Patent Publication Number: US-2021168664-A1

Title: Communication device, user terminal, communication system, notification method, and program for handover communications

Description:
CROSS-REFERENCE TO RELATED DISCLOSURE 
     This application is a continuation of International Patent Application No. PCT/JP2019/014315 filed Mar. 29, 2019, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure is related to a communication device, user terminal, communication system, and program for handover connections. 
     BACKGROUND 
     An operator at a remote location may operate and move a vehicle using remote driving technology. One element with remote driving may be to suppress communication delay between an operator device operated by an operator performing remote driving and a user terminal provided in a vehicle. 
     SUMMARY 
     As a user terminal moves, handover occurs by switching the wireless base station to which the user terminal is connected. Delay time at the moment of handover differs based on the type of handover. If the user terminal knows the handover type, the user terminal may perform an operation based on the delay time. An object of the present disclosure is to provide technology for allowing a user terminal to perform a process based on the delay time. 
     In an embodiment, a communication device is provided that may: specify a type of handover executed by a user terminal; and notify the user terminal of information related to the specified handover type. 
     In an embodiment, a user terminal may perform a process based on the delay time. 
     In an embodiment, a communication device is provided that comprises a memory storing instructions when executed by a processor causes the to processor to specify a type of handover to be executed by a user terminal, and notify the user terminal of information related to the specified handover type. 
     In an embodiment, a user terminal is provided that comprises a memory storing instructions when executed by a processor causes the processor to receive information related to a handover type from a communication device. 
     In an embodiment, a communication system is provided that comprises a communication device and a user terminal. The communication device comprises a memory storing instructions when executed by a processor causes the processor to specify a handover type to be executed by the user terminal, and notify the user terminal of information related to the specified handover type. The user terminal comprises a memory storing instructions when executed by a processor causes the processor to receive information related to the specified handover type from the communication device. 
     In an embodiment, a computer-implemented handover method executed by a user terminal is provided. The method comprises receiving information related to a handover type from a communication device, and executing a predetermined traveling condition control if the handover type is a predetermined type or if a communication delay for the handover type is greater than a threshold value. The method may also comprise notifying the communication device of a planned travel route of the user terminal, and determining a communication delay required for handover on the planned travel route based on the information related to the handover type received from the communication device. The information related to the handover type may comprise a source wireless base station and a target wireless base station along the planned travel route for the handover. 
     In an embodiment, a computer-implemented handover method executed by a communication device is provided. The method comprises specifying a type of handover executed by a user terminal, and notifying the user terminal of information related to the specified handover type. The method may also comprise receiving a planned travel route of the user terminal, and providing a handover instruction to the user terminal after notifying the user terminal of information related to the specified handover type. The information related to the specified handover type may comprise at least two wireless base stations having overlapping coverage on the planned travel route and an order in which the user terminal passes through the coverage of each. One of the at least two wireless base stations may be specified as a source wireless base station and another of the at least two wireless base stations may be specified as a target wireless base station. 
     Other features and advantages of the present disclosure will be apparent based on the following description with reference to the attached drawings. Note that in the attached drawings, the same or similar configurations are denoted by the same reference numerals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The attached drawings are included in the specification, configure a portion thereof, indicate embodiments of the present disclosure, and are used along with descriptions thereof to describe the principles of the present disclosure. 
         FIG. 1  is a block diagram describing an exemplary configuration of a communication system in accordance with one aspect of the present disclosure. 
         FIG. 2  is a block diagram describing an exemplary configuration of a vehicle in accordance with one aspect of the present disclosure. 
         FIG. 3  is a block diagram describing an exemplary configuration of a wireless base station in accordance with one aspect of the present disclosure. 
         FIG. 4  is a sequence diagram describing an exemplary operation of a communication system in accordance with one aspect of the present disclosure. 
         FIG. 5  is a sequence diagram describing an exemplary operation of a communication system in accordance with one aspect of the present disclosure. 
         FIG. 6  is a sequence diagram describing an exemplary operation of a communication system in accordance with one aspect of the present disclosure. 
         FIG. 7  is a sequence diagram describing an exemplary operation of a communication system in accordance with one aspect of the present disclosure. 
         FIG. 8  is a flowchart describing an exemplary operation of a user terminal in accordance with one aspect of the present disclosure. 
         FIG. 9  is a flowchart describing an exemplary operation of a user terminal in accordance with one aspect of the present disclosure. 
     
    
    
     DESCRIPTION 
     Embodiments are described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the disclosure according to the claims, and not all combinations of the features described in the embodiments are essential to the disclosure. Two or more of a plurality of features described in the embodiments may be arbitrarily combined. 
     A configuration example of a communication system according to some embodiments will be described while referring to  FIG. 1 . A communication system based on an EPC (Evolved Packet Core) used in a 4G network is described below as an example. The EPC may also be used as a core network for a 5G network in NSA (non-standalone) mode. Alternatively, the present disclosure may be applied to other communication standards such as 3G core networks, 5G cores, and the like. When applied to other communication standards, the names of network entities and messages described below are appropriately replaced. 
     The communication system includes a user terminal (UE: User Equipment)  110 , a plurality of wireless base stations  120   a ,  120   b ,  120   c , and  120   d , a plurality of MMEs (Mobility Management Entity)  130   a  and  130   b , a plurality of S-GWs (Serving Gateway)  140   a  and  140   b , and a P-GW (Packet Data Network Gateway)  150 . The MMEs  130   a  and  130   b , S-GWs  140   a  and  140   b , and P-GW  150  are included in a core network. Other network entities included in the core network may, for example, have an existing configuration, and therefore, a description is omitted. The plurality of wireless base stations  120   a  to  120   d  are collectively referred to as a wireless base station  120 . A description of the wireless base station  120  below applies to the plurality of wireless base stations  120   a  to  120   d . Similarly, the plurality of MMEs  130   a  to  130   b  are collectively referred to as an MME  130 , and the plurality of S-GWs  140   a  to  140   b  are collectively referred to as an S-GW  140 . 
     The user terminal  110  is a communication device that receives a communication service from a communication network, and may also be referred to as a terminal device. The user terminal  110  may be various types of communication devices such as vehicles, portable terminals, and monitoring cameras. A case where the user terminal  110  is a vehicle (specifically, a communication device incorporated in the vehicle or brought into the vehicle) is described below. 
     The wireless base station  120  is a communication device for providing a wireless connection with the user terminal  110 . The wireless base station  120  may be referred to as an eNode B in a 4G network and a gNode B in a 5G network. The MME  130  is a network entity that authenticates the user terminal  110  or makes a request for setting a communication path to an opposing party. The S-GW  140  is a network entity that provides a user packet routing function. The P-GW  150  is a network entity that functions as a connection point with an external IP network. 
     In a non-limiting example as shown in  FIG. 1 , the wireless base station  120   a  and wireless base station  120   b  are mutually connected by an X2 interface. The wireless base station  120   c  and wireless base station  120   d  are mutually connected by an X2 interface. The MME  130   a  and wireless base station  120   a  are mutually connected by an S1 interface. The MME  130   a  and wireless base station  120   b  are mutually connected by an S1 interface. The MME  130   b  and wireless base station  120   c  are mutually connected by an S1 interface. The MME  130   b  and wireless base station  120   d  are mutually connected by an S1 interface. The S-GW  140   a  and MME  130   a  are mutually connected by an S11 interface. The S-GW  140   b  and MME  130   b  are mutually connected by an S11 interface. The P-GW  150  and S-GW  140   a  are mutually connected by an S5 interface. The P-GW  150  and S-GW  140   b  are mutually connected by an S5 interface. The MME  130   a  is further connected to an SGSN (Serving GPRS Support Node)  160  serving as a network entity that transfers user traffic in a 3G network via an S3 interface. 
     A configuration example of the user terminal  110  is described while referring to  FIG. 2 . The user terminal  110  includes a processor  111 , a memory  112 , an inputting part  113 , an outputting part  114 , a communicating part  115 , a sensor group  116 , and a travel controlling part  117 . If the user terminal  110  is not in a vehicle, the user terminal  110  includes a processor  111 , a memory  112 , a communicating part  115 , and a component unique to each user terminal (for example, an image sensor for a monitoring camera, or the like). In  FIG. 2 , primarily components used in the description of the embodiment are described, and components unique to the user terminal  110  such as a steering wheel, brake, or the like are omitted. 
     The processor  111  controls operation of the entire user terminal  110 . The processor  111  functions, for example, as a CPU. The memory  112  stores a program used for operation of the user terminal  110 , temporary data, and the like. The memory  112  is achieved, for example, by a ROM, a RAM, or the like. Furthermore, the memory  112  may include a secondary storage such as a hard disk drive. The inputting part  113  is used by a user (for example, a driver or an occupant) of the user terminal  110  to input to the user terminal  110 . The outputting part  114  is used to output information from the user terminal  110  to the user, and is achieved, for example, by a displaying device (display) or acoustic device (speaker). The communicating part  115  provides a function where the user terminal  110  communicates with another device such as the wireless base station  120 , another vehicle, or the like, and is achieved, for example, by an antenna, baseband processor, or the like. 
     The sensor group  116  is one or more sensors for acquiring a condition of the user terminal  110 , a condition of the driver, and peripheral information of the user terminal  110 . The sensor group  116 , for example, includes a camera for photographing outside of the vehicle, a LiDAR (Light Detection and Ranging) or millimeter-wave radar for detecting a target outside of the vehicle or measuring a distance to the target, and a GPS (Global Positioning System) for measuring a geographical position of the user terminal  110 . 
     The travel controlling part  117  automatically controls at least one of steering or acceleration/deceleration of the user terminal  110 . The travel controlling part  117  is configured, for example, from an ECU. The user terminal  110  may be in a remote driving condition, automatic driving condition, or manual driving condition. 
     The remote driving condition is a condition where the user terminal  110  travels based on a command from outside of the user terminal  110 . For example, the travel controlling part  117  transmits information obtained by the sensor group  116  to a device of the operator located away from the user terminal  110  via the wireless base station  120  and core network. The operator generates a command for operating the user terminal  110  based on the information and then transmits the command to the user terminal  110 . The travel controlling part  117  automatically controls at least one of steering or acceleration/deceleration of the user terminal  110  in accordance with the command. 
     The automatic driving condition is a condition where the user terminal  110  travels based on the information from the sensor group  116 . For example, the travel controlling part  117  sets a path for the user terminal  110  based on the information obtained by the sensor group  116 , and automatically controls at least one of steering and acceleration/deceleration of the user terminal  110  such that the user terminal  110  travels along the path. The manual driving condition is a condition where the driver of the user terminal  110  manually drives. During manual driving, driving assistance by the user terminal  110  may be performed. 
     A configuration example of the wireless base station  120  is described while referring to  FIG. 3 . The wireless base station  120  includes a processor  121 , a memory  122 , an inputting part  123 , an outputting part  124 , and a communicating part  125 . 
     The processor  121  controls an operation of the entire wireless base station  120 . The processor  121  functions, for example, as a CPU. The memory  122  stores a program used for operation of the wireless base station  120 , temporary data, and the like. The memory  122  is achieved, for example, by a ROM, a RAM, or the like. Furthermore, the memory  122  may include a secondary storage such as a hard disk drive. The inputting part  123  is used by the user of the wireless base station  120  to input to the wireless base station  120 . The outputting part  124  is used to output information from the wireless base station  120  to the user, and is implemented, for example, by a displaying device (display) or acoustic device (speaker). The communicating part  125  provides a function where the wireless base station  120  communicates with another device such as user terminal  110 , MME  130 , or the like, and is implemented, for example, by an antenna, baseband processor, or the like. 
     Automation of the communication system when handover is performed in contrast to current communications by the user terminal  110  will be described while referring to  FIG. 4  and  FIG. 5 . Each step of the method described in  FIG. 4  and  FIG. 5  is performed, for example, by the processors of the devices (user terminal  110 , wireless base station  120 , and the like) executing a program stored in the memory. Alternatively, some or all steps of the method may be implemented in hardware such as an ASIC (Application-Specific Integrated Circuit). At the start of an operation in  FIG. 4  and  FIG. 5 , the user terminal  110  shall be in a condition communicating with the communication system via the wireless base station  120 . In the following description, unless otherwise specified, a signal function may be the same as that in a conventional handover process, and therefore, a detailed description is omitted. 
       FIG. 4  illustrates a case where the user terminal  110  moves within a coverage of the wireless base station  120   a , and handover is performed from the wireless base station  120   b  to the wireless base station  120   a.    
     In step S 401 , the wireless base station  120   b  transmits, for example, an RRC MEASUREMENT CONTROL message to the user terminal  110  to request the user terminal  110  to start measurement and reporting. In step S 402 , the user terminal  110  measures the quality of radio waves from the wireless base stations around the user terminal  110 , and transmits the measurement results to the wireless base station  120   b  by, for example, an RRC MEASUREMENT REPORT message. 
     In step S 403 , the wireless base station  120   b  determines that handover may be performed from the wireless base station  120   b  to the wireless base station  120   a  based on the received measurement results. In the handover, a source wireless base station is the wireless base station  120   b , and a target wireless base station is the wireless base station  120   a . In this manner, the wireless base station  120   b  specifies its own station (wireless base station  120   b ) to as a source wireless base station, and specifies the wireless base station  120   a  other than its own station as a target wireless base station. In step S 404 , the wireless base station  120   b  specifies a handover type. For example, the wireless base station  120   b  specifies the handover type by specifying a type of interface used to request handover. Specifically, the wireless base station  120   b  specifies that an X2 interface is established between the wireless base station  120   a  and wireless base station  120   b , and specifies that a handover request is transmitted to the wireless base station  120   a  via the X2 interface. The handover may be referred to as a handover between wireless base stations or an X2 handover. 
     In step S 405 , the wireless base station  120   b  notifies the user terminal  110  of information related to the specified handover type. For example, the information related to the handover type may contain information related to the type of interface used to request the handover. Additionally or alternatively, the information related to the handover type may contain information related to whether or not the handover is a soft handover or a hard handover. The information related to the interface type may be the interface type itself or may be information determined based on the interface type. Specifically, the wireless base station  120   b  may notify the user terminal  110  that the handover request is performed via the X2 interface. Alternatively or additionally, the wireless base station  120   b  may provide notification of information related to the interface type, such as an estimated value of time required for the handover process based on the interface type, a delay estimated value associated therewith, and the like. The estimated value of time required for the handover process based on the interface type or delay estimated value associated therewith may be managed in a table for each handover type. The notification is transmitted, for example, as a message in RRC. In step S 406 , the user terminal  110  may perform a predetermined operation based on the received notification. A specific example of the predetermined operation is described later. 
     In step S 407 , the wireless base station  120   b  transmits a handover request to the wireless base station  120   a  via the X2 interface. The request includes, for example, information related to an E-RAB (E-UTRAN Radio Access Bearer) to be set by the wireless base station  120   a . In step S 408 , the wireless base station  120   a  transmits a confirmation response to the wireless base station  120   b  via the X2 interface. 
     In step S 409 , the wireless base station  120   b  transmits a handover instruction to the user terminal  110 . Upon receiving the instruction, the user terminal  110  starts to execute handover. An operation hereinafter may be the same as an existing operation, and therefore, a description is omitted. 
       FIG. 5  illustrates a case where the user terminal  110  moves within a coverage of the wireless base station  120   c , and handover is performed from the wireless base station  120   b  to the wireless base station  120   c.    
     Operations in step S 501  and S 502  are similar to the operations in step S 401  and S 402 . In step S 503 , the wireless base station  120   b  determines that handover is performed from the wireless base station  120   b  to the wireless base station  120   c  based on the received measurement results. In the handover, a source wireless base station is the wireless base station  120   b , and a target wireless base station is the wireless base station  120   c . In this manner, the wireless base station  120   b  specifies its own station (wireless base station  120   b ) as a source wireless base station, and specifies the wireless base station  120   c  other than its own station as a target wireless base station. In step S 504 , the wireless base station  120   b  specifies a handover type. Specifically, the wireless base station  120   b  specifies that an X2 interface is not established between the wireless base station  120   b  and wireless base station  120   c , and determines that a handover request is transmitted to the wireless base station  120   c  via an S1 interface. The handover may be referred to as a handover between MMEs or an S1 handover. 
     In step S 505 , the wireless base station  120   b  notifies the user terminal  110  of information related to the specified handover type. Specifically, the to wireless base station  120   b  notifies the user terminal  110  that the handover will be performed via the S1 interface. The notification is transmitted, for example, as a message in RRC. Similar to step S 405 , notification of other information related to the handover type may be provided. In step S 506 , the user terminal  110  may perform a predetermined operation based on the notification received. A specific example of the predetermined operation is described later. 
     In step S 507 , the wireless base station  120   b  transmits to the MME  130   a  to which the wireless base station  120   b  is connected a handover request to the wireless base station  120   c . In step S 508 , the MME  130   a  transmits an MME relocation request to the MME  130   b  serving as a change destination. 
     In step S 509 , the MME  130   b  transmits a bearer setting request to the S-GW  140   b  serving as a change destination. In response thereto, in step S 510 , the S-GW  140   b  transmits an S-GW address of a bearer of which to notify the wireless base station  120   c  to the MME  130   b.    
     In step S 511 , the MME  130   b  transmits a parameter of an E-RAB to be set to the wireless base station  120   c . In step S 512 , the wireless base station  120   c  transmits the set E-RAB information to the MME  130   b.    
     In step S 513 , the MME  130   b  notifies the MME  130   a  that relocation is completed. In step S 514 , the MME  130   a  notifies the wireless base station  120   b  that handover preparation is complete. In step S 515 , the wireless base station  120   b  transmits a handover instruction to the user terminal  110 . Upon receiving the instruction, the user terminal  110  starts to execute handover. An operation hereinafter may be the same as an existing operation, and therefore, a description is omitted. 
     An operation of the communication system when handover is performed with regard to travel destination communications by the user terminal  110  will be described while referring to  FIG. 6 . The operation is executed in cooperation by the user terminal  110  and a communication device  600 . The communication device  600  may be a wireless base station  120   b  in a condition communicating with the user terminal  110 , a wireless base station (wireless base station  120   a  or the like) in a condition not communicating with the user terminal  110 , a communication device with a core network (for example, MME  130   a ,  130   b ), or another communication device connected to a core network by the Internet or the like. If the communication device  600  is a communication device other than the wireless base station  120   b  in a condition communicating with the user terminal  110 , communication between the user terminal  110  and communication device  600  may be performed via a path that passes through the wireless base station  120   b  or another path. A configuration example of the communication device  600  may be similar to the configuration example of the wireless base station  120  described in  FIG. 3 , and therefore, a description is omitted. Each step of the method described in  FIG. 6  is performed, for example, by the processors of the devices (user terminal  110  and communication device  600 ) executing a program stored in the memory. Alternatively, some or all steps of the method may be implemented in hardware such as an ASIC (Application-Specific Integrated Circuit). 
     In step S 601 , the user terminal  110  determines a planned travel route of the user terminal  110 . For example, if the user terminal  110  is a vehicle, the user terminal  110  determines a route to a destination instructed from the driver. The determined route is referred to as planned route. In step S 602 , the user terminal  110  transmits the planned route to the communication device  600 . The planned route is an example of information that may specify the source wireless base station and target wireless base station of the handover with regard to travel destination communication by the user terminal  110 . 
     In step S 603 , the communication device  600  specifies wireless base stations having overlapping coverage on the planned route and an order in which the user terminal  110  passes through each coverage. Information related to the coverage of the wireless base stations provided by the communication to system may be stored in the communication device  600  in advance or an inquiry may be made to the wireless base stations. Furthermore, the communication device  600  specifies two consecutive wireless base stations as a source wireless base station and target wireless base station. For example, the user terminal  110  currently within a covered region of the wireless base station  120   b  is scheduled to travel on a route that passes through a covered region of the wireless base station  120   c  and then passes through a covered region of the wireless base station  120   d . In this manner, the communication device  600  specifies the wireless base station  120   c  other than the wireless base station  120   b  as a source wireless base station, and specifies the wireless base station  120   d  other than its own station as a target wireless base station. 
     In step S 604 , the communication device  600  specifies the type of handover used to request handover from a source wireless base station (for example, wireless base station  120   c ) to a target wireless base station (for example, wireless base station  120   d ). In this example, the communication device  600  specifies that an X2 interface is established between the wireless base station  120   c  and wireless base station  120   d  and that X2 handover is performed. The specification may be performed by the communication device  600  making an inquiry to the wireless base station  120   c  and/or wireless base station  120   d.    
     In step S 605 , the communication device  600  notifies the user terminal  110  of information related to the handover type from the source wireless base station (for example, wireless base station  120   c ) to the target wireless base station (for example, wireless base station  120   d ). Along with the notification, the communication device  600  may notify the user terminal  110  of information related to at least one covered region of the source wireless base station (for example, wireless base station  120   c ) and target wireless base station (for example, wireless base station  120   d ). Information related to the covered region includes a geographical position of a wireless base station, a communicable to distance, communication direction, and the like. Based on the information related to the handover type, the user terminal  110  may predict how much delay will occur due to the handover executed on the planned route. Furthermore, based on the information related to the handover type and information related to the covered region, the user terminal  110  may predict how much delay will occur due to the handover executed at what position on the planned route. 
     In steps S 604  and S 605 , when a plurality of sets of source wireless base stations and target wireless base stations are present on the planned route, the communication device  600  may notify the user terminal  110  of the handover type (and, if necessary, information related to the covered region) for the sets. 
     In step S 606 , the user terminal  110  may perform a predetermined operation based on the notification received. A specific example of the predetermined operation is described later. 
     A modification of the operation of the communication system in  FIG. 4  will be described while referring to  FIG. 7 . In the example in  FIG. 4 , the wireless base station  120   b  in a condition communicating with the user terminal  110  executes step S 404  and step S 405 . However, in  FIG. 7 , the communication device  700  other than the wireless base station  120   b  executes step S 404  and step S 405 . The communication device  700  may be a wireless base station (wireless base station  120   a  or the like) in a condition not communicating with the user terminal  110 , a communication device with a core network (for example, MME  130   a ,  130   b ), or another communication device connected to a core network by the Internet or the like. Communication between the user terminal  110  and communication device  700  may be performed on a route passing through the wireless base station  120   b  or another route. A configuration example of the communication device  700  may be similar to the configuration example of the wireless base station  120  described in  FIG. 3 , and therefore, a description is omitted. Each step of the method described in  FIG. 7  is performed, for example, by the processors of the devices (user terminal  110  and communication device  700 ) executing a program stored in the memory. Alternatively, some or all steps of the method may be implemented in hardware such as an ASIC (Application-Specific Integrated Circuit). 
     The operations of steps S 401  to S 403  are the same as  FIG. 4 . In step S 701 , the wireless base station  120   b  transmits information specifying a source wireless base station (for example, wireless base station  120   b ) and target base station (for example, wireless base station  120   a ) of the specified handover to the communication device  700 . In step S 404 , the communication device  700  specifies the handover type based on the information. In step S 405 , the communication device  700  notifies the user terminal  110  of the information related to the handover type. The operations of steps S 406  to S 409  are the same as  FIG. 4 . 
     An operation of the communication system in  FIG. 5  may be modified as shown in  FIG. 7 . In other words, instead of the wireless base station  120   b  executing step S 504  and step S 505 , the communication device  700  may execute these steps. In this case, the wireless base station  120   b  transmits information specifying a source wireless base station (for example, wireless base station  120   b ) and target base station (for example, wireless base station  120   c ) of the specified handover to the communication device  700  during step S 503  and step S 504 . 
     A specific example of a process executed in the aforementioned steps S 406 , S 506 , and S 606  will be described while referring to  FIG. 8 . In step S 801 , the user terminal  110  determines a communication delay occurring in the user terminal  110  based on the notified information. For example, the user terminal  110  may determine a delay time by storing a delay time corresponding to the handover type in the memory  112  in advance and then reading the delay time based on the notified handover type from the memory  112 . Alternatively, the user terminal  110  may receive a value of time required for handover as information related to the handover type from a communication device (for example, wireless base station) and then determine a delay time based on the time. 
     In step S 802 , the user terminal  110  determines whether or not the determined delay time is greater than a threshold value. If the condition is satisfied (“YES” in step S 802 ), the user terminal  110  transitions the process to step S 803 , and if the condition is not satisfied (“NO” in step S 802 ), the user terminal  110  transitions the process to step S 804 . 
     In step S 803 , the user terminal  110  executes a predetermined control to be performed when the delay time is greater than the threshold value. For example, when notification is provided that the handover is performed through an S1 interface, serving as a different interface from an X2 interface, the delay time when executing S1 handover is relatively long. Therefore, the user terminal  110  during travel (travel controlling part  117 ) may, for example, reduce the traveling speed or turn on a hazard light. Additionally or alternatively, the user terminal  110  during travel (travel controlling part  117 ) in remote driving or automatic driving may execute safe driving control (predetermined traveling condition control) such as canceling (limiting) remote driving or automatic driving, and the like. The threshold value in step S 802  may be a value based on a predetermined control executed in step S 803 . 
     In step S 804 , the user terminal  110  maintains a current traveling condition control. The predetermined traveling condition control executed in step S 803  may be at least one of (1) a traveling condition control of reducing a traveling speed of the vehicle, (2) a traveling condition control of reducing an operating authority of a remote driving operator, (3) a traveling condition control of reducing an automatic control function or item, and (4) a traveling condition control of increasing information content with regard to a traffic participant outside of the vehicle, rather than the traveling condition control maintained (executed) in step S 804 . 
     Another specific example of a process executed in the aforementioned steps S 406 , S 506 , and S 606  will be described while referring to  FIG. 9 . In the example in  FIG. 8 , the user terminal  110  determines a communication delay occurring in the user terminal  110  based on the notified information. However, it is possible to grasp that a long communication may occur without determining a specific value of the communication delay, based on the type of notified handover. Therefore, in step S 901 , the user terminal  110  determines whether or not the information related to the notified handover type is information related to a predetermined handover type. The predetermined handover type is, for example, a type of handover where a communication delay occurring in the user terminal  110  is greater than the threshold value (for example, handover using the S1 interface). 
     If the condition in step S 901  is satisfied (“YES” in step S 901 ), the user terminal  110  transitions the process to step S 902 , and if the condition is not satisfied (“NO” in step S 901 ), the user terminal  110  transitions the process to step S 903 . Steps S 902  and S 903  are the same as steps S 803  and S 804 . 
     In the aforementioned embodiment, the X2 interface and S1 interface are exemplified as the handover type notified to the user terminal  110 . However, the notified handover type is not limited to this. For example, when handover is performed to another communication system including an SGSN  160 , a handover request is transmitted via an S3 message between the MME  130   a  and SGSN  160  (so-called S3 handover). In this case, the wireless base station  120   b , communication device  600 , or communication device  700  notifies the user terminal  110  that an S3 interface is used. 
     In the aforementioned embodiment, the handover wireless base station  120   b  (so-called source wireless base station) notifies the user terminal  110  of the type of handover used to request handover to the target wireless base station. Therefore, the user terminal  110  may predict a delay time for handover, to and thus the user terminal may perform a process based on the delay time. Furthermore, notification (S 405 , S 505 ) of the handover type is performed prior to the handover instruction (S 409 , S 515 ). Therefore, the user terminal  110  may predict a delay time for handover at an early stage. 
     In an embodiment, a communication device ( 120   b ,  600 ,  700 ) is provided, including: a memory storing instructions when executed by a processor causes the processor to: specify a type of handover executed by a user terminal ( 110 ); and notify the user terminal of information related to the specified handover type. 
     According to this embodiment, the user terminal may predict a delay time required for handover, and thus the user terminal may perform a process based on the delay time. 
     Optionally, where: the communication device is a wireless base station ( 120   b ); and specifying the type of handover comprises using the communication device as a source wireless base station. 
     According to this embodiment, the user terminal may predict a delay time required for handover of a current communication. 
     Optionally, wherein the memory storing instructions when executed by the processor causes the processor to transmit a handover instruction to the user terminal, and wherein notifying the user terminal comprises providing the information related to the type of the handover prior to transmitting the handover instruction to the user terminal (S 409 , S 515 ). 
     According to this embodiment, the user terminal may predict a delay time required for handover at an early stage. 
     Optionally, where: the communication device is a source wireless base station ( 120   b ); and specifying the type of handover comprises using a second wireless base station ( 120   c ) other than the communication device as a target wireless base station of the handover. 
     According to this embodiment, the user terminal may predict a delay time required for handover of travel destination communication. 
     Optionally, wherein notifying the user terminal comprises information related to coverage of at least one of the source wireless base station and the target wireless base station of the handover (S 605 ). 
     According to this embodiment, the user terminal may know the position where handover is performed at the travel destination. 
     Optionally, where specifying the type of the handover is based on a type of an interface used to request handover. 
     According to this embodiment, a type of handover may be specified based on a type of interface. 
     Optionally, where the interface type includes at least one of an interface between a source wireless base station and a target wireless base station of the handover and an interface between the source wireless base station and a core network ( 130   a ). 
     According to this embodiment, the user terminal may know about handover between wireless base stations and handover including a core network. 
     In an embodiment, a program is provided for causing a computer to function as the communication device according to any one of configurations. 
     According to this embodiment, the aforementioned configuration may be provided in a program form. 
     In an embodiment, a user terminal ( 11 ) is provided. The user terminal includes a memory storing instructions when executed by a processor causes the processor to receive ( 111 , S 405 , S 505 , S 605 ) information related to a handover type from a communication device ( 120   b ,  600 ,  700 ). 
     According to this embodiment, the user terminal may predict a delay time required for handover, and thus the user terminal may perform a process based on the delay time. 
     Optionally, the memory storing instructions when executed by the processor causes the processor to notify ( 111 , S 601 ) the communication device of information for specifying a source wireless base station and a target wireless base station of the handover. 
     According to this configuration, a delay time required for handover of travel destination communication may be predicted. 
     Optionally, where the information includes a planned travel route of the user terminal. 
     According to this embodiment, a delay time required for handover occurring on a planned travel route may be predicted. 
     Optionally, the memory storing instructions when executed by the processor causes the processor to execute a control instruction ( 111 , S 801  to S 803 ) based on the information related to the handover type. 
     According to this embodiment, the user terminal may predict a delay time to required for handover, and thus the user terminal may perform a process based on the delay time. 
     Optionally, the user terminal is a vehicle ( 110 ); and the control instruction determines, based on the information related to the handover type, whether or not a communication delay occurring in the user terminal is greater than a threshold value ( 111 , S 802 ), and executes a predetermined traveling condition control if the communication delay is greater than the threshold value ( 111 , S 803 ). 
     According to this embodiment, a vehicle serving as the user terminal may execute control based on a delay time required for handover. 
     Optionally, where: the user terminal is a vehicle ( 110 ); and the control instruction determines if the information related to the type of the handover corresponds to a type of predetermined handover ( 111 , S 901 ), and executes a predetermined traveling condition control if the information related to the handover type corresponds to the predetermined handover type ( 111 , S 902 ). 
     According to this embodiment, a vehicle serving as the user terminal may execute control based on the handover type. 
     Optionally, where the predetermined handover type is a type of handover where a communication delay occurring in the user terminal is greater than a threshold value. 
     According to this embodiment, a vehicle serving as the user terminal may execute control based on the type of handover with a large communication delay during handover. 
     Optionally, where the predetermined traveling condition control is a to traveling condition control where a traveling speed of the vehicle is reduced as compared to a traveling condition control (S 804 , S 903 ) executed when the communication delay is deemed to be greater than the threshold value or when the information related to the handover type is deemed to not be information related to the predetermined handover type. 
     According to this embodiment, a vehicle serving as the user terminal may decelerate based on the communication delay or handover type. 
     In an embodiment, a program is provided for causing a computer of the user terminal to perform the methods or functions according to any one of the embodiments alone or in combination. 
     According to this embodiment, the aforementioned configuration may be provided in a program form. 
     In an embodiment, a communication system is provided comprising: a communication device ( 120   b ,  600 ,  700 ), and a user terminal ( 110 ). The communication device includes a memory storing instructions when executed by a processor causes the processor to: specify a type of handover to be executed by the user terminal; and notify the user terminal of information related to the specified handover type. The user terminal includes a memory storing instructions when executed by a processor causes the processor to receive information related to the specified handover type from the communication device. 
     According to this embodiment, the user terminal may predict a delay time required for handover, and thus the user terminal may perform a process based on the delay time. 
     The present disclosure is not limited to the aforementioned embodiments, and various changes and modifications may be made without to departing from the spirit and scope of the present disclosure. Therefore, the following claims are attached to publish the scope of the present disclosure.