JP5482822B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication technology, and more particularly, to a wireless communication technology that determines an appropriate communication method in consideration of both peripheral conditions and application requirements.

  In order to increase the frequency use efficiency, research on cognitive radio in which the radio communication device adaptively changes the frequency and radio scheme used for radio communication by recognizing and recognizing the surrounding radio wave environment is underway. In cognitive radio, a mode is considered in which a radio communication device detects and uses a vacant frequency autonomously and actively (Patent Document 1).

  However, there is no existing research on which part of the detected vacant frequency (white space) is used.

  In addition, when a wireless communication device moves at a high speed such as a vehicle wireless network, the radio wave environment changes greatly. Therefore, even when the same frequency and radio system are used, it is necessary to adaptively change communication parameters and the like in order to maintain communication performance. Although it is known that wireless communication performance is highly dependent on the surrounding situation (context), existing research is only able to adaptively change a small number of communication parameters based on limited information about the surrounding situation. not exist.

JP 2010-136291 A

  As the number of sensors mounted on the vehicle increases, more information about the surrounding situation can be obtained. However, the prior art as described above can only optimize limited communication parameters, and lacks scalability for optimizing more communication parameters.

  An object of the present invention is to provide a technique for selecting an appropriate communication parameter according to the surrounding situation of a wireless communication device.

  The wireless communication apparatus of the present invention changes the communication parameter to be used according to the surrounding situation with the following configuration. That is, the wireless communication device of the present invention has a peripheral situation of the first and second wireless communication devices when performing communication between the first and second wireless communication devices using a predetermined communication parameter, A learning database that associates and stores communication parameters and communication performance in the communication, a plurality of sensors, a surrounding state determination unit that determines a surrounding state of the device from information obtained from the plurality of sensors, a communication partner Communication partner peripheral status acquisition means for acquiring the peripheral status from the wireless communication device and communication parameter determination for determining appropriate communication parameter candidates in the peripheral status of the own device and the peripheral status of the communication partner with reference to the learning database And wireless communication means for performing communication using the communication parameter determined by the communication parameter determination means.

The learning database stores the peripheral conditions of the transmission source and transmission destination wireless communication devices, communication parameters used for communication, and communication performance at that time. The learning data stored in the learning database may be generated based on communication actually performed by the own device, or may be generated based on communication performed by other wireless communication devices. It does not matter. Further, the learning data may be generated from the result of simulation instead of the communication actually performed.

  By adopting such a learning database, communication performance can be derived from the surrounding situation of the transmission source, the surrounding situation of the transmission destination, and the communication parameters. That is, if the peripheral conditions of the transmission source and the transmission destination are known, it is possible to determine a communication parameter that can improve the communication performance. In the present invention, in particular, since appropriate communication parameters are determined in consideration of the surrounding conditions of the wireless communication devices at both ends for communication, it is more than the case of considering only the surrounding conditions of one of the wireless communication devices. More appropriate communication parameters can be determined.

  It can be said that it is preferable to finally determine what communication parameter should be adopted according to a request of an application that performs communication. Therefore, in the present invention, the communication parameter determining means determines communication parameter candidates suitable for the surrounding conditions of the own device and the communication partner, and uses communication among these candidates based on the requirements required for communication. It is preferable to determine the parameters.

  It should be noted that the “communication partner” wireless communication device from which the peripheral state should be acquired is not necessarily a single wireless communication device. For example, in the case of performing broadcast or multicast communication with a plurality of wireless communication devices, there are a plurality of “communication partner” wireless communication devices. However, even in such a case, it is not necessary to acquire the peripheral conditions of all the communication partners, and the communication parameters may be determined only from the peripheral conditions of some communication partners.

In the present invention, the communication parameter may be one or more parameters for each of the transport layer, network layer, data link layer, and physical layer. And a communication parameter determination means determines the suitable candidate according to the surrounding condition about each of these parameters. Examples of communication parameters include protocol selection (connection orientation) and congestion window value (congestion window) in the transport layer. In the network layer, a communication connection form, a routing method, a routing metric, and the like can be given. In the data link layer, contention window value, selection of MAC system (CSMA, TDMA, FDMA, etc.) and the like can be mentioned. In the physical layer, a modulation and coding scheme, a MIMO scheme, a bandwidth, a use frequency, a transmission rate, a transmission power, and the like can be given. However, the communication parameters to be adjusted in the present invention may be arbitrary, and other communication parameters may be changed according to the surrounding situation. In addition, the communication parameters for some layers may be changed without changing the communication parameters for all layers of the transport layer, the network layer, the data link layer, and the physical layer.

  The wireless communication device according to the present invention can be an in-vehicle wireless communication device mounted on a vehicle. Here, the in-vehicle wireless communication device means not only a wireless communication device installed in a vehicle, but also a wireless communication device that can be carried in the vehicle, and information from the plurality of sensors for determining the surrounding situation. It also includes a wireless communication device that can acquire. For example, it includes a wireless communication device that can connect to an in-vehicle network by wired connection or wireless connection and acquire information from various sensors of the vehicle.

In the present invention, it is preferable to use at least one of the position / speed / acceleration of the vehicle and the number of surrounding vehicles as sensor information for determining the surrounding situation. The position of the vehicle can be obtained from the GPS device. Further, the position information obtained from the GPS device may be corrected by matching the information obtained from the gyroscope or the vehicle speed sensor with the map information. The location information not only indicates latitude / longitude information, but also indicates whether it is an urban area, suburb area, or rural area, or an expressway, a national road, or a general road. May be. Such information can be obtained by combining GPS information and map information. The speed and acceleration of the vehicle can be obtained from a speed sensor or an acceleration sensor. The number of surrounding vehicles can be obtained by wireless communication means or an in-vehicle camera. For example, when each vehicle periodically communicates, the number of surrounding vehicles can be grasped by receiving the communication. Further, the number of surrounding vehicles may be acquired by performing image processing on an image obtained from an in-vehicle camera of the own vehicle. Furthermore, when the roadside device knows the number of vehicles by a camera or the like and notifies by wireless communication, the number of surrounding vehicles can also be grasped by receiving the notification. Incidentally, as the sensor information, other than the above information, the distance between the periphery of the vehicle and obstacles, the presence or absence of rain, the brightness Sana etc. Various information can be used to determine surrounding conditions.

  Further, in the present invention, history information storage means for associating and storing communication parameters and performance of communication performed by the wireless communication means as history information in association with the current surrounding state of the own device and the surrounding state of the communication partner Preferably, the apparatus further comprises history information transmission means for transmitting history information stored in the history information storage means to a server device.

  Further, in the present invention, history information storage means for associating and storing communication parameters and performance of communication performed by the wireless communication means as history information in association with the current surrounding state of the own device and the surrounding state of the communication partner Preferably, the apparatus further comprises history information transmitting means for transmitting history information stored in the history information storage means to a server apparatus, and history information communication means for receiving history information stored in the server apparatus.

  As described above, the communication parameters actually used by the wireless communication device and the communication performance at that time are stored in association with each other, stored in the server device, and distributed to other wireless communication devices, thereby collecting and storing history information. Thus, appropriate communication parameters can be determined with high accuracy.

  The present invention can be understood as a wireless communication apparatus having at least a part of the above means. The present invention can also be understood as a wireless communication method for executing the above processing or a program for realizing the method. 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, it is possible to select an appropriate communication parameter according to the surrounding situation of the wireless communication device.

It is a block diagram which shows the function structure of the radio | wireless communication apparatus concerning 1st Embodiment. It is a figure explaining the acquisition method of history data in a 1st embodiment. It is a figure explaining selection of a communication parameter candidate in a 1st embodiment. It is a figure explaining selection of a communication parameter candidate in a 1st embodiment. It is a flowchart which shows the creation process of the history database in 1st Embodiment. It is a flowchart which shows the determination process of the communication parameter in 1st Embodiment. It is a flowchart which shows the preparation process of the classifier in 2nd Embodiment. It is a figure which shows the example of the classifier (decision tree) produced in 2nd Embodiment.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
The wireless communication apparatus according to the present embodiment determines a surrounding situation (context) from sensor information, selects an appropriate communication parameter corresponding to the context, and performs communication. In the present embodiment, an in-vehicle wireless communication device mounted on a vehicle will be described as an example. However, the present invention is not limited to the in-vehicle wireless communication device, and may be implemented as a wireless communication device mounted on an arbitrary mobile body, a wireless communication device that can be carried by humans, or a fixed wireless communication device. Absent.

<Constitution>
FIG. 1 is a schematic diagram illustrating a functional configuration of a wireless communication apparatus according to the present embodiment. The wireless communication device 1 includes a plurality of sensors 2, a sensor information collection unit 3, another vehicle information collection unit 12, a map information storage unit 4, a history database 5, a context determination unit 6, a communication parameter candidate determination unit 7, an application program 8, A communication control unit 9, a wireless communication unit 10, and a history data transmission / reception unit 11 are included. Note that each functional unit such as the sensor information collection unit 3, the context determination unit 6, the communication parameter candidate determination unit 7, and the communication control unit 9 is, for example, an FPGA (Field Programmable Gate Array).
However, it may be mounted as an ASIC (Application Specified Integrated Circuit) or MPU (Micro Processor Unit).

The sensor 2 is a sensor for collecting information regarding the vehicle itself on which the wireless communication device 1 is mounted and the environment in which the vehicle is placed. For example, the sensor 2 includes GPS (Global
Positioning System) device, a speed sensor, an acceleration sensor, a steering angle sensor, a brake sensor, a millimeter wave radar, laser radar, an ultrasonic sensor, an external camera, an infrared camera, rain sensor, include etc. brightness sensor. The current position of the vehicle (latitude, longitude, altitude) can be determined by the GPS device, and combined with map information, the nature of the current location (by city / suburb / region, by highway / national / general road, etc.) ). The millimeter wave radar, laser radar, and ultrasonic sensor can grasp distances to other vehicles and other objects. The distance to other vehicles and other objects can also be grasped by an external camera, and the number of surrounding vehicles can also be acquired. The infrared sensor is used to detect surrounding objects at night or the like. The rain detection sensor may be a so-called rain sensor or a sensor that detects on / off of the wiper. The lightness sensor may also be a sensor provided with a light receiving element, but may also be a sensor that detects on / off of the light.

  Further, the sensor 2 can include wireless communication means. For example, various types of information transmitted from a roadside machine, for example, information on traffic jams or information on weather may be received. In addition, it is conceivable that the roadside device acquires the traffic volume (number of vehicles), the average moving speed, and the like with a camera, a vehicle speed sensor, and the like, and notifies the vehicle wirelessly. In addition, when each vehicle (on-vehicle wireless communication device) periodically transmits information, the wireless communication means of the wireless communication device 1 may receive this communication to grasp the number of vehicles existing around. it can.

  The sensor information collection unit 3 collects sensor information from the plurality of sensors 2 and transmits it to the context determination unit 6.

  In addition, the sensor information collected by the sensor information collecting unit 3 is broadcast to surrounding vehicles by inter-vehicle communication. This broadcast can be made periodically (eg, once every 100 milliseconds).

  The other vehicle information collection unit 12 receives sensor information transmitted from another vehicle and transmits it to the context determination unit 6. As described above, the sensor information collected by each vehicle is broadcast and received by surrounding vehicles, so that each vehicle can acquire the sensor information measured by the surrounding vehicles.

  In this specification, the term “sensor information” is used in the sense of “combination of a plurality of sensor information” to simplify the description. However, this is not the case when it is specified that individual sensor information is expressed, or when it is clear from the context that individual sensor information is expressed. The “sensor information” includes not only information measured by the sensor of the host vehicle but also information measured by a sensor of another vehicle.

  The map information storage unit 4 stores map information including information such as roads and buildings. The map information may store information such as the nature of each place, for example, the amount of traffic, the average moving speed, the amount of wireless communication, the frequency usage status, and the like. In addition, some categories such as urban areas, suburban areas, and rural areas may be set as appropriate, and information regarding which category corresponds to each place may be stored.

  The history database 5 stores contexts, communication parameters, and communication performance in association with each other. Specifically, the communication performance when communication is performed using a certain communication parameter in a certain context is stored. Although the “history” database is named, it is not necessary to store the communication performance of the actually performed communication. For example, a value obtained by performing statistical processing on the communication performance of actually performed communication may be stored. In addition, communication performance obtained by simulation or the like without performing actual communication may be stored.

  There are several methods for obtaining data for creating the history database 5 (hereinafter referred to as history data). As shown in FIG. 2A, the first method is a method of generating history data based on communication performed by itself and storing it in the history database 5. The wireless communication device 100 can obtain the surrounding situation around the own device from the sensor 2 of the own device. The surrounding situation around the wireless communication device 200 of the communication partner can be acquired by the sensor of the communication partner 200 and can be acquired by communication. Communication parameters and communication performance can be acquired by the wireless communication apparatus 100. Therefore, the wireless communication device 100 can generate the history data 101 and store it in the history database 5.

  In the second method, as shown in the lower left of FIG. 2B, data generated based on communication performed between the other wireless communication devices 210 and 220 is directly transmitted from the wireless communication device 210 or 220 via wireless communication. Or it is the method of acquiring via the server apparatus 230. As described above, the wireless communication devices 210 and 220 can create the data 215 related to the peripheral status, communication parameters, and communication performance related to the communication between the wireless communication devices 210 and 220. The wireless communication device 210 or 220 transmits the history data 215 to the wireless communication device 100 by wireless communication, and the wireless communication device 100 stores the history data in the history database 5. The wireless communication device 210 or 220 may transmit to the server device 230, and the server device 230 may accumulate history data from a plurality of wireless communication devices and distribute the history data to the wireless communication device 100.

As shown in the lower right of FIG. 2B, the third method performs a simulation when communication is performed using arbitrary communication parameters between vehicles placed in an arbitrary surrounding situation using the computer 300. The communication performance is calculated. Therefore, the computer 300 can acquire the relationship among the surrounding situation, communication parameters, and communication performance when wireless communication is executed. The computer 300 transmits these data to the wireless communication apparatus 100 by wireless communication or other methods, and the wireless communication apparatus 100 stores the history data in the history database 5. Although not shown, history data may be distributed to the wireless communication device 100 via the server device in the same manner as described above.

  In order to achieve the purpose of determining communication parameters according to the context, it is only necessary to store the communication performance when communication is performed with specific communication parameters for each context, and the history information itself is not necessarily required. Need not be stored. That is, it can be said that it is sufficient if a learning result based on history information is stored. However, in this embodiment, since the purpose is to perform further learning by measuring the communication performance of the wireless communication even during operation, the history information is stored in the history database 5. Thus, the history database 5 in this embodiment serves as both a learning database and history information storage means in the present invention.

Here, any communication performance can be used as long as it is an index representing communication performance. For example, throughput, round trip time (RTT), signal noise ratio (SNR: Signal) to Noise Ratio), bit error rate (BER), packet error rate (PER), etc. can be employed.

  Note that various methods are conceivable as to how the “context” is defined.

  One method is to use a combination of acquired sensor information as one context. In other words, when there are N sensors in each of the transmission / reception vehicles, a context is defined by a combination of 2N values. In this method, the context and the sensor information are identified, and the implementation is simple. Moreover, since the raw data is used without being processed, the history information can be effectively used. However, since a lot of history data must be held, a large amount of storage capacity is required.

  Another way is for the designer to define a context based on some sensor information. As a simple example, on the basis of the number of surrounding vehicles (many / small) and the moving speed (fast / slow) of the vehicle, four situations are assumed for each of the transmission / reception vehicles, and a total of 16 combinations of these are assumed. It is possible to define the context of. Of course, not only two pieces of sensor information but also more pieces of sensor information may be used, and each piece of sensor information may be divided into more stages. This method is advantageous in that the number of context types can be set to an appropriate number. However, if the context definition is not appropriate, it may not be possible to select an optimal communication parameter.

  As yet another method, a method of automatically setting a context definition based on collected sensor information and communication performance is conceivable. The distance (similarity) between the sensor information can be defined by introducing an appropriate distance measure for the sensor information (combination of a plurality of sensor information). Similarly, the distance (similarity) between the communication performances can be defined by introducing an appropriate distance measure for the communication performances. In this method, similar sensor information that can provide similar communication performance when communicating using the same communication parameters is regarded as the same context. What level of similarity is required to determine the same context may be appropriately designed according to the required accuracy. Even if communication is performed using the same communication parameters under the same environment (sensor information), the communication performance varies. Therefore, as history collection progresses, it may happen that the contexts that have been determined to be the same are determined to be different contexts, or vice versa. Although this processing method increases the amount of computation, it can be said that the context can be defined more appropriately.

Note that the context need not be exclusive. That is, a context may be defined so that one situation belongs to a plurality of contexts. Therefore, the number of surrounding vehicles (many / small), position (urban / suburban / regional), road shape (straight / curve, multi-lane / narrow), traffic jam (smooth / traffic), vehicle driving status (high speed / Low speed, acceleration / deceleration), date and time (time zone, date, day of the week, season), etc. can be defined as one context.

  The history database 5 stores the context, communication parameters, and communication performance regarding the communication performed by the wireless communication device 1. The history data stored in the history database 5 is preferably transmitted to the center server when the wireless communication environment is good. Conversely, it is also preferable to obtain history data from the center server. In particular, when information about a certain context is not stored in the history database 5, it is preferable to inquire the center server and acquire communication parameter and communication performance information about the context.

  Based on the sensor information acquired via the sensor information collection unit 2, the context determination unit 6 determines the surrounding situation (context) in which the device itself and the communication partner device are currently placed. With reference to the context definition method described above, the method for determining the context from the sensor information will be apparent.

  As shown in FIG. 3, the communication parameter candidate determination unit 7 uses the peripheral situation (context) where the own device is placed and the peripheral situation (context) where the communication partner device is placed, to store the history database 5. Referring to some of the preferred communication parameter candidates in the current context. Note that it is preferable to adaptively select one or more communication parameters for each of a plurality of protocol layers (transport layer, network layer, data link layer, physical layer). Here, the communication parameter candidate determining unit 7 excludes communication parameters that are not preferable in the current context rather than determining the optimal communication parameters in the current context, so that the best selection is included. Determine parameter candidates. It should be noted that how many values are selected as candidates for one communication parameter may be appropriately designed.

  An example of an unfavorable communication parameter is a high transmission rate (high modulation multi-value number) in an urban area. This is because in urban areas, the influence of multipath becomes large, and communication becomes impossible if the modulation multi-level number is too large. Therefore, in the context of urban areas, the communication parameter candidate determination unit 7 selects, as candidates, communication parameters with the modulation multi-level number (transmission rate) excluding the highest order (for example, 64QAM).

  In a context where the number of surrounding vehicles is large, strong transmission power is not preferable because it causes interference. Conversely, in a context where the number of surrounding vehicles is small, weak transmission power is not preferable because communication is unlikely to be established.

  Such a determination is preferably made in consideration of the situation of both the host vehicle and the communication partner. For example, there may be a case where the number of vehicles around the host vehicle is small but the number of vehicles around the communication partner vehicle is large. In this case, the communication capacity (or communication frequency) can be increased only from the surrounding situation of the own vehicle, but it is preferable to suppress the communication capacity in consideration of the situation where the communication partner vehicle is placed. Therefore, when either the own device or the communication partner device has a large number of surrounding vehicles, it is conceivable to suppress the communication capacity. In this way, if any one of the devices is present, it is conceivable to employ a specific communication parameter. It is also possible to determine that a specific communication parameter is adopted when both the own apparatus and the communication partner are in a specific situation.

  The communication parameter candidate determination unit 7 excludes an unfavorable selection for one or more parameters for each protocol stack. As shown in FIG. 4, a combination of communication parameters from which undesirable communication parameters are removed for each protocol stack is determined and notified to the communication control unit 9.

  The application program 8 notifies the communication control unit 9 of QoS (Quality of Service) related to wireless communication. For example, in the case of an application related to vehicle safety, it is necessary to perform reliable communication with low delay even if throughput is low. Conversely, if the application sends entertainment information, it is preferable to perform communication with high throughput even if reliability is low. The application program 8 notifies the communication control unit 9 of such an application request.

  The communication control unit 9 determines an appropriate communication parameter from the communication parameter candidates sent from the communication parameter candidate determination unit 7 in response to a request from the application program 8. This selection can be implemented using conventional adaptive protocol techniques. At this time, obviously unfavorable communication parameters are excluded from the candidates, and communication performance is improved by performing communication using the determined communication parameters.

  Note that the communication control unit 9 measures the communication performance as a result of communication using the determined communication parameter. The communication parameters used for communication and the context at that time are stored in the history database 5.

<processing>
[History data collection processing]
First, a method of creating the history database 5 (learning process) will be described. 5A and 5B are flowcharts showing examples of a method of creating the history database 5, respectively.

  FIG. 5A shows a method of creating the history database 5 when a context definition is given in advance. First, the current sensor information of the host vehicle is acquired from the plurality of sensors 2, and the current sensor information of the other vehicle is acquired from the other vehicle information collection unit 12 (S301). Further, communication parameters used for wireless communication and communication performance when communication is performed using the communication parameters are acquired (S302). The sensor information, communication parameters, and communication performance preferably use information when the wireless communication apparatus 1 is actually operated, but these information may be acquired by computer simulation.

  The current context is determined according to a predetermined definition from the sensor information of the host vehicle and other vehicles acquired in this way (S303). When the current context is thus determined from the sensor information, the context, communication parameters, and communication performance are stored in association with the history database 5 (S304). In this way, by accumulating communication performance for various contexts and various communication parameters, it becomes possible to grasp the communication performance when using any communication parameter in any context.

  FIG. 5B shows a method of creating the history database 5 when the context definition itself is also changed according to the measurement result. First, the current sensor information of the own vehicle is acquired from the plurality of sensors 2, and the current sensor information of the other vehicle is acquired from the other vehicle information collection unit 12 (S311). Also, parameters used for wireless communication and communication performance when communication is performed using the communication parameters are acquired (S312). Then, the acquired sensor information, communication parameters, and communication performance are associated with each other and stored in the history database 5 (S313).

  Next, based on the similarity of the sensor information and the similarity of the communication performance, similar sensor information that can obtain similar communication performance when communicating using the same communication parameters is determined to be the same context. (S314). The similarity between sensor information and communication performance can be defined by introducing an appropriate distance measure into the information. Specifically, the context can be determined by determining the discrimination parameter of the discriminator by machine learning such as a neural network, a support vector machine (SVM), or a Bayesian filter. It is also possible to obtain a decision tree by machine learning and determine the context using the obtained decision tree.

  When the definition of the context is determined, the correspondence between the communication parameter and the communication performance is stored for each context (S315). Here, as the communication performance, a value obtained by actual communication may be used as it is, but it is also preferable to use a value obtained by performing statistical processing such as average or variance.

[Communication parameter decision processing]
Next, communication parameter determination processing will be described with reference to the flowchart of FIG. First, the sensor information collection unit 3 acquires sensor information from a plurality of sensors 2 (S401), and the context determination unit 6 determines the current context based on the acquired sensor information (S402). The communication parameter candidate determination unit 7 refers to the history database 5 and determines an appropriate communication parameter candidate in the current context (S403). This process is performed by excluding communication parameters with poor communication performance and leaving candidates with excellent communication performance.

  If the communication performance for each communication parameter in the current context is not stored in the history database 5, the communication performance in the current context may be acquired from the center server via the history data transmission / reception unit 11. good.

  The communication control unit 9 acquires the performance required for communication from the application program 8 (S404), and determines a combination of communication parameters suitable for the application request from the candidates selected in step S403 (S405). The communication control unit 9 performs wireless communication using the determined communication parameter (S406).

  In order to update the history database 5 based on the communication actually performed, the communication control unit 9 measures the communication performance and stores it in the history database 5 together with the current context and the communication parameters used for the communication ( S407). The details of this processing can be equivalent to the processing in FIGS. 5A and 5B, and thus detailed description thereof is omitted here.

<Operation example>
A specific example of the process of adaptively changing the communication parameter based on the context will be described below. In the present embodiment, the communication protocol is selected without replacing the existing protocol stack.

First, communication parameter selection in the physical layer and data link layer based on SNR measurement values will be described. A technique for adapting a transmission rate, a modulation scheme, a coding scheme, and the like based on SNR measurement values is known. In this embodiment, selectable modulation schemes and encoding schemes are limited according to the current context, and the adaptive protocol is an appropriate modulation scheme and encoding scheme based on SNR measurement values from a limited combination. Select. For example, in urban areas, it is known that even if the SNR measurement value is high, high communication performance cannot be obtained when a high-order modulation / coding scheme is employed. Therefore, in the context that at least one of the own device or the communication partner device is located in an urban area, communication parameters other than higher-order modulation / coding schemes are passed as candidates to the communication control unit, and the communication control unit receives them. A modulation / coding scheme is selected from the candidates. By doing so, it is possible to avoid higher-order modulation / coding schemes in urban areas and improve communication performance in the context of urban areas.

Next, processing for adapting the contention window value in CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) according to the number of surrounding wireless communication devices will be described. CSMA / CA is a protocol of the MAC layer, and each wireless communication device senses the usage status of a carrier before transmitting a packet, and starts transmission if it is unused for a certain period of time. Here, a sensing time is determined using a random number for each wireless communication device to avoid packet collision between terminals. The range that this random number can take is the contention window. The contention window (CW) depends on the number of retransmissions at the time of packet transmission and is determined as CW = (CW _min + 1) * 2 ⁿ -1. Here, n is the number of retransmissions and CW _min is the initial value of CW.

  In such a system, there is a problem that the total total throughput decreases as the number of terminals on the carrier increases. It has been reported that when packet collisions are repeated, it takes about 80 times the maximum time for packet transmission (when the number of terminals is 40) compared to the case where there is no collision.

  The above problem is considered to be because the initial value of the contention window value is uniquely determined by the wireless system regardless of the number of wireless communication devices (presence density). That is, with the increase in the number of terminals, the probability of random number duplication increases and unnecessary retransmission is considered to be performed.

  Therefore, by appropriately setting the initial value of the contention window value according to the number of wireless communication devices, it is possible to avoid packet collision and reduce the waiting time associated with data retransmission, thereby reducing the overall throughput. Can be suppressed.

  In the present embodiment, information that the contention window value at which the communication performance increases as the number of peripheral wireless communication devices increases increases in the history database. Therefore, the communication parameter candidate determination unit according to the present embodiment determines a contention window value range that excludes a range that is clearly inferior in communication performance as a candidate, according to context information such as the number of peripheral wireless communication devices. The communication control unit determines an appropriate contention window value from the candidates according to an application request or the like, and uses it for wireless communication. Thereby, collision of packets can be avoided, and overall throughput reduction can be suppressed.

  As a similar operation example, it is also possible to determine which frequency band in the white space is to be used using history data. In the history database, communication performance in any frequency band is stored for each place (and may be classified for each time). Note that the communication performance includes information on whether or not the frequency band is available. Therefore, the communication parameter candidate determination unit of the present embodiment can narrow down suitable frequency band candidates according to the current context.

  In the above description, an example in which one of the communication parameters is adaptively selected according to the context has been shown. However, a plurality of communication parameters can be adaptively selected according to the context by a combination of the above methods or other methods. Those skilled in the art will readily understand that the above can be changed.

<Operation and effect of the embodiment>
According to the present embodiment, communication parameters can be adaptively changed based on contexts obtained from various sensor information, and communication performance and reliability can be improved. Further, according to the present embodiment, it is possible not only to change specific communication parameters in a specific communication protocol but also to change arbitrary communication parameters. Since there is no limitation on the number of communication parameters to be changed and the number of sensor information that determines the context, the scalability is excellent. In addition, since the communication protocol itself is not changed, there is an advantage that it can be easily combined with existing technology.

(Second Embodiment)
In the first embodiment, the communication parameter and the communication performance are stored in association with each context, and the communication parameter that improves the communication performance in each context is selected. In the present embodiment, the context is defined focusing on communication performance. That is, the context is defined so that the communication parameters that can exhibit the best communication performance are the same in one context.

  Hereinafter, a description will be given based on specific examples. Here, for simplification, only two modulation methods and packet length are considered as communication parameters. There are three modulation schemes, BPSK, QPSK, and 16QAM, and two packet lengths, 100 bytes and 1000 bytes. These combinations are assumed to be six combinations.

  As vehicle sensor information, three types of received power, moving speed, and channel mode are used. The channel mode represents, for example, whether it is an urban area, a suburban area, or a rural area, or an expressway, a national road, or a general road. In addition, since one-to-one communication is considered here, the sensor information is used on both the transmission and reception sides.

  Next, processing (learning processing) for creating the history database 5 based on such sensor information and communication parameters will be described with reference to FIG. Here, an example in which simulation is used instead of actual measurement will be described, but similar processing is possible by actual measurement.

  First, an arbitrary situation is assumed (S501). That is, the received power, the moving speed, and the channel mode are determined for both vehicles that perform communication. Then, under this situation, communication performance is calculated by the communication simulator when adoptable communication parameters (six types described above) are adopted (S502). The communication performance similar to that shown in the first embodiment can be adopted. In addition, any existing communication simulator can be used. Then, in the situation assumed in step S501, a communication parameter that gives the best communication performance is determined (S503). The processes in steps S501 to S503 are repeated for the number of situations to be assumed.

  Next, a classifier that determines which communication parameter is optimal when an arbitrary situation is given is created by machine learning processing using the data obtained by the above processing as teacher data (S504). That is, a multi-class classifier that classifies situations into six classes is created by focusing on communication parameters that give the best communication performance with a combination of communication parameters as one class. Such a classifier can be created by an existing description. For example, a neural network, SVM (support vector machine), Bayesian filter, decision tree, or the like may be employed.

  FIG. 8 is a diagram illustrating an example of a decision tree created by machine learning. In the figure, the one enclosed by a solid square represents the situation of the host vehicle, and the one enclosed by a dotted square represents the situation of the communication partner vehicle.

  Even in this embodiment, it is possible to determine appropriate communication parameters according to the situation of the host vehicle and the communication partner vehicle.

  In the example described here, one optimal communication parameter is selected according to the situation of the host vehicle and the communication partner vehicle. This is different from the first embodiment in which suitable communication parameter candidates are obtained according to the situation, and one communication parameter is determined from the candidates according to the application request. However, by modifying this embodiment, the same configuration as that of the first embodiment can be obtained. That is, by creating a multi-class classifier in the same manner as described above with a combination of preferable plural (or one) communication parameters as one class, as in the first embodiment, communication parameters according to the situation. Can be determined, and the one to be actually used is selected from among the candidates according to the request of the application.

  Here, the communication performance when communication was performed using each communication parameter in each situation using a communication simulator was obtained, but the same classifier was measured by measuring the communication performance using various communication parameters in an actual environment. It will be clear that it can be created.

DESCRIPTION OF SYMBOLS 1 Wireless communication apparatus 2 Sensor 3 Sensor information collection part 4 Map information storage part 5 History database 6 Context determination part 7 Communication parameter candidate determination part 8 Application program 9 Communication control part 10 Wireless communication part 11 History data transmission / reception part 12 Other vehicle information collection Part

Claims (8)

A wireless communication device capable of changing communication parameters to be used according to the surrounding situation,
When performing communication between the first and second wireless communication devices using predetermined communication parameters, the peripheral conditions of the first and second wireless communication devices, the communication parameters, and the communication performance in the communication A learning database that associates and stores
Multiple sensors,
From the information obtained from the plurality of sensors, the surrounding situation determining means for determining the surrounding situation of the device itself,
A communication partner peripheral status acquisition means for acquiring a peripheral status from the wireless communication device of the communication partner;
Referring to the learning database, communication parameter determining means for determining an appropriate communication parameter in the surrounding situation of the device and the communication partner;
Wireless communication means for performing communication using the communication parameter determined by the communication parameter determination means;
A wireless communication device comprising: The communication parameter determination means includes
Referring to the learning database, determine appropriate communication parameter candidates in the surrounding situation of the device and the communication partner,
Based on requirements required for communication, communication parameters used for communication are determined from the candidates.
The wireless communication apparatus according to claim 1. The communication parameter candidate determination means determines candidates for one or more communication parameters for each of the transport layer, network layer, data link layer, and physical layer.
The wireless communication apparatus according to claim 2. The wireless communication device is mounted on a vehicle,
The radio | wireless communication apparatus in any one of Claims 1-3. The surrounding situation is related to information on the nature of the position of the vehicle and traffic at the position of the vehicle.
Information relating to the distance between the vehicle and surrounding objects, and information relating to the weather at the position of the vehicle.
The wireless communication apparatus according to claim 4. The plurality of sensors include at least one of a GPS device, a speed sensor, an acceleration sensor, a steering angle sensor, a brake sensor, a distance measuring sensor, a camera, a rain detection sensor, a brightness sensor, and a wireless communication unit .
The wireless communication apparatus according to claim 4 or 5 . History information storage means for storing communication parameters and communication performance of communication performed by the wireless communication means and the current situation of the own device and the communication partner as history information in association with each other,
History information transmitting means for transmitting history information stored in the history information storage means to a server device, and history information communication means for receiving history information stored in the server device,
The wireless communication apparatus according to any one of claims 1 6. A wireless communication method in which communication parameters to be used can be changed according to surrounding conditions,
From the information obtained from a plurality of sensors, the surrounding situation determination step for determining the surrounding situation of the own device,
A communication partner peripheral situation acquisition step for acquiring a peripheral situation from the wireless communication device of the communication partner;
When performing communication between the first and second wireless communication devices using predetermined communication parameters, the peripheral conditions of the first and second wireless communication devices, the communication parameters, and the communication performance in the communication A communication parameter determination step for determining an appropriate communication parameter in the surrounding situation of the own device and the communication partner with reference to a learning database that stores and correlates
A wireless communication step for performing communication using the communication parameter determined in the communication parameter determination step;
A wireless communication method including:

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