Techniques for handling timing advance in wireless networks

Abstract

The application relates to devices and components including apparatuses, systems, and methods for handling timing advance in a wireless network.

Description

Technical Field

[0001] The present application relates generally to communication networks, and in particular to techniques for handling timing advance in wireless networks. Background Art

[0002] Cellular communications can be defined in various standards to enable communication between user equipment and cellular networks. For example, the Third Generation Partnership Project (3GPP) provides technical specifications (TSs) designed to improve data transmission speed, reliability, availability, etc. Aspects of these standards include providing and using timing advance to enable coordination and correct reception of uplink communications from user equipment to the network. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 A network environment according to some embodiments is illustrated.

[0004] Figure 2 A signaling diagram according to some embodiments is illustrated.

[0005] Figure 3 A network environment according to some embodiments is illustrated.

[0006] Figure 4 A network environment according to some embodiments is illustrated.

[0007] Figure 5 An operational flow / algorithm structure according to some embodiments is illustrated.

[0008] Figure 6 An operational flow / algorithm structure according to some embodiments is illustrated.

[0009] Figure 7 An operational flow / algorithm structure according to some embodiments is illustrated.

[0010] Figure 8 An operational flow / algorithm structure according to some embodiments is illustrated.

[0011] Figure 9 User equipment according to some embodiments is illustrated.

[0012] Figure 10 A network node according to some embodiments is illustrated. DETAILED DESCRIPTION

[0013] The following detailed description refers to the accompanying drawings. The same reference numerals may be used in different figures to identify the same or similar elements. In the following description, specific details, such as particular structures, architectures, interfaces and / or technologies, are set forth for purposes of illustration and not limitation, so as to provide a thorough understanding of various aspects of some embodiments. However, it will be apparent to those skilled in the art who benefit from this disclosure that various aspects of the various aspects may be practiced in other examples that deviate from these specific details. In some cases, descriptions of well-known devices, circuits and methods are omitted so as not to obscure the description of various aspects due to unnecessary details. For the purposes of this document, the phrase "A or B" means (A), (B) or (A and B); and the phrase "based on A" means "based at least in part on A", for example, it can be "based only on A" or it can be "based in part on A".

[0014] The following is a glossary of terms that may be used in this disclosure.

[0015] As used herein, the term "circuit" refers to, is part of, or includes a hardware component such as an electronic circuit, a logic circuit, a processor (shared, dedicated, or group) or memory (shared, dedicated, or group), an application specific integrated circuit (ASIC), a field programmable device (FPD) (e.g., a field programmable gate array (FPGA), a programmable logic device (PLD), a complex PLD (CPLD), a high capacity PLD (HCPLD), a structured ASIC, or a programmable system on a chip (SoC)), and / or a digital signal processor (DSP) configured to provide the described functionality. In some aspects, a circuit may execute one or more software or firmware programs to provide at least some of the described functionality. The term "circuit" may also refer to a combination of one or more hardware elements (or a combination of circuits used in an electrical or electronic system) and program code for executing the functionality of the program code. In these aspects, the combination of hardware elements and program code may be referred to as a specific type of circuit.

[0016] As used herein, the term "processor circuit" refers to, is part of, or includes circuitry that is capable of sequentially and automatically performing a series of arithmetic or logical operations; or recording, storing, or transferring digital data. The term "processor circuit" may refer to an application processor; a baseband processor; a central processing unit (CPU); a graphics processing unit; a single-core processor; a dual-core processor; a triple-core processor; a quad-core processor; or any other device capable of executing or otherwise operating computer-executable instructions (such as program code); a software module; or a functional process.

[0017] As used herein, the term "interface circuitry" refers to circuitry that enables, is part of, or includes information exchange between two or more components or devices. The term "interface circuitry" may refer to one or more hardware interfaces, such as a bus, an I / O interface, a peripheral component interface, or a network interface card.

[0018] As used herein, the term "user equipment" or "UE" refers to a device that has radio communication capabilities and can represent a remote user of network resources in a communication network. Furthermore, the terms "user equipment" or "UE" may be considered synonymous and may be referred to as a client, mobile phone, mobile device, mobile terminal, user terminal, mobile unit, mobile station, mobile user, subscriber, user, remote station, access agent, user agent, receiver, radio equipment, reconfigurable radio equipment, reconfigurable mobile device, etc. Furthermore, the term "user equipment" or "UE" may include any type of wireless / wired device or any computing device that includes a wireless communication interface.

[0019] As used herein, the term "computer system" refers to any type of interconnected electronic devices, computing devices, or components thereof. Additionally, the term "computer system" or "system" may refer to various components of a computer that are communicatively coupled to one another. Furthermore, the term "computer system" or "system" may refer to multiple computing devices or multiple computing systems that are communicatively coupled to one another and configured to share computing resources or networked resources.

[0020] As used herein, the term "resource" refers to a physical or virtual device, a physical or virtual component within a computing environment, or a physical or virtual component within a specific device, such as computer equipment, mechanical equipment, memory space, processor / CPU time, processor / CPU utilization, processor and accelerator load, hardware time or utilization, power, input / output operations, ports or network sockets, channel / link allocation, throughput, memory utilization, storage, network, database, and application or workload units. "Hardware resources" may refer to computer, storage, or network resources provided by physical hardware elements. "Virtualized resources" may refer to computer, storage, or network resources provided by a virtualization infrastructure to an application, device, system, etc. The terms "network resources" or "communication resources" may refer to resources accessible to a computer device / system via a communication network. The term "system resource" may refer to any type of shared entity that provides a service and may include computing resources or network resources. System resources may be considered a set of coherent functions, network data objects, or services that can be accessed through a server, where such system resources reside on a single host or multiple hosts and can be clearly identified.

[0021] As used herein, the term "channel" refers to any tangible or intangible transmission medium for conveying data or data streams. The term "channel" may be synonymous or equivalent with "communication channel," "data communication channel," "transmission channel," "data transmission channel," "access channel," "data access channel," "link," "data link," "carrier," "radio frequency carrier," or any other similar term representing a path or medium through which data is conveyed. Additionally, as used herein, the term "link" refers to a connection between two devices for the purpose of sending and receiving information.

[0022] As used herein, the terms "instantiate" and "instantiate" and the like refer to the creation of an instance. "Instance" also refers to a concrete occurrence of an object, which may occur, for example, during the execution of program code.

[0023] The term "connected" may mean that two or more elements at a common communication protocol layer have an established signaling relationship with each other through a communication channel, link, interface, or reference point.

[0024] As used herein, the term "network element" refers to physical or virtualized equipment or infrastructure used to provide wired or wireless communication network services. The term "network element" may be considered synonymous with or referred to as a networked computer, networking hardware, network equipment, network node, or virtualized network function, etc.

[0025] The term "information element" refers to a structural element that contains one or more fields. The term "field" refers to the individual contents of an information element or a data element that contains the contents. An information element may include one or more additional information elements.

[0026] Figure 1 A network environment 100 according to some embodiments is illustrated. The network environment 100 may include a UE 104 coupled to a source serving cell of a radio access network (RAN) 108. The source cell 108 may be provided by one or more base stations that provide an air interface compatible with 3GPP technical specifications, such as those defining fifth generation (5G) NR or higher system standards.

[0027] In some embodiments, the source cell 108 may be provided by multiple geographically dispersed nodes (e.g., transmit receive points (TRPs)). To effectively communicate with these TRPs, the UE 104 may be configured with different uplink timing advances (TAs). Generally, the UE 104 may have a TA for each location. Each location may include one TRP or multiple co-located TRPs.

[0028] In some embodiments, the source cell 108 may include a primary serving cell (PCell) and one or more secondary serving cells (SCells). Serving cells that include the same uplink TA may be part of a TA group (TAG). If a TAG includes a PCell, the TAG may be referred to as a primary TAG (pTAG). If a TAG includes only SCells, the TAG may be referred to as a secondary TAG (sTAG). 3GPP TS 38.321 v17.3.0 (2023-01-13) provides methods, procedures, and variables for handling TAs for pTAGs and sTAGs at the medium access control (MAC) layer.

[0029] In addition to the source cell 108, the network environment 100 may also include one or more target cells 112. In some embodiments, the target cell 112 may be a candidate cell for a target of a layer 2 triggered mobility (LTM) cell handover. When the network provides an LTM cell handover command to the UE 104, an LTM cell handover may occur. The LTM cell handover command may be an L2 command (e.g., a MAC control element (CE)) provided to the UE 104. The network may determine whether an LTM cell handover is desired based on lower layer measurement results (e.g., measurements at layer 1 (L1) or L2) reported by the UE 104. In LTM, the UE 104 may perform a random access channel (RACH) operation on the target cell before receiving the LTM cell handover command from the source cell 108. This may allow the UE 104 to obtain the TA value of the target cell in a timely manner to reduce the latency of the LTM cell handover.

[0030] In other embodiments, the target cell 112 may be used in a multi-TRP (mTRP) operation in which the UE 104 maintains concurrent connections with both the source cell 108 and the target cell 112. In some cases, the concurrency of the connections may be relatively short to facilitate, for example, a make-before-break handover.

[0031] In the traditional mTRP scenario, only one TA is supported. In other words, the UE's UL transmission towards the mTRP will need to be configured within the same TAG. This may generally inhibit LTM cell handover and mTRP operation.

[0032] Embodiments of the present disclosure describe support for multiple TAs to facilitate LTM cell handover and other mTRP operations. Specifically, the embodiments provide a process for handling additional TA values ​​and associated management of the additional TA values ​​in cases where the TA / TAG is not considered secondary but primary. This can be, for example, a case where the additional TA value is associated with the primary serving cell (e.g., sPCell) after an LTM cell handover. The embodiments describe the handling of associated timers, handling when the original / new timer expires, and error handling at the source / target cell before an LTM cell handover.

[0033] Figure 2 2 is a signaling operation 200 according to some embodiments. Signaling operation 200 may include signals / actions performed by source node 204, UE 104, and target node 208. Source node 204 may be a base station / TRP providing a source serving cell (e.g., a serving cell of source cell 108). Target node may be a base station / TRP providing a target cell, such as target cell 112.

[0034] The signaling operation 200 may include, at 212, the source node transmitting a trigger request to the UE 104. The trigger request may include an index of a configuration for a target cell / node. Although not specifically shown in the signaling operation 200, the network (e.g., the source node 204) may provide the configuration for each of the plurality of target cells / nodes to the UE 104. The trigger request may request the UE 104 to obtain a TA associated with the indicated target cell / node.

[0035] The signaling operations 200 may also include, at 216, the UE 104 transmitting an uplink transmission to the target node 208. The uplink transmission may serve as a basis for the target node 208 to determine a TA value that the UE 104 should use in UL communications toward the target cell. In some embodiments, the uplink transmission may be a RACH transmission. For example, the UE 104 may transmit a message 1 (Msg1) transmission that includes a random access preamble in a time domain instance provided by the source node 204. In some embodiments, the UE 104 may transmit a sounding reference signal (SRS). From a physical layer (PHY) perspective, the SRS may be similar to an RA preamble. Figure 3 1 is a network environment 100 according to some embodiments, wherein a UE 104 sends an uplink transmission (eg, a RACH / SRS transmission) toward a target LTM cell 304 to obtain a TA value. The target LTM cell 304 may be provided by a target node 208.

[0036] At 220, the target node 208 may determine a TA value based on the UL transmission. The TA value may be determined based on the RACH, SRS, or another method that may be specific to the network implementation. For example, a network providing small cells may provide the same initial TA value to all UEs, and this value may be fine-tuned later in subsequent transmit / receive transactions. Once determined, the TA value may be provided to the UE 104 according to one or more options. In option 224, at 228, the target node 208 may provide the TA value directly to the UE 104. This may be in, for example, a random access response (Msg2). In this case, the UE 104 may monitor a common channel for the random access response and determine whether the random access response is for the UE 104 or for another UE. In option 232, at 236, the target node 208 may transmit the TA value to the source node 204, and at 240, the source node 204 may provide the TA value to the UE 104.

[0037] At 228 or 240, the TA value may be provided to the UE 104 in a MAC CE or in downlink control information (DCI) sent in a physical downlink control channel (PDCCH). The message conveying the TA value may include one or more fields to provide the TA value or an identifier (ID) that may be used to identify a target cell associated with the TA.

[0038] The TA value can be an absolute value (e.g., similar to an absolute timing advance command MAC CE) or a relative value. If the TA value is a relative value, it can be relative to: the current source serving cell; a candidate target cell (e.g., a DL reference signal determined by synchronization with the target cell); a pTAG; or an sTAG.

[0039] The ID that can be used to identify the target cell can be defined based on one or more of the following options. In a first option, the ID can be the physical cell identity (PCI) of the target cell where the UE 104 performs RACH / SRS. In a second option, the ID can be a configuration index that links the ID to a target LTM cell that the UE 104 was previously configured with. In a third option, the ID can be a separate TAG ID for which the UE 104 was previously required to perform RACH / SRS.

[0040] Upon receiving the TA value, the UE 104 may use the ID associated with the TA value to determine whether the TA value is for the target LTM cell 304. If the TA value is for the target LTM cell 304, the UE 104 may store the TA value for the associated index. For example, the TA value may be stored with configuration information associated with the target LTM cell 304.

[0041] In some embodiments, multiple separate TA groups may be provided to the UE 104. Each TA group may be associated with multiple cells, each of which has a TA. The UE 104 may transmit UL transmissions and receive TAs for each of the TA groups. The number of TA groups for which the UE 104 can obtain and store associated TA values ​​may be based on the UE's capabilities. This capability may be signaled to the source serving cell so that the network does not trigger uplink transmissions on more target LTM cells than the UE 104 can handle.

[0042] In some embodiments, the UE 104 may have a TA timer associated with each TA group. Upon receiving a TA associated with a TA group, the TA timer may be started / restarted. For example, if the TA group of the first target LTM cell is configured with a first TA timer, upon receiving a TA associated with the ID of the first target LTM cell (or TA group), the first TA timer may be started / restarted. Expiration of the TA timer may invalidate the associated TA. In some embodiments, the new TA timer may not affect the legacy timing advance timer associated with the current serving cell.

[0043] In some embodiments, rather than relying on a TA timer, the validity of the TA value obtained for LTM operation towards non-serving cells may be controlled by the network. For example, the TA value provided by the network may simply be considered valid and not expired. In these cases, the network may be responsible for triggering a TA update if the current TA is no longer valid.

[0044] If the UE 104 determines based on the ID that the received TA value is not for the target LTM cell, the UE 104 may follow existing procedures for handling TA commands as part of TA reception as defined in 3GPP TS 38.321.

[0045] The signaling operations 200 may also include, at 244, the source node 204 transmitting an LTM cell handover command to the UE 104. The LTM cell handover command may be an L2 message based on lower layer measurements provided to the network.

[0046] Signaling operations 200 may also include, at 248, UE 104 performing an uplink transmission with target node 208. This uplink transmission may be part of or a result of an LTM cell handover. In some embodiments, UE 104 may determine whether the TA value provided at 228 or 240 is still valid. If so, UE 104 may use the TA value. If not, UE 104 may need to acquire a new TA value. This may be accomplished, for example, by performing a RACH procedure.

[0047] As briefly mentioned above, in some embodiments, the validity of the TA value can be based on an associated TA timer. For example, the UE 104 can determine whether it has a valid (e.g., unexpired) TA timer associated with the ID of the target LTM cell when the LTM cell handover command is received at 244. If the TA timer is valid, the UE 104 can determine that the TA value is also valid. Therefore, the UE 104 can apply the TA value to uplink transmissions on the LTM target cell.

[0048] In implementations where there is no TA timer associated with the target LTM cell (eg, there is only a legacy TA timer associated with the serving cell), one or more of the following three options may be used.

[0049] In a first option, if the legacy TA timer is running, UE 104 may consider the TA value associated with the target LTM cell to be valid. Therefore, UE 104 may apply the TA value to uplink transmissions on the LTM target cell. In this option, the legacy TA timer may be either the pTAG timer or the sTAG timer. The network may provide UE 104 with an explicit indication of which timer to use. Alternatively, the timer to use may be predefined, for example, by the 3GPP TS. For example, UE 104 may always apply the pTAG timer as the legacy timer to verify the TA value associated with the target LTM cell.

[0050] In a second option, the UE 104 may always apply the provided TA value to uplink transmissions to the target LTM cell. In this option, no RACH procedure will be performed after receiving the LTM cell handover command at 244, and the legacy TA timer will not be considered relative to the TA value associated with the target LTM cell.

[0051] In a third option, the LTM cell handover command sent at 244 may include an indicator field to indicate one or more of the following procedures for uplink timing advance. In a first procedure, the UE 104 may use the current TA value associated with the target LTM cell. In a second procedure, the LTM cell handover command may include an updated TA value that the UE 104 will use for uplink transmissions to the target LTM cell. In a third procedure, the indicator field may include a value for triggering a contention-free random access (CFRA) or contention-based random access (CBRA) procedure to obtain an updated TA value during LTM operation. The UE 104 may perform the CFRA procedure using a dedicated random access preamble provided to the UE 104 by the network. The UE 104 may perform the CBRA procedure by randomly selecting a preamble from a pool of preambles shared with other UEs.

[0052] The expiration of the legacy TA timer of the current serving cell may be handled according to one or more of the following options.

[0053] In a first option, the UE 104 may not invalidate any TA timers for the target LTM cell, but may not consider any new MAC CEs (or DCIs) with new TA values ​​received after the legacy TA timer expires. For example, consider a first TA timer that is running based on receiving a first TA value received for a first target LTM cell. If the UE 104 receives an updated TA value for the first target LTM cell after the legacy TA timer has expired, the UE 104 may not consider the updated TA value. In this case, the UE 104 may not restart the first TA timer or update the first TA value based on receiving the updated TA value.

[0054] In a second option, the operation of the UE 104 may not be affected by the expiration of the legacy TA timer. The UE 104 may continue to operate / manage LTM-specific TA values / timers and consider them valid independently of the legacy TA timers. If the UE 104 receives a new downlink MAC CE / DCI with an update of the TA value for the target LTM cell, the UE 104 may consider these TA values ​​valid and apply them (and start / restart any associated timers). The UE 104 may do this regardless of whether the legacy TA timer is running or expired.

[0055] In a third option, upon determining that the legacy TA timer has expired, the UE 104 may invalidate all TA values ​​for the target LTM cell and stop the associated timers.

[0056] In the event that the UE 104 determines that the TA timer associated with the first target LTM cell has expired, the UE 104 may perform one or more of the following three options.

[0057] In a first option, UE 104 may invalidate the TA value for the first target LTM cell. If an LTM cell handover occurs to the target LTM cell, UE 104 may initiate a RACH procedure (e.g., a CBRA procedure) for the target LTM cell to obtain an updated TA value. The UE may perform a RACH procedure even if the no-RACH option is configured. Relative to the first option, the operation of the legacy TA timer and transmission / TA management of the legacy serving cell may not be changed.

[0058] In the second option, in addition to invalidating the TA value for the first LTM cell as described above with respect to the first option, the UE 104 will also invalidate the context of all other target LTM cells with respect to their TA values / timers.

[0059] In a third option, in addition to invalidating the context of all other target LTM cells, the UE 104 also considers the legacy TA timer of the serving cell to be expired.

[0060] Using the expiration of the TA timer associated with the first target LTM cell to invalidate the TA values / timers associated with other target LTM cells and even the serving cell (as described in the second and third options) may be a result of the network being responsible for managing the TA values ​​for all cells. To prevent invalidation of the TA value, the network may update the TA value in a timely manner to restart the associated TA timer. In the event that the update is not timely, the TA value may be invalidated to ensure that an outdated TA value is not used.

[0061] Figure 4 A network environment 100 is illustrated in which a UE 104 participates in mTRP operation according to some embodiments. In this embodiment, the UE 104 may be configured to transmit uplink transmissions to a first TRP of a source cell 108 using a first TA (TA1), and may be configured to transmit uplink transmissions to a second TRP of a target cell 404 in a target cell 112 using a second TA (TA2). The target cell 112 may or may not be a target LTM cell. In some embodiments, the UE 104 may be configured to maintain concurrent uplink communications with both the first TRP and the second TRP for a time period. The time period may be in the context of a transition (e.g., a handover or switch). In some cases, the UE 104 may be configured to communicate with the second TRP concurrently with the first TRP in a make-before-break handover to reduce mobility disruptions. In some cases, the UE 104 and the first and second TRPs may perform multi-DCImTRP operation in which UL / DL transmissions to the first TRP / second TRP are scheduled using DCI sent by the corresponding TRPs.

[0062] The difference between the timing of the uplink transmission to the first TRP and the uplink transmission to the second TRP, which may be referred to as the transmit timing difference (TTD), may be limited by a predetermined threshold. For example, for both intra-cell mTRP operation and inter-cell mTRP operation in frequency range 1 (FR1), the maximum TTD may be CP+M1 microseconds, where CP is the length of the cyclic prefix and M1 is the first offset for FR1. For UEs capable of supporting scenarios where the round trip delay (RTD) is greater than the cyclic prefix in FR1, the maximum TTD may be 34.6 microseconds. For both intra-cell multi-DCI mTRP and inter-cell multi-DCI mTRP operation in frequency range 2 (FR2), the maximum TTD may be CP+M2 microseconds, where CP is the length of the cyclic prefix and M2 is the second offset for FR2. For UEs capable of supporting scenarios where the RTD is greater than the cyclic prefix in FR2, the maximum TTD may be 8.5 microseconds.

[0063] Some embodiments describe TA handling in the event that the TTD exceeds a maximum TTD. TA handling may be according to one or more of the following two options.

[0064] In a first option, UE 104 may suspend transmission on one of the TRPs (e.g., the first TRP or the second TRP). The TA value linked to the TRP for which transmission was suspended may be considered invalid. The TA timer associated with the suspended TRP may be stopped. This option may be based on the assumption that the TA timer is restarted when a new TA value is received. The new TA value may be received when the network performs a reconfiguration of the communication link.

[0065] In a second option, a TTD exceeding a predetermined threshold may not be associated with a change in the handling of the TA timer. For example, if the associated TA timer is running, the UE 104 may continue to communicate with TRP 1 using TA1, and if the associated TA timer is running, the UE may also continue to communicate with TRP 2 using TA2.

[0066] Many of the above embodiments describe TA handling when the network provides a new TA value to the UE 104. However, in some cases, the change of the TA association for LTM or TRP may be accomplished with a change in the Transmission Configuration Indicator (TCI) state. For example, the UE 104 may be given an updated TCI state relative to the target cell. Although the TCI state may refer to a downlink reference signal, this may also result in a change in uplink transmission characteristics. For example, the UE 104 may measure the downlink reference signal indicated by the TCI state to obtain a channel estimate value, which is then applied to the uplink transmission. Therefore, a change in the TCI state of the downlink reference signal used as the basis for determining the channel estimate value for the uplink transmission may change the TA association for a particular target cell.

[0067] In cases where the TA association change for the target cell is accomplished using a TCI state change, the UE 104 may view the TA association change as an assignment of a new TA value for the current target LTM cell / mTRP. The UE 104 may apply the new TA value in uplink communications in the target cell. The validity of the TA value may be based on a TA timer associated with the target cell, as discussed elsewhere herein. Additionally or alternatively, the validity of the TA value may be accomplished without a TA timer specifically configured for the target cell, as discussed elsewhere herein. In these embodiments, the legacy TA timer may not be changed based on the TA association change.

[0068] Figure 5 An operational flow / algorithm structure 500 for TA handling according to some embodiments is illustrated. The operational flow / algorithm structure 500 may be implemented by a UE (such as, for example, UE 104 or 900) or a component therein (eg, processing circuit 904).

[0069] The operational flow / algorithm structure 500 may include receiving a trigger signal at 504. The trigger signal may be received from a serving cell and may direct the UE to obtain a TA value associated with a target LTM cell.

[0070] The operational flow / algorithm structure 500 may further include transmitting an uplink signal toward the target LTM cell at 508. The uplink signal may be a RACH signal (eg, msg1 transmission) or an SRS.

[0071] The operational flow / algorithm structure 500 may also include, at 512, determining a TA value associated with the target LTM cell. The UE may receive the TA value in a MAC CE or DCI from the source serving cell or the target LTM cell. The TA value may be sent along with an identifier of the target LTM cell, a configuration index associated with the target LTM cell, or a TA group. The TA value may be an absolute value, relative to the timing of the serving cell, relative to the timing of the target LTM cell, relative to the timing of the pTAG, or relative to the timing of the sTAG.

[0072] Upon receiving the TA value, the UE may store the TA value along with the configuration associated with the target LTM cell. In some embodiments, the UE may be able to store / maintain TA values ​​for a number of TA groups. In these embodiments, the UE may provide the base station with an indication of the number of TA groups for which the UE can maintain TA information. If the TA value is associated with a TA timer, the UE may restart the TA timer upon receiving the TA value.

[0073] The operational flow / algorithm structure 500 may further include receiving an LTM cell handover command at 516. The LTM cell handover command may be received from a source cell and may direct the UE to perform an LTM cell handover to a target LTM cell.

[0074] The operational flow / algorithm structure 500 may also include, at 520, determining whether the TA value is valid. In some embodiments, the TA value may be considered valid until an updated TA value is received. In other embodiments, the validity of the TA value may be determined based on whether an associated TA timer is running. The TA timer may be specifically associated with the target LTM cell, may be associated with another target LTM cell, or may be associated with the source cell. If the UE determines that the TA value is valid, the operational flow / algorithm structure may continue to use the TA value for uplink transmissions toward the target LTM cell at 524.

[0075] If the UE determines that the TA value is not valid (e.g., the associated TA timer has expired), the operational flow / algorithm structure may proceed to obtain a new TA value when using the new TA value for uplink transmission. In some embodiments, the new TA value may be obtained by performing a RACH operation with the target LTM cell.

[0076] Figure 6 An operational flow / algorithm structure 600 for LTM cell handover operations according to some embodiments is illustrated. The operational flow / algorithm structure 600 may be implemented by a base station or a TRP, such as, for example, the source node 204, the network node 1000, or a component thereof (e.g., the processing circuit 1004). The base station or TRP may provide a serving cell for the source cell 108.

[0077] The operational flow / algorithm structure 600 may include providing a trigger signal to the UE at 604. The trigger signal may indicate that the UE is to obtain a TA value relative to a target LTM cell.

[0078] In some embodiments, the TA value may be provided to the UE directly from the target LTM cell.In other embodiments, the target LTM cell may provide the TA value to the base station, which may then provide the TA value to the UE.

[0079] The operational flow / algorithm structure 600 may also include providing an LTM cell handover command to the UE at 608. The LTM cell handover command may trigger an LTM cell handover to a target LTM cell. In some embodiments, the LTM cell handover command may include a TA value and potentially an associated TA timer.

[0080] Figure 7 700 according to some embodiments. The operation flow / algorithm structure 700 may be implemented by a UE (eg, UE 104 or UE 900) or a component thereof (eg, processor 904).

[0081] The operational flow / algorithm structure 700 may include, at 704, obtaining first and second TA values ​​corresponding to a first cell and a second cell, respectively. In some embodiments, the first and second cells may include a source cell and a target LTM cell. In some embodiments, the first and second cells may be provided by first and second TRPs, respectively, in an mTRP operation.

[0082] In some implementations, a TA timer may be associated with each of the first cell and the second cell.These TA timers may be started / restarted upon receipt of the first TA value / second TA value.

[0083] The operational flow / algorithm structure 700 may further include determining, at 708, that the TTD exceeds a predefined threshold. The threshold may be statically defined by, for example, the 3GPP TS or may be dynamically configured by the network. In some embodiments, the threshold may be based on whether the UE is operating in FR1 or FR2.

[0084] The operational flow / algorithm structure 700 may further include invalidating the second TA value at 712. If the TA timer is associated with the second TA value, the TA timer may also be stopped.

[0085] Figure 8 8 is an operational flow / algorithm structure 800 for TA handling according to some embodiments. The operational flow / algorithm structure 600 may be implemented by a UE (such as, for example, UE 104 or 900) or a component therein (eg, processing circuit 904).

[0086] The operational flow / algorithm structure 800 may include receiving an indication of a TCI status for a target cell at 804. The indication may be sent in a DCI that updates the TCI status in the target cell. The target cell may be a target LTM cell or provided by a TRP as part of an mTRP operation.

[0087] The operational flow / algorithm structure 800 may also include determining a TA value associated with the target cell based on the TCI status, at 808. In some embodiments, the TA value may be associated with a TA timer that is started / restarted upon receiving an indication of the TCI status.

[0088] The operational flow / algorithm structure 800 may also include, at 812, using the TA value to transmit an uplink transmission to the target cell. In some embodiments, the uplink transmission may be the result of an LTM cell handover. For example, the UE may perform an uplink transmission after receiving an LTM cell handover command. In some cases, the UE may determine whether the TA value is valid before using it for the uplink transmission. This may be based on a TA timer associated with the TA value. Alternatively, the TA value may be assumed to be valid unless an updated TA value is received. If the TA value is not valid after receiving the LTM cell handover command, the UE may perform a RACH on the target cell to obtain an updated TA value.

[0089] Figure 9 UE 900 according to some embodiments is illustrated. UE 900 may be similar to Figure 1 UE 104 and is essentially interchangeable therewith.

[0090] UE 900 can be any mobile or non-mobile computing device, such as, for example, a mobile phone, a computer, a tablet, an XR device, glasses, an industrial wireless sensor (e.g., a microphone, a carbon dioxide sensor, a pressure sensor, a humidity sensor, a thermometer, a motion sensor, an accelerometer, a laser scanner, a fluid level sensor, an inventory sensor, a voltage / current meter, or an actuator), a video surveillance / monitoring device (e.g., a camera or a camcorder), a wearable device (e.g., a smart watch), or an IoT device.

[0091] UE 900 may include a processor 904, RF interface circuitry 908, memory / storage 912, a user interface 916, sensors 920, driver circuitry 922, a power management integrated circuit (PMIC) 924, antenna structures 926, and a battery 928. The components of UE 900 may be implemented as integrated circuits (ICs), portions of integrated circuits, discrete electronic devices or other modules, logic, hardware, software, firmware, or combinations thereof. Figure 9 The block diagram is intended to illustrate a high-level view of some of the components of the UE 900. However, some of the components shown may be omitted, additional components may be present, and different arrangements of the components shown may occur in other implementations.

[0092] Components of the UE 900 may be coupled to various other components via one or more interconnects 932, which may represent any type of interface, input / output, bus (local, system, or extension), transmission line, trace, or optical connection that allows various circuit components (on a common or different chip or chipsets) to interact with each other.

[0093] The processor 904 may include processor circuits such as, for example, a baseband processor circuit (BB) 904A, a central processor unit circuit (CPU) 904B, and a graphics processor unit circuit (GPU) 904C. The processor 904 may include any type of circuit or processor circuit that executes or otherwise operates computer-executable instructions (such as program code, software modules, or functional processes from the memory / storage device 912) to cause the UE 900 to perform operations as described herein.

[0094] In some embodiments, the baseband processor circuit 904A can access the communication protocol stack 936 in the memory / storage device 912 to communicate over a 3GPP-compatible network. Generally speaking, the baseband processor circuit 904A can access the communication protocol stack 936 to perform user plane functions at the PHY layer, MAC layer, RLC sublayer, PDCP sublayer, SDAP sublayer, and upper layers; and to perform control plane functions at the PHY layer, MAC layer, RLC sublayer, PDCP sublayer, RRC layer, and NAS layer. In some embodiments, PHY layer operations can additionally / alternatively be performed by components of the RF interface circuit 908.

[0095] The baseband processor circuit 904A may generate or process baseband signals or waveforms that carry information in 3GPP-compliant networks. In some embodiments, the waveforms used for NR may be based on cyclic prefix OFDM (CP-OFDM) in the uplink or downlink, and discrete Fourier transform spread OFDM (DFT-S-OFDM) in the uplink.

[0096] The memory / storage device 912 may include one or more non-transitory computer-readable media including instructions (e.g., the communication protocol stack 936) that may be executed by one or more processors in the processor 904 to cause the UE 900 to perform various TA handling / management operations described herein. For example, the processor 904 may cause the UE to execute the operational flow / algorithm structure 500, 700, or 800 or any other method or process described herein. In some embodiments, some or all of these TA handling / management operations may be performed by the MAC layer of the UE 900.

[0097] The memory / storage 912 includes any type of volatile or non-volatile memory that may be distributed throughout the UE 900. In some embodiments, some of the memory / storage 912 may be located on the processor 904 itself (e.g., L1 cache and L2 cache), while other memory / storage 912 is external to the processor 904 but accessible via a memory interface. The memory / storage 912 may include any suitable volatile or non-volatile memory, such as, but not limited to, dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory, or any other type of memory device technology.

[0098] The RF interface circuit 908 may include transceiver circuitry and a radio frequency front-end module (RFEM) that allows the UE 900 to communicate with other devices via a radio access network. The RF interface circuit 908 may include various components arranged in a transmit path or a receive path. These components may include, for example, switches, mixers, amplifiers, filters, synthesizer circuits, and control circuits.

[0099] In the receive path, the RFEM receives the radiated signal from the air interface via the antenna structure 926 and further filters and amplifies the signal (using a low-noise amplifier). The signal can be provided to the transceiver's receiver, which downconverts the RF signal to a baseband signal that is provided to the baseband processor of the processor 904.

[0100] In the transmit path, the transmitter of the transceiver up-converts the baseband signal received from the baseband processor and provides an RF signal to the RFEM. The RFEM may amplify the RF signal through a power amplifier before radiating the signal across the air interface via the antenna structure 926.

[0101] In various embodiments, the RF interface circuit 908 may be configured to send / receive signals in a manner compatible with NR access technology.

[0102] The antenna structure 926 may include antenna elements for converting electrical signals into radio waves to travel through the air and converting received radio waves into electrical signals. These antenna elements may be arranged into one or more antenna panels. The antenna structure 926 may have antenna panels that are omnidirectional, directional, or a combination thereof to achieve beamforming and multiple-input, multiple-output communications. The antenna structure 926 may include microstrip antennas, printed antennas manufactured on the surface of one or more printed circuit boards, patch antennas, or phased array antennas. The antenna structure 926 may have one or more panels designed for specific frequency bands, including frequency bands in FR1 or FR2.

[0103] The user interface 916 includes various input / output (I / O) devices designed to enable a user to interact with the UE 900. The user interface 916 includes input device circuitry and output device circuitry. The input device circuitry includes any physical or virtual component for accepting input, including, in particular, one or more physical or virtual buttons (e.g., a reset button), a physical keyboard, a keypad, a mouse, a touchpad, a touch screen, a microphone, a scanner, or a head-mounted device. The output device circuitry includes any physical or virtual component for displaying or otherwise conveying information (such as sensor readings, actuator positioning, or other similar information). The output device circuitry may include any number or combination of audio or visual displays, including, in particular, one or more simple visual outputs / indicators (e.g., binary state indicators such as light-emitting diodes (LEDs) and multi-character visual outputs), or more complex outputs such as a display device or touch screen (e.g., a liquid crystal display (LCD), an LED display, a quantum dot display, and a projector), where the output, such as characters, graphics, and multimedia objects, is generated or produced by the operation of the UE 900.

[0104] Sensors 920 may include devices, modules, or subsystems designed to detect events or changes in their environment and transmit information about the detected events (sensor data) to some other device, module, or subsystem. Examples of such sensors include: an inertial measurement unit including an accelerometer, gyroscope, or magnetometer; a microelectromechanical system or nanoelectromechanical system including a 3-axis accelerometer, 3-axis gyroscope, or magnetometer; a liquid level sensor; a flow sensor; a temperature sensor (e.g., a thermistor); a pressure sensor; a barometric pressure sensor; a gravity meter; an altimeter; an image capture device (e.g., a camera or lensless aperture); a light detection and ranging sensor; a proximity sensor (e.g., an infrared radiation detector, etc.); a depth sensor; an ambient light sensor; an ultrasonic transceiver; and a microphone or other similar audio capture device.

[0105] The driver circuitry 922 may include software and hardware components that operate to control a particular device embedded in, attached to, or otherwise communicatively coupled to the UE 900. The driver circuitry 922 may include various drivers to allow other components to interact with or control various I / O devices that may be present within or connected to the UE 900. For example, the driver circuitry 922 may include circuitry for facilitating coupling a UICC (e.g., UICC 98) to the UE 900. In additional examples, the driver circuitry 922 may include: a display driver for controlling and enabling access to a display device; a touch screen driver for controlling and enabling access to a touch screen interface; a sensor driver for obtaining sensor readings from, and controlling and enabling access to, the sensor 920; a driver for obtaining actuator positioning or controlling, and enabling access to, an electromechanical component; a camera driver for controlling and enabling access to an embedded image capture device; and an audio driver for controlling and enabling access to one or more audio devices.

[0106] The PMIC 924 may manage power provided to various components of the UE 900. Specifically, with respect to the processor 904, the PMIC 924 may control power source selection, voltage scaling, battery charging, or DC-DC conversion.

[0107] In some embodiments, the PMIC 924 may control or otherwise be part of various power saving mechanisms of the UE 900, including DRX, as discussed herein.

[0108] The battery 928 can power the UE 900, but in some examples, the UE 900 can be installed and deployed in a fixed location and can have a power source coupled to the power grid. The battery 928 can be a lithium-ion battery and a metal-air battery (such as a zinc-air battery, an aluminum-air battery, a lithium-air battery), etc. In some specific implementations, such as in vehicle-based applications, the battery 928 can be a typical lead-acid car battery.

[0109] Figure 10 Illustrated is a network node 1000 according to some embodiments. The network node 1000 may be similar to, and essentially interchangeable with, a base station or TRP providing one or more serving cells for the source cell 108 or the target cell 112.

[0110] Network node 1000 may include a processor 1004 , RF interface circuitry 1008 (if implemented as an access node), core network (CN) interface circuitry 1012 , memory / storage circuitry 1016 , and antenna structures 1026 .

[0111] Components of network node 1000 may be coupled to various other components via one or more interconnects 1028 .

[0112] The processor 1004, RF interface circuit 1008, memory / storage 1016 (including communication protocol stack 1010), antenna structure 1026 and interconnect 1028 may be similar to those of reference Figure 9 Like-named elements are shown and described.

[0113] The memory / storage device 1016 may include one or more non-transitory computer-readable media that include instructions (e.g., the communication protocol stack 1010) that are executable by one or more processors in the processor 1004 to cause the network node 1000 to perform various TA handling / management operations described herein. For example, the processor 1004 may cause the network node 1000 to perform the operational flow / algorithm structure 600 or any other method or process described herein.

[0114] The CN interface circuitry 1012 can provide connectivity to a core network (e.g., a 5th Generation Core Network (5GC) using a 5GC-compatible network interface protocol, such as a Carrier Ethernet protocol or some other suitable protocol). Network connectivity can be provided to / from the network node 1000 via optical fiber or wireless backhaul. The CN interface circuitry 1012 can include one or more dedicated processors or FPGAs for communicating using one or more of the aforementioned protocols. In some implementations, the CN interface circuitry 1012 can include multiple controllers for providing connectivity to other networks using the same or different protocols.

[0115] In some embodiments, the network node 1000 may be coupled to a transmit receive point (TRP) using antenna structures 1026, CN interface circuitry, or other interface circuitry.

[0116] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly stated to users.

[0117] For one or more aspects, at least one of the components described in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, or methods described in the following embodiments. For example, the baseband circuitry described above in conjunction with one or more of the preceding figures may be configured to operate in accordance with one or more of the embodiments described below. For another example, circuitry associated with the UE, base station, network element, etc. described above in conjunction with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples described in the following embodiments.

[0118] Example

[0119] In the following sections, additional exemplary aspects are provided.

[0120] Embodiment 1 includes a method of operating a user equipment (UE), the method comprising: receiving a trigger signal from a source cell; sending an uplink signal toward a target layer 2 triggered mobility (LTM) cell based on the trigger signal; receiving a timing advance (TA) value associated with the target LTM cell; receiving an LTM cell switching command; determining whether the TA value is valid; and performing an LTM cell switching based on receiving the LTM cell switching command and determining whether the TA value is valid.

[0121] Embodiment 2 includes a method according to embodiment 1 or some other embodiment herein, wherein determining whether the TA value is valid includes determining that the TA value is valid, and the method further includes: performing the LTM cell handover by transmitting an uplink transmission to the target LTM cell using the TA value.

[0122] Embodiment 3 includes a method according to embodiment 1 or some other embodiment herein, wherein the TA value is a first TA value, determining whether the first TA value is valid includes determining that the first TA value is not valid, and the method further includes: obtaining a second TA value; and using the second TA value to perform the LTM cell switching.

[0123] Embodiment 4 includes the method of embodiment 1 or some other embodiment herein, wherein the uplink signal is one of a random access channel (RACH) transmission or a sounding reference signal (SRS) transmission.

[0124] Embodiment 5 includes the method according to embodiment 1 or some other embodiment herein, further comprising: receiving the TA value from the source cell or the target LTM cell in a medium access control (MAC) control element (CE) or downlink control information (DCI).

[0125] Embodiment 6 includes a method according to embodiment 5 or some other embodiment herein, wherein the MAC CE or DCI includes an identifier associated with the target LTM cell, the identifier being a physical cell identifier (PCI) of the target LTM cell, a configuration index associated with the target LTM cell, or a TA group identifier.

[0126] Embodiment 7 includes a method according to embodiment 1 or some other embodiment herein, wherein the TA value is a first TA value, and the first TA value is: an absolute value; timing relative to the source cell; timing relative to the target LTM cell; timing relative to the primary timing advance group; or timing relative to the secondary timing advance group.

[0127] Embodiment 8 includes the method of embodiment 1 or some other embodiment herein, further comprising: receiving a configuration associated with the target LTM cell; and storing the TA value with the configuration.

[0128] Embodiment 9 includes the method of embodiment 1 or some other embodiment herein, further comprising providing an indication to a base station of a number of TA groups for which the UE can maintain TA information.

[0129] Embodiment 10 includes the method according to embodiment 1 or some other embodiment herein, further comprising: determining whether a timer has expired based on receiving the LTM cell switching command; and determining whether the TA value is valid based on the determination of whether the timer has expired.

[0130] Embodiment 11 includes the method of embodiment 10 or some other embodiment herein, wherein the timer is associated with the target LTM cell, and the method further comprises starting or restarting the timer based on receiving the TA value.

[0131] Embodiment 12 includes a method according to embodiment 11 or some other embodiment herein, the method further comprising: determining that a TA timer associated with the source cell has expired; and invalidating the TA value and stopping the timer associated with the target LTM cell based on determining that the TA timer associated with the source cell has expired.

[0132] Embodiment 13 includes a method according to embodiment 11 or some other embodiment herein, wherein determining whether the timer has expired includes determining that the timer has expired, and the method further includes: invalidating the TA value and performing a random access channel (RACH) procedure as part of performing the LTM cell handover; invalidating the TA value, performing a random access channel (RACH) procedure as part of performing the LTM cell handover, and invalidating one or more additional TA values ​​associated with one or more additional target LTM cells respectively; or invalidating the TA value, performing a random access channel (RACH) procedure as part of performing the LTM cell handover, invalidating one or more additional TA values ​​associated with one or more additional target LTM cells respectively, and deeming the TA timer associated with the source cell to have expired.

[0133] Embodiment 14 includes the method of embodiment 10 or some other embodiment herein, wherein the timer is associated with the source cell, a primary TA group, or a secondary TA group.

[0134] Embodiment 15 includes a method according to embodiment 1 or some other embodiment herein, wherein the TA value is a first TA value, and the method further includes: determining that a TA timer associated with the source cell expires; receiving a second TA value associated with the target LTM cell; and discarding the second TA value based on determining that the TA timer associated with the source cell expires.

[0135] Embodiment 16 includes a method according to embodiment 1 or some other embodiment herein, wherein the TA value is a first TA value, and the LTM cell switching command includes an indication to use the following for uplink transmission to the target LTM cell: the first TA value; a second TA value in the LTM cell switching command; or a second TA value to be obtained through a random access channel (RACH) procedure.

[0136] Embodiment 17 includes a method of operating a base station, the method comprising: providing a trigger signal to a user equipment (UE) to trigger sending an uplink signal toward a target layer 2 triggered mobility (LTM) cell to obtain a timing advance (TA) value; and providing an LTM cell switching command to the UE to trigger LTM cell switching to the target LTM cell.

[0137] Embodiment 18 includes the method of embodiment 17 or some other embodiment herein, further comprising: receiving the TA value from the LTM cell; and providing the TA value to the UE.

[0138] Embodiment 19 includes the method of embodiment 18 or some other embodiment herein, wherein providing the TA value comprises providing the TA value in the LTM cell handover command.

[0139] Embodiment 20 includes a method of operating a user equipment (UE), the method comprising: obtaining a first timing advance (TA) value associated with a first cell; obtaining a second set of TA values ​​associated with a second cell; determining a transmit timing difference (TTD) based on the first TA value and the second TA value; determining that the TTD exceeds a predefined threshold; and invalidating the second TA value based on determining that the TTD exceeds the predefined threshold.

[0140] Embodiment 21 includes a method according to embodiment 20 or some other embodiment herein, the method further comprising: starting or restarting a timer associated with the second cell based on obtaining the second TA value; and stopping the timer based on determining that the TTD exceeds the predefined threshold.

[0141] Embodiment 22 includes the method of embodiment 20 or some other embodiment herein, wherein the first cell is a source cell and the second cell is a target cell.

[0142] Embodiment 23 includes the method of embodiment 22 or some other embodiment herein, wherein the target cell is a layer 2 triggered mobility (LTM) cell.

[0143] Embodiment 24 includes a method according to embodiment 20 or some other embodiment herein, wherein the UE is configured for multiple transmit reception point (TRP) operation.

[0144] Embodiment 25 includes a method of operating a user equipment (UE), the method comprising: receiving an indication of a transmit configuration indicator (TCI) state for a target cell; determining a timing advance (TA) value associated with the target cell based on the TCI state; and using the TA value to transmit an uplink transmission to the target cell.

[0145] Embodiment 26 includes a method according to embodiment 25 or some other embodiment herein, the method further comprising: starting or restarting a timer based on the indication of the TCI state; receiving a layer 2 triggered mobility (LTM) cell switching command; determining that the timer has not expired based on receiving the LTM cell switching command; and based on the determination that the timer has not expired, using the TA value to transmit the uplink transmission to the target cell.

[0146] Embodiment 27 includes a method according to embodiment 25 or some other embodiment herein, wherein the UE is configured for multi-TRP operation.

[0147] Another embodiment may include one or more non-transitory computer-readable media, which include instructions that, when executed by one or more processors of an electronic device, cause the electronic device to perform one or more elements of a method described or related to any one of Embodiments 1 to 27 or any other method or process described herein.

[0148] Another embodiment may include an apparatus comprising logic components, modules, or circuits for performing one or more elements of the method described in accordance with or related to any of Embodiments 1 to 27, or any other method or process described herein.

[0149] Another embodiment may include a method, technique, or process described according to or in connection with any one of Embodiments 1 to 27, or a portion or component thereof.

[0150] Another embodiment may include a device comprising: one or more processors; and one or more computer-readable media, wherein the one or more computer-readable media include instructions that, when executed by the one or more processors, cause the one or more processors to perform methods, techniques, or processes described in accordance with or related to any one of embodiments 1 to 27 or portions thereof.

[0151] Another embodiment comprises a signal as described or relating to any one of embodiments 1 to 27, or parts or components thereof.

[0152] Another embodiment may include a datagram, information element, packet, frame, segment, PDU or message as described or related to any one of embodiments 1 to 27 or part or component thereof or otherwise described in this disclosure.

[0153] Another embodiment may include a signal encoded with data as described or associated with any one of embodiments 1 to 27, or portions or components thereof, or as otherwise described in this disclosure.

[0154] Another embodiment may include a signal encoded with a datagram, IE, packet, frame, segment, PDU, or message as described or related to any one of embodiments 1 to 27 or parts or components thereof or otherwise described in this disclosure.

[0155] Another embodiment may include an electromagnetic signal carrying computer-readable instructions, wherein execution of the computer-readable instructions by one or more processors will cause the one or more processors to perform a method, technique, or process described in accordance with or related to any one of embodiments 1 to 27 or a portion thereof.

[0156] Another embodiment may include a computer program comprising instructions, wherein execution of the program by a processing element causes the processing element to perform a method, technique, or process as described or related to any one of embodiments 1 to 27 or a portion thereof.

[0157] Another embodiment may include signals in a wireless network as shown and described herein.

[0158]

[0011] Another embodiment may include a method of communicating in a wireless network as shown and described herein.

[0159]

[0011] Another embodiment may include a system for providing wireless communications as shown and described herein.

[0160]

[0011] Another embodiment may include an apparatus for providing wireless communications as shown and described herein.

[0161] Unless expressly stated otherwise, any of the above embodiments may be combined with any other embodiment (or combination of embodiments). The foregoing description of one or more specific implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the various aspects to the precise forms disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the various aspects.

[0162] Although the above aspects have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to encompass all such variations and modifications.

Claims

1. One or more computer-readable media having instructions that, when executed by one or more processors, cause a user equipment (UE) to: receiving a trigger signal from a source cell; sending an uplink signal towards a target layer 2 triggered mobility (LTM) cell based on the trigger signal; receiving a timing advance (TA) value associated with the target LTM cell; Receive LTM cell switching command; Determining whether the TA value is valid; as well as An LTM cell handover is performed based on receiving the LTM cell handover command and determining whether the TA value is valid.

2. The one or more computer-readable media of claim 1 , wherein determining whether the TA value is valid determines that the TA value is valid, and the instructions, when executed, further cause the UE to: The LTM cell handover is performed by transmitting an uplink transmission to the target LTM cell using the TA value.

3. The one or more computer-readable media of claim 1 , wherein the TA value is a first TA value, determining whether the first TA value is valid comprises determining that the first TA value is not valid, and the instructions, when executed, further cause the UE to: obtaining a second TA value; and The LTM cell handover is performed using the second TA value.

4. The one or more computer-readable media of claim 1, wherein the uplink signal is a random access channel (RACH) transmission or a sounding reference signal (SRS) transmission.

5. The one or more computer-readable media of claim 1 , wherein the instructions, when executed, further cause the UE to: The TA value is received from the source cell or the target LTM cell in a medium access control (MAC) control element (CE) or downlink control information (DCI).

6. The one or more computer-readable media of claim 5, wherein the MAC CE or DCI includes an identifier associated with the target LTM cell, the identifier being a physical cell identifier (PCI) of the target LTM cell, a configuration index associated with the target LTM cell, or a TA group identifier.

7. The one or more computer-readable media of claim 1, wherein the TA value is a first TA value that: is an absolute value; is relative to the timing of the source cell; Timing relative to the target LTM cell; Timing of the advance group relative to the master timing; Or relative to the timing of the secondary timing advance group.

8. The one or more computer-readable media of claim 1 , wherein the instructions, when executed, further cause the UE to: receiving a configuration associated with the target LTM cell; and The TA value is stored with the configuration.

9. The one or more computer-readable media of claim 1 , wherein the instructions, when executed, further cause the UE to: An indication is provided to a base station of a number of TA groups for which the UE can maintain TA information.

10. The one or more computer-readable media of claim 1 , wherein the instructions, when executed, further cause the UE to: determining whether a timer has expired based on receiving the LTM cell switch command; and Whether the TA value is valid is determined based on the determining whether the timer has expired.

11. The one or more computer-readable media of claim 10, wherein the timer is associated with the target LTM cell, and the instructions, when executed, further cause the UE to: The timer is started or restarted based on receiving the TA value.

12. The one or more computer-readable media of claim 11, wherein the instructions, when executed, further cause the UE to: determining that a TA timer associated with the source cell has expired; and The TA value is invalidated and the timer associated with the target LTM cell is stopped based on determining that the TA timer associated with the source cell has expired.

13. The one or more computer-readable media of claim 11 , wherein determining whether the timer has expired comprises determining that the timer has expired, and the instructions, when executed, further cause the UE to: invalidating the TA value and performing a random access channel (RACH) procedure as part of performing the LTM cell handover; invalidating the TA value, performing a random access channel (RACH) procedure as part of performing the LTM cell handover, and invalidating one or more additional TA values ​​respectively associated with one or more additional target LTM cells; or The TA value is invalidated, a random access channel (RACH) procedure is performed as part of performing the LTM cell handover, one or more additional TA values ​​respectively associated with one or more additional target LTM cells are invalidated, and a TA timer associated with the source cell is deemed expired.

14. The one or more computer-readable media of claim 10, wherein the timer is associated with the source cell, a primary TA group, or a secondary TA group.

15. The one or more computer-readable media of claim 1 , wherein the TA value is a first TA value, and the instructions, when executed, further cause the UE to: Determining that a TA timer associated with the source cell has expired; receiving a second TA value associated with the target LTM cell; and The second TA value is discarded based on determining that the TA timer associated with the source cell expires.

16. One or more computer-readable media according to claim 1, wherein the TA value is a first TA value, and the LTM cell handover command includes an indication to use, for uplink transmissions to the target LTM cell: the first TA value; a second TA value in the LTM cell handover command; or a second TA value to be obtained through a random access channel (RACH) procedure.

17. A method of operating a base station, the method comprising: providing a trigger signal to a user equipment (UE) to trigger the transmission of an uplink signal towards a target layer 2 triggered mobility (LTM) cell to obtain a timing advance (TA) value; as well as An LTM cell handover command is provided to the UE to trigger an LTM cell handover to the target LTM cell.

18. The method according to claim 17, further comprising: receiving the TA value from the LTM cell; as well as The TA value is provided to the UE.

19. The method of claim 18, wherein providing the TA value comprises providing the TA value in the LTM cell handover command.

20. A method of operating a user equipment (UE), the method comprising: obtaining a first timing advance (TA) value associated with a first cell; obtaining a second TA value associated with a second cell; determining a transmit timing difference (TTD) based on the first TA value and the second TA value; determining that the TTD exceeds a predefined threshold; as well as The second TA value is invalidated based on a determination that the TTD exceeds the predefined threshold.

21. The method according to claim 20, further comprising: starting or restarting a timer associated with the second cell based on obtaining the second TA value; as well as The timer is stopped based on determining that the TTD exceeds the predefined threshold.

22. The method of claim 20, wherein the first cell is a source cell and the second cell is a target cell.

23. The method of claim 22, wherein the target cell is a Layer 2 Triggered Mobility (LTM) cell.

24. The method of claim 20, wherein the UE is configured for multiple transmit reception point (TRP) operation.

25. An apparatus for use in a user equipment (UE), the apparatus comprising: a receiving circuit configured to receive an indication of a transmit configuration indicator (TCI) status for a target cell; processing circuitry for determining a timing advance (TA) value associated with the target cell based on the TCI state; and A transmitting circuit is configured to transmit an uplink transmission to the target cell using the TA value.

26. The apparatus of claim 25, wherein the processing circuit is further configured to: starting or restarting a timer based on the indication of the TCI status; receiving, via the receiving circuit, a layer 2 triggered mobility (LTM) cell handover command; determining that the timer has not expired based on receiving the LTM cell handover command; as well as Based on the determination that the timer has not expired, the uplink transmission is transmitted to the target cell using the TA value via the transmitting circuitry.

27. An apparatus according to claim 25, wherein the UE is configured for multi-TRP operation.

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