Handover method, handover system, and handover device

Abstract

This handover method includes: acquiring a scheduled future movement route of a mobile body (S101, S301); extracting, from a communication information storage unit, area information of a candidate base station, to which station a communication device can be connected via the scheduled movement route (S102, S302); predicting a movement time required for a mobile body to move the scheduled movement route included in a handover area where, among the communication areas indicated by the extracted area information, the communication area of a connection source base station which is one candidate base station and the communication area of another candidate base station overlap, and where handover from the connection source base station to another candidate base station is possible (S103, S303); selecting a connection destination base station to which the communication device is handed over from the connection source base station from among the other candidate base stations on the basis of the movement time (S153); and handing over the base station to which the communication device is connected from the connection source base station to the connection destination base station when the mobile body has moved to the handover area (S155).

Description

Handover method, handover system, and handover device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2024-097722, filed on June 17, 2024, the contents of which are incorporated herein by reference.

[0002] The present application relates to a handover method for handing over a base station to which a communication device mounted on a mobile object such as a car is connected, a handover system for executing the handover method, and a handover device.

[0003] As wireless communication becomes more widespread, opportunities to communicate using wireless communication are increasing in various places. In particular, for mobile objects such as automobiles, technologies that use wireless communication functions to provide driving assistance and autonomous driving control are attracting attention. As a result, vehicles are increasingly equipped with communication functions, and the so-called "connected vehicles" trend is progressing.

[0004] When a communication terminal moves, such as in a vehicle, it is necessary to switch the base station device that communicates with it as it moves, a process known as handover.If there are multiple base stations that can be connected to at the destination, it is necessary to select an appropriate base station device from among the available base stations.

[0005] For example, Patent Document 1 describes that a wireless terminal device sets priorities for target APs that are candidates for handover destinations based on connection history information of the wireless base station device to which it was wirelessly connected before handing over to the current AP, and when performing a handover, it attempts to establish a wireless connection with the target AP according to the set priorities, and hands over to the target AP with which it was able to establish a wireless connection first.

[0006] JP 2009-49922 A

[0007] Here, the inventors have found the following problem after detailed investigation. Handovers are usually performed near the boundary of the communication area of ​​a wireless base station device. This is done to prevent communication interruptions by performing handovers in an area where multiple wireless base stations are connectable. However, in wireless communication using a terminal device mounted on a mobile object moving at high speed, the terminal device only stays within the communication area of ​​a wireless base station for a short period of time. In particular, when using a communication method such as Wi-Fi, where the communication area of ​​each wireless base station is relatively narrow, the mobile object may quickly pass through an area where multiple wireless base stations are connectable, and there is a possibility that wireless communication will be interrupted because there will not be enough time to switch wireless base stations.

[0008] Therefore, the present disclosure aims to prevent wireless communication interruptions by having a communication device mounted on a mobile body select a base station device that can ensure sufficient time for switching wireless base stations as the base station to connect to.

[0009] A handover method according to one aspect of the present disclosure is a handover method for handing over a base station to which a communication device mounted on a mobile body is connected, the handover method comprising: acquiring a future planned movement route of the mobile body; extracting area information of candidate base stations, which are base stations that the communication device can connect to along the planned movement route, from a communication information storage unit that stores area information indicating communication areas in which the base stations can communicate; predicting a travel time required for the mobile body to move along the planned movement route included in a handover area in which the communication area of ​​one of the candidate base stations, which is a connection source base station, overlaps with the communication areas of other candidate base stations and in which handover from the connection source base station to the other candidate base station, based on the travel time; selecting a connection destination base station from the other candidate base stations to which the communication device will hand over from the connection source base station; and when the mobile body moves into the handover area, handing over the base station to which the communication device is connected from the connection source base station to the connection destination base station.

[0010] According to another aspect of the present disclosure, there is provided a handover system (S) for handing over a base station to which a communication device mounted on a mobile body is connected, the handover system comprising: a route acquisition unit that acquires a future planned movement route of the mobile body; an area information extraction unit that extracts area information of candidate base stations that are base stations that can be connected to the communication device along the planned movement route from a communication information storage unit that stores area information indicating communication areas in which the base stations can communicate; a movement time prediction unit that predicts a movement time required for the mobile body to move along the planned movement route included in a handover area in which, among the communication areas indicated by the extracted area information, the communication area of ​​a connection source base station that is one of the candidate base stations overlaps with the communication areas of other candidate base stations and in which handover from the connection source base station to the other candidate base station is possible; a base station selection unit that selects a connection destination base station to which the communication device will hand over from the connection source base station from among the other candidate base stations based on the movement time; and a base station switching unit that, when the mobile body moves into the handover area, hands over the base station to which the communication device is connected from the connection source base station to the connection destination base station.

[0011] According to another aspect of the present disclosure, a handover device that hands over a base station to which a communication device mounted on a mobile body is connected includes: a base station information acquisition unit that acquires base station information indicating candidate base stations that can be connected along a future planned movement route of the mobile body; a travel time information acquisition unit that acquires travel time information indicating a predicted travel time required for the mobile body to travel along the planned movement route included in a handover area where a communication area in which one of the candidate base stations, a source base station, can communicate and a communication area in which another candidate base station can communicate overlap, and where handover from the source base station to the other candidate base station is possible; a base station selection unit that selects a destination base station to which the communication device will hand over from the source base station from among the other candidate base stations based on the travel time indicated by the travel time information; and a base station switching unit that, when the mobile body moves into the handover area, hands over the base station to which the communication device is connected from the source base station to the destination base station.

[0012] It should be noted that the numbers in parentheses in the claims indicate the correspondence between the present invention and the embodiments described below, and are not intended to limit the present invention.

[0013] With the above-described configuration, the handover method and the like of the present disclosure can prevent wireless communication from being interrupted when a handover is performed from a source base station to a destination base station.

[0014] FIG. 1 is an overall diagram showing devices used in a handover system of each embodiment and their interrelationships; FIG. 2 is a block diagram showing an example of the configuration of a server device and an in-vehicle device of the first embodiment; FIG. 3 is a diagram explaining a communication information storage unit of the first embodiment; FIG. 4 is a diagram explaining a communication area and a planned travel route of the first embodiment; FIG. 5 is a diagram explaining a travel time prediction process in a travel time prediction unit of the first embodiment; FIG. 6 is a diagram explaining a travel time prediction process in a travel time prediction unit of the first embodiment; 16 is a flowchart illustrating the operation of the handover system according to the third embodiment; FIG. 17 is a diagram illustrating the base station selection process according to the first modification; FIG. 18 is a diagram illustrating the base station selection process according to the first modification; FIG. 19 is a flowchart illustrating the operation of the base station selection unit according to the first modification; and FIG. 20 is a block diagram illustrating an example of the configuration of the in-vehicle device according to the second modification.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0016] The present invention described below refers to the invention described in the claims and is not limited to the following embodiments. Furthermore, at least the words in double quotation marks refer to the words described in the claims and are not limited to the following embodiments.

[0017] The configurations and methods recited in the dependent claims are optional configurations and methods in the inventions recited in the independent claims. The configurations and methods of the embodiments corresponding to the configurations and methods recited in the dependent claims, as well as the configurations and methods recited only in the embodiments without being recited in the claims, are optional configurations and methods in the present invention. The configurations and methods recited in the embodiments when the recitation of the claims is broader than the recitation of the embodiments are also optional configurations and methods in the present invention, in the sense that they are examples of the configurations and methods of the present invention. In either case, by being recited in the independent claims, they become essential configurations and methods of the present invention.

[0018] The effects described in the embodiments are effects obtained when the configurations of the embodiments are provided as examples of the present invention, and are not necessarily effects that the present invention has.

[0019] When there are multiple embodiments, the configurations disclosed in each embodiment are not limited to each embodiment, but can be combined across the embodiments. For example, a configuration disclosed in one embodiment may be combined with another embodiment. Also, configurations disclosed in multiple embodiments may be collected and combined.

[0020] The problems described in this disclosure are not publicly known problems, but have been independently discovered by the inventors, and together with the configuration and method of this disclosure, these facts affirm the inventive step of the invention.

[0021] 1. Interrelationships of Related Devices in Each Embodiment First, an overall configuration showing the devices used in the handover system S of each embodiment and their interrelationships will be described with reference to FIG.

[0022] Fig. 1(a) shows that the handover system S is a system having a server device 1 provided outside a vehicle, which is a "mobile body," and an in-vehicle device 2 "mounted" on the vehicle. Fig. 1(b) shows that the handover system S is a system consisting of an in-vehicle device 2 "mounted" on a vehicle, which is a "mobile body." In addition to the in-vehicle device 2, the vehicle is equipped with a communication device 3.

[0023] Here, "mobile body" refers to an object that can move, and can move at any speed. It also naturally includes cases where the mobile body is stationary. Examples include, but are not limited to, automobiles, motorcycles, bicycles, pedestrians, ships, aircraft, and objects mounted on these. "Mounted" includes not only cases where the object is directly fixed to the mobile body, but also cases where the object is not fixed to the mobile body but moves with the mobile body. For example, it may be carried by a person riding the mobile body, or mounted on cargo placed on the mobile body.

[0024] The handover system S described in the first and second embodiments corresponds to Fig. 1(a), and the handover system S described in the third embodiment corresponds to Fig. 1(b). In the first embodiment, the server device 1 corresponds to the handover information providing device 100, and the in-vehicle device 2 corresponds to the handover device 150. In the second embodiment, the server device 1 corresponds to the handover instruction device 200, and the in-vehicle device 2 corresponds to the handover device 250. In the third embodiment, the in-vehicle device 2 corresponds to the handover device 350.

[0025] Although the in-vehicle device 2 and the communication device 3 are shown as separate devices in FIG. 1, the communication device 3 may be provided with the functions of the in-vehicle device 2 in each embodiment described below.

[0026] The communication device 3 mounted on the vehicle performs wireless communication via a base station. The communication device 3 performs communication using a communication network that uses a wireless communication method such as IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), W-CDMA (Wideband Code Division Multiple Access), HSPA (High Speed ​​Packet Access), LTE (Long Term Evolution), LTE-A (Long Term Evolution Advanced), 4G, or 5G.

[0027] The communication device 3 is connected to the server device 1 via the above-mentioned communication network. The communication device 3 may be further connected to another server device (not shown) that controls the autonomous driving of the vehicle or collects logs generated by the vehicle. In Fig. 1(a), a base station connecting the server device 1 and the communication device 3 is omitted.

[0028] In the following embodiment, a configuration in which the communication device 3 communicates using a Wi-Fi wireless communication system will be described as an example. When communicating using the Wi-Fi wireless communication system, the communication device 3 transmits a connection request to a base station. The communication device 3 may transmit authentication information (e.g., a password) required for connection to the base station along with the connection request. Once the communication device 3 is authenticated by the base station, it becomes possible for the communication device 3 to communicate via the base station.

[0029] The communication device 3 may have multiple communication modules and may be a device capable of communicating using multiple communication methods. For example, the communication device 3 may have two Wi-Fi communication modules, and each of the two communication modules may communicate using Wi-Fi. Alternatively, the communication device 3 may have a Wi-Fi communication module and a 4G communication module, and each of the two communication modules may communicate using a different communication method.

[0030] 2. First Embodiment (1) Configuration of Server Device 1 (Handover Information Providing Device 100) The configuration of the server device 1 of this embodiment will be described with reference to Fig. 2. In this embodiment, the server device 1 has the function of the handover information providing device 100.

[0031] The handover information providing device 100, which is the server device 1, includes a route acquisition unit 101, a communication status acquisition unit 102, a communication information storage unit 103, a control unit 104, and a handover information transmission unit 107. The control unit 104 realizes a communication information extraction unit 105 and a travel time prediction unit 106.

[0032] The route acquisition unit 101 acquires route information indicating a planned future travel route of the vehicle. For example, the route acquisition unit 101 acquires the route information indicating a planned travel route derived by a navigation device or the like provided in the vehicle by receiving it from the vehicle via wireless communication. Alternatively, the route acquisition unit 101 may acquire the route information from a route derivation unit (not shown) provided outside the vehicle that acquires vehicle current position information and destination information from the vehicle and derives a planned travel route.

[0033] While the vehicle is moving, the route may be changed due to traffic congestion or the passenger's request. In such a case, the route acquisition unit 101 may timely acquire route information indicating the planned route after the change. The planned route may also be a part of the route from the current position of the vehicle to the destination.

[0034] The communication status acquisition unit 102 acquires communication status information indicating the communication status of the base station. For example, the communication status acquisition unit 102 acquires, from the communication device 3 that has attempted to connect to the base station, information such as the reception strength of a radio signal from the base station and whether or not connection to the base station is possible, as the communication status information. Alternatively, the communication status acquisition unit 102 may acquire, directly from the base station, information such as whether or not the base station is operating and whether or not the number of communication devices that can connect to the base station has been reached, as the communication status information.

[0035] The communication status acquisition unit 102 may further acquire handover record information indicating the time actually required for the communication device 3 to perform handover from one base station to another base station (corresponding to the "handover time").

[0036] The communication information storage unit 103 is a storage unit that stores base station information indicating a base station and area information indicating a communication area in which communication with the base station is possible. The base station information may include, for example, location information of the base station, a service set identifier (SSID) of the base station, a password required for connection to the base station, etc. The communication information storage unit 103 further stores the communication status information and handover record information acquired by the communication status acquisition unit 102.

[0037] FIG. 3 shows an example of information stored in the communication information storage unit 103. In the example of FIG. 3, base station information including a base station ID and base station location information is stored. Furthermore, while the area information in FIG. 3 is simply illustrated as A1 to A9, the communication area may also be indicated by, for example, the distance from the base station's location to the outer edge of the communication area, or by latitude and longitude. Furthermore, FIG. 3 stores communication status information indicating whether the base station is in a communication-enabled state (normal) or a communication-disabled state (communication disabled). The example of FIG. 3 indicates that base station 7 (BS7), base station 8 (BS8), and base station 9 (BS9) are each in a communication-disabled state (communication disabled). Note that, unlike base stations 7 and 8, no communication abnormality has occurred with base station 9, and the base station is also active. However, if the reception strength of the wireless signal from a base station is below a preset threshold and sufficient communication quality is not obtained, such a base station may be determined to be in a communication-disabled state.

[0038] The communication information extraction unit 105 (corresponding to the "area information extraction unit") of the control unit 104 extracts base station information indicating base stations that the communication device 3 mounted on the mobile body can connect to along a planned travel route, and area information corresponding to the base station information, from the communication information storage unit 103. Hereinafter, of the base stations indicated by the base station information stored in the communication information storage unit 103, base stations that the communication device 3 can connect to along a planned travel route will be referred to as candidate base stations.

[0039] If the communication status information corresponding to a candidate base station indicates that the base station is in a "communication-unable" state, the communication information extraction unit 105 extracts the base station information of the candidate base stations excluding the candidate base station (corresponding to a "specific base station") that is in a communication-unable state, and the corresponding area information.

[0040] Here, "unable to communicate" includes not only cases where the base station is in a state where communication is not possible, but also cases where the base station is in a state where communication is possible but the quality of communication is not sufficient.

[0041] Fig. 4 is a diagram that schematically illustrates the communication areas of candidate base stations. The ovals in Fig. 4 indicate the communication areas (A1 to A7) of the base stations. The communication areas shown in Fig. 4 correspond to the communication areas of the base stations (BS1 to BS7) illustrated in Fig. 3. The straight lines in Fig. 4 indicate the planned route of travel of the vehicle, with S indicating the current position of the vehicle and G indicating the destination of the vehicle. P1 to P8 indicate the points where the planned route intersects with the outer edge of each communication area.

[0042] According to Fig. 4, the planned travel route of the vehicle passes through communication areas A1 to A7. Therefore, the candidate base stations to which the vehicle's communication device 3 can connect along the planned travel route are base stations BS1 to BS7. However, as shown in Fig. 3, base station BS7 is not activated and is therefore unable to communicate. Therefore, the communication information extraction unit 105 selects base stations BS1 to BS6 excluding base station BS7 as candidate base stations, and extracts base station information indicating base stations BS1 to BS6 and area information indicating communication areas A1 to A6.

[0043] The travel time prediction unit 106 derives an area where two communication areas overlap from among the communication areas indicated by the area information extracted by the communication information extraction unit 105. An area where two communication areas overlap is a handover area where handover from one candidate base station to another candidate base station is possible. Hereinafter, a candidate base station before handover in the handover area will be referred to as a source base station, and a base station to which handover will be performed will be referred to as a destination base station. The travel time prediction unit 106 further predicts the travel time required for the vehicle to travel a planned travel route included in the handover area.

[0044] In one example, the travel time prediction unit 106 first calculates the distance of the planned travel route included in each handover area. Then, based on the calculated distance L [m] and the speed limit V [m / s] of the planned travel route included in the handover area, the travel time prediction unit 106 derives the travel time T [s] (= L / V) predicted to be required for the vehicle to travel the planned travel route included in the handover area.

[0045] The travel time prediction unit 106 may predict the travel time using the speed of other vehicles currently traveling on the planned travel route or the current vehicle speed instead of the speed limit.

[0046] The travel time prediction process in the travel time prediction unit 106 will be further described with reference to Figures 5 and 6. Figure 5 shows the distances (L1 to L9) between each of the points shown in Figure 4, the speed limits (V1 to V9) between each of the points, and the travel times (T1 to T9) predicted to be required for a vehicle to travel each distance.

[0047] 6 shows the correspondence between the handover areas of each candidate base station shown in FIG. 4, points on the planned travel route included in the handover area, and the distance and travel time of the planned travel route included in the handover area. In FIG. 6, handover areas where two communication areas overlap are simply indicated using the symbol (^). For example, the handover area where communication area A1 and communication area A2 overlap is represented by (A1^A2). FIG. 6 also shows the distance and travel time from a point where the planned travel route intersects with a communication area (A4, A6) that includes the destination (G) but is not a handover area, to the destination (G).

[0048] For example, the handover area (A1^A2) where the communication area A1 of candidate base station BS1 and the communication area A2 of candidate base station BS2 overlap includes points S, P1, P2, and P3 on the planned travel route. Therefore, the distance of the planned travel route included in the handover area (A1^A2) is the sum (L1+L2+L3) of the distance L1 from point S to point P1, the distance L2 from point P1 to point P2, and the distance L3 from point P2 to point P3. Furthermore, the travel time of the planned travel route included in the handover area (A1^A2) is the sum (T1+T2+T3) of the travel time T1 from point S to point P1, the travel time T2 from point P1 to point P2, and the travel time T3 from point P2 to point P3.

[0049] The handover information transmitting unit 107 transmits handover information including the base station information extracted by the communication information extracting unit 105 and travel time information indicating the travel time predicted by the travel time predicting unit 106 to the in-vehicle device 2. The handover information may further include area information of the candidate base stations.

[0050] The handover information will be described with reference to Figure 7. Figure 7(a) is a diagram visually representing the candidate base stations indicated by the base station information included in the handover information and the travel time indicated by the travel time information. Figure 7(b) is a diagram representing Figure 7(a) using matrix A. The arrows shown in Figure 7(a) indicate that handover from one candidate base station to another candidate base station is possible, and the numbers attached to the arrows indicate the travel time within the handover area. The travel times shown in Figures 7(a) and 7(b) correspond to the travel times calculated in Figure 6.

[0051] (2) Configuration of the In-Vehicle Device 2 (Handover Device 150) Next, the configuration of the in-vehicle device 2 of this embodiment will be described with reference to FIG. 2. In this embodiment, the in-vehicle device 2 has the function of the handover device 150. The handover device 150 mainly has a base station selection function and a base station switching function. FIG. 2 illustrates a configuration in which these functions are provided in a single device. However, the device having the base station selection function and the device having the base station switching function may be provided in different devices. For example, the communication device 3 may be configured to have a base station switching unit 154, which will be described later.

[0052] The handover device 150 includes a handover information receiving unit 151 , a handover information storage unit 152 , a base station selecting unit 153 , and a base station switching unit 154 .

[0053] The handover information receiving unit 151 receives handover information from the handover information providing device 100. The handover information saving unit 152 saves the handover information received by the handover information receiving unit 151.

[0054] Based on the handover information stored in the handover information storage unit 152, the base station selection unit 153 selects a destination base station to which the communication device 3 will hand over from a source base station, which is one of the candidate base stations. Specifically, based on the travel time indicated by the travel time information, the base station selection unit 153 selects the candidate base station with the longest travel time from among other candidate base stations that can be handed over from the source base station as the destination base station to be connected next to the source base station. The base station selection unit 153 then repeatedly performs the destination base station selection process from the source base station whose communication area includes the vehicle's current location (corresponding to the "first point") until it selects a destination base station whose communication area includes the vehicle's destination (corresponding to the "second point"). The destination base station selection process in the base station selection unit 153 will be described with reference to FIG. 7(a).

[0055] 7(a), when the source base station is base station 1, the candidate base stations to which base station 1 can hand over are base station 2, base station 3, and base station 4, and the travel times to their respective handover areas are 18, 10, and 4. Therefore, the base station selection unit 153 selects base station 2, which has the longest travel time among the candidate base stations, as the destination base station to which base station 1 is to hand over.

[0056] Next, the base station selection unit 153 sets base station 2, which is the selected destination base station, as the next source base station, and selects a destination base station from among the candidate base stations (base station 3, base station 4, and base station 5) to which handover is possible from base station 2. In this example, the travel times between the handover areas of base station 2 and base station 3, base station 4, and base station 5 are 13, 7, and 2, respectively, and base station 3 is the base station with the longest travel time. Therefore, the base station selection unit 153 selects base station 3 as the destination base station to hand over from base station 2.

[0057] Similarly, the base station selection unit 153 sets base station 3, which is the selected destination base station, as the next source base station, and selects a destination base station from among the candidate base stations (base station 4, base station 5, and base station 6) that can be handed over from base station 3. In this example, base station 4, which takes the longest travel time within the handover area, is selected as the destination base station for handover from base station 3.

[0058] Here, the communication area of ​​base station 4, which is the selected destination base station, includes point G. Therefore, the base station selector 153 ends the destination base station selection process.

[0059] FIG. 8 shows the same handover information as FIG. 7(a), but the destination base station selected by the base station selection unit 153 and the handover from the source base station to the destination base station are shown in bold.

[0060] In this embodiment, the planned travel route is a route from the current position (point S) of the vehicle to the destination (point G), and the base station selection unit 153 pre-selects a destination base station for handover from point S to point G. However, the base station selection unit 153 may be configured to sequentially select destination base stations as the vehicle moves.

[0061] When the vehicle moves into the handover area of ​​the selected destination base station, the base station switching unit 154 hands over the base station to which the communication device 3 is connected from the source base station to the destination base station. Whether the vehicle has moved into the handover area may be determined based on vehicle location information. For example, when vehicle location information acquired from a GPS or the like installed in the vehicle indicates that the vehicle is within the range indicated by the area information of the destination base station, it may be determined that the vehicle has moved into the handover area. Alternatively, it may be determined that the vehicle has moved into the handover area when the communication device 3 receives radio waves from the base station.

[0062] It is also possible that the base station switching unit 154 may attempt to perform a handover from the source base station to the destination base station, but may find that the handover to the destination base station is not possible. For example, the destination base station may have been active when the handover information was received from the server device 1, but may subsequently stop operating. In such a case, the base station selecting unit 153 reselects a new destination base station based on the handover information.

[0063] (3) Operation of the Handover System 1 The operation of the handover information providing device 100 and the handover device 150 will be described below using the flowcharts in Figures 9 and 10. The order of these processes is not limited to the order shown in Figures 9 and 10. In other words, the order may be changed as long as there are no constraints, such as a relationship in which a certain step uses the result of the previous step. The same applies to the flowcharts of the embodiments described later.

[0064] The route acquisition unit 101 of the handover information providing device 100 acquires route information indicating a future planned travel route of the vehicle (S101). The communication information extraction unit 105 extracts, from the communication information storage unit 103, base station information indicating candidate base stations connectable along the planned travel route indicated by the route information acquired by the communication device 3 in S101 and area information indicating the communication areas of the candidate base stations (S102). The travel time prediction unit 106 predicts the travel time required for the vehicle to travel along the planned travel route included in a handover area where the communication area of ​​one candidate base station overlaps with the communication area of ​​another candidate base station, among the communication areas indicated by the area information extracted in S102 (S103). Then, the handover information transmission unit 107 transmits handover information including the base station information extracted in S102 and the travel time information indicating the travel time predicted in S103 to the in-vehicle device 2 (S104).

[0065] The handover information receiving unit 151 of the handover device 150 provided in the in-vehicle device 2 receives the handover information transmitted in S104 (S151). The handover information storage unit 152 stores the handover information received in S151 (S152). The base station selecting unit 153 selects a destination base station to be handed over from the source base station based on the travel time information included in the handover information stored in S152 (S153). The destination base station selection process will be described later with reference to FIG. 10. If the vehicle moves into the handover area (S154: Y), the base station switching unit 154 hands over the base station to which the communication device 3 is connected from the source base station to the destination base station selected in S153 (S155).

[0066] Furthermore, in S104, if communication status information is received after transmitting handover information to the in-vehicle device 2 (S105: Y), the communication information storage unit 103 updates the stored communication status information (S106). Then, if the updated communication status information indicates that a specific base station is not able to communicate (S107: Y), candidate base stations excluding the base station with which communication is not possible are extracted again (S102).

[0067] Next, the destination base station selection process of S153 will be described with reference to FIG. 10. First, one of the candidate base stations whose communication area includes point S is selected as the source base station (S1531). Next, among the candidate base stations whose communication area overlaps with that of the source base station selected in S1531, the candidate base station with the longest travel time is selected as the destination base station (S1532). Here, if the communication area of ​​the destination base station selected in S1532 includes point G (S1533: Y), the base station selection process ends. On the other hand, if the communication area of ​​the destination base station selected in S1532 does not include point G, the destination base station selected in S1532 is set as the next source base station, and a destination base station for handover is selected from the next source base station (S1534). Then, the destination base station selection process (S1532 to S1534) is repeated until point G is included in the communication area of ​​the destination base station selected in S1532.

[0068] It should be noted that the vehicle's travel route may change midway after the destination base station is selected by the process shown in Fig. 9. In such a case, route information indicating the planned travel route after the change is acquired in S101, and the process shown in Fig. 9 is executed again.

[0069] (4) When the communication device has multiple communication modules Next, in this embodiment, a case where the communication device 3 has multiple communication modules will be described. When the communication device 3 has multiple communication modules, the communication modules may use the same communication method or may use different communication methods. Each case will be described below.

[0070] (a) Case where multiple communication modules use different communication methods A case where multiple communication modules included in the communication device 3 each use a different communication method will be described. As an example, a case where one of the two communication modules included in the communication device 3 is capable of communication using Wi-Fi and the other is capable of communication using 4G will be described. In this example, candidate base stations are extracted for each of the Wi-Fi and 4G communication methods, and travel times within each handover area are predicted, and a destination base station is selected based on the travel times.

[0071] When the communication methods are different, not only the base station to which the communication device 3 connects but also the communication area in which the base station can communicate differs. Therefore, it is necessary to select a different base station to connect to for each communication method.

[0072] The same applies when the communication device 3 uses multiple cellular lines operated by different carriers. Each carrier installs its own base station in a cellular line. Therefore, the base station and communication area to which the communication device 3 connects are different for each cellular line operated by a different carrier.

[0073] (b) Case where multiple communication modules use the same communication method Next, a case where multiple communication modules included in the communication device 3 use the same communication method will be described. In this embodiment, a case where there are two communication modules is described as an example, but the communication device 3 may have three or more communication modules.

[0074] The following description will be given taking as an example a case where the communication device 3 has a first communication module that communicates using a first communication line and a second communication module that communicates using a second communication line. Because the first communication line and the second communication line use the same communication method, the communication device 3 can communicate with the source base station and the destination base station using either the first communication line or the second communication line.

[0075] As an example, the base station selection unit 153 selects the same destination base station for the first communication module and the second communication module. That is, the base station selection unit 153 selects the candidate base station with the longest travel time as the destination base station to be connected via the first communication line and the second communication line.

[0076] In this case, the base station switching unit 154 performs a handover from the source base station to the destination base station using the first communication line, and then performs a handover from the source base station to the destination base station using the second communication line.

[0077] During handover, communication using the communication module performing the handover becomes temporarily unavailable. Therefore, while handover is being performed on one communication line, the other communication line continues communication by connecting to the source base station, and after handover of one communication line is completed, handover is performed on the other communication line, and the communication line that completed handover first connects to the destination base station and continues communication. This makes it possible to prevent communication from being interrupted while handover is being performed.

[0078] As another example, the base station selection unit 153 selects different destination base stations for the first communication module and the second communication module, respectively. The selection of destination base stations for the first communication line and the second communication line in this example will be described with reference to FIG. 11 .

[0079] Figure 11 shows the same handover information as Figure 7(a). Point S is included in the communication areas of base station 1 and base station 2. Therefore, base station 1 (corresponding to the "first source base station") is selected as the base station to connect to first using the first communication line, and base station 2 (corresponding to the "second source base station") is selected as the base station to connect to first using the second communication line. Figure 11(a) shows base stations to connect to using the first communication line with solid lines and base stations to connect to using the second communication line with dashed lines.

[0080] After the base station selection unit 153 selects base station 1 and base station 2, it first selects as the next destination base station the base station with the longest travel time between the handover areas of base station 1 and the other candidate base stations and between base station 2 and the other candidate base stations, but does not select a base station that has already been selected as the destination base station.

[0081] 11, the longest travel time among the travel time between base station 1 and the other candidate base stations (base station 3, base station 4) and the travel time between base station 2 and the other candidate base stations (base station 3, base station 4) is the travel time (13) from base station 2 to base station 3. Therefore, base station 3 (corresponding to the "second destination base station") is selected as the destination base station for handover from base station 2 using communication line 2.

[0082] Next, a destination base station for handover from base station 1 is selected using communication line 1, but base stations 2 and 3 have already been selected. Therefore, base station 4 (corresponding to the "first destination base station") is selected as the destination base station for handover from base station 1 using communication line 1. Here, the communication area of ​​base station 4 includes point G. Therefore, the destination base station selection process for communication line 1 is terminated (see FIG. 11(b)).

[0083] Meanwhile, in communication line 2, of base stations 5 and 6, which are candidate base stations excluding base station 4, base station 5, which has the longest travel time, is selected as the destination base station for handover from base station 3. Next, since base station 6 is the only candidate base station to which handover is possible from base station 5, base station 6 is selected as the destination base station for handover from base station 5. The communication area of ​​base station 6 includes point G. Therefore, the destination base station selection process for communication line 2 is terminated (see FIG. 11(c)).

[0084] In this example, the base station connectable via communication line 1 is the same as the base station connectable via communication line 2. However, as shown in Fig. 11, different base stations are selected as destination base stations for communication line 1 and communication line 2 to perform handover.

[0085] In addition, when the timing of handovers for communication line 1 and communication line 2 overlap, it is desirable to perform handover for one communication line after completing handover for the other communication line. This is because if handovers for two communication lines are performed at the same time, communication will be interrupted. In this case, it is desirable to give priority to the handover with the longer travel time so that handover for at least one of the two communication lines is reliably completed.

[0086] 12 is a diagram illustrating another embodiment. In this example, if the mobile station does not connect to base station 5 and base station 7 before moving from point S to point G on the planned travel route, a communication interruption will occur. In such a case, both the first communication line and the second communication line may be connected to base station 5 and base station 7.

[0087] In the same manner as in Fig. 11 , the base station selection unit 153 selects candidate base stations to connect to via communication line 1 and communication device 2. Fig. 12(b) shows the candidate base stations to connect to via communication line 1 with bold lines, and Fig. 12(c) shows the candidate base stations to connect to via communication line 2 with bold lines. As shown in Fig. 12(b) and Fig. 12(c), both communication line 1 and communication device 2 have selected base station 5 and base station 7 as the candidate base stations to connect to.

[0088] In addition, the base station selection unit 153 selects the base station 7 (corresponding to the "first destination base station") with the longest travel time as the destination base station for handover from the base station 5 in the communication line 1, and selects the base station 6 (corresponding to the "second destination base station") with the second longest travel time in the communication line 2. In this way, even if the source base station is the same, the destination base stations to be connected to in the communication lines 1 and 2 are selected to be different.

[0089] (5) Summary As described above, according to this embodiment, by selecting the base station that will result in the longest travel time within the handover area from among multiple candidate base stations and performing handover, it is possible to achieve base station handover even when the communication device is mounted on a mobile object that moves at high speed.

[0090] Furthermore, in this embodiment, high-load processing such as deriving travel time can be performed by the server device 1. Furthermore, the in-vehicle device 2 receives handover information from the server device 1 and selects a destination base station, so that even if connection to the intended destination base station cannot be established, the in-vehicle device 2 can immediately select another destination base station based on the handover information.

[0091] 3. Embodiment 2 In the first embodiment, the in-vehicle device 2 has a function of selecting a destination base station. In this embodiment, a configuration in which the server device 1 has a function of selecting a destination base station will be described. The following describes the differences from the first embodiment, and the same components and processes as those in the first embodiment are denoted by the same reference numerals in the drawings, and the description of the first embodiment will be quoted.

[0092] (1) Configuration of Server Device 1 (Handover Instructing Device 200) The configuration of the server device 1 of this embodiment will be described with reference to Fig. 13. In this embodiment, the server device 1 has the function of the handover instructing device 200.

[0093] The handover instruction device 200, which is the server device 1, includes a route acquisition unit 101, a communication status acquisition unit 102, a communication information storage unit 103, a control unit 204, and a handover instruction transmission unit 202. The control unit 204 implements a communication information extraction unit 105, a travel time prediction unit 106, and a base station selection unit 201. The main difference from the server device 1 of the first embodiment is that in this embodiment, the server device 1 includes a base station selection device 201 and transmits handover instruction information instead of handover information.

[0094] The base station selection unit 201 selects a destination base station based on the base station information extracted by the communication information extraction unit 105 and the travel time for handover of each candidate base station predicted by the travel time prediction unit 106. The method by which the base station selection unit 201 selects a destination base station is the same as in the first embodiment.

[0095] The handover instruction transmitting unit 202 transmits handover instruction information to the in-vehicle device 2 to instruct the in-vehicle device 2 to perform a handover to the destination base station selected by the base station selecting unit 201 .

[0096] The handover instruction transmitter 202 may transmit handover instruction information including all base station information indicating all destination base stations connected along the planned travel route. When the base station selector 201 selects the destination base stations shown in Fig. 8, the handover instruction information includes, for example, information indicating base station 1, base station 2, base station 3, and base station 4 in Fig. 8, and instruction information instructing to perform handover in this order.

[0097] Alternatively, the handover instruction information may include only base station information indicating a destination base station to be connected next after the base station currently connected by the communication device 3 and instruction information instructing the communication device 3 to perform a handover to the destination base station. In this case, for example, after the communication device 3 completes the handover from the source base station to the destination base station, the handover instruction transmitter 202 transmits, to the in-vehicle device 2, base station information indicating the next destination base station to which the communication device 3 will perform a handover from the destination base station (i.e., the next source base station) and instruction information to perform a handover to the destination base station, via communication via the destination base station. In the example of Fig. 8, after the communication device 3 completes the handover from base station 1 to base station 2, the communication device 3 transmits, to the in-vehicle device 2, handover instruction information including base station information indicating the next destination base station, i.e., base station 3, and instruction information instructing the communication device 3 to perform a handover to base station 3, via communication via base station 2.

[0098] (2) Configuration of In-Vehicle Device 2 (Handover Device 250) Next, the configuration of the in-vehicle device 2 of this embodiment will be described with reference to Fig. 13. In this embodiment, the in-vehicle device 2 has the function of the handover device 250.

[0099] The handover device 250, which is the in-vehicle device 2, has a handover instruction receiving unit 251 and a base station switching unit 154. The difference from the in-vehicle device 2 of the first embodiment is that the in-vehicle device 2 of this embodiment does not have a base station selection function.

[0100] The handover instruction receiving unit 251 receives handover instruction information from the server device 200. The base station switching unit 154 performs a handover from the source base station to which the communication device 3 is connected to the destination base station instructed in the handover instruction information received by the handover instruction receiving unit 251.

[0101] (3) Operation of Handover System 1 The operation of the handover instruction device 200 and the handover device 250 will be described with reference to the flowchart of FIG.

[0102] The base station selection unit 201 of the handover command device 200 selects a destination base station based on the travel time predicted in S103 (S201). In S201, the destination base station selection process described in Fig. 10 is executed. The handover command transmission unit 202 transmits handover command information to the handover device 250, instructing the handover to the destination base station selected in S201 (S202).

[0103] The handover instruction receiving unit 251 of the handover device 250 receives handover instruction information from the handover instruction device 200 (S251). Then, when the vehicle moves into the handover area between the source base station and the destination base station included in the handover instruction information (S154: Y), the base station switching unit 154 performs handover from the source base station to the destination base station (S155).

[0104] (4) Summary As described above, according to this embodiment, in addition to predicting travel time, the server device 1 can select a connection source base station, which can further reduce the processing involved in handover in the vehicle-mounted device 2.

[0105] 4. Embodiment 3 In the first and second embodiments, the server device 1 is configured to extract base station information and communication area information. In this embodiment, the vehicle-mounted device 2 performs handover processing, destination base station selection processing, and base station information and communication area information extraction processing. That is, in this embodiment, all processing of the handover system S is performed by the vehicle-mounted device 2. Below, differences from the first embodiment will be described, and configurations and processing similar to those of the first embodiment will be denoted by the same reference numerals in the drawings, and the description of the first embodiment will be quoted.

[0106] (1) Configuration of the In-Vehicle Device 2 (Handover Device 350) The configuration of the in-vehicle device 2 of this embodiment will be described with reference to Fig. 15. In this embodiment, the in-vehicle device 2 has the function of the handover device 350.

[0107] The handover device 350, which is the in-vehicle device 2, includes a route acquisition unit 351, a communication status acquisition unit 352, a communication information storage unit 353, a control unit 354, and a base station switching unit 154. The control unit 354 realizes a communication information extraction unit 355, a travel time prediction unit 356, and a base station selection unit 153.

[0108] The configurations and processes of the route acquisition unit 351, communication status acquisition unit 352, communication information storage unit 353, communication information extraction unit 355, and travel time prediction unit 356 of the handover device 350 are the same as those of the route acquisition unit 101, communication status acquisition unit 102, communication information storage unit 103, communication information extraction unit 105, and travel time prediction unit 106 in the first and second embodiments. However, while these configurations are provided in the server device 1 in the first embodiment, they are provided in the in-vehicle device 2 in the present embodiment.

[0109] In the first and second embodiments, the communication status acquisition unit 102 provided in the server device 1 acquires communication status information of base stations from base stations and vehicles. However, if the communication status acquisition unit 352 is provided in a vehicle, it may be difficult to acquire communication status information from base stations to which the vehicle cannot connect, and there is a risk that communication status information of base stations located far from the current location of the vehicle may not be acquired from other vehicles. Therefore, in the present embodiment, the communication status acquisition unit 352 may not be provided, or communication status information and handover record information may be received from a server device that collects communication status information from base stations and vehicles.

[0110] (2) Operation of Handover System 1 The operation of the handover device 350 will be described with reference to the flowchart of FIG.

[0111] The route acquisition unit 351 of the handover device 350 acquires route information indicating the planned travel route of the vehicle (S301). The communication information extraction unit 355 extracts, from the communication information storage unit 353, base station information indicating candidate base stations that can be connected along the planned travel route indicated by the route information acquired in S301 and area information indicating the communication areas of the candidate base stations (S302). The travel time prediction unit 356 predicts the travel time required for the vehicle to travel along the planned travel route included in a handover area where the communication area of ​​one candidate base station overlaps with the communication area of ​​another candidate base station among the communication areas indicated by the area information extracted in S302 (S303). The base station selection unit 153 selects a destination base station to which the communication device 3 will hand over from the source base station from the candidate base stations based on the travel time predicted in S303 (S153). In S153, the destination base station selection process described in FIG. 10 is executed.

[0112] Furthermore, in S153, if communication status information is received after selecting a destination base station (S304: Y), the communication information storage unit 353 updates the stored communication status information (S305). Then, if the updated communication status information indicates that a specific base station is not available for communication (S306: Y), candidate base stations are extracted again, excluding the specific base station with which communication is not available (S302).

[0113] Then, when the vehicle moves into the handover area (S154: Y), the base station switching unit 154 hands over the base station to which the communication device 3 is connected from the source base station to the destination base station selected in S153 (S155).

[0114] (3) Summary As described above, according to this embodiment, not only the handover process but also the travel time prediction and the destination base station selection process are performed by the in-vehicle device 2. In this embodiment, although the processing load of the in-vehicle device 2 increases, the amount of communication with the server device 1 can be reduced.

[0115] 5. Modification 1 In the above-described embodiments, the candidate base station with the longest travel time within the handover area is determined as the destination base station. In this modification, a configuration will be described in which a candidate base station other than the candidate base station with the longest travel time is selected as the destination base station.

[0116] (1) Selection Process of Destination Base Station This modification will be described with reference to Figures 17 and 18. Figure 17 shows a schematic diagram of the communication areas (B1 to B6) of the candidate base stations. Figure 18 visually shows the travel time between the candidate base stations and the handover areas of their communication areas shown in Figure 17.

[0117] If the travel time between the handover areas of the communication areas shown in Fig. 17 is the travel time shown in Fig. 18(a), selecting a destination base station using the techniques of embodiments 1 to 3 results in the result shown in Fig. 18(b). That is, base stations 1 to 6 are all selected as destination base stations. However, if the frequency of handovers is high like this, the processing load related to handovers increases.

[0118] Therefore, as shown in Figure 18(b), if selecting the candidate base station with the longest travel time as the destination base station would increase the frequency of handovers, specifically, if the total number of destination base stations selected from point S (corresponding to the "first point") to point G (corresponding to the "second point") on the planned travel route is greater than a predetermined threshold, the destination base station is selected so that the total number of destination base stations is "less than" the predetermined threshold.

[0119] Here, "greater than or equal to" and "less than or equal to" include both cases where the value is the same as the comparison target and cases where it is not.

[0120] However, the travel time between the handover areas of the destination base station and the source base station must be longer than the time required to complete the handover process. Therefore, it is desirable to select the destination base station so that the travel time between the handover areas of the destination base station and the source base station is "longer" than a predetermined time.

[0121] For example, the actual handover time required for a handover from a source base station to a destination base station is set as the predetermined time. When the communication status acquisition unit (102, 352) of each embodiment acquires handover history information indicating the actual handover time required for another vehicle to handover from a source base station to a destination base station, the handover history information is stored in the communication information storage unit (103, 353). Therefore, the base station selection unit (153, 201) sets the handover time indicated by the handover history information stored in the communication information storage unit (103, 353) as the predetermined time, and selects a destination base station so that the handover time is equal to or greater than the predetermined time. With this configuration, it is possible to reduce the total number of destination base stations on the planned travel route while ensuring the travel time required for handover.

[0122] Alternatively, instead of the actual handover time, a predetermined time may be set in advance.

[0123] An example of base station selection in this modification is shown in Figure 18(c). In this example, it is assumed that handover in each handover area takes 4 seconds, and the predetermined time is set to 4. It is also assumed that the threshold for the number of destination base stations is set to 5.

[0124] The number of destination base stations selected in Figure 18(b) is 6, and the total number of destination base stations is greater than the threshold. Therefore, in Figure 18(c), base station 3 is not selected as the destination base station for handover from base station 2, and base station 4 is selected instead. The total number of destination base stations selected in Figure 18(c) is 5, which is less than the threshold.

[0125] Here, in order to reduce the number of destination base stations on the planned movement route, for example, base station 3 can be selected as the destination base station for handover from base station 1, and base station 5 can be selected as the destination base station for handover from base station 2. However, the travel time between the handover areas of base station 1 and base station 3 is 3, and the travel time between the handover areas of base station 2 and base station 5 is 1, and these travel times are less than a predetermined time (4). Therefore, base station 3 is not selected as the destination base station for handover from base station 1, and base station 5 is not selected as the destination base station for handover from base station 2.

[0126] 18, for ease of explanation, the number of destination base stations from the current location of the vehicle to the destination has been described. However, it may be the total number of destination base stations from any point on the planned travel route to another any point. Alternatively, a threshold value for the number of base stations per predetermined distance (e.g., 1 km) on the planned travel route may be set in advance, and the threshold value may be set according to the total distance of the planned travel route.

[0127] (2) Operation of the Base Station Selector Next, the operation of the base station selector (153, 201) in this modification will be described with reference to Fig. 19. The process shown in Fig. 19 is executed in place of Fig. 10 at S153 in Fig. 9 and Fig. 16 and at S201 in Fig. 14.

[0128] The processes of S1531 to S1534 are the same as those in FIG. 10. In this modification, if the communication area of ​​the selected destination base station includes point G (S1533: Y), it is determined whether the total number of destination base stations selected from point S to point G is equal to or less than a threshold (S1535). Here, if the total number of destination base stations is equal to or less than the threshold, the process ends (S1535: Y). On the other hand, if the total number of destination base stations is greater than the threshold (S1535: N), another destination base station whose communication area includes point S and whose handover area travel time is equal to or longer than a predetermined time is selected again, and the processes of S1533, S1534, and S1532 are repeated.

[0129] (3) Summary According to this modification, when multiple communication areas overlap on a planned travel route, it is possible to select a destination base station that can secure the time required for handover processing while preventing frequent handovers.

[0130] 6. Modification 2 In the above-described embodiments, a configuration has been described in which the candidate base station with the longest travel time is selected as the destination base station. However, even if the destination base station with the longest travel time is selected, the travel time within the handover area may be shorter than the time required for handover processing. In this modification, vehicle speed control in such a case will be described.

[0131] Fig. 20 is a diagram illustrating a configuration example of an in-vehicle device 2 to which this modification is applied. The in-vehicle device 2 of this modification has a speed control function. Note that Fig. 20 illustrates a case in which this modification is applied to the in-vehicle device 2 of embodiment 1, but this modification may also be applied to the in-vehicle devices 2 of embodiments 2 and 3, or the server device 1 of embodiment 2 may be provided with a speed control function.

[0132] The handover device 150 shown in FIG. 20 includes a speed determination unit 155 and a speed instruction unit 156 in addition to the components shown in the first embodiment.

[0133] In this modified example, the handover information received by the handover information receiving unit 151 includes, in addition to base station information and travel time information, handover performance information indicating the handover time required for handover from one candidate base station indicated by the base station information to another candidate base station.

[0134] As explained in the first to third embodiments, the base station selection unit 153 of this modification selects, as the destination base station, the base station with the longest travel time among the candidate base stations.

[0135] Here, if the travel time in the handover area between the destination base station and the source base station selected by the base station selection unit 153 is shorter than the handover information indicated by the handover performance information, the speed determination unit 155 determines the speed at which the vehicle will travel along the planned travel route included in the handover area so that the travel time is longer than the handover time.

[0136] For example, if the distance of the planned travel route included in the handover area between the communication area A1 of the base station 1 and the communication area A2 of the base station 2 is L, １２ [m], and the speed limit in the handover area is V １２ In this case, the estimated travel time T required for the vehicle to move between handover areas is １２ [s] is L １２ / V １２ is.

[0137] Here, it is assumed that the handover record information indicates that the handover time required for handover from base station 1 to base station 2 is T [s]. １２ If T>T, the communication device 3 can complete handover from the base station 1 to the base station 2 in the handover area. １２ In this case, the communication device 3 cannot complete the handover from the base station 1 to the base station 2 while moving through the handover area. １２ The vehicle speed is determined so that

[0138] Specifically, the vehicle speed is V ｘ Then, T≦L １２ / V ｘ If V is satisfied, the handover can be completed in the handover area. ｘ ≦L １２ / T is satisfied by the velocity V ｘ is determined as the speed of the vehicle.

[0139] The speed indicator 156 outputs speed information indicating the speed determined by the speed determiner 155 to, for example, an electronic control device that controls the speed of the vehicle.

[0140] In addition, if the speed determination function is provided in the server device 1 of the second embodiment, the speed information is transmitted to the in-vehicle device 1 together with the handover instruction information.

[0141] In addition, when a vehicle has multiple communication lines, the speed of the vehicle may be determined so that all of the multiple communication lines can be handed over in the handover area. For example, in the above example, since the time required for two communication lines to complete handover in the handover area is 2T [s], the speed determination unit 155 determines 2T≦T １２ Therefore, the speed determination unit 155 determines the vehicle speed so that V ｘ ≦L １２ / 2T ｘ is determined as the speed of the vehicle.

[0142] Alternatively, the speed of the vehicle may be determined so that only one of the multiple lines can be handed over.

[0143] According to this modification, the speed of the vehicle is determined, and the vehicle travels through the handover area at the determined speed, thereby making it possible to complete the handover from the source base station to the destination base station.

[0144] 7. Summary The features of the handover system and the like in each embodiment of the present disclosure have been described above.

[0145] The terms used in each embodiment are merely examples and may be replaced with synonymous terms or terms having the same functions.

[0146] The block diagrams used to explain the embodiments classify and organize the device configuration by function. The blocks representing each function can be realized by any combination of hardware or software. Furthermore, because they represent functions, the block diagrams can also be understood as disclosures of method inventions and program inventions that realize the methods.

[0147] The order of the functional blocks that can be understood as the processes, flows, and methods described in each embodiment may be changed as long as there are no constraints, such as one step utilizing the results of another step that precedes it.

[0148] The terms first, second, through Nth (N is an integer) used in each embodiment and in the claims are used to distinguish between two or more configurations or methods of the same type, and do not limit the order or superiority or inferiority.

[0149] Examples of the form of each device constituting the handover system of the present disclosure include the following: Examples of component forms include semiconductor elements, electronic circuits, modules, and microcomputers; Examples of semi-finished product forms include electronic control devices (ECUs (Electric Control Units)) and system boards; Examples of finished product forms include mobile phones, smartphones, tablets, personal computers (PCs), workstations, and servers; and Other devices including devices with communication functions, such as video cameras, still cameras, and car navigation systems.

[0150] Furthermore, necessary functions such as an antenna and a communication interface may be added to each device that constitutes the handover system.

[0151] The present disclosure can be realized not only by dedicated hardware having the configuration and functions described in each embodiment, but also by a combination of a program for realizing the present disclosure recorded on a recording medium such as a memory or a hard disk, and general-purpose hardware having a dedicated or general-purpose CPU and memory that can execute the program.

[0152] A program stored in a non-transient physical recording medium (for example, an external storage device (hard disk, USB memory, CD / BD, etc.) or an internal storage device (RAM, ROM, etc.)) of dedicated or general-purpose hardware can be provided to the dedicated or general-purpose hardware via the recording medium, or via a communication line from a server without using a recording medium. This makes it possible to always provide the latest functions through program upgrades.

[0153] The present disclosure is primarily directed to a method for handing over a base station connected to a communication device mounted on an automobile, but may also be directed to a handover method for a communication device mounted on any mobile body other than an automobile.

Claims

1. A handover method for handing over a base station to which a communication device mounted on a mobile body is connected, comprising: acquiring a future planned movement route of the mobile body (S101, S301); extracting area information of candidate base stations that are base stations that can be connected to the communication device along the planned movement route from a communication information storage unit that stores area information indicating communication areas in which the base stations can communicate (S102, S302); predicting a travel time required for the mobile body to move along the planned movement route included in a handover area in which the communication area of ​​one of the candidate base stations, a connection source base station, overlaps with the communication area of ​​another candidate base station among the communication areas indicated by the extracted area information, and in which handover from the connection source base station to the other candidate base station is possible (S103, S303); selecting a destination base station to which the communication device will hand over from the connection source base station from the other candidate base stations based on the travel time (S153); When the mobile unit moves into the handover area, the base station to which the communication device is connected is handed over from the source base station to the destination base station (S155).

2. The handover method according to claim 1, wherein the destination base station is the candidate base station with the longest travel time among the other candidate base stations.

3. A handover method according to claim 1, wherein the communication device, the source base station, and the destination base station are capable of communicating using a first communication line and a second communication line that use the same communication method, and after a handover from the source base station to the destination base station is performed using the first communication line, a handover from the source base station to the destination base station is performed using the second communication line.

4. A handover method as claimed in claim 1, wherein the communication device and the first and second source base stations, which are the source base stations, and the second and second destination base stations, which are the destination base stations, are capable of communicating using a first communication line and a second communication line that use the same communication method, and wherein a handover is performed from the first source base station to the first destination base station using the first communication line, and a handover is performed from the second source base station to the second destination base station using the second communication line.

5. A handover method according to claim 1, wherein the communication device, the source base station, and the destination base stations, namely, a first destination base station and a second destination base station, are capable of communicating with each other using a first communication line and a second communication line that use the same communication method, the first destination base station is the candidate base station with the longest travel time among the other candidate base stations, and the second destination base station is the candidate base station with the second longest travel time among the other candidate base stations, and a handover is performed from the source base station to the first destination base station using the first communication line, and a handover is performed from the source base station to the second destination base station using the second communication line.

6. The handover method according to claim 1, wherein the travel time is predicted based on a distance and a speed limit of the planned travel route included in the handover area.

7. A handover method according to claim 1, wherein the planned travel route is a route from a first point to a second point, the destination base station is set as the next source base station, and a process of selecting the next destination base station to hand over to from the next source base station is repeatedly executed from the source base station whose communication area includes the first point to the destination base station whose communication area includes the second point.

8. The handover method according to claim 7, wherein the destination base station is selected so that the total number of destination base stations selected from the first location to the second location is equal to or less than a threshold, and the travel time between the handover areas of the source base station and the destination base station is equal to or greater than a predetermined time.

9. The handover method according to claim 8, further comprising the step of acquiring handover record information indicating the handover time required for a communication device other than the communication device to perform a handover from the source base station to the destination base station, wherein the handover time is set to the predetermined time.

10. The handover method according to claim 1, further comprising the steps of: acquiring handover record information indicating the handover time required for a communication device other than the communication device to perform a handover from the source base station to the destination base station; if the travel time between the source base station and the destination base station in the handover area is shorter than the handover time, determining a speed at which the mobile body will travel along the planned travel route included in the handover area so that the travel time is equal to or longer than the handover time; and outputting speed information indicating the determined speed.

11. The handover method according to claim 1, further comprising the step of receiving communication status information indicating the communication status of the base station, and if the communication status information indicates that a specific base station is not capable of communication, extracting the area information of the candidate base stations excluding the specific base station.

12. The handover method according to claim 1 further includes the steps of: transmitting handover information to the communication device, the handover information including travel time information indicating the travel time and base station information indicating the candidate base stations (S104); receiving the handover information at the mobile body (S151); and selecting the destination base station at the mobile body.

13. The handover method according to claim 1, further comprising the steps of: transmitting handover instruction information to the communication device instructing the communication device to hand over to the destination base station (S202); and receiving the handover instruction information at the mobile device (S251); and the mobile device performing a handover from the source base station to the destination base station based on the handover instruction information.

14. The handover method of claim 1, wherein the handover method is performed in the mobile station.

15. A handover system for handing over a base station to which a communication device mounted on a mobile body is connected, comprising: a route acquisition unit (101, 351) for acquiring a future planned movement route of the mobile body; an area information extraction unit (105, 355) for extracting area information of candidate base stations that are base stations that can be connected to the communication device along the planned movement route from a communication information storage unit (103, 353) that stores area information indicating communication areas in which the base stations can communicate; a movement time prediction unit (106, 356) for predicting a movement time required for the mobile body to move along the planned movement route included in a handover area in which the communication area of ​​one of the candidate base stations, a connection source base station, overlaps with the communication area of ​​another candidate base station among the communication areas indicated by the extracted area information, and in which handover from the connection source base station to the other candidate base station is possible; and a base station selection unit (153, 201) for selecting a destination base station to which the communication device will hand over from the connection source base station from among the other candidate base stations based on the movement time; a base station switching unit (154) that, when the mobile body moves into the handover area, hands over a base station to which the communication device is connected from the source base station to the destination base station.

16. A handover device (150, 350) for handing over a base station to which a communication device mounted on a mobile body is connected, comprising: a base station information acquisition unit (151, 355) for acquiring base station information indicating candidate base stations that are connectable along a future planned movement route of the mobile body; a travel time information acquisition unit (151, 356) for acquiring travel time information indicating the estimated travel time required for the mobile body to travel along the planned movement route included in a handover area where a communication area in which a connection source base station that is one of the candidate base stations can communicate overlaps with a communication area in which another candidate base station can communicate, and where handover from the connection source base station to the other candidate base station is possible; a base station selection unit (153) for selecting a destination base station to which the communication device will be handed over from the connection source base station from among the other candidate base stations based on the travel time indicated by the travel time information; and a base station switching unit (154) for handing over the base station to which the communication device is connected from the connection source base station to the connection destination base station when the mobile body moves into the handover area. A handover device comprising:

Images