Method and apparatus for reducing cell handover delay in ltm

Abstract

Examples of devices (e.g., user equipment) for reducing cell handover latency in LTM are described. The device receives an LTM cell handover command from a serving cell. The device determines whether a first time or frequency tracking on the target cell is activated prior to the LTM cell handover command. The apparatus determines whether an L1 reference signal received power measurement period is not greater than a predetermined value. The apparatus determines, if at least one condition is satisfied, that the second T / F tracking is not performed before the first uplink message is transmitted on the target cell. The at least one condition includes activation of a first T / F tracking of the target cell prior to the LTM cell handover command, and the L1-RSRP measurement period is not greater than a predetermined value.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is part of the non-provisional application claiming priority to PCT Application No. PCT / CN2023 / 108583, filed on July 21, 2023, the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure generally relates to mobile communications, and more particularly, to reducing cell handover delay in Layer 1 (L1) or Layer 2 (L2) triggered mobility (LTM). BACKGROUND

[0003] The methods described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

[0004] In mobile communications, handover refers to the process of transferring an ongoing communication session of a user equipment (UE) from one cell to another to ensure seamless connectivity and service continuity for the user, especially when the user is moving. In the conventional handover (e.g., a type of cell handover) defined in 3GPP R17, the serving cell handover is triggered by Layer 3 (L3) measurements and radio resource control (RRC) signaling to switch from a serving cell to a target cell. This L3-based mobility involves reconfiguration of upper layers (e.g., RRC layer and / or packet data convergence protocol (PDCP) layer) and resetting of lower layers (e.g., medium access control (MAC) layer and / or physical (PHY) layer), which inevitably leads to long delay, large signaling overhead, and long interruption time. In the upgrade to R18, low-layer triggered mobility (or referred to as LTM) is introduced to enable the cell handover procedure through L1 or L2 signaling, which can maintain the configuration of the upper layers and / or minimize the change of lower layer configuration to reduce the delay in the cell handover procedure.

[0005] In the application of LTM in 5G New Radio (NR) systems, a base station (BS) can trigger a cell handover procedure through an LTM cell handover command to change the serving cell of a UE, and the UE can switch from the serving cell to a target cell through a candidate configuration previously prepared and provided to the UE. After receiving the LTM cell handover command, the UE can need to perform operations such as LTM cell handover command processing / decoding, LTM processing of RRC signaling, LTM processing, and time or frequency (T / F) tracking in order to switch to the target cell. However, the above operations can cause cell handover delay in the ongoing communication session of the UE, which can impair the user experience.

[0006] Therefore, there is a need to provide solutions to improve the cell handover procedure and reduce the cell handover delay in LTM. SUMMARY

[0007] The following summary is illustrative only and is not intended to be limiting in any way. That is, the following summary is provided to introduce some concepts, aspects, benefits and advantages of the novel and non-obvious technology described herein. Selected implementations are described in further detail in the following detailed description. Thus, the following summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter in any way.

[0008] It is an object of the present invention to propose solutions or schemes to address the above-mentioned problems related to cell handover delay in LTM. It is believed that the above-mentioned problems can be avoided or alleviated by implementing one or more of the suggested schemes described herein.

[0009] In one aspect, a method can involve a processor of a device receiving an LTM cell handover command from a serving cell. In response, the method can involve the processor determining whether a first time or frequency tracking on a target cell was activated prior to the LTM cell handover command. The method can further involve the processor determining whether an L1 reference signal received power (L1-RSRP) measurement period is not greater than a predetermined value. Accordingly, the method can involve the processor determining that a second time or frequency tracking is not performed prior to transmitting a first uplink (UL) message on the target cell in the event that at least one condition is met. The at least one condition can include the first time or frequency tracking on the target cell being activated prior to the LTM cell handover command and the L1-RSRP measurement period being not greater than the predetermined value.

[0010] In another aspect, an apparatus can include a transceiver that, during operation, communicates with a serving cell and a target cell of a network. The apparatus can include a processor communicatively coupled with the transceiver. The processor can receive, via the transceiver, an LTM cell handover command from the serving cell. In response, the processor can determine whether a first time or frequency tracking on the target cell was activated prior to the LTM cell handover command. The processor can further determine whether an L1-RSRP measurement period is not greater than a predetermined value. Accordingly, the processor can determine that a second time or frequency tracking is not performed prior to transmitting a first UL message on the target cell in the event that at least one condition is met. The at least one condition can include the first time or frequency tracking on the target cell being activated prior to the LTM cell handover command and the L1-RSRP measurement period being not greater than the predetermined value.

[0011] It is worth noting that although the description provided herein can be in the context of certain radio access technologies, networks, and network topologies, such as NR systems, the proposed concepts, solutions, and any variants / derivatives thereof can be implemented in other types of wireless and wired communication technologies, networks, and network topologies, such as, but not limited to, Ethernet, Universal Terrestrial Radio Access Network (UTRAN), Evolved UTRAN, Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS) / Enhanced Data Rates for Global Evolution (EDGE) Radio Access Network (GERAN), Long Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro, Internet of Things (IoT), Industrial Internet of Things (IIoT), Narrow Band-IoT (NB-IoT), and any future developed network technologies. Therefore, the scope of the present application is not limited to the examples described herein. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings are included to provide a further understanding of the present content and are incorporated in and constitute a part of the present content. These drawings illustrate embodiments of the present content and, together with the description, serve to explain the principles of the present content. It is noted that the drawings are not necessarily to scale, as some components can be shown exaggerated in scale or with exaggerated proportions in order to illustrate the concept of the present content.

[0013] Figure 1 is a schematic diagram of an example network system according to embodiments of the present application.

[0014] Figure 2A is a schematic diagram of an example deployment scenario for intra-DU inter-cell beam management according to embodiments of the present application.

[0015] Figure 2B is a schematic diagram of an example deployment scenario for inter-DU inter-cell beam management according to embodiments of the present application.

[0016] Figure 3 is a schematic diagram of an LTM first solution according to embodiments of the present application.

[0017] Figure 4 is a schematic diagram of an LTM second solution according to embodiments of the present application.

[0018] Figure 5 illustrates another example communication system having at least an example communication device and an example network device according to embodiments of the present application.

[0019] Figure 6 illustrates an example flow according to embodiments of the present application. DETAILED DESCRIPTION

[0020] This invention discloses detailed embodiments and implementations of the claimed subject matter. However, it should be understood that the inventive embodiments and implementations are merely illustrative of the claimed subject matter, which can be implemented in various forms. Moreover, the invention can be implemented in many different forms and should not be construed as limited to the exemplary embodiments and implementations set forth herein. Rather, these exemplary embodiments and implementations are provided to make the specification of this invention comprehensive and complete, and to fully convey the scope of the invention to those skilled in the art. In the following description, details of known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments and implementations.

[0021] Overview This invention relates to various techniques, methods, schemes, and / or solutions for reducing cell handover delay in LTM. According to this invention, multiple possible schemes can be implemented individually or in combination. That is, although these possible solutions may be described individually below, two or more of these possible solutions may be implemented in a combination or other combined manner.

[0022] Figure 1 An example mobile communication network 100 according to an embodiment of the present invention is shown. Figure 1 As shown, the mobile communication network 100 supports various wireless communication services and can operate functionally across at least the core network (CN) 110 and multiple base stations (e.g., evolved Node Bs (eNBs), next-generation Node Bs (gNBs), or transmit and receive points (TRPs)) with different protocol segmentation options. In some implementations, the multiple BSs can be gNBs implemented as a central unit (CU) 120 and distributed units (DUs) 130-132 associated with service coverage / cells (e.g., cell 1, cell 2, and cell 3). In some implementations, the Serving Data Application Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers can reside in the CU 120, while the Radio Link Control (RLC), Media Access Control (MAC), and Physical (PHY) layers can reside in the DUs 130-132.

[0023] Figure 2A An example deployment scenario 200 for inter-cell beam management within a DU, according to an embodiment of the present invention, is illustrated. Figure 2AAs shown, CU 201 is connected to two DUs 202 and 203 via an F1 interface, and each DU is connected to multiple Radio Units (RUs). For example, DU 202 is connected to RUs 210-212, while DU 203 is connected to RUs 220-222. Each RU can correspond to a cell that can independently provide wireless communication services within its coverage area, and a DU connected to at least one RU can correspond to an integrated coverage area / cell. For example, integrated coverage area / cell 240 corresponds to DU 202, while integrated coverage area / cell 250 corresponds to DU 203.

[0024] like Figure 2A As shown, User Equipment (UE) 230 is moving from the edge of one cell (e.g., cell 241) to another cell (e.g., cell 242) within the same DU (e.g., DU 202), and these two cells share a common protocol stack. In deployment scenario 200, intra-DU inter-cell beam management can be applied to replace the traditional handover process, thereby reducing interruptions and improving throughput and handover reliability (measured by UE handover failure rate). In some implementations, a single protocol stack on the UE side (i.e., a common RLC / MAC) can be used to handle L1 or L2 inter-cell beam management with mobility.

[0025] Figure 2B An example deployment scenario 260 for inter-DU inter-cell beam management according to an embodiment of the present invention is shown. Figure 2A The deployment scenario 200 is similar. Figure 2BDeployment scenario 260 includes CU 201, two DUs 202 and 203, multiple RUs 210-212 and 220-222, and integrated coverage / cells 240 and 250. The difference is that UE 230 is moving from the edge of one cell (e.g., cell 242) to another cell (e.g., cell 251), where cells 242 and 251 correspond to different DUs (e.g., cell 242 corresponds to DU 202, and cell 251 corresponds to DU 203) and share a common CU (e.g., CU 201). Therefore, the lower-layer (e.g., RLC and MAC) user planes may differ in the two DUs, while the higher-layer (e.g., PDCP) may remain unchanged. Inter-DU inter-cell beam management can be applied to deployment scenario 260 to replace the traditional handover process, thereby reducing interruptions and improving throughput and handover reliability (measured by UE handover failure rate). In some implementations, a single protocol stack on the UE side (i.e., a common RLC / MAC) can be used to handle mobility-based L1 or L2 inter-cell beam management. In other implementations, dual protocol stacks on the UE side (i.e., separate RLC / MAC) can be used to handle mobility-based L1 or L2 inter-cell beam management.

[0026] In Release 17 (R17), handover (e.g., a cell handover) was triggered via L3 measurement and RRC signaling to switch from the serving cell to the target cell. With the upgrade to R18, LTM was introduced to enable the cell handover process via L1 or L2 signaling (i.e., lower-layer signaling), which can effectively reduce latency, overhead, and downtime during the cell handover process. In some embodiments, LTM can support... Figure 2A The intra-DU inter-cell beam management shown in the figure Figure 2B The diagram illustrates at least one of inter-DU (Digital Unit) beam management and inter-CU (Digital Unit) beam management. Therefore, during LTM (Large Term Injection), the user plane can be used continuously on the target cell without being reset (i.e., within the DU) to avoid additional delays in data loss and data recovery.

[0027] In some implementations, when LTM is introduced in an NR system, if the serving cell (or its base station) initiates a cell handover procedure, the UE may be configured with at least one candidate cell to measure the candidate cell. After the UE reports the corresponding measurements to the serving cell, the serving cell may instruct the UE to perform a cell handover procedure to switch to a target cell via an LTM cell handover command (e.g., MAC control element (CE) or other signaling). During the measurement of at least one candidate cell, the UE may perform pre-tracking (e.g., first time or frequency tracking (T / F tracking)) via a reference signal (RS) to synchronize with the candidate cell. Specifically, the RS may include a synchronization signal and a Physical Broadcast Channel (PBCH) block (SSB) or Tracking Reference Signal (TRS) from the target cell. In some implementations, first time or frequency tracking may be activated by a Transport Configuration Indicator (TCI) state activation command (e.g., MAC CE). If a TCI state activation command is received, the UE may periodically perform first time or frequency tracking on the target cell.

[0028] In some implementations, after receiving an LTM cell handover command from the serving cell (e.g., via MAC CE or other signaling), the UE may perform an operation that includes LTM cell handover command processing / decoding, LTM processing of RRC signaling, LTM processing, and another time or frequency tracking (e.g., second time or frequency tracking, or fine tracking). These operations may result in additional delays (defined as cell handover delay) until the UE completes the cell handover process to successfully hand over from the serving cell to the target cell.

[0029] Figure 3 An example scenario 300 of cell handover delay in LTM according to an embodiment of the present invention is illustrated. For example... Figure 3 As shown, in some implementations, the UE may sequentially receive a MAC CE for activating the TCI state of the target cell from the serving cell, and an LTM cell handover command indicating the cell handover process (e.g., via another MAC CE). In some implementations, the aforementioned MAC CE for activating first time or frequency tracking, the TCI state of the target cell, and / or the LTM cell handover command received by the UE may be transmitted separately or adaptively integrated according to different requirements, and this invention does not impose limitations. Next, in response to receiving the LTM cell handover command, the UE may perform the aforementioned operations related to the cell handover delay (denoted as T1), which may include an LTM cell handover command processing period T. cmd RRC signaling processing time T LTM_RRC_processing LTM processing cycle T LTM_processing(L1 / L2 / L3 processing, including L2 and / or L3 reconfiguration, and / or radio frequency retuning, and / or baseband retuning, and / or security update, etc.), a second time or frequency tracking period T T / F_tracking and a time T to wait for the first uplink occasion LTM_IU wherein the second time or frequency tracking is also used to synchronize to the target cell in downlink and / or uplink transmissions. After processing the above operations and successfully handover to the target cell, the UE can perform the first uplink message / transmission (e.g., physical random access channel (PRACH) and / or physical uplink shared channel (PUSCH)) on the target cell.

[0030] In view of the above operations, since the first time or frequency tracking has already been performed on the target cell, and the second time or frequency tracking is also performed on the target cell to achieve the same function / purpose (e.g., to synchronize to the target cell in downlink transmissions), there can be redundant processing to sequentially perform the first time or frequency tracking and the second time or frequency tracking under certain conditions. In order to reduce the cell handover delay, some proposed schemes are introduced below to adaptively skip the redundant time or frequency tracking for improvement.

[0031] According to a first proposed scheme of the present disclosure, after receiving the LTM cell handover command from the serving cell, the UE can determine two judgment conditions, including determining whether the first time or frequency tracking on the target cell is activated before receiving the LTM cell handover command (denoted as judgment condition D1-1), and determining whether the L1-RSRP measurement period is not greater than a predetermined value (denoted as judgment condition D1-2). Specifically, the predetermined value can be 160 milliseconds (ms) or other integer values according to different requirements, as specified in R18 or other versions of 3GPP specifications.

[0032] If the UE determines that both judgment conditions D1-1 and D1-2 are true (i.e., the first time or frequency tracking on the target cell is activated before receiving the LTM cell handover command, and the L1-RSRP measurement period is not greater than the predetermined value), the UE can determine not to perform the second time or frequency tracking (i.e., fine tracking) before transmitting the first uplink message on the target cell. That is, the UE can directly utilize the information (e.g., downlink synchronization information) obtained from the first time or frequency tracking on the target cell during the cell handover process, and skip the second time or frequency tracking on the target cell, which can effectively reduce the additional processing time and shorten the cell handover delay. Of course, in addition to the judgment conditions D1-1 and D1-2, more determinations can be applicable to the UE to determine whether to perform the second time or frequency tracking before transmitting the first uplink message on the target cell, which is not limited by the present disclosure.

[0033] Alternatively, if the user equipment determines that at least one of the two judgment conditions D1-1 and D1-2 is not true (i.e., the first time or frequency tracking on the target cell is not activated and / or the L1-RSRP measurement period is greater than a predetermined value before receiving the LTM cell handover command), the UE can determine to perform the second time or frequency tracking before transmitting the first uplink message (e.g., PRACH and / or PUSCH) on the target cell. That is, the UE still needs to perform the second time or frequency tracking on the target cell because the information related to the target cell (e.g., downlink synchronization information) can have expired and needs to be re-acquired / updated before switching to the target cell.

[0034] According to a second proposal of the present application, after receiving the LTM cell handover command from the serving cell, the UE can determine three judgment conditions, including determining whether the transmission configuration indicator (TCI) state of the target cell indicated in the LTM cell handover command is in the active TCI state list (denoted as judgment condition D2-1), determining whether the time difference (denoted as t1) between receiving the MAC CE activating the target TCI state and the LTM cell handover command is at least the duration related to processing the first time or frequency tracking (denoted as judgment condition D2-2), which is the period X (i.e., the duration X is long enough for the UE to perform the first time or frequency tracking) allowing the UE to completely complete the first time or frequency tracking operation, and determining whether the L1-RSRP measurement period is not greater than a predetermined value (denoted as judgment condition D2-3). Specifically, according to different requirements, the predetermined value can be 160 milliseconds or other integer values, as specified in the R18 or other versions of 3GPP specifications.

[0035] If the UE determines that all three judgment conditions D2-1, D2-2 and D2-3 are true (i.e., the target TCI state of the target cell indicated in the LTM cell handover command is in the active TCI state list, the time difference t1 is at least the duration X (i.e., t1 is equal to or greater than X), and the L1-RSRP measurement period is not greater than the predetermined value), the UE can determine not to perform the second time or frequency tracking before transmitting the first UL message (e.g., PRACH and / or PUSCH) on the target cell. Of course, in addition to the judgment conditions D2-1, D2-2 and D2-3, more judgment conditions can be applied for the UE to determine whether to perform the second time or frequency tracking before transmitting the first UL message on the target cell, which is not limited by the present application. For example, an additional judgment condition can be adaptively incorporated into the second proposal, in which the UE determines whether the time difference t1 is not greater than 160 milliseconds, so that the judgment condition is true if X < t1 < 160 milliseconds.

[0036] Alternatively, if the UE determines that at least one of the three judgment conditions D2-1, D2-2, and D2-3 is not met (i.e., the target TCI state of the target cell indicated in the LTM cell handover command is not in the list of active TCI states, the time difference t1 is not at least the duration X, and / or the L1-RSRP measurement period is greater than a predetermined value), then the UE can determine to perform a second time or frequency tracking before transmitting the first UL message (e.g., PRACH and / or PUSCH) on the target cell, so that the UE can update / obtain information related to the target cell (e.g., downlink synchronization information) in a timely manner before transmitting the first UL message (e.g., PRACH and / or PUSCH) on the target cell.

[0037] Of course, the above order and / or combination related to the judgment conditions D1-1 and D1-2 in the first proposed scheme and the judgment conditions D2-1, D2-2 and D2-3 in the second proposed scheme can be adaptively adjusted according to different requirements / capabilities of the NR system or UE, and this invention does not impose any limitations. Furthermore, other judgment conditions can be adaptively applied to the first proposed scheme and / or the second proposed scheme according to different requirements / capabilities of the NR system or UE, and this invention does not impose any limitations.

[0038] like Figure 3 As shown, when it is determined that the time difference t1 is not at least the duration X (i.e., t1 is less than the duration X derived from Formula 1), the UE can determine to perform a second time or frequency tracking before transmitting the first UL message (e.g., PRACH and / or PUSCH) on the target cell.

[0039] Figure 4 This is an example scenario 400 of LTM cell handover delay according to an embodiment of the present invention. Scenario 400 is similar to scenario 300, except that scenario 400 is an exemplary demonstration under the condition that a second time or frequency tracking is not performed before the UE determines to transmit the first UL message (e.g., PRACH and / or PUSCH) on the target cell. Specifically, if the UE applies one of the first, second, and third proposed schemes described above to adaptively skip the second time or frequency tracking during cell handover triggered by an LTM cell handover command, the UE may incur another cell handover delay T2 during the cell handover process, including the LTM cell handover command processing period T. cmd RRC signaling processing time T LTM_RRC_processing LTM processing cycle T LTM_processing (i.e., L1 / L2 / L3 processing, including L2 and / or L3 reconfiguration, and / or RF retuning, and / or baseband retuning, and / or security updates, etc.), second time or frequency tracking period T T / F_tracking And the time T spent waiting for the first UL opportunityLTM_IU wherein the cell switch delay T2 is significantly shorter than the cell switch delay T1 to reduce the second time or frequency tracking period T T / F_tracking .

[0040] In some implementations, when applying the above first, second and third suggested solutions, the LTM in NR system can be implemented through a random access channel (RACH) based handover procedure or a RACH-less handover procedure. Specifically, in one example of the RACH based handover procedure, before transmitting the first uplink message (i.e., PRACH) on the target cell, the user equipment can transmit a PRACH preamble to the target cell. Next, the UE can receive a random access response (RAR) from the target cell, where the RAR can include an UL grant for transmitting the first UL message on the target cell. In this way, if the UE determines to perform the second time or frequency tracking in the cell switch procedure, the base station can exclude the UE from random access resource allocation, i.e., more random access resources can be allocated to other UEs in the same serving cell.

[0041] In one example of the RACH-less handover procedure, before transmitting the first UL message (i.e., PUSCH) on the target cell, no PRACH is needed on the target cell, and the UE can only receive a downlink control information (DCI) from the target cell for scheduling the first UL message on the target cell. In this way, the network can decide when to transmit the DCI to the UE depending on whether the UE performs or skips the second time or frequency tracking. For example, if the UE determines not to perform the second time or frequency tracking, the base station can transmit the DCI to the UE earlier, so that the UE can transmit the first UL message on the target cell as soon as possible.

[0042] Based on the above judgment conditions (e.g., D1-D3), when applying the LTM in NR system through the RACH or RACH-less based cell switch procedure, since the UE can adaptively determine not to perform the second time or frequency tracking (i.e., fine tracking) in the case that the first time or frequency tracking (i.e., pre-tracking) has been completed with the applicable / latest downlink synchronization information of the target cell, the cell switch delay can be effectively shortened, thereby reducing the delay, signaling overhead and interruption time in the cell switch procedure.

[0043] Illustrative Implementation Figure 5is an example communication system 500 that includes at least an example communication device 510 and an example network device 520 in accordance with an embodiment of the application. The device 510 and the device 520 can perform various functions to implement the schemes, techniques, processes, and methods described herein related to reducing cell handover delay in LTM, including the various proposed designs, concepts, schemes, systems (including the network system 100), and methods described above, as well as the processes described below.

[0044] Each of the device 510 and the device 520 can be part of an electronic apparatus, which can be a network apparatus or a UE (e.g., the UE 230), such as a portable or mobile apparatus, a wearable apparatus, an in-vehicle device or vehicle, a wireless communication apparatus, or a computing apparatus. For example, each of the device 510 and the device 520 can be implemented in a smartphone, a smartwatch, a personal digital assistant, an electronic control unit (ECU) in a vehicle, a digital camera, or a computing device (e.g., a tablet, a notebook, or a laptop). Each of the device 510 and the device 520 can also be part of a machine-type apparatus, which can be an Internet of Things (IoT) apparatus, such as a fixed or stationary apparatus, a home appliance, a roadside unit (RSU), a wired communication apparatus, or a computing apparatus. For example, each of the device 510 and the device 520 can be implemented in a smart thermostat, a smart refrigerator, a smart door lock, a wireless speaker, or a home control center. When implemented in a network apparatus, the device 510 and / or the device 520 can be implemented in an eNB in an LTE, LTE-Advanced, or LTE-Advanced Pro network, or in a gNB, a satellite, a relay, or a transmission reception point (TRP) in a 5G, NR, or IoT network.

[0045] In certain implementations, each of the device 510 and the device 520 can be implemented in the form of one or more integrated circuit (IC) chips, such as (but not limited to) one or more single-core processors, one or more multi-core processors, one or more complex instruction set computing (CISC) processors, or one or more reduced instruction set computing (RISC) processors. In the various schemes described above, each of the device 510 and the device 520 can be implemented in a network apparatus or a UE. Each of the device 510 and the device 520 can include at least some of the components shown in FIG. 5, such as the processor 512 and the processor 522. Each of the device 510 and the device 520 can also include one or more other components (e.g., an internal power supply, a display device, and / or a user interface device) that are not related to the proposed schemes of the application, although for simplicity and brevity, these components are not shown in FIG. 5 and are not described below. Figure 5 Figure 5 Each of the device 510 and the device 520 can be part of an electronic apparatus, which can be a network apparatus or a UE (e.g., the UE 230), such as a portable or mobile apparatus, a wearable apparatus, an in-vehicle device or vehicle, a wireless communication apparatus, or a computing apparatus. For example, each of the device 510 and the device 520 can be implemented in a smartphone, a smartwatch, a personal digital assistant, an electronic control unit (ECU) in a vehicle, a digital camera, or a computing device (e.g., a tablet, a notebook, or a laptop). Each of the device 510 and the device 520 can also be part of a machine-type apparatus, which can be an Internet of Things (IoT) apparatus, such as a fixed or stationary apparatus, a home appliance, a roadside unit (RSU), a wired communication apparatus, or a computing apparatus. For example, each of the device 510 and the device 520 can be implemented in a smart thermostat, a smart refrigerator, a smart door lock, a wireless speaker, or a home control center. When implemented in a network apparatus, the device 510 and / or the device 520 can be implemented in an eNB in an LTE, LTE-Advanced, or LTE-Advanced Pro network, or in a gNB, a satellite, a relay, or a transmission reception point (TRP) in a 5G, NR, or IoT network.

[0046] ​In one aspect, the processor 512 and the processor 522 can be implemented in the form of one or more single-core processors, one or more multi-core processors, or one or more complex-instruction-set computing (CISC) or reduced-instruction-set computing (RISC) processors. That is, although the singular term "processor" is used to refer to the processor 512 and the processor 522, each of the processor 512 and the processor 522 can include multiple processors in accordance with certain implementations of the present application, as well as a single processor in other implementations. In another aspect, each of the processor 512 and the processor 522 can be implemented in the form of hardware (and, optionally, firmware), the electronic components including, for example and without limitation, one or more transistors, one or more diodes, one or more capacitors, one or more resistors, one or more inductors, one or more memristors, and / or one or more varactors, the components being configured and arranged to achieve a particular purpose in accordance with the present application. In other words, each of the processor 512 and the processor 522 is, in at least some implementations, a special purpose machine specially designed, arranged, and configured to perform particular tasks, including those related to reducing cell handover delays in LTMs in accordance with various implementations of the present application.

[0047] In some implementations, the device 510 can also include a transceiver 516 coupled to the processor 512. The transceiver 516 can wirelessly transmit and receive data. In some implementations, the transceiver 516 can wirelessly communicate with different types of wireless networks of different RATs. In some implementations, the transceiver 516 can be equipped with multiple antenna ports (not shown), such as four antenna ports. That is, the transceiver 516 can be equipped with multiple transmit antennas and multiple receive antennas for multiple-input multiple-output (MIMO) wireless communications. In some implementations, the device 520 can also include a transceiver 526 coupled to the processor 522. The transceiver 526 can include a transceiver capable of wirelessly transmitting and receiving data. In some implementations, the transceiver 526 can wirelessly communicate with different types of UEs / wireless networks of different RATs. In some implementations, the transceiver 526 can be equipped with multiple antenna ports (not shown), such as four antenna ports. That is, the transceiver 526 can be equipped with multiple transmit antennas and multiple receive antennas for MIMO wireless communications.

[0048] In some implementations, the device 510 can further include a memory 514 coupled with and accessible by the processor 512 and capable of storing data. In some implementations, the device 520 can further include a memory 524 coupled with and accessible by the processor 522 and capable of storing data. Each of the memory 514 and the memory 524 can include a random access memory (RAM), such as dynamic RAM (DRAM), static RAM (SRAM), thyristor RAM (T-RAM), and / or zero capacitor RAM (Z-RAM). Alternatively, or additionally, each of the memory 514 and the memory 524 can include a read-only memory (ROM), such as a mask ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), and / or electrically erasable programmable ROM (EEPROM). Alternatively, or additionally, each of the memory 514 and the memory 524 can include a non-volatile random access memory (NVRAM), such as flash memory, solid-state memory, ferroelectric RAM (FeRAM), magnetoresistive RAM (MRAM), and / or phase change memory. Alternatively, or additionally, each of the memory 514 and the memory 524 can include a UICC.

[0049] Each of the device 510 and the device 520 can be a communication entity capable of communicating using various proposed solutions in accordance with the present disclosure. For illustrative purposes and without loss of generality, the capabilities of the device 510 are provided below as a UE (e.g., the UE 230) and / or a network node (e.g., the RUs 210-212) of a wireless network.

[0050] In accordance with certain proposed solutions of the present disclosure relating to reducing cell switch delay in LTM, the processor 512 in the device 510 (as or implemented in the UE 230) can receive, via the transceiver 516, an LTM cell switch command from a serving cell. Further, the processor 512 can determine whether a first time or frequency tracking on a target cell is activated prior to the LTM cell switch command. Further, the processor 512 can determine whether a L1-RSRP measurement period is not greater than a predetermined value. Accordingly, the processor 512 can determine not to perform a second time or frequency tracking on the target cell prior to transmitting a first UL message on the target cell in a case that at least one condition is satisfied. The at least one condition can include the first time or frequency tracking on the target cell being activated prior to the LTM cell switch command and the L1-RSRP measurement period being not greater than the predetermined value.

[0051] In some implementations, the processor 512 can determine to perform a second time or frequency tracking on the target cell before transmitting the first UL message on the target cell if at least one condition is met. The at least one condition can include that the first time or frequency tracking on the target cell is not activated before the LTM cell switch command, or that a L1-RSRP measurement period is greater than a predetermined value.

[0052] In some implementations, determining whether the first time or frequency tracking on the target cell is activated before the LTM cell command can include determining whether a TCI state of the target cell indicated in the LTM cell switch command is in an active TCI state list, and determining not to perform the second time or frequency tracking on the target cell before transmitting the first UL message on the target cell if at least one condition is met. The at least one condition can include that a target TCI state of the target cell indicated in the LTM cell switch command is in the active TCI state list.

[0053] In some implementations, the active TCI state list can include an LTM candidate cell active TCI state list or a serving cell active TCI state list.

[0054] In certain implementations, the processor 512 can receive a medium access control control element activating a target TCI state of the target cell.

[0055] In certain implementations, the processor 512 can determine whether a time difference between receiving the MAC CE activating the target TCI state and the LTM cell switch command is at least a duration related to processing the first time or frequency tracking and no more than a predetermined value, and determine not to perform the second time or frequency tracking before transmitting the first uplink message on the target cell if at least one condition is met. The at least one condition can include that the time difference between receiving the MAC CE activating the target TCI state and the LTM cell switch command is at least the duration and no more than the predetermined value.

[0056] In certain implementations, the predetermined value can be 160 milliseconds.

[0057] In certain implementations, the processor 512 can transmit a physical random access channel preamble to the target cell and receive a random access response from the target cell, where the RAR can include an UL grant for transmitting the first UL message on the target cell.

[0058] In certain implementations, the processor 512 can receive a downlink control information scheduling the first UL message on the target cell.

[0059] In certain implementations, the first time or frequency tracking and the second time or frequency tracking can include synchronizing with the target cell using a reference signal from the target cell.

[0060] Illustrative Process Figure 6 An example process 600 in accordance with an embodiment of the present application is shown. Process 600 can be representative of implementing some or all of the designs, concepts, schemes, systems, and methods including the various proposals described above. More specifically, process 600 can be representative of an aspect of the proposed concepts and schemes related to reducing cell handover delay in an LTM. Process 600 can include one or more operations, actions, or functions shown by one or more of blocks 610 through 640. Although shown as discrete blocks, each block of process 600 can be divided into more blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. Further, blocks / sub-blocks of process 600 can be performed in the order shown in FIG. 6, or in a different order. Additionally, one or more blocks / sub-blocks of process 600 can be performed iteratively. Process 600 can be implemented by or in devices 510 and 520, and any variants thereof. For illustrative purposes only and without limitation of the scope, process 600 is described in the following with device 510 as a user equipment (e.g., user equipment 230) and device 520 as a communication entity of a wireless network (e.g., remote unit 210-212). Process 600 can start at block 610. Figure 6

[0061] At 610, process 600 can involve processor 512 of device 510 implementing or as user equipment 230 receiving an LTM cell handover command from a serving cell. Process 600 can proceed from 610 to 620.

[0062] At 620, process 600 can involve processor 512 determining whether a first time or frequency tracking on a target cell was activated prior to the LTM cell handover command. Process 600 can proceed from 620 to 630.

[0063] At 630, process 600 can involve processor 512 determining whether a L1-RSRP measurement period is not greater than a predetermined value. Process 600 can proceed from 630 to 640.

[0064] At 640, process 600 can involve processor 512 determining that a second time or frequency tracking is not performed prior to transmitting a first UL message on the target cell in a case where at least one condition is met. The at least one condition includes the first time or frequency tracking on the target cell being activated prior to the LTM cell handover command and the L1-RSRP measurement period being not greater than the predetermined value.

[0065] ​In certain implementations, the process 600 can further involve the processor 512 determining to perform the second time or frequency tracking before transmitting the first UL message on the target cell if at least one condition is met. The at least one condition includes that the first time or frequency tracking on the target cell is not activated before the LTM cell switch command, or that the L1-RSRP measurement period is greater than a predetermined value.

[0066] In certain implementations, determining whether the first time or frequency tracking on the target cell is activated before the LTM cell command can include determining whether a TCI state of the target cell indicated in the LTM cell switch command is in an active TCI state list, and determining not to perform the second time or frequency tracking before transmitting the first UL message on the target cell if at least one condition is met. The at least one condition can include that a target TCI state of the target cell indicated in the LTM cell switch command is in the active TCI state list.

[0067] In certain implementations, the active TCI state list can include an LTM candidate cell active TCI state list or a serving cell active TCI state list.

[0068] In certain implementations, the process 600 can further involve the processor 512 receiving a MAC CE activating a target TCI state of the target cell.

[0069] In certain implementations, the process 600 can further involve the processor 512 determining whether a time difference between receiving the MAC CE activating the target TCI state and the LTM cell switch command is at least a duration related to processing the first time or frequency tracking and no more than a predetermined value, and determining not to perform the second time or frequency tracking before transmitting the first UL message on the target cell if at least one condition is met. The at least one condition can include that the time difference between receiving the MAC CE activating the target TCI state and the LTM cell switch command is at least the duration and no more than the predetermined value.

[0070] In certain implementations, the predetermined value can be 160 milliseconds.

[0071] In certain implementations, the process 600 can further involve the processor 512 transmitting a PRACH preamble to the target cell and receiving a RAR from the target cell, where the RAR can include an UL grant for transmitting the first UL message on the target cell.

[0072] In some implementations, the process 600 can further involve the processor 512 receiving a DCI for scheduling the first UL message on the target cell.

[0073] In some implementations, the first time or frequency tracking and the second time or frequency tracking can include synchronizing with the target cell using a reference signal from the target cell.

[0074] Additional Description The subject matter described can, in some implementations, be implemented to include a variety of different components in addition to or in place of the components depicted. It will be appreciated that many implementations of the subject matter described here can be manufactured and sold, and hence are expressly incorporated herein in their entirety. It will be appreciated that any component or module described herein can be updated, either by a software update or by a hardware update, to add or modify functionality. It will be further appreciated that any component or module described herein can be implemented to operate on a virtual machine or other virtual operating environment.

[0075] Still further, with respect to any plurality and / or singular terms used herein, those of ordinary skill in the art can convert from the plural to the singular and / or from the singular to the plural as is appropriate for the content and / or the application at hand. It is intended that the disclosure be construed broadly and in a literal and / or broad sense.

[0076] Further, those skilled in the art will appreciate that, in general, the terms used in the present application, and particularly in the appended claims (e.g., in the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes, but is not limited to," etc.). Those skilled in the art will further appreciate that if an introduced claim recitation lists a specific number of an item, that number of that item is intended to be a definite recitation unless specifically stated otherwise (e.g., "at least one" is intended to be a definite recitation). For example, to help understand, the appended claims can include the use of introductory phrases such as "at least one" and "one or more." However, the use of such phrases is not meant to imply that the claim recitation by an indefinite article "a" or "an" limits the claim to only one such recited item, even when the same claim uses such definite articles in conjunction with a transitive term, such as "comprises" or "comprising." Such definite articles merely provide one skilled in the art with assurance that the claims use a sufficiently broad interpretation to encompass that specific number of that recited item. Similarly, the indefinite article "a" or "an" preceding an element does not exclude the existence of more than one of the element in a claim. A single claim featuring indefinite articles can recite a number of elements, and such claim should be interpreted to embrace one or more of the recited elements. Likewise, the singular word forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a" or "the" element is likely to include a plurality of such elements unless the context clearly dictates otherwise. Similarly, the terms "another," "at least one," and "one or more" are understood to mean one or more unless the context clearly dictates otherwise. Additionally, the term "plurality" is understood to mean two or more unless the context clearly dictates otherwise. Further, to the extent that any preamble language, as set forth in the appended claims, is used in the application, that preamble language should not be used to limit the claims. For example, a preamble recitation of "comprising at least one of A and B" should not be used to limit the claims to only those embodiments that literally include A or B, but not both. Similarly, a preamble recitation of "comprising at least one of A, B, or C" should not be used to limit the claims to only those embodiments that literally include A, B, or C, but not both. The mere inclusion of a preamble recitation does not limit the claims in any way, and the claims should not be interpreted to be limited to only those embodiments that literally include the recited elements.

[0077] From the foregoing, it will be appreciated that various embodiments of the application have been described herein for purposes of illustration, and that various modifications can be made without departing from the scope and spirit of the present application. Accordingly, the various embodiments disclosed herein are not intended to limit the true scope and spirit of the present application, which is defined by the claims.

Claims

1. A method comprising: The device's processor receives a Layer 1 or Layer 2 mobility LTM cell handover command triggered by the serving cell; The processor determines whether first time or frequency tracking on the target cell is activated before the LTM cell handover command; The processor determines whether the measurement period of the Layer 1 reference signal received power L1-RSRP is not greater than a predetermined value; as well as The processor determines that, if at least one condition is met, a second time or frequency tracking will not be performed before transmitting the first uplink UL message on the target cell. The at least one condition includes that the first time or frequency tracking of the target cell was activated before the LTM cell handover command, and that the L1-RSRP measurement period is not greater than the predetermined value.

2. The method as described in claim 1, characterized in that, Further includes: The processor determines that, prior to transmitting the first UL message on the target cell, it performs the second time or frequency tracking of the target cell if at least one condition is met. The at least one of the conditions includes that the first time or frequency tracking of the target cell was not activated before the LTM cell handover command, or that the L1-RSRP measurement period is greater than the predetermined value.

3. The method as described in claim 1, characterized in that: Determining whether the first time or frequency tracking of the target cell is activated before the LTM cell handover command includes determining whether the target transmission configuration indicator (TCI) status of the target cell indicated in the LTM cell handover command is in the list of active TCI statuses. as well as If at least one condition is met, it is determined that a second time or frequency tracking on the target cell will not be performed before the first UL message is transmitted on the target cell. The at least one condition includes the target TCI status of the target cell indicated in the LTM cell handover command in the list of active TCI statuses.

4. The method as described in claim 3, characterized in that, The activity TCI status list includes either the LTM candidate cell activity TCI status list or the serving cell activity TCI status list.

5. The method as described in claim 3, characterized in that, Further includes: The processor receives the Media Access Control (MAC) control element (CE) that activates the target TCI state of the target cell.

6. The method as described in claim 5, characterized in that, Further includes: The processor determines whether the time difference between receiving the MAC CE activating the target TCI state and the LTM cell handover command is at least the duration associated with processing the first time or frequency tracking, and not greater than the predetermined value. Where at least one condition is met, the second time or frequency tracking is not performed before the first UL message is transmitted on the target cell. The at least one condition includes that the time difference between receiving the MAC CE that activates the target TCI state and the LTM cell handover command is at least the duration and not greater than the predetermined value.

7. The method as described in claim 1, characterized in that, The preset value is 160 milliseconds.

8. The method as described in claim 1, characterized in that, Further includes: The processor transmits the Physical Random Access Channel (PRACH) preamble to the target cell; as well as The processor receives a Random Access Response (RAR) from the target cell, wherein the RAR includes a UL authorization for transmitting the first UL message on the target cell.

9. The method as described in claim 1, characterized in that, Further includes: The processor receives downlink control information (DCI) for scheduling the transmission of the first UL message on the target cell.

10. The method as described in claim 1, characterized in that, The first time or frequency tracking and the second time or frequency tracking include synchronizing with the target cell using a reference signal from the target cell.

11. An apparatus comprising: The transceiver communicates wirelessly with the serving cell and the target cell of the network during operation; as well as A processor, communicatively coupled to the transceiver, performs the following operations during operation: Receive LTM cell handover commands from the serving cell; Determine whether first time or frequency tracking on the target cell was activated before the LTM cell handover command was given; Determine whether the L1-RSRP measurement period is not greater than the predetermined value; and If at least one condition is met, a second time or frequency tracking on the target cell will not be performed until the first UL message is transmitted on the target cell. The at least one condition includes that the first time or frequency tracking of the target cell was activated before the LTM cell handover command, and that the L1-RSRP measurement period is not greater than the predetermined value.

12. The device as claimed in claim 11, characterized in that, During operation, the processor further performs the following operations: Before the transceiver transmits the first UL message on the target cell under at least one condition, the second time or frequency tracking of the target cell is performed. The at least one condition includes that the first time or frequency tracking of the target cell was not activated before the LTM cell handover command, or that the L1-RSRP measurement period is greater than the predetermined value.

13. The device as claimed in claim 11, characterized in that: Determining whether the first time or frequency tracking of the target cell was activated prior to the LTM cell handover command includes determining whether the target TCI state of the target cell indicated in the LTM cell handover command is in the list of active TCI states, and If at least one condition is met, it is determined that a second time or frequency tracking on the target cell will not be performed before the first UL message is transmitted on the target cell. The at least one condition includes the target TCI status of the target cell indicated in the LTM cell handover command in the list of active TCI statuses.

14. The device as claimed in claim 13, characterized in that, The activity TCI status list includes either the LTM candidate cell activity TCI status list or the serving cell activity TCI status list.

15. The device as claimed in claim 13, characterized in that, During operation, the processor further performs the following operations: The transceiver receives the MAC CE that activates the target TCI state of the target cell.

16. The device as claimed in claim 15, characterized in that, During operation, the processor further performs the following operations: The transceiver determines whether the time difference between receiving the MAC CE activating the target TCI state and the LTM cell handover command is at least the duration associated with processing the first time or frequency tracking, and not greater than the predetermined value. Specifically, if at least one condition is met, it is determined that a second time or frequency tracking on the target cell will not be performed before the first UL message is transmitted on the target cell. The at least one condition includes that the time difference between the MAC CE that receives the activation of the target TCI state and the LTM cell handover command is at least the duration and not greater than the predetermined value.

17. The device as claimed in claim 11, characterized in that, The preset value is 160 milliseconds.

18. The device as claimed in claim 11, characterized in that, During operation, the processor further performs the following operations: The transceiver transmits the PRACH preamble to the target cell; and The transceiver receives a RAR from the target cell, wherein the RAR includes a UL authorization for transmitting the first UL message on the target cell.

19. The device as claimed in claim 11, characterized in that, During operation, the processor further performs the following operations: The transceiver receives the DCI used to schedule the transmission of the first UL message on the target cell.

20. The device as claimed in claim 11, characterized in that, The first time or frequency tracking and the second time or frequency tracking include synchronizing with the target cell using a reference signal from the target cell.

Images