Terminal and program

Abstract

To secure a low delay performance or the like when performing a handover in a NSA construction.SOLUTION: A radio communication terminal that can be simultaneously communicated by a first communication system and a second communication system, comprises: a detection part that detects deterioration of a radio quality of a cell of the second communication system that is currently connected; a first determination part that determines a target cell of the second communication system that becomes a candidate destination of the handover; a band of a cell of the first communication system that is currently connected; a determination part that determines whether or not a combination of bands of a target cell of the second communication system is a combination of an acceptable band; and a handover control part that controls the handover of the cell of the first and second communication systems on the basis of a determination result of the determination part.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a terminal and a program. [Background technology]

[0002] 3GPP (3rd Generation Partnership Project (registered trademark)), an international standardization organization, is studying New Radio (NR), a new radio access technology for fifth-generation (5G) cellular systems. NR is a technology that is being studied to enable a wider variety of services than LTE and LTE-Advanced, the fourth-generation (4G) cellular systems.

[0003] For example, in the case of 5G cellular systems, a scenario is being considered for a non-stand alone (NSA) network system (hereafter referred to as NSA configuration) in which 4G LTE core networks and base stations (cells) will be retained while 5G base stations (cells) will be introduced from some base stations. In the NSA configuration, handovers occur in the NR and LTE cells, but in 5G there are many use cases that require real-time communication (i.e. low latency), including vehicle platooning and remote control (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Yoshiki Yamazaki, “Overview of 5G and its use cases” [online], February 21, 2020, Association of Radio Industries and Businesses, [Retrieved April 12, 2023], Internet <chrome-extension: / / efaidnbmnnnibpcajpcglclefindmkaj / https: / / www.kiai.gr.jp / jigyou / h31 / PDF / 0221p2.pdf> Summary of the Invention [Problem to be solved by the invention]

[0005] In order to achieve low latency in an NSA configuration, it is necessary to minimize the time during which a terminal is not connected to an NR cell (in other words, the time during which a terminal is connected only to an LTE cell and is disconnected from an NR cell), but there is no technology yet that can fully satisfy this requirement.

[0006] The present disclosure has been made in consideration of the above points, and aims to provide a handover support technology that can ensure low latency, etc., when performing a handover in an NSA configuration. [Means for solving the problem]

[0007] A terminal according to one embodiment of the present disclosure is a terminal capable of simultaneous communication in both a first communication method and a second communication method, and includes a detection unit that detects deterioration in wireless quality of a currently connected cell of the second communication method, a determination unit that determines a target cell of the second communication method that is a candidate destination for handover when deterioration in wireless quality is detected, a determination unit that determines whether a combination of the band of the currently connected cell of the first communication method and the band of the target cell of the second communication method is an acceptable band combination, and a handover control unit that controls handover of the cell of the first communication method and the cell of the second communication method based on a determination result of the determination unit. Effect of the Invention

[0008] According to the present disclosure, it is possible to ensure low latency, etc., when performing handover in an NSA configuration. [Brief description of the drawings]

[0009] [Figure 1] This is a diagram for explaining an overview of handover specifications in the current NSA configuration. [Diagram 2] FIG. 1 is a diagram illustrating a standard specification related to a measurement report (event type). [Diagram 3] A diagram to explain a case where handover between NR cells is not possible. [Figure 4] FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system. [Diagram 5] FIG. 2 is a diagram illustrating an example of a hardware configuration of a terminal and a base station. [Figure 6] FIG. 2 is a diagram illustrating an example of a functional block configuration of a terminal. [Figure 7A] FIG. 11 is an explanatory diagram for the case where the LTE-NR band combination is OK. [Figure 7B] FIG. 11 is an explanatory diagram for a case where LTE-NR band combination is NG. [Figure 8] 13 is a flowchart showing an example of a handover support process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same or similar configurations.

[0011] A. This embodiment (Summary of handover specifications in the current NSA configuration) First, the handover specifications in the current NSA configuration will be explained with reference to FIG.

[0012] A wireless communication terminal receives radio waves from a destination base station and neighboring base stations a and b adjacent to the destination base station, and measures wireless qualities such as radio wave strength (RSRP: Reference Signal Received Power) and signal to interference plus noise ratio (SINR) (step S1).Then, the wireless communication terminal transmits the measurement results to the destination base station by a Measurement Report message (step S2).

[0013] The base station that has received the measurement report message determines which adjacent base station to perform handover to (i.e., the handover candidate base station) based on information on radio quality such as radio wave strength, signal-to-interference-plus-noise ratio, and radio resources included in the measurement report message (step S3). When the handover candidate base station (adjacent base station a in FIG. 1) is determined, the wireless communication terminal starts a handover procedure with the handover candidate adjacent base station a (step S4).

[0014] Thus, in order for the base station to determine the handover destination, it is necessary to receive a measurement report message from the wireless communication terminal. The timing at which the wireless communication terminal transmits the measurement report message is determined based on a transmission trigger set in the wireless communication terminal. There are two types of transmission triggers that determine the transmission timing of the measurement report message: a "periodic type trigger" in which the wireless communication terminal transmits at regular intervals, and an "event type trigger" in which the wireless communication terminal transmits only when specific radio wave conditions are satisfied. The event type trigger is specified in 3GPP TS 38.331 (see FIG. 2), and currently, events A1 to A6, B1, B2, etc. are specified.

[0015] As an example, events A1 and A2 specify conditions regarding the wireless quality of the serving cell (the cell on which the wireless communication terminal is camped), events A3 to A6 specify conditions regarding the wireless quality of adjacent cells (cells adjacent to the serving cell), and events B1 and B2 specify conditions regarding the wireless quality of Inter RAT (Radio Access Technology).

[0016] The wireless communication terminal transmits a measurement report message to the base station in accordance with the transmission trigger conditions (hereinafter, event conditions) shown in FIG.

[0017] As already explained, in the NSA configuration in which both NR and LTE radio links can be used simultaneously, cell handover occurs in each of NR and LTE. For example, when a wireless communication terminal detects deterioration of NR radio quality, it attempts to perform NR handover according to the event conditions shown in FIG. 2. However, handover is not always possible because of the following constraints. For example, in the communication field standards (e.g., ARIB STD-T120-38 / 101-3), combinations of LTE and NR bands (frequencies) in the NSA configuration (EN-DC: E-UTRA NR Dual Connectivity) are specified, and there are combinations of LTE and NR bands that are allowed (combinations OK) and combinations that are not allowed (combinations NG) depending on the difference in frequency and communication method (FDD (Frequency Division Duplex) / TDD (Time Division Duplex)).

[0018] For example, the combination of LTE band B8 (900 MHz band) and NR band n28 (700 MHz band) is not allowed, and the combination of LTE band B42 and NR band n3 (or n28, etc.) is also not allowed because the former is TDD and the latter is FDD. Note that the judgment conditions (combination judgment conditions) for judging whether the combination of LTE and NR is OK or not can be set based on the standard and the specifications of the wireless communication terminal.

[0019] In this way, in the NSA configuration, because of the above restrictions on the combination of LTE and NR bands, even if the NR wireless quality deteriorates, handover between NR cells is not possible, and communication with the NR cell is cut off (i.e., the connection with the NR cell is lost). In such cases, it is necessary to respond by waiting until the NR wireless quality improves, which causes a problem of long delay times.

[0020] Figure 3 is an explanatory diagram of a case where handover between NR cells in an NSA configuration is not possible. In Figure 3, it is assumed that the combination of LTE and NR bands, LTE band "a" and NR band "β", and the combination of LTE band "b" and NR band "α", are "combinations OK". Also, the dotted lines in the middle of Figure 3 indicate the wireless quality threshold (quality threshold) Qth1 for determining whether or not handover is required between NR cells in an NSA configuration.

[0021] In the example shown in FIG. 3, when the wireless quality of the NR band falls below a quality threshold Qth1, the connection with the NR cell is lost (see "NR off-zone A" in FIG. 3). In this case, the wireless communication terminal attempts to handover from NR band "α" in NR off-zone A to NR band "β" with better wireless quality, but the LTE band that can be combined with NR band "β" is not the currently connected LTE band "b" but LTE band "a". For this reason, currently, handover between NR cells cannot be performed, and it is necessary to wait until the NR wireless quality improves, resulting in a long delay time (see "Delay Time" in Zone A shown in FIG. 3).

[0022] (Measures) In order to solve the above problem, in this embodiment, even if the wireless quality of NR deteriorates in a 5G NR configuration, the combination of the LTE band and the NR band is taken into consideration, and the connection is switched between LTE cells based on the wireless quality of NR, and then the connection is switched to an NR cell with good wireless quality (i.e., a handover is performed), thereby shortening the time it takes to lose connection with the NR cell and enabling low latency to be achieved. Note that in the present invention, the term "handover" is used to refer to not only handover processing between base stations according to the standard, but also processing to switch the base station to be connected.

[0023] <System configuration> A wireless communication system according to this embodiment will be described. The wireless communication system according to this embodiment assumes an NSA-configured system that introduces LTE-NR dual connectivity, in which data is divided between a base station (eNB: evolved NodeB) of an LTE system and a base station (gNB: g NodeB) of an NR system, and data is simultaneously transmitted and received by these base stations. Note that the wireless communication system according to this embodiment may apply either a TDD (Time Division Duplex) or an FDD (Frequency Division Duplex) method, and a different method may be applied to each cell formed by each base station.

[0024] FIG. 4 is a diagram showing an example of the configuration of a wireless communication system 1 according to the present embodiment. A wireless communication terminal (UE: User Equipment) 10 can be wirelessly connected to a base station 20 of the LTE system and a base station 20 of the NR system simultaneously. The wireless communication terminal 10 can be applied to any terminal compatible with the 5G NSA configuration, including smartphones, mobile terminals, wearable terminals, tablet terminals, personal computers (PCs), notebook PCs, as well as various IoT terminals (e.g., home appliances such as televisions, cameras, and game consoles, medical equipment, various sensors, etc.), and connected terminals for moving objects such as vehicles and drones (e.g., navigation systems, etc.).

[0025] The wireless communication terminal 10 is connected to the base station 20. The wireless communication terminal 10 may be connected (carrier aggregation) to the base station 20 using a plurality of cells. When the wireless communication terminal 10 is connected (dual connectivity) via a plurality of base stations 20, the base station (here, eNB) 20 to which the wireless communication terminal 10 is initially connected is called a master node (MN: Master Node), and the base station (here, gNB) 20 to which the wireless communication terminal 10 is additionally connected is called a secondary node (SN: Secondary Node). Among the plurality of cells to which the wireless communication terminal 10 is connected, one or more cells provided by the master node include a primary cell (PCell). On the other hand, one or more cells provided by the secondary node include a primary secondary cell (PSCell). In the following description, it is assumed that the base station 20 of the LTE system provides a PCell, and the base station 20 of the NR system provides a PSCell, but this is not intended to be limiting.

[0026] The base stations 20 are connected to each other via a base station interface. The base stations 20 and the core network device 30 are also connected to each other via a core network interface. The base station interface is used to exchange control signals necessary for handover and coordinated operations between the base stations 20. The core network device 30 has the base stations 20 under its control, and mainly handles load control between the base stations 20, calling (paging) the wireless communication terminal 10, and mobility control such as location registration.

[0027] The wireless communication terminal 10 and the base station 20 transmit and receive RRC messages in the Radio Resource Control (RRC) layer. In addition, the wireless communication terminal 10 and the base station 20 transmit and receive MAC control elements (MAC CEs) in the Medium Access Control (MAC) layer. The RRC messages are transmitted as RRC Protocol Data Units (PDUs), and the logical channels to which they are mapped include a Common Control Channel (CCCH), a Dedicated Control Channel (DCCH), a Paging Control Channel (PCCH), a Broadcast Control Channel (BCCH), or a Multicast Control Channel (MCCH). The MAC CEs are transmitted as MAC PDUs (or MAC subPDUs). The MAC subPDUs are equivalent to a Service Data Unit (SDU) in the MAC layer plus an 8-bit header, and the MAC PDUs include one or more MAC subPDUs.

[0028] <Hardware configuration> 5 is a diagram showing an example of a hardware configuration of the wireless communication terminal 10 and the base station 20. The wireless communication terminal 10 and the base station 20 each include a processor 11, a memory 12, a storage device 13, a communication device 14 for performing wired or wireless communication, an input device 15 for accepting input operations, an output device 16 for outputting information, and an antenna 17.

[0029] The processor 11 is, for example, a CPU (Central Processing Unit), and controls the wireless communication terminal 10 and the base station 20.

[0030] The memory 12 is composed of, for example, a Read Only Memory (ROM), an Erasable Programmable ROM (EPROM), an Electrically Erasable Programmable ROM (EEPROM), and / or a Random Access Memory (RAM).

[0031] The storage device 13 is configured by storage such as a hard disk drive (HDD), a solid state drive (SSD), and / or an embedded multi media card (eMMC).

[0032] The communication device 14 is a device that performs communication via a wired and / or wireless network, and is, for example, a network card, a communication module, etc. The communication device 14 may also include an amplifier, an RF (Radio Frequency) device that performs processing related to wireless signals, and a BB (Base Band) device that performs baseband signal processing.

[0033] The RF device performs, for example, D / A conversion, modulation, frequency conversion, power amplification, etc. on the digital baseband signal received from the BB device to generate a radio signal to be transmitted from the antenna 17. The RF device also performs frequency conversion, demodulation, A / D conversion, etc. on the radio signal received from the antenna 17 to generate a digital baseband signal and transmit it to the BB device. The BB device performs a process of converting the digital baseband signal into packet data (e.g., IP packets) and a process of converting the IP packets into a digital baseband signal.

[0034] The input device 15 is, for example, a keyboard, a touch panel, a mouse, and / or a microphone, etc. The output device 16 is, for example, a display and / or a speaker, etc.

[0035] <Function block configuration> (Terminal) FIG. 6 is a diagram showing an example of a functional block configuration of the wireless communication terminal 10. The wireless communication terminal 10 includes a transmitting unit 110, a receiving unit 120, a monitoring unit 130, a measuring unit 140, a detecting unit 150, a deciding unit 160, a judging unit 170, and a handover control unit 180. FIG. 6 shows main functional blocks in this embodiment. The transmitting unit 110 and the receiving unit 120 may be realized by, for example, the communication device 14, or may be realized by the processor 11 executing a program stored in the storage device 13 in addition to the communication device 14. The monitoring unit 130, the measuring unit 140, the detecting unit 150, the deciding unit 160, the judging unit 170, and the handover control unit 180 may be realized by the processor 11 executing a program stored in the storage device 13. The program can be stored in a storage medium. The storage medium storing the program may be a non-transitory computer readable storage medium. The non-transitory storage medium is not particularly limited, and may be, for example, a storage medium such as a USB memory or a CD-ROM.

[0036] The transmitter 110 generates and transmits an uplink signal to be transmitted to the base station 20 , while the receiver 120 receives a downlink signal from the base station 20 .

[0037] The monitoring unit 130 monitors the communication status of each application being executed in the wireless communication terminal 10. Specifically, the monitoring unit 130 determines whether or not communication with an NR cell (NR communication) is mandatory (in other words, whether or not communication with an LTE cell (LTE communication) alone is sufficient) by referring to the settings, specifications, etc. of each application being executed. The settings, specifications, etc. of each application will be specifically described using as an example a case where a communication type setting is made such that "application A requires NR communication, and application B does not require NR communication." First, before starting up the wireless communication terminal 10, the communication type is set in the terminal itself or in the server providing each application. When an application is executed on the wireless communication terminal 10 after the wireless communication terminal 10 is started, the monitoring unit 130 of the wireless communication terminal 10 determines whether or not NR communication is required for the application being executed based on the communication type setting. For example, if the application being executed is application A, the monitoring unit 130 determines that NR communication is required, whereas if the application being executed is application B, the monitoring unit 130 determines that NR communication is not required and that only LTE communication is sufficient. When the communication type setting is not performed, the monitoring unit 130 may determine whether to use NR communication for the application in progress or whether LTE communication alone is sufficient, based on uplink throughput information obtained from the base station 20. In this case, it is possible to determine whether to use NR communication regardless of the application in progress in the terminal 10. In addition, there are various applications executed on the wireless communication terminal 10, but for example, game applications using VR (Virtual Reality) / AR (Augmented Reality) that require ultra-high speed and large capacity data communication, applications related to autonomous driving and remote control of robots that require ultra-low latency, etc. are considered to be applications that require NR communication. Of course, applications that require NR communication are not limited to these.

[0038] The measurement unit 140 measures radio quality (RSRP, SINR, etc.) for an NR cell (NR band) or an LTE cell (LTE band) and outputs the measurement result. The radio quality is not limited to RSRP or SINR, and may be RSRQ (Reference Signal Received Quality) or RSSI (received signal strength indicator), etc.

[0039] When the monitoring unit 130 determines that the application being executed requires NR communication, the detection unit 150 detects deterioration of the wireless quality of the currently connected NR cell (here, PSCell). In detail, the detection unit 150 detects whether the wireless quality of the NR band has deteriorated by comparing the quality threshold Qth1 stored in the storage device 13 with the wireless quality of the NR band measured by the measurement unit 140. As an example, the detection unit 150 determines that the wireless quality of the NR band has deteriorated when the measured wireless quality of the NR band is below the quality threshold Qth1. Note that the method of detecting deterioration of the wireless quality of the NR band and the criteria for determining whether the wireless quality of the NR band has deteriorated are not limited to the above. For example, the wireless quality of the route and area used by the wireless communication terminal 10 may be measured and stored in advance, and the deterioration of the wireless quality of the NR band may be detected by using this.

[0040] The determination unit 160 determines NR target cells that are candidate destinations for handover. In detail, when the detection unit 150 detects deterioration of the wireless quality of an NR cell (PSCell), the determination unit 160 determines an NR cell with good wireless quality as an NR target cell based on the measurement result by the measurement unit 140, etc. The method of determining the NR target cell is not limited to this, and for example, when a priority band such as a throughput-oriented band is set in advance, the NR target cell may be determined taking into account the setting. As an example, when the NR band n28 / n23 is set as a priority band in the uplink (UL: Up Link) and the NR band n77 is set as a priority band in the downlink (DL: Down Link), the determination unit 160 may determine the NR target cell taking into account the set priority band.

[0041] The determination unit 170 determines whether or not the currently connected LTE cell (i.e., PCell) can be combined with the NR target cell. In detail, the determination unit 170 determines whether or not the combination of the band of the currently connected PCell and the band of the NR target cell (hereinafter also referred to as "LTE-NR band combination") is OK based on the combination determination condition stored in the storage device 13.

[0042] Based on the determination result by the determination unit 170, the handover control unit 180 controls handover of the currently connected LTE cell (PCell) and NR cell (PSCell).

[0043] FIG. 7A is an explanatory diagram of a case where the LTE-NR band combination is OK, and FIG. 7B is an explanatory diagram of a case where the LTE-NR band combination is NG.

[0044] (If LTE-NR band combination is OK) As shown in FIG. 7A, when it is determined that the combination of the band of the currently connected PCell and the band of the NR target cell is OK, the handover control unit 180 performs handover from the currently connected PSCell to the NR target cell in accordance with information compliant with the standard (hereinafter, standard-related information) indicating the event conditions, etc. shown in FIG. 2.

[0045] (If LTE-NR band combination is not allowed) As shown in FIG. 7B, when it is determined that the combination of the band of the currently connected PCell and the band of the NR target cell is NG, the handover control unit 180 executes the following process.

[0046] First, the handover control unit 180 identifies an LTE band that can be combined with the band of the NR target cell. Then, the handover control unit 180 determines a cell of an LTE band with good wireless quality from among the identified LTE bands as the LTE target cell based on the measurement results by the measurement unit 140, etc. Note that, when a priority band is set, etc., the LTE target cell may be determined in consideration of the priority band.

[0047] Next, the handover control unit 180 performs handover support setting for performing a handover from the currently connected PCell to the determined LTE target cell.

[0048] As an example, the handover control unit 180 may dynamically set or change the band to be used by inputting a command to the wireless communication terminal 10, or may dynamically set or change the band to be used by using a frequency-variable filter that can change the passband.

[0049] When the handover control unit 180 performs handover support configuration in this manner, it disconnects the currently connected PCell and PSCell and performs handover (connection switching) from the PCell to the LTE target cell in accordance with the standard-related information shown in Fig. 2. Furthermore, the handover control unit 180 performs handover (connection switching) from the PSCell to the NR target cell in accordance with the standard-related information shown in Fig. 2.

[0050] When the connection to the LTE target cell and the connection to the NR target cell are completed, the handover control unit 180 cancels the handover support setting. Next, the handover support process executed by the radio communication terminal 10 will be described with reference to FIG.

[0051] (Handover support processing) 8 is a flowchart showing an example of handover support processing. It is assumed that the quality threshold value Qth1, the combination judgment condition, the standard related information shown in FIG.

[0052] First, the wireless communication terminal 10 determines whether NR communication is mandatory by referring to the settings, specifications, etc. of each application running on the wireless communication terminal 10 (step S101).

[0053] When the wireless communication terminal 10 determines that the application being executed does not require NR communication, that is, LTE communication alone is sufficient (step S101; NO), the wireless communication terminal 10 ends the process without executing the steps shown below. On the other hand, when the wireless communication terminal 10 determines that the application being executed requires NR communication (step S101; YES), the wireless communication terminal 10 starts measuring the wireless quality of the currently connected NR cell (here, PSCell) (step S102). Then, the wireless communication terminal 10 detects deterioration of the wireless quality of the PSCell based on the measurement result of the wireless quality of the PSCell (step S103). Specifically, the wireless communication terminal 10 detects deterioration of the wireless quality of the NR band by comparing the quality threshold Qth1 stored in the storage device 13 with the measured wireless quality of the NR band. When deterioration of the wireless quality of the NR band is not detected (step S103; NO), the wireless communication terminal 10 returns to step S102. On the other hand, when deterioration of the wireless quality of the NR band is detected (step S103; YES), the wireless communication terminal 10 determines an NR cell with good wireless quality as an NR target cell based on the measurement result of the NR band, etc. (step S104). Note that the details of the method for determining the NR target cell have already been described and will be omitted.

[0054] The wireless communication terminal 10 determines whether or not the currently connected LTE cell (here, PCell) can be combined with the NR target cell (step S105). Specifically, the wireless communication terminal 10 determines whether or not the combination of the band of the currently connected PCell and the band of the NR target cell (i.e., LTE-NR band combination) is OK based on the combination determination condition stored in the storage device 13. When the wireless communication terminal 10 determines that the LTE-NR band combination is OK (step S105; YES), it executes a handover from the currently connected PSCell to the NR target cell in accordance with the standard related information shown in FIG. 2 (step S106), and ends the process.

[0055] On the other hand, when the wireless communication terminal 10 determines that the LTE-NR band combination is NG (step S105; NO), it first identifies an LTE band that can be combined with the band of the currently connected PCell (step S107). Then, the wireless communication terminal 10 determines a cell of an LTE band with good wireless quality from among the identified LTE bands based on the measurement results of the LTE bands, etc., as a target cell of LTE (step S108).

[0056] Next, the wireless communication terminal 10 performs handover support setting for performing handover from the currently connected PCell to the determined LTE target cell (step S109). Note that details regarding the handover support setting have already been described, and will not be repeated here.

[0057] When the wireless communication terminal 10 performs the handover support setting, the wireless communication terminal 10 disconnects the currently connected PCell and PSCell and performs a handover (connection switching) from the PCell to the LTE target cell in accordance with the standard-related information shown in Fig. 2 (step S110). After that, the wireless communication terminal 10 performs a handover (connection switching) from the PSCell to the NR target cell in accordance with the standard-related information shown in Fig. 2 (step S111).

[0058] When the wireless communication terminal 10 completes the connection to the LTE target cell and the connection to the NR target cell, the wireless communication terminal 10 cancels the handover support setting (step S112) and ends the process.

[0059] As described above, according to the present embodiment, even if the wireless quality of NR deteriorates in the 5G NR configuration, the combination of the LTE band and the NR band is taken into consideration, and handover is performed between LTE cells based on the wireless quality of NR, and then handover is performed to an NR cell with good wireless quality. This makes it possible to suppress the time during which the connection with the NR cell is lost, thereby realizing low latency. In addition, according to the present embodiment, since the wireless communication terminal performs the setting of parameters necessary for handover, the base station does not need to perform the complicated process of setting new parameters. Therefore, the present embodiment can be easily introduced into the existing wireless communication system (NSA configuration).

[0060] B.Other The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The flow charts, sequences, elements included in the embodiment, and their arrangements, materials, conditions, shapes, sizes, etc., described in the embodiment are not limited to those exemplified, and may be modified as appropriate.

[0061] <Summary> According to the present disclosure described above, it is possible to ensure low latency and the like when performing handover in an NSA configuration. Therefore, the technology disclosed herein can contribute to achieving Goal 9 of the Sustainable Development Goals (SDGs), "Build resilient infrastructure and promote inclusive and sustainable industrialization." [Explanation of symbols]

[0062] 1...wireless communication system, 10...wireless communication terminal, 11...processor, 12...memory, 13...storage device, 14...communication device, 15...input device, 16...output device, 17...antenna, 20...base station, 110...transmitter, 120...receiver, 130...monitoring unit, 140...measuring unit, 150...detector, 160...determiner, 170...judgment unit, 180...handover control unit, Qth1...quality threshold

Claims

1. A terminal capable of simultaneous communication in both the first communication method and the second communication method, A detection unit that detects deterioration of wireless quality of a currently connected cell of a second communication method; a determination unit that determines a target cell of the second communication method as a candidate destination for handover when deterioration of the wireless quality is detected; a determination unit that determines whether a combination of a band of a currently connected cell of a first communication method and a band of a target cell of the second communication method is an allowable band combination; a handover control unit that controls handover of the cell of the first communication method and the cell of the second communication method based on a determination result of the determination unit; A terminal comprising:

2. A monitoring unit that monitors applications running on the terminal is further provided, The monitoring unit determines whether the application being executed requires communication in the second communication method; The terminal according to claim 1 , wherein the detection unit detects deterioration of wireless quality of a cell for the second communication method when it is determined that the application being executed requires communication in the second communication method.

3. A measurement unit that measures radio quality of a cell of the first communication method and a cell of the second communication method, The terminal according to claim 1 , wherein the detection unit detects deterioration of wireless quality of a currently connected cell of the second communication method based on a measurement result by the measurement unit.

4. The handover control unit, The terminal according to claim 1 , wherein, when it is determined that the combination of bands is permissible, a handover is performed from a currently connected cell of the second communication method to a target cell of the second communication method.

5. The handover control unit, When it is determined that the combination of bands is not an allowable combination, a band of a cell of the first communication method that can be combined with the band of the target cell of the second communication method is identified, and the cell of the first communication method of the identified band is determined as a target cell of the first communication method; The terminal according to claim 1 , further comprising: a handover support setting for performing a handover to a target cell of the first communication method.

6. The handover control unit, 6. The terminal according to claim 5, wherein when determining a target cell for the first communication method, if there are a plurality of the identified bands, a cell for the first communication method in a band having good wireless quality from among the plurality of bands is determined as the target cell for the first communication method.

7. The handover control unit, The terminal according to claim 5, wherein, when the handover support setting is performed, the currently connected cell of the first communication method and the cell of the second communication method are disconnected, and then a handover is performed to a target cell of the first communication method based on the handover support setting, and then a handover is performed to a target cell of the second communication method.

8. The handover control unit, The terminal according to claim 7 , further comprising: a terminal configured to cancel the handover support setting after performing a handover to a target cell of the second communication method.

9. A terminal capable of simultaneous communication by both the first communication method and the second communication method, a detection step of detecting deterioration of wireless quality of a currently connected cell of a second communication method; a determining step of determining a target cell of the second communication method as a candidate destination for handover when the deterioration of the wireless quality is detected; a determination step of determining whether a combination of a band of a currently connected cell of a first communication method and a band of a target cell of the second communication method is an allowable band combination; a handover control step of controlling handover between the cell of the first communication method and the cell of the second communication method based on a result of the determination step; A program for executing.

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