently, there are two ways to deliver TA adjustment to the UE: 1) via a random access response (RAR) or MsgB as part of the random access procedure, or 2) via a MAC control element (MAC CE).

[0045] In the first option (i.e., RAR or MsgB), the timing correction can be calculated by the network based on the random access preamble or MsgA received from the UE. The UE determines the timing advance value from two different MAC layer commands according to the situation. In the first uplink message after the random access procedure, the UE applies the timing advance value extracted from the RAR or MsgB. Thereafter, if the UE receives a timing advance MAC CE, the UE can apply the timing advance value extracted from the timing advance MAC CE.

[0046] In the second option (i.e., MAC CE), the estimation of TA is performed in the network based on one or more reference signals such as the demodulation reference signal (DMRS) or SRS transmitted from the UE. As described above, the UE can adjust the UL transmission timing based on the RAR during the random access procedure. After the initial attach is completed, the UE can adjust the UL transmission based on the MAC CE timing advance. The timing advance command field may be, for example, 6 bits, which means a total of 64 steps from -32 to 32T at the actual timing. c When T c is 0.509 ns, the range of the physical timing is from -16.3 μs to 16.3 μs at a 15 kHz subcarrier spacing.

[0047] TAG is configured by the RRC and may include a group of serving cells that can use the same timing reference cell and the same timing advance value for UL-configured cells. A TAG that includes the special cell (SpCell) of the MAC entity is called the primary timing advance group (PTAG), and the term secondary timing advance group (STAG) refers to other TAGs.

[0048] (For each TAG) A parameter called timeAlignmentTimer is set via the RRC, and the MAC entity can control the time when the serving cells belonging to the associated TAG are considered to be in uplink time alignment.

[0049] When receiving the timing advance command MAC CE and the indicated TAG is maintained, the MAC entity can apply the timing advance command of the indicated TAG and start or restart the timeAlignmentTimer associated with the indicated TAG. TA If the indicated TAG is maintained, the MAC entity can apply the timing advance command of the indicated TAG and start or restart the timeAlignmentTimer associated with the indicated TAG.

[0050] When a timing advance command is received in the RAR for the serving cell belonging to the TAG, or in the MsgB for the SpCell, if the random access preamble is not selected by the MAC entity among the contention-based random access preambles, the MAC entity can apply the timing advance command for this TAG and start or restart the timeAlignmentTimer associated with this TAG.

[0051] If the timeAlignmentTimer associated with this TAG is not running, the MAC entity can apply the timing advance command for this TAG and start the timeAlignmentTimer associated with this TAG. If contention resolution is considered to have failed, or if contention resolution is considered to have succeeded for a system information (SI) request, after transmitting the hybrid automatic repeat request (HARQ) feedback of the MAC protocol data unit (PDU) including the UE contention resolution identity MAC CE, the MAC entity may stop the timeAlignmentTimer associated with this TAG.

[0052] Otherwise, the MAC entity may ignore the timing advance command received in the RAR message.

[0053] When an absolute timing advance command is received in response to the transmission of MsgA including the cell radio network temporary identifier (C-RNTI) MAC CE, the MAC entity can apply the timing advance command for the PTAG and start or restart the timeAlignmentTimer associated with the PTAG.

[0054] When the timeAlignmentTimer expires and the timeAlignmentTimer is associated with the PTAG, the MAC entity flushes all HARQ buffers for all serving cells, notifies the RRC to release the PUCCH (if configured) for all serving cells, notifies the RRC to release the SRS (if configured) for all serving cells, clears the configured downlink allocation and the configured uplink allocation, clears the PUSCH resources for semi-persistent channel state information (CSI) reporting, considers that all running timeAlignmentTimers have expired, and maintains the N of all TAGs TA may be maintained. Here, flushing the HARQ buffer may mean emptying the HARQ buffer. The UE may be composed of multiple HARQ processes, and each HARQ process may have a buffer or be associated with a buffer. This HARQ buffer can be used to buffer the transport block (TB) (or packet) corresponding to the HARQ process, for example, to enable retransmission of this TB based on the request of the gNB when the gNB fails to correctly receive the first transmission.

[0055] Otherwise, when the timeAlignmentTimer is associated with the STAG, for all serving cells belonging to this TAG, the MAC entity can perform flushing all HARQ buffers, notifying the RRC to release the PUCCH (if configured), notifying the RRC to release the SRS (if configured), clearing the configured downlink allocation and the configured uplink allocation, clearing any PUSCH resources for semi-persistent CSI reporting, and maintaining the N of this TAG TA when the timeAlignmentTimer expires.

[0056] If a MAC entity stops the uplink transmission of a secondary cell (S cell) due to the fact that the maximum uplink transmission timing difference between the tags of the MAC entity or the maximum uplink transmission timing difference between the tags of any MAC entity of the UE exceeds the limit, the MAC entity can consider that the timeAlignmentTimer associated with the S cell has expired.

[0057] If the timeAlignmentTimer associated with the TAG to which the serving cell belongs is not running, the MAC entity cannot perform uplink transmission on the serving cell, except for random access preamble and MsgA transmission. Furthermore, if the timeAlignmentTimer associated with the PTAG is not running, the MAC entity cannot perform uplink transmission on any serving cell, except for random access preamble and MsgA transmission on the SpCell.

[0058] In NR Release 18 and later, considering aspects such as capacity and reliability (e.g., PUCCH repetition, PUSCH repetition), a simultaneous (or parallel) UL transmission scheme may be specified to enable non-coordinated UL transmissions (e.g., PUCCH / PUSCH, PUCCH / PUCCH, other UL overlapping channels) expected in multi-DCI for multi-TRP operation. DCI is the abbreviation of downlink control information. Simultaneous UL transmission may include permitting simultaneous or parallel PUCCH / PUSCH and PUSCH / PUCCH / SRS transmissions from two or more UE antenna panels (e.g., using different UL beams in FR2). Multi-TRP operation can support two or more TRPs.

[0059] Figure 3 shows simultaneous (or parallel) multi-panel UL transmission for multi-TRP operation. UE 300 performs a first UL transmission to the first TRP 304-1 via the first uplink beam 311. UE 300 performs a second UL transmission to the second TRP 304-2 via the second uplink beam 312, and the first UL transmission and the second UL transmission overlap at least partially in time. It should be noted that two or more UL transmissions may be transmitted to two or more TRPs simultaneously. The first UL transmission and the second UL transmission may be transmitted from different UE antenna panels. For example, the first UL transmission may be transmitted from the first antenna panel of UE 300, and the second UL transmission may be transmitted from the second antenna panel of UE 300. The first TRP 304-1 and the second TRP 304-2 may belong to a single access node 304 (e.g., gNB), or may belong to different access nodes (e.g., multiple gNBs). The UE 300 in FIG. 3 may correspond to the UE 100 in FIG. 1. Further, the access node 304 in FIG. 3 may correspond to the access node 104 in FIG. 1.

[0060] In this specification, it should be noted that an uplink (UL) beam may also be referred to as spatial relationship information, a (separate) UL transmission configuration indicator (TCI) state, a common or shared TCI state, a spatial filter, power control information (or a set of power control parameters), an antenna panel or panel identifier (ID), etc. In other words, these terms may be used interchangeably in this specification. Further, a TRP may be identified by at least one of an SRS resource set, a beam failure detection reference signal (BFD-RS) set, a subset or set of UL beams, a control resource set pool index (CORESETPoolIndex) (if configured), and / or a physical cell identifier (PCI). Further, it should be noted that a given UE antenna panel may be identified by a panel ID. Alternatively, or additionally, a given antenna panel may be identified or associated with by at least one (DL) reference signal or by a UL beam.

[0061] In NR Release 18, there is an objective to include two TAs for both intra-cell and inter-cell multi-DCI multi-TRP operations. This feature may be called multi-TA enhancement or two-TA enhancement. However, this feature may affect existing or legacy procedures.

[0062] In multi-DCI, there may be a plurality of physical downlink control channels (PDCCH), each of which schedules a PDSCH or UL transmission, and each PDSCH or UL transmission is transmitted from or to a separate TRP, and a higher layer parameter coresetPoolIndex that identifies a given TRP. Multi-DCI may be more suitable for a non-ideal backhaul (however, it can also be used in the case of an ideal backhaul).

[0063] In contrast, in single DCI, the DL / UL transmission or iterative operation of multi-TRP is scheduled by one DCI. Single DCI may be more suitable for an ideal backhaul.

[0064] Some exemplary embodiments relate to time alignment operations and procedures, and provide solutions considering the impact of introducing multi-TA enhancements to multi-TRP operations.

[0065] Hereinafter, exemplary embodiments will be described using the principles and terms of NR technology without being limited to an NR communication system.

[0066] In an exemplary embodiment, operations and procedures related to a timeAlignmentTimer considering the multi-TA operation of multi-TRP can be defined. For example, an operation of whether to flush the HARQ buffer of one or more cells is defined in this embodiment.

[0067] In some exemplary embodiments, a UE supporting multi-DCI-based multi-TRP operation (inter-cell or intra-cell) may be composed of at least two TAGs for each cell, and each TAG corresponds to a TRP, PCI, or CORESETPoolIndex, and the TAG is applicable to one or more (serving) cells (a prerequisite for supporting multi-TA operation in the UE). Here, the term "cell" may refer to a radio cell.

[0068] The UE can assume a time alignment timer (timeAlignmentTimer) individually for each TRP / PCI / CORESETPoolIndex considering the following points.

[0069] In an exemplary embodiment, if there are at least two primary TAGs (which may be associated with at least one same serving cell or different cells), when the time alignment timer of one or both of the primary TAGs, each corresponding to a TRP / PCI / CORESETPoolIndex, expires, if the time alignment timers of the primary TAGs expire (substantially) simultaneously or at different times but within a pre-defined or set period (e.g., within a certain threshold), the UE can flush the HARQ buffers of all the (active) serving cells configured for the UE. To achieve this, one way is that the UE is composed of a dedicated timer triggered each time one of the time alignment timers expires, and if the second time alignment timer expires before the dedicated timer expires, the UE flushes the HARQ buffers of all its serving cells and stops the dedicated timer. The dedicated timer is also referred to as the third timer herein. Otherwise, if the second time alignment timer does not expire before the dedicated timer expires, the UE may not flush the HARQ buffer of any cell. This is shown in Figure 4.

[0070] Figure 4 shows a flowchart according to an exemplary embodiment of a method executed by a device such as a user equipment, or a device including the user equipment, or a device included in the user equipment.

[0071] Referring to Figure 4, in block 401, the device detects that the first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with the first PTAG.

[0072] In block 402, in response to the expiration of the first time alignment timer, a dedicated timer is started. The dedicated timer is also referred to as the third timer in this specification. The third timer may correspond to a predetermined period (threshold), that is, the third timer may be configured to expire when it reaches a value of time corresponding to the predetermined period.

[0073] In block 404, if the second time alignment timer associated with the second PTAG expires before the dedicated timer (third timer) expires (Yes in 403), that is, if the second time alignment timer expires within a predetermined period with respect to the expiration of the first time alignment timer, the apparatus flushes the HARQ buffer(s) corresponding to the plurality of cells. The plurality of cells may refer to all the serving cells set (and active) for this apparatus.

[0074] Alternatively, in block 405, if the second time alignment timer does not expire before the dedicated timer (third timer) expires (No in 403), that is, if the second time alignment timer does not expire within a predetermined period with respect to the expiration of the first time alignment timer, the apparatus does not flush the HARQ buffer(s) of any cell.

[0075] In other words, the determination of whether to flush the HARQ buffer can be made based on the expiration of the first time alignment timer with respect to the expiration of the second time alignment timer, that is, based on whether the second time alignment timer expires before the dedicated timer (third timer) expires.

[0076] Here, the terms "first time alignment timer" and "second time alignment timer" are used to distinguish the timers and do not necessarily mean a specific order or specific identification number of the timers.

[0077] Such use of the expiration of one time alignment timer relative to another time alignment timer is beneficial considering the following. If two time alignment timers (e.g., each corresponding to a TRP) expire within a short period, there may not be enough time to obtain and adjust the first TA before the second time alignment timer expires. This should be seen as all HARQ buffers should be flushed because there is no available synchronous UL. On the other hand, if the second time alignment timer expires after a predetermined time has elapsed since the expiration of the first time alignment timer, there is enough time to obtain and adjust the first TA (before the second time alignment timer expires). As a result, since there is at least one available synchronous UL, it is not necessary to flush the HARQ buffer. In this case, HARQ retransmission directed to a TRP different from the TRP for the first transmission is assumed.

[0078] FIG. 5 shows an example corresponding to the exemplary embodiment of FIG. 4, where the UE is set (e.g., via RRC) with a threshold (predetermined period) related to the expiration of two time alignment timers (time alignment timer 0 and time alignment timer 1). In this example, time alignment timer 1 and time alignment timer 0 expire within a period 500 shorter than the threshold (501, 502), and since these timers correspond to the primary TAG, the UE flushes the HARQ buffer for all serving cells set (and active) for the UE. Time alignment timer 1 may sometimes be referred to as the first time alignment timer in this specification, and time alignment timer 0 may sometimes be referred to as the second time alignment timer in this specification. TAG#1 may sometimes be referred to as the first timing advance group in this specification, and TAG#0 may sometimes be referred to as the second timing advance group in this specification.

[0079] Figure 5 shows that the time alignment timer 1 expires before the time alignment timer 0, but the time alignment timer 0 may also expire before the time alignment timer 1. In this case, after the time alignment timer 0 expires, if the time alignment timer 1 expires within a period shorter than the threshold and these timers correspond to the primary TAG, the UE may flush the HARQ buffers of all the serving cells configured (and active) for the UE. In other words, the relative expiration of the time alignment timers can be used to trigger the flushing of the HARQ buffers for all serving cells, regardless of the specific order in which the time alignment timers expire.

[0080] In an exemplary embodiment, if there are at least two secondary TAGs (which may be associated with at least one same serving cell or different cells), when the time alignment timers of both secondary TAGs corresponding to the TRP / PCI / CORESETPoolIndex expire, if the time alignment timers of the secondary TAGs expire (substantially) simultaneously or at different times but within a predetermined period or a configured period (i.e., within a certain threshold), the UE can flush the HARQ buffers of these TAGs. To achieve this, the same method as described for the primary TAG can be adopted here. This is shown in Figure 6.

[0081] Figure 6 shows a flowchart according to an exemplary embodiment of a method performed by a device such as a user equipment, or a device including the user equipment, or a device included in the user equipment.

[0082] Referring to Figure 6, in block 601, the device detects that a first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with the first STAG.

[0083] In block 602, in response to the expiration of the first time alignment timer, a dedicated timer is started. The dedicated timer may also be referred to herein as the third timer. The third timer may correspond to a predetermined period (threshold value), that is, the third timer may be set to expire when it reaches the value of the time corresponding to the predetermined period.

[0084] In block 604, if the second time alignment timer associated with the second STAG expires before the dedicated timer (third timer) expires (in 603, "Yes"), that is, if the second time alignment timer expires within a predetermined period with respect to the expiration of the first time alignment timer, the device flushes the HARQ buffer(s) corresponding to the first STAG and the second STAG.

[0085] Alternatively, in block 605, if the second time alignment timer does not expire before the dedicated timer (third timer) expires (in 603, "No"), that is, if the second time alignment timer does not expire within a predetermined period with respect to the expiration of the first time alignment timer, the device does not flush the HARQ buffer(s) of the STAG.

[0086] In an exemplary embodiment (see Figure 7), when there are two TAGs each corresponding to a TRP / PCI / CORESETPoolIndex, if the time alignment timer corresponding to the first TAG or the first TRP expires and the UE does not receive the TAC corresponding to the second TAG or TRP before the expiration of the time alignment timer of the second TAG, the UE may flush the HARQ buffers of all (configured and active) serving cells for the UE if the TAG is the primary TAG. If the two TAGs are secondary TAGs, the UE may flush the HARQ buffers of the cells within these TAGs. Otherwise, if the time alignment timer corresponding to the first TAG or the first TRP expires and the UE receives the TAC corresponding to the second TAG before the expiration of the time alignment timer of the second TAG, if the TAG is the primary TAG, the UE does not flush the HARQ buffer of any cell. If the two TAGs are secondary TAGs, the UE does not flush the HARQ buffer of any cell within these TAGs. The reception of the TAC may correspond to the reception of the last symbol of the physical downlink control channel (PDCCH) that schedules the physical downlink shared channel (PDSCH) carrying the TAC, or the last symbol of the PDSCH carrying the TAC (including the RAR), or the first or last symbol of the physical uplink control channel / physical uplink shared channel (PUCCH / PUSCH) that transmits the hybrid automatic repeat request acknowledgement (HARQ-ACK) corresponding to the PDSCH containing the TAC, or may correspond to a certain period before and after the reception or transmission of this PDCCH, PDSCH or PUCCH / PUSCH.

[0087] Figure 7 shows a flowchart according to an exemplary embodiment of a method executed by a device such as a user equipment, or a device including the user equipment, or a device included in the user equipment.

[0088] Referring to Figure 7, in block 701, the device detects that the first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with the first TAG.

[0089] In block 703, if the TAC corresponding to the second TAG is not received (in 702, "No") after the expiration of the first time alignment timer and before the expiration of the second time alignment timer associated with the second TAG, the device flushes one or more HARQ buffers. If the first TAG and the second TAG are PTAGs, the device can flush the HARQ buffer(s) of all the serving cells configured (and active) for the device. If the first TAG and the second TAG are STAGs, the device can flush the HARQ buffers of the cells within the first TAG and the second TAG.

[0090] Alternatively, in block 704, if the TAC corresponding to the second TAG is received (in 702, "Yes") before the expiration of the second time alignment timer associated with the second TAG, the device does not flush one or more HARQ buffers. If the first TAG and the second TAG are primary TAGs, the device does not flush the HARQ buffer of any cell. If the first TAG and the second TAG are secondary TAGs, the device does not flush the HARQ buffer of any cell within these TAGs.

[0091] In an exemplary embodiment (see FIG. 8), when there are two tags each corresponding to a TRP / PCI / CORESETPoolIndex, if the time alignment timer corresponding to the first tag or the first TRP expires and the UE does not receive a PDCCH command corresponding to the second tag or the TRP before the expiration of the time alignment timer of the second tag, the UE may flush the HARQ buffers of all the serving cells configured (and active) for the UE if the tag is the primary tag. If the two tags are secondary tags, the UE may flush the HARQ buffers of the cells within these tags. Otherwise, if the time alignment timer corresponding to the first tag or the first TRP expires and the UE receives a PDCCH command corresponding to the second tag before the expiration of the time alignment timer of the second tag, the UE does not flush the HARQ buffer of any cell if the tag is the primary tag. If the two tags are secondary tags, the UE does not flush the HARQ buffer of any cell within these tags. The reference point for the reception of the PDCCH command in this case may be the last symbol of the PDCCH command, the last symbol of the physical random access channel (PRACH), or a random access procedure message (which may be either a two-step or a four-step random access procedure) transmitted by or received by the UE (triggered by the PDCCH command), or a certain period after the transmission or reception of these messages / signals.

[0092] FIG. 8 shows a flowchart according to an exemplary embodiment of a method performed by a device such as a user equipment, or by a device including the user equipment, or by a device included in the user equipment.

[0093] Referring to FIG. 8, in block 801, the device detects that the first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with the first tag.

[0094] In block 803, if, after the expiration of the first time alignment timer and before the expiration of the second time alignment timer associated with the second TAG, the PDCCH command corresponding to the second TAG is not received (in 802, "No"), the device flushes one or more HARQ buffers. If the first TAG and the second TAG are PTAGs, the device may flush the HARQ buffers of all the serving cells configured (and active) for the device. If the first TAG and the second TAG are STAGs, the device can flush the HARQ buffers of the cells within the first TAG and the second TAG.

[0095] Alternatively, in block 804, if the PDCCH command corresponding to the second TAG is received before the expiration of the second time alignment timer associated with the second TAG (in 802, "Yes"), the device does not flush one or more HARQ buffers. If the first TAG and the second TAG are primary TAGs, the device does not flush the HARQ buffers of any cell. If the first TAG and the second TAG are secondary TAGs, the device does not flush the HARQ buffers of any cell within these TAGs.

[0096] In an exemplary embodiment, for a cell, if there is a first TAG for which the time alignment timer has expired and a second TAG for which the time alignment timer has not expired, the UE may be configured not to flush the HARQ buffer of this cell and to flush the HARQ buffer associated with the TAG related to the expired time alignment timer. For example, if the expired time alignment timer is associated with the first TAG, the UE may flush the HARQ buffer associated with the first TAG, but not necessarily flush the HARQ buffer associated with the second TAG. This is shown in FIG. 9. This enables the TRP to retransmit the transport block (TB) for which the corresponding time alignment timer has not expired.

[0097] Figure 9 shows a flowchart according to an exemplary embodiment of a method performed by an apparatus such as a user equipment, or an apparatus including the user equipment, or an apparatus included in the user equipment.

[0098] Referring to Figure 9, at block 901, the apparatus detects that a first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with a first TAG.

[0099] At block 903, if the second time alignment timer associated with the second TAG has not expired (``No'' at 902) and the first time alignment timer has expired, the apparatus flushes the HARQ buffer(s) of the first TAG (and does not flush the HARQ buffer of the second TAG).

[0100] Alternatively, at block 904, if both the second time alignment timer and the first time alignment timer have expired (``Yes'' at 902), the apparatus flushes the HARQ buffer(s) of the first TAG and the second TAG.

[0101] In an exemplary embodiment, if a cell is composed of (or belongs to) a single TAG for which the time alignment timer has expired, the UE may flush all HARQ buffers of this cell. If this TAG is a primary TAG, i.e., the cell is a special cell that supports at least contention-based random access, the UE can flush the HARQ buffers of all serving cells configured (and active) for the UE. This is shown in Figure 10.

[0102] Figure 10 shows a flowchart according to an exemplary embodiment of a method performed by an apparatus such as a user equipment, or an apparatus including the user equipment, or an apparatus included in the user equipment.

[0103] Referring to FIG. 10, in block 1001, the apparatus detects that the first time alignment timer among at least two time alignment timers has expired. The first time alignment timer is associated with the first TAG. In an exemplary embodiment, the cell is composed of a single TAG (i.e., the first TAG).

[0104] In block 1003, if the first TAG is a PTAG (Yes in 1002), that is, if the cell is a special cell, the apparatus flushes the HARQ buffer(s) of all the serving cells configured (and active) for the apparatus.

[0105] Alternatively, in block 1004, if the first TAG is not a PTAG (No in 1002), the apparatus flushes the HARQ buffer(s) of the cell associated with the first TAG. However, the apparatus does not flush the HARQ buffers of other cells if the first TAG is not a PTAG.

[0106] In other words, the apparatus may flush the HARQ buffer(s) of one or more cells according to whether the first TAG is a PTAG or not, and one or more cells include at least the cell composed of a single TAG (i.e., the first TAG).

[0107] In an exemplary embodiment, if the UE does not support HARQ retransmission via a TRP different from the TRP used for the first transmission (to allow UL retransmission towards the same TRP used for UL transmission), the following considerations may be further defined. In an exemplary embodiment, in the case of a cell composed of two TAGs, each TAG corresponds to or is associated with a TRP / PCI / CORESETPoolIndex, and the HARQ buffer of this cell can be divided into two groups, each corresponding to a TAG or a TRP / PCI / CORESETPoolIndex. Note that the cell may be composed of only one TAG. In this case, this TAG corresponds to or is associated with a default CORESETPoolIndex such as CORESETPoolIndex0. When the time alignment timer of one TAG or CORESETPoolIndex expires, for each cell composed of this TAG or CORESETPoolIndex, the HARQ buffer corresponding to this TAG or CORESETPoolIndex may be flushed. This is shown in FIG. 11.

[0108] FIG. 11 shows a flowchart according to an exemplary embodiment of a method executed by a device such as a user equipment, or a device including the user equipment, or a device included in the user equipment.

[0109] In an exemplary embodiment of this example, the plurality of HARQ buffers of the cell are divided into at least two groups.

[0110] Referring to FIG. 11, in block 1101, the apparatus detects that the first time alignment timer among at least two time alignment timers has expired. The first time alignment timer may be associated with at least one of a first timing advance group, a first transceiver point, a first cell identity, and / or a first control resource set pool index. Here, the term "cell identity" may refer to, for example, a physical cell identity (PCI).

[0111] In block 1102, in response to the expiration of the first time alignment timer, the apparatus flushes the first group among at least two groups of the HARQ buffer. The first group may be associated with at least one of a first timing advance group, a first transceiver point, a first cell identity, and / or a first control resource set pool index associated with the expired first time alignment timer.

[0112] In block 1103, the apparatus detects that the second time alignment timer among at least two time alignment timers has expired. The second time alignment timer may be associated with at least one of a second timing advance group, a second transceiver point, a second cell identity, and / or a second control resource set pool index.

[0113] In block 1104, in response to the expiration of the second time alignment timer, the apparatus flushes the second group among at least two groups of the HARQ buffer. The second group may be associated with at least one of a second timing advance group, a second transceiver point, a second cell identity, and / or a second control resource set pool index associated with the expired second time alignment timer.

[0114] FIG. 12 shows an example corresponding to the exemplary embodiment of FIG. 11, where the UE is configured (e.g., via RRC) such that the HARQ buffer of the cell is divided into two groups, namely group #0 and group #1, each corresponding to a TAG or a CORESETPoolIndex. In this embodiment, when the time alignment timer 1 of TAG#1 expires (1201), the UE flushes the HARQ buffer corresponding to TAG#1 (1203). When the time alignment timer 0 for TAG#0 expires (1202), the UE flushes the HARQ buffer corresponding to TAG#0 (1204). The time alignment timer 1 may also be referred to herein as the first time alignment timer, and the time alignment timer 0 may also be referred to herein as the second time alignment timer. TAG#1 may also be referred to herein as the first timing advance group, and TAG#0 may also be referred to herein as the second timing advance group.

[0115] FIG. 13 shows a flowchart according to an exemplary embodiment of a method performed by an apparatus such as a user equipment, or an apparatus including the user equipment, or an apparatus included in the user equipment.

[0116] Referring to FIG. 13, at block 1301, the apparatus determines whether to flush one or more hybrid automatic repeat request (HARQ) buffers based on the expiration of at least one of at least two time alignment timers. The at least two time alignment timers may be set for the apparatus by a network (e.g., gNB).

[0117] At least two time alignment timers may comprise at least a first time alignment timer and a second time alignment timer. The first time alignment timer among the at least two time alignment timers may be associated with a first timing advance group, and the second time alignment timer among the at least two time alignment timers may be associated with a second timing advance group. The first timing advance group and the second timing advance group may be, for example, a primary timing advance group or a secondary timing advance group.

[0118] The first timing advance group may correspond to at least one of a first transmit-receive point, a first cell identity, and / or a first control resource set pool index. The second timing advance group may correspond to at least one of a second transmit-receive point, a second cell identity, and / or a second control resource set pool index.

[0119] As used herein, “at least one of the following, <list of two or more elements>”, “at least one of <list of two or more elements>”, and similar expressions where a list of two or more elements is joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0120] Note that some exemplary embodiments are applicable to other operations than flushing of the HARQ buffer, for example, operations such as the following.

[0121] 1) If set, notify the RRC to release the PUCCH for at least some of the serving cells. Assuming there is an association between the PUCCH and the TAG or CORESETPoolIndex / PCI / TRP, when the time alignment timer of the TAG expires, the UE can release the PUCCH corresponding to or associated with that TAG or CORESETPoolIndex / PCI / TRP.

[0122] 2) If set, notify the RRC to release the SRS for all serving cells. Assuming there is an association between the SRS resource or resource set and the TAG or CORESETPoolIndex / PCI / TRP, when the time alignment timer of the TAG expires, the UE can release the SRS corresponding to or related to that TAG or CORESETPoolIndex / PCI / TRP.

[0123] 3) Clear the configured downlink assignment and the configured uplink grant. Assuming there is an association between the configured DL assignment / configured grant or their respective resources and the TAG or CORESETPoolIndex / PCI / TRP, when the time alignment timer of the TAG expires, the UE can clear the configured DL assignment / configured grant corresponding to or related to that TAG or CORESETPoolIndex / PCI / TRP.

[0124] 4) Clear the PUSCH resources for semi - persistent CSI reporting. Assuming there is an association between the PUSCH resources (for semi - persistent CSI) and the TAG or CORESETPoolIndex / PCI / TRP, when the time alignment timer of the TAG expires, the UE can clear the PUSCH resources for semi - persistent CSI corresponding to or related to that TAG or CORESETPoolIndex / PCI / TRP.

[0125] Note that the conditions for the cells to which the above applies may be similar to those defined to flush the HARQ buffer.

[0126] The blocks and related functions described above with reference to FIGS. 4, 6 to 11, and 13 are not in absolute chronological order, and some of them may be executed simultaneously or in an order different from the described order. Also, other functions may be executed between or within them, other information may be transmitted, and / or other rules may be applied. Also, some of the blocks, or parts of the blocks, may be omitted or replaced with corresponding blocks or parts of the blocks.

[0127] FIG. 14 shows an exemplary embodiment of apparatus 1400, which may be an apparatus such as a user equipment, an apparatus including a user equipment, or an apparatus included in a user equipment. The user equipment may correspond to one of the user equipments (100, 102) in FIG. 1. The user equipment may also be referred to as a subscriber unit, a mobile station, a remote terminal, an access terminal, a user terminal, a terminal device, or a user equipment (UE).

[0128] Apparatus 1400 includes at least one processor 1410. The at least one processor 1410 interprets computer program instructions and processes data. The at least one processor 1410 may include one or more programmable processors. The at least one processor 1410 may include programmable hardware having embedded firmware, and alternatively or additionally, may include one or more application specific integrated circuits (ASICs).

[0129] At least one processor 1410 is connected to at least one memory 1420. The at least one processor is configured to read and write data to and from the at least one memory 1420. The at least one memory 1420 may comprise one or more memory units. The memory units may be volatile or non-volatile. In some exemplary embodiments, there may be one or more units of non-volatile memory and one or more units of volatile memory, or there may be one or more units of non-volatile memory, or there may be one or more units of volatile memory. Note that volatile memory is, for example, random access memory (RAM), dynamic random access memory (DRAM), or synchronous dynamic random access memory (SDRAM). Non-volatile memory is, for example, read only memory (ROM), programmable read only memory (PROM), electronically erasable programmable read only memory (EEPROM), flash (registered trademark) memory, an optical storage device or a magnetic storage device. Generally, memory may be referred to as a non-transitory computer-readable medium. The at least one memory 1420 stores computer-readable instructions to be executed by the at least one processor 1410 to perform one or more of the above-described exemplary embodiments. For example, the non-volatile memory stores the computer-readable instructions and the at least one processor 1410 executes the instructions using volatile memory for temporary storage of data and / or instructions.

[0130] The computer-readable instructions may be pre-stored in at least one memory 1420, or alternatively or additionally, may be received by the apparatus via an electromagnetic carrier signal and / or may be copied from a physical entity such as a computer program product. By executing the computer-readable instructions by at least one processor 1410, the apparatus 1400 executes one or more of the exemplary embodiments described above. That is, at least one processor and at least one memory for storing instructions can provide means for providing any of the methods and / or blocks described above or means for causing them to be executed.

[0131] In the context of this specification, "memory" or "computer-readable medium" or "plural computer-readable media" may be any non-transitory medium or plural media or means capable of storing, storing, communicating, propagating, or carrying instructions for use by or in connection with an instruction execution system, apparatus, or device such as a computer. As used herein, the term "non-transitory" does not limit the persistence of data storage (e.g., RAM vs. ROM), but rather limits the medium itself (i.e., it is tangible and not a signal).

[0132] The apparatus 1400 further comprises or is connected to an input unit 1430. The input unit 1430 may comprise one or more interfaces for receiving inputs. The one or more interfaces may comprise, for example, one or more temperature sensors, motion sensors, and / or orientation sensors, one or more cameras, one or more acceleration sensors, one or more microphones, one or more buttons, and / or one or more touch detection units. Further, the input unit 1430 may comprise an interface to which an external device may be connected.

[0133] The device 1400 may also include an output unit 1440. The output unit may include or be connected to one or more displays capable of rendering visual content, such as a light-emitting diode (LED) display, a liquid crystal display (LCD), and / or a liquid crystal on silicon (LCoS) display. The output unit 1440 may further include one or more audio output units. The one or more audio output units may be, for example, speakers.

[0134] The device 1400 further includes a connection unit 1450. The connection unit 1450 enables a wireless connection to one or more external devices. The connection unit 1450 may be integrated into the device 1400 or include at least one transmitter and at least one receiver to which the device 1400 can be connected. The at least one transmitter includes at least one transmitting antenna, and the at least one receiver includes at least one receiving antenna. The connection unit 1450 may include an integrated circuit or a set of integrated circuits that provides a wireless communication function to the device 1400. Alternatively, the wireless connection part may be a hard-wired application-specific integrated circuit (ASIC). The connection unit 1450 may include one or more components such as a power amplifier, a digital front end (DFE), an analog / digital converter (ADC), a digital / analog converter (DAC), a frequency converter, a modulator, a demodulator, and / or an encoder / decoder circuit, which are controlled by a corresponding control unit.

[0135] It should be noted that the device 1400 may further include various components not shown in FIG. 14. The various components may be hardware components and / or software components.

[0136] As used herein, the term "circuit" may refer to one or more or all of: a) a hardware-only circuit implementation (such as an implementation only in analog circuits and / or digital circuits), and b) a combination of a hardware circuit and software, for example (where applicable), i) a combination of analog and / or digital hardware circuit(s) and software / firmware, and ii) any portion of a hardware processor(s) and software (including a digital signal processor(s), software, and memory(ies) that cooperate to perform various functions in a device such as a mobile phone), and c) a hardware circuit(s) and / or processor(s) such as a microprocessor(s) or a portion of a microprocessor(s) that require software (such as firmware) to operate, but may not have software present when not required for operation.

[0137] This definition of circuit applies to all uses of this term in this application, including those included in any claims. As a further example, in the context of the present embodiment, the term "circuit" is also intended to cover a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor, and the implementation of the accompanying software and / or firmware thereto. Also, the term "circuit" is intended to cover, for example, a baseband integrated circuit or a processor integrated circuit for a portable device, or a similar integrated circuit in a server, a cellular network device, or other computing or network device, if applicable to the elements of a particular claim.

[0138] The technologies and methods described in this specification can be implemented in various means. For example, these technologies can be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. In the case of hardware implementation, the device(s) of exemplary embodiments can be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), processors, controllers, microcontrollers, microprocessors, other electronic units designed to execute the functions described in this example, or combinations thereof. For firmware or software, implementation can be performed through modules (e.g., procedures, functions, etc.) of at least one chipset that execute the functions in this example. The software code can be stored in a memory unit and executed by a processor. The memory unit can be implemented within the processor or outside the processor. In the latter case, as is known in the art, it can be communicably connected to the processor through various means. Furthermore, the components of the system described in this specification can be rearranged and / or supplemented by additional components to facilitate the achievement of various aspects and the like described therein, and they are not limited to the exact configuration shown in a given figure, as will be understood by those skilled in the art.

[0139] With the progress of technology, it will be apparent to those skilled in the art that the concept of the present invention can be implemented in various ways. This embodiment is not limited to the exemplary embodiments described above and can be modified within the scope of the claims. Therefore, all words and expressions should be interpreted broadly and are intended to illustrate rather than limit the exemplary embodiments.

Claims

1. at least one processor; When executed by the at least one processor, the apparatus: determining whether to flush a hybrid automatic repeat request (HARQ) buffer based on expiration of at least one time alignment timer of the at least two time alignment timers; a first time alignment timer of the at least two time alignment timers is associated with a first timing advance group, and a second time alignment timer of the at least two time alignment timers is associated with a second timing advance group; determining that the HARQ buffer corresponds to the first timing advance group and the second timing advance group, the first timing advance group and the second timing advance group being secondary timing advance groups; and at least one memory storing instructions to cause at least the following to be executed: The instructions cause the device to flush the HARQ buffer in response to not receiving a timing advance command corresponding to the second timing advance group after the first time alignment timer expires and before the second time alignment timer expires. Device.

2. the first timing advance group corresponds to at least one of a first transmission / reception point, a first cell identity, or a first control resource set pool index; the second timing advance group corresponds to at least one of a second transmission / reception point, a second cell identity, or a second control resource set pool index; 10. The apparatus of claim 1.

3. 3. The apparatus of claim 1 or 2, wherein the apparatus comprises or is comprised within a user equipment.

4. determining whether to flush a hybrid automatic repeat request (HARQ) buffer based on expiration of at least one time alignment timer of the at least two time alignment timers; a first time alignment timer of the at least two time alignment timers is associated with a first timing advance group, and a second time alignment timer of the at least two time alignment timers is associated with a second timing advance group; determining that the HARQ buffer corresponds to the first timing advance group and the second timing advance group, the first timing advance group and the second timing advance group being secondary timing advance groups; flushing the HARQ buffer in response to not receiving a timing advance command corresponding to the second timing advance group after the first time alignment timer expires and before the second time alignment timer expires; A method comprising:

5. When executed by an apparatus, the method causes the apparatus to determine whether to flush a hybrid automatic repeat request (HARQ) buffer based on expiration of at least one time alignment timer of at least two time alignment timers, a first time alignment timer of the at least two time alignment timers is associated with a first timing advance group, and a second time alignment timer of the at least two time alignment timers is associated with a second timing advance group; determining that the HARQ buffer corresponds to the first timing advance group and the second timing advance group, the first timing advance group and the second timing advance group being secondary timing advance groups; flushing the HARQ buffer in response to not receiving a timing advance command corresponding to the second timing advance group after the first time alignment timer expires and before the second time alignment timer expires; A non-transitory computer-readable medium containing program instructions for causing at least

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