WO2025152129A1

WO2025152129A1 - Devices and methods for communication

Info

Publication number: WO2025152129A1
Application number: PCT/CN2024/073139
Authority: WO
Inventors: Gang Wang
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2024-01-18
Filing date: 2024-01-18
Publication date: 2025-07-24
Anticipated expiration: 2026-07-18

Abstract

Embodiments of the present disclosure provide a solution for cell configuration in a LTM procedure. In a solution, a first network device transmits, to a second network device in a radio access network, configuration request information about a LTM procedure for a cell switch from a source cell associated with the first network device in the radio access network to a target cell. The second network device is associated with a candidate cell for the cell switch.

Description

DEVICES AND METHODS FOR COMMUNICATION

FIELDS

Example embodiments of the present disclosure generally relate to the field of communication techniques and in particular, to devices and methods for cell configuration in a mobility (LTM) procedure.

BACKGROUND

A LTM procedure is a layer 1 or layer 2 triggered mobility procedure. Generally, a LTM procedure includes a network triggered LTM and/or a conditional LTM procedure. The network triggered LTM is a LTM procedure in which a next generation NodeB (gNB) receives L1 measurement report (s) from user equipment (UE) , and on their basis the gNB changes UE’s serving cell by a cell switch command signaled via a Medium Access Control (MAC) Control Element (CE) . The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through Radio Resource Control (RRC) signaling. Then the UE switches to the target cell according to the cell switch command. The conditional LTM procedure is a LTM procedure initiated when one or more LTM execution conditions are satisfied. The LTM procedure can be used to reduce the mobility latency.

SUMMARY

In a first aspect, there is provided a first network device comprising: a processor configured to cause the first network device to: transmit, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch.

In a second aspect, there is provided a second network device comprising: a processor configured to cause the second network device to: receive, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch.

In a third aspect, there is provided a terminal device comprising: a processor configured to cause the terminal device to: transmit, to a first network device in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

In a fourth aspect, there is provided a communication method performed by a first network device. The method comprises: transmitting, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch.

In a fifth aspect, there is provided a communication method performed by a second network device. The method comprises: receiving, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch.

In a sixth aspect, there is provided a communication method performed by a terminal device. The method comprises: transmitting, to a first network device in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

In a seventh aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the fourth, fifth, or sixth aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

FIG. 1A illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 1B illustrates another example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 2 illustrates a signaling flow of cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 3A illustrates a signaling flow of requesting a cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 3B illustrates another signaling flow of requesting a cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 4 illustrates a signaling flow of transmission of cancel information in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 5 illustrates another signaling flow of transmission of cancel information in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 6 illustrates a signaling flow of transmission of reference signal (RS) configuration in a LTM procedure in accordance with some embodiments of the present disclosure;

FIG. 7 illustrates a signaling flow of a LTM process in accordance with some embodiments of the present disclosure;

FIG. 8 illustrates a flowchart of a method implemented at a first network device according to some example embodiments of the present disclosure;

FIG. 9 illustrates a flowchart of a method implemented at a second network device according to some example embodiments of the present disclosure;

FIG. 10 illustrates a flowchart of a method implemented at a terminal device according to some example embodiments of the present disclosure; and

FIG. 11 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term ‘terminal device’ refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Ultra-reliable and Low Latency Communications (URLLC) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, devices on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , Space borne vehicles or Air borne vehicles in Non-terrestrial networks (NTN) including Satellites and High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) , eXtended Reality (XR) devices including different types of realities such as Augmented Reality (AR) , Mixed Reality (MR) and Virtual Reality (VR) , the unmanned aerial vehicle (UAV) commonly known as a drone which is an aircraft without any human pilot, devices on high speed train (HST) , or image capture devices such as digital cameras, sensors, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. The ‘terminal device’ can further has ‘multicast/broadcast’ feature, to support public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast delivery, IPTV, smart TV, radio services, software delivery over wireless, group communications and IoT applications. It may also incorporate one or multiple Subscriber Identity Module (SIM) as known as Multi-SIM. The term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device.

The term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNB) , a transmission reception point (TRP) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an IAB node, a low power node such as a femto node, a pico node, a reconfigurable intelligent surface (RIS) , and the like.

The terminal device or the network device may have Artificial intelligence (AI) or Machine learning capability. It generally includes a model which has been trained from numerous collected data for a specific function, and can be used to predict some information.

The terminal or the network device may work on several frequency ranges, e.g., FR1 (e.g., 450 MHz to 6000 MHz) , FR2 (e.g., 24.25GHz to 52.6GHz) , frequency band larger than 100 GHz as well as Tera Hertz (THz) . It can further work on licensed/unlicensed/shared spectrum. The terminal device may have more than one connection with the network devices under Multi-Radio Dual Connectivity (MR-DC) application scenario. The terminal device or the network device can work on full duplex, flexible duplex and cross division duplex modes.

The embodiments of the present disclosure may be performed in test equipment, e.g., signal generator, signal analyzer, spectrum analyzer, network analyzer, test terminal device, test network device, channel emulator. In some embodiments, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs) . In some embodiments, the first network device may be a first RAT device and the second network device may be a second RAT device. In some embodiments, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In some embodiments, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In some embodiments, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

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. The term ‘includes’ and its variants are to be read as open terms that mean ‘includes, but is not limited to. ’ The term ‘based on’ is to be read as ‘at least in part based on. ’ The term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment. ’ The term ‘another embodiment’ is to be read as ‘at least one other embodiment. ’ The terms ‘first, ’ ‘second, ’ and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as ‘best, ’ ‘lowest, ’ ‘highest, ’ ‘minimum, ’ ‘maximum, ’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

As used herein, the term “resource, ” “transmission resource, ” “uplink resource, ” or “downlink resource” may refer to any resource for performing a communication, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

In embodiments of the present disclosure, a LTM procedure is a cell switch procedure that may include, for example, the network triggered LTM procedure via MAC CE based on L1 measurements and the conditional LTM procedure which is initiated when corresponding condition (s) are satisfied.

Principles and implementations of the present disclosure will be described in detail below with reference to the figures.

FIG. 1A illustrates a schematic diagram of an example communication environment 100A in which example embodiments of the present disclosure can be implemented. In the communication environment 100A, a plurality of communication devices, including a first network device 110, a second network device 120 and a terminal device 130, can communicate with each other. The first network device 110 may include one or more units or devices, which may, for example, communicate with each other. Likewise, the second network device 120 may include one or more units or devices, which may, for example, communicate with each other. The units or devices may include, for instance, a centralized unit (CU) , for example, a gNB-CU, at least one distributed unit (DU) , for example, gNB-DU (s) , or other suitable units or devices.

The gNB-CU may be a logical node hosting RRC, Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) protocols of the gNB or RRC and PDCP protocols of the En-gNB that controls the operation of one or more gNB-DUs. The gNB-CU may terminate the F1 interface connected with the gNB-DU.

The gNB-DU may be a logical node hosting Radio Link Control (RLC) , MAC and Physical layer (PHY) layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU may terminate the F1 interface connected with the gNB-CU.

In the communication environment 100A, the terminal device 130 may be a UE, and the first network device 110 and second network device 120 may be network devices (e.g., base stations) , one is serving the UE and the other one is to serve the UE. For example, in a LTM procedure for a cell switch from the source cell to a target cell, the first network device 110 may be associated with the source cell which is currently serving the terminal device 130, and the second network device 120 may be associated with a candidate cell, which may be selected as the target cell.

FIG. 1B illustrates a schematic diagram of an example communication environment 100B in which example embodiments of the present disclosure can be implemented. Similar to the communication environment 100A, the communication environment 100B may include a plurality of communication devices, for example, but not limited to, the first network device 110 and the second network device 120 and the terminal device 130. Both the first network device 110 and the second network device 120 may have a CU-DU split architecture.

In contrast to the communication environment 100A, in embodiments discussed with reference to FIG. 1B, more details about the first network device 110 and the second network device 120 are provided.

Specifically, as shown in FIG. 1B, the first network device 110 includes a CU (also referred to as a “first CU” ) 111 and a DU (also referred to as a “first DU” ) 112, and the second network device 120 includes a CU (also referred to as a “second CU” ) 121 and a DU (also referred to as a “second DU” ) 122. The first CU 111 and the second CU 121 may communicate with each other, e.g., via an Xn interface. In some embodiments, for example, the first network device 110 and the second network device 120 may communicate with each other, e.g., via the Xn interface. The first CU 111 and the first DU 112 may communicate with each other, e.g., via an F1 interface. Likewise, the second CU 121 and the second DU 122 may communicate with each other, e.g., via an F1 interface.

In some embodiments where the first network device 110 is serving the UE, the source cell in a LTM procedure may be the cell managed by the first network device 110. That is, the first network device 110 is associated with the source cell. In such cases, the first CU 111 may be referred to as a source CU 111, the first DU 112 may be referred to as a source DU 112 It is to be understood that although FIG. 1B shows merely one DU, i.e., the first DU 112, in the first network device 110, it is just an example, rather than suggest any limitation. In embodiments of the present disclosure, the first network device 110 may include one or more DUs other than the first DU 112.

In the LTM procedure, there may be one or more candidate cells for the cell switch and the target cell is one of these candidate cells. One candidate cell may be associated or managed by one network device (e.g., gNB) . In the embodiments of FIGS. 1A and 1B, the second network device 120 is associated with a candidate cell for the LTM procedure. In such cases, the second CU 121 may be referred to as a candidate CU 121, the second DU 122 may be referred to as a candidate DU 122. It is to be understood that although FIG. 1B shows merely one DU, i.e., the second DU 122, is included in the second network device 120, it is just an example, rather than suggest any limitation. In embodiments of the present disclosure, the second network device 120 may include more than one DU.

In some example embodiments, the first network device 110 may be discussed as a first Next Generation Radio Access Network (NG-RAN) (also referred to as a source NG-RAN) and the second network device 120 may be discussed as a second NG-RAN (also referred to as a candidate NG-RAN, or sometimes, target NG-RAN) which is different from the first NG-RAN. In some example embodiments, the first network device 110 may be referred to as a source NG-RAN. The second network device 120 may be referred to as a candidate NG-RAN, or sometimes, target NG-RAN. A NG-RAN node may include, for example, a gNB or an NG-eNB.

The gNB may be a node providing NR user plane and control plane protocol terminations towards UE, and connected via a NG interface to the 5GC. The NG-eNB may be a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

It is to be understood that the number of devices and their connections shown in FIG. 1A or FIG. 1B are only for the purpose of illustration without suggesting any limitation. The communication environment 100A or 100B may include any suitable number of devices configured to implementing example embodiments of the present disclosure. It is noted that although illustrated as a network device, the first network device 110 and second network device 120 may be other devices than network devices. Although illustrated as a terminal device, the terminal device 130 may be another device than a terminal device.

In the following, for the purpose of illustration, some example embodiments are described with the first network device 110 and the second network device 120 operating as a base station and the terminal device 130 operating as a UE. However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

In some example embodiments, a link from the first network device 110 or the second network device 120 to the terminal device 130 is referred to as a downlink (DL) , while a link from the terminal device 130 to the first network device 110 or the second network device 120 is referred to as an uplink (UL) . In DL, the first network device 110 or the second network device 120 is a transmitting (TX) device (or a transmitter) and the terminal device 130 is a receiving (RX) device (or a receiver) . In UL, the terminal device 130 is a TX device (or a transmitter) and the first network device 110 or the second network device 120 is a RX device (or a receiver) .

The communications in the communication environment 100A or 100B may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , New Radio (NR) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , Machine Type Communication (MTC) and the like. The embodiments of the present disclosure may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or the sixth generation (6G) networks.

Depending on the availability of a valid timing advance (TA) value, the UE may perform either a random access channel (RACH) -less LTM or RACH-based LTM cell switch. A RACH-less LTM may be an LTM cell switch procedure where UE skips the random access procedure. If the TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no TA value is provided in the cell switch command, the UE applies the TA value by itself if available. Meanwhile, the UE performs RACH-less LTM cell switch upon receiving the cell switch command or when conditions for LTM cell switch is satisfied. If no valid TA value is available, the UE performs RACH-based LTM cell switch.

A subsequent LTM may be a LTM cell switch procedure between candidate cells without RRC reconfiguration by the network in between.

In embodiments of the present disclosure which are discussed below, the LTM procedure may be either a network triggered LTM procedure or a conditional LTM procedure, or other suitable LTM procedure. The network triggered LTM procedure may be triggered by a LTM command MAC CE. The conditional LTM procedure may be executed in response to that at least one LTM execution condition is met. More particular, the conditional LTM procedure may be also discussed as a conditional handover or a conditional cell switch, which is a handover procedure that is executed only when execution condition (s) are met.

Currently, only intra-centralized unit (CU) LTM, including intra-distributed unit (DU) and inter-DU LTM within one CU, is supported. To further extend scenario of LTM, there is a need to support inter-CU LTM procedure.

Additionally, for a conditional LTM with short mobility interruption time, the UE evaluates the conditions and triggers the LTM cell switch procedure if the condition associated with the conditional LTM is fulfill, instead of triggered by MAC CE.

Reference is made to FIG. 2, which illustrates a signaling flow 200 of cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 200 will be discussed with reference to FIG. 1A, for example, by using the first network device 110, the second network device 120 and the terminal device 130.

As discussed, the LTM procedure may be a network triggered LTM procedure, which is triggered by a LTM command MAC CE, or a conditional LTM procedure that is executed in response to that at least one LTM execution condition is met.

In the signaling flow 200, the first network device 110 transmits (206) , to the second network device 120, configuration request information about a LTM procedure for a cell switch from a source cell a target cell. The first network device 110 is associated with the source cell and the second network device 120 is associated with a candidate cell for the cell switch. The second network device 120 receives (208) the configuration request information. Thus, the second network device 120 knows that the first network device 110 wants to obtain configuration information from the second network device 120.

The configuration request information may be transmitted via a handover request message on the Xn interface between the first network device 110 and the second network device 120, or via other suitable message (s) or way (s) . In some embodiments, the configuration request information about the LTM procedure may be included in HANDOVER REQUEST message. For example, the configuration request information may be in a LTM information request information element (IE) , and the LTM information request IE is included in HANDOVER REQUEST message.

The first network device 110 may have various implementations and the second network device 120 may be implemented in a variety of ways. In some example embodiments, the first network device 110 may include the first CU 111 and the second network device 120 may include the second CU 121. Alternatively, the first network device 110 may refer to a first NG-RAN or source NG-RAN, and the second network device 120 may refer to a second NG-RAN or candidate NG-RAN, which is different from the first NG-RAN.

In some example embodiments, the first network device 110 and the second network device 120 may communicate via an Xn interface. For example, the configuration request information may be transmitted from the first network device 110, in particular, the first CU 111, to the second network device 120, specifically, the second CU 121, via the Xn interface. In some further embodiments, other information, such as cancel information and configuration information (e.g., RS configuration) , may be also transmitted via the Xn interface between the first network device 110 and the second network device 120.

The configuration request information may include various information, for example, but not limited to, an LTM indication, a first identification of a terminal device over an Xn interface within the first network device (e.g., denoted by Target NG-RAN node UE XnAP ID) , a second identification of a terminal device over an Xn interface within the second network device (e.g., denoted by Source NG-RAN node UE XnAP ID) , an estimated arrival probability, a list of LTM cells to be released or cancelled, a request for a lower layer configuration, a LTM reference configuration, and/or a reference signal configuration for the LTM procedure. It is to be understood that the configuration request information may include at least one of the aforesaid items, and/or other suitable information which is not listed here.

In some embodiments, the LTM indication used to indicate whether the configuration request information is for the LTM procedure or a cause of the LTM procedure. In some embodiments, an estimated arrival probability included in configuration request information may be used for NG-RAN to allocate the resources for the terminal device 130. In some embodiments, a list of LTM cells to be released or cancelled may be used to release or cancel the LTM candidate cell (s) related the cell global ID. In some embodiments, a request for a lower layer configuration used to request the lower layer configuration for LTM candidate cell, for example, the lower layer configuration in CellGroupConfig IE. In some embodiments, the LTM reference configuration is contained in the configuration request information message, the second network device may, if supported, take it into account for generating the LTM lower layer configuration. In some embodiments, a reference signal configuration may include the SSB or CSI.

In some embodiments, the LTM indication indicates whether the configuration request information is for LTM procedure. In some example embodiments, the LTM indication indicates that the configuration request is for NW triggered LTM. In some example embodiments, the LTM indication indicates that the configuration request is for conditional LTM.

In an implementation, the cause of the LTM procedure may include an LTM initiation, LTM replace or update, or LTM release or remove or cancel. For example, if it set to “LTM-initiation” , the second network device 120 may consider that the configuration request information concerns a LTM cell switch for the included target cell global ID, and the target/candidate NG-RAN may regard it as a reconfiguration with synchronization.

In embodiments of the present disclosure, the term “cancel” , “release” , “remove” , or “delete” may be used in different embodiments or scenarios. In embodiments of the present disclosure, each of the term “LTM cancel” , “LTM release” , “LTM remove” , or “LTM delete” may indicate that a cell is no longer used as a candidate cell for a LTM procedure. Optionally, a related terminal device and/or a related network device may delete or remove configuration information for the candidate cell. It is to be understood that the embodiments involving any of the terms “cancel” , “release” , “remove” , and “delete” are all applicable, unless explicitly indicated otherwise.

If the cause is set to “LTM-replace” , the second network device 120 may replace the existing prepared LTM mobility identified by the information element (IE) of Target NG-RAN node UE XnAP ID and the IE of target cell global ID.

If the cause is set to “LTM-release” , the second network device 120 may consider that the configured candidate cells in the LTM cells to be released list are about to be released by the first network device 110, e.g., the source NG-RAN.

In some embodiments, the field of Target NG-RAN node UE XnAP ID may be be present if the LTM indicator is present and "LTM-replace" is set.

In some embodiments, early synchronization information may be transmitted from the first network device to the second network device. In some example embodiments, the early synchronization information may be RACH configuration request IE.Alternatively, in some example embodiments, the early synchronization information may be included in RACH configuration request. The early synchronization information may be transmitted via the same message as the configuration request information, or a separate message. In some implementations, the configuration request information may be transmitted via a handover request message, and the handover request message may also include the early synchronization information. It is to be understood that this just an example, rather than suggest any limitation. In some embodiments, the early synchronization information may be included in a message without the configuration request information.

In response to the configuration request information, the second network device 120 may transmit (210) , to the first network device 110, an acknowledgement message of the configuration request information. Accordingly, the first network device 110 receives (212) the acknowledgement message from the second network device 120.

In some example embodiments, the acknowledgement message may include various information, for example, but not limited to, an identification of the candidate cell, a maximum number of prepared LTM candidate cells, or an identification of the second DU 122 of the second network device 120, a reference signal (RS) configuration for LTM, an early RACH configuration, a RRC container including a RRC reconfiguration message, a first identification of a terminal device over an Xn interface within the first network device 110 (e.g., denoted by Target NG-RAN node UE XnAP ID) , a second identification of a terminal device over an Xn interface within the second network device 120 (e.g., denoted by Source NG-RAN node UE XnAP ID) , and/or a condition for switching to the candidate cell associated with the second network device 120. It is to be understood that the acknowledgement message may include at least one of the aforesaid items, and/or other suitable information which is not listed here.

In some example embodiments, an identification of the candidate cell may be the cell global ID. In some example embodiments, a maximum number of prepared LTM candidate cells is used to indicate the maximum number of concurrently prepared LTM candidate cells for a UE at a second NG-RAN node. In some example embodiments, if the early synchronization information is included in the configuration request information and set to "true" , the second network device may, if supported, include the early RACH Configuration IE for early TA acquisition (early UL synchronization) , in the acknowledgement message. In some embodiments, if the LTM indication in configuration request information indicates the request is for conditional LTM, a condition for switching to the candidate cell associated with the second network device 120 may be included in the acknowledgement message.

In some example embodiments, the acknowledgement message may be a handover request message acknowledgement message. In a case where the configuration request information may be transmitted via the handover request message, the second network device 120 may response with the handover request message acknowledgement message to provide the acknowledgement.

In embodiments of the present disclosure, cancel information may indicate canceling of the candidate cell for the LTM procedure. The cancel information may be transmitted from either the first network device 110 or the second network device 120. That is, both the first network device 110 and the second network device 120 is capable of initiating the transmission of the cancel information.

In some example embodiments, the first network device 110 may transmit (214) cancel information to the second network device 120, and the second network device 120 receives (216) the cancel information accordingly.

As an alternative, the cancel information may be transmitted from the second network device 120. In this case, the first network device 110 may receive the cancel information from the second network device, instead of transmitting (214) the cancel information.

Likewise, the second network device 120 may receive the cancel information from the first network device 110, or transmit the cancel information to the first network device 110.

The cancel information may comprise various information items, for example, but not limited to, a cause indicating a reason for canceling of the candidate cell, a list of candidate cells for a network triggered LTM procedure that are to be cancelled, and/or a list of candidate cells for a conditional LTM procedure that are to be cancelled. The list of candidate cells for the LTM procedure that are to be cancelled may include at least one identification of the target cell. In some example embodiments, a cause indicating a reason for canceling of the candidate cell may be used to indicate to cancel the network triggered LTM candidate cell (s) or cancel the conditional LTM candidate cell (s) .

In some example embodiments, the first network device 110 may transmit (218) configuration information to the second network device 120. The configuration information may include, for example, a RS configuration of the source cell. Alternatively, or in addition, the first network device 110 may transmit (218) to the second network device 120 configuration information comprising a RS configuration of a further candidate cell associated with a further network device (referred to as third network device) . In some embodiments, the configuration information may be transmitted (218) via an Xn Transfer message to the second network device 120.

The second network device 120 may receive (220) , from the first network device 110, the configuration information comprising a RS configuration of the source cell associated with the first network device 110. Alternatively, or addition, the second network device 120 may receive (220) , from the first network device 110, further configuration information comprising a RS configuration of a candidate cell associated with the third network device. As a further alternative, the second network device 120 may receive, from the third network device, further configuration information comprising a RS configuration of a candidate cell associated with the third network device. As such, the second network device 120 will have the knowledge of configurations of the source cell and/or other candidate cell (s) .

In addition to the RS configuration, the configuration information may further include, for instance, an identification of the source cell, an identification of the candidate cell associated with the third network device, an identification of a terminal device over an Xn interface associated with the first network device 110, an identification of a terminal device over an Xn interface associated with the third network device, an identification of a DU of the first network device 110 or third network device, and/or a LTM candidate cell configuration.

In addition to the above, the terminal device 130 may transmit (202) its own capability information for the LTM procedure to the first network device 110. The capability information may indicate the maximum number of LTM candidate cell (s) . The capability information may be transmitted, for example, via a RRC signaling. In particular, the capability information may be transmitted via UECapabilityInformation.

The first network device may receive (204) , from the terminal device 130, the capability information of the terminal device 130.

In some embodiments, the capability information may include, for example, a total number of candidate cells for network triggered inter-CU and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, and/or a total number of candidate cells for conditional LTM procedures.

In view of the above, an Xn signaling is transmitted to configure the LTM candidate cell (s) . For example, Xn signalling is transmitted to configure the NW triggered inter-CU LTM candidate cell (s) or conditional LTM candidate cells. Furthermore, an Xn signaling is transmitted to cancel/release the LTM candidate candite for inter-CU case. Alternatively or in addition, an Xn signaling is transmitted to support the LTM candidate cell configuration between candidate gNBs.

FIG. 3A illustrates a signaling flow 300A of requesting a cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 300A will be discussed with reference to FIG. 1A, for example, by using the first network device 110 and the second network device 120.

As discussed, a LTM procedure may comprise a network triggered LTM procedure, which is triggered by a LTM command MAC CE, or a conditional LTM procedure that is executed in response to that at least one LTM execution condition is met. In the following discussion, the embodiments discussed with reference to FIG. 3A are related to the network triggered LTM procedure, and the embodiments discussed with reference to FIG. 3B are related to the conditional LTM procedure.

In the embodiments of FIG. 3A, the configuration request information is referred to as LTM information, which may be included in, e.g., an IE of LTM information request (also referred to as the LTM information request IE) , in a Handover Request message.

In the signaling flow 300A, the first network device 110 transmits (302) the Handover Request message to the second network device 120, where the Handover Request message includes the configuration request information in the LTM information request IE.

The LTM information request IE may include an LTM indication (also refereed to as LTM indicator) . The LTM indication indicates whether the configuration request information is for LTM procedure or a cause of the LTM procedure. Specifically, in some embodiments, the value of the LTM indicator may be “true” . If it set to “true” , the second network device 120 (for example, the target/candidate NG-RAN) may, if supported, consider that the request concerns a LTM procedure for the included Target Cell Global ID.

Alternatively, or in addition, in some embodiments, a new XnAP cause for the LTM procedure is introduced, which may be, e.g. LTM initiation, LTM replace or LTM release.

In some embodiments, the value of the LTM indicator may be “LTM-initiation” or “LTM-replace or update” or “LTM-release or remove or cancel” . If it set to “LTM-initiation” , the target/candidate NG-RAN may consider that the request concerns a LTM cell switch for the included target cell global ID, the target/candidate NG-RAN may regard it as a reconfiguration with sync as defined in TS 38.331.

If it set to “LTM-replace” , the target/candidate NG-RAN may replace the existing prepared LTM mobility identified by the Target NG-RAN node UE XnAP ID IE and the target cell global ID IE.

If it set to “LTM-release” , the target/candidate NG-RAN may consider that the configured candidate cells in the LTM cells to be released list are about to be released by the first network device (also referred to as source NG-RAN) 110.

In addition to the LTM indication, or as an alternative of the LTM indication, the LTM information request may include a Source NG-RAN node UE XnAP ID and/or a Target NG-RAN node UE XnAP ID. The Source NG-RAN node UE XnAP ID may refer to an identification of the terminal device 130 over an Xn interface within the first network device 110. Target NG-RAN node UE XnAP ID may refer to an identification of the terminal device 130 over an Xn interface within the second network device 120. Optionally, the field/IE of Target NG-RAN node UE XnAP ID may be present if the IE of LTM indicator is present and "LTM-replace" is set.

In addition or alternatively, the LTM information request may include the Estimated Arrival Probability, which may be used for a NG-RAN to allocate the resources for a UE.

In addition or alternatively, the LTM information request may include a LTM cells to be released/cancelled list, that is, a list of LTM cells to be released or cancelled. A list of LTM cells to be released or cancelled contains at least one identification of candidate cells. The target/candidate NG-RAN may, if supported, release the configured candidate cells in the list. Optionally, this field/IE may be present if the IE of LTM indicator is present and "LTM-release" is set.

In addition or alternatively, the LTM information request may include a lower layer configuration IE used to request the lower layer configuration for LTM candidate cell. For example, the lower layer configuration refers to the lower layer configuration in CellGroupConfig IE.

In addition or alternatively, the LTM information request may include LTM reference configuration, and the second network device 120 may, for example the candidate NG-RAN, take it into account for generating the LTM lower layer configuration.

In addition or alternatively, the LTM information request may include RS configuration for LTM. In some embodiment, the RS configuration may include CSI resource configuration and/or SSB resource configuration. In some embodiments, the LTM information request may include TCI state configuration.

The Handover Request message may also include the early synchronization information. In some example embodiment, the early synchronization information may be RACH configuration request. Alternatively, in some example embodiment, the early synchronization information may be included in RACH configuration request.

Table 1 shows an example of the Handover Request message which includes the LTM information request, early synchronization information and other suitable information elements for example. The LTM information request may include a plurality of fields containing information as discussed above. This Handover Request message may be sent by the source NG-RAN node to the candidate NG-RAN or target NG-RAN node to request the preparation of candidate cells for a handover.

Table 1

The second network device 120 (the target/candidate NG-RAN node) receives (304) the LTM information request contained in the Handover Request message, and may consider that the request concerns a LTM cell switch. Then the second network device 120 (the target/candidate NG-RAN node) may transmit (306) an acknowledgement message of the configuration request information to the first network device 110, for example, a Handover Request Acknowledgement (ACK) message. As shown in FIG. 3A, the second network device 120 transmits (306) the LTM Information Acknowledge in a Handover Request Acknowledgement message. The first network device 110 receives (308) the Handover Request Acknowledgement message and thus will have information about the candidate cell/the candidate NG-RAN node.

The Handover Request Acknowledgement message may include LTM related information, for example, LTM Information Acknowledge IE, which may contain an identification of the candidate cell, for example, a requested target/candidate cell ID, such as a Target Cell Global ID, where the target cell may be indicated in the corresponding Handover Request message.

Alternatively or in addition, the Handover Request Acknowledgement message may include an IE of a maximum number of prepared LTM candidate cells, such as a maximum number of LTM preparations. Alternatively, IE of a maximum number of prepared LTM candidate cells may be included in LTM related information IE, for example LTM Information Acknowledge IE, in Handover Request Acknowledge message. This IE indicates the maximum number of concurrently prepared LTM candidate cells for a UE at a candidate/target NG-RAN node.

Alternatively or in addition, the Handover Request Acknowledgement message may include an identification of a DU of the second network device 120, which may be represented as Candidate or target gNB-DU ID. Alternatively, identification of a DU of the second network device 120 may be included in LTM related information IE, for example LTM Information Acknowledge IE, in Handover Request Acknowledge message.

Alternatively or in addition, the Handover Request Acknowledgement message may further include, for example, but not limited to, RS configuration for LTM, an early RACH configuration, other information, for example, a RRC container including RRCReconfiguration message, Source NG-RAN node UE XnAP ID, and/or Target NG-RAN node UE XnAP ID. In some example embodiments, if the RS Configuration in the LTM information request IE is included in the Handover Request message, the target NG-RAN shall, if supported, use it to generate the LTM RS reporting configuration (s) in the CellGroupConfig for the requested LTM candidate cell. The RS may be the SSB or CSI. In further example embodiments, the target CU send the RS configuration request to the target DU and the target DU use it to generate the LTM RS reporting configuration (s) in the CellGroupConfig for the requested LTM candidate cell. In some embodiments, if the Request for RACH Configuration IE is contained in the Early Sync Information IE included in the Handover Request message and set to "true" , the target NG-RAN may, if supported, include the RACH Configuration IE for early TA acquisition (early UL synchronisation) , in the Handover Request Acknowledge message. In some further embodiments, the target DU generate the RACH Configuration IE for early TA acquisition and send it to target CU.

Table 2 shows an example of the Handover Request Acknowledgement message which may include the LTM information acknowledge, Early Sync Information, LTM configuration, and/or the like. The LTM information Acknowledge may include a plurality of fields containing information as discussed above. This Handover Request Acknowledgement message may be sent by the candidate NG-RAN or target NG-RAN node to inform the source NG-RAN node about the prepared resources at the target.

Table 2

FIG. 3B illustrates another signaling flow 300B of requesting a cell configuration in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 300B will be discussed with reference to FIG. 1A, for example, by using the first network device 110 and the second network device 120.

As discussed above, the embodiments of FIG. 3B are related to the conditional LTM procedure that is executed in response to that at least one LTM execution condition is met.

In the signaling flow 300B, the first network device 110 transmits (312) configuration request information, also referred to as conditional LTM information request, to the second network device 120. The conditional LTM information request may be transmitted (312) in an IE of conditional LTM information request (conditional LTM information request IE) in a Handover Request message.

The conditional LTM information request may include similar information or fields as the LTM information request in the Handover Request message. The details may be referred to the discussion with respect to FIG. 3A and thus omitted here.

The Handover Request message in FIG. 3B is also similar to the Handover Request message discussed with reference to FIG. 3A, and thus details of it is omitted here.

It is to be understood that although both FIG. 3A and FIG. 3B show a Handover Request message, the Handover Request message may have different IE (s) in both cases. Specifically, the conditional LTM information request IE in the Handover Request message of FIG. 3B may be not included in the Handover Request message of FIG. 3A. In some implementations, the Handover Request message of FIG. 3B may be obtained by replacing the LTM information request IE of the Handover Request message in FIG. 3A with the conditional LTM information request IE. Alternatively, the Handover Request message of FIG. 3B may contain both the LTM information request IE and the conditional LTM information request IE.

The second network device 120 (the target/candidate NG-RAN node) receives (314) the conditional LTM information request contained in the Handover Request message, and may consider that the request concerns a LTM cell switch. Then the second network device 120 (the target/candidate NG-RAN node) may transmit (316) an acknowledgement message of the configuration request information to the first network device 110, for example, a handover request acknowledgement message. As shown in FIG. 3B, the second network device 120 transmits (316) conditional LTM Information Acknowledge in a Handover Request Acknowledgement message. The first network device 110 receives (318) the Handover Request Acknowledgement message and thus may obtain the conditional LTM Information Acknowledge.

The acknowledgement message for the conditional LTM procedure, for example, the Handover Request Acknowledgement message in FIG. 3B, may include similar information contained in the acknowledgement message for the network triggered LTM procedure, as discussed in FIG. 3A. In contrast, the acknowledgement message for the conditional LTM procedure may further include a condition for the terminal device 130 to perform a conditional LTM procedure to switch to the candidate cell associated with the second network device 120. In this way, the condition for performing the conditional LTM procedure is indicated to the first network device 110.

In further embodiments, the candidate NG-RAN or the candidate CU determine that the LTM information request indicate that request is for conditional LTM candidate cell, the candidate CU may indicate the candidate DU about the request is for conditional LTM. The candidate DU generates a condition for conditional LTM execution. The candidate DU transmits the condition to the candidate CU. The target CU includes the condition for switching to the candidate cell into the Handover Request Acknowledgement message.

In view of embodiments discussed with reference to FIGS. 3A and 3B, new information in an Xn signaling is introduced to configure the LTM candidate cell and/or the (conditional) LTM candidate cell. In this way, the LTM candidate cell can be configured for the inter-CU scenario. Thus, the NW can be supported to configure the inter-CU (conditional) LTM candidate cells to UE.

For inter-CU LTM cell switch, the LTM candidate/target cell preparation procedure is initiated by the first network device 110 (also referred to as the source gNB 110) , for example, the first CU (source CU) 111 of the first network device 110. The second network device 120 (also referred to as the candidate/target gNB 120) , for example, the second CU (candidate CU) 121 of the second network device 120 may provide the LTM candidate cell configuration.

In the embodiments of FIGS. 4 and 5, once the LTM candidate cell is configured, both the source gNB 110or source CU 111 or the candidate gNB 120 or candidate CU 121 is able to cancel the LTM candidate cell. Specifically, in FIG. 4, a candidate/target gNB initiated LTM candidate cell cancel procedure is discussed. In FIG. 5, a source gNB initiated LTM candidate cell cancel procedure is discussed. With the embodiments of FIGS. 4 and 5, a LTM candidate cell can be canceled by either the target gNBor target NG-RAN or target CU or the source gNB or source NG-RAN or source CU.

Now reference is made to FIG. 4, which illustrates a signaling flow 400 of transmission of cancel information in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 400 will be discussed with reference to FIG. 1A, for example, by using the first network device 110 (also referred to as the source NG-RAN node 110) and the second network device 120 (also referred to as the target NG-RAN node 120) .

In embodiments of FIG. 4, a new cause is introduced for LTM or C-LTM in XnAP Cause IE is to indicate the reason for a particular event (e.g., a LTM procedure or network triggered LTM procedure or a conditional LTM procedure) for the XnAP protocol. For example, the new cause may be “LTM resources to be released or changed or update” , which means that the prepared resources for the LTM procedure for a UE are to be released. For another example, the new cause may be “LTM resources to be released or changed or update” , which means that the prepared resources for the network triggered LTM procedure for a UE are to be released. For another example, the new cause may be “conditional LTM resources to be released or changed or update” , which means that the prepared resources for the conditional LTM procedure for a UE are to be released. It is to be understood that the cause may have other suitable values, for example, but not limited to “LTM candidate cells to be released. ”

The embodiments of FIG. 4 are related to the scenario of a candidate cell (also referred to as LTM candidate cell) cancel procedure initiated by the first network device 110, i.e., the source NG-RAN node 110.

The first network device 110 may include a LTM candidate cell cancel IE in a first message for transmitting on the Xn interface between the first network device 110 and the second network device 120. The first message may be, for example, a Handover Cancel message or a new Xn message. This message may be applicable for both the network triggered LTM procedure and the conditional LTM procedure, for example, by including corresponding IEs for different LTM procedures. In some embodiment, the LTM candidate cell cancel related IE may include a list, and the list may contain, for example, Target Cell ID for a LTM candidate cell to be canceled or released.

In some example embodiment, for the network triggered LTM procedure, the first message may include a list of candidate cells for the network triggered LTM procedure that are to be cancelled, and the list may at least include an identification (ID) of at least one candidate cell. Alternatively or in addition, the first message may include a cause indicating a reason for canceling of the candidate cell, for example, LTM resources to be released or NW triggered LTM resources to be released.

In another example embodiment, the first message may include a list of candidate cells for the conditional LTM procedure that are to be cancelled which at least includes an ID of at least one candidate cell. Alternatively or in addition, the first message may include a cause indicating a reason for canceling of the candidate cell, for example, LTM resources to be released or conditional LTM resources to be released.

As shown in FIG. 4, the first network device 110 transmits (402) the Handover Cancel message to the second network device 120, and the second network device 120 receives (404) the Handover Cancel message accordingly. The cancel information, for example, included in a LTM candidate cell cancel related IE is contained in the Handover Cancel message.

The cancel information may include a cause indicating a reason for canceling of the candidate cell. Alternatively or in addition, the cancel information may include a list of candidate cells for the LTM procedure that are to be cancelled, where the LTM procedure is a network triggered LTM procedure. Alternatively or in addition, the cancel information may include a list of candidate cells for the LTM procedure that are to be cancelled, where the LTM procedure is a conditional LTM procedure.

The target NG-RAN node 120 obtains the cancel information from the received Handover Cancel message, and may consider that the source NG-RAN node 110 is cancelling only the LTM cell switch associated to the candidate cells identified by the included NG-RAN Cell Global Identifier (CGI) , and associated to the same UE-associated signaling connection identified by the Source NG-RAN node UE XnAP ID and, if included, also by the Target NG-RAN node UE XnAP ID.

Table 3 shows an example of the Handover Cancel message. As shown, the IE of LTM Candidate Cells To Be Cancelled/released List corresponds to the NW triggered LTM procedure, and has a range from 0 to maxnoofCellsinLTM. The maxnoofCellsinLTM indicates the maximum number of cells that can be prepared for a network (NW) triggered LTM cell switch. Table 3 also shows an IE of Conditional LTM Candidate Cells To Be Cancelled/released List, which corresponds to the conditional LTM procedure and has a range from 0 to maxnoofCellsinCLTM. The maxnoofCellsinCLTM indicates the maximum number of cells that can be prepared for a conditional LTM cell switch.

Table 3

As an alternative to the Handover Cancel message shown in Table 3, the cancel information may be transmitted via a new message, e.g., on the Xn interface. This new message may have similar IEs as the Handover Cancel message in Table 3. In contrast, the new message may not include the IE of Candidate Cells To Be Cancelled List, which is shown in Table 3.

FIG. 5 illustrates another signaling flow 500 of transmission of cancel information in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 500 will be discussed with reference to FIG. 1A, for example, by using the first network device 110 (also referred to as the source NG-RAN node 110) and the second network device 120 (also referred to as the target NG-RAN node 120) .

The embodiments of FIG. 5 are related to the scenario of a LTM candidate cell cancel procedure initiated by the second network device 120, i.e., the target NG-RAN node 120.

In embodiments of FIG. 5, a new cause is introduced for LTM or C-LTM in XnAP Cause IE is to indicate the reason for a particular event (e.g., a LTM procedure or network triggered LTM procedure or a conditional LTM procedure) for the XnAP protocol. For example, the new cause may be “LTM resources to be released or changed or update” , which means that the prepared resources for the LTM procedure for a UE are to be released. For another example, the new cause may be “conditional LTM resources to be released or changed or update” , which means that the prepared resources for the conditional LTM procedure for a UE are to be released. It is to be understood that the cause may have other suitable values, for example, but not limited to “LTM candidate cells to be released. ”

In these embodiments, a LTM candidate cell cancel related IE may be included in a second message to include the LTM candidate cell (s) cancel information. The second message may be the conditional handover cancel message or a new Xn message. In some embodiments, at least one of the conditional LTM or the NW triggered LTM candidate cell cancel related IEs may be included in the second message. In some embodiments, for both the conditional LTM procedure and the NW triggered LTM procedure, corresponding LTM candidate cell cancel related IEs may be included in the second message separately.

In some example embodiment, for the network triggered LTM procedure, the second message may include a list of candidate cells for the network triggered LTM procedure that are to be cancelled, and the list may at least include an identification (ID) of at least one candidate cell. Alternatively or in addition, the second message may include a cause indicating a reason for canceling of the candidate cell, for example, LTM resources to be released or NW triggered LTM resources to be released. In another example embodiment, the first message may include a list of candidate cells for the conditional LTM procedure that are to be cancelled which at least includes an ID of at least one candidate cell. Alternatively or in addition, the second message may include a cause indicating a reason for canceling of the candidate cell, for example, or LTM resources to be released or conditional LTM resources to be released.

Alternatively, in some embodiments, the second message may be a new message used for target NG-RAN initiated LTM candidate cell cancel procedure. The LTM candidate cell cancel related IE, and the cause may be included in the new message. In addition, Source and Target NG-RAN node UE XnAP ID may also be included in the new message. The new message may be, for example, a LTM Handover Cancel message.

As shown in FIG. 5, the second network device 120 transmits (502) a LTM Handover Cancel message including the cancel information to the first network device 110, and the first network device 110 receives (504) the LTM Handover Cancel message accordingly. The cancel information is similar as that discussed with respect to FIGS. 2 and 4, and its details are thus repeated here.

The source NG-RAN node 110 obtains the cancel information from the received second message, the source NG-RAN node 110 may consider that only the LTM cell switch associated to the candidate cells identified by the included NG-RAN Cell Global Identifier (CGI) are about to be released.

Alternatively, in some embodiments, the second message may be Conditional Handover Cancel message used for target NG-RAN initiated LTM candidate cell cancel procedure. At least one of the conditional LTM or the NW triggered LTM candidate cell cancel related IEs included in Conditional Handover Cancel message.

In some example embodiments, the conditional LTM candidate cell cancel related IEs included in the Conditional Handover Cancel message, the NW triggered LTM candidate cell cancel related IEs in the LTM Handover Cancel message.

Table 4 shows an example of the Handover Cancel message. As shown, the LTM candidate cell cancel related IE may be a List, and the Target Cell ID for LTM candidate cell to be canceled or released may be contained in the List.

Similar as Table 3, the maxnoofCellsinLTM in Table 4 also indicates the maximum number of cells that can be prepared for a network (NW) triggered LTM cell switch, and the maxnoofCellsinCLTM also indicates the maximum number of cells that can be prepared for a conditional LTM cell switch.

Table 4

As an alternative to the Handover Cancel message shown in Table 4, the cancel information may be transmitted via a new message, e.g., on the Xn interface. This new message may have similar IEs as the Handover Cancel message in Table 4.

FIG. 6 illustrates a signaling flow 600 of transmission of reference signal (RS) configuration or other LTM candidate cell configuration between the NG-RANs in a LTM procedure in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 600 will be discussed with reference to FIGS. 1A and 1B, for example, by using the first CU (also referred to as the source CU hereafter) 111 and the first DU (also referred to as the source DU hereafter) 112 of the first network device 110, the second CU (also referred to as the candidate CU hereafter) 121 and the second DU (also referred to as the candidate DU hereafter) 122 of the second network device 120, and the terminal device 130 (also referred to as UE 130 hereafter) .

In the embodiments of FIG. 6, a subsequent LTM procedure without need for RRC configuration can be supported. In order to support the subsequent LTM, each candidate NG-RAN or candidate CU may need to know the other candidate cell configuration so that to determine the LTM cell configuration and update candidate cell. In this regard, the embodiments of FIG. 6 introduce a new Xn signaling to transfer the candidate cell configuration between the NG-RANs or CUs.

In the embodiments of FIG. 6, each candidate DU needs to know the RS configuration of other candidate DUs in order to provide the LTM candidate configuration. In some embodiments, the RS configuration may include at least one of the SSB, CSI or TCI state configuration. In some embodiments, the source CU transmits to each candidate CU the RS configuration of the source DU (if this is an LTM candidate cell) and/or other candidate DUs, and each candidate CU sends its own RS configuration to the candidate DU, to generate the corresponding L1 configuration for LTM.

In some embodiments, a candidate DU generates a RS configuration and send to the candidate CU. The candidate CU transmits to the Source CU the RS configuration per LTM candidate cell and the associated LTM candidate (when the candidate CU receives LTM candidate configuration (s) from the candidate DU) .

In some embodiments, the candidate NG-RAN transmits the corresponding RS configuration to other candidate NG-RAN.

In some embodiments, the source NG-RAN or source CU or candidate NG-RAN or candidate CU may send the LTM candidate cell configuration to other candidate NG-RAN or candidate CU. A new Xn message may be used to transfer the above configuration information, including at least one of the RS configuration, LTM candidate cell configuration, early synchronization configuration, and/or other suitable information.

As shown in FIG. 6, the first network device 110 transmits (602) configuration information to the second network device 120. In this example, the configuration information is transmitted via an Xn Transfer message. It is to be understood that this is just an example of a message on the Xn interface, and other suitable Xn message is also applicable for carrying the configuration information. The configuration information may comprise a reference signal (RS) configuration of the source cell, and/or further configuration information comprising a RS configuration of a candidate cell associated with a third network device. The second network device 120 receives (604) the configuration information via the Xn Transfer message.

In some embodiments, the configuration information may include, for example, at least one of: an identification of the source cell, an identification of the candidate cell associated with the third network device, an identification of a terminal device over an Xn interface associated with the first network device, an identification of a terminal device over an Xn interface associated with the third network device, an identification of a distributed unit (DU) of the first network device or third network device, or a LTM candidate cell configuration.

In an implementation, the configuration information may at least include one or more of the following: RS configuration, Candidate NG-RAN node UE XnAP ID, Candidate gNB-DU ID, LTM candidate cell configuration. E. g. LTM-Candidate, and/or LTM-Config, and so on.

FIG. 7 illustrates a signaling flow 700 of a LTM process in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 700 will be discussed with reference to FIG. 1B. Specifically, a source CU 751 in FIG. 7 corresponds to the first CU 111 and a source DU 752 corresponds to the first DU 112 of the first network device 110. Furthermore, a candidate CU 761 corresponds to the second CU 121 and a candidate DU 762 corresponds to the second DU 122 of the second network device 120. FIG. 7 also shows a UE 770, which corresponds to the terminal device 130 in FIG. 1B.

In the signaling flow 700, the source CU 751 sends (702) a Handover Request message to the candidate CU 761. In case of the LTM process (also referred to as LTM Handover) . The configuration request information as discussed above may be included in the Handover Request message.

In case of a network trigger LTM procedure (handover) , the second network device 120 may be regarded as a candidate gNB which is only accessed by the UE 770 when the LTM cell change notification is received.

In case of a conditional LTM procedure (handover) , the second network device 120 may be regarded as a candidate gNB which is only accessed by the UE 770 when the conditional LTM condition (s) are fulfilled.

A UE context Setup procedure is performed (704) between the candidate CU 761 and the candidate DU 762. The candidate CU 761 sends (706) a Handover Request Acknowledge message to the source CU 751. The acknowledgement message of the configuration request information may be included in the Handover Request Acknowledge message. Details of the acknowledgement message have been discussed with respect to FIGS. 2, 3A and 3B, and thus are omitted here.

The source CU 751 sends (708) a DL RRC Message Transfer message to the source DU 752, which includes the generated RRCReconfiguration message with the LTM configuration. The source DU 752 sends (710) the received RRCReconfiguration message to the UE 770.

The UE 770 sends (712) an RRCReconfigurationComplete message to the source DU 752. The source DU 752 sends (714) the RRCReconfigurationComplete message to the source CU 751 via an UL RRC Message Transfer message.

FIG. 8 illustrates a flowchart of a communication method 800 implemented at a first network device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the first network device 110 in FIG. 1A and FIG. 1B.

At block 810, the first network device 110 transmits, to a second network device 120 in a RAN, configuration request information about a LTM procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell. The second network device is associated with a candidate cell for the cell switch.

In some example embodiments, the configuration request information comprises at least one of: an LTM indication indicating whether the configuration request information is for LTM procedure or a cause of the LTM procedure, a first identification of a terminal device over an Xn interface within the first network device, a second identification of a terminal device over an Xn interface within the second network device, an estimated arrival probability, a list of LTM cells to be released or cancelled, a request for a lower layer configuration, a LTM reference configuration, or a reference signal configuration for the LTM procedure.

In some example embodiments, the cause comprises at least one of: an LTM initiation, LTM replace, or LTM release.

In some example embodiments, early synchronization information is transmitted from the first network device to the second network device.

In some example embodiments, the early synchronization information is transmitted via the same message as the configuration request information.

In some example embodiments, the configuration request information is transmitted via a handover request message.

In some example embodiments, the first network device 110 may receive, from the second network device, an acknowledgement message of the configuration request information.

In some example embodiments, the acknowledgement message comprises at least one of: an identification of the candidate cell, a maximum number of prepared LTM candidate cells, or an identification of a distributed unit (DU) of the second network device, a reference signal (RS) configuration for LTM, an early random access channel (RACH) configuration, a radio resource control (RRC) container including a RRC reconfiguration message, a first identification of a terminal device over an Xn interface within the first network device, a second identification of a terminal device over an Xn interface within the second network device, or a condition for switching to the candidate cell associated with the second network device.

In some example embodiments, the acknowledgement message is a handover request message acknowledgement message.

In some example embodiments, the first network device 110 may transmit, to the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some example embodiments, the first network device 110 may receive, from the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some example embodiments, the cancel information comprises at least one of: a cause indicating a reason for canceling of the candidate cell, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a network triggered LTM procedure, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a conditional LTM procedure, wherein the list of candidate cells for the LTM procedure that are to be cancelled comprise at least one identification of the target cell.

In some example embodiments, the first network device 110 may transmit, to the second network device, configuration information comprising a reference signal (RS) configuration of the source cell, and/or further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with a third network device.

In some example embodiments, the configuration information further comprises at least one of: an identification of the source cell, an identification of the candidate cell associated with the third network device, an identification of a terminal device over an Xn interface associated with the first network device, an identification of a terminal device over an Xn interface associated with the third network device, an identification of a distributed unit (DU) of the first network device or third network device, or a LTM candidate cell configuration.

In some example embodiments, the first network device 110 may receive, from a terminal device, capability information of a terminal device for the LTM procedure, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

In some example embodiments, the LTM procedure comprises at least one of: a network triggered LTM procedure, which is triggered by a LTM command MAC CE, or a conditional LTM procedure that is executed in response to that at least one LTM execution condition is met.

In some example embodiments, the first network device comprises a first centralized unit (CU) and the second network device comprises a second CU other than the first CU, or wherein the first network device comprises a first Next Generation Radio Access Network (NG-RAN) and the second network device comprises a second NG-RAN other than the first NG-RAN.

In some example embodiments, the first network device and the second network device communicate via an Xn interface.

FIG. 9 illustrates a flowchart of a communication method 900 implemented at a second network device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the second network device 120 in FIG. 1A and FIG. 1B.

At block 910, the second network device 120 receives, from a first network device 110 in a RAN, configuration request information about a LTM procedure for a cell switch from a source cell associated with the first network device to a target cell. The second network device is in the RAN and being associated with a candidate cell for the cell switch.

In some example embodiments, early synchronization information is received at the second network device from the first network device.

In some example embodiments, the early synchronization information is received via the same message as the configuration request information.

In some example embodiments, the configuration request information is received via a handover request message.

In some example embodiments, the second network device 120 may transmit, to the first network device, an acknowledgement message of the configuration request information.

In some example embodiments, the second network device 120 may receive, from the first network device, cancel information indicating canceling of the candidate cell for the LTM procedure; or transmit, to the first network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some example embodiments, the cancel information comprises at least one of: a cause indicating a reason for canceling of the candidate cell, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a network triggered LTM procedure, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a conditional LTM procedure, or wherein the list of candidate cells for the LTM procedure that are to be cancelled comprise at least one identification the target cell.

In some example embodiments, the second network device 120 may perform at least one of: receive, from the first network device, configuration information comprising a reference signal (RS) configuration of the source cell associated with the first network device; receive, from the first network device, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device; or receive, from a third network device in the RAN, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device.

In some example embodiments, the first network device 110 comprises a first centralized unit (CU) and the second network device comprises a second CU other than the first CU, or wherein the first network device 110 comprises a first Next Generation Radio Access Network (NG-RAN) and the second network device comprises a second NG-RAN other than the first NG-RAN.

In some example embodiments, the first network device 110 and the second network device 120 communicate via an Xn interface.

FIG. 10 illustrates a flowchart of a communication method 1000 implemented at a terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the terminal device 130 in FIG. 1A and FIG. 1B.

At block 1010, the terminal device 130 transmits, to a first network device 110 in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell. The capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

FIG. 11 is a simplified block diagram of a device 1100 that is suitable for implementing embodiments of the present disclosure. The device 1100 may be considered as a further example implementation of any of the devices as shown in FIG. 1A and FIG. 1B. Accordingly, the device 1100 may be implemented at or as at least a part of the terminal device 130, the first network device 110 and the second network device 120.

As shown, the device 1100 includes a processor 1110, a memory 1120 coupled to the processor 1110, a suitable transceiver 1140 coupled to the processor 1110, and a communication interface coupled to the transceiver 1140. The memory 1120 stores at least a part of a program 1130. The transceiver 1140 may be for bidirectional communications or a unidirectional communication based on requirements. The transceiver 1140 may include at least one of a transmitter 1142 and a receiver 1144. The transmitter 1142 and the receiver 1144 may be functional modules or physical entities. The transceiver 1140 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME) /Access and Mobility Management Function (AMF) /SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN) , or Uu interface for communication between the eNB/gNB and a terminal device.

The program 1130 is assumed to include program instructions that, when executed by the associated processor 1110, enable the device 1100 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGS. 1A to 10. The embodiments herein may be implemented by computer software executable by the processor 1110 of the device 1100, or by hardware, or by a combination of software and hardware. The processor 1110 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1110 and memory 1120 may form processing means 1150 adapted to implement various embodiments of the present disclosure.

The memory 1120 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1120 is shown in the device 1100, there may be several physically distinct memory modules in the device 1100. The processor 1110 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1100 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

According to embodiments of the present disclosure, a first network device comprising a circuitry is provided. The circuitry is configured to: transmit, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first network device as discussed above.

According to embodiments of the present disclosure, a second network device comprising a circuitry is provided. The circuitry is configured to: receive, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second network device as discussed above.

According to embodiments of the present disclosure, a terminal device comprising a circuitry is provided. The circuitry is configured to: transmit, to a first network device in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the terminal device as discussed above.

The term “circuitry” used herein may refer to hardware circuits and/or combinations of hardware circuits and software. For example, the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware. As a further example, the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (ies) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions. In a still further example, the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation. As used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.

According to embodiments of the present disclosure, a first network apparatus is provided. The first network apparatus comprises means for transmitting, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch. In some embodiments, the first apparatus may comprise means for performing the respective operations of the method 800. In some example embodiments, the first apparatus may further comprise means for performing other operations in some example embodiments of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second network apparatus is provided. The second network apparatus comprises means for receiving, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch. In some embodiments, the second apparatus may comprise means for performing the respective operations of the method 900. In some example embodiments, the second apparatus may further comprise means for performing other operations in some example embodiments of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a terminal apparatus is provided. The terminal apparatus comprises means for transmitting, to a first network device in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, wherein the capability information comprises at least one of: means for a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, means for a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, means for a total number of candidate cells for network triggered inter-CU LTM procedures, or means for a total number of candidate cells for conditional LTM procedures. In some embodiments, the third apparatus may comprise means for performing the respective operations of the method 1000. In some example embodiments, the third apparatus may further comprise means for performing other operations in some example embodiments of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In summary, embodiments of the present disclosure provide the following aspects.

In an aspect, it is proposed a first network device comprising: a processor configured to cause the first network device to: transmit, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch.

In some embodiments, the configuration request information comprises at least one of: an LTM indication indicating whether the configuration request information is for LTM procedure or a cause of the LTM procedure, a first identification of a terminal device over an Xn interface within the first network device, a second identification of a terminal device over an Xn interface within the second network device, an estimated arrival probability, a list of LTM cells to be released or cancelled, a request for a lower layer configuration, a LTM reference configuration, or a reference signal configuration for the LTM procedure.

In some embodiments, the cause comprises at least one of: an LTM initiation, LTM replace, or LTM release.

In some embodiments, early synchronization information is transmitted from the first network device to the second network device.

In some embodiments, the early synchronization information is transmitted via the same message as the configuration request information.

In some embodiments, the configuration request information is transmitted via a handover request message.

In some embodiments, the first network device is further caused to: receive, from the second network device, an acknowledgement message of the configuration request information.

In some embodiments, the acknowledgement message comprises at least one of: an identification of the candidate cell, a maximum number of prepared LTM candidate cells, or an identification of a distributed unit (DU) of thesecond network device, a reference signal (RS) configuration for LTM, an early random access channel (RACH) configuration, a radio resource control (RRC) container including a RRC reconfiguration message, a first identification of a terminal device over an Xn interface within the first network device, a second identification of a terminal device over an Xn interface within the second network device, or a condition for switching to the candidate cell associated with the second network device.

In some embodiments, the acknowledgement message is a handover request message acknowledgement message.

In some embodiments, the first network device is further caused to: transmit, to the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some embodiments, the first network device is further caused to: receive, from the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some embodiments, the cancel information comprises at least one of: a cause indicating a reason for canceling of the candidate cell, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a network triggered LTM procedure, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a conditional LTM procedure, wherein the list of candidate cells for the LTM procedure that are to be cancelled comprise at least one identification of the target cell.

In some embodiments, the first network device is further caused to: transmit, to the second network device, configuration information comprising a reference signal (RS) configuration of the source cell, and/or further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with a third network device.

In some embodiments, the configuration information further comprises at least one of: an identification of the source cell, an identification of the candidate cell associated with the third network device, an identification of a terminal device over an Xn interface associated with the first network device, an identification of a terminal device over an Xn interface associated with the third network device, an identification of a distributed unit (DU) of the first network device or third network device, or a LTM candidate cell configuration.

In some embodiments, the first network device is further caused to: receive, from a terminal device, capability information of a terminal device for the LTM procedure, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

In some embodiments, the LTM procedure comprises at least one of: a network triggered LTM procedure, which is triggered by a LTM command MAC CE, or a conditional LTM procedure that is executed in response to that at least one LTM execution condition is met.

In some embodiments, the first network device comprises a first centralized unit (CU) and the second network device comprises a second CU other than the first CU, or wherein the first network device comprises a first Next Generation Radio Access Network (NG-RAN) and the second network device comprises a second NG-RAN other than the first NG-RAN.

In some embodiments, the first network device and the second network device communicate via an Xn interface.

In an aspect, it is proposed a second network device comprising: a processor configured to cause the second network device to: receive, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch.

In some embodiments, early synchronization information is received at the second network device from the first network device.

In some embodiments, the early synchronization information is received via the same message as the configuration request information.

In some embodiments, the configuration request information is received via a handover request message.

In some embodiments, the second network device is further caused to: transmit, to the first network device, an acknowledgement message of the configuration request information.

In some embodiments, the second network device is further caused to: receive, from the first network device, cancel information indicating canceling of the candidate cell for the LTM procedure; or transmit, to the first network device, cancel information indicating canceling of the candidate cell for the LTM procedure.

In some embodiments, the cancel information comprises at least one of: a cause indicating a reason for canceling of the candidate cell, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a network triggered LTM procedure, a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a conditional LTM procedure, or wherein the list of candidate cells for the LTM procedure that are to be cancelled comprise at least one identification the target cell.

In some embodiments, the second network device is further caused to perform at least one of: receive, from the first network device, configuration information comprising a reference signal (RS) configuration of the source cell associated with the first network device; receive, from the first network device, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device; or receive, from a third network device in the RAN, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device.

In an aspect, it is proposed a terminal device comprising: a processor configured to cause the terminal device to: transmit, to a first network device in a radio access network (RAN) , capability information of the terminal device for a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, wherein the capability information comprises at least one of: a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures, a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures, a total number of candidate cells for network triggered inter-CU LTM procedures, or a total number of candidate cells for conditional LTM procedures.

In an aspect, a first network device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the first network device discussed above.

In an aspect, a second network device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the second network device discussed above.

In an aspect, a terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first network device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second network device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first network device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second network device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the terminal device discussed above.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to FIGS. 1 to 11. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first network device comprising:

a processor configured to cause the first network device to:

transmit, to a second network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device in the RAN to a target cell, the second network device being associated with a candidate cell for the cell switch.
The device of claim 1, wherein the configuration request information comprises at least one of:

an LTM indication indicating whether the configuration request information is for LTM procedure or a cause of the LTM procedure,

a first identification of a terminal device over an Xn interface within the first network device,

a second identification of a terminal device over an Xn interface within the second network device,

an estimated arrival probability,

a list of LTM cells to be released or cancelled,

a request for a lower layer configuration,

a LTM reference configuration, or

a reference signal configuration for the LTM procedure.
The device of claim 2, wherein the cause comprises at least one of: an LTM initiation, LTM replace, or LTM release.
The device of claim 1, wherein early synchronization information is transmitted from the first network device to the second network device.
The device of claim 4, wherein the early synchronization information is transmitted via the same message as the configuration request information.
The device of any of claims 1 to 5, wherein the configuration request information is transmitted via a handover request message.
The device of claim 1, wherein the first network device is further caused to:

receive, from the second network device, an acknowledgement message of the configuration request information.
The device of claim 7, wherein the acknowledgement message comprises at least one of:

an identification of the candidate cell,

a maximum number of prepared LTM candidate cells, or

an identification of a distributed unit (DU) of the second network device,

a reference signal (RS) configuration for LTM,

an early random access channel (RACH) configuration,

a radio resource control (RRC) container including a RRC reconfiguration message,

a first identification of a terminal device over an Xn interface within the first network device,

a second identification of a terminal device over an Xn interface within the second network device, or

a condition for switching to the candidate cell associated with the second network device.
The device of claim 7 or 8, wherein the acknowledgement message is a handover request message acknowledgement message.
The device of any of claims 1 to 9, wherein the first network device is further caused to:

transmit, to the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.
The device of any of claims 1 to 9, wherein the first network device is further caused to:

receive, from the second network device, cancel information indicating canceling of the candidate cell for the LTM procedure.
The device of claim 10 or 11, wherein the cancel information comprises at least one of:

a cause indicating a reason for canceling of the candidate cell,

a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a network triggered LTM procedure,

a list of candidate cells for the LTM procedure that are to be cancelled, wherein the LTM procedure is a conditional LTM procedure,

wherein the list of candidate cells for the LTM procedure that are to be cancelled comprise at least one identification of the target cell.
The device of any of claims 1 to 12, wherein the first network device is further caused to:

transmit, to the second network device, configuration information comprising a reference signal (RS) configuration of the source cell, and/or further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with a third network device.
The device of claim 13, wherein the configuration information further comprises at least one of:

an identification of the source cell,

an identification of the candidate cell associated with the third network device,

an identification of a terminal device over an Xn interface associated with the first network device,

an identification of a terminal device over an Xn interface associated with the third network device,

an identification of a distributed unit (DU) of the first network device or third network device, or

a LTM candidate cell configuration.
The device of any of claims 1 to 14, wherein the first network device is further caused to:

receive, from a terminal device, capability information of a terminal device for the LTM procedure, wherein the capability information comprises at least one of:

a total number of candidate cells for network triggered inter-centralized unit (CU) and intra-CU LTM and conditional LTM procedures,

a total number of candidate cells for network triggered inter-CU LTM and intra-CU LTM procedures,

a total number of candidate cells for network triggered inter-CU LTM procedures, or

a total number of candidate cells for conditional LTM procedures.
The device of any of claims 1 to 15, wherein the LTM procedure comprises at least one of:

a network triggered LTM procedure, which is triggered by a LTM command Medium Access Control (MAC) Control Element (CE) , or

a conditional LTM procedure that is executed in response to that at least one LTM execution condition is met.
The device of any of claims 1 to 16, wherein the first network device comprises a first centralized unit (CU) and the second network device comprises a second CU other than the first CU, or

wherein the first network device comprises a first Next Generation Radio Access Network (NG-RAN) and the second network device comprises a second NG-RAN other than the first NG-RAN.
A second network device comprising:

a processor configured to cause the second network device to:

receive, from a first network device in a radio access network (RAN) , configuration request information about a Layer 1 or Layer 2 (L1/L2) triggered mobility (LTM) procedure for a cell switch from a source cell associated with the first network device to a target cell, the second network device being in the RAN and being associated with a candidate cell for the cell switch.
The device of claim 18, wherein the second network device is further caused to perform at least one of:

receive, from the first network device, configuration information comprising a reference signal (RS) configuration of the source cell associated with the first network device;

receive, from the first network device, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device; or

receive, from a third network device in the RAN, further configuration information comprising a reference signal (RS) configuration of a candidate cell associated with the third network device.
The device of claim 19, wherein the configuration information further comprises at least one of:

an identification of the source cell,

an identification of the candidate cell associated with the third network device,

an identification of a terminal device over an Xn interface associated with the first network device,

an identification of a terminal device over an Xn interface associated with the third network device,

an identification of a distributed unit (DU) of the first network device or third network device, or

a LTM candidate cell configuration.