Connection auxiliary device

Abstract

The present invention provides a connection assistance device that enables smooth handover even when terminal device handovers occur in a concentrated period of time on a train traveling along a predetermined route. [Solution] The connection assistance device is mounted on a train traveling along a predetermined route and comprises a database and a control unit. The database stores the identification information of each of the multiple base stations located along the route, associating it with the location information of each of the multiple base stations and the location where a handover occurs. Based on the measurement results report, train information, and the handover locations stored in the database, the control unit determines the timing for each of the multiple terminal devices located inside the train to hand over from the first base station to the second base station. The control unit transmits instruction signals to the multiple terminal devices to instruct them to hand over so that the timings are distributed.

Description

Technical Field

[0001] This disclosure relates to a technique for assisting handover of terminal devices in a train running on a predetermined route.

Background Art

[0002] The communication method described in Patent Document 1 realizes handover according to the mobility capability of a terminal device by transmitting a handover request including the mobility capability information of the terminal device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a large number of passengers are using terminal devices in a train running on a predetermined route, since a large number of terminal devices move in the same direction simultaneously, handovers of a large number of terminal devices occur concentrated in time and space. Therefore, even if each terminal device transmits mobility capability information as in the above communication method, handover failures and delays may occur.

[0005] This disclosure provides a connection assistance device that can realize smooth handover even when handovers of terminal devices occur concentrated in a short time in a train running on a predetermined route.

Means for Solving the Problems

[0006] One aspect of the present disclosure, a connection assist device, is mounted on a train traveling along a predetermined route and comprises a database and a control unit. The database stores identification information for each of a plurality of base stations located along the route, associated with the location information of each of the plurality of base stations and the location where a handover occurs. The plurality of base stations include a first base station and a second base station. The control unit transmits a request signal to each of the plurality of terminal devices located in the train, requesting a report of the measured signal strength. The control unit receives the measurement result report from each of the plurality of terminal devices. The control unit acquires train information, including the train's position and speed. Based on the measurement result report, the train information, and the handover location stored in the database, the control unit determines the timing for each of the plurality of terminal devices located in the train to hand over from the first base station to the second base station. Based on the fulfillment of a predetermined condition, the control unit transmits an instruction signal to the plurality of terminal devices, instructing them to hand over at a staggered timing. Based on the failure of the predetermined condition, the control unit guides the first base station so that the plurality of terminal devices hand over at staggered timings.

[0007] One aspect of the connection assistance device of this disclosure instructs multiple terminal devices within a train to perform a handover so that the handover timing is distributed, or guides the first base station to perform a handover at a distributed timing among the multiple terminal devices within the train. This suppresses the temporal concentration of handovers among multiple terminal devices. Therefore, the connection assistance device enables smooth handovers among multiple terminal devices within a train.

[0008] A connection assist device in another aspect of the present disclosure is mounted on a train traveling along a predetermined route and comprises a database and a control unit. The database stores the identification information, location information, and handover locations of each of a plurality of base stations located along the route, in association with each base station. The plurality of base stations include a first base station and a second base station. The control unit transmits a request signal to each of a plurality of terminal devices located within the train, requesting a report of the measured signal strength. The control unit receives the measurement results from each of the plurality of terminal devices. The control unit obtains train information, including the train's position and speed. Based on the measurement results, the train information, and the handover locations stored in the database, the control unit determines when each of the plurality of terminal devices located within the train should hand over from the first base station to the second base station. The control unit is configured to transmit instruction signals to the plurality of terminal devices, instructing them to hand over so that the timings are distributed.

[0009] Another aspect of the present disclosure, a connection assist device, instructs multiple terminal devices within a train to perform a handover so that the timing of the handover is distributed. This suppresses the temporal concentration of handovers between multiple terminal devices. Therefore, the connection assist device enables smooth handovers between multiple terminal devices within a train.

[0010] A connection assist device in yet another aspect of the present disclosure is mounted on a train traveling along a predetermined route and comprises a database and a control unit. The database stores the identification information, location information, and handover locations of each of a plurality of base stations located along the route, in association with each base station. The plurality of base stations include a first base station and a second base station. The control unit transmits a request signal to each of a plurality of terminal devices located in the train, requesting a report of the measured signal strength. The control unit receives the measurement results from each of the plurality of terminal devices. The control unit obtains train information, including the train's position and speed. Based on the measurement results, the train information, and the handover locations stored in the database, the control unit determines when each of the plurality of terminal devices located in the train should hand over from the first base station to the second base station. The control unit is configured to guide the first base station so that the plurality of terminal devices hand over at distributed timings.

[0011] One aspect of the connection assistance device of this disclosure guides the first base station to perform handovers at distributed timings for multiple terminal devices within the train. This suppresses the temporal concentration of handovers between multiple terminal devices. Therefore, the connection assistance device enables smooth handovers between multiple terminal devices within the train. [Brief explanation of the drawing]

[0012] [Figure 1] This diagram shows the configuration of the connection assistance device according to the first embodiment. [Figure 2] This figure shows the database of the connection assistance device according to the first embodiment. [Figure 3] This is a diagram showing an overview of the connection assistance device according to the first embodiment. [Figure 4] This diagram illustrates the problems that arise when multiple terminal devices in a vehicle traveling along a predetermined route undergo a handover. [Figure 5] This diagram illustrates a typical scenario where a small number of terminal devices are being handed over. [Figure 6]Figure 6A shows the transmission of control signals and user data during a handover using a connection assistance device according to the first embodiment. Figure 6B shows the transmission of control signals and user data during a handover without using a connection assistance device. [Figure 7] This is a sequence diagram showing signal transmission during handover using a connection assistance device according to the first embodiment. [Figure 8] This figure shows signal transmission during handover without the use of connection assistance devices. [Figure 9] Figure 9A shows the situation without adjusting the time difference in the handover timing. Figure 9B shows the situation after the connection assist device according to the first embodiment has been adjusted to widen the time difference in the handover timing of each vehicle. [Figure 10] Figure 10A shows the time difference in handover timing that occurs depending on the vehicle's position. Figure 10B shows the time difference in handover timing for each vehicle, which is set to be greater than the time difference that occurs depending on the vehicle's position. Figure 10C shows the time difference in handover timing for each vehicle, which is set to prioritize handovers in a specific vehicle. [Figure 11] This figure shows how the connection assistance device according to the first embodiment instructs a handover so that the handover timing becomes earlier for terminal devices with lower handover processing capacity. [Figure 12] This figure shows how the connection assistance device according to the first embodiment transmits a control signal that sets the handover start conditions. [Figure 13] This diagram shows how the connection assistance device according to the first embodiment transmits the specifications of the target base station to the terminal device and transmits the specifications of the terminal device to the target base station before handover. [Figure 14] This figure shows how the connection assistance device according to the first embodiment transmits a control signal requesting a reception strength measurement result report to each of a plurality of terminal devices at different times. [Figure 15]It is a diagram showing the state where the connection assistance device according to the first embodiment performs handover by itself. [Figure 16] It is a diagram showing the state where the connection assistance device according to the first embodiment completes handover before the terminal device. [Figure 17] It is a diagram showing the state where the connection assistance device according to the second embodiment transmits the rewritten reception intensity measurement result to the base station to which the terminal device is connected so that handover is executed at the intended timing.

Mode for Carrying Out the Invention

[0013] (1. First Embodiment) <1-1. Configuration of Connection Assistance Device> Referring to FIG. 1, the configuration of the connection assistance device 100 according to the present embodiment will be described. The connection assistance device 100 is mounted on a train running on a predetermined route. The train has one or more vehicles. The train is, for example, a Shinkansen, a linear motor car, an existing line (express train, rapid train, local train, etc.). The connection assistance device 100 assists in switching the base stations of a plurality of terminal devices (UEs) in the vehicle (that is, handover). The terminal device is a terminal having a communication function with a communication carrier, such as a smartphone, a tablet terminal, a personal computer, a wearable terminal, etc.

[0014] [[ID=2,2]]FIG. 5 shows the handover of a plurality of terminal devices in a general situation; FIG. 4 shows the handover of a plurality of terminal devices in a train. The hexagonal cells in FIGS. 5 and 6 indicate the connection range of one base station. As shown in FIG. 5, in a general situation, handover occurs while a small number of terminal devices move in various directions at a low speed. Therefore, in a general situation, handover occurs dispersedly in space and time, and it is difficult for switching to a specific base station to occur concentratedly in a short time.

[0015] On the other hand, as shown in Figure 4, handovers occur inside a train as numerous terminal devices move along the rail RL. That is, handovers occur as numerous terminal devices move simultaneously in the same direction at high speed. Therefore, inside a train, handovers occur in a concentrated manner both spatially and temporally, with a concentration of handovers to a specific base station in a short period of time. In particular, inside high-speed trains such as Shinkansen, handovers to a specific base station occur in a very concentrated period of time.

[0016] When handovers to a specific base station occur in a concentrated period of time, some handovers are more likely to fail or be delayed. This can ultimately lead to a decrease in the user experience. As shown in Figure 3, the connection assistance device 100 is installed on the train to assist with handovers of multiple terminal devices within the train, suppressing handover failures and delays. The connection assistance device 100 is installed in each train car, for example. Furthermore, the connection assistance device 100 differs depending on the telecommunications carrier. For example, if telecommunications carriers A and B operate telecommunications services, each train car will be equipped with a connection assistance device 100 for terminal devices contracted with telecommunications carrier A and a connection assistance device 100 for terminal devices contracted with telecommunications carrier B.

[0017] As shown in Figure 1, the connection assistance device 100 comprises a control unit 10, a database 30, a first communication module 20, a second communication module 40, and a Global Navigation Satellite System (GNSS) module 50. The first communication module 20 is a communication module for Long Term Evolution (LTE), 5G, etc., and includes an antenna and a wireless communication terminal. The first communication module 20 is a module for communication with the user's terminal device. The control unit 10 includes a CPU and communicates with each of the multiple terminal devices under its umbrella via the first communication module 20. When the control unit 10 communicates with terminal devices via the first communication module 20, the connection auxiliary device 100 mainly functions as a base station. That is, the connection auxiliary device 100 generates control signals on behalf of the base station and transmits the generated control signals to each of the terminal devices under its umbrella. The control signals include request signals and instruction signals.

[0018] More specifically, the control unit 10 generates a request signal requesting a Measurement Report of the received signal strength measurement results and transmits the request signal to each of its subordinate terminal devices via the first communication module 20. The control unit 10 also receives the Measurement Report of the received signal strength measurement results from each of the multiple terminal devices via the first communication module 20. Furthermore, the control unit 10 generates an instruction signal instructing a handover and transmits the instruction signal to each of the multiple terminal devices via the first communication module 20.

[0019] The second communication module 40 is a communication module for LTE, 5G, etc., and includes an antenna and a wireless communication terminal. The second communication module 40 is a module for communication with base stations. The control unit 10 communicates with each of the multiple base stations located along the train route via the second communication module 40. When the control unit 10 communicates with base stations via the second communication module 40, the connection auxiliary device 100 mainly functions as a terminal device. For example, the control unit 10 can transmit a report of the received signal strength measurement result of the terminal device to the base station via the second communication module 40.

[0020] The GNSS module 50 receives GNSS signals and calculates the train's current position (specifically, its latitude and longitude). The control unit 10 calculates the train's speed from the time series of the train's position or from the Doppler frequency shift of the carrier wave of the received signal from the GNSS satellite, or receives information from the train's running control device, thereby acquiring train information including the train's position and speed.

[0021] Database 30 stores information on multiple base stations located along the train route. Since the train travels back and forth along a predetermined route daily, unique information on base stations along the route can be collected in advance. Specifically, as shown in Figure 2, Database 30 stores the identification information (ID) of each of the multiple base stations along the route, associating it with the base station location (specifically, latitude and longitude), the location where a handover occurred, and the specifications of the base station. For example, the location where a handover occurs is indicated by the distance from a starting point such as Tokyo. Since the train moves along a predetermined route, the locations where handovers occur for each base station can be collected in advance. Among the handovers, those with a particularly high risk of failure, delay, or deterioration of the user's experience often occur at prefectural borders, tunnel exits, tunnel entrances, etc.

[0022] The control unit 10 determines the timing for each of the multiple terminal devices to perform a handover (hereinafter referred to as HO timing) based on the received signal strength measurement results, the acquired train information, and the handover location stored in the database 30. The control unit 10 then instructs each of the multiple terminal devices to perform a handover so that the HO timings of the multiple terminal devices are distributed over time.

[0023] <1-2. Overview of handover using connection assistance devices> Referring to Figures 6A and 67, an overview of the handover using the connection assistance device 100 will be described. In this embodiment, the communication network between the terminal device and the base station is separated into a user plane (U-Plane) and a control plane (C-Plane). The U-Plane is a layer for transmitting user data such as voice and images, and the C-Plane is a layer for transmitting control signals. Furthermore, in the communication network, the base station to which the U-Plane is connected may be different from the base station to which the C-Plane is connected. That is, the C-Plane of the terminal device may be connected to a first base station, and the U-Plane of the terminal device may be connected to a second base station.

[0024] The connection assistance device 100 relays the C-Plane but not the U-Plane. Specifically, the C-Planes of terminal devices PT1, PT2, and PT3 connect to the base station via the connection assistance device 100. The U-Planes of terminal devices PT1, PT2, and PT3 connect directly to the base station. In this embodiment, the U-Plane may be connected using broadband 5G, and the C-Plane may be connected using LTE. When terminal devices PT1, PT2, and PT3 approach the connection assistance device 100 and the received signal strength from the connection assistance device 100 becomes stronger than the received signal strength from the base station, the C-Planes of terminal devices PT1, PT2, and PT3 connect to the connection assistance device 100, and terminal devices PT1, PT2, and PT3 come under the control of the connection assistance device 100.

[0025] As shown in Figure 6B, when the connection assistance device 100 is not used, both the C-Plane and U-Plane of terminal devices PT1, PT2, and PT3 are directly connected to the base station. Therefore, terminal devices PT1, PT2, and PT3 each individually transmit and receive control signals to and from the base station.

[0026] In response to this, the connection assistance device 100 intervenes in the transmission and reception of control signals between its subordinate terminal devices PT1, PT2, and PT3 and the base station, and actively controls the control signals. Ultimately, the connection assistance device 100 controls the HO timing so that the HO timing of the terminal devices PT1, PT2, and PT3 is distributed over time.

[0027] In detail, the connection assistance device 100 sends a request signal to terminal devices PT1, PT2, and PT3 as a control signal, requesting a report of the received signal strength measurement results. The connection assistance device 100 receives the received signal strength measurement results report from terminal devices PT1, PT2, and PT3 as a control signal, and transmits the received received signal strength measurement results report to the first base station. The first base station may be the base station to which the U-Planes of terminal devices PT1, PT2, and PT3 are connected, or it may be a base station to which they are not connected.

[0028] The connection assistance device 100 transmits instruction signals to terminal devices PT1, PT2, and PT3 to instruct a handover from the first base station to the second base station. Based on the instruction signals, the connection assistance device 100 sets a time difference ΔT in the HO timing of terminal devices PT1, PT2, and PT3, thereby distributing the HO timing. In response to the instruction signals, terminal devices PT1, PT2, and PT3 switch the U-Plane connection destination from the first base station to the second base station, but maintain the C-Plane connection destination at the connection assistance device 100 without changing it. The connection assistance device 100 actively manages the U-Plane HO timing of terminal devices PT1, PT2, and PT3 to suppress the degree of concentration of HO timing, handover failures, and delays.

[0029] <1-3. Signal Transmission for Handover> The signal transmission for the handover according to this embodiment will be explained with reference to Figure 7. In Figure 7, the dashed line indicates signal transmission at C-Plane (Layer 3), the dotted line indicates signal transmission at U-Plane, and the solid line indicates signal transmission at Layer 1 or Layer 2. The first base station is the base station to which the terminal device is currently connected, and the second base station is the base station to which the terminal device will next connect, and is located in front of the train in the direction of travel. The MME is a Mobility Management Entity and is a gateway that relays control signals. The Serving Gateway (hereinafter referred to as SGW) is a gateway that relays user data. Hereafter, terminal devices in the train will be collectively referred to as terminal devices PT.

[0030] In S10, a restricted communication area is established between the source base station and the SGW. Next, in S11, the connection support device 100 sends a request signal to the terminal device PT requesting a report of the received signal strength measurement results.

[0031] Next, in S12, the terminal device PT transmits packet data to the first base station, and the second base station transmits the received packet data to the SGW. Next, in S13, the connection support device 100 assigns an uplink to the terminal device PT. The uplink is a transmission path for transmitting data from the terminal device PT to the connection support device 100.

[0032] Next, in S14, the terminal device PT transmits a report of the received signal strength measurement result to the connection auxiliary device 100. Next, in S15, the connection assistance device 100 decides on a handover. For example, the connection assistance device 100 may decide on a handover if the reception strength of the second base station is stronger than the reception strength of the first base station. Alternatively, in order to distribute the HO timing, the connection assistance device 100 may decide on a handover even if the reception strength of the first base station is stronger than the reception strength of the second base station. Furthermore, in order to distribute the HO timing, the connection assistance device 100 may decide on a handover after making each terminal device PT wait for a different amount of time, even if the reception altitude of the second base station becomes stronger than the reception strength of the first base station.

[0033] Next, in S16, the connection assistance device 100 requests a handover to the first base station and the second base station. Next, in S17, the second base station performs admission control. Specifically, the target base station secures the necessary communication resources, such as bandwidth, before initiating communication with the terminal device PT.

[0034] Next, in S18, the first base station and the second base station transmit a response to the handover request to the connection assistance device 100. Next, in S19, the connection support device 100 assigns a downlink to the terminal device PT. The downlink is a transmission path for transmitting data from the connection support device 100 to the terminal device PT.

[0035] Next, in S20, the connection assistance device 100 transmits an instruction signal to the terminal device PT to instruct it to perform a handover. Specifically, the connection assistance device 100 transmits configuration information for Radio Resource Control (RRC) connection reset as an instruction signal. The configuration information for RRC connection reset is information for handover from the first base station to the second base station. By transmitting the configuration information, the connection assistance device 100 distributes the HO timing of multiple terminal devices. Details of the distribution of HO timing will be described later.

[0036] Next, in S21, the terminal device PT is disconnected from the cell within the connection range of the first base station and synchronizes with the cell within the connection range of the second base station. Next, in S22, the first base station hands over the packets it holds in its buffer and the packets it is sending to the source base station to the second base station.

[0037] Next, in S23, the first base station transmits information about the terminal device PT that is receiving the handover to the second base station. Next, in S24, the first base station forwards the data received from the terminal device PT to the second base station.

[0038] Next, in S25, the second base station receives buffer packets from the first base station. Next, in S26, the terminal device PT synchronizes with the second base station.

[0039] Next, in S27, the terminal device PT assigns an uplink to the second base station and adjusts the timing. The uplink is the transmission path used to send data from the terminal device to the second base station.

[0040] Next, in S28, the terminal device PT notifies the connection support device 100 that the handover is complete, and the connection support device 100 notifies the second base station that the handover is complete. Next, in S29, the terminal device PT transmits packet data to the second base station, which receives the packet data and transmits it to the SGW.

[0041] Next, in S30, the second base station requests a route switch from the MME. Specifically, the second base station requests the MME to transmit data via the second base station instead of the first base station.

[0042] Next, in S31, the MME requests a bearer switchover to the SGW. Next, in S32, the SGW switches the downlink path. The downlink path is the transmission path from the SGW to the base station.

[0043] Next, in S33, the SGW notifies the first base station that it will not transmit data. Next, in S34, the SGW transmits packet data to the second base station. Next, in S35, the first base station notifies the second base station that the data transfer is complete.

[0044] Next, in S36, the SGW sends a bearer switching response to the MME. Next, in S37, the MME sends a route switching response to the second base station. Next, in S38, the second base station notifies the first base station that it may release the context for the terminal device PT. Next, in S39, the first base station releases resources for the terminal device PT.

[0045] Figure 8 shows the signal transmission during handover when the connection assistance device 100 is not used. In this case, instead of the connection assistance device 100, the first base station performs the processes S11, S13, S15, S16, S19, and S20. Also, in the process of S14, the terminal device PT transmits a report of the received signal strength measurement result to the first base station instead of the connection assistance device 100.

[0046] <1-3. Variance in handover timing> Next, with reference to Figures 9-12, we will explain the distribution of HO timing of multiple terminal devices PT, which is performed by the control unit 10 of the connection assistance device 100.

[0047] Figures 9A and 10A show the HO timing of each vehicle when the vehicle is not equipped with a connection assist device 100 and the time difference ΔT of the HO timings of the multiple terminal devices PT is not adjusted. The time difference ΔT is the time difference from the earliest HO timing among the HO timings of the multiple terminal devices PT. When the time difference ΔT is not adjusted, the time difference ΔT depends on the distance between vehicles and the travel speed. For example, the HO timing of terminal device PT2 in vehicle 2 RC2 is 0.3 seconds later than the HO timing of terminal device PT1 in vehicle 1 RC1. The HO timing of terminal device PT16 in vehicle 16 RC16 is 4.7 seconds later than the HO timing of terminal device PT1 in vehicle 1 RC1.

[0048] The control unit 10 sets the HO timing for each vehicle so that the time difference ΔT is larger than if it were not adjusted. The connection auxiliary device 100 has information on which vehicle it is installed in, and based on that information, it sets the time difference ΔT of the terminal device PT in the vehicle on which it is installed.

[0049] Figures 9B and 10B show the HO timing of each vehicle when the time difference ΔT is adjusted. For example, the HO timing of terminal device PT1 in vehicle 1 RC1 is the timing when the control unit 10 in vehicle 1 RC1 decides to hand over. The HO timing of terminal device PT2 in vehicle 2 RC2 is 1 second later than the HO timing of terminal device PT1 in vehicle 1 RC1. That is, the HO timing of terminal device PT2 is 0.7 seconds later than the timing when the control unit 10 in vehicle 2 RC2 decides to hand over. The HO timing of terminal device PT16 in vehicle 16 RC16 is 15 seconds later than the HO timing of terminal device PT1 in vehicle 1 RC1.

[0050] If the time difference ΔT is not adjusted, the handover of terminal devices PT1 within vehicles RC1 (vehicle 1) to RC16 (vehicle 16) will be concentrated within 4.7 seconds. In contrast, if the time difference ΔT is adjusted, the handover of terminal devices PT1 within vehicles RC1 (vehicle 1) to RC16 (vehicle 16) will be distributed within 15 seconds. Therefore, by adjusting the time difference ΔT, the temporal concentration of handovers is suppressed, which in turn reduces handover failures and delays.

[0051] The control unit 10 (i) transmits an instruction signal to its subordinate terminal device PT at a timing corresponding to the time difference ΔT, instructing it to immediately begin the handover. In other words, the further back the vehicle is in the vehicle, the later the control unit 10 transmits the instruction signal to its subordinate terminal device PT.

[0052] Alternatively, as shown in Figure 12, the control unit 10 may (ii) set a condition for initiating a handover in the instruction signal and transmit the instruction signal to the subordinate terminal device PT before the HO timing. The conditions to be set are time conditions or location conditions, such as arriving at XX seconds later, XX time, or XX location.

[0053] When the control unit 10 performs (i) above, it is necessary to precisely measure the time difference ΔT and adjust the timing of the instruction signal transmission. The more terminal devices PT under the connection auxiliary device 100 there are, the greater the processing load on the control unit 10. Also, from the perspective of the terminal devices PT, there is no time to spare between receiving the instruction signal and performing the handover. Therefore, there is a possibility that the terminal devices PT may miss the instruction signal and miss the HO timing while receiving a retransmission of the instruction signal from the connection auxiliary device 100. In contrast, when the control unit 10 performs (ii) above, the processing load on the control unit 10 is reduced, and the terminal devices PT gain time to spare between receiving the instruction signal and starting the handover.

[0054] When a terminal device (PT) establishes communication with a target base station, it captures the signal broadcast by the base station, recognizes its frequency, period, and identification information, and sends and receives signals with the base station to search for available time slots. Therefore, the terminal device (PT) needs to collect various information before establishing a connection with the base station. In addition, the target base station needs to collect information about the capabilities of the terminal device (PT), such as the frequencies it can handle.

[0055] Therefore, as shown in Figure 13, the control unit 10 may acquire specifications from each of its subordinate terminal devices PT before the handover and transmit the specifications of each of the subordinate terminal devices PT to the second base station. Furthermore, the control unit 10 may read the specifications of the second base station stored in the database 30 before the handover and transmit the specifications of the second base station to the subordinate terminal devices PT. This allows the subordinate terminal devices PT to perform the handover smoothly and quickly.

[0056] Furthermore, the control unit 10 may set the handover priority of the terminal devices PT under its control according to the level of the communication continuation request of the terminal devices PT, and may set the time difference ΔT so that the HO timing becomes earlier the higher the priority. For example, as shown in Figure 9C, the priority of terminal devices PT in a particular vehicle may be set higher than that of terminal devices PT in other vehicles. A particular vehicle is one that requires the provision of high-quality in-car services, such as a Green Car or a semi-private compartment car.

[0057] The control unit 10 of the connection assistance device 100 installed in a specific vehicle sets a higher priority for its subordinate terminal devices PT. For example, if an earlier HO timing for a terminal device PT is more advantageous in suppressing handover failures or delays than a later HO timing, it sets a time difference ΔT so that the HO timing of its subordinate terminal devices PT is earlier than that of terminal devices PT in other vehicles. In this case, the control unit 10 of the connection assistance device 100 installed in other vehicles sets a lower priority for its subordinate terminal devices PT and sets a time difference ΔT so that the HO timing of its subordinate terminal devices PT is later than that of the terminal devices PT in the specific vehicle. In Figure 9C, terminal devices PT8 to PT10 in green vehicles RC8 to RC10 are given priority, and the HO timing of terminal device PT1 in vehicle RC1 is 1 second after the HO timing of terminal device PT10.

[0058] Furthermore, the control unit 10 may set a time difference ΔT in the HO timing of the multiple terminal devices PT under its control, depending on the handover processing capacity of the multiple terminal devices PT under its control. The control unit 10 learns the handover processing capacity of each of the multiple terminal devices PT under its control based on the handover performance of each of the multiple terminal devices PT under its control. The handover performance includes the time from the start to the completion of the handover, the number of handover failures, the number of retries, etc.

[0059] As shown in Figure 11, the control unit 10 sets a time difference ΔT for the HO timing of multiple terminal devices PT under its control, based on the learning results of the handover processing capacity, so that the HO timing becomes earlier the lower the handover processing capacity. For example, the control unit 10 classifies the terminal devices PT under its control into five groups in order of increasing processing capacity: Group 1 PTa, Group 2 PTb, Group 3 PTc, Group 4 PTd, and Group 5 PTe. Group 1 PTa has the lowest processing capacity and is prone to handover failures. Group 5 PTe has the highest processing capacity and is less prone to handover failures. The control unit 10 sets the time difference ΔT for Group 1 PTa so that the HO timing is the earliest. The control unit 10 sets the time difference ΔT for Group 5 PTe so that the HO timing is the latest.

[0060] Furthermore, the terminal device PT includes a first terminal device capable of exclusively connecting to one base station and a second terminal device capable of simultaneously connecting to two base stations. The control unit 10 may change the handover instructions according to the capabilities of each of the terminal devices PT under its control. Specifically, the control unit 10 instructs the second terminal device to temporarily connect to both the first base station before the switchover and the second base station to which it will switch. Then, after the handover of the first terminal device is completed, the control unit 10 instructs the second terminal device to disconnect from the first base station before the switchover.

[0061] <1-4. Dispersion of the timing of sending reports of received signal strength measurement results> Referring to Figure 14, the distribution of the transmission timing of the received signal strength measurement result report will be explained. The control unit 10 sends a request signal that triggers a handover to multiple terminal devices PT under its control, and receives the received signal strength measurement result report from each of the multiple terminal devices PT. If the timing of receiving the received signal strength measurement result report is concentrated, the processing load of the control unit 10 will be concentrated in a short period of time. Therefore, the control unit 10 distributes the reply times of the received signal strength measurement result reports from multiple terminal devices PT under its control.

[0062] Specifically, the control unit 10 (i) sends a request signal to each of the multiple terminal devices PT at a different transmission time, and / or (ii) sends a request signal to each of the multiple terminal devices PT with a different reply time set. The reply time is the time at which the report of the received signal strength measurement result is sent.

[0063] <1-5. Handover of connection support devices> Referring to Figures 15 and 16, the handover of the connection assistance device 100 will be explained. The connection assistance device 100 is connected to the base station and transmits and receives control signals. Therefore, a handover of the connection assistance device 100 itself occurs. If the handover of the connection assistance device 100 fails, it may have a negative impact on the terminal devices PT under its control. Therefore, it is necessary to improve the reliability of the handover of the connection assistance device 100.

[0064] Therefore, as shown in Figure 15, when a handover occurs from the first base station to the second base station, the connection assist device 100 simultaneously connects to both the first and second base stations from before the handover begins until after it is completed. After the handover is completed, the connection assist device 100 disconnects from the first base station. This improves the reliability of the handover by the connection assist device 100. For example, before the handover begins, the distance from the first base station is within a predetermined first distance, and the distance to the second base station is within a predetermined second distance.

[0065] Furthermore, when the connection assistance device 100 performs a handover, the flow of control signals from the connection assistance device 100 to the multiple terminal devices PT changes, and it may be necessary to reconnect all terminal devices PT under the umbrella of the connection assistance device 100 in a manner similar to a handover. Therefore, as shown in Figure 16, the control unit 10 shifts the HO timing of the connection assistance device 100 from the HO timing of the multiple terminal devices PT under its umbrella. For example, the control unit 10 controls the HO timing of the multiple terminal devices PT so that after the handover of the connection assistance device 100 from the first base station to the second base station is completed, the multiple terminal devices PT under its umbrella begin handover from the first base station to the second base station.

[0066] <1-6. Suppression of handover chattering> The control unit 10 can refer to the base station information stored in the database 30 and select an appropriate base station as the switching destination for the train's current location. In other words, the control unit 10 does not need to unnecessarily attempt to connect to multiple candidate base stations.

[0067] On the other hand, terminal device PT does not have prior information about base stations compared to connection assistance device 100. Terminal device PT can only recognize which base station's radio waves are being received at any given time. Therefore, even if terminal device PT is connected to a base station ahead in the direction of travel, if the radio wave strength of a base station behind temporarily increases, it may send a report of the received signal strength measurement result to connection assistance device 100 prompting a handover to the base station behind.

[0068] Therefore, in order to suppress handover chattering, the control unit 10 evaluates the reported reception strength measurement results and discards or rewrites reports of reception strength measurement results that would encourage a handover to an inappropriate base station.

[0069] Specifically, the control unit 10 may (i) evaluate the received signal strength measurement results received from its subordinate terminal device PT and discard reports of received signal strength measurement results that prompt a handover to a base station located behind the current driving position in the direction of travel.

[0070] Furthermore, the control unit 10 may discard the received signal strength measurement results reported by the subordinate terminal device PT without evaluating them until a certain period of time has elapsed after the handover of the subordinate terminal device PT is completed.

[0071] Furthermore, the control unit 10 (iii) rewrites the received signal strength measurement results report received from the subordinate terminal device PT to prompt a handover to a base station located behind the current driving position in the direction of travel. In other words, the control unit 10 rewrites the received signal strength measurement results report so that the received signal strength of the currently connected base station is higher than the received signal strength of the base station located behind, in order to prevent unnecessary handovers.

[0072] <1-7. Effects> According to the first embodiment described above, the following effects are achieved. (1) The connection assist device 100 instructs multiple terminal devices PT within the train to perform a handover so that the HO timing is distributed. This suppresses the temporal concentration of handovers among multiple terminal devices PT. Therefore, the connection assist device 100 enables smooth handovers among multiple terminal devices PT within the train.

[0073] (2) The connection assistance device 100 can suppress handover failures and delays for terminal devices PT in specific vehicles by setting a higher handover priority for those terminal devices PT in specific vehicles. Consequently, the connection assistance device 100 can provide stable communication continuity even when a handover occurs for terminal devices PT in specific vehicles.

[0074] (3) The connection assistance device 100 learns the handover processing capacity of each of the multiple terminal devices PT, and the lower the handover processing capacity of the terminal devices PT, the more it instructs the terminal devices PT to perform a handover at a timing that is advantageous to them. In this way, the connection assistance device 100 can distribute the handover timing of the multiple terminal devices PT while shortening the overall communication interruption time for the multiple terminal devices PT.

[0075] (4) The connection assist device 100 sets a time difference ΔT for the HO timing of the terminal device PT for each vehicle. This makes it possible to distribute the HO timing of multiple terminal devices PT within the train when multiple vehicles are coupled together, such as in a Shinkansen, thereby suppressing temporal concentration.

[0076] (5) The connection support device 100 sends request signals to its subordinate terminal devices PT at different transmission times, thereby distributing the timing at which the subordinate terminal devices PT return reports of received signal strength measurement results to the connection support device 100. Therefore, it is possible to suppress the short-term concentration of processing load on the connection support device 100.

[0077] (6) The connection support device 100 sends request signals to its subordinate terminal devices PT with different reply times set, thereby distributing the timing at which the subordinate terminal devices PT return reports of received signal strength measurement results to the connection support device 100. Therefore, it is possible to suppress the short-term concentration of processing load on the connection support device 100.

[0078] (7) The connection auxiliary device 100 can transmit an instruction signal earlier than the HO timing by setting the conditions for initiating the handover. Therefore, the processing load on the connection auxiliary device 100 can be reduced compared to when the instruction signal is transmitted at the HO timing. Furthermore, each of the subordinate terminal devices PT can have a grace period between receiving the instruction signal and initiating the handover.

[0079] (8) When the connection assist device 100 performs its own handover, it simultaneously connects to the base station before the handover and the base station to which it is being switched over from before the handover begins until after it is completed. This allows the connection assist device 100 to increase the success rate of its own handover.

[0080] (9) The connection assistance device 100 can suppress the occurrence of unnecessary reconnections by shifting its own HO timing from the HO timing of each of the terminal devices PT under its control. (10) Before the handover, the connection support device 100 transmits the specifications of the destination base station to the subordinate terminal devices PT, and transmits the specifications of each of the subordinate terminal devices PT to the destination base station. This enables the subordinate terminal devices PT to perform the handover smoothly in a short amount of time.

[0081] (11) The connection assistance device 100 can suppress the occurrence of chattering during the handover of its subordinate terminal device PT by discarding the report of the received strength measurement result that prompts a handover to a base station located behind the direction of travel of the train.

[0082] (12) The connection assistance device 100 can suppress the occurrence of chattering during the handover of its subordinate terminal devices PT by discarding the report of the received signal strength measurement result until a certain period of time has elapsed after the handover of the subordinate terminal devices PT is completed.

[0083] (13) The connection assistance device 100 can suppress the occurrence of chattering during the handover of its subordinate terminal device PT by rewriting the report of the received strength measurement result that prompts a handover to a base station located behind the direction of travel of the train.

[0084] (14) The connection support device 100 can perform a smooth and quick handover of its subordinate terminal devices PT by changing the handover instructions according to the capabilities of the terminal devices PT.

[0085] (2. Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0086] In the first embodiment described above, the connection assistance device 100 controlled the handover of the subordinate terminal devices PT so that the HO timings of the subordinate terminal devices PT were distributed. In contrast, in the second embodiment, the connection assistance device 100 does not directly control the handover of the terminal devices PT, but instead guides the base station before switching so that the HO timings are distributed.

[0087] As in the first embodiment, in order for the connection assistance device 100 to directly instruct a handover to its subordinate terminal device PT, the connection assistance device 100 needs to have the authority and capability to autonomously issue handover instructions. However, there may be cases where the connection assistance device 100 does not have such authority or capability.

[0088] In such cases, the connection assistance device 100 guides the base station before the switchover so that the subordinate terminal device PT performs a handover at the intended timing. Specifically, as shown in Figure 17, the connection assistance device 100 rewrites the received signal strength measurement result report received from the subordinate terminal device PT so that a handover occurs at the intended timing.

[0089] When the connection assistance device 100 performs a handover from the first base station to the second base station, it rewrites the received signal strength measurement result report, which indicates that the received signal strength of the first base station is higher than that of the second base station, to indicate that the received signal strength of the second base station is higher than that of the first base station. The connection assistance device 100 then transmits the rewritten received signal strength measurement result reports from each of its subordinate terminal devices PT to the first base station at different times. In other words, the connection assistance device 100 transmits the received signal strength measurement result reports from each of its subordinate terminal devices PT to the first base station with a time difference. As a result, a time difference occurs in the HO timing of the subordinate terminal devices PT according to the difference in the transmission times of the received signal strength measurement result reports.

[0090] <2-3. Effects> According to the second embodiment described above, the following effects are achieved. (15) The connection assistance device 100 guides the base station before switching so that the multiple terminal devices PT in the train perform a handover at a distributed HO timing. This suppresses the temporal concentration of the handover of the multiple terminal devices PT. Therefore, the connection assistance device 100 enables a smooth handover of the multiple terminal devices PT in the train.

[0091] (16) The connection assistance device 100 can prompt the base station before the switchover to perform a handover of the terminal device PT at the intended timing by rewriting the report of the received signal strength measurement result and transmitting it to the base station before the switchover. Consequently, even if the connection assistance device 100 does not have the authority to autonomously issue handover instructions to multiple terminal devices, it is possible to suppress the temporal concentration of handovers of multiple terminal devices PT in the train.

[0092] (3. Third Embodiment) In the third embodiment, the connection assistance device 100 performs a combination of the first and second embodiments. Specifically, if predetermined conditions are met, the connection assistance device 100 controls the handover of the subordinate terminal devices PT, as in the first embodiment. If the predetermined conditions are not met, the connection assistance device 100 guides the base station before switching so that the HO timing of the subordinate terminal devices PT is distributed, as in the second embodiment.

[0093] The predetermined condition is that the first time is shorter than the second time. The connection assistance device 100 estimates the first time and the second time. The first time corresponds to the time required from the start of the handover until the completion of the handover of all subordinate terminal devices PT when the connection assistance device 100 transmits an instruction signal to the subordinate terminal devices PT. The second time corresponds to the time required from the start of the handover until the completion of the handover of all subordinate terminal devices PT when the connection assistance device 100 guides the base station before switching so that the HO timing of the subordinate terminal devices PT is distributed.

[0094] According to the third embodiment described above, the following effects are achieved. (17) Depending on whether predetermined conditions are met, the connection assistance device 100 switches between instructing the multiple terminal devices PT in the train to perform a handover or guiding the base station before the switchover, so that the HO timing of the multiple terminal devices PT in the train is distributed. This enables the connection assistance device 100 to perform a handover of the multiple terminal devices PT in the train more quickly and smoothly.

[0095] (4. Other Embodiments) Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0096] (a) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, some of the configuration of the above embodiment may be omitted. Furthermore, at least some of the configuration of the above embodiment may be added to or replaced with the configuration of other above embodiments.

[0097] (b) In addition to the connection assistance device described above, the present disclosure can also be realized in various forms, such as a system comprising the connection assistance device, a program for causing a computer to function as the connection assistance device, a non-transitional physical recording medium such as a semiconductor memory on which the program is recorded, and a connection assistance method. [Explanation of Symbols]

[0098] 10...Control unit, 20...First communication module, 30...Database, 40...Second communication module, 50...GNSS module, 100...Connection support device, PT...Terminal device.

Claims

1. A connecting assist device installed on a train traveling along a predetermined route, A database that stores the identification information of each of the multiple base stations located along the aforementioned route, associated with the location information of each of the multiple base stations and the location where a handover occurred. It comprises a control unit and, The aforementioned plurality of base stations include a first base station and a second base station, The control unit, A request signal is transmitted to each of the multiple terminal devices located inside the aforementioned train, requesting a report of the measurement results of the received signal strength. The measurement results are received from each of the aforementioned multiple terminal devices. The train information, including the train's position and speed, is acquired. Based on the reported measurement results, the train information, and the location of the handover stored in the database, each of the multiple terminal devices located within the train determines the timing for handover from the first base station to the second base station. Based on the fulfillment of predetermined conditions, an instruction signal is sent to the multiple terminal devices to instruct them to perform the handover so that the timings are distributed. Based on the failure of a predetermined condition, the system is configured to guide the first base station to perform a handover at the distributed timings of the multiple terminal devices. Connection support device.

2. A connecting assist device installed on a train traveling along a predetermined route, A database that stores the identification information, location information, and handover location of each of the multiple base stations located along the aforementioned route, in association with each other. It comprises a control unit and, The aforementioned plurality of base stations include a first base station and a second base station, The control unit, A request signal is transmitted to each of the multiple terminal devices located inside the aforementioned train, requesting a report of the measurement results of the received signal strength. The measurement results are received from each of the aforementioned multiple terminal devices. The train information, including the train's position and speed, is acquired. Based on the reported measurement results, the train information, and the location of the handover stored in the database, each of the multiple terminal devices located within the train determines the timing for handover from the first base station to the second base station. The system is configured to transmit instruction signals to the multiple terminal devices instructing the handover so that the timing is distributed among them. Connection support device.

3. A connecting assist device installed on a train traveling along a predetermined route, A database that stores the identification information, location information, and handover location of each of the multiple base stations located along the aforementioned route, in association with each other. It comprises a control unit and, The aforementioned plurality of base stations include a first base station and a second base station, The control unit, A request signal is transmitted to each of the multiple terminal devices located inside the aforementioned train, requesting a report of the measurement results of the received signal strength. The measurement results are received from each of the aforementioned multiple terminal devices. The train information, including the train's position and speed, is acquired. Based on the reported measurement results, the train information, and the location of the handover stored in the database, each of the multiple terminal devices located within the train determines the timing for handover from the first base station to the second base station. The configuration is such that the multiple terminal devices guide the first base station to perform a handover at the distributed timings. Connection support device.

4. The control unit, Depending on the level of the communication continuation request from each of the multiple terminal devices, the handover priority for each of the multiple terminal devices is set. The system is configured to set a time difference in the timing of the multiple terminal devices such that the higher the set priority, the earlier the timing becomes. The connection assist device according to claim 2.

5. The control unit, Based on the handover performance of each of the aforementioned multiple terminal devices, the handover processing capacity of each of the aforementioned multiple terminal devices is learned. Based on the learning results of the processing capacity, the system is configured to set a time difference in the timing of the multiple terminal devices such that the lower the processing capacity, the earlier the timing becomes. The connection assist device according to claim 2.

6. The aforementioned train has multiple carriages, The control unit is configured to set a time difference for the timing of the terminal device located in each of the plurality of vehicles. The connection assist device according to claim 2.

7. The control unit is configured to transmit the request signal to each of the multiple terminal devices at different transmission times. The connection assist device according to claim 2.

8. The control unit, The request signal is configured to include a time for the report of the measurement results. To make the reply times of the multiple terminal devices different, The connection assist device according to claim 2.

9. The control unit is configured to set the instruction signals to the plurality of terminal devices to have reached different start times or different locations as conditions for initiating the handover. The connection assist device according to claim 2.

10. The connection assist device is configured to simultaneously connect to the first base station and the second base station from before the start of the handover to after its completion when the connection assist device performs a handover from the first base station to the second base station. The connection assist device according to claim 2.

11. The control unit is configured to stagger the timing of the handover of the connection assistance device from the first base station to the second base station with the timing of each of the plurality of terminal devices. The connection assist device according to claim 2.

12. The control unit is configured to transmit the specifications of the second base station to the plurality of terminal devices and to transmit the specifications of each of the plurality of terminal devices to the second base station before transmitting the instruction signal to the plurality of terminal devices. The connection assist device according to claim 2.

13. The database stores the respective specifications of each of the multiple base stations in association with the respective identification information of each of the multiple base stations. The connection assist device according to claim 2.

14. The control unit is configured to discard, from among the measurement result reports received from each of the plurality of terminal devices, any measurement result report that prompts a handover to a base station located behind the direction of travel of the train. The connection assist device according to claim 2.

15. The control unit is configured to discard the measurement result reports received from each of the multiple terminal devices until a certain period of time has elapsed after the handover of the multiple terminal devices is completed. The connection assist device according to claim 2.

16. The control unit is configured to rewrite the measurement result reports received from each of the plurality of terminal devices to the reports that prompt a handover to a base station located behind the direction of travel of the train. The connection assist device according to claim 2.

17. The plurality of terminal devices include a first terminal device that can connect to only one base station and a second terminal device that can connect to two base stations. The control unit, The second terminal device is instructed to temporarily connect to both the first base station and the second base station, The system is configured to cause the second terminal device to disconnect from the first base station after the handover of the first terminal device is completed. The connection assist device according to claim 2.

18. The control unit, The report of the measurement results showing that the reception strength of the first base station is higher than that of the second base station is rewritten to show that the reception strength of the second base station is higher than that of the first base station. The system is configured to transmit the measurement results from each of the multiple terminal devices to the first base station at different times. The connection assist device according to claim 3.

19. The control unit estimates the first time and the second time, The first time corresponds to the time required for the handover of the multiple terminal devices to be completed when the instruction signal is transmitted to the multiple terminal devices so that the timing is distributed among them. The second time corresponds to the time required for the handover of the multiple terminal devices to be completed when the first base station is guided to perform a handover at the distributed timing of the multiple terminal devices. The aforementioned predetermined condition is that the first time is shorter than the second time. The connection assist device according to claim 1.

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