KR101624053B1 - Congestion Control Method and Device in Vehicle Network - Google Patents

Abstract

Disclosed are a congestion control device and a method in a vehicle network. The device comprises: a congestion judging unit which judges whether a congestion situation occurs or not; and a message transmission controller which predicts the number of messages from a remote vehicle received to a sub frame dividing a time frame, a message transmission period, into a predetermined unit, detects available sub frames and transmits a message in the detected sub frame section. According to the disclosed device and the method, the safety of a driver in a vehicle network congestion is increased and a process load is minimized and a message transmission can be efficiently controlled.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a congestion control method and apparatus,

The present invention relates to a congestion control apparatus and method, and more particularly, to a congestion control apparatus and method in a vehicle network.

Inter-vehicle communication technologies are being actively researched and applied to vehicle safety systems aimed at improving vehicle safety, increasing transportation efficiency, and operating convenience. Inter-vehicle communication is a short-range wireless communication technology based on CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) based communication (e.g., 5.9GHz) when the vehicle is in a communicable area : Wireless Access in Vehicular Environment (WAVE) communication).

The vehicle safety system based on inter-vehicle communication periodically broadcasts the position, speed, moving direction, and control information of the vehicle to neighboring vehicles in order to monitor the surrounding driving situation in real time. Each vehicle predicts the collision situation based on the driving information of the nearby vehicles received through the inter-vehicle communication, and warns the driver or the nearby vehicle if necessary.

In the vehicle network, each vehicle sends and receives messages in the same manner as described above. When the number of nearby vehicles increases rapidly, the probability of data transmission drops drastically due to frequent changes in the topology and data collision due to hidden nodes.

Therefore, in a congestion situation where the number of vehicles increases and messages increase, congestion control procedures for controlling transmission and reception of messages of vehicles are required for safety.

In this regard, Korean Patent Registration No. 10-1394884 proposes a method of changing the time frame setting, but since a considerable operation is required for changing the time frame and new scheduling is performed, the load of the processor is rapidly increased There was a problem.

An aspect of the present invention is to provide a congestion control apparatus and method for controlling message transmission in order to secure the driver's safety in a vehicle network congestion state.

Another aspect of the present invention is to provide a congestion control apparatus and method for efficiently controlling message transmission while minimizing a process load in a vehicle network congestion state.

According to an aspect of the present invention, there is provided a congestion control apparatus comprising: And a message transmission control unit for searching for available subframes by predicting the number of messages from a remote vehicle received in a subframe divided by a predetermined unit and transmitting the message in the searched subframe period A congestion control device is provided in the vehicle network.

The congestion control apparatus further includes a transmission probability setting unit for setting a transmission probability of a message to be transmitted when the congestion state is determined, and the transmission probability setting unit generates a random variable reflecting the set transmission probability.

The message transmission control unit performs a message transmission control operation when a message is to be transmitted based on the random variable.

The message transmission control unit determines whether there is an empty subframe that is predicted not to receive a message from the remote vehicle and controls to transmit a message in the corresponding subframe period if there is an empty subframe.

The message transmission control unit determines whether or not there is a subframe that is predicted to receive N messages or less and determines that there is a minimum number of messages among the subframes predicted to receive N or less messages And transmits the message in the subframe period that is predicted to be the base station.

The message transmission control unit waits for a predetermined backoff time when there is no subframe predicted to receive N messages or less, and if the available subframe is not detected during the backoff time, the message transmission control unit .

The message transmission probability is set based on the speed of the vehicle.

When the acceleration of the vehicle is equal to or greater than a predetermined threshold value, the message transmission probability is set to 1 regardless of the vehicle speed.

The congestion control apparatus further includes a transmission power determining unit for adjusting a transmission power of the message and a data rate determining unit for adjusting a data rate when it is determined that the congestion occurs, .

According to another aspect of the present invention, there is provided a congestion control apparatus comprising:

A received message predicting unit for predicting the number of messages from a remote vehicle received in a subframe in which a time frame as a message transmission period is divided by a predetermined unit; A sub-frame searching unit for searching for available sub-frames based on the number of messages received for each sub-frame; And a message transmission unit for controlling transmission of a message in an available subframe period, wherein the subframe search unit selects a corresponding subframe as an available subframe when an empty subframe exists, and if the empty subframe does not exist There is provided a congestion control apparatus in a vehicular network that selects a subframe that is predicted to receive the smallest number of messages among subframes predicted to receive a predetermined N or less messages.

According to another aspect of the present invention, And estimating the number of messages from a remote vehicle received in a subframe in which a time frame as a message transmission period is divided by a predetermined unit to search for available subframes and transmitting the message in the searched subframe period. A congestion control method is provided in the network.

According to the embodiments of the present invention, it is possible to secure the driver in a congested state of the vehicle network, and to efficiently control the message transmission while minimizing the process load.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an operation structure of an adaptive vehicle radar device according to an embodiment of the present invention; FIG.
2 is a view showing a beam pattern of an adaptive vehicle radar device according to an embodiment of the present invention.
3 is a block diagram showing a module configuration of an adaptive vehicle radar device according to an embodiment of the present invention;
4 is a block diagram showing a module configuration of a signal analysis unit 350 according to an embodiment of the present invention.
5 is a view illustrating a structure of a radar radiator and a beam pattern control unit according to an embodiment of the present invention.
6 is a block diagram illustrating the structure of a beam control module according to an embodiment of the present invention;
7 is a block diagram showing the structure of a beam control module according to another embodiment of the present invention;

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram showing the structure of a general vehicle communication network.

Referring to FIG. 1, a vehicle communication network includes a host vehicle (HV) and a plurality of remote vehicles (RVs), which are its own vehicles.

Each vehicle that constitutes the vehicle communication network periodically broadcasts a message. Each vehicle broadcasts a message including its own status information and status information of the neighboring vehicles, and neighboring vehicles receive the broadcasted message.

For example, the message transmitted from the host vehicle HV is transmitted through broadcasting to the first remote vehicle RV1 as the peripheral vehicle. Information of a message transmitted from the host vehicle HV may be transmitted from the first remote vehicle RV1 to the second remote vehicle RV2.

Each vehicle periodically transmits a message at a predetermined transmission time point, and a message transmission time point of each vehicle is determined for each vehicle.

The vehicle communication network to which the present invention is applied may be a vehicle communication network using the WAVE protocol, but the present invention may be applied to a vehicle communication network using various protocols.

Each vehicle constituting the vehicle network judges a dangerous situation by using a message received from another vehicle and provides a warning message to the driver in a dangerous situation so that safe operation can be performed.

When many remote vehicles are generated around the host vehicle, the message transmitted by each vehicle increases exponentially. Since messages that can be received and processed in a specific time interval are determined, if all the vehicles transmit messages without controlling message transmission, network congestion will occur and a large number of messages will be lost.

In such a network congestion situation, messages that are directly related to safety may be lost, which can lead to fatal defects in safety services related to the life of the driver.

The present invention provides an apparatus and method for congestion control in a vehicular communication network that appropriately controls the transmission time and the number of messages transmitted by each vehicle in a network congestion state to minimize loss of messages.

2 is a block diagram showing a schematic configuration of a congestion control apparatus for a vehicular communication network according to an embodiment of the present invention.

2, a congestion control apparatus for a vehicle network according to an exemplary embodiment of the present invention includes a congestion estimating unit 200, a message transmission control unit 210, a transmission power determination unit 220, and a data rate determination unit 230, .

The congestion estimating unit 200 determines whether the current network state is a congested state. Congestion estimation in existing vehicular communication networks mainly uses information of CBR (Channel Busy Ratio). However, with CBR alone, it is difficult to determine the exact congestion situation due to the packet collision caused by the hidden node, which is a major issue of the vehicle communication network.

According to the preferred embodiment of the present invention, the congestion estimating unit 200 performs congestion estimation that can solve the problem by the hidden node by reflecting the information of the multi-hop network without determining the load of only the single hop network.

In the present invention, each node constituting the vehicle network calculates the channel congestion degree (CBRLOCAL) of the local network and broadcasts the channel congestion of the local network calculated in the neighboring vehicle.

Also, each node constituting the vehicle network calculates the maximum value of the channel congestion degree of the received local network and estimates the 1-HOP channel congestion degree (CBR1-HOP) and broadcasts it to the surrounding vehicles.

Also, each node constituting the vehicle network calculates the 2-HOP channel congestion (CBR2-HOP) at the maximum value among the CBR1-HOPs received from the neighboring vehicle.

The congestion estimating unit 200 calculates a maximum value among the 2-HOP channel congestion degree (CBR2-HOP), the 1-HOP channel congestion degree (CBR1-HOP) and the local channel congestion degree (CBRLOCAL) obtained in the above- Estimate the congestion level (CBRGLOBAL).

The message transmission control unit 210 determines whether a message is transmitted and a message transmission time when it is determined that a congestion state exists.

The message transmission control unit 210 determines a transmission time in consideration of the number of received messages in a congestion state, and determines whether to transmit a message based on packet transmission probability information determined based on the vehicle state.

If it is not a congested state, each vehicle node broadcasts the message in a predetermined cycle. For example, if it is assumed that a message is set to be transmitted at a time interval of 100 ms in a non-congested state, in a congested state, the message transmission control unit 210 does not transmit a message in a preset period, And transmits a message at a time determined by the control unit 210. [

3 is a block diagram illustrating a structure of a message transmission control unit in a vehicle communication network congestion control apparatus according to an embodiment of the present invention.

3, the message transmission control unit of the congestion control apparatus according to an exemplary embodiment of the present invention includes a transmission probability setting unit 300, a received message predicting unit 310, an available subframe searching unit 320 And a message transmission unit 330. [

Before describing the message transmission control unit, the time frame of the vehicle communication network will be described first. The time frame is the transmission period of the message, for example, the time frame may be set to 100 ms.

A subframe is a frame obtained by dividing a time frame into a predetermined time period. For example, when the time frame is 100 ms, the subframe may be set to 10 ms. In this case, one time frame includes 10 subframes.

The transmission probability setting unit 300 sets the transmission probability of the message based on the state information of the vehicle. According to a preferred embodiment of the present invention, the transmission probability setting unit sets a transmission probability of a message based on the speed of the vehicle.

The transmission probability setting unit 300 sets the transmission probability higher when the vehicle is traveling at a high speed and sets the transmission probability to be low when the vehicle is traveling at a slow speed.

For example, if the vehicle speed is 30 km or less, the message transmission probability is set to 1/3, and if the vehicle speed is 100 km or more, the message transmission probability may be set to 1. [ If the speed of the vehicle is high, the message will always be transmitted because the impact on safety is significant.

The transmission probability setting unit 300 generates a random variable that reflects a predetermined transmission probability for transmitting a message with a transmission probability determined based on the vehicle speed. For example, if the determined transmission probability is 1/3, the transmission probability setting unit 300 generates a random variable to transmit the message once at the third time.

For example, if the random variable reflecting the transmission probability is 1, it determines to transmit the message, and if the random variable is 0, decides not to transmit the message.

The transmission message predicting unit 310, the available subframe searching unit 320 and the message transmitting unit 330 operate when the transmission probability setting unit 300 determines to transmit the message.

The received message predicting unit 310 predicts how many messages are to be received in each subframe. The number of messages received in each subframe is predicted based on the fact that the transmission period of the remote vehicle also has the same time frame. For example, if a message is received from the first remote vehicle in the first subframe (0 to 10 ms) of the first time frame (0 to 100 ms), a message is received from the first remote vehicle in the first subframe of the second time frame Can be predicted.

Since not all vehicles have the same message transmission timing, a plurality of messages may be received in a specific subframe, and no message may be received in a specific subframe.

The available subframe search unit 320 searches for an available subframe based on the information predicted by the received message predicting unit 310. [

The available sub-frame search unit 320 primarily searches for an empty sub-frame in which no message is received. If there is an empty sub-frame in which no message is received, the available sub-frame search unit selects the sub-frame as a sub-frame to transmit the message. When there are a plurality of empty subframes, the available subframe search unit 320 randomly selects a subframe or a nearest subframe at a start point of the timeframe.

When no empty sub-frame is searched, the available sub-frame searching unit 320 searches for a sub-frame in which the number of received messages is equal to or less than a preset natural number N. [ For example, if N = 3, the number of received messages is 3 or less.

If there are subframes having a predetermined number N or less of the received messages, the available subframe search unit 320 selects the smallest subframe of the received message.

If it is predicted that a message exceeding N is received in all subframes, the available subframe searching unit 320 determines that no available subframe exists.

Meanwhile, according to a preferred embodiment of the present invention, the number of messages receivable in one subframe is set to N in advance. When N or more messages are predicted to be received in a specific subframe, a message is received in a contention manner by the CSMA / CA scheme so that only N messages are set to be received in one subframe.

The message transmission unit 330 transmits a message to an available subframe to be searched by the available subframe search unit 320. [ For example, if N or more messages are predicted to be received in all subframes except for the first subframe, N messages are expected to be received in the first subframe, and the first subframe is selected as an available subframe, The transmitting unit 330 transmits (broadcasts) a message prepared in the first sub-frame.

If there is no available subframe, the message transmission unit 300 waits for a predetermined back-off time, and if the available subframe can not be detected during the back-off waiting time, the message transmission unit 300 immediately transmits a message .

4 is a diagram illustrating a concept of a time frame according to an embodiment of the present invention.

Referring to FIG. 4, a time frame according to an embodiment of the present invention includes a plurality of subframes 400, 402, 404, 406, 408, 410, 412, 414, 416, 418, Messages are received from another remote vehicle (RV).

According to the example shown in Fig. 4, it can be seen that a message is received from two remote vehicles in the first sub-frame 400, but no message is received from the other remote vehicles in the second sub-frame 402. [

In this case, the available sub-frame search unit 320 can select the second sub-frame 402 as an available sub-frame.

Referring again to FIG. 2, the transmission power determination unit 220 determines a transmission power of a message when the network state is a congested state.

According to a preferred embodiment of the present invention, the transmission power determination unit 220 determines a transmission power based on a PER (Packet Error Ratio) and a congestion degree for each distance. Here, the PER (Packet Error Ratio) according to distance means an error ratio according to the distance distant from the host vehicle. The error ratio according to the distance can be obtained in various ways, and a detailed description thereof will be omitted.

The data rate determining unit 230 controls the data rate when it is determined that the vehicle network state is a congested state.

According to a preferred embodiment of the present invention, the transmit power and the data rate are adjusted together and are not independently adjusted.

When the transmission power determining unit 220 and the data rate determining unit 230 are determined to be congested, the transmission power determining unit 220 and the data rate determining unit 230 gradually reduce the transmission power and gradually increase the data rate To adjust the transmission power and the data rate so as to reach the desired congestion degree.

5 is a flowchart illustrating a message transmission procedure when it is determined that the congestion state is determined according to an embodiment of the present invention.

First, a packet received for each subframe is predicted (step 500). A packet received for each subframe can be predicted using the reception time of a packet received in a previous time frame.

If a packet received for each subframe is predicted, it is determined whether there is an empty subframe in which a packet is not received (step 502).

If an empty subframe exists, the corresponding subframe is reserved (step 504). If there are a plurality of empty subframes, it is preferable to reserve the subframe nearest to the start point of the timeframe.

The prepared message is broadcasted in the reserved subframe period (step 506).

If there is no empty sub-frame, a sub-frame predicted to receive N or less messages is searched (step 508).

If there is a subframe that is predicted to receive N or less messages, the subframe is reserved and a message is transmitted.

If there is no subframe that is predicted to receive N or less messages, it waits for a preset backoff time (step 510).

A procedure 508 for searching for available subframes during the backoff wait time is performed, and if no available subframe is found during the backoff wait time, the ready message is immediately transmitted (step 512).

6 is a flowchart illustrating a procedure for generating a random variable reflecting a message transmission probability according to an exemplary embodiment of the present invention.

Referring to FIG. 6, first, an average speed of the vehicle is measured (step 600). The vehicle speed information may be obtained from the vehicle and may also be obtained from the GPS or a separate speed sensor.

When the vehicle speed information is obtained periodically, the vehicle speed information obtained periodically is used to calculate an average speed during a specific time.

In addition, the acceleration of the vehicle is calculated using the vehicle speed information obtained periodically, and it is determined whether or not the acceleration of the vehicle is equal to or greater than a preset threshold value (step 602).

If the acceleration of the vehicle is equal to or greater than a preset threshold value, the message transmission probability is set to 1 regardless of the average speed of the vehicle (step 606). If the acceleration of the vehicle is high, the average speed of the vehicle suddenly increases. Therefore, the transmission probability of the message is set to 1 for safety.

A transmission probability of a message is set based on the average speed of the vehicle when the acceleration of the vehicle is less than a predetermined threshold (step 604). The lower the vehicle speed, the lower the message transmission probability.

If the message transmission probability is set, a random variable reflecting the message transmission probability is generated (step 608). The decision as to whether or not to send a message is made using the corresponding random variable value.

7 is a flowchart illustrating a process of adjusting transmission power and data rate in a congestion state according to an embodiment of the present invention.

Referring to FIG. 7, the congestion degree and per-distance PER information are obtained (step 700).

When the congestion degree and PER per distance are obtained, it is determined whether power adjustment and date rate adjustment are necessary (step 702).

If the congestion level is higher than the preset reference congestion level, the transmission power is gradually reduced to a predetermined step size and the data rate is gradually increased to a predetermined step size (step 704).

Step 704 determines whether the congestion degree reaches a predetermined reference congestion level (step 706). When the congestion degree reaches the reference congestion level, the power adjustment and data rate adjustment operation are stopped and fixed at the transmission power and data rate at the time of reaching the reference mixing degree (step 708).

If the congestion level is lower than the preset reference congestion level, the transmission power is gradually increased to a predetermined step size and the data rate is gradually reduced to a predetermined step size (step 710).

Step 708 determines whether the congestion has reached a preset reference congestion (step 712), suspends the power adjustment and data rate adjustment operation, and performs message transmission with the transmission power and data rate when the reference mixing degree is reached (Step 708).

The above-described technical features may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (17)

A congestion judging unit for judging whether or not the congestion state is present; And
A message transmission control unit for searching for available subframes by predicting the number of messages from a remote vehicle received in a subframe obtained by dividing a time frame, which is a message transmission period, by a preset unit, and for transmitting the message in the searched subframe period ,
Wherein the message transmission control unit determines whether or not there is an empty subframe that is predicted not to receive a message from the remote vehicle and controls to transmit a message in the corresponding subframe period if there is an empty subframe. Congestion control device.
The method according to claim 1,
Further comprising a transmission probability setting unit configured to set a transmission probability of a message to be transmitted when it is determined that a congestion state exists, and wherein the transmission probability setting unit generates a random variable reflecting the set transmission probability, .
3. The method of claim 2,
Wherein the message transmission control unit performs a message transmission control operation when a message is to be transmitted based on the random variable.
delete The method according to claim 1,
The message transmission control unit determines whether or not there is a subframe that is predicted to receive N messages or less and determines that there is a minimum number of messages among the subframes predicted to receive N or less messages The control unit controls to transmit the message in the sub-frame period that is predicted to be the congestion control unit in the vehicle network.
6. The method of claim 5,
The message transmission control unit waits for a predetermined backoff time when there is no subframe predicted to receive N messages or less, and if the available subframe is not detected during the backoff time, the message transmission control unit The congestion control apparatus comprising:
3. The method of claim 2,
Wherein the message transmission probability is set based on the speed of the vehicle.
8. The method of claim 7,
Wherein the message transmission probability is set to 1 regardless of the vehicle speed when the acceleration of the vehicle is equal to or greater than a predetermined threshold value.
The method according to claim 1,
Further comprising a transmission power determining unit for adjusting a transmission power of a message and a data rate determining unit for adjusting a data rate when it is determined that the congestion state is a congestion state, A congestion control device in the network.
A congestion judging unit for judging whether or not the congestion state is present;
A received message predicting unit for predicting the number of messages from a remote vehicle received in a subframe in which a time frame as a message transmission period is divided by a predetermined unit;
A sub-frame searching unit for searching for available sub-frames based on the number of messages received for each sub-frame; And
And a message transmitter for controlling transmission of a message in an available subframe period,
The sub-frame searching unit selects the sub-frame as an available sub-frame when there is an empty sub-frame, and selects the smallest number of sub-frames predicted to receive a predetermined N or less message when there is no empty sub- And selects a subframe in which a message is predicted to be received.
11. The method of claim 10,
Wherein the message transmitter waits for a preset backoff time when no available subframe is present and controls to immediately transmit a message if no available subframe is found during the backoff time Congestion control device.
(A) judging whether or not the congestion state is present; And
(B) of estimating the number of messages from a remote vehicle received in a subframe in which a time frame, which is a message transmission period divided by a predetermined unit, is predicted, searching for available subframes, and transmitting a message in the searched subframe period However,
Wherein the step (b) determines whether there is an empty subframe that is predicted not to receive a message from the remote vehicle, and if there is an empty subframe, the message is transmitted in the corresponding subframe period Control method.
13. The method of claim 12,
Further comprising setting a transmission probability of a message to be transmitted when the congestion state is determined, and generating a random variable reflecting a set transmission probability.
14. The method of claim 13,
Wherein the step (b) performs a message transmission operation when a message is to be transmitted based on the random variable.
delete 13. The method of claim 12,
The step (b) determines whether there are subframes predicted to receive N messages or less. If the number of the subframes predicted to receive N or less messages is the smallest And a message is transmitted in a sub-frame period that is predicted to be a congested state in the vehicle network.
17. The method of claim 16,
The step (b) waits for a predetermined backoff time when there is no subframe predicted to receive N messages or less, and if the available subframe is not detected during the backoff time, And immediately transmitting the congestion control message to the vehicle network.

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