Condition-based LTM

Abstract

Example embodiments of the present disclosure relate to RAN units, methods, apparatuses, and computer-readable media for condition-based LTM. In the technical scheme, the RAN CU can send a first request message to a target RAN CU, and the first request message comprises an indication of a condition-based LTM and an LTM candidate cell. Thus, the target RAN CU may know that the UE will perform the condition-based LTM, and thus the target RAN DU may prepare a configuration for the condition-based LTM associated with the LTM candidate cell. Therefore, the switching efficiency of the UE can be ensured.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to wireless communications, and more particularly to radio access network (RAN) elements, methods, apparatuses, and computer readable media for conditional Layer 1 / Layer 2 triggered mobility (LTM). BACKGROUND

[0002] A wireless communication system can include one or more network communication devices, such as base stations, which can additionally be referred to as eNodeBs (eNBs), next generation NodeBs (gNBs), or other suitable terminology. Each network communication device, such as a base station, can support wireless communication for one or more user communication devices, which can additionally be referred to as user equipment (UE), or other suitable terminology. A wireless communication system can support wireless communication with one or more user communication devices by utilizing resources of the wireless communication system, e.g., time resources (e.g., symbols, time slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers). Furthermore, a wireless communication system can support wireless communication across multiple radio access technologies, including third generation (3G) radio access technologies, fourth generation (4G) radio access technologies, fifth generation (5G) radio access technologies, and other suitable 5G beyond radio access technologies (e.g., sixth generation (6G)).

[0003] In the Third Generation Partnership Project (3GPP), a work item on further New Radio (NR) mobility enhancements, named LTM, was approved to change a serving cell via Layer 1 / Layer 2 (L1 / L2) signaling in order to reduce latency, overhead, and interruption time. LTM refers to a network-based L1 measurement triggered PCell (primary cell of a master cell group) or PSCell (primary cell of a secondary cell group) cell change procedure via medium access control (MAC) control element (CE). LTM can be performed intra-gNB or inter-gNB, e.g., a UE can be handed over to a target distributed unit (DU) that belongs to the same central unit (CU) as the source DU or a different CU. SUMMARY

[0004] The present disclosure relates to RAN elements, methods, apparatuses, and computer readable media for conditional LTM. According to the proposed technical solution, enhancements for supporting LTM are proposed.

[0005] In some implementations, a RAN CU is provided. The RAN CU comprises: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the RAN CU to: transmit, to a target RAN CU, a first request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a user equipment (UE); and receive, from the target RAN CU, a first response message comprising a first configuration for the LTM candidate cell.

[0006] In some implementations, a RAN CU is provided. The RAN CU comprises: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the RAN CU to: transmit, to a target RAN DU, a second request message comprising an indication of a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a UE; and receive, from the target RAN DU, a second response message comprising a second configuration for the LTM candidate cell.

[0007] In some implementations, a target RAN CU is provided. The target RAN CU comprises: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the target RAN CU to: receive, from a RAN CU, a first request message indicating: a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a UE; transmit, to a target RAN DU, a second request message indicating the condition-based LTM and the LTM candidate cell; receive, from the target RAN DU, a second response message comprising a second configuration associated with the LTM candidate cell; and transmit, to the RAN CU, a first response message comprising a first configuration for the LTM candidate cell, wherein the first configuration comprises at least the second configuration.

[0008] In some implementations, a target RAN DU is provided. The target RAN DU includes at least one memory and at least one processor coupled with the at least one memory and configured to cause the target RAN CU to: receive, from a RAN CU or a target RAN CU, a second request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of the condition by a UE; and send, to the RAN CU or the target RAN CU, a second response message including a second configuration associated with the LTM candidate cell.

[0009] In some implementations, a source RAN DU is provided. The source RAN DU includes at least one memory and at least one processor coupled with the at least one memory and configured to cause the source RANDU to: receive, from a RAN CU, a message for requesting the RAN DU to determine at least one condition for an LTM candidate cell based on layer 1 measurements, wherein the at least one condition for the LTM candidate cell based on layer 1 measurements is used for a condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of the condition by a UE; and determine, based on the message, the at least one condition for the LTM candidate cell based on layer 1 measurements; and send, to the RAN CU, the at least one condition for the LTM candidate cell based on layer 1 measurements.

[0010] In some implementations, a UE is provided. The UE includes at least one memory and at least one processor coupled with the at least one memory and configured to cause the UE to: receive, from a RAN CU, a first configuration for an LTM candidate cell associated with a condition-based LTM and one or more corresponding conditions for triggering the LTM; and perform a handover to the LTM candidate cell in accordance with a determination that one corresponding condition of the one or more corresponding conditions is satisfied.

[0011] In some implementations, a method performed by a RAN CU is provided. The method includes: sending, to a target RAN CU, a first request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of the condition by a user equipment (UE); and receiving, from the target RAN CU, a first response message including a first configuration for the LTM candidate cell.

[0012] In some implementations, a method performed by a RAN CU is provided. The method includes sending, to a target RAN DU, a second request message including a condition-based LTM and an indication of an LTM candidate cell associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by a UE; and receiving, from the target RAN DU, a second response message including a second configuration for the LTM candidate cell.

[0013] In some implementations, a method performed by a target RAN CU is provided. The method includes receiving, from a RAN CU, a first request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by a UE; sending, to a target RAN DU, a second request message indicating the condition-based LTM and the LTM candidate cell; receiving, from the target RAN DU, a second response message including a second configuration associated with the LTM candidate cell; and sending, to the RAN CU, a first response message including a first configuration for the LTM candidate cell, where the first configuration comprises at least the second configuration.

[0014] In some implementations, a method performed by a target RAN DU is provided. The method includes receiving, from a RAN CU or a target RAN CU, a second request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by a UE; and sending, to the RAN CU or the target RAN DU, a second response message including a second configuration associated with the LTM candidate cell.

[0015] In some implementations, a method performed by a source RAN DU is provided. The method includes receiving, from a RAN CU, a message for requesting the RAN DU to determine at least one condition for an LTM candidate cell based on layer 1 measurements, where the at least one condition for the LTM candidate cell based on layer 1 measurements is used for a condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by a UE; and determining, based on the message, the at least one condition for the LTM candidate cell based on layer 1 measurements; and sending, to the RAN CU, the at least one condition for the LTM candidate cell based on layer 1 measurements.

[0016] In some implementations, a method performed by a UE is provided. The method includes receiving, from a RAN CU, a first configuration for a LTM candidate cell associated with a condition-based LTM and one or more corresponding conditions for triggering the LTM; and performing a handover to the LTM candidate cell in accordance with a determination that one of the one or more corresponding conditions is satisfied.

[0017] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: transmit, to a target RAN CU, a first request message indicating a condition-based LTM and a LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a UE; and receive, from the target RAN CU, a first response message including a first configuration for the LTM candidate cell.

[0018] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: transmit, to a target RAN DU, a second request message including an indication of a condition-based LTM and a LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a UE; and receive, from the target RAN DU, a second response message including a second configuration for the LTM candidate cell.

[0019] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: receive, from a RAN CU, a first request message indicating a condition-based LTM and a LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a UE; transmit, to a target RAN DU, a second request message indicating the condition-based LTM and the LTM candidate cell; receive, from the target RAN DU, a second response message including a second configuration associated with the LTM candidate cell; and transmit, to the RAN CU, a first response message including a first configuration for the LTM candidate cell, wherein the first configuration includes at least the second configuration.

[0020] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: receive, from a RAN CU or a target RAN CU, a second request message indicating a condition-based LTM and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of the condition by a UE; and transmit, to the RAN CU or the target RAN CU, a second response message including a second configuration associated with the LTM candidate cell.

[0021] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: receive, from a RAN CU, a message for requesting the RAN DU to determine at least one condition for an LTM candidate cell based on layer 1 measurements, wherein the at least one condition for the LTM candidate cell based on layer 1 measurements is used for a condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of the condition by a UE; and determine, based on the message, the at least one condition for the LTM candidate cell based on layer 1 measurements; and transmit, to the RAN CU, the at least one condition for the LTM candidate cell based on layer 1 measurements.

[0022] In some implementations, a processor for wireless communication is provided. The processor includes at least one controller coupled with at least one memory and configured to cause the processor to: receive, from a RAN CU, a first configuration for an LTM candidate cell associated with a condition-based LTM and one or more corresponding conditions for triggering the LTM; and perform a handover to the LTM candidate cell in accordance with a determination that one of the one or more corresponding conditions is satisfied.

[0023] In some implementations of the methods and RAN CUs described herein, further comprising: transmitting, to the UE, the first configuration for the LTM candidate cell and the one or more corresponding conditions for triggering the LTM.

[0024] In some implementations of the methods and RAN CUs described herein, further comprising: generating a condition for the LTM candidate cell based on layer 3 measurements, wherein the one or more corresponding conditions include the condition for the LTM candidate cell based on layer 3 measurements.

[0025] In some implementations of the methods and RAN CUs described herein, further comprising: transmitting, to the RAN DU, a message for requesting the RAN DU to determine at least one condition for the LTM candidate cell based on the layer 1 measurement; and receiving, from the RAN DU, the at least one condition, wherein the one or more corresponding conditions comprise the at least one condition for the LTM candidate cell based on the layer 1 measurement.

[0026] In some implementations of the methods and RAN CUs described herein, further comprising: receiving, from the UE via the RAN DU, information indicating one of: the condition is satisfied, or a beam selected for the LTM candidate cell.

[0027] In some implementations of the methods and RAN CUs described herein, further comprising: receiving, from the target RAN CU, a first cancelation indication indicating that the LTM candidate cell configured for the condition-based LTM is canceled.

[0028] In some implementations of the methods and RAN CUs described herein, further comprising: determining to cancel the LTM candidate cell configured for the condition-based LTM; and transmitting, to the target RAN CU, a second cancelation indication indicating that the LTM candidate cell configured for the condition-based LTM is canceled.

[0029] In some implementations of the methods and RAN CUs described herein, the first response message further indicates random access channel (RACH) resources for early timing advance (TA) acquisition, further comprising: selecting, for the RAN DU, some of the RACH resources for early TA acquisition; and transmitting, to the RAN DU, configuration information indicating the some of the RACH resources for early TA acquisition.

[0030] In some implementations of the methods and target RAN CUs described herein, further comprising: determining to cancel the LTM candidate cell configured for the condition-based LTM; and transmitting, to the RAN CU, a first cancelation indication indicating that the LTM candidate cell configured for the condition-based LTM is canceled.

[0031] In some implementations of the methods and target RAN CUs described herein, further comprising: receiving, from the RAN CU, a second cancelation indication indicating that the LTM candidate cell configured for the condition-based LTM is canceled; and transmitting, to the target RAN DU, a third cancelation indication indicating that the LTM candidate cell is canceled by the RAN CU.

[0032] In some implementations of the methods and target RAN CUs described herein, further comprising: receiving, from the RAN CU or the target RAN CU, a cancellation indication indicating that the LTM candidate cell configured for the condition-based LTM is cancelled.

[0033] In some implementations of the methods and RAN DUs described herein, further comprising: receiving, from the RAN CU, some of random access channel (RACH) resources for early TA acquisition, wherein the RACH resources for early TA acquisition are determined by the target RAN DU for the RAN CU.

[0034] In some implementations of the methods and UEs described herein, further comprising: transmitting, to the RAN CU via the RAN DU, information indicating one of: the condition is satisfied, or a beam selected for the LTM candidate cell.

[0035] In some implementations of the methods and UEs described herein, further comprising: in accordance with a determination that the condition is satisfied for both the LTM candidate cell and another LTM candidate cell, determining to switch to the LTM candidate cell based on a higher priority of the LTM candidate cell.

[0036] In some implementations of the methods and UEs described herein, further comprising: performing early timing advance (TA) acquisition based on a physical downlink control channel (PDCCH) command or based on UE-based TA measurement.

[0037] In some implementations of the methods and UEs described herein, further comprising: receiving, from the RAN CU or the RAN DU, a cell handover command to trigger a cell handover; and performing the handover to the LTM candidate cell based on the cell handover command even though none of the one or more corresponding conditions are satisfied.

[0038] In some implementations of the methods, RAN CUs, RAN DUs, and UEs described herein, the first request message further indicates whether at least one subsequent LTM is supported by the condition-based LTM.

[0039] In some implementations of the methods, RAN CUs, RAN DUs, and UEs described herein, the first request message further includes information of the RAN DU, and the first request message further requests RACH resources for early TA acquisition associated with the RAN DU.

[0040] In some implementations of the methods, RAN CUs, RAN DUs, and UEs described herein, the second request message further indicates one of: an estimated probability of reaching the LTM candidate cell associated with the condition-based LTM, or whether the estimated probability is applied to at least one subsequent LTM.

[0041] In some implementations of the methods, RAN CUs, RAN DUs, and UEs described herein, the second request message further requests RACH resources for early TA acquisition associated with the RAN CU, and wherein the second response message further indicates the RACH resources for early TA acquisition associated with the RAN CU.

[0042] In some implementations of the methods, RAN CUs, RAN DUs, and UEs described herein, the first request message further includes information of the RAN DU, and the first request message further requests RACH resources for early TA acquisition associated with the RAN DU, and wherein the second response message further indicates the RACH resources for early TA acquisition associated with the RAN CU. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 FIGURE 1 illustrates an example of a wireless communication system, in which some embodiments of the disclosure can be implemented;

[0044] Figure 2 FIGURE 2 illustrates a schematic diagram of an example communication network, in which some embodiments of the disclosure can be implemented;

[0045] Figure 3 FIGURE 3 illustrates a signaling diagram illustrating a communication procedure for LTM based on inter-CU conditions, in accordance with some example embodiments of the disclosure;

[0046] Figure 4 FIGURE 4 illustrates a signaling diagram illustrating a communication procedure for LTM based on intra-CU conditions, in accordance with some example embodiments of the disclosure;

[0047] Figure 5 FIGURE 5 illustrates a signaling diagram illustrating a communication procedure for determining RACH resources for early TA acquisition for inter-CU LTM, in accordance with some example embodiments of the disclosure;

[0048] Figure 6 FIGURE 6 illustrates an example of a device suitable for implementing embodiments of the disclosure;

[0049] Figure 7 FIGURE 7 illustrates an example of a processor suitable for implementing some embodiments of the disclosure;

[0050] Figure 8 FIGURE 8 illustrates a flow diagram of an example method implemented at a RAN CU, in accordance with aspects of the present disclosure;

[0051] Figure 9 FIGURE 9 illustrates a flow diagram of an example method implemented at a RAN CU, in accordance with aspects of the present disclosure;

[0052] Figure 10 FIG. illustrates a flow diagram of an example method implemented at a target RAN CU, according to aspects of the present disclosure;

[0053] Figure 11 FIG. illustrates a flow diagram of an example method implemented at a target RAN DU, according to aspects of the present disclosure;

[0054] Figure 12 FIG. illustrates a flow diagram of an example method implemented at a source RAN DU, according to aspects of the present disclosure; and

[0055] Figure 13 FIG. illustrates a flow diagram of an example method implemented at a UE, according to aspects of the present disclosure.

[0056] In all the drawings, like reference numerals refer to like elements throughout. DETAILED DESCRIPTION

[0057] The principles of the present disclosure will now be described with reference to some embodiments. It should be understood that these embodiments are only for illustrative purposes and help those skilled in the art to understand and implement the present disclosure, and do not imply any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways other than those described below. In the following description and above claims, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present disclosure belongs, unless otherwise defined.

[0058] The reference to “one embodiment”, “an example embodiment”, “embodiment”, “some embodiments”, etc. in the present disclosure indicates that the described embodiment(s) can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment(s). Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that, unless otherwise expressly stated, it is within the purview of the skilled person to effect such feature, structure, or characteristic in connection with other embodiments, whether or not apparent.

[0059] It should be understood that, although the terms“first” and“second” among others can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be called a first element without departing from the scope of the embodiments. As used herein, the term“and / or” includes any and all combinations of one or more of the associated listed terms. In some examples, a value, process, or apparatus is referred to as“best,”“lowest,”“highest,”“smallest,”“largest,” etc. It will be recognized that such descriptions are intended to indicate that a selection among many used function alternatives can be made, and such selections are not necessarily better, smaller, higher, or otherwise better than other selections.

[0060] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments. As used herein, the singular forms“a,”“an” and“the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, it will be further understood that the terms“comprises,”“comprising,”“includes,”“including,”“has,”“have,”“having,”“includes” and / or“containing” when used herein, specify the presence of stated features, elements, components, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. For example, the term“comprising” and its variations are to be construed as open-ended terms that mean“one or more of the stated elements are present, but not excluding others.” The term“based on” is to be construed as“based at least in part on.” The term“one embodiment” and“an embodiment” are to be construed as“at least one embodiment.” The term“another embodiment” is to be construed as“at least one other embodiment.” The use of the term“about” in relation to a value is to be construed as “at least approximately.” Other explicit or implicit definitions can be included below.

[0061] Figure 1An example of a wireless communication system 100 in which some embodiments of the disclosure can be implemented is illustrated. The wireless communication system 100 can include one or more network entities 102 (also referred to as network equipment (NE)), one or more UEs 104, a core network 106, and a packet data network 108. The wireless communication system 100 can support various radio access technologies. In some implementations, the wireless communication system 100 can be a 4G network, such as a Long Term Evolution (LTE) network or a LTE-Advanced (LTE-A) network. In some other implementations, the wireless communication system 100 can be a 5G network, such as a New Radio (NR) network. In other implementations, the wireless communication system 100 can be a combination of 4G and 5G networks, or other suitable radio access technologies, including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20. The wireless communication system 100 can support radio access technologies beyond 5G. Additionally, the wireless communication system 100 can support technologies such as time division multiple access (TDMA), frequency division multiple access (FDMA), or code division multiple access (CDMA).

[0062] The one or more network entities 102 can be dispersed throughout the geographic region to provide coverage to a wide area or a small area. One or more of the network entities 102 described herein can be or include or can be referred to as a network node, a base station, a network element, a radio access network (RAN), a transceiver base station, an access point, a NodeB, an eNodeB (eNB), a next generation NodeB (gNB), or other suitable terminology. The network entities 102 and the UEs 104 can communicate via communication links 110, which can be wireless connections or wired connections. For example, the network entities 102 and the UEs 104 can perform wireless communication (e.g., receive signaling, transmit signaling) over a Uu interface.

[0063] The network entity 102 can provide a geographic coverage area 112 for which the network entity 102 can support service (e.g., voice, video, packet data, messaging, broadcast, etc.) to one or more UEs 104 within the geographic coverage area 112. For example, the network entity 102 and UEs 104 can support wireless communication of signals associated with service (e.g., voice, video, packet data, messaging, broadcast, etc.) in accordance with one or more radio access technologies. In some implementations, the network entity 102 can be mobile, such as a satellite associated with a non-terrestrial network. In some implementations, different geographic coverage areas 112 associated with the same or different radio access technologies can overlap, but different geographic coverage areas 112 can be associated with different network entities 102. Information and signals described herein can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0064] The one or more UEs 104 can be dispersed throughout the geographic area of wireless communication system 100. A UE 104 can comprise or can be referred to as a mobile device, wireless device, remote device, remote unit, handset, or subscriber device, or some other suitable terminology where appropriate. In some implementations, a UE 104 can be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally, or alternatively, a UE 104 can be referred to as an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a machine type communications (MTC) device, among other examples. In some implementations, a UE 104 can be fixedly installed in a geographic area of wireless communication system 100. In some other implementations, a UE 104 can be mobile in a geographic area of wireless communication system 100.

[0065] The one or more UEs 104 can be devices in different forms or having different capabilities. Some examples of UEs 104 are shown in FIG. 1. A UE 104 can be capable of communicating with various types of devices, such as a network entity 102, another UE 104, or a network device (e.g., a core network 106, a packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network device) as shown in FIG. 1. Additionally, or alternatively, a UE 104 can support communicating with other network entities 102 or UEs 104 that can act as relays in wireless communication system 100. Figure 1 Some examples of UEs 104 are shown in FIG. 1. A UE 104 can be capable of communicating with various types of devices, such as a network entity 102, another UE 104, or a network device (e.g., a core network 106, a packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network device) as shown in FIG. 1. Additionally, or alternatively, a UE 104 can support communicating with other network entities 102 or UEs 104 that can act as relays in wireless communication system 100. Figure 1 Some examples of UEs 104 are shown in FIG. 1. A UE 104 can be capable of communicating with various types of devices, such as a network entity 102, another UE 104, or a network device (e.g., a core network 106, a packet data network 108, a relay device, an integrated access and backhaul (IAB) node, or another network device) as shown in FIG. 1. Additionally, or alternatively, a UE 104 can support communicating with other network entities 102 or UEs 104 that can act as relays in wireless communication system 100.

[0066] The UEs 104 can also be able to communicate directly with one another using one or more sidelink channels. For example, the UEs 104 can use a PC5 interface to communicate with one another directly over the communications link 114. In some implementations, such as a vehicle-to-vehicle (V2V) deployment, a vehicle-to- everything (V2X) deployment, or a cellular V2X (C-V2X) deployment, the communications link 114 can be referred to as a sidelink (SL).

[0067] The network entity 102 can support communication with the core network 106, or with another network entity 102, or with both. For example, the network entity 102 can interface with the core network 106 through one or more backhaul links 116 (e.g., via an SI, N2, N3, or another network interface). The network entities 102 can communicate with one another through backhaul links 116 (e.g., via an X2, Xn, or another network interface). In some implementations, the network entities 102 can communicate directly with one another (e.g., between network entities 102). In some other implementations, the network entities 102 can communicate with, or indirectly communicate through, one another (e.g., via the core network 106). In some implementations, one or more network entities 102 can include subcomponents, such as an access network entity, which can be an example of an access node controller (ANC). The ANC can communicate with one or more UEs 104 through one or more other access network transmission entities, which can be referred to as a radio head, a smart radio head, or a transmission-reception point (TRP).

[0068] In some implementations, the network entity 102 can be configured to employ a disaggregated architecture, which can be configured to utilize a protocol stack that is physically or logically distributed between two or more network entities 102, such as an integrated access backhaul (IAB) network, an open RAN (O-RAN) (e.g., a network configuration sponsored by the O-RAN Alliance), or a virtualized RAN (vRAN) (e.g., a cloud RAN (C-RAN)). For example, the network entity 102 can include one or more of the following: a central unit (CU), a distributed unit (DU), a radio unit (RU), a RAN intelligent controller (RIC) (e.g., a Near-RT RIC, a Non-RT RIC), a service management and orchestration (SMO) system, or any combination thereof.

[0069] A RU can also be referred to as a radio head, a smart radio head, a remote radio head (RRH), a remote radio unit (RRU), or a transmission reception point (TRP). One or more components of a network entity 102 employing a disaggregated RAN architecture can be co-located, or one or more components of a network entity 102 can be located in distributed locations (e.g., separate physical locations). In some implementations, one or more network entities 102 of a disaggregated RAN architecture can be implemented as virtual units (e.g., a virtual CU (VCU), a virtual DU (VDU), a virtual RU (VRU)).

[0070] The division of functions among the CU, the DU, and the RU can be flexible and can support different functions depending on which functions (e.g., network layer functions, protocol layer functions, baseband functions, radio frequency functions, and any combination thereof) are performed at the CU, the DU, or the RU. For example, a division of functions of a protocol stack can be employed between the CU and the DU such that the CU can support one or more layers of the protocol stack, while the DU can support one or more different layers of the protocol stack. In some implementations, the CU can host higher layer protocol layer (e.g., layer 3 (L3), layer 2 (L2)) functions and signaling (e.g., radio resource control (RRC), service data adaptation protocol (SDAP), packet data convergence protocol (PDCP)). The CU can be connected to one or more DUs or RUs, while the one or more DUs or RUs can host lower layer protocol layers, such as layer 1 (LI) (e.g., physical (PHY) layer) or L2 (e.g., radio link control (RLC) layer, medium access control (MAC) layer) functions and signaling, and can each be at least partially controlled by the CU.

[0071] Additionally, or alternatively, a division of functions of a protocol stack can be employed between the DU and the RU such that the DU can support one or more layers of the protocol stack, while the RU can support one or more different layers of the protocol stack. The DU can support one or more different cells (e.g., via one or more RUs). In some implementations, the division of functions between the CU and the DU, or between the DU and the RU, can be within a protocol layer (e.g., some functions for a protocol layer can be performed by one of the CU, the DU, or the RU, while other functions of the protocol layer are performed by a different one of the CU, the DU, or the RU).

[0072] A CU can be further functionally divided into a CU control plane (CU-CP) and a CU user plane (CU-UP) function. A CU can be connected to one or more DUs via a midhaul communication link (e.g., Fl, Fl-C, Fl-U), while a DU can be connected to one or more RUs via a front-haul communication link (e.g., an open front-haul (FH) interface). In some implementations, a midhaul or front-haul communication link can be implemented according to an interface (e.g., a channel) between layers of a protocol stack supported by respective network entities 102 that communicate via such a communication link.

[0073] The core network 106 can support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. The core network 106 can be an evolved packet core (EPC), or a 5G core (5GC), which can comprise control plane entities (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) to manage access and mobility and user plane entities (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)) to route packets or interconnect to external networks. In some implementations, the control plane entities can manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management (e.g., data bearers, signaling bearers, etc.) for one or more UEs 104 served by one or more network entities 102 associated with the core network 106.

[0074] The core network 106 can communicate with the packet data network 108 through one or more backhaul links 116 (e.g., via an SI, N2, N3, or other network interface). The packet data network 108 can include application server 118. In some implementations, the one or more UEs 104 can communicate with the application server 118. The UE 104 can establish a session (e.g., a protocol data unit (PDU) session, etc.) with the core network 106 via a network entity 102. The core network 106 can route traffic (e.g., control information, data, etc.) between the UE 104 and the application server 118 using the established session (e.g., the established PDU session). The PDU session can be an example of a logical connection between the UE 104 and the core network 106 (e.g., one or more network functions of the core network 106).

[0075] In the wireless communication system 100, the network entity 102 and the UE 104 can perform various operations (e.g., wireless communications) using resources (e.g., time resources (e.g., symbols, slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers)) of the wireless communication system 100. In some implementations, the network entity 102 and the UE 104 can support different resource structures. For example, the network entity 102 and the UE 104 can support different frame structures. In some implementations, such as in 4G, the network entity 102 and the UE 104 can support a single frame structure. In some other implementations, such as in 5G and other suitable radio access technologies, the network entity 102 and the UE 104 can support various frame structures (i.e., multiple frame structures). The network entity 102 and the UE 104 can support various frame structures based on one or more numerologies.

[0076] One or more numerologies can be supported in the wireless communication system 100, and a numerology can include a subcarrier spacing and a cyclic prefix. A first numerology (e.g., m = 0) can be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. In some implementations, the first numerology (e.g., m = 0) associated with the first subcarrier spacing (e.g., 15 kHz) can utilize one slot per subframe. A second numerology (e.g., m = 1) can be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., m = 2) can be associated with a third subcarrier spacing (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth numerology (e.g., m = 3) can be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g., m = 4) can be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

[0077] Time intervals can be expressed in multiples of a TTI, which can be a single symbol period. In some implementations, a resource can be organized according to radio frames of 10 milliseconds (ms) each, where a frame can be comprised of a set of 10 equally sized subframes. In some implementations, a subframe can be comprised of two sets of 6 equally sized slots, each slot containing 12 consecutive symbol periods. In some implementations, a resource can be organized according to frames of 10 ms each, with each frame including 10 subframes. In some implementations, a subframe can include 2 slots, and a slot can include 12 symbol periods. In some implementations, a frame can include 5 subframes across 5 frequency ms In some implementations, each frame can include multiple subframes. For example, each frame can include 10 subframes, and each subframe can have a duration of, for example, 1 ms In some implementations, each frame can have the same duration. In some implementations, each subframe of a frame can have the same duration.

[0078] Additionally or alternatively, time intervals of resources (e.g., communication resources) can be organized as slots, for example. A subframe can include a number (e.g., quantity) of slots. The number of slots in each subframe can also depend on the parameter set(s) supported in the wireless communications system 100. For example, a first, second, third, fourth, and fifth parameter set (i.e., m = 0, m = 1, m = 2, m = 3, m = 4) associated with respective subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz can utilize a single slot per subframe, two slots per subframe, four slots per subframe, eight slots per subframe, and 16 slots per subframe, respectively. Each slot can include a number (e.g., quantity) of symbols (e.g., OFDM symbols). In some implementations, the number (e.g., quantity) of slots for a subframe can depend on the parameter set. For a normal cyclic prefix, one slot can include 14 symbols. For an extended cyclic prefix (e.g., applicable to 60 kHz subcarrier spacing), one slot can include 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame can depend on the parameter set for normal and extended cyclic prefixes. It will be understood that a first parameter set (e.g., m = 0) associated with a first subcarrier spacing (e.g., 15 kHz) can be used interchangeably between subframes and slots.

[0079] In the wireless communications system 100, the electromagnetic (EM) spectrum can be partitioned into various classes, bands, frequency channels, and so on. By way of example, the wireless communications system 100 can support one or more operating bands, such as frequency range FR1 (410 MHz - 7.125 GHz), FR2 (24.25 GHz - 52.6 GHz), FR3 (7.125 GHz - 24.25 GHz), FR4 (52.6 GHz - 114.25 GHz), FR4a or FR4-1 (52.6 GHz - 71 GHz), and FR5 (114.25 GHz - 300 GHz). In some implementations, the network entity 102 and the UE 104 can perform wireless communications over one or more of these operating bands. In some implementations, FR1 can be used by the network entity 102 and the UE 104, among other devices or apparatuses, for cellular communications traffic (e.g., control information, data). In some implementations, FR2 can be used by the network entity 102 and the UE 104, among other devices or apparatuses, for short-range, high data rate communications.

[0080] FR1 can be associated with one or more numerologies (e.g., at least three numerologies). For example, FR1 can be associated with a first numerology (e.g., m=0) that includes 15 kHz subcarrier spacing; a second numerology (e.g., m=l) that includes 30 kHz subcarrier spacing; and a third numerology (e.g., m=2) that includes 60 kHz subcarrier spacing. FR2 can be associated with one or more numerologies (e.g., at least 2 numerologies). For example, FR2 can be associated with the third numerology (e.g., m=2) that includes 60 kHz subcarrier spacing; and a fourth numerology (e.g., m=3) that includes 120 kHz subcarrier spacing.

[0081] As previously mentioned, LTM is a network-based cell handover procedure triggered via MAC CE based on LI measurements. Potential applicable scenarios for LTM include intra-CU intra-DU mobility, intra-CU inter-DU mobility, and inter-CU mobility. Specifically, within intra-CU intra-DU mobility, a UE can move between different cells within a DU. Within intra-CU inter-DU mobility, a UE can move between different cells belonging to different DUs but within a CU. In inter-CU mobility, a UE can move between different cells belonging to different DUs, where the DUs belong to different CUs.

[0082] In some cases, a UE accesses a serving gNB and reports L3 measurement results based on configuration from the serving gNB. If the gNB (e.g., the CU of the gNB) decides to handover the UE to a candidate cell based on the measurement results, the serving gNB requests the target DU(s) to prepare configuration for one or more candidate cells. After receiving the candidate cell configuration from the target DU, the serving gNB sends an RRC reconfiguration message including one or more candidate cells to the UE. For example, the CU of the serving gNB sends the RRC reconfiguration message to the UE via the source DU.

[0083] The UE sends an RRC reconfiguration complete message to the serving gNB (e.g., CU) via the source DU of the gNB. The UE can ensure UL / DL synchronization before receiving the cell handover command. For example, the UE can obtain TA via random access or preamble transmission. The UE reports LI measurement results for dynamic handover purposes. The serving gNB (e.g., source DU) sends a cell handover command (e.g., MAC CE or downlink control information (DCI)) to the UE. The UE can then apply the RRC reconfiguration message and start a timer after receiving the lower layer command.

[0084] A condition-based LTM scheme is proposed for discussion, however, some further details need to be investigated.

[0085] Embodiments of the present disclosure provide a technical solution of communication. In the technical solution, the RAN CU can send a first request message to the target RAN CU, wherein the first request message comprises an indication of the condition-based LTM and the LTM candidate cell. Therefore, the target RAN CU can know that the UE will perform the condition-based LTM, and thus prepare the configuration of the condition-based LTM related to the LTM candidate cell. Therefore, the efficiency of the handover of the UE can be guaranteed. The principles and implementation manners of the present disclosure will be described in detail below with reference to the drawings.

[0086] Figure 2 A schematic diagram of an example communication network 200 in which some embodiments of the present disclosure can be implemented is illustrated. As shown in Figure 2 , the communication network 200 can comprise a RAN CU 210, a RAN CU 220, a RAN DU 230, a RAN DU 241, a RAN DU 242 and a UE 250.

[0087] The RAN CU 210 can be a base station, such as a gNB; or the RAN CU 210 can be regarded as a CU of a base station (such as a gNB), and the RAN DUs 230 and 241 can be regarded as DUs of the base station (such as a gNB). The base station can serve a plurality of UEs, which can comprise the UE 250 as shown in Figure 2 .

[0088] The RAN CU 220 and the RAN DU 242 can be another base station, for example, the RAN CU 220 is a CU of the other base station, and the RAN DU 242 is a DU of the other base station.

[0089] The RAN CU 210 can be regarded as a source CU, and the RAN DU 230 can be regarded as a source DU, while considering the mobility of the UE 250. The UE 250 can hand over to the RAN DU 241, for example, the UE 250 can move to the location 251, in which case the RAN DU 241 is a target DU, and the mobility is performed within the same CU (the same gNB), which can be referred to as intra-CU inter-DU mobility. The UE can hand over to the RAN DU 242, for example, the UE 250 can move to the location 252, in which case the RAN CU 220 is a target CU, and the RAN DU 242 is a target DU, and the mobility is inter-CU (inter-gNB) mobility.

[0090] It should be understood that Figure 2 the number of devices in

[0091] For ease of description, some relevant terms are provided below:

[0092] LTM candidate cell: A candidate cell configured to a UE for LTM. There can be multiple LTM candidate cells prepared for a UE, where the LTM candidate cells can belong to the same or different candidate DUs.

[0093] LTM candidate cell configuration: A configuration associated with an LTM candidate cell. The LTM candidate cell configuration can be a full LTM candidate cell configuration or a delta (difference) configuration relative to an LTM reference configuration. Each LTM candidate cell configuration is identified by an index, which is referred to as an LTM candidate cell configuration index, LTM candidate configuration index, or other names. In one example, the LTM candidate cell configuration index is LTM-Candidateld, which is used to identify the LTM candidate cell configuration. For better understanding, the LTM candidate cell configuration is also referred to as an LTM delta configuration.

[0094] LTM reference configuration: A configuration provided by the network to the UE, which is common to all configured LTM candidate cells. The configuration is used by the UE to generate a full LTM candidate cell configuration (i.e., by applying the LTM candidate cell configuration on top of the LTM reference configuration).

[0095] Full LTM candidate cell configuration: A configuration containing all fields required to perform an LTM cell handover procedure. The configuration itself can be an LTM candidate cell configuration or generated by applying an LTM candidate cell configuration on top of an LTM reference configuration.

[0096] Further reference Figure 3 which illustrates a signaling diagram illustrating a communication procedure 300 for inter-CU condition based LTM, in accordance with some example embodiments of the present disclosure. The procedure 300 can involve a UE 250, a RAN DU (source DU) 230, a RAN CU (source CU) 210, a RAN CU (target CU) 220, and a RAN DU (target DU) 242, as shown in Figure 2 It will be understood that the procedure 300 can be applied to other communication scenarios, which will not be described in detail.

[0097] The procedure 300 can be considered as an inter-CU condition based LTM, where the target DU and the source DU belong to different CUs (i.e., different gNBs). The source CU 210 can also be referred to as a source gNB, and the target CU 220 can also be referred to as a target gNB.

[0098] In process 300, source CU 210 sends a first request message to target CU 220 at 310. In some example embodiments, the first request message can indicate a condition-based LTM and an LTM candidate cell associated with the condition-based LTM. In some examples, the LTM candidate cell associated with the condition-based LTM can be referred to as a candidate cell associated with the condition-based LTM. In some examples, the LTM candidate cell or candidate cell can be a target cell.

[0099] In some implementations, source CU 210 can determine to prepare a condition-based LTM for UE 250. In some example embodiments, source CU 210 can be an MCG gNB or an SCG gNB of UE 250. In some implementations, the first request message can be a handover request, e.g., over an Xn interface.

[0100] In some implementations, the first request message can include an indication of the condition-based LTM, which can also be referred to as a conditional LTM in some examples. In some implementations, the first request message can also include an indication of the LTM candidate cell, e.g., the condition-based LTM is to be applied to the LTM candidate cell.

[0101] In some implementations, the first request message can also indicate whether at least one subsequent LTM is supported by the condition-based LTM. In some examples, the first request message can include information of the subsequent LTM(s), e.g., the message can indicate that the prepared LTM should support (or be applied to) the subsequent LTM(s).

[0102] In process 300, target CU 220 sends a second request message to target DU 242 at 320. In some example embodiments, the second request message can indicate the condition-based LTM and the LTM candidate cell.

[0103] In some implementations, upon receiving the first request message from source CU 210, target CU 220 can send the second request message to target DU 242. In some example embodiments, the second request message can be a UE context setup request, e.g., over an Fl interface.

[0104] In some implementations, the second request message can include an indication of the condition-based LTM. In some implementations, the second request message can also include an indication of the LTM candidate cell, e.g., the condition-based LTM is to be applied to the LTM candidate cell.

[0105] In some example embodiments, the indication of the condition-based LTM can be of an enumerated type, e.g., an enumerated value can indicate one of: a condition LTM start, a condition LTM replace, or a condition LTM cancel.

[0106] For example, if the indication of the condition-based LTM is set to a condition LTM start, the target DU 242 receiving the second request message should consider the request to be related to a condition LTM for the MCG or SCG associated with the candidate cell.

[0107] For example, if the indication of the condition-based LTM is set to a condition LTM replace, the target DU 242 receiving the second request message should replace an existing prepared condition LTM identified by the UE ID (e.g., gNB-DU UE F1 Application Protocol (F1AP) ID) and the candidate cell ID.

[0108] For example, if the indication of the condition-based LTM is set to a condition LTM cancel, the target DU 242 receiving the second request message should consider that the RAN CU 220 is about to remove any reference to the candidate cell associated with the UE and release any resources previously reserved for the candidate cell associated with the UE.

[0109] In some implementations, the second request message can also indicate an estimated probability for reaching the LTM candidate cell related to the condition-based LTM. In some example embodiments, an information element (IE) “estimated reach probability” can be included in the second request message, e.g., which can be a probability value for the LTM candidate cell.

[0110] Alternatively, the second request message can also include information indicating whether the estimated probability (the probability value in the “estimated reach probability” IE) can be applied to the subsequent LTM(s). For example, the second request message can also include information indicating that the estimated probability is not applied to the subsequent LTM, in other words, the estimated probability is only applied to the initial LTM.

[0111] In the process 300, the target DU 242 sends a second response message to the target CU 220 at 330. In some example embodiments, the second response message is a response to the second request message.

[0112] In some implementations, upon receiving the second request message from the target CU 220, the target DU 242 can determine to accept the request for the condition-based LTM related to the LTM candidate cell; and the target DU 242 can also respond with the second response message.

[0113] In some implementations, the second response message can include a second configuration associated with the LTM candidate cell. In some examples, the second configuration is to be used by the UE 250 to access the LTM candidate cell (i.e., the LTM target cell). In some examples, the second configuration can also be referred to as an RRC configuration for the LTM candidate cell (i.e., the LTM target cell).

[0114] In the process 300, the target CU 220 sends, at 340, a first response message to the source CU 210. In some example embodiments, the first response message can include a first configuration for the LTM candidate cell.

[0115] In some implementations, the first configuration can include a second configuration determined by the target DU 242 and another configuration determined by the target CU 220.

[0116] In the process 300, the source CU 210 sends, at 350, the first configuration and one or more corresponding conditions for triggering the LTM to the UE 250. In some examples, a configuration message can be sent to the UE 250, e.g., over a Uu interface, where the configuration message indicates the first configuration and the one or more corresponding conditions.

[0117] In some example embodiments, the one or more corresponding conditions can include a condition for the LTM candidate cell based on layer 3 (L3) measurements, and / or one or more conditions for the LTM candidate cell based on layer 1 (L1) measurements.

[0118] In some examples, the source CU 210 can determine (or generate) a condition for the LTM candidate cell based on L3 measurements, e.g., an L3 measurement based condition or an L3 condition. For example, the condition for the LTM candidate cell based on L3 measurements can be similar to condition A3, A4, or A5 for conditional handover (CHO).

[0119] In some examples, the source CU 210 can send (not shown in FIG. 3) a message for requesting the source DU 230 to determine at least one condition for the LTM candidate cell based on L1 measurements. In some examples, the source DU 230 can determine (or generate) at least one condition for the LTM candidate cell based on L1 measurements, e.g., L1 measurement based condition(s). In some examples, the source DU 230 can send the at least one condition for the LTM candidate cell based on L1 measurements to the source CU 210. For example, the at least one condition for the LTM candidate cell based on L1 measurements can be similar to condition A4 (similar A4) for CHO. Figure 3

[0120] ​In the procedure 300, the UE 250 starts condition evaluation at 360. In some example embodiments, the UE 250 can start evaluating the one or more corresponding conditions after receiving the information of the one or more corresponding conditions from the source CU 210.

[0121] Additionally or alternatively, the UE 250 can perform early TA acquisition at 370. In some example embodiments, the UE 250 can acquire (obtain) the early TA based on the PDCCH order or according to the UE-based TA measurement. In some examples, if the UE 250 performs the early TA acquisition (obtains the early TA) based on the PDCCH order, the UE 250 can send a preamble to the LTM candidate cell. In some examples, after the source DU 230 (or the source CU 210) acquires the TA value, the source DU 230 (or the source CU 210) sends the early TA to the UE 250.

[0122] In the procedure 300, the UE 250 performs the condition-based LTM at 380, e.g., when the condition for the LTM candidate cell is met. In some examples, the UE 250 can switch to the LTM candidate cell (e.g., the LTM target cell provided by the target DU 242).

[0123] In some implementations, if the L3 measurement based condition is met, the RRC layer of the UE 250 can directly perform the condition-based LTM (by applying the first configuration), e.g., as soon as it is determined that the L3 measurement based condition is met.

[0124] In some implementations, if the L1 measurement based condition is met, the L1 layer (i.e., the PHY layer) of the UE 250 can notify the RRC layer that the L1 measurement based condition is met; and the RRC layer of the UE 250 can thus perform the condition-based LTM (by applying the first configuration).

[0125] Additionally or alternatively, the UE 250 can also send information to the source CU 210 via the source DU 230 indicating one of: the condition is met, or the beam selected for the LTM candidate cell. In some example embodiments, the information indicating that the condition is met can be sent by the UE 250 if one of the one or more corresponding conditions is met. In some examples, the UE 250 indicates this information to the source cell as soon as the condition is met within a TTT (timer for triggering) or the entry condition of the LTM execution condition is met.

[0126] In some examples, there can be multiple candidate cells, each of which meets the condition. In this case, the candidate cell with the valid early TA can be determined as the target cell.

[0127] In some implementations, as mentioned above, the first request message can indicate at least one subsequent LTM supported by the condition-based LTM. In some examples, if the condition-based LTM can support the subsequent LTM(s), the UE 250 needs to continue to hold the condition. In some examples, if condition A4 is used, the UE 250 can continue to evaluate another candidate cell. In some examples, if condition A3 / A5 is used, the UE 250 can continue (or stop) to evaluate its source serving cell. In some examples, condition A3 / A5 can be associated with a specific source cell (e.g., cell #0). For example, if the UE 250 is served by cell #0, the UE 250 starts to evaluate condition A3 related to the source cell #0; however, if the UE 250 is served by cell #1, the UE 250 will not evaluate condition A3 related to the source cell #0.

[0128] According to some example embodiments, when the condition for triggering the LTM is satisfied, the condition-based LTM can be performed by the UE. In some other examples, the UE 250 can receive an LTM cell switch command (e.g., a MAC CE) from the source CU 210 or the source DU 230 before operation 380. For example, none of the conditions is satisfied, but a MAC CE for a switch command is received. In some examples, the UE 250 can perform a cell switch to a candidate cell based on the switch command. In this case, the first configuration can be used, and one or more corresponding conditions can be ignored by the UE 250. Figure 3

[0129] In some examples, the satisfaction of the condition or the reception of the MAC CE can trigger the LTM.

[0130] In some other example embodiments, a candidate cell for the condition-based LTM can be cancelled, e.g., before operation 380. In some examples, the target CU 220 can determine to cancel the candidate cell, e.g., the target CU 220 can send a first cancellation indication to the source CU 210, where the first cancellation indication can indicate that the candidate cell has been cancelled, e.g., resources reserved for the UE 250 can be released by the target DU 242. For example, the first cancellation indication can be a conditional switch cancellation, e.g., over an Xn interface.

[0131] In some other examples, the source CU 210 can determine to cancel the candidate cell, e.g., the source CU 210 can send a second cancellation indication to the target CU 220, where the second cancellation indication can indicate that the candidate cell has been cancelled by the source CU 210. For example, the target CU 220 can forward the second cancellation indication to the target DU 242, and the target DU 242 can release resources reserved for the UE 250. ​

[0132] In some examples, the source CU 210 can inform the source DU 230 of the cancellation of the candidate cell.

[0133] According to reference Figure 3 Some embodiments discussed, enhancements for Uu interface, F1 interface and Xn interface are proposed for condition-based LTM. In addition, both L1 and L3 conditions can be considered for condition-based LTM.

[0134] Further reference Figure 4 which illustrates a signaling diagram illustrating a communication procedure 400 for LTM based on intra-CU conditions according to some example embodiments of the present disclosure. The procedure 400 can involve a UE 250, a RAN DU (source DU) 230, a RAN CU 210, and a RAN DU (target DU) 241, as shown in Figure 2 It will be appreciated that the procedure 400 can be applied to other communication scenarios, which will not be described in detail.

[0135] The procedure 400 can be considered as LTM based on intra-CU conditions, where the target DU and the source DU belong to the same CU (i.e., the same gNB).

[0136] In the procedure 400, the RAN CU 210 sends a second request message to the target DU 241 at 420. In some example embodiments, the second request message can be a UE context setup request, e.g., over the F1 interface.

[0137] In some implementations, the RAN CU 210 can determine to prepare a condition-based LTM for the UE 250. In some implementations, details of the second request message can refer to what discussed in connection with 320 in Figure 3

[0138] In the procedure 400, the target DU 241 sends a second response message to the RAN CU 210 at 430. In some implementations, the second response message can include a second configuration associated with the LTM candidate cell. In some implementations, details of the second response message can refer to what discussed in connection with 330 in Figure 3

[0139] In the procedure 400, the RAN CN 210 sends the first configuration and one or more corresponding conditions for triggering the LTM to the UE 250 at 450. In some implementations, the first configuration can include the second configuration determined by the target DU 241 and another configuration determined by the RAN CU 210.

[0140] ​​In some examples, a configuration message can be sent to the UE 250, e.g., over the Uu interface, where the configuration message indicates the first configuration and one or more corresponding conditions. In some implementations, details of the one or more conditions can refer to what is discussed in connection with 350 in Figure 3

[0141] In the process 400, the UE 250 starts condition evaluation at 460. In addition or alternatively, the UE 250 can also perform early TA acquisition at 470. And the UE 250 performs condition-based LTM at 380. In some implementations, details of operations 460-480 can refer to operations 360-380 discussed above in connection with Figure 3

[0142] According to some embodiments discussed in reference to Figure 4 In current intra-CU LTM, the source DU can share preamble resources among multiple UEs, e.g., the PDCCH order for intra-CU LTM can include information identifying the allocated contention-free random access (CFRA) resources, such as synchronization signal (SS) index, physical broadcast channel (PBCH) index, random access channel (RACH) occasion, and random access preamble index. RAN3 assumes that the CFRA resources can only be shared among UEs in a single gNB-DU to avoid RACH access collisions between UEs from different DUs. However, when LTM is extended to inter-CU LTM, there seems to be no need to keep the RACH resources at the granularity of the source DU.

[0143]

[0144] Further reference is made to Figure 5 which illustrates a signaling diagram illustrating a communication process 500 for determining RACH resources for early TA acquisition for inter-CU LTM, according to some example embodiments of the present disclosure. The process 500 can involve the UE 250, the RAN DU (source DU) 230, the RAN CU (source CU) 210, the RAN CU (target CU) 220, and the RAN DU (target DU) 242, as shown in Figure 2 It will be appreciated that the process 500 can be applied to other communication scenarios, which will not be described in detail.

[0145] The process 500 can be considered as inter-CU LTM, where the target DU 242 and the source DU 230 belong to different CUs (i.e., different gNBs).

[0146] ​​​In process 500, UE 250 sends a measurement report to source CU 210 at 510. In some example embodiments, UE 250 can be accessing a serving gNB that includes source CU 210 and source DU 230. In some example embodiments, UE 250 can send the measurement report to the serving gNB.

[0147] In some implementations, dual connectivity (DC) can be configured for UE 250, e.g., both a MCG and a SCG are configured for UE 250.

[0148] In process 500, source CU 210 sends a first request message to target CU 220 at 520. In some implementations, source CU 210 can determine to prepare an LTM configuration for UE 250, e.g., initiate an LTM. In some example embodiments, source CU 210 can be a MCG gNB or a SCG gNB for UE 250. In some implementations, the first request message can be a handover request, e.g., over an Xn interface. In some implementations, the first request message can indicate a candidate cell.

[0149] In some implementations, the first request message can include a request for RACH resources for early TA acquisition. In some example embodiments, the first request message can request RACH resources for source CU 210, e.g., can include an index or ID of source CU 210. In some other example embodiments, the first request message can request RACH resources for source DU 230, e.g., can include an index or ID of source DU 230.

[0150] In process 500, target CU 220 sends a second request message to target DU 242 at 530. In some example embodiments, the second request message can

[0151] In some implementations, upon receiving the first request message from source CU 210, target CU 220 can send the second request message to target DU 242. In some example embodiments, the second request message can be a UE context setup request, e.g., over an Fl interface.

[0152] In some implementations, the second request message can indicate a candidate cell.

[0153] In some implementations, the second request message can include a request for RACH resources for early TA acquisition. In some example embodiments, the second request message can include an index or ID of the source CU 210, and the second request message can request RACH resources for the source CU 210. In some other example embodiments, if the first request message includes an index or ID of the source DU 230, the second request message can include an index or ID of the source DU 230, and the second request message can request RACH resources for the source DU 230.

[0154] For example, the second request message can include a request indication for RACH resources for early TA acquisition and a corresponding index / ID of the source CU 210 or the source DU 230.

[0155] In the process 500, the target DU 242 sends a second response message to the target CU 220 at 540. In some example embodiments, the second response message can include a second configuration associated with the candidate cell. In some example embodiments, the second response message can indicate a RACH source for early TA acquisition as requested by the second request message. In some examples, the second configuration can also be referred to as an RRC configuration of the candidate cell (i.e., the LTM target cell).

[0156] In some implementations, upon receiving the second request message from the target CU 220, the target DU 242 can determine to accept the request for LTM related to the candidate cell; and the target DU 242 can also respond with the second response message, e.g., over the Fl interface. In some implementations, the second response message can include one of the following: RACH resources for early TA acquisition, an indication that a TA value is equal to 0, or an indication that a TA value of the candidate cell is equal to that of the source cell.

[0157] In some implementations, the target DU 242 can determine RACH resources per CU (per gNB) or per DU.

[0158] In some example embodiments, if the second request message includes a request indication for RACH resources for early TA acquisition and a corresponding index / ID of the source CU 210, the target DU 242 can determine RACH resources for early TA acquisition associated with the source CU 210. For example, the target DU 242 can allocate different RACH resources for different CUs (or gNBs).

[0159] In some other example embodiments, if the second request message includes a request indication for RACH resources for early TA acquisition and a corresponding index / ID of the source DU 230, the target DU 242 can determine the RACH resources for early TA acquisition associated with the source DU 230.

[0160] In the process 500, the target CU 220 sends a first response message to the source CU 210 at 550. In some implementations, the first response message can be a handover request acknowledge, e.g., over an Xn interface.

[0161] In some implementations, the first response message can include a first configuration, which can include the second configuration determined by the target DU 242 and another configuration determined by the target CU 220.

[0162] In some implementations, the first response message can include the RACH resources as indicated in the second resource message. In some example embodiments, the first response message can include the RACH resources for early TA acquisition associated with the source CU 210. In some other example embodiments, the first response message can include the RACH resources for early TA acquisition associated with the source DU 230.

[0163] In the process 500, the source CU 210 sends the configurations to the source DU 230 and the UE 250, respectively, at 560.

[0164] In some example embodiments, the first response message can include the RACH resources for early TA acquisition associated with the source CU 210.

[0165] In some examples, the source CU 210 can select some of the RACH resources for early TA acquisition. In some examples, the source CU 210 can send a configuration message to the source DU 230 including some of the RACH resources for early TA acquisition. For example, there can be more than one DU served by the source CU 210. And the source CU 210 will select different RACH resources for different DUs, thus different UEs served by different DUs will perform early TA acquisition via different RACH resources.

[0166] In some examples, when selecting some of the RACH resources for the target DU 230, the number of UEs performing early TA acquisition can also be considered. For example, referring to Figure 2, there are DUs 230 and 241 served by the source CU 210, the source CU 210 can select a first portion of RACH resources for the DU 230 and a second portion of RACH resources for the DU 241 based on the number of UEs performing early TA acquisition.

[0167] In some other example embodiments, the first response message can include RACH resources associated with the source DU 230 for early TA acquisition.

[0168] In some examples, the source CU 210 can send a configuration message including RACH resources for early TA acquisition to the source DU 230.

[0169] In some implementations, the source CU 210 can generate and send an RRC configuration message to the UE 250. For example, the RRC configuration message can be generated based on the first configuration in the first response message. For example, the RRC configuration message can be sent to the UE 250 by the source DU 230. In some examples, the RRC configuration message can include configurations for LTM associated with the candidate cells. In some examples, the RRC configuration message can include some of the RACH resources for early TA acquisition selected by the source CU 210 or include the RACH resources for early TA acquisition.

[0170] Thus, the UE 250 receives the RRC configuration message for LTM configuration associated with one or more candidate cells.

[0171] In the process 500, the source DU 230 sends a PDCCH order to the UE 250 at 570 for triggering TA acquisition related to a particular candidate cell. In some examples, the UE 250 can send a preamble for TA acquisition to the candidate cell (target DU 242) upon receiving the PDCCH order, for example, the preamble can be sent to the target DU 242 via the source DU 230, the source CU 210 and the target CU 220.

[0172] In some examples, if the candidate cell (target DU 242) can calculate TA based on the received preamble, the candidate cell (target DU 242) can send the preamble along with corresponding RACH occasion, beam indication, UE ID, RA-RNTI, target cell ID, TCI state index for the target cell, etc. In some examples, the preamble along with the corresponding information (RACH occasion, beam indication, UE ID, RA-RNTI, target cell ID, TCI state index for the target cell, etc.) can be sent from the target DU 242 to the target CU 220, which can then be forwarded to the source CU 210 and further to the source DU 230. In some examples, the source DU 230 receives the early TA value from the source CU 210.

[0173] In the process 500, the source DU 230 sends an LTM switch command to the UE 250 at 580. In some implementations, the LTM switch command can be used to trigger a cell switch related to the candidate cell. In some implementations, the LTM switch command can be implemented as a MAC CE.

[0174] Additionally or alternatively, the source DU 230 can also send information associated with the triggered LTM to the source CU 210. In some examples, once the source DU 230 triggers (or decides to trigger) the LTM, the source DU 230 needs to indicate this information to the source CU 210. In some examples, the information can include at least one of the following: cell ID (e.g., NR Cell Global Identifier (NCGI), Physical Cell Identifier (PCI)), selected beam (e.g., Transmission Configuration Indicator (TCI) state), indication of RACH-less based LTM or RACH based LTM. Once the source CU 210 receives the information from the source DU, the source CU 210 communicates the information to the target CU 220, which can also communicate the information to the target DU 242.

[0175] In the process 500, the UE 250 performs the LTM based on the LTM switch command at 590. In some example embodiments, upon receiving the LTM switch command, the UE 250 performs an LTM cell switch towards the candidate cell indicated by the LTM switch command.

[0176] In some examples, the UE 250 performs an LTM cell switch in response to receiving the LTM switch command. In some examples, the target DU 242 can receive information from the target CU 220, and the target DU 242 can transmit a PDCCH addressed by a cell radio network temporary identifier (C-RNTI) or monitor a configured CG (configured grant). Thus, the UE 250 can successfully access the target cell of the target DU 242.

[0177] According to reference Figure 5 Some embodiments discussed, the RACH resources for early TA acquisition can be allocated by the target DU at the granularity of the CU or DU, thus, the RACH resources can be used more efficiently and collisions can be avoided.

[0178] It should be appreciated that some additional example embodiments can also be obtained by combining some embodiments discussed above, in some examples, the procedure 300 and the procedure 500 can be combined, for example, the RACH resources for early TA acquisition can be determined for each DU or each CU based conditional LTM.

[0179] Figure 6 An example of an apparatus 600 suitable for implementing embodiments of the disclosure is illustrated. The apparatus 600 can be an example of a RAN node as described herein. The apparatus 600 can support wireless communication with a RAN CU 210, a RAN CU 220, a RAN DU 230, a RAN DU 241, a RAN DU 242, a UE 250, or any combination thereof. The apparatus 600 can include components for bi-directional communication including components for transmitting and receiving communications, such as a processor 602, a memory 604, a transceiver 606, and an optional I / O controller 608. These components can be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses). The processor 602, the memory 604, the transceiver 606, or various combinations thereof or various components thereof, can be an example of

[0180] The processor 602, the memory 604, the transceiver 606, or various combinations thereof or various components thereof, can be an example of means for performing various aspects of the disclosure as described herein. For example, the processor 602, the memory 604, the transceiver 606, or various combinations or components thereof, can support a method for performing one or more of the operations described herein.

[0181] In some embodiments, the processor 602, the memory 604, the transceiver 606, or various combinations or components thereof can be implemented in hardware (e.g., within communication management circuitry). This hardware can include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic, discrete hardware components, or any combination thereof, which are configured to or otherwise support a means for performing the functions described in the present disclosure. In some implementations, the processor 602 and the memory 604 coupled with the processor 602 can be configured to perform one or more of the functions described herein (e.g., the processor 602 executing instructions stored in the memory 604).

[0182] For example, the processor 602 can support wireless communications at the device 600 in accordance with examples as disclosed herein. The processor 602 can be configured to be operable to support means for the operations discussed above.

[0183] The processor 602 can include an intelligent hardware device, (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some implementations, the processor 602 can be configured to operate a memory array using a memory controller. In some other implementations, a memory controller can be integrated into the processor 602. The processor 602 can be configured to execute computer-readable instructions stored in a memory (e.g., the memory 604) to cause the device 600 to perform various functions of the present disclosure.

[0184] The memory 604 can include random access memory (RAM) and read-only memory (ROM). The memory 604 can store computer-readable, computer-executable code including instructions that, when executed by the processor 602, cause the device 600 to perform various functions described herein. The code can be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some implementations, the code can not be directly executable by the processor 602 but can cause a computer (e.g., when compiled and executed) to perform functions described herein. In some implementations, the memory 604 can include, among other things, a basic I / O system (BIOS), which can control basic hardware or software operation such as the interaction with peripheral components or devices.

[0185] The I / O controller 608 can manage input and output signals for the device 600. The I / O controller 608 can also manage peripherals not integrated into the device 600. In some implementations, the I / O controller 608 can represent a physical connection or port to the external peripherals. In some implementations, the I / O controller 608 can utilize an operating system such as iOS®, ANDROID®, MS-WINDOWS®, OS / 2®, UNIX®,

[0186] In some implementations, the device 600 can include a single antenna 610. However, in some other implementations the device 600 can have more than one antenna 610, i.e., multiple antennas, including multiple antenna panels or antenna arrays, which can transmit or receive multiple wireless transmissions simultaneously. The transceiver 606 can be configured to communicate bi-directionally with another wireless transceiver via the one or more antennas 610, wired, or wireless links as described herein. For example, the transceiver 606 can represent a wireless transceiver and can communicate bi-directionally with another wireless transceiver. The transceiver 606 can also include a modem to modulate the packets and to provide the modulated packets to the one or more antennas 610 for transmission, and to demodulate packets received from the one or more antennas 610. The transceiver 606 can include one or more transmitters, one or more receivers, or a combination thereof.

[0187] The transmit chain can be configured to generate and transmit signals (e.g., control information, data, packets). The transmit chain can include at least one modulator to modulate data onto a carrier signal, to prepare the signal for transmission over a wireless medium. The at least one modulator can be configured to support one or more techniques, such as amplitude modulation (AM), frequency modulation (FM), or a digital modulation scheme, like phase-shift keying (PSK) or quadrature amplitude modulation (QAM). The transmit chain can also include at least one power amplifier configured to amplify the modulated signal to an appropriate level of power suitable for transmission over a wireless medium. The transmit chain can also include one or more antennas 610 to send the amplified signal into the air or wireless medium.

[0188] The receiver chain can be configured to receive signals (e.g., control information, data, packets) via a wireless medium. For example, the receiver chain may include one or more antennas 610 for receiving signals over the air or via a wireless medium. The receiver chain may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. The receiver chain may include at least one demodulator configured to demodulate the received signal and obtain the transmitted data by reversing the modulation technique applied during signal transmission. The receiver chain may include at least one decoder for decoding and processing the demodulated signal to receive the transmitted data.

[0189] Figure 7 An example of a processor 700 suitable for implementing some embodiments of the present disclosure is illustrated. The processor 700 may be an example of a processor configured to perform various operations according to the examples described herein. The processor 700 may include a controller 702 configured to perform various operations according to the examples described herein. The processor 700 may optionally include at least one memory 704, such as an L1 / L2 / L3 cache. Additionally, or alternatively, the processor 700 may optionally include one or more arithmetic logic units (ALUs) 706. One or more of these components may be electronically communicated or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses).

[0190] Processor 700 may be a processor chipset and includes a protocol stack (e.g., a software stack) executed by the processor chipset to perform various operations (e.g., receive, acquire, retrieve, send, output, forward, store, determine, identify, access, write, read) according to examples as described herein. The processor chipset may include one or more cores, one or more caches (e.g., memory native to or included in the processor chipset (e.g., processor 700)) or other memory (e.g., random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), static RAM (SRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phase-change memory (PCM), and others).

[0191] The controller 702 can be configured to manage and coordinate the various operations (e.g., signaling, receiving, obtaining, retrieving, sending, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) of the processor 700 such that the processor 700 supports the various operations in accordance with examples as described herein. For example, the controller 702 can operate as a control unit of the processor 700, generating control signals that manage the operation of the individual components of the processor 700. These control signals include enabling or disabling functional units, selecting data paths, initiating memory accesses, and coordinating the timing of operations.

[0192] The controller 702 can be configured to fetch (e.g., obtain, retrieve, receive) instructions from the memory 704 and determine subsequent instruction(s) to execute such that the processor 700 supports the various operations in accordance with examples as described herein. The controller 702 can be configured to track memory addresses of instructions associated with the memory 704. The controller 702 can be configured to decode instructions to determine operations to perform and operands involved. For example, the controller 702 can be configured to interpret instructions and determine control signals to output to other components of the processor 700 such that the processor 700 supports the various operations in accordance with examples as described herein. Additionally, or alternatively, the controller 702 can be configured to manage the flow of data within the processor 700. The controller 702 can be configured to control the transfer of data between registers, arithmetic logic units (ALUs), and other functional units of the processor 700.

[0193] The memory 704 can include one or more caches (e.g., memory local to or included in the processor 700) or other memory, such as RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash, etc. In some implementations, the memory 704 can reside within or on a processor chipset (e.g., local to the processor 700). In some other implementations, the memory 704 can reside outside of the processor chipset (e.g., remote from the processor 700).

[0194] Memory 704 can store computer-readable, computer-executable code including instructions that, when executed by processor 700, cause processor 700 to perform various functions described herein. The code can be stored in a non-transitory computer-readable medium such as system memory or another type of memory. Controller 702 and / or processor 700 can be configured to execute the computer-readable instructions stored in memory 704 to cause processor 700 to perform the various functionalities described herein. For example, processor 700 and / or controller 702 can be coupled with or to memory 704, and processor 700, controller 702, and memory 704 can be configured to perform the various functionalities described herein. In some examples, processor 700 can include multiple processors, and memory 704 can include multiple memories. One or more of the multiple processors can be coupled with one or more of the multiple memories, which can be configured, individually or collectively, to perform the various functionalities described herein.

[0195] One or more ALUs 706 can be configured to support various operations in accordance with examples as described herein. In some implementations, the one or more ALUs 706 can reside within or on a processor chipset (e.g., processor 700). In some other implementations, the one or more ALUs 706 can reside outside of a processor chipset (e.g., processor 700). The one or more ALUs 706 can perform one or more computations on data, such as addition, subtraction, multiplication, and division. For example, the one or more ALUs 706 can receive input operands and an opcode, which determines the operation to be performed. The one or more ALUs 706 can be configured with various logic and arithmetic circuits, including adders, subtractors, shifters, and logic gates, to process and manipulate data according to the operation. In addition, or alternatively, the one or more ALUs 706 can support logical operations such as AND, OR, exclusive OR (XOR), not OR (NOR), and not AND (NAND), thereby enabling the one or more ALUs 706 to handle conditional operations, comparisons, and bitwise operations.

[0196] Processor 700 can support wireless communications in accordance with examples as disclosed herein. Processor 700 can be configured to or operable for supporting components for operations described in some embodiments of the present disclosure.

[0197] Figure 8 A flow diagram illustrating a method 800 performed by a RAN CU, in accordance with aspects of the present disclosure is shown. The operations of method 800 can be implemented by a device or its components as described herein. For example, the operations of method 800 can be performed by a RAN CU as described with reference to FIGs. 1 through 7. Figure 2by the RAN CU 210 as described with reference to FIG. 1. In some implementations, the apparatus can execute sets of instructions to control the functional elements of the apparatus to perform the described functions. Additionally or alternatively, the apparatus can perform aspects of the described functions using special-purpose hardware.

[0198] At 810, the method can include transmitting, to the target RAN CU, a first request message indicating a condition-based LTM and LTM candidate cells, where the condition-based LTM is to be performed based on evaluation of a condition by the UE. The operations of 810 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 810 can be performed by a RAN CU 210 as described with reference to FIG. 1. Figure 2

[0199] At 820, the method can include receiving, from the target RAN CU, a first response message including a first configuration for the LTM candidate cells. The operations of 820 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 820 can be performed by a RAN CU 210 as described with reference to FIG. 1. Figure 2

[0200] Figure 9 FIGURE 13 illustrates a flow diagram of a method 1300 performed by a RAN CU, in accordance with aspects of the present disclosure. The operations of method 1300 can be implemented by a device or its components as described herein. For example, the operations of method 1300 can be performed by a RAN CU 210 as described with reference to FIG. 1. Figure 2 by the RAN CU 210 as described with reference to FIG. 1. In some implementations, the apparatus can execute sets of instructions to control the functional elements of the apparatus to perform the described functions. Additionally or alternatively, the apparatus can perform aspects of the described functions using special-purpose hardware.

[0201] At 910, the method can include transmitting, to the target RAN DU, a second request message including a condition-based LTM and an indication of LTM candidate cells associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by the UE. The operations of 910 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 910 can be performed by a RAN CU 210 as described with reference to FIG. 1. Figure 2

[0202] At 920, the method can include receiving, from the target RAN DU, a second response message including a second configuration for the LTM candidate cells. The operations of 920 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 920 can be performed by a RAN CU 210 as described with reference to FIG. 1. Figure 2 ​​​The described RAN CU 210 performs.

[0203] Figure 10 FIGURE illustrates a flow chart of a method 1000 performed by a target RAN CU, in accordance with aspects of the present disclosure. Operations of the method 1000 can be implemented by a device as described herein, or a component thereof. For example, operations of the method 1000 can be performed by a RAN CU 220 as described with reference to FIGURE Figure 2 In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware.

[0204] At 1010, the method can include receiving, from the RAN CU, a first request message indicating a condition-based LTM and LTM candidate cells associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of a condition by the UE. The operations of 1010 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1010 can be performed by a RAN CU 220 as described with reference to FIGURE Figure 2

[0205] At 1020, the method can include transmitting, to the target RAN DU, a second request message indicating the condition-based LTM and the LTM candidate cells. The operations of 1020 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1020 can be performed by a RAN CU 220 as described with reference to FIGURE Figure 2

[0206] At 1030, the method can include receiving, from the target RAN DU, a second response message including a second configuration associated with the LTM candidate cells. The operations of 1030 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1030 can be performed by a RAN CU 220 as described with reference to FIGURE Figure 2

[0207] At 1040, the method can include transmitting, to the RAN CU, a first response message including a first configuration for the LTM candidate cells, where the first configuration includes at least the second configuration. The operations of 1040 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1040 can be performed by a RAN CU 220 as described with reference to FIGURE Figure 2

[0208] Figure 11 ​​​​A flow diagram illustrating a method 1100 performed by a target RAN DU, in accordance with aspects of the present disclosure is shown. The operations of method 1100 can be implemented by a device such as described herein or its components. For example, the operations of method 1100 can be performed by a RAN DU 241 or 242 in a network environment as described with reference to FIGS. 1-2. Figure 2 In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware.

[0209] At 1110, the method can include receiving, from the RAN CU or the target RAN CU, a second request message indicating a condition-based LTM and LTM candidate cells associated with the condition-based LTM, where the condition-based LTM is to be performed based on evaluation of the condition by the UE. The operations of 1110 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1110 can be performed by a RAN DU 241 or 242 as described with reference to FIGS. 1-2. Figure 2 In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware.

[0210] At 1120, the method can include transmitting, to the RAN CU or the target RAN CU, a second response message including a second configuration associated with the LTM candidate cells. The operations of 1120 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1120 can be performed by a RAN DU 241 or 242 as described with reference to FIGS. 1-2. Figure 2 In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware.

[0211] Figure 12 A flow diagram illustrating a method 1200 performed by a RAN DU, in accordance with aspects of the present disclosure is shown. The operations of method 1200 can be implemented by a device such as described herein or its components. For example, the operations of method 1200 can be performed by a RAN DU 230 in a network environment as described with reference to FIGS. 1-2. Figure 2 In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware.

[0212] At 1210, the method can include receiving, from the RAN CU, a message for requesting the RAN DU to determine at least one condition for a layer 1 measurement based LTM candidate cell, where the at least one condition for the layer 1 measurement based LTM candidate cell is used for a condition-based LTM, where the condition-based LTM is to be performed based on evaluation of the condition by the UE. The operations of 1210 can be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1210 can be performed by a RAN DU 241 or 242 as described with reference to FIGS. 1-2. Figure 2The described RAN DU 230 performs.

[0213] At 1220, the method can include determining, based on the message, at least one condition for the LTM candidate cell based on the layer 1 measurement. The operations of 1220 can be performed according to the examples as described herein. In some implementations, aspects of the operations of 1220 can be performed by a RAN DU 230 as described with reference to Figure 2 The described RAN DU 230 performs.

[0214] At 1230, the method can include transmitting, to the RAN CU, the at least one condition for the LTM candidate cell based on the layer 1 measurement. The operations of 1230 can be performed according to the examples as described herein. In some implementations, aspects of the operations of 1230 can be performed by a RAN DU 230 as described with reference to Figure 2 The described RAN DU 230 performs.

[0215] Figure 13 A flow diagram illustrating a method 1300 performed by a UE, in accordance with aspects of the present disclosure, is shown. The operations of method 1300 can be implemented by a device or its components as described herein. For example, the operations of method 1300 can be performed by UE 250 in FIG. 12A. In some implementations, the device can execute a set of instructions to control the functional elements of the device to perform the described functions. Additionally or alternatively, the device can perform aspects of the described functions using special-purpose hardware. Figure 2 The described RAN DU 230 performs.

[0216] At 1310, the method can include receiving, from the RAN CU, a first configuration for the LTM candidate cell associated with the condition-based LTM and one or more corresponding conditions for triggering the LTM. The operations of 1310 can be performed according to the examples as described herein. In some implementations, aspects of the operations of 1310 can be performed by a UE 250 as described with reference to Figure 2 The described RAN DU 230 performs.

[0217] At 1320, the method can include performing a handover to the LTM candidate cell in accordance with a determination that one of the one or more corresponding conditions is satisfied. The operations of 1320 can be performed according to the examples as described herein. In some implementations, aspects of the operations of 1320 can be performed by a UE 250 as described with reference to Figure 2 The described RAN DU 230 performs.

[0218] It should be noted that the methods described herein describe possible implementations, and that the operations and the steps can be rearranged or otherwise modified and that other implementations can be possible. Further, aspects from two or more of the methods can be combined.

[0219] The various illustrative blocks and components described in connection with the disclosure herein can be implemented or performed with a general-purpose processor, a DSP, an ASIC, a CPU, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0220] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions can also be physically located at various positions, including being distributed such that portions of functions are implemented at different locations.

[0221] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, non-transitory computer-readable media can include RAM, ROM, electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

[0222] As used herein, including in the claims, the article "a" is not limited to one and is understood to mean "at least one" or "one or more." The terms "a," "at least one," "one or more," and "at least one of one or more" are used interchangeably. As used herein, including in the claims, "or" as used in a list of items (for example, a list of items prefaced by a phrase such as "at least one of" or "one or more of") indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as "based on condition A" can be based on both a condition A and a condition B, and need not be limited to only be based on a condition A without a condition B. In other words, as used herein the phrase "based on" shall be construed in the same manner as the phrase "based at least in part on." Moreover, as used herein, including in the claims, "set" can include one or more elements.

[0223] The description herein is to be construed in a manner consistent with the definition of what is meant by terms in art. Various patents and publications are cited herein in order to more fully describe the state of the art to which this disclosure pertains. The interposition of a summary of the prior art is not to be construed as an admission that the art described is prior art to the present disclosure. The citation of documents is not to be construed as an admission that it is prior art to the present disclosure. The citation of a patent or publication does not constitute an admission that the patent or publication is a prior art to the present disclosure. The description herein is to be construed in a manner consistent with the definition of what is meant by terms in art. Various patents and publications are cited herein in order to more fully describe the state of the art to which this disclosure pertains. The interposition of a summary of the prior art is not to be construed as an admission that the art described is prior art to the present disclosure. The citation of documents is not to be construed as an admission that it is prior art to the present disclosure. The citation of a patent or publication does not constitute an admission that the patent or publication is a prior art to the present disclosure.

Claims

1. A radio access network (RAN) central unit (CU), comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the RAN CU to: send, to a target RAN CU, a first request message indicating a condition-based layer 1 or layer 2 triggered mobility (LTM) and an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a user equipment (UE); and receive, from the target RAN CU, a first response message including a first configuration for the LTM candidate cell.

2. The RAN CU of claim 1, wherein the first request message further indicates whether at least one subsequent LTM is supported by the condition-based LTM.

3. The RAN CU of claim 1, wherein the at least one processor is further configured to cause the RAN CU to: send, to the UE, the first configuration for the LTM candidate cell and one or more corresponding conditions for triggering LTM.

4. The RAN CU of claim 3, wherein the at least one processor is further configured to cause the RAN CU to: generate a condition for the LTM candidate cell based on layer 3 measurements, wherein the one or more corresponding conditions include: the condition for the LTM candidate cell based on layer 3 measurements.

5. The RAN CU of claim 3, wherein the at least one processor is further configured to cause the RAN CU to: send, to a RAN distributed unit (DU), a message for requesting the RAN DU to determine at least one condition for the LTM candidate cell based on layer 1 measurements; and receive, from the RAN DU, the at least one condition, wherein the one or more corresponding conditions include: the at least one condition for the LTM candidate cell based on layer 1 measurements.

6. The RAN CU of claim 3, wherein the at least one processor is further configured to cause the RAN CU to: receive, from the UE via a RAN DU, information indicating one of: a condition is satisfied, or a beam selected for the LTM candidate cell.

7. The RAN CU of claim 1, wherein the at least one processor is further configured to cause the RAN CU to: receive, from the target RAN CU, a first cancellation indication indicating that the LTM candidate cell configured for the condition-based LTM is cancelled.

8. The RAN CU of claim 1, wherein the at least one processor is further configured to cause the RAN CU to: determine to cancel the LTM candidate cell configured for the condition-based LTM; and send, to the target RAN CU, a second cancellation indication indicating that the LTM candidate cell configured for the condition-based LTM is cancelled.

9. The RAN CU of claim 1, wherein the first response message further indicates random access channel (RACH) resources for early timing advance (TA) acquisition, and wherein the at least one processor is further configured to cause the RAN CU to: select some of the RACH resources for the early TA acquisition for the RAN DU; and send, to the RAN DU, configuration information indicating the some of the RACH resources for the early TA acquisition.

10. The RAN CU of claim 1, wherein the first request message further includes information of a RAN DU, and the first request message further requests: RACH resources for early TA acquisition associated with the RAN DU.

11. A radio access network (RAN) central unit (CU), comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the RAN CU to: send, to a target RAN distributed unit (DU), a second request message including: a condition-based layer 1 or layer 2 triggered mobility (LTM) and an indication of an LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a user equipment (UE); and receive, from the target RAN DU, a second response message including a second configuration for the LTM candidate cell.

12. The RAN CU of claim 11, wherein the second request message further indicates whether at least one subsequent LTM is supported by the condition-based LTM.

13. The RAN CU of claim 11, wherein the second request message further indicates one of: an estimated probability of reaching the LTM candidate cell associated with the condition-based LTM, or whether the estimated probability is applied to at least one subsequent LTM.

14. The RAN CU of claim 11, wherein the at least one processor is further configured to cause the RAN CU to: send, to the UE, a first configuration for the LTM candidate cell and one or more corresponding conditions for triggering LTM, wherein the first configuration includes at least the second configuration.

15. The RAN CU of claim 14, wherein the at least one processor is further configured to cause the RAN CU to: generate a condition for the LTM candidate cell based on layer 3 measurements, wherein the one or more corresponding conditions include: the condition for the LTM candidate cell based on layer 3 measurements.

16. The RAN CU of claim 14, wherein the at least one processor is further configured to cause the RAN CU to: sending a message to a RAN distributed unit (DU), the message requesting the RAN DU to determine at least one condition for the LTM candidate cell based on layer 1 measurements; and receiving the at least one condition from the RAN DU, wherein the one or more corresponding conditions include: the at least one condition for the LTM candidate cell based on layer 1 measurements.

17. The RAN CU of claim 14, wherein the at least one processor is further configured to cause the RAN CU to: receive, from the UE via a RAN DU, information indicating one of: a condition is satisfied, or a beam selected for the LTM candidate cell.

18. The RAN CU of claim 11, wherein the at least one processor is further configured to cause the RAN CU to: determine to cancel the LTM candidate cell configured for the condition-based LTM; and send, to the target RAN DU, a second cancellation indication indicating the LTM candidate cell configured for the condition-based LTM is cancelled.

19. A target radio access network (RAN) central unit (CU), comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the target RAN CU to: receive, from a RAN CU, a first request message indicating a condition-based layer 1 or layer 2 triggered mobility (LTM) and a LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a user equipment (UE); send, to a target RAN distributed unit (DU), a second request message indicating the condition-based LTM and the LTM candidate cell; receive, from the target RAN DU, a second response message including a second configuration associated with the LTM candidate cell; and send, to the RAN CU, a first response message including a first configuration for the LTM candidate cell, wherein the first configuration includes at least the second configuration.

20. A target radio access network (RAN) distributed unit (DU), comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the target RAN DU to: receive, from a RAN central unit (CU) or a target RAN CU, a second request message indicating a condition-based layer 1 or layer 2 triggered mobility (LTM) and a LTM candidate cell associated with the condition-based LTM, wherein the condition-based LTM is to be performed based on evaluation of a condition by a user equipment (UE); and send, to the RAN CU or the target RAN CU, a second response message including a second configuration associated with the LTM candidate cell.

Images