JP6540439B2 - Wireless communication method and wireless communication device - Google Patents

Description

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

  When a wireless communication device mounted on a vehicle supports a plurality of wireless communication methods (3G, LTE, DSRC, WiFi, etc.), it is general to perform communication using the most efficient wireless communication method at that time It is

  Patent Document 1 discloses switching between vehicle-to-vehicle communication and road-to-vehicle communication according to availability of service. Moreover, patent document 2 discloses switching the antenna (a non-directional antenna, a directional antenna, etc.) to utilize based on the position of a vehicle, and communication whether communication is vehicle-to-vehicle communication or road-to-vehicle communication. Further, Patent Document 3 discloses that when another vehicle is present between the host vehicle and the roadside machine, the other vehicle is used as a relay vehicle to avoid shadowing.

JP, 2014-131236, A JP, 2011-191946, A JP, 2009-152700, A

  If each vehicle communicates with the roadside device using the most efficient wireless communication scheme at that time, the communication efficiency as viewed across the system of multiple vehicles is not maximized. This is because the roadside unit equally allocates bandwidth (for example, slots and carriers) to all the communicating vehicles, but vehicles far from the roadside unit can use only low-level modulation and coding schemes and throughput is low. It is.

  An object of the present invention is to improve the efficiency of wireless communication of the entire system in an environment where a plurality of vehicles communicate with each other using a plurality of wireless communication methods.

  In order to achieve the above object, according to a first aspect of the present invention, a communication method used by a vehicle and timing for performing communication are dynamically determined to perform wireless communication, and communication for the cost of communication is performed. Wireless communication is performed with timing and wireless communication system with high utility.

More specifically, the wireless communication method according to this aspect is
Estimating the position of the vehicle at multiple points in the future;
Acquiring, for each of a plurality of communication methods, the cost of communication and the utility of communication at the position of the vehicle at each of the plurality of future points in time;
Determining an optimal communication scheme, which is the communication scheme having the smallest ratio of the cost of communication to the utility of communication, for each of the plurality of future points in time;
Selecting a predetermined number in order from the one with the smallest ratio among the future optimal communication schemes at a plurality of points in time;
Communicating at the selected time using the optimal communication scheme at that time;
including.

  According to such a configuration, it is possible to perform communication using a communication method with the highest effect on the cost of communication, and therefore, it is possible to streamline communication in the entire system including a plurality of wireless communication devices.

  The position of the vehicle at future points in time can be determined from the expected travel path. For example, when the route to the destination is set in the navigation system, it is possible to estimate the future position of the vehicle from this route. In addition, even if the route is not explicitly set, if the travel route can be predicted from the user's past travel history or date and time, the future vehicle position can be estimated using this predicted travel route. it can. The positions of the vehicle at a plurality of future points in time divide the time into time steps at predetermined intervals, divide the road into road sections at predetermined distances, and identify the road section where the vehicle is located at each time step. It is good to specify by.

  The utility of communication of a certain wireless communication scheme may be determined based on, for example, the throughput when communicating using the wireless communication scheme or the amount of communication that can be performed in one time step. Here, when the required communication amount can be clearly understood, it is preferable to use a value obtained by normalizing the communication amount that can be performed in one time step with the necessary communication amount.

  The cost of communication of a certain wireless communication system may be determined based on, for example, communication overhead, communication cost (charge), and / or security strength of communication. Communication overhead may be determined based on the ratio of actual throughput to the maximum throughput of the wireless communication scheme.

  The utility and cost of communication can be determined based on the distance from the wireless base station of each wireless communication scheme. That is, a model (which may be a calculation formula or a table) in which the cost and utility of communication according to the distance from the wireless base station are associated with each other is stored in advance, and the position of the wireless base station The cost and utility of communication may be obtained by referring to the above-mentioned model using the distance between and the position of the vehicle at a future time. The position of the wireless base station may be stored in advance by the vehicle or may be acquired from an external device by wireless communication.

  Alternatively, the utility and cost of communication can be obtained by referring to a table storing communication costs and utilities for each location and for each wireless communication scheme. The table may be stored in advance by the vehicle, or may be acquired by wireless communication from another device. Also, even if the table itself is possessed by another device such as a server device, the vehicle makes an inquiry including position information to the server device to acquire the utility and cost of communication corresponding to the position. Good.

  The above table can be generated, for example, based on the actual communication history. If the cost and the utility of the communication when the vehicle performs communication are transmitted to the server device together with the position where the vehicle performs communication, and the server device generates the table based on the information acquired from the plurality of vehicles. Good. Also, the above table may be generated by a method such as simulation.

  In addition, this invention can also be grasped as a communication method which performs at least one part of the said process. The present invention can be understood as a wireless communication apparatus provided with means for performing at least a part of the above-mentioned processing. Also, the present invention can be regarded as a computer program for causing a computer to execute this method, or a computer readable storage medium storing this computer program non-temporarily. Each of the above means and processes can be combined with one another as much as possible to constitute the present invention.

  According to the present invention, in an environment in which a plurality of vehicles communicate with each other using a plurality of wireless communication methods, it is possible to improve the efficiency of wireless communication of the entire system.

BRIEF DESCRIPTION OF THE DRAWINGS The functional block diagram of the vehicle-mounted communication apparatus concerning embodiment. The flowchart of the radio | wireless communication method concerning embodiment. The example of the model which matches the throughput according to the distance from a wireless base station. The figure which illustrates the specific example which determines the area and radio | wireless communication system which perform radio | wireless communication by the radio | wireless communication method concerning embodiment.

  This embodiment is a wireless communication method suitable in a situation where it is necessary for a wireless communication device mounted on a vehicle to communicate data of a certain capacity within a predetermined time. For example, it is assumed that data such as map data, software (application program) or update information thereof is downloaded. Since such communication allows a certain degree of delay and there is no need to immediately start communication, communication at a time when communication efficiency is good can improve the communication efficiency of the entire system.

  The on-vehicle communication device 10 according to the present embodiment will be described. The in-vehicle communication device 10 is a wireless communication device mounted (provided or brought into) the vehicle 1 and capable of communication by a plurality of wireless communication methods. The in-vehicle communication device 10 includes a plurality of wireless communication units 16 corresponding to each of a plurality of wireless communication methods, or one wireless communication unit 16 compatible with a plurality of wireless communication methods. The in-vehicle communication device 10 also includes a central processing unit, a storage device such as a RAM or a ROM, an input / output device, a communication interface, etc., and the central processing unit executes a program to perform the functions shown in FIG. To realize. That is, the in-vehicle communication device 10 functions as a position estimation unit 11, a cost / utility acquisition unit 12, a base station position storage unit 13, a communication zone / communication method determination unit 14, and a communication control unit 15. Note that part or all of these functions may be realized by a dedicated hardware circuit.

  FIG. 2 is a flowchart showing the flow of processing when the on-vehicle communication device 10 performs wireless communication. The details of the wireless communication method of the in-vehicle communication device 10 in the present embodiment will be described below with reference to FIG.

  First, in step S1, the position estimation unit 11 specifies road sections S1 to Sn in which the vehicle 1 is located in time steps t1 to tn after the present. Specifically, the position estimation unit 11 acquires, for example, the planned traveling route set in the navigation device, and the road of the vehicle 1 at each time step t based on the planned traveling route and the predicted traveling speed. Section S is identified. In the present embodiment, the road section S has a predetermined distance (for example, 100 m), and each time step t is a predetermined time interval (for example, one second). It is desirable to set the road section S and the time step t so that the communication situation can be considered identical within one section and within one time step. In addition, how many seconds after the current road section should be specified, that is, the value of n should be determined based on the time to complete communication (allowable delay time), but a predetermined value is set as the upper limit value It is also good.

Next, the process of the following loop L1 is executed for each of the identified road sections S1 to Sn. Hereinafter, the variable i represents a road section to be processed. Note that road segment Si, since the position of the vehicle 1 at time step t _i, it can be said to represent the time step.

  In the loop L1, first, the processes of steps S2 and S3 are executed for each wireless communication method in the process of the loop L2. Hereinafter, the variable j represents a wireless communication method to be processed.

ここで、ｔｈ_ｉｊは道路区間Ｓ_ｉにおいて無線通信方式ｊを用いて通信をした場合のスループット（単位時間あたりの通信量）、Δｔは１タイムステップの時間、Ｂはアプリケーション等から要求される必要な通信量（例えば、ダウンロードする３次元地図データのデータ容量）を表す。すなわち、本実施形態においては、通信の効用ｕ_ｉｊは、道路区間Ｓ_ｉにおいて無線通信方式ｊを用いて通信できる通信量を、必要な（要求される）通信量で正規化した値である。 In step S2, the cost / utility acquisition unit 12 acquires the utility u _ij and the cost c _ij of the communication when the communication is performed using the wireless communication method j in the road section S _i . In the present embodiment, the utility u _ij of communication is defined by the following equation.

Here, th _ij is the throughput (the amount of communication per unit time) when communication is performed using the wireless communication method j in the road section S _i , Δt is the time of one time step, and B is required from the application etc. Communication amount (for example, data capacity of 3D map data to be downloaded). That is, in the present embodiment, the utility u _ij of communication is a value obtained by normalizing the amount of communication that can be communicated using the wireless communication method j in the road section S _i with the required (required) amount of communication.

ここで、ｔｈ_ｍａｘ ^ｊは、無線通信方式ｊにおいて可能な最大スループットを表す。定義から明らかなように、本実施形態においてはコストｃ_ｉｊは通信効率の補数であり、最大スループットで通信可能であればコストが小さく、オーバーヘッドが大きいほどコストが大きくなる。 Further, in the present embodiment, the cost c _ij is defined by the following equation.

Here, th _max ^j represents the maximum throughput possible in the wireless communication scheme j. As is clear from the definition, in the present embodiment, the cost c _ij is the complement of the communication efficiency, and the cost is smaller if communication is possible at the maximum throughput, and the cost is larger as the overhead is larger.

The utility u _ij and cost c _ij of communication can be determined based on the distance between the road section S _i and the position of the wireless base station of the wireless communication system j. For example, the cost / utility acquisition unit 12 may determine the utility and the utility with reference to a model (calculation formula or table) that defines the relationship between the distance from the wireless base station and the throughput as illustrated in FIG. In FIG. 3, models (solid line and dotted line) for two wireless communication methods are depicted. The position of the wireless base station may be stored in advance in the base station position storage unit 13 or may be obtained by wireless communication.

In step S3, the cost / utility acquisition unit 12 calculates the evaluation value r _ij of the wireless communication system j in the road section S _i . The evaluation value r _ij is a value that defines the efficiency of communication using the wireless communication system j based on the cost of communication c _ij and the utility u _ij . The evaluation value r _ij can be defined to take a larger value as the cost c _ij is smaller, and as the utility u _ij is larger, based on the communication cost c _ij and the utility u _ij . In the present embodiment, the evaluation value r _ij is defined by the ratio of the communication cost c _ij to the utility u _ij as expressed by the following equation.

By the processing of loop L2, costs c _ij , utilities u _ij and evaluation values r _ij for all the wireless communication methods j in the road section S _i are calculated. As mentioned above, since the road section S _i is the position of the vehicle 1 at the time step t _i , c _ij , u _ij and r _ij are the cost, utility and evaluation of the wireless communication system j at the time step t _i It can be said that it is a value.

In step S4, the communication section and communication method determination unit 14 determines, for the road section S _i , the wireless communication method j that minimizes the evaluation value r _ij . Hereinafter, it referred the wireless communication method with the optimum communication method M _i in road section S _i, also referred to as the minimum evaluation value r _i of the evaluated value of the optimum communication method M _i. Moreover, the utility and cost of the optimal communication method _{M i} in road section _{S i,} each represents a _{u i} and _{c i.}

The process of the loop L1, repeats the processing of steps S2 to S4, all the road sections S _i, the cost and utility of the optimal communication method M _i and the communication are calculated.

  The communication section / communication method determination unit 14 selects a predetermined number of minimum evaluation values in order from the optimum communication methods in each road section, and selects the optimum communication method selected in the selected road section (time step). It is determined that communication is to be performed by using (steps S5 to S9). Hereinafter, this process will be described more specifically.

In step S5, the communication section and communication method determination unit 14 initializes the variable U to zero. Then, in step S6, the communication section and communication mode determination unit 14 selects the smallest road segment S _k is the minimum evaluation value r _i of the road section S _i. In step S7, the communication path and communication scheme determining unit 14, the variable U, added utility _{u k} of the optimum communication method _{M k} in the road section _{S k.}

  In step S8, the communication section and communication method determination unit 14 determines whether the variable U is equal to or greater than a threshold. One can be used as the threshold. The utility is the ratio of the communicable amount of traffic in the road section to the necessary amount of traffic, so that if the sum of the utility is 1 or more, the necessary communications can be performed. That is, the section (timing) in which communication is performed can be made the requested amount of communication the smallest possible number of communication. However, in consideration of safety, the threshold may be a value larger than 1, for example, 1.2.

In the case the variable U is less than the threshold (S8-NO), the process returns to step S6, by selecting the smallest road segment minimum evaluation value r _i from the road section that is not selected, the above processing is repeated. If the variable U is equal to or greater than the threshold (S8-YES), the process proceeds to step S9.

  In step S9, the communication section / communication method determination unit 14 determines that communication will be performed using the optimal communication method in the road section selected in the above process. Specifically, the communication control unit 15 determines whether or not the vehicle 1 has reached the selected road section, and when the vehicle 1 has reached, communication is performed using the optimal communication method in the road section. , And the wireless communication unit 16.

  The above process will be specifically described with reference to FIGS. 4 (A) to 4 (C). In the examples of FIGS. 4A to 4C, in order to simplify the description, it is assumed that two types of wireless communication methods can be used. In addition, four road sections S1 to S4 are targeted in consideration of up to four time steps.

FIG. 4A shows an example of utility u _ij and cost c _ij in each of the road section S _i and the wireless communication system j. In the figure, the value on the left is the utility, and the value on the right is the cost. For example, the utility u ₁₁ of the wireless communication method 1 in the road section S1 is 0.1, and the cost c ₁₁ is 0.5.

In such circumstances, the optimum communication method M _i for each road section S _i is determined as enclosed manner by the dotted rectangle in FIG. 4 (B) (step S4). For example, in the road section S2, the evaluation value of the wireless communication system 1 is 6 (= 0.6 / 0.1), and the evaluation value of the wireless communication system 2 is 0.25 (= 0.2 / 0.8) Because of this, the wireless communication method 2 with the smallest evaluation value is selected as the optimum communication method.

Minimum evaluation value of the optimum communication method _{M i} for each road section _{S i,} as shown outside the dotted line box in FIG. 4 (B), M1 is 5, M2 is 0.25, M3 is 0.375, M4 is eight. Here, when selecting from the wireless communication system having the smallest minimum evaluation value, first, the optimal communication system M2 (the optimal wireless communication system in the road section S2 = the wireless communication system 2) is selected. At this time, since the total of the utilities is 0.8 and not more than the threshold (here, 1), the next optimum communication scheme is selected. The smallest evaluation value is the second smallest because it is the optimum communication method M3 (the optimum wireless communication method in the road section S3 = the wireless communication method 2), so this is selected. Here, since the total of the utilities becomes 1.6 and becomes equal to or more than the threshold, the selection processing is ended.

  As described above, in the situation shown in FIG. 4A, it is determined that communication is performed using the wireless communication method 2 in the road section S2 and the wireless communication method 2 in the road section S3. In this example, the road sections to be selected are continuous, and there is no switching to the wireless communication method. However, as is clear from the selection method described above, the road sections to be communicated need to be always continuous. Alternatively, when communication is performed in continuous road sections, the wireless communication scheme may be switched for each road section.

  It is preferable to periodically and repeatedly execute the determination process of the road section and the wireless communication system in which the communication shown in FIG. 2 is performed. This is because the optimal communication method may change in accordance with the change in situation.

  According to the present embodiment, it is possible to perform communication using an appropriate wireless communication method at an appropriate timing in consideration of the utility and cost of communication, and therefore, when individual wireless communication devices perform communication in a best effort manner Communication efficiency of the whole system is improved more than that. Further, since the above-described processing is processing performed by each wireless communication device in an autonomous distributed manner, communication efficiency of the entire system can be improved without cooperation among the wireless communication devices in the system.

<Modification>
The above description exemplifies the present invention, and does not limit the present invention. The present invention can be variously modified within the scope of the technical idea.

  In the above description, although the cost and utility of communication are calculated according to the distance from the radio base station as shown in FIG. 3, the method of determining the cost and utility of communication is not limited to this. For example, since the throughput of communication changes depending on the number of vehicles performing communication, reference is made to a model (calculation formula or table) in which the distance from the wireless base station and the density of vehicles in the periphery are associated with the cost and utility of communication. You may decide. The number of vehicles in the vicinity may be determined from the vehicle identifier included in the received radio signal. In addition, it is preferable to calculate the cost and utility of communication in consideration of parameters related to the surrounding conditions other than the distance from the radio base station and the vehicle density.

Further, the in-vehicle communication device 10 may obtain the communication cost and the utility by referring to the table storing the communication cost and the utility for each position and each wireless communication method. A table storing communication cost and utility of each position and each wireless communication scheme may be generated based on, for example, an actual communication history, or may be generated based on a simulation. When the table is generated based on the actual communication history, it is preferable to transmit, to the server device, information related to the position, the wireless communication method, the cost, and the utility when the in-vehicle communication device 10 actually performs communication. . This transmission does not have to be performed in real time, and may be collectively transmitted at an appropriate timing. The server device can generate the table based on communication history information transmitted from a number of vehicles. The information generated by the server device may be appropriately transmitted to the in-vehicle communication device 10, or the server device may communicate with the communication cost and utility in response to an inquiry from the in-vehicle communication device 10 without transmitting to the in-vehicle communication device 10. It may be acquired based on the table and notified to the in-vehicle communication device 10. In the case of creating the table, it is also preferable to define the communication cost and utility not only for the position but also for the number of vehicles in the vicinity and other surrounding conditions.

  The utility and costs of communication are not limited to those described above. For example, the utility of communication may be any indicator that indicates the benefit or satisfaction to the user or application. For example, a value related to the time required for communication can also be adopted as a utility of communication. In addition, any cost may be adopted as long as it is an index that it is desirable to minimize. For example, values related to the bandwidth to be used, the cost for communication, the security cost, etc. can be adopted as the cost. Also, a value obtained by combining a plurality of factors such as these and communication overhead can be adopted as the cost.

  In the above embodiment, the road has been described as being divided into road sections of a predetermined distance in advance, but without defining the road sections in advance, the sections that start and end the position at the start time and end time of the time step It may be determined as a road section corresponding to the time step.

10: in-vehicle communication device 11: position estimation unit 12: cost / utility acquisition unit 13: base station position storage unit 14: communication section / communication method determination unit 15: communication control unit 16: wireless communication unit

Claims (10)

A wireless communication method of a vehicle, wherein a communication method to be used and a timing of performing communication are dynamically determined.
Estimating the position of the vehicle at multiple points in the future;
Acquiring, for each of a plurality of communication methods, the cost of communication and the utility of communication at the position of the vehicle at each of the plurality of future points in time;
Determining an optimal communication scheme, which is the communication scheme having the smallest ratio of the cost of communication to the utility of communication, for each of the plurality of future points in time;
Selecting a predetermined number in order from the one with the smallest ratio among the future optimal communication schemes at a plurality of points in time;
Communicating at the selected time using the optimal communication scheme at that time;
Wireless communication method, including: The predetermined number is a minimum number capable of communicating the requested amount of communication,
The wireless communication method according to claim 1. The utility of communication of the communication scheme is determined based on the amount of communication that can be performed using the communication scheme at each point in time,
A wireless communication method according to claim 1 or 2. The cost of communication of the communication system is determined based on at least one of communication overhead, communication costs, and security strength of communication.
The wireless communication method according to any one of claims 1 to 3. The cost of communication of the communication scheme is determined based on the throughput of the communication scheme for the maximum throughput achievable with the plurality of communication schemes.
The wireless communication method according to any one of claims 1 to 3. The step of obtaining the cost and utility of communication is
Acquiring the position of the radio base station of each communication scheme;
Obtaining a cost and utility of communication at a future point in time of the vehicle with reference to a model in which the distance from the wireless base station is associated with the cost and utility of communication for each wireless communication system;
The wireless communication method according to any one of claims 1 to 5, comprising: The step of obtaining the cost and utility of communication is
Obtaining a cost and utility of communication at a future point in time of the vehicle with reference to a table storing the cost and utility of communication for each position and communication system;
The wireless communication method according to any one of claims 1 to 5, comprising: The method further includes the step of transmitting to the server apparatus the cost and utility of communication when the vehicle performs communication, and the position where the vehicle has performed communication.
The table is generated by the server device based on information transmitted from a plurality of vehicles.
The wireless communication method according to claim 7.   A program for causing a computer to execute the steps of the method according to any one of claims 1 to 8. A wireless communication apparatus, which dynamically determines and performs a communication method to be used and timing to perform communication,
Position estimation means for estimating the position of the wireless communication device at a plurality of future times;
Cost / utility acquisition means for acquiring, for each of a plurality of communication methods, the cost of communication and the utility of communication at the position of the wireless communication device at each of the plurality of future points in time;
For each of the plurality of future points in time, the optimal communication method, which is the communication method with the smallest ratio of the cost of communication to the utility of communication, is determined, and the ratio is small among the optimum communication methods of the plurality of future points Determining means for selecting a predetermined number of items in order from the ones and determining that communication will be performed using the optimal communication scheme at that time at the selected time;
Wireless communication device comprising:

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