Method and device for performing conditional switching in a wireless communication network

Abstract

Embodiments of the present invention disclose a method for performing conditional switching by a UE in a wireless communication network. The method may include receiving an RRC reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a switching configuration and determine whether a CHO configuration can be provided in the switching configuration. In addition, the method may include performing one of the following: in response to determining that a CHO configuration is provided in the switching configuration, continuing an RLM timer and an RLM process for the source cell; and in response to determining that a CHO configuration is not provided in the switching configuration, stopping the RLM timer and suspending a radio link monitoring process with respect to the source cell. Then, the method may include performing a CHO from the source cell to a candidate target cell based on the CHO configuration in the wireless communication network.

Description

Technical Field

[0001] The present disclosure relates to wireless communications, and more particularly, to a method and user equipment (UE) for performing conditional handover in a wireless communication network. Background Art

[0002] In order to meet the demand for wireless data services that has increased since the deployment of the fourth generation (4G) communication system, efforts have been made to develop improved fifth generation (5G) or pre-5G communication systems. 5G or pre-5G communication systems are also referred to as "super 4G networks" or "post-long term evolution (LTE) systems". 5G communication systems are considered to be implemented in higher frequency (mmWave) bands, such as the 60 GHz band, in order to achieve higher data rates. In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple input multiple output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large antenna technologies are discussed with respect to 5G communication systems. In addition, in 5G communication systems, system network improvements are being developed based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, mobile networks, collaborative communications, coordinated multi-point (CoMP), receiving-end interference elimination, etc. In 5G systems, hybrid frequency shift keying (FSK) and Ferndale quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) are developed as advanced coded modulation (ACM), and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) are developed as advanced access technologies.

[0003] The Internet, a human-centric connected network where humans generate and consume information, is now evolving into the Internet of Things (IoT), where distributed entities such as objects exchange and process information without human intervention. The Internet of Everything (IoE), which is the combination of IoT technology and big data processing technology through connection with cloud servers. Technology elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology" and "security technology" have recently been studied for IoT implementation, sensor networks, machine-to-machine (M2M) communication, machine-type communication (MTC), etc. This IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated between connected objects. Through the convergence and combination between existing information technology (IT) and various industrial applications, IT can be applied to various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart devices and advanced medical services.

[0004] In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, MTC, and M2M communications can be implemented through beamforming, MIMO, and array antennas. The application of cloud RAN, which is the above-mentioned big data processing technology, can also be considered an example of the fusion of 5G technology and IoT technology.

[0005] As described above, various services can be provided according to the development of wireless communication systems, and thus a method for easily providing such services is required. Summary of the invention

[0006] [Technical solution]

[0007] Therefore, the embodiments herein disclose a method for performing conditional switching by a UE (user equipment) in a wireless communication network. The method may include receiving an RRC (radio resource control) reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a switching configuration, and determine whether a conditional switching configuration may be provided in the switching configuration. The conditional switching configuration may include multiple conditions and multiple target cell configurations for performing conditional switching. In addition, the method may include performing one of the following: in response to determining that a conditional switching configuration is provided in the switching configuration, continuing an RLM (radio link monitoring) timer and an RLM process for the source cell; and in response to determining that a conditional switching configuration is not provided in the switching configuration, stopping the RLM timer and suspending the radio link monitoring process with respect to the source cell. Then, the method may include performing a conditional switching from a source cell in multiple target cells to a candidate target cell in the wireless communication network based on the conditional switching configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts:

[0009] Figure 1A A system for performing conditional handover in a wireless communication network according to embodiments disclosed herein is shown;

[0010] Figure 1B A block diagram of a user equipment (UE) for performing conditional handover in a wireless communication network according to embodiments disclosed herein is shown;

[0011] Figure 2A A flow chart of a method for performing conditional handover by a UE in a wireless communication network according to an embodiment disclosed herein is shown;

[0012] Figure 2B A flowchart of a method for triggering an RRC state transition indication by a UE in a wireless communication network according to an embodiment disclosed herein is shown;

[0013] Figure 3A A signaling diagram illustrating immediate suspension of a Radio Link Monitoring (RLM) timer upon receipt of a Handover Command (HO) according to embodiments disclosed herein;

[0014] Figure 3B A signaling diagram showing the continuation of the RLM timer for the source cell until the HO is performed based on the conditional handover configuration provided in the HO command according to the embodiments disclosed herein;

[0015] Figure 4 shows a flow chart of RLM monitoring during HO execution according to embodiments disclosed herein;

[0016] Figure 5A shows a signaling diagram for active neighbor cell preparation for reestablishment according to embodiments disclosed herein;

[0017] Figure 5B shows a signaling diagram for target cell preparation for HO execution according to the embodiments disclosed herein;

[0018] Figure 6 A flow chart showing a cell selection priority (order) when attempting re-establishment according to an embodiment disclosed herein;

[0019] Fig. 7A A signaling diagram illustrating a method of performing a UE controlled RRC_CONNECTED to RRC_INACTIVE state transition with respect to a configured threshold according to an embodiment disclosed herein;

[0020] Figure 7B A signaling diagram illustrating a method for performing a UE controlled RRC_CONNECTED to RRC_INACTIVE state transition with respect to a configured timer according to an embodiment disclosed herein;

[0021] Figure 7C A signaling diagram showing a method for performing a UE autonomous RRC_CONNECTED to RRC_IDLE state transition with respect to a configured timer according to an embodiment disclosed herein;

[0022] Figure 8 shows a gNB according to the embodiments disclosed herein; and

[0023] Fig. 9 A user equipment (UE) according to embodiments disclosed herein is shown. DETAILED DESCRIPTION

[0024] Therefore, the embodiments herein disclose a method for performing conditional switching by a UE in a wireless communication network. The method may include receiving an RRC reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a switching configuration. The method may also include determining whether a CHO configuration is provided in the switching configuration. The CHO configuration may include multiple conditions and multiple target cell configurations for performing CHO. In addition, the method may include performing one of the following: in response to determining that a CHO configuration is provided in the switching configuration, continuing an RLM timer and an RLM process for the source cell; and in response to determining that a CHO configuration is not provided in the switching configuration, stopping the RLM timer and suspending the radio link monitoring process for the source cell. Then, the method may include performing CHO from the source cell to a candidate target cell in a plurality of target cells in the wireless communication network based on the CHO configuration.

[0025] In one embodiment, CHO from a source cell to a candidate target cell among multiple target cells performed by a UE in a wireless communication network based on a CHO configuration may include determining that a condition for performing CHO from the source cell to the candidate target cell is met; suspending an RLM timer and a radio link monitoring process of the source cell; and performing a conditional switching from the source cell to the candidate target cell in the wireless communication network based on a candidate target cell configuration among the multiple target cell configurations.

[0026] In one embodiment, the CHO configuration may include conditions for performing CHO for a candidate target cell and a candidate target cell configuration.

[0027] In one embodiment, multiple target cell configurations may be carried as an OCTET string in the RRC reconfiguration message.

[0028] In one embodiment, the CHO configuration may be an incremental configuration of the current source cell configuration.

[0029] In one embodiment, multiple target cell configurations in a CHO configuration cannot be changed by the source cell.

[0030] In one embodiment, the conditions for performing CHO may be determined by the source cell and appended to the CHO configuration.

[0031] In one embodiment, the RLM timer may be a T310 timer.

[0032] Therefore, embodiments herein disclose a user equipment (UE) for performing conditional switching in a wireless communication network. The UE may include a transceiver, a memory, and at least one processor. At least one processor may be configured to control the transceiver to receive an RRC reconfiguration message from a source cell of the wireless communication network, wherein the UE is in an RRC connected state and wherein the RRC reconfiguration message includes a switching configuration. At least one processor may be further configured to determine whether a conditional switching (CHO) configuration is provided in the switching configuration, wherein the CHO configuration may include multiple conditions and multiple target cell configurations for performing CHO. In addition, at least one processor may also be configured to perform one of the following operations: in response to determining that a CHO configuration is provided in the switching configuration, continuing a radio link monitoring (RLM) timer and a radio link monitoring process with respect to the source cell; and in response to determining that a CHO configuration is not provided in the switching configuration, stopping the RLM timer and suspending the radio link monitoring process with respect to the source cell. In addition, at least one processor may also be configured to perform CHO from a source cell to a candidate target cell in a plurality of target cells in the wireless communication network based on the CHO configuration.

[0033] Therefore, embodiments herein disclose a method for triggering an RRC state transition indication by a UE in a wireless communication network. The method includes receiving, by the UE, a radio resource control (RRC) reconfiguration message from the wireless communication network, wherein the RRC reconfiguration message includes a configuration setting. In addition, the method includes enabling, by the UE, a capability to trigger an RRC state transition indication to the wireless communication network based on the configuration setting, and determining, by the UE, a condition that satisfies the triggering of the RRC state transition indication to the wireless communication network. In addition, the method includes triggering, by the UE, an RRC state transition indication by sending a UE assistance information message to the wireless communication network.

[0034] Therefore, embodiments herein disclose a user equipment (UE) for triggering an RRC state transition indication in a wireless communication network. The UE includes a communicator, a memory, and a processor. The communicator is configured to receive a radio resource control (RRC) reconfiguration message from the wireless communication network, wherein the UE is in an RRC_CONNECTED state, and wherein the RRC reconfiguration message includes a configuration setting. The processor is configured to enable the ability to trigger an RRC state transition indication to the wireless communication network based on the configuration setting. In addition, the processor is further configured to determine a condition for triggering an RRC state transition indication to the wireless communication network; and trigger the RRC state transition indication by sending a UE assistance information message to the wireless communication network.

[0035] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and accompanying drawings. However, it should be understood that the following description, although indicating preferred embodiments and many of their specific details, is provided by way of illustration and not limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit of the present invention, and the embodiments herein include all such modifications.

[0036] A primary object of the embodiments herein is to provide a method and UE for performing conditional handover in a wireless communication network.

[0037] Another object of embodiments herein is to receive an RRC reconfiguration message including a handover configuration from a source cell of a wireless communication network.

[0038] Another object of embodiments herein is to determine a CHO configuration including a plurality of conditions for performing CHO and a plurality of target cell configurations provided in a handover configuration.

[0039] Another object of the embodiments herein is to continue the RLM timer and the radio link monitoring process for the source cell in response to determining that a CHO configuration is provided in the handover configuration. And in response to determining that a CHO configuration is not provided in the handover configuration, stop the RLM timer and suspend the radio link monitoring process for the source cell.

[0040] Another object of embodiments herein is to perform CHO from a source cell to a candidate target cell among a plurality of target cells in a wireless communication network based on a CHO configuration.

[0041] It is another object of embodiments herein to suspend the RLM timer and the radio link monitoring procedure with respect to the source cell when conditions for performing CHO from the source cell to the candidate target cell are met.

[0042] Another object of embodiments herein is to cause a UE to send an RRC state transition indication to a wireless communication network based on configuration settings received in an RRC reconfiguration message.

[0043] Another object of embodiments herein is to determine that at least one condition for triggering an RRC state transition indication to a wireless communication network is met.

[0044] Another object of the embodiments herein is to trigger an RRC state transition indication by sending a UE assistance information message to a wireless communication network.

[0045] Another object of the embodiments herein is to append the UE's preferred RRC state in the UE assistance information message.

[0046] Before proceeding to the following detailed description, it may be helpful to set forth definitions of certain words and phrases used in this patent document: the terms "include" and "comprising" and their derivatives mean including but not limited to; the term "or" is inclusive, referring to and / or; the phrases "associated with" and "associated with" and their derivatives may mean including, included within, interconnected with, containing, contained within, connected to or connected with, coupled to or coupled with, communicable with, cooperating with, interleaved, juxtaposed, adjacent, bound to or bound with, having, having a property, etc.; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such device may be implemented in hardware, firmware, or software, or a combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0047] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and is contained in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data, or parts thereof suitable for implementation in appropriate computer-readable program codes. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable media excludes wired, wireless, optical or other communication links that transmit temporary electrical signals or other signals. A non-transitory computer-readable medium includes a medium that can permanently store data, and a medium that can store data and then rewrite data, such as a rewritable optical disc or an erasable storage device.

[0048] Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to past, as well as future uses of such defined words and phrases.

[0049] Invented Pattern

[0050] Discussed below Figures 1A to 9 The various embodiments used to describe the principles of the present disclosure in this patent document are merely exemplary and should not be interpreted in any way to limit the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present invention can be implemented in any suitably arranged system or device.

[0051] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present invention as defined by the claims and their equivalents. It includes various specific details to assist in understanding, but these are considered to be exemplary only. Therefore, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and structures may be omitted for clarity and brevity.

[0052] The term "connection" and its derivatives refer to any direct or indirect communication between two or more elements, whether or not these elements are in physical contact with each other. The terms "send", "receive" and "communication" and their derivatives include direct and indirect communication. The terms "include" and "comprise" and their derivatives mean to include without limitation. The term "or" is inclusive, meaning and / or. The phrase "associated with" and its derivatives mean to include, be included in, be interconnected with, include, be included in, be connected to or be connected with, be connected to or be connected with, be able to communicate with, collaborate with, interweave, and, be close to, be bound to or be bound with, have, have the characteristics of, have a relationship with, etc. The term "processor" or "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of," when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0053] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and is contained in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data, or parts suitable for implementation in appropriate computer-readable program codes. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable media does not include wired, wireless, optical or other communication links that transmit temporary electrical signals or other signals. A non-transitory computer-readable medium includes a medium that can permanently store data, and a medium that can store data and then rewrite data, such as a rewritable optical disc or an erasable storage device.

[0054] For this specification, the terms wireless communication network and network can be used interchangeably throughout the specification and mean one and the same meaning. The terms source cell and source node can be used interchangeably throughout the specification and mean one and the same meaning. The terms "target cell" and "target node" can be used interchangeably throughout the specification and mean one and the same meaning.

[0055] Definitions for certain other words and phrases are provided throughout this disclosure. Those skilled in the art should understand that in many, if not most, instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0056] Aspects, features and advantages of the present disclosure will become apparent from the following detailed description simply by illustrating a number of specific embodiments and implementations including the best mode contemplated for carrying out the present disclosure. The present disclosure is also capable of other and different embodiments, and its several details may be modified in various obvious respects, all without departing from the spirit and scope of the present disclosure. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive. The present disclosure is shown by way of example and not by way of limitation in the figures of the accompanying drawings.

[0057] In order to meet the demand for increased wireless data services since the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also called "super 4G networks" or "post-LTE systems."

[0058] 5G communication systems are considered to be implemented in higher frequency (mmWave) bands, such as the 60 GHz band, in order to achieve higher data rates. In order to reduce the propagation loss of radio waves and increase transmission coverage, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, large antenna technology, etc. are discussed in 5G communication systems.

[0059] In addition, in the 5G communication system, system network improvements are being developed based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul communication, mobile networks, collaborative communications, coordinated multi-point (CoMP) transmission and reception, interference mitigation and elimination, etc.

[0060] In the 5G system, hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) are used as adaptive modulation and coding (AMC) technologies, filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) are used as advanced access technologies.

[0061] Generally, as the number of users of wireless communication networks increases, the need to provide uninterrupted and high quality services to users is of great importance to the telecommunications industry.

[0062] A wireless communication network supports communication for multiple user equipments (UEs). Each UE communicates with one or more base stations via transmissions on a forward link and a reverse link. The forward link (or downlink) refers to the radio link from the base station to the UE, while the reverse link (or uplink) refers to the radio link from the UE to the base station. In a wireless communication network, radio link monitoring (RLM) is a mechanism by which the UE monitors the quality of the downlink (DL) to determine if the radio link is good enough to continue transmission.

[0063] The base station of the source cell where the UE is currently located contributes to the communication of the UE. Due to the movement, the UE may enter a coverage area associated with another base station, which may be able to better serve the UE. However, the UE needs to perform a handover process from the base station serving the source cell to the new base station. In the traditional mobile process, when the UE receives a handover command, the UE suspends radio link monitoring (i.e., stops the RLM timer T310). In addition, when the handover command is received from the wireless communication network, the handover process to the target cell is immediately initiated. One aspect of improved mobile robustness during the handover process is conditional handover (CHO), which is agreed to be supported on both long-term evolution (LTE) and new radio (NR). In the CHO scenario, the candidate cell (or potential target cell) is configured to the UE using the CHO configuration received as part of the handover command, and then the CHO execution is initiated based on the condition that the UE meets the network configuration. Unlike the traditional handover process, the UE in CHO does not immediately perform a handover execution when receiving a handover command from the wireless communication network. Therefore, if RLM is suspended (or if T310 is running, if T310 is stopped), the UE may be forced to be locked to a weak cell and cannot recover, thus becoming inefficient. However, during CHO execution, the UE continues to receive signals from the source cell based on radio / RF capabilities. If RLM is performed during the CHO execution time (e.g., if T310 is not stopped, if T310 is running), the UE encounters a radio link failure (RLF) in the wireless communication network.

[0064] Another aspect of the UE that needs to be addressed in order to achieve higher efficiency is to reduce the power consumption of the UE. The reduction of the power consumption of the UE is achieved by using mechanisms such as discontinuous reception (DRX), overheat assistance, etc. In LTE systems, the UE is configured to send a power preference indication (PPI), which has a very general purpose of being interpreted by the wireless communication network as the UE requesting to optimize power consumption. However, the situation in which the UE transitions from the radio resource control (RRC) connected state to one of the RRC idle state or the RRC inactive state is based on the judgment of the wireless communication network. There is no feedback from the UE, and therefore the UE is more likely to increase power consumption and inefficient power consumption.

[0065] According to the existing standard specifications, there is no mechanism by which the UE can indicate to the wireless communication network that the radio resource control (RRC) connection can be released, thereby reducing possible power consumption. Even if there is no data transmission with the UE, the wireless communication network still maintains the RRC connection for the duration of the inactivity timer. The inactivity timer is not defined in the existing standard specifications, but is maintained by the wireless communication network according to implementation-specific parameters. However, all wireless communication networks use the inactivity timer and do not release the RRC connection immediately to ensure that there are no frequent requests for the RRC connection from the UE, resulting in unnecessary power consumption.

[0066] Therefore, an embodiment herein discloses a method for performing conditional handover by a UE in a wireless communication network. The method may include receiving an RRC reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a handover configuration, and determine whether a conditional handover (CHO) configuration is provided in the handover configuration. The CHO configuration may include multiple conditions for performing CHO and multiple target cell configurations. In addition, the method may include performing one of the following: in response to determining that a CHO configuration is provided in the handover configuration, continuing an RLM timer (180) and an RLM process for the source cell; and in response to determining that a CHO configuration is not provided in the handover configuration, stopping the RLM timer and suspending a radio link monitoring process for the source cell. The method may then include performing a CHO from the source cell to a candidate target cell among multiple target cells in the wireless communication network based on the CHO configuration.

[0067] Referring now to the drawings, and more particularly to the drawings Figures 1A to 7C Preferred embodiments are shown, with like reference numerals indicating corresponding features throughout the drawings.

[0068] Figure 1A A system for performing conditional handover (CHO) in a wireless communication network according to embodiments disclosed herein is shown.

[0069] Reference Figure 1A, a system for performing CHO in a wireless communication network may include a UE (100), a source gNB (1000a) of a source cell within range of the UE (100), a target gNB (1000b) of a candidate target cell, and a plurality of target cells. The UE (100) may be mobile and may be in an RRC connected state with the source gNB. Due to mobility, the UE (100) may be closer to a coverage area associated with a candidate target cell that provides better signal strength, and the UE (100) needs to perform a handover from the source gNB (1000a) to the target gNB (1000b). Radio link monitoring (RLM) may be a continuous process performed by the UE (100) to monitor the quality of a downlink (DL) to continue transmission. The UE (100) may be instructed to perform a handover by sending an RRC reconfiguration message from the source cell.

[0070] Unlike conventional methods and systems, in the proposed method, the UE (100) may not initiate a handover procedure / CHO immediately upon receiving a handover command from the wireless communication network. In addition, the UE (100) may not suspend the RLM procedure for the source cell (i.e., the RLM timer T310 is not stopped), and thus continue to lock onto the source cell even when a handover procedure is initiated.

[0071] Therefore, the UE (100) may not be forced to be locked to a weak cell without providing better efficiency. In addition, in the proposed method, during CHO execution, the UE (100) may suspend RLM during the CHO execution time (i.e., if the RLM timer T310 is running, stop the RLM timer T310), which ensures that the UE (100) does not encounter a radio link failure (RLF) in the wireless communication network.

[0072] Figure 1B A block diagram of a UE (100) for performing CHO in a wireless communication network according to embodiments disclosed herein is shown.

[0073] Reference Figure 1B , the UE (100) may be, for example, a mobile phone, a smart phone, a personal digital assistant (PDA), a tablet computer, a wearable device, etc. In one embodiment, the UE (100) may include a communicator (120), a memory (140), a processor (160), and an RLM timer (180). The UE (100) may be in an RRC connected state.

[0074] In one embodiment, the processor (160) may include one or more processors or other processing devices that control the proposed functions, processes and / or methods. The operations of the UE 100 may be implemented by the processor (160).

[0075] In one embodiment, the communicator (120) may be configured to receive a radio resource control (RRC) reconfiguration message from a source cell of the wireless communication network. The RRC reconfiguration message may include a handover configuration. The handover configuration may be a set of instructions for configuring parameters and settings of the UE (100) to enable the UE (100) to perform a handover from the source cell to the target cell. In addition, the handover configuration may also include a target cell configuration that the UE (100) will apply to the candidate target cell once the handover process is successfully completed.

[0076] In another embodiment, the communicator (120) may be further configured to receive an RRC reconfiguration message including a configuration setting. Without the configuration setting, the UE (100) may not be able to send a state transition indication to the wireless communication network. The configuration setting may include information indicating to the UE (100) that the UE (100) is allowed to send a state transition request to the wireless communication network.

[0077] The memory (140) may include a non-volatile storage element. Examples of such non-volatile storage elements may include a magnetic hard disk, an optical disk, a floppy disk, a flash memory, or an electrically programmable memory (EPROM) or an electrically erasable programmable (EEPROM) memory. In addition, in some examples, the memory (140) may be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not implemented in a carrier or propagating signal. However, the term "non-transitory" should not be interpreted as the memory (140) being non-removable. In some instances, the memory (140) may be configured to store a larger amount of information than the memory. In some instances, the non-transitory storage medium may store data that may change over time (e.g., in a random access memory (RAM) or a cache memory).

[0078] In one embodiment, the processor (160) may include a CHO determination engine (162), an RLM management engine (164), a HO management engine (166), an RRC state transition management engine (168), a timer management engine (170), and a UE assistance information message management engine (172).

[0079] In one embodiment, the CHO determination engine (162) may be configured to determine that a conditional handover (CHO) configuration is provided in the handover configuration. The CHO configuration may include multiple conditions for performing CHO and multiple target cell configurations associated with multiple target cells. The multiple target cell configurations may be carried as an OCTET string in the RRC reconfiguration message. The CHO configuration may be an incremental configuration that details the changes required for the current source cell configuration in order to configure the target cell and perform the handover, that is, the target cell configuration is a combination of the current source configuration and the incremental configuration included in the CHO configuration. However, the source cell cannot change the multiple target cell configurations in the CHO configuration.

[0080] In one embodiment, the RLM management engine (164) can be configured to determine that when a CHO configuration is provided in the handover configuration, the radio link monitoring (RLM) timer (180) and the radio link monitoring process for the source cell are continued. The RLM management engine (164) can be configured to determine that when a CHO configuration is not provided in the handover configuration, the RLM timer (180) is stopped and the radio link monitoring process for the source cell is suspended. The RLM timer (180) can be a T310 timer. In addition, the RLM management engine (164) can receive an indication to suspend the RLM timer (180) and the radio link monitoring process for the source cell from the HO management engine (166) when the conditions for performing CHO are met, and suspend the RLM timer (180) and the radio link monitoring process for the source cell.

[0081] In one embodiment, the HO management engine (166) may be configured to determine conditions for performing CHO from a source cell to a candidate target cell among a plurality of target cells, and determine that the conditions for performing CHO are met. The conditions for performing CHO may be determined by the source cell and attached to the CHO configuration.

[0082] In addition, the HO management engine (166) can be configured to instruct the RLM management engine (164) to suspend the RLM timer (180) and the radio link monitoring process for the source cell, and perform a CHO from the source cell to the candidate target cell in the wireless communication network based on the candidate target cell configuration.

[0083] In one embodiment, the RRC state transition management engine (168) can be configured to enable the ability to trigger an RRC state transition indication to a wireless communication network. The ability can be enabled by activating a condition that triggers an RRC state transition indication based on an RRC reconfiguration message, which enables the ability to send UE assistance information for indicating an RRC state transition. The condition can be one of a timer-based threshold and a counter-based threshold. In addition, the state transition management engine (168) can be configured to determine that at least one condition for triggering an RRC state transition indication to the wireless communication network is met. The activation condition based on the timer threshold can be one of the following: determining that the UE (100) is explicitly configured with a dataInactivityTimer; when the UE (100) is not explicitly configured with a dataInactivityTimer, configuring an inactiveIndicationTimer; and determining the threshold condition as one of the following percentages of time: the dataInactiveTimer and the inactiveIndicationTimer are met while the timers are running. The counter threshold based activation condition may include determining that a drxInactivityTimer has not been started at least once upon the triggering condition and that no transmission or reception has occurred between the UE (100) and the wireless communication network for a configured number of DRX cycles, wherein the drxInactivityTimer is part of the RRC_CONNECTED state DRX cycle configuration.

[0084] When the UE (100) is not explicitly configured with a dataInactivityTimer, the configuration of the inactiveIndicationTimer may include determining that the UE (100) is not explicitly configured with a dataInactivityTimer by the wireless communication network, and configuring the UE (100) with an inactiveIndicationTimer by the UE (100). One of the following conditions: starting an inactiveIndicationTimer and restarting the inactiveIndicationTimer may be the same as one of the following conditions: starting a dataInactiveTimer and restarting the dataInactiveTimer.

[0085] Furthermore, the state transition management engine (168) may be configured to switch from the RRC_CONNECTED state to one of the RRC IDLE state and the RRC INACTIVE state based on an RRL release message received from the wireless communication network.

[0086] In one embodiment, the UE assistance information message management engine (170) may be configured to determine whether a preferred RRC state for the UE (100) to switch from the RRC_CONNECTED state is available. In addition, when it is determined that the preferred RRC state of the UE (100) to switch from the RRC_CONNECTED state is available, the UE assistance information message management engine (170) may be configured to attach the preferred RRC state of the UE (100) to a UE assistance information message, which is then sent to the wireless communication network. When the preferred RRC state of the UE (100) is indicated in the UE assistance information, the preferred RRC transition state may be an RRC_INACTIVE state. When it is determined that the preferred RRC state for the UE (100) to switch from the RRC_CONNECTED state is not available, the UE assistance information message management engine (170) may be configured to send the UE assistance information message to the wireless communication network without the preferred RRC state of the UE (100). When the preferred RRC state of the UE (100) is not indicated in the UE assistance information, the state transition may indicate one of the RRC_INACTIVE state and the RRC_IDLE state. The UE assistance information may be an indication to the wireless communication network to trigger a state transition from the RRC connected state.

[0087] although Figure 1B The hardware elements of UE (100) are shown, but it should be understood that other embodiments are not limited thereto. In other embodiments, UE (100) may include fewer or more elements. In addition, the markings or names of the elements are only for illustrative purposes and do not limit the scope of the present disclosure. One or more components may be combined together to perform the same or substantially similar functions.

[0088] Figure 2A A flowchart 200a is shown of a method for a UE to perform CHO in a wireless communication network according to an embodiment disclosed herein.

[0089] Reference Figure 2A In step 202a, the UE may receive an RRC reconfiguration message from a source cell of the wireless communication network. Figure 1B In the illustrated UE (100), the communicator (120) may be configured to receive an RRC reconfiguration message from a source cell of the wireless communication network.

[0090] In step 204a, the UE may determine whether a conditional handover (CHO) configuration is provided in the handover configuration. Figure 1B In the illustrated UE (100), the processor (160) may be configured to determine that a conditional handover (CHO) configuration is provided in the handover configuration.

[0091] In step 206a, in response to determining that a CHO configuration is provided in the handover configuration, the UE may continue a radio link monitoring (RLM) timer and a radio link monitoring process for the source cell. Figure 1B In the illustrated UE (100), the processor (160) may be configured to, in response to determining that a CHO configuration is provided in a handover configuration, continue a radio link monitoring (RLM) timer and a radio link monitoring procedure for a source cell.

[0092] In step 208a, in response to determining that the CHO configuration is not provided in the handover configuration, the UE may stop a radio link monitoring (RLM) timer and suspend the radio link monitoring process for the source cell. Figure 1B In the UE (100) shown, the processor (160) may be configured to, in response to determining that no CHO configuration is provided in the handover configuration, stop a radio link monitoring (RLM) timer (180) and suspend a radio link monitoring process for a source cell.

[0093] In step 210a, the UE may meet the conditions for determining to perform CHO from the source cell to the candidate target cell. Figure 1B In the illustrated UE (100), the processor (160) may be configured to determine whether a condition for performing a CHO from a source cell to a candidate target cell is satisfied.

[0094] At step 212a, the UE may suspend the RLM timer (180) and the radio link monitoring process of the source cell. Figure 1B In the illustrated UE (100), the processor (160) may be configured to suspend the RLM timer (180) and the radio link monitoring process for the source cell.

[0095] At step 214a, the UE may perform a CHO from the source cell to the candidate target cell in the wireless communication network based on the candidate target cell configuration in the plurality of target cell configurations. Figure 1B In the UE (100) shown in FIG. 1 , the processor (160) may be configured to perform CHO from a source cell to a candidate target cell in a wireless communication network based on a candidate target cell configuration among a plurality of target cell configurations.

[0096] The various actions, behaviors, blocks, steps, etc. in the method may be performed in the order presented, in a different order, or simultaneously. In addition, in some embodiments, some of the actions, behaviors, blocks, steps, etc. may be omitted, added, modified, skipped, etc. without departing from the scope of the present invention.

[0097] Figure 2BA flowchart 200b is shown of a method for triggering an RRC state transition indication by a UE (100) in a wireless communication network according to an embodiment disclosed herein.

[0098] Reference Figure 2B In step 202b, the UE may receive a radio resource control (RRC) reconfiguration message from the wireless communication network. Figure 1B The communicator (120) of the illustrated UE (100) is configured to receive a radio resource control (RRC) reconfiguration message from a wireless communication network.

[0099] At step 204b, the UE can send an RRC state transition indication to the wireless communication network based on the configuration settings received in the RRC reconfiguration message. Figure 1B The processor (160) of the illustrated UE is configured to enable the UE (100) to send an RRC state transition indication to a wireless communication network based on configuration settings received in an RRC reconfiguration message.

[0100] In step 206b, the UE may determine that at least one condition for triggering an RRC state transition indication to the wireless communication network is satisfied. Figure 1B The processor (160) of the illustrated UE (100) is configured to determine that at least one condition for triggering an RRC state transition indication to a wireless communication network is satisfied.

[0101] At step 208b, the UE may determine whether a preferred RRC state for the UE (100) to switch from the RRC_CONNECTED state is available. Figure 1B The processor (160) of the illustrated UE (100) is configured to determine whether a preferred RRC state to which the UE (100) switches from the RRC_CONNECTED state is available.

[0102] In step 210b, in response to determining that the preferred RRC state for the UE to switch from the RRC_CONNECTED state is available, the UE may attach the preferred RRC state of the UE in the UE assistance information message. Figure 1B The processor (160) of the illustrated UE (100) is configured to append the preferred RRC state of the UE (100) to a UE assistance information message.

[0103] In step 212b, the UE may trigger an RRC state transition indication by sending a UE assistance information message to the wireless communication network. Figure 1B The processor (160) of the illustrated UE (100) is configured to trigger an RRC state transition indication by sending a UE assistance information message to a wireless communication network.

[0104] In response to determining at step 208b that the preferred RRC state to which the UE switches from the RRC_CONNECTED state is not available, the UE may loop to step 212b.

[0105] The various actions, behaviors, blocks, steps, etc. in the method may be performed in the order presented, in a different order, or simultaneously. In addition, in some embodiments, some of the actions, behaviors, blocks, steps, etc. may be omitted, added, modified, skipped, etc. without departing from the scope of the present invention.

[0106] Figure 3A A signaling diagram showing a UE (100) suspending the RLM timer (180) immediately upon receiving a handover (HO) command according to embodiments disclosed herein.

[0107] Reference Figure 3A ,In step 302a, consider that the UE (100) is in an RRC connected state with the source gNB (1000a). In the RRC connected state, in step 304a, the source gNB (1000a) sends a measurement configuration to the UE (100). In addition, in step 306a, the UE (100) sends a measurement report to the source gNB (1000a). The measurement report includes the current configuration associated with the UE (100). The UE (100) performs RLM by estimating the downlink radio link quality and compares the downlink radio link quality with a preset threshold Qout for monitoring the downlink radio link quality of the source cell (PSCell) to detect a radio link failure (RLF). The predetermined threshold Qout is defined as the level at which the downlink radio link cannot be reliably received and should correspond to the out-of-sync block error rate (BLERout).

[0108] In addition, the UE (100) measures a block error rate (BLER) of a physical downlink control channel (PDCCH) during a predetermined time period. In addition, at step 308a, the UE (100) determines that the BLER during the predetermined time period drops below a preset threshold (Qout), and generates an out-of-sync indication in a physical (PHY) layer. When a preset N310 consecutive out-of-sync indications are reported from the PHY layer to the RRC layer, an RLM timer (180) is initiated by the RRC layer (step 310a).

[0109] At step 312a, the source gNB (1000a) sends an RRCReconfiguration message to the UE (100). In conventional methods and systems, the UE (100) in response to receiving the RRC reconfiguration message, stops the RLM timer (180) from starting at step 314a, and suspends the RLM process at step 316a. In addition, at step 318a, the UE (100) performs a handover from the source cell to the target cell, and at step 320a, sends a reconfiguration complete message to the target gNB (1000b).

[0110] However, the signaling in the CHO scenario may be similar to the signaling in the HO scenario with some changes. The HO signaling for the CHO scenario may include some restrictions, such as:

[0111] 1) Whether candidate target cells controlled by different target nodes are supported (this may affect radio signaling)

[0112] 2) Whether candidate target cells on different carrier frequencies / MOs are supported (this may affect the CHO configuration provided for the candidate)

[0113] 3) Whether the same handover configuration parameters can be signaled by the target node at the time of CHO preparation. In addition, the CHO configuration may only include the most basic parameters that need to be updated in the source cell configuration.

[0114] To implement CHO, configuration parameters are typically configured by the source node (source cell) and the target node (target cell) at CHO configuration time (i.e., in signaling to the UE (100)) and are assumed to be known.

[0115] 1) The source node controls the CHO candidates to be configured, so the source node sets:

[0116] CHO condition, i.e., A3 or A5 based (might only need to indicate an offset based on measurement conditions to add CHO candidates)

[0117] b) A validity timer, ie, the UE (100) releases the CHO configuration when the timer expires (ie, the source node manages multiple CHO candidates but may not always successfully release at least one of the multiple CHO candidates).

[0118] Furthermore, at least for the CHO condition, the UE (100) should be allowed to set different values ​​for each CHO candidate.

[0119] 2) The target node sets the configuration to be used when the UE (100) moves from initial access to CHO. However, some important considerations regarding the configuration of the target node include:

[0120] A.reconfigurationWithSync is the most basic configuration parameter, especially:

[0121] a) Contention-free random access (CFRA) resource based (e.g. for all wide / cell specific beams with a given delay between CHO configuration and execution)

[0122] b) PCell (dedicated and universal) configuration

[0123] c) T304 (to protect the actual CHO execution phase, i.e., starts after the CHO condition is fulfilled)

[0124] B. The network may include other configurations, such as: radioBearerConfig, RLC bearerConfig, MACconfig, measConfig. However, to avoid the need for reconfiguration, the network may only include the most essential parameters in the CHO configuration. Configurations that are not essential may be temporarily suspended / deactivated and then resumed / reactivated at the first subsequent reconfiguration (i.e., when the network can be modified).

[0125] a) measConfig may need to be changed, i.e., continue to measure on the new primary frequency (for the case of inter-frequency CHO).

[0126] If multiple CHO candidates are configured, other configurations may not be the same for all candidates, ie, for example, when the candidates are on different frequencies (different measConfig) or controlled by different target nodes (with different capabilities / typical settings).

[0127] C. The CHO configuration is assumed to be a delta configuration compared to the existing source configuration (ie, the source configuration used at the time of the CHO configuration).

[0128] Additionally, after initiating the CHO configuration, the source node should be able to modify the source configuration to:

[0129] I. Some reconfigurations cannot be postponed. For example, adding QoS flows or DRBs when activating a service with specific QoS requirements

[0130] II. Some source reconfigurations affect the configuration to be used after CHO is performed, for example, if new QoS flows or DRBs are added, they should continue after the CHO configuration, i.e., affect the CHO configuration.

[0131] Therefore, the specification changes of CHO can be limited in the existing methods and systems.

[0132] In the proposed method, the basic starting point for performing conditional switching can be as follows:

[0133] a) (At least) the source node sets the CHO condition, and the source node should be able to configure different values ​​for different candidates.

[0134] b) Determine whether the CHO target cell configuration should override parameters other than reconfigurationWithSync, such as, for example: MeasConfig, radioBearerConfig and / or L2 Config instead of the cell-specific L1Config. In addition, in the case where the CHO target cell configuration should override the above parameters, determine whether the target node should be able to set different values ​​for the configuration parts of different CHO candidates.

[0135] When source reconfiguration affects CHO configuration, the method for signaling the configuration change may require that the source node should be able to modify the source configuration after initiating CHO configuration, and in some cases, modify the configuration to be used in CHO candidates after CHO execution is affected.

[0136] Consider the case where the source node initiates a configuration change that should continue after CHO execution (i.e., for example, adding a QoS flow or DRB). As mentioned before, we assume that the CHO configuration is indicated by signaling a delta compared to the existing source configuration (i.e., at the time of CHO configuration). To ensure that changes to the source cell configuration continue after CHO execution, the source node can indicate the target cell of CHO by signaling:

[0137] NΔ compared to the updated source cell configuration

[0138] BΔ compared to previous CHO configuration

[0139] Option a) is the simplest since the source cell configuration is the same as used in the initial CHO configuration.

[0140] Furthermore, another question is whether the changes of the source cell configuration and the target cell configuration should be signaled together (i.e. in the same message) or can be signaled separately (i.e. in different messages):

[0141] 1) When signaling a change in source cell configuration and target cell configuration together:

[0142] a) The change will jointly succeed / fail (+)

[0143] b) Some method will be needed to distinguish which part of the configuration refers to the source CHO configuration and which part refers to the target CHO configuration

[0144] 2) When signaling changes to the source cell configuration and the target cell configuration respectively:

[0145] a) There may be a collision problem, i.e., the UE (100) performs a CHO between two messages. This may apply even if the two messages are sent together (when processing is done sequentially).

[0146] In one embodiment of the proposed method, the CHO configuration may be indicated by signaling a delta compared to the current source configuration (ie, at initial setup and reconfiguration of the CHO configuration).

[0147] In another embodiment, conditional handover may support simultaneous reconfiguration of the source cell and CHO configuration, ie, together within the same message.

[0148] Furthermore, another issue is how to signal the source cell configuration and the target cell configuration parts, i.e., using containers / fields for example. Typically, both the source cell and the target cell generate some configuration parameters to be provided to the UE (100). There are different ways to signal configuration parameters to the UE (100), for example:

[0149] A. You can use regular reconfiguration messages, including parameters generated by the source and target nodes; that is:

[0150] A1: The source node can forward the parameters generated by the source node to the target node, which generates a Uu message including these source control parameters

[0151] A2: The source node can decode the message generated by the target and add parameters

[0152] B. A container may be added to the reconfiguration message, ie for carrying the configuration generated by the target node (similar to the case of Inter Radio Access Technology Handover (IRAT HO)).

[0153] B.1: Octet strings / containers can carry reconfiguration messages

[0154] B.2: An octet string / container may carry an IE that includes a subset of the fields of the reconfiguration message.

[0155] Furthermore, when a container is added to the reconfiguration message, it is easier to support signaling changes to the source cell configuration and the CHO candidate configuration together. Furthermore, the fields related to the CHO configuration are clearly defined. However, when conventional reconfiguration messages are used to signal configuration parameters to the UE (100), the process is not straightforward. For example, specific fields for the CHO candidate configuration may need to be introduced, such as separate spCellConfig, measConfig. Furthermore, the use of conventional reconfiguration messages may require specifying fields that the target cell may set / change as part of the CHO configuration, i.e., it limits network implementation.

[0156] Option B.1 is preferred and avoids the need to discuss details about which fields can be set as part of the CHO configuration, and therefore in the proposed approach, an octet string / container is added to the reconfiguration message to carry the CHO configuration generated by the target node (similar to the case of IRAT HO). This octet string carries the reconfiguration message.

[0157] In addition, another issue is about signaling the target configuration for multiple CHO candidates, such as sending a separate message for each candidate. There is also the issue of how to signal the CHO configuration when there are multiple CHO candidates. Available techniques include signaling that uses:

[0158] I: Single message

[0159] II: One message per CHO candidate

[0160] When a single message is used to signal CHO configuration to multiple CHO candidates, an option to include multiple spCells / reconfigurationWithSync fields needs to be added. The same applies to other fields whose values ​​may be different for each CHO candidate.

[0161] Using a separate message for each CHO candidate to signal the CHO configuration to multiple CHO candidates can provide a more flexible signaling structure:

[0162] 1) Specification changes will be limited to the introduction of multiple octet string containers.

[0163] 2) This option can support CHO candidates on different target nodes

[0164] 3) Signaling is the future

[0165] Furthermore, the issue concerns the result of requiring RAN2 to check and confirm the general starting point.The issue also concerns adding an octet string / container to the reconfiguration message to carry the CHO configuration which touches on the same aspect of whether the signalling should be flexible or restrictive.

[0166] In another embodiment of the proposed method, a list of octet strings / containers may be added to the reconfiguration message, where each of the octet strings / containers carries the CHO configuration of a single CHO candidate generated by the target node (similar in the case of IRAT HO). Each octet string may carry a reconfiguration message.

[0167] Signaling a CHO configuration to multiple CHO candidates using a separate message for each CHO candidate may result in repeated transmission of other configurations that are the same across multiple candidates. However, duplication of configurations may be avoided, for example, by indicating that the value is the same as the value of another entry in the list.

[0168] According to the earlier embodiment, (at least) the source can set the CHO condition and signal each candidate CHO condition. There are two different ways to provide each candidate CHO condition:

[0169] II.1: The source node includes a CHO candidate list field for these source control parameters (eg, conditions).

[0170] II.2: The source node forwards the parameters to the target node, which includes the CHO condition in the target generation message (for each candidate)

[0171] Option II.1 may be slightly more preferred in the spirit of the proposed approach. On the other hand, from the UE (100) perspective, it may be simplest to not have a separate CHO candidate list field associated with the target generation container. Option II.2 may therefore be preferred.

[0172] Therefore, in an embodiment of the proposed method, the source node may forward the CHO candidate parameters that it controls to the target node, and the target node may include it in the target generation message (for each candidate).

[0173] Another issue that needs to be resolved is regarding when the CHO Complete message is sent by the UE.

[0174] Available techniques may include:

[0175] 1. When CHO is performed, i.e. after the initial visit in the candidate cell (as done for the normal HO case)

[0176] 2. Immediately, i.e., when the CHO is configured (in this case, some other signals may need to be sent when the CHO is executed).

[0177] In order to select a technique for sending a CHO complete message by the UE (100), concerns about the actions required at CHO configuration time need to be addressed, including the case where the UE (100) is unable to comply with the CHO configuration. In addition, it is assumed that the UE (100) performs re-establishment, but the UE (100) may perform actions at CHO configuration time or at CHO execution time. Moreover, there may be no practical benefit in delaying re-establishment until CHO is performed. However, if the UE (100) is able to comply, then it seems that no RRC message is required to confirm receipt and correct understanding (i.e., L2 ACK seems sufficient); that is, option 1 consistent with conventional HO seems sufficient.

[0178] Consider the case where the reconfiguration message also includes a source cell configuration change. The UE can then return a Done message to confirm the source cell reconfiguration. However, it does not seem necessary to include any indication about the CHO reconfiguration.

[0179] In one embodiment, the UE may return a CHO complete message when performing CHO, i.e., after initial access in a candidate cell (for a regular HO). If the message including the CHO configuration also includes a source cell reconfiguration, the UE may return a complete message immediately (without an explicit acknowledgement of receipt / understanding of the CHO reconfiguration). In the case of not understanding the CHO configuration, the UE may perform reestablishment immediately (i.e., without delay until CHO is performed).

[0180] In the conventional radio link monitoring process currently available in LTE and NR and performed during mobility, RLM can be suspended immediately upon receiving a HO command from the network (RLM timer (180) T310 is stopped if T310 is running). The HO process can be performed when the signal quality of the source cell becomes weak and the signal quality of the neighboring cell becomes strong, making the neighboring cell more suitable for serving the UE. As a result, the HO command can be signaled to the UE, typically when the signal condition of the source cell is weak. In addition, due to the deterioration of the signal condition of the serving cell, the UE cannot successfully receive the HO command from the network, so there is a high possibility that the handover cannot be performed. In order to reduce handover failures caused by failure to receive the HO command, early handover provisioning using the CHO mechanism is also discussed in RAN2. In addition, when the signal condition of the serving cell is weak and there may be a HO failure due to failure to successfully receive the message, the HO command can be signaled to the UE (100).

[0181] Considering that the UE (100) is configured with enhanced make-before-break (eMBB) handover, it is expected that the UE (100) synchronizes with the target cell and initiates a random access procedure while the connection to the source cell is still valid, although the signal conditions may still be weak. There may be two different possibilities for handover failure, namely, the source cell may experience RLF or the target cell may experience handover failure. However, when it is detected that the serving cell signal condition has become weaker and the neighboring cell (the target cell for handover) has better signal conditions and is thus more suitable for serving the UE (100), a handover command may be provided to the UE (100). Therefore, the probability of encountering a radio link failure on the source cell may be higher than the probability of a handover failure on the target cell. In addition, in eMBB handover, the probability of encountering a radio link failure on the source cell may be higher than the probability of a handover failure on the target cell.

[0182] Therefore, if the UE (100) continues to perform radio link monitoring on the source cell during HO execution, the UE (100) may declare RLF on the source cell, whereby the UE (100) must abort the HO execution on the target cell and will cause the UE (100) to perform a re-establishment procedure. If the UE (100) does not initiate the re-establishment procedure when a radio link failure is detected on the source cell while handover execution on the target cell is still in progress, premature suspension of the HO execution can be avoided, allowing the UE (100) to continue the handover execution on the target cell without any interruption. Alternatively, the radio link monitoring on the source cell can be suspended when a handover command is received. However, the two methods are used to achieve similar purposes and neither method is better than the other.

[0183] Unlike conventional methods and systems, in the proposed method, radio link monitoring is suspended upon receipt of a HO command, as this is consistent with the behavior defined in the specifications of existing mobility mechanisms. Furthermore, the result of suspending radio link monitoring of the source cell upon receipt of a HO command from the network is similar to the result of the UE (100) not initiating re-establishment in the event that RLF is declared on the source cell while HO execution to the target cell is ongoing.

[0184] In one embodiment, the UE (100) may suspend the radio link monitoring of the source cell upon receiving the HO command including the make-before-break indication. Figure 1A and Figure 1B This can also be applied to any handover type where the UE (100) performs an immediate handover upon receiving a HO command from the network.

[0185] Consider the case where the UE (100) is configured with conditional handover (CHO). In the case of the CHO mechanism, it is expected that the HO command will be received much earlier than the expected time when the handover is actually performed. In the case of CHO, the HO command can be sent in advance to avoid handover failure due to the UE (100) not successfully receiving the handover command. In this case, it may be incorrect to suspend monitoring the radio link when the HO command is received from the network. Therefore, when CHO is configured to the UE (100), the UE (100) can continue to perform radio link monitoring on the source cell. When the UE (100) performs handover on the target cell when the conditions defined in the HO command are met, the UE (100) should suspend radio link monitoring of the source cell, that is, stop T310 (if running). If the UE (100) continues RLM when initiating handover execution on the target cell, there is a risk of encountering RLF on the source cell, resulting in premature failure of the handover to the target cell. Therefore, when the conditions defined in the HO command are met and the handover execution is initiated, the radio link monitoring of the source cell should be suspended.

[0186] In one embodiment, when the UE (100) is configured with conditional handover (CHO), when a handover command is received from the network, the radio link monitoring of the source cell may continue. In another embodiment, when the UE (100) is configured with conditional handover (CHO), when the conditions configured in the handover command are met, when the UE (100) initiates handover execution to the target cell, the radio link monitoring of the source cell may be suspended. In one embodiment, the UE (100) may support one of an LTE RAT and an NR RAT.

[0187] Figure 3B A signaling diagram showing the continuation of the RLM timer (180) for the source cell until a HO command is executed based on the CHO configuration according to embodiments disclosed herein.

[0188] Combination Figure 3A Reference Figure 3B , Figure 3B Steps 302b to 312b in can be substantially the same as Figure 3A 302a to 312a in are the same. Therefore, repeated descriptions are omitted. In step 314b, unlike conventional methods and systems, the UE (100) may continue the T310 timer upon receiving the HO command, and in step 316b, may also continue the RLM process on the source cell. In addition, in step 318b, the UE (100) may monitor whether the conditions provided in the HO command for performing conditional switching are met. In step 320b, in response to determining that the conditions for performing conditional switching are met, the UE (100) may suspend RLM for the source cell when initiating the HO execution process (stop T310 if T310 is running). In addition, in step 322b, the HO execution process may be completed, and in step 324b, the UE (100) may send a reconfiguration completion message to the target gNB (1000b).

[0189] When the UE (100) is configured with enhanced Make Before Break (eMBB) and Conditional Handover (CHO) for the same target cell, then an MBB / eMBB configuration may be provided in addition to the CHO criteria in the HO command. In this type of HO, since the HO execution criteria are included, the HO command may be received earlier in time than the need to perform the HO execution. During this period, the serving cell conditions may be expected to be sufficient to serve the UE (100), and the neighboring cells may not be suitable for handling the UE (100) under the current signal conditions. If radio link monitoring of the source cell is suspended in this case, the UE (100) may be locked to the serving cell without a mechanism to recover from link degradation and related problems when the UE (100) moves towards the cell edge or out of the coverage of the serving cell. Therefore, if a Make Before Break (MBB / eMBB) handover is indicated in conjunction with CHO, the UE (100) may need to continue the RLM process on the serving cell when the HO command is received.

[0190] However, HO execution may be initiated by the UE (100) only when the CHO conditions are met, where the UE (100) follows the MBB / eMBB configuration provided in the HO command. When the CHO conditions are met, then the serving cell signal conditions may begin to degrade, and the neighboring cells may become more suitable for further serving the UE (100). In this case, since the target cell has met the conditions required to perform HO, the probability of radio link failure on the source cell can be expected to be higher than the probability of HO failure on the target cell.

[0191] In one embodiment, the UE (100) is configured with a HO type combining a make-before-break handover configuration and a CHO condition. When the conditions configured in the HO command are met, when the HO execution on the target cell is initiated, the UE (100) suspends the radio link monitoring of the source cell.

[0192] In another embodiment, when the UE (100) is configured with a HO type combining a make-before-break configuration and a CHO condition, upon receiving a HO command from the network, the UE (100) may continue to perform radio link monitoring on the source cell.

[0193] In yet another embodiment, when the UE (100) is configured with a HO type combining an enhanced make-before-break configuration and a CHO condition, upon receiving a HO command from the network, the UE (100) may continue to perform radio link monitoring on the source cell.

[0194] In yet another embodiment, when the UE (100) is configured with a HO type that combines an enhanced make-before-break configuration and a CHO condition, when the conditions configured in the HO command are met, when initiating HO execution to the target cell, the UE (100) may suspend radio link monitoring to the source cell. The behavior of the UE (100) is Figure 3B Shown in.

[0195] Therefore, unlike conventional methods and systems, in the proposed method, whenever conditions for performing CHO are provided, or whenever conditions are specified via a HO command, RLM monitoring of the source cell is continued even after a HO command is received from the network. RLM of the source cell is suspended only when HO execution of the target cell is initiated (when the UE (100) satisfies the conditions in the HO command).

[0196] Figure 4 A flow chart 400 is shown of radio link monitoring during HO execution according to embodiments disclosed herein.

[0197] In one embodiment, consider Figure 4 As shown, RLM monitoring of the NR UE controlled by the NR UE. The UE may be a NR UE. In step 402, when the NR UE is in the RRC CONN state, an MR (measurement report) may be sent to the source cell, and in step 404, an RRC CONN state process may be performed. In addition, in step 406, the NR UE may determine whether a HO command is received from the network. In response to determining in step 406 that the HO command is not received, the NR UE may loop back to step 404. In response to determining in step 406 that the HO command is received, in step 408, the NR UE may determine whether the HO command includes a CHO configuration.

[0198] In response to determining that the HO command includes the HO type indicated as Rel 15HO or Rel 16MBB / eMBB HO, in step 418, the NR UE may immediately stop the RLM timer (180), i.e., the T310 timer, upon receiving the HO command, and suspend RLM for the source cell.

[0199] In response to determining that the HO command includes a HO type indicated as one of: conditional handover criteria, or a combination of Rel 15 HO or Rel 16 MBB / eMBB HO and conditional handover criteria, then at step 410, the NR UE may continue the RLM timer (if the T310 timer is already running) and continue the RLM process for the source cell.

[0200] In addition, at step 412, the NR UE may determine whether the conditional handover criteria are met. In response to determining that the conditional handover criteria are not met, the NR UE may loop to step 410. In response to determining that the conditional handover criteria are met, the NR UE may initiate HO execution at step 414 and also suspend RLM for the source cell (i.e., stop the T310 timer if the T310 timer is running). In addition, at step 416, the NR UE may perform a handover and switch from the source cell to the candidate target cell.

[0201] In one embodiment, the UE may be an LTE UE. In step 408, when the HO type indicated to the LTE UE is RE116eMBB HO or any pre-Rel 16 HO, then in step 422, the UE immediately stops T310 (suspends RLM to the source cell) upon receiving the HO command.

[0202] At step 408, when the HO type indicated to the LTE UE is one of the following: conditional handover criteria, and Rel16eMBB or any combination of pre-Rel 16 HO and conditional handover criteria, the UE will continue the T310 timer (if the T310 timer is running) and the RLM process with respect to the source cell at step 410. In addition, when the HO execution starts when the conditional handover criteria are met (at step 412), the UE may suspend the RLM of the source cell (if the T310 timer is running, stop the T310 timer) (as shown in step 414).

[0203] Figure 5A A signaling diagram is shown for the former active neighbor cell preparation for reestablishment to perform handover failure recovery according to the embodiments disclosed herein.

[0204] Figure 5B A signaling diagram is shown for target cell preparation for HO execution according to embodiments disclosed herein.

[0205] Consider a situation where the UE (100) encounters a radio link failure (RLF). In response to the RLF, the UE (100) may perform a cell selection procedure to select a suitable cell to reestablish a connection with the network. If a suitable cell is selected while the timer T311 is still running, the UE (100) may attempt to reestablish the RRC connection, otherwise the UE (100) may transition to an idle state. In addition, the UE (100) may decide a target cell for reestablishment based on a cell search order and cell signal quality.

[0206] By helping the UE (100) prepare cells on which the UE (100) can perform reestablishment, the network can reduce the waiting time incurred in the handover failure recovery phase. However, the assistance information can only become useful if the source cell (on which the RLF was triggered) has prepared potential target cells (on which the UE (100) can perform reestablishment) using the UE (100) context before the UE (100) encountered the RLF. Therefore, the UE (100) can pre-notify the network of the existence of certain neighboring cells via measurement reports, which in turn allows the network to proactively prepare the neighboring cells to accommodate potential reestablishment from the UE (100). Preparation of the target cell for reestablishment may include: At step 502a, the UE (100) may receive a measurement configuration from the source gNB (1000a). At step 504a, the UE (100) may send a measurement report to the source gNB (1000a). In addition, the source gNB (1000a) may communicate with the target gNB (1000b) and prepare the target cell for performing reestablishment. In addition, the target gNB (1000b) may send an RRC reconfiguration with a list of target cells available for reestablishment.

[0207] The sequence of procedures and signaling involved to support early preparation of the target cell for reestablishment is similar to the sequence of handover signaling (as described in steps 502b-508b, except for step 506b, where the source gNB (1000a) prepares the target cell for performing the handover). Therefore, the network does not need to assist the UE (100) with a list of prepared cells. Instead, the network may choose to perform the handover.

[0208] Figure 6 A flow chart 600 illustrates cell selection priorities (orders) when a UE (100) attempts to reestablish a connection with a wireless communication network according to embodiments disclosed herein.

[0209] In another embodiment, a target cell may be selected for handover failure recovery, for example, by prioritizing cells for which measurement reports have been sent to the source cell. Upon receiving the measurement report from the UE, the source cell may have already prepared the target cell using the UE context. The UE may utilize the fact that the source cell has already prepared the target cell using the UE context and attempt to perform failure recovery on the target cell. In addition, when the UE selects a suitable cell to perform reestablishment of the RRC connection, if T311 is still running on the UE, the UE may initiate a random access procedure and may start T301. T301 may be used to monitor and control the success / failure of the random access procedure and therefore cannot be optimized.

[0210] At the same time, after successfully receiving the re-establishment request from the UE, the target cell may attempt to extract the UE context from the source cell. A reduction in UE context retrieval time is possible if the UE (100) attempts re-establishment on the cell for which the measurement report was sent to the source cell. Upon receiving the measurement report from the UE (100), the source cell may have successfully prepared the target cell before the UE (100) encountered the radio link failure. This situation can be handled if the UE (100) follows a prioritized cell selection procedure.

[0211] In the prioritized cell selection process, during a handover failure or radio link failure recovery process, a higher priority is given to cells that sent measurement reports to the source cell before the RLF. Therefore, the UE (100) can attempt to reestablish a connection to a cell that may have been prepared for the UE based on the measurement report previously sent to the source cell. In addition, the next higher priority can be given to a cell that was detected while on the source cell, but for which no measurement report was triggered. Reestablishment can be attempted for the next higher priority cell because there is a high probability that the UE is still near the detected cell while attempting to perform reestablishment. In addition, the next priority can be given to all remaining other cells.

[0212] Figure 6 The process sequence involved in target cell selection for handover failure or radio link failure recovery is shown. At step 602, the UE in the RRC CONN state may perform an RLM procedure. At step 604, the UE may determine whether RLF is declared. In response to determining that RLF is not declared, the UE may continue the RLM procedure. In response to determining that RLF is declared, at step 606, the UE may determine whether a measurement report is sent for the source cell.

[0213] Upon determining that a measurement report is sent for the source cell, the UE may attempt target cell selection on the target cell for which the MR is sent, at step 608. In addition, at step 610, the UE may determine whether a suitable target cell (candidate target cell) is found for which the UE may perform reestablishment. In response to determining that a suitable target cell is found, at step 620, the UE may select a target cell and perform a reestablishment procedure.

[0214] In response to determining that a suitable target cell is not found, the UE may attempt target cell selection for the target cell detected and measured in the RRC CONN state at step 612. In addition, at step 614, the UE may again determine whether a suitable target cell is found on which the UE may perform reestablishment. In response to determining that a suitable target cell is not found, at step 616, the UE may attempt target cell selection on other target cells, and then may again check at step 618 whether a suitable target cell is found. At steps 614 and 618, in response to determining that a suitable target cell is found, the UE may select a target cell and perform a reestablishment procedure (step 620).

[0215] Fig. 7A A signaling diagram illustrating a method of performing a UE-controlled state transition from an RRC_CONNECTED state to an RRC_INACTIVE state with respect to a configured threshold according to embodiments disclosed herein.

[0216] Figure 7B A signaling diagram of a method for performing a UE-controlled state transition from an RRC_CONNECTED state to an RRC_INACTIVE state with respect to a configured timer according to an embodiment disclosed herein is shown.

[0217] Figure 7C A signaling diagram of a method for performing a UE autonomous state transition from an RRC_CONNECTED state to an RRC_IDLE state with respect to a configured timer according to an embodiment disclosed herein is shown.

[0218] In summary, 3GPP is studying methods to reduce power consumption in UE (100) and make the power of UE (100) more efficient. Generally, when UE (100) is in RRC CONN state, UE (100) consumes maximum power, and when UE (100) is in one of RRC IDLE state and RRC INACTIVE state, UE (100) consumes minimum power. Therefore, in order to improve power efficiency, when there is no expected data transmission, UE (100) can transition from RRC_CONN state to one of RRC_IDLE state and RRC_INACTIVE state.

[0219] Reference Fig. 7AIn step 702a, the UE (100) may be in an RRC connected state, and in step 704a, the UE (100) may share a UE capability exchange indicating support for UE-assisted transition to an inactive state. In step 706a, an RRC reconfiguration including a configuration allowing the UE (100) to send an indication for transition from an RRC CONN state to an RRC INACTIVE state is performed. In addition, in step 708a, the UE (100) may monitor the state of one of a timer and a counter to trigger an RRC inactive state transition request. The timer may be, for example, a DataInactivityTimer. In addition, in step 710a, the UE (100) may determine that a condition for requesting a state transition to the network is satisfied, and in step 712a, the UE (100) may send an indication of the state transition to the wireless communication network. In addition, in response to the indication of the state transition, the gNB (1000) of the wireless communication network may send an RRC release message with an optional recovery id.

[0220] In one embodiment, if the UE (100) is configured with dataInactiveTimer, the UE (100) in the RRC connected state may be allowed to send an indication for state transition.

[0221] In one embodiment, if DataInactivityTimer is running, the UE (100) in the RRC connected state may monitor conditions such as inactiveIndicationThreshold (step 708a) to trigger a state transition indication. Upon determining that the inactiveIndicationThreshold is satisfied (step 710a), the UE (100) may trigger a state transition indication to the network (step 712a), such as Fig. 7A In addition, when dataInactiveTimer is running, the inactiveIndicationThreshold condition can be specified as a percentage of dataInactiveTimer or dataInactiveTimer, or the inactiveIndicationThreshold condition can be specified in C-DRX cycle.

[0222] In one embodiment, the state transition indication may be a request to the network to transition the UE (100) from the RRC connected state to the RRC inactive state.

[0223] In one embodiment, after triggering the state transition indication, upon expiration of the inactiveIndicationTimer, the UE (100) may move to the RRC_IDLE state.

[0224] In another embodiment, if the UE (100) is explicitly configured with a dataInactiveTimer, the UE (100) may be allowed to send an indication for a state transition.

[0225] In one embodiment, the conditions for initiating / re-initiating inactiveIndicationTimer may be the same as dataInactiveTimer, regardless of whether dataInactiveTimer is configured. Figure 7B , when the inactiveIndicationTimer expires (710b), the UE (100) in the RRC connected state (702b) may trigger a state transition indication (712b) to the network, such as Figure 7B shown.

[0226] Reference Figure 7C , steps 702c to 712c may be substantially the same, and thus repeated descriptions are omitted. At step 716c, the UE may not receive the RRC release message (100) with the resume ID. In one embodiment, after triggering the state transition indication, the UE (100) may start a waitTimer, and upon expiration of the waitTimer (step 716c), the UE (100) may move to the RRC idle state, such as Figure 7C shown.

[0227] In another embodiment, if the UE (100) is explicitly configured with an inactiveIndicationTimer and furthermore the UE (100) is configured with a dataInactivityTimer, the UE (100) may be allowed to send an indication for a state transition.

[0228] In one embodiment, the conditions for initiating / re-initiating inactiveIndicationTimer may be the same as those for dataInactivityTimer.

[0229] In one embodiment, if dataInactivityTimer is running, the UE (100) in RRC connected state can trigger a state transition indication to the network when inactiveIndicationTimer expires.

[0230] In one embodiment, after the state transition indication is triggered, a waitTimer may be started, and when the waitTimer or dataInactivityTimer expires, the UE (100) may move to the RRC_DLE state.

[0231] Unlike conventional methods and systems, the proposed method may allow the UE (100) to inform the network of UE capabilities for requesting or assisting the serving gNB in ​​making a state transition from RRC CONN to RRC INACTIVE. Upon receiving the UE capabilities, the network may select one of the following: allowing the UE (100) to request a state transition when necessary, not allowing the UE (100) to request a state transition when necessary. If the serving gNB chooses to allow the UE (100) to request a state transition, the UE (100) may monitor conditions and criteria that may ultimately trigger a request to the network.

[0232] In an RRC message (e.g., an RRC reconfiguration message), the network may provide the UE (100) with the necessary configuration required to request a state transition. Thus, an RRC message with the configuration required to request a state transition may allow the UE (100) to monitor the required conditions and trigger an indication to the network for a state transition from RRC CONN to the required RRC INACTIVE. The network may provide the configuration as a timer-based configuration or a counter-based configuration for one of the following: triggering an indication to the network, requesting a state transition / connection release. In the current Release 15 specification, dataInactivityTime is used to allow the UE (100) to implicitly transition to the RRC idle state.

[0233] The details of the timer processing can be provided as follows:

[0234] Start or restart dataInactivityTimer:

[0235] If a MAC entity receives the MAC SDU of the DTCH / DCCH / CCCH logical channel.

[0236] If a MAC entity sends a MAC SDU for a DTCH / DCCH logical channel

[0237] iDataInactive Timer expires:

[0238] Indicates expiration of dataInactivityTimer to RRC

[0239] RRC processing when receiving dataInactivityTime expiration indication:

[0240] Execute action when transitioning to RRC_IDLE, release reason is "RRC connection failure"

[0241]

[0242] Proposed timer-based configuration: This configuration can be provided based on the existence of DataInactivityTimer.

[0243]

[0244] The MAC-CellGroupConfig field description is provided in [Table 1] and the conditional presence is described in [Table 2].

[0245] [Table 1]

[0246]

[0247]

[0248] [Table 2]

[0249]

[0250] Handling of inactiveIndicationTimer: The MAC may handle this timer based on data activity on the MAC entity and indicate to the RRC once the configured threshold timer condition is met.

[0251] 5.19 Data inactivity monitoring (38.321)

[0252] The UE may be configured with a data inactivity monitoring function through RRC. When in RRC_CONNECTED, RRC controls the data inactivity operation by configuring the timer dataInactivityTimer.

[0253] When dataInactivityTimer is configured, the UE shall:

[0254] 1) If inactiveIndicationTimer is not configured;

[0255] 2) If any MAC entity receives a MAC SDU for a DTCH logical channel or a CCCH logical channel; or

[0256] 2) If any MAC entity sends a MAC SDU for a DTCH logical channel or a CCCH logical channel;

[0257] 3) Start or restart dataInactivityTimer.

[0258] 2) If dataInactivityTimer expires:

[0259] 3) Indicate to higher layers that dataInactivityTimer has expired.

[0260] 1) Otherwise, if inactiveIndicationTimer is configured;

[0261] 2) If any MAC entity receives a MAC SDU for a DTCH logical channel or a CCCH logical channel; or

[0262] 2) If any MAC entity sends a MAC SDU for a DTCH logical channel or a CCCH logical channel;

[0263] 3) Start or restart inactiveIndicationTimer.

[0264] 2) If inactiveIndicationTimer expires:

[0265] 3) Indicate to higher layers that inactiveIndicationTimer has expired.

[0266] 5.3.8.6UE performs actions when inactiveIndicationTimer expires (38.331)

[0267] Upon receiving expiry of inactiveIndicationTimer from lower layers during RRC_CONNECTED, the UE shall:

[0268] 1) Initiate transmission of a UEAssistanceMessage with inactiveIndication set

[0269] Alternatively, the network may configure the inactiveIndicationTimer for the UE independently of the dataInactivityTimer. In this case, the process is as follows:

[0270] Configuration:

[0271]

[0272] In addition, the MAC-CellGroupConfig field description is provided in [Table 3].

[0273] [Table 3]

[0274]

[0275]

[0276] Handling of inactiveIndicationTimer: The MAC may handle this timer based on data activity on the MAC entity and indicate to the RRC once the configured threshold timer condition is met.

[0277] 5.19 Data inactivity monitoring (38.321)

[0278] The UE may be configured with a data inactivity monitoring function through RRC. When in RRC_CONNECTED, RRC controls the data inactivity operation by configuring the timer dataInactivityTimer.

[0279] When dataInactivityTimer is configured, the UE shall:

[0280] 1) If any MAC entity receives a MAC SDU of a DTCH logical channel, a CCCH logical channel, or a DCCH logical channel; or

[0281] 1) If any MAC entity sends a MAC SDU of a DTCH logical channel or a DCCH logical channel;

[0282] 2) Start or restart dataInactivityTimer.

[0283] 1) If dataInactivityTimer expires:

[0284] 2) Indicate to higher layers that dataInactivityTimer has expired.

[0285] 5.X Inactivity Indicator Monitoring (38.321)

[0286] When dataInactivityTimer is configured, the UE shall:

[0287] 1) If any MAC entity receives a MAC SDU of a DTCH logical channel, a CCCH logical channel, or a DCCH logical channel; or

[0288] 1) If any MAC entity sends a MAC SDU of a DTCH logical channel or a DCCH logical channel;

[0289] 2) Start or restart inactiveIndicationTimer.

[0290] 1) If inactiveIndicationTimer expires:

[0291] 2) Indicate to higher layers that inactiveIndicationTimer has expired.

[0292] 5.3.8.6UE performs actions when inactiveIndicationTimer expires (38.331)

[0293] Upon receiving expiry of inactiveIndicationTimer from lower layers during RRC_CONNECTED, the UE shall:

[0294] 1) Initiate transmission of a UEAssistanceMessage with inactiveIndication set

[0295] Proposed counter-based configuration: The need to transition to the inactive state can be monitored based on counting of DRX cycles without data inactivity. If a configured number of DRX cycles have passed without any transmission or reception (without even starting a drxInactivityTimer during this duration), the UE (100) initiates the sending of a state transition indication to the network.

[0296]

[0297]

[0298] In addition, a DRX-Config field description is provided in [Table 4].

[0299] [Table 4]

[0300]

[0301]

[0302] 5.3.8.x UE performs an action when inactiveIndicationCounter is met (38.331)

[0303] While in RRC_CONNECTED and satisfying the inactiveIndicationCounter count for DRX from lower layers with no DL reception or UL transmission, the UE shall:

[0304] 1) Initiate transmission of a UEAssistanceMessage with inactiveIndication set

[0305] [Table 5] shows the throughput measurement of NR calculated at the radio link control (RLC) layer based on the amount of data between reference time points at the RLC layer. A method for performing Layer 2 throughput measurement by the gNB / NG-eNB is described. Performance measurements of 5G networks including throughput measurements at the gNB are defined in SA5TS28.552 "5G Performance Measurements". RAN2 also studied the feasibility of SA5-defined measurements related to RAN2. Typically, throughput measurements are calculated at the PDCP SDU level based on the amount of data between reference time points at the PDCP layer in LTE. However, the throughput measurement of NR is calculated at the RLC layer based on the amount of data between reference time points at the RLC layer, as shown in Table 5.

[0306] [Table 5]

[0307]

[0308]

[0309]

[0310] Furthermore, throughput measurements defined by SA5 for NR can be performed at the RLC layer, whereas in LTE, they are measured at the PDCP layer.

[0311] QoS flow can be the smallest granularity on which the network can perform QoS verification. The mapping between QoS flow and DRB in NR is not always one-to-one, it can also be many-to-one. Therefore, performing throughput measurement only at the RLC layer is not sufficient to verify QoS and identify the throughput of each QoS flow. The following shows the analysis of the adequacy of RLC-level throughput measurement for different possible bearer configurations on NR:

[0312] [Table 6]

[0313]

[0314]

[0315] If the throughput measurement is done only based on the amount of RLC data at the RLC layer, the QoS can be estimated correctly for all bearer types configured on NR.

[0316] In NR, a PDU session can include multiple QoS flows, and the SDAP entity can map one or more QoS flows to a single DRB. The restriction of QoS flow to DRB mapping is that only one QoS flow is mapped to one DRB at a time. For radio bearers on NR connected to 5GC, the QoS termination point on the gNB is the SDAP entity. Therefore, in order to verify the QoS on the IP flows of the bearers connected to 5GC, the throughput must be measured at the SDAP layer. For radio bearers on NR connected to EPC, the QoS termination point on the eNB is the PDCP entity. In order to verify the QoS of the IP flows of the bearers connected to EPC, the throughput must be measured at the PDCP entity. The method proposes that for NR and LTE bearers connected to 5GC, throughput measurements must be made based on SDAP SDUs at the SDAP layer. The method proposes that for NR and LTE bearers connected to EPC, throughput measurements must be made based on PDCP SDUs at the PDCP layer.

[0317] In case of split bearers, the PDCP throughput may not always be reflected as the sum of the throughputs of the RLC entities to which it is connected. For radio bearers for which PDCP duplication is configured, throughput measurement must be performed based on the PDCP SDU amount. The method proposes that for radio bearers configured with PDCP duplication, throughput measurement must be performed based on the PDCP SDU at the PDCP layer.

[0318] In the MR-DC case, there is a split bearer which can be configured with a termination point on gNB / NR and a split branch on eNB / LTE. In this case, to measure the throughput on the DRB, the gNB has to take into account the throughput provided on both branches. Therefore, the gNB will increase the throughput on the NR RLC entity and the LTE RLC entity. However, according to the current Release 15 specifications, throughput measurement is not performed on LTE RLC. Provision has to be introduced to measure the throughput based on RLC SDU on LTE for the split bearer terminated on gNB. It is recommended to introduce RLC SDU based throughput measurement at the RLC layer on eNB when a split bearer terminated on gNB is configured to a UE (100).

[0319] Figure 8 A gNB according to the embodiments disclosed herein is shown.

[0320] The above-mentioned gNBs, eNBs, or BSs may correspond to the gNB 800. For example, Figure 1A The source gNB (1000a) and / or target gNB (1000b) shown may correspond to gNB 800.

[0321] Reference Figure 8, gNB 800 may include a processor 830, a transceiver 810, and a memory 820. However, not all of the components shown are required. gNB 800 may include Figure 8 The components shown may be implemented with more or fewer components. In addition, according to another embodiment, the processor 830 and the transceiver 810 and the memory 820 may be implemented as a single chip.

[0322] The above-mentioned components will now be described in detail.

[0323] The processor 830 may include one or more processors or other processing devices that control the proposed functions, processes and / or methods. The operations of the gNB 800 may be implemented by the processor 830.

[0324] When the UE is in the RRC connected state, the processor 830 may control the transceiver 810 to send a radio resource control (RRC) reconfiguration message to the UE. The RRC reconfiguration message may include a handover configuration.

[0325] The transceiver 810 may include an RF transmitter for up-converting and amplifying a transmission signal, and an RF receiver for down-converting the frequency of a reception signal. However, according to another embodiment, the transceiver 810 may be implemented by more or less components than those illustrated in the components.

[0326] The transceiver 810 may be connected to the processor 830 and transmit and / or receive signals. The signal may include control information and data. In addition, the transceiver 810 may receive a signal through a wireless channel and output the signal to the processor 830. The transceiver 810 may transmit a signal output from the processor 830 through a wireless channel.

[0327] The memory 820 may store control information or data included in a signal obtained by the gNB 800. The memory 820 may be connected to the processor 830 and store at least one instruction or protocol or parameter for the proposed function, process and / or method. The memory 830 may include a read-only memory (ROM) and / or a random access memory (RAM) and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage devices.

[0328] Fig. 9 A user equipment (UE) according to embodiments disclosed herein is shown.

[0329] The above UE may correspond to UE 900. For example, Figure 1A and 1B The shown UE 100 may correspond to UE 900 .

[0330] Reference Fig. 9UE 900 may include a processor 930, a transceiver 910, and a memory 920. However, not all of the components shown are required. UE 900 may include a processor 930, a transceiver 910, and a memory 920. Fig. 9 The components shown in the figure may be implemented with more or fewer components. In addition, according to another embodiment, the processor 930, the transceiver 910, and the memory 920 may be implemented as a single chip.

[0331] The above-mentioned components will now be described in detail.

[0332] The processor 930 may include one or more processors or other processing devices that control the proposed functions, processes and / or methods. The operations of the UE 900 may be implemented by the processor 930.

[0333] The processor 930 may control the transceiver 910 to receive a radio resource control (RRC) reconfiguration message from a source cell of a wireless communication network, wherein the UE is in an RRC connected state, and wherein the RRC reconfiguration message includes a handover configuration. In addition, the processor 930 may determine whether a CHO configuration is provided in the handover configuration, wherein the CHO configuration includes multiple conditions and multiple target cell configurations for performing CHO. The processor 930 may perform one of the following operations: in response to determining that a CHO configuration is provided in the handover configuration, continuing a radio link monitoring (RLM) timer and a radio link monitoring process for the source cell, and in response to determining that a CHO configuration is not provided in the handover configuration, stopping the RLM timer and suspending the radio link monitoring process with respect to the source cell. The processor 930 may perform CHO from a source cell to a candidate target cell in a plurality of target cells based on the CHO configuration in the wireless communication network.

[0334] The transceiver 910 may include an RF transmitter for up-converting and amplifying a transmission signal, and an RF receiver for down-converting the frequency of a reception signal. However, according to another embodiment, the transceiver 910 may be implemented by more or less components than those illustrated in the components.

[0335] The transceiver 910 may be connected to the processor 930 and transmit and / or receive a signal. The signal may include control information and data. In addition, the transceiver 910 may receive a signal through a wireless channel and output the signal to the processor 930. The transceiver 910 may transmit a signal output from the processor 930 through a wireless channel.

[0336] The memory 920 may store control information or data included in a signal obtained by the UE 900. The memory 920 may be connected to the processor 920 and store at least one instruction or protocol or parameter for the proposed function, process and / or method. The memory 920 may include a read-only memory (ROM) and / or a random access memory (RAM) and / or a hard disk and / or a CD-ROM and / or a DVD and / or other storage devices.

[0337] The embodiments disclosed herein may be implemented by at least one software program running on at least one hardware device and performing network management functions to control the elements.

[0338] The foregoing description of the specific embodiments will so completely reveal the general nature of the embodiments herein that others can easily modify and / or adapt for various applications by applying current knowledge, without departing from the general concept, and therefore, such adaptations and modifications should and are intended to be included in the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the words or terms used herein are for descriptive purposes rather than for limiting purposes. Therefore, although the embodiments herein have been described according to preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced by modification within the spirit and scope of the embodiments described herein.

[0339] Although the present disclosure has been described with various embodiments, various changes and modifications may occur to those skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. A user equipment UE in a wireless communication system, the UE comprising: Transceiver; as well as At least one processor configured to: controlling the transceiver to receive a radio resource control RRC reconfiguration message including first conditional handover CHO configuration information from a base station BS, identifying one or more execution conditions and a plurality of target cell configurations for performing CHO included in the first CHO configuration information, continuing the radio link monitoring RLM timer and the RLM process for the source cell of the BS until a first candidate target cell among a plurality of candidate target cells satisfies at least one execution condition of the one or more execution conditions for performing CHO, and When the first candidate target cell satisfies at least one execution condition of the one or more execution conditions for performing CHO, based on the first candidate target cell configuration corresponding to the first candidate target cell among the multiple target cell configurations included in the first CHO configuration information, CHO is performed from the source cell to the first candidate target cell and the RLM timer is stopped.

2. The UE according to claim 1, wherein the first CHO configuration information includes an execution condition for performing CHO on the first candidate target cell and the first candidate target cell configuration, and Each of the multiple target cell configurations is carried in the RRC reconfiguration message as an OCTET string. The UE according to claim 1 , wherein the RLM timer is a T310 timer.

4. The UE according to claim 1, wherein the configurations of the multiple target cells cannot be changed by the source cell, and The multiple execution conditions for executing CHO are determined by the source cell and attached to the CHO configuration information.

5. A source base station BS of a source cell, the source BS comprising: Transceiver; as well as At least one processor configured to: controlling the transceiver to send a radio resource control RRC reconfiguration message including first conditional handover CHO configuration information to a user equipment UE, wherein the first conditional handover CHO configuration information includes one or more execution conditions and multiple target cell configurations for performing CHO, and identifying that a radio link monitoring RLM process on the source cell continues until a first candidate target cell among a plurality of candidate target cells satisfies at least one execution condition of one or more execution conditions for performing CHO; as well as When the first candidate target cell satisfies at least one execution condition of one or more execution conditions for performing CHO, it is identified that the RLM process on the source cell is suspended.

6. The source BS of claim 5, wherein the at least one processor is further configured to: controlling the transceiver to send a handover command without second CHO configuration information to the UE before the first candidate target cell satisfies at least one of the one or more execution conditions, and Regardless of the first CHO configuration information, it is identified that the RLM process on the source cell is suspended.

7. The source BS of claim 5, wherein the RLM timer is a T310 timer.

8. The source BS according to claim 5, wherein the plurality of target cell configurations cannot be changed by the source BS of the source cell, and The plurality of execution conditions for performing CHO are determined by the source BS of the source cell and attached to the CHO configuration information.

9. A method performed by a user equipment UE in a wireless communication system, the method comprising: receiving a radio resource control RRC reconfiguration message including first conditional handover CHO configuration information from a base station BS; identifying one or more execution conditions and a plurality of target cell configurations for performing CHO included in the first CHO configuration information; continuing a radio link monitoring RLM timer and an RLM process for a source cell of the BS until a first candidate target cell among a plurality of candidate target cells satisfies at least one execution condition of the one or more execution conditions for performing CHO; as well as When the first candidate target cell satisfies at least one execution condition of the one or more execution conditions for performing CHO, based on the first candidate target cell configuration corresponding to the first candidate target cell among the multiple target cell configurations included in the first CHO configuration information, CHO is performed from the source cell to the first candidate target cell and the RLM timer is stopped.

10. The method according to claim 9, wherein the first CHO configuration information comprises an execution condition for performing CHO on the first candidate target cell and the first candidate target cell configuration, and Each of the multiple target cell configurations is carried in the RRC reconfiguration message as an OCTET string. The method of claim 9 , wherein the RLM timer is a T310 timer.

12. The method according to claim 9, wherein the configurations of the multiple target cells cannot be changed by the source cell, and The multiple execution conditions for executing CHO are determined by the source cell and attached to the CHO configuration information.

13. A method performed by a source base station BS of a source cell in a wireless communication system, the method comprising: The source BS sends a radio resource control RRC reconfiguration message including first conditional handover CHO configuration information to the user equipment UE, wherein the first conditional handover CHO configuration information includes one or more execution conditions for performing CHO and multiple target cell configurations; identifying that the radio link monitoring RLM process on the source cell continues until a first candidate target cell among the multiple candidate target cells satisfies at least one execution condition of the one or more execution conditions for performing CHO; as well as When the first candidate target cell satisfies at least one execution condition of one or more execution conditions for performing CHO, it is identified that the RLM process on the source cell is suspended.

14. The method according to claim 13, further comprising: Before the first candidate target cell satisfies at least one of the one or more execution conditions, sending a handover command without second CHO configuration information to the UE; as well as Regardless of the first CHO configuration information, it is identified that the RLM process on the source cell is suspended.

15. The method of claim 13, wherein the RLM timer is a T310 timer.

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