JP2017108332A - Radio communication apparatus method and radio communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve communication efficiency of an entire system by enabling a mobile radio unit to autonomously select a communication mode.SOLUTION: A radio communication method includes: a measurement step for measuring communication loads in a plurality of communication modes for each communication mode; a reception steps for receiving the communication load for each of the plurality of communication modes of peripheral vehicles; a transmission step for transmitting to the peripheral mobile radio units the communication load for each of the plurality of communication modes measured in the measurement step and the communication load for each of the plurality of communication modes received in the reception step and measured by a second mobile radio unit; an estimation step for estimating an estimation communication load of second and third mobile radio units regarding a changed communication mode on the assumption that a first mobile radio unit changes the communication mode; and a determination step for determining based on the estimation communication load whether to change a communication mode to be utilized for a communication by the first mobile radio unit and, in the case where the communication mode is to be changed, the changed communication mode.SELECTED DRAWING: Figure 4

Description

  The present invention relates to wireless communication, and more particularly to wireless communication in which communication is performed by dynamically determining a communication method to be used.

  In a mobile environment such as a vehicle, surrounding conditions and application requirements change, so it is not efficient to use only a single communication method (communication profile). In order to improve communication efficiency, it is necessary to dynamically select a communication method according to the surrounding situation.

  Patent Document 1 discloses that transmission performance is improved by using a plurality of antennas and adjusting the directivity according to the installation state of the wireless communication device. Patent Document 2 discloses that radio interference is suppressed and communicated by lowering the power level or the modulation rate when the position of the vehicle is in or near a region where the degree of radio wave interference with digital television broadcasting is high. It is disclosed that the maintenance of performance is compatible. In Patent Document 3, a communication management device captures an image of a vehicle, identifies a vehicle having a high possibility of collision, and assigns a dedicated communication channel. The vehicle performs situation determination and crisis avoidance using the assigned dedicated communication channel.

JP 2014-050028 A JP 2011-015115 A JP 2005-032010 A

  In Patent Documents 1 and 2, since only the situation of the own apparatus is taken into consideration, it is impossible to control the communication system in consideration of the situation of the peripheral apparatus. If a centralized management apparatus such as Patent Document 3 or a mobile phone system is installed, control can be performed after grasping all the situations, but the introduction cost is high.

  The present invention provides a mobile wireless device that autonomously selects a wireless communication method in an environment where communication is performed using a plurality of wireless communication methods for each of a plurality of mobile wireless devices, thereby improving communication efficiency of the entire system. Objective.

  In order to achieve the above object, in the first aspect of the present invention, the mobile radio apparatus collects the communication status of surrounding mobile radio apparatuses, estimates the influence after switching the communication method, and uses it. Determine the communication method.

  More specifically, the wireless communication method according to this aspect is a wireless communication method performed by the first mobile wireless device by dynamically determining a communication method, and includes a measurement step, a reception step, and a transmission A step, an estimation step, and a determination step.

In the measurement step, the first mobile radio apparatus measures the communication load. The communication load is defined for each communication method, and the communication load in each communication method is measured in the measurement step. A communication load in a certain communication method is an index for evaluating an adverse effect exerted on communication using the communication method. As the communication load, any one or a combination of communication congestion, channel utilization rate, communication error rate, and the like can be adopted. The measurement timing need not be synchronized with other mobile radio devices. Each mobile radio device may measure at an appropriate timing.

  The communication method means a combination of methods and parameters that can be selected when performing communication. The communication method can also be expressed as a combination of communication resources in each layer provided by the communication stack. The communication method is defined by a combination of a transport protocol, a network protocol, an access technology, and a channel (frequency band), for example. The communication method is also called a communication profile.

  In the reception step, the first mobile radio apparatus receives a communication status from a mobile radio apparatus (second mobile radio apparatus) capable of direct communication. The communication status transmitted by the second mobile radio device includes the communication load measured by the second mobile radio device and the second mobile radio device received from the surrounding mobile radio device (third mobile radio device). Communication load (measured by the third mobile radio device) is included.

  In the transmission step, the first mobile radio apparatus transmits a communication status to a mobile radio apparatus (second mobile radio apparatus) capable of direct communication. The communication status transmitted by the first mobile radio apparatus includes the communication load measured by the first mobile radio apparatus and the communication load measured by the second mobile radio apparatus (received in the reception step). Information to be transmitted in the transmission step includes conditions other than the communication load such as the position, moving direction, moving speed, available (supportable) communication method, and the density or number of surrounding mobile wireless devices. Is also preferable.

  Through the measurement step, the reception step, and the transmission step, the mobile radio devices constituting the system can grasp the communication status of the surrounding mobile radio devices up to two hops away. These processes are preferably executed repeatedly at regular intervals. In the transmission step, not only the communication status of the mobile radio device one hop ahead (second mobile radio device) but also the communication status of the mobile radio device N (N is an integer of 2 or more) hops is transmitted together. By doing so, it is possible to grasp the communication status of the surrounding mobile radio apparatuses up to N + 1 hops away.

  In the estimation step, when it is assumed that the first mobile radio apparatus has changed the communication method, how the communication load of the surrounding mobile radio apparatuses (second and third mobile radio apparatuses) changes is determined. presume. Hereinafter, the estimated communication load is referred to as an estimated communication load. The change in communication load can be estimated based on a predetermined value for each communication method, the distance from the first mobile radio apparatus, the density (number) of peripheral mobile radio apparatuses, and the like.

  In the determination step, the first mobile radio apparatus determines whether to change the communication scheme used by the first mobile radio apparatus for communication based on the estimated communication load. When changing the communication method, it is also determined which communication method is used.

Whether to change the communication method used for communication can be determined as follows. First, when the first mobile radio apparatus changes the communication system, the maximum estimated communication load of the second and third mobile radio apparatuses for the changed communication system is obtained. This is obtained by referring to the estimated communication load estimated in the estimation step. Next, it is determined whether there is a communication method other than the currently used communication method that satisfies the following conditions. If there is a communication method that satisfies the conditions, it is determined that the communication method to be used is changed.
(Condition) The maximum value of the communication load of the second and third mobile radio apparatuses for the communication system after the change is that of the second and third mobile radio apparatuses for the communication system before the change (currently being used). It is less than or equal to a value obtained by multiplying the maximum value of the communication load by a coefficient β (0 <β <1).

  The value of the coefficient β may be appropriately determined in consideration of the overhead required for switching the communication method. Further, the value of the coefficient β may be different for each changed communication method, or may be the same value regardless of the changed communication method.

  When it is determined that the communication method is to be changed, for example, the communication method to be changed can be determined by any of the following methods.

・ Randomly select a communication method that satisfies the above conditions ・ Select a communication method that satisfies the above conditions with the minimum estimated communication load ・ Select a communication method that satisfies the above conditions Select the one with the smallest (or largest) channel number

  In the determination step, factors other than the communication load may be taken into consideration to determine whether or not to change the communication method and to which communication method to change. For example, when there is a request for communication, a condition that communication according to the changed communication method satisfies the request can be added to the above condition.

  In the above determination step, the determination is performed considering only the estimated communication load of the second and third mobile radio apparatuses, but the determination may be performed also considering the estimated communication load of the first mobile radio apparatus. preferable. In this case, in the estimation step, when it is assumed that the first mobile radio apparatus has changed the communication system, it is also necessary to estimate the communication load of the first mobile radio apparatus for the changed communication system.

  In this way, it is possible for the first mobile radio apparatus to autonomously determine an appropriate communication method in consideration of the situation of the second and third mobile radio apparatuses.

  The wireless communication method according to this aspect preferably further includes a notification step of transmitting a notification to that effect to surrounding mobile wireless devices when it is determined in the determination step that the communication method is changed. It is desirable to send this notification before actually changing the communication method. And when said notification is received from the surrounding mobile radio | wireless apparatus, it is preferable not to change a communication system for a predetermined period. This notification is regarded as a communication system change suppression notification. The predetermined period during which the communication method is not changed is preferably equal to or longer than the measurement step execution interval.

  If a plurality of mobile radio apparatuses are allowed to change the communication scheme at the same time, the plurality of mobile radio apparatuses may change to the same communication scheme at the same time. If it does so, the communication load by the said communication system will increase extremely, and efficient communication cannot be performed. By adopting the above configuration, such a situation can be avoided.

  The execution timing of the estimation step and the determination step in this aspect may be any of the following. The first is executed when the communication load of the first mobile radio apparatus for a currently used communication method is equal to or greater than a predetermined threshold. The second is executed when the maximum value of the communication load of the first, second, and third mobile radio apparatuses for the currently used communication method is greater than or equal to a predetermined threshold. The third is executed at predetermined time intervals. The communication load threshold may be a value that prevents efficient communication. The predetermined time interval may be a predetermined multiple (for example, two times, five times, ten times) of the measurement step execution interval.

According to the first and second methods, unnecessary switching of communication methods can be suppressed, and the number of executions of the estimation step and the determination step can be suppressed. Therefore, the processing load can be reduced. According to the third method, an increase in the communication load of a certain communication method can be suppressed, although the number of times of switching the communication method increases.

  In the present invention, the mobile wireless device includes a wireless communication device mounted on or provided in a moving body such as a vehicle, a flying object, and a ship, and a portable wireless communication device (including a smartphone, a computer with a communication function, etc.) included.

  Note that the present invention can also be understood as a communication method for executing at least a part of the above processing. The present invention can be understood as a wireless communication apparatus including means for executing at least a part of the above processing. The present invention can also be understood as a computer program for causing a computer to execute this method, or a computer-readable storage medium in which this computer program is stored non-temporarily. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  According to the present invention, in an environment where communication is performed using a plurality of wireless communication methods for each of a plurality of mobile wireless devices, the mobile wireless device autonomously selects a wireless communication method to improve the communication efficiency of the entire system. be able to.

FIG. 1A is a configuration diagram of the in-vehicle communication device according to the present embodiment, and FIG. 1B is a functional block diagram of the in-vehicle communication device according to the present embodiment. FIG. 2 is a flowchart of a wireless communication method (communication method determination method) in the present embodiment. FIG. 3 is a diagram illustrating an example of a positional relationship of vehicles that perform wireless communication in the present embodiment. FIG. 4 is a diagram showing an example of the measurement timing of the communication status in this embodiment. FIG. 5 is a diagram showing an example of a communication status table in the present embodiment. FIG. 6 is a diagram for explaining a method for determining a communication method in the present embodiment. FIG. 7 is a diagram for explaining a method of determining a communication method according to this embodiment.

  Below, the vehicle network comprised from the some vehicle (vehicle-mounted radio | wireless communication apparatus) corresponding to a some radio | wireless communication system is demonstrated. Each vehicle autonomously determines an appropriate communication method in consideration of the communication status of surrounding vehicles. In addition, although the following embodiment is an example which applied this invention to the vehicle-mounted radio | wireless communication apparatus, this invention is applicable with respect to arbitrary mobile radio | wireless apparatuses.

In the following description, the communication method means a combination of methods, parameters, and the like that can be selected when performing communication. The communication method can also be expressed as a combination of communication resources in each layer provided by the communication stack. The communication method is defined by a combination of a transport protocol, a network protocol, an access technology, and a channel (frequency band), for example. Communication method is Communication Profile
It may also be abbreviated as CP.

<Configuration>
FIG. 1A is a diagram illustrating a device configuration of a vehicle 100 configuring a vehicle network according to the present embodiment. The vehicle 100 includes an arithmetic device 1, a memory 2, a GPS device 3, an input / output device 4, and a plurality of wireless communication devices 5.

The arithmetic device 1 is a general-purpose processor such as a microprocessor or a CPU (central processing unit), and provides functions described below by executing a program stored in the memory 2. The memory 2 includes a main storage device and an auxiliary storage device. The above program is stored in the auxiliary storage device. The GPS device 3 is a device that receives satellite signals and acquires position information of the vehicle 100. If position information can be acquired, a satellite positioning system other than GPS, a mobile base station positioning system, or the like can be used. The input / output device 4 includes an input device such as a switch, a button, and a keyboard, and an output device such as a display and a speaker, and inputs and outputs information to and from the user.

The plurality of wireless communication devices 5 are wireless communication devices corresponding to different wireless communication standards. As an example of available wireless communication standards, LTE (Long Term Evolution), 5 GHz band DSRC (Dedicated Short-Range Communication), 2.4 GHz band WiFi, 5.6
Examples include, but are not limited to, a GHz band WiFi. With the plurality of wireless communication devices, the vehicle 100 can perform wireless communication using different communication methods.

  Note that the wireless communication device 5 may be a software wireless communication device capable of switching the wireless communication method by changing the control software. In this case, only one software defined wireless communication device may be used without using a plurality of wireless communication devices.

  FIG. 1B is a functional block diagram showing a functional configuration of the vehicle 100 according to the present embodiment. When the arithmetic device 1 executes the program, the communication status measurement unit 11, the communication status reception unit 12, the communication status storage unit 13, the communication status transmission unit 14, the communication status estimation unit 15, the communication method change determination unit 16, and the communication control. Each function part of the part 17 is provided. FIG. 1B shows only functions related to the communication method change processing. In addition to the functions shown in FIG. 1B, vehicle 100 is also provided with functions executed by various application programs, functions for performing wireless communication in accordance with instructions from the application programs, and the like. Some or all of the functional units shown here may be realized by a dedicated logic operation circuit such as an ASIC.

  Details of each functional unit will be described together with processing of the following wireless communication method.

(Method)
FIG. 2 is a flowchart showing a flow of processing particularly related to determination of a communication method among wireless communication methods performed by the vehicle 100. Details of the wireless communication method of the vehicle 100 in the present embodiment will be described with reference to FIG. The vehicle 100 repeatedly executes the process shown in the flowchart of FIG.

  In step S10, first, it is determined whether the communication status receiving unit 12 has received a communication status notification from another vehicle. The communication status receiving unit 12 appropriately receives communication status notifications from surrounding vehicles via the wireless communication device 5. If a communication status notification has been received (S10-YES), the process proceeds to step S12. If not (S10-NO), the process proceeds to step S14.

  Although details will be described later, the communication status notification includes the communication status of the transmission source vehicle and surrounding vehicles for each communication method. The communication status of the transmission source vehicle is measured by the transmission source vehicle. The communication status of surrounding vehicles is measured by the surrounding vehicles and notified to the transmission source vehicle. In the present embodiment, the communication status notification is included in the communication status of the transmission source vehicle and the 1-hop vehicle. In addition to the communication status, information such as the acquisition date / time of the communication status, the position of the vehicle, and the number of hops of the vehicle is also included.

  In step S12, the communication status reception unit 12 updates the communication status table stored in the communication status storage unit 13 based on the received communication status notification. Prior to the description of the update process of the communication status table, the configuration of the communication status table will be described with reference to FIG.

FIG. 5 is a diagram illustrating a configuration example of the communication status table, and is an example of the communication status table held by the vehicle A when the vehicles A to D are in the positional relationship illustrated in FIG. 3. The communication status table includes the number of hops, the last reception time, the last update time, the position, and the communication load for each communication method (CP _{1 to} CP _N ) for each vehicle. The number of hops represents the number of hops from the table holding vehicle. The last reception time represents the time when the communication status notification is directly received from the target vehicle. The last update time represents the time when the communication status of the target vehicle was last updated. In addition, although the last reception time and the last update time are represented by the difference with the present time in FIG. 5, you may represent using absolute time. The position represents the position of the target vehicle. In FIG. 5, the position of the vehicle is expressed by distances in the X direction and the Y direction from the reference point, but may be expressed by latitude and longitude information. The communication load represents the degree of congestion of communication using each communication method.

  In step S12, the communication status table is updated based on the communication status notification received from another vehicle. Specifically, the communication status table is updated based on each data included in the communication status notification. The number of hops is updated with a value obtained by adding 1 to the value included in the communication status notification. The final reception time is updated with the reception time only for the transmission source vehicle of the reception status notification. The last update time is updated with the reception time for all the vehicles included in the reception status notification. The position and communication load are updated with the position and communication load included in the reception status notification for all vehicles included in the reception status notification. The communication load may be replaced with a value included in the communication status notification, but may be replaced with a moving average (exponential moving average) using a forgetting factor.

  In step S14, the communication status measurement unit 11 determines whether or not the communication status measurement timing has arrived. If the measurement timing has arrived (S14-YES), the process proceeds to step S16, and if not (S14-NO), the process proceeds to S22.

  In the present embodiment, the measurement of the communication status is performed by each vehicle at a predetermined time interval. This time interval may be appropriately set based on a request required for communication, and may be a value such as 10 seconds, 30 seconds, or 1 minute. In step S14, the communication status measuring unit 11 may determine whether the predetermined time interval has elapsed since the previous measurement.

  In the present embodiment, it is not necessary to synchronize the measurement timing of each vehicle, and each vehicle may measure the communication status at an appropriate timing as shown in FIG. Further, the measurement interval of the communication status is preferably common to all the vehicles, but the measurement may be performed at different time intervals for each vehicle.

  In step S <b> 16, the communication status measurement unit 11 measures a communication load in communication using each communication method using the plurality of wireless communication devices 5. As the communication load, it is possible to employ a degree of communication congestion, a channel utilization rate, a communication error rate, and the like.

  In step S18, the communication status measurement unit 11 updates the communication status table in the communication status storage unit 13 using the measurement result. Specifically, the communication load of each communication method for the host vehicle is updated to the measured communication load. Further, the last update time is updated to the measurement time, and the position is updated to the position acquired from the GPS device 3 at the time of measurement.

In step S <b> 20, the communication status transmission unit 14 transmits information about the communication status of the host vehicle and the one-hop ahead vehicle toward surrounding vehicles. Specifically, the communication status transmission unit 14 refers to the communication status table, and notifies the communication status including information about the host vehicle and the vehicle one hop ahead (vehicles A, B, and C in the example of FIG. 5). A message is generated and transmitted from the wireless communication device 5. The communication status notification may be transmitted using a communication channel dedicated to inter-vehicle communication that is always used by each vehicle. However, the transmission of the communication status notification may be performed using any one or a plurality or all of the communication methods used by each vehicle. The reception process in step S10 is performed in accordance with the communication status notification transmission method.

  In step S22, it is determined whether or not it is time to determine whether to change the communication method. If the change determination timing has arrived (S22-YES), the process proceeds to step S24. If not (S22-NO), the process returns to step S10 and the process is repeated.

  The execution timing of the communication system change determination is preferably any of the following.

(1) Execute at a predetermined time interval (2) Execute when the communication load of communication in the currently used communication method exceeds the threshold

  In the method (1), for example, a predetermined time interval (for example, 1 time, 2 times, 5 times, 10 times, or the like) can be employed as the predetermined time interval. The threshold value of the communication load in the case of the method (2) may be determined as appropriate. If the predetermined time interval is shortened or the communication load threshold is reduced, the communication method can be switched before the communication load becomes too large. For example, although the communication load of other communication methods is small, a situation in which the communication method is not changed can be suppressed. On the other hand, it is also assumed that the frequency of changing the communication method will increase. Conversely, if the predetermined time interval is lengthened or the communication load threshold is increased, frequent changes in the communication method can be suppressed. However, the communication load may increase. As described above, in setting the execution interval and the threshold, there is a trade-off between the change frequency of the communication method and the suppression of the increase in communication load. Therefore, it is preferable to set an appropriate value using a demonstration experiment or a simulation.

  Even if either of the above conditions (1) or (2) is satisfied, if a communication mode change notification (described later) is received from a surrounding vehicle, It is preferable not to carry out the communication system change determination during the predetermined period. This period may be longer than the measurement process execution interval. When a plurality of vehicles change the communication method at the same time, the plurality of vehicles may change to the same communication method at the same time. If it does so, the communication load by this communication system will increase extremely. When other vehicles change the communication method, such a situation can be avoided by suppressing the change of the communication method.

  In step S24, when it is assumed that the communication state estimation unit 15 has changed the communication method, the communication state estimation unit 15 estimates how the communication load of the surrounding vehicle changes. The communication load applied to surrounding vehicles changes depending on the distance between the vehicles, and the degree of change varies depending on the communication method. Therefore, the communication status estimation unit 15 estimates the communication load after changing the communication method (estimated communication load) based on the distance between the vehicles and the changed communication method.

  FIG. 6 is a diagram illustrating a process for estimating the communication load of the surrounding vehicle B when the vehicle A communicating with the communication method CP1 switches the communication method. An example of a communication status table currently held by the vehicle A is shown in the upper right part of FIG. Here, there are three communication systems, CP1 to CP3. Further, the distance in the table is calculated from the positions of the vehicles A and B.

The upper left part of FIG. 6 is a diagram schematically showing the relationship between the distance from the vehicle A and the amount of interference for each communication method. In the figure, the solid line represents the amount of interference of communication method CP1, the broken line represents communication method CP2, and the dotted line represents the amount of interference of communication method CP3. Since the relationship between the distance and the amount of interference is obtained approximately in advance for each communication method, it may be stored in the form of a lookup table or function. The relationship between the distance and the amount of interference varies depending on the surrounding terrain, the communication method, or the amount of communication at a close frequency, as well as the distance. Therefore, the amount of interference is estimated in consideration of the surrounding conditions. It is also preferable.

  In the above example, it is estimated that the vehicle A gives a communication load of 10% to the vehicle B by the communication method CP1, 4% by the communication method CP2, and 8% by the communication method CP3. The communication status estimation unit 15 adds the communication load amount to the communication load stored in the current communication status table to obtain an estimated communication load after changing the communication method. Since it is assumed that the vehicle A communicates with the communication method CP1, the communication load (10% in the above example) applied by the vehicle A to the vehicle B is determined as the communication method CP1. There is no need to add to the current communication load for CP1.

  Note that the estimation process in step S24 is not necessarily performed for all communication methods. What is necessary is to perform only the communication method that satisfies the communication requirements (for example, throughput, security, communication fee, etc.) required by the application program or the like.

  In step S26, the communication system change determination unit 16 determines whether or not the communication system needs to be changed based on the estimated communication load. Specifically, this determination can be performed as follows.

  First, the communication system change determination unit 16 obtains the maximum value of the estimated communication load of each vehicle for each communication system after the change when the communication system is changed. For example, when the estimated communication load as shown in FIG. 7 is obtained, 44% is obtained as the maximum communication load for the communication method CP1, 33% for the communication method CP2, and 59% for the communication method CP3. In FIG. 7, the communication method CP4 is not targeted because it does not satisfy the communication request.

  Next, the communication method change determination unit 16 determines whether there is a communication method CPk satisfying the following conditions among the communication methods CPk that satisfy the communication request conditions requested by the application program or the like.

(conditions)
Maximum value of estimated communication load of communication method CPk ≤ β x Maximum value of estimated communication load of communication method CP0

  Here, the communication method CP0 represents the communication method currently used by the vehicle 100 (the vehicle that is performing the determination process in step S26) (that is, the communication method before the change). The coefficient β is a real number that satisfies 0 <β <1. The coefficient β may be appropriately determined in consideration of the overhead required for changing the communication method. For example, a value of about 0.8 can be adopted as the coefficient β. The coefficient β may be a different value for each changed communication method, or may be the same value regardless of the changed communication method.

  If there is one or more communication methods that satisfy the above conditions, the communication method change determination unit 16 determines that the communication method needs to be changed (S26-YES), and the process proceeds to step S28. On the other hand, if there is no communication method that satisfies the above conditions, the communication method change determination unit 16 determines that there is no need to change the communication method (S26-NO), and repeats the processing from step S10.

In step S28, the communication system change determination unit 16 determines a communication system after the change from among communication systems that satisfy the above conditions. The determination algorithm when there are a plurality of communication methods that satisfy the condition may be arbitrary. For example, the communication method to be changed can be determined by the following method.
・ Randomly select a communication method that satisfies the above conditions ・ Select a communication method that satisfies the above conditions with the minimum estimated communication load ・ Select a communication method that satisfies the above conditions Select the one with the smallest (or largest) channel number

  In step S30, a notification to change the communication method is transmitted to surrounding vehicles. As described in relation to step S22, the vehicle that has received this notification suppresses the communication method change process for a predetermined period. That is, this notification has a function of notifying the change of the communication method in addition to the function as the notification of the change of the communication method.

  In step S32, the communication control unit 17 performs control so that communication is performed after changing to the communication method determined in step S28.

(Advantageous effects of this embodiment)
According to the present embodiment, efficient wireless communication using a communication method with a low communication load can be realized in a system composed of a plurality of vehicles (vehicle-mounted wireless communication devices). At this time, each vehicle can autonomously determine a communication method capable of performing efficient communication in consideration of not only the communication status of vehicles that can communicate directly but also the communication status of vehicles ahead of two hops (or more).

  Also, since changing the communication method involves overhead, it is desirable to set the change frequency appropriately. In the present embodiment, the change frequency can be set to an appropriate value by adjusting the value of the coefficient β in the communication method change necessity determination process or adjusting the execution timing of the determination process.

(Modification)
The above description is illustrative of the present invention and is not intended to limit the present invention. The present invention can be variously modified within the scope of its technical idea.

  In the above description, as an example of a communication method, a wireless communication standard such as LTE, 5 GHz band DSRC, 2.4 GHz band WiFi, 5.6 GHz band WiFi, and the like is cited. It is not limited to these. In addition, when a modulation rate and a use frequency band can be selected in one wireless communication standard, a different communication method can be used for each combination.

  In the above description, the communication method change is determined by paying attention to the communication load of the surrounding wireless communication devices, that is, the cost. However, in the application of the present invention, the communication method may be changed by paying attention to other elements. For example, it is also preferable to perform the communication system change determination in consideration of communication utility such as the communication throughput (communication amount per unit time) of the vehicle that performs the change determination.

  In the above description, in the communication status transmission step (S20), only the communication status of the host vehicle and the vehicle that can directly communicate with the host vehicle is transmitted, but N (N is an integer of 2 or more) from the host vehicle. You may make it transmit also the communication condition of the vehicle of a hop destination. In this way, it is possible to grasp the communication status of surrounding vehicles up to N + 1 hops ahead, and based on this, it is possible to determine whether to change the communication method.

In the above description, in the determination of whether or not the change determination timing has arrived (S22), if a change notification is received from a surrounding vehicle, the change determination process is not performed. However, even in this case, the change determination process may be performed, the communication method indicated in the change notification may be excluded from the change destination communication method, and the same process as described above may be performed. In this way, it is possible to prevent a plurality of vehicles from changing to the same communication method at the same time.

  In the above description, an example in which the present invention is applied to a vehicle network system including a vehicle equipped with a wireless communication device has been described. However, the present invention is a plurality of wireless communication devices that can support a plurality of communication methods. The present invention is applicable to a system including the wireless communication device.

100: Vehicle (on-vehicle wireless communication device)
11: Communication status measurement unit 12: Communication status reception unit 13: Communication status storage unit 14: Communication status transmission unit 15: Communication status estimation unit 16: Communication system change determination unit 17: Communication control unit

Claims (9)

A wireless communication method performed by dynamically determining a communication method performed by a first mobile wireless device,
A measurement step for measuring the communication load in a plurality of communication methods for each communication method;
A communication load for each of a plurality of communication methods measured by the second mobile radio apparatus from the second mobile radio apparatus and a plurality of communications measured by the third mobile radio apparatus received by the second mobile radio apparatus A reception step of receiving a communication load for each method;
The communication load for each of the plurality of communication schemes measured in the measurement step and the communication load for each of the plurality of communication schemes measured by the second mobile radio device received in the reception step with respect to surrounding mobile radio devices Sending step to send,
An estimation step of estimating an estimated communication load of the second and third mobile radio apparatuses for the communication system after the change, assuming that the first mobile radio apparatus has changed the communication system;
A determination step of determining whether to change the communication method used by the first mobile radio device for communication based on the estimated communication load, and determining the changed communication method when changing the communication method;
A wireless communication method comprising: The determination step further includes a notification step of transmitting a notification to that effect to surrounding mobile radio devices when it is determined to change the communication method,
If the notification is received from surrounding wireless communication devices, the communication method is not changed for a predetermined period.
The wireless communication method according to claim 1. In the determination step,
When the first mobile radio apparatus changes the communication method, the maximum value of the estimated communication load of the second and third mobile radio devices for the changed communication method is obtained,
The maximum value of the estimated communication load is equal to or less than a value obtained by multiplying the maximum value of the communication load of the second and third mobile radio apparatuses for the communication method before the change by a coefficient β (0 <β <1). If there is a communication method that satisfies the condition, determine the changed communication method from among the communication methods that satisfy the condition,
The wireless communication method according to claim 1 or 2. In the estimation step, a communication method in which the maximum value of the estimated communication load is minimum is determined as a communication method after change from among communication methods satisfying the condition.
The wireless communication method according to claim 3. In the estimation step, a communication method after change is randomly determined from communication methods that satisfy the condition.
The wireless communication method according to claim 3. When the communication load of the first mobile radio device or the maximum value of the communication load of the first, second, and third mobile radio devices is greater than or equal to a predetermined threshold for the currently used communication method, the estimation Executing the step and the determining step;
The wireless communication method according to claim 1. Performing the estimation step and the determination step at predetermined time intervals;
The wireless communication method according to claim 1.   The program for making a computer perform the radio | wireless communication method of any one of Claim 1 to 7. A wireless communication device that dynamically determines a communication method,
Measuring means for measuring the communication load in a plurality of communication methods for each communication method;
The communication load for each of the plurality of communication methods measured by the second mobile radio device and the third mobile radio device received by the second mobile radio device from the second mobile radio device which is another mobile radio device in the vicinity Receiving means for receiving a communication load for each of a plurality of communication methods measured by the mobile radio device;
The surrounding mobile radio apparatus includes a communication load for each of the plurality of communication schemes measured by the measurement unit and a communication load for each of the plurality of communication schemes measured by the second mobile radio apparatus received by the reception unit. A transmission means for transmitting to
When it is assumed that the communication system has been changed, an estimation means for estimating the estimated communication load of the second and third mobile radio apparatuses for the communication system after the change,
Whether to change the communication method used for communication based on the estimated communication load, and a determination unit that determines the changed communication method when changing the communication method;
A wireless communication device comprising:

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