JP2022075905A - Terminal device, base station device, control method, and program for autonomous handover by terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a terminal device to select an appropriate handover destination.

SOLUTION: A terminal device is configured to: include information corresponding to service requested by the terminal device in a registration request message when registering the information to a network to transmit it; establish connection with a base station device based on service requested by the terminal device; receive information from a serving base station device on a candidate base station device which is a connection switch destination from the serving base station device which has established connection; acquires identification information on a surrounding base station device from a wireless signal transmitted by the surrounding base station device; and performs handover to the candidate base station device corresponding to the identification information based on the information on the candidate base station device without an instruction by the serving base station device when the identification information corresponds to identification information on any of candidate base station devices according to a condition including that quality of the wireless signal from the serving base station device falls below predetermined level after receiving the information on the candidate base station device.

SELECTED DRAWING: Figure 5

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a terminal device-driven handover technique.

In the next-generation cellular communication system, it is expected that a beam covering a narrow area (cell) will be formed and effective utilization of frequency resources will be achieved. Further miniaturization of such cells can increase the frequency of handovers when the terminal device moves. Therefore, it is important to shorten the service interruption time in one handover. Non-Patent Document 1 describes a method in which a serving base station (serving cell) notifies in advance information for accessing a target cell candidate for the terminal device to perform an autonomous handover, an event dedicated to the autonomous handover, and the like. Have been described.

3GPP Contribution, R2-1708840, August 2017

In the 5th generation cellular communication system, a network is created for each service such as voice call, video and music streaming, high-speed and large-capacity communication, connection by multiple terminals, and ultra-reliable and low-delay communication. Slicing is done. The terminal device can receive appropriate services by connecting to a network slice according to the requested service, for example. On the other hand, the technique described in Non-Patent Document 1 does not consider such a network slice, and it is conceivable that the terminal device connects to an inappropriate network slice. As a result, the terminal device cannot receive appropriate services at the handover destination, and further handover may be required.

The present invention has been made in view of the above problems, and an object of the present invention is to enable a terminal device to select an appropriate handover destination.

The terminal device according to one aspect of the present invention is the terminal between the base station device and the transmission means for including and transmitting the information corresponding to the service requested by the terminal device in the registration request message when registering in the network. Information on the establishment means for establishing the connection based on the service requested by the apparatus and the candidate base station apparatus to which the connection is switched from the serving base station apparatus for which the connection is established by the establishment means is received from the serving base station apparatus. From the receiving means, the acquisition means for acquiring the identification information of the surrounding base station apparatus from the radio signal transmitted by the surrounding base station apparatus, and the serving base station apparatus after receiving the information of the candidate base station apparatus. If the identification information corresponds to the identification information of any one of the candidate base station devices, depending on the condition including that the quality of the radio signal is below a predetermined level, it is based on the information of the candidate base station device. Therefore, it has an execution means for executing handover to the candidate base station apparatus to which the identification information corresponds, without being instructed by the serving base station apparatus.

The base station device according to one aspect of the present invention is a candidate base station to which the terminal device, the establishment means for establishing the connection based on the service required by the terminal device, and the connection of the terminal device from the base station device are switched. It has a selection means for selecting a device and a transmission means for transmitting the selected information on the candidate base station device to the terminal device, after the terminal device receives the information on the candidate base station device. It is characterized in that the handover is executed without instructing the base station apparatus.

According to the present invention, the terminal device can select an appropriate handover destination.

It is a figure which shows the configuration example of a wireless communication system. It is a figure which shows the hardware configuration example of the apparatus. It is a figure which shows the functional composition example of a base station apparatus. It is a figure which shows the functional composition example of a terminal apparatus. The figure which shows the 1st example of the flow of processing executed in a wireless communication system. The figure which shows the 2nd example of the flow of processing executed in a wireless communication system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of wireless communication system)
FIG. 1 shows a configuration example of a wireless communication system according to the present embodiment. The wireless communication system includes a first base station device 101, a second base station device 102, and a terminal device 103. The first base station device 101 is a serving base station connected to the terminal device 103, and the second base station device 102 is a non-serving base station not connected to the terminal device 103. The first base station apparatus 101 can be configured to provide a plurality of cells (beams) by, for example, beamforming, and in this case, the first cell (the first cell being connected among the plurality of cells) (in this case). In the serving cell), it operates as a serving base station, and in a second cell (non-serving cell) that is not connected, it operates as a non-serving base station. In the following, when one base station device provides both a serving cell and a non-serving cell, the portion of the base station device that provides the non-serving cell is treated as the second base station device 102, and the portion that provides the serving cell. Is treated as the first base station device 101. Further, when the terminal device 103 switches (handovers) the serving cell, the base station device that provides the switched serving cell functions as the first base station device 101, and the handover source base station device is the second. It becomes the base station apparatus 102. That is, the first base station device 101 and the second base station device 102 may be configured so as to differ only in whether or not they are connected to the terminal device 103. Note that FIG. 1 is an example, and generally, there are a large number of base station devices and a large number of terminal devices, and unless otherwise specified, the following will be described between each base station device and each terminal device. The steps are performed individually.

In the present embodiment, the terminal device 103 has another base station device (for example, a second base station device) that is a candidate for switching the connection from the serving base station (first base station device 101) to which the terminal device 103 is connected. The information of the base station apparatus 102) of the above is acquired in advance as the information of the candidate base station apparatus of the handover destination. The information of the candidate base station device may include, in one example, the cell identification information provided by the candidate base station device and the information used in the connection procedure with the candidate base station device. Here, the identification information may be, for example, the NR Cell Global ID (NCGI) of the candidate base station apparatus. The NCGI is a global ID of a cell determined by a combination of a Public Land Mobile Network ID (PLMN ID) and an NR Cell Identity (NCI). Further, the connection procedure is, for example, a random access procedure, and the information used in the connection procedure includes, for example, beam information, routing information (Tracking Area ID (TAI)), frequency information, and the like formed by the candidate base station apparatus. sell.

Then, the terminal device 103 communicates with the serving base station while holding the information of the candidate base station device in this way, and while the communication environment with the serving base station is good, the terminal device 103 and the serving base station as it is. Communication can be continued. Then, when the quality of the radio signal from the serving base station falls below a predetermined level, the identification information of the surrounding base station equipment is acquired from the radio signal transmitted from the surrounding base station equipment and held. Compare with the identification information of the candidate base station equipment. Here, the identification information of the surrounding base station apparatus may be, for example, a Physical Cell ID (PCI). The terminal device 103 is, for example, when the identification information of the surrounding base station device acquired from the radio signal received with the radio quality of a predetermined level or higher corresponds to the identification information (NCGI) of the candidate base station device, the identification information. Determines the corresponding candidate base station device as the connection switching destination. When the identification information of the plurality of surrounding base station devices corresponds to the identification information of the candidate base station devices, the terminal device 103 has the best radio quality among the surrounding base station devices. , Or by randomly selecting one base station device from among the base station devices whose radio quality exceeds the threshold level, one candidate base station device to be switched can be selected. Then, the terminal device 103 executes the handover to the candidate base station device of the connection switching destination without going through the serving base station. For example, the terminal device 103 can establish a connection with a candidate base station device to which the connection is switched by executing a random access procedure. At this time, the terminal device 103 may transmit the context information (UE context) of the terminal device 103 to the candidate base station device to which the connection is switched. After that, the candidate base station device of the connection switching destination notifies the switching source base station device (former serving base station) that the terminal device 103 has autonomously executed the handover, and the data addressed to the terminal device 103. Request a transfer. When the switching source base station device receives the notification that the terminal device 103 has been handed over and the data transfer request, it transfers the data addressed to the terminal device 103 to the candidate base station device to which the connection is switched. Then, the transferred data addressed to the terminal device 103 is transmitted from the candidate base station device to which the connection is switched to the terminal device 103. As a result, the terminal device 103 can autonomously execute the handover without going through the serving base station, so that the connection destination can be quickly connected when the quality of the radio signal from the serving base station falls below a predetermined level. Switching of base station equipment will be performed. As a result, the length of the period during which the communication service for the terminal device 103 cannot be provided can be shortened. The terminal device 103 may start an autonomous handover in response to a trigger other than the quality of the radio signal from the serving base station falling below a predetermined level. For example, another trigger such as the delay in communication with the serving base station becoming larger than a predetermined value or the amount of resources allocated by the serving base station being insufficient initiates autonomous handover. You may.

In the 5th generation cellular communication system (NR, New Radio), network slicing technology that defines a network for each service is used. And the network slices supported by each base station device can be different. That is, some base station appliances may support all network slices and provide all services, while some other base station appliances may support only some network slices and some services. May not be available. At this time, when the serving base station notifies the terminal device 103 of the information of other base station devices adjacent to each other as the information of the candidate base station device regardless of the service requested by the terminal device 103, the terminal device 103 autonomously. As a result of the handover, the candidate base station device to which the connection is switched may not be able to support the service requested by the terminal device 103.

On the other hand, in the present embodiment, the serving base station is a terminal device 103 among other base station devices (for example, adjacent to the serving base station) that are candidates for switching the connection from the serving base station. Select a candidate base station device based on the information of the service requested by. Here, the service information requested by the terminal device 103 is, for example, Network Slice Selection Assistance Information (NSSAI). The NSSAI comprises one or more Single-NSSAI (S-NSSAI), and each network slice is uniquely identified by the S-NSSAI. Note that a particular network slice only supports a particular Access and Mobility management Function (AMF). Each base station device includes information on other base station devices (for example, adjacent to the own device) that are candidates for switching the connection from the own device, such as NCGI, beam information, routing information, and frequency information. In addition, the AMF ID (or information of a plurality of S-NSSAIs) of the other base station apparatus can be managed. Each base station device acquires NSSAI, which is information on the service requested by the terminal device 103, and among other base station devices that are candidates for switching the connection from its own device, the AMF ID corresponding to the acquired NSSAI. Alternatively, another base station device having S-NSSAI information is selected as a candidate base station device to be connected. Then, the base station device transmits the information of the selected candidate base station device to the terminal device 103 connected to the own device. The information of the candidate base station apparatus transmitted here is the same as described above. After acquiring such information, the terminal device 103 can autonomously execute the handover as described above in response to the occurrence of a predetermined trigger. According to such a configuration, the terminal device 103 is provided with information on the base station device capable of providing the service requested by the own device as the information on the candidate base station device to which the connection is switched. It is possible to continue to receive the communication service more reliably after switching the connection.

The serving base station may transmit information on the candidate base station device based on the service information requested by the terminal device 103 by individual signaling to the terminal device 103. The individual signaling here may be performed, for example, by radio resource control (RRC) messages or on-demand system information (on-demand SI). Further, the terminal device 103 can register the service requested on the network side by including the information of the requested service (NSSAI) in the registration request message when registering in the RAN (Radio Access Network) of the NR. .. In this case, the base station apparatus can acquire the information of the service requested by the terminal apparatus 103 by searching the information registered on the network side. That is, it is not necessary to newly transmit the NSSAI from the terminal device 103 to the base station device. However, the terminal device 103 may transmit information on the service requested by NSSAI or the like to the base station device. For example, the terminal device 103 may transmit to the serving base station including the information of the requested service in the signal requesting the information of the candidate of the connection switching destination (for example, the message requesting the adjacent cell list). As a result, the serving base station does not need to search for the service information requested by the terminal device 103 for the terminal device 103 that requests the information of the candidate for the connection switching destination, and can quickly obtain the information of the candidate base station device. It is possible to notify the terminal device 103.

Further, the serving base station may acquire information on the requested service for each of the plurality of terminal devices 103, and group the terminal devices 103 so that the terminal devices requesting the same service are in the same group, for example. Then, the serving base station selects a candidate base station device for each group, and transmits the information of the selected candidate base station device to one or more terminal devices 103 belonging to the group by one signal. Can be done. The transmission of information by this one signal can be done, for example, by broadcasting system information. It should be noted that the multicast signal for which the group is specified may be transmitted, or the broadcast signal may be transmitted to all the terminal devices. When a broadcast signal is transmitted to all terminal devices, information specifying a target group or a target service may be included inside the signal. The grouping of the plurality of terminal devices 103 may be performed based on different criteria depending on whether or not the same service is requested. That is, when a plurality of services are processed in the same network slice, the terminal devices that can be accommodated in the same network slice may be grouped into one group. As a result, the amount of radio resources used for notification of the candidate base station device can be reduced.

Hereinafter, an example of the configuration of each device and the flow of processing to be executed will be described.

(Hardware configuration)
FIG. 2 shows an example of hardware configuration of a base station device and a terminal device. In one example, the base station device and the terminal device have a hardware configuration as shown in FIG. 2, and include, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication circuit 205. In the base station device and the terminal device, for example, a program recorded in any one of the ROM 202, the RAM 203, and the external storage device 204 that realizes each function of the base station device and the terminal device as described above is executed by the CPU 201.

Then, the base station device and the terminal device control the communication circuit 205 by, for example, the CPU 201 to communicate with other devices. The communication circuit 205 of the base station device can communicate with other base station devices and other network nodes, for example, through a wired line. Further, the communication circuit 205 of the base station device may be capable of forming one or more (plural) beams and wirelessly communicating with the terminal device. Further, in this case, the communication circuit 205 of the terminal device can be connected to the base station device for wireless communication via at least one of the beams formed by the communication circuit 205 of the base station device. It is composed. In the configuration of FIG. 2, the base station device and the terminal device are shown in a schematic diagram such that they have one communication circuit 205, but the present invention is not limited to this, and a plurality of communication circuits may be provided. For example, a base station device may have a first communication circuit for wired communication with another base station device and a second communication circuit for wireless communication with the terminal device. Further, the terminal device may have, for example, a first communication circuit for NR and a second communication circuit for LTE (Long Term Evolution). Further, the terminal device may have a wireless communication circuit related to a standard other than cellular such as a wireless LAN, and may further have a wired communication circuit used for a wired connection such as a USB connection.

The base station device and the terminal device may be provided with dedicated hardware for executing each function, or a part may be executed by the hardware and the other part may be executed by the computer running the program. .. Also, all functions may be performed by a computer and a program.

(Functional configuration)
FIG. 3 shows an example of a functional configuration of a base station device (first base station device 101 and second base station device 102). The base station apparatus includes, for example, a communication unit 301, a request service acquisition unit 302, an adjacent information storage unit 303, a candidate base station selection unit 304, and a candidate base station notification unit 305. Further, the base station apparatus may have, for example, an optional grouping unit 306.

The communication unit 301 executes wired / wireless communication with other base station devices and wireless communication with the connected terminal device 103.

The request service acquisition unit 302 acquires information on the service requested by the terminal device 103. For example, the request service acquisition unit 302 receives a message requesting registration (registration request) from an unregistered terminal device 103, and acquires NSSAI in the message as information on the service requested by the terminal device 103. Can be done. Further, the request service acquisition unit 302 can acquire information on the service requested by the terminal device 103, which is managed by the predetermined node in the network for the registered terminal device 103, from the predetermined node. Further, in some cases, the request service acquisition unit 302 may acquire information on the service requested by the terminal device 103 from the base station device of the handover source when the terminal device 103 has handed over.

The adjacency information storage unit 303 stores information on other base station devices that are adjacent to the own device. Here, the adjacent information storage unit 303 stores information about a base station device (cell) that is a candidate for a connection switching destination as information of another base station device having an adjacent relationship. That is, the other stored base station equipment does not have to be in direct adjacency with the base station equipment, for example, in the case of switching connections using relay, for cells that are not geographically adjacent. Information can be stored. Information on other base station devices may include, for example, NCGI, beam information, routing information, and AMF ID (or information on multiple S-NSSAIs). The adjacency information storage unit 303 may have an Automatic Neighbor relation (ANR) function that automatically builds an adjacency relationship when the number of base station devices in the adjacency relationship increases or decreases.

The candidate base station selection unit 304 of other base station devices in an adjacent relationship is based on the service information requested by the terminal device 103 acquired by the request service acquisition unit 302 and the information stored in the adjacent information storage unit 303. Select another base station device that can provide the required service from the list as a candidate base station device to switch the connection to. For example, the candidate base station selection unit 304 has an AMF ID or S- corresponding to NSSAI, which is information on the service requested by the terminal device 103, among other base station devices that are candidates for switching the connection from the own device. Another base station device having NSSAI information is selected as a candidate base station device to be connected. The selection of the candidate base station apparatus may not be executed by the serving base station, and for example, this selection may be executed by a network node different from the serving base station.

The candidate base station notification unit 305 notifies the terminal device 103 of the candidate base station device selected by the candidate base station selection unit 304. For example, the candidate base station notification unit 305 notifies the information of the candidate base station device according to the service requested by the terminal device 103 by individual signaling to the terminal device 103 by RRC message or on-demand system information. The information of the candidate base station device notified here may include, for example, in one example, the identification information of the cell provided by the candidate base station device and the information used in the connection procedure with the candidate base station device. ..

The grouping unit 306 groups a plurality of terminal devices 103 for each requested service and a network slice required to execute the service. For example, among the terminal devices 103 connected to the base station device, the group is formed so that the terminal devices requesting the same service or the terminal devices to be connected to the same network slice are in the same group. When the grouping unit 306 groups the terminal devices, the candidate base station selection unit 304 selects the candidate base station devices for each group, and the candidate base station notification unit 305 receives one multicast signal for the terminal devices belonging to the group. The information of the candidate base station equipment is transmitted by or by one broadcast signal to all terminal equipment.

FIG. 4 is a diagram showing a functional configuration example of the terminal device 103. The terminal device 103 has, for example, a communication unit 401, a candidate information acquisition unit 402, a trigger determination unit 403, a peripheral information acquisition unit 404, a handover execution unit 405, and a request service notification unit 406.

The communication unit 401 performs wireless communication with the connected base station device (first base station device 101). Further, the communication unit 401 can receive a radio signal from a base station device that is not connected and acquire cell identification information (for example, PCI) included in the radio signal.

The candidate information acquisition unit 402 acquires information on the candidate base station device to be connected, which is selected by the connected base station device (or other network node) according to the service information requested by the terminal device 103. do. The information of the candidate base station device here is, for example, the identification information of the cell formed by the candidate base station device (for example, NCGI) and the information used in the connection procedure with the candidate base station device (for example, beam information, routing). Information, frequency information, etc.) can be included.

In the trigger determination unit 403, for example, the delay amount corresponding to the quality of the radio signal from the serving base station falling below the predetermined level, the load of the serving base station exceeding the predetermined value, etc. becomes larger than the predetermined value. It determines the trigger for the terminal device 103 to start the handover, such as that the amount of resources allocated from the serving base station is not more than a predetermined amount. The trigger determination unit 403 can determine an arbitrary trigger for the terminal device 103 to autonomously start the handover.

Peripheral information acquisition unit 404, for example, when the trigger determination unit 403 detects a trigger for starting handover, observes radio signals from non-connected base station devices existing in the surroundings, and identifies information of those base station devices. (PCI) is acquired. The peripheral information acquisition unit 404 can also measure the wireless quality such as the received power of the wireless signal from the peripheral base station apparatus. Then, the peripheral information acquisition unit 404 determines whether or not the identification information of the peripheral base station apparatus corresponds to the identification information in the information of the candidate base station apparatus acquired by the candidate information acquisition unit 402. The peripheral information acquisition unit 404 determines a peripheral base station device having identification information corresponding to the information of the candidate base station device as a handover target. When the identification information of the plurality of peripheral base station devices corresponds to the information of the candidate base station devices, the peripheral information acquisition unit 404 uses the base with the best radio quality among the plurality of peripheral base station devices. One base station device randomly selected from station devices or those whose radio quality exceeds a predetermined standard can be determined as a handover target. Further, the peripheral information acquisition unit 404 observes radio signals from the surrounding non-connected base station devices and the base station devices thereof before the trigger determination unit 403 detects the trigger for the start of the handover. Identification information may be acquired and received power may be measured. For example, when the peripheral information acquisition unit 404 periodically observes radio signals from surrounding base station devices and retains the results, and the trigger determination unit 403 detects a trigger for starting handover. , The target of the handover may be determined based on the retained information. Further, when the peripheral information acquisition unit 404 observes the radio signal from the surrounding base station apparatus in advance, the peripheral information acquisition unit 402 corresponds to the identification information in the information of the candidate base station apparatus acquired by the candidate information acquisition unit 402. You may want to keep only the results for. According to this, the peripheral information acquisition unit 404 does not have to perform a process of extracting information about the candidate base station device from the information held after the trigger determination unit 403 detects the trigger for starting the handover. As a result, it is possible to shorten the time required for processing after the trigger for starting the handover is detected.

The handover execution unit 405 executes the handover determined by the peripheral information acquisition unit 404 to the target base station apparatus of the handover without going through the serving base station. The handover execution unit 405 executes, for example, a random access procedure with the target base station device. Further, the handover execution unit 405 may transmit the context information of the terminal device 103 to the target base station device at this time.

The request service notification unit 406 notifies the network side of the service information requested by the terminal device 103. The request service notification unit 406 notifies the network side of the service information requested by the terminal device 103, for example, by transmitting the registration request message when the terminal device 103 registers with the NR including the NSSAI. Further, the request service notification unit 406 may transmit, for example, the request message when requesting the information of the candidate base station device from the serving base station, including the information of the service requested by the terminal device 103. The request service notification unit 406 may notify the network side of the service information requested by the terminal device 103 via the serving base station by signaling other than these.

(Process flow)
Next, an example of the flow of processing executed in the wireless communication network will be described. FIG. 5 shows an example of the first processing flow.

In the process of FIG. 5, first, the first base station device 101, which is the serving base station of the terminal device 103, acquires the information of the service requested by the terminal device 103 (S501). In FIG. 5, in the message requesting the information of the candidate base station device to which the connection is switched from the terminal device 103, the service information requested by the terminal device 103 is notified to the first base station device 101. An example is shown. When requesting registration to the network, the terminal device 103 may notify the network side of the information of the service requested by the own device. In this case, the first base station device 101 is in the network. This information can be obtained from other nodes (eg, other base station equipment). Then, the first base station device 101 is a candidate base station device capable of responding to the service based on the information of the service requested by the terminal device 103 from among the other base station devices in the adjacent relationship. Is selected (S502). For example, the first base station device 101 acquires NSSAI as information on the service requested by the terminal device 103, and selects the base station device constituting the network slice corresponding to the NSSAI as the candidate base station device. If the service information requested by the terminal device 103 cannot be acquired, the base station device corresponding to the default AMF is selected as the candidate base station device. Further, the first base station device 101 is a terminal device that requests the same service in order to prevent a plurality of terminal devices from being handed over to the same candidate base station device all at once in consideration of the load of the candidate base station device. Information on different candidate base station devices may be selected for. The first base station device 101 notifies the terminal device 103 of the information of the selected candidate base station device (S503). At this time, the first base station device 101 may notify the terminal device 103 of the information by individual signaling such as an RRC message or on-demand system information.

When the terminal device 103 receives the information of the candidate base station, the terminal device 103 holds the information. Then, the terminal device 103 continues to monitor whether or not a trigger requiring handover has occurred during communication with the first base station device 101. Here, when the terminal device 103 detects a trigger such that the quality of the radio signal from the first base station device 101 falls below a predetermined level (S504), the radio signal from the surrounding base station devices is subsequently transmitted. Observe and acquire the identification information of each base station device (cell provided by each base station device) from the radio signal. Then, the terminal device 103 compares the acquired identification information with the identification information of the candidate base station device, and detects a surrounding base station device having identification information corresponding to any of the identification information of the candidate base station device. (S505). When a plurality of base station devices are detected at this time, the terminal device 103 determines the base station device to be the target of the handover, for example, based on the quality of the radio signal from those base station devices. Then, the terminal device 103 executes a random access procedure with the base station device (second base station device 102) determined as the target of the handover (S506). At this time, the terminal device 103 can execute the random access procedure using, for example, the routing information (TAI) and the beam information of the second base station device 102 determined as the target of the handover. Further, at this time, the terminal device 103 transmits the context information (UE contact) of the terminal device 103 to the second base station device 102.

After that, the second base station device 102 notifies the first base station device 101, which is the handover source, of the notification that the terminal device 103 has autonomously handed over and the request for data transfer to the terminal device 103. Transmit (S507). Then, the first base station device 101 transfers the buffered data and packets addressed to the terminal device 103 to the second base station device 102 (S508), and at the same time, the state of the sequence number (SN) and the like. Information on the communication status is transmitted to the second base station device 102 (S509). By these procedures, the handover is completed (S510), and thereafter, the second base station device 102 communicates with the terminal device 103 as a serving base station. Then, the second base station device 102 executes, for example, the operation as the first base station device 101 in FIG.

As described above, in the present embodiment, the base station device capable of providing the service requested by the terminal device 103 is notified to the terminal device 103 as the candidate base station device of the handover destination. Then, the terminal device 103 can autonomously execute the handover (without being instructed by the serving base station) by using the information of the candidate base station device. This makes it possible to prevent erroneous connection to a base station device that has a short service interruption period and cannot provide the service requested by the terminal device 103. As a result, the terminal device 103 can more reliably and continuously receive the service.

Subsequently, FIG. 6 shows a second example of the process. Note that FIG. 6 shows the flow until the serving base station notifies the terminal device of the information of the candidate base station device, and the processing after the notification of the information is the same as the processing after S504 in FIG. Therefore, the illustration is omitted.

In the process of FIG. 6, the first base station device 101 acquires the information of the service requested by each of the plurality of connected terminal devices (S601). It should be noted that this information acquisition is performed by notifying the network side from the terminal device when each terminal device requests registration from the network or when requesting information on the candidate base station device for switching the connection destination. Can be done. The first base station device groups a plurality of connected terminal devices based on the acquired information (S602). Grouping can be done by criteria, for example, such that terminals requesting the same service belong to the same group, or terminals that should be connected to the same network slice belong to the same group. .. Then, the first base station apparatus 101 selects a candidate base station apparatus for each group (S603). Then, the first base station device 101 transmits the information of the selected candidate base station device to one or more terminal devices belonging to the group by one signal (S604). The information may be transmitted by one multicast signal destined for one or more terminal devices belonging to the group, or may be transmitted by one broadcast signal including information for identifying the group. ..

If multiple terminals request the same service or connect to the same network slice, those terminals will be notified of the same candidate base station equipment information, and these terminals will be individually notified. When the information is notified to, the same signal is transmitted as many as the number of terminal devices. On the other hand, by grouping as shown in FIG. 6 and notifying the terminal devices belonging to the group of the information of the candidate base station device with one signal, the radio required for notifying the information of the candidate base station device. It is possible to reduce resources.

Claims (14)

It ’s a terminal device,
A transmission means for including and transmitting information corresponding to the service requested by the terminal device in a registration request message when registering in the network.
An establishment means for establishing a connection with the base station device based on the service required by the terminal device, and
A receiving means for receiving information from the serving base station device to which the connection is switched from the serving base station device for which the connection has been established by the establishment means is received from the serving base station device.
An acquisition means for acquiring identification information of a surrounding base station device from a radio signal transmitted by the surrounding base station device, and an acquisition means.
The identification information is any of the candidate base station devices, depending on the condition including that the quality of the radio signal from the serving base station device is below a predetermined level after receiving the information of the candidate base station device. When corresponding to the identification information, the execution means for executing the handover to the candidate base station device corresponding to the identification information based on the information of the candidate base station device without instructing the serving base station device. When,
A terminal device characterized by having. The condition includes that the quality of the radio signal from the serving base station device is lower than the first predetermined level and the quality of the radio signal from the candidate base station device is higher than the predetermined level. The terminal device according to claim 1. The terminal device according to claim 1 or 2, wherein the receiving means receives information on the candidate base station device by individual signaling. The information of the candidate base station apparatus includes claims 1 to 3 including cell identification information provided by the candidate base station apparatus and information used in a connection procedure with the candidate base station apparatus. The terminal device according to any one of the above items. The terminal device according to any one of claims 1 to 4, wherein the transmission means transmits Network Slice Selection Assistance Information (NSSAI) as information corresponding to the service requested by the terminal device. The transmission means transmits the signal requesting the information of the candidate base station device including the information corresponding to the service requested by the terminal device.
The terminal device according to any one of claims 1 to 5. When executing the handover, the executing means transmits the context information of the terminal device to the base station device to which the connection is switched by the handover.
The terminal device according to any one of claims 1 to 6, wherein the terminal device is characterized by the above. It ’s a base station device,
A terminal device and an establishment means for establishing a connection based on the service required by the terminal device.
A selection means for selecting a candidate base station device to switch the connection of the terminal device from the base station device, and
A transmission means for transmitting the selected information of the candidate base station device to the terminal device, and
Have,
After receiving the information of the candidate base station device, the terminal device executes the handover without instructing the base station device.
A base station device characterized by that. The base station apparatus according to claim 8, wherein the establishment means acquires Network Slice Selection Assistance Information (NSSAI) as information corresponding to the service requested by the terminal apparatus and establishes the connection. .. The base station device according to claim 8 or 9, wherein the transmission means transmits information of the candidate base station device to the terminal device by individual signaling. A control method performed by a terminal device
The transmission process of including the information corresponding to the service requested by the terminal device in the registration request message when registering in the network and transmitting the information.
An establishment process for establishing a connection with the base station device based on the service required by the terminal device, and
A receiving step of receiving information from the serving base station device to which the connection is switched from the serving base station device for which the connection was established in the establishment step is received from the serving base station device.
The acquisition process of acquiring the identification information of the surrounding base station equipment from the radio signal transmitted by the surrounding base station equipment, and
The identification information is any of the candidate base station devices, depending on the condition including that the quality of the radio signal from the serving base station device is below a predetermined level after receiving the information of the candidate base station device. When corresponding to the identification information, the execution step of executing the handover to the candidate base station device corresponding to the identification information based on the information of the candidate base station device without instructing the serving base station device. When,
A control method characterized by having. A control method performed by a base station device,
The establishment process of establishing a connection between the terminal device and the service required by the terminal device, and
A selection step of selecting a candidate base station device to switch the connection of the terminal device from the base station device, and
A transmission step of transmitting information on the selected candidate base station device to the terminal device, and
Have,
After receiving the information of the candidate base station device, the terminal device executes the handover without instructing the base station device.
A control method characterized by that. A program for causing a computer to function as the terminal device according to any one of claims 1 to 7. A program for operating a computer as the base station apparatus according to any one of claims 8 to 10.

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