Base station device, terminal device, communication system, and communication control method

In order to prospectively avoid communication failures or reduction in throughput of each user terminal, thereby improving users' satisfaction with communication service, a base station is configured to control wireless communication with a terminal device by using any of multiple transmission beams formed by the base station or those formed by another base station and includes a wireless communication device and a controller configured to acquire correction information used for correcting a measurement value for evaluating reception status of each transmission beam and cause the wireless communication device to transmit the correction information to the user terminal so as to thereby promote the user terminal to use, or inhibit the user terminal from using a specific transmission beam.

TECHNICAL FIELD

The present invention relates to a base station device, a terminal device, a communication system and a communication control method for controlling wireless communication performed by the terminal device by using any of multiple transmission beams formed by the base station device.

BACKGROUND ART

Presently, 5G systems (Fifth generation mobile communication systems) are being considered for introduction into general use in wireless communications. In 5G systems, wireless communication systems enable communications at high transmission capacities of more than 1 Gbps by utilizing high SHF bands or EHF bands. However, since such wireless communications utilizing high frequency bands generally provide short transmission ranges, utilization of a transmission beam forming technique is considered in order to extend the transmission range of such a system.

When a transmission beam forming technique is utilized, a user terminal needs to select a proper transmission beam as necessary when performing communication. Known technologies related to such selection of a transmission beam include selecting a proper transmission beam based on received powers of respective transmission beams at a user terminal (See Patent Document 1). In this case, the wider a formed transmission beam is, the lower a received transmission beam power at a user terminal is. Thus, this prior art technology uses an offset value added to a measurement value of received power of each transmission beam at a user terminal in order to achieve more proper evaluation of the received power at the user terminal for selection of a transmission beam by eliminating effects of a variation of widths of transmission beams on measurement values of received power of transmission beams at the user terminal.

PRIOR ART DOCUMENT (S)

SUMMARY OF THE INVENTION

Task to be Accomplished by the Invention

Communication schemes utilizing high frequency bands, which are adopted in 5G systems, can provide communications at high transmission capacities. However, since higher-frequency electromagnetic waves tend to travel in straight lines, such communication schemes involve a problem that, when an obstacle is located on a communication path line, a decrease in communication quality occurs, which can cause communication failures such as communication link disconnection. Moreover, when a lot of user terminals concurrently use one transmission beam, the throughput of each user terminal is reduced. Such communication failures and reduction in throughput of each user terminal can reduce current users' satisfaction with communication service. Accordingly, there is a need for a technology which makes it possible to prospectively avoid reduction in throughput of a user terminal caused due to communication failures by obstruction and communication link congestion.

However, a configuration which only selects a transmission beam based on the received powers of respective transmission beams as the above-described prior art technology, is not capable of prospectively avoiding occurrence of communication failures by obstruction and/or reduction in throughput of each user terminal due to communication link congestion.

The present invention has been made in view of the problem of the prior art, and a primary object of the present invention is to provide a base station device, a terminal device, a communication system and a communication control method, which makes it possible to prospectively avoid occurrence of communication failures by obstruction and/or reduction in throughput of each terminal device due to communication link congestion, thereby improving users' satisfaction with communication service.

Means to Accomplish the Task

An aspect of the present invention provides a base station device configured to control wireless communication performed by a terminal device using any of multiple transmission beams formed by the base station device or another base station device, the base station device comprising: a wireless communication device configured to wirelessly communicate with the terminal device; and a controller configured to acquire correction information used for correcting a measurement value for evaluating reception status of each transmission beam and cause the wireless communication device to transmit the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam.

Another aspect of the present invention provides a terminal device configured to perform wireless communication with a base station device by using any of multiple transmission beams formed by the base station device, the terminal device comprising: a wireless communication device configured to wirelessly communicate with the base station device; and a controller configured such that, when the wireless communication device receives correction information transmitted from the base station device, the controller corrects a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the controller performs wireless communication with the base station device using the selected transmission beam.

Yet another aspect of the present invention provides a communication system in which a terminal derive performs wireless communication with a base station by using any of multiple transmission beams formed by the base station, wherein the base station comprises: a wireless communication device configured to wirelessly communicate with the terminal device; and a controller configured to acquire correction information used for correcting a measurement value for evaluating reception status of each transmission beam and cause the wireless communication device to transmit the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam, and wherein the terminal device comprises: a terminal wireless communication device configured to wirelessly communicate with the base station device; and a terminal controller configured such that, when the terminal wireless communication device receives the correction information transmitted from the base station device, the terminal controller corrects a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the terminal controller performs wireless communication with the base station device using the selected transmission beam.

Yet another aspect of the present invention provides a communication control method for controlling wireless communication performed by a terminal device by using any of multiple transmission beams formed by a base station, comprising: the base station acquiring correction information used for correcting a measurement value for evaluating reception status of each transmission beam and transmitting the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam; and upon receiving the correction information transmitted from the base station device, the terminal device correcting a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the terminal device performing wireless communication with the base station device using the selected transmission beam.

Effect of the Invention

A configuration according to the present invention can promote a terminal device to use a specific transmission beam, or inhibit the terminal device from using the specific transmission beam. As such, the configuration makes it possible to prospectively avoid communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A first aspect of the present invention made to achieve the above-described object is a base station device configured to control wireless communication performed by a terminal device using any of multiple transmission beams formed by the base station device or another base station device, the base station device comprising: a wireless communication device configured to wirelessly communicate with the terminal device; and a controller configured to acquire correction information used for correcting a measurement value for evaluating reception status of each transmission beam and cause the wireless communication device to transmit the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam.

This configuration can promote a terminal device to use a specific transmission beam, or inhibit the terminal device from using the specific transmission beam. As such, this configuration makes it possible to prospectively avoid communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service.

A second aspect of the present invention is the base station device of the first aspect, wherein the controller acquires the correction information including an offset value used for increasing or decreasing a measurement value of received power at the terminal device as the measurement value for evaluating reception status of each transmission beam.

In this configuration, by subtracting an offset value from a measurement value of received power of a transmission beam at a terminal device, the base station device can correct the measurement value of received power at the terminal device to be lower than the actual measurement value, thereby decreasing an evaluation of the transmission beam so as to inhibit the terminal device from using the transmission beam. Also, by adding an offset value to a measurement value of received power of a transmission beam at a terminal device, the base station device can correct the measurement value of received power at the terminal device to be higher than the actual measurement value, thereby increasing an evaluation of the transmission beam so as to promote the terminal device to use the transmission beam.

A third aspect of the present invention is the base station device of the first aspect, wherein the controller broadcasts the correction information to all terminal devices present in its coverage area, including one or more terminal devices which are currently not connected to the base station device.

In this configuration, the base station device can promote non-connected terminal devices present within its cell to use a transmission beam, or inhibit the non-connected terminal devices from using the transmission beam. As such, this configuration can restrict terminal devices newly connectable to a specific transmission beam or can lead a terminal device to newly connect to the specific transmission beam.

A fourth aspect of the present invention is the base station device of the first aspect, wherein the controller selects the terminal device among multiple terminal devices currently performing communication by using the specific transmission beam, wherein the selection is made by according to a predetermined condition, and transmits the correction information to the selected terminal device.

This configuration can promote a specific terminal device to use a specific transmission beam, or inhibit the specific terminal device from using the specific transmission beam. As such, this configuration can lead a terminal device currently using a specific transmission beam to change the transmission beam used for communication to another transmission beam, thereby achieving load dispersion and promotion of communication efficiency for a specific transmission beam.

A fifth aspect of the present invention is the base station device of the first aspect, wherein the multiple transmission beams are placed in a predetermined order and grouped into groups each including an equal number of transmission beams, and wherein the controller acquire the correction information which include the number of transmission beams in a group and a corresponding offset value for one or more measurement values of the transmission beams of each group.

This configuration can reduce an amount of data of correction information.

A sixth aspect of the present invention is the base station device of the first aspect, wherein the multiple transmission beams are placed in a predetermined order and grouped into groups each having a corresponding offset value for one or more measurement values of the transmission beams of the group, and wherein the controller acquire the correction information which include an ID of a first transmission beam and a number of the transmission beams for each group, and a corresponding offset value for one or more measurement values of the transmission beams of the group.

This configuration can reduce an amount of data of correction information while maintaining a degree of freedom in determination of offset values.

A seventh aspect of the present invention is the base station device of the first aspect, wherein the controller determines current congestion status of each transmission beam, and acquires the correction information user for correcting each measurement value so as to inhibit the terminal device from using any transmission beam determined to be in congestion status.

This configuration can inhibit a terminal device from using any transmission beam in congestion status to thereby prospectively avoid reduction in throughput of the terminal device. With regard to non-connected terminal devices, this configuration can perform control such that a non-connected terminal device starts communication using another transmission beam which is not in congestion status. When a currently-connected device uses a transmission base in congestion status, this configuration can perform control such that the terminal device changes the transmission beam to another transmission beam which is not in congestion status.

An eighth aspect of the present invention is the base station device of the first aspect, further comprising a storage for storing correction information used for correcting each measurement value so as to inhibit the terminal device from using any transmission beam which is constantly in a bad communication environment, wherein the controller is configured to acquire the correction information stored in the storage.

This configuration inhibits terminal devices from using any transmission beam which is constantly in a bad communication environment, and thus can prospectively avoid communication failures and/or reduction in throughput of each terminal device.

A ninth aspect of the present invention is the base station device of the first aspect, wherein the controller configured to acquire correction information used for correcting each measurement value so as to inhibit the terminal device from using any transmission beam for which a communication environment deteriorates during a current time of day.

This configuration inhibits terminal devices from using any transmission beam for which a communication environment deteriorates during a current time of day and thus can prospectively avoid communication failures and/or reduction in throughput of each terminal device.

A tenth aspect of the present invention is the base station device of the first aspect, wherein the controller is configured to acquire correction information used for correcting each measurement value so as to inhibit the terminal device from using any transmission beam for a traffic lane in which an indication of a traffic signal permits traffic to travel based on traffic signal control information.

This configuration inhibits a terminal device provided in a vehicle traveling under a green light from using any transmission beam for another traffic lane in which traffic is permitted to travel under a green light, and thus can prospectively avoid communication failures.

An eleventh aspect of the present invention is the base station device of the first aspect, wherein the controller is configured to acquire correction information used for correcting each measurement value so as to inhibit the terminal device from using any transmission beam which is directed towards sky by reflection.

This configuration inhibits a terminal device provided in a flying object from using any transmission beam directed towards sky by reflection, and thus can prospectively avoid communication failures.

A twelfth aspect of the present invention is the base station device of the first aspect, wherein the controller is configured to acquire correction information used for correcting each measurement value such that, when the base station device is located on a rear side of a moving direction of a currently-connected terminal device, the controller promotes the terminal device to use a transmission beam formed by an adjacent base station device located on a front side of the moving direction of the currently-connected terminal device, or inhibits the terminal device from using any transmission beam formed by the base station device.

This configuration enables a currently-communicating terminal device to change the transmission beam to be used to a transmission beam of an adjacent base station device before communication failures occur.

A twelfth aspect of the present invention is the base station device of the twelfth aspect, further comprising a storage for storing information on past transmission beams used before as historical used-beam information, wherein the controller is configured to acquire correction information used for correcting each measurement value such that, when the controller determines, based on the historical used-beam information, that the currently-connected terminal device uses a transmission beam formed closest to a coverage of the adjacent base station device, the controller promotes the terminal device to use a transmission beam formed by the adjacent base station device, or inhibits the terminal device from using any transmission beam formed by the base station device.

This configuration enables a currently-communicating terminal device to change the transmission beam to be used to a transmission beam of an adjacent base station device before communication failures occur without a need to acquire information on a moving direction of the terminal device.

A fourteenth aspect of the present invention is a terminal device configured to perform wireless communication with a base station device by using any of multiple transmission beams formed by the base station device, the terminal device comprising: a wireless communication device configured to wirelessly communicate with the base station device; and a controller configured such that, when the wireless communication device receives correction information transmitted from the base station device, the controller corrects a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the controller performs wireless communication with the base station device using the selected transmission beam.

This configuration makes it possible to prospectively avoid communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service in the same manner as the first aspect of the present invention.

A fifteenth aspect of the present invention is the terminal device of the fourteenth aspect, further comprising a storage for storing the correction information received from the base station device, wherein the controller is configured such that, when losing the transmission beam currently used for communication, the controller corrects the measurement value based on the correction information stored in the storage.

In this configuration, even when a terminal device loses the transmission beam currently used for communication and thus becomes unable to acquire correction information from the bases station device, the terminal device can correct a measurement value by using correction information stored in the storage. When new correction information is provided from the base station device, the terminal device can update the correction information in the storage.

A sixteenth aspect of the present invention is the terminal device of the fifteenth aspect, wherein the controller deletes the correction information stored in the storage after a lapse of a predetermined data retention period.

This configuration can prevent a wasteful use of a storage capacity of the storage by unnecessary correction information. Preferably, a data retention period is provided to a terminal device form the base station.

A seventeenth aspect of the present invention is a communication system in which a terminal derive performs wireless communication with a base station by using any of multiple transmission beams formed by the base station, wherein the base station comprises: a wireless communication device configured to wirelessly communicate with the terminal device; and a controller configured to acquire correction information used for correcting a measurement value for evaluating reception status of each transmission beam and cause the wireless communication device to transmit the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam, and wherein the terminal device comprises: a terminal wireless communication device configured to wirelessly communicate with the base station device; and a terminal controller configured such that, when the terminal wireless communication device receives the correction information transmitted from the base station device, the terminal controller corrects a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the terminal controller performs wireless communication with the base station device using the selected transmission beam.

This configuration makes it possible to prospectively avoid communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service in the same manner as the first aspect of the present invention.

An eighteenth aspect of the present invention is a communication control method for controlling wireless communication performed by a terminal device by using any of multiple transmission beams formed by a base station, comprising: the base station acquiring correction information used for correcting a measurement value for evaluating reception status of each transmission beam and transmitting the correction information to the terminal device so as to thereby promote the terminal device to use, or inhibit the terminal device from using a specific transmission beam; and upon receiving the correction information transmitted from the base station device, the terminal device correcting a measurement value for evaluating reception status of each transmission beam, and after selection of a transmission beam based on the corrected measurement value, the terminal device performing wireless communication with the base station device using the selected transmission beam.

This configuration makes it possible to prospectively avoid communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service in the same manner as the first aspect of the present invention.

First Embodiment

FIG. 1is a diagram showing a general configuration of a communication system according to a first embodiment of the present invention.

The communication system includes user terminals1(communication devices), cellular communication base stations2, a wireless LAN base station3(access point, base station device), and a communication control device4.

A user terminal1may be a smartphone, a tablet terminal, and any other suitable terminal device. A user terminal1is capable of being connected to a cellular communication base station2. A user terminal1can connect to the wireless LAN base station3, and communicate with a counterpart station (such as a server) on the Internet via the wireless LAN base station3.

A cellular communication base station2performs wireless communication using a high SHF band or EHF band (millimeter wave band), which can comply with 5G NR (New Radio). Transmission beam forming is done at a cellular communication base station2such that multiple transmission beams are formed, and the cellular communication base station2transmits a user terminal1via any one of the multiple transmission beams.

The wireless LAN base station3performs wireless communication using a communication scheme which utilizes a high SHF band or higher frequency bands such as WiGig (Registered Trademark). Transmission beam forming is done at the wireless LAN base station3such that multiple transmission beams are formed, and the wireless LAN base station3transmits a user terminal1via any one of the multiple transmission beams in the same manner as the cellular communication base station2.

When a cellular communication base station2or the wireless LAN base station3transmits a measurement request signal and performs transmission beam forming, the transmission directions of respective transmission beams are fixed.

A user terminal1measures a measurement value for evaluating reception status, i.e. a received power of each transmission beam formed by a cellular communication base station2or the wireless LAN base station3, and after selection of a transmission beam base on the measured received powers of the respective transmission beams, the user terminal1performs wireless communication with the cellular communication base station2or the wireless LAN base station3.

The communication control device4may be configured to control communication using a cellular communication base station2such as a device for providing SMF (Session Management Function) or UPF (User Plane Function).

Next, an outline of processing operations performed by a user terminal1and a cellular communication base station2according to the first embodiment of the present invention.FIG. 2is an explanatory view showing a situation where there are user terminals1and transmission beams of a base station2.

When an obstacle is located on a communication path between a user terminal and a base station2, a decrease in communication quality occurs, thereby causing communication failures such as communication link disconnection. For example, when a transmission beam of a base station2is formed so as to cross a vehicular road with a large traffic volume of vehicles, communication failures are likely to occur. Also, when a transmission beam of the base station2is formed in a direction where there are many obstacles such as signboards and street trees, communication failures are likely to occur. Since the likelihood of occurrence of such a communication failure by such obstruction depends on the situation of obstacles, the likelihood does not greatly vary with time.

In this view, in the present invention, an offset value (initial offset value), which is a constant value, is determined such that a user terminal1is inhibited from using any transmission beam which is constantly in a bad communication environment, and the user terminal1corrects a measurement value of received power of the transmission beam based on the offset value.

As such, since a decrease in evaluation of a transmission beam which is constantly in a bad communication environment at a user terminal1results in that the user terminal1is inhibited from using the transmission beam, it becomes possible to n prospectively avoid communication failures.

Moreover, when a lot of user terminals concurrently use one transmission beam; that is, the transmission beam is in congestion status, the throughput of each user terminal is reduced. The likelihood of occurrence of reduction in throughput at each user terminal varies depending on a degree of congestion of the transmission beam.

In this view, in the present embodiment, a base station is configured to determine current congestion status of each transmission beam, and set an offset value so as to inhibit user terminals1from using any transmission beam in congestion status, and correct a measurement value of received power of the transmission beam based on the offset value. More specifically, in the present embodiment, an offset value different from an initial offset value is prepared for congestion status, and when a transmission beam is determined to be in congestion status, an offset value to be used is updated to the offset value for congestion status.

As a result, a user terminal is inhibited from using any transmission beam for which reduction in throughput due to traffic congestion is likely to occur. Thus, when a user terminal1newly connects to a base station2, the user terminal1can select a transmission beam so as not to use any transmission beam in congestion status, and when a user terminal1is currently connecting to the base station2, the user terminal1is controlled so as not to connect to any transmission beam in congestion status when changing its transmission beam to be used. Accordingly, it becomes possible to prospectively avoid reduction in the throughput at the user terminal.

For any transmission beam in congestion status, an offset value may be updated to a constant offset value for transmission beams in congestion status (congestion offset value). However, a congestion offset value for such a congested transmission beam may be changed according to a degree of congestion.

In the present embodiment, when a measurement value of received power of a transmission beam at a user terminal1is equal to or less than a predetermined reference power (a reference of received power detected in a transmission beam, for example, −120 dBm), the transmission beam is not regarded as an available transmission beam. Thus, when a measurement value of received power is corrected to be close to the predetermined reference power, a transmission beam for the measurement value is less likely to be selected. In some embodiment, when a user terminal1newly connects to a base station2, a measurement value for a transmission beam, which is not to be selected, may be corrected to less than the predetermined reference power so that the transmission beam cannot be selected. When a user terminal1is currently connecting to the base station2, a measurement value for a currently-connected transmission beam is preferably corrected so as not to be equal to or lower than the predetermined reference power because such a correction to a measurement value can result in disconnection of the user terminal from the currently-connected transmission beam. Thus, the preferable control of correction made to a measurement value enables such a currently-connected user terminal1to start to use a new transmission beam when necessary without disconnecting from the currently-connected transmission beam until the change of transmission beam to be used.

Next, a general configuration of a cellular communication base station2according to the first embodiment of the present invention will be described.FIG. 3is a block diagram showing a general configuration of a cellular communication base station2.

The cellular communication base station2includes a wireless communication device11, a wired communication device12, a controller13, and a storage14.

The wireless communication device11performs wireless communication with user terminals1.

The wired communication device12performs wired communication with the communication control device4and/or one or more nearby base stations2.

The storage14stores information on user terminals1, information on nearby base stations2, and programs executable by a processor which implements the controller13. The storage also stores information registered in an offset information database. Information registered in the offset information database includes offset values for correcting measurement values, i.e. values of received power of respective transmission beams measured by user terminals1. The offset values are comprised of initial offset values and congestion offset values for transmission beams in congestion status.

The controller13includes a wireless communication controller21and a wired communication controller22. The controller13is implemented by the processor, and each part of the controller13is implemented by the processor executing a corresponding program stored in the storage14.

The wired communication controller22is configured to exchange information on connection destinations of each user terminal1or some other information through wired communication with the communication control device4, and/or the nearby base stations2.

The wireless communication controller21includes a congestion determiner31, a terminal selector32, an offset information acquirer33, and a message controller34.

The congestion determiner31is configured to determine whether or not each transmission beam is in congestion status. In the present embodiment, the congestion determiner31determines whether or not each transmission beam is in congestion status based on the number of currently-communicating user terminals1for the transmission beam, i.e., the user terminals1currently performing communication by using the transmission beam. More specifically, the congestion determiner31determines whether or not the number of currently-communicating user terminals for a target transmission beam is equal to or greater than a predetermined threshold, and if the number of currently-communicating user terminals for the target transmission beam is equal to or greater than the threshold, the congestion determiner31determines that the target transmission beam is in congestion status.

The threshold for the number of currently-communicating user terminals for a target transmission beam is the upper limit of the number of user terminals1which are allowed for the use of the target transmission beam at one time. By using the threshold to restrict the number of currently-communicating user terminals1for a transmission beam, each user terminal1is allowed to maintain its high throughput.

The terminal selector32is configured to select a user terminal1to which offset information is transmitted among the currently-communicating user terminals. In the present embodiment, the terminal selector32selects, among the currently-communicating user terminals1which are using transmission beams in congestion status, a user terminal1capable of using a different transmission beam which is not in congestion status. If the terminal selector32finds two or more user terminals1capable of using one or more different transmission beams which are not in congestion status, the terminal selector32selects a user terminal1which is performing communication with a lowest communication quality level among the found user terminals.

The offset information acquirer33is configured to acquire offset information (correction information) which defines offset values for respective transmission beams. In the present embodiment, an offset value for each transmission beam is set based on congestion status thereof. Specifically, for a congested transmission beam, an offset value for correcting measurement values of received power is set so as to inhibit user terminals from using the congested transmission beam, and for a non-congested transmission beam, an initial offset value stored in the storage14is continued to be used.

When one or more user terminal1newly connect to a base station2, the message controller34generates a broadcast information message for providing information including offset information acquired by the offset information acquirer33, and transmits the broadcast information message to all the user terminals1located within a coverage area of the base station. The broadcast information message is transmitted to user terminals1which hare not performing communication with the base station, and thus the same information is transmitted to all such user terminals1. When a user terminal1is currently connecting to the base station2, the message controller34generates a measurement-related information message including offset information, and transmits the measurement-related information message to the currently-connected user terminal1. The measurement-related information message is transmitted to one or more currently-communicating user terminals1, whereby a corresponding piece of information is transmitted to each corresponding currently-communicating user terminal1.

InFIG. 3, the general configuration of the cellular communication base station2is shown. However, the wireless LAN access point3has substantially the same general configuration as the cellular communication base station.

Next, a general configuration of a user terminal1according to the first embodiment of the present invention will be described.FIG. 4is a block diagram showing a general configuration of a user terminal1.

The user terminal1includes a wireless communication device41, a controller42, and a storage43.

The wireless communication device41performs communication with the cellular communication base station2and the wireless LAN base station3and transmits and receives data to and from a counterpart station (such as a server) on the Internet.

The storage34stores information on the user terminal itself, information on base stations2,3and programs executable by a processor, which implement the controller42. The storage34also stores offset information included in messages received from the base station2.

The controller42includes a connection destination controller51, an offset processor52, a beam selector53, a message controller54, and a beam reception controller55. The controller42is implemented by the processor, and each part of the controller42is implemented by the processor executing a corresponding program stored in the storage43.

The connection destination controller51performs a cell search operation for searching for a connectable cell. In addition, the connection destination controller51performs a proper cell determination operation to determine whether or not a cell selected by the beam selector53meets criteria for a proper cell on which the user terminal1can camp. Also, the connection destination controller51performs a camp-on processing operation to shift to a camp state where the user terminal monitors information on a system of a cell which is determined to be a proper cell.

The offset processor52acquires offset information included in messages received from the base station2, acquires an offset value for each transmission beam based on the offset information, and corrects a measurement value of received power of each transmission beam based on the acquired offset value to obtain a corrected measurement value of received power.

The offset processor52corrects a measurement value of received power of a transmission beam by subtracting an offset value from an measurement value of received power or adding an offset value to an measurement value of received power. Thus, by subtracting an offset value from a measurement value of received power of a transmission beam at the user terminal, the base station can correct a measurement value of received power at the user terminal to be lower than the actual measurement value, thereby decreasing an evaluation of the transmission beam so as to inhibit the user terminal1from using the transmission beam. Also, by adding an offset value to a measurement value of received power of a transmission beam at the user terminal, the base station can correct a measurement value of received power at the user terminal to be higher than the actual measurement value, thereby increasing an evaluation of the transmission beam so as to promote the user terminal1to use the transmission beam.

The beam selector53selects a proper transmission beam based on a corrected measurement value of received power acquired by the offset processor52when the user terminal1newly connects the base station. When the user terminal1is currently connecting to the base station2, the base station2selects an optimal transmission beam.

When the user terminal1is currently connecting to the base station2, the message controller54determines whether or not the user terminal needs to report a measurement value of received power based on the corrected measurement value of received power obtained by the offset processor52(Report event determination). If reporting is necessary, the message controller54generates a beam measurement report message including a corrected measurement value of received power, and transmits the beam measurement report message to the base station2.

When the user terminal1newly connects to the base station2, the beam reception controller55controls transmission beam reception so that the user terminal starts communication using a transmission beam selected by the beam selector53. Also, when the user terminal1is currently connecting to the base station2, upon receiving a beam designation message transmitted from the base station2, the beam reception controller55changes the transmission beam to a transmission beam designated by the message.

Next, offset information on each offset value to be added to a broadcast information message and a measurement-related information message according to the first embodiment of the present invention will be described.FIG. 5is an explanatory view showing offset information on each offset value to be added to a broadcast information message.FIG. 6is an explanatory view showing offset information on each offset value to be added to a measurement-related information message.

In the present embodiment, offset information (correction information) including an offset value for each transmission beam is added to a broadcast information message (a message for transmitting the same information to all the user terminals1located within a coverage area of a base station) and a measurement-related information message (a message for transmitting respective pieces of information to the different currently-communicating user terminals1), and then transmitted to the user terminals. Since a base station2forms a lot of transmission beams, for example, 100 to 200 transmission beams, if an offset value included in offset information is individually defined for each transmission beam, the amount of transmitted data becomes too large. Therefore, offset information to be added to messages is determined as described below. It should be noted that examples for broadcast information messages shown inFIG. 5assumes that only 10 transmission beams are formed for the purpose of illustration.

In a first method as shown inFIG. 5A-1, multiple transmission beams placed in order of beam ID and equally grouped; that is, grouped into some beam groups such that each beam group includes an equal number of transmission beams, an offset value is defined for each beam group. Then, as shown inFIG. 5A-2, offset information to be added to messages includes the number of beams per group and an offset value for each beam group ID.

In this case, the user terminal1can, based on the number of transmission beams per group, specify which beam group each transmission beam belongs to. Then, for each transmission beam, the user terminal can specify a corresponding offset value based on respective offset values for beam group IDs.

In this first method, the number of beams per group can be changed. However, a same offset value is used for all the transmission beams belonging to each beam group.

In a second method as shown inFIG. 5B-1, multiple transmission beams placed in order of beam ID and grouped into beam groups such that each beam group includes transmission beams having consecutive beam IDs for which a same offset value is to be used. Then, as shown inFIG. 5(B-2), offset information to be added to messages includes the beam ID (identifier) of the first transmission beam (beginning beam) of each beam group, the number of transmission beams included in the beam group (the number of transmission beams with consecutive beam IDs), and a corresponding offset value for the beam group.

In this second method, since determination of offset values is not restricted by the definition of beam groups as the first method shown inFIG. 5A, a degree of freedom in determination of offset values is higher than in the first method.

In the examples for a measurement-related information message shown inFIG. 6, offset information to be added to a message includes each beam ID and an offset value acquired for a user terminal1to which measurement-related information message is to be transmitted.

Next, offset information on offset values stored in each user terminal1according to the first embodiment of the present invention will be described.FIG. 7is an explanatory view showing offset information on offset values stored in each user terminal1.

In the present embodiment, when a user terminal1receives a broadcast information message and a measurement-related information message from a base station2serving a cell in which the user terminal is present, the storage43of the user terminal stores offset information included in the messages. As the user terminal1moves, a cell in which the user terminal is present can change from one cell to another. As a result, the user terminal1can acquire, for each cell, corresponding offset information from a base station2serving the cell, and thus the user terminal1stores offset information accumulated in the storage34for each of the cells on a moving route along which the user terminal1traveled in the past. When a new offset value is provided from a base station, the user terminal can update the offset information stored in the storage34so that newest offset information is stored in the storage34.

When temporally losing a transmission beam currently used for communication, the user terminal1becomes unable to receive measurement-related information messages, and thus unable to acquires offset information from a base station2. In this case, the user terminal1acquires offset information for the cell in which the user terminal is present from all offset information for respective cells stored in the storage43, and corrects a measurement value of received power using the acquired offset information.

Moreover, in the present embodiment, the base station2transmits, in addition to offset information, information on a data retention period for the offset information to the user terminal1. The user terminal1deletes offset information stored in the storage43after a lapse of a data retention period therefor.

AlthoughFIG. 7shows an example of offset information generated by the first method as shown inFIG. 5A, the discussion about this example of offset information can similarly apply to offset information generated by the second method as shown inFIG. 5B.

Next, an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2according to the first embodiment of the present invention will be described.FIG. 8is a flowchart showing an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2.

As shown inFIG. 8A, first, the offset information acquirer33in the base station2acquires an initial offset value for each transmission beam from the storage14(ST101). Next, the congestion determiner31determines the congestion status of each transmission beam (ST102). If there is a transmission beam in congestion status (Yes in ST103), the offset information acquirer33corrects an offset value for the transmission beam to a different offset value for congestion status; that is, updates the offset value for the transmission beam to a congestion offset value used to correct a measurement value of received power in the congested transmission beam so as to inhibit user terminals from using the congested transmission beam (ST104).

Next, the message controller34generates a broadcast information message including one or more updated offset values for congested transmission beams and one or more initial offset values for non-congested transmission beams (ST105). Then, the message controller broadcasts the broadcast information message to user terminals1located in the coverage area of the base station2(ST106).

When there is no transmission beam in congestion status (No in ST103), the message controller34generates a broadcast information message including initial offset values for the respective transmission beams without updating any offset value (ST104). Then, the message controller broadcasts the broadcast information message to user terminals1located in the coverage area of the base station2(ST106).

As shown inFIG. 8B, when determining the congestion status of each transmission beam (ST102), the congestion determiner31acquires the number of currently-communicating user terminals of each transmission beam; that is, the number of user terminals1communicating with the base station by using each transmission beam (ST201). Then, congestion determiner31determines whether or not the number of currently-communicating terminals of a target transmission beam is equal to or greater than a predetermined threshold (ST202). If the number of currently-communicating user terminals is equal to or larger than the threshold value (Yes in ST202), the congestion determiner31determines that the target transmission beam is in congestion status (ST203). The processing operations of ST202and ST203are repeated in order until the processing operations are completed for all the transmission beams (Yes in ST204).

Next, an operation procedure of operations performed by a user terminal1when the user terminal newly connects to the base station according to the first embodiment of the present invention will be described.FIG. 9is a flowchart showing an operation procedure of operations performed by a user terminal1when the user terminal newly connects to the base station2.

As shown inFIG. 9A, in the user terminal1, first, the connection destination controller51performs the cell search operation for searching for a connectable cell (ST301). Then, when the connection destination controller51finds a connectable cell (Yes in ST302), the wireless communication device41receives a broadcast information message transmitted from the base station2corresponding to each detected connectable cell (ST303).

Next, the wireless communication device41measures the received power of each transmission beam (ST304). Next, the beam selector53performs a beam selection operation for selecting a proper transmission beam (ST305). Next, the connection destination controller51performs the proper cell determination operation; that is, determines whether or not the selected cell meets the criteria for proper cell on which the user terminal1can camp (ST306).

If the selected cell meets the criteria for proper cell (Yes in ST307), the connection destination controller51determines that the selected cell to be a proper cell, and the connection destination controller51camps on the selected cell; that is, shifts to a camp state where the user terminal monitors information on a system of the selected cell (ST308).

If the selected cell does not meet the criteria for proper cell (No in ST307), the process returns to ST301.

As shown inFIG. 9B, when performing the beam selection operation (ST305), the offset processor52acquires a beam group ID to which each transmission beam belongs based on the offset information (seeFIG. 5) included in the broadcast information message (ST401). Next, the offset processor52acquires an offset value for each transmission beam based on the offset value for each beam group ID (ST402).

Next, the offset processor52corrects a measurement value of received power of each transmission beam based on the offset value for each transmission beam (ST403). Specifically, for each transmission beam, the offset processor52subtracts or adds a corresponding offset value from or to a measurement value of received power. Next, the beam selector53selects a transmission beam in which the largest corrected measurement value of received power is obtained (ST404).

Next, an operation procedure of operations performed by the base station2when a user terminal1is currently connecting to the base station2according to the first embodiment of the present invention will be described.FIG. 10is a flowchart showing an operation procedure of operations performed by the base station2when a user terminal1is currently connecting to the base station2.

As shown inFIG. 10A, in the base station2, first, the offset information acquirer33acquires an initial offset value for each transmission beam from the storage14(ST501). Next, the congestion determiner31performs a congestion determination operation; that is, determines whether or not each transmission beam is in congestion status (ST502).

When there is at least one congested transmission beam (Yes in ST503), the terminal selector32performs a terminal selection operation for selecting, among the user terminals1using congested transmission beams, one or more user terminals1which can change their transmission beams to other transmission beams which are not in congestion status (ST504).

Next, the offset information acquirer33updates one or more offset values among the offset values for transmission beams used by the user terminals1selected by the terminal selector32. Specifically the offset information acquirer33updates offset values for congested transmission beams to congestion offset values, where the congestion offset values are offset values used to correct measurement values of received power in the transmission beams so as to inhibit the user terminals1from using the transmission beams in congestion status (ST505).

Next, the message controller34generates a measurement-related information message including the updated congestion offset values for the congested transmission beams and the initial offset values for the non-congested transmission beams (ST506). Then, the wireless communication device11transmits the measurement-related information message to the selected user terminals1(ST507).

When there is no transmission beam in congestion status (Yes in ST503), the controller13ends the operation without any further processing.

In the above-described embodiment, the controller is configured to set offset values for congested transmission beams so as to inhibit user terminals1from using the congested transmission beams. However, the controller may be configured to set offset values for congested transmission beams so as to promote user terminals1to use different transmission beams which are not in congestion status.

As shown inFIG. 10B, in the congestion determination operation (ST502), the congestion determiner31determines the number of currently-communicating terminals for each transmission beam; that is, the number of currently-communicating user terminals1using each transmission beam (ST601). Then, the congestion determiner31determines whether or not the number of currently-communicating terminals for a target transmission beam is equal to or greater than a predetermined threshold Th (ST602). If the number of currently-communicating terminals is equal to or greater than the predetermined threshold value (Yes in ST602), the congestion determiner31determines that the target transmission beam is in congestion status, or “congested” (ST603). The processing operations of ST602and ST603are repeated in order until the processing operations are completed for all the transmission beams (Yes in ST604).

As shown inFIG. 10C, in the terminal selection operations (ST504), the terminal selector32extracts multiple currently-communicating user terminals1using congested transmission beams (ST701). Next, the terminal selector32extracts one or more user terminals1capable of using other transmission beams which are not in congestion status (ST702). If two or more such user terminals are extracted (No in ST703), the terminal selector32selects a user terminal1which is performing communication with a lowest communication quality level among the extracted user terminals (ST704). As a result, frequency usage efficiency is improved. When fair availability to different user terminals1is important, the selection operations (ST703to ST704) to narrow the user terminals down to one user terminal may be omitted.

If the selection operations narrows the extracted user terminals down to one user terminal1(Yes in ST703), the process ends at that point.

Next, an operation procedure of operations performed by a user terminal1when the user terminal1is currently connecting to the base station2according to the first embodiment of the present invention will be described.FIG. 11is a flowchart showing an operation procedure of operations performed by a user terminal1when the user terminal1is currently connecting to the base station2.

In the user terminal1, first, upon receiving a measurement-related information message transmitted from the base station2(Yes in ST801), the wireless communication device41measures the received power in each transmission beam (ST802).

Next, the offset processor52acquires a beam group ID to which each transmission beam belongs based on offset information included in the measurement-related information message (ST803). Then, the offset processor52acquires an offset value for each transmission beam from the offset information in the storage43(seeFIG. 7) based on the offset values for respective beam group IDs (ST804). Nest, the offset processor52corrects a measurement value of received power in each transmission beam based on the offset values for respective transmission beams (ST805). Specifically, for each transmission beam, the offset processor52subtracts or adds a corresponding offset value from or to a measurement value of received power in each transmission beam to thereby correct the measurement value.

Next, the message controller54performs a report event determination operation to determine whether or not the user terminal needs to report a measurement value of received power based on the corrected measurement value of received power (ST806). If reporting is necessary, the wireless communication device41transmits to the base station2a beam measurement report message including the corrected measurement value of received power (ST807). When the wireless communication device41receives a beam designation message transmitted from the base station2(Yes in ST808), the beam reception controller55changes the transmission beam to be used to a transmission beam designated by the message (ST809).

If reporting is not necessary (No in ST806) or if the wireless communication device41does not receive a beam designation message (No in ST808), the process returns to ST801.

AlthoughFIGS. 8 and 10show the operation procedure of operations performed by the cellular communication base station2, the discussion about the procedure can similarly apply to operations performed by the wireless LAN base station3. AlthoughFIGS. 9 and 11show an exemplary case in which a connection destination of the user terminal1is the cellular communication base station2, the discussion about this case can similarly apply to a case in which a connection destination of the user terminal1is the wireless LAN base station3.

Second Embodiment

Next, a second embodiment of the present invention will be described. Except for what will be discussed here, this embodiment is the same as the above-described embodiment. Although an exemplary case in which a connection destination of a user terminal1is the cellular communication base station2will be described here, the discussion about this case similarly applies to a case in which a connection destination of a user terminal1is the wireless LAN base station3.

Since a traffic volume of vehicles as obstacles changes with time of day, the frequency of occurrence of communication failures changes depending on time of day. Also, as a traffic volume of people with user terminals1changes with time of day, utilization of transmission beams changes depending on time of day.

In this view, in the present invention, the offset information acquirer33determines whether the current time is (i) the time of day in which a communication environment (such as a traffic volume of vehicles or a traffic volume of people) is deteriorated or (ii) the current time is the time of day in which a communication environment is good, and then the offset information acquirer33sets offset values according to result of the determination. More specifically, in the present invention, for each transmission beam, a middle-night offset value and a standard offset value are preset and stored in the storage14, and the offset information acquirer33determines whether or not the current time is a middle-night time (for example, 0:00 to 5:00 AM), and acquires middle-night offset values or standard offset values in the storage14according to result of the determination.

Next, an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2according to the second embodiment of the present invention will be described.FIG. 12is a flowchart showing an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2.

In the base station2, first, the offset information acquirer33determines whether or not the current time is in a middle-night time (ST111). If the current time is the middle-night time (Yes in ST111), the offset information acquirer33acquires a middle-night offset value for each transmission beam from the storage14(ST112). Next, the message controller34generates a broadcast information message including the middle-night offset value for each transmission beam (ST105), and broadcasts the broadcast information message to the user terminals1located in a coverage area of the base station (ST106).

If the current time is not in the middle-night time (No in ST111), the offset information acquirer33acquires a standard offset value for each transmission beam from the storage14(ST112). Next, the message controller34generates a broadcast information message including the standard offset value for each transmission beam (ST105), and broadcasts the broadcast information message to the user terminals1located in a coverage area of the base station (ST106).

Third Embodiment

Next, a third embodiment of the present invention will be described. Except for what will be discussed here, this embodiment is the same as the above-described embodiments. Although an exemplary case in which a connection destination of a user terminal1is the cellular communication base station2will be described here, the discussion about this case similarly applies to a case in which a connection destination of a user terminal1is the wireless LAN base station3.FIG. 13is an explanatory view showing a situation where there are user terminals1and transmission beams formed by base stations2.

A transmission beam directed to a vehicular road is formed, an occupant of a vehicle can communicate with the base station2using a user terminal1owned by the occupant or a user terminal1mounted on the vehicle through the transmission beam. In this case, when the vehicle is traveling at an intersection under a green light of a traffic signal5(in the left-right direction inFIG. 13) and thus the user terminal1moves at a high speed at the intersection, a communication failure is likely to occur. When the vehicle stops under a red right (in the vertical direction inFIG. 13), a communication failure is unlikely to occur, which allows for stable wireless communication.

In this view, in the present invention, the offset information acquirer33sets offset values for each state of a traffic signal5. More specifically, in the present invention, a base station2is configured to: acquire control information on control of traffic signals5from a signal control device6; identify a traffic lane in which a green light permits traffic to travel and a traffic lane in which a red light inhibits traffic from traveling based on the acquired control information; and set an offset value for each transmission beam for a corresponding traffic lane according to traffic flow permission status of the traffic lane.

Specifically, for each of the transmission beams B1and B2formed for the traffic lane in which the green light permits traffic to travel, an offset value is set so as to inhibit user terminals1from using the transmission beam, whereas, for each of the transmission beams B3and B4formed for the traffic lane in which the red light inhibits traffic from traveling, a different offset value is set so as to promote user terminals1to use the transmission beam.

As a result, since a user terminal1mounted on a vehicle traveling under a green light is inhibited from using a transmission beam formed for the traffic lane in which the green light permits traffic to travel, it becomes possible to prospectively avoid occurrence of a communication failure due to high speed traveling. Also, since a user terminal1mounted on a vehicle stopping under a red light is promoted to use a transmission beam formed for the traffic lane in which the red light inhibits traffic from traveling, it becomes possible for the user terminal to perform communication with a base station2.

Next, an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2according to the third embodiment of the present invention will be described.FIG. 14is a flowchart showing an operation procedure of operations performed by a base station2when a user terminal1newly connects to the base station2.

First, the offset information acquirer33in the base station2acquires an initial offset value for each transmission beam from the storage14(ST101). Next, the offset information acquirer33acquires control information on traffic signals5from the signal control device6, and performs a signal state determination operation based on the acquired control information in order to determine in which traffic lane at the intersection, vehicular traffic is permitted to travel (ST121).

Next, the offset information acquirer33determines whether or not an area for which a target transmission beam is formed is a travel-permitted lane; that is, a lane in which vehicular traffic is permitted to travel (ST122). If the area for which the target transmission beam is formed is a travel-permitted lane (Yes in ST122), the offset information acquirer33updates the offset value used in a user terminal1to such an offset value as to inhibit the user terminal1from using the target transmission beam (ST123). If the area for which the target transmission beam is formed is not a travel-permitted lane (No in ST122), the offset information acquirer33updates the offset value used in the user terminal1to such an offset value as to promote the user terminal1to use the target transmission (ST124).

The processing operations of ST122to ST124are repeated in order until the processing operations are completed for all the transmission beams (Yes in ST204).

Next, the message controller34generates a broadcast information message including one or more updated offset values for respective transmission beams (ST105). Then, the message controller broadcasts the broadcast information message to user terminals1located in the coverage area of the base station2(ST106).

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described. Except for what will be discussed here, this embodiment is the same as the above-described embodiments. Although an exemplary case in which a connection destination of a user terminal1is the cellular communication base station2will be described here, the discussion about this case similarly applies to a case in which a connection destination of a user terminal1is the wireless LAN base station3.FIG. 15is an explanatory view showing a situation in which a user terminal1and base stations2forming respective transmission beams are present.

In an example shown inFIG. 15, a person moves carrying a user terminal1moves from the left to the right in the drawing. In this case, when the user terminal1uses a transmission beam formed by a base station2located behind the person carrying the user terminal1; that is, located on the rear side of the moving direction (the base station on the left inFIG. 15), the person body can be an obstacle for the user terminal, by which a communication failure can occurs. In this case, the user terminal1preferably changes the transmission beam used for communication to a transmission beam formed by the adjacent base station2located in front of the person carrying the user terminal1; that is, located on the front side of the moving direction (the base station on the right inFIG. 15).

In this view, in the present invention, the base station2accumulate in the storage14historical information on transmission beams used by each user terminal1before as historical used-beam information, and the base station2sets an offset value so that the user terminal1can change the transmission beams used for communication based on the historical used-beam information.

Next, an operation procedure of operations performed by the base station2when a user terminal1is currently connecting to the base station2according to the fourth embodiment of the present invention will be described.FIG. 16is an explanatory view showing historical used-beam information on transmission beams used before.FIG. 17is a flowchart showing an operation procedure of operations performed by the base station2when a user terminal1is currently connecting to the base station2.

In the base station2, first, the offset information acquirer33acquires an initial offset value for each transmission beam from the storage14(ST501). Then, the offset information acquirer33acquires historical used-beam information for a target transmission beam in the storage14(ST511). The historical used-beam information (seeFIG. 16) include a cell ID and a beam ID for each user terminal1as a history of transmission beams used by the user terminal1.FIG. 16shows an example in which, when the used base station (cell ID) is changed from 1 to 2, the used transmission beam ID transits from 7 to 10.

In this view, in the present invention, the offset information acquirer33determines whether or not a target user terminal1currently uses a transmission beam formed closest to a coverage of an adjacent base station based on the historical used-beam information of the user terminal (ST512). If the user terminal1uses the transmission beam (beam ID:7) formed closest to a coverage of the adjacent base station (Yes in ST512), the offset information acquirer33updates the offset value of a transmission beam with a beam ID of10formed by the adjacent base station to a new offset value, which is such an offset value as to promote the user terminal1to use the transmission beam (beam ID:10) formed by the adjacent base station (ST513).

Next, the message controller34generates a measurement-related information message (seeFIG. 6) including the updated offset value (ST506). Then, the wireless communication device11transmits the measurement-related information message to the target user terminal1(ST507).

The user terminal1, based on the offset value included in the measurement-related information message received from the base station2, corrects an measurement value of received power of the transmission beam (in this case, beam ID:10) formed by the adjacent base station2located on the front side in the moving direction such that the measurement value is corrected to be an increased measurement value of received power. Next, the user terminal1generates a measurement-related information message including a corrected measurement value of received power, and transmits the corrected measurement value to the current base station2. Then, the current base station2transmits a beam designation message, which designates the transmission beam (beam ID:10) formed by the adjacent base station2, to the user terminal1so that the user terminal1changes the transmission beam used for communication to the designated transmission beam (beam ID:10).

If the user terminal1does not use the transmission beam closest to the coverage of the adjacent base station (No in ST512), the offset information acquirer33updates the offset value of the transmission beam based on offset information in an offset information database stored in the storage14(ST514).

In the present embodiment, the user terminal is configured to correct a measurement value of received power in a transmission beam formed by an adjacent base station2located in the front side in the moving direction so as to increase evaluation of the transmission beam. However, the user terminal may be configured to correct a measurement value of received power in a transmission beam formed by a currently-connected base station2located on the rear side so as to decrease evaluation of the transmission beam, whereby the user terminal1is promoted to change the transmission beam used for communication to a transmission beam formed by the adjacent base station2.

Moreover, in the present embodiment, the currently-connected base station2is configured to transmit offset information for a transmission beam formed by an adjacent base station2to the user terminal1. However, a currently-connected base station may be configured such that the base station in cooperation with an adjacent base station2, promotes a user terminal1to use a transmission beam formed by the adjacent base station2. Specifically, the base station2transmits to the adjacent base station2an instruction message to change evaluation of a transmission beam of the adjacent base station2by using an offset value, so that the adjacent base station2transmits offset information for its transmission beam to the user terminal1.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described. Except for what will be discussed here, this embodiment is the same as the above-described embodiments. Although an exemplary case in which a connection destination of a user terminal1is the cellular communication base station2will be described here, the discussion about this case similarly applies to a case in which a connection destination of a user terminal1is the wireless LAN base station3.FIG. 18is an explanatory view showing a situation in which user terminals1and a base station2forming its transmission beams are present.

A user terminal1mounted on a flying object7such as a drone performs communication by using a transmission beam formed by a base station and directed from the base station2towards sky. Meanwhile, a transmission beam intended for a moving object on the ground can be reflected by a road surface or a wall surface of a building to be directed towards the sky. In this case, the user terminal1mounted on the flying object7may find the reflected transmission beam directed towards the sky to start communication by using the reflected transmission beam. Use of such a reflected transmission beam is likely to cause a communication failure due to interference.

In this view, in the present invention, the base station2sets an offset value used for changing a measurement value of received power so as to inhibit the user terminal1mounted on the flying object7from using such a reflected transmission beam directed towards the sky. Accordingly, since the user terminal1mounted on the flying object7is inhibited from using any reflected transmission beam directed towards the sky, it becomes possible to prospectively avoid a communication failure regarding the user terminal mounted on the flying object.

While specific embodiments of the present invention are described herein for illustrative purposes, the present invention is not limited thereto. It will be understood that various changes, substitutions, additions, and omissions may be made for elements of the embodiments without departing from the scope of the invention. In addition, elements and features of the different embodiments may be combined with each other as appropriate to yield an embodiment which is within the scope of the present invention.

For example, in the above-described embodiments, a cellular communication base station or a wireless LAN base station controls wireless communication performed by a user terminal by using a transmission beam formed by the base station itself, or by using a transmission beam formed by a different base station; that is, an adjacent base station. In other embodiments, a macro cell base station is configured to perform wireless communication using LTE (Long Term Evolution) scheme functioning as a C-plane (Control-plane) cell, and controls wireless communication performed by a user terminal by using a transmission beam formed by a small cell base station as a U-Plane (User-plane) cell; that is, a cellular communication base station in the above-described embodiments.

Also, although, in the above-described embodiments, a measurement value of received power such as RSRP (Reference Signal Received Power) is used as an evaluation indicator for evaluating reception status of a transmission beam in order to select a proper transmission beam, a diffident measurement value may be used as an evaluation indicator to be corrected. In other cases, a measurement value of communication quality of a received transmission beam such as RSRQ (Reference Signal Received Quality) may be used as an evaluation indicator to be corrected. In other embodiments, a combination of a measurement value of received power and a measurement value of communication quality may be used for evaluation in such a manner that both measurement values are corrected.

In addition, although, in the above-described embodiments, a measurement value for a transmission beam is corrected by adding an offset value to or subtracting the same from such a measurement value. Methods of correcting a measurement value for a transmission beam is not limited to the use of subtraction and addition as described above, but may be any method which can correct a measurement value by increasing or decreasing an actual measurement value. For example, a measurement value may be corrected by multiplexing or dividing a measurement value by an offset value.

INDUSTRIAL APPLICABILITY

A base station device, a terminal device, a communication system and a communication control method according to the present invention achieve an effect of making it possible to prospectively avoid occurrence of communication failures and/or reduction in throughput of each terminal device, thereby improving users' satisfaction with communication service, and are useful as a base station device, a terminal device, a communication system and a communication control method for controlling wireless communication performed by the terminal device by using any of multiple transmission beams formed by the base station device.

Glossary