Method and device for supporting terminal mobility in wireless communication system

Abstract

Provided are a base station and a base station method for supporting terminal mobility in a wireless communication system based on beamforming. The method includes generating beam-related information for multiple terminals according to beam measurement results respectively received from the multiple terminals, detecting a path within a base station coverage area according to the beam-related information, and sending a message supporting mobility to a terminal determined to be moving along the path based on the beam-related information.

Description

Technical Field

[0001] The present disclosure relates to fifth generation (5G) wireless communication (or next generation wireless communication). More specifically, the present disclosure relates to a method and apparatus for supporting mobility of a terminal in a wireless communication system. Background Art

[0002] In order to meet the growing demand for wireless data services since the deployment of the fourth generation (4G) communication system, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also referred to as "beyond 4G network" communication systems or "post-long term evolution (LTE) systems".

[0003] In order to achieve higher data rates, 5G communication systems are being considered for implementation in ultra-high frequency (mmWave) bands (e.g., 60 GHz bands). In order to reduce the propagation loss of radio waves and increase the transmission distance of radio waves at ultra-high frequencies, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technologies are being discussed for 5G communication systems.

[0004] In addition, in the 5G communication system, research and development of system network improvements are being carried out based on evolved small cells, advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, mobile networks, cooperative communications, coordinated multi-point (CoMP), receiving-end interference elimination, etc.

[0005] In addition, in the 5G system, frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) systems, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies have been developed.

[0006] On the other hand, the Internet (a human-centered connected network in which people generate and consume information) is evolving into the Internet of Things (IoT), in which distributed entities (such as things) exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of IoT technology and big data processing technology through connection with cloud servers, has emerged. Technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology" and "security technology" are required for IoT implementation, so sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have been studied recently. Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated among connected things. Through the aggregation and combination between existing information technology (IT) and various industrial applications, IoT can be applied to various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances and advanced medical services.

[0007] In line with this, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, M2M communications, and MTC can be implemented through beamforming, MIMO, and array antennas (which correspond to 5G communication technologies). The application of cloud RAN, which is the above-mentioned big data processing technology, can also be considered as an example of the aggregation between 5G technology and IoT technology.

[0008] One of the main technologies of the 5G communication system as described above is to use ultra-high frequency (mmWave), whose wavelength is much shorter than that of existing radio frequency, in order to achieve faster communication with a large bandwidth. However, high frequency bands have very low penetration and diffraction, so the communication system using ultra-high frequency should operate based on beamforming to increase the transmission / reception rate and widen the coverage area.

[0009] Specifically, compared with the 4G mobile communication system, the 5G communication system plans to achieve a maximum download speed of 20Gbps and a response speed of 1ms or less. In addition, the 5G communication system aims at the above-mentioned realization, even in an environment with a connection of more than 1,000,000 devices and a high speed of 500 kilometers per hour. To this end, the 5G communication system plans to use an extended bandwidth compared to LTE by using an ultra-high frequency band of 28GHz that has not yet been used as an existing mobile communication frequency. However, because the high frequency band leads to a small service coverage area and low permeability and diffraction, a beamforming scheme is used to gather signals to one location and provide the gathered signals to the terminal.

[0010] The above information is provided as background information only to assist with understanding the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0011]

Technical issues

[0012] In the beam-based communication system as described above, the mobility function of the terminal is performed by beam changing and switching. Such beam-based communication guarantees the mobility of the terminal in a beam-to-beam manner, in which communication drifts from one beam to another.

[0013] According to the beamforming technology, since a signal to be transmitted or received is focused to a specific point, the transmission / reception lines should always be aligned, and if this alignment is distorted during the beam changing process, the electric field may suddenly deteriorate.

[0014] For example, in the case of a moving high-speed train, a handover is triggered after an event occurs in which the signal strength of the beam of the target cell becomes higher than the signal strength of the beam of the serving cell. In this case, the transmit / receive alignment between the serving beam of the terminal and the terminal located in the moving high-speed train may be distorted, thereby suddenly deteriorating the electric field, and this may cause handover failure, performance degradation, and call drops.

[0015]

Problem Solution

[0016] Aspects of the present disclosure are to address at least the above-mentioned problems and / or disadvantages and provide at least the advantages described below. Therefore, one aspect of the present disclosure is to provide a method and apparatus for supporting mobility of a terminal in a wireless communication system.

[0017] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0018] According to one aspect of the present disclosure, a method performed by a base station is provided. The method includes generating beam-related information for multiple terminals according to beam measurement results received from the multiple terminals, detecting a path in a coverage area of ​​the base station using the beam-related information, and sending a message for supporting mobility to a terminal determined to be moving along the path based on the beam-related information.

[0019] According to an embodiment of the present disclosure, detecting a path may also include identifying similarities between beam-related information of two terminals among a plurality of terminals by comparing the beam-related information of the two terminals with each other, and if the similarity meets specific conditions, determining that the routes along which the two terminals move form a path.

[0020] According to an embodiment of the present disclosure, identifying similarity may include comparing the number of beam identifiers (IDs), beam ID values, and beam ID sequences included in the beam-related information of the two terminals, and comparing the ratios of the dwell times of the beam IDs included in the beam-related information of the two terminals.

[0021] According to an embodiment of the present disclosure, beam-related information may include information about at least one of the following: the reason why a specific terminal configures a connection with a base station; the reason why a specific terminal releases a connection with a base station; the ID of a service beam experienced by a specific terminal when moving in a coverage area of ​​a base station; the residence time of a specific terminal in each service beam experienced by the specific terminal when moving in a coverage area of ​​a base station; a handover result; or a handover target, wherein the information included in the beam-related information is stored as a profile for multiple terminals.

[0022] According to an embodiment of the present disclosure, the method may further include determining whether the specific terminal moves along the detected path, wherein the determination is performed by comparison to determine whether the beam measurement result reported by the specific terminal is similar to at least a portion of the path.

[0023] According to an embodiment of the present disclosure, the method may further include determining the service beam ID, service beam order and service beam allocation time assigned to the specific terminal based on beam-related information corresponding to the detected path if it is determined that the specific terminal moves along the detected path.

[0024] According to an embodiment of the present disclosure, the method may further include changing the service beam of the specific terminal according to the determined service beam ID, service beam order, and service beam allocation time if it is determined that the specific terminal moves along the detected path.

[0025] According to an embodiment of the present disclosure, a message for supporting mobility may include a handover command message instructing handover to a target cell, wherein the handover command message includes information about the target cell and a first serving beam determined based on beam-related information.

[0026] According to an embodiment of the present disclosure, the information about the target cell and the first serving beam included in the handover command message may be generated based on beam-related information about which handover to the target cell has been successful, among beam-related information of a plurality of terminals.

[0027] According to an embodiment of the present disclosure, a handover command message may be sent to a terminal at a time determined based on beam-related information at which a handover to a target cell has succeeded.

[0028] According to another aspect of the present disclosure, a base station is provided. The base station includes a transceiver configured to send and receive signals, and a controller configured to generate beam-related information for multiple terminals according to beam measurement results received from the multiple terminals, detect a path in a coverage area of ​​the base station using the beam-related information, and send a message for supporting mobility to a terminal determined to be moving along the path based on the beam-related information.

[0029] [Advantageous Effects of the Invention]

[0030] According to an embodiment of the present disclosure, since a base station can collect a movement pattern and history of a terminal and support the mobility of the terminal based thereon, a process related to the mobility of the terminal can be simplified.

[0031] According to an embodiment of the present disclosure, since the terminal movement time, the target cell and the target beam as the movement purpose can be obtained in advance, the electric field of the service beam of the terminal can be prevented from suddenly dropping. Therefore, the stability of the communication connection between the terminal and the base station can be ensured, and the communication performance perceived by the user can also be improved.

[0032] The technical tasks to be accomplished by the present disclosure are not limited to those described above, and a person of ordinary skill in the art to which the present disclosure belongs may consider unmentioned or other technical effects from the embodiments of the present disclosure to be described below.

[0033] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0035] Figure 1 is a diagram for explaining a beam-based communication system according to an embodiment of the present disclosure;

[0036] Figure 2 is a diagram for explaining a handover process in a fifth generation (5G) communication system according to an embodiment of the present disclosure;

[0037] Figure 3 is a diagram for explaining a communication environment according to an embodiment of the present disclosure;

[0038] Figure 4 is a flow chart showing an operation method of a base station according to an embodiment of the present disclosure;

[0039] Figure 5 is a diagram for explaining a path detection process according to an embodiment of the present disclosure;

[0040] Figure 6 is a diagram for explaining a path derivation process according to an embodiment of the present disclosure;

[0041] Figure 7 is a flow chart showing a terminal path determination process according to an embodiment of the present disclosure;

[0042] Figure 8 is a flowchart illustrating a terminal mobility support process according to an embodiment of the present disclosure;

[0043] Fig. 9 is a diagram showing a structure of a terminal according to an embodiment of the present disclosure; and

[0044] Fig.10 is a diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0045] Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. DETAILED DESCRIPTION

[0046] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details that are helpful for understanding, but these are to be considered as 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 conciseness.

[0047] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it will be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and is not intended to limit the present disclosure as defined by the appended claims and their equivalents.

[0048] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes one or more of such surfaces.

[0049] While describing the embodiments in the specification, explanations of technical contents well known in the technical field to which the present disclosure pertains and not directly related to the present disclosure will be omitted if it is determined that they obscure the subject matter of the present disclosure with unnecessary detail.

[0050] For the same reason, in the accompanying drawings, some components are exaggerated, omitted or roughly shown. In addition, the sizes of some components may not fully reflect their actual sizes. In the accompanying drawings, the same reference numerals in different drawings are used for the same elements.

[0051] By referring to the embodiments that will be described in detail with reference to the accompanying drawings, various aspects and features of the present disclosure and methods for implementing these aspects and features will become apparent. However, the present disclosure is not limited to the embodiments disclosed below, but can be implemented in various forms. The contents defined in the specification, such as detailed construction and elements, are only specific details provided to help those of ordinary skill in the art to fully understand the present disclosure, and the present disclosure is only defined within the scope of the attached claims. Throughout the description of the present disclosure, the same reference numerals in different drawings are used for the same elements.

[0052] It will be understood that each block of the flowchart illustration and the combination of blocks in the flowchart illustration can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine so that the instructions executed by the processor of the computer or other programmable data processing device create components for implementing the functions specified in the (multiple) flowchart blocks. These computer program instructions can also be stored in a non-transitory computer-usable or computer-readable storage device, which can instruct a computer or another programmable data processing device to operate in a specific manner so that the instructions stored in the non-transitory computer-usable or computer-readable storage device produce an article of manufacture including an instruction device that implements the functions specified in the (multiple) flowchart blocks. The computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operations are performed on the computer or other programmable device, thereby producing a computer-implemented process so that the instructions executed on the computer or other programmable device provide operations for implementing the functions specified in the (multiple) flowchart blocks.

[0053] In addition, each block of the flowchart diagram may represent a module, a code segment or a code portion, which includes one or more executable instructions for implementing (multiple) specified logical functions. It should also be noted that in some alternative implementations, the functions mentioned in the blocks may not occur in order. For example, depending on the functions involved, two blocks shown in succession may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order.

[0054] The term "~unit" used in the embodiment refers to but is not limited to software or hardware components that perform specific tasks, such as field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC). However, "~unit" does not mean to be limited to software or hardware. The term "~unit" can be advantageously configured to reside on an addressable storage medium and configured to execute on one or more processors. Therefore, "~unit" can include, for example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays and variables. The functions provided in components and "~units" can be combined into fewer components and "~units", or further divided into additional components and "~units". In addition, components and "~units" can be implemented as one or more central processing units (CPUs) in operating devices or secure multimedia cards.

[0055] Figure 1 is a diagram for explaining a beam-based communication system according to an embodiment of the present disclosure.

[0056] refer to Figure 1 , the base station 120 of the beam-based communication system 100 operates a plurality of different beams in its coverage area. The plurality of beams formed by the base station 120 for transmitting signals can be distinguished by beam identifiers (IDs) assigned to the respective beams, and Figure 1 18 beams are exemplarily shown, which is half of the 36 beams operated by the base station 120 .

[0057] The terminal 110 located in the coverage area of ​​the base station 120 measures the beam power periodically or aperiodically, and reports the measured beam power to the base station 120. That is, the terminal 110 selects the best beam with the best beam reference signal received power from the transmit beams of the base station 120 to report the selected best beam to the base station 120, and the base station 120 selects the serving beam of the terminal 110 based on the result reported by the terminal 110, and performs communication with the terminal 110.

[0058] Through the beam-based communication as described above, the base station 120 can obtain the specific location and residence time of the terminal 110 in the coverage area in the unit further subdivided than the cell unit. The mobility of the terminal is guaranteed in a beam-to-beam manner. In addition, because the mobility function of the terminal 110 is supported by beam change and switching, the mobility of the terminal can be guaranteed in a beam-to-beam manner.

[0059] Figure 2 2 is a diagram for explaining a switching process in a fifth generation (5G) communication system according to an embodiment of the present disclosure.

[0060] refer to Figure 2 , shows the case of applying a function split scheme, in which some layer functions of the base station are implemented in different entities. Figure 2In the entities shown as the source cell access unit (access unit, AU) and the target cell AU in the switching process 200, the functions of the physical (physical, PHY), media access control (media access control, MAC) and partial radio link control (partial radio link control, RLC) layers in the layer functions of the base station in the related technology can be implemented, and in the base station entity shown as vNB, the remaining RLC, packet data convergence protocol (packet data convergence protocol, PDCP) and radio resource control (radioresource control, RRC) layer functions can be implemented. However, this functional division scheme is merely exemplary, and any other functional division scheme can be implemented between AU and vNB. In addition, the following explanation can also be applied to the switching process between the source cell and the target cell in which no functional division is applied. In the following, both the entity (AU) including part of the functions including PHY and the entity (vNB) including part of the functions including RRC can be referred to as "base station".

[0061] The 5G communication system also maintains a switching function to support the mobility of the terminal, which may also be referred to as a user equipment (UE). In short, two types of switching can be defined: the first is a network-controlled switching similar to the switching in the related art, and the second is a user equipment-based switching provided for a sudden loss of the electric field. Figure 2 The general network-controlled switching process is exemplarily shown.

[0062] As described above, in the communication system based on beamforming, in operation 205, each AU transmits a beam reference signal (BRS) for beam measurement to the terminal, and in operation 210, the terminal measures the received power of the BRS received from the neighboring base station, and in operation 215, reports the measurement result to the base station (vNB) ( Figure 2 In such a 5G cell measurement report process, the terminal can report the beam ID of the best beam, i.e., the beam with the measured best beam received power, to the base station.

[0063] If an event occurs in which the power of the BRS transmitted from the AU of the neighboring target cell is better than the power of the BRS transmitted from the AU of the current serving cell, the base station (vNB) that has received the report of the measurement result from the terminal determines the handover of the terminal in operation 220. Then, in operation 225, the base station configures resources for the target cell AU to support the terminal, and establishes a general packet radio service (GPRS) tunneling protocol (GPRS tunneling protocol, GTP) tunnel in association with a network entity of the next generation core (NGC) network.

[0064] In operation 230, the base station commands the terminal to perform handover by sending an RRC connection reconfiguration message including a "Mobility Control Info" parameter to the terminal, and in operation 235, the terminal having received the message sends a random access preamble to the AU of the target cell, and receives a random access response to access the target cell in operation 240. In operation 245, the terminal having accessed the target cell sends an RRC connection reconfiguration complete message to the base station (vNB), and then performs a PDCP status reporting process for downlink and uplink in operations 250 and 255. If the handover process is completed, the radio resources of the source cell AU are released in operation 260, and the previous GTP tunnel is also released.

[0065] As described above, even in a communication system to which beamforming is applied, a handover procedure may be performed to support the mobility of a terminal.

[0066] Figure 3 is a diagram for explaining a communication environment 300 according to an embodiment of the present disclosure.

[0067] refer to Figure 3 , which explains the above reference Figure 1 Another example of the beamforming-based communication environment.

[0068] As described above, in a communication environment based on beamforming, the base station 310 communicates with the terminal using multiple different beams. In this case, in order to determine the service beam of the terminal, the base station periodically or non-periodically receives a report of the beam measurement result from the terminal, and in an environment where the terminal moves at high speed, the reliability of the beam measurement result may not be fully guaranteed. For example, in the case of a terminal of a user traveling on a high-speed train, in the case of a terminal in a vehicle moving along a highway, or in the case of a passenger's terminal, when performing beam measurement and reporting the result of the beam measurement, the optimal beam may have been changed. In this case, selecting a service beam based on the report of the terminal may be an inaccurate and inefficient process, and it is necessary to improve this process.

[0069] Figure 3 FIG. 3 shows a situation where the terminal moves along a predetermined path in the coverage area of ​​the base station 310. Figure 3 , when a high-speed train travels along a railway, a terminal of a user traveling on the high-speed train moves along a path 320, and when a vehicle travels on a highway, a terminal of the vehicle or a terminal of a passenger moves along a path 330.

[0070] In this case, even if the terminal moving along the path 320 or 330 moves at a high speed, the mobility of the terminal is relatively constant. That is, because the multiple terminals moving along the path 320 as a railway and the path 330 as a highway move in the same direction or a very similar direction, the beam changes of the base station 310 experienced by each terminal are exactly the same or extremely similar to each other. As a specific example, the terminal moving along the path 320 is subjected to beam changes in the order of beam IDs of 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5 and 4, and the terminal moving along the path 330 is subjected to beam changes in the order of beam IDs of 9, 8, 7, 6, 5, 4, 3, 2 and 1. If the terminal moving along such a fixed path moves at a substantially constant speed in the coverage area of ​​the base station 310, the ratio of the time of the multiple beams to the total time experienced by the terminal in the coverage area can also be similar to each other.

[0071] Hereinafter, an embodiment for supporting terminal mobility in consideration of characteristics of a terminal moving along a fixed path in a beamforming communication system environment as described above will be described in detail.

[0072] Figure 4 is a flowchart illustrating an operation method of a base station according to an embodiment of the present disclosure.

[0073] refer to Figure 4, first, in operation 410, the base station according to the operation method 400 collects beam histories from multiple terminals located in the coverage area of ​​the base station itself. The collection of beam histories means that the base station receives, stores and manages beam measurement results reported periodically or aperiodically by multiple terminals. The terminal moving along the path will report to the base station the change of the best beam experienced by the terminal, and if the beam measurement result is reported from the terminal, the base station can store the acquired beam-related historical information. The beam history information may include one or more beam-related information, such as the beam ID of the best beam reported by the terminal, the total time the terminal experiences the best beam, and the reception strength of the best beam experienced by the terminal.

[0074] In operation 420, the base station detects a path in the base station coverage area. The detection of the path may mean detecting a route along which a terminal located in the base station coverage area tends to move. The base station may detect a path along which a terminal in the coverage area moves relatively fixedly by comparing and analyzing beam histories collected from multiple terminals. Figure 3 As an example, the base station 310 may detect a first path 320 and a second path 330 located in the coverage area. One or more paths may exist in the coverage area of ​​the base station and will be referenced. Figure 5 and Figure 6 Describe the detailed process of base station detection path.

[0075] In operation 430, the base station that has detected the path determines whether the terminal moving in the coverage area of ​​the base station moves along the path. That is, the base station determines whether the terminal connected to the base station receives the service and moves in the path previously detected in operation 420, and this determination process can be performed based on the beam-related information reported by the terminal to the base station. The base station can determine whether the terminal that has reported the beam-related information moves in one or more paths detected in operation 420 by comparing the beam-related information reported by the terminal with the beam history owned by the base station itself. Figure 7 This determination process is described in detail.

[0076] In operation 440, the base station that has determined that the terminal has moved in the path performs a process for optimizing the switching of the corresponding terminal. By analyzing the beam history collected in operation 410, the base station can identify a target cell outside the coverage area of ​​the base station to which the terminal is connected through switching, and can identify what service beam is allocated to the terminal when connected to the corresponding target cell. Therefore, if the terminal identified as moving in the path in operation 430 continues to move along the path, the base station can predict or estimate which service beam of which target cell the terminal will be connected to. Therefore, the base station can include such information in a message sent to the terminal (e.g., a switching-related message or a switching command message) to support the mobility of the terminal, and thus can reduce unnecessary signaling overhead or delay that would otherwise be required for the terminal to connect to the target cell. Will refer to Figure 8 Describe the detailed handover optimization process.

[0077] Figure 5 is a diagram for explaining a path detection process according to an embodiment of the present disclosure.

[0078] refer to Figure 5 Table 500 illustrates a method in which a base station collects beam-related information reported by a terminal for storing and managing beam history. Figure 5 The configuration of the beam history shown in FIG. 1 is merely exemplary, and the base station may further add and manage other parameters of the beam-related information reported from the terminal, or may store and manage information other than the beam history. Figure 5 The beam history outside of the partial content shown.

[0079] refer to Figure 5 , the beam history information may include a specific beam ID, a dwell time (i.e., duration) in an area corresponding to the corresponding beam ID, performance indicators, and other information. The beam history information may be managed by the terminal by accumulating and storing beam-related information reported by the terminal through beam measurement. The beam-related information may be stored and managed in the form of a beam-related profile for each terminal.

[0080] like Figure 5 As shown in , the terminal reports beam-related information to the base station immediately after configuring the connection with the base station, and this connection may occur due to various reasons, such as call establishment, handover entry (i.e., received handover), and RRC connection reestablishment. The base station can manage this connection configuration reason as a "start reason" item. Thereafter, the terminal periodically or aperiodically reports beam-related information until the connection with the base station is released, and the base station can manage various connection release reasons, such as call release and handover out (i.e., handover to the target cell), as "end reason" items.

[0081] While maintaining the connection, the terminal periodically or aperiodically reports beam-related information to the base station, and the beam-related information may be the beam ID of the beam measured by the terminal with the best reception strength. If the terminal continuously reports the best beam, the base station may store the beam ID reported by the terminal in association with the residence time in the corresponding beam. If the same beam ID is continuously reported, it means that the residence time in the corresponding beam area is relatively long. In addition, the base station may also manage beam-related information in association with performance indicators based on the received signal strength reported by the terminal in the corresponding beam area.

[0082] If the best beam of the beam-related information received by the base station from a specific terminal in each unit time Ts is b 1 、b 2 、b 3 、b 4 ,......b k , the terminal can determine that the stay time of the terminal in the area corresponding to the specific beam is the time of continuous reception of the same beam ID. The following Table 1 shows an example.

[0083]

Table 1

[0084] <![CDATA[b 1 ]]> <![CDATA[b 2 ]]> <![CDATA[b 3 ]]> <![CDATA[b 4 ]]> <![CDATA[b 5 ]]> <![CDATA[b 6 ]]> <![CDATA[b 7 ]]> <![CDATA[b 8 ]]> <![CDATA[b 9 ]]> ... Beam ID 5 12 12 12 12 12 12 12 13 ...

[0085] Therefore, if the beam ID is as reported in Table 1 above, the base station can estimate that the total stay time of the terminal in the area with beam ID number 12 is T=7*T s The base station can track how long each terminal stays in the area corresponding to which beam in the base station's own coverage area, and it can Figure 5 The information is stored and managed in the form of a table (or a configuration file of the terminal) shown in . As described above, due to various reasons in the coverage area of ​​the base station, the terminal can release the connection, and in this case, due to the mobility of the terminal, the terminal can perform a handover to another base station. In this case, the base station stores the result of the handover in the beam history to manage the result of the handover. If the handover is successful, the base station can store and manage the ID of the target cell to which the terminal is connected by the handover and the beam ID of the target cell assigned to the terminal when the terminal is first connected to the target cell.

[0086] The base station is based on the above reference Figure 5 The beam history information is used to determine whether the terminal in the base station coverage area moves along the path, and in the following, reference will be made to Figure 6 and Figure 7 This is described in detail.

[0087] The base station derives the paths existing in the coverage area before determining whether the terminal moves in the path.

[0088] Figure 6 is a diagram for explaining a path derivation process according to an embodiment of the present disclosure.

[0089] refer to Figure 6 In the path derivation process 600, the base station 610 continuously receives reports of beam-related information from a plurality of terminals moving along the path 620. In this case, the terminals moving along the path 620 move on a fixed route (e.g., a road) as the path 620, and the order of beams experienced by the terminals is very similar to each other. Figure 6 In the example shown in , the terminal moving along path 620 has a very high probability of reporting the best beam in the order of beams 9, 8, 7, ..., and 1. In other words, multiple terminals moving along path 620 report beam-related information at different time points and intervals, but the order of beam IDs reported by each terminal and the ratio of the dwell time will be approximately the same or extremely similar to each other. In other words, the base station configures and stores the beam-related information (i.e., beam profile) reported by the terminals moving along path 620 as beam history 630, and if the beam history has a high similarity, the base station can identify the corresponding beam history as a specific path.

[0090] Will refer to Figure 7 Describes the detailed process by which a base station identifies a path and determines the movement of a terminal along the path.

[0091] Figure 7 is a flowchart illustrating a terminal path determination process according to an embodiment of the present disclosure.

[0092] refer to Figure 7 First, at operation 710, the process 700 of the base station identifying a path may start by clustering beam history information. For example, the clustering process may be performed whenever the number of aggregated beam histories (i.e., profiles) collected by the base station from the terminals in the cell becomes equal to or greater than a predetermined number, or the clustering process may be performed at specific time intervals, or the clustering process may be performed aperiodically according to the input of an entrepreneur or manager.

[0093] During the clustering process, the base station considers that candidate pairs with a total residence time of 5*Ts or less have low reliability in the candidate pair list, each candidate pair consisting of "beam ID" and "dwell time", and excludes low reliability candidate pairs from the candidate pair list. In other words, if the total number of reports of terminals in the beam history owned by a specific terminal is less than a predetermined number, the base station can exclude the corresponding history from the path derivation process. The threshold number of such reports can be adjusted to another value. According to one embodiment, the beam history candidate pairs that are clustering targets may correspond only to beam history candidate pairs in which the connection to the target cell through switching has been successful in the coverage area of ​​the base station. This is because only the information of the terminal that has been handed over from the coverage area through successful handover can be used for other terminals.

[0094] Then, the base station performs a clustering process for the candidate pairs with safety reliability and determines similarities between the candidate pairs in operation 720. The similarity determination process is performed by selecting two of the plurality of beam history candidate pairs, and the similarity determination process is performed relative to the number of all cases in which two of all beam history candidate pairs with safety reliability are selected.

[0095] For example, assuming that the beam history candidate pair reported by the first terminal is U i,1 = {b i,1 ,t i,1}, and i may be the ID of the beam experienced by the corresponding terminal. Similarly, assuming that the beam history candidate pair reported by the second terminal is U i,2 = {b i,2 ,t i,2 Then, the base station first includes the two beam history candidate pairs U i,1 and U i,2 The number of IDs of the beams in the two candidate pairs is compared with each other. If the number of IDs of the beams included in the two candidate pairs is not equal to each other, the two terminals are likely to move along different paths. If the number of IDs of the beams included in the two candidate pairs is equal to each other, the base station determines that the IDs of the beams included in the two candidate pairs are equal to each other. i,1} and {b i,2} are equal to each other in terms of value and order. This process can be expressed as in the following formula 1.

[0096] [Formula 1]

[0097] Is {b 1，1 , b 2，1 , b 3，1 , b 4，1 , …, b i，1}={b 1，2 , b 2，2 , b 3，2 , b4，2 , …, b i，2}

[0098] If Equation 1 is satisfied, the base station determines the similarity by comparing the beam IDs and the corresponding dwell times included in the two beam history candidate pairs with each other. This process may be performed according to Equation 2 below.

[0099] [Formula 2]

[0100]

[0101] In formula 2, T 1 =t 1,1 +t 2,1 +t 3,1 +...+t i,1 and T 2 =t 1,2 +t 2,2 +t 3,2 +...+t i,2 represents the total time that the two terminals as comparison targets stay in the base station coverage area, and t i,j represents the time that the jth terminal stays in the area corresponding to the i-th beam ID. In Formula 2, the stay time is divided into T 1 and T 2 The reason (i.e., the reason) is to derive accurate results by comparing the ratio of the time experienced by the two terminals to the total time when the terminals move at different speeds. In Formula 2, since the term "i" corresponds to the number of all beam IDs included in the beam history candidate pair, and the number of beams experienced by the two terminals is equal to each other, the term "i" will be applied equally to the two terminals. The left side of Formula 2 corresponds to the result value obtained by comparing the difference between the residence times of the two terminals with each other, and if the result value on the left side of Formula 2 is less than ε on the right side, it can be considered that the residence times experienced by the two terminals are similar to each other. The value of ε is a certain adjustable value, and since the value is configured to be low, the similarity between the terminals can be determined.

[0102] If Equation 2 is satisfied, in operation 730, the base station may determine that terminals corresponding to two candidate pairs as comparison targets have passed through the same path in the coverage area, and the path may be derived by the definition in Equation 3 below.

[0103] [Formula 3]

[0104] P n = {B i,n ,T i,n , N}

[0105] B 1，n , B 2，n , B3，n , B 4，n , …, B i，1}={b 1，1 , b 2，1 , b 3，1 , b 4，1 , …, b i，1}={b 1，2 , b 2，2 , b 3，2 , b 4，2 , …, b i，2}

[0106]

[0107] According to an embodiment of the present disclosure, a handover command message may be sent to a terminal at a time determined based on beam-related information at which a handover to a target cell has succeeded.

[0108] In formula 3, P n Represents the derived path, and n represents the path index in the coverage area. N represents the number of terminals that have passed through the path (i.e., the number of beam histories), and it becomes N=2 at the initial path derivation time. B represents a set of beam IDs included in the path, and the number and order of beam IDs are the same as the number and order of beam IDs experienced by the candidate pair. T represents the reference time experienced by the terminal moving along the corresponding path, and as described above with reference to Formula 2, it can be the ratio of the time the terminal stays in a specific beam ID area to the total experienced time.

[0109] Then, if a specific path is derived, the base station can obtain the derived path P by combining another beam history that the base station itself has with the derived path P n The comparison is performed to determine the similarity. That is, operation 720 may be repeatedly performed for the entire beam history candidate owned by the base station. Through such a process, the result value moving along a specific route is accumulated and corrected, and thus the derived path may be strengthened, and the accuracy and reliability of the path may be gradually improved.

[0110] Specifically, the following formula 4 is similar to formula 1, but it differs from formula 1 in that the two initial candidate pairs are not compared with each other, but the derived path P n The order of beam IDs is compared with the order of beam IDs in the beam history of the new terminal.

[0111] [Formula 4]

[0112] Is {b 1，1 , b 2，1 , b 3，1 , b 4，1 , …, b i，1}={b 1，2, b 2，2 , b 3，2 , b 4，2 , …, bi，2}

[0113] Then, if equation 4 is satisfied, the dwell time of the beam ID of the corresponding terminal is determined by comparison with the path P n Whether the ratios of the residence times are similar to each other, and comparison can be performed according to the following Formula 5.

[0114] [Formula 5]

[0115]

[0116] Where T n =T 1，2 +T 2,n +T 3,n +…+T i，n

[0117] If equation 5 is satisfied, it can be determined that the terminal that has reported the corresponding beam profile has passed path P n , and the path can be enhanced according to the following formula 6. The base station can update P according to the following formula 6 n .

[0118] [Formula 6]

[0119]

[0120] According to the above process, in operations 740 and 750, the base station determines whether the corresponding terminal moves on the derived path by comparing the beam-related information reported by the new terminal with the derived path. Figure 8 The process by which a base station determines that a specific terminal moves on a corresponding path is described in detail, and independently of this determination process, the base station can use the beam-related information of the specific terminal to continuously update the database of the path.

[0121] Then, through such path derivation and terminal determination, a process in which the base station supports the mobility of the terminal will be described.

[0122] Figure 8 is a flowchart illustrating a terminal mobility support process according to an embodiment of the present disclosure.

[0123] refer to Figure 8 , as referenced above Figure 4 As described above, in the terminal mobility support process 800, the base station can optimize the handover process by supporting the mobility of the terminal determined to be moving on the path. Figure 5 , 6The path derived by the process described in 7 is performed using the beam history of the terminal that has moved to the coverage area of ​​another cell by successfully performing handover. That is, the derived path reflects the result that the specific terminal has successfully connected from the base station to the adjacent base station, and if the specific terminal determined to move on the path performs handover based on the result that the previous terminal has successfully performed handover, the probability that the specific terminal will successfully connect to the adjacent base station is very high.

[0124] Based on this, we will describe in more detail Figure 7 Operation 740. The base station first identifies whether the beam-related information reported by a certain terminal corresponds to at least a portion of the derived path, so as to determine whether the specific terminal moves along the path. This process can be performed according to the following equation 7.

[0125] [Formula 7]

[0126] Is {b 1，1 , b 2，1 , b 3，1 , b 4，1 , …, b i，1}={b 1，n , b 2，n , b 3，n , b 4，n , …, b j，n}

[0127] In Formula 7, j may represent the number of beam IDs reported by the terminal before the comparison time, and may have a value less than the total number i of beam ID sets included in the path. That is, the base station determines the similarity between the collected beam IDs reported by a specific terminal in the coverage area, the beam ID of the path, and a portion of the residence time candidate pair by comparison. If it is determined according to Formula 7 that the beam ID value and the order are the same, the ratios of the residence times are compared with each other according to the following Formula 8.

[0128] [Formula 8]

[0129]

[0130] Where T = T 1 +T 2 +T 3 +…T j , T n =T l，n +T 2，n +T 3,n +…+T j，n

[0131] In addition, ε 2is a specific adjustable value, and Equation 8 corresponds to a process of determining whether the ratio of the stay time of the terminal until the jth beam ID satisfies Equation 7 is similar to the ratio of the stay time of the path. If Equation 8 is satisfied, the base station can determine that the corresponding terminal is passing through the path P n and it can be estimated that the corresponding terminal passes through the area corresponding to the remaining beam ID on the path Pn {B j+1,n ,B j+2,n ,…,B i,n In addition, the base station can estimate that the corresponding terminal will stay in the area corresponding to each beam ID through which the corresponding terminal will pass for a time as shown in the following formula 9.

[0132] [Formula 9]

[0133]

[0134] Therefore, because the base station can predict the beam ID that the corresponding terminal will pass through, in operation 810, when the terminal moves forward, the base station can determine what service beam to allocate to the terminal in order to communicate with the terminal. Then, the base station can calculate how long the terminal will stay in the area corresponding to each beam ID, and thus it can The time at which it will allocate the corresponding serving beam to the terminal is predicted. Therefore, the base station can change the serving beam even if no separate feedback on the beam measurement result or beam-related information is reported from the terminal at the predicted time.

[0135] The base station already knows which target cell the terminal will perform handover to on the path, and information about the service beam to be first allocated in the target cell. That is, because the path is derived from the beam history of the terminal that has successfully switched, the base station can determine the time to send a handover command message to the terminal in operation 820, and can also determine the ID of the target cell as the handover target and the first service beam to be allocated in the target cell in operation 830.

[0136] Therefore, in operation 840, the base station sends a handover message to the terminal, which includes information about the target cell ID and the beam ID of the target cell, and the time of sending the handover command message is the time derived in operation 820, and can be an appropriate time when the terminal should prepare for handover before moving away from the coverage area of ​​the base station. In other words, the base station refers to the history of other terminals that have successfully switched, and if a specific terminal moves on the same path as the path of the corresponding terminal, the base station can prevent unnecessary overhead and delay caused by handover failure by optimizing the handover time and process of the specific terminal. Due to the mobility of the terminal, the handover preparation process is quite time-consuming, and if the terminal performs handover in a state where the terminal already knows the target cell and what service beam to use, the stability of the handover can be greatly guaranteed. In particular, in the case of high-speed movement of the terminal, the time required for handover preparation is shortened, so greater advantages can be obtained by operating according to the embodiment.

[0137] Fig. 9 is a diagram showing a structure of a terminal according to an embodiment of the present disclosure.

[0138] refer to Fig. 9 , the terminal 900 may include a transceiver 910, a terminal controller 920, and a memory 930. In the present disclosure, the terminal controller 920 may be defined as a circuit or an application specific integrated circuit or at least one processor.

[0139] The transceiver 910 transmits and receives signals with another network entity. The transceiver 910 may receive a synchronization signal from, for example, a base station, and may be implemented in the form of a radio frequency (RF) unit including a modem.

[0140] According to the embodiments proposed in the present disclosure, the terminal controller 920 can control the overall operation of the terminal. For example, the terminal controller 920 can control the transceiver 910 and the memory 930 to perform the operation according to the embodiments described above with reference to the accompanying drawings. Specifically, the terminal controller 920 can measure the beam-related information according to the beam received from the base station to report the measurement result to the base station, and can perform communication with the base station by allocating a service beam from the base station. In addition, the terminal controller 920 can use the information included in the handover message received from the base station to perform a handover to a neighboring target cell.

[0141] The memory 930 may store at least one of information transmitted and received through the transceiver 910 or information generated by the terminal controller 920 .

[0142] Fig.10 is a diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0143] refer to Fig.10, the base station 1000 may include a transceiver 1010, a base station controller 1020, and a memory 1030. In the present disclosure, the base station controller 1020 may be defined as a circuit or an application specific integrated circuit or at least one processor.

[0144] The transceiver 1010 transmits and receives signals with another network entity. The transceiver 1010 may transmit, for example, a synchronization signal to the terminal, and may be implemented in the form of an RF unit including a modem.

[0145] According to the embodiments proposed in the present disclosure, the base station controller 1020 can control the overall operation of the base station. For example, the base station controller 1020 can control the transceiver 1010 and the memory 1030 to perform the operations according to the embodiments described above with reference to the accompanying drawings. Specifically, the base station controller 1020 can store and manage the beam history of the terminal according to the beam measurement results received from the terminal, detect the path in the coverage area based on the stored beam history, and determine whether the terminal moves on the path. In addition, the base station controller 1020 can select the best beam according to the mobility of the terminal to allocate the selected best beam to the terminal as a service beam, and send a switching-related message including information about the target cell and the specific beam to the terminal, so that the terminal performs the switching.

[0146] The memory 1030 may store at least one of information transmitted and received by the transceiver 1010 or information generated by the base station controller 1020 .

[0147] According to the embodiments described above, the signaling overhead and delay that may occur when a terminal moves in a communication system applying beamforming can be reduced. In particular, the handover process of a terminal moving at high speed can be optimized, and user-perceived performance can also be improved.

[0148] While the invention has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A method performed by a base station in a wireless communication system, the method comprising: generating beam-related information of the plurality of terminals based on beam measurement results received from the plurality of terminals, wherein the beam-related information includes information about the number of beam identifiers (IDs) and dwell times relative to the beam IDs; identifying similarities between dwell times included in beam-related information of two terminals among the plurality of terminals by: comparing the dwell times of the two terminals with each other; identifying a path within the coverage of the base station based on the similarity between the identified stay times of the two terminals; In the case where the similarity between the identified stay times of the two terminals satisfies a specific condition, determining that the routes along which the two terminals move form the path; and A message for supporting handover is transmitted to a terminal determined to move along the formed path based on the beam-related information.

2. The method according to claim 1, wherein the identification of the similarity comprises: comparing the number of beam identifiers (IDs), the values ​​of the beam IDs, and the order of the beam IDs included in the beam-related information of the two terminals with each other; and Ratios of the dwell times with respect to the beam IDs included in the beam-related information of the two terminals are compared with each other.

3. The method according to claim 1, in, The dwell time includes the dwell time that a specific terminal stays in each service beam experienced by the specific terminal when moving in the coverage area of ​​the base station, and The beam-related information further includes information about at least one of the following: a reason why a specific terminal configures a connection with a base station; a reason why the specific terminal releases a connection with a base station; an identifier (ID) of a service beam experienced by the specific terminal when moving in a coverage area of ​​the base station; a handover result; a handover target, and The information included in the beam-related information is stored as a profile of the plurality of terminals.

4. The method according to claim 1, further comprising determining whether the terminal moves along the identified path, Wherein a determination is performed by comparison to determine whether beam measurements reported by a particular terminal are similar to at least a portion of the path.

5. The method according to claim 4, further comprising: In a case where it is determined that the specific terminal moves along the identified path, determining a service beam identifier (ID), a service beam order, and a service beam allocation time allocated to the specific terminal based on beam-related information corresponding to the identified path; as well as In case it is determined that the specific terminal moves along the identified path, the service beam of the specific terminal is changed according to the determined service beam ID, the determined service beam order, and the determined service beam allocation time.

6. The method according to claim 1, The message for supporting handover includes a handover command message indicating handover to a target cell, The handover command message includes information about the target cell and the first serving beam determined based on the beam-related information, in, The information about the target cell and the first serving beam included in the handover command message is generated based on beam-related information for which handover to the target cell has succeeded, among beam-related information of the plurality of terminals, and The handover command message is sent to the terminal at a time determined based on beam-related information that the handover to the target cell has been successful.

7. A base station in a wireless communication system, the base station comprising: a transceiver configured to transmit and receive signals; and The controller is configured as: generating beam-related information of the plurality of terminals based on beam measurement results received from the plurality of terminals, wherein the beam-related information includes information about the number of beam identifiers (IDs) and dwell times relative to the beam IDs; identifying similarities between dwell times included in beam-related information of two terminals among the plurality of terminals by: comparing the dwell times of the two terminals with each other; identifying a path within the coverage of the base station based on the similarity between the identified stay times of the two terminals; In the case where the similarity between the identified stay times of the two terminals satisfies a specific condition, determining that the routes along which the two terminals move form the path; and A message for supporting handover is transmitted to a terminal determined to move along the formed path based on the beam-related information.

8. The base station according to claim 7, wherein: The controller is also configured to: comparing the number of beam IDs, the values ​​of the beam IDs, and the order of the beam IDs included in the beam-related information of the two terminals with each other, and Ratios of the dwell times with respect to the beam IDs included in the beam-related information of the two terminals are compared with each other.

9. The base station according to claim 7, wherein the dwell time includes the dwell time that the specific terminal stays in each service beam experienced by the specific terminal when moving in the coverage area of ​​the base station, and wherein the beam-related information further includes information about at least one of the following: a reason why the specific terminal configures a connection with the base station; a reason why the specific terminal releases a connection with the base station; an identifier (ID) of a serving beam experienced by the specific terminal when moving in the coverage of the base station; a handover result; a handover target, and The information included in the beam-related information is stored as a profile of the plurality of terminals.

10. The base station according to claim 7, wherein: The controller is further configured to determine whether a particular terminal moves along an identified path, and perform a comparison to determine whether beam measurements reported by the particular terminal are similar to at least a portion of the path.

11. The base station according to claim 10, in, The controller is further configured to determine, in a case where it is determined that the specific terminal moves along the identified path, a service beam identifier (ID), a service beam order, and a service beam allocation time allocated to the specific terminal based on beam-related information corresponding to the identified path, and The controller is further configured to change the service beam of the specific terminal according to the determined service beam ID, the determined service beam order and the determined service beam allocation time when it is determined that the specific terminal moves along the identified path.

12. The base station according to claim 7, wherein the message for supporting handover comprises a handover command message instructing handover to a target cell, and The handover command message includes information about the target cell and the first serving beam determined based on the beam-related information.

13. The base station according to claim 12, in, The information about the target cell and the first serving beam included in the handover command message is generated based on beam-related information for which handover to the target cell has succeeded, among beam-related information of the plurality of terminals, and The handover command message is sent to the terminal at a time determined based on beam-related information that the handover to the target cell has been successful.

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