CN120226409A

CN120226409A - Method and equipment for TA acquisition

Info

Publication number: CN120226409A
Application number: CN202380079419.8A
Authority: CN
Inventors: 吴联海; 杨水根; 岳然; 汪海明
Original assignee: Lenovo Beijing Ltd
Current assignee: Lenovo Beijing Ltd
Priority date: 2023-01-12
Filing date: 2023-01-12
Publication date: 2025-06-27
Also published as: WO2024073972A1; KR20250133869A; EP4595574A1; GB202506645D0; GB2639430A

Abstract

Embodiments of the present application relate to methods and devices for performing timing advance (TA) acquisition under a 3rd Generation Partnership Project (3GPP) 5G system or the like. According to embodiments of the present application, a candidate distributed unit (DU) of a base station (BS) includes a transceiver, and a processor coupled to the transceiver, wherein the processor is configured to receive a signal for timing advance (TA) acquisition associated with a candidate cell from a user equipment (UE) via the transceiver; transmit a TA value associated with the candidate unit to a source DU of the BS via the transceiver via a CU of the BS, or transmit the TA value to the UE via a random access response (RAR) message; and one of the candidate DU, the CU, the source DU, and the UE determines whether the TA value associated with the candidate cell is valid.

Description

Method and equipment for TA acquisition

Technical Field

Embodiments of the present disclosure relate generally to wireless communication technology and, more particularly, relate to methods and apparatus for Timing Advance (TA) acquisition.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, and so on. Wireless communication systems may employ multiple-access techniques capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of wireless communication systems may include fourth generation (4G) systems, such as Long Term Evolution (LTE) systems, LTE-advanced (LTE-a) systems, or LTE-a Pro systems, and fifth generation (5G) systems, which may also be referred to as new air interface (NR) systems.

At present, details about handling TA values during or after TA acquisition have not been discussed in 3gpp 5g technology.

Disclosure of Invention

Some embodiments of the present disclosure provide candidate Distributed Units (DUs) for a Base Station (BS). The candidate DU includes a transceiver and a processor coupled to the transceiver, and the processor is configured to receive a signal from a User Equipment (UE) via the transceiver for Timing Advance (TA) acquisition associated with a candidate cell, transmit a TA value associated with the candidate cell to a source DU of the BS or the UE via the transceiver, and determine whether the TA value associated with the candidate cell is valid.

In some embodiments, the signal is at least one of a preamble, or a Sounding Reference Signal (SRS).

In some embodiments, the processor of the candidate DU is configured to calculate the TA value based on the received signal and the TA value is transmitted to the source DU via a Centralized Unit (CU) of the BS.

In some embodiments, the processor of the candidate DU is configured to transmit at least one of Identifier (ID) information of the candidate cell, or ID information of the UE, to the source DU via the CU.

In some embodiments, the TA value is transmitted to the UE in a Random Access Response (RAR) message based on the received signal.

In some embodiments, the determination of whether the TA value is valid is based on a condition, wherein the condition based on which the TA value is determined to be invalid includes at least one of an expiration of an early TA timer, or a difference between a first Reference Signal Received Power (RSRP) value and a second RSRP value being greater than or equal to a threshold related to an RSRP change.

In some embodiments, the processor of the candidate DU is configured to receive configuration information regarding the condition from the CU via the transceiver, and the configuration information includes at least one of a value of the early TA timer, or the threshold related to RSRP change.

In some embodiments, the processor of the candidate DU is configured to start the early TA timer upon receipt of the signal or upon calculation of the TA value.

In some embodiments, the first RSRP value is an RSRP value when the candidate DU receives the signal or when the candidate DU calculates the TA value, and the second RSRP value is an RSRP value received from the CU or the source DU.

In some embodiments, the processor of the candidate DU is configured to receive, via the transceiver, at least one of a layer 1 (L1) measurement of the UE from the source DU, or a layer 3 (L3) measurement of the UE from the CU, wherein the second RSRP value is included in at least one of the L1 measurement or the L3 measurement.

In some embodiments, in response to determining that the TA value is invalid, the processor of the candidate DU is configured to transmit information indicating that the TA value is invalid to the source DU via the transceiver via the CU.

In some embodiments, the processor of the candidate DU is configured to transmit configuration information regarding Random Access Channel (RACH) resources for TA acquisition associated with the candidate cell to the source DU via the transceiver via the CU.

Some embodiments of the present disclosure provide a Centralized Unit (CU) of a Base Station (BS). The CU includes a transceiver and a processor coupled to the transceiver, and the processor is configured to receive a Timing Advance (TA) value associated with a candidate cell from a candidate Distributed Unit (DU) of the BS via the transceiver, and transmit the TA value associated with the candidate cell to a source DU of the BS via the transceiver.

In some embodiments, the processor of the CU is configured to receive Identifier (ID) information of the candidate cell and ID information of a User Equipment (UE) from the candidate DU via the transceiver, and transmit the ID information of the candidate cell and the ID information of the UE to the source DU via the transceiver.

In some embodiments, the processor of the CU is configured to determine whether the TA value associated with the candidate cell is valid.

In some embodiments, the processor of the CU is configured to determine that the TA value is invalid if a difference between a first Reference Signal Received Power (RSRP) value and a second RSRP value is greater than or equal to a threshold.

In some embodiments, the first RSRP value is an RSRP value when the CU receives the TA value, and the second RSRP value is an RSRP value received from the UE via the source DU.

In some embodiments, in response to determining that the TA value is invalid, the processor of the CU is configured to transmit, via the transceiver, an indication of TA acquisition associated with the candidate cell to the source DU.

In some embodiments, in response to determining that the TA value is invalid, the processor of the CU is configured to transmit, via the transceiver, information indicating that the TA value is invalid or a request for Random Access Channel (RACH) resources for TA acquisition associated with the candidate cell to the candidate DU.

In some embodiments, the processor of the CU is configured to transmit configuration information regarding conditions associated with determining TA value validity to at least one of the candidate DU or the source DU via the transceiver.

In some embodiments, the configuration information includes at least one of a value of an early TA timer, or a threshold related to a RSRP change.

Some embodiments of the present disclosure provide a source Distributed Unit (DU) of a Base Station (BS). The source DU includes a transceiver and a processor coupled to the transceiver, and the processor is configured to transmit a first indication for Timing Advance (TA) acquisition associated with a candidate cell to a User Equipment (UE) via the transceiver, and to transmit a second indication for TA acquisition associated with the candidate cell to the UE via the transceiver.

In some embodiments, at least one of the first indication or the second indication is included in at least one of Downlink Control Information (DCI), medium Access Control (MAC) Control Element (CE), or Radio Resource Control (RRC) signaling.

In an embodiment, after transmitting the first indication, the processor of the source DU is configured to receive at least one of a first TA value associated with the candidate cell, identifier (ID) information of the candidate cell, ID information of the UE, or configuration information regarding a condition for determining whether the first TA value associated with the candidate cell is valid.

In an embodiment, the condition based on which the first TA value is determined to be invalid includes at least one of an expiration of an early TA timer, or a difference between a first Reference Signal Received Power (RSRP) value and a second RSRP value being greater than or equal to a threshold related to an RSRP change.

In an embodiment, the configuration information about the condition includes at least one of a value of the early TA timer, or the threshold value related to RSRP change.

In an embodiment, the first RSRP value is an RSRP value when the source DU transmits the first indication or when the source DU receives the first TA value, and the second RSRP value is an RSRP value received from the UE.

In an embodiment, the processor of the source DU is configured to receive a layer 1 (L1) measurement of the UE from the UE via the transceiver, wherein the second RSRP value is included in the L1 measurement.

In an embodiment, the processor of the source DU is configured to determine whether the first TA value associated with the candidate cell is valid based on the condition.

In an embodiment, the second indication is transmitted in response to determining that the first TA value is invalid.

In an embodiment, after transmitting the second indication, the processor of the source DU is configured to release configuration information regarding Random Access Channel (RACH) resources or Sounding Reference Signal (SRS) resources used to acquire the first TA value.

In an embodiment, the RACH resources include at least one of a preamble, or a time-frequency domain resource.

Some embodiments of the present disclosure provide a User Equipment (UE). The UE includes a transceiver and a processor coupled to the transceiver, and the processor is configured to receive, via the transceiver, a first indication from a source Distributed Unit (DU) of a Base Station (BS) for Timing Advance (TA) associated with a candidate cell, transmit, via the transceiver, a first signal for TA acquisition to the candidate Distributed Unit (DU) of the BS based on the first indication, receive, via the transceiver, a second indication from the source DU for TA acquisition associated with the candidate cell, and transmit, via the transceiver, a second signal for TA acquisition to the candidate DU based on the second indication.

In an embodiment, at least one of the first indication or the second indication is included in at least one of Downlink Control Information (DCI), medium Access Control (MAC) Control Element (CE), or Radio Resource Control (RRC) signaling.

In an embodiment, at least one of the first signal or the second signal is at least one of a preamble, or a Sounding Reference Signal (SRS).

In an embodiment, the processor of the UE is configured to receive a first TA value associated with the candidate cell from the candidate DU via the transceiver after transmitting the first signal and determine whether the first TA value associated with the candidate cell is valid.

In an embodiment, the first TA value is included in a cell switch command or a Random Access Response (RAR) message prior to the cell switch command.

In an embodiment, the processor of the UE is configured to determine that the first TA value is invalid based on a condition, and the condition includes at least one of an expiration of an early TA timer, or a difference between a first Reference Signal Received Power (RSRP) value and a second RSRP value being greater than or equal to a threshold related to an RSRP change.

In an embodiment, the processor of the UE is configured to receive configuration information regarding the condition from the CU via the transceiver, and the configuration information is configured by the CU or the candidate DU.

In an embodiment, the configuration information includes at least one of a value of the early TA timer, or the threshold value related to an RSRP change.

In an embodiment, the processor of the UE is configured to start the early TA timer when the UE receives the first indication or when the UE receives the first TA value.

In an embodiment, the first RSRP value is an RSRP value when the UE transmits the first signal, and the second RSRP value is an RSRP value measured by the UE after the UE receives the first TA value.

In an embodiment, the second signal is transmitted in response to determining that the first TA value is invalid.

In an embodiment, in response to determining that the first TA value is invalid, the processor of the UE is configured to transmit, via the transceiver, information to the source DU indicating that the first TA value is invalid.

Some embodiments of the present disclosure provide a method performed by a candidate Distributed Unit (DU) of a Base Station (BS). The method includes receiving a signal from a User Equipment (UE) for Timing Advance (TA) acquisition associated with a candidate cell, transmitting a TA value associated with the candidate cell to a source DU of the BS or the UE, and determining whether the TA value associated with the candidate cell is valid.

Some embodiments of the present disclosure provide a method performed by a Centralized Unit (CU) of a Base Station (BS). The method includes receiving a Timing Advance (TA) value associated with a candidate cell from a candidate Distributed Unit (DU) of the BS, and transmitting the TA value associated with the candidate cell to a source DU of the BS.

Some embodiments of the present disclosure provide a method performed by a source Distributed Unit (DU) of a Base Station (BS). The method includes transmitting a first indication to a User Equipment (UE) for Timing Advance (TA) acquisition associated with a candidate cell, and transmitting a second indication to the UE for TA acquisition associated with the candidate cell.

Some embodiments of the present disclosure provide a method performed by a UE. The method includes receiving a first indication of Timing Advance (TA) associated with a candidate cell from a source Distributed Unit (DU) of a Base Station (BS), transmitting a first signal for TA acquisition to a candidate Distributed Unit (DU) of the BS based on the first indication, receiving a second indication for TA acquisition associated with the candidate cell from the source DU, and transmitting a second signal for TA acquisition to the candidate DU based on the second indication.

Some embodiments of the present disclosure provide an apparatus for wireless communication. The apparatus comprises a non-transitory computer-readable medium having stored thereon computer-executable instructions, receive circuitry, transmit circuitry, and a processor coupled to the non-transitory computer-readable medium, the receive circuitry, and the transmit circuitry, wherein the computer-executable instructions cause the processor to implement the above-mentioned method performed by a UE or a network node, such as a Base Station (BS), CU, or DU.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

In order to describe the manner in which the advantages and features of the application can be obtained, a description of the application is presented by reference to particular embodiments of the application illustrated in the accompanying drawings. These drawings depict only example embodiments of the application and are not therefore to be considered limiting of its scope.

Fig. 1 illustrates a schematic diagram of a wireless communication system in accordance with some embodiments of the present application.

Fig. 2 illustrates a schematic diagram of inter-cell layer 1/layer 2 (L1/L2) mobility, according to some embodiments of the present disclosure.

Fig. 3-6 illustrate exemplary flowcharts associated with TA acquisition according to some embodiments of the present disclosure.

Fig. 7-10 illustrate exemplary flowcharts of TA acquisition according to some embodiments of the present disclosure.

FIG. 11 illustrates a block diagram of an exemplary apparatus according to some embodiments of the present disclosure.

Detailed Description

The detailed description of the drawings is intended as a description of the preferred embodiments of the application and is not intended to represent the only form in which the application may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the application.

Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under a particular network architecture and new service scenarios (e.g., 3GPP 5g, 3GPP LTE release 8, etc.). It is contemplated that all embodiments of the present application are applicable to similar technical problems as network architectures and new service scenarios develop, and furthermore, the terms enumerated in the present application may be changed, which should not affect the principles of the present application.

Fig. 1 illustrates a schematic diagram of a wireless communication system in accordance with some embodiments of the present application. As shown in fig. 1, a wireless communication system 100 includes at least one Base Station (BS) 101 and at least one User Equipment (UE) 102. In particular, for illustrative purposes, the radio communication system 100 includes one BS101 and two UEs 102 (e.g., UE 102a and UE 102 b). Although a particular number of BSs and UEs are illustrated in fig. 1 for simplicity, it is contemplated that the wireless communication system 100 may include more or fewer BSs and UEs in some other embodiments of the present disclosure.

The wireless communication system 100 is compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular telephone networks, time Division Multiple Access (TDMA) based networks, code Division Multiple Access (CDMA) based networks, orthogonal Frequency Division Multiple Access (OFDMA) based networks, LTE networks, 3GPP based networks, 3GPP 5g networks, satellite communication networks, high altitude platform networks, and/or other communication networks.

The BS101 may communicate via an interface with a Core Network (CN) node (not shown), such as a Mobility Management Entity (MME) or serving gateway (S-GW), a mobility management function (AMF) or User Plane Function (UPF), or the like. A BS may also be referred to as an access point, access terminal, base, macrocell, node B, enhanced node B (eNB), gNB, home node B, relay node, or device, or described using other terms used in the art. In 5G NR, BS may also refer to a RAN node or network equipment. Each BS may serve several UEs within a service area (e.g., cell or cell sector) via wireless communication links. The neighbor BSs may communicate with each other as needed, for example, during a handover procedure of the UE.

UE 102 (e.g., UE 102a and UE 102 b) should be understood to be any type of terminal device that may include a computing device such as a desktop computer, a laptop computer, a Personal Digital Assistant (PDA), a tablet computer, a smart television (e.g., a television connected to the internet), a set-top box, a game console, a security system (including a security camera), an in-vehicle computer, a network device (e.g., a router, switch, and modem), or the like. According to embodiments of the present disclosure, the UE 102 may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identity module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals over a wireless network. In some embodiments, the UE 102 includes a wearable device, such as a smart watch, a fitness bracelet, an optical head mounted display, or the like. Further, UE 102 may be referred to as a subscriber unit, mobile device, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, user terminal, or apparatus, or described using other terminology used in the art. UE 102 may communicate directly with BS101 via Uplink (UL) communication signals.

In 3GPP release 18, supporting inter-cell mobility based on layer 1/layer 2 (L1/L2) signaling has been discussed. In particular, configurations from multiple cells may be provided to the UE in advance, and the BS (e.g., the gNB) may use L1/L2 signaling to handover the UE to a new cell taking into account the received physical layer measurements. According to the 3GPP standard documents, a BS may be composed of a BS Centralized Unit (CU) and one or more BS Distributed Units (DU). The BS-CU and BS-DU are connected via an F1 interface as a logical interface. One BS-DU is connected to only one BS-CU.

Fig. 2 illustrates a schematic diagram of inter-cell layer 1/layer 2 (L1/L2) mobility, according to some embodiments of the present disclosure. As shown in fig. 2, a CU may communicate with two DUs (i.e., DU1 or DU 2) via an F1 interface. The CU in fig. 2 may implement legacy mobility decisions based on layer 3 (L3) measurements. Either DU1 or DU2 in FIG. 2 may implement the L1/L2 mobility decision based on physical layer measurements.

L1/L2 mobility is considered faster, with less processing and signaling delay than legacy L3 mobility. In legacy L3 mobility, a CU (e.g., a CU as shown in fig. 2) makes mobility decisions based on received Radio Resource Management (RRM) measurement reports. Unlike legacy L3 mobility, in L1/L2 mobility, a DU (e.g., DU1 or DU2 as shown in fig. 2) makes mobility decisions based on physical layer measurements carried in, for example, channel State Information (CSI) reports. Further, in legacy L3 mobility, a handover command is sent from the SN CU to the UE via RRC signaling, while in L1/L2 mobility, a "handover" command is sent from the DU to the UE via L1/L2 signaling (e.g., downlink Control Information (DCI) or Medium Access Control (MAC) Control Elements (CEs)). The "handover" command in L1/L2 mobility may be with respect to cell activation or deactivation, e.g. activating a new serving PCell while deactivating an old serving PCell.

At present, the problem of how to handle TA values during or after TA acquisition in the lower layer based mobility case has not been solved. Embodiments of the present disclosure aim to address such issues. For example, in some embodiments of the present disclosure, after the target DU successfully calculates the TA value, the target DU may communicate it to the source DU via the CU. However, the TA value is not always valid. Once the TA value is invalid, TA acquisition may be triggered again. Some embodiments of the present disclosure aim to devise a mechanism how to determine whether an acquired TA value is invalid and how to acquire or acquire a TA value again after a candidate DU, CU, source DU or UE determines that an acquired TA value of a candidate cell is invalid.

In the embodiments of the present application, TA acquisition or early TA acquisition means that the UE is expected to perform a TA acquisition procedure before a cell handover procedure. TA reacquiring or early TA reacquiring means that the UE is expected to perform a TA reacquiring procedure before the cell handover procedure. The TA acquisition, early TA acquisition, TA re-acquisition, or early TA re-acquisition may be triggered by receiving an indication from the serving BS, e.g., as a PDCCH order of DCI.

Some embodiments of the present disclosure may be applicable to the case of "lower layer triggered mobility" or "L1/L2 triggered mobility", and where the abbreviation of at least one may be "LTM". In the LTM case, the UE may access a serving BS (e.g., serving gNB). The UE may report layer 3 (L3) measurements based on the configuration from the serving gNB. If the serving gNB (e.g., CU of the serving gNB) decides to handover the UE to a candidate cell based on the measurement, the serving gNB may request the target DU to prepare a configuration for one or more candidate cells. Upon receiving the candidate cell configuration from the target DU of the serving gNB, the serving gNB may transmit an RRC reconfiguration message to the UE including ID information of one or more candidate cells. For example, a CU may transmit an RRC reconfiguration message to the UE via a source DU serving the gNB. The UE may transmit an RRC reconfiguration complete message to the serving gNB (e.g., CU) via the source DU. The UE may ensure UL synchronization or DL synchronization before receiving the cell handover command. For example, the UE may obtain or acquire the TA value via Random Access (RA) or preamble transmission. The UE may report layer 1 (L1) measurements for dynamic handover purposes. The serving gNB (e.g., source DU) may transmit a cell handover command, such as a MAC CE or DCI. The UE may apply the RRC reconfiguration message and start a timer upon receiving the lower layer command.

In particular, in the embodiments of FIGS. 3-11 of the present disclosure, both inter-DU mobility scenarios and intra-DU mobility scenarios are considered, such as inter-gNB-DU LTM or intra-gNB-DU LTM. inter-DU mobility means that the connection to the CU remains unchanged, whereas the UE may change from a source cell associated with the source DU to a target cell associated with the target DU due to mobility, both of which are managed by the CU. intra-DU mobility means that the connection to the CU remains unchanged, whereas the UE may change from the source cell to the target cell associated with the same DU due to mobility. Further details will be described below in conjunction with the drawings.

Fig. 3 illustrates an exemplary flow chart associated with TA acquisition according to some embodiments of the present disclosure. The exemplary flowchart 300 in the embodiment of fig. 3 may be performed by a candidate DU (e.g., DU1 or DU2 or candidate DU 703 shown and described in fig. 2 or 7). In some cases, the candidate DU may also be named target DU. Although described with respect to candidate DUs, it should be understood that other devices may be configured to perform a flow chart similar to the flow chart of fig. 3. The details described in all other embodiments of the present application apply to the embodiment in fig. 3. Furthermore, the details described in the embodiment of fig. 3 apply to all embodiments of fig. 1, 2 and 4 to 11. A specific example of the embodiment of fig. 3 is described below in the embodiment of fig. 7.

In the exemplary flowchart 300, in operation 301, a candidate DU of a BS (e.g., candidate DU 703 shown and described in fig. 7) may receive signals acquired from a UE (e.g., UE 701 shown and described in fig. 7) of a TA associated with a candidate cell. In some embodiments, the signal is a sequence. For example, the signal is a preamble and/or a Sounding Reference Signal (SRS).

In operation 302, the candidate DU may transmit a TA value associated with the candidate cell to a source DU of the BS (e.g., source DU 702 shown and illustrated in fig. 7) or the UE.

In some embodiments, the candidate DU may calculate a TA value associated with the candidate cell based on the signal received in operation 301 and transmit the TA value to the source DU via a CU of the BS (e.g., CU 704 shown and illustrated in fig. 7). In some embodiments, the candidate DU may transmit at least one of (1) ID information of the candidate cell, or (2) ID information of the UE, to the source DU via the CU.

In some other embodiments, the TA value associated with the candidate cell is transmitted by the candidate DU to the UE in a Random Access Response (RAR) message based on the signal received in operation 301.

In operation 303, the candidate DU may determine whether a TA value associated with the candidate cell is valid. In some embodiments, whether the TA value is valid is determined based on a condition. The condition based on which the TA value is determined to be invalid includes at least one of:

(1) The expiration of the TA timer is advanced. In some embodiments, the candidate DU may start an early TA timer upon receipt of the signal in operation 301 or upon calculation of the TA value.

(2) The difference between the RSRP value (denoted rsrp#1 for simplicity) and the other RSRP value (denoted rsrp#2) is greater than or equal to a threshold value (denoted threshold # 1) related to RSRP changes. In some embodiments, rsrp#1 is an RSRP value when the candidate DU receives a signal in operation 301 or when the candidate DU calculates a TA value, and rsrp#2 is an RSRP value received from a CU or a source DU.

In some embodiments, the candidate DU may receive configuration information about conditions from the CU, and the configuration information includes a value of an early TA timer and/or a threshold related to RSRP change (e.g., threshold # 1).

In some embodiments, the candidate DU may receive at least one of (1) a layer 1 (L1) measurement from a UE of the source DU, or (2) a layer 3 (L3) measurement from a UE of the CU. Rsrp#2 may be included in the L1 measurement and/or the L3 measurement.

In some embodiments, in response to determining that the TA value is invalid, the candidate DU may transmit information indicating that the TA value is invalid to the source DU via the CU.

In some embodiments, the candidate DU may transmit configuration information regarding RACH resources for TA acquisition associated with the candidate cell to the source DU via the CU.

Fig. 4 illustrates a further exemplary flow chart associated with TA acquisition according to some embodiments of the present disclosure. The exemplary flowchart 400 in the embodiment of fig. 4 may be performed by a CU (e.g., CU or CU 804 shown and described in fig. 2 or 8). Although described with respect to a CU, it should be understood that other devices may be configured to perform a flowchart similar to the flowchart of fig. 4. The details described in all other embodiments of the present application apply to the embodiment in fig. 4. Furthermore, the details described in the embodiment of fig. 4 apply to all embodiments of fig. 1 to 3 and 5 to 11. A specific example of the embodiment of fig. 4 is described below in the embodiment of fig. 8.

In the exemplary flowchart 400 shown in fig. 4, in operation 401, a CU (e.g., CU 804 shown and described in fig. 8) may receive TA values associated with candidate cells from candidate DUs of a BS (e.g., candidate DU 803 shown and described in fig. 8). In operation 402, the CU may transmit a TA value associated with the candidate cell to a source DU to the BS (e.g., source DU 802 shown and illustrated in fig. 8).

In some embodiments, a CU may receive ID information of a candidate cell and ID information of a UE (e.g., UE 801 shown and described in fig. 8) from a candidate DU, and transmit the ID information of the candidate cell and the ID information of the UE to a source DU.

In some embodiments, the CU may determine whether a TA value associated with the candidate cell is valid. In an embodiment, if the difference between the RSRP value (denoted rsrp#3 for simplicity) and another RSRP value (denoted rsrp#4 for simplicity) is greater than or equal to a threshold (e.g., a threshold related to RSRP change, denoted threshold # 2), the CU may determine that the TA value is invalid. For example, rsrp#3 is an RSRP value when the CU receives a TA value, and rsrp#4 is an RSRP value received from the UE via the source DU.

In some embodiments, in response to determining that the TA value is invalid, the CU may transmit "an indication of TA acquisition associated with the candidate cell" to the source DU.

In some embodiments, in response to determining that the TA value is invalid, the CU may transmit "information indicating that the TA value is invalid" or "a request for RACH resources for TA acquisition associated with the candidate cell" to the candidate DU.

In some embodiments, the CU may transmit "configuration information regarding conditions associated with determining TA value validity" to the candidate DU and/or source DU. In an embodiment, the configuration information includes a value of an early TA timer and/or a threshold related to RSRP change (e.g., threshold # 2).

Fig. 5 illustrates another exemplary flow chart associated with TA acquisition according to some embodiments of the present disclosure. The exemplary flowchart 500 in the embodiment of fig. 5 may be performed by a source DU (e.g., DU2 or DU1 or source DU 902 shown and illustrated in fig. 2 or 9). Although described with respect to a source DU, it should be understood that other devices may be configured to perform a flow chart similar to the flow chart of fig. 5. The details described in all other embodiments of the present application apply to the embodiment in fig. 5. Furthermore, the details described in the embodiment of fig. 5 apply to all embodiments of fig. 1 to 4 and 6 to 11. A specific example of the embodiment of fig. 5 is described below in the embodiment of fig. 9.

In the exemplary flowchart 500 shown in fig. 5, in operation 501, a source DU (e.g., source DU 902 shown and described in fig. 9) may transmit an indication of TA acquisition associated with a candidate cell (denoted as indication #1 for simplicity) to a UE (e.g., UE 901 shown and described in fig. 9).

In operation 502, the source DU may transmit another indication of TA acquisition associated with the candidate cell (denoted as indication # 2) to the UE.

In some embodiments, indication #1 and/or indication #2 may be included in at least one of DCI, MAC CE, or RRC signaling.

In some embodiments, after transmitting indication #1, the source DU may receive at least one of (1) a TA value associated with the candidate cell, (2) ID information of the candidate cell, ID information of the UE, or (3) configuration information regarding conditions for determining whether the TA value associated with the candidate cell is valid.

In some embodiments, the condition based on which the TA value is determined to be invalid includes at least one of (1) an expiration of an early TA timer, or (2) a difference between the RSRP value (denoted as RSRP#5) and another RSRP value (denoted as RSRP#6) being greater than or equal to a threshold (denoted as threshold#3) related to the RSRP change.

In some embodiments, the configuration information about the condition includes a value of an early TA timer and/or a threshold related to RSRP change (e.g., threshold # 3).

In some embodiments, rsrp#5 is the RSRP value when the source DU transmits indication #1 or when the source DU receives the TA value, and rsrp#6 is the RSRP value received from the UE.

In some embodiments, the source DU may receive layer 1 (L1) measurements of the UE from the UE, with rsrp#6 included in the L1 measurements.

In some embodiments, the source DU may determine whether the TA value associated with the candidate cell is valid based on the condition.

In some embodiments, indication #2 is transmitted in response to determining that the TA value is invalid.

In some embodiments, after transmitting indication #2, the source DU may release configuration information on RACH resources or SRS resources for acquiring a TA value. In an embodiment, the RACH resources include a preamble and/or time-frequency domain resources.

Fig. 6 illustrates yet another exemplary flow chart associated with TA acquisition according to some embodiments of the present disclosure. The exemplary flowchart 600 in the embodiment of fig. 6 may be performed by a UE (e.g., UE 102 or UE 1001 shown and described in fig. 1 or 10). Although described with respect to a UE, it should be understood that other devices may be configured to perform a flow chart similar to the flow chart of fig. 6. The details described in all other embodiments of the present application apply to the embodiment in fig. 6. Furthermore, the details described in the embodiment of fig. 6 apply to all embodiments of fig. 1 to 5 and 7 to 11. A specific example of the embodiment of fig. 6 is described below in the embodiment of fig. 10.

In the exemplary flowchart 600 shown in fig. 6, in operation 601, a UE (UE 1001 shown and described in fig. 10) may receive an indication (denoted as indication #3 for simplicity) of a TA associated with a candidate cell from a source DU of a BS (e.g., source DU 1002 shown and described in fig. 10). In operation 602, the UE may transmit a TA acquired signal (denoted as signal # 1) to a candidate DU of the BS (e.g., candidate DU 1003 shown and illustrated in fig. 10) based on the indication # 3.

In operation 603, the UE may receive another indication (denoted as indication # 4) of TA acquisition associated with the candidate cell from the source DU. In operation 604, the UE may transmit another signal (denoted as signal # 2) of TA acquisition to the candidate DU based on the indication # 4.

In some embodiments, indication #3 and/or indication #4 is included in at least one of DCI, MAC CE, or RRC signaling.

In some embodiments, signal # and/or signal #2 is a sequence, such as a preamble and/or SRS.

In some embodiments, the UE may receive a TA value associated with the candidate cell from the candidate DU after transmitting the signal #1 and determine whether the TA value associated with the candidate cell is valid.

In some embodiments, the TA value is included in a cell switch command (e.g., a MAC CE command), or a RAR message prior to the cell switch command.

In some embodiments, the UE may determine that the TA value is invalid based on a condition, and the condition includes at least one of (1) an expiration of an early TA timer, or (2) a difference between the RSRP value (denoted as RSRP#7) and another RSRP value (denoted as RSRP#8) being greater than or equal to a threshold related to the RSRP change (denoted as threshold#4).

In some embodiments, the UE may receive configuration information about conditions from the CU, and the configuration information is configured by the CU or the candidate DU. In an embodiment, the configuration information includes at least one of (1) a value of an early TA timer, or (2) a threshold related to a change in RSRP (e.g., threshold # 4).

In some embodiments, the UE may start an early TA timer when the UE receives indication #3 or when the UE receives a TA value.

In some embodiments, rsrp#7 is the RSRP value when the UE transmits signal #1, and rsrp#8 is the RSRP value measured by the UE after the UE receives the TA value.

In some embodiments, signal #2 is transmitted in response to determining that the TA value is invalid.

In some embodiments, in response to determining that the TA value is invalid, the UE may transmit information to the source DU indicating that the TA value is invalid.

The following text describes particular embodiments of the flow diagrams shown and described in any of figures 3-6. It will be appreciated by those of skill in the art that the sequence of operations in any of the exemplary flowcharts 700, 800, 900, and 1000 in fig. 7-10 may be altered and that some of the operations in any of the exemplary flowcharts 700, 800, 900, and 1000 in fig. 7-10 may be eliminated or modified without departing from the spirit and scope of this disclosure.

Fig. 7 illustrates an exemplary flow chart of TA acquisition according to some embodiments of the present disclosure. The embodiment of fig. 7 relates to a candidate cell triggered TA reacquisition scenario, wherein the candidate DU determines whether the TA value is valid. The details described in all other embodiments of the present disclosure apply to the embodiment shown in fig. 7.

As shown in fig. 7, BS 705 is in a CU-DU architecture and includes a CU 704, a source DU 702, and a candidate DU 703. In the embodiment of fig. 7, the cell handover operation performed by the UE 701 may refer to an intra-DU case in which the source cell and the target cell are in the same DU, or to an inter-DU case in which the source cell and the target cell are located at different DUs. For example, for exemplary purposes, the flowchart 700 shown in fig. 7 shows only cell handover operations in the inter-DU case. If source DU 702 and candidate DU 703 are the same DU, flowchart 700 may also be applied to the intra-DU case.

In the exemplary flowchart 700 shown in fig. 7, in operation 711, the UE 701 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 705). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with a CU and DU. There is an F1 interface between the DU and CU. For example, as shown in fig. 7, BS 705 includes CU 704, source DU 702, and candidate DU 703.BS 705 may include one or more other candidate DUs (not shown in fig. 7).

In operation 712, CU 704 may determine to initiate L1/L2-based inter-cell mobility configuration and transmit a request message, such as UE CONTEXT SETUP REQUEST message, to one or more candidate DUs (e.g., candidate DU 703) associated with the one or more candidate cells. In some embodiments, conditions for determining the TA value from CU 704 may be sent to candidate DU 703. The condition may be the value of the early TA timer or a threshold related to RSRP change (e.g., threshold #1 described in the embodiment of fig. 3).

In operation 713, if the candidate DU 703 decides to accept the request for the LTM configuration, the candidate DU 703 may generate a lower layer RRC configuration for the accepted one or more candidate cells and send a response message including the generated lower layer RRC configuration to the CU 704. The response message may be UE CONTEXT SETUP REQUEST messages.

In operation 714, CU 704 may generate RRCReconfiguration a message based on the received configuration of the accepted candidate cell from candidate DU 703 and transmit RRCReconfiguration message associated with the candidate cell for LTM configuration to UE 701 via source DU 702.

In operation 715, the UE 701 may receive information from the source DU 702 to trigger TA acquisition for candidate cells within the candidate cells. In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH order.

In some embodiments, after the source DU 702 transmits information (e.g., PDCCH order) to the UE 701 to trigger TA acquisition associated with the candidate cell, the source DU 702 may release dedicated RACH configurations, such as dedicated preambles and/or dedicated time-frequency domain resources, for TA acquisition. In some other embodiments, source DU 702 may reserve dedicated RACH resources for TA acquisition.

In operation 716, the UE 701 may transmit a TA acquired signal (e.g., sequence, e.g., dedicated preamble or SRS) to the candidate DU 703.

In operation 717, after the candidate DU 703 successfully receives the TA acquired signal, the candidate DU 703 may calculate or generate a TA value associated with the candidate cell.

In operation 718, the candidate DU 703 may transmit a message to the CU 704 via the F1 interface, the message including the calculated TA value, the ID information of the corresponding candidate cell, and/or the ID information of the UE 701. The F1 message may be a UL RRC MESSAGE TRANSFER message or UE Context Modification Request message.

After the CU 704 receives the TA value, the CU 704 transmits the received TA value to the source DU 702 in operation 719. In some embodiments, CU 704 will transmit the TA value, ID information of the corresponding candidate cell, and/or ID information of UE 701 to source DU 702 via the F1 interface.

In operation 720, after the source DU 702 receives the TA value, the source DU 702 stores the TA value, ID information of the corresponding candidate cell, and/or ID information of the UE 701. In some embodiments, if source DU 702 receives the TA value of the same candidate cell and UE 701, source DU 702 stores the latest TA value.

In operation 721, the candidate DU 703 determines whether the current TA value associated with the candidate cell is invalid. In some embodiments, the candidate DU 703 may determine whether the TA value associated with the candidate cell is valid, e.g., based on a condition, until the TA value is determined to be invalid.

In an embodiment, rsrp#1 is an RSRP value when candidate DU 703 receives a preamble (or SRS) in operation 716 or when candidate DU 703 calculates or generates a TA value in operation 717. Rsrp#2 is an RSRP value received from CU 704 or source DU 702. In an embodiment, source DU 702 may receive measurement reports, e.g., L1 measurements, which are to be communicated to candidate DU 703 via CU 704. In addition, CU 704 may transmit L3 measurements to candidate DU 703. Rsrp#2 may be included in the L1 measurement and/or the L3 measurement. For example, if the RSRP change (rsrp#2-rsrp#1) is equal to or greater than or equal to a threshold (e.g., threshold # 1), then the TA value is deemed invalid. Once the RSRP change (rsrp#2-rsrp#1) is greater than or equal to the threshold, the candidate DU 703 determines that the TA value is invalid.

In another embodiment, a timer (e.g., an early TA timer) is used to determine whether the TA value is invalid. The candidate DU 703 may start a timer upon receiving a TA acquired signal (e.g., preamble or SRS) in operation 716 or upon calculating the TA value in operation 717. The value of the timer may be configured by the CU 704. If the timer expires, the TA value is deemed invalid. Upon expiration of the timer, the candidate DU 703 determines that the TA value is invalid.

In operation 722, if the candidate DU 703 determines that the current TA value is invalid based on the L1 or L3 measurements, the candidate DU 703 will be indicated to the source DU 702 via the CU 704. For example, the candidate DU 703 transmits an indication indicating that the current TA value is invalid. New RACH resources may also be transmitted to source DU 702.

In operation 723, the source DU 702 may again transmit information (e.g., PDCCH order) to trigger TA acquisition associated with the candidate cell to the UE 701 to acquire the latest TA value of the candidate cell.

Fig. 8 illustrates a further exemplary flow chart of TA acquisition according to some embodiments of the present disclosure. The embodiment of fig. 8 relates to a CU triggered TA reacquisition scenario, wherein the CU determines if the TA value is valid. The details described in all other embodiments of the present disclosure apply to the embodiment shown in fig. 8.

As shown in fig. 8, BS 805 is in a CU-DU architecture and includes a CU 804, a source DU 802, and a candidate DU 803. In the embodiment of fig. 8, the cell handover operation performed by the UE 801 may refer to an intra-DU case in which the source cell and the target cell are in the same DU, or to an inter-DU case in which the source cell and the target cell are located at different DUs. For example, for exemplary purposes, the flowchart 800 shown in fig. 8 shows only cell handover operations in the case of inter-DU. Flowchart 800 may also be applied to intra-DU cases if source DU 802 and candidate DU 803 are the same DU.

In the exemplary flowchart 800 shown in fig. 8, in operation 811, the UE 801 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 805). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with a CU and DU. There is an F1 interface between the DU and CU. For example, as shown in fig. 8, BS 805 includes CU 804, source DU 802, and candidate DU 803.BS 805 may include one or more other candidate DUs (not shown in fig. 8).

In operation 812, the CU 804 may determine to initiate L1/L2 based inter-cell mobility configuration and transmit a request message, such as UE CONTEXT SETUP REQUEST message, to one or more candidate DUs (e.g., candidate DUs 803) associated with the one or more candidate cells.

In operation 813, if the candidate DU 803 decides to accept the request for LTM configuration, the candidate DU 803 may generate a lower layer RRC configuration for the accepted one or more candidate cells and send a response message including the generated lower layer RRC configuration to the CU 804. The response message may be UE CONTEXT SETUP REQUEST messages.

In operation 814, the CU 804 may generate RRCReconfiguration a message based on the configuration of the accepted candidate cell from the candidate DU 803 and transmit RRCReconfiguration message associated with the candidate cell for LTM configuration to the UE 801 via the source DU 802.

In operation 815, the UE 801 receives information for triggering TA acquisition for a candidate cell within the candidate cells. In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH order.

In some embodiments, after the source DU 802 transmits information (e.g., PDCCH order) to the UE 801 to trigger TA acquisition associated with the candidate cell, the source DU 802 may release or store dedicated RACH resources (e.g., dedicated preamble and/or dedicated time-frequency domain resources) or dedicated SRS resources for TA acquisition.

In operation 816, the UE 801 may transmit a TA acquired signal (e.g., sequence, e.g., dedicated preamble or SRS) to the candidate DU 803.

In operation 817, after the candidate DU 803 successfully receives the TA acquired signal, the candidate DU 803 may calculate or generate a TA value associated with the candidate cell.

In operation 818, the candidate DU 803 may transmit a message to the CU 804 via the F1 interface, the message including the calculated TA value, the ID information of the corresponding candidate cell, and/or the ID information of the UE 801. The F1 message may be a UL RRC MESSAGE TRANSFER message or UE Context Modification Request message.

In operation 819, after the CU 804 receives the TA value, the CU 804 transmits the received TA value to the source DU 802. In some embodiments, CU 804 will transmit the TA value, ID information of the corresponding candidate cell, and/or ID information of UE 801 to source DU 802 via the F1 interface.

In operation 820, after the source DU 802 receives the TA value, the source DU 802 stores the TA value, ID information of the corresponding candidate cell, and/or ID information of the UE 801.

In operation 821, the CU 804 determines whether the current TA value associated with the candidate cell is valid. In some embodiments, CU 804 may determine whether the TA value associated with the candidate cell is valid, e.g., based on a condition, until it is determined that the TA value is invalid.

In some embodiments, CU 804 may determine whether the current TA value is valid based on the L3 measurement. In an embodiment, the CU 804 determines whether the RSRP change is greater than or equal to a threshold associated with the RSRP change. For example, rsrp#3 is an RSRP value when CU 804 receives a TA value, and rsrp#4 is an RSRP value included in L3 measurements received by CU 804 from UE 801 via source DU 802. If the RSRP change (RSRP#4-RSRP#3) is equal to or greater than or equal to a threshold (e.g., threshold #2 described in the embodiment of FIG. 4), then the TA value is deemed invalid. Once the RSRP change (rsrp#4-rsrp#3) is greater than or equal to the threshold, the CU 804 determines that the TA value is invalid.

In operation 822, once the CU determines that the TA is invalid, the CU 804 transmits an indication of TA reacquiring to the source DU 802. Before the CU 804 transmits an indication to the source DU 802, the CU 804 may request the latest RACH resource from the candidate DU 803.

In operation 823, the source DU 802 may again transmit information (e.g., PDCCH order) to trigger TA acquisition associated with the candidate cell to the UE 801 to acquire the latest TA value of the candidate cell.

Fig. 9 illustrates another exemplary flow chart of TA acquisition according to some embodiments of the present disclosure. The embodiment of fig. 9 relates to a source DU triggered TA reacquisition scenario wherein the source DU determines whether the TA value is valid. The details described in all other embodiments of the present disclosure apply to the embodiment shown in fig. 9.

As shown in fig. 9, BS 905 is in a CU-DU architecture and includes CU 904, source DU 902, and candidate DU 903. In the embodiment of fig. 9, a cell change of UE 901 may refer to an intra-DU case where the source cell and the target cell are in the same DU, or to an inter-DU case where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, the flowchart 900 shown in fig. 9 only shows cell change in the case of inter-DU. If source DU 902 and candidate DU 903 are the same DU, flowchart 900 may be applied to the intra-DU case.

In the exemplary flowchart 900 shown in fig. 9, in operation 911, the UE 901 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 905). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with a CU and DU. There is an F1 interface between the DU and CU. For example, as shown in fig. 9, BS 905 includes CU 904, source DU 902, and candidate DU 903. The BS 905 may include one or more other candidate DUs (not shown in fig. 9).

In operation 912, the CU 904 may determine to initiate L1/L2-based inter-cell mobility configuration and transmit a request message, such as a UE CONTEXT SETUP REQUEST message, to one or more candidate DUs (e.g., candidate DU 903) associated with the one or more candidate cells.

In operation 913, if the candidate DU 903 decides to accept the request for LTM configuration, the candidate DU 903 may generate lower layer RRC configurations for the accepted one or more candidate cells and send a response message including the generated lower layer RRC configurations to the CU 804. The response message may have a UE CONTEXT SETUP REQUEST message.

In operation 914, the CU 904 will generate RRCReconfiguration a message based on the configuration of the accepted candidate cell from the candidate DU 903 and transmit RRCReconfiguration message associated with the candidate cell for LTM configuration to the UE 901 via the source DU 902.

In operation 915, the UE 901 may receive information (e.g., indication #1 described in the embodiment of fig. 5) from the source DU 902 for triggering TA acquisition for a candidate cell within the candidate cells. In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH order.

In some embodiments, after source DU 902 transmits information (e.g., PDCCH order) to UE 901 to trigger TA acquisition associated with the candidate cell, source DU 902 may release or store dedicated RACH resources (e.g., dedicated preamble and/or dedicated time-frequency domain resources) or dedicated SRS resources for TA acquisition.

In operation 916, the UE 901 may transmit a TA acquired signal (e.g., sequence, e.g., dedicated preamble or SRS) to the candidate DU 903.

In operation 917, after the candidate DU 903 successfully receives the TA acquired signal, the candidate DU 903 will calculate or generate a TA value associated with the candidate cell.

In operation 918, the candidate DU 903 transmits a message to the CU 904 via the F1 interface, the message including the calculated TA value, ID information of the corresponding candidate cell, and/or ID information of the UE 901. The F1 message may be a UL RRC MESSAGE TRANSFER message or UE Context Modification Request message.

In operation 919, after the CU 904 receives the TA value, the CU 904 transmits the received TA value to the source DU 902. In some embodiments, CU 904 may transmit the TA value, ID information of the corresponding candidate cell, and/or ID information of UE 901 to source DU 902 via the F1 interface.

In operation 920, after the source DU 902 receives the TA value, the source DU 902 stores the TA value, ID information of the corresponding candidate cell, and/or ID information of the UE 901.

In operation 921, the source DU 902 determines whether the current TA value associated with the candidate cell is valid. In some embodiments, source DU 902 may determine whether the TA value associated with the candidate cell is valid, e.g., based on a condition, until it is determined that the TA value is invalid.

In some embodiments, source DU 902 may maintain configuration information regarding conditions for determining whether the TA value is valid. The configuration information may include a value of an early TA timer and/or a threshold associated with RSRP changes. Configuration information may be provided to source DU 902 by CU 904 or candidate DU 903.

In an embodiment, with respect to RSRP changes, rsrp#5 may be the RSRP when source DU 902 transmits information (e.g., PDCCH order) to trigger TA acquisition in operation 915, or may be the RSRP when source DU 902 receives TA values from candidate DU 903. Rsrp#6 is an RSRP value received from UE 901. In an embodiment, source DU 902 may receive layer 1 (L1) measurements of UE 901 from UE 901, wherein rsrp#6 is included in the L1 measurements. For example, if the RSRP change (rsrp#6-rsrp#5) is equal to or greater than or equal to a threshold (e.g., threshold #3 described in the embodiment of fig. 5), then the TA value is deemed invalid. Source DU 902 determines that the TA value is invalid once the RSRP change (rsrp#6-rsrp#5) is greater than or equal to the threshold.

In another embodiment, a timer (e.g., an early TA timer) is used to determine whether the TA value is invalid. In operation 915, when source DU 902 transmits information (e.g., PDCCH order) to trigger TA acquisition associated with the candidate cell, source DU 902 may start a timer. The value of the timer may be configured by the CU 904. If the timer expires, the TA value is deemed invalid. Upon expiration of the timer, source DU 902 determines that the TA value is invalid.

In operation 922, once source DU 902 determines that the TA value of the candidate cell is invalid, source DU 902 again transmits information (e.g., indication #2 described in the embodiment of fig. 5) to trigger TA acquisition associated with the candidate cell to UE 901 (e.g., PDCCH order) to acquire the latest TA value of the candidate cell. In some embodiments, source DU 902 may request the latest RACH resources from candidate DU 903 before source DU 902 transmits information to UE 901 to trigger TA acquisition.

Fig. 10 illustrates another exemplary flow chart of TA acquisition according to some embodiments of the present disclosure. The embodiment of fig. 10 relates to a UE-triggered TA reacquisition scenario, wherein the UE determines whether the TA value is valid. The details described in all other embodiments of the present disclosure apply to the embodiment shown in fig. 10.

As shown in fig. 10, BS1005 is in a CU-DU architecture and includes a CU 1004, a source DU 1002, and a candidate DU 1003. In the embodiment of fig. 10, a cell change of UE 1001 may refer to an intra-DU case where the source cell and the target cell are in the same DU, or to an inter-DU case where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, the flowchart 1000 shown in fig. 10 shows only cell change in the inter-DU case. If the source DU 1002 and the candidate DU 1003 are the same DU, flowchart 1000 may be applied to the intra-DU case.

In the exemplary flowchart 1000 shown in fig. 10, in operation 1011, the UE 1001 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 1005). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with a CU and DU. There is an F1 interface between the DU and CU. For example, as shown in fig. 10, BS1005 includes CU 1004, source DU 1002, and candidate DU 1003.BS1005 may include one or more other candidate DUs (not shown in fig. 10).

In operation 1012, the CU 1004 may determine to initiate L1/L2 based inter-cell mobility configuration and transmit a request message, such as UE CONTEXT SETUP REQUEST message, to one or more candidate DUs (e.g., candidate DU 1003) associated with the one or more candidate cells.

In operation 1013, if the candidate DU 1003 decides to accept the request for the LTM configuration, the candidate DU 1003 may generate a lower layer RRC configuration for the accepted one or more candidate cells and send a response message including the generated lower layer RRC configuration to the CU 1004. The response message may have a UE CONTEXT SETUP REQUEST message.

In operation 1014, CU 1004 may generate RRCReconfiguration a message based on the configuration of the accepted candidate cell from candidate DU 1003 and transmit RRCReconfiguration message associated with the candidate cell for LTM configuration to UE 1001 via source DU 1002.

In operation 1015, the UE 1001 may receive information (e.g., indication #3 described in the embodiment of fig. 6) for triggering TA acquisition for a candidate cell within the candidate cell. In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH order.

In some embodiments, after the source DU 1002 transmits information (e.g., PDCCH order) to the UE 1001 to trigger TA acquisition associated with the candidate cell, the source DU 1002 may release or store dedicated RACH resources (e.g., dedicated preamble and/or dedicated time-frequency domain resources) or dedicated SRS resources for TA acquisition.

In operation 1016, the UE 1001 may transmit a TA acquired signal (e.g., sequence, such as a dedicated preamble or SRS) to the candidate DU 1003 (e.g., signal #1 described in the embodiment of fig. 6).

In operation 1017, after the candidate DU 1003 successfully receives the TA acquired signal, the candidate DU 1003 may calculate or generate a TA value associated with the candidate cell.

In operation 1018, the candidate DU 1003 may transmit a message to the CU 1004 via the F1 interface, the message including the calculated TA value, the ID information of the corresponding candidate cell, and/or the ID information of the UE 801. The F1 message may be a UL RRC MESSAGE TRANSFER message or UE Context Modification Request message.

In operation 1019, there may be two cases in different embodiments, namely case 1 and case 2 as follows. (1) Case 1 in operation 1019, the UE 1001 may receive a TA value included in a cell handover command (e.g., a MAC CE command). In case 1, UE 1001 does not receive the RAR message. It is not desirable for the UE 1001 to maintain the TA value prior to cell handover.

(2) Case 2 in operation 1019, the UE 1001 will receive a RAR message containing the TA value before the cell handover.

In case 2, UE 1001 needs to maintain the TA value before cell handover.

In operation 1020, the UE 1001 may determine whether a current TA value associated with the candidate cell is valid. In some embodiments, UE 1001 may determine whether the TA value associated with the candidate cell is valid, e.g., based on a condition, until it is determined that the TA value is invalid.

In some embodiments, UE 1001 may maintain configuration information regarding conditions for determining whether the TA value is valid. The configuration information may include a value of an early TA timer and/or a threshold associated with RSRP changes. Configuration information may be provided by the CU 1004 or the candidate DU 1003.

In an embodiment, in operation 1020, upon the UE 1001 receiving information (e.g., PDCCH order) to trigger TA acquisition in operation 1015 or receiving a TA value in operation 1019, the UE 1001 starts a timer (e.g., an early TA timer). The value of the timer may be configured by the CU 904. If the timer expires, the TA value is deemed invalid. Upon expiration of the timer, UE 1001 determines that the TA value is invalid.

In another embodiment, with respect to RSRP changes, rsrp#7 may be the RSRP when UE 1001 transmits a TA acquired signal (e.g., a dedicated preamble or SRS) in operation 1016. Rsrp#8 is an RSRP value measured by the UE after the UE receives the TA value. For example, if the RSRP change (rsrp#8-rsrp#7) is equal to or greater than or equal to a threshold (e.g., threshold #4 described in the embodiment of fig. 6), then the TA value is deemed invalid. Once the RSRP change (rsrp#8-rsrp#7) is greater than or equal to the threshold, the UE 1001 determines that the TA value is invalid.

After UE 1001 determines that the TA value is invalid, there may be two options in different embodiments, namely option 1 and option 2 as follows.

(1) Option 1 after the UE 1001 receives information (e.g., PDCCH order) to trigger TA acquisition in operation 1015, the UE 1001 transmits a TA acquired signal (e.g., a dedicated preamble or SRS) (e.g., signal # 1) to the candidate DU 1003 in operation 1016. In operation 1021A (optional), once the UE 1001 determines that the TA value of the candidate cell is invalid, the UE 1001 is again triggered to transmit a TA acquired signal (e.g., a dedicated preamble or SRS) to the candidate DU 1003 (e.g., signal #2 described in the embodiment of fig. 6).

(2) Option 2 in operation 1021B (optional), once UE 1001 determines that the TA value of the candidate cell is invalid, UE 1001

Information indicating that the TA value is invalid is transmitted to the network (e.g., source DU 1002). In operation 1022B (optional), the source DU1002 may transmit information (e.g., an indication #4 described in the embodiment of fig. 6) to the UE 1001 to trigger the TA acquisition associated with the candidate cell again (e.g., a PDCCH order). In operation 1022B, there may be two options in different embodiments, namely option a and option B as follows.

A) Option a in the inter-DU case, once the source DU 1002 receives information indicating that the TA value is invalid from the UE 1001, the source DU 1002 transmits information indicating that the TA value is valid to the candidate DU 1003 via the CU 1004. The candidate DU 1003 then transmits RACH resources (e.g., dedicated preambles or dedicated time-frequency resources) to the source DU 1002 via the CU 1004. Finally, source DU 1002 transmits information (e.g., an indication #4, e.g., PDCCH order) to UE 1001 to trigger TA reacquisition.

B) Option B-in the intra-DU case, once source DU 1002 receives information from UE 1001 indicating that the TA value is invalid, source DU 1002 transmits information to UE 1001 based on RACH resources (e.g., indication #4,

E.g., PDCCH order) to trigger TA acquisition.

FIG. 11 illustrates a block diagram of an exemplary apparatus 1100 according to some embodiments of the present disclosure. As shown in fig. 11, apparatus 1100 may include at least one processor 1106 and at least one transceiver 1102 coupled to processor 1106. Although elements such as the at least one transceiver 1102 and the processor 1106 are depicted in the singular in this drawing, the plural is contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present disclosure, transceiver 1102 may be split into two devices, such as receive circuitry and transmit circuitry. In some embodiments of the present disclosure, apparatus 1100 may further comprise an input device, memory, and/or other components.

In some embodiments of the present disclosure, apparatus 1100 may be a UE or a network node (e.g., BS, CU, or DU). The transceiver 1102 and the processor 1106 may interact with each other in order to perform the operations described above with respect to a UE or network node, for example in any of fig. 1-10.

In some embodiments of the present disclosure, the apparatus 1100 may further comprise at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may have stored thereon computer-executable instructions to cause the processor 1106 to implement a method as described above with respect to a UE or network node (e.g., BS, CU, or DU). For example, computer-executable instructions, when executed, cause the processor 1106 to interact with the transceiver 1102 to perform the operations described in fig. 1-10 with respect to a UE or network node.

Those of ordinary skill in the art will appreciate that the operations or steps of a method described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of a method may reside as one or any combination or set of codes and/or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

In this document, the term "comprises/comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Elements beginning with "a" or the like do not exclude the presence of additional equivalent elements in a process, method, article, or apparatus that comprises a list of elements does not include any additional constraint. Furthermore, the term another is defined as at least a second or more. The term "having," as used herein, and the like, is defined as "comprising. For example, an expression of "a and/or B" or "at least one of a and B" may include any and all combinations of words enumerated with the expression. For example, the expression "a and/or B" or "at least one of a and B" may include A, B or both a and B. The terms "first", "second" or the like are used only to clearly illustrate embodiments of the present application, but are not intended to limit the essence of the present application.

Claims

1. A candidate distributed unit DU of a base station BS, comprising:

Transceiver and method for manufacturing the same

A processor coupled to the transceiver, wherein the processor is configured to:

Receiving, via the transceiver, a signal from a user equipment, UE, for timing advance, TA, acquisition associated with a candidate cell;

Transmitting a TA value associated with the candidate cell to a source DU of the BS or the UE via the transceiver, and

A determination is made as to whether the TA value associated with the candidate cell is valid.

2. The candidate DU of claim 1, wherein the signal is at least one of:

Preamble, or

The sounding reference signal SRS.

3. The candidate DU of claim 1, wherein the processor of the candidate DU is configured to calculate the TA value based on the received signal and the TA value is transmitted to the source DU via a centralized unit CU of the BS.

4. The candidate DU of claim 3, wherein the processor of the candidate DU is configured to transmit at least one of the following to the source DU via the CU:

The identifier ID information of the candidate cell, or

ID information of the UE.

5. The candidate DU of claim 1 wherein the TA value is transmitted to the UE in a random access response, RAR, message based on the received signal.

6. The candidate DU of claim 1, wherein determining whether the TA value is valid based on a condition, wherein the condition based on which the TA value is determined to be invalid includes at least one of:

Early TA timer expiration, or

The difference between the first reference signal received power, RSRP, value and the second RSRP value is greater than or equal to a threshold associated with RSRP changes.

7. The candidate DU of claim 6, wherein the processor of the candidate DU is configured to receive configuration information regarding the condition from the CU via the transceiver and the configuration information includes at least one of:

the value of the early TA timer, or

The threshold value associated with RSRP changes.

8. The candidate DU of claim 6, wherein the processor of the candidate DU is configured to start the early TA timer upon receipt of the signal or upon calculation of the TA value.

9. The candidate DU of claim 6 wherein the first RSRP value is an RSRP value when the candidate DU receives the signal or when the candidate DU calculates the TA value and the second RSRP value is an RSRP value received from the CU or the source DU.

10. The candidate DU of any one of claims 1, 6 and 9, wherein the processor of the candidate DU is configured to receive at least one of the following via the transceiver:

layer 1L1 measurements of the UE from the source DU, or

Layer 3L3 measurements of the UE from the CU,

Wherein the second RSRP value is included in at least one of the L1 measurement or the L3 measurement.

11. The candidate DU of claim 1 or claim 6, in response to determining that the TA value is invalid, the processor of the candidate DU is configured to transmit information indicating that the TA value is invalid to the source DU via the transceiver via the CU.

12. The candidate DU of claim 11, wherein the processor of the candidate DU is configured to transmit configuration information regarding random access channel, RACH, resources for TA acquisition associated with the candidate cell to the source DU via the transceiver via the CU.

13. A centralized unit CU of a base station BS, comprising:

Transceiver and method for manufacturing the same

A processor coupled to the transceiver, wherein the processor is configured to:

receiving a timing advance, TA, value associated with a candidate cell from a candidate distributed unit, DU, of the BS via the transceiver, and

The TA value associated with the candidate cell is transmitted via the transceiver to a source DU of the BS.

14. A source distributed unit DU of a base station BS, comprising:

Transceiver and method for manufacturing the same

A processor coupled to the transceiver, wherein the processor is configured to:

transmitting a first indication for timing advance, TA, acquisition associated with a candidate cell to a user equipment, UE, via the transceiver

A second indication of TA acquisition associated with the candidate cell is transmitted to the UE via the transceiver.

15. A user equipment, UE, comprising:

Transceiver and method for manufacturing the same

A processor coupled to the transceiver, wherein the processor is configured to:

receiving, via the transceiver, a first indication of a timing advance, TA, associated with a candidate cell from a source distributed unit, DU, of a base station, BS;

transmitting a first signal for TA acquisition to a candidate distributed unit DU of the BS via the transceiver based on the first indication;

Receiving a second indication from the source DU via the transceiver for TA acquisition associated with the candidate cell, and

A second signal for TA acquisition is transmitted to the candidate DU via the transceiver based on the second indication.